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Title:
PROCESS FOR PREPARING PHOSPHORAMIDATE DERIVATIVES OF NUCLEOSIDE COMPOUNDS FOR TREATMENT OF VIRAL INFECTIONS
Document Type and Number:
WIPO Patent Application WO/2014/047117
Kind Code:
A1
Abstract:
Processes for the production of nucleoside phosphoramidate compounds having the following Formula I are provided.

Inventors:
SCHMIDT, Michael (1 Squibb DriveNew Brunswick, New Jersey, 08903, US)
SILVERMAN, Steven (1 Squibb DriveNew Brunswick, New Jersey, 08903, US)
EASTGATE, Martin D. (1 Squibb DriveNew Brunswick, New Jersey, 08903, US)
Application Number:
US2013/060306
Publication Date:
March 27, 2014
Filing Date:
September 18, 2013
Export Citation:
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Assignee:
BRISTOL-MYERS SQUIBB COMPANY (Route 206 and Province Line Road, Princeton, New Jersey, 08543, US)
International Classes:
C07H1/02; C07H19/06; C07H19/16
Domestic Patent References:
WO2012040127A1
WO2010081082A2
WO2012040124A1
WO2008048128A1
WO2010081082A2
WO2010081102A2
Foreign References:
US7964580B2
US7429572B2
Other References:
BARANIAK J ET AL: "Synthesis of nucleoside-amino acid conjugates containing boranephosphate, boranephosphorothioate and boranephosphoramidate linkages", TETRAHEDRON LETTERS, PERGAMON, vol. 45, no. 4, 19 January 2004 (2004-01-19), pages 671-675, XP004481315, ISSN: 0040-4039, DOI: 10.1016/J.TETLET.2003.11.066
Attorney, Agent or Firm:
GIBBONS, Maureen S. et al. (Bristol-Myers Squibb Company, P.O. Box 4000Princeton, New Jersey, 08543-4000, US)
Download PDF:
Claims:
We claim:

1. A process for making a compound having the following Formula I:

I

comprising the steps of:

(1) contacting a compound having the formula II:

II wherein

X is a BH3 or S;

Ar is selected from phenyl, naphthyl,

any of which are optionally substituted with Ci-C6alkyl, Ci-C6alkoxy, di(Ci-C6)alkylamino or Ci-C6alkylcarboxy(Ci-C6)alkyl-; R4 and R5 are independently selected from hydrogen, Ci-C6alkyl optionally substituted with alkylthio, benzyl optionally substituted with one or more

halo,Ci-C6alkyl, or Ci-C6alkoxy, phenyl optionally substituted with one or more halo, Ci-C6alkyl, or Ci-C6alkoxy;

R6 is selected from Ci-Cioalkyl, Cs-Cscycloalkyl, Cs-Cscycloalkyl-alkyl-, phenyl(Ci-C6)alkyl- optionally substituted with Ci-C6alkyl, Ci-C6alkoxy, and halo, indanyl and heterocycloalkyl; and

LG is selected from the group consisting of halo, -P(0)R20, -S02R21, -COR22,

20 21 22

wherein R is alkoxy, aryloxy or iodide; and R and R are alkyl, alkoxy or aryl;

-pentafluorophenol, -p-nitrophenol, and optionally substituted heteroaryl; with a compound having the formula III:

Base is a naturally occurring or modified purine or pyrimidine base linked to the furanose ring through a carbon or nitrogen atom;

R3 is O or -OH;

R7 is selected from the group consisting of -OH, halo, and alkyl; and R8 is selected from the group consisting of -OH, halo, alkyl, alkenyl, and alkynyl; and

R9 is selected from the group consisting of H, lower alkyl, CN, vinyl, O-lower alkyl, hydroxyl lower alkyl, -CH2F, -CH2CN, -CH2NH2, CH2NHCH3, -N3, alkyne, and halo for a time and under conditions sufficient to yield a compound having the following formula IV:

IV

and

(2) contacting the compound of formula IV

with an oxidant under time and conditions sufficient to yield the compound of formula I.

2. The process of claim 1 wherein X is S.

3. The process of claim 1 wherein X is BH3.

4. The process of claim 1 wherein said oxidant is selected from the group consisting of m-chloroperbenzoic acid, MMPP, tetra-n-butylammonium oxone, peracetic acid, hydrogen peroxide, alkyl peroxide, cumene hydroperoxide, perboric acid, oxone, and dioxiranes.

A process for making a compound having the following Formula IA:

comprising the steps of:

(1) contacting a compound having the formula IIA:

IIA wherein

X is a BH3 or S; and

LG is selected from the group consisting of -p-nitrophenol, LG is selected from the group consisting of halo, -P(0)R20, -S02R21, -COR22, wherein R20 is alkoxy, aryloxy or iodide; and R21 and R22 are alkyl, alkoxy or aryl; -pentafluorophenol, -p-nitrophenol, and optionally substituted heteroaryl; with a compound having the formula IIIA:

for a time and under con ing the formula IVA:

IVA

and

(2) contacting the compound of formula IVA

with an oxidant under time and conditions sufficient to yield the compound of formula IA.

The process of claim 5 wherein X is S. The process of claim 5 wherein X is BH3.

8. A process for making a compound having the following Formula IB:

IB

comprising the steps of:

(1) contacting a compound having the formula IIB:

IIB

wherein

X is a BH3 or S; and

LG is selected from the group consisting of halo, -P(0)R20, -S02R21, -COR22,

20 21 22

wherein R is alkoxy, aryloxy or iodide; and R and R are alkyl, alkoxy or aryl; -pentafluorophenol, -p-nitrophenol, and optionally substituted heteroaryl; with a compound having the for

IIIB

for a time and under conditions sufficient to yield a compound having the formula IVB

(2) contacting the compound of formula IVB

with an oxidant under time and conditions sufficient to yield the compound of formula IB.

9. The process of claim 8 wherein X is S. 10. The process of claim 8 wherein X is BH3.

11. A compound having the following Formula IIA:

IIA

wherein X is S or BH3 and LG is selected from the group consisting of -p-nitrophenol, halo, -P(0)R20, -S02R21, -COR22, wherein R20 is alkoxy, aryloxy or iodide; and R21 and R22 are alkyl, alkoxy or aryl; -pentafluorophenol, -p-nitrophenol, and optionally substituted heteroaryl.

12. The compound of claim 12 wherein LG is -p-nitrophenol.

13. A compound having the following Formula IIB :

wherein

X is a BH3 or S; and

LG is selected from the group consisting of -p-nitrophenol, wherein X is S or BH3 and LG is selected from the group consisting of -p-nitrophenol, halo, -P(0)R20, -SO2R21,

-COR , wherein R is alkoxy, aryloxy or iodide; and R and R are alkyl, alkoxy or aryl; -pentafluorophenol, -p-nitrophenol, and optionally substituted heteroaryl.

14. The compound of claim 13 wherein LG is p-nitrophenol.

15. The process according to claim 1 wherein Base is:

wherein R17, R18, R19, R30, and R11 are independently, H, F, CI, Br, I, OH, OR', SH, amino, lower alkyl, halogenated lower alkyl, or lower alkoxy.

Description:
PROCESS FOR PREPARING PHOSPHORAMIDATE DERIVATIVES OF NUCLEOSIDE COMPOUNDS FOR TREATMENT OF VIRAL INFECTIONS

[0001] This application claims the benefit of U.S. Provisional Application Serial Number 61/702,537 filed September 18, 2012.

FIELD OF THE INVENTION

[0002] This application relates to novel methods for preparing nucleoside

phosphoramidates that are useful as agents for treating viral diseases.

BACKGROUND OF THE INVENTION

[0003] 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.

[0004] 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.

[0005] 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

[0006] 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.

[0007] International Patent Publication No. WO 2010/081082 discloses novel phosphoramidate nucleoside prodrugs with improved properties over known therapeutics. Additional nucleoside prodrugs are disclosed in U.S. Patent Nos. 7,964,580 and

7,429,572. There is a need in the art for improved methods for making these prodrugs.

SUMMARY OF THE INVENTION

The present invention is directed to a process for making a compound having the following Formula I:

I a compound having the formula II:

II wherein

X is a BH 3 or S;

Ar is selected from phenyl, naphthyl,

any of which are optionally substituted with Ci-C 6 alkyl, Ci-C 6 alkoxy,

di(Ci-C6)alkylamino or Ci-C 6 alkylcarboxy(Ci-C6)alkyl-;

R 4 and R 5 are independently selected from hydrogen, Ci-C 6 alkyl optionally substituted with alkylthio, benzyl optionally substituted with one or more

halo,Ci-C 6 alkyl, or Ci-C 6 alkoxy, phenyl optionally substituted with one or more halo, Ci-C 6 alkyl, or Ci-C 6 alkoxy;

R 6 is selected from Ci-Cioalkyl, Cs-Cscycloalkyl, Cs-Cscycloalkyl-alkyl-, phenyl(Ci-C6)alkyl- optionally substituted with Ci-C 6 alkyl, Ci-C 6 alkoxy, and halo, indanyl and heterocycloalkyl; and

LG is selected from the group consisting of halo, -P(0)R 20 , -S0 2 R 21 , -COR 22 ,

20 21 22

wherein R is alkoxy, aryloxy or iodide; and R and R are alkyl, alkoxy or aryl;

-pentafluorophenol, -p-nitrophenol, and optionally substituted heteroaryl; with a compound having the formula III

III

wherein

Base is a naturally occurring or modified purine or pyrimidine base linked to the furanose ring through a carbon or nitrogen atom;

R 3 is O or -OH;

R 7 is selected from the group consisting of -OH, halo, and alkyl; and

R 8 is selected from the group consisting of -OH, halo, alkyl, alkenyl, and alkynyl; and R 9 is selected from the group consisting of H, lower alkyl, CN, vinyl, O-lower alkyl, hydroxyl lower alkyl, -CH 2 F, -CH 2 CN, -CH 2 NH 2 , CH 2 NHCH 3 , -N 3 , alkyne, and halo for a time and under conditions sufficient to yield a compound having the following formula IV:

and

(2) contacting the compound of formula IV

with an oxidant under time and conditions sufficient to yield the compound of formula I.

[0008]

[0009] According to one embodiment of the present invention, a process for making a compound having the following Formula IA is provided:

comprising the steps of: contacting a compound having the formula IIA:

wherein

X is a BH 3 or S; and

LG is selected from the group consisting of -p-nitrophenol, LG is selected from

20 21 22 20

the group consisting of halo, -P(0)R , -SO2 , -COR , wherein R is alkoxy, aryloxy or iodide; and R 21 and R 22 are alkyl, alkoxy or aryl; -pentafluorophenol, -p-nitrophenol, and optionally substituted heteroaryl; with a compound having the formula IIIA:

IIIA

a time and under conditions sufficient to yield a compound having the formula IVA:

IVA

and

(2) contacting the compound of formula IVA

with an oxidant under time and conditions sufficient to yield the compound of formula IA. [0010] According to one embodiment of the present invention, a process for making a compound having the following Formula IB is provided:

IB

comprising the steps of:

(1) contacting a compound having the formula IIB:

IIB

wherein

X is a BH 3 or S; and

LG is selected from the group consisting of halo, -P(0)R 20 , -S0 2 R 21 , -COR 22 ,

20 21 22

wherein R is alkoxy, aryloxy or iodide; and R and R are alkyl, alkoxy or aryl;

-pentafluorophenol, -p-nitrophenol, and optionally substituted heteroaryl; with a compound having the formula IIIB:

IIIB

a time and under conditions sufficient to yield a compound having the formula IVB

IVB

and

(2) contacting the compound of formula IVB

with an oxidant under time and conditions sufficient to yield the compound of formula

IB.

DETAILED DESCRIPTION

Definitions

[0011] 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 (lower alkyl), 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, neopentyl and dodecyl. The term "Cs-Cs cycloalkyl" refers to cyclic alkyl group comprising from about 3 to about 8 C atoms. The term "C3-C8 cycloalkyl-alkyl" refers to an acyclic alkyl group substituted by a cyclic alkyl group comprising from about 3 to about 8 C atoms.

[0012] 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.

[0013] 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.

[0014] As use herein, the term "alkoxy" or the term "alkyloxy" refers to the group alkyl-O-, 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, iso-propoxy, n- butoxy, tert-butoxy, sec-butoxy, n-pentoxy, n-hexoxy and

1,2-dimethylbutoxy. The term "cycloalkyloxy" refers to the group cyclicalkyl-O-, 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.

[0015] As used herein, the term "alkylthio" refers to 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, iso-propylthio, n-butylthio, tert-butylthio, sec-butylthio, n-pentylthio, n-hexoxy and

1 ,2-dimethylbutylthio.

[0016] The term "alkylamino" refers to a group alkyl-NR R 2 -, wherein R 1 and R 2 are H, alkyl, aryl and where alkyl is defined as above.

[0017] As used herein, the term "halo" refers to halogen atoms such as I, Br, CI and F.

[0018] 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.

[0019] 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.

[0020] 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.

[0021] 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.

[0022] 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.

[0023] As used herein, the term "aryl(Ci-C6)alkyl-" refers to a Ci-Ce 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(Ci-C6)alkyl- groups include benzyl, 1 -phenylethyl, 3-phenylpropyl, 4-chlorobenzyl, 4-fluorobenzyl, 2,4-difluorobenzyl, and the like.

[0024] As used herein, the term "alkylcarboxy(Ci-C6)alkyl-" refers to a Ci-Ce 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(Ci-C6)alkyl- groups include acetoxymethyl [CH 3 C(=0)0-CH 2 -], propanoyloxyethyl [CH 3 CH 2 C(=0)0-CH 2 CH2-], weopentoyloxypropyl

[(CH 3 ) 3 CCH 2 C(=0)0-CH 2 CH 2 CH 2 -] and the like.

[0025] 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. [0026] 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), Ci-C 6 monoalkylamino, Ci-C6 dialkylamino, thiol, chloro, bromo, fluoro, iodo, SO3H, -SH, -SR', wherein R' is independently selected from halo, Ci-C 6 alkoxy, and Ci-C 6 alkyl.

[0027] 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 20 " or "C5-C 10 " 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 atom. By way of non-limiting examples, suitable heterocycloalkyl groups include tetrahydrofuranyl, tetrahydropyranyl, pyrrolidinyl, morpholinyl, tetrahydrothiopyranyl, thiomorpholinyl, and piperidinyl [0028] the term "indanyl" refers to the fused bicyclic substituent of structure, rein the point of attachment of the radical to the rest of the molecule is on any available non-aromatic carbon atom.

[0029] 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, (Ci-C6)alkylamino, (Ci-C6)dialkylamino, thiol, chloro, bromo, fluoro and iodo.

[0030] 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.

[0031] As used herein the term "LG" refers to - please provide a functional definition here. The term "LG" refers to a group with a propensity to be easily substituted by another group.

[0032] As used herein the term "oxidant" refers to - please provide a definition here and a list of examples. This list can be broader than the oxidants that we actually claim specifically. The term "oxidant", in this particular invention refers to a chemical or chemicals that can transfer an oxygen atom to the substrate, replacing the P=X with a P=0. For example m-chloroperbenzoic acid, MMPP, tetra-n-butylammonium oxone, m-chloroperbenzoic acid, MMPP, peracetic acid, hydrogen peroxide, alkyl peroxides, such as ?-butylhydrogen peroxide and cumene hydroperoxide, oxone, perboric acid, or dioxiranes, such as DMDO or TFDO. [0033] The "S" and "R" designations as used herein are determined using the

Cahn-Ingold-Prelog method.

[0034] The term "diastereomerically enriched" as used herein refers to an instance where, due to the stereochemical information at phosphorus, the mole amount of one diastereomer (Rp or Sp) exceeds the mole amount of the other diastereomer. Recognizing that the phosphorus atoms in the compounds of the present invention are stereogenic, one of ordinary skill will understand that a composition, comprised of the compounds of the present invention, comprises mixtures of diastereomers. "Diastereomerically enriched" means a composition having at least about 51 mol% to about 100 mol% of one diastereomer (with stereochemistry at phosphorous of either Sp or Rp) and at most 49 mol% to 0 mol% of the other diastereoisomer (Rp or Sp). Within this meaning,

"diastereomerically enriched" includes a composition comprised of about at least about 60 mol% of one diastereomer to about 40 mol% of the other, about 70 mol% of one diastereomer to about 30 mol% of the other, about 80 mol% of one diastereomer to about 20 mol% of the other, about 90 mol% of one diastereomer to about 10 mol% of the other, about 95 mol% of one diastereomer to about 5 mol% of the other, about 97 mol% to about 5 mol% of the other, about 98 mol% to about 2 mol% of the other, of about 99 mol% of diastereomer to about 1 mol% of the other, about 99.5 mol% of one

diastereomer to about 0.5 mol% of the other, about 99.9 mol% of one diastereomer to about 0.1 mol% of the other.

[0035] The term "salt" refers to organic and inorganic salt forms of the phosphoric acids of the present invention. These salts may be derived from a variety of organic and inorganic counter ions well known in the art and include, by way of example, quinine salt, DBU salt, calcium salts and zinc salts. These salt forms may also contain a range of hydrates and solvates.

[0036] Unless otherwise indicated, the term "alkylthio", "arylthio" or "aralkylthio" as employed herein alone or as part of another group includes any of the above alkyl, aralkyl or aryl groups linked to a sulfur atom.

[0037] The term "acyl" as used herein alone or as part of another group refers to a radical linked to a carbonyl (C=0) group which radical can be, for example, lower alkyl, aryl, heterocyclo, heteroaryl, cycloalkyl, lower alkoxy or amino. [0038] The term "naturally occurring or modified purine or pyrimidine base" refers to those naturally occurring and modified nucleoside bases such as adenine, N 6 -alkylpurines, N 6 -acylpurines (wherein acyl is C(0)(alkyl, aryl, alkylaryl, or arylalkyl),

N 6 -benzylpurine, N 6 -halopurine, N 6 -vinylpurine, N 6 -acetylenic purine, N 6 -acyl purine, N 6 -hydroxyalkyl purine, N 6 -allylaminopurine, N 6 -thioallyl purine, N 2 -alkylpurines, N 2 -alkyl-6-thiopurines, thymine, cytosine, 5-fluorocytosine, 5-methylcytosine,

6-azapyrimidine, including 6-azacytosine, 2- and/or 4-mercaptopyrmidine, uracil, 5-halouracil, including 5-fluorouracil, C 5 -alkylpyrimidines, C 5 -benzylpyrimidines, C 5 -halopyrimidines, C 5 -vinylpyrimidine, C 5 -acetylenic pyrimidine, C 5 -acyl pyrimidine, C 5 -hydroxy alky 1 purine, C 5 -amidopyrimidine, C 5 -cyanopyrimidine, C 5 -5-iodopyrimidine, C 6 -iodo-pyrimidine, C 5 -Br-vinyl pyrimidine, C 5 -Br-vinyl-pyrimidine, C 5 -nitropyrimidine, C 5 -amino-pyrimidine, N 2 -alkylpurines, N 2 -alkyl-6-thiopurines, 5-azacytidinyl,

5-azauracilyl, triazolopyridinyl, imidazolopyridinyl, pyrrolopyrimidinyl, and

pyrazolopyrimidinyl. Purine bases include, but are not limited to, guanine, adenine, hypoxanthine, 2,6-diaminopurine, and 6-chloropurine. Additional non-classical purine bases include pyrrolo[l,2-fJ[l,2,4]triazines, imidazo[l,5-fJ[l,2,4]triazines,

imidazo[l,2-fJ[l,2,4]triazines, and [l,2,4]triazolo[4,3-fJ[l,2,4]triazines, all of which are optionally substituted. The purine and pyrimidine bases of Formula I are linked to the ribose sugar, or analog thereof, through a nitrogen atom or carbon atom of the base.

Functional oxygen and nitrogen groups on the base can be protected as necessary or desired. Suitable protecting groups are well known to those skilled in the art, and include, but are not limited to, trimethylsilyl, dimethylhexylsilyl, ?-butyldimethylsilyl, and ?-butyldiphenylsilyl, trityl, alkyl groups, and acyl groups such as acetyl and propionyl, methanesulfonyl, and p-toluenesulfonyl.

[0039] The present invention is directed to processes and intermediates that are useful for preparing nucleoside phosphoramidate prodrugs having the following Formula I:

I

comprising the steps of:

(1) contacting a compound having the formula II:

wherein

X is a BH 3 or S;

Ar is selected from phenyl, naphthyl,

any of which are optionally substituted with Ci-C 6 alkyl, Ci-C 6 alkoxy,

di(Ci-C6)alkylamino or Ci-C 6 alkylcarboxy(Ci-C6)alkyl-;

R 4 and R 5 are independently selected from hydrogen, Ci-C 6 alkyl optionally substituted with alkylthio, benzyl optionally substituted with one or more

halo,Ci-C 6 alkyl, or Ci-C 6 alkoxy, phenyl optionally substituted with one or more halo, Ci-C 6 alkyl, or Ci-C 6 alkoxy; R 6 is selected from Ci-Cioalkyl, Cs-Cscycloalkyl, Cs-Cscycloalkyl-alkyl-, phenyl(Ci-C6)alkyl- optionally substituted with Ci-C 6 alkyl, Ci-C 6 alkoxy, and halo, indanyl and heterocycloalkyl; and

LG is selected from the group consisting halo, -P(0)R 20 , -S0 2 R 21 , -COR 22 ,

1

wherein R is alkoxy, aryloxy or iodide; R and R are alkyl, alkoxy or aryl;

-pentafluorophenol, -p-nitrophenol, and optionally substituted heteroaryls, preferably 2-hydroxypyridyl, HOBt, HATU and hydroxysuccinidide; with a compound having the formul wherein

Base is a naturally occurring or modified purine or pyrimidine base linked to the furanose ring through a carbon or nitrogen atom;

R 3 is O or -OH;

R 7 is selected from the group consisting of -OH, halo, and alkyl; and

R 8 is selected from the group consisting of -OH, halo, alkyl, alkenyl, and alkynyl; for a time and under conditions sufficient to yield a compound having the following formula IV:

IV

and

(2) contacting the compound of formula IV

with an oxidant under time and conditions sufficient to yield the compound of formula I. According to one embodiment of the present invention, Base is selected from

[0041] In one preferred embodiment of the present invention, Base is selected from:

wherein R 17 , R 18 , R 19 , R 30 , and R 11 are independently, H, F, CI, Br, I, OH, OR', SH, amino, lower alkyl, halogenated lower alkyl, or lower alkoxy. [0042] According to one embodiment of the present invention, X is S.

[0043] According to one embodiment of the present invention, X is BH 3 .

[0044] According to one embodiment of the present invention, the oxidant is selected from m-chloroperbenzoic acid, MMPP, tetra-n-butylammonium oxone, m- chloroperbenzoic acid, MMPP, peracetic acid, hydrogen peroxide, alkyl peroxides, such as ?-butylhydrogen peroxide and cumene hydroperoxide, oxone, perboric acid, or dioxiranes, such as DMDO or TFDO. [0045] According to one preferred embodiment of the present invention, a process for making a compound having the following Formula IA is provided:

comprising the steps of:

(1) contacting a compound having the formula IIA:

IIA

wherein

X is a BH 3 or S; and

LG is selected from the group consisting halo, -P(0)R 20 , -S0 2 R 21 , -COR 22 , wherein R is alkoxy, aryloxy or iodide; R and R are alkyl, alkoxy or aryl;

-pentafluorophenol, -p-nitrophenol, and optionally substituted heteroaryls, preferably 2-hydroxypyridyl, HOBt, HATU and hydroxysuccinidide defined as above and is preferably -p-nitrophenol, with a compound having the formula IIIA:

IIIA

for a time and under conditions sufficient to yield a compound having the formula IVA:

IVA

and

(2) contacting the compound of formula IVA

with an oxidant under time and conditions sufficient to yield the compound of formula IA.

[0046] According to some embodiments of the present invention, processes for making the following compound IB are provided:

IB

comprising the steps of:

(1) contacting a compound having the formula IIB:

IIB

wherein X is a BH 3 or S; and

LG is selected from the group consisting of halo, -P(0)R 20 , -S0 2 R 21 , -COR 22 , wherein R is alkoxy, aryloxy or iodide; R and R are alkyl, alkoxy or aryl

-pentafluorophenol, -p-nitrophenol, or optionally substituted heteroaryl; with a compound having the for

IIIB

a time and under conditions sufficient to yield a compound having the formula IVB

(2) contacting the compound of formula IVB

with an oxidant under time and conditions sufficient to yield the compound of formula IB.

[0047] The processes of the present invention are illustrated in the synthetic schemes below. SCHEMES

Scheme 1

Step 1 : Direct synthesis from phosphorous trichloride:

-78 °C, 2 h;

BH 3 , 30 min

Ari, Ar 2 = phenyl, naphthyl (should -OAr 2 = LG.

[0048] In the direct synthesis approach, a cooled (-78 to -50 °C) solution of PX 3 (e.g., X is halogen, such as CI or any leaving group) is charged with all three reagents, which may be added in any order, an amino acid derivative (as an HCl salt or free base), and two aryl or heteroaryl alcohols (AriOH, ΑΓ 2 ΟΗ) in any combination. At the cooled temperature, a trialkylamine or any suitable alternative base is added. The reaction is allowed to warm to room temperature, and the amine hydrochloride salt is removed via filtration. The filtrate is concentrated in vacuo, and redissolved in an organic solvent (preferably dichloromethane), cooled (optimally to -78 °C) and a source of BH 3 (1.0 equivalent, preferably a borane-tetrahydrofuran complex, 1.0 M in tetrahydrofuran) is added. The mixture is warmed to room temperature, then directly purified by methods such as distillation, crystallization or, flash column chromatography.

Step 2: Serial displacements from tris(dimethylamino)phosphine:

[0049] In the serial displacement approach, a tris(dialkyl or arylamino)phosphine is dissolved in an organic solvent (preferably dichloromethane at 10 mL/g) and reacted sequentially with two aryl, or heteroaryl alcohols in any combination at an appropriate temperature (20 to 40 °C) monitoring the complete formation by suitable analytical techniques such as TLC, HPLC, ¾ 13 C or 31 P NMR. The phosphoramidite is treated with a strong acid (mineral or organic, pKa > 0, optimally 2.0 equivalents), then filtered into the amino acid derivative in the presence of a suitable base (tertiary alkyl or aryl amine) and stirred for 0.5-2 h at 0-25 °C. The reaction is allowed to warm to room temperature, and the amine hydrochloride salt is removed via filtration. The filtrate is concentrated in vacuo, and redissolved in an organic solvent (preferably

dichloromethane), cooled (optimally to -78 °C) and a source of BH 3 (1.0 equivalent, preferably a borane-tetrahydrofuran complex, 1.0 M in tetrahydrofuran) is added. The mixture is warmed to room temperature, then directly purified by methods such as distillation, crystallization or, flash column chromatography.

Alternate Step 2: Displacement

R 7 = Alkyl

[0050] In the displacement, the phosphino borane and an alcohol are dissolved in an organic solvent or a mixture of organic solvents, then treated with an appropriate base (optimally a strong amine base) at an appropriate temperature (-30 to 50 °C). The reaction is monitored to completion with suitable analytical techniques such as TLC, HPLC, ¾, U B, 13 C or 31 P NMR. After completion of the reaction, the mixture is purified using standard aqueous acidic and/or basic washes then purified by methods such as distillation, crystallization or, flash column chromatography.

Step 3: Oxidation

R 18 = Alkyl, Aryl [0051] The oxidation of the borane to the aminophosphate ester is accomplished by dissolving the borane in a suitable organic solvent (optimally dichloromethane), then reacting with an oxidant (a peracid, optimally meto-chloroperbenzoic acid, optimally 4 equivalents or greater) at mild temperatures (0 to room temperature). The product is purified using standard aqueous acidic and/or basic washes then purified by methods such as distillation, crystallization or, flash column chromatography.

Scheme 2

Sequential displacements from thiophosphoryl chloride:

1. Ar 1 OH

[0052] In the sequential displacement approach, the appropriate nucleophile (Ar 1 = phenyl, naphthyl) was dissolved in an organic solvent (tert-butyl methyl ether is preferred, but dichloromethane and tetrahydrofuran also show reactivity) and the mixture was cooled to -78 °C. Thiophosphoryl chloride was added, followed by triethylamine or similar amine base. The mixture was allowed to warm to room temperature slowly. Upon reaching room temperature, the residual salts were removed by filtration and the filtrate, containing the product was used in the subsequent displacement. The process was repeated with an amine nucleophile (R 1 , R 2 , R 3 = alkyl). The purity of the resulting monochloride species can be judged by suitable analytical techniques (NMR, HPLC, or TLC) and can be further purified if necessary. The compound is then dissolved in dichloromethane, tetrahydrofuran, or acetonitrile (10-20 mL/g) and the third nucleophile is added (R 4 = alkyl or aryl). Triethylamine was added and the mixture stirred for 3-14 hours at room temperature to 65 °C. The mixture can be monitored by HPLC or TLC for disappearance of the chloride intermediate. Upon completion of the reaction, the compound can be purified by silica gel chromatography. Oxidation of the thio hosphoramidate [0053] The oxidation of the thiophosphoramidate to the phosphoramidate is accomplished by dissolving the thiophosphoramidate in dichloromethane and reacting it with a suitable oxidant at room temperature. Meto-chloroperbenzoic acid was found to be optimal, but other oxidants such as MMPP and te?ra-«-butylammonium oxone were also found to be effective. Three equivalents of the oxidant were used. The product is purified using a basic wash.

EXAMPLES

Example 1

Step 1 :

10 %

(25)-Neopentyl 2-(((naphthalen- 1 -yloxy)(4-nitrophenoxy)phosphino)amino)propanoate Borane:

[0054] To a 500 mL round bottomed flask was added 1-naphthol (2.48 g, 17.17 mmol, 1.00 equiv.), ara-nitrophenol (2.39 g, 17.17 mmol, 1.00 equiv), L-alanine neopentyl ester hydrochloride (3.36 g, 17.17 mmol, 1.00 equiv.), and methyl-tert-butyl ether (147 mL). The slurry was cooled in a dry ice / acetone bath and phosphorus trichloride (1.50 mL, 17.17 mmol, 1.00 equiv.) was added, followed by triethylamine (9.80 mL, 70.40 mmol, 4.10 equiv.) slowly over 1 min. The cooling bath was removed, and the mixture was allowed to warm to room temperature and held for 2 h with vigorous stirring. The heterogeneous mixture was filtered over a Buchner filter and the cake was washed with methyl-tert-butyl ether (2 x 50 mL), and then concentrated in vacuo to afford a yellow oil. The oil was dissolved in dichloromethane (80 mL) and cooled in a dry ice / acetone bath. A 1.0 M solution of borane-tetrahydrofuran complex in tetrahydrofuran (17.2 mL, 17.20 mmol, 1.00 equiv) was added slowly over 3 min. The yellow color faded. The cooling bath was removed and the mixture was allowed to warm to room temperature and held for 2 h. The reaction mixture was concentrated in vacuo and purified directly by flash column chromatography over silica gel twice (eluent:

toluene). A mixture of product 1 and 1-naphthol resulted. The product was purified by flash column chromatography over silica gel (eluent: dichloromethane) to afford the product as a clear, colorless gel (859 mg, 10%). ¾ NMR (500 MHz, C 6 D 6 , 22 °C): δ 8.20 (app t, J= 7.4 Hz, 1 H), 7.65-7.70 (m, 2 H), 7.52-7.56 (m, 2 H), 7.39 (app t, J= 8.8 Hz, 1 H), 7.27-7.30 (m, 1 H), 7.19-7.23 (m, 1H), 7.09-7.14 (m, 1 H), 6.90 (dd, J= 9.1, 1.3 Hz, 2 H), 4.27-4.33 (m, l H), 3.98-4.04 (m, 1 H), 3.71 (d, J= 10.4 Hz, 1 H), 3.55 (dd, J = 10.4, 4.7 Hz, 1 H), 1.04 (dd, J= 7.2, 5.4 Hz, 3 H), 1.00-2.00 (br m, 3 H), 0.68 (d, J= 10.1 Hz, 9 H). 13 C MR (125.8 MHz, C 6 D 6 , 22 °C): δ 173.2 (d, J= 5.5 Hz), 173.1 (d, J= 5.5 Hz), 156.0 (d, J= 4.6 Hz), 147.55 (d, J= 4.6 Hz), 147.50 (d, J= 4.6 Hz), 145.5, 135.7 (d, J= 3.7 Hz), 128.7, 127.7 (d, J= 3.7 Hz), 127.4 (d, J= 1.8 Hz), 127.2 (d, J= 3.7 Hz), 126.1 (d, J= 3.7 Hz), 126.0, 125.9, 122.3 (d, J= 10.1 Hz), 121.98 (d, J= 2.8 Hz), 121.96 (d, J= 3.7 Hz), 116.5 (app t, J= 4.6 Hz), 75.2, 50.2, 50.1, 31.6 (d, J= 4.6 Hz), 26.5 (d, J = 1.8 Hz), 21.4 (app t, J= 4.6 Hz). 31 P NMR (202.4 MHz, C 6 D 6 , 22 °C): δ 128.1 (br s).

Alternate Step 1 : Serial Displacement

(25)-Neopentyl 2-(((naphthalen- 1 -yloxy)(4-nitrophenoxy)phosphino)amino)propanoate Borane:

[0055] To a 100 mL round bottomed flask was added 1-naphthol (3.95 g, 27.38 mmol, 1.00 equiv.) and dichloromethane (45 mL). The mixture was stirred for 1 minute to dissolve. Tris(dimethylamino)phosphine (5.00 mL, 27.38 mmol, 1.00 equiv.) was added, and the mixture was stirred for 1 h, then concentrated in vacuo to afford a yellowish oil. The oil was dissolved in dichloromethane (70 mL) and ara-nitrophenol (3.81 g, 27.38 mmol, 1.00 equiv.) was added. The mixture was stirred at room temperature, and the dimethylamine was removed via vacuum every 15 min for 1.5 h. The slurry was concentrated in vacuo, then suspended in a solution of dichloromethane (15 mL) and hexane (30 mL). The slurry was filtered through a 0.2 μιη PTFE filter and cone, in vacuo to afford a yellow oil (9.96 g).

[0056] A portion of the yellow oil (8.80 g, 24.70 mmol, 1.00 equiv.) was dissolved in toluene (88.0 mL) and a solution of HQ in dioxane (4 N, 12.66 mL, 50.63 mmol, 2.05 equiv.) was added. A mild exotherm was noted. The slurry was stirred for 1.5 h. The mixture was filtered rapidly through a 0.45 μιη PTFE filter into a 500 mL round bottomed flask containing a slurry of L-alanine neopentyl ester hydrochloride (4.83 g, 24.70 mmol, 1.00 equiv.) and triethylamine (6.88 mL, 49.39 mmol, 2.00 equiv.) in methyl-tert-butyl ether (88.0 mL) cooled to 0 °C. The filter cake was washed with methyl-tert-butyl ether (50.0 mL). The slurry was allowed to stir at room temperature for 1 h, then it was filtered over a Buchner filter and the cake was washed with methyl-tert-butyl ether (2 x 50 mL), and then concentrated in vacuo to afford a yellow oil. The oil was dissolved in dichloromethane (88.0 mL) and cooled in a dry ice / acetone bath. A 1.0 M solution of borane-tetrahydrofuran complex in tetrahydrofuran (24.70 mL, 24.70 mmol, 1.00 equiv) was added slowly over 3 min. The yellow color faded. The cooling bath was removed and the mixture was allowed to warm to room temperature and held for 1 h. The reaction mixture was concentrated in vacuo and purified directly by flash column chromatography over silica gel twice (eluent: toluene). A mixture of product 1 and 1-naphthol resulted. The product was purified by flash column chromatography over silica gel (eluent:

dichloromethane) to afford the product as a clear, colorless gel (4.90 g, 41%). For structural characterization, see above.

Step 2: Displacement

(25)-Neopentyl-2-(((((2R,3R,4R,5R)-5-(2-amino-6-methoxy-9 H-purin-9-yl)-3,4- dihydroxy-4-methyltetrahydrofuran-2-yl)methoxy)(naphthalen- 1 - yloxy)phosphino)amino)propanoate Borane:

[0057] To a vial was added the furanoside, which can be made according to the procedures outlined in WO 2010/081 102, the disclosure of which is herein incorporated by reference (420 mg, 1.35 mmol, 1.00 equiv.) and DMF (3.15 mL). The mixture was stirred until dissolved (~5 min). A solution of the phosphino-borane (849 mg, 1.75 mmol, 1.30 equiv.) in tetrahydrofuran (3.15 mL) was added, followed by DBU (203 μί, 1.35 mmol, 1.00 equiv.). The bright yellow solution was allowed to stir for 2 h, then was diluted with ethyl acetate (70 mL) and washed with a saturated, aqueous solution of ammonium chloride (50 mL), then brine (2 x 50 mL). The organic layer was dried over sodium sulfate, filtered and cone, in vacuo to afford a yellow oil. The oil was purified by flash column chromatography over silica gel (eluent: 100% ethyl acetate to remove para- nitrophenol, then a gradient of 0 to 10% methanol in dichloromethane) to afford the product as an off-white foam (389 mg, 43%). Note: Running this reaction at -40 °C, gives the product as a 62:38 mixture of diastereomers, which after oxidation with m- CPBA, afforded the phosphates in a 60:40 ratio favoring the V s isomer. X H NMR (500 MHz, C 6 D 6 , 22 °C): δ 8.44 (app dd, J= 13.4, 8.5 Hz, 1 H), 7.92 (br m, 1 H), 7.64 (m, 1 H), 7.56 (app dd, J= 16.4, 8.2 Hz, 1 H), 7.37-7.43 (m, 2 H), 7.22-7.25 (m, 1 H), 6.13 (br s, 1 H), 4.59 (br s, 1 H), 4.48 (br s, 2 H), 4.28-4.37 (m, 3 H), 4.23 (br s, 1 H), 4.12 (br s, 1 H), 3.78-3.86 (br m, 4 H), 3.56-3.72 (br m, 3 H), 1.40 (br s, 3 H), 1.08-1.18 (br m, 4 H), 0.98 (d, J= 6.0 Hz, 3 H), 0.97 (d, J= 6.3 Hz, 3 H), 0.70-0.77 (m, 12 H). 13 C NMR (125.8 MHz, C 6 D 6 , 22 °C): δ 174.3 (br d, J= 3.7 Hz), 174.1 (br d, J= 4.6 Hz), 162.3 (br s), 160.9 (br s), 154.1 (br s), 148.0 (br d, J= 5.5 Hz), 147.8 (br d, J= 5.5 Hz), 138.3 (br s), 135.6 (br d), 127.9 (br s), 127.3 (br s), 127.1 (br s), 126.2 (br s), 125.6 (br s), 122.7 (br s), 116.5 (br s), 1 16.4 (br s), 1 15.6 (br s), 92.2 (br s), 82.1 (br s), 80.0 (br s), 79.9 (br s), 75.1 (br d, J= 5.5 Hz), 74.6 (br s), 67.1 (br s), 66.7 (br s), 54.4 (br s), 50.4 (br s), 50.3 (br s), 50.0 (br s), 31.7, 31.6, 31.6, 26.7 (br s), 26.6 (br s), 21.6 (br d, J= 2.8 Hz), 21.5 (br d, J= 3.7 Hz), 20.9 (br s). 31 P NMR (202.4 MHz, C 6 D 6 , 22 °C): δ 129.5 (br s). HPLC

(PHENOMENEX® Lux Cellulose 1 , A=0.01 M NH 4 OAc in MeCN/water (5 :95), B=0.01 M NH 4 OAc in MeCN/water (95:5), t=0, B=40%; t=20 min, B=70%, t=25 min, B=100%, t=30 min, B=100%), 12.38 min and 15.28 min.

Step 3: Oxidation

(25)-Neopentyl-2-(((((2R,3R,4R,5R)-5-(2-amino-6-methoxy-9H-p urin-9-yl)-3,4- dihydroxy-4-methyltetrahydrofuran-2-yl)methoxy)(naphthalen- 1 - yloxy)phosphoryl)amino)propanoate:

[0058] To a solution of the borane (21.5 mg, 32.8 μιηοΐ, 1.0 equiv) in

dichloromethane (1.0 mL) was added meto-chloroperbenzoic acid (70%, 34.0 mg, 137.8 μιηοΐ, 4.2 equiv), and the mixture stirred for 15 min. The reaction mixture was purified by flash chromatography to afford the product. 31 P NMR (202.4 MHz, DMSO-d 6 , 22 °C): δ 4.2, 3.9. HPLC (SUPELCO® Ascentis Express, A=0.05% TFA in MeCN/water (5:95), B=0.05% TFA in MeCN/water (95:5), t=0, B=15%; t=20 min, B=60%, t=30 min, B=90%, t=33 min, B=100%), 17.90 min and 18.28 min.

Example 2

Step 1 : Preparation of chlorothiophosphoramidate

CH 2 CI 2 , -78 °C→ RT

[0059] In a 250 mL round bottom flask, a solution of 1-naphthol (7.21 g, 50.0 mmol) in tert-butyl methyl ether (72 mL) was cooled to -78 °C. Thiophosphoryl chloride (5.12 mL, 50.0 mmol) was added, followed by triethylamine (6.97 mL, 50.0 mmol) over 15 minutes. The cloudy mixture was allowed to gradually warm to room temperature overnight. Filtration and concentration gave the intermediate dichlorothiophosphate as a clear oil. ¾ NMR (500 MHz, CDC1 3 ): δ 8.14 (d, J=8.2 Hz, 1H), 7.94 - 7.91 (m, 1H), 7.86 - 7.82 (m, 1H), 7.68 - 7.58 (m, 3H), 7.53 - 7.48 (m, 1H). 31 P NMR (CDC1 3 ): δ 53.3. The clear oil was dissolved in dichloromethane (72 mL) and (S)-l-(neopentyloxy)-!- oxopropan-2-aminium chloride (9.78 g, 50.0 mmol) was added. The mixture was cooled to -78 °C and triethylamine (13.9 mL, 100.0 mmol) was added over 15 minutes. The reaction was allowed to warm to room temperature overnight, concentrated, and diluted with tert-butyl methyl ether (100 mL). The mixture was filtered and concentrated to give the chlorothiophosphoramidate as a clear, pale yellow oil in 100% yield and 91% HPLC purity. X H NMR (500MHz, CDC1 3 ) δ 8.13 - 8.11 (m, 2H), 7.91 - 7.88 (m, 2H), 7.77 - 7.74 (m, 2H), 7.71 - 7.68 (m, 2H), 7.60-7.55 (m, 4H), 7.49 - 7.45 (m, 2H), 4.78 (dd, J= 15.0, 10.0 Hz, 1H), 4.65 (t, J= 10.0 Hz, 1H), 4.55 - 4.43 (m, 2H), 4.00 - 3.85 (m, 4H), 1.64 (d, J=6.9 Hz, 3H), 1.60 (d, J=7.3 Hz, 3H), 1.01 (s, 9H), 0.97 (s, 9H). 31 P NMR (CDC1 3 ): δ 64.5, 64.3. LCMS(ES + ): calculated for [M+H] + :400.09, found 400.30.

Step 2: Preparation of (2S)-neopentyl 2-(((naphthalen- 1 -yloxy)(4- nitrophenoxy)phosphorothioyl)amino)propanoate

[0060] To a solution of ara-nitrophenol (696 mg, 5.0 mmol) and triethylamine (1.05 mL, 7.5 mmol) in dichloromethane (13.9 mL) was added (2S)-neopentyl 2- ((chloro(naphthalen-l-yloxy)phosphorothioyl)amino)propanoate (2.0 g, 5.0 mmol) as a solution in dichloromethane (7.0 mL). The mixture was stirred for 14 hours at 23 °C and concentrated. The crude material was purified by Isco chromatography (5% to 20% ethyl acetate in hexanes chloride) to give the desired product as a pale yellow oil following concentration. LCMS(ES + ): calculated for C 2 4H 28 N 2 0 6 PS [M+H] + : 503.14, found 503.33. Step 3: Preparation of the thiophosphoramidate penultimate

[0061] To a suspension of (2R,3R,4R,5R)-2-(2-amino-6-methoxy-9H-purin-9-yl)-5- (hydroxymethyl)-3-methyltetrahydrofuran-3,4-diol (1.56 g, 5.0 mmol) and triethylamine (1.05 mL, 7.5 mmol) in acetonitrile (31.1 mL) was added (2S)-neopentyl 2- ((chloro(naphthalen-l-yloxy)phosphorothioyl)amino)propanoate (3.0 g, 7.5 mmol) as a solution in acetonitrile (7.8 mL). The mixture was stirred for 3 hours at 65 °C, cooled to room temperature, filtered, and concentrated. The crude material was purified by Isco chromatography (2.5% to 5% methanol in methylene chloride) to give the desired product as a white solid (1.15 grams, 34%) in 94.9% HPLC purity following concentration. X H NMR (500MHz, CDC1 3 ) δ 8.16 - 8.13 (m, 2H), 7.87 - 7.83 (m, 2H), 7.79 (s, 1H), 7.76 (s, 1H), 7.70 - 7.67 (m, 2H), 7.56-7.50 (m, 6H), 7.43 - 7.39 (m, 2H), 5.94 (d, J= 10.0 Hz, 2H), 5.07 (br s, 4H), 4.08 (s, 6H), 1.49 (d, J=5.0 Hz, 3H), 1.42 (d, J=5.0 Hz, 3H), 0.93 (s, 9H), 0.91 (s, 9H). 31 P NMR (CDC1 3 ): δ 68.7, 67.9. LCMS(ES + ): calculated for

C 3 oH4oN 6 0 8 PS [M+H] + : 675.24, found 675.13.

Step 4: Oxidation

[0062] To a solution of (2S)-neopentyl 2-(((((2R,3R,4R,5R)-5-(2-amino-6-methoxy- 9H-purin-9-yl)-3,4-dihydroxy-4-methyltetrahydrofuran-2-yl)me thoxy)(naphthalen-l- yloxy)phosphorothioyl)amino)propanoate (67.5 mg, 0.1 mmol) in dichloromethane (0.7 mL) was added a solution of m-chloroperbenzoic acid (74.0 mg, 0.3 mmol, 70 wt%) in dichloromethane (0.3 mL) over 5 minutes at room temperature. The solution was stirred for 10 minutes, at which time complete disappearance of the starting material was observed by HPLC. The mixture was diluted with dichloromethane (5 mL), washed with saturated aqueous sodium bicarbonate (5 mL), dried over sodium sulfate, filtered and concentrated to give the desired product as a white solid (58 mg, 88%) in 89% HPLC purity. LCMS(ES + ): calculated for C 3 oH4o 6 0 9 P [M+H] + : 659.26, found 659.20.

[0063] 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.