TECHNICAL FIELD OF THE INVENTION The present invention relates to a novel class of compounds which are aspartyl protease inhibitors. In one embodiment, this invention relates to a novel class of mannitol-derived HIV aspartyl protease inhibitors characterized by specific structural and physicochemical features. This invention also relates to pharmaceutical compositions comprising these compounds. The compounds and pharmaceutical compositions of this invention are particularly well suited for inhibiting the activity of HIV aspartyl protease. Accordingly, they may be advantageously used as anti-viral agents against HIV viruses, including the HIV-1 and HIV-2 viruses.

BACKGROUND OF THE INVENTION The human immunodeficiency virus ("HIV") retrovirus is the causative agent for acquired immunodeficiency syndrome ("AIDS") — a disease characterized by the destruction of the immune system, particularly of CD4 ⁺ T-cells (J. of NIH Res.. 3, pp. 23-25 (1991)) , with attendant susceptibility to opportunistic infections; its precursor AIDS-related complex ("ARC") — a syndrome characterized by symptoms such as persistent generalized lymphadenopathy, fever,

weight loss; and its precursor — asymptomatic HIV infection.

As in the case of several other retroviruses, HIV encodes the production of a protease which carries out post-translational cleavage of precursor polypeptides in a process necessary for the formation of infectious virions (S. Crawford et al., "A Deletion Mutation in the 5' Part of the pol Gene of Moloney Murine Leukemia Virus Blocks Proteolytic Processing of the gag and pol Polyproteins", J. Virol.. 53, p. 899 (1985)). These gene products include pol, which encodes the virion RNA-dependent DNA polymerase (reverse transcriptase) , an endonuclease, HIV protease, and gag, which encodes the core-proteins of the virion (H. Toh et al. , "Close Structural Resemblance Between Putative Polymerase of a Drosophila Transposable Genetic Element 17.6 and pol gene product of Moloney Murine Leukemia Virus", EMBO J.. 4, p. 1267 (1985); L.H. Pearl et al. , "A Structural Model for the Retroviral Proteases", Nature, pp. 329-351 (1987); M.D. Power et al. , "Nucleotide Sequence of SRV-1, a Type D Simian Acquired Immune Deficiency Syndrome Retrovirus", Science. 231, p. 1567 (1986)).

A number of synthetic anti-viral agents have been designed to target various stages in the replication cycle of HIV. These agents include compounds which block viral binding to CD4 ⁺ T-lymphocytes (for example, soluble CD4) , and compounds which interfere with viral replication by inhibiting viral reverse transcriptase (for example, didanosine and zidovudine (AZT) ) and inhibit integration of viral DNA into cellular DNA (M.S. Hirsh and R.T. D'Aqulia, "Therapy for Human Immunodeficiency Virus Infection", N. Eng. J. Med.. 328, p. 1686 (1993)). However, such agents, which are directed primarily to early stages of

viral replication, do not prevent the production of infectious virions in chronically infected cells. Furthermore, administration of some of these agents in effective amounts has led to cell-toxicity and unwanted side effects, such as anemia and bone marrow suppression.

More recently, the focus of anti-viral drug design has been to create compounds which inhibit the formation of infectious virions by interfering with the processing of viral polyprotein precursors. Processing of these precursor proteins requires the action of virus-encoded proteases which are essential for replication (Science. 231, pp. 1580-1584 (1986); Kohl, N.E. et al. "Active HIV Protease is Required for Viral Infectivity" Proc. Natl. Acad. Sci. USA. 85, p. 4686 (1988)). The anti-viral potential of HIV protease inhibition has been demonstrated using peptidal inhibitors. Such peptidal compounds, however, are typically large and complex molecules that tend to exhibit poor bioavailability and are not generally consistent with oral administration. Accordingly, the need still exists for compounds that can effectively inhibit the action of viral proteases, for use as agents for preventing and treating chronic and acute viral infections, such as HIV.

SUMMARY OF THE INVENTION The present invention provides a novel class of compounds, including pharmaceutically acceptable derivatives thereof, that have an affinity for aspartyl proteases, in particular, HIV aspartyl proteases.

Based on that affinity, these compounds are useful as inhibitors of such proteases. These compounds can be used alone or in combination with other therapeutic or prophylactic agents, such as anti-virals, antibiotics,

immunomodul tors or vaccines, for the treatment or prophylaxis of viral infection.

According to a preferred embodiment, the compounds of this invention are capable of inhibiting HIV viral replication in human CD ₄ ⁺ T-cells, by inhibiting the ability of HIV aspartyl proteases to catalyze the hydrolysis of peptide bonds. These novel compounds can thus serve to reduce the production of infectious virions from chronically infected cells, and can inhibit the initial or further infection of host cells. Accordingly, these compounds are useful as therapeutic and prophylactic agents to treat or prevent infection by HIV-1 and related viruses, which may result in asymptomatic HIV-1 infection, AIDS-related complex ("ARC") , acquired immunodeficiency syndrome

("AIDS") , AIDS-related dementia, or similar disease of the immune system.

It is a principal object of this invention to provide a novel class of mannitol derivatives which are aspartyl protease inhibitors, and particularly, HIV aspartyl protease inhibitors. This novel class of mannitol derivatives is represented by formula I:

and pharmaceutically acceptable derivatives thereof, including pharmaceutically acceptable salts thereof, wherein each n is independently selected from the group consisting of 0, l and 2;

each A and A' is independently selected from the group consisting of a naturally occurring alpha- amino acid and an unnatural alpha-amino acid (e.g., Ala, Asn, Cys, Gly, Gin, His, lie. Leu, Met, Phe, Pro, Ser, Thr, Trp, Val or trifluoroalanine) , wherein the amino group of each A or A' is bonded to G or G' or to the carboxy group of the adjacent residue A or A' , whichever is appropriate, and the carboxy group of A or A' is bonded to the amino group of the adjacent residue A or A' or to the oxygen of the structure, whichever is appropriate; each G and G' is independently covalently attached to the amino group of the adjacent residue A or A' or to the oxygen of the structure (if the adjacent n = 0) , and is selected from the group consisting of:

1) trityl;

2) hydrogen;

3) C _j^ -Cg alkyl; 4) R ₃ -co-,

5) phthaloyl, wherein the aromatic ring thereof is optionally substituted with one or more substituents R ₄ ;

6) R ₅ (R ₆ R ₇ C)__.CO-, wherein = 1-3; 7) ₅ (RgR ₇ C) _m W-, wherein m = 1-3 and each is independently selected from the group consisting of -OCO- and -S0 ₂ ~, provided that is not -S0 ₂ - when is attached to the oxygen of the structure; 8) Rg- -, provided that is not -

SO,- when is attached to the oxygen of the structure;

9) R ₅ (R ₆ R ₇ C) _m -P(0) (OR ₉ )-, wherein m =

1-3; and

10) R ₈ -P(0) (OR ₉ )-;

each R ₃ is independently selected from the group consisting of: 1) hydrogen; 2) C^C _g alkyl or C ₂ -C ₆ alkenyl, both of which may be optionally substituted with one or more substituents selected from the group consisting of hydroxyl, chlorine and fluorine; and 3) phenyl or naphthyl, both of which may be optionally substituted with one or more substituents

R ₄ ; each R ₄ is independently selected from the group consisting of C ₁ -C ₁ alkyl, C ₂ -C ₄ alkenyl, halogen (e.g., F, Cl, Br or I), hydroxyl, nitro, C _j -^ alkoxy and -CO-N(R ₁₀ ) (R ₁₀ ) ; each R ₅ , R ₆ and R _? is independently selected from the group consisting of hydroxyl; hydrogen; chlorine; fluorine; C ₁ ~C ₃ alkoxy; a 5-7 membered heterocycle; C _χ -C ₃ alkyl; phenyl; and naphthyl; said C ₁ -C ₃ alkyl being optionally substituted with one or more substituents selected from the group consisting of chlorine, fluorine, and hydroxyl; and said phenyl and naphthyl being optionally substituted with one or more substituents R ₄ ; or R ₅ , R ₆ and R ₇ of a particular G or G' taken individually, or together in any combination, may be optionally joined to form a monocyclic, bicyclic, or tricyclic ring system, each ring of which is C ₃ -C ₆ cycloalkyl, with the proviso that R ₅ , R _g or Ε _j may not be chlorine, fluorine or hydroxyl if it is present on the carbon adjacent to W; each R ₈ is independently selected from the group consisting of phenyl, naphthyl, and a 5-7 membered heterocycle (e.g., pyridyl, furyl or benzisoxazolyl) , wherein said phenyl or naphthyl may be substituted with one or more substituents R ₄ ; each R ₉ is independently selected from the group consisting of C ₁ -C ₄ alkyl and phenyl;

each R ₁₀ is independently selected from the group consisting of hydrogen, C^C^ alkyl, and a 5-7 membered heterocycle (e.g., pyridyl, furyl, or benzisoxazoyl) ; wherein each B and B' is independently selected from the group consisting of oxygen and sulfur; wherein each D and D' is independently selected from the group consisting of H ₂ , oxygen and sulfur; wherein each E and E' is independently selected from the group consisting of Ar and N(R, ₁ R ₁ _) ; wherein each R _χl and R ₁₂ is independently selected from the group consisting of C.-C ₆ alkyl and ^C ₂ ^_C ₆ alkenyl; and wherein each Ar is independently selected from the group consisting of phenyl, phenyl substituted with one or more substituents R ₄ and a 5-7 membered heterocycle, optionally substituted with one or more substituents R ₄ (e.g., 3-pyridyl, 4-(l,2,3-thiadiazol)- yl, or 4-morpholine) .

It is also an object of this invention to provide pharmaceutical compositions comprising the mannitol derivatives of formula I and methods for their use as inhibitors of aspartyl proteases, including HIV aspartyl proteases.

DETAILED DESCRIPTION OF THE INVENTION In order that the invention herein described may be more fully understood, the following detailed description is set forth. In the description, the following abbreviations are used:

Designation Reagent or Fragment

Et ethyl

Trityl triphenylmethyl

Ala D- or L-alanine Asn D- or L-asparagine Cys D- or L-cysteine Gly D- or L-glycine Gin D- or L-glutamine His D- or L-histidine lie D- or L-isoleucine Leu D- or L-leucine Met D- or L-methionine Phe D- or L-phenylalanine Pro D- or L-proline Ser D- or L-serine Thr D- or L-threonine Trp D- or L-tryptophan Val D- or L-valine Cbz benzyloxycarbony1 (carbobenzyloxy) EDC 1-(3-dimethy1aminopropy1)-3- ethylcarbodiimide hydrochloride

TFA trifluoroacetic acid

EtOAc ethyl acetate

DMF dimethy1formamide

AZT zidovudine

TIBO 4,5,6,7-tetrahydro-5- methylimidazo[4,5,1-jk] [1,4] benzodiazepin-2(1H)-one

IL-2 interleukin-2 GM-CSF granulocyte macrophage colony stimulating factor rEPO recombinant erythropoietin

EtOH ethyl alcohol

MeOH methyl alcohol

THF tetrahydrofuran

DMAP 4-dimethylaminopyridine

Et ₂ 0 diethyl ether.

The following terms are employed herein: Unless expressly stated to the contrary, the term "-P(O) (0R ₉ )-" as used herein refers to a phosphonate derivative (i.e., both appended groups linked to the P) , and not a phosphinate ester.

The term "Ar" refers to either a saturated or an unsaturated moiety.

The term "the oxygen of the structure" refers to the oxygen of a primary hydroxl group of the mannitol backbone of the compounds of this invention.

The term "heterocycle" refers to a stable 5- 7 membered monocycle or 5-7 membered bicyclic heterocycle, which is either saturated or unsaturated, and which may be optionally benzofused if monocyclic. Each heterocycle consists of carbon atoms and from one to four heteroatoms selected from the group consisting of nitrogen, oxygen and sulfur. As used herein, the terms "nitrogen and sulfur heteroatoms" include any oxidized form of nitrogen and sulfur, and the quaternized form of any basic nitrogen. The heterocyclic ring may be attached by any heteroatom or carbon atom of the cycle which results in the creation of a stable structure. Preferred heterocycles defined above include, but are not limited to, benzimidazolyl, imidazolyl, imidazolinoyl, imidazolidinyl, quinolyl, isoquinolyl, indolyl, pyridyl, pyrrolyl, pyrrolinyl, pyrazolyl, pyrazinyl, quinoxolyl, piperidinyl, morpho- linyl, thiamorpholinyl, furyl, thienyl, triazolyl, thi- azolyl, β-carbolinyl, tetrazolyl, thiazolidinyl, benzo- fuanoyl, thiamorpholinyl sulfone, benzoxazolyl, oxopiperidinyl, oxopyrroldinyl, oxoazepinyl, azepinyl, isoxazolyl, tetrahydropyranyl, tetrahydrofuranyl, thiadiazolyl, thiadiazoyl, benzodioxolyl, thiophenyl, tetrahydro-thiophenyl, nicotinoyl, orpholine- carbodithioyl and sulfolanyl.

The terms "HIV protease" and "HIV aspartyl protease" are used interchangeably and refer to the aspartyl protease encoded by the human immunodeficiency virus type 1 or 2. In a preferred embodiment of this invention, these terms refer to the human immunodeficiency virus type 1 aspartyl protease.

The term "pharmaceutically effective amount" refers to an amount effective in treating HIV infection in a patient. The term "prophylactically effective amount" refers to an amount effective in preventing HIV infection in a patient. As used herein, the term "patient" refers to a mammal, including a human.

The terms "pharmaceutically acceptable carrier or adjuvant" and "physiologically acceptable vehicle" refer to a non-toxic carrier or adjuvant that may be administered to a patient, together with a compound of this invention, and which does not destroy the pharmacological activity thereof.

As used herein, the compounds of this invention, including the compounds of formula I, are defined to include pharmaceutically acceptable derivatives thereof. A "pharmaceutically acceptable derivative" means any pharmaceutically acceptable salt, ester, or salt of such ester, of a compound of this invention or any other compound which, upon administration to a recipient, is capable of providing (directly or indirectly) a compound of this invention or an anti-virally active metabolite or residue thereof. Salts derived from appropriate bases include alkali metal (e.g., sodium), alkaline earth metal (e.g., magnesium), ammonium and N-(C _| _ ₄ alkyl) ₄ ⁺ salts.

The term "unnatural alpha-amino acids" refers to alpha-amino acids which do not occur in nature but which can be derived from naturally occurring alpha-

amino acids or other chemical reagents by methods known to those skilled in the art.

The compounds of this invention contain one or more asymmetric carbon atoms and thus may occur as racemates and racemic mixtures, single enantiomers, diastereomeric mixtures and individual diastereomers. All such isomeric forms of these compounds are expressly included in the present invention. Each stereogenic carbon may be of the R or S configuration. Additionally, the compounds of the invention may be C ₂ -symmetric, wherein A = A' , B = B', D = D ¹ , E = E' and G = G' .

Combinations of substituents and variables envisioned by this invention are only those that result in the formation of stable compounds. The term

"stable", as used herein, refers to compounds- which possess stability sufficient to allow manufacture and administration to a mammal by methods known in the art. Typically, such compounds are stable at a temperature of 40°C or less, in the absence of moisture or other chemically reactive conditions, for at least a week.

Pharmaceutically acceptable salts of the compounds of this invention include those derived from pharmaceutically acceptable inorganic and organic acids and bases. Examples of such acid salts include: ace¬ tate, adipate, alginate, aspartate, benzoate, benzene- sulfonate, bisulfate, butyrate, citrate, camphorate, carophorsulfonate, cyclopentanepropionate, digluconate, dodecylhydrogen-sulfate, dodecylsulfate, ethanesulfonate, formate, fumarate, glucoheptanoate, glycerophosphate, glycollate, hemisulfate, heptanoate, hexanoate, hydrochloride, hydrobromide, hydroiodide, ₂ -hydroxy-ethanesulfonate, lactate, maleate, malonate, methanesulfonate, 2-naphthalenesulfonate, nicotinate, nitrate, oxalate, pamoate, pectinate, perchlorate,

persulfate, 3-phenylpropionate, phosphate, picrate, pivalate, propionate, salicylate, succinate, sulfate, tartrate, thiocyanate, tosylate and undecanoate. This invention also envisions the quaternization of any basic nitrogen-containing groups of the compounds disclosed herein. The basic nitrogen can be quaternized with any agents known to those of ordinary skill in the art including, for example, lower alkyl halides, such as methyl, ethyl, propyl and butyl chloride, bromides and iodides; dialkyl sulfates including dimethyl, diethyl, dibutyl and diamyl sulfates; long chain halides such as decyl, lauryl, yristyl and stearyl chlorides, bromides and iodides; and aralkyl halides including benzyl and phenethyl bromides. Water or oil-soluble or dispersible products may be obtained by such quaternization.

The novel mannitol derivatives of this invention are those of formula I:

wherein: each n is independently selected from the group consisting of 0, 1 and 2; each A and A' is independently selected from the group consisting of a naturally occurring alpha- amino acid and an unnatural alpha-amino acid, wherein the amino group of each A or A ¹ is bonded to G or G' or to the carboxy group of the adjacent residue A or A',

whichever is appropriate, and the carboxy group of A or A' is bonded to the amino group of the adjacent residue A or A' or to the oxygen of the structure, whichever is appropriate; each G and G' is independently covalently attached to the amino group of the adjacent residue A or A' or to the oxygen of the structure (if the adjacent n = 0) and is selected from the group consisting of trityl; hydrogen; C^-C ₈ alkyl; R ₃ -CO-; R ₅ (R _g R ₇ C) _m CO-; R ₅ (R _g R ₇ C) _n W-; R _g -W-; R ₅ (R _g R _? C) _a -P(0) (OR ₉ )-; R ₈ -P(0) (0R ₉ )-; and phthaloyl, which may be optionally substituted with one or more substituents R ₄ ; wherein = 1-3; each W is independently selected from the group consisting of -OCO- and -S0 ₂ ~, with the proviso that W is not -S0 ₂ - when W is attached to the oxygen of the structure; each R ₃ is independently selected from the group consisting of hydrogen; C _j -C ₈ alkyl; C ₂ -C ₈ alkenyl; phenyl; and naphthyl; said C _j^ -C ₈ alkyl and C ₂ -

C _g alkenyl being optionally substituted with one or more substituents selected from the group consisting of hydroxyl, chlorine, and fluorine; and said phenyl and naphthyl being optionally substituted with one or more substituents R ₄ ; each R ₄ is independently selected from the group consisting of C ₁ -C ₄ alkyl; C ₂ -C ₄ alkenyl; halogen; hydroxyl; nitro; C ₁ ~C ₃ alkoxy; and -CO-N(R ₁₀ ) (R ₁₀ ) ; each R ₅ , R _g and R ₇ is independently selected from the group consisting of hydroxyl; hydrogen; chlorine; fluorine; C ₁ ~C ₃ alkoxy; a 5-7 membered heterocycle; ₁ ~C ₃ alkyl; phenyl; and naphthyl; said C _χ - C ₃ alkyl being optionally substituted with one or more substituents selected from the group consisting of

chlorine, fluorine, and hydroxyl; and said phenyl and naphthyl being optionally substituted with one or more substituents R ₄ ; or R ₅ , R ₆ and R _? of a particular G or G' taken individually, or together in any combination, may be optionally joined to form a monocyclic, bicyclic, or tricyclic ring system, each ring of which is C ₃ -C ₆ cycloalkyl; with the proviso that R ₅ , R _fi , or , may not be chlorine, fluorine, or hydroxyl if it is present on the carbon adjacent to W; each R ₈ is independently selected from the group consisting of a 5-7 membered heterocycle; phenyl; and naphthyl; said phenyl and naphthyl being optionally substituted with one or more substituents R ₄ ; each R _g is independently selected from the group consisting of C^C^ alkyl and phenyl; each R ₁₀ is independently selected from the group consisting of hydrogen; C ₁ -C ₄ alkyl; and a 5-7 membered heterocycle; each B and B* is independently selected from the group consisting of oxygen and sulfur; each D and D ¹ is independently selected from the group consisting of H ₂ , oxygen and sulfur; each E and E' is independently selected from the group consisting of Ar and ^N (R ₁₁ R ₁₂ ) » each Ar is independently selected from the group consisting of phenyl and a 5-7 membered heterocycle; said phenyl and heterocycle being optionally substituted with one or more substituents R ₄ (e.g., 3-pyridyl, 4-(1,2,3-thiadiazol)yl or 4-morpholine) ; and each _lχ and R ₁₂ is independently selected from the group consisting of C _j -C ₈ alkyl and C ₂ -C ₆ alkenyl.

Another embodiment of this invention includes compounds of formula I, as described above, wherein substituents n. A, A', G, G', R ₃ , R ₄ , R ₅ , R _g , R _? , m, , ^' R ₈ , R ₉ , R ₁₀ , B, B', D, D\ E, E', R _lχ , R ₁₂ , and Ar are defined as above for formula I, with the proviso that when both n = 0, E and E' are not 3-pyridyl or diethylamino.

Except where expressly provided to the contrary, as used herein, the definitions of variables A, A', B, B', D, D ¹ , E, E', G, G', n, R ₃ -R ₁₂ , m, Ar and W are to be taken as they are defined immediately above.

An alternate embodiment of this invention includes compounds of formula I, wherein: each n is independently selected from the group consisting of 0, 1 and 2; each A and A' is independently selected from the group consisting of a naturally occurring alpha- amino acid and an unnatural alpha-amino acid, wherein the amino group of each A or A' is bonded to G or G' or to the carboxy group of the adjacent residue A or A' , whichever is appropriate, and the carboxy group of A or A' is bonded to the amino group of the adjacent residue A or A* or to the oxygen of the structure, whichever is appropriate; each G and G' is independently covalently attached to the amino group of the adjacent A or A' or to the oxygen of the structure (if the adjacent n = 0) , and is selected from the group consisting of trityl; C _j -C ₈ alkyl; R ₃ -CO-; R ₅ (R _g R ₇ C) _a CO-; R ₅ (R _g ^C)^-; R _g -W-;

R ₅ (R ₆ R ₇ C) _ιn -P(θ) (OR ₉ )-; R _g -P(O) (OR ₉ )-; and phthaloyl, which may be optionally substituted with one or more substituents R ₄ ; wherein = 1-3; each W is independently selected from the group consisting of -OCO- and -S0 ₂ ~, with the proviso

that W is not -S0 ₂ - when W is attached to the oxygen of the structure; each R ₃ is selected from the group consisting of hydrogen; ^-C ₈ alkyl; C ₂ -C ₆ alkenyl; phenyl; and naphthyl; said ₁ -C ₆ alkyl and C ₂ -C ₆ alkenyl being optionally substituted with one or more substituents selected from the group consisting of hydroxyl, chlorine, and fluorine; and said phenyl and naphthyl being optionally substituted with one or more substituents R ₄ ; each R ₄ is independently selected from the group consisting of C^C^ alkyl; C ₂ -C ₄ alkenyl; halogen; hydroxyl; nitro; C ₁ ~C ₃ alkoxy; and -CO-N(R ₁₀ ) (R ₁₀ ) ; each R ₅ , R ₆ and R _? is independently selected from the group consisting of hydroxyl; hydrogen; chlorine; fluorine; C ₁ -C ₃ alkoxy; a 5-7 membered heterocycle; C _χ -C ₃ alkyl; phenyl; and naphthyl; said C ₁ -C ₃ alkyl being optionally substituted with one or more substituents selected from the group consisting of chlorine, fluorine and hydroxyl; and said phenyl and naphthyl being optionally substituted with one or more substituents R ₄ ; or R ₅ , R ₆ and R ₇ of a particular G or G ¹ taken individually, or together in any combination, may be optionally joined to form a monocyclic, bicyclic, or tricyclic ring system, each ring of which is C ₃ -C ₆ cycloalkyl; with the proviso that R ₅ , R _g , and R ₇ may not be chlorine, fluorine, or hydroxyl if it is present on the carbon adjacent to W; each R _g is independently selected from the group consisting of a 5-7 membered heterocycle; phenyl; and naphthyl; said phenyl and naphthyl being optionally substituted with one or more substituents R ₄ ; each R _g is independently selected from the group consisting of C _χ -C ₄ alkyl and phenyl;

each R ₁₀ is independently selected from the group consisting of hydrogen; C _j -^ alkyl; and a 5-7 membered heterocycle; each B and B' is independently selected from the group consisting of oxygen and sulfur; each D and D' is independently selected from the group consisting of H ₂ , oxygen and sulfur; each E and E' is independently selected from the group consisting of Ar and N(R ₁₂ R ₁₂ ) ; each Ar is independently selected from the group consisting of phenyl and a 5-7 membered heterocycle; said phenyl and heterocycle being optionally substituted with one or more substituents R ₄ (e.g., 3-pyridyl, 4-(1,2,3-thiadiazol)yl or 4- morpholine) ; and each R _ιχ and R ₁₂ is independently selected from the group consisting of ^-C ₈ alkyl and C ₂ -C ₈ alkenyl.

Another embodiment of this invention includes compounds of formula I:

wherein substituents n, A, A', G, G', R ₃ , R ₄ , R _g , R _g , R ₇ , m, W, R ₈ , R ₉ , R ₁₀ , B, B', D, D', E, E' , R _χι , R ₁₂ , and Ar are defined as above for formula I, with the proviso that when both n = 0, E and E' are not 3-pyridyl or diethylamino.

Still another embodiment of this invention includes a subclass of compounds of formula I wherein:

each n is independently selected from the group consisting of 0, 1 and 2; each A and A' is independently selected from the group consisting of a naturally occurring alpha- amino acid and an unnatural alpha-amino acid, wherein the amino group of each A or A ¹ ) is bonded to G or G' or to the carboxy group of the adjacent residue A or A' , whichever is appropriate, and the carboxy group of A or A' is bonded to the amino group of the adjacent residue A or A* or to the oxygen of the structure, whichever is appropriate; each G and G' is independently covalently attached to the amino group of the adjacent residue A or A' or to the oxygen of the structure (if the adjacent n = 0) , and is selected from the group consisting of ^-C ₈ alkyl; R ₃ CO-; R ₅ (R _g R ₇ C) _m CO-; R _s (R _g R ₇ C) _m W-; and phthaloyl, which may be optionally substituted with one or more substituents R ₄ ; wherein = 1-3; each W is independently selected from the group consisting of -OCO- and -S0 ₂ ~, with the proviso that W is not -S0 ₂ ~ when W is attached to the oxygen of the structure; each R ₃ is independently selected from the group consisting of ^-C ₈ alkyl; phenyl; and naphthyl; said C _χ -C ₆ alkyl being optionally substituted with one or more substituents selected from the group consisting of hydroxyl, chlorine, and fluorine; and said phenyl and naphthyl being optionally substituted with one or more substituents R ₄ ; each R ₄ is independently selected from the group consisting of C ₁ ~C ₄ alkyl; halogen; hydroxyl; nitro; and C ₁ -C ₃ alkoxy;

each R ₅ , R _g and R ₇ is optionally and independently selected from the group consisting of hydrogen; chlorine; fluorine; a 5-7 membered heterocycle; phenyl; naphthyl; and C ₁ -C ₃ alkyl, wherein said C ₁ -C ₃ alkyl may be optionally substituted with one or more substituents selected from the group consisting of chlorine, fluorine, and hydroxyl; and wherein said phenyl and naphthyl may be optionally substituted with one or more substituents R ₄ ; or R ₅ , R _g and R _? of a particular G or G' taken individually, or together in any combination, may be optionally joined to form a monocyclic, bicyclic, or tricyclic ring system, each ring of which is C ₃ -C ₈ cycloalkyl; with the proviso that R ₅ , R ₆ , and R ₇ may not be chlorine, fluorine, or hydroxyl if it is present on the carbon adjacent to W; each B and B' is independently selected from the group consisting of oxygen and sulfur; each D and D' is independently selected from the group consisting of H ₂ ; oxygen and sulfur; each E and E' is independently selected from the group consisting of Ar and N(R _lχ R ₁₂ ) ; each Ar is selected from the group consisting of phenyl and a 5-7 membered heterocycle; wherein said phenyl and 5-7 membered heterocycle may be optionally substituted with one or more substituents R ₄ ; and each R _χl and R ₁₂ is independently C ₁ ~C ₆ alkyl.

According to still another embodiment of this invention, a subclass of compounds are those compounds of formula I wherein: each n is independently selected from the group consisting of 0, 1 and 2; each A and A' is independently selected from the group consisting of a naturally occurring alpha- amino acid and an unnatural alpha-amino acid, wherein the amino group of each A or A' is bonded to G or G ¹ or

to the carboxy group of the adjacent residue A or A' , whichever is appropriate, and the carboxy group of A or A' is bonded to the amino group of the adjacent residue A or A ¹ or to the oxygen of the structure, whichever is appropriate; each G and G ¹ is independently covalently attached to the amino group of the adjacent residue A or A ¹ or to the oxygen of the structure (if the adjacent n = 0) , and is selected from the group consisting of hydrogen; C _j -C ₈ alkyl; R ₃ CO-;

R ₅ (R _g R ₇ C) _m CO-; R ₅ (R _g R ₇ C) _n .W-; and phthaloyl, which may be optionally substituted with one or more substituents R ₄ ; wherein m = 1-3; each W is independently selected from the group consisting of -OCO- and -S0 ₂ ~, with the proviso that W is not -S0 ₂ - when W is attached to the oxygen of the structure; each R ₃ is independently selected from the group consisting of C _χ -C ₆ alkyl; phenyl; and naphthyl; said _~ - ₁ ~C ₆ alkyl being optionally substituted with one or more substituents selected from the group consisting of hydroxyl, chlorine, and fluorine; and said phenyl and naphthyl being optionally substituted with one or more substituents R ₄ ; each R ₄ is independently selected from the group consisting of C _χ -C ₄ alkyl; halogen; hydroxyl; nitro; and ₁ ~C ₃ alkoxy; each R ₅ , R _g , and R ₇ is independently selected from the group consisting of hydrogen; chlorine; fluorine; C ₁ -C ₃ alkyl; C ₁ ~C ₃ alkoxy; a 5-7 membered heterocycle; phenyl; and naphthyl; said CJ-CJ alkyl being optionally substituted with one or more substituents selected from the group consisting of chlorine, fluorine, and hydroxyl; and said phenyl and

naphthyl being optionally substituted with one or more substituents R ₄ ; or R ₅ , R _g , and R _? of a particular G or G' taken individually, or together in any combination, may be optionally joined to form a monocyclic, bicyclic, or tricyclic ring system, each ring of which is C ₃ -C ₈ cycloalkyl; with the proviso that R _g , R _fi , or L may not be chlorine, fluorine, or hydroxyl if it is present on the carbon adjacent to W; each B and B ¹ is independently selected from the group consisting of oxygen and sulfur; each D and D' is independently selected from the group consisting of H ₂ ; oxygen and sulfur; each E and E* is independently selected from the group consisting of Ar and N(R _lχ R ₁₂ ) , with the proviso that each E and E' is not 3-pyridyl or diethylamino when both n = 0; each Ar is independently selected from the group consisting of phenyl and a 5-7 membered heterocycle; wherein said phenyl and 5-7 membered heterocycle may be optionally substituted with one or more substituents R ₄ ; and each R _χι and R ₁₂ is independently C ₁ -C ₈ alkyl.

A subclass of compounds of this invention are those compounds of formula I, wherein: each n = 1; each A and A ¹ is independently a naturally occurring alpha-amino acid, wherein the amino group of each A or A' is bonded to G or G' or to the carboxy group of the adjacent residue A or A' , whichever is appropriate, and the carboxy group of A or A' is bonded to the amino group of the adjacent residue A or A' or to the oxygen of the structure, whichever is appropriate; each G and G* is independently covalently attached to the amino group of the adjacent residue A

or A ¹ or to the oxygen of the structure (if the adjacent n = 0) , and is selected from the group consisting of hydrogen and R ₅ (R _g R- _j C^W-, wherein W is -OCO- and m = 1; each R ₅ , R _fi , and ₇ is independently selected from the group consisting of hydrogen; chlorine; fluorine; C ₁ -C ₃ alkyl; a 5-7 membered heterocycle; phenyl; and naphthyl; said C ₁ -C ₃ alkyl being optionally substituted with one or more substituents selected from the group consisting of chlorine, fluorine, and hydroxyl; and wherein said phenyl and naphthyl may be optionally substituted with one or more substituents R ₄ ; or each R ₅ , R ₆ , and R _? of a particular G or G' taken individually, or together in any combination, may be optionally joined to form a onocyclic, bicyclic, or tricyclic ring system, each ring of which is C ₃ ~C ₆ cycloalkyl; with the proviso that R ₅ , R ₆ , or R _? may not be chlorine, fluorine, or hydroxyl if it is present on the carbon adjacent to W; each R ₄ is independently selected from the group consisting of C ₁ ~C ₄ alkyl; halogen; hydroxyl; nitro; and C ₁ ~C ₃ alkoxy; each B and B ¹ is independently selected from the group consisting of oxygen and sulfur; each D and D' is independently selected from the group consisting of H ₂ ; oxygen and sulfur; each E and E' is independently selected from the group consisting of Ar and N(R ₁₁ R ₁₂ ); each Ar is independently selected from the group consisting of phenyl and a 5-7 membered heterocycle; wherein said phenyl and 5-7 membered heterocycle may be optionally substituted with one or more substituents R ₄ ; and each R _χι and R ₁₂ is independently C-^-Cg alkyl.

A preferred subclass of compounds of this invention are those compounds of formula II:

wherein: each B and B' is independently selected from the group consisting of oxygen and sulfur; each D and D' is independently selected from the group consisting of H ₂ ; oxygen and sulfur;- each E and E' is independently selected from the group consisting of Ar and NEt ₂ ; and each Ar is selected from the group consisting of phenyl; 3-hydroxyphenyl; 3-pyridyl; 4-(1,2,3- thiadiazol) -yl; and 4-morpholinyl.

Preferred mannitol derivatives of formula II of this invention are those in which (A) _n , (A') _n , G and G' are independently CbzVal; and groups B, D and E taken together are selected from the group consisting of: 1) benzoate; 2) 3-hydroxybenzoate; 3) nicotinoate; 4) 4-(l,2,3-thiadiazoate) ; 5) benzyloxy; 6) thiobenzoate; 7) 4-morpholinecarbodithioate; and 8) N,N-diethylcarbodithioate. The preferred configuration of positions l, 1', 2 and 2' is (S) , (S) , (R) and (R) , respectively, and are derived from the starting material, such as from L-mannitol. Such preferred compounds include those depicted in Table I.

TABLE 1

It should be understood that for all compounds of formula I and formula II, as defined herein, B, D, and E taken together may be selected from the group consisting of benzoate; 3-hydroxybenzoate; nicotinoate; 4-(l,2,3-thiadiazoate) ; benzyloxy; thiobenzoate; 4-morpholinecarbodithioate; and N,N- diethylcarbodithioate. In addition, A and G taken together may form carbobenzyloxyvaline.

Preferred compounds of this invention are: l,6-Di-0-benzoyl-2,5-di-O-(N-carbobenzyloxyvalyl)- L-mannitol (compound 1) ; l,6-Di-θ-(3-hydroxy)benzoyl-2,5-di-O-(N- carbobenzyloxyvalyl-L-mannitol (compound 2) ; 1,6-Di-0-nicotinoyl-2,5-di-O-(N- carbobenzyloxyvalyl-L-mannitol (compound 3) ;

1,6-Di-O-[4-(1,2,3-thiadiazol)-y1]-2,5-di-O-(N- carbobenzyloxyvalyl-L-mannitol; (compound 4) ; l,6-Di-θ-benzyl-2,5-di-O-(N-carbobenzyloxyvalyl)- L-mannitol (compound 5) ; 1,6-Di-S-benzoyl-2,5-di-O-(N-carbobenzyloxyvalyl)-

L-mannitol (compound 6) ; l,6-Di-S-(4-morpholinothiocarbonyl)-2,5-di-θ-(N- carbobenzyloxyvalyl)-L-mannitol (compound 7); and

1,6-Di-S-(N,N-diethylthiocarbonyl)-2,5-di-O-(N- carbobenzyloxyvalyl)-L-mannitol (compound 8).

The compounds of this invention may be synthesized using conventional techniques. Advantageously, these compounds are conveniently synthesized from readily available starting materials. The compounds of this invention are among the most readily synthesized HIV protease inhibitors known. Previously described HIV protease inhibitors often contain more than six chiral centers, numerous peptide linkages and/or require air-sensitive reagents (such as organo etallic complexes) to effect their syntheses.

The relative ease with which the compounds of this invention can be synthesized represents an enormous advantage in the large scale production of these compounds. In general, mannitol derivatives of formula I and formula II are conveniently obtained from D- or L-mannitol. Such enantiomeric or diastereomeric mannitol derivatives may be conveniently prepared from commercially available D-or L-mannitol using known techniques. Although this invention envisions the use of either D- or L-mannitol, or racemic mixtures thereof, as the scaffold upon which to append various functional groups, L-mannitol is preferred.

Using standard techniques, D- or L-mannitol may be derivatized according to Scheme I, as depicted below:

mannitol

Scheme 1

D- or L-mannitol may be converted to its monoketal using acetone or other ketones known to those skilled in the art (T.W. Greene, Protective Groups in Organic Synthesis. John Wiley and Sons (1991) and references cited therein) . The ketal may then be converted to its bis epoxide, first by selective tosylation of the primary hydroxyl groups and then by treatment with potassium carbonate base to effect bis epoxidation with concomitant departure of tosylate. An epoxide functionality may then be opened at its least hindered carbon atom with a nucleophile having the general formula E(CD)B, wherein E, D and B are defined as above for the compounds of formula I, giving the monoaddition product (alcohol epoxide) . The resulting hydroxyl group may then be esterified in the presence of EDC (l-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride) and DMAP (4-dimethylaminopyridine) with an N-protected alpha-amino acid having the general formula G-(A) _n -OH, wherein G, A, and n are defined as above for the compounds of formula I, to give an alpha- amino acid-functionalized epoxide. The remaining epoxide may then be opened with a nucleophile having the general formula E'fCD'JB', wherein E', D' and B* are defined as above for the compounds of formula I, the resulting diol esterified with G'-(A ^, ) _n -OH, wherein G' and A* are defined as above for the compounds of formula I, and the ketal protecting group removed with aqueous acid to give compounds of the general formula I. For examples of methods to obtain enantiomeric or diastereomeric D- or L-mannitol derivatives by the procedures illustrated in Scheme 1, see L.F. Wiggins, J. Che . Soc.. p. 13 (1946); Y. Le Merrer et al. , Tetrahedron Lett.. 26, pp. 319-22 (1985) and Y. Le Merrer et al., Heterocvcles. 25, pp.

541-48 (1987) . Alternatively, enantiomeric or diastereomeric glycols may be obtained from the oxidation of a suitable olefin-containing precursor with, for example, osmium tetroxide, which may optionally be used in conjunction with another oxidizing agent, such as N-ethylmorpholine N-oxide (see, van Rheenen et al., Tetrahedron Lett.. pp. 1973- 76 (1976) and Evans and Kaldor, J. Pro. Chem.. 55, pp. 1698-1700 (1990)). The osmium tetroxide-promoted oxidation may also be carried out in the presence of various chiral ligands to promote asymmetric (i.e., face-selective) oxidation of the olefin (Wai et al., J. Am. Chem. Soc.. Ill, p. 1123 (1989)). Another method for constructing the glycol nucleus includes the reductive coupling of two appropriately derivatized aldehydes, which may be the same or different, in a pinacol reaction. This reaction can be carried out using low valent metals, including titanium (J.E. McMurry, Ace. Chem. Res.. 16, pp. 405-411 (1983)) and vanadium (Freudenberger et al., J. Am. Chem. Soc.. Ill, pp. 8014-16 (1989)), and by various lanthanide iodides (Namy et al., Tetrahedron Lett.. 24, pp. 765-66 (1983) and Imamoto et al., Tetrahedron Lett.. 23, pp. 1353-56 (1982) ) . Compounds of the present invention may be synthesized using known techniques. D- or L-mannitol may be converted to the ketal of formula III (shown below) using acid catalysts known to those skilled in the art and carbonyl compounds of the type ZC(0)Z'; wherein Z and Z' are independently selected from the group consisting of hydrogen, C ₁ -C ₂₀ alkyl, C ₃ -C ₈ cycloalkyl, phenyl, naphthyl, and a 5-7 membered heterocycle; wherein said C _j -C^ alkyl, C ₃ -c _g cycloalkyl, phenyl, naphthyl, and 5-7 membered heterocycle groups may be optionally substituted with

one or more substituents selected from the group consisting of halogen, hydroxyl, alkoxyl, phenoxyl, nitro, carboxylate and sulfonate; and wherein Z and Z' may optionally be joined to form a cyclic ketone.

Such ketones may be obtained commercially or may be synthesized by known methods. Acetone is especially preferred, using sulfuric acid as the reaction catalyst.

The ketal of formula III may then be selectively esterified at the primary hydroxyl positions with carboxylic acids, or acid derivatives thereof, having the general formula E-C(D)-X, wherein E and D are defined as above for the compounds of formula I and X is a leaving group which suitably activates the C=D carbonyl. Such leaving groups are well known in the art and include halides, hydroxide, alkoxides, phenoxides, and sulfonates. The esterification may optionally be run in the presence of an organic base, such as triethylamine, diisopropylamine, ethyldiiso- propylamine, pyridine, 4-dimethylaminopyridine, or mixtures thereof. Preferred leaving groups include the halides, and chlorine is especially preferred. Preferred organic bases include pyridine and 4- dimethylaminopyridine, and especially preferred are mixtures thereof. In a preferred embodiment of the invention, E-C(D) taken together is benzoate. In a second preferred embodiment, E-C(D) is 3-hydroxyben- zoate. In a third preferred embodiment, E-C(D) is

nicotinoate. In a fourth preferred embodiment, E-C(D) is 1,2, 3-thiadiazole-4-carboxylate. The esterification of the compound of formula III with E-C(D)-X leads to compounds of the formula IV:

IV

wherein Z and Z' are defined as above for formula III. The diol of formula IV may then be further esterified with compounds having the general formula G-(A) _n -X, wherein G, A and n are defined as above for the compounds of formula I, and X is a leaving group which enhances the electrophilicity of G (when n = 0) , or A. Suitable leaving groups are well known in the art and include but are not limited to halides, hydroxyl, alkoxides, phenoxides, and sulfonates. The esterification may optionally proceed in the presence of a reaction catalyst such as 4- dimethylamionpyridine, 1-(3-dimethylaminopropy1)-3- ethylcarbodiimide hydrochloride (EDC) , dicyclohexyl- carbodiimide (DCC) , diisopropylcarbodiimide (DIC) , and mixtures thereof. In a preferred embodiment of the invention, the leaving group is hydroxyl and the esterification catalyst is a mixture of EDC and 4-dimethylaminopyridine. In an especially preferred embodiment of the invention, G = benzyloxycarbonyl (Cbz) , A = valine (Val) and n = 1. The esterification of the compound of formula IV with G-(A) _n ~X leads to compounds of the formula V:

wherein Z, Z ¹ , E, C, and D are defined as above for formula IV. The compound of. formula V may then be treated with water and acid to remove the ketal protecting group and yield mannitol derivatives of formula I. Suitable acids used to remove ketal protecting groups are well known to those skilled in the art and include but are not limited to hydrochloric, sulfuric, acetic, p-toluenesulfonic and trifluoroacetic acid. A preferred acid is trifluoroacetic acid.

Alternatively, compounds of the present invention may be obtained directly from D- or L- mannose. In a preferred embodiment of the invention, L-mannose is the chosen enantiomer. Mannose may be reduced to mannitol by the action of a hydride donor. Hydride donors are well known to those skilled in the art and include but are not limited to sodium borohydride, sodium cyanoborohydride, lithium aluminium hydride, lithium tri-sec-butylborohydride and potassium tri-sec-butylborohydride. The reduction of mannose to mannitol may take place in a common solvent such as water, methanol, ethanol, 1-propanol, 2- propanol, tetrahydrofuran and mixtures thereof. In a preferred embodiment of the invention, the hydride donor is sodium borohydride and the solvent is methanol.

Mannitol may then be converted to the ketal of formula III by methods described above. The ketal of formula III may then be selectively condensed at the primary hydroxyl positions with an electrophile which, after forming a stable covalent bond with oxygen, can itself serve as a leaving group. Such electrophiles are known to those skilled in the art and include but are not limit-eα to acid halide and acid annydride derivatives of p-toluenesulfonic acid, 4- bromobenzenesulfonic acid, methanesulfonic acid and trifluoromethanesulfonic acid. Preferred is p-toluenesulfonyl chloride. The resulting bis adduct may be treated with base in a common solvent (defined above) to effect intramolecular bis-epoxidation via attack of the remaining hydroxyl groups at the terminal carbons with concomitant departure of the electrophile- oxygen leaving group. Such bases are well known to those skilled in the art and include, but are not limited to metal hydroxides such as sodium hydroxide, potassium hydroxide and lithium hydroxide, metal carbonates such as sodium carbonate, potassium carbonate and lithium carbonate, and metal hydrogen carbonates such as sodium bicarbonate, potassium bicarbonate and lithium bicarbonate. In a preferred embodiment of the invention, the base is potassium carbonate and the common solvent is methanol. Bis epoxides of this type are represented below in formula VI:

VI

wherein Z and Z' are defined as above for formula III. The bis epoxide of formula VI may be alkylated at the least hindered carbon atoms with a nucleophile having the formula E-C(D)-BH, wherein E, D and B are defined as above for the compounds of formula I, to give a diol. In a preferred embodiment of the invention, E-C(D)-BH is benzyl alcohol. In a second preferred embodiment, E-C(D)-BH is thiobenzoic acid. In a third preferred embodiment, E-C(D)-BH is 4- morpholinecarbodithioic acid. Diols obtained by this method are represented below in formula VII:

wherein Z, Z', E, C, and B are defined as above for formula IV. The diol of formula VII may then be further esterified with compounds having the general formula G-(A) _n ~X, wherein G, A and n are defined as above for the compounds of formula I, and X is a leaving group which enhances the electrophilicity of G (when n = 0) , or A. Suitable leaving groups are well known in the art and include but are not limited to halides, hydroxyl, alkoxides, phenoxides, and sulfonates. The esterification may optionally proceed in the presence of a reaction catalyst, such as 4- dimethylamion-pyridine, 1-(3-dimethylaminopropyl)-3- ethylcarbodiimide hydrochloride (EDC) , dicyclohexyl- carbodiimide (DCC) , diisopropylcarbodiimide (DIC) , and mixtures thereof. In a preferred embodiment of the invention, the leaving group is hydroxyl and the

esterification catalyst is a mixture of EDC and 4- dimethylamino-pyridine. In an especially preferred embodiment of this invention, G = benzoyloxycarbonyl (Cbz) , A = valine (Val) and n = 1. The esterification of the compound of formula IV with G-(A) _n -X leads to compounds of the formula VIII:

wherein Z, Z', E, C, B, G, A, and n are defined as above for formula V. The compound of formula VIII may then be treated in a similar fashion as the compound of formula V, wherein the ketal protecting group is liberated to afford mannitol derivatives of formula I. In a preferred embodiment of the invention, the acid used in conjunction with water is trifluoroacetic acid. Mannitol derivatives of the preferred embodiment of the invention were synthesized from 3,4- O-isopropylidine-L-mannitol (IC) , which was derived from L-mannitol (see Schemes 2-3 below) , according to procedures described by L.F. Wiggins, J. Chem. Soc.. p. 13, (1946); Le Merrer et al., Tetrahedron Lett.. 26, pp. 319-22 (1985) and Le Merrer et al. , Heterocvcles. 25, pp. 541-48 (1987) , wherein D-mannitol was used. The bis-ester core series of L-mannitol derivatives 1-4 were obtained by selective acylation of both primary hydroxyl groups of compound IC with an either a carboxylie acid halide in the presence of pyridine, or a carboxylie acid in the presence of EDC and DMAP, followed by coupling the resulting diol with

carbobenzyloxy-L-valine (CbzVal-OH) in the presence of EDC and DMAP. Subsequent treatment with aqueous trifluoroacetic acid to remove the acetonide protecting group yielded L-mannitol derivatives 1-4 (Scheme 2) .

R=C ₆ H ₅ , 1

R=3-(OH)-C ₆ H ₄ ,2

R=3-pyridyl, 3

R-4-(1,2.3-thiadiazol)-yl,4

Scheme2

L-mannitol derivatives 5-8 were similarly derived from compound IC, which was obtained from the sodium borohydride reduction of L-mannose, followed by tris ketalization with acetone and sulfuric acid, and subsequent removal of the terminal ketals with acetic acid and water (Scheme 3).

L-Mannose

XR

OH X

CbzVal-O.

^* 0-ValCbz

X OH

RX

RX = OBn. 5

RX = SCOPh, 6

RX = SCSN(CH ₂ CH ₂ ) ₂ 0. 7

RX = SCSNEt ₂ , 8

Scheme 3

Acetonide IC was then selectively tosylated at each primary hydroxyl site with p-toluenesulfonyl chloride in pyridine, and then treated with potassium carbonate in methanol to afford bis epoxide 5A (see, L.F. Wiggins, J. Chem. Soc.. p. 13, (1946); Le Merrer et al., Tetrahedron Lett.. 26, 319 (1985) and Le Merrer et al., Heterocvcles. 25, p. 541 (1987)). Mannitol derivatives 5 and 6 were obtained by treating bis epoxide 5A with either an alcohol or a thiocarboxylic acid using aluminum oxide as a catalyst (see, Posner et al.. Tetrahedron Lett.. 42, p. 3596 (1975) and Posner et al. , J. Am. Chem. Soc.. 99, pp. 25 and 8208 (1977)), esterifying the resulting diols with CbzVal- OH in the presence of EDC and DMAP, and removing the acetonide protecting group with TFA/water. Mannitol derivatives 7 and 8 were obtained by treating bis epoxide 5A with a dithioic acid salt, in the presence dimethyIformamide solvent (for an analogous reaction wherein an N-acylaziridine is ring-opened with mercaptan nucleophiles, see Kempf et al. , European patent application 402646 Al) . The dithioic acid salt may be used directly or generated in situ from reaction with an amine base. The resulting diols were then esterified with CbzVal-OH in the presence of EDC and DMAP, and the acetonide protecting group was removed with TFA and water.

As can be appreciated by the skilled artisan, the above synthetic schemes are not intended to comprise a comprehensive list of all means by which the compounds described and claimed in this application may be synthesized. Further methods will be evident to those of ordinary skill in the art.

The compounds of this invention may be modified by appending appropriate functionalites to enhance selective biological properties. Such

modifications are known in the art and include those which increase biological penetration into a given biological system (e.g., blood, lymphatic system, central nervous system) , increase oral availability, increase solubility to allow administration by injection, alter metabolism and alter rate of excretion.

As discussed above, the novel compounds of the present invention are excellent ligands for aspartyl proteases, particularly HIV-1, HIV-2 and HTLV- 1 proteases. Accordingly, these compounds are capable of targeting and inhibiting late stage events in HIV replication, i.e., the processing of the viral polyproteins by HIV encoded proteases. Compounds according to this invention advantageously inhibit the ability of the HIV-i virus to infect immortalized human T cells over a period of days, as determined by an assay of extracellular p24 antigen — a specific marker of viral replication (see. Meek et al.. Nature, 343, pp. 90-92 (1990)).

In addition to their use in the prophylaxis or treatment of HIV or HTLV infection, the compounds according to this invention may also be used as inhibitory or interruptive agents for other viruses which depend on aspartyl proteases, similar to HIV or

HTLV aspartyl proteases, for obligatory events in their life cycle. Such compounds inhibit the proteolytic processing of viral polyprotein precursors by inhibiting aspartyl protease. Because aspartyl protease is essential for the production of mature virions, inhibition of that processing effectively blocks the spread of virus by inhibiting the production and reproduction of infectious virions, particularly from chronically infected cells. The compounds of this invention advantageously inhibit enzymatic activity of

aspartyl proteases and inhibit the ability of aspartyl proteases to catalyze the hydrolysis of peptide bonds.

The compounds of this invention may be employed in a conventional manner for the treatment or prevention of HIV, HTLV, and other viruses which depend on aspartyl proteases for obligatory events in their life cycle. Such methods of treatment, their dosage levels and requirements may be selected by those of ordinary skill in the art from available methods and techniques. For example, a compound of this invention may be combined with a pharmaceutically acceptable adjuvant for administration to a virally-infected patient in a pharmaceutically acceptable manner and in an amount effective to lessen the severity of the viral infection.

Alternatively, the compounds of this invention may be used in vaccines and methods for protecting individuals against viral infection over an extended period of time. The compounds may be employed in such vaccines either alone or together with other compounds of this invention in a manner consistent with the conventional utilization of protease inhibitors in vaccines. For example, a compound of this invention may be combined with pharmaceutically acceptable adjuvants conventionally employed in vaccines and administered in prophylactically effective amounts to protect individuals over an extended period time against viral infections, such as HIV infection. As such, the novel protease inhibitors of this invention can be administered as agents for treating or preventing viral infections, including HIV infection, in a mammal.

The compounds of this invention may be administered to a healthy or HIV-infected patient either as a single agent or in combination with other

anti-viral agents which interfere with the replication cycle of HIV. By administering the compounds of this invention with other anti-viral agents which target different events in the viral life cycle, the therapeutic effect of these compounds is potentiated. For instance, the co-administered anti-viral agent can be one which targets early events in the life cycle of the virus, such as cell entry, reverse transcription and viral DNA integration into cellular DNA. Anti-HIV agents targeting such early life cycle events include, didanosine (ddl) , alcitabine (ddC) , d4T, zidovudine (AZT) , polysulfated polysaccharides, sT4 (soluble CD4) — which blocks attachment or adsorption of the virus to host cells — and other compounds which block binding of virus to CD4 receptors on CD4-bearing T- lymphocytes. Other retroviral reverse transcriptase inhibitors, such as derivatives of AZT, may also be co- administered with the compounds of this invention to provide therapeutic treatment for substantially reducing or eliminating viral infectivity and the symptoms associated therewith. Examples of other anti¬ viral agents include ganiclovir, dideoxycytidine, trisodium phosphonoformate, eflornithine, ribavirin, acyclovir, alpha interferon and trimenotrexate. Additionally, non-nucleoside inhibitors of reverse transcriptase, such as TIBO or nevirapine, may be used to potentiate the effect of the compounds of this invention, as may viral uncoating inhibitors, inhibitors of trans-activating proteins such as tat or rev, or inhibitors of the viral integrase. These compounds may also be co-administered with other inhibitors of HIV aspartyl protease.

Combination therapies according to this invention exert a synergistic effect in inhibiting HIV replication because each component agent of the

combination acts on a different site of HIV replication. The use of such combinations also advantageously reduces the dosage of a given conventional anti-retroviral agent which would be required for a desired therapeutic or prophylactic effect as compared to when that agent is administered as a monotherapy. These combinations may reduce or eliminate the side effects of conventional single anti- retroviral agent therapies while not interfering with the anti-retroviral activity of those agents. These combinations reduce potential of resistance to single agent therapies, while minimizing any associated toxicity. These combinations may also increase the efficacy of the conventional agent without increasing the associated toxicity. In particular, we have discovered that these compounds act synergistically in preventing the replication of HIV in human T cells. Preferred combination therapies include the administration of a compound of this invention with AZT, ddl, ddC or d4T.

Alternatively, the compounds of this invention may also be co-administered with other HIV protease inhibitors such as Ro 31-8959 (Roche) , L-735,524 (Merck), XM 323 (Du-Pont Merck) and A-80,987 (Abbott) to increase the effect of therapy or prophylaxis against various viral mutants or members of other HIV quasi species.

We prefer administering the compounds of this invention as single agents or in combination with retroviral reverse transcriptase inhibitors, such as derivatives of AZT, or other HIV aspartyl protease inhibitors. We believe that the co-administration of the compounds of this invention with retroviral reverse transcriptase inhibitors or HIV aspartyl protease inhibitors may exert a substantial synergistic effect,

thereby preventing, substantially reducing, or completely eliminating viral infectivity and its associated symptoms.

The compounds of this invention can also be administered in combination with immunomodulators (e.g., bropirimine, anti-human alpha interferon antibody, IL-2, GM-CSF, methionine enkephalin, interferon alpha, diethyldithiocarba ate, tumor necrosis factor, naltrexone and rEPO) ; antibiotics (e.g., pentamidine isethiorate) or vaccines to prevent or combat infection and disease associated with HIV infection, such as AIDS and ARC.

When the compounds of this invention are administered in combination therapies with other agents, they may be administered sequentially or concurrently to the patient. Alternatively, pharmaceutical or prophylactic compositions according to this invention may be comprised of a combination of an aspartyl protease inhibitor of this invention and another therapeutic or prophylactic agent.

Although this invention focuses on the use of the compounds disclosed herein for preventing and treating HIV infection, the compounds of this invention can also be used as inhibitory agents for other viruses which depend on similar aspartyl proteases for obligatory events in their life cycle. These viruses include, but are not limited to, other AIDS-like _d iseases caused by retroviruses, such as simian immunodeficiency viruses, HTLV-I and HTLV-II. In addition, the compounds of this invention may also be used to inhibit other aspartyl proteases, and in particular, other human aspartyl proteases, including renin and aspartyl proteases that process endothelin precursors.

Pharmaceutical compositions of this invention comprise any of the compounds of the present invention, and pharmaceutically acceptable salts thereof, with any pharmaceutically acceptable carrier, adjuvant or vehicle. Pharmaceutically acceptable carriers, adjuvants and vehicles that may be used in the pharmaceutical compositions of this invention include, but are nor limited to, ion exchangers, alumina, aluminum stearate, lecithin, serum proteins, such as human serum albumin, buffer substances such as phosphates, glycine, sorbic acid, potassium sorbate, partial glyceride mixtures of saturated vegetable fatty acids, water, salts or electrolytes, such as protamine sulfate, disodium hydrogen phosphate, potassium hydrogen phosphate, sodium chloride, zinc salts, colloidal silica, magnesium trisilicate, polyvinyl pyrrolidone, cellulose-based substances, polyethylene glycol, sodium carboxymethylcellulose, polyacrylates, waxes, polyethylene-polyoxypropylene-block polymers, polyethylene glycol and wool fat.

The pharmaceutical compositions of this invention may be administered orally, parenterally, by inhalation spray, topically, rectally, nasally, buccally, vaginally or via an implanted reservoir. We prefer oral administration or administration by injection. The pharmaceutical compositions of this invention may contain any conventional non-toxic pharmaceutically-acceptable carriers, adjuvants or vehicles. The term "parenteral" as used herein includes subcutaneous, intracutaneous, intravenous, intramuscular, intra-articular, intrasynovial, intrasternal, intrathecal, intralesional and intracranial injection or infusion techniques.

The pharmaceutical compositions may be in the form of a sterile injectable preparation, for example,

as a sterile injectable aqueous or oleaginous suspension. This suspension may be formulated according to techniques known in the art using suitable dispersing or wetting agents (such as, for example, Tween 80) and suspending agents. The sterile injectable preparation may also be a sterile injectable solution or suspension in a non-toxic parenterally- acceptable diluent or solvent, for example, as a solution in l,3-butanediol. Among the acceptable vehicles and solvents that may be employed are mannitol, water, Ringer's solution and. isotonic sodium chloride solution. In addition, sterile, fixed oils are conventionally employed as a solvent or suspending medium. For this purpose, any bland fixed oil may be employed, including synthetic mono- or diglycerides. Fatty acids, such as oleic acid and its glyceride derivatives are useful in the preparation of injectables, as are natural pharmaceutically-acceptable oils, such as olive oil or castor oil, especially in their polyoxyethylated versions. These oil solutions or suspensions may also contain a long-chain alcohol diluent or dispersant, such as Ph. Helv or a similar alcohol.

The pharmaceutical compositions of this invention may be orally administered in any orally acceptable dosage form including, but not limited to, capsules, tablets, and aqueous suspensions and solutions. In the case of tablets for oral use, carriers which are commonly used include lactose and corn starch. Lubricating agents, such as magnesium stearate, are also typically added. For oral administration in a capsule form, useful diluents include lactose and dried corn starch. When aqueous suspensions are administered orally, the active ingredient is combined with emulsifying and suspending

agents. If desired, certain sweetening and/or flavoring and/or coloring agents may be added.

The pharmaceutical compositions of this invention may also be administered in the form of suppositories for rectal administration. These compositions can be prepared by mixing a compound of this invention with a suitable non-irritating excipient which is solid at room temperature but liquid at the rectal temperature and therefore will melt in the rectum to release the active components. Such materials include, but are not limited to, cocoa butter, beeswax and polyethylene glycols.

Topical administration of the pharmaceutical compositions of this invention is especially useful when the desired treatment involves areas or organs readily accessible by topical application. For application topically to the skin, the pharmaceutical composition should be formulated with a suitable ointment containing the active components suspended or dissolved in a carrier. Carriers for topical administration of the compounds of this invention include, but are not limited to, mineral oil, liquid petroleum, white petroleum, propylene glycol, polyoxy- ethylene polyoxypropylene compound, emulsifying wax and water. Alternatively, the pharmaceutical compositions can be formulated with a suitable lotion or cream containing the active compound suspended or dissolved in a carrier. Suitable carriers include, but are not limited to, mineral oil, sorbitan monostearate, polysorbate 60, cetyl esters wax, cetearyl alcohol,

2-octyldodecanol, benzyl alcohol and water. The pharmaceutical compositions of this invention may also be topically applied to the lower intestinal tract by rectal suppository formulation or in a suitable enema formulation. Topically-transdermal patches are also included in this invention.

The pharmaceutical compositions of this invention may be administered by nasal aerosol or inhalation. Such compositions are prepared according to techniques well-known in the art of pharmaceutical formulation and may be prepared as solutions in saline, employing benzyl alcohol or other suitable preservatives, absorption promoters to enhance ioavailability, fluorocarbons, and/or other solubilizing or dispersing agents known in the art. Dosage levels of between about .01 and about

25 mg/kg body weight per day, preferably between about 0.5 and about 25 mg/kg body weight per day of the active ingredient compound are useful in the prevention and treatment of viral infection, including HIV infection. Typically, the pharmaceutical compositions of this invention will be administered from about 1 to about 5 times per day or alternatively, as a continuous infusion. Such administration can be used as a chronic or acute therapy. The amount of active ingredient that may be combined with the carrier materials to produce a single dosage form will vary depending upon the patient treated and the particular mode of administration. A typical preparation will contain from about 5% to about 95% active compound (w/w) . Preferably, such preparations contain from about 20% to about 80% active compound.

Upon improvement of a patient's condition, a maintenance dose of a compound, composition or combination of this invention may be administered, if necessary. Subsequently, the dosage or frequency of administration, or both, may be reduced, as a function of the symptoms, to a level at which the improved condition is retained. When the symptoms have been alleviated to the desired level, treatment should cease. Patients may, however, require intermittent

treatment on a long-term basis, upon any recurrence of disease symptoms.

As the skilled artisan will appreciate, lower or higher doses than those recited above may be required. Specific dosage and treatment regimens for any particular patient will depend upon a variety of factors, including the activity of the specific compound employed, the age, body weight, general health status, sex, diet, time of administration, rate of excretion, drug combination, the severity and course of the infection, the patient's disposition to the infection and the judgment of the treating physician.

The compounds of this invention are also useful as commercial reagents which effectively bind to aspartyl proteases, particularly HIV aspartyl protease. As commercial reagents, the compounds of this invention, and their derivatives, may be used to block proteolysis of a target peptide, such as an aspartyl protease, or may be derivatized to bind to a stable resin as a tethered substrate for affinity chromatography applications. These and other uses which characterize commercial aspartyl protease inhibitors will be evident to those of ordinary skill in the art. This invention also includes methods for synthesizing aspartyl protease inhibitors. One method comprises the steps of:

(a) treating mannitol with a carbonyl compound in the presence of an acid to yield a ketal derivative; said carbonyl compound being selected from the group consisting of acetone, cyclopentanone, cyclohexanone, and benzaldehyde; and said acid being selected from the group consisting of sulfuric, hydrochloric, acetic, trifluoroacetic, and mixtures thereof;

(b) esterifying said ketal derivative at each primary hydroxyl site thereof with a sulfonyl chloride to yield a bis sulfonate ester; said sulfonyl chloride being selected from the group consisting of p-toluenesulfonyl chloride, 4-bromobenzenesulfonyl chloride, methanesulfonyl chloride, and trifluoromethanesulfony1 chloride;

(c) reacting said bis sulfonate ester with a base to yield a bis epoxide; said base being selected from the group consisting of metal hydroxides, metal carbonates, and metal bicarbonates; and said bis epoxide having two least hindered sites;

(d) opening said bis epoxide at each least hindered site thereof with a nucleophile to yield a diol; said nucleophile being selected from the group consisting of an aryl alcohol, and arylthioic acid, and a heterocyclic dithioic acid;

(e) esterifying said diol with an alpha-amino acid optionally bearing an N-protecting group to yield a diester; said N-protecting group being selected from the group consisting of benzyloxycarbonyl and t-butoxycarbonyl; and

(f) treating said diester with a mixture of water and said acid of step (a) to yield said aspartyl protease inhibitor.

Another method for synthesizing aspartyl protease inhibitors according to this invention comprises the steps of:

(a) treating mannitol with a carbonyl compound in the presence of an acid to yield a ketal derivative; said carbonyl compound being selected from the group consisting of acetone, cyclopentanone, cyclohexanone, and benzaldehyde; and said acid being selected from the group consisting of sulfuric.

hydrochloric, acetic, trifluoroacetic, and mixtures thereof;

(b) esterifying said ketal derivative at each primary hydroxyl site thereof with an esterifying agent to yield a diol; said esterifying agent being selected from the group consisting of a carboxylic acid, a carboxylic acid halide, and a carboxylic acid anhydride;

(c) esterifying said diol with an alpha-amino acid optionally bearing an N-protecting group to yield a diester; said N-protecting group being selected from the group consisting of benzyloxycarbonyl and t-butoxycarbonyl; and

(d) treating said diester with a mixture of water and said acid of step (a) to yield said aspartyl protease inhibitor.

EXAMPLES

In order that this invention be more fully understood, the following examples are set forth. These examples are for the purpose of illustration only and are not to be construed as limiting the scope of the invention in any way.

Materials and Methods

The Al ₂ 0 ₃ employed for epoxide ring-opening reactions with heteroatom nucleophiles was preferably Brockman Super I, Woelm 200 neutral (from ICN flow). L-mannitol was prepared by the reduction of L-mannose which was purchased from Sigma. Commercial L-amino acid derivatives were employed where relevant. Analytical thin layer chromatography (TLC) was carried out with 0.25 mm silica gel E. Merck 60 F ₂₅₄ plates and eluted with the indicated solvent systems.

Preparative chromatography was performed either by flash chromatography, using Silica Gel 60 (EM Science) with the indicated solvent systems and a positive N ₂ pressure for elutions, or by thick layer chromatography, again employing E. Merck 60 F ₂₅₄ plates of 0.5, 1.0, or 2.0 mm thickness. Detection of the compounds was carried out by exposing eluted plates (analytical or preparative) to UV light and treating analytical plates with a 20% solution of phosphomolybdic acid in EtOH, followed by heating, unless otherwise indicated.

All analytical HPLC was carried out with a Waters Delta Pak, 5μM silica, C-18 reverse-phase column with dimensions of 3.90 mm ID x 15 cm, using a flow rate of 1.5 ml/min. , with the following mobile phase and gradient profile:

Mobile phase: A-O.1% trifluoroacetic acid in H ₂ 0;

B=0.1% trifluoroacetic acid in CH ₃ CN Gradient: T=θ min. , A (95%), B (5%) ; T=20 min., A (0%), B (100%);

T=22.5 min., A (0%), B (100%)

Nuclear magnetic resonance (NMR) spectra were recorded on a Bruker AMX 500 equipped with a reverse or QNP probe. Samples were dissolved in deuteriochloroform or deuteriomethanol for data acquisition, using the respective internal protic solvent frequencies as standards. Chemical shifts (in parts per million) and multiplicities (denoted as s for singlet, d for doublet, dd for doublet of doublets, t for triplet, q for quartet, m for ultiplet, and br for broad) are provided herein, and the number of hydrogens listed for all C ₂ -symmetric compounds is half of that present in the molecule.

The following compounds were prepared from L-mannitol using the procedures described by Le Merrer et al., Heterocvcles, 25, pp. 541-48, (1987), wherein D-mannitol was utilized for compounds IB, IC, ID, and 5A.

EXAMPLE 1 A. L-mannitol (Compound 1A) .

To a commercial sample of L-mannose as a mixture of anomers (27.2 g, 0.15 mol) in MeOH (700 ml) was placed sodium borohydride (12.6 g, 0.33 mol) in portions at 0°C, and the reaction was acidified to pH-1 by the dropwise addition of concentrated HCl at 0°C, then solid K ₂ C0 ₃ (excess) was added and the solution was vacuum filtered using MeOH for quantitative transfer. Concentration of the filtrate afforded a white solid that was azeotroped with benzene (2 x 200 mL) . This was followed by crystallization of the solid from alcohol (1.8 L) , which was effected by heating the solution at reflux and filtering it immediately. L-mannitol crystallized rapidly as white needles to provide 17.3 g of the product, compound 1A (63% yld) . TLC: R _f (9% NH ₄ OH/18% MeOH/CH ₂ Cl ₂ ) = 0.6 (visualized with ninhydrin) ; NMR (CD ₃ OD) : 3.86 (dd, 1H, ABX) , 3.68 (dd, 1H, ABX), 3.82 (s, 1H) , 3.74 (m, 1H) .

Bj_ 1.2:3.4:5.6-tris-O-isopropylidene-L-mannitol (Compound IB) .

L-Mannitol (15.5 g, 0.09 mol) was diluted with acetone (193 ml) and sulfuric acid (1.55 ml), and the reaction (which remained heterogeneous throughout) stirred at room temperature for 12 hours. It was neutralized with 30% NH ₄ 0H (5.6 ml) and solid K ₂ C0 ₃ (9.8 g) , with continued stirring for 2 hours, followed by vacuum filtration. Concentration of the filtrate

afforded a white solid which crystallized from wet alcohol by adding enough EtOH and warming until homogeneous, then adding H ₂ 0 dropwise with swirling until the solution became slightly cloudy. After crystallization, compound IB was recovered by vacuum filtration as white, crystalline needles (21 g) . More compound could be recovered from the mother liquor, if desired. NMR (CDC1 ₃ ) : 4.16 (m, 1H) , 4.05 (dd, 1H, ABX), 3.95 (dd, 1H, ABX), 3.92 (dd, 1H) , 1.40 (s, 3H) , 1.35 (s, 3H) , 1.32 (s, 3H) .

C. 3.4-O-isopropylidene-L-mannitol (Compound IC) .

To a mixture of distilled H ₂ 0 (120 mL) and glacial acetic acid (280 L) was added compound IB (19.8 g, 0.66 mol) at 40°C, and the reaction was maintained at this temperature for 2.5 hours.- The aqueous acetic acid was removed immediately in vacuo _r maintaining the bath temperature between 40-50°C. The resulting white solid was diluted with acetone (150 ml) , and the undissolved white precipitate (L-mannitol) was removed by vacuum filtration. Concentration of the filtrate provided a clear, viscous oil which soon crystallized in vacuo. Recrystallization from benzene afforded compound IC as a white, crystalline product (8.3 g) . NMR (CD-,OD) : 3.98 (dd, 1H) , 3.81 (dd, 1H, ABX), 3.66 (dd, 1H, ABX), 3.69 (m, 1H) , 1.41 (s, 3H) .

D. 1.6-di-Q-benzoyl-3.4-O-isopropylidene-L-mannitol (Compound ID) .

To a solution of compound IC (45 mg, 0.20 mmol) and pyridine (0.83 mL, 10.26 mmol) in CH ₂ C1 ₂ (1 ml) was added benzoyl chloride (47 μl , 0.41 mmol) at

-78°C, the system under a N ₂ atmosphere. After stirring for 2 hours at this temperature, the reaction was warmed to 20°C and poured into cold 6N HCl (2 ml) , then

extracted with CH ₂ C1 ₂ . The organic layer was washed with saturated NaHC0 ₃ and dried over MgS0 ₄ . After filtration and concentration, the resulting residue was flash chromatographed (9% Et ₂ 0/CH ₂ C1 ₂ ) to yield compound ID (25 mg) . NMR (CDC1 ₃ ) : 8.04 (d, 2H) , 7.56 (t, 1H) , 7.41 (t, 2H) , 4.69 (dd, 1H, ABX), 4.42 (dd, 1H, ABX), 4.05 (s, 1H) , 3.98 (m, 1H) , 1.39 (s, 3H) .

E. 1.6-di-Q-benzoyl-2.5-di-O-(N-carbobenzyloxwalyl)- 3.4-O-isopropylidene-L-mannitol (Compound IE). Compound ID (25 mg, 0.06 mmol) was stirred in

CH ₂ C1 ₂ (2 ml) in the presence of carbobenzyloxyvaline (CbzVal-OH; 73 mg, 0.29 mmol), 1-(3-dimethy1- aminopropyl)-3-ethylcarbodiimide hydrochloride (EDC; 56 mg, 0.29 mmol), and dimethylaminopyridine (DMAP; catalytic) , for 12 hours at ambient temperature. The reaction mixture was then diluted with CH ₂ C1 ₂ , and the organic layer was washed with saturated NaHC0 ₃ and dried over MgS0 ₄ . After filtration and concentration, the resulting residue was flash chromatographed (10% Et ₂ 0/CH ₂ C1 ₂ ) to afford compound IE as a colorless oil (20 mg) . NMR (CDC1 ₃ ) : 7.99 (d, 2H) , 7.51 (t, 1H) , 7.21-7.40 ( , 1H) , 5.31 (m, 2H) , 5.08 (d, 1H, AB) , 4.95 (d, 1H, AB) , 4.77 (d, 1H, ABX), 4.41 (dd, 1H, ABX), 4.35 (m, 1H) , 4.25 (d, 1H) , 2.17 (m, 1H) , 1.46 (s, 3H) , 0.93 (d, 3H) , 0.82 (d, 3H) .

F. l.6-di-Q-benzoyl-2.5-di-O-(N-carbobenzyloxyvalyl)- L-mannitol (Compound 1) .

Deprotection of the acetonide was effected by stirring compound IE (5 mg) with 90% aqueous trifluoroacetic acid (TFA; 1 ml) , at 0°C for 70 minutes, then removing the solvent in vacuo. The resulting residue was purified by flash chromatography using 25% Et ₂ 0/CH ₂ C1 ₂ as eluent, which afforded compound

1 ( 1. 4 mg) . TLC : R _f ( 25% Et ₂ 0/CH ₂ C1 ₂ ) = 0. 3 ; analytical HPLC : R _fc = 19 . 1 minutes .

EXAMPLE 2

A. 3-(t-butyldimethylsiloxy)-benzoic acid (Compound 2A) .

A solution of 3-hydroxybenzoic acid (219 mg, 1.59 mmol), t-butyldimethylsilyl chloride (717 mg, 4.76 mmol), and imidazole (324 mg, 4.76 mmol) in DMF (3 ml) was stirred for 12 hours at room temperature. The reaction mixture was diluted with EtOAc and washed with saturated NH ₄ C1. The organic layer was washed with H ₂ 0 (two times) and dried over MgS0 ₄ . Filtration and concentration gave a colorless liquid (831.4 mg) . The resulting colorless liquid product (565 mg) was dissolved in 60%/20%/20%, acetic acid/H ₂ 0/THF (5 ml), and the reaction proceeded at room temperature for 90 minutes. Removal of the solvent in vacuo afforded compound 2A (125 mg) as a solid. NMR (CDC1 ₃ ) : 7.70 (d, 1H) , 7.55 (br s, 1H) , 7.32 (t, 1H) , 7.07 (d, 1H) , 0.99 (s, 9H) , 0.21 (s, 6H) .

B. 1.6-di-Q-r3-(t-butyldimethylsiloxy)-benzoyl1- 3.4-O-isopropylidene L-mannitol (Compound 2B) .

To a solution of 3-(t-butyldimethylsiloxy)- benzoic acid (compound 2A) (125 mg, 0.50 mmol) and compound IC (55 mg, 0.25 mmol) in CH ₂ C1 ₂ (3 ml) was placed EDC (95 mg, 0.50 mmol) and DMAP (catalytic), and the resulting mixture was stirred for 12 hours. Removal of the solvent in vacuo gave a residue which was flash chromatographed with 9% Et ₂ 0/CH ₂ C1 ₂ , affording compound 2B as a colorless residue (78.4 mg) which was used in the next reaction without purification.

C. 1.6-di-O-r3-(t-butyldimethylsiloxy)-benzoyl1-2.5- di-O-(N-carbobenzyloxyvalyl)-3.4-O-isopropylidene-L- mannitol (Compound 2C) .

Following the method of Example IE, compound 2B (28.4 mg) , CbzVal-OH (52 mg, 0.21 mmol), EDC (39 mg, 0.21 mmol) and DMAP (catalytic in 2 ml CH ₂ C1 ₂ ) were allowed to react. Removal of the solvent in vacuo provided a residue which was flash chromatographed with 9% Et ₂ 0/CH ₂ C1 ₂ , affording compound 2C as a colorless oil (51.5 g) . TLC: R _f (9% Et ₂ 0/CH ₂ C1 ₂ ) = 0.72.

D. 1.6-di-Q-(3-hvdroxy)benzoyl-2.5-di-Q-(N- carbobenzyloxyvalyl)-L-mannitol (Compound 2).

Following the method of Example IF, compound 2C (44.1 mg, 0.05 mmol) was converted to 22.2 mg of compound 2 (concomitant silyl and acetonide removal occurred under the reaction conditions) after preparative TLC (0.25 mm) using 5% MeOH/CH ₂ Cl ₂ as eluent. TLC: R _f (5% MeOH/CH ₂ Cl ₂ ) = 0.59; analytical HPLC: R _fc =l7.0 minutes.

EXAMPLE 3

A. 1.6-di-Q-nicotinoyl-3,4-O-isopropylidene-L- mannitol (Compound 3A) .

Nicotinoyl chloride hydrochloride (324.1 mg, 1.82 mmol) was added in one portion to a -78°C solution of compound IC (202.4 mg, 0.91 mmol) in pyridine (3.6 ml) and CH ₂ C1 ₂ (3.6 ml). The reaction was allowed to stir for 5 hours, while slowly warming to room temperature. The reaction was poured onto CH ₂ C1 ₂ (40 ml) and washed with H ₂ 0 (three times) and saturated aqueous NaCl, then dried over Na ₂ S0 ₄ and concentrated in vacuo. Flash chromatography using 15% isopropa- nol/CH ₂ Cl ₂ as eluent gave compound 3A (209 mg) . NMR (CDC1 ₃ ) : 9.20 (s, 1H) , 8.72 (d, 1H) , 8.29 (d, 1H) , 7.38

(m , 1H) , 5 . 23 ( br s , 1H) , 4 . 74 ( d , 1H) , 4 . 47 (m , 1H) , 4 . 03 (dd , 2H) , 1. 42 ( s , 3H) .

B. 1.6-di-0-nicotinoyl-2.5-di-O-(N- carbobenzyloxyvalyl)-3.4-O-isopropylidene-L-mannitol (Compound 3B) .

CbzVal-OH (815.7 mg, 3.25 mmol) and compound 3A (200 mg, 0.46 mmol) in CH ₂ C1 ₂ (5 ml) was treated with EDC (620.7 mg, 3.23 mmol) and DMAP (11.3 mg, 0.09 mmol) , and the resulting mixture was stirred for 48 hours. The reaction was diluted with CH ₂ C1 ₂ (40 ml) and washed with H ₂ 0 (two times) and saturated aqueous NaCl, then dried over Na ₂ S0 ₄ and concentrated in vacuo. Flash chromatography with 3.5% isopropanol/CH ₂ Cl ₂ as eluent provided compound 3B (340 mg) as a white foam. NMR (CDC1 ₃ ) : 9.20 (s, 1H) , 8.74 (d, 1H) , 8.23 (d, 1H) ,

7.20-7.40 ( , 7H) , 5.32 (m, 2H) , 5.02 (dd, 2H) , 4.80 (d, 1H) , 4.50 (m, 1H) , 4.31 (m, 1H) , 4.23 (d, 1H) , 2.20 (m, 1H) , 1.45 (s, 3H) , 0.93 (d, 3H) , 0.84 (d, 3H) .

C. 1,6-di-Q-nicotinoyl-2.5-di-O-(N- carbobenzyloxyvalyl)-L-mannitol (Compound 3).

Compound 3B (320 mg, 0.36 mmol) was stirred with 90% aqueous trifluoroacetic acid (1.1 ml) and CH ₂ C1 ₂ (2 ml) for 18 hours at room temperature, followed by concentration in vacuo. Preparative HPLC (reverse-phase C-18 column, 30 mm x 30 cm, 100 angstrom, mobile phase: 70% to 20% A/B over a 60 minute gradient elution) gave 59.6 mg of compound 3 and 158.8 mg of recovered compound 3B. TLC: R _f (7% isopropanol/CH ₂ Cl ₂ ) = 0.42; analytical HPLC: R _fc = 14.9 minutes.

EXAMPLE 4

A. 1.6-di-O-r4-(1,2.3-thiadiazo)-yll-3.4-O-isopropyl- idene-L-mannitol (Compound 4A) .

Following the method of Example ID, compound ic (49.0 mg, 0.22 mmol) was treated with 1,2,3- thiadiazole-4-carbonyl chloride (0.57 mmol). Preparative TLC (0.5 mm) using 5% MeOH/CH ₂ Cl ₂ as eluent gave 20.9 mg of compound 4A as a yellow solid. NMR (CDCl ₃ /DMSO-d ₆ ) : 9.8 (s, IH) , 5.63 (br s, IH) , 4.67 (d, IH) , 4.40 (dd, IH) , 4.11 (d, IH) , 4.01 (br s, IH) , 1.41 (s, 3H).

B. 1.6-di-Q-f4-(1.2.3-thiadiazo)-yl1-2.5-di-O- (N-carbobenzyloxyvalyl)-3,4-O-isopropylidene-L-mannitol (Compound 4B) . CbzVal-OH (72.3 mg, 0.29 mmol) and compound

4A (18 mg, 0.04 mmol) in DMF (1.2 ml) were treated with EDC (53.3 g, 0.28 mmol) and DMAP (2.4 mg, 0.02 mmol), and the resulting mixture was stirred for 24 hours. The reaction was diluted with EtOAc and washed with cold 3N HCl (two times) , cold aqueous 5% NaHC0 ₃ (two times) , and saturated aqueous NaCl, then dried over Na ₂ S0 ₄ and concentrated in vacuo. Preparative TLC (0.5 mm) with 4% MeOH/CH ₂ Cl ₂ as eluent gave 27.4 mg of compound 4B as a white foam. NMR (CDC1 ₃ ) : 9.28 (s, IH) , 7.20-7.40 ( , 5H) , 5.25-5.35 (m, 2H) , 4.98-5.15 (m, 2H) , 4.90 (d, IH) , 4.51 (dd, 2H) , 4.30 (m, IH) , 2.20 (br s, IH) , 1.45 (s, 3H) , 0.97 (d, 3H) , 0.85 (s, 3H) .

C. 1.6-di-Q-r4-l.2.3-thiadiazol1-yl-2.5-di-Q-(N- carbobenzyloxyvalyl-L-mannitol (Compound 4).

Following the method of Example 3C, compound 4B (27.2 mg, 0.03 mmol) was converted to 5.7 mg of compound 4 after preparative TLC (0.5 mm) using 5%

isopropanol/CH ₂ Cl ₂ as eluent. TLC: R _f (5% isopropanol/CH ₂ Cl ₂ ) = 0.50; analytical HPLC: 1^ = 16.9 minutes.

EXAMPLE 5 ___ 1.2.5.6-dianhvdro-3.4-O-isopropylidene L-mannitol (Compound 5A) .

To compound IC (5.2 g, 0.02 mol) in pyridine (75 ml, 0.93 mol) was added p-toluenesulfonyl chloride (9.2 g, 0.05 mol) in portions at 0°c. After stirring for 3 hours at this temperature, the reaction mixture was poured into a cold 6N HCl (160 ml)/Et ₂ 0 (75 ml) mixture, and the organic layer was separated and washed with a 3% NaHCθ ₃ solution (100 ml) , then was dried over MgS0 ₄ . Filtration and concentration afforded the desired bis-tosylate, which was used immediately in the next reaction without purification.

Anhydrous K ₂ C0 ₃ (16.2 g, 0.12 mol) was added to a solution of the preceding isolate in anhydrous MeOH (150 ml) , and the reaction proceeded at room temperature for 3 hours. The reaction mixture was then diluted with CH ₂ C1 ₂ and washed successively with H ₂ 0 and saturated NH ₄ C1, followed by drying over MgS0 ₄ . Filtration and concentration gave the crude bis-epoxide as a pale yellow liquid, which was distilled under reduced pressure (-0.5 mm Hg) to provide compound 5A (2.1 g) as a colorless oil (b.p.: 75-82°C) . NMR (CDC1 ₃ ) : 3.80 (dd, IH) , 3.08 (dd, IH) , 2.81 (t, IH) , 2.68 (dd, IH) , 1.40 (s, 3H) .

B. 1.6-di-Q-benzyl-3.4-O-isopropylidene-L-mannitol (Compound 5B) .

Benzyl alcohol (104 μl, 1.00 mmol) was added to a slurry of Al ₂ 0 ₃ (1.35 g) in Et ₂ 0 (3 ml), and after

stirring for 5 minutes, a solution of the bis-epoxide compound 5A (34.2 mg, 0.18 mmol) in Et ₂ 0 (2 ml) was added. The reaction proceeded at room temperature for 12 hours, then MeOH (20 ml) was added to the reaction mixture and the solution was allowed to stand for 4 hours. After vacuum filtration of the solution over a Celite® pad, concentration gave a residue which was purified by thick layer chromatography (0.5 mm) using 9% Et ₂ 0/CH ₂ C1 ₂ as eluent to provide compound 5B (3.0 mg) .

C. 1.6-di-Q-benzyl-2.5-di-O-(N-carbobenzyloxyvalyl)- 3,4-O-isopropylidene-L-mannitol (Compound 5C) .

Compound 5B (3.0 mg, 0.01 mmol) was stirred in CH ₂ C1 ₂ (2 ml) in the presence of CbzVal-OH (10 mg, 0.04 mmol), EDC (8 mg, 0.04 mmol), and DMAP (catalytic) for 12 hours. Concentration of the reaction mixture, followed by flash chromatography of the residue (9% Et ₂ 0/CH ₂ C1 ₂ ) , gave the coupled product, compound 5C (1.9 mg) .

D _j . 1.6-di-Q-benzyl-2.5-di-O-(N-carbobenzyloxyvalyl)- L-mannitol (Compound 5) .

Acetonide removal was effected by stirring compound 5C (1.9 mg, 2.19 μmol) with 90% aqueous trifluoroacetic acid (1.5 ml) at 0°C for 75 minutes, then removing the solvent in vacuo. The resulting residue was purified by thick layer chromatography (0.5 mm) using 17% Et ₂ 0/CH ₂ C1 ₂ as eluent, which afforded compound 5 (1.6 mg) as a white solid. TLC: R _f (50% hexane/EtOAc) = 0.3; NMR (CDC1 ₃ ) : 7.18-7.40 ( , 10H) , 5.20 (br d, IH) , 4.95-5.15 (m, 3H) , 4.49 (m, 2H) , 4.30 (dd, IH) , 3.85 (t, IH) , 3.75 (br s, 2H) , 2.98 (d, IH) , 2.15 (m, IH) , 0.93 (d, 3H) , 0.81 (d, 3H) .

EXAMPLE 6

A. 1.6-di-S-benzoγl-3.4-O-isopropylidene-L-mannitol (Compound 6A) .

To a solution of thiobenzoic acid (136 μl, 1.15 mmol) and Al ₂ 0 ₃ (1.51 g) in Et ₂ 0 (2 ml) was placed, after 5 minutes, a solution of the epoxide compound 5A (42.9 mg, 0.23 mmol) in THF (1 ml), and the reaction stirred at room temperature for 12 hours. MeOH (20 ml) was added, and the reaction mixture stirred for 3 hours, then was vacuum filtered. After removal of the solvent in vacuo. the residue was dissolved in EtOAc and washed with saturated NaHC0 ₃ , then dried over MgS0 ₄ . Filtration and concentration gave compound 6A as a purple oil (77.1 mg) , which was used in the next reaction without purification. TLC: R _f (50% hexane/EtOAc) = 0.63.

B. 1.6-di-S-benzoyl-2.5-di-O-(N-carbobenzyloxwalyl)- 3.4-O-isopropylidene-L-mannitol (Compound 6B) .

Compound 6A (77.1 mg) was stirred in CH ₂ C1 ₂ (2 ml) in the presence of CbzVal-OH (293 mg, 1.17 mmol),

EDC (224 mg, 1.17 mmol) and DMAP (4 mg, 0.03 mmol), and the resulting mixture was stirred for 12 hours. Removal of the solvent in vacuo and purification of the residue by preparative TLC (3X 1.0 mm) with 25% EtOAc/hexane as eluent gave compound 6B (124 mg) . TLC: R _f (50% hexane/EtOAc) = 0.82.

C. 1.6-di-S-benzoyl-2.5-di-O-(N-carbobenzyloxy- valyl)-L-mannitol (Compound 6).

Following the method of Example IF, compound 6B (23.4 mg, 0.03 mmol) was converted to 6.4 mg of compound 6 after preparative TLC (0.5 mm) using 25% Et ₂ 0/CH ₂ C1 ₂ . TLC: R _f (25% Et ₂ 0/CH ₂ C1 ₂ ) = 0.43; analytical HPLC: R _t = 19.8 minutes.

EXAMPLE 7

A. l.6-di-S-r4-morpholinothiocarbonyl)-3,4-0- isopropylidene-L-mannitol (Compound 7A) .

To a solution of 4-morpholinecarbodithioic acid with morpholine as a 1:1 complex (239 mg, 0.95 mmol) in DMF (1.5 ml) was added a solution of the bis-epoxide compound 5A (59.2 mg, 0.32 mmol) in Et ₂ 0 (0.5 ml), and the reaction proceeded at room temperature for 12 hours. After dilution with EtOAc, the reaction mixture was washed with H^O (three times) , and the combined aqueous layers were extracted with EtOAc, which in turn was washed with H ₂ 0 (two times) . The combined organic layers were dried over MgS0 ₄ . Filtration and concentration afforded a residue which was purified by thick layer chromatography (l.o mm) using EtOAc as eluent to yield diol compound 7A (78 mg) as a white solid. TLC: R _f (EtOAc) = 0.63.

B. 1.6-di-S-(4-morpholinothiocarbonyl)-2.5-di-Q-(N- carbobenzyloxyvalyl)-3,4-O-isopropylidene-L-mannitol (Compound 7B) .

Compound 7A (38.9 mg, 0.08 mmol) was stirred in CH ₂ C1 ₂ (1 ml) in the presence of CbzVal-OH (133 mg, 0.53 mmol), EDC (102 mg, 0.53 mmol), and DMAP (catalytic) for 48 hours. The reaction mixture was then diluted with CH ₂ Cl ₂ and washed with saturated NaHC0 ₃ , and the organic layer was dried over MgS0 ₄ . Filtration and concentration gave a residue which was purified by thick layer chromatography (1.0 mm) using 50% hexane/EtOAc as eluent to provide the coupled product, compound 7B (46 mg) . TLC: R _f (50% hexane/EtOAc) = 0.34.

C. l.6-di-S-(4-morpholinothicarbonyl)-2.5-di-θ-(N- carbobenzyloxyvalyl)-L-mannitol (Compound 7).

The acetonide was removed by stirring compound 7B (12.6 mg, 0.01 mmol) with 90% aqueous trifluoroacetic acid (1 ml) at 0°C, and allowing the reaction mixture to reach ambient temperature over a 2.5 hour period. After removal of the solvent in vacuo, the resulting residue was purified by thick layer chromatography (0.5 mm) using 5% MeOH/CH ₂ Cl ₂ as eluent, which afforded compound 7 (7.4 mg) as a colorless oil. TLC: R _fc (5% MeOH/CH ₂ Cl ₂ ) = 0.51; analytical HPLC: R _t = 18.1 minutes.

EXAMPLE 8

A. 1.6-di-S-(N.N-diethylthiocarbonyl)-3.4-Q- isopropylidene L-mannitol (Compound 8A) .

Following the method of Example 7A, the ammonium salt of diethyldithiocarbamic acid (133 mg, 0.80 mmol) and the epoxide compound 5A (49.8 mg, 0.27 mmol) were reacted to provide compound 8A (88 mg) , which was used in the next reaction without purification.

B. 1.6-di-S-(N.N-diethylthiocarbonyl)-2.5-di-O-(N- carbobenzyloxyvalyl)-3.4-O-isopropylidene L-mannitol (Compound 8B) . Compound 8A (88 mg) was stirred in CH ₂ C1 ₂ (3 ml) in the presence of CbzVal-OH (319 mg, 1.27 mmol), EDC (244 mg, 1.27 mmol), and DMAP (catalytic) for 12 hours. The reaction mixture was then diluted with CH ₂ C1 ₂ and washed with saturated NaHC0 ₃ , and the organic layer was dried over MgS0 ₄ . Filtration and concentration gave a residue which was purified by flash chromatography with 33% EtOAc/hexane as eluent to

afford the coupled product, compound 8B (180 mg) . TLC: R _f (33% EtOAc/hexane) = 0.25.

C. 1.6-di-S-(N.N-diethylthiocarbonyl)-2.5-di-O-(N- carbobenzyloxyvalyl-L-mannitol (Compound 8) . Following the method of Example IF, compound

8B (28.7 mg, 0.03 mmol) was converted to 12.1 mg of compound 8 after preparative TLC (2 x 0.25 mm) using 5% MeOH/CH ₂ Cl ₂ as eluent. TLC: R _f (5% MeOH/CH ₂ Cl ₂ ) = 0.6; analytical HPLC: R _t = 19.8 minutes.

EXAMPLE 9

As recorded in Table II, we measured the inhibition constants of various compounds of this invention against HIV-1 protease, using the method described essentially by M.W. Pennington et al., Peptides 1990. Gimet, E. and D. Andrew, Eds., Escom; Leiden, Netherlands (1990) .

TABLE II

Compound K^ (nM)

1 35 2 130

3 100

4 400

5 60

6 400 7 20

8 250

As demonstrated in Table II, all of the compounds tested displayed inhibitory and anti-viral activity. While we have described a number of embodiments of this invention, it is apparent that our basic constructions may be altered to provide other embodiments which utilize the products and processes of this invention. Therefore, it will be appreciated that

the scope of this invention is to be defined by the appended claims, rather than by the specific embodiments which have been presented by way of example.