PHOSPHORODIAMIDATE DERIVATIVES OF GUANOSINE NUCLEOSIDE COMPOUNDS FOR TREATMENT OF VIRAL INFECTIONS

[0001] CROSS REFERENCE TO RELATED APPLICATION

[0002] The present application claims the benefit of U.S. Provisional Application Ser. No.

61/390,357, filed October 6, 2010, the entire disclosure of which is incorporated herein by reference.

[0003] FIELD OF THE INVENTION

[0004] This application relates to novel nucleoside phosphorodiamidates and their use as agents for treating viral diseases. Such compounds are inhibitors of RNA- dependant RNA viral replication and specifically, inhibitors of HCV NS5B polymerase. As inhibitors of HCV replication, such compounds are useful for treatment of hepatitis C infection in mammals.

[0005] BACKGROUND OF THE INVENTION

[0006] HCV is a member of the Flaviviridae family of RNA viruses that affect animals and humans. The genome is a single 9.6-kilobase strand of RNA, and consists of one open reading frame that encodes for a polyprotein of approximately 3000 amino acids flanked by untranslated regions at both 5' and 3' ends (5'- and 3'-UTR). The polyprotein serves as the precursor to at least 10 separate viral proteins critical for replication and assembly of progeny viral particles.

[0007] Hepatitis C Virus (HCV) infection is a major health problem that leads to chronic liver disease, such as cirrhosis and hepatocellular carcinoma, in a substantial number of infected individuals, estimated to be 2-15% of the world population. There are an estimated 4.5 million infected people in the United States alone, according to the U.S. Center for Disease control. According to the World Health Organization, there are more than 200 million infected individuals worldwide, with at least 3 to 4 million people being infected each year. Once infected, about 20% of people clear the virus, but the remainder can harbor HCV for the rest of their lives. [0008] Ten to twenty percent of chronically infected individuals eventually develop liver- destroying cirrhosis or cancer. The viral disease is transmitted parenterally by contaminated blood and blood products, contaminated needles, or sexually and vertically from infected mothers or carrier mothers to their offspring

[0009] At present, the standard treatment for chronic HCV is interferon alpha (IFN-alpha) in combination with ribavirin, which requires at least six (6) months of treatment. However, treatment of HCV with interferon has frequently been associated with adverse side effects such as fatigue, fever, chills, headache, myalgias, arthralgias, mild alopecia, psychiatric effects and associated disorders, autoimmune phenomena and associated disorders and thyroid dysfunction.

[0010] Ribavirin, an inhibitor of inosine 5 '-monophosphate dehydrogenase (IMPDH),

enhances the efficacy of IFN-alpha in the treatment of HCV. Despite the introduction of ribavirin, more than 50% of the patients do not eliminate the virus with the current standard therapy of interferon- alpha and ribavirin. By now, standard therapy of chronic hepatitis C has been changed to the combination of pegylated IFN-alpha plus ribavirin. However, a number of patients still have significant side effects, primarily related to ribavirin.

[0011] Ribavirin causes significant hemolysis in 10-20% of patients treated at currently recommended doses, and the drug is both teratogenic and embryotoxic. Even with recent improvements, a substantial fraction of patients do not respond with a sustained reduction in viral load and there is a clear need for more effective antiviral therapy of HCV infection.

[0012] A number of other approaches are being pursued to combat the virus. They include, for example, application of antisense oligonucleotides or ribozymes for inhibiting HCV replication. Furthermore, low-molecular weight compounds that directly inhibit HCV proteins and interfere with viral replication are considered as attractive strategies to control HCV infection. Among the viral targets, the NS3/4A protease/helicase and the NS5B RNA-dependent RNA polymerase are considered the most promising viral targets for new drugs.

[0013] A number of patents disclose and claim inventions relating to HCV NS5B inhibitors.

For example, WO 2006/046039, WO 2006/046030 and WO 2006/029912, incorporated by reference herein, relate to tetracyclic indole compounds and pharmaceutically acceptable salts thereof, for the treatment or prevention of infection by hepatitis C virus. WO 2005/080399, incorporated by reference herein, relates to fused hetero tetracyclic compounds, pharmaceutically acceptable salts thereof; and their use in aiding to remedy hepatitis C infection as potent (HCV) polymerase inhibitors. WO 2003007945, incorporated by reference herein, relates to HCV NS5B inhibitors. Further, WO 2003010140, incorporated by reference herein, relates to specific inhibitors of RNA dependent RNA polymerases, particularly viral polymerases within the Flaviviridae family, more particularly to HCV polymerase. WO 200204425, incorporated by reference herein, relates to specific inhibitors of RNA dependent RNA polymerases, particularly viral polymerases within the Flaviviridae family, and more particularly the NS5B polymerase of HCV. WO 200147883, incorporated by reference herein, relates to specific fused-ring compounds or the like or pharmaceutically acceptable salts thereof. Such compounds and salts exhibit an anti-HCV (hepatitis C virus) activity by virtue of their inhibitory activity against HCV polymerase, thus being useful as therapeutic or preventive agents for hepatitis C.

[0014] However, in view of the worldwide epidemic level of HCV and other members of the

Flaviviridae virus family, and in view of the limited treatment options, there is a strong need for new effective drugs for treating infections caused by these viruses.

[0015] SUMMARY OF THE INVENTION

[0016] This invention is directed to novel compounds that are useful in the treatment of viral infections in mammals mediated, at least in part, by a virus in the Flaviviridae family of viruses. According to some embodiments, the present invention provides for novel compounds of formula (I) having the structure:

(I)

wherein R ² , R ³ , and R ⁴ are each independently

wherein

R 7' and R 8° are each independently

hydrogen,

Ci-Cgalkyl,

Ci-Csalkylaryl,

CH ₃ XCH ₂ -,

CH ₃ XCH ₂ CH ₂ - ,

R ⁹ XC(0)CH ₂ - benzyl,

benzyl optionally substituted by halogen,

benzyl optionally substituted by Q-Cgalkyl benzyl optionally substituted by Q-Cealkoxy phenyl,

phenyl optionally substituted by halogen,

phenyl optionally substituted by Q-Cgalkyl or phenyl optionally substituted by Q-Cealkoxy wherein X is O or S; and

R ⁹ is independently

hydrogen,

Ci-Cgalkyl optionally substituted by C ₃ -C ₆ cycloalkyl,

C ₄ -Cgcycloalkyl,

tetrahydropyranyl,

benzyl,

benzyl optionally substituted by halogen

benzyl optionally substituted by Q-Cgalkyl benzyl optionally substituted by Q-Cealkoxy

2-phenylethyl optionally substituted on the phenyl ring halogen,

or

2-indanyl,

• hydrogen,

• Q-Cgalkyl optionally substituted by C3-C ₆ cycloalkyl,

• R ⁹ 0 ₂ CCH ₂ CH ₂ -

• Cs-Cgcycloalkyl,

• C ₆ -C ₁₀ aryl optionally substituted by halogen,

or

• benzyl optionally substituted by halogen;

or

R 1 and R 2 when taken together with the N atom to which they are attached, may form

• a heterocyclic ring containing from 3 to 5 C atoms,

• a morpholine ring,

• a piperazine ring,

• a thiomorpholine ring, or

• a ring of formula

or

R ³ and R ⁴ when taken together with the N atom to which they are attached, may form

• a heterocyclic ring containing from 3 to 5 C atoms

• a morpholine ring,

• a piperazine ring,

• a thiomorpholine ring, or

• a ring of formula

wherein X' is O or S,

R ⁶ is selected from H, Ci-Cgalkyl optionally substituted by Ce-Qoaryl, and

CrCscycloalkyl, and

R ¹⁰ and R ¹¹ are independently selected from H, C Csalkyl optionally substituted by C6-C ₁₀ aryl, and C -C ₈ cycloalkyl;

and the pharmaceutically acceptable salts thereof. In addition to salts, the present invention includes other forms of all of the disclosed compounds including solvates, hydrates and polymorphs. Such compounds are inhibitors of RNA-dependant RNA viral replication and inhibitors of HCV NS5B polymerase and thus may be utilized in methods wherein such inhibition is desired.

[0017] According to other embodiments, the present invention extends to a pharmaceutical composition comprising one or more compounds of formula I and a pharmaceutically acceptable carrier, excipient or diluent. The pharmaceutically acceptable carrier, excipient or diluent may be pure sterile water, phosphate buffered saline or an aqueous glucose, solution.

[0018] Also provided are methods for treating a viral infection in a mammal mediated at least in part by a virus in the Flaviviridae family wherein an instant method comprises administering to a mammal that has been diagnosed with said viral infection a pharmaceutical composition comprising compounds of formula I..

[0019] Also provided are methods for treating a viral infection in a human or animal patient that is mediated at least in part by a virus in the Flaviviridae family wherein an instant method comprises administering to a human or animal patient in need thereof an effective amount of a pharmaceutical composition comprising compounds of formula I.

[0020] In one embodiment, the virus is hepatitis C virus (or HCV). The present methods further extend to combination treatment comprising administration of a therapeutically effective amount of one or more agents active against hepatitis C virus. Such active agents against hepatitis C virus may include interferon- alpha or pegylated interferon-alpha alone or in combination with ribavirin or levovirin. [0021] DETAILED DESCRIPTION OF THE INVENTION

[0022] The present invention relates to chemical compounds, their preparation and their use in the treatment of viral infections particularly in mammals. Particularly, although not exclusively, the present invention relates to chemical compounds useful as anti-hepatitis C virus (HCV) agents.

[0023] Specifically, the present invention describes certain nucleoside phosphorodiamidates, their synthesis, and their use as inhibitors of RNA-dependent RNA viral polymerase, particularly their use as inhibitors of hepatitis C virus (HCV) NS5-B polymerase, as inhibitors of HCV replication, and for the treatment of hepatitis C infection. The compounds can also be precursors for such inhibitors.

[0024] It is an object of the present invention to provide novel chemical compounds useful for treatment of viral infections in mammals, specifically for treatment of hepatitis C infection in mammals.

[0025] The present invention relates to novel compounds of formula (I) having the structure:

(I)

wherein R ² , R ³ , and R ⁴ are each independently

wherein

R 7' and R 8° are each independently

hydrogen,

Ci-Cgalkyl, Ci-C ₃ alkylaryl,

CH ₃ XCH ₂ -,

CH ₃ XCH ₂ CH ₂ - ,

R ⁹ XC(0)CH ₂ - benzyl,

benzyl optionally substituted by halogen,

benzyl optionally substituted by Q-Cgalkyl benzyl optionally substituted by Q-Cealkoxy phenyl,

phenyl optionally substituted by halogen,

phenyl optionally substituted by Q-Cgalkyl, or phenyl optionally substituted by Q-Cealkoxy and

R ⁹ is independently

hydrogen,

Q-Cgalkyl optionally substituted by C ₃ -C ₆ cycloalkyl,

C4-Cgcycloalkyl,

tetrahydropyranyl,

benzyl,

benzyl optionally substituted by halogen

benzyl optionally substituted by Q-Cgalkyl benzyl optionally substituted by Q-Cealkoxy

2-phenylethyl optionally substituted on the phenyl ring halogen,

or

2-indanyl,

• hydrogen,

• Q-Cgalkyl optionally substituted by C ₃ -C ₆ cycloalkyl,

• R ⁹ 0 ₂ CCH ₂ CH ₂ -

• CrCgcycloalkyl,

• C6-C ₁₀ aryl optionally substituted by halogen, • benzyl optionally substituted by halogen;

or

R 1 and R 2 when taken together with the N atom to which they are attached, may form

• a heterocyclic ring containing from 3 to 5 C atoms,

• a morpholine ring,

• a piperazine ring,

• a thiomorpholine ring, or

• a ring of formula

or

R ³ and R ⁴ when taken together with the N atom to which they are attached, may form

• a heterocyclic ring containing from 3 to 5 C atoms

• a morpholine ring,

• a piperazine ring,

• a thiomorpholine ring, or

• a ring of formula

and

R ⁵ is selected from CI, X'R ⁶ and NR ¹⁰ R ^U ,

wherein

X' is O or S,

R ⁶ is selected from H, CrCsalkyl optionally substituted by C6-C ₁₀ aryl, and

CrCgcycloalkyl, and

R ¹⁰ and R ¹¹ are independently selected from H, CrCgalkyl optionally substituted by C6-C ₁₀ aryl, and Cs-Cgcycloalkyl;

and the pharmaceutically acceptable salts thereof. In addition to salts, the present invention includes other forms of all of the disclosed compounds including solvates, hydrates and polymorphs. [0026] In each case, the above compounds are provided along with their phosphorus diastereomers. For example, phosphorous diastereomers may be possible in cases where Rl and R2 are not identical to R3 and R4.

[0027] In accordance with the present invention there are provided the following specific embodiments of the above compounds:

11 and the pharmaceutically acceptable salts thereof.

[0038] In accordance with the present invention there are provided the following specific embodiments of the above compounds:

[0039] (25,2'5)-Dineopentyl-((((2R,35,4R,5R)-5-(2-amino-6-methoxy-9 H-purin-9-yl)-3,4- dihydroxy-4-methyltetrahydrofuran-2-yl)methoxy) phosphoryl)(2,2')-bis-amino- dipropanoate

[0040] (2S,2'S)-Dimethyl 2,2'-((((2R,3R,4R,5R)-5-(2-amino-6-methoxy-9H-purin-9-yl)-3, 4- dihydroxy-4-methyltetrahydrofuran-2- yl)methoxy)phosphoryl)bis(azanediyl)dipropanoate

[0041] (25,2'5)-Diethyl 2,2'-((((2R,3R,4R,5R)-5-(2-amino-6-methoxy-9H-purin-9-yl)-3, 4- dihydroxy-4-methyltetrahydrofuran-2- yl)methoxy)phosphoryl)bis(azanediyl)dipropanoate

[0042] (25,2 '5)-Dipropyl-((((2R,35,4R,5R)-5-(2-amino-6-methoxy-9H-purin- 9-yl)-3,4- dihydroxy-4-methyltetrahydrofuran-2-yl)methoxy) phosphoryl)-(2,2')-bis-amino- dipropanoate

[0043] (25,2'5)-Dibutyl 2,2'-((((2R,3R,4R,5R)-5-(2-amino-6-methoxy-9H-purin-9-yl)-3, 4- dihydroxy-4-methyltetrahydrofuran-2- yl)methoxy)phosphoryl)bis(azanediyl)dipropanoate

[0044] (2S,2'S)-dipentyl 2,2'-((((2R,3R,4R,5R)-5-(2-amino-6-methoxy-9H-purin-9-yl)-3, 4- dihydroxy-4-methyltetrahydrofuran-2- yl)methoxy)phosphoryl)bis(azanediyl)dipropanoate [0045] (2S,2'S)-bis(3,3-dimethylbutyl) 2,2'-((((2R,3R,4R,5R)-5-(2-amino-6-methoxy-9H- purin-9-yl)-3,4-dihydroxy-4-methyltetrahydrofuran-2- yl)methoxy)phosphoryl)bis(azanediyl)dipropanoate

[0046] (25,2'5)-Diisobutyl-((((2R,35,4R,5R)-5-(2-amino-6-methoxy-9H -purin-9-yl)-3,4- dihydroxy-4-methyltetrahydrofuran-2-yl)methoxy) phosphoryl)(2,2')-bis-amino- dipropanoate

[0047] (2S,2W)-Bis(cyclopropylmethyl) 2,2'-((((2R,3R,4R,5R)-5-(2-amino-6-methoxy-9H- purin-9-yl)-3,4-dihydroxy-4-methyltetrahydrofuran-2- yl)methoxy)phosphoryl)bis(azanediyl)dipropanoate

[0048] (25,2'5)-Dibenzyl-((((2R,35,4R,5R)-5-(2-amino-6-methoxy-9H-p urin-9-yl)-3,4- dihydroxy-4-methyltetrahydrofuran-2-yl)methoxy) phosphoryl)-(2,2')-bis-amino- dipropanoate

[0049] (25,2'5)-Diisopropyl-((((2R,35,4R,5R)-5-(2-amino-6-methoxy-9 H-purin-9-yl)-3,4- dihydroxy-4-methyltetrahydrofuran-2-yl)methoxy) phosphoryl)-(2,2')-bis-amino- dipropanoate

[0050] (2S,2'S)-sec- uty\ 2,2'-((((2R,3R,4R,5R)-5-(2-amino-6-methoxy-9H-purin-9-yl)-3, 4- dihydroxy-4-methyltetrahydrofuran-2- yl)methoxy)phosphoryl)bis(azanediyl)dipropanoate

[0051] (2S,2'S)-Dicyclobutyl 2,2'-((((2R,3R,4R,5R)-5-(2-amino-6-methoxy-9H-purin-9-yl)- 3,4-dihydroxy-4-methyltetrahydrofuran-2- yl)methoxy)phosphoryl)bis(azanediyl)dipropanoate

[0052] (2S,2'S)-Dicyclopentyl 2,2'-((((2R,3R,4R,5R)-5-(2-amino-6-methoxy-9H-purin-9-yl)- 3,4-dihydroxy-4-methyltetrahydrofuran-2- yl)methoxy)phosphoryl)bis(azanediyl)dipropanoate

[0053] (25,2'5)-Dicyclohexyl-((((2R,35,4R,5R)-5-(2-amino-6-methoxy- 9H-purin-9-yl)-3,4- dihydroxy-4-methyltetrahydrofuran-2-yl)methoxy) phosphoryl)-(2,2')-bis-amino- dipropanoate [0054] (2S,2'S)-Bis(tetrahydro-2H-pyran-4-yl) 2,2'-((((2R,3R,4R,5R)-5-(2-amino-6-methoxy- 9H-purin-9-yl)-3,4-dihydroxy-4-methyltetrahydrofuran-2- yl)methoxy)phosphoryl)bis(azanediyl)dipropanoate

[0055] (25,2'5)-(5)-Phenylethyl-((((2R,35,4R,5R)-5-(2-amino-6-metho xy-9H-purin-9-yl)-

3,4-dihydroxy-4-methyltetrahydrofuran-2-yl)methoxy) phosphoryl)-(2,2')-bis- amino-dipropanoate

[0056] (2S,2'S)-Bis(2,3-dihydro- lH-inden-2-yl) 2,2'-((((2R,3R,4R,5R)-5-(2-amino-6- methoxy-9H-purin-9-yl)-3,4-dihydroxy-4-methyltetrahydrofuran -2- yl)methoxy)phosphoryl)bis(azanediyl)dipropanoate

[0057] (2S)-Benzyl 2-((((2R,3R,4R,5R)-5-(2-amino-6-methoxy-9H-purin-9-yl)-3,4- dihydroxy-4-methyltetrahydrofuran-2-yl)methoxy)(( _l S')-l-(neopentyloxy)-l- oxopropan-2-ylamino)phosphorylamino)propanoate

[0058] (2S)-Cyclohexyl 2-((((2R,3R,4R,5R)-5-(2-amino-6-methoxy-9H-purin-9-yl)-3,4- dihydroxy-4-methyltetrahydrofuran-2-yl)methoxy)(( _l S')-l-(neopentyloxy)-l- oxopropan-2-ylamino)phosphorylamino)propanoate

[0059] (25 iert-Butyl 2-((((2R,3R,4R,5R)-5-(2-amino-6-methoxy-9H-purin-9-yl)-3,4- dihydroxy-4-methyltetrahydrofuran-2-yl)methoxy)(( _l S')-l-(neopentyloxy)-l- oxopropan-2-ylamino)phosphorylamino)propanoate

[0060] (25 Methyl 2-((((2R,3R,4R,5R)-5-(2-amino-6-methoxy-9H-purin-9-yl)-3,4- dihydroxy-4-methyltetrahydrofuran-2-yl)methoxy)(( _l S')-l-(neopentyloxy)-l- oxopropan-2-ylamino)phosphorylamino)-3-methylbutanoate

[0061] Methyl l-((((2R,3R,4R)-5-(2-amino-6-methoxy-9H-purin-9-yl)-3,4-dihy droxy-4- methyltetrahydrofuran-2-yl)methoxy)(( _l S')-l-(neopentyloxy)-l-oxopropan-2- ylamino)phosphoryl)pyrrolidine-2-carboxylate

[0062] (2S)-Benzyl 2-((((2R,3R,4R,5R)-5-(2-amino-6-methoxy-9H-purin-9-yl)-3,4- dihydroxy-4-methyltetrahydrofuran-2- yl)methoxy)(butylamino)phosphorylamino)propanoate [0063] (2S)-Neopentyl 2-((((2R,3R,4R,5R)-5-(2-amino-6-methoxy-9H-purin-9-yl)-3,4- dihydroxy-4-methyltetrahydrofuran-2- yl)methoxy)(butylamino)phosphorylamino)propanoate

[0064] (2S)-Neopentyl 2-((((2R,3R,4R,5R)-5-(2-amino-6-methoxy-9H-purin-9-yl)-3,4- dihydroxy-4-methyltetrahydrofuran-2- yl)methoxy)(benzylamino)phosphorylamino)propanoate

[0065] (2S)-Neopentyl 2-((((2R,3R,4R)-5-(2-amino-6-methoxy-9H-purin-9-yl)-3,4- dihydroxy-4-methyltetrahydrofuran-2- yl)methoxy)(diethylamino)phosphorylamino)propanoate

[0066] (2S)-Neopentyl 2-((((2R,3R,4R,5R)-5-(2-amino-6-methoxy-9H-purin-9-yl)-3,4- dihydroxy-4-methyltetrahydrofuran-2-yl)methoxy) (pyrrolidin- 1 - yl)phosphorylamino)propanoate

[0067] (2S)-Neopentyl 2-((((2R,3R,4R,5R)-5-(2-amino-6-methoxy-9H-purin-9-yl)-3,4- dihydroxy-4-methyltetrahydrofuran-2- yl)methoxy)(phenylamino)phosphorylamino)propanoate

[0068] (2S)-Neopentyl 2-((((2R,3R,4R)-5-(2-amino-6-methoxy-9H-purin-9-yl)-3,4- dihydroxy-4-methyltetrahydrofuran-2-yl)methoxy) (naphthalen- 1 - ylamino)phosphorylamino)propanoate

[0069] (25,2'5)-Dibenzyl-((((2R,35,4R,5R)-5-(2-amino-6-methoxy-9H-p urin-9-yl)-3,4- dihydroxy-4-methyltetrahydrofuran-2-yl)methoxy) phosphoryl)-(2,2')-bis-amino- diethanoate

[0070] (25,2'5)-Dineopentyl-((((2R,35,4R,5R)-5-(2-amino-6-methoxy-9 H-purin-9-yl)-3,4- dihydroxy-4-methyltetrahydrofuran-2-yl)methoxy) phosphoryl)-(2,2')-bis-amino- dipropanoate ethanoate

[0071] (2R,2'R)-Neopentyl 2,2'-((((2R,3R,4R,5R)-5-(2-amino-6-methoxy-9H-purin-9-yl)-3, 4- dihydroxy-4-methyltetrahydrofuran-2- yl)methoxy)phosphoryl)bis(azanediyl)dipropanoate [0072] (2S,2'S)-Benzyl 2,2'-((((2R,3R,4R,5R)-5-(2-amino-6-methoxy-9H-purin-9-yl)-3, 4- dihydroxy-4-methyltetrahydrofuran-2- yl)methoxy)phosphoryl)bis(azanediyl)bis(4-methylpentanoate)

[0073] (25,2'5)-Dineopentyl-((((2R,35,4R,5R)-5-(2-amino-6-methoxy-9 H-purin-9-yl)-3,4- dihydroxy-4-methyltetrahydrofuran-2-yl)methoxy) phosphoryl)-(2,2')-bis-amino- 4-methylthiobutanoate

[0074] (2S,2'S)-Benzyl 2,2'-((((2R,3R,4R,5R)-5-(2-amino-6-methoxy-9H-purin-9-yl)-3, 4- dihydroxy-4-methyltetrahydrofuran-2- yl)methoxy)phosphoryl)bis(azanediyl)bis(3methyl butanoate)

[0075] (2S,2'S)-Dicyclohexyl 2,2'-((((2R,3R,4R,5R)-5-(2-amino-6-methoxy-9H-purin-9-yl)- 3,4-dihydroxy-4-methyltetrahydrofuran-2-yl)methoxy)phosphory l)

bis (azanediyl)bis (3methylbutanoate)

[0076] (2S,2'S)-Neopentyl 2,2'-((((2R,3R,4R,5R)-5-(2-amino-6-methoxy-9H-purin-9-yl)-3, 4- dihydroxy-4-methyltetrahydrofuran-2- yl)methoxy)phosphoryl)bis(azanediyl)bis(2-phenylacetate)

[0077] (2S,2'S)-Dicyclohexyl 2,2'-((((2R,3R,4R,5R)-5-(2-amino-6-methoxy-9H-purin-9-yl)- 3,4-dihydroxy-4-methyltetrahydrofuran-2- yl)methoxy)phosphoryl)bis(azanediyl)bis(2-phenylacetate)

[0078] (25,2'5)-Dibenzyl-((((2R,35,4R,5R)-5-(2-amino-6-methoxy-9H-p urin-9-yl)-3,4- dihydroxy-4-methyltetrahydrofuran-2-yl)methoxy) phosphoryl)-bis-pyrrolidine-2- methanoate

[0079] ((2R,3R,4R,5R)-5-(2-Amino-6-methoxy-9H-purin-9-yl)-3,4-dihyd roxy-4- methyltetrahydrofuran-2-yl)methyl di-N-butylphosphinate

[0080] ((2R,3R,4R,5R)-5-(2-Amino-6-methoxy-9H-purin-9-yl)-3,4-dihyd roxy-4- methyltetrahydrofuran-2-yl)methyl dimorpholinophosphinate

[0081] (2S,2'S)-2,4-Difluorobenzyl 2,2'-((((2R,3R,4R,5R)-5-(2-amino-6-methoxy-9H-purin- 9-yl)-3,4-dihydroxy-4-methyltetrahydrofuran-2-yl)methoxy) phosphoryl) bis(azanediyl)dipropanoate [0082] (2S,2'S)-Dicyclohexyl 2,2'-((((2R,3R,4R,5R)-5-(2-amino-6-ethoxy-9H-purin-9-yl)- 3,4-dihydroxy-4-methyltetrahydrofuran-2- yl)methoxy)phosphoryl)bis(azanediyl)dipropanoate

[0083] (2S,2'S)-Benzyl 2,2'-((((2R,3R,4R,5R)-5-(2-amino-6-ethoxy-9H-purin-9-yl)-3,4 - dihydroxy-4-methyltetrahydrofuran-2- yl)methoxy)phosphoryl)bis(azanediyl)dipropanoate

[0084] (2S,2'S)-Neopentyl 2,2'-((((2R,3R,4R,5R)-5-(2-amino-6-ethoxy-9H-purin-9-yl)-3,4 - dihydroxy-4-methyltetrahydrofuran-2- yl)methoxy)phosphoryl)bis(azanediyl)dipropanoate

[0085] (2S)-Cyclohexyl 2-((((2R,3R,4R,5R)-5-(2-amino-6-methoxy-9H-purin-9-yl)-3,4- dihydroxy-4-methyltetrahydrofuran-2-yl)methoxy)((S)- l-(cyclopentyloxy)- l- oxopropan-2-ylamino)phosphorylamino)propanoate

[0086] (2S)-Neopentyl 2-((((2R,3R,4R,5R)-5-(2-amino-6-methoxy-9H-purin-9-yl)-3,4- dihydroxy-4-methyltetrahydrofuran-2- yl)methoxy)(pentylamino)phosphorylamino)propanoate

[0087] (2S)-Benzyl 2-((((2R,3R,4R,5R)-5-(2-amino-6-methoxy-9H-purin-9-yl)-3,4- dihydroxy-4-methyltetrahydrofuran-2- yl)methoxy)(morpholino)phosphorylamino)propanoate

[0088] (2S)-Neopentyl 2-((((2R,3R,4R,5R)-5-(2-amino-6-methoxy-9H-purin-9-yl)-3,4- dihydroxy-4-methyltetrahydrofuran-2- yl)methoxy)(cyclopropylamino)phosphorylamino)propanoate

[0089] (2S,2'S)-Neopentyl 2,2'-((((2R,3R,4R,5R)-5-(2-amino-6-methoxy-9H-purin-9-yl)-3, 4- dihydroxy-4-methyltetrahydrofuran-2- yl)methoxy)phosphoryl)bis(azanediyl)bis(4-methylpentanoate)

[0090] (2S,2'S)-Dicyclohexyl 2,2'-((((2R,3R,4R,5R)-5-(2-amino-6-methoxy-9H-purin-9-yl)- 3,4-dihydroxy-4-methyltetrahydrofuran-2- yl)methoxy)phosphoryl)bis(azanediyl)bis(4-methylpentanoate) [0091] (2S,2'S)-Dibenzyl 2,2'-((((2R,3R,4R,5R)-5- 2-amino-6-methoxy-9H-purin-9-yl)-3,4- dihydroxy-4-methyltetrahydrofuran-2- yl)methoxy)phosphoryl)bis(azanediyl)bis 4-methylthiobutanoate)

[0092] (2S,2'S)-Dicyclohexyl 2,2'-((((2R,3R,4R,5R -amino-6-methoxy-9H-purin-9-yl)

3,4-dihydroxy-4-methyltetrahydrofuran-2

yl)methoxy)phosphoryl)bis(azanediyl)bis 4-methylthiobutanoate)

[0093] (2S,2'S)-Benzyl 2,2'-((((2R,3R,4R,5R)-5- 2-amino-6-methoxy-9H-purin-9-yl)-3,4- dihydroxy-4-methyltetrahydrofuran-2- yl)methoxy)phosphoryl)bis(azanediyl)bis 3 -phenylpropanoate)

[0094] (2S,2'S)-Neopentyl 2,2'-((((2R,3R,4R,5R)-5- 2-amino-6-methoxy-9H-purin-9-yl)-3,4- dihydroxy-4-methyltetrahydrofuran-2- yl)methoxy)phosphoryl)bis(azanediyl)bis 3 -phenylpropanoate)

[0095] (2S,2'S)-Dicyclohexyl 2,2'-((((2R,3R,4R,5R -amino-6-methoxy-9H-purin-9-yl)

3,4-dihydroxy-4-methyltetrahydrofuran-2

yl)methoxy)phosphoryl)bis(azanediyl)bis 3 -phenylpropanoate)

[0096] (2S,2'S)-Dicyclohexyl 2,2'-((((2R,3R,4R,5R -amino-6-methoxy-9H-purin-9-yl)

3,4-dihydroxy-4-methyltetrahydrofuran-2

yl)methoxy)phosphoryl)bis(azanediyl)bis 3-(4-tert-butoxyphenyl)propanoate)

[0097] (2S,2'S)-Neopentyl 2,2'-((((2R,3R,4R,5R)-5- 2-amino-6-methoxy-9H-purin-9-yl)-3,4- dihydroxy-4-methyltetrahydrofuran-2- yl)methoxy)phosphoryl)bis(azanediyl)bis 3 -methylbutanoate)

[0098] (2S,2'S,3R,3'R)-Benzyl 2,2'-((((2R,3R,4R,5R -amino-6-methoxy-9H-purin-9-yl)

3,4-dihydroxy-4-methyltetrahydrofuran-2

yl)methoxy)phosphoryl)bis(azanediyl)bis 3 -methylpentano ate)

[0099] (2S,2'S,3R,3'R)-Dimethyl 2,2'-((((2R,3R,4R,5R)-5-(2-amino-6-methoxy-9H-purin-9- yl)-3,4-dihydroxy-4-methyltetrahydrofuran-2- yl)methoxy)phosphoryl)bis(azanediyl)bis(3-methylpentanoate) [00100] (2S,2'S,3R,3'R)-Neopentyl 2,2'-((((2R,3R,4R,5R)-5-(2-amino-6-methoxy-9H- purin-9-yl)-3,4-dihydroxy-4-methyltetrahydrofuran-2- yl)methoxy)phosphoryl)bis(azanediyl)bis(3-methylpentanoate)

[00101] (2S,2'S,3R,3'R)-Dicyclohexyl 2,2'-((((2R,3R,4R,5R)-5-(2-amino-6-methoxy-9H- purin-9-yl)-3,4-dihydroxy-4-methyltetrahydrofuran-2- yl)methoxy)phosphoryl)bis(azanediyl)bis(3-methylpentanoate)

[00102] Neopentyl l,r-((((2R,3R,4R,5R)-5-(2-amino-6-methoxy-9H-purin-9-yl)-3,4 - dihydroxy-4-methyltetrahydrofuran-2-yl)methoxy)phosphoryl)di pyrrolidine-2- carboxylate

[00103] (25,2'5)-l,4-Dibenzyl 2,2'-((((2R,3R,4R,5R)-5-(2-amino-6-methoxy-9H-purin-9- yl)-3,4-dihydroxy-4-methyltetrahydrofuran-2- yl)methoxy)phosphoryl)bis(azanediyl)disuccinate

[00104] (2S,2'S)-Tetramethyl 2,2'-((((2R,3R,4R,5R)-5-(2-amino-6-methoxy-9H-purin-9- yl)-3,4-dihydroxy-4-methyltetrahydrofuran-2- yl)methoxy)phosphoryl)bis(azanediyl)disuccinate

[00105] Benzyl 3,3'-((((2R,3R,4R,5R)-5-(2-amino-6-methoxy-9H-purin-9-yl)-3, 4- dihydroxy-4-methyltetrahydrofuran-2- yl)methoxy)phosphoryl)bis(azanediyl)dipropanoate

[00106] (2S,2'S)-Neopentyl 2,2'-((((2R,3R,4R,5R)-5-(2-amino-6-methoxy-9H-purin-9-yl)- 3,4-dihydroxy-4-methyltetrahydrofuran-2- yl)methoxy)phosphoryl)bis(azanediyl)bis(3-methylthiopropanoa te)

[00107] (2S,2'S)-Cyclohexyl 2,2'-((((2R,3R,4R,5R)-5-(2-amino-6-methoxy-9H-purin-9- yl)-3,4-dihydroxy-4-methyltetrahydrofuran-2- yl)methoxy)phosphoryl)bis(azanediyl)bis(3-methylthiopropanoa te)

[00108] In accordance with the present invention there are provided the following additional compounds:

[00109] Accordingly, compounds in accordance with the present invention include:

[00110] (2S,2'S)-Neopentyl 2,2'-((((2R,3R,4R,5R)-5-(2-amino-6-ethoxy-9H-purin-9-yl)-4- fluoro-3-hydroxy-4-methyltetrahydrofuran-2- yl)methoxy)phosphoryl)bis(azanediyl)dipropanoate; and

[00111] (2R,2'R)-Neopentyl 2,2'-((((2R,3R,4R,5R)-5-(2-amino-6-ethoxy-9H-purin-9-yl)-4- fluoro-3-hydroxy-4-methyltetrahydrofuran-2- yl)methoxy)phosphoryl)bis(azanediyl)dipropanoate and the pharmaceutically acceptable salts thereof.

[00112] Once again, in each case with regard to the foregoing specific compounds, it is contemplated that the invention will include phosphorus diastereomers thereof.

[00113] Compounds according to the present invention have surprisingly been found to have enhanced anti-viral activity and this can be used in methods of treating Flaviviridae viral infections. In particular, compounds according to the present invention have been found to have enhanced potency with respect to hepatitis C virus. [00114] Definitions

[00115] As used herein, the term "alkyl" refers to a straight or branched saturated

monovalent cyclic or acyclic hydrocarbon radical, having the number of carbon atoms as indicated (or where not indicated, an acyclic alkyl group preferably has 1-20, more preferably 1-6, more preferably 1-4 carbon atoms and a cyclic alkyl group preferably has 3-20, preferably 3-10, more preferably 3-7 carbon atoms), optionally substituted with one, two, three or more substituents independently selected from the group set out above. By way of non- limiting examples, suitable alkyl groups include methyl, ethyl, propyl, butyl, pentyl, hexyl, octyl, nonyl, isopropyl, 2-butyl, cyclopropyl, cyclohexyl, cyclopentyl and dodecyl. The term "C3-C ₈ cycloalkyl" refers to cyclic alkyl group comprising from about 3 to about 8 C atoms. The term "Cs-Cscycloalkyl-alkyl" refers to an acyclic alkyl group substituted by a cyclic alkyl group comprising from about 3 to about 8 C atoms.

[00116] As used herein, the term "alkenyl" refers to a straight or branched unsaturated monovalent acyclic or cyclic hydrocarbon radical having one or more C=C double bonds and having the number of carbon atoms as indicated (or where not indicated, an acyclic alkenyl group preferably has 2-20, more preferably 2-6, more preferably 2-4 carbon atoms and a cyclic alkenyl group preferably has 4-20, more preferably 4-6 carbon atoms), optionally substituted with one, two, three or more substituents independently selected from the group set out above. By way of non- limiting examples, suitable alkenyl groups include vinyl, propenyl, butenyl, pentenyl and hexenyl.

[00117] As used herein, the term "alkynyl" refers to a straight or branched unsaturated monovalent acyclic or cyclic hydrocarbon radical having one or more triple C/C bonds and having the number of carbon atoms as indicated (or where not indicated, an acyclic alkynyl group preferably has 2-20, more preferably 2-6, more preferably 2-4 carbon atoms and a cyclic alkynyl group preferably has 7-20, more preferably 8-20 carbon atoms), optionally substituted with one, two, three or more substituents independently selected from the group set out above.

[00118] As use herein, the term "alkoxy" or the term "alkyloxy" refers to the group alkyl- 0-, where alkyl is as defined above and where the alkyl moiety may optionally be substituted by one, two, three or more substituents as set out above for alkyl. By way of non-limiting examples, suitable alkoxy groups include methoxy, ethoxy, n- propoxy, isopropoxy, n- butoxy, ie/t-butoxy, sec-butoxy, w-pentoxy, w-hexoxy and 1,2-dimethylbutoxy. The term "cycloalkyloxy" refers to the group cyclicalkyl - 0-, where cyclicalkyl is as defined above and where the cyclicalkyl moiety may be optionally substituted by one, two, three or more substituents as set out above for alkyl.

[00119] As used herein, the term "alkylthio" refers the group alkyl-S-, where alkyl is as defined above and where the alkyl moiety may optionally be substituted by one, two, three or more substituents as set out above for alkyl. By way of non-limiting examples, suitable alkylthio groups include methylthio, ethylthio, n- propylthio, isopropylthio, w-butylthio, iert-butylthio, sec-butylthio, w-pentylthio, w-hexoxy and 1,2-dimethylbutylthio.

[00120] As used herein, the term "aryloxy" refers to the group aryl-O-, where aryl is as defined below and where the aryl moiety may optionally be substituted by one, two, three or more substituents as set out above with respect to the group Ar.

[00121] As used herein, the term "alkoxyalkyl" refers to an alkyl group having an alkoxy substituent. Binding is through the alkyl group. The alkyl moiety and the alkoxy moiety are as defined herein with respect to the definitions of alkyl and alkoxy, respectively. The alkoxy and alkyl moieties may each be substituted by one, two, three or more substituents as set out above with regard to the definition of alkyl.

[00122] As used herein, the term "alkylthioalkyl" refers to an alkyl group having an

alkylthio substituent. Binding is through the alkyl group. The alkyl moiety and the alkylthio moiety are as defined herein with respect to the definitions of alkyl and alkylthio, respectively. The alkylthio and alkyl moieties may each be substituted by one, two, three or more substituents as set out above with regard to the definition of alkyl.

[00123] As used herein, the term "alkoxyaryl" refers to an aryl group having an alkoxy substituent. Binding is through the aryl group. The alkoxy moiety and the aryl moiety are as defined herein with respect to the definitions of alkoxy and aryl, respectively. The alkoxy and aryl moieties may each be substituted by one, two, three or more substituents, as defined herein with regard to the definitions of alkoxy and aryl, respectively.

[00124] As used herein, the term "cycloalkylaryl" refers to an aryl group having a cyclic alkyl substituent. Binding is through the aryl group. The cycloalkyl moiety and the aryl moiety are as defined herein with respect to the definitions of cycloalkyl and aryl, respectively.

[00125] As used herein, the term "aryl(C ₁ -C ₆ )alkyl-" refers to a CrC ₆ alkyl group substituted at any carbon by an aryl group. Binding is through the alkyl group. The aryl moiety and the alkyl moiety are as defined herein with respect to the definitions of aryl and alkyl. The aryl group may be substituted. By way of non- limiting examples, suitable aryl(C ₁ -C ₆ )alkyl- groups include benzyl, 1- phenylethyl, 3-phenylpropyl, 4-chlorobenzyl, 4-fluorobenzyl, 2,4-difluorobenzyl, and the like.

[00126] As used herein, the term "alkylcarboxy(C ₁ -C ₆ )alkyl-" refers to a C -C alkyl group substituted at any carbon by an alkylcarboxy [alkyl-C(=0)0-] group. The alkyl moiety is as defined hereinabove. By way of non-limiting examples, suitable alkylcarboxy(C ₁ -C ₆ )alkyl- groups include acetoxymethyl [CH ₃ C(=0)0-CH ₂ -], propanoyloxyethyl [CH CH ₂ C(=0)0-CH ₂ CH ₂ -], weopentoyloxypropyl [(CH ₃ ) ₃ CCH ₂ C(=0)0-CH ₂ CH ₂ CH ₂ -] and the like.

[00127] A cycloalkyl moiety and the aryl moiety may each be optionally substituted by one, two, three or more substituents as set out herein with regard to the definitions of alkyl and aryl, respectively.

[00128] As used herein the term "aryl" refers to a monovalent unsaturated aromatic

carbocyclic radical having one, two, three, four, five or six rings, preferably one, two or three rings, which may be fused or bicyclic. An aryl group may optionally be substituted by one, two, three or more substituents as set out above with respect to optional substituents that may be present on the group Ar. Preferred aryl groups are: an aromatic monocyclic ring containing 6 carbon atoms; an aromatic bicyclic or fused ring system containing 7, 8, 9 or 10 carbon atoms; or an aromatic tricyclic ring system containing 10, 11, 12, 13 or 14 carbon atoms. Non-limiting examples of aryl include phenyl and naphthyl. These compounds may include substituent groups, preferably those substituent groups independently selected from hydroxy (-OH), acyl (R'- C(=0)), acyloxy (R'-C(O)-O-), nitro (-N0 ₂ ), amino (-NH ₂ ), carboxyl (-COOH), cyano (-CN), CrCemonoalkylamino, Q-C 6dialkylamino, thiol, chloro, bromo, fluoro, iodo, SO ₃ H, -SH, -SR', wherein R' is independently selected from halo, Q-Cealkoxy^nd Q-Cealkyl.

[00129] As used herein, the term "heterocycloalkyl " refers to a saturated or partially

unsaturated heterocyclic ring system having one, two, three, four, five or six rings, preferably one, two or three rings, which may be fused or bicyclic, and having contained within the ring or rings at least one member selected from the group consisting of N, O and S. The prefix "C5-C ₂ o" or "C5-C used before heterocycloalkyl means, respectively, a five to twenty or a five to ten-membered ring system at least one of which members is selected from the group consisting of N, O and S. Preferred heterocycloalkyl systems are: a monocyclic ring system having five members of which at least one member is a N, O or S atom and which optionally contains one additional O atom or one, two or three additional N atoms; a monocyclic ring having six members of which one, two or three members are a N or O atom; a bicyclic ring system having nine members of which at least one member is a N, O or S atom and which optionally contains one, two or three additional N atoms; or a bicyclic ring system having ten members of which one, two or three members are a N atom. By way of non-limiting examples, suitable heterocycloalkyl groups include tetrahydrofuranyl, tetrahydropyranyl, pyrrolidinyl, morpholinyl, tetrahydrothiopyranyl, thiomorpholinyl, and piperidinyl

[00130] When a radical is drawn as a structure, e.g.,

[00131] "indanyl" refers to the fused bicyclic radical of structure, point of attachment of the radical to the rest of the molecule is on any available non-aromatic carbon atom.

[00132] Available carbon atoms and/or heteroatoms of the " heterocycloalkyl " ring

systems described above may be substituted on the ring with one or more heteroatoms. Where the ring(s) is substituted with one or more heteroatoms, heteroatom substituents are selected from oxygen, nitrogen, sulphur and halogen (F, CI, Br and I). Where the ring(s) is substituted with one or more heteroatoms, preferably there are 1, 2, 3 or 4 heteroatom substituents selected from the group consisting of oxygen, nitrogen and/or halogen. Preferred substituent groups are independently selected from hydroxy, acyl, acyloxy, nitro, amino, S0 ₃ H, SH, SR', wherein R' is independently selected from the same groups as R; carboxyl, cyano, (C ₁ -C ₆ )alkylamino, (C ₁ -C ₆ )dialkylamino, thiol, chloro, bromo, fluoro and iodo.

[00133] Furthermore, the compounds of this invention contain one or more chiral centers.

Accordingly, if desired, such compounds can be prepared or isolated as pure stereoisomers, i.e., as individual enantiomers or diastereomers, or as stereoisomer- enriched mixtures. All such stereoisomers (and enriched mixtures) are included within the scope of this invention. Pure stereoisomers (or enriched mixtures) may be prepared using, for example, optically active starting materials or stereoselective reagents well-known in the art. Alternatively, racemic mixtures of such compounds can be separated using, for example, chiral column chromatography, chiral resolving agents and the like.

[00134] The compounds of this invention may contain one or more asymmetric centers, depending upon the location and nature of the various substituents desired. Asymmetric carbon atoms or phosphorous atoms may be present in the (R) or (S) configuration or (R,S) configuration. In certain instances, asymmetry may also be present due to restricted rotation about a given bond, for example, the central bond adjoining two substituted aromatic rings of the specified compounds. Substituents on a ring may also be present in either cis or trans form, and a substituent on a double bond may be present in either Z or E form. It is intended that all such configurations (including enantiomers and diastereomers) are included within the scope of the present invention. Preferred compounds are those with the absolute configuration of the compound of this invention which produces the more desirable biological activity. Separated, pure or partially purified isomers or racemic mixtures of the compounds of this invention are also included within the scope of the present invention. Such compounds can be prepared or isolated as pure stereoisomers, i.e., as individual enantiomers or diastereomers, or as stereoisomer-enriched mixtures. All such stereoisomers (and enriched mixtures) are included within the scope of this invention. Pure stereoisomers (or enriched mixtures) may be prepared using, for example, optically active starting materials or stereoselective reagents well-known in the art. Alternatively, racemic mixtures of such compounds can be separated using, for example, chiral column chromatography, chiral resolving agents and the like, also well-known in the art and exemplified the experimental examples below.

[00135] The term "pharmaceutically acceptable salt" refers to pharmaceutically acceptable salts of a compound, which salts are derived from a variety of organic and inorganic counter ions well known in the art and include, by way of example only, sodium, potassium, calcium, magnesium, ammonium, tetraalkylammonium, and the like; and when the molecule contains a basic functionality, salts of organic or inorganic acids, such as hydrochloride, hydrobromide, tartrate, mesylate, acetate, maleate, oxalate and the like.

[00136] The term "pharmaceutically acceptable partial salts" in included in the term

"pharmaceutically acceptable salts" and refers to compounds having a substituent capable of having more than one group form a salt but less than the maximum amount of such groups actually form a salt. For example, a diphospho group can form a plurality of salts and, if only partially ionized, the resulting group is sometimes referred to herein as a partial salt. It is understood that in all substituted groups defined above, polymers arrived at by defining substituents with further substituents to themselves (e.g., substituted aryl having a substituted aryl group as a substituent which is itself substituted with a substituted aryl group, etc.) are not intended for inclusion herein. In such cases, the maximum number of such substituents is three. That is to say that each of the above definitions is constrained by a limitation that, for example, substituted aryl groups are limited to -substituted aryl- (substituted aryl)-substituted aryl. Similarly, it is understood that the above definitions are not intended to include impermissible substitution patterns (e.g., methyl substituted with 5 fluoro groups or a hydroxyl group pendent to a carbon atom of an ethenylic or acetylenic unsaturation). Such impermissible substitution patterns are well known to the skilled artisan. As also indicated above, the present compounds include other known forms of the compounds including solvates, hydrates and polymorphs. General Synthetic Methods

[00137] The compounds of this invention can be prepared from readily available starting materials using the following general methods and procedures. It will be appreciated that where typical or preferred process conditions (i.e., reaction temperatures, times, mole ratios of reactants, solvents, pressures, etc.) are given, other process conditions can also be used unless otherwise stated. Optimum reaction conditions may vary with the particular reactants or solvent used, but such conditions can be determined by one skilled in the art by routine optimization procedures.

[00138] Additionally, as will be apparent to those skilled in the art, conventional

protecting groups may be necessary to prevent certain functional groups from undergoing undesired reactions. Suitable protecting groups for various functional groups as well as suitable conditions for protecting and deprotecting particular functional groups are well known in the art. For example, numerous protecting groups are described in T. W. Greene and G. M. Wuts, Protecting Groups in Organic Synthesis, Third Edition, Wiley, New York, 1999, and references cited therein.

[00139] The starting materials for the following reactions are generally known compounds or can be prepared by known procedures or obvious modifications thereof. For example, many of the starting materials are available from commercial suppliers such as Aldrich Chemical Co. (Milwaukee, Wis., USA), Bachem (Torrance, Calif., USA), Emka-Chemce or Sigma (St. Louis, Mo., USA). Others may be prepared by procedures, or obvious modifications thereof, described in standard reference texts such as Fieser and Fieser's Reagents for Organic Synthesis, Volumes 1-15 (John Wiley and Sons, 1991), Rodd's Chemistry of Carbon Compounds, Volumes 1-5 and Supplementals (Elsevier Science Publishers, 1989), Organic Reactions, Volumes 1-40 (John Wiley and Sons, 1991), March's Advanced Organic Chemistry, (John Wiley and Sons, 4 ^th Edition), and Larock's Comprehensive Organic Transformations (VCH Publishers Inc., 1989). Specifically, the compounds of this invention may be prepared by various methods known in the art of organic chemistry in general and nucleoside and nucleotide analogue synthesis in particular. General reviews of the preparation of nucleoside and nucleotide analogues include 1) Michelson A. M., "The Chemistry of Nucleosides and Nucleotides," Academic Press, New York, 1963; 2) Goodman L., "Basic Principles in Nucleic Acid Chemistry," Academic Press, New York, 1974, vol. 1, Ch. 2; and 3) "Synthetic Procedures in Nucleic Acid Chemistry," Eds. Zorbach W. & Tipson R., Wiley, New York, 1973, vol. 1 & 2.

Strategies available for synthesis of compounds of this invention are illustrated in the synthetic schemes below. For example, Reaction Scheme 1 illustrates a general method of preparation of symmetrical phosphorodiamidates.

[00141] Reaction Scheme 1

(I)

[00142] In this scheme, the nucleoside (II), prepared as described in International

Application PCT/US 10/20632 , is dissolved in a neutral aprotic solvent such as THF or triethyl phosphate or similar solvent and cooled to below ambient temperature, preferably to 0-5°C. Phosphorus oxychloride (phosphoryl chloride) of high quality is added to the solution with careful protection from moisture. The reaction is stirred for 1-48 h at temperatures from -20 °C to 20 °C and optimally for 24 h at 5 °C forming compound (III). The solution is diluted with an aprotic solvent, preferably DCM, and a primary or secondary amine, such as the HC1 or tosylate salt of an amino acid ester, is added at reduced temperatures -78 °C to 5 °C and preferably at 0 °C. This is followed by the addition of a non-nucleophilic base such as a tertiary amine such as triethylamine, or preferably diisopropylethylamine. The solution is stirred for 1 h to 10 days at reduced temperatures and preferably at 5 °C for 5 days, forming phosphorodiamidate (I).

[00143] Alternatively the nucleoside (II) can be dissolved in a neutral aprotic solvent such as THF or triethyl phosphate or similar solvent, but preferably THF, and a non- nucleophilic base such as a tertiary amine or diisopropylethylamine or preferably triethylamine is added and stirred for a period of 5 min to 1 h, preferably 30 min. The solution is then cooled to -100 °C to rt, or preferably -78 °C, and phosphorus oxychloride (phosphoryl chloride) of high quality is added slowly to the solution with careful protection from moisture. The reaction is stirred for 5 min to 2 h at temperatures from -100 °C to 0°C and optimally for 30 min at -78 °C, then warmed to ambient temperature for 5 min to 2 h, preferably 30 min forming compound (III). The solution is further diluted with an aprotic solvent, preferably DCM, and a primary or secondary amine, such as the HC1 or tosylate salt of an amino acid ester, is added followed by the addition of a non-nucleophilic base such as a tertiary amine preferably triethylamine at reduced temperatures -78 °C to 5 °C and preferably at -78 °C. The solution is warmed to ambient temperature and stirred for 1 h to 48 h, preferably 24 h, forming phosphorodiamidate (I). The reaction can be worked up using standard methods familiar to one skilled in the art, for example extraction with a sodium chloride solution, drying with sodium sulfate and purification by silica gel chromatography. Changes to this procedure including solvent switches and optimization of the temperature, familiar to those skilled in the art of organic chemistry would be anticipated. Reaction Scheme 2 illustrates a general method of preparation of asymmetrical phosphoramidates.

[00145] Reaction Scheme 2

HNR ¹ (R ² ) (V) D I EA or TEA

[00146] In this scheme a general method for synthesizing asymmetrical phosphorodiamidates is described. The nucleoside (II) can be dissolved in a neutral aprotic solvent such as THF or triethyl phosphate or similar solvent, but preferably THF, and a non-nucleophilic base such as a tertiary amine or diisopropylethylamine or preferably triethylamine is added and stirred for a period of 5 min to 1 h, preferably 30 min. The solution is then cooled to -100 °C to rt, or preferably -78 °C, and phosphorus oxychloride (phosphoryl chloride) of high quality is added slowly to the solution with careful protection from moisture. The reaction is stirred for 5 min to 2 h at temperatures ranging from -100 °C to 0 °C and optimally for 30 min at -78 °C, then warmed to ambient temperature for 5 min to 2 h, preferably 30 min forming compound (III). The solution is further diluted with an aprotic solvent, preferably DCM, and one equivalent of a primary or secondary amine of formula (V), such as the HC1 or tosylate salt of an amino acid ester, is added followed by the addition of a non-nucleophilic base such as a tertiary amine preferably triethylamine at reduced temperatures -78 °C to 5 °C and preferably at -78°C. The solution is warmed to ambient temperature and stirred for 1 h to 48 h, preferably 24 h, forming phosphorodiamidate (IV). A phosphorus NMR can be acquired to determine the status of the reaction. The solution is then cooled to -100 °C to rt, or preferably -78 °C. One to 10 equivalents, preferably 5 equivalents, of a primary or secondary amine of formula (VI), such as the HCl or tosylate salt of an amino acid ester, can be added. This is followed by the addition of an excess of a non-nucleophilic base such as a tertiary amine, preferably triethylamine (5-10 equivalents) at reduced temperatures -78 °C to 5 °C and preferably at -78 °C. The solution is warmed to ambient temperature and stirred for 1 h to 48 h, preferably 24 h, forming phosphorodiamidate (I). The reaction is worked up using standard methods familiar to one skilled in the art, for example extraction with a sodium chloride solution, drying with sodium sulfate and purification by silica gel chromatography. Changes to this procedure including solvent switches and optimization of the temperature, familiar to those skilled in the art of organic chemistry would be anticipated. Reaction Scheme 3 illustrates an alternative method for synthesizing asymmetrical phosphorodiamidates.

[00148] Reaction Scheme 3

(IV)

HNR ³ (R ⁴ ) (VI)

D I EA or TEA

(I)

[00149] This scheme describes a second general method for synthesizing asymmetrical phosphorodiamidates. The nucleoside (II) can be dissolved in a neutral aprotic solvent such as THF or triethyl phosphate or similar solvent, but preferably THF. A non-nucleophilic base such as a tertiary amine or diisopropylethylamine or preferably triethylamine is added in excess, preferably 1.2 equivalents. The solution can be stirred at ambient temperature and 1 to 3 equivalents of an amino acid ester dichloridate (VII), can be added. Compounds of the general structure (VII) can be synthesized using techniques familiar to one skilled in the art. A phosphorus NMR can be acquired to determine the status of the formation of the compound of formula (IV) The solution is then cooled to -100 °C to rt, or preferably -78 °C, and 1 to 10 equivalents, preferably 5 equivalents, of a primary or secondary amine of formula (VI) are added. The solution is warmed to ambient temperature and stirred for 1 h to 48 h, preferably 24 h, forming phosphorodiamidate (I). The reaction is worked up using standard methods familiar to one skilled in the art, for example extraction with a sodium chloride solution, drying with sodium sulfate and purification by silica gel chromatography. Changes to this procedure including solvent switches and optimization of the temperature, familiar to those skilled in the art of organic chemistry would be anticipated.

[00150] The general schemes above are preferably carried out in the presence of a suitable solvent. Suitable solvents include hydrocarbon solvents such as benzene and toluene; ether type solvents such as diethyl ether, tetrahydrofuran, diphenyl ether, anisole and dimethoxybenzene; halogenated hydrocarbon solvents such as methylene chloride, chloroform and chlorobenzene; ketone type solvents such as acetone, methyl ethyl ketone and methyl isobutyl ketone; alcohol type solvents such as methanol, ethanol, propanol, isopropanol, w-butyl alcohol and iert-butyl alcohol; nitrile type solvents such as acetonitiile, propionitrile and benzonitrile; ester type solvents such as ethyl acetate and butyl acetate; carbonate type solvents such as ethylene carbonate and propylene carbonate; and the like. These may be used singly or two or more of them may be used in admixture. Preferably an inert solvent is used in the process of the present invention. The term "inert solvent" means a solvent inert under the conditions of the reaction being described in conjunction therewith including, for example, benzene, toluene, acetonitrile, tetrahydrofuran, dimethylformamide, chloroform, methylene chloride (or dichloromethane), diethyl ether, ethyl acetate, acetone, methylethyl ketone, methanol, ethanol, propanol, isopropanol, ie/t-butanol, dioxane, pyridine, and the like.

[00151] Dosages and routes of administration.

[00152] In general, the compounds of this invention will be administered in a

therapeutically effective amount by any of the accepted modes of administration for agents that serve similar utilities. The effective amount will be that amount of the compound of this invention that would be understood by one skilled in the art to provide therapeutic benefits, i.e., the active ingredient, and will thus depend upon numerous factors such as the severity of the disease to be treated, the age and relative health of the subject, the potency of the compound used, the route and form of administration, and other factors. The drug can be administered more than once a day, and in the preferred mode the drug is administered once or twice a day. As indicated above, all of the factors to be considered in determining the effective amount will be well within the skill of the attending clinician or other health care professional..

[00153] For example, therapeutically effective amounts of compounds of Formula I may range from approximately 0.05 to 50 mg per kilogram body weight of the recipient per day; preferably about 0.1-25 mg/kg/day, more preferably from about 0.5 to 10 mg/kg/day. Thus, for administration to a 70 kg person, the dosage range would most preferably be about 35-700 mg per day. In general, compounds of this invention will be administered as pharmaceutical compositions by any one of the following routes: oral, systemic (e.g., transdermal, intranasal or by suppository), or parenteral (e.g., intramuscular, intravenous or subcutaneous) administration. The preferred manner of administration is oral using a convenient daily dosage regimen that can be adjusted according to the degree of affliction. Compositions can take the form of tablets, pills, capsules, semisolids, powders, sustained release formulations, solutions, suspensions, elixirs, aerosols, or any other appropriate compositions. Another preferred manner for administering compounds of this invention is inhalation. This is an effective method for delivering a therapeutic agent directly to the respiratory tract (see U.S. Pat. No. 5,607,915, said patent incorporated herein by reference).

[00154] The choice of formulation depends on various factors such as the mode of drug administration and bioavailability of the drug substance. For delivery via inhalation the compound can be formulated as liquid solution, suspensions, aerosol propellants or dry powder and loaded into a suitable dispenser for administration. There are several types of pharmaceutical inhalation devices- nebulizer inhalers, metered dose inhalers (MDI) and dry powder inhalers (DPI). Nebulizer devices produce a stream of high velocity air that causes the therapeutic agents (which are formulated in a liquid form) to spray as a mist that is carried into the patient's respiratory tract. MDI's typically are formulation packaged with a compressed gas. Upon actuation, the device discharges a measured amount of therapeutic agent by compressed gas, thus affording a reliable method of administering a set amount of agent. DPI dispenses therapeutic agents in the form of a free flowing powder that can be dispersed in the patient's inspiratory air- stream during breathing by the device. In order to achieve a free flowing powder, the therapeutic agent is formulated with an excipient such as lactose. A measured amount of the therapeutic agent is stored in a capsule form and is dispensed with each actuation.

[00155] Recently, pharmaceutical formulations have been developed especially for drugs that show poor bioavailability based upon the principle that bioavailability can be increased by increasing the surface area i.e., decreasing particle size. For example, U.S. Pat. No. 4,107,288 describes a pharmaceutical formulation having particles in the size range from 10 to 1,000 nm in which the active material is supported on a crosslinked matrix of macromolecules. U.S. Pat. No. 5,145,684 describes the production of a pharmaceutical formulation in which the drug substance is pulverized to nanoparticles (average particle size of 400 nm) in the presence of a surface modifier and then dispersed in a liquid medium to give a pharmaceutical formulation that exhibits remarkably high bioavailability. These patents are incorporated herein by reference.

[00156] As indicated above, the compositions in accordance with the invention generally comprise a compound of formulas (I- VI) in combination with at least one pharmaceutically acceptable carrier, excipient or diluent. Some examples of acceptable excipients are those that are non-toxic, will aid administration, and do not adversely affect the therapeutic benefit of the compound of the invention. Such excipient may be any solid, liquid, semi-solid or, in the case of an aerosol composition, gaseous excipient that is generally available to one of skill in the art.

[00157] Solid pharmaceutical excipients useful in the invention may include starch,

cellulose, talc, glucose, lactose, sucrose, gelatin, malt, rice, flour, chalk, silica gel, magnesium stearate, sodium stearate, glycerol monostearate, sodium chloride, dried skim milk and the like. Liquid and semisolid excipients may be selected from glycerol, propylene glycol, water, ethanol and various oils, including those of petroleum, animal, vegetable or synthetic origin, e.g., peanut oil, soybean oil, mineral oil, sesame oil, etc. Preferred liquid carriers, particularly for injectable solutions, include water, saline, aqueous dextrose, and glycols. Compressed gases may be used to disperse a compound of this invention in aerosol form. Inert gases suitable for this purpose are nitrogen, carbon dioxide, etc. Other suitable pharmaceutical excipients and their formulations are described in Remington's Pharmaceutical Sciences, edited by E. W. Martin (Mack Publishing Company, 18th ed., 1990). The amount of the compound in a formulation can vary within the full range employed by those skilled in the art. For example, the formulation will contain, on a weight percent (wt %) basis, from about 0.01-99.99 wt % wherein the compound is a compound of formula I based on the total formulation, with the balance being one or more suitable pharmaceutical excipients. Preferably, the compound is present at a level of about 1-80 wt %.

Pharmaceutical formulations containing a compound in accordance with the invention are described further below.

[00158] Additionally, the present invention is directed to a pharmaceutical composition comprising a therapeutically effective amount of a compound of the present invention in combination with a therapeutically effective amount of another active agent against RNA-dependent RNA virus and, in particular, against HCV. Agents active against HCV include, but are not limited to, ribavirin, levovirin, viramidine, thymosin alpha- 1, an inhibitor of HCV NS3 serine protease, interferon-a, pegylated interferon-a (peginterferon-a), a combination of interferon-a and ribavirin, a combination of peginterferon-a and ribavirin, a combination of interferon-a and levovirin, and a combination of peginterferon-α and levovirin. Interferon-α includes, but is not limited to, recombinant interferon-a2a (such as Roferon interferon available from Hoffman-LaRoche, Nutley, N.J.), interferon- a2b (such as Intron-A interferon available from Schering Corp., Kenilworth, N.J., USA), a consensus interferon, and a purified interferon-α product. For a discussion of ribavirin and its activity against HCV, see J. O. Saunders and S. A. Raybuck, "Inosine Monophosphate Dehydrogenase: Consideration of Structure, Kinetics and Therapeutic Potential," Am. Rep. Med. Chem., 35:201-210 (2000).

[00159] Even further, the present invention is directed to a pharmaceutical composition comprising a therapeutically effective amount of a compound of the present invention in combination with a therapeutically effective amount of another agent active against hepatitis C virus. Such agents include those that inhibit HCV proteases, HCV polymerase, HCV helicase, HCV NS4B protein, HCV entry, HCV assembly, HCV egress, HCV NS5A protein, and inosine 5'-monophosphate dehydrogenase. Other agents include nucleoside analogs for the treatment of an HCV infection. Still other compounds include those disclosed in WO 2004/014313 and WO 2004/014852 and in the references cited therein. The patent applications WO 2004/014313 and WO 2004/014852 are hereby incorporated by references in their entirety. Specific antiviral agents include Omega IFN (BioMedicines Inc.), BILN-2061 (Boehringer Ingelheim), Summetrel (Endo Pharmaceuticals Holdings Inc.), Roferon A (F. Hoffman-La Roche), Pegasys (F. Hoffman-La Roche), Pegasys/Ribaravin (F. Hoffman-La Roche), CellCept (F. Hoffman-La Roche), Wellferon (GlaxoSmithKline), Albuferon-a (Human Genome Sciences Inc.), Levovirin (ICN Pharmaceuticals), IDN-6556 (Idun Pharmaceuticals), IP-501 (Indevus Pharmaceuticals), Actimmune (InterMune Inc.), Infergen A (InterMune Inc.), ISIS 14803 (ISIS Pharmaceuticals Inc.), JTK- 003 (Japan Tobacco Inc.), Pegasys/Ceplene (Maxim Pharmaceuticals), Ceplene (Maxim Pharmaceuticals), Civacir (Nabi Biopharmaceuticals Inc.), Intron A/Zadaxin (RegeneRx), Levovirin (Ribapharm Inc.), Viramidine(Ribapharm Inc.), Heptazyme (Ribozyme Pharmaceuticals), Intron A (Schering-Plough), PEG- Intron (Schering-Plough), Rebetron (Schering-Plough), Ribavirin (Schering- Plough), PEG-Intron/Ribavirin (Schering-Plough), Zadazim (SciClone), Rebif (Serono), IFN-p/EMZ701 (Transition Therapeutics), T67 (Tularik Inc.), VX-497 (Vertex Pharmaceuticals Inc.), VX-950/LY-5703 10 (Vertex Pharmaceuticals Inc.), Omniferon (Viragen Inc.), XTL-002 (XTL Biopharmaceuticals), SCH 503034 (Schering-Plough), isatoribine and its prodrugs ANA971 and ANA975 (Anadys), R1479 (Roche Biosciences), Valopicitabine (Idenix), NIM811 (Novartis), and Actilon (Coley Pharmaceuticals).

[00160] In some embodiments, the compositions and methods of the present invention contain a compound of formula I- VI and interferon. In some aspects, the interferon is selected from the group consisting of interferon alpha 2B, pegylated interferon alpha, consensus interferon, interferon alpha 2A, and lymphoblastiod interferon tau.

[00161] In other embodiments the compositions and methods of the present invention utilize a combination of a compound of formula I- VI and a compound having anti- HCV activity such as those selected from the group consisting of interleukin 2, interleukin 6, interleukin 12, a compound that enhances the development of a type 1 helper T cell response, interfering RNA, anti- sense RNA, Imiqimod, ribavirin, an inosine 5' monophospate dehydrogenase inhibitor, amantadine, and rimantadine.

[00162] Anti-hepatitis C Activity Assays

[00163] Compounds can exhibit anti-hepatitis C activity by inhibiting HCV polymerase, by inhibiting other enzymes needed in the replication cycle, or by other pathways. A number of assays have been published to assess these activities. A general method that assesses the gross increase of HCV virus in culture was disclosed in U.S. Pat. No.5,738, 985 to Miles et al. In vitro assays have been reported in Ferrari et al. J. of Vir., 73: 1649-1654, 1999; Ishii et al., Hepatology, 29:1227- 1235, 1999; Lohmann et al., J. Bio. Chem., 274: 10807-10815, 1999; and Yamashita et al., J. of Bio. Chem., 273:15479-15486, 1998.

[00164] WO 97/12033 relates to HCV polymerase assay that can be used to evaluate the activity of the of the compounds described herein. Another HCV polymerase assay has been reported by Bartholomeusz, et al., Hepatitis C Virus (HCV) RNA polymerase assay using cloned HCV non- structural proteins; Antiviral Therapy 1996: 1 (Supp 4) 18-24.

[00165] Screens that measure reductions in kinase activity from HCV drugs were

disclosed in U.S. Pat. No. 6,030,785, to Katze et al., U.S. Pat. No. 6,228,576, Delvecchio, and U.S. Pat. No.5,759,795 to Jubin et al. Screens that measure the protease inhibiting activity of proposed HCV drugs were disclosed in U.S. Pat. No. 5,861,267 to Su et al., U.S. Pat. No. 5,739,002 to De Francesco et al., and U.S. Pat. No. 5,597,691 to Houghton et al. All of said patents, and all patent and non-patent references disclosed in this application, are incorporated herein by reference. [00166] Examples

[00167] Embodiments of the present invention will now be described by way of example only with respect to the following examples.

[00168] General Procedures

[00169] All experiments involving water-sensitive compounds were conducted under scrupulously dry conditions. Anhydrous tetrahydrofuran (THF) and

dichloromethane were purchased from Aldrich and used directly. The sugar derivative (2 _l S',3R,4R,5R)-5-(benzoyloxymethyl)-3-methyltetrahydrofu ran-2,3,4- triyl tribenzoate or equivalently: 2,3,4,5-tetra-0-benzoyl-2-C-methyl- ?-D- ribofuranose was purchased from CarboSynth Limited, 8&9 Old Station Business Park, Compton, Berkshire, RG20 6NE, UK. The purine derivative 2-amino-6- chloropurine or equivalently, 6-chloro-9H-purin-2-amine, was purchased from Aldrich. 2'-C-Methylguanosine (2-amino-9-((3R,4R,5R)-3,4-dihydroxy-5- (hydroxymethyl)-3-methyltetrahydrofuran-2-yl)- lH-purin-6(9H)-one) is a commercial reagent and was purchased from CarboSynth Limited, 8&9 Old Station Business Park, Compton, Berkshire, RG20 6NE, UK. Salts of amino acid esters were prepared as described in PCT Int. Appl. (2010), WO 2010081082 A2 20100715. Column chromatography refers to flash column chromatography carried out using Merck silica gel 60 (40-60 μνη) as stationary phase. Proton, carbon, and phosphorus nuclear magnetic resonance ( 1 Η, 13 C, 31 P NMR) spectra were recorded on Bruker Avance spectrometers operating either at 500, 125, and 202 MHz or at 300, 75, and 121 MHz or a Varian Unity Inova instrument operating at 400, 100, and 161.9 MHz. The solvents used are indicated for each compound. All 13 C and 31 P spectra were recorded proton decoupled. Chemical shifts for 1 H and 13 C spectra are in parts per million downfield from

tetramethylsilane. Coupling constants are referred to as J values. Signal splitting patterns are described as singlet (s), doublet (d), triplet (t), quartet (q), broad signal (br), doublet of doublet (dd), doublet of triplet (dt), or multiplet (m).

Chemical shifts for 31 P spectra are in parts per million relative to an external phosphoric acid standard. Some of the proton and carbon NMR signals were split because of the presence of (phosphate) diastereoisomers in the samples. The mode of ionization for mass spectrometry was fast atom bombardment (FAB) using MNOBA (m-nitrobenzyl alcohol) as matrix for some compounds. Electrospray mass spectra were obtained using a Waters LCT time-of-flight mass spectrometer coupled to a Waters M600 HPLC pump. Samples were dissolved in methanol and injected into the solvent stream via a Rheodyne injector. The mobile phase used was methanol at a flow rate of 200 /zL/min. The electrospray source was operated at a temperature of 130 °C with a desolvation temperature of 300 °C, a capillary voltage of 3 kV, and cone voltage of 30 V. Data were collected in the continuum mode over the mass range 100-2000 amu and processed using Masslynx 4.1 software. Accurate mass measurements were facilitated by the introduction of a single lockmass compound of known elemental composition into the source concurrently with sample.

[00170] Analytical and semipreparative HPLC were conducted by Varian Prostar (LC

Workstation- Varian prostar 335 LC detector) using Varian Polaris C18-A (10 μΜ) as an analytic column and Varian Polaris CI 8- A (10 μΜ) as a semipreparative column; elution was performed using a mobile phase consisting of water/acetonitrile ingradient (System 1, 90/10 to 0/100 v/v in 30 min) or water/methanol (System 2, 90/10 to 0/100 v/v in 30 min).

[00171] Example 1.

[00172] (2R,3R,4R,5R)-2-(2-Amino-6-chloro-9H-purin-9-yl)-5-(benzoylo xymethyl)-3- methyltetrahydrofuran-3,4-diyl dibenzoate

[00173] To a pre-cooled (0 °C) solution of (2S,3R,4R,5R)-5-(benzoyloxymethyl)-3- methyltetrahydrofuran-2,3,4-triyl tribenzoate (or 2,3,4,5-tetra-0-benzoyl-2-C- methyl- ?-D-ribofuranose) (CarboSynth Ltd, 10.0 g, 17.22 mmol), 2-amino-6- chloropurine (Aldrich, 3.2 g, 18.87 mmol), and l,8-diazabicycl[5.4.0]undec-7-ene (DBU) (7.7 mL, 51 mmol) in anhydrous acetonitrile (200 mL), was added trimethysilyl triflate (12.5 mL, 68.8 mmol) dropwise. The reaction mixture was then heated at 65 °C for 4 to 6 h, allowed to cool down to room temperature, poured into saturated aqueous sodium bicarbonate (300 mL), and extracted with dichloromethane (3x150 mL). The combined organic phase was dried over sodium sulfate and evaporated under reduced pressure. The residue was precipitated from dichloromethane and methanol, filtrated, the solid was washed 2 times with methanol and dried to give the desired compound (8.5 g, 79 %) as a white solid (yields are from 65% (column) up to 90% (precipitation)).

[00174] The following are the NMR results analyzing the synthesized compounds:

1H NMR (500 MHz, DC\ d4) δ 8.13 (dd, J = 1.2, 8.3, 2H), 8.02 - 7.94 (m, 5H), 7.65 - 7.60 (m, 1H), 7.58 - 7.45 (m, 4H), 7.35 (q, J = 7.7, 4H), 6.65 (s, 1H), 6.40 (d, J = 6.7, 1H), 5.31 (s, 2H), 5.08 (dd, J = 4.2, 11.6, 1H), 4.79 (dd, J = 6.4, 11.6, 1H), 4.74 (td, J = 4.2, 6.5, 1H), 1.60 (s, 3H).

¹³ C NMR (125 MHz, CDCl ₃ -d4) δ 166.31(C=0), 165.38(C=0), 165.32(C=0), 159.13(C2), 152.87(C6), 152.06(C4), 141.42(C8), 133.77(C-H Bn), 133.69 (C-H Bn), 133.28(C-H Bn), 129.90(C-H Bn), 129.82(C-H Bn), 129.78 (C Bn), 129.70(C-H Bn), 129.41(C Bn), 128.78(C Bn), 128.61(C-H Bn), 128.50(C-H Bn), 128.41(C-H Bn), 126.00(C5), 88.84(C1 '), 85.68(C2'), 79.43(C4'), 76.07(C3'), 63.57(C5'), 17.77(2' -Me).

[00175] Example 2.

[00176] (2R,3R,4R,5R)-2-(2-Amino-6-methoxy-9H-purin-9-yl)-5-(hydroxy methyl)-3- methyltetrahydrofuran-3,4-diol

[00177] To a suspension of (2R,3R,4R,5R)-2-(2-amino-6-chloro-9H-purin-9-yl)-5-

(benzoyloxymethyl)-3-methyltetrahydrofuran-3,4-diyl dibenzoate (3.0 g, 4.78 mmol) in methanol (36 mL) at 0 °C was added NaOMe in methanol (5.4 mL, 25% w/w). The mixture was stirred at room temperature for 24 h then quenched by addition of amberlite (H ⁺ ). The mixture was then filtrated and methanol was removed under reduced pressure. The resultant residue was dissolved in water (50 mL) and extracted with hexane (50 mL). The organic layer was then extracted with water (50 mL), and the combined water fractions were concentrated under reduced pressure. The residue was purified by silica gel chromatography (CHCl ₃ /MeOH 85: 15) to give the pure compound (1.125 g, 76 %) as a white solid.

[00178] The following are the NMR, HPLC and CHN results analyzing the synthesized compound:

1HNMR (500 MHz, MeOD-J4) δ 8.26 (s, 1H), 5.99 (s, 1H), 4.24 (d, J = 9.1, 1H), 4.08 (s, 3H), 4.04 (ddd, J = 2.3, 5.7, 8.6, 2H), 3.87 (dd, J = 3.0, 12.4, 1H), 0.96 (s, 3H).

¹³ C NMR (125 MHz, MeOD-J4) δ 162.75(C6), 161.86(C2), 154.50(C4), 139.35(C8), 115.36(C5), 93.00(C1'), 84.15(C4'), 80.34(C2'), 73.57(C3'), 61.17(C5'), 54.25(6-OMe), 20.35(2' -Me).

HPLC : t _R = 9.00 min; column: Varian Pursuit XRs 5, C18, 150x4.6 mm The method is : Linear gradient H ₂ 0/ACN : 0% to 100% ACN in 30 min).

Elemental analysis: calculated for C ₁₂ H ₁₇ N ₅ 0 ₅ + 0.75 H ₂ 0 : G44.37,

H:5.74, N:21.56; Found: C:44.24, H:5.49, N:20.83.

[00179] General Methods for Preparation of Diamidates

[00180] Method A: Symmetrical phosphoramidates using triethyl phosphate and phosphoryl chloride

[00181] To a solution of the nucleoside (e.g., Example 2) (1 equiv) in anhydrous triethyl phosphate is added phosphoryl chloride (2 equiv) at 0 °C. The reaction mixture is stirred 24 h at 5 °C. Anhydrous dichloromethane is added to the reaction mixture followed by amino acid ester (5 equiv) and diisopropylethylamine (10 equiv) at 0 °C. After stirring at 5 °C for 5 days, water is added and the layers are separated. The aqueous phase is extracted with dichloromethane and the organic phase washed with brine. The combined organic layers are dried over anhyd sodium sulfate, filtered and evaporated to dryness. The resulting residue is purified by silica gel column chromatography using as eluent a gradient of methanol in dichloromethane. A subsequent repurification, if necessary, is accomplished either by preparative HPLC (gradient of methanol in water) or preparative TLC.

[00182] Method B: Symmetrical phosphoramidates using THF and phosphoryl chloride

[00183] To a suspension of (2R,3R,4R,5R)-2-(2-amino-6-methoxy-9H-purin-9-yl)-5- (hydroxymethyl)-3-methyltetrahydrofuran-3,4-diol (e.g., Example 2) (1 equiv) in anhyd tetrahydrofuran is added triethylamine (1.2 equiv). After stirring for 30 min at room temperature, phosphoryl chloride (1.2 equiv) is added dropwise at -78 °C. The reaction mixture is stirred 30 min at -78 °C then allowed to warm to room temperature over 30 min. Anhydrous dichloromethane is added, followed by amino acid ester (5 equiv) and triethylamine (10 equiv) at -78 °C. After stirring at room temperature for 20 h, water is added and the layers are separated. The aqueous phase is extracted with dichloromethane and the organic phase washed with brine. The combined organic layers are dried over anhyd sodium sulfate, filtered and evaporated to dryness. The resulting residue is purified by silica gel column chromatography using as eluent a gradient of methanol in dichloromethane. In some cases, a subsequent repurification is necessary either by preparative HPLC (gradient of methanol in water) or preparative TLC.

[00184] Method C: Asymmetrical phosphorodiamidates with phosphorus chloride

[00185] To a suspension of the nucleoside (e.g., Example 2) (1 equiv) in anhydrous tetrahydrofuran, is added triethylamine (1.2 equiv). After stirring for 30 min at room temperature, phosphoryl chloride (1.2 equiv) is added dropwise at -78 °C. The reaction mixture is stirred 30 min at -78 °C then allowed to warm to room temperature over 30 min. Anhydrous dichloromethane is added, followed by a first amino acid ester or amine (1 equiv) and triethylamine (2 or 1 equiv respectively) at -78 °C. The solution is warmed to room temperature and

31

monitored by P NMR. When NMR indicates completion of the reaction (no starting material, presence of mono-substituted product) a second amino acid ester or amine (5 equiv) is added followed by the addition of triethylamine (10 or 5 equiv respectively) at -78 °C. After stirring at room temperature for 20 h, water is added and the layers are separated. The aqueous phase is extracted with dichloromethane and the organic phase is washed with brine. The combined organic layers are dried over anhydrous sodium sulfate, filtered and evaporated to dryness. The resulting residue is purified by silica gel column chromatography using as eluent a gradient of methanol in chloroform (0-5%).

[00186] Method D: Asymmetrical phosphorodiamidates using amino acid ester phosphordichloridate

[00187] To a suspension of the nucleoside (e.g., Example 2) (1 equiv) in anhydrous tetrahydrofuran is added triethylamine (1.2 equiv). After stirring for 30 min at room temperature an amino acid ester phosphordichloridate (2 equiv) is added. After stirring at room temperature for 20 h, the solution is cooled to -78 °C and a primary amine is added (5 equiv) followed by triethylamine (5 equiv). The solution is warmed to room temperature and stirred for 20 h. Water is added and the layers are separated. The aqueous phase is extracted with dichloromethane and the organic phase washed with brine. The combined organic layers are dried over anhydrous sodium sulfate, filtered and evaporated to dryness. The resulting residue is purified by silica gel column chromatography using as eluent a gradient of methanol in chloroform (0-5%)

[00188] Example 3.

[00189] (25,2'5)-Dineopentyl-((((2R,35,4R,5R)-5-(2-amino-6-methoxy-9 H-purin-9-yl)-

3,4-dihydroxy-4-methyltetrahydrofuran-2-yl)methoxy) phosphoryl)(2,2')-bis- amino-dipropanoate

[00191] The phosphorodiamidate prodrug was synthesized using Method B. [00192] In the first step, a suspension of (2R,3R,4R,5R)-2-(2-amino-6-methoxy-9H-purin-

9-yl)-5-(hydroxymethyl)-3-methyltetrahydrofuran-3,4-diol (Example 2, 250 mg, 0.803 mmole) in anhyd tetrahydrofuran (4 mL) was allowed to react with triethylamine (135 μί, 0.964 mmole) and phosphoryl chloride (89 μί, 0.964 mmole).

[00193] In the second step, anhyd dichloromethane (4 mL), the tosylate salt of neopentyloxy-L- alanine (1.33 g, 4.02 mmol) and triethylamine (1.12 mL, 8.03 mmol) were added to the mixture from step 1.. After work-up and silica gel column chromatography, 151 mg of the prodrug was obtained in 28% yield as an off white solid.

[00194] The following are the NMR results of the synthesized compound:

[00195] 1H NMR (500 MHz, MeOD-J4) δ 7.98 (s, IH), 5.99 (s, IH), 4.41-4.36 (m, 2H),

4.29 (d, IH, J=9.0), 4.22-4.16 (m, IH), 4.07 (s, 3H), 4.04-3.91 (m, 2H), 3.87, 3.85, 3.84, 3.82 (2 AB system, /AB= 10.0 Hz, 2H), 3.75, 3.73, 3.70, 3.68 (2 AB system, /AB= 10.0, 2H), 1.40 and 1.36 (2d, 6H, J=7.1 Hz), 0.99 (s, 3H), 0.93 and 0.94 (2s, 18H).

[00196] ³¹ P NMR (202 MHz, MeOD-J4) δ 14.01.

[00197] HPLC i _R = 27.95 min (column: Varian Pursuit XRs 5, C ₁₈ , 150x4.6 mm; method:

linear gradient of MeOH (10% to 100%) in H ₂ 0 in 30 min).

[00198] Example 4.

[00199] (2S,2'S)-Dimethyl 2,2'-((((2R,3R,4R,5R)-5-(2-amino-6-methoxy-9H-purin-9-yl)- 3,4-dihydroxy-4-methyltetrahydrofuran-2- yl)methoxy)phosphoryl)bis(azanediyl)dipropanoate

[00200] [00201] The phosphorodiamidate prodrug was synthesized using Method B.

[00202] A suspension of 6-O-methyl-2'-C-methylguanosine (250 mg, 0.803 mmole) in anhydrous tetrahydrofuran (4 mL) was reacted with triethylamine (135 μί, 0.964 mmole) and phosphoryl chloride (89 μί, 0.964 mmole). Anhydrous dichloromethane (4 mL), the HCl salt of methyloxy-L-alanine (561.1 mg, 4.02 mmol) and triethylamine (1.12 mL, 8.03 mmol) were added to the previous mixture. After work-up, silica gel column chromatography and preparative HPLC, 19.8 mg of the prodrug was obtained in 4.4% yield as an off white solid.

[00203] The following are the NMR results of the synthesized compound:

[00204] IH NMR (500 MHz, MeOD-J4) δ 7.99 (s, IH), 5.99 (s, IH), 4.44-4.34 (m, 2H),

4.31 (d, IH, J=8.9 Hz), 4.21-4.16 (m, IH), 4.07 (s, 3H), 3.98-3.89 (m, 2H), 3.70, 3.69 (2s, 6H), 1.33 and 1.32 (2d, 6H, J=7.1 Hz), 1.00 (s, 3H).

[00205] 3 IP NMR (202 MHz, MeOD- d4) δ 14.00.

[00206] HPLC t _R = 8.86 min (column: Varian Pursuit XRs 5, C ₁₈ , 150x4.6 mm; method:

linear gradient of ACN (10% to 100%) in H ₂ 0 in 30 min).

[00207] Example 5.

[00208] (2S,2'S)-Diethyl 2,2'-((((2R,3R,4R,5R)-5-(2-amino-6-methoxy-9H-purin-9-yl)-3, 4- dihydroxy-4-methyltetrahydrofuran-2- yl)methoxy)phosphoryl)bis(azanediyl)dipropanoate

[00210] The phosphorodiamidate prodrug was synthesized using Method B.

[00211] A suspension of 6-O-methyl-2'-C-methylguanosine (250 mg, 0.803 mmole) in anhydrous tetrahydrofuran (4 mL) was reacted with triethylamine (135 μί, 0.964 mmole) and phosphoryl chloride (89 μί, 0.964 mmole). Anhydrous dichloromethane (4 mL), the HCl salt of ethyloxy-L-alanine (645.16 mg, 4.02 mmol) and triethylamine (1.12 mL, 8.03 mmol) were added to the previous mixture. After work-up and silica gel column chromatography, 199.8 mg of the prodrug was obtained in 42 % yield as an off white solid.

[00212] The following are the NMR results of the synthesized compound:

[00213] 1H NMR (500 MHz, MeOD-J4) δ 7.99 (s, 1H), 6.00 (s, 1H), 4.44-4.34 (m, 2H),

4.31 (d, 1H, J=8.9 Hz), 4.23-4.08 (m, 5H), 4.07 (s, 3H), 3.98-3.88 (m, 2H), 1.40- 1.20 (m, 12H), 1.00 (s, 3H).

[00214] 3 IP NMR (202 MHz, MeOD-J4) δ 14.02.

[00215] HPLC i _R = 10.87 min (column: Varian Pursuit XRs 5, C ₁₈ , 150x4.6 mm; method:

linear gradient of ACN (10% to 100%) in H ₂ 0 in 30 min).

[00216] Example 6.

[00217] (25,2'5)-Dipropyl-((((2R,35,4R,5R)-5-(2-amino-6-methoxy-9H-p urin-9-yl)-3,4- dihydroxy-4-methyltetrahydrofuran-2-yl)methoxy) phosphoryl)-(2,2')-bis-amino- dipropanoate

[00219] The phosphorodiamidate prodrug was synthesized using Method A.

[00220] In the first step, a solution of (2R,3R,4R,5R)-2-(2-amino-6-methoxy-9H-purin-9- yl)-5-(hydroxymethyl)-3-methyltetrahydrofuran-3,4-diol (Example 2, 250 mg, 0.803 mmole) in anhyd triethylphosphate (1 mL) was allowed to react with phosphorus oxychloride (148 \L, 1.61 mmole). In the second step, anhyd dichloromethane (4 mL), the hydrochloride salt of propyloxy-L- alanine (673 g, 4.02 mmol) and diisopropylethylamine (1.40 mL, 8.03 mmol) were added to the mixture obtained in step one. After work-up, silica gel column chromatography and preparative TLC, 36 mg of the prodrug was obtained in 7.2% yield as an off white solid.

[00221] The following are the NMR results of the synthesized compound:

[00222] 1H NMR (500 MHz, MeOD-J4) δ 7.99 (s, 1H), 6.00 (s, 1H), 4.43-4.33 (m, 2H),

4.30 (d, 1H, J=8.9 Hz), 4.22-4.17 (m, 1H), 4.11-3.90 (m, 9H), 1.68-1.61 (m, 4H), 1.37 and 1.34 (2d, 6H, J=7.1 Hz), 1.00 (s, 3H), 0.96-0.90 (m, 6H).

[00223] ³¹ P NMR (202 MHz, CD ₃ OD) δ 14.00.

[00224] HPLC i _R = 13.16 min (column: Varian Pursuit XRs 5, C ₁₈ , 150x4.6 mm; method:

linear gradient of ACN (10% to 100%) in H ₂ 0 in 30 min).

[00225] Example 7.

[00226] (25,2'5)-Dibutyl 2,2'-((((2R,3R,4R,5R)-5-(2-amino-6-methoxy-9H-purin-9-yl)-3, 4- dihydroxy-4-methyltetrahydrofuran-2- yl)methoxy)phosphoryl)bis(azanediyl)dipropanoate

The compound was prepared according to Method B from (2R,3R,4R,5R)-2-(2- amino-6-methoxy-9H-purin-9-yl)-5-(hydroxymethyl)-3-methyltet rahydrofuran-

3,4-diol, (Example 2, 250 mg, 0.80 mmol), POCl ₃ (0.07 mL, 0.80 mmol), Et ₃ N (0.11 mL, 0.80 mmol), L-alanine butyl ester hydrochloride salt (0.43g, 2.41 mmol), and Et ₃ N (0.67 mL, 4.82 mmol) in 10 mL of 1 : 1 mixture of dry THF and DCM. Crude product was purified by column chromatography using a gradient of CHC1 ₃ to CHC1 ₃ : MeOH 95:5, to give a pure product as a white foam (75 mg, 14%). [00229] ³¹ P NMR (202 MHz, MeOD-J4) δ 14.02. [00230] 1H NMR (500 MHz, MeOD-J4) δ 7.99 (s, 1H, ¾), 6.01 (s, 1H, H _r ), 4.40-4.37

(m, 2H, ¾·), 4.29 (d, J= 9.0 Hz, 1H, H3'), 4.21- 4.19 (m, 1H, H4'), 4.15- 4.01 (m, 7H, 60CH3 and 2 x OCH ₂ ester), 3.94 (q, J=8.0 Hz, 2H, 2 x CHa Ala), 1.63- 1.56 (m, 4 H, 2 x OCH ₂ CH ₂ CH ₂ CH ₃ ester), 1.41- 1.34 (m, 10H, 2 x OCH ₂ CH ₂ CH ₂ CH ₃ ester and 2 x CH3 Ala), 1.00 (s, 3H, 2'CCH3), 0.93 (t, J= 7.5 Hz, 6H, 2 x OCH ₂ CH ₂ CH ₂ CHj ester).

[00231] ¹³ C NMR (125 MHz, MeOD-J4) δ 175.72, 175.65 (2 x d, 3J C-C-N-P= 6.30 Hz,

C=0 ester), 162.74 (C6), 161.91 (C2), 154.60 (C4), 139.30 (C8), 115.55 (C5), 93.14 (CI '), 82.35 (d, ³ J _C -c-o-p = 8.8 Hz, C4'), 80.06 (C2'), 74.81 (C3'), 66.22 (d, 2Jc-o-p = 5.0 Hz, C5'), 66.13 (OCH ₂ CH ₂ CH ₂ CH ₃ ester), 66.11 (OCH ₂ CH ₂ CH ₂ CH ₃ ester), 54.26 (60CH3), 51.06 (d, ² / _C -N-P = 10.0 Hz, 2 x Ccc Ala), 31.75 (2 x OCH ₂ CH ₂ CH ₂ CH ₃ ester), 21.03 (d, 5.0 Hz, CH ₃ Ala), 20.86 (d, ³ / _C -C-N- P= 5.00 Hz, CH3 Ala), 20.33 (2'CCH3), 20.13 (2 x OCH ₂ CH ₂ CH ₂ CH ₃ ester), 14.07 (CH3 ester), 14.06 (CH3 ester).

[00232] HPLC t _R = 15.23 min. [00233] Example 8. [00234] (2S,2'S)-Dipentyl 2,2'-((((2R,3R,4R,5R)-5-(2-amino-6-methoxy-9H-purin-9-yl)-

3,4-dihydroxy-4-methyltetrahydrofuran-2- yl)methoxy)phosphoryl)bis(azanediyl)dipropanoate

[00236] The phosphorodiamidate prodrug was synthesized using Method B.

[00237] A suspension of (2R,3R,4R,5R)-2-(2-amino-6-methoxy-9H-purin-9-yl)-5- (hydroxymethyl)-3-methyltetrahydrofuran-3,4-diol (Example 2, 250 mg, 0.803 mmole) in anhyd tetrahydrofuran (4 mL) was allowed to react with triethylamine (135 μί, 0.964 mmole) and phosphoryl chloride (89 μί, 0.964 mmole). Anhydrous dichloromethane (4 mL), and the hydrochloride salt of pentoxy-L- alanine (0.79 g, 4.02 mmol) and triethylamine (1.12 mL, 8.03 mmol) were added as described in Method B. After work-up and silica gel column chromatography, 260 mg of the prodrug was obtained in 40% yield as an off white solid.

[00238] The following are the NMR results of the synthesized compound:

[00239] ³¹ P NMR (202 MHz, MeOD-J4) δ 14.05.

[00240] 1H NMR (500 MHz, CD ₃ OD) δ 8.00 (s, 1H, ¾), 6.03 (s, 1H, H _r ), 4.44-4.35 (m,

2H, ¾·), 4.29 (d, J= 8.5 Hz, 1H, ¾·), 4.22- 4.13 (m, 1H, ¾·), 4.13- 3.93 (m, 9H, 60CH ₃ and 2 x OCH ₂ ester and 2 x CHcc Ala), 1.62- 1.59 (m, 4 H, 2 x OCH ₂ CH ₂ CH ₂ CH ₂ CH ₃ ester), 1.38- 1.31 (m, 14H, 2 x OCH ₂ CH ₂ CH ₂ CH ₂ CH ₃ ester, 2 x OCH ₂ CH ₂ CH ₂ CH ₂ CH ₃ ester and 2 x CH ₃ Ala), 1.00 (s, 3H, 2'CCH ₃ ), 0.89 (t, J= 5.00 Hz, 6H, 2 x OCH ₂ CH ₂ CH ₂ CH ₂ CH _∑ ester).

[00241] ¹³ C NMR (125 MHz, CD ₃ OD) δ 175.72, 175.67 (2 x d, 6.3 Hz, C=0 ester), 162.75 (C6), 161.92 (C2), 154.61 (C4), 139.26 (C8), 115.56 (C5), 93.07 (CI'), 82.34 (d, 3JC-C-0-P = 7.6 Hz, C4'), 80.11 (C2'), 74.81 (C3'), 66.43 (d, ² J c-o-p = 2.5 Hz, C5'), 66.25 (OCH ₂ CH ₂ CH ₂ CH ₂ CH ₃ ester), 66.22 (OCH ₂ CH ₂ CH ₂ CH ₂ CH ₃ ester), 54.34 (60CH ₃ ), 51.16 (d, ² / _C -N-P= 11.3 Hz, Ca Ala), 51.07 (d, ² / _C -N-P = 10.0 Hz, Ca Ala), 29.39 (2 x OCH ₂ CH ₂ CH ₂ CH ₂ CH ₃ ester), 29.16 (2 x OCH ₂ CH ₂ CH ₂ CH ₂ CH ₃ ester), 23.38 (2 x OCH ₂ CH ₂ CH ₂ CH ₂ CH ₃ ester), 21.12, 21.01 (2 x d, 6.3 Hz, CH ₃ Ala), 20.43 (2'CCH3), 14.07 (CH3 ester), 14.42 (OCH ₂ CH ₂ CH ₂ CH ₂ CH ₃ ester).

[00242] HPLC t _R = 18.68 min.

[00243] MS (TOF ES+) m/z: 674.32 (M+H ⁺ , 100%).

[00244] HRMS C ₂₈ H ₄₈ N ₇ O ₁₀ Pi Calculated: 674.3279, found: 674.3246.

[00245] Example 9. [00246] (2S,2'S)-Bis(3,3-dimethylbutyl) 2,2'-((((2R,3R,4R,5R)-5-(2-amino-6-methoxy-9H- purin-9-yl)-3,4-dihydroxy-4-methyltetrahydrofuran-2- yl)methoxy)phosphoryl)bis(azanediyl)dipropanoate

[00248] The compound was prepared according to Method B from (2R,3R,4R,5R)-2-(2- amino-6-methoxy-9H-purin-9-yl)-5-(hydroxymethyl)-3-methyltet rahydrofuran- 3,4-diol, (Example 2, 250 mg, 0.80 mmol), POCl ₃ (0.07 mL, 0.80 mmol), Et N (0.11 mL, 0.80 mmol), L-alanine 3,3-dimethylbutyl ester tosylate salt (0.83 g, 2.41 mmol), and Et ₃ N (0.67 mL, 4.82 mmol) in 10 mL of 1: 1 mixture of dry THF and DCM. Crude product was purified by column chromatography using a gradient of CHC1 ₃ to CHC1 ₃ : MeOH 95:5, to give a pure product as a white foam (52 mg, 9%).

[00249] ³¹ P NMR (202 MHz, MeOD-J4) δ 14.03.

[00250] 1H NMR (500 MHz, MeOD-J4) δ 7.99 (s, 1H, ¾), 6.00 (s, 1H, H _r ), 4.42-4.36

(m, 2H, Hs , 4.28 (d, J= 9.0 Hz, 1H, ¾·), 4.23- 4.09 (m, 5H, H4' and 2 x OCH ₂ ester), 4.07 (s, 3H, 60CH ₃ ), 3.92 (q, J=7.0 Hz, 2H, 2 x CHcc Ala), 1.60 (t, J= 7.0 Hz, 4H, 2 x OCH ₂ CH ₂ ester), 1.37 (d, J= 7.0 Hz, 6H, 2 x CH ₃ Ala), 0.99 (s, 3H, 2'CCH ₃ ), 0.97 (s, 9H, 3 x CH ₃ ester), 0.94 (s, 9H, 3 x CH ₃ ester).

[00251] ¹³ C NMR (125 MHz, MeOD-J4) δ 175.67, 175.59 (2d, 6.3 Hz, C=0 ester), 162.74 (C6), 161.91 (C2), 154.61 (C4), 139.24 (C8), 115.58 (C5), 93.13 (CI'), 82.35 (d, ³ Jc-c-o-p = 8.8 Hz, C4'), 80.06 (C2'), 74.75 (C3'), 66.22 (d, 2J C- O-P = 5.00 Hz, C5'), 66.96 (OCH ₂ ester), 66.94 (OCH ₂ ester), 54.24 (60CH3), 51.07 (d, ² Jc- _N -p = 10.0 Hz, 2 x Ccc Ala), 42.85 (OCH ₂ CH ₂ ester), 42.83 (OCH ₂ CH ₂ ester), 30. 59 (C ester), 30.55 (C ester), 30.03 (6 x CH ₃ ester), 20.96 (d, 6.3 Hz, CH ₃ Ala), 20.79 (d, 6.3 Hz, CH ₃ Ala), 20.34 (2'CCH ₃ ).

[00252] HPLC ¾= 20.12 min. [00253] Example 10. [00254] (25,2'5)-Diisobutyl-((((2R,35,4R,5R)-5-(2-amino-6-methoxy-9H -purin-9-yl)-3,4- dihydroxy-4-methyltetrahydrofuran-2-yl)methoxy) phosphoryl)(2,2')-bi5 ^, -amino- dipropanoate

[00256] The phosphorodiamidate prodrug was synthesized using Method B. [00257] A suspension of 6-0-methyl-2'-C-methylguanosine (250 mg, 0.803 mmole) in anhydrous tetrahydrofuran (4 mL) was reacted with triethylamine (135 μί, 0.964 mmole) and phosphoryl chloride (89 μί, 0.964 mmole). Anhydrous dichloromethane (4 mL), the tosylate salt of isobutyloxy-L-alanine (1.27 g, 4.02 mmol) and triethylamine (1.12 mL, 8.03 mmol) were added. After work-up, silica gel column chromatography and preparative HPLC, 66.1 mg of the prodrug was obtained in 13% yield as an off white solid.

[00258] The following are the NMR results of the synthesized compound: [00259] IH NMR (500 MHz, MeOD-J4) δ 7.98 (s, IH), 5.99 (s, IH), 4.41-4.37 (m, 2H),

4.29 (d, IH, J=9.0 Hz), 4.22-4.17 (m, IH), 4.07 (s, 3H), 4.00-3.77 (m, 6H), 1.95- 1.86 (m, 2H), 1.38, 1.35 (2d, 6H, J=7.1 Hz), 0.99 (s, 3H), 0.94-0.89 (m, 12H).

[00260] 3 IP NMR (202 MHz, MeOD-J4) δ 14.00. [00261] HPLC ¾ = 16.36 min (column: Varian Pursuit XRs 5, C ₁₈ , 150x4.6 mm; method: linear gradient of CH ₃ CN (10% to 100%) in H ₂ 0 in 30 min).

[00262] Example 11. [00263] (2S,2'S)-Bis (cyclopropylmethyl) 2,2'-((((2R,3R,4R,5R)-5-(2-amino-6-methoxy-

9H-purin-9-yl)-3,4-dihydroxy-4-methyltetrahydrofuran-2- yl)methoxy)phosphoryl)bis(azanediyl)dipropanoate

[00265] The phosphorodiamidate prodrug was synthesized using Method B.

[00266] A suspension of (2R,3R,4R,5R)-2-(2-amino-6-methoxy-9H-purin-9-yl)-5- (hydroxymethyl)-3-methyltetrahydrofuran-3,4-diol (0.2881 g, 0.93 mmol) in anhydrous tetrahydrofuran (5 mL) are allowed to react with triethylamine (0.16 mL, 1.12 mmol, 1.2 equiv) and phosphoryl chloride (0.11 mL, 1.12 mmol, 1.2 equiv). Anhydrous dichloromethane (8 mL), and tosylate salt of L-Ala-O- cyclopropylmethyl (1.4695 g, 4.65 mmol) and anhydrous triethylamine (1.30 mL, 9.3 mmol, 10 equiv) are added as describe in Method B. The residue is purified by flash chromatography using CHCl ₃ /MeOH (6%) to give product (0.0336g, 0.063 mmol 18%) as an off white solid.

[00267] The following are the mass and NMR results of the synthesized compound: [00268] 1H NMR (500 MHz, CDC\ d4) δ 7.77 (s, 1H, H ₈ ), 5.99 (s, 1H, H _r ), 4.54 (m, 1H,

1H CH ₂ s , 4.43 (m, 1H, ¾·), 4.34-4.31 (m, 1H, 1H CH _{2 5} , 4.22-4.21 (m, 1H, H ₄ <), 4.03 (s, 3H, OCH ₃ ), 3.99-4.86 (m, 6H, 2xO(CH ₂ -cyclopropyl) & 2xNHCH(CH ₃ )CO-0-cyclopropylmethyl), 1.38 (d, 3H, J = 5 Hz, NHCH(CJi)CO-O-cyclopropylmethyl), 1.35 (d, 3H, J = 7 Hz, NHCH(CH ₃ )CO- O-cyclopropylmethyl), 1.08 (m, 2H, 2xCH cyclopropylmethyl), 0.99 (s, 3H, CH ₃ r), 0.52 & 0.23 (2 broad s, 8H, 4xCH ₂ cyclopropylmethyl). [00269] C NMR (125 MHz, CDCl ₃ -d4) 5 _C 174.43 (CO NHCH(CH ₃ )CO-0- cyclopropylmethyl), 174.30 (CO NHCH(CH ₃ )CO-0-cyclopropylmethyl), 161.54 (C ₆ ), 159.66 (C ₂ ), 152.99 (C ₄ ), 137.87 (C ₈ ), 115.56 (C ₅ ), 91.69 (s, C _r ), 81.11 (C ₄ ^< ), 79.34 (s, Cr), 74.21 (C ₃ , 64.98 (CH _{2 5} , 53.80 (OCH ₃ ), 49.91 & 49.78 (d, 2xNHCH(CH ₃ )CO-0-cyclopropylmethyl), 20.94 & 20.89 (d, NHCH(CH ₃ )CO-0- cyclopropylmethyl), 20.27 (s, CH ₂ ·), 9.63 (s, 2xCH cyclopropylmethyl), 3.23 & 3.17 (d, 4xCH ₂ cyclopropylmethyl).

[00270] ³¹ P NMR (202 MHz, CDC1 ₃ -J4) 13.17.

[00271] MS : 641.61 (M), found 642.2630 (M+H), calculated 642.2653 (M+H) 664.2481

(M+ Na ⁺ ), 680.2184 (M+ K ⁺ ).

[00272] Example 12.

[00273] (25,2'5)-Dibenzyl-((((2R,35,4R,5R)-5-(2-amino-6-methoxy-9H-p urin-9-yl)-3,4- dihydroxy-4-methyltetrahydrofuran-2-yl)methoxy) phosphoryl)-(2,2')-bis-amino- dipropanoate

[00275] The phosphorodiamidate prodrug was synthesized using Method A.

[00276] In the first step, a solution of (2R,3R,4R,5R)-2-(2-amino-6-methoxy-9H-purin-9- yl)-5-(hydroxymethyl)-3-methyltetrahydrofuran-3,4-diol (Example 2, 250 mg, 0.803 mmole) in anhyd triethylphosphate (1 mL) was allowed to react with phosphorus oxychloride (148 μί, 1.61 mmole). In the second step, anhyd dichloromethane (4 mL), the tosylate salt of benzyloxy-L- alanine (1.41 g, 4.02 mmol) and diisopropylethylamine (1.40 mL, 8.03 mmol) were added to the mixture obtained in step one. After work-up, silica gel column chromatography and preparative HPLC, 50.1 mg of the prodrug was obtained in 8.7% yield as an off white solid. [00277] The following are the NMR results of the synthesized compound:

[00278] 1H NMR (500 MHz, MeOD-J4) δ 7.96 (s, IH), 7.34-7.25 (m, 10H), 5.99 (s, IH),

5.16-5.02 (m, 4H), 4.41-4.31 (m, 2H), 4.29 (d, IH, J=9.0 Hz), 4.21-4.15 (m, IH), 4.04 (s, 3H), 4.02-3.94 (m, 2H), 1.33 (d, 6H, J=7.1 Hz), 0.99 (s, 3H).

[00279] ³¹ P NMR (202 MHz, MeOD-J4) δ 13.93.

[00280] HPLC i _R = 13.91 min (column: Varian Pursuit XRs 5, C ₁₈ , 150x4.6 mm; method:

linear gradient of ACN (10% to 100%) in H ₂ 0 in 30 min).

[00281] Example 13.

[00282] (25,2'5)-Diisopropyl-((((2R,35,4R,5R)-5-(2-amino-6-methoxy-9 H-purin-9-yl)-

3,4-dihydroxy-4-methyltetrahydrofuran-2-yl)methoxy) phosphoryl)-(2,2')-bis- amino-dipropanoate

[00284] The phosphorodiamidate prodrug was synthesized using Method B.

[00285] In the first step, a suspension of (2R,3R,4R,5R)-2-(2-amino-6-methoxy-9H-purin-

9-yl)-5-(hydroxymethyl)-3-methyltetrahydrofuran-3,4-diol (Example 2, 250 mg, 0.803 mmole) in anhyd tetrahydrofuran (4 mL) was allowed to react with triethylamine (135 \L, 0.964 mmole) and phosphorus oxychloride (89 \L, 0.964 mmole). In the second step, anhyd dichloromethane (4 mL), the hydrochloride salt of isopropyloxy-L-alanine (673.8 mg, 4.02 mmol) and triethylamine (1.12 mL, 8.03 mmol) were added to the mixture obtained in step one. After work-up and silica gel column chromatography, 55 mg of the prodrug was obtained in 14% yield, as an off white solid.

[00286] The following are the NMR results of the synthesized compound: [00287] 1H NMR (500 MHz, MeOD-J4) δ 7.99 (s, 1H), 5.99 (s, 1H), 5.03-4.89 (m, 2H), 4.44-4.34 (m, 2H), 4.31 (d, 1H, J=8.9 Hz), 4.23-4.16 (m, 1H), 4.07 (s, 3H), 3.94- 3.83 (m, 2H), 1.35 and 1.32 (2d, 6H, J=7.1 Hz), 1.27-1.19 (m, 12H), 1.00 (s, 3H).

[00288] ³¹ P NMR (202 MHz, MeOD-J4) δ 14.07.

[00289] HPLC t _R = min (column: Varian Pursuit XRs 5, C ₁₈ , 150x4.6 mm; method: linear. [00290] Example 14.

[00291] (2S,2'S)-sec-Butyl 2,2'-((((2R,3R,4R,5R)-5-(2-amino-6-methoxy-9H-purin-9-yl)- 3,4-dihydroxy-4-methyltetrahydrofuran-2- yl)methoxy)phosphoryl)bis(azanediyl)dipropanoate

[00293] The phosphorodiamidate prodrug was synthesized using Method B.

[00294] A suspension of (2R,3R,4R,5R)-2-(2-amino-6-methoxy-9H-purin-9-yl)-5- (hydroxymethyl)-3-methyltetrahydrofuran-3,4-diol (Example 2, 250 mg, 0.803 mmole) in anhydrous tetrahydrofuran (4 mL) was allowed to react with triethylamine (135 \L, 0.964 mmole) and phosphoryl chloride (89 \L, 0.964 mmole). Anhydrous dichloromethane (4 mL), and the hydrochloride salt of 2- butoxy-L- alanine (0.73 g, 4.02 mmol) and triethylamine (1.12 mL, 8.03 mmol) were added as described in Method B. After work-up and silica gel column chromatography, 90 mg of the prodrug was obtained in 17% yield as an off white solid.

[00295] The following are the NMR results of the synthesized compound: [00296] ³¹ P NMR (202 MHz, MeOD-J4) 14.05. [00297] 1H NMR (500 MHz, MeOD-J4) 7.99 (s, IH, H8), 6.00 (s, IH, HI'), 4.80- 4.78 (m, 2H, 2 x CH ester), 4.41- 4.39 (m, 2H, H5'), 4.30 (d, J= 8.50 Hz, IH, H3'), 4.21- 4.20 (m, IH, H4'), 4.07 (s, 3H, 60CH ₃ ), 3.92-3.90 (m, 2H, 2 x CHa Ala), 1.63- 1.51 (M, 4H, 2 x CH ₂ ester), 1.37- 1.33 (m, 6H, 2 x CH ₃ Ala), 1.24- 1.17 (m, 6H, 2 x CH ₃ p ester), 1.00 (s, 3H, 2'CCH ₃ ), 0.89 (t, J= 6.00 Hz, 2 x CH ₃ y ester).

[00298] 13C-NMR (125 MHz, MeOD-J4) 175.30 (d, 3.8 Hz, C=0 ester), 162.74

(C6), 161.89 (C2), 154.58 (C4), 139.37 (C8), 115.58 (C5), 93.19 (CF), 82.38 (d,

7.6 Hz, C4'), 80,06 (C2'), 74.91 (C3'), 74.59, 74.55 (CH ester), 66.40 (d, 2Jc-o-p= 3.8 Hz, C5'), 54.27 (60CH ₃ ), 51.19 (d, ² / _C -N-P= 7.6 Hz, Ca Ala), 51.14 (d, 2Jc-N-p= 8.8 Hz, Ca Ala), 29.78, 29.74 (CH ₂ ester), 21.17 (d, 6.2 Hz, CH3 Ala), 21.04 (d, 2.5 Hz, CH ₃ Ala), 21.01 (CH ₃ Ala), 20.91(d, ³ J _C -c- N-P= 5.3 Hz, CH3 Ala), 20.89 (2'CCH ₃ ), 19.76, 19.61 (CH ₃ p ester), 10.05 (CH ₃ y ester)..

[00299] HPLC t _R = 15.12 min.

[00300] MS (TOF ES+) m/z: 668.28 (M+Na ⁺ , 100%).

[00301] HRMS C ₂₆ H ₄₄ N ₇ O ₁₀ Pi calculated: 646.2966 found: 646.2961.

[00302] Example 15.

[00303] (2S,2'S)-Dicyclobutyl 2,2'-((((2R,3R,4R,5R)-5-(2-amino-6-methoxy-9H-purin-9- yl)-3,4-dihydroxy-4-methyltetrahydrofuran-2- yl)methoxy)phosphoryl)bis(azanediyl)dipropanoate

[00305] The phosphorodiamidate prodrug was synthesized using Method B. [00306] A suspension of 6-0-methyl-2'-C-methylguanosine (250 mg, 0.803 mmole) in anhydrous tetrahydrofuran (4 mL) was reacted with triethylamine (135 μί, 0.964 mmole) and phosphorus oxychloride (89 μί, 0.964 mmole). Anhydrous dichloromethane (4 mL), the HCl salt of cyclobutyl-L-alanine (722.2 mg, 4.02 mmol) and triethylamine (1.12 mL, 8.03 mmol) were added to the previous mixture. After work-up, silica gel column chromatography and preparative HPLC, 65.1 mg of the phosphorodiamidate was obtained in 13% yield as an off white solid.

[00307] The following are the NMR results of the synthesized compound:

[00308] 1H NMR (500 MHz, MeOD-J4) δ 7.98 (s, 1H), 5.99 (s, 1H), 5.01-4.83 (m, 2H),

4.43-4.32 (m, 2H), 4.30 (d, 1H, J=8.9 Hz), 4.22-4.15 (m, 1H), 4.07 (s, 3H), 3.94- 3.84 (m, 2H), 2.38-2.24 (m, 4H), 2.16- 1.99 (m, 4H), 1.86- 1.74 (m, 2H), 1.71-1.57 (m, 2H), 1.36, 1.33 (2d, 6H, J=7.1 Hz), 1.00 (s, 3H).

[00309] 3 IP NMR (202 MHz, MeOD-J4) δ 14.01.

[00310] HPLC t _R = 14.33 min (column: Varian Pursuit XRs 5, C ₁₈ , 150x4.6 mm; method:

linear gradient of ACN (10% to 100%) in H ₂ 0 in 30 min).

[00311] Example 16.

[00312] (2S,2'S)-Dicyclopentyl 2,2'-((((2R,3R,4R,5R)-5-(2-amino-6-methoxy-9H-purin-9- yl)-3,4-dihydroxy-4-methyltetrahydrofuran-2- yl)methoxy)phosphoryl)bis(azanediyl)dipropanoate

[00314] The phosphorodiamidate prodrug was synthesized using Method B. [00315] The compound of Example 2, ((2R,3R,4R,5R)-2-(2-amino-6-methoxy-9H-purin-9- yl)-5-(hydroxymethyl)-3-methyltetrahydrofuran-3,4-diol, 0.3179 g, 1.02 mmol) was dissolved in anhyd THF (5 mL) and to it was added anhyd Et ₃ N (0.17 mL, 1.22 mmol, 1.2 equiv). The mixture was allowed to stir at rt for 30 min, after which the solution was cooled to -78 °C and POCl ₃ (0.12 mL, 1.22 mmol, 1.2 equiv) was added dropwise. The solution was stirred 30 min at -78 °C and then 30 min at rt. The formation of the intermediate was monitored by phosphorus NMR. Then 5 equiv of L-Ala-O-cyclopentyl pTSA salt (1.6832 g, 5.10 mmol) and anhydrous dichloromethane (8 mL) were added and the reaction was cooled to -78 °C, at which time anhyd Et N (1.42 mL, 10.2 mmol, 10 equiv) was added dropwise. The solution was then allowed to return to rt and stirred overnight, at the of which time phosphorus NMR monitoring suggested the formation of the diamidate. The solvent was evaporated under reduced pressure and the residue was purified by flash chromatography using CHCl ₃ /MeOH (up to 4%) to recover the desired phosphorodiamidate which was washed with water to remove the excess Et ₃ N.

[00316] HPLC : t _R = 15.35 min

[00317] 1H NMR (500 MHz, CDC1 ₃ -J4) δ 7.70 (s, 1H, ¾ guanine), 5.89 (s, 1H, H _r ), 5.06

(m, 2H, O-CH cyclopentyl), 4.46-4.42 (m, 1H, 1H CH _{2 5} ), 4.37 (d, 1H, J = 8.5 Hz, ¾·), 4.26-4.22 (m, 1H, 1H CH _{2 5} ·), 4.11-4.08 (m, 1H, ¾·), 3.94 (s, 3H, OCH ₃ guanine), 3.83-3.70 (m, 2H, 2x NHCH(CH ₃ )CO-0-cyclopentyl), 1.73-1.45 (m, 16H, 8 x CH ₂ cyclopentyl), 1.31 (d, 3H, J = 8 Hz, NHCH(C¾)CO-Q- cyclopentyl), 1.29 (d, 3H, J = 8 Hz, NHCH(CH ₃ )CO-0-cyclopentyl), 1.02 (s, 3H, CH _{3 r} ).

[00318] ¹³ C NMR (125 MHz, CDC1 ₃ -J4) 5 _C 174.00 (CO NHCH(CH ₃ )CO-0-cyclopentyl),

173.90 (CO NHCH(CH ₃ )CO-0- cyclopentyl), 161.37 (s, C ₆ guanine), 159.56 (s, C ₂ guanine), 152.99 (s, C ₄ guanine), 137.97 (s, Cg guanine), 115.50 (s, C ₅ guanine), 91.76 (s, C _r ), 81.14 (s, C ₄ <), 79.22 (s, C ₂ <), 78.18 & 78.10 (2s, 2 OCH- cyclopentyl), 73.93(s, C ₃ <), 64.95 (s, CH _{2 5} , 53.70 (s, OCH3 guanine), 49.81 & 49.67 (2s, 2xNHCH(CH ₃ )CO-0-cyclopentyl), 32.56 & 32.34 (2s, 4 CH ₂ ortho cyclopentyl), 23.55 (s, 4 CH ₂ meta cyclopentyl), 20.75 & 20.71 (2s, NHCH(C¾)CO-0-cvclopentvl), 20.27 (s, CH _{3 2} <). [00319] ³¹ P NMR (202 MHz, CDCl ₃ -d4) 12.99 ppm (s). [00320] Example 17.

[00321] (25,2'5)-Dicyclohexyl-((((2R,35,4R,5R)-5-(2-amino-6-methoxy- 9H-purin-9-yl)-

3,4-dihydroxy-4-methyltetrahydrofuran-2-yl)methoxy) phosphoryl)-(2,2')-bis- amino-dipropanoate

[00323] The phosphorodiamidate prodrug was synthesized using Method A.

[00324] In the first step, a solution of(2R,3R,4R,5R)-2-(2-amino-6-methoxy-9H-purin-9- yl)-5-(hydroxymethyl)-3-methyltetrahydrofuran-3,4-diol (Example 2, 250 mg, 0.803 mmole) in anhyd triethylphosphate (1 mL) was allowed to react with phosphorus oxychloride (148 \L, 1.61 mmole). In the second step, anhyd dichloromethane (4 mL), the hydrochloride salt of cyclohexyloxy-L-alanine (834 mg, 4.02 mmol) and diisopropylethylamine (1.40 mL, 8.03 mmol) were added to the mixture obtained in step one. After work-up and silica gel column chromatography, 36.0 mg of the prodrug was obtained in 6.4% yield, as an off white solid.

[00325] The following are the NMR results of the synthesized compound:

[00326] 1H NMR (500 MHz, CD ₃ OD) δ 7.98 (s, IH), 5.99 (s, IH), 4.76-4.64 (m, 2H),

4.41-4.35 (m, 2H), 4.29 (d, IH, J=9.0), 4.22-4.16 (m, IH), 4.07 (s, 3H), 3.94-3.86 (m, 2H), 1.91-1.25 (m, 26H), 0.99 (s, 3H).

[00327] ³¹ P NMR (202 MHz, CD ₃ OD) δ 14.07. [00328] HPLC i _R = 17.60 min (column: Varian Pursuit XRs 5, C ₁₈ , 150x4.6 mm; method: linear gradient of ACN (10% to 100%) in H ₂ 0 in 30 min).

[00329] Example 18.

[00330] (2S,2'S)-Bis(tetrahydro-2H-pyran-4-yl) 2,2'-((((2R,3R,4R,5R)-5-(2-amino-6- methoxy-9H-purin-9-yl)-3,4-dihydroxy-4-methyltetrahydrofuran -2- yl)methoxy)phosphoryl)bis(azanediyl)dipropanoate

[00332] Prepared according to Method C from (2R,3R,4R,5R)-2-(2-amino-6-methoxy-9H- purin-9-yl)-5-(hydroxymethyl)-3-methyltetrahydrofuran-3,4-di ol, (Example 2, 250 mg, 0.80 mmol), POCl ₃ (0.07 mL, 0.80 mmol), Et3N (0.11 mL, 0.80 mmol), L- alanine tetrahydropyranyl ester tosylate salt (1.38g, 4.02 mmol), Et ₃ N (1.12 mL, 8.04 mmol) in 10 mL of 1 : 1 mixture of dry THF and DCM. Crude product was purified by column chromatography using a gradient of CHC1 ₃ to CHC1 ₃ : MeOH 95:5, to give a pure product as a white foam (75 mg, 14%).

[00333] ³¹ P NMR (202 MHz, MeOD-J4) δ 13.94.

[00334] 1H NMR (500 MHz, MeOD-J4) δ 7.99 (s, 1H, ¾), 5.99 (s, 1H, H _r ), 4.94- 4.83

(m, 2H, 2 x OCH ester), 4.39-4.38 (m, 2H, ¾·), 4.28 (d, J= 9.0 Hz, 1H, H3'), 4.21- 4.18 (m, 1H, H4'), 4.07 (s, 3H, 60CH3), 3.99- 3.83 (m, 6H, 2 x CHa Ala and 4 x OCH _2a ester), 3.56- 3.45 (m, 4H, 4 x OCH _2b ester), 1.93- 1.83 (m, 4 H, 4 x OCH _2a ester), 1.69- 1.59 (m, 4 H, 4 x OCH _2d ester), 1.38 (d, J= 7.0 Hz, 3H, CH ₃ Ala), 1.36 (d, J= 7.0 Hz, 3H, CH ₃ Ala), 0.99 (s, 3H, 2'CCH3).

[00335] ¹³ C NMR (125 MHz, MeOD-J4) δ 175.00, 174.92 (2d, 5.00 Hz, C=0 ester), 162.75 (C6), 161.94 (C2), 154.63 (C4), 139.36 (C8), 115.54 (C5), 93.14 (CI '), 82.41 (d, 3J C-C-O-P = 8.8 Hz, C4'), 80.03 (C2'), 74.89 (C3'), 71.27 (OCH ester), 71.23 (OCH ester), 66.47 (d, ² J _C -o-p = 5.0 Hz, C5'), 66.18 (4x OCH ₂ ester), 54.29 (60CH ₃ ), 51.15 (d, ² / _C -N-P = 6.3 Hz, 2 x Ccc Ala), 32.64 (4x CH ₂ ester), 20.98 (d, ³ J c-c-N-p= 6.3 Hz, CH ₃ Ala), 20.79 (d, 6.3 Hz, CH ₃ Ala), 20.31 (2'CCH ₃ ).

[00336] HPLC t _R = 9.57 min. [00337] Example 19. [00338] (25,2'5)-(5)-Phenylethyl-((((2R,35,4R,5R)-5-(2-amino-6-metho xy-9H-purin-9-yl)- 3,4-dihydroxy-4-methyltetrahydrofuran-2-yl)methoxy) phosphoryl)-(2,2')-bis- amino-dipropanoate

[00339] [00340] The phosphorodiamidate prodrug was synthesized using Method A.

[00341] In the first step, a solution of (2R,3R,4R,5R)-2-(2-amino-6-methoxy-9H-purin-9- yl)-5-(hydroxymethyl)-3-methyltetrahydrofuran-3,4-diol (Example 2, 250 mg, 0.803 mmole) in anhyd triethylphosphate (1 mL) was allowed to react with phosphorus oxychloride (148 μί, 1.61 mmole). In the second step, anhyd dichloromethane (4 mL), the tosylate salt of (2 _l S')-phenylethyloxy-L-alanine (1.46 g, 4.02 mmol) and diisopropylethylamine (1.40 mL, 8.03 mmol) were added to the mixture obtained in step one. After work-up, silica gel column chromatography and preparative TLC, 27.1 mg of the prodrug was obtained in 4.5% yield as an off white solid.

[00342] The following are the NMR results of the synthesized compound: [00343] 1H NMR (500 MHz, MeOD-J4) δ 7.98 (s, 1H), 7.41-7.24 (m, 10H), 5.99 (s, 1H), 5.86-5.80 and 5.78-5.73 (2m, 2H), 4.40-4.32 (m, 2H), 4.29 (d, 1H, J=9. l Hz), 4.21-4.14 (m, 1H), 4.06 (s, 3H), 4.00-3.91 (m, 2H), 1.53 and 1.47 (2d, 6H, J=6.6 Hz), 1.31 and 1.28 (2d, 6H, J=7.1 Hz), 0.99 (s, 3H).

[00344] ³¹ P NMR (202 MHz, MeOD-J4) δ 13.99. [00345] HPLC i _R = 18.48 min (column: Varian Pursuit XRs 5, C ₁₈ , 150x4.6 mm; method:

linear gradient of ACN (10% to 100%) in H ₂ 0 in 30 min).

[00346] Example 20. [00347] (2S,2'S)-Bis(2,3-dihydro- lH-inden-2-yl) 2,2'-((((2R,3R,4R,5R)-5-(2-amino-6- methoxy-9H-purin-9-yl)-3,4-dihydroxy-4-methyltetrahydrofuran -2- yl)methoxy)phosphoryl)bis(azanediyl)dipropanoate

[00349] The compound was prepared according to Method B from (2R,3R,4R,5R)-2-(2- amino-6-methoxy-9H-purin-9-yl)-5-(hydroxymethyl)-3-methyltet rahydrofuran- 3,4-diol, (Example 2, 250 mg, 0.80 mmol), POCl ₃ (0.07 mL, 0.80 mmol), E _t3 N (0.11 mL, 0.80 mmol), L-alanine 2-indanolyl ester tosylate salt (0.91g, 2.41 mmol), and Et ₃ N (0.67 mL, 4.82 mmol) in 10 mL of 1 : 1 mixture of dry THF and DCM. Crude product was purified by column chromatography using a gradient of CHC1 ₃ to CHC1 ₃ : MeOH 95:5, to give a pure product as a white foam (52 mg, 9%).

[00350] ³¹ P NMR (202 MHz, MeOD-J4) δ 13.94. [00351] 1H NMR (500 MHz, MeOD-J4) δ 7.95 (s, IH, ¾), 7.19-7.10 (m, 8H, 8 x CH ester), 5.99 (s, IH, H _r ), 5.49- 5.46 (m, IH, OCH ester), 5.42- 5.40 (m, IH, OCH ester), 4.34-4.25 (m, 3H, H ₅ < and H3'), 4.16- 4.14 (m, IH, H4'), 4.03 (s, 3H, 60CH ₃ ), 3.83 (q, J=7.0 Hz, 2H, 2 x CHcc Ala), 3.28-3.16 (m, 4H, 2 x CH ₂ ester), 3.01- 2.90 (m, 4H, 2 x CH ₂ ester), 1.25 (d, J= 7.0 Hz, 3H, CH ₃ Ala), 1.24 (d, J= 7.0 Hz, 3H, CH ₃ Ala), 0.98 (s, 3H, 2'CCH ₃ ).

[00352] ¹³ C NMR (125 MHz, MeOD-J4) δ 175.53, 175.48 (2d, 5.00 Hz, C=0 ester), 162.73 (C6), 161.89 (C2), 154.57 (C4), 141.59, 141.51, 141.47 (4 x C ester), 139.30 (C8), 127.84 (4x CH ester), 125.59 (4x CH ester), 115.58 (C5), 93.13 (CI '), 82.35 (d, ³ J _C -c-o-p = 8.8 Hz, C4'), 80.04 (C2'), 77.70 (OCH ester), 77.67 (OCH ester), 74.81 (C3'), 66.28 (d, ² J _C -o-p = 5.0 Hz, C5'), 54.29 (60CH ₃ ), 51.11 (d, ² Jc-N-p = 10.0 Hz, 2 x Ccc Ala), 40.42 (2x CH ₂ ester), 40.36 (2 x CH ₂ ester), 20.76 (d, 6.3 Hz, CH3 Ala), 20.62 (d, 6.3 Hz, CH ₃ Ala), 20.38 (2'CCH ₃ ).

[00353] Example 21.

[00354] (2S)-Benzyl 2-((((2R,3R,4R,5R)-5-(2-amino-6-methoxy-9H-purin-9-yl)-3,4- dihydroxy-4-methyltetrahydrofuran-2-yl)methoxy)(( _l S')-l-(neopentyloxy)- l- oxopropan-2-ylamino)phosphorylamino)propanoate

[00356] The phosphorodiamidate prodrug was synthesized using Method C.

[00357] A suspension of (2R,3R,4R,5R)-2-(2-amino-6-methoxy-9H-purin-9-yl)-5-

(hydroxymethyl)-3-methyltetrahydrofuran-3,4-diol (Example 2, 250 mg, 0.803 mmole) in anhyd tetrahydrofuran (5 mL) was allowed to react with triethylamine (110 \L, 0.803 mmole) and phosphoryl chloride (70 \L, 0.803 mmole). The tosylate salt of benzoxy L-alanine (282 mg, 0.803 mmol) and triethylamine (110 μί, 0.803 mmol) were added. Anhydrous dichloromethane (4 mL), and the tosylate salt of neopentyloxy-L-alanine (1.33 g, 4.02 mmol) and triethylamine (1.12 mL, 8.03 mmol) were added as described in Method C. After work-up and silica gel column chromatography, 25 mg of the prodrug was obtained in 4% yield as an off white solid.

[00358] The following are the NMR results of the synthesized compound:

[00359] ³¹ P NMR (202 MHz, MeOD-J4) 13.98, 13.94.

[00360] 1H NMR (500 MHz, MeOD-J4) 7.97, 7.96 (2 s, 1H, H8), 7.36-7.30 (m, 5H, Ph),

5.98, 5.97 (2s, 1H, HI'), 5.18- 5.09 (m, 2H, CH ₂ ester), 4.39- 4.33 (m, 2H, H5'), 4.28 (d, J= 8.0 Hz, 1H, H3'), 4.20- 4.16 (m, 1H, H4'), 4.06, 4.05 (2s, 3H, 60CH ₃ ), 4.02- 3.94 (m, 2H, 2 x CHa Ala), 3.84, 3.82, 3.72, 3.67 (2AB, /AB= 10.5 Hz, 2H, CH ₂ neopentyl ester), 1.39- 1.32 (m, 6H, 2 x CH ₃ Ala), 0.97 (s, 3H, 2'CCH ₃ ), 0.93, 0.91 (2s, 9H, 3 x CH ₃ neopentyl ester).

[00361] ¹³ C-NMR (125 MHz, MeOD-J4) 175.54, 175.43, 175.39 (C=0 ester), 162.73,

162.71 (C6), 161.93, 161.89 (C2), 154.57, 154.55 (C4), 139.32, 139.08 (C8), 137.39 (ipso Ph), 129.55, 129.35, 129.25, 129.23, 129.20, 129.16, 128.27, 128.00 (Ph), 116.19, 115.54 (C5), 93.34, 93.18 (CI'), 82.39, 82.33 (C4'), 80.01, 79.99 (C2'), 75.34, 75.04 (CH ₂ neopentyl ester), 74.84, 74.82 (C3'), 67.88, 67.85 (CH ₂ benzyl ester), 67.86 (d, ² J _C -o-p= 3.8 Hz, C5'), 66.36 (d, ² J _C -o-p= 5.5 Hz, C5'), 54.18, 54.01 (60CH ₃ ), 49.69, 49.64, 49.52, 49.46 (2 x Ca Ala), 32.28, 32.25 (C ester), 26.74, 26.71 (3 x CH ₃ neopentyl ester), 21.07, 20.90, 20.79, 20.66 (4d, ³ J _C - C-N-P= 6.3 Hz, 2 x CH ₃ Ala), 20.39, 20.25 (2'CCH ₃ ).

[00362] HPLC t _R = 16.11, 16.80 min.

[00363] MS (TOF ES+) m/z: 716.28 (M+Na ⁺ , 100%).

[00364] HRMS C ₃₀ H ₄₄ N ₇ O ₁₀ Pi calculated: 694.2966 found: 694.2956.

[00365] Example 22. [00366] (2S)-Cyclohexyl 2-((((2R,3R,4R,5R)-5-(2-amino-6-methoxy-9H-purin-9-yl)-3,4- dihydroxy-4-methyltetrahydrofuran-2-yl)methoxy)(( _l S')-l-(neopentyloxy)- l- oxopropan-2-ylamino)phosphorylamino)propanoate

[00368] The phosphorodiamidate prodrug was synthesized using Method C. [00369] A suspension of 6-O-methyl-2'-C-methylguanosine (250 mg, 0.803 mmole) in anhydrous tetrahydrofuran (4 mL) was reacted with triethylamine (135 μί, 0.964 mmole) and phosphorus oxychloride (89 μί, 0.964 mmole). Anhydrous dichloromethane (4 mL), the HCl salt of cyclohexyloxy-L-alanine (167 mg, 0.803 mmol) and triethylamine (224 μί, 1.61 mmole) were added. Finally, the tosylate salt of neopentyloxy-L-alanine (1.33 g, 4.02 mmol) and triethylamine (1.12 mL, 8.03 mmol) were added. After work-up and silica gel column chromatography, 92.6 mg of the prodrug was obtained in 17% yield as an off white solid.

[00370] The following are the NMR results of the synthesized compound: [00371] 1H NMR (500 MHz, MeOD-J4) δ 7.98 (s, 1H), 5.99 (s, 1H), 4.76-4.66 (m, 1H),

4.41-4.36 (m, 2H), 4.29, 4.28 (2d, 1H, J=9.0 Hz), 4.22-4.12 (m, 1H), 4.07 (2s, 3H), 4.01-3.78 (m, 4H), 1.90-1.68, 1.61-1.24 (2m, 16H), 0.99 (s, 3H), 0.94 and 0.92 (2s, 9H).

[00372] 3 IP NMR (202 MHz, MeOD-J4) δ 14.03 and 14.00. [00373] HPLC i _R = 27.77 and 28.17 min (column: Varian Pursuit XRs 5, C ₁₈ , 150x4.6 mm; method: linear gradient of MeOH (10% to 100%) in H ₂ 0 in 30 min).

[00374] Example 23. [00375] (25 ieri-Butyl 2-((((2R,3R,4R,5R)-5-(2-amino-6-methoxy-9H-purin-9-yl)-3,4- dihydroxy-4-methyltetrahydrofuran-2-yl)methoxy)(( _l S')-l-(neopentyloxy)- l- oxopropan-2-ylamino)phosphorylamino)propanoate

[00377] The phosphorodiamidate prodrug was synthesized using Method C.

[00378] A suspension of 6-O-methyl-2'-C-methylguanosine (250 mg, 0.803 mmole) in anhydrous tetrahydrofuran (4 mL) was reacted with triethylamine (135 μί, 0.964 mmole) and phosphorus oxychloride (89 μί, 0.964 mmole). Anhydrous dichloromethane (4 mL), the HCl salt of ie/t-butyloxy-L-alanine (175.2 mg, 0.964 mmol) and triethylamine (269 μί, 1.93 mmole) were added. Finally, the tosylate salt of neopentyloxy-L-alanine (1.33 g, 4.02 mmol) and triethylamine (1.12 mL, 8.03 mmol) were added. After work-up, silica gel column chromatography and preparative HPLC, 26.1 mg of the phosphorodiamidate was obtained in 4% yield as an off white solid.

[00379] The following are the NMR results of the synthesized compound: [00380] 1H NMR (500 MHz, MeOD-J4) δ 7.98 (2s, 1H), 5.98 (2s, 1H), 4.42-4.36 (m, 2H),

4.31, 4.29 (2d, 1H, J=9.1 Hz), 4.22-4.16 (m, 1H), 4.07 (s, 3H), 3.89-3.64 (m, 4H), 1.49- 1.28 (m, 15H), 0.99 (s, 3H), 0.94 and 0.91 (2s, 9H).

[00381] 3 IP NMR (202 MHz, MeOD-J4) δ 14.10, 14.08. [00382] HPLC ¾ = 26.24 min (column: Varian Pursuit XRs 5, C ₁₈ , 150x4.6 mm; method:

linear gradient of MeOH (10% to 100%) in H ₂ 0 in 30 min).

[00383] Example 24. [00384] (25 Methyl 2-((((2R,3R,4R,5R)-5-(2-amino-6-methoxy-9H-purin-9-yl)-3,4- dihydroxy-4-methyltetrahydrofuran-2-yl)methoxy)(( _l S ^, )-l-(neopentyloxy)- l- oxopropan-2-ylamino)phosphorylamino)-3-methylbutanoate

[00386] The phosphorodiamidate was synthesized using Method C. [00387] A suspension of 6-O-methyl-2'-C-methylguanosine (250 mg, 0.803 mmole) in anhydrous tetrahydrofuran (4 mL) was reacted with triethylamine (135 μί, 0.964 mmole) and phosphorus oxychloride (89 μί, 0.964 mmole). Anhydrous dichloromethane (4 mL), the HCl salt of methyloxy-L-valine (161.7 mg, 0.964 mmol) and triethylamine (269 μί, 1.93 mmole) were added. The tosylate salt of neopentyloxy-L-alanine (1.33 g, 4.02 mmol) and triethylamine (1.12 mL, 8.03 mmol) were added. After work-up and silica gel column chromatography, 58.2 mg of the phosphorodiamidate was obtained in 11% yield as an off white solid.

[00388] The following are the NMR results of the synthesized compound: [00389] 1H NMR (500 MHz, MeOD-J4) δ 7.98 (2s, IH), 6.00 (s, IH), 4.45-4.35 (m, 2H),

4.34, 4.31 (2d, IH, J=9.1 Hz), 4.23-4.16 (m, IH), 4.06 (2s, 3H), 4.01-3.93 (m, IH), 3.91, 3.88, 3.84, 3.81 (2AB, 2H, J=10.5 Hz), 3.72-3.67 (m, 4H), 2.10- 1.94 (m, IH), 1.38- 1.35 (2d, 3H, J=7.2 Hz), 1.02-0.83 (m, 18H).

[00390] ³¹ P NMR (202 MHz, MeOD-J4) δ 14.62, 14.49. [00391] HPLC t _R = 25.24, 24.81 min (column: Varian Pursuit XRs 5, C18, 150x4.6 mm;

method: linear gradient of MeOH (10% to 100%) in H20 in 30 min).

[0001] Example 25. Methyl l-((((2R,3R,4R)-5-(2-amino-6-methoxy-9H-purin-9-yl)-3,4-dihy droxy-4- methyltetrahydrofuran-2-yl)methoxy)(( _l S')-l-(neopentyloxy)-l-oxopropan-2- ylamino)phosphoryl)pyrrolidine-2-carboxylate

[00394] The phosphorodiamidate prodrug was synthesized using Method C.

[00395] A suspension of 6-O-methyl-2'-C-methylguanosine (250 mg, 0.803 mmole) in anhydrous tetrahydrofuran (4 mL) was reacted with triethylamine (135 μί, 0.964 mmole) and phosphorus oxychloride (89 μί, 0.964 mmole). Anhydrous dichloromethane (4 mL), the HC1 salt of methyloxy-L-proline (145.9 mg, 0.803 mmol) and triethylamine (224 μί, 1.61 mmole) were added to the mixture. In a third step, the tosylate salt of neopentyloxy-L-alanine (1.33 g, 4.02 mmol) and triethylamine (1.12 mL, 8.03 mmol) were added to the mixture. After work-up and silica gel column chromatography, 71 mg of the prodrug was obtained in 14% yield as an off white solid.

[00396] The following are the NMR results of the synthesized compound:

[00397] 1H NMR (500 MHz, MeOD-J4) δ 7.99, 7.96 (2s, 1H), 6.00, 5.96 (2s, 1H), 4.50- 4.15 (m, 5H), 4.15-3.97 (m, 4H), 3.88, 3.81, 3.79 (3d, 2H, J=10.4 Hz), 3.70, 3.68 (2s, 3H), 3.35-3.22 (m, 2H), 2.30-2.18, 2.12-2.03, 2.00-1.74, 1.74- 1.63 (4m, 4H), 1.42, 1.38 (2d, 3H, J=7.1 Hz), 1.00, 0.99 (s, 3H), 0.96, 0.92 (2s, 9H).

[00398] 3 IP NMR (202 MHz, MeOD-J4) δ 12.82, 12.49.

[00399] HPLC t _R = 24.53 min (column: Varian Pursuit XRs 5, C ₁₈ , 150x4.6 mm; method:

linear gradient of MeOH (10% to 100%) in H ₂ 0 in 30 min).

[00400] Example 26. [00401] (2S)-Benzyl 2-((((2R,3R,4R,5R)-5-(2-amino-6-methoxy-9H-purin-9-yl)-3,4- dihydroxy-4-methyltetrahydrofuran-2- yl)methoxy)(butylamino)phosphorylamino)propanoate

[00403] The phosphorodiamidate prodrug was synthesized using Method D. [00404] A suspension of (2R,3R,4R,5R)-2-(2-amino-6-methoxy-9H-purin-9-yl)-5- (hydroxymethyl)-3-methyltetrahydrofuran-3,4-diol (Example 2, 200 mg, 0.642 mmole) in anhyd tetrahydrofuran (5 mL) was allowed to react with triethylamine (105 μί, 0.771 mmole) and benzoxy-L-alaninyl phosphorodichloridate (380 mg, 1.29 mmole). Butylamine (317 μί, 3.21mmol) and triethylamine (447 μί, 3.21 mmol) were added as described in Method D. After work-up and silica gel column chromatography, 43 mg of the prodrug was obtained in 11% yield as an off white solid.

[00405] The following are the NMR results of the synthesized compound: [00406] ³¹ P NMR (202 MHz, MeOD-J4) δ 16.25, 16.09. [00407] 1H NMR (500 MHz, MeOD-J4) δ 7.99, 7.98 (2 x s, 1H, H8), 5.99, 5.98 (2s, 1H,

HI'), 4.35- 4.34 (m, 2H, H5') 4.27 (d, J= 9.0 Hz, 1H, H3'), 4.19- 4.17 (m, 1H, H4'), 4.07 (s, 3H, 60CH ₃ ), 3.91- 3.79 (m, 1H, CHa Ala), 3.83, 3.70 (AB, J _AB = 12.0 Hz, 2H, CH ₂ ester), 2.92- 2.87 (m, 2H, NH-CH ₂ CH ₂ CH ₂ CH ₃ ), 1.47- 1.43 (m, 2H, NH-CH ₂ CH ₂ CH ₂ CH ₃ ), 1.37 (d, J= 7.5 Hz, 3H, CH ₃ Ala), 1.33- 1.29 (m, 2H, NH-CH ₂ CH ₂ CH ₂ CH ₃ ), 0.99, 0.98 (2 x s, 3H, 2'CCH ₃ ), 0.94, 0.93 (2s, 9H, 3 x CH ₃ ester), 0.89 (t, J= 7.5 Hz, 3H, NH-CH ₂ CH ₂ CH ₂ CH ₃ ).

[00408] HPLC t _R = 13.79 min. [00409] MS (TOF EI+) m/z: 607.25 (MH ⁺ , 100%). [00410] HRMS CaeHsgNvOgPi Calculated: 607.2520 found: 607.2504. [00411] Example 27. [00412] (2S)-Neopentyl 2-((((2R,3R,4R,5R)-5-(2-amino-6-methoxy-9H-purin-9-yl)-3,4- dihydroxy-4-methyltetrahydrofuran-2- yl)methoxy)(butylamino)phosphorylamino)propanoate

[00414] The phosphorodiamidate prodrug was synthesized using Method D.

[00415] A suspension of (2R,3R,4R,5R)-2-(2-amino-6-methoxy-9H-purin-9-yl)-5- (hydroxymethyl)-3-methyltetrahydrofuran-3,4-diol (Example 2, 200 mg, 0.642 mmole) in anhyd tetrahydrofuran (5 mL) was allowed to react with triethylamine (105 \L, 0.771 mmole) and 2,2-dimethoxy-L-alaninyl phosphorodichloridate (355 mg, 1.29 mmole). Butylamine (317 \L, 3.21mmol) and triethylamine (447 \L, 3.21 mmol) were added as described in Method D. After work-up and silica gel column chromatography, 11 mg of the prodrug was obtained in 3% yield as an off white solid.

[00416] The following are the NMR results of the synthesized compound: [00417] 3 IP NMR (202 MHz, MeOD-J4) δ 16.25, 16.09. [00418] 1H NMR (500 MHz, MeOD-J4) δ 7.99, 7.98 (2s, 1H, H8), 5.99, 5.98 (2s, 1H,

HI'), 4.35- 4.34 (m, 2H, H5') 4.27 (d, J= 9.0 Hz, 1H, H3'), 4.19- 4.17 (m, 1H, H4'), 4.07 (s, 3H, 60CH ₃ ), 3.91- 3.79 (m, 1H, CHcc Ala), 3.83, 3.70 (AB, J _AB = 12.0 Hz, 2H, CH ₂ ester), 2.92- 2.87 (m, 2H, NH-CH ₂ CH ₂ CH ₂ CH ₃ ), 1.47- 1.43 (m, 2H, NH-CH ₂ CH ₂ CH ₂ CH ₃ ), 1.37 (d, J= 7.5 Hz, 3H, CH ₃ Ala), 1.33- 1.29 (m, 2H, NH-CH ₂ CH ₂ CH ₂ CH ₃ ), 0.99, 0.98 (2s, 3H, 2'CCH ₃ ), 0.94, 0.93 (2s, 9H, 3 x CH ₃ ester), 0.89 (t, J= 7.5 Hz, 3H, NH-CH ₂ CH ₂ CH ₂ CH ₃ ). [00419] HPLC i _R = 14.71 min (System 1) [00420] MS (TOF EI+) m/z: 587.28 (MH ⁺ , 100%). [00421] HRMS C ₂₄ H ₄₂ N ₇ O ₈ P ₁ Calculated: 587.2833 found: 587.2813. [00422] Example 28. [00423] (2S)-Neopentyl 2-((((2R,3R,4R,5R)-5-(2-amino-6-methoxy-9H-purin-9-yl)-3,4- dihydroxy-4-methyltetrahydrofuran-2- yl)methoxy)(benzylamino)phosphorylamino)propanoate

[00425] This phosphorodiamidate was synthesized using Method C. [00426] A suspension of 6-O-methyl-2'-C-methylguanosine (250 mg, 0.803 mmole) in anhydrous tetrahydrofuran (4 mL) was reacted with triethylamine (135 μί, 0.964 mmole) and phosphorus oxychloride (89 μί, 0.964 mmole). Anhydrous dichloromethane (4 mL), benzylamine (88 μί, 0.803 mmole) and triethylamine (112 μί, 0.803 mmole) were added. Finally, the tosylate salt of neopentyloxy-L- alanine (1.33 g, 4.02 mmol) and triethylamine (1.12 mL, 8.03 mmol) were added. After work-up, silica gel column chromatography and preparative HPLC, 22.4 mg of the prodrug was obtained in 5% yield as an off white solid.

[00427] The following are the NMR results of the synthesized compound: [00428] IH NMR (500 MHz, MeOD-J4) δ 7.98, 7.93 (2s, IH), 7.42-7.16 (m, 5H), 5.98 (s,

IH), 4.94-4.82 (m, 2H), 4.42-4.31 (m, 2H), 4.27, 4.21 (2d, IH, J=9.1 Hz), 4.20- 4.12 (m, IH), 4.07 (2s, 3H), 3.97-3.87 (m, IH), 3.85, 3.79, 3.71, 3.65 (2AB, 2H, J=10.6 Hz), 1.34 (pt, 3H), 0.99, 0.96 (2s, 3H), 0.92, 0.90 (2s, 9H).

[00429] 3 IP NMR (202 MHz, MeOD-J4) δ 15.84 and 15.78. [00430] HPLC i _R = 21.57 and 21.92 min (column: Varian Pursuit XRs 5, C ₁₈ , 150x4.6 mm; method: linear gradient of CH ₃ OH (10% to 100%) in H ₂ 0 in 30 min).

[00431] Example 29.

[00432] (2S)-Neopentyl 2-((((2R,3R,4R)-5-(2-amino-6-methoxy-9H-purin-9-yl)-3,4- dihydroxy-4-methyltetrahydrofuran-2- yl)methoxy)(diethylamino)phosphorylamino)propanoate

[00434] The phosphorodiamidate prodrug was synthesized using Method C.

[00435] A suspension of (2R,3R,4R,5R)-2-(2-amino-6-methoxy-9H-purin-9-yl)-5- (hydroxymethyl)-3-methyltetrahydrofuran-3,4-diol (Example 2 300 mg, 0.963 mmole) in anhyd tetrahydrofuran (5 mL) was allowed to react with triethylamine (160 \L, 1.16 mmole) and phosphoryl chloride (110 \L, 1.16 mmole). Diethylamine (100 \L g, 0.963 mmol) and triethylamine (134 \L, 0.963 mmol) were added. Anhydrous dichloromethane (4 mL), and the tosylate salt of neopentyloxy-L- alanine (1.56g, 4.82 mmol) and triethylamine (1.34 mL, 9.64 mmol) were added as described in Method C. After work-up and silica gel column chromatography, 15 mg of the prodrug was obtained in 3% yield as an off white solid.

[00436] The following are the NMR results of the synthesized compound:

[00437] ^J1 P NMR (202 MHz, MeOD-J4) δ 16.76, 16.68.

[00438] 1H NMR (500 MHz, MeOD-J4) δ 7.99, 7.95 (2s, 1H, H8), 5.99, 5.97 (2s, 1H,

HI'), 4.41- 4.28 (m, 3H, H5' and H3'), 4.21- 4.17 (m, 1H, H4'), 4.08 (s, 3H, 60CH ₃ ), 3.91- 3.79 (m, 3H, CHa Ala and CH ₂ ester), 3.18- 3.11 (m, 4H, 2 x CH ₂ amine), 1.40 (d, J= 7.5 Hz, 3H, CH ₃ Ala), 1.11 (t, J= 7.0 Hz, 6H, 2 x CH ₃ amine), 0.99 (s, 3H, 2'CCH ₃ ), 0.96, 0.93 (2 x s, 9H, 3 x CH ₃ ester).

[00439] HPLC ¾ = 11.68 min. [00440] MS (TOF EI+) m/z: 587.28 (MH ⁺ , 100%). [00441] HRMS C ₂ 4H42N ₇ 0 ₈ P ₁ Calculated: 587.2833 found: 587.2813. [00442] Example 30. [00443] (2S)-Neopentyl 2-((((2R,3R,4R,5R)-5-(2-amino-6-methoxy-9H-purin-9-yl)-3,4- dihydroxy-4-methyltetrahydrofuran-2-yl)methoxy) (pyrrolidin- 1 - yl)phosphorylamino)propanoate

[00444] [00445] The phosphorodiamidate prodrug was synthesized using Method C.

[00446] A suspension of (2R,3R,4R,5R)-2-(2-amino-6-methoxy-9H-purin-9-yl)-5- (hydroxymethyl)-3-methyltetrahydrofuran-3,4-diol (Example 2, 250 mg, 0.803 mmole) in anhyd tetrahydrofuran (5 mL) was allowed to react with triethylamine (110 μί, 0.803 mmole) and phosphoryl chloride (70 μί, 0.803 mmole). Pyrrolidine (67 μί, 0.803 mmol) and triethylamine (110 μί, 0.803 mmol) were added. Anhydrous dichloromethane (4 mL), and the tosylate salt of neopentyloxy- L-alanine (1.33 g, 4.02 mmol) and triethylamine (1.12 mL, 8.03 mmol) were added as described in Method C. After work-up and silica gel column chromatography, 38 mg of the prodrug was obtained in 8% yield as an off white solid.

[00447] The following are the NMR results of the synthesized compound: [00448] ³¹ P NMR (202 MHz, MeOD-J4) δ 14.54, 14.42. [00449] 1H NMR (500 MHz, MeOD-J4) δ 8.01, 7.99 (2s, IH, H8), 6.00, 5.99 (2s, IH, HI'), 4.38- 4.35 (m, 2H, H5'), 4.31- 4.28 (m, IH, H3'), 4.21- 4.19 (m, IH, H4'), 4.08, 4.07 (2s, 3H, 60CH ₃ ), 3.93- 3.91 (m, IH, CHcc Ala), 3.88- 3.71 (m, 2H, CH ₂ ester), 3.22- 3.19 (m, 4H, 2 x N-CH ₂ pyrrolidine), 1.87- 1.75 (m, 4H, 2 x CH ₂ pyrrolidine), 1.40, 1.37 (2 x d, J=7.0 Hz, 3H, CH ₃ Ala), 1.00, 0.99 (s, 3H, 2'CCH ₃ ), 0.95, 0.92 (2s, 9H, 3 x CH ₃ ester).

[00450] ¹³ C NMR (125 MHz, MeOD-J4) δ 175.71, 175.67 (C=0 ester), 162.75, 162.73

(C6), 161.93 (C2), 154.56, 154.52 (C4), 139.16 (C8), 116.19, 115.57 (C5), 93.32, 93.16 (CI'), 82.44, 82.40 (d, ³ J _C -c-o-p = 7.6 Hz, C4'), 80.09, 80.03 (C2'), 75.34, 75.29 (CH ₂ ester), 74.64, 74.60 (C3'), 65.86 (d, ² J _C -o-p = 8.8 Hz, C5'), 65.80 (d, 2Jc-o-p = 5.00 Hz, C5'), 54.24 (60CH ₃ ), 51.14, 51.02 (Ccc Ala), 47.84 (d, ² / _C -N-P = 3.77 Hz, N-CH2 pyrrolidine), 47.84 (d, ² / _C -N-P = 3.8 Hz, N-CH2 pyrrolidine), 32.33 (C ester), 27.34, 27.27 (2 x d, Hz, 2 x CH ₂ pyrrolidine), 26.78, 26.74 (CH ₃ ester), 21.20, 21.04 (2 6.3 Hz, CH ₃ Ala), 20.32, 20.26 (2'CCH ₃ ).

[00451] HPLC t _R = 13.41 min.

[00452] MS (TOF EI+) m/z: 585.27 (MH ⁺ , 100%).

[00453] HRMS C24H40N7O8P1 Calculated: 585.2676 found: 585.2662.

[00454] Example 31.

[00455] (2S)-Neopentyl 2-((((2R,3R,4R,5R)-5-(2-amino-6-methoxy-9H-purin-9-yl)-3,4- dihydroxy-4-methyltetrahydrofuran-2- yl)methoxy)(phenylamino)phosphorylamino)propanoate

[00457] The phosphorodiamidate prodrug was synthesized using Method C. [00458] A suspension of 6-0-methyl-2'-C-methylguanosine (250 mg, 0.803 mmole) in anhydrous tetrahydrofuran (4 mL) was reacted with triethylamine (135 μί, 0.964 mmole) and phosphorus oxychloride (89 μί, 0.964 mmole). Anhydrous dichloromethane (4 mL), aniline (73 μί, 0.803 mmole) and triethylamine (112 μί, 0.803 mmole) were added. Finally, the tosylate salt of neopentyloxy-L- alanine (1.33 g, 4.02 mmol) and triethylamine (1.12 mL, 8.03 mmol) were added. After work-up and silica gel column chromatography, 63.0 mg of the prodrug was obtained in 13% yield as an off white solid.

[00459] The following are the NMR results of the synthesized compound:

[00460] 1H NMR (500 MHz, MeOD-J4) δ 7.98, 7.91 (2s, IH), 7.22-7.05, 6.92-6.81 (2m,

5H), 6.05, 6.01 (2s, IH), 4.56-4.42 (m, 2H), 4.32, 4.28 (2d, IH, J=9.0 Hz), 4.27- 4.20 (m, IH), 4.05 (s, 3H), 4.03-3.91 (m, IH), 3.89, 3.79, 3.78 (3d, 2H, J=10.6 Hz), 1.36 (pt, 3H), 1.00, 0.95 (s, 3H), 0.89, 0.85 (2s, 9H).

[00461] ³¹ P NMR (202 MHz, MeOD-J4) δ 8.76 and 8.67.

[00462] HPLC i _R = 15.08 and 15.31 min (column: Varian Pursuit XRs 5, C ₁₈ , 150x4.6 mm; method: linear gradient of ACN (10% to 100%) in H ₂ 0 in 30 min).

[00463] Example 32.

[00464] (2S)-Neopentyl 2-((((2R,3R,4R)-5-(2-amino-6-methoxy-9H-purin-9-yl)-3,4- dihydroxy-4-methyltetrahydrofuran-2-yl)methoxy) (naphthalen- 1 - ylamino)phosphorylamino)propanoate

A suspension of 6-O-methyl-2'-C-methylguanosine (250 mg, 0.803 mmole) in anhydrous tetrahydrofuran (4 mL) was reacted with triethylamine (135 μί, 0.964 mmole) and phosphorus oxychloride (89 μί, 0.964 mmole). Anhydrous dichloromethane (4 mL), 1-naphthylamine (115 mg, 0.803 mmole) and triethylamine (112 μί, 0.803 mmole) were added to the previous mixture. In a third step, the tosylate salt of neopentyloxy-L-alanine (1.33 g, 4.02 mmol) and triethylamine (1.12 mL, 8.03 mmol) were added to the mixture. After work-up, silica gel column chromatography and preparative HPLC, 9.3 mg of the prodrug was obtained in 2% yield as an off white solid.

[00467] The following are the NMR results of the synthesized compound:

[00468] 1H NMR (500 MHz, MeOD-J4) δ 8.09-7.93 (m, 2H), 7.83, 7.79 (2d, IH, J=7.7

Hz), 7.57-7.28 (m, 5H), 6.01, 6.00 (2s, IH), 4.62-4.48 (m, 2H), 4.37, 4.31 (2d, IH, J=9.9 Hz), 4.29-4.23 (m, IH), 4.07-3.93 (m, 4H), 3.75, 3.71, 3.58 (3d, 2H, J=10.5), 1.34, 1.24 (2d, 3H, J=7.2 Hz), 1.00, 0.96 (s, 3H), 0.85, 0.84 (2s, 9H).

[00469] ³¹ P NMR (202 MHz, MeOD-J4) δ 10.12 and 9.70.

[00470] HPLC t _R = 23.49 and 23.75 min (column: Varian Pursuit XRs 5, C ₁₈ , 150x4.6 mm; method: linear gradient of CH ₃ OH (10% to 100%) in H ₂ 0 in 30 min).

[00471] Example 33.

[00472] (25,2'5)-Dibenzyl-((((2R,35,4R,5R)-5-(2-amino-6-methoxy-9H-p urin-9-yl)-3,4- dihydroxy-4-methyltetrahydrofuran-2-yl)methoxy) phosphoryl)-(2,2')-bis-amino- diethanoate

[00474] The phosphorodiamidate prodrug was synthesized using Method B.

[00475] In the first step, a suspension of (2R,3R,4R,5R)-2-(2-amino-6-methoxy-9H-purin-

9-yl)-5-(hydroxymethyl)-3-methyltetrahydrofuran-3,4-diol (Example 2, 250 mg, 0.803 mmole) in anhyd tetrahydrofuran (4 mL) was allowed to react with triethylamine (135 μί, 0.964 mmole) and phosphorus oxychloride (89 μί, 0.964 mmole). In the second step, anhyd dichloromethane (4 mL), the hydrochloride salt of benzyloxy-L- glycine (1.35 g, 4.02 mmol) and triethylamine (1.12 mL, 8.03 mmol) were added to the mixture obtained in step one. After work-up, silica gel column chromatography and preparative HPLC, 77.1 mg of the prodrug was obtained in 14% yield as an off white solid.

[00476] The following are the NMR results analyzing the synthesized compound:

[00477] 1H NMR (500 MHz, MeOD-J4) δ 8.03 (s, 1H), 7.34-7.24 (m, 10H), 6.01 (s, 1H),

5.10 and 5.09 (2s, 4H), 4.47-4.33 (m, 2H), 4.28 (d, 1H, J=8.9 Hz), 4.21-4.15 (m, 1H), 4.03 (s, 3H), 3.78 and 3.76 (2d, 4H, J=8.0 Hz), 0.98 (s, 3H).

[00478] ³¹ P NMR (202 MHz, MeOD-J4) δ 16.55.

[00479] HPLC t _R = 23.89 min (column: Varian Pursuit XRs 5, C ₁₈ , 150x4.6 mm; method:

linear gradient of MeOH (10% to 100%) in H ₂ 0 in 30 min).

[00480] Example 34

[00481] (25,2'5)-Dineopentyl-((((2R,35,4R,5R)-5-(2-amino-6-methoxy-9 H-purin-9-yl)-

3,4-dihydroxy-4-methyltetrahydrofuran-2-yl)methoxy) phosphoryl)-(2,2')-bis- amino-dipropanoate ethanoate

[00483] The phosphorodiamidate prodrug was synthesized using Method B.

[00484] In the first step, a suspension of (2R,3R,4R,5R)-2-(2-amino-6-methoxy-9H-purin-

9-yl)-5-(hydroxymethyl)-3-methyltetrahydrofuran-3,4-diol (Example 2, 250 mg, 0.803 mmole) in anhyd tetrahydrofuran (4 mL) is allowed to react with triethylamine (135 μί, 0.964 mmole) and phosphorus oxychloride (89 μί, 0.964 mmole). In the second step, anhydrous dichloromethane (4 mL), the tosylate salt of neopentyloxy-L- glycine (1.27 g, 4.02 mmol) and triethylamine (1.12 mL, 8.03 mmol) are added to the mixture obtained in step one. After work-up and silica gel column chromatography, 84.8 mg of product is obtained in 16% yield as an off white solid.

[00485] The following are the NMR results of the synthesized compound: [00486] 1H NMR (500 MHz, MeOD-J4) δ 8.05 (s, 1H), 6.02 (s, 1H), 4.50-4.35 (m, 2H),

4.28 (d, 1H, J=8.9 Hz), 4.23-4.17 (m, 1H), 4.06 (s, 3H), 3.82-3.73 (m, 8H), 1.00 (s, 3H), 0.91 and 0.90 (2s, 18H).

[00487] ³¹ P NMR (202 MHz, MeOD-J4) δ 16.62. [00488] HPLC ¾= 26.27 min (column: Varian Pursuit XRs 5, C ₁₈ , 150x4.6 mm; method:

linear gradient of MeOH (10% to 100%) in H ₂ 0 in 30 min).

[00489] Example 35. [00490] (2R,2'R)-Neopentyl 2,2'-((((2R,3R,4R,5R)-5-(2-amino-6-methoxy-9H-purin-9-yl)-

3,4-dihydroxy-4-methyltetrahydrofuran-2- yl)methoxy)phosphoryl)bis(azanediyl)dipropanoate

[00492] This phosphorodiamidate was synthesized using Method B.

[00493] A suspension of 6-O-methyl-2'-C-methylguanosine (250 mg, 0.803 mmole) in anhydrous tetrahydrofuran (4 mL) was reacted with triethylamine (135 μί, 0.964 mmole) and phosphoryl chloride (89 μί, 0.964 mmole). Anhydrous dichloromethane (4 mL), the tosylate salt of neopentyloxy-D-alanine (1.33 g, 4.02 mmol) and triethylamine (1.12 mL, 8.03 mmol) were added. After work-up and silica gel column chromatography, 89.9 mg of the phosphorodiamidate was obtained in 17% yield as an off white solid.

[00494] The following are the NMR results of the synthesized compound:

[00495] 1H NMR (500 MHz, MeOD-J4) δ 8.03 (s, 1H), 5.99 (s, 1H), 4.42-4.31 (m, 2H),

4.29 (d, 1H, J=9.0 Hz), 4.19-4.14 (m, 1H), 4.07 (s, 3H), 4.02-3.92 (m, 2H), 3.88, 3.80, 3.73, 3.68 (2AB, 4H, J=10.5 Hz), 1.40 (pt, 6H), 1.00 (s, 3H), 0.92 and 0.91 (2s, 18H).

[00496] ³¹ P NMR (202 MHz, MeOD-J4) δ 14.11.

[00497] HPLC i _R = 18.33 min (column: Varian Pursuit XRs 5, C ₁₈ , 150x4.6 mm; method:

linear gradient of CH ₃ CN (10% to 100%) in H ₂ 0 in 30 min).

[00498] The phosphoramidate of Eample 35 ((2R,2'R)-Neopentyl 2,2'-((((2R,3R,4R,5R)-5- (2-amino-6-methoxy-9H-purin-9-yl)-3,4-dihydroxy-4-methyltetr ahydrofuran-2- yl)methoxy)phosphoryl)bis(azanediyl)dipropanoate) optimally could be made by the following three step process.

[00499] Ste l.

[00500] To a solution of N-Boc-D-Alanine, (1 in the above scheme) (lOOgm, 0.529 mol) in CH ₂ C1 ₂ (750 mL) was added neopentyl alcohol (44.2 gm, 0.503 mol) at 0 °C followed by addition of EDCI (152 gm, 0.79 mol) in 3 portions. To this mixture a catalytic amount of DMAP (5 mol %) was added at 0 °C and stirred at room temperature for 12 hrs. This mixture was diluted with CH ₂ C1 ₂ and washed with water (2 X 1L), 10% aq.NaHS0 ₄ (2 X 1L) and brine. The organic layers were dried under anhydrous Na ₂ S0 ₄ , filtered, concentrated and dried to afford 126.8 gm of crude material (of compound 2) and was taken to next step without further purification.

[00501] Step 2 [00502] The crude mixture from the above step was dissolved in dioxane (500 mL) followed by addition of HC1 (4M in dioxane) (5eq, 612 mL) at 0 °C and heated to 40 °C for 15 hrs. This mixture was cooled to room temperature and the volatiles were removed under reduced pressure. Trace amounts of dioxane was removed by azetroping with toluene (2 X 200 mL). To this solid was added anhydrous diethyl ether (1L) and stirred vigorously for lhr. The solids were filtered off and dried under vacuum to afford 87.3 gm of D-alanine neopentyl ester hydrochloride salt (3 in above scheme).

[00503] Step 3

[00504] A suspension of (2R,3R,4R,5R)-2-(2-amino-6-methoxy-9H-purin-9-yl)-5- (hydroxymethyl)-3-methyltetrahydrofuran-3,4-diol (35 gm, 0.112 mol), and POCl ₃ (10.5 mL, 0.112 mol) in THF (500 mL) was cooled to -78 °C. Et ₃ N (15.7 mL, 0.112 mol) was added slowly, and the solution was stirred at -78 °C for 30

31

min. At this stage P NMR confirms the completion conversion to dichloridate. To this mixture was added the compound from step 2 (D-Alanine neopentyl ester hydrochloride salt) (110 gm, 0.563 mol) dissolved in CH ₂ C1 ₂ (1L) at -78 °C. Et ₃ N (125.5 mL, 0.900 mol) was added in dropwise fashion and the solution was stirred at -78 °C for 1 hr. This mixture was slowly warmed to room temperature and stirred for 15 hrs. Then the solids were filtered off and the filtrate was concentrated and purified by column chromatography using a stepwise gradient of methanol (2-5%) in CH ₂ C1 ₂ to obtain 36.6 g (0.544 mmol) of the phosphorodiamidate (2R,2'R)-neopentyl 2,2'-((((2R,3R,4R,5R)-5-(2-amino-6- methoxy-9H-purin-9-yl)-3,4-dihydroxy-4-methyltetrahydrofuran -2- yl)methoxy)phosphoryl)bis(azanediyl)dipropanoate.

[00505] Example 36.

[00506] (2S,2'S)-Benzyl 2,2'-((((2R,3R,4R,5R)-5-(2-amino-6-methoxy-9H-purin-9-yl)-3, 4- dihydroxy-4-methyltetrahydrofuran-2- yl)methoxy)phosphoryl)bis(azanediyl)bis(4-methylpentanoate)

[00508] The phosphorodiamidate prodrug was synthesized using Method B.

[00509] (2R,3R,4R,5R)-2-(2-amino-6-methoxy-9H-purin-9-yl)-5-(hydroxy methyl)-3- methyltetrahydrofuran-3,4-diol (0.3192 g, 1.03 mmol) in anhyd. tetrahydrofuran (5.5 mL) was allowed to react with triethylamine (1.2 equiv, 0.18 mL) and phosphoryl chloride (0.11 mL, 1.2 equiv). Anhydrous dichloromethane (8 mL) and the tosylate salt of H-Leu-OBzl (5 equiv, 5.15 mmol, 2.0356 g) and anh. triethylamine (10.3 mmol, 1.55 mL) were added as describe in Method B. After work-up, the residue was purified by flash chromatography using CHCl ₃ /MeOH (4%) to recover the wanted prodrug (0.2248 g, 0.28 mmol, 28%).

[00510] The following are the mass and NMR results of the synthesized compound:

[00511] 1H NMR (500 MHz, CDC\ ₃ -d4) δ 7.72 (s, 1H, H8 guanine), 7.33 (m, 10H, 2 x 5H

Bz), 5.92 (s, 1H, H 1'), 5.15 (m, 4H, 2 x NH-CH(CH ₂ -CH(CH ₃ ) ₂ )-CO-0-CH ₂ - Ph), 4.55 (m, 1H, H5'), 4.49 (m, 1H, H3'), 4.22 (m, 1H, H5'), 4.12 (m, 1H, H4'), 4.05 (s, 3H, OCH ₃ G), 3.59 (t, 2H, 2 x NH-CH(CH ₂ -CH(CH ₃ ) ₂ )-CO-0-CH ₂ -Ph), 1.66 (m, 2H, 2 x NH-CH(CH ₂ -CH(CH ₃ ) ₂ )-CO-0-CH ₂ -Ph), 1.53 (m, 2H, NH- CH(CH ₂ -CH(CH ₃ ) ₂ )-CO-0-CH ₂ -Ph), 1.44 (m, 2H, NH-CH(CH ₂ -CH(CH ₃ ) ₂ )-CO- 0-CH ₂ -Ph), 0.97 (s, 3H, CH ₃ 2'C), 0.87 (m, 12H, 4 x NH-CH(CH ₂ -CH(CH ₃ ) ₂ )- CO-0-CH ₂ -Ph).

[00512] ¹³ C NMR (CDC1 ₃ -J4) δ 174.61 (s, CO H-Leu-O-Bz), 174.22 (s, CO H-Leu-O- Bz), 161.61 (s, C6 guanine), 159.62 (s, C2 guanine), 152.86 (s, C4 guanine), 137.94 (s, C8 guanine), 135.45 (d, 2 x Q Bz), 128.56 (m, IOC, 2 x C _para Bz & 4 x C _meta Bz & 4 x C _ortho Bz), 115.72 (s, C5 guanine), 91.84 (s, C 1'), 81.07 (s, C 4'), 79.41 (s, C 2'), 74.40 (s, C 3'), 67.05 (d, 2 x NH-CH(CH ₂ -CH(CH ₃ ) ₂ )-CO-0-CH ₂ - Ph), 65.07 (s, C5'), 53.84 (s, OC¾ G), 50.47 (d, 2 x NH-CH(CH ₂ -CH(CH ₃ ) ₂ )- CO-0-CH ₂ -Ph), 43.36 (d, 2 x NH-CH(CH2-CH(CH ₃ ) ₂ )-CO-0-CH ₂ -Ph), 24.64 (d, 2 x NH-CH(CH ₂ -CH(CH ₃ ) ₂ )-CO-0-CH ₂ -Ph), 22.71 (m, 4 x NH-CH(CH ₂ - CH(CH3) ₂ )-CO-0-CH ₂ -Ph), 20.32 (s, CH ₃ 2'C).

[00513] ³¹ P NMR (CDC\ ₃ -d4) δ 13.87. [00514] MS: 797.83 (M), found 798.3611 (M+H), calculated 798.3592 (M+H)

820.3420 (M+Na ⁺ ), 836.3176 (M+K ⁺ ).

[00515] Example 37. [00516] (25,2'5)-Dineopentyl-((((2R,35,4R,5R)-5-(2-amino-6-methoxy-9 H-purin-9-yl)- 3,4-dihydroxy-4-methyltetrahydrofuran-2-yl)methoxy) phosphoryl)-(2,2')-bis- amino-4-methylthiobutanoate

[00517] [00518] The phosphorodiamidate prodrug was synthesized using Method A.

[00519] In the first step, a solution of (2R,3R,4R,5R)-2-(2-amino-6-methoxy-9H-purin-9- yl)-5-(hydroxymethyl)-3-methyltetrahydrofuran-3,4-diol (Example 2, 250 mg, 0.803 mmole) in anhyd triethylphosphate (1 mL) was allowed to react with phosphorus oxychloride (148 μί, 1.61 mmole). In the second step, anhyd dichloromethane (4 mL), the tosylate salt of neopentyloxy-L-methionine (1.41 g, 4.02 mmol) and diisopropylethylamine (1.40 mL, 8.03 mmol) were added to the mixture obtained in step one. After work-up, silica gel column chromatography and preparative TLC, 7 mg of the prodrug was obtained in 1.1% yield as an off white solid.

[00520] The following are the NMR results of the synthesized compound: [00521] 1H NMR (500 MHz, MeOD-J4) δ 7.99 (s, 1H), 5.98 (s, 1H), 4.45-4.35 (m, 2H), 4.33 (d, 1H, J=8.8 Hz), 4.25-4.16 (m, 1H), 4.07 (s, 3H), 3.97-3.68 (m, 6H), 2.71- 2.45 (m, 4H), 2.19- 1.80 (m, 10H), 1.00 (s, 3H), 0.95 and 0.93 (2s, 18H).

[00522] ³¹ P NMR (202 MHz, MeOD-J4) δ 14.14. [00523] HPLC ¾= 21.97 min (column: Varian Pursuit XRs 5, C ₁₈ , 150x4.6 mm; method:

linear gradient of ACN (10% to 100%) in H ₂ 0 in 30 min).

[00524] Example 38. [00525] (2S,2'S)-Benzyl 2,2'-((((2R,3R,4R,5R)-5-(2-amino-6-methoxy-9H-purin-9-yl)-3, 4- dihydroxy-4-methyltetrahydrofuran-2- yl)methoxy)phosphoryl)bis(azanediyl)bis(3methyl butanoate)

[00527] The compound was prepared according to Method B from (2R,3R,4R,5R)-2-(2- amino-6-methoxy-9H-purin-9-yl)-5-(hydroxymethyl)-3-methyltet rahydrofuran- 3,4-diol, (Example 2, 250 mg, 0.80 mmol), POCl ₃ (0.07 mL, 0.80 mmol), Et N (0.11 mL, 0.80 mmol), L-valine benzyl ester tosylate salt (0.91g, 2.41 mmol), and Et ₃ N (0.67 mL, 4.82 mmol) in 10 mL of 1 : 1 mixture of dry THF and DCM. Crude product was purified by column chromatography in gradient CHC1 ₃ to CHC1 ₃ : MeOH 95:5, to give a pure product as a white foam (64 mg, 10%).

[00528] ³¹ P NMR (202 MHz, MeOD-J4) δ 15.11. [00529] 1H NMR (500 MHz, MeOD-J4) δ 7.94 (s, 1H, H ₈ ), 5.98 (s, 1H, H _r ), 5.19- 5.06

(m, 4H, 2 x CH2 ester), 4.40-4.34 (m, 2H, ¾' and H3'), 4.20- 4.18 (m, 1H, H4'), 4.04 (s, 3H, 60CH ₃ ), 3.72-3.68 (m, 2H, 2 x CHa Val), 2.02- 1.94 (m, 2H, 2 x CH Val), 0.99 (s, 3H, 2'CCH3), 0.87 (d, J= 7.00 Hz, 3H, CH ₃ Val), 0.84 (d, J= 7.00 Hz, 3H, CH ₃ Val), 0.79(d, J= 7.0 Hz, 3H, CH ₃ Val), 0.77 (d, J= 7.0 Hz, 3H, CH ₃ Val).

[00530] ¹³ C NMR (125 MHz, MeOD-J4) δ 174.53 (C=0 ester), 162.75 (C6), 161.90 (C2),

154.54 (C4), 139.46 (C8), 137.21 (ipso Ph), 137.14 (ipso Ph), 129.61, 129.59, 129.58, 129.55, 129.41, 129.36 (2Ph), 115.68 (C5), 93.29 (CI '), 82.49 (d, ³ J _C -c-o-p = 8.8 Hz, C4'), 79.94 (C2'), 74.97 (C3'),67.93 (2 x CH2 ester), 66.89 (d, ² J _C -o-p = 5.0 Hz, C5'), 61.09 (d, ² / _C -N-P = 4.50 Hz, 2 x Ccc Val), 54.27 (60CH3), 33.20 (d, J=6.3 Hz, 2 x C Val), 20.37 (2'CCH ₃ ), 19.50 (CH ₃ Val), 19.42 (CH ₃ Val), 18.17 (CH ₃ Val), 18.12 (CH ₃ Val).

[00531] HPLC t _R = 19.63 min.

[00532] Example 39.

[00533] (2S,2'S)-Dicyclohexyl 2,2'-((((2R,3R,4R,5R)-5-(2-amino-6-methoxy-9H-purin-9- yl)-3,4-dihydroxy-4-methyltetrahydrofuran-2-yl)methoxy)phosp horyl) bis(azanediyl)bis(3methylbutanoate)

The compound was prepared according to Method B from (2R,3R,4R,5R)-2-(2- amino-6-methoxy-9H-purin-9-yl)-5-(hydroxymethyl)-3-methyltet rahydrofuran-

3,4-diol, (Example 2, 250 mg, 0.80 mmol), POCl ₃ (0.07 mL, 0.80 mmol), Et ₃ N (0.11 mL, 0.80 mmol), L- valine cyclohexyl ester chloridate salt (0.57g, 2.41 mmol), and Et ₃ N (0.67 mL, 4.82 mmol) in 10 mL of 1 : 1 mixture of dry THF and DCM. Crude product was purified by column chromatography using a gradient of CHC1 ₃ to CHC1 ₃ : MeOH 95:5, to give a pure product as a white foam (32 mg, 5%). [00536] ³¹ P NMR (202 MHz, MeOD-J4) δ 15.28.

[00537] 1H NMR (500 MHz, MeOD-J4) δ 7.96 (s, 1H, ¾), 5.98 (s, 1H, H _r ), 4.81-4.76

(m, 2H, 2 x OCH ester), 4.21-4.35 (m, 2H, ¾·), 4.33 (d, J= 9.0 Hz, 1H, H3'), 4.20- 4.17 (m, 1H, H4'), 4.07 (s, 3H, 60CH ₃ ), 3.66-3.63 (m, 2H, 2 x CHa Val), 2.07- 1.98 (m, 2H, 2 x CH Val), 1.85- 1.80 (m, 4H, 2 x CH ₂ ester), 1.75- 1.71 (m, 4H, 2 x CH ₂ ester), 1.55- 1.29 (m, 12H, 6 x CH ₂ ester), 1.00 (s, 3H, 2'CCH3), 0.95 (d, J= 6.5 Hz, 3H, CH ₃ Val), 0.90 (d, J= 6.5 Hz, 3H, CH ₃ Val), 0.89(d, J= 6.5 Hz, 3H, CH ₃ Val), 0.82 (d, J= 6.5 Hz, 3H, CH ₃ Val).

[00538] ¹³ C NMR (125 MHz, CD ₃ OD) δ 174.12 (d, 5.0 Hz, C=0 ester), 162.77

(C6), 161.94 (C2), 154.56 (C4), 139.47 (C8), 115.66 (C5), 93.34 (CI '), 82.55 (d, 3Jc-c-o-p = 6.30 Hz, C4'), 79.91 (C2'), 75.02 (C3'), 74.86 (OCH ester), 74.84 (OCH ester), 67.06 (d, ² J _C -o-p = 5.0 Hz, C5'), 61.04 (d, ² / _C -N-P = 4.5 Hz, 2 x Ccc Val), 54.22 (60CH3), 33.21 (2 x C Val), 32.60 (4x CH ₂ ester), 26.43 (CH ₂ ester), 26.40 (CH ₂ ester), 24.68 (2 x CH ₂ ester), 24.64 (2x CH ₂ ester), 20.27 (2'CCH ₃ ), 19.48 (CH ₃ Val), 19.37 (CH ₃ Val), 18.08 (CH ₃ Val), 18.02 (CH ₃ Val).

[00539] HPLC t _R = 22.99 min.

[00540] Example 40.

[00541] (2S,2'S)-Neopentyl 2,2'-((((2R,3R,4R,5R)-5-(2-amino-6-methoxy-9H-purin-9-yl)- 3,4-dihydroxy-4-methyltetrahydrofuran-2- yl)methoxy)phosphoryl)bis(azanediyl)bis(2-phenylacetate)

[00543] The phosphorodiamidate prodrug was synthesized using Method B. [00544] A suspension of 6-0-methyl-2'-C-methylguanosine (250 mg, 0.803 mmole) in anhydrous tetrahydrofuran (4 mL) was reacted with triethylamine (135 μί, 0.964 mmole) and phosphoryl chloride (89 μί, 0.964 mmole). Anhydrous dichloromethane (4 mL), the tosylate salt of neopentyloxy-L-phenylglycine (1.58 g, 4.02 mmol) and triethylamine (1.12 mL, 8.03 mmol) were added. After workup and silica gel column chromatography, 181.6 mg of the phosphorodiamidate was obtained in 28% yield as an off white solid.

[00545] The following are the NMR results of the synthesized compound:

[00546] 1H NMR (500 MHz, MeOD-J4) δ 7.79 (s, 1H), 7.38-7.19 (m, 10H), 5.97 (s, 1H),

5.02-4.92 (m, 2H), 4.35-4.25 (m, 2H), 4.14-4.01 (m, 5H), 3.88, 3.81, 3.66, 3.56 (4d, 4H, J=10.4 Hz), 0.92 (s, 3H), 0.74 and 0.71 (2s, 18H).

[00547] ³¹ P NMR (202 MHz, MeOD-J4) δ 13.55.

[00548] HPLC t _R = 23.51 min (column: Varian Pursuit XRs 5, C ₁₈ , 150x4.6 mm; method:

linear gradient of CH ₃ CN (10% to 100%) in H ₂ 0 in 30 min).

[00549] Example 41.

[00550] (2S,2'S)-Dicyclohexyl 2,2'-((((2R,3R,4R,5R)-5-(2-amino-6-methoxy-9H-purin-9- yl)-3,4-dihydroxy-4-methyltetrahydrofuran-2- yl)methoxy)phosphoryl)bis(azanediyl)bis(2-phenylacetate)

[00552] The phosphorodiamidate prodrug was synthesized using Method B.

[00553] A suspension of 6-O-methyl-2'-C-methylguanosine (250 mg, 0.803 mmole) in anhydrous tetrahydrofuran (4 mL) was reacted with triethylamine (135 \L, 0.964 mmole) and phosphoryl chloride (89 μί, 0.964 mmole). Anhydrous dichloromethane (4 mL), the tosylate salt of cyclohexyloxy-L-phenylglycine (1.63 g, 4.02 mmol) and triethylamine (1.12 mL, 8.03 mmol) were added to the previous mixture. After work-up, silica gel column chromatography and preparative HPLC, 85.7 mg of the prodrug as a mixture of 3 stereoisomers ((R,R), (S,R), (S,S)), was obtained in 13% yield as an off white solid.

[00554] The following are the NMR results of the synthesized compound: [00555] 1H NMR (500 MHz, MeOD-J4) δ 7.93, 7.80, 7.78 (3s, 1H), 7.41-7.19 (m, 10H),

5.98, 5.95, 5.94 (3s, 1H), 4.96-4.87 (m, 2H), 4.78-4.61 (m, 2H), 4.35-4.25 (m, 2H), 4.15-4.02 (m, 5H), 1.82- 1.16 (m, 20H), 0.99, 0.97, 0.91 (3s, 3H).

[00556] ³¹ P NMR (202 MHz, MeOD-J4) δ 13.62, 13.57, 13.53. [00557] HPLC ¾ = 31.61 min (column: Varian Pursuit XRs 5, C ₁₈ , 150x4.6 mm; method:

linear gradient of CH ₃ OH (10% to 100%) in H ₂ 0 in 30 min).

[00558] Example 42. [00559] (25,2'5)-Dibenzyl-((((2R,35,4R,5R)-5-(2-amino-6-methoxy-9H-p urin-9-yl)-3,4- dihydroxy-4-methyltetrahydrofuran-2-yl)methoxy) phosphoryl)-bis-pyrrolidine-2- methanoate

[00561] The phosphorodiamidate prodrug was synthesized using Method A.

[00562] In the first step, a solution of (2R,3R,4R,5R)-2-(2-amino-6-methoxy-9H-purin-9- yl)-5-(hydroxymethyl)-3-methyltetrahydrofuran-3,4-diol (Example 2, 150 mg, 0.482 mmole) in anhyd triethylphosphate (1 mL) was allowed to react with phosphorus oxychloride (89 μί, 0.964 mmole). In the second step, anhyd dichloromethane (2.4 mL), the hydrochloride salt of benzyloxy-L-proline (583 mg, 2.41 mmol) and diisopropylethylamine (840 μί, 4.82 mmol) were added to the mixture obtained in step one. After work-up, silica gel column chromatography and preparative TLC, 8.4 mg of the prodrug was obtained in 2.3% yield as an off white solid.

[00563] The following are the NMR results of the synthesized compound:

[00564] 1H NMR (500 MHz, MeOD-J4) δ 7.94 (s, 1H), 7.36-7.27 (m, 10H), 5.93 (s, 1H),

5.86-5.80 and 5.78-5.72 (2m, 4H), 4.43-4.32 (m, 3H), 4.27 (q, 2H, J=4.2 Hz), 4.19-4.12 (m, 1H), 4.05 (s, 3H), 3.36-3.09 (m, 4H), 2.24-2.14, 2.04-1.64 and 1.61- 1.52 (3m, 8H), 1.00 (s, 3H).

[00565] ³¹ P NMR (202 MHz, MeOD-J4) δ 11.40.

[00566] HPLC i _R =28.05 min (column: Varian Pursuit XRs 5, C ₁₈ , 150x4.6 mm; method:

linear gradient of MeOH (10% to 100%) in H ₂ 0 in 30 min).

[00567] Example 43.

[00568] ((2R,3R,4R,5R)-5-(2-Amino-6-methoxy-9H-purin-9-yl)-3,4-dihyd roxy-4- methyltetrahydrofuran-2-yl)methyl di-N- butylphosphinate

[00570] The compound of Example 2, ((2R,3R,4R,5R)-2-(2-amino-6-methoxy-9H-purin-9- yl)-5-(hydroxymethyl)-3-methyltetrahydrofuran-3,4-diol, 1.0428 g, 3.35 mmol) was dissolved in anhyd THF (17 mL), and to it was added anhyd Et ₃ N (0.56 mL, 4.02 mmol, 1.2 equiv). The mixture was allowed to stir at rt for 30 min, after which the solution was cooled to -78 °C, and POCl ₃ (0.38 mL, 4.08 mmol, 1.2 equiv) was added dropwise. The solution was allowed to return to rt over 1.5 h. The formation of the intermediate was monitored by phosphorus NMR (7.88 ppm). Then 5 equiv of w-butylamine (1.70 mL, 17.2 mmol) was added, followed by anhyd dichloromethane (17 mL) up to total dissolution. The reaction was cooled to -78 °C after which anhyd Et ₃ N (4.7 mL, 33.7 mmol, 10 equiv) was added dropwise. The solution was then allowed to return to rt and stirred for an additional 5 h, at the end of which time phosphorus NMR monitoring suggested the formation of the diamidate (17.06 ppm). The solvent was evaporated under reduced pressure and the residue was purified by flash chromatography using CHCl ₃ /MeOH. The resulting residue was washed several times with water to removed the excess of triethylamine, yielding 0.4172 g (0.83 mmol, 25%) of desired product.

[00571] HPLC : ¾= 12.31 min.

[00572] 1H NMR (CDC1 ₃ ): 7.86 ppm (s, 1H, ¾ guanine), 6.05 ppm (s, 1H, H _r ), 5.68 ppm

(broad s, 2H, NH2 guanine), 4.44 - 4.23 ppm (m, 4H, CH _{2 5} · & ¾· & ¾·), 4.04 ppm (s, 3H, OCH ₃ guanine), 2.88 ppm (m, 4H, 2xNHCH ₂ CH ₂ CH ₂ CH ₃ ), 1.41 ppm(m, 4H, 2xNHCH ₂ CH ₂ CH ₂ CH ₃ ), 1.27 ppm (m, 4H, 2x NHCH ₂ CH ₂ CH ₂ CH ₃ ), 0.99 ppm (s, 3H, CH3 ₂ <), 0.82 ppm (m, 6H, 2x NHCH ₂ CH ₂ CH ₂ CH ₃ ).

[00573] ¹³ C NMR (CDC1 ₃ ) 161.40 ppm (s, C6 guanine), 159.69 ppm (s, C2 guanine),

153.07 ppm (s, C4 guanine), 137.64 ppm (s, CH8 guanine), 115.24 ppm (s, C5 guanine), 91.36 ppm (s, CHI'), 81.11 ppm (s, CH4'), 79.36 ppm (s, C2'), 73.41 ppm (s, CH3'), 64.02 ppm (s, CH25'), 53.75 ppm (s, OCH3), 40.84 ppm (s, 2xNHCH2CH2CH2CH3), 33.91 ppm (s, 2xNHCH2CH2CH2CH3), 20.22 ppm (s, CH32'), 20.22 ppm (s, NHCH2CH2CH2CH3), 19.76 ppm (s, NHCH2CH2CH2CH3), 13.63 ppm (s, NHCH2CH2CH2CH3), 13.45 ppm (s, NHCH2CH2CH2CH3).

[00574] ³¹ P NMR (CDC1 ₃ ) 17.40 ppm (s).

[00575] MS: (M + H ⁺ ), calculated: 502.2543, found: 502.2562 , 524.2374

(M + H ⁺ + Na), 565.249 (M + H ⁺ + MeCN + Na). [00576] Example 44. [00577] ((2R,3R,4R,5R)-5-(2-amino-6-methoxy-9H-purin-9-yl)-3,4-dihyd roxy-4- methyltetrahydrofuran-2-yl)methyl dimorpholinophosphinate

[00578] [00579] The compound of Example 2, ((2R,3R,4R,5R)-2-(2-amino-6-methoxy-9H-purin-9- yl)-5-(hydroxymethyl)-3-methyltetrahydrofuran-3,4-diol, 0.9088 g, 2.92 mmol) was dissolved in anhyd THF (14 mL) and to it was added anhyd Et ₃ N (0.49 mL, 3.50 mmol, 1.2 equiv). The mixture was allowed to stir at rt for 30 min, after which the solution was cooled to -78 °C and POCl ₃ (0.33 mL, 3.50 mmol, 1.2 equiv) was added dropwise. The solution was allowed to return to rt over 1.5 h. The formation of the intermediate was monitored by phosphorus NMR (8.54 ppm). Then 5 equiv of morpholine (1.26 mL, 14.6 mmol) was added followed by anhyd dichloromethane (24 mL). The dissolution was not totally complete. The reaction mixture was cooled to -78 °C after which anhyd Et N (4.10 mL, 29.2 mmol, 10 equiv) was added dropwise. The solution was then allowed to return to rt and stirred for an additional 5 h, at the end which time phosphorus NMR monitoring suggested the formation of the diamidate (14.66 ppm). The solvent was evaporated under reduced pressure and the residue was purified by flash chromatography using CHCl ₃ /MeOH (up to 6%). Then the resulting residue was washed several times with water to removed the excess of triethylamine. The triethylamine as well as some of the final product moved to the aqueous layer, so a back wash of the aqueous layer was undertaken with EtOAc to recover the desired phosphorodiamidate product. (Yield: 0.0336 g, 0.063 mmol 18%).

[00580] HPLC : ¾= 3.72 min. [00581] 1H NMR (CDC1 ₃ ) 7.75 ppm (s, 1H, H8 guanine), 6.00 ppm (s, 1H, HI '), 5.51-4.48 ppm (m, 1H, CH2 5'), 4.41 - 4.35 ppm (m, 2H, CH2 5' & H3'), 4.28-4.26 ppm (m, 1H, H4'), 4.07 ppm (s, 3H, OCH3 guanine), 3.66-3.62 ppm (m, 8H, 4xO(CH2CH2)2N morpholine), 3.19-3.12 ppm (m, 8H, 4xO(CH2CH2)2N morpholine), 1.03 ppm (s, 3H, CH3 2').

[00582] ¹³ C NMR (CDC1 ₃ ) 161.71 ppm (s, C ₆ guanine), 159.54 ppm (s, C ₂ guanine),

152.87 ppm (s, C ₄ guanine), 137.33 ppm (s, C¾ guanine), 115.87 ppm (s, C ₅ guanine), 91.56 ppm (s, CH _r ), 81.21 ppm (s, CH ₄ <), 79.36 ppm (s, C ₂ <), 74.43 ppm (s, CH ₃ <), 67.05-67.01 ppm (d, 4xO(CH ₂ CH ₂ ) ₂ N morpholine) 64.86-64.82 ppm (d, CH2 ₅ , 53.96 ppm (s, OCH3 guanine), 44.72-44.69 ppm (d, 4xO(CH ₂ CH2) ₂ N), 20.35 ppm (s, CH ₃ v).

[00583] ³¹ P NMR (CDC1 ₃ ) 14.85 ppm (s).

[00584] Example 45

[00585] (2S,2'S)-2,4-Difluorobenzyl 2,2'-((((2R,3R,4R,5R)-5-(2-amino-6-methoxy-9H- purin-9-yl)-3,4-dihydroxy-4-methyltetrahydrofuran-2-yl)metho xy) phosphoryl) bis(azanediyl)dipropanoate

[00586] The phosphorodiamidate was prepared according to the Method B.

[00587] In a first step, a solution of ((2R,3R,4R,5R)-2-(2-amino-6-methoxy-9H-purin-9- yl)-5-(hydroxymethyl)-3-methyltetrahydrofuran-3,4-diol (300 mg, 0.96 mmol) in anhydrous tetrahydrofuran (5 mL) was reacted with triethylamine (0.13 mL, 0.96 mmol) and phosphorus oxychloride (87 \L, 0.96 mmol). In a second step, anhydrous dichloromethane (5 mL), L-alanine 2,4-difluorobenzyl ester tosylate salt (1.86 g, 4.80 mmol) and triethylamine (1.30 mL, 9.62 mmol) were added. After work-up, silica gel column chromatography 108 mg of the phosphorodiamidate was obtained in 15% yield as an off white solid [00588] 1H NMR (500MHz, CD ₃ OD) : δ 7.95 (s, IH, ¾), 7.45 (m, 2H, OCH ₂ P/i), 6.9 (m, 4H, OCH ₂ Ph), 5.05-5.2 (m, 4H, 2x OCH ₂ Ph), 4.45-4.37 (m, 2Η, ¾·), 4.35 (d, 1Η, Η3 ), 4.25 (m, 1Η, ¾·), 3.95 (q, 2Η, CHa-Ala), 1.35-1.24 (m, 9H, CH ₃ -Ala and 60CH ₃ ), 1.05 (s, 3H, 2'CCH ₃ ),

[00589] ¹³ C NMR (125 MHz, CD ₃ OD): δ 175.30 (C=0), 162.76 (C6), 161.63 (C2),

154.54 (C4), 139.21 (C8), 131.60 (ipso Ph), 115.71 (C5), 112.41 (dd, J= 3.8, 21.5 Hz, Ph C-C-F), 104.81 (t, J= 25.4 Hz, Ph F-C-F), 93.08 (CI'), 82.29 (d, ³ J _P -o-c-c= 7.6 Hz, C4'), 80.13 (C2'), 74.81 (C3'), 66.20 (d, ² J _P _ ₀ -c= 5.5 Hz, C5'), 61.26 (d, J= 3.7, OCH ₂ ester), 61.23 (d, J= 3.7 Hz, OCH ₂ ester), 54.43 (60CH ₃ ), 51.07 (2x Ca Ala), 20.92, 20.84 (2d, ² J _P _ _N _ _C = 5.94 Hz, CH ₃ Ala), 20.51 (2'CCH ₃ ),

[00590] ³¹ P NMR (202 MHz, CD ₃ OD): δ 13.84

[00591] ¹⁹ F (470 MHz, CD ₃ OD) δ: -113.71, -111.13

[00592] HPLC t _R : 18.57 min (Varian Polaris C18-A (10 μΜ) column using a mobile phase of water/acetonitrile ingradient (90/10 to 0/100 v/v in 30 min, System 1)

[00593] MS (ES+): m/z (M + H ⁺ ) - 786.22; Accurate mass calculated for: C ₃₂ H ₃ 7F ₄ N ₇ O ₁₀ P

- 786.2276

[00594] Example 46

[00595] (2S,2'S)-Dicyclohexyl 2,2'-((((2R,3R,4R,5R)-5-(2-amino-6-ethoxy-9H-purin-9- yl)-3,4-dihydroxy-4-methyltetrahydrofuran-2- yl)methoxy)phosphoryl)bis(azanediyl)dipropanoate

[00596] The phosphorodiamidate was synthesized using Method B. [00597] In a first step, a solution of ((2R,3R,4R,5R)-2-(2-amino-6-methoxy-9H-purin-9- yl)-5-(hydroxymethyl)-3-methyltetrahydrofuran-3,4-diol (300 mg, 0.92 mmol) in anhydrous tetrahydrofuran (5 mL) was reacted with triethylamine (0.12 mL, 0.92 mmol) and phosphorus oxychloride (84 μί, 0.92 mmol). In a second step, anhydrous dichloromethane (4 mL), L-alanine cyclohexyl ester tosylate salt (954 mg, 4.61 mmol) and triethylamine (1.20 mL, 9.22 mmol) were added. After workup and silica gel column chromatography, 43 mg of phosphorodiamidate was obtained in 6.6% yield, as an off white solid.

[00598] 1H NMR (500 MHz, CD ₃ OD): δ 7.95 s (1H, ¾), 6.0 s (1H, H _r ), 4.7 m (2H, 2x

OCH cHex), 4.58 (q, 4H, J= 7.0 Hz, 2x CH ₂ cHex), 4.4 (m, 2H, ¾·), 4.38 (m, 1H, ¾·), 4.2 (m, 1H, H ₄ , 3.91 (m, 2H, 2x CHa Ala), 1.4- 1.9 (m, 20H, 2x cHex), 1.45 (t, 3H, J= 7.32Hz, 60CH ₂ CH ₃ ), 1.34 d of d (6Η, J= 7.5 Hz 2x CH ₃ Ala), 0.98 s (3H, 2'CMe),

[00599] ¹³ C NMR (125 MHz, CD ₃ OD): δ 175.10 (d, ³ J _P _ _N _c-c= 6.0Hz, C=0), 175.04 (d,

3JP_ _N _c-c= 6.0 Hz, C=0), 162.41 (C6), 161.89 (C2), 154.60 (C4), 139.24 (C8), 115.63 (C5), 93.17 (CI '), 82.36 (d ³ J _P - ₀ -c-c= 7.67Hz, C4'), 80.04 (C2'), 74.86, 74.80 (2x OCH cHex), 74.59 (C3'), 66.41 (d, ² J _P _ ₀ -c= 4.86Hz, C5'), 61.57 (OCH ₂ CH ₃ ), 51.20 (CHa Ala), 36.32 (CH ₂ cHex), 32.50 (CH ₂ cHex), 32.47 (CH ₂ cHex), 32.43 (CH ₂ cHex), 26.45 (CH ₂ cHex), 25.36 (CH ₂ cHex), 24.69 (CH ₂ cHex), 24.65 (CH ₂ cHex), 21.09 (d, J=5.9, 2x CH ₃ Ala), 20.32 (2'CCH ₃ ), 14.52 (OCH ₂ CH ₃ ),

[00600] ³¹ P NMR (202 MHz, CD ₃ OD): 514.10

[00601] HPLC = 19.55 min (System 1).

[00602] MS (ES+)m z: 712.34 (M+H ⁺ ). Accurate mass calculated for C ₃₁ H ₅₁ N ₇ O ₁₀ P - 712.3435

[00603] Example 47

[00604] (2S,2'S)-Benzyl 2,2'-((((2R,3R,4R,5R)-5-(2-amino-6-ethoxy-9H-purin-9-yl)-3,4 - dihydroxy-4-methyltetrahydrofuran-2- yl)methoxy)phosphoryl)bis(azanediyl)dipropanoate

[00605] The phosphorodiamidate was synthesized using Method B.

[00606] In a first step, a solution of ((2R,3R,4R,5R)-2-(2-amino-6-methoxy-9H-purin-9- yl)-5-(hydroxymethyl)-3-methyltetrahydrofuran-3,4-diol (300 mg, 0.92 mmol) in anhydrous tetrahydrofuran (5 mL) was reacted with triethylamine (0.12 mL, 0.92 mmol) and phosphorus oxychloride (84 μί, 0.92 mmol). In a second step, anhydrous dichloromethane (4 mL), L-alanine benzyl ester tosylate salt (1.62 g, 4.61 mmol) and and triethylamine (1.20 mL, 9.22 mmol) were added. After workup and silica gel column chromatography, 96 mg of phosphorodiamidate was obtained in 14% yield, as an off white solid.

[00607] 1H NMR (500 MHz, CD ₃ OD): δ 8.05 (s, IH, ¾), 7.2-7.4 m (10H, OCH ₂ P/i), 6.0

(s, IH, Hr), 5.1 (m, 4H, 2x OCH ₂ Ph), 4.5 (q, 2Η, 60CH ₂ CH ₃ ), 4.4 (m, 2H, ¾·), 4.25 (d, IH, ¾·), 4.2 m (IH, ¾·), 3.95 (q, 2H, J= 7.2 Hz, 2x CHa Ala), 1.4 (t, 3H, J=7.3 Hz, 60CH ₂ CH ₃ ), 1.3 (d, 3Η, J= 2.4 Hz, CH ₃ Ala), 0.95 (s, 3H, 2'CCH ₃ ).

[00608] ¹³ C NMR (125 MHz, CD ₃ OD): 175.85 (C=0), 175.48 (C=0), 162.23 (C6), 161.78

(C2), 154.10 (C4), 139.12 (C8), 129.79, 129.67, 129.65, 129.62, 129.41, 129.39, 129.34, 129.32, 129.25, 129.24 (OCH ₂ P/i), 114.87 (C5), 93.24 (CI '), 82.51 (d, 3J _P _o-c-c= 7.8 Hz, C4'), 80.08 (C2'), 74.75 (C3'), 68.00, 67.97 (OCH ₂ Ph), 66.21 (d, ² J _P _o-c= 5.4 Hz, C5'), 63.92 (OCH ₂ CH ₃ ), 51.14 (d, J= 4.2 Hz, CHa Ala), 20.98 (d, J= 6.1 Hz, CH ₃ Ala), 20.93 (d, J= 6.1 Hz, CH ₃ Ala), 20.49 (2'CCH ₃ ), 14.96 (OCH ₂ H ₃ ).

[00609] ³ *P NMR (202 MHz, CD ₃ OD) : δ 13.92. [00610] HPLC t _R = 17.59 min (System 1).

[00611] MS (ES+) m/z : 728.28 (M+H ⁺ ). Accurate mass found for C ₃₃ H4 ₃ N ₇ O ₁₀ P - 728.2809. [00612] Example 48

[00613] (2S,2'S)-Neopentyl 2,2'-((((2R,3R,4R,5R)-5-(2-amino-6-ethoxy-9H-purin-9-yl)- 3,4-dihydroxy-4-methyltetrahydrofuran-2- yl)methoxy)phosphoryl)bis(azanediyl)dipropanoate

[00614] The phosphorodiamidate was synthesized using Method B.

[00615] In a first step, a solution of ((2R,3R,4R,5R)-2-(2-amino-6-methoxy-9H-purin-9- yl)-5-(hydroxymethyl)-3-methyltetrahydrofuran-3,4-diol (300 mg, 0.92 mmol) in anhydrous tetrahydrofuran (5 mL) was reacted with triethylamine (0.12 mL, 0.92 mmol) and phosphorus oxychloride (84 \L, 0.92 mmol). In a second step, anhydrous dichloromethane (4 mL), L-alanine 2,2-dimethylpropyl ester tosylate salt (1.52 g, 4.61 mmol) and triethylamine (1.20 mL, 9.22 mmol) were added. After work-up and silica gel column chromatography, 80 mg of phosphorodiamidate was obtained in 12% yield, as an off white solid.

[00616] 1H NMR (500 MHz, MeOD-J4) δ 8.0 (s, IH, ¾), 5.95 (s, IH, H _r ), 4.55 (q, 2H,

J= 7.02Hz, OCH ₂ CH ₃ ), 4.4 (m, 2H, ¾·), 4.3 (d, IH, J= 9.1 Hz, ¾·), 4.2 (m, IH, H ₄ , 4.0 (q, 2H, J= 8.4 Hz, Ha Ala), 3.85-3.82 (m, 2H, OCH ₂ ester), 1.45 (t, 3H, J=7.0 Hz, OCH ₂ CH ₃ ), 1.3 (d, 3Η, J= 2.4 Hz, CH ₃ Ala), 0.96 (s, 3H, 2'CCH ₃ ), 0.95 (2s, 18H, 2x OCH ₂ C(CH ₃ )).

[00617] ¹³ C NMR (125 MHz, MeOD-J4) δ 175.68 (C=0), 175.61 (C=0), 162.39 (C6),

161.91 (C2), 154.60 (C4), 139.27 (C8), 115.56 (C5), 93.16 (CI '), 82.35 (d, ³ J _P _ ₀ -c- c= 8.4 Hz, C4'), 80.03 (C2'), 75.37 (2x O H ₂ C(CH ₃ ) ₃ ), 74.85 (C3'), 66.42 (d, ² J _P _ o-c= 4.9 Hz, C5'), 63.52 (OCH ₂ CH ₃ ), 51.06 (d, ² J _P _ _N -c= 8.73 Hz, Ccc Ala), 32.27 (2x OCH ₂ C(CH ₃ ) ₃ ), 26.77 (s, OCH ₂ C(CH ₃ ) ₃ ), 20.99 (CH ₃ Ala), 20.28 (2'C H ₃ ), 14.87 (OCH ₂ H ₃ ) [00618] ³¹ P NMR (202 MHz, MeOD-J4): δ 14.00 [00619] HPLC i _R = 19.65 min (System 1). [00620] MS (ES+)m z: 688.34 (M+H ⁺ ). Accurate mass found for C^HsiNvOioP - 688.3435

[00621] Example 49 [00622] (2S)-Cyclohexyl 2-((((2R,3R,4R,5R)-5-(2-amino-6-methoxy-9H-purin-9-yl)-3,4- dihydroxy-4-methyltetrahydrofuran-2-yl)methoxy)((S)-l-(cyclo pentyloxy)-l- oxopropan-2-ylamino)phosphorylamino)propanoate

[00623] The phosphorodiamidate was prepared according to Method C. [00624] In the first step, a solution of 6-O-methyl-2' -C-methylguanosine (550 mg, 1.76 mmol) in anhydrous tetrahydrofuran (8 mL) was allowed to react with triethylamine (300 \L, 2.11 mmol) and phosphorus oxychloride (200 \L, 2.11 mmole). L-alanine cyclohexyl ester tosylate salt (370 mg, 1.76 mmol) and triethylamine (0.5 mL, 3.52 mmol) were added. Anhydrous dichloromethane (2 mL), and the L-alanine cyclopentyl ester tosylate salt (2.90 g, 8.80 mmol) and triethylamine (2.50 mL, 17.60 mmol) were added. After work-up and silica gel column chromatography, 280 mg of the prodrug was obtained in 23% yield as an off white solid.

[00625] 1H NMR (500 MHz, CDC1 ₃ ) 57.74 (s, 1H, ¾), 5.96 (s, 1H, H _r ), 5.18 (m, 1H, H

3·), 4.76 (m, 1H, cyclopentyl or cyclohexyl), 4.61 (m, 1H, 1H H ₅ ), 4.51 (m, 1H, CH cyclopentyl or cyclohexyl), 4.32 (m, 1H, 1H ¾·), 4.23 (m, 1H, ¾·), 4.06 (s, 60CH ₃ ), 3.92 (m, 2H, 2x CHcc Ala), 1.86-1.57 (m, 18H, 4x CH ₂ cyclopentyl and 5x CH ₂ cyclohexyl), 1.36 (m, 6H, 2x CH ₃ Ala), 1.00 (s, 3H, 2'CCH ₃ ). [00626] ³¹ P NMR (202 MHz, CDC1 ₃ ) δ 13.68, 13.48 [00627] HPLC i _R = 14.97 min (System 1). [00628] HPLC t _R = 17.37 min (System 2).

[00629] MS (TOF ES ⁺ ) m/z: 684.32 (M+H ⁺ ), 706.27 (M+Na ⁺ ), 722.27 (M+K ⁺ ); accurate mass: calculated for C29H47N7O10P: 684.3122, found 684.3154.

[00630] Example 50

[00631] (2S)-Neopentyl 2-((((2R,3R,4R,5R)-5-(2-amino-6-methoxy-9H-purin-9-yl)-3,4- dihydroxy-4-methyltetrahydrofuran-2- yl)methoxy)(pentylamino)phosphorylamino)propanoate

[00632] The phosphorodiamidate was synthesized using Method D.

[00633] In a first step, a suspension of ((2R,3R,4R,5R)-2-(2-amino-6-methoxy-9H-purin-9- yl)-5-(hydroxymethyl)-3-methyltetrahydrofuran-3,4-diol (200 mg, 0.642 mmol) in anhydrous tetrahydrofuran (5 mL) was allowed to react with triethylamine (105 μί, 0.771 mmol) and L-alaninyl neopentyl ester phosphorodichloridate (355 mg, 1.29 mmol). Pentylamine (0.56 mL, 3.21mmoles) and triethylamine (0.67 mL, 3.21 mmol) were added. After work-up and silica gel column chromatography, 11 mg of phosphorodiamidate was obtained in 3% yield as an off white solid.

1H NMR (500 MHz, MeOO-d ₄ ) δ 8.02, 8.01 (2 s, IH, ¾), 6.00, 5.99 (2 s, IH, Hi , 4.36- 4.33 (m, 2H, ¾■) 4.29, 4.28 (2d, J= 9.0 Hz, IH, ¾■), 4.20- 4.17 (m, IH, H4 , 4.07 (s, 3H, 60CH ₃ ), 3.94- 3.90 (m, IH, CHa Ala), 3.87, 3.83, 3.75, 3.70 (2AB, JAB= 10.5 Hz, 2H, CH ₂ ester), 2.90- 2.85 (m, 2H, NH- CH ₂ CH ₂ CH ₂ CH ₂ CH ₃ ), 1.50- 1.43 (m, 2H, NH-CH ₂ CH ₂ CH ₂ CH ₃ ), 1.39, 1.37 (2d, J= 6.0 Hz, 3H, CH ₃ Ala), 1.31-1.21 (m, 4H, NH-CH ₂ CH ₂ CH ₂ CH ₂ CH ₃ and NH- CH ₂ CH ₂ CH ₂ CH ₂ CH ₃ ), 0.99, 0.98 (2s, 3H, 2'CCH ₃ ), 0.94, 0.93 (2s, 9Η, OCH ₂ C(CH ₃ ) ₃ ), 0.87-85 (m, 3Η, NH-CH ₂ CH ₂ CH ₂ CH ₂ CH _J ).

[00635] ¹³ C NMR (125 MHz, MeOO-d ₄ ) δ 175.75, 175.68 (C=0 ester), 162.72 (C6),

161.92 (C2), 154.61, 154.57 (C4), 139.25, 139.11 (C8), 115.43 (C5), 93.05, 92.94 (CI '), 82.41, 82.34 (2d, Hz, C4'), 80.08, 80.04 (C2'), 75.34, 75.31 (OCH ₂ C(CH ₃ ) ₃ ), 74.60, 74.37 (C3'), 65.90, 65.49 (2d, ² J _C -o-p=5.0 Hz, C5'), 54.21 (60CH ₃ ), 51.27, 51.16 (Ca Ala), 42.06 (NH- H ₂ CH ₂ CH ₂ CH ₂ CH ₃ ), 32.76 (d, ³ J _C - C- _N - _P =5.0 Hz NH-CH ₂ H ₂ CH ₂ CH ₂ CH ₃ ), 32.72 (d, ³ / _C - _C - _N - _P =6.3 HZ NH- CH ₂ CH ₂ CH ₂ CH ₂ CH ₃ ), 32.27 (O H ₂ C(CH ₃ ) ₃ ), 30.11, 30.08 (NH- CH ₂ CH ₂ CH ₂ CH ₂ CH ₃ ), 26.74, 26.72 (OCH ₂ C(CH ₃ ) ₃ ), 23.46 (NH- CH ₂ CH ₂ CH ₂ H ₂ CH ₃ ), 21.19, 21.96 (2d, ³ / _C - _C - _N - _P =6.3 HZ, CH ₃ Ala), 20.24 (2'CCH ₃ ), 14.40 (NH-CH ₂ CH ₂ CH ₂ CH ₂ H ₃ ).

[00636] ³¹ P NMR (202 MHz, MeOD-<¾) δ 16.28, 16.12.

[00637] HPLC ¾ = 17.11 min (System 1).

[00638] MS (TOF EI+) m/z: 624.34 (MNa ⁺ , 100%);

[00639] HRMS C ₂₅ H ₄₅ N ₇ 0 ₈ P ₁ Calculated: 602.3067 found: 602.3057

[00640] Example 51

[00641] (2S)-Benzyl 2-((((2R,3R,4R,5R)-5-(2-amino-6-methoxy-9H-purin-9-yl)-3,4- dihydroxy-4-methyltetrahydrofuran-2- yl)methoxy)(morpholino)phosphorylamino)propanoate

[00643] The phosphorodiamidate was prepared according to Method C.

[00644] In the first step, a solution of ((2R,3R,4R,5R)-2-(2-amino-6-methoxy-9H-purin-9- yl)-5-(hydroxymethyl)-3-methyltetrahydrofuran-3,4-diol (250 mg, 0.803 mmol) in anhydrous tetrahydrofuran (5 mL) was allowed to react with triethylamine (110 μί, 0.803 mmol) and phosphorus oxychloride (70μί, 0.803 mmole). The morpholine (70 μί, 0.803 mmol) and triethylamine (110 μί, 0.803 mmol) were added. Anhydrous dichloromethane (4 mL), and the L-alanine benzyl ester tosylate salt (1.41 g, 4.02 mmol) and triethylamine (1.12 mL, 8.03 mmol) were added as described in Method C. After work-up and silica gel column chromatography, 108 mg of phosphorodimaidate was obtained in 22% yield as an off white solid.

[00645] 1H NMR (500 MHz, MeOD-d ₄ ) 7.96, 7.95 (2s, IH, H8), 7.37-7.30 (m, 5H,

OCH ₂ Ph), 5.98, 5.97 (2s, IH, HI'), 5.20-5.12 (m, 2H, OCH ₂ Ph), 4.42-4.33 (m, 3Η, Η5' and Η3'), 4.22-4.18 (m, 1Η, Η4'), 4.07, 4.06 (2s, 3Η, 60CH ₃ ), 3.96-3.82 (m, IH, CHa Ala), 3.52-3.79 (m, 4H, 2x 0(CH ₂ ) ₂ ), 3.11-3.08 (m, 4Η, 2x N(CH ₂ ) ₂ ), 1.38, 1.33 (2d, J=7.5 Hz, 3H, CH ₃ Ala), 1.01, 1.00 (2s, 3H, 2'CCH ₃ ).

[00646] ¹³ C NMR (125 MHz, MeOO-d ₄ ) 175.38, 175.34 (2d, 3.8 Hz, C=0 ester), 162.79, 162.75 (C6), 161.91 (C2), 154.52, 154.47 (C4), 139.40, 139.31 (C8), 137.31 (ipso OCH ₂ P/i), 129.60, 129.57, 129.47, 129.38, 129.32 (OCH ₂ P/i), 115.71, 115.60 (C5), 93.46, 93.30 (CI'), 82.39, 82.33 (2d, 3.8 Hz, C4'), 80.04 (C2'), 74.98, 74.82 (C3'), 68.05 (d, ² J _C -o-p= 3.8 Hz, C5'), 67.97 (d, ² J _C -o-p= 5.0 Hz, C5'), 66.53, 66.49 (O H ₂ Ph and 0( H ₂ ) ₂ ), 54.23 (60CH ₃ ), 51.24, 50.99 (Ca Ala), 45.74 (N(CH ₂ ) ₂ ), 20.79 (d, 5.0 Hz, CH ₃ Ala), 20.55 (d, ³ / _C -C-N- P= 6.3 Hz, CH ₃ Ala), 20.29, 20.23 (2'CCH ₃ ).

[00647] ³¹ P NMR (202 MHz, MeOD-d ₄ ) 14.65, 14.30.

[00648] HPLC ¾ = 11.29, 11.60 min (System 1)

[00649] MS (TOF ES+) m/z: 644.22 (M+Na ⁺ , 100%);

[00650] HRMS calculated: 622.2390 found: 622.2381 [00651] Example 52 [00652] (2S)-Neopentyl 2-((((2R,3R,4R,5R)-5-(2-amino-6-methoxy-9H-purin-9-yl)-3,4- dihydroxy-4-methyltetrahydrofuran-2- yl)methoxy)(cyclopropylamino)phosphorylamino)propanoate

[00653] The phosphorodiamidate was synthesized using Method D. [00654] In a first step, a suspension of ((2R,3R,4R,5R)-2-(2-amino-6-methoxy-9H-purin-9- yl)-5-(hydroxymethyl)-3-methyltetrahydrofuran-3,4-diol (200 mg, 0.642 mmol) in anhydrous tetrahydrofuran (5 mL) was allowed to react with triethylamine (105 \L, 0.771 mmol) and 2,2-dimethylpropoxy-L-alaninyl phosphorodichloridate (355 mg, 1.29 mmol). Cyclopropylamine (0.33 mL, 3.21mmoles) and triethylamine (0.67 mL, 3.21 mmol) were added. After work-up and silica gel column chromatography, 14 mg of phosphorodiamidate was obtained in 3% yield as an off white solid.

[00655] 1H NMR (500 MHz, MeOD-<¾) δ 8.04, 8.03 (2s, IH, ¾), 6.01, 5.99 (2s, IH, H _r ),

4.42- 4.31 (m, 2H, ¾■) 4.29-4.25 (m, IH, ¾■), 4.20- 4.17 (m, IH, ¾■), 4.08, 4.07 (2s, 3H, 60CH ₃ ), 3.97- 3.92 (m, IH, CHcc Ala), 3.87, 3.82, 3.75, 3.68 (2AB, /AB= 10.5 Hz, 2H, OCH ₂ C(CH ₃ ) ₃ ), 2.41-2.36 (m, IH, CH cyclopropylamine), 1.39, 1.38 (2d, J=6.5 Hz, 3H, CH ₃ Ala), 0.99, 0.98 (2s, 3H, 2'CCH ₃ ), 0.94, 0.92 (2s, 9H, OCH ₂ C(CH ₃ ) ₃ ester), 0.58-52 (m, 4Η, 2 x CH ₂ cyclopropylamine).

[00656] ¹³ C NMR (125 MHz, MeOD-<¾) δ 175.70, 175.67 (C=0 ester), 162.71 (C6),

161.99 (C2), 154.62, 154.56 (C4), 139.24, 139.00 (C8), 115.42, 115.33 (C5), 93.07, 92.82 (CI '), 82.40, 82.24 (2d, Hz, C4'), 80.10, 80.04 (C2'), 75.35, 75.30 (O H ₂ C(CH ₃ ) ₃ ). 74.56, 74.23 (C3'), 65.86, 65.23 (2d, ² J _C -o-p=5.0Hz, C5'), 54.20 (60CH ₃ ), 51.30, 51.14 (Ca Ala), 32.26 (OCH ₂ C(CH ₃ ) ₃ ), 26.73, 26.70 (OCH ₂ C( H ₃ )3), 23.46 (CH cyclopropylamine), 21.23, 20.99 (2d,

Hz, CH ₃ Ala), 20.23 (2'CCH ₃ ), 7.46, 7.26 (2x H ₂ cyclopropylamine).

[00657] ³¹ P NMR (202 MHz, MeOD-d ₄ ) δ 16.03, 15.77.

[00658] HPLC ¾ = 13.17 min (System 1).

[00659] MS (TOF EI+) m/z: 594.29 (MNa ⁺ , 100%);

[00660] HRMS C ₂₃ H ₃₉ N ₇ 0 ₈ P ₁ Calculated: 572.2587 found: 572.2598

[00661] Example 53

[00662] (2S,2'S)-Neopentyl 2,2'-((((2R,3R,4R,5R)-5-(2-amino-6-methoxy-9H-purin-9-yl)- 3,4-dihydroxy-4-methyltetrahydrofuran-2- yl)methoxy)phosphoryl)bis(azanediyl)bis(4-methylpentanoate)

[00663] The phosphorodiamidate was prepared according to Method B.

[00664] In a first step, a suspension of ((2R,3R,4R,5R)-2-(2-amino-6-methoxy-9H-purin-9- yl)-5-(hydroxymethyl)-3-methyltetrahydrofuran-3,4-diol (250 mg, 0.80 mmol) in anhydrous tetrahydrofuran (4.3 mL) was reacted with triethylamine (130 μί, 0.96 mmol) and phosphorus oxychloride (90 μί, 0.96 mmol). In a second step, anhydrous dichloromethane (2.3 mL), L-leucine 2,2-dimethylpropyl ester tosylate salt (1.51 g, 4.05 mmol) and triethylamine (1.12 mL, 8.04 mmol) were added. After work-up and silica gel column chromatography, 5 mg of phosphorodiamidate was obtained in 1% yield as an off white solid.

1H NMR (500 MHz, CDC1 ₃ ) δ 7.67 (s, IH, ¾), 5.90 (s, IH, H _r ), 4.74 (m, IH, IH HsO, 4.66 (m, IH, ¾·), 4.25 (m, IH, IH ¾·), 4.23 (m, IH, ¾·), 4.06 (s, 3H, 60CH ₃ ), 3.97-3.91 (2m, 2H, 2 x CHa Leu), 3.82-3.75 (m, 4H, 2x OCH ₂ C(CH ₃ ) ₃ ), 1.73- 1.68 (m, 2H, 2x CHy Leu), 1.58- 1.45 (m, 4H, 2x CH ₂ Leu), 1 1.00 (s, 3H, 2'CCH ₃ ), 0.97-0.93 (m, 30H, 4x CH ₃ Leu, 2x OCH ₂ C(CH ₃ ) ₃ ).

[00666] ¹³ C NMR (125 MHz, CDC1 ₃ ) δ 175.20 (C=0 Leu), 174.58 (C=0 Leu), 161.61

(C6), 159.63 (C2), 152.86 (C4), 137.05 (C8), 115.96 (C5), 91.25 (CI '), 81.33 (C4'), 79.65 (C2'), 75.19 (C3'), 74.77, 74.65 (2x O H ₂ C(CH ₃ ) ₃ ), 65.59 (C5'), 53.65 (60CH ₃ ), 52.96, 52.82 (2x Ca Leu ), 43.77 (2x <¾β Leu), 31.34, 31.24 (2x OCH ₂ C(CH ₃ ) ₃ ), 26.52, 26.38 (2x OCH ₂ C(CH ₃ ) ₃ ), 24.62, 24.56 (2x CHy Leu), 22.68 (2x CH ₃ Leu), 22.01 (2x CH ₃ Leu), 20.43 (2'C H ₃ ).

[00667] ³¹ P NMR (202 MHz, CDC1 ₃ ) δ 13.76.

[00668] HPLC t _R = 25.39 min (System 1).

[00669] MS (TOF ES ⁺ ) m/z: 758.42 (M+H ⁺ ), 780.40 (M+Na ⁺ ); accurate mass: calculated for C ₃ 4H ₆₁ N ₇ O ₁₀ P: 758.4218, found 758.4201.

[00670] Example 54

[00671] (2S,2'S)-Dicyclohexyl 2,2'-((((2R,3R,4R,5R)-5-(2-amino-6-methoxy-9H-purin-9- yl)-3,4-dihydroxy-4-methyltetrahydrofuran-2- yl)methoxy)phosphoryl)bis(azanediyl)bis(4-methylpentanoate)

[00672] The phosphorodiamidate was prepared according to Method B.

[00673] In a first step, a suspension of ((2R,3R,4R,5R)-2-(2-amino-6-methoxy-9H-purin-9- yl)-5-(hydroxymethyl)-3-methyltetrahydrofuran-3,4-diol (590 mg, 1.89 mmol) in anhydrous tetrahydrofuran (8 mL) was reacted with triethylamine (320 \L, 2.27 mmol) and phosphorus oxychloride (210 \L, 2.27 mmol). In a second step, anhydrous dichloromethane (5.4 mL), L-leucine cyclohexyl ester tosylate salt (3.64 g, 9.45 mmol) and triethylamine (2.67 mL, 18.9 mmol) were added. After work-up and silica gel column chromatography, 100 mg of phosphorodiamidate was obtained in 7% yield as an off white solid.

[00674] 1H NMR (500 MHz, CDC1 ₃ ) δ 7.71 (s, 1H, ¾), 5.95 (s, 1H, H _r ), 4.76-4.70 (m,

2H, 2 x OCH cyclohexyl), 4.60 (m, 1H, ¾·), 4.48-4.47 (m, 1H, ¾·), 4.25-4.23 (m, 1H, ¾·), 4.20-4.17 (m, 1H, ¾·), 4.02 (s, 3H, 60CH ₃ ), 3.89-3.77 (m, 2H, 2x CHa Leu), 1.79 (m, 4H, 2x CH ₂ cyclohexyl), 1.67- 1.65 (m, 4H, 2x CH ₂ cyclohexyl), 1.50- 1.24 (m, 10H, 2x CH ₂ cyclohexyl, 2x CH ₂ Leu and 2x CHy Leu), 1.24 (s, 3H, CH ₃ 2'), 0.98-0.84 (m, 12H, 4x CH ₃ Leu).

[00675] ¹³ C NMR (125 MHz, CDC1 ₃ -J4) δ 174.25 (C=0 Leu), 173.84 (C=0 Leu), 161.55

(C6), 159.71 (C2), 152.93 (C4), 137.87 (C8), 115.68 (C5), 91.93 (CI '), 81.12 (C4'), 79.41 (C2'), 74.71 (C3'), 73.87, 73.72 (2x OCH cyclohexyl), 65.23 (C5'), 53.43 (60CH ₃ ), 52.94, 52.80 (2x Ca Leu), 43.60, 43.54 (2s, 2x <¾β Leu), 31.46 (4x CH ₂ cyclohexyl), 25.23 (2x CH ₂ cyclohexyl), 24.56, 24.51 (2x CHj Leu), 23.59 (4x CH ₂ cyclohexyl), 22.61, 22.03 (2x CH ₃ Leu), 20.31 (s, 2'CCH ₃ ).

[00676] ³¹ P NMR (202 MHz, CDC1 ₃ -J4) δ 13.78

[00677] HPLC ¾=20.11 min (System 1).

[00678] MS (TOF ES ⁺ ) m/z: 782.42 (M+ H ⁺ ), 804.41 (M+Na ⁺ ); accurate mass: calculated for C ₃ 6H ₆₁ N ₇ O ₁₀ P: 782.4218, found 782.4234.

[00679] Example 55

[00680] (2S,2'S)-Dibenzyl 2,2'-((((2R,3R,4R,5R)-5-(2-amino-6-methoxy-9H-purin-9-yl)- 3,4-dihydroxy-4-methyltetrahydrofuran-2- yl)methoxy)phosphoryl)bis(azanediyl)bis(4-methylthiobutanoat e)

[00681]

[00682] The phosphorodiamidate was prepared according to Method B.

[00683] In a first step, a suspension of ((2R,3R,4R,5R)-2-(2-amino-6-methoxy-9H-purin-9- yl)-5-(hydroxymethyl)-3-methyltetrahydrofuran-3,4-diol (300 mg, 0.96 mmol) in anhydrous tetrahydrofuran (5 mL) was reacted with triethylamine (130 μί, 0.96 mmol) and phosphorus oxychloride (90 μί, 0.96 mmol). In a second step, anhydrous dichloromethane (5 mL), L-methionine benzyll ester tosylate salt (1.98 g, 4.82 mmol) and triethylamine (1.34 mL, 9.63 mmol) were added. After workup and silica gel column chromatography, 130 mg of phosphorodiamidate was obtained in 16% yield as an off white solid.

[00684] 1H NMR (500 MHz, CD ₃ OD) δ 7.95 (s, 1H, ¾), 7.36-7.30 (2x OCU ₂ Ph) 5.97 (s,

1H, H _r ), 5.19-5.05 (m, 2x OCH ₂ Ph), 4.41-4.31 (m, 2Η, ¾< and ¾·), 4.19-4.17 (m, 1Η, ¾·), 4.04 (s, 3Η, 60C¾), 4.07-4.03 (m, 2Η, 2x CHD Met), 2.51-2.39 (m, 4H, 2x CH ₂ y Met), 1.99, 1.95 (2s, 6H, 2x CH ₃ Met), 1.90-1.80 (m, 4H, 2x CH ₂ D Met), 1.00 (s, 3H, CH ₃ ).

[00685] ¹³ C NMR (125 MHz, CD ₃ OD) δ 173.78, 173.75 (2d, ³ J _C -C-N-P = 4.8 Hz, 2x C=0

Met), 161.91 (C6), 161.04 (C2), 153.73 (C4), 138.55 (C8), 136.39, 136.35 (2x ipso OCH ₂ Ph), 128.77, 128.66, 128.63, 128.56, 128.53 (2x OCH ₂ Ph), 114.79 (C5), 92.37 (CI '), 81.59 (d, ³ J _C -c-o-p = 7.3 Hz, C4'), 79.20 (C2'), 74.00 (C3'), 67.25 (d, ² J c-o-p = 56.3 Hz, C5'), 65.81, 65.77 (2x OCH ₂ Ph), 53.87, 53.72 (2x CH Met), 53.42 (OCH ₃ ), 33.62, 33.57 (2x Cy Met), 29.98, 29.93 (2x CD Met), 19.50 (2'CCH ₃ ), 14.36, 14.30 (SCH ₃ ).

[00686] ³¹ P NMR (202 MHz, CD ₃ OD) δ 14.11

[00687] HPLC t _R = 19.05 min (System 1). [00688] MS (TOF ES+) mJ . 856.25 (M+Na ⁺ , 100%); [00689] HRMS C ₃₄ H ₅₇ N ₇ O ₁₀ PiS ₂ calculated: 834.2720 found: 834.2692 [00690] Example 56 [00691] (2S,2'S)-Dicyclohexyl 2,2'-((((2R,3R,4R,5R)-5-(2-amino-6-methoxy-9H- yl)-3,4-dihydroxy-4-methyltetrahydrofuran-2- yl)methoxy)phosphoryl)bis(azanediyl)bis(4-methylthiobutanoat e)

[00692]

[00693] The phosphorodiamidate was prepared according to Method B. [00694] In a first step, a suspension of ((2R,3R,4R,5R)-2-(2-amino-6-methoxy-9H-purin-9- yl)-5-(hydroxymethyl)-3-methyltetrahydrofuran-3,4-diol (300 mg, 0.96 mmol) in anhydrous tetrahydrofuran (5 mL) was reacted with triethylamine (130 \L, 0.96 mmol) and phosphorus oxychloride (90 \L, 0.96 mmol). In a second step, anhydrous dichloromethane (5 mL), L-methionine cyclohexyl ester tosylate salt (1.94 g, 4.82 mmol) and triethylamine (1.34 mL, 9.63 mmol) were added. After work-up and silica gel column chromatography, 160 mg of phosphorodiamidate was obtained in 20% yield as an off white solid.

[00695] ¹ H NMR (500 MHz, CD ₃ OD) δ 8.07 (s, 1H, ¾), 6.00 (s, 1H, H _r ), 4.79-4.74,

4.73-4.70 (2m, 2H, 2x OCH ester), 4.45-4.36 (m, 2Η, ¾·), 4.30 (d, 1Η, J=8.5 Hz, ¾·), 4.23-4.20 (m, 1H, H ₄ <), 4.08 (s, 3H, 60CH ₃ ), 4.02-3.97 (m, 2H, 2x CHD Met), 2.61-2.48 (m, 4Η, 2x CH ₂ y Met), 2.07, 2.05 (2s, 6H, 2x CH ₃ Met), 2.02- 1.87 (m, 4H, 2x CH ₂ Met), 1.86- 1.79 (m, 4H, 2x CH ₂ ester), 1.73- 1.71 (m, 4H, 2x CH ₂ ester), 1.47- 1.30 (m, 12H, 6x CH ₂ ester), 1.01 (s, 3H, CH ₃ ), 0.95 and 0.93 (2s, 18H, 6x CH ₃ ester).

[00696] ¹³ C NMR (125 MHz, CD ₃ OD) δ 174.30, 174.21 (2d, ³ J _C -C-N-P = 5.3 Hz, 2x C=0),

162.66 (C6), 161.987 (C2), 154.19 (C4), 139.34 (C8), 115.05 (C5), 93.33 (CI '), 82.61 (d, ³ Jc-c-o-p = 6.5 Hz, C4'), 80.03 (C2'), 75.07, 75.02 (2x OCH ester), 74.84 (C3'), 66.74 (d, ² J c-o-p = 5.3 Hz, C5'), 54.87, 54.79 (2x CD Met), 54.41 (OCH ₃ ), 34.67, 34.62 (2d, ³ J _C -C-N-P = 2.6 Hz, 2x CH ₂ Met), 32.53 (CH ₂ ester), 30.95, 30.87 (2x CH ₂ Met), 26.47 (CH ₂ ester), 26.44 (CH ₂ ester), 26.41 (2x CH ₂ y Ile), 24.71 (2 x CH ₂ ester), 24.68 (2 x CH ₂ ester), 20.33 (2'CCH ₃ ), 15.29, 15.23 (SCH ₃ ).

[00697] ³¹ P NMR (202 MHz, CD ₃ OD) δ 14.26.

[00698] HPLC t _R = 21.60 min (System 1).

[00699] MS (TOF ES+) m/z: 840.32 (M+Na ⁺ , 100%);

[00700] HRMS C ₃₄ H ₅₇ N ₇ O ₁₀ PiS ₂ calculated: 818.3346 found: 818.3359

[00701] Example 57

[00702] (2S,2'S)-Benzyl 2,2'-((((2R,3R,4R,5R)-5-(2-amino-6-methoxy-9H-purin-9-yl)-3, 4- dihydroxy-4-methyltetrahydrofuran-2- yl)methoxy)phosphoryl)bis(azanediyl)bis(3-phenylpropanoate)

[00703] The phosphorodiamidate was prepared according to Method B.

In a first step, a suspension of ((2R,3R,4R,5R)-2-(2-amino-6-methoxy-9H-purin-9- yl)-5-(hydroxymethyl)-3-methyltetrahydrofuran-3,4-diol (150 mg, 0.47 mmol) in anhydrous tetrahydrofuran (2.5 mL) was reacted with triethylamine (80 μί, 0.56 mmol) and phosphorus oxychloride (50 μί, 0.56 mmol). In a second step, anhydrous dichloromethane (3.6 mL), L-phenylalanine benzyl ester tosylate salt (1.00 g, 2.34 mmol) and triethylamine (0.65 mL, 4.68 mmol) were added. After work-up and silica gel column chromatography, 40 mg of phosphorodiamidate was obtained in 9% yield as an off white solid.

[00705] 1H NMR (500 MHz, CDC1 ₃ ) δ 7.66 (s, 1H, ¾), 7.33-7.26 (m, 10H, OCH ₂ Ph and

Phe), 7.19-1.17 (m, 6H, Phe), 7.02-7.00 (m, 4H, OCH ₂ Ph), 5.91 (s, 1H, H _r ), 5.14- 5.02 (m, 4H, 2x OCH ₂ Ph), 4.45 (m, 1Η, ¾·), 4.34 (m, 1Η, ¾·), 4.18 (m, 3Η, 2x CHcc Phe and ¾·), 4.05 (s, 3H, 60CH ₃ ), 2.92-2.84 (m, 2H, 2x CH ₂ Phe), 0.97 (s, 3H, 2'CCH ₃ ).

[00706] ¹³ C NMR (125 MHz, CDC1 ₃ ) δ 173.18 (C=0 Phe), 172.69 (C=0 Phe), 161.62

(C6), 159.57 (C2), 152.90 (C4), 137.94 (C8), 135.94, 135.87 (2x ipso Phe), 135.13 (2x ipso OCH ₂ Ph), 129.50, 129.46 (Phe and OCH ₂ Ph), 128.59, 128.49 (Phe and OCH ₂ Ph), 127.04, 127.02 (Phe), 115.86 (C5), 91.82 (CI'), 81.04 (C4'), 79.51 (C2'), 74.94 (C3'), 67.33, 67.19 (2s, 2x O H ₂ Ph), 65.16 (C5'), 55.30, 55.24 (2x Ca Phe), 53.44 (60CH ₃ ), 40.15 (2x CH ₂ Phe), 20.37 (2'CCH ₃ ).

[00707] ³¹ P NMR (202 MHz, CDC1 ₃ ) δ 13.20.

[00708] HPLC t _R = 21.16 min (System 1).

[00709] MS (TOF ES ⁺ ) m/z: 866.33 (M+H ⁺ ), 888.35 (M + Na ⁺ ); accurate mass: calculated for C ₄₄ H ₄₉ N ₇ O ₁₀ P: 866.3279, found 866.3281.

[00710] Example 58

[00711] (2S,2'S)-Neopentyl 2,2'-((((2R,3R,4R,5R)-5-(2-amino-6-methoxy-9H-purin-9-yl)- 3,4-dihydroxy-4-methyltetrahydrofuran-2- yl)methoxy)phosphoryl)bis(azanediyl)bis(3-phenylpropanoate)

[00712] The phosphorodiamidate was prepared according to Method B.

[00713] In a first step, a suspension of ((2R,3R,4R,5R)-2-(2-amino-6-methoxy-9H-purin-9- yl)-5-(hydroxymethyl)-3-methyltetrahydrofuran-3,4-diol (180 mg, 0.57 mmol) in anhydrous tetrahydrofuran (3.1 mL) was reacted with triethylamine (100 μί, 0.69 mmol) and phosphorus oxychloride (70 μί, 0.69 mmol). In a second step, anhydrous dichloromethane (4.4 mL), L-phenylalanine 2,2-dimethylpropyl ester tosylate salt (1.12 g, 2.87 mmol) and triethylamine (0.80 mL, 5.73 mmol) were added. After work-up and silica gel column chromatography, 50 mg of phosphorodiamidate was obtained in 11% yield as an off white solid.

[00714] 1H NMR (500 MHz, CDC1 ₃ ) δ _Η 7.68 (s, 1H, ¾), 7.25-7.08 (m, 10H, 2 x H aPhe),

5.92 (s, 1H, H _r ), 4.42 (m, 1H, ¾·), 4.35 (m, 1H, 1H ¾·), 4.19 (m, 2H, ¾· and CHa Phe), 4.17-4.08 (m, 2H, Η ₅ · and CHa Phe), 4.04 (s, 3H, 60CH ₃ ), 3.79-3.70 (m, 4H, 2x OCH ₂ C(CH ₃ ) ₃ ), 2.98-2.84 (2m, 4H, 2x CH ₂ Phe), 0.98 (s, 3H, 2'CCH ₃ )..

[00715] ¹³ C NMR (125 MHz, CDC1 ₃ ) δ 173.50 (C=0 Phe), 173.03 (C=0 Phe), 161.60

(C6), 159.58 (C2), 152.96 (C ₄ ), 137.90 (C8), 136.16, 136.03 (2x ipso Phe), 129.48, 129.39 (Phe), 128.55, 128.27 (Phe), 127.05, 127.01 (Phe), 115.77 (C5), 91.82 (CI'), 81.09 (C4'), 79.47 (C2'), 74.89 (C3'), 74.77 (2x O H ₂ C(CH ₃ ) ₃ ), 65.20 (C5'), 55.22 (2x Ca Phe), 53.80 (60CH ₃ ), 45.78 (2x CH ₂ Phe), 31.21, 31.15 (2x OCH ₂ C(CH ₃ ) ₃ ), 26.73, 26.37 (2x OCH ₂ C(CH ₃ ) ₃ ), 20.36 (2'CCH ₃ ).

[00716] ³¹ P NMR (202 MHz, CDC1 ₃ ) δ 13.10.

[00717] HPLC ¾ = 24.91 min (System 1). [00718] MS (TOF ES ⁺ ) m/z: 826.39 (M+H ⁺ ), 848.50 (M+Na ⁺ ); accurate mass: calculated for C ₄₀ H ₅₇ N ₇ O ₁₀ P: 826.3905, found 866.3281.

[00719] Example 59 [00720] (2S,2'S)-Dicyclohexyl 2,2'-((((2R,3R,4R,5R)-5-(2-amino-6-methoxy-9H-purin-9- yl)-3,4-dihydroxy-4-methyltetrahydrofuran-2- yl)methoxy)phosphoryl)bis(azanediyl)bis(3-phenylpropanoate)

[00721] The phosphorodiamidate was prepared according to the Method B. [00722] In a first step, a suspension of ((2R,3R,4R,5R)-2-(2-amino-6-methoxy-9H-purin-9- yl)-5-(hydroxymethyl)-3-methyltetrahydrofuran-3,4-diol (310 mg, 1.01 mmol) in anhydrous tetrahydrofuran (4.3 mL) was reacted with triethylamine (170 \L, 1.21 mmol) and phosphorus oxychloride (110 \L, 1.21 mmol). In a second step, anhydrous dichloromethane (4.0 mL), L-phenylalanine cyclohexyl ester tosylate salt (2.13 g, 5.05 mmol) and triethylamine (1.41 mL, 10.1 mmol) were added. After work-up and silica gel column chromatography, 40 mg of the phosphorodiamidate was obtained in 5% yield as an off white solid.

[00723] 1H NMR (500 MHz, CDC1 ₃ ) δ 7.65 (s, 1H, ¾), 7.28-7.11 (m, 12H, Phe), 5.91 (s,

1H, Hr), 4.48 (m, 1H, ¾·), 4.38 (m, 1H, ¾·), 4.13-4.12 (m, 2H, ¾· and ¾·), 4.06 (s, 3H, 6OCH ₃ ), 4.02 (m, 1H, CHa Phe), 2.98-2.85 (m, 4H, 2x CH ₂ Phe), 1.80- 1.67 (m, 8Η, cHex), 1.51 (m, 2H, 2x CH ₂ cHex), 1.32-1.23 (m, 8H, cHex), 0.98 (s, 3H, 2'CCH ₃ ).

Ill [00724] C NMR (125 MHz, CDC1 ₃ ) δ 172.76 (C=0 Phe), 172.28 (C=0 Phe), 161.58 (C6), 159.65 (C2), 152.96 (C4), 137.81 (C8), 136.23, 136.14 (2x ipso Phe), 129.58, 129.52 (Phe), 128.81,128.12 (Phe), 126.97, 126.92 (Phe), 115.72 (C5), 91.76 (CI'), 81.06 (C4'), 79.46 (C2'), 74.81 (C3'), 74.21, 74.06 (2x OCR cHex), 65.17 (C5'), 55.30, 55.26 (2d, 2x CHa Phe), 53.81 (60CH ₃ ), 40.40, 40.34 (2d, 2x CH ₂ Phe), 31.49, 31.40 (4x H ₂ cHex), 25.22, 23.67 ( H ₂ cHex), 20.34 (2'CCH ₃ ).

[00725] ^{3 X} P NMR (202 MHz, CDC1 ₃ ) δ 13.16 (s). [00726] HPLC t _R =20.32 min (System 1).

[00727] MS (TOF ES ⁺ ) m/z: 850.39 (M+H ⁺ ), 872.37 (M + Na ⁺ ); accurate mass: calculated for C ₄ oH57N70 ₁₀ P: 850.3905, found 850.3882.

[00728] Example 60

[00729] (2S,2'S)-Dicyclohexyl 2,2'-((((2R,3R,4R,5R)-5-(2-amino-6-methoxy-9H-purin-9- yl)-3,4-dihydroxy-4-methyltetrahydrofuran-2- yl)methoxy)phosphoryl)bis(azanediyl)bis(3-(4-tert-butoxyphen yl)propanoate)

[00730] The phosphorodiamidate was prepared according to Method B.

In a first step, a solution of ((2R,3R,4R,5R)-2-(2-amino-6-methoxy-9H-purin-9- yl)-5-(hydroxymethyl)-3-methyltetrahydrofuran-3,4-diol (260 mg, 0.85 mmol) in anhydrous tetrahydrofuran (4.5 mL) was reacted anhydrous triethylamine (140 μί, 1.02 mmol) with phosphorus oxychloride (90 μί, 1.02 mmol). In a second step, anhydrous dichloromethane (3.4 mL), L-tyrosine i-butyl ether cyclohexyl ester hydrochloride salt (1.07 g, 4.25 mmol) and triethylamine (1.19 mL, 8.5 mmol) were added. After work-up, silica gel column chromatography and preparative TLC, 120 mg of phosphorodiamidate was obtained in 16% yield as an off white solid.

[00732] 1H NMR (500 MHz, CDC1 ₃ ) δ 7.69 (s, 1H, ¾), 7.03-7.02 (d, 2H, J=8.4 Hz, 2x H ortho Tyr), 6.98-6.97 (d, 2H, J=8.4 Hz, 2x H ortho Tyr), 6.87-6.85 (dd, 4H, J=3.0 Hz & 8.40 Hz, 4x H meta Tyr), 5.95 (s, 1H, H _r ), 5.45 (bs, 2H, 2x NH Tyr), 4.35- 4.30 (m, 2H, H ₃ < and ¾·), 4.09-4.06 (m, 3H, 2x CH Tyr and ¾·), 4.05 (s, 3H, 60CH ₃ ), 4.01-3.96 (m, 1H, ¾·), 3.63, 3.62 (2s, 6H, 2x OCH ₃ ), 3.31-3.28 (m, 4H, 2x CH ₂ Tyr), 1.31, 1.30 (2s, 18H, 6x CH ₃ iBu), 1.98 (s, 3H, 2'CCH ₃ ).

[00733] ¹³ C NMR (125 MHz, CDC1 ₃ ) δ 173.68 (C=0 Tyr), 173.32 (C=0 Tyr), 161.60

(C6), 159.61 (C2), 154.40, 154.15 (2s, 2x C para Tyr), 153.03 (C4), 137.85 (C8), 131.30, 130.80 (2s, 2x ipso Tyr), 130.29, 129.87 (Tyr), 124.20, 124.12 (Tyr), 115.70 (C5), 91.47 (CI '), 80.80 (C4'), 79.36 (C2'), 78.68, 78.42 (2x OC(CH ₃ ) ₃ ), 74.39 (C3'), 64.77 (C5'), 55.37, 55.22 (2x CH Tyr), 53.81 (60CH ₃ ), 52.24, 52.18 (2x OCH ₃ ), 39.63 (2x CH ₂ Tyr), 28.82, 22.77 (2x OC(CH ₃ ) ₃ ), 20.29 (2'CCH ₃ ).

[00734] ³¹ P NMR (202 MHz, CDC1 ₃ ) δ 13.31.

[00735] HPLC ¾ =20.40 min. (System 1).

[00736] MS (TOF ES ⁺ ) m/z: 858.38 (M+H ⁺ ), 880.37 (M+Na ⁺ ); accurate mass: calculated for C ₄ oH ₅₇ N ₇ Oi ₂ P: 858.3803, found 858.3804.

[00737] Example 61

[00738] (2S,2'S)-Neopentyl 2,2'-((((2R,3R,4R,5R)-5-(2-amino-6-methoxy-9H-purin-9-yl)- 3,4-dihydroxy-4-methyltetrahydrofuran-2- yl)methoxy)phosphoryl)bis(azanediyl)bis(3-methylbutanoate)

[00739] The phosphorodiamidate was prepared according to Method B.

[00740] In a first step, a suspension of ((2R,3R,4R,5R)-2-(2-amino-6-methoxy-9H-purin-9- yl)-5-(hydroxymethyl)-3-methyltetrahydrofuran-3,4-diol (300 mg, 0.96 mmol) in anhydrous tetrahydrofuran (5 mL) was reacted with triethylamine (130 μί, 0.96 mmol) and phosphorus oxychloride (90 μί, 0.96 mmol). In a second step, anhydrous dichloromethane (5 mL), L-valine 2,2-dimethylpropyl ester tosylate salt (1.98 g, 4.82 mmol) and triethylamine (1.34 mL, 9.63 mmol) were added. After work-up and silica gel column chromatography 42 mg of phosphorodiamidate was obtained in 6% yield as an off white solid.

[00741] 1H NMR (500 MHz, CD ₃ OD) δ 7.99 (s, 1H, ¾), 5.99 (s, 1H, H _r ), 4.41-4.35 (m,

2H, Hs , 4.33 (d, J= 9.0 Hz, 1H, ¾·), 4.20- 4.17 (m, 1H, ¾·), 4.09 (s, 3H, 60CH ₃ ), 3.87-3.68 (m,6H, 2x CHa Val and 2x OCH ₂ C(CH ₃ ) ₃ ), 2.11-1.98 (m, 2H, 2x Οϊβ Val), 0.99, 0.98 (2s, 3H, 2'CCH ₃ ), 0.89- 0.83 (m, 12Η, 2x C¾).

[00742] ¹³ C NMR (125 MHz, CD ₃ OD) δ 174.87, 174.80 (2d, ³ J _C -C-N-P = 2.5 Hz, 2x C=0),

162.77 (C6), 161.92 (C2), 154.54 (C4), 139.49 (C8), 115.68 (C5), 93.35 (CI '), 82.55 (d, ³ Jc-c-o-p = 8.8 Hz, C4'), 79.92 (C2'), 75.65, 75.58 (CH ₂ ester), 75.03 (C3'), 67.11 (d, ² Jc-o-p = 5.0 Hz, C5'), 61.09, 61.03(Ca Val), 54.24 (60CH ₃ ), 33.23 (d, ³ JC-C-N-P = 6.3 Hz, 2x C Val), 32.14, 32.08 (2x OCH ₂ C(CH ₃ ) ₃ ), 26.89 (2x OCH ₂ C( H ₃ ) ₃ ), 20.32 (2'C H ₃ ), 18.09, 18.07 (2 x CH ₃ Val).

[00743] ³ *P NMR (202 MHz, CD ₃ OD) 5 15.16

[00744] HPLC ¾ = 22.15 min (System 1).

[00745] MS (TOF ES+) m/z: 752.37 (M+Na ⁺ , 100%);

[00746] HRMS C ₃₂ H ₅₆ N ₇ O ₁₀ NaiPi calculated: 752.3724 found: 752.3736. [00747] Examples 62 [00748] (2S,2'S,3R,3'R)-Benzyl 2,2'-((((2R,3R,4R,5R)-5-(2-amino-6-methoxy-9H-purin-9- yl)-3,4-dihydroxy-4-methyltetrahydrofuran-2- yl)methoxy)phosphoryl)bis(azanediyl)bis(3-methylpentanoate)

[00749] The phosphorodiamidate was prepared according to Method B. [00750] In a first step, a suspension of ((2R,3R,4R,5R)-2-(2-amino-6-methoxy-9H-purin-9- yl)-5-(hydroxymethyl)-3-methyltetrahydrofuran-3,4-diol (300 mg, 0.96 mmol) in anhydrous tetrahydrofuran (5 mL) was reacted with triethylamine (130 μί, 0.96 mmol) and phosphorus oxychloride (90 μί, 0.96 mmol). In a second step, anhydrous dichloromethane (5 mL), L-isoleucine benzyl ester tosylate salt (1.89 g, 4.82 mmol) and triethylamine (1.34 mL, 9.63 mmol) were added. After work-up and silica gel column chromatography, 200 mg of phosphorodiamidate was obtained in 16% yield as an off white solid.

[00751] 1H NMR (500 MHz, CD ₃ OD) δ 7.92 (s, 1H, ¾), 7.42-7.28 (m, 10H, 2x OCH ₂ P/i

), 5.99 (s, 1H, H _r ), 5.21-5.18 (m, 4H, 2x OCH ₂ Ph), 4.43-4.40 (m, 2Η, ¾·), 4.37 (d, J= 8.5 Hz, 1H, H ₃ <), 4.19- 4.15 (m, 1H, ¾·), 4.03 (s, 3H, 60CH ₃ ), 3.74-3.73 (m, 2H, 2x CHcc He), 1.75- 1.73 (m, 2H, 2x ΟΙβ He), 1.37- 1.29 (m, 2H, CH ₂ He), 1.15- 1.02 (m, 2H, CH ₂ He), 1.00 (s, 3H, 2'CCH ₃ ), 0.83-0.69 (m, 12H, 4x CH ₃ He).

[00752] ¹³ C NMR (125 MHz, CD ₃ OD) δ 174.47 (2x C=0 ester), 162.77 (C6), 161.90

(C2), 154.58 (C4), 139.42 (C8), 137.19, 137.12 (2x ipso OCH ₂ P/i), 129.93, 129.59, 129.42, 129.39 (2x OCH ₂ P/i), 115.68 (C5), 93.22 (CI '), 82.49 (d, ³ J _C -c-o- P = 7.5 Hz, C4'), 79.95 (C2'), 74.91 (C3'), 67.91, 67.75 (2x O H ₂ Ph), 66.77 (d, ² J c-o-p = 5.0 Hz, C5'), 60.19, 60.10 (2x Ccc He), 54.31 (60CH ₃ ), 40.16 (d, ³ / _C -C-N-P = 3.8 Hz C lie), 40.11 (d, ³ / _C -C-N-P = 3.8 Hz C He), 25.96, 25.92 (2x CH ₂ y He), 20.42 (2'CCH ₃ ), 15.87, 15.74 (2x CH ₃ y He), 11.95, 11.92 (2x H ₃ lie).

[00753] ³¹ P NMR (202 MHz, CD ₃ OD) δ 14.93

[00754] HPLC ¾ = 20.88 min (System 1).

[00755] MS (TOF ES+) m/z: 820.34 (M+Na ⁺ , 100%);

[00756] HRMS C ₃₈ H ₅₂ N ₇ O ₁₀ NaiPi calculated: 820.3411 found: 820.3378

[00757] Example 63

[00758] (2S,2'S,3R,3'R)-Dimethyl 2,2'-((((2R,3R,4R,5R)-5-(2-amino-6-methoxy-9H-purin- 9-yl)-3,4-dihydroxy-4-methyltetrahydrofuran-2- yl)methoxy)phosphoryl)bis(azanediyl)bis(3-methylpentanoate)

[00759] The phosphorodiamidate was prepared according to Method B.

[00760] In a first step, a suspension of ((2R,3R,4R,5R)-2-(2-amino-6-methoxy-9H-purin-9- yl)-5-(hydroxymethyl)-3-methyltetrahydrofuran-3,4-diol (300 mg, 0.96 mmol) in anhydrous tetrahydrofuran (5 mL) was reacted with triethylamine (130 μί, 0.96 mmol) and phosphorus oxychloride (90 μί, 0.96 mmol). In a second step, anhydrous dichloromethane (5 mL), L-isoleucine methyl ester hydrochloride salt (1.15 g, 4.82 mmol) and triethylamine (1.34 mL, 9.63 mmol) were added. After work-up and silica gel column chromatography, 135 mg of (37) was obtained in 22% yield as an off white solid.

1H NMR (500 MHz, CD ₃ OD) δ 8.01 (s, 1H, ¾), 5.99 (s, 1H, H _r ), 4.47-4.38 (m, 2H, ¾·), 4.34 (d, J= 9.0 Hz, 1H, ¾·), 4.20- 4.18 (m, 1H, ¾·), 4.07 (s, 3H, 60CH ₃ ), 3.87-3.83 (m, 2H, 2x CHcc He), 3.72, 3.70 (2s, 6H, OCH ₃ ), 1.74- 1.69 (m, 2H, 2x Οϊβ lie), 1.44-1.36 and (m, 2H, CH ₂ He), 1.09- 1.03 (m, 2H, CH ₂ lie), 1.00 (s, 3H, 2'CCH ₃ ), 0.91 (d, J= 6.5 Hz, 3H, CH ₃ He), 0.89 (d, J= 6.5 Hz, 3H, CH ₃ He), 0.84 (d, J= 6.5 Hz, 3H, CH ₃ He), 0.82 (d, J= 6.5 Hz, 3H, CH ₃ Ile).

[00762] ¹³ C NMR (125 MHz, CD ₃ OD) δ 175.17 (d, 3.8 Hz, 2x C=0 ester),

162.74 (C6), 161.91 (C2), 154.46 (C4), 139.40 (C8), 115.44 (C5), 93.27 (CI '), 82.51 (d, ³ J c-c-o-p = 7.5 Hz, C4'), 79.97 (C2'), 74.87 (C3'), 66.72 (d, ² J _C -o-p = 5.0 Hz, C5'), 60.02, 60.00 (2d, ² / _C -N-P = 4.5 Hz, 2x Ca He), 54.37 (60CH ₃ ), 52.54, 52.51 (2x O H ₃ ester), 33.21 (d, ³ / _C -C-N-P = 3.8 Hz C He), 33.21 (d, ³ / _C -C-N-P = 7.5 Hz C He), 26.10, 26.08 (2x CH ₂ y He), 20.41 (2'CCH ₃ ), 15.91, 15.83 (2x H ₃ y He), 11.93 (CH ₃ He).

[00763] ³¹ P NMR (202 MHz, CD ₃ OD) δ 14.88 [00764] HPLC t _R = 10.87 min (System 1). [00765] MS (TOF ES+) m/z: 668.28 (M+Na ⁺ , 100%); [00766] HRMS C ₂₆ H ₄₄ N ₇ 0 ₁ oNa ₁ P ₁ calculated: 668.2785 found: 668.2759 [00767] Example 64 [00768] (2S,2'S,3R,3'R)-Neopentyl 2,2'-((((2R,3R,4R,5R)-5-(2-amino-6-methoxy-9H- purin-9-yl)-3,4-dihydroxy-4-methyltetrahydrofuran-2- yl)methoxy)phosphoryl)bis(azanediyl)bis(3-methylpentanoate)

[00769] The phosphorodiamidate was prepared according to Method B. [00770] In a first step, a suspension of 6-O-methyl-2' -C-methylguanosine (300 mg, 0.96 mmol) in anhydrous tetrahydrofuran (5 mL) was reacted with triethylamine (130 \L, 0.96 mmol) and phosphorus oxychloride (90 \L, 0.96 mmol). In a second step, anhydrous dichloromethane (5 mL), L-isoleucine 2,2-dimethylpropyl ester tosylate salt (1.80 g, 4.82 mmol) and triethylamine (1.34 mL, 9.63 mmol) were added. After work-up and silica gel column chromatography, 210 mg of (40) was obtained in 29% yield as an off white solid.

[00771] 1H NMR (500 MHz, CD ₃ OD) δ 7.96 (s, 1H, ¾), 6.00 (s, 1H, H _r ), , 4.41-4.40 (m,

2H, ¾·), 4.34 (d, J= 8.5 Hz, 1H, ¾·), 4.21- 4.20 (m, 1H, ¾·), 4.07 (s, 3H, 60CH ₃ ), 3.84-3.72 (m, 6H, 2x OCH ₂ C(CH ₃ ) ₃ and 2x CHa He), 1.81-1.78 (m, 2H, 2x CH He), 1.46- 1.41, 1.39-1.33 (2m, 2H, CH ₂ He), 1.16- 1.11, 1.07- 1.04 (2m, 2H, CH ₂ He), 1.00 (s, 3H, 2'CCH ₃ ), 0.95, 0.94 (2s, 2x OCH ₂ C(CH ₃ ) ₃ ), 0.91-0.81 (m, 12Η, 4x C¾ He).

[00772] ¹³ C NMR (125 MHz, CD ₃ OD) δ 174.79, 174.72 (2d, 3.8 Hz, 2x C=0 ester), 162.79 (C6), 161.90 (C2), 154.58 (C4), 139.46 (C8), 115.70 (C5), 93.28 (CI '), 82.56 (d, ³ J c-c-o-p = 6.3 Hz, C4'), 79.97 (C2'), 75.72, 75.64 (2x O H ₂ C(CH ₃ ) ₃ ), 74.98 (C3'), 67.00 (d, ² J _C -o-p = 5.0 Hz, C5'), 60.17, 60.07 (2x Ca He), 54.32 (60CH ₃ ), 40.30, 40.25 (2x C He), 32.14, 32.09 (2x OCH ₂ C(CH ₃ ) ₃ , 27.08, 26.98 (2x OCH ₂ C( H ₃ ) ₃ , 26.04 (2x CH ₂ y He), 20.43 (2'CCH ₃ ), 16.14, 16.03 (2x CH ₃ y He), 12.13, 12.09 (2x CH ₃ He).

[00773] ³¹ P NMR (202 MHz, CD ₃ OD) δ 14.93

[00774] HPLC ¾ = 24.55 min (System 1).

[00775] MS (TOF ES+) m/z: 780.40 (M+Na ⁺ , 100%);

[00776] HRMS C ₃ 4H ₆₁ N7O ₁₀ Pi calculated: 758.4218 found: 758.4196

[00777] Example 65

[00778] (2S,2'S,3R,3'R)-Dicyclohexyl 2,2'-((((2R,3R,4R,5R)-5-(2-amino-6-methoxy-9H- purin-9-yl)-3,4-dihydroxy-4-methyltetrahydrofuran-2- yl)methoxy)phosphoryl)bis(azanediyl)bis(3-methylpentanoate)

[00779] The phosphorodiamidate was prepared according to Method B.

In a first step, a suspension of ((2R,3R,4R,5R)-2-(2-amino-6-methoxy-9H-purin-9- yl)-5-(hydroxymethyl)-3-methyltetrahydrofuran-3,4-diol (300 mg, 0.96 mmol) in anhydrous tetrahydrofuran (5 mL) was reacted with triethylamine (130 μί, 0.96 mmol) and phosphorus oxychloride (90 μί, 0.96 mmol). In a second step, anhydrous dichloromethane (5 mL), L-isoleucine cyclohexyl ester tosylate salt (1.86 g, 4.82 mmol) and triethylamine (1.34 mL, 9.63 mmol) were added. After work-up and silica gel column chromatography, 140 mg of phosphorodiamidate was obtained in 19% yield as an off white solid.

[00781] 1H NMR (500 MHz, CD ₃ OD) δ 7.97 (s, 1H, ¾), 6.00 (s, 1H, H _r ), 4.80-4.74 (m,

2H, 2x OCH ester), 4.43-4.39 (m, 2Η, ¾·), 4.33 (d, J= 9.0 Hz, 1H, ¾·), 4.22- 4.19 (m, 1H, ¾·), 4.07 (s, 3H, 60CH ₃ ), 3.74-3.73 (m, 2H, 2x CHa He), 1.82- 1.80 (m, 4H, 2x CH ₂ ester), 1.75- 1.70 (m, 6H, 2x CH ₂ ester and CH He), 1.55- 1.29 (m, 14H, 6x CH ₂ ester and CH ₂ He), 1.15-1.02 (m, 2H, CH ₂ He), 1.00 (s, 3H, 2'CCH ₃ ), 0.91 (d, J= 6.5 Hz, 3H, CH ₃ He), 0.88 (d, J= 6.5 Hz, 3H, CH ₃ He), 0.85 (d, J= 6.5 Hz, 3H, CH ₃ He), 0.83 (d, J= 6.5 Hz, 3H, CH ₃ Ile).

[00782] ¹³ C NMR (125 MHz, CD ₃ OD) δ 174.05, 174.03 (2d, 3.8 Hz, 2x C=0 ester), 162.79 (C6), 161.91 (C2), 154.59 (C4), 139.44 (C8), 115.69 (C5), 93.26 (CI '), 82.54 (d, ³ J c-c-o-p = 7.5 Hz, C4'), 79.97 (C2'), 74.98 (C3'), 74.82 (2x OCH ester), 66.11 (d, ² J _C -o-p = 5.0 Hz, C5'), 60.02 (2x Ccc He), 54.33 (60CH ₃ ), 40.30 (4x CH ₂ ester), 32.64 (d, ³ J _C -C-N-P = 3.8 Hz C He), 32.60 (d, ³ J _C -C-N-P = 7.5 Hz C He), 26.47 (CH ₂ ester), 26.44 (CH ₂ ester), 26.09 (2x OLj Ile), 24.69 (2 x CH ₂ ester), 24.67 (2 x CH ₂ ester), 20.42 (2'CCH ₃ ), 16.01, 15.91 (2x CH ₃ y He), 12.14, 12.08 (2x CH ₃ He). [00783] ³¹ P NMR (202 MHz, CD ₃ OD) δ 15.04

[00784] HPLC i _R = 25.45 min (System 1).

[00785] MS (TOF ES+) mJz: 804.41 (M+Na ⁺ , 100%);

[00786] HRMS C ₃₆ H ₆ iN ₇ O ₁₀ Pi calculated: 782.4218 found: 782.4234

[00787] Example 66

[00788] Neopentyl l,l'-((((2R,3R,4R,5R)-5-(2-amino-6-methoxy-9H-purin-9-yl)-3, 4- dihydroxy-4-methyltetrahydrofuran-2-yl)methoxy)phosphoryl)di pyrrolidine-2- carboxylate

[00789] The phosphorodiamidate was prepared according to Method B.

[00790] In a first step, a solution of 6-O-methyl-2'-C-methylguanosine (300 mg, 0.96 mmol) in anhydrous tetrahydrofuran (1 mL) was reacted anhydrous triethylamine (130 \L, 0.96 mmol) with phosphorus oxychloride (87 \L, 0.96 mmol). In a second step, anhydrous dichloromethane (3 mL), L-proline 2,2-dimethylpropyl ester tosylate salt (1.71 g, 4.81 mmol) and triethylamine (1.30 mL, 9.61 mmol) were added. After work-up, silica gel column chromatography and preparative TLC, 50 mg of phosporodiamidate was obtained in 7% yield as an off white solid.

[00791] 1H NMR (500 MHz, CD ₃ OD): δ 7.92 (s, 1H, ¾), 5.92 (s, 1H, H _r ), 4.48 (m, 1H,

¾·), 4.25 (m, 1H, ¾¾), 4.12 (m, 2H, ¾· and H ₅ < _a ), 3.8 (m, 4H, 2x OCH ₂ C(CH ₃ ) ₃ ), 3.45 (m, 2H, 2x CHa Pro), 2.2-2.4 (m, 2H, 2x Pro), 2.2 (s, 3H, 6OCH ₃ ), 1.15-2.1 m (m, 10H, 2x Pro), 1.05 (s, 3H, 2'CCH ₃ ), 0.95 (2s ,18H, 2xOCH ₂ C(CH ₃ ) ₃ ).

[00792] ¹³ C NMR (125 MHz, CD ₃ OD): δ 175.91 (C=0), 175.65 (C=0), 162.78 (C6),

161.90 (C2), 154.41 (C4), 139.70 (C8), 115.73 (C5), 93.68 (CI '), 82.55 (d, ³ J _P _o-c- c= 9.2 Hz, C4'), 79.98 (C2'), 75.18 (C3'), 75.08, 75.06 (2x O H ₂ C(CH ₃ ) ₃ ), 67.00 (d, ² JP_o-c = 4.3 Hz, C5'), 54.21 (Ca Pro), 48.05 (d, ² J _P - _N -c = 5.3 Hz, NHCH ₂ ), 47.91 (d, ² J _P - _N -c = 5.3 Hz, NH H ₂ ), 32.70 (d, J= 7.5 Hz, CH ₂ Pro), 32.45 (d, J= 7.5 Hz, CH ₂ Pro), 26.84, 26.83 (2x OCH ₂ C( H ₃ ) ₃ ), 26.10 (d, J= 8.4 Hz, CH ₂ Pro), 26.03 (d, J= 8.4 Hz,CH ₂ Pro), 20.34 (2'CCH ₃ ).

[00793] ³¹ P NMR (202 MHz, CD ₃ OD): δ 11.52.

[00794] HPLC ¾ = 20.57 min (System 1).

[00795] MS (ES+) m/z = (M+H ⁺ ): 726.35; Accurate mass calculated for C ₃₂ H ₅₃ N ₇ O ₁₀ P - 726.3592

[00796] Examples 67

[00797] (2S,2'S)-1,4-Dibenzyl 2,2'-((((2R,3R,4R,5R)-5-(2-amino-6-methoxy-9H-purin-9- yl)-3,4-dihydroxy-4-methyltetrahydrofuran-2- yl)methoxy)phosphoryl)bis(azanediyl)disuccinate

[00798] The phosphorodiamidate was prepared according to Method B. [00799] In a first step, a suspension of ((2R,3R,4R,5R)-2-(2-amino-6-methoxy-9H-purin-9- yl)-5-(hydroxymethyl)-3-methyltetrahydrofuran-3,4-diol (500 mg, 1.50 mmol) in anhydrous tetrahydrofuran (8 mL) was reacted with triethylamine (0.25 mL, 1.80 mmol) and phosphoryl chloride (0.13mL, 1.50 mmol). In a second step, anhydrous dichloromethane (8 mL), L-aspartic acid tetra-benzyl ester tosylate salt (3.6 g, 7.50 mmol) and triethylamine (2.1 mL, 15.0 mmol) were added. After column chromatography (MeOH/ dichloromethane 1 :9), 150 mg of phosphorodiamidate was obtained of the in 10% yield as an off white solid.

[00800] 1H NMR (500 MHz, CD ₃ OD) δ 7.92 (s, 1H, ¾), 7.30-7.20 (m, 20H, Ph), 5.97 (s,

1H, H _r ), 5.10-4.89 (m, 8H, CH2Ph), 4.47-4.24 (m, 5H, H ₃ <, 2xCHcc L- Aspartic acid), 4.19-4.1 1 (m, 1H, ¾·), 3.99 (s, 3H, OCH ₃ ), 2.91-2.79 (m, 4H, CH2C=0), 0.97 (s, 3H, 2'CH ₃ ).

[00801] ¹³ C NMR (125 MHz, CD ₃ OD) 173.3 (C=0), 173.2 (C=0), 172.0 (C=0), 171.9

(C=0), 162.7 (C6), 161.9 (C2), 154.61 (C4), 139.3 (C-8), 137.2(C ipso), 137.1(C ipso), 137.0(C ipso), 136.9 (C ipso), 129.6, 129.5, 129.5, 129.4, 129.4, 129.3, 129.3 129.2, 129.0, 115.6 (C5), 93.1 (CI '), 82.2 (d, J= 7.3 Hz, C4'), 80.0 (C2'), 74.8 (C3'), 68.4 (CH ₂ Ph), 67.7 (CH ₂ Ph), 66.5 (d, J= 4.9 Hz, C5'), 54.2 (CH L- Aspartic acid), 52.2 (60Me), 39.6 (CH ₂ C=0), 39.5 (CH ₂ C=0), 39.5 (CH ₂ C=0), 39.4 (CH ₂ C=0), 20.4 (2'C H ₃ ).

[00802] ³¹ P NMR (202 MHz, CD ₃ OD) δ 13.58.

[00803] HPLC t _R = 30.88 min (System 2).

[00804] Example 68

[00805] (2S,2'S)-Tetramethyl 2,2'-((((2R,3R,4R,5R)-5-(2-amino-6-methoxy-9H-purin-9- yl)-3,4-dihydroxy-4-methyltetrahydrofuran-2- yl)methoxy)phosphoryl)bis(azanediyl)disuccinate

[00806] The phosphorodiamidate was prepared according to Method B. [00807] In a first step, a suspension of ((2R,3R,4R,5R)-2-(2-amino-6-methoxy-9H-purin-9- yl)-5-(hydroxymethyl)-3-methyltetrahydrofuran-3,4-diol (500 mg, 1.50 mmol) in anhydrous tetrahydrofuran (8 mL) was reacted with triethylamine (0.25 mL, 1.80 mmol) and phosphoryl chloride (0.13mL, 1.50 mole). In a second step, anhydrous dichloromethane (8 mL), L-aspartic acid tetra methyl ester tosylate salt (3.6 g, 7.50 mmol) and triethylamine (2.1 mL, 15.0 mmol) were added. After column chromatography (MeOH/ dichloromethane 1 :9) and TLC preparative, 10 mg of phosphorodiamidate was obtained in 10% yield as an off white solid.

[00808] 1H NMR (500 MHz, CD ₃ OD) δ 7.97 (s, 1H, ¾), 5.99 (s, 1H, H _r ), 4.45-4.20 (m,

5H, H ₃ <, 2xCHcc L-aspartic acid), 4.20-4.11 (m, 1H, ¾·), 3.73 (s, 3H, C=OOC¾), 3.71 (s, 3H, C=OOC¾), 3.67 (s, 3H, C=OOC¾), 3.62 (s, 3H, C=OOC¾), 2.89-2.75 (m, 4H, CH ₂ C=0), 1.01 (s, 3Η, 2'C¾).

[00809] ¹³ C NMR (125 MHz, CD ₃ OD) 174.1 (C=0), 172.8 (C=0), 172.7 (C=0), 162.7

(C6), 161.9 (C2), 154.6 (C4), 139.4 (C8), 115.6 (C-5), 93.2 (CI '), 82.2 (d, J= 7.5 Hz, C4'), 80.0 (C2'), 74.7 (C3'), 66.4 (d, J= 5.6 Hz, C-5'), 54.2, 53.08, 52.4, 52.1 (CH AA), 39.3 (d, J= 5.6 Hz, CH ₂ C=0), 39.2 (d, J= 5.6 Hz, CH ₂ C=0), 20.3 (2'CCH ₃ ).

[00810] ³¹ P NMR (202 MHz, CD ₃ OD) δ 13.63. [00811] HPLC t _R = 15.71 min (System 2). [00812] Example 69 [00813] Benzyl 3,3'-((((2R,3R,4R,5R)-5-(2-amino-6-methoxy-9H-purin-9-yl)-3, 4- dihydroxy-4-methyltetrahydrofuran-2- yl)methoxy)phosphoryl)bis(azanediyl)dipropanoate

[00814] The phosphorodiamidate was prepared according to Method B.

[00815] In a first step, a suspension of ((2R,3R,4R,5R)-2-(2-amino-6-methoxy-9H-purin-9- yl)-5-(hydroxymethyl)-3-methyltetrahydrofuran-3,4-diol (300 mg, 0.96 mmol) in anhydrous tetrahydrofuran (5 mL) was reacted with triethylamine (130 μί, 0.96 mmol) and phosphorus oxychloride (90 μί, 0.96 mmol). In a second step, anhydrous dichloromethane (5 mL), β-alanine benzyl ester tosylate salt (1.69 g, 4.82 mmol) and triethylamine (1.34 mL, 9.63 mmol) were added. After work-up and silica gel column chromatography 170 mg of phosphorodiamidate was obtained in 25% yield as an off white solid.

[00816] 1H NMR (500 MHz, CD ₃ OD) δ 8.00 (s, 1H, ¾), 7.32-7.25 (m, 10H, 2x OCH ₂ Ph),

6.00 (s, 1H, H _r ), 5.07, 5.06 (2s, 4H, 2x OCH ₂ Ph), 4.33-4.26 (m, 3H, H ₅ ' and ¾·), 4.20- 4.17 (m, 1H, ¾·), 4.03 (s, 3H, 60CH ₃ ), 3.21-3.15 (m, 4H, 2x NH-CH ₂ β- Ala), 2.56 (t, J= 6.7 Hz, 2H, CH ₂ β-Ala), 2.55 (t, J= 6.7 Hz, 2H, CH ₂ β-Ala), 0.97 (s, 3H, 2'CCH ₃ ).

[00817] ¹³ C NMR (125 MHz, CD ₃ OD) δ 173.42 (C=0 ester), 162.72 (C6), 161.89 (C2),

154.63 (C4), 139.10 (C8), 137.52 (2x ipso OCH ₂ P/i), 129.87, 129.55, 129.21, 129.18 (2x OCH ₂ P/i), 115.53 (C5), 92.96 (CI '), 82.28 (d, ³ J _C -c-o-p = 8.8 Hz, C4'), 79.51 (C2'), 74.44 (C3'), 67.33 (2x OCH ₂ Ph), 65.48 (d, ² J _C -o-p = 5.0 Hz, C5'), 54.29 (6OCH3), 38.10 (d, ³ / _C -C-N-P =5.0 Hz, NH- H ₂ β-Ala), 37.99 (d, ³ / _C -C-N-P =3.8 Hz, NH- H ₂ β-Ala), 37.38 (CH ₂ β-Ala), 37.34 (CH ₂ β-Ala), 20.36 (2'CCH3).

[00818] ³¹ P NMR (202 MHz, CD ₃ OD) δ 17.45. [00819] HPLC i _R =16.12 min.

[00820] MS (TOF ES+) m/z: 736.32 (M+Na ⁺ , 100%);

[00821] HRMS C ₃ H ₄ iN ₇ O ₁₀ Pi calculated: 714.2653 found: 714.2623

[00822] Example 70

[00823] (2S,2'S)-Neopentyl 2,2'-((((2R,3R,4R,5R)-5-(2-amino-6-methoxy-9H-purin-9-yl)- 3,4-dihydroxy-4-methyltetrahydrofuran-2- yl)methoxy)phosphoryl)bis(azanediyl)bis(3-methylthiopropanoa te)

[00825] Following the standard procedure B.

In the first step, a solution of ((2R,3R,4R,5R)-2-(2-amino-6-methoxy-9H-purin-9- yl)-5-(hydroxymethyl)-3-methyltetrahydrofuran-3,4-diol (330 mg, 1.05 mmol) in anhydrous tetrahydrofuran (5.61 mL) was allowed to react with triethylamine (180 μί, 1.25 mmol) and phosphorus oxychloride (Ι ΙΟμί, 0.803 mmole). In the second step L-methylcysteine neopentyl ester tosylate salt (1.98, 5.25 mmol), anhydrous dichloromethane (6 mL) and triethylamine (1.44 mL, 10.5 mmol) were added as described in Method B. After work-up and silica gel column chromatography, 97 mg of phosphorodiamidate was obtained in 12% yield as an off white solid. [00827] 1H NMR (500 MHz, MeOO-d ₄ ) δ 7.98 (s, 1H, H8), 5.98 (s, 1H, HI '), 4.47-4.38 (m, 2H, CH ₂ 5'), 4.38 (d, J = 9.0 Hz, 1H, H3'), 4.21-4.14 (m, 2H, 2x CHcc Cys), 4.07 (s, 3H, 60CH3), 3.86-3.73 (m, 5H, H4' and 2x OCH ₂ C(CH ₃ ) ₃ ), 2.89-2.83 (m, 4H, 2x CH ₂ Cys), 2.13 , 2.09 (2s, 6H, 2x CH ₃ SCH ₃ Cys), 0.99 (s, 3H, 2'CH ₃ ), 0.96, 0.94 (2s, 18Η, OCH ₂ C(CH ₃ ) ₃ ).

[00828] ¹³ C NMR (125 MHz, MeOD-d ₄ ) δ 173.72 (C=0), 173.68 (d, ³ / _C -C-N-P = 6.3 Hz,

C=0), 162.76 (C6), 161.92 (C2), 154.59 (C4), 139.48 (C8), 115.60 (C5), 93.25 (CI '), 82.43 (d, J3 = 7.56 Hz, C4'), 79.99 (C2'), 75.76, 74.96 (2x OCH ₂ C(CH ₃ ) ₃ ), 74.91 (C3'), 66.88 (C5'), 55.32, 55.00 (2x CHcc Cys), 54.21 (60CH ₃ ), 39.43, 39.35 (2x CH ₂ Cys), 32.25, 32.20 (2x OCH ₂ C(CH ₃ ) ₃ ), 26.84, 26.57 (2x OCH ₂ C(CH ₃ ) ₃ ), 20.26 (2'C H ₃ ), 16.15, 16.11 (2x SCH ₃ Cys).

[00829] ³¹ P NMR (202 MHz, MeOD-d ₄ ) δ 13.36.

[00830] HPLC t _R = 19.89 min (System 1).

[00831] MS (TOF ES+) m/z: 788.28 (M+Na ⁺ , 100%);

[00832] HRMS CsoHsiNvOioPiSiNai calculated 788.2852, found: 788.2844 (M+Na+). [00833] Example 71

[00834] (2S,2'S)-Cyclohexyl 2,2'-((((2R,3R,4R,5R)-5-(2-amino-6-methoxy-9H-purin-9- yl)-3,4-dihydroxy-4-methyltetrahydrofuran-2- yl)methoxy)phosphoryl)bis(azanediyl)bis(3-methylthiopropanoa te)

[00836] Following the standard procedure B. [00837] In the first step, a solution of ((2R,3R,4R,5R)-2-(2-amino-6-methoxy-9H-purin-9- yl)-5-(hydroxymethyl)-3-methyltetrahydrofuran-3,4-diol (550 mg, 1.77 mmol) in anhydrous tetrahydrofuran (9.5 mL) was allowed to react with triethylamine (300 μί, 2.12 mmol) and phosphorus oxychloride (200μί, 2.12 mmole). In the second step L-methylcysteine cyclohexyl ester hydrochloride salt (1.98, 5.25 mmol), anhydrous dichloromethane (10 mL) and triethylamine (2.43 mL, 17.7 mmol) were added as described in Method B. After work-up and silica gel column chromatography, 110 mg of phosphorodiamidate was obtained in 8% yield as an off white solid.

[00838] 1H NMR (500 MHz, CDCl ₃ -£¾ δ 7.78 (s, 1H, H8), 5.96 (s, 1H, HI '), 5.52 (broad s, 2H, 2 NH Cys), 4.78-4.73 (m, 2H, 2 CH cHex), 4.57-4.54 (m, 2H, CH2 5'), 4.43 (m, H3'), 4.33-4.11 (m, 3H, 2 CH Cys & H4'), 4.03 (s, 3H, 60CH3), 2.86- 2.06 (m, 4H, 2 CH2 Cys), 2.10 (s, 3H, SCH3), 2.06 (s, 3H, SCH3), 1.79 (m, 4H, 2x CH2 cHex), 1.67 (m, 4H, 2x CH2 cHex), 1.49 (m, 2H, CH2 cHex), 1.40-1.19 (m, 10H, 5x CH2 cHex), 0.97 (s, 3H, 2'CH3).

[00839] ¹³ C NMR (125 MHz, CDCl ₃ -<¾) δ 171.77, 171.60 (2d, ³ J _C -c-o-p = 5.0 Hz, C=0

Cys), 161.56 (C6), 159.62 (C2), 152.90 (C4), 137.90 (C8), 115.51 (C5), 91.68 (CI '), 80.98 (d, ), 79.33 (C2'), 74.54 (C3'), 74.48, 74.23 (2x OCR cHex), Hz, C5'), 55.86 & 53.80 (2x CHcc Cys), 53.73 (60CH3), 38.86, 38.78 (2x H ₂ Cys), 31.41 , 31.37 (CH ₂ cHex), 25.19 ( H ₂ cHex), 23.59 (CH ₂ cHex), 20.25 (2CCH ₃ ), 16.17 (2x CH ₃ Cys).

[00840] ³¹ P NMR (202 MHz, CDCl ₃ -<¾) δ 13.31.

[00841] HPLC ¾ =20.10 min (System 1),

[00842] MS (TOF ES+) m/z: 790.30 (M+H ⁺ , 100%);

[00843] HRMS C ₃₂ H ₅₂ N ₇ OioPiS ₂ calculated 790.3033, found; 790.3000

[00844] Example 72

[00845] (2S,2'S)-Neopentyl 2,2'-((((2R,3R,4R,5R)-5-(2-amino-6-ethoxy-9H-purin-9-yl)-4- fluoro-3-hydroxy-4-methyltetrahydrofuran-2- yl)methoxy)phosphoryl)bis(azanediyl)dipropanoate

[00847] The nucleoside (2R,3R,4R,5R)-5-(2-amino-6-ethoxy-9H-purin-9-yl)-4-fluoro-2- (hydroxymethyl)-4-methyltetrahydrofuran-3-ol was prepared using methods familiar to one skilled in the art, for example as described in Clark, J. L.; Mason, J. C; Hollecker, L.; Stuyver, L. J.; Tharnish, P. M.; McBrayer, T. R.; Otto,M. J.; Furman, P. A.; Schinazi, R. F.; Watanabe, K. A. Synthesis and antiviral activity of 2'-deoxy-2'-fluoro-2'-C-methyl purine nucleosides as inhibitors of hepatitis C virus RNA replication. Bioorg. Med. Chem. Lett. 2006, 16, 1712-1715.

[00848] The phosphorodiamidate was prepared according to the standard procedure B.

[00849] In a first step, a suspension of (2R,3R,4R,5R)-5-(2-amino-6-ethoxy-9H-purin-9- yl)-4-fluoro-2-(hydroxymethyl)-4-methyltetrahydrofuran-3-ol (150 mg, 0.458 mmol) in anhydrous tetrahydrofuran (3 mL) was reacted with triethylamine (60 μί, 0.458 mmol) and phosphorus oxychloride (40 μί, 0.458 mmol). In a second step, anhydrous dichloromethane (3 mL), L-alanine neopentyl ester tosylate salt (760 mg, 2.29 mmol) and triethylamine (640 μί, 4.58 mmol) were added. After work-up and silica gel column chromatography, 30 mg of phosphorodiamidate was obtained in 9% yield as an off white solid.

[00850] 1H NMR (500 MHz, CD ₃ OD) δ 7.97 (s, 1H, H-8), 6.17 (d, Hz, 1H, H- 1 '), 4.57-4.53 (m, 3H, 60CH ₂ CH ₃ and H-3'), 4.44-4.36 (m, 2H, H-5'), 4.23-4.19 (m, 1H, H-4'), 3.99-3.95 (m, 2H, 2x CHcc Ala), 3.84, 3.82, 3.72, 3.66 (2AB, J=10.5 Hz, 4H, 2x OCH ₂ C(CH ₃ ) ₃ ), 1.45 (t, J=7.3 Hz, 3H, 60CH ₂ CH ₃ ), 1.39 (d, 3Η, J=7.1 Hz, CH ₃ Ala), 1.35 (d, 3H, J=7.1 Hz, CH ₃ Ala), 1.23 (d, Hz, 1H, 2'CCH ₃ ), 0.94 (s, 9Η, OCH ₂ C(CH ₃ ) ₃ ), 0.92 (s, 9Η, OCH ₂ C(CH ₃ ) ₃ ). [00851] ¹³ C NMR (125 MHz, CD ₃ OD) δ 175.65 (d, 6.3 Hz, C=0), 175.60 (d,

(C4), 139.42 (C8), 39 Hz, CI '), 81.92 (d, ³ J c-c-o-p = 7.5 Hz, C4'), 75.38 (OCH ₂ C(CH ₃ ) ₃ ), 75.36 (O H ₂ C(CH ₃ ) ₃ ), 74.04 (d, ² Jc-c-F= 18 Hz, C3'), 66.15 (d, ² J _C -o-p = 3.8 Hz, C5'), 63.58 (60CH ₂ CH ₃ ), 51.11 (Ca Ala), 51.06 (Ccc Ala), 32.32 (OCH ₂ C(CH ₃ ) ₃ ), 32.28 (OCH ₂ C(CH ₃ ) ₃ ), 26.80 (OCH ₂ C( H ₃ ) ₃ ), 26.77 (OCH ₂ C(CH ₃ ) ₃ ), 21.11 (CH ₃ Ala), 20.98 (CH ₃ Ala), 16.89 (d, ² Jc-c-F= 25 Hz 2'C H ₃ ), 14.88 (60CH ₂ CH ₃ ).

[00852] ³¹ P NMR (202 MHz, CD ₃ OD) δ 13.98.

[00853] ¹⁹ F NMR (470 MHz, CD ₃ OD) δ - 162.26.

[00854] HPLC t _R = 20.63 min (System 1).

[00855] MS (TOF ES+) m/z: 712.31 (M+Na ⁺ , 100%);

[00856] Example 73

[00857] (2R,2'R)-neopentyl 2,2'-((((2R,3R,4R,5R)-5-(2-amino-6-ethoxy-9H-purin-9-yl) 4- fluoro-3-hydroxy-4-methyltetrahydrofuran-2- yl)methoxy)phosphoryl)bis(azanediyl)dipropanoate

[00858] The phosphorodiamidate was prepared according to the standard procedure B. [00859] A solution of nucleoside (2R,3R,4R,5R)-5-(2-amino-6-ethoxy-9H-purin-9-yl)-4- fluoro-2-(hydroxymethyl)-4-methyltetrahydrofuran-3-ol (0.15 g, 0.46 mmol) and anhydrous NEt (0.08 mL, 0.55 mmol) in anhydrous tetrahydrofuran (2.4 mL) was stirred at RT for 30 min, then cooled to -78°C and POCl ₃ (0.05 mL, 0.55 mmol) was added dropwise. The solution was stirred for 1 hr at -78°C and then at RT for 30 min. The formation of the intermediate was monitored by phosphorus NMR. Then D-Alanine neopentyl ester /?ara-toluene sulfonic acid salt (0.76 g, 2.30 mmol) and anhydrous dichloromethane (3.5 mL) were added and the reaction was cooled to -78°C. Anhydrous NEt ₃ (0.64 mL, 4.60 mmol, 10 eq) was added dropwise and the solution was returned to RT and stirred overnight. After work up, and silica gel chromatography with methanol (2.5%) in chloroform, 0.022 g (0.03 mmol) of the phosphorodiamidate was obtained as an off white solid.

[00860] 1H NMR (d-CDCls) δ 7.76 (s, 1H, H8 guanine), 6.06, 6.02 (d, 1H, J ³ _F _ _H = 18.75

Hz, HI '), 5.31 (broad s, 1H, NH D-Ala), 4.90 (broad s, 1H, NH D-Ala), 4.65-4.61 (m, 1H, H5'), 4.58-4.54 (q, 1H, J = 6.6 Hz, CH ₂ Et), 4.35-4.31 (m, 1H, H5'), 4.19- 4.18 (m, 1H, H4'), 4.07-3.98 (m, 2H, 2 CH D-Ala), 3.91-3.88 (dd, 2H, J = 4.55 & 10.45 Hz, CH ₂ neopentyl), 3.73-3.71 (dd, 2H, J = 1.15 & 10.45 Hz, CH ₂ neopentyl), 1.48- 1.45 (t, 3H, J = 7.1 Hz, CH ₃ Et), 1.44- 1.42 (t, 6H, J = 6.47 Hz, 2 CH ₃ D-Ala), 1.29 & 1.25 (d, 3H, , J ³ _F _ _H = 22.70 Hz, CH ₃ 2'), 0.94 & 0.92 (2s, 18H, 6 CH ₃ neopentyl).

[00861] ¹³ C NMR (d-CDCl ₃ ) 5 _C (ppm): 175.15 (s, CO D-Ala), 174.28 (d, J ³ _P _ _C = 5.04 Hz,

CO D-Ala), 161.32 (s, C6 guanine), 159.59 (s, C2 guanine), 153.20 (s, C4 guanine), 137.37 (s, C8 guanine), 115.71 (s, C5 guanine), 101.92 & 100.48 (2s, C2'), 89.23 (d, f _F _c = 40.32 Hz, CI '), 79.97 (d, J ³ _P _ _C = 7.56 Hz, C4'), 74.82 (2s, 2 OCH ₂ C(CH ₃ ) ₃ ), 71.93 (s, C3'), 63.03 (s, CH ₂ Et), 62.71 & 62.57 (2d, J ² _P _ _C = 17.64 Hz, C5'), 49.78 & 49.43 (2s, 2 CH D-Ala), 31.36 & 31.23 (2s, 2 OCH ₂ C(CH ₃ ) ₃ ), 26.33 & 26.25 & 26.14 (3s, 2 OCH^CiCH^ ). 21.35 & 21.00 (2d, J ³ P_ _C = 6.30 & 8.87 Hz, 2 CH ₃ D-Ala), 16.59 (d, f _F . _c = 25.20 Hz, CH ₃ 2'), 14.47 (s, CH ₃ Et).

[00862] ³¹ P NMR (d-CDCl ₃ ) δ _Ρ (ppm): 13.86 (s).

[00863] MS (TOF ES ⁺ ): 690.34 (M + H ⁺ ), 712.33 (M + Na ⁺ ); accurate mass: calculated for

C ₂₉ H ₅ oN ₇ 0 ₉ FP: 690.3392, found: 690.3406 (M + H ⁺ ), 712.3275 (M+Na ⁺ ). [00864] Further to the above Examples, representative compounds, prepared according to the examples were tested for potency in an HCV replicon assay (Genotype lb) for activity against the virus (EC ₅₀ ) and toxicity to the cells (CC ₅₀ ). These results are set forth below.

[00865] Huh7 Replicon Cell Lines and Cell Culture Conditions: A luciferase-reporter genotype lb subgenomic replicon cell line, and a genotype la full-length replicon cell line were obtained from Apath, LLC, Brooklyn, NY: All cell lines were passaged twice a week by splitting 4 or 6 fold. Cells were maintained in DMEM- high glucose medium (HyClone, Logan, UT) supplemented with 9% FBS (HyClone), 2 mM glutamine (Invitrogen, Carlsbad, CA), 100 U/ml PenStrep (Invitrogen). Media also contained 0.25 mg/ml of the antibiotic G-418 to maintain stable expression of the replicon (Invitrogen). Incubation was performed at 37 °C in 5% C0 ₂ atmosphere. Replicon cell lines were used until they accumulated 15- to-18 passages, after which cells were restarted from the frozen stock. Seeding cell counts were routinely determined using an automatic Cedex HiRes cell counter (Flownomics Analytical Instruments, Madison, WI) or manually using INCYTO

C-Chip Disposable Hemacytometers (Fisher Scientific, Pittsburg, PA). [00866] The anti-HCV assays were done accordingly:

[00867] Luciferase Genotype lb Replicon Potency Assay. Replicon cells were seeded into white 96- well plates (Nunc/VWR) at a density of 2xl0 ⁴ cells/well in medium without G-418. A Stacker Multidrop Liquid Dispenser (MTX Lab Systems, Vienna, VA) was employed to ensure uniform and fast cell seeding into multiple plates. 18-24 h after cell plating, inhibitors were added and cells were incubated for additional 24, 48, or 72 h (as indicated). Compounds were tested in triplicates and quadruplicates at 3X or 4X serial dilutions over a range of 0.0001-to-lO μΜ concentrations. HCV replication was monitored by Renilla luciferase reporter activity assay using Renilla luciferase reporter (Promega, Madison, WI) and a Veritas Luminometer (Turner Biosystems, Sunnyvale, CA). 50% and 90% inhibitory concentration (IC ₅₀ and IC ₉₀ ) values were calculated as the concentration of compound that results correspondingly in 50% and 90% decreases in the reporter expression as compared to untreated cells. The values were determined by non-linear regression (four-parameter sigmoidal curve fitting) analysis.

[00868] The cell cytotoxicity assay data was obtained as described below:

[00869] Cytotoxicity Assay. Cells were seeded into 96-well plates at a density of 2xl0 ⁴ cells per well. 24 h after cell plating, 11 serial 2X compound dilutions, starting with 100 μΜ, were applied to the testing plates (3 repeats per compound dilution). Each testing plate was run with a "no-compound" control. Incubation with compounds was continued at 37 °C in a C0 ₂ incubator for 72 h. To determine cell viability, the CellTiter-Glo® assay (Promega, Madison, WI) was performed according to the manufacturer's protocol. The compound concentration resulting in 50% luminescent signal was reported as the CC ₅₀ concentration.

[00870] The results of the assay in terms of IC ₅₀ (μΜ) and CC ₅₀ (μΜ) are given in Table 1 below:

[00871] Table 1



] While the invention has been described with reference to particularly preferred embodiments and examples, those skilled in the art recognize that various modifications may be made to the invention without departing from the spirit and scope thereof. [00873] All of the above U.S. patents, U.S. patent application publications, U.S. patent applications, foreign patents, foreign patent applications and non-patent publications referred to in this specification and/or listed in the Application Data Sheet are incorporated herein by reference, in their entirety.

[00874] Abbreviations and Acronyms

[00875] A number of abbreviations and acronyms are used herein, and a full description of these are provided as follows:

ACN acetonitrile

AIBN azobisisobutryonitrile

anhy anhydrous

Bn benzyl (phenylmethyl)

Boc benzyloxycarbonyl

BSA benzenesulfonic acid

Bu butyl

n-BuOH w-butanol

i-BuOH ie/t-butanol

i-BuOK potassium -iert-butoxide

ie/t-BuMgCl ie/t-butylmagnesium chloride

CDCI ₃ deuterochloroform

CD ₃ OD methanol-<¾

CI-MS chemical ionization mass spectrometry

13 C NMR carbon- 13 nuclear magnetic resonance spectroscopy cone concentrated

d doublet (NMR)

dd doublet of doublets (NMR)

ddd double doublet of doublets (nmr

DBU diaza(l,3)bicyclo[5.4.0]undecane

DCC dicyclohexylcarbodiimide

DCM dichloromethane

DMAP 4-dimethylaminopyridine

DMF N,N-dimethylformamide

DMSO dimethyl sulfoxide

dt doublet of triplets (NMR) EDCI 1 -(3-dimethylamnopropyl)-3-ethylcarbodiimide hydrochloride

ee enantiomeric excess

El-MS electron impact mass spectrometry

equiv equivalent(s)

ESI electrospray ionization

ES-MS electrospray mass spectrometry

Et ₃ N triethylamine

Et ₂ 0 ethyl ether

EtOAc ethyl acetate

EtOH ethanol

g gram(s)

GC-MS gas chromatography-mass spectrometry h hour

HCV hepatitis C virus

1H NMR proton nuclear magnetic resonance spectroscopy

HPLC high performance liquid chromatography

HRMS high resolution mass spectrometry

IMPDH inosine 5 'monophosphate dehydroxgenase

J NMR coupling constant

LC/MS liquid chromatography-mass spectrometry

LG leaving group

LHMDS Lithium hexamethyldisilazide

m multiplet (NMR)

MDI methylenediphenyldisocyanate

Me methyl

MeOH methanol

mg milligram

MHz megahertz

mL milliliter

mmol millimole

mp melting point

m/z mass-to-charge ratio

MTBE methyl t-butyl ether

NaOMe sodium methoxide NMI N-methylimidazole

NMO N-methylmorpholine-N-oxide

NMR nuclear magnetic resonance

31 P NMR phosphorous-31 nuclear magnetic resonance spectroscopy

ppm part per million

q quartet (NMR)

pTSA /7-toluenesulfonic acid

RBV ribavirin

Red-Al® sodium bis(2-methoxyethoxy)aluminumhydride

R _f retention factor (TLC)

rt room temperature

s singlet (NMR)

t triplet (NMR)

TBAF tetra-w-butylammonium fluoride

TBPPS tetra-w-butylphosphonium persulfate

TEA triethylamine

TFA trifluoroacetic acid

THF tetrahydrofuran

TMS tetramethylsilane

TMSOTf trimethylsilyl trifluoromethanesulfonate i _R retention time

TLC thin layer chromatography

UV ultraviolet

VCD Vibrational Circular Dichroism