α- and β- amino acid hydroxyethylamino sulfonamides useful as retroviral protease inhibitors

Abstract

α- and β-amino acid hydroxyethylamino sulfonamide compounds are effective as retroviral protease inhibitors, and in particular as inhibitors of HIV protease.

1. A compound represented by the formula: 
       
         
           
           
               
               
           
         
       
       or a pharmaceutically acceptable salt[, prodrug] or ester thereof, wherein
 R 2  is an alkyl, aryl, cycloalkyl, cycloalkylalkyl or aralkyl radical, which radical is optionally substituted with a radical selected from the group consisting of alkyl, halo, nitro, cyano, CF 3 , —OR 9 , and -SR 9 , wherein R 9  is a radical selected from the group consisting of hydrogen and alkyl; 
 R 3  is a hydrogen, alkyl, haloalkyl, alkenyl, alkynyl, hydroxyalkyl, alkoxyalkyl, alkylthioalkyl, alkylsulfonylalkyl, cycloalkyl, cycloalkylalkyl, heterocycloalkyl, heteroaryl, heterocycloalkylalkyl, aryl, aralkyl, heteroaralkyl, aminoalkyl or mono- or disubstituted aminoalkyl radicals, wherein said substituents are selected from the group consisting of alkyl, aryl, aralkyl, cycloalkyl, cycloalkylalkyl, heteroaryl, heteroaralkyl, heterocycloalkyl and heterocycloalkylalkyl radicals; or where said aminoalkyl radical is disubstituted, said substituents along with the nitrogen atom to which they are attached, form a heterocycloalkyl or a heteroaryl radical; 
 R 4  is an alkyl, haloalkyl, alkenyl, alkynyl, hydroxyalkyl, alkoxyalkyl, cycloalkyl, cycloalkylalkyl, heterocycloalkyl, heteroaryl, heterocycloalkylalkyl, aryl, aralkyl, aralkenyl, heteroaralkyl, aminoalkyl or mono- or disubstituted aminoalkyl radical, wherein said substituents are selected from the group consisting of alkyl, aryl, aralkyl, cycloalkyl, cycloalkylalkyl, heteroaryl, heteroaralkyl, heterocycloalkyl and heterocycloalkylalkyl radicals; or where said aminoalkyl radical is disubstituted, said substituents along with the nitrogen atom to which they are attached, form a heterocycloalkyl or a heteroaryl radical; 
 R 6  is a hydrogen or alkyl radical; 
 x is 1 or 2; 
 t is 0 or 1; and 
 Y is O or S; and 
 A is an alkoxy, alkenoxy, aralkoxy, alkyl, cycloalkyl, cycloalkylalkoxy, cycloalkylalkyl, aralkyl, aryl, aryloxy, heterocycloalkyl, heterocycloalkoxy, heterocycloalkylalkyl, heterocycloalkylalkoxy, heteroaralkyl, heteroaralkoxy, heteroaryloxy, heteroaryl, alkenyl, aryloxyalkyl, heteroaryloxyalkyl, hydroxyalkyl, amino, or mono- or disubstituted amino radical, wherein the substituents are selected from the group consisting of alkyl, aryl, aralkyl, cycloalkyl, cycloalkylalkyl, heteroaryl, heteroaralkyl, heterocycloalkyl and heterocycloalkyalkyl radicals; or where said amino radical is disubstituted, said substituents along with the nitrogen atom to which they are attached form a heterocycloalkyl or heteroaryl radical; or is represented by the formula 
 
       
         
           
           
               
               
           
         
       
       wherein R is a hydrogen, alkoxycarbonyl, aralkoxycarbonyl, alkylcarbonyl, cycloalkylcarbonyl, cycloalkylalkoxycarbonyl, cycloalkylalkanoyl, carboxyalkanoyl, alkanoyl, aralkanoyl, aroyl, aryloxycarbonyl, aryloxycarbonylalkyl, aryloxyalkanoyl, heterocyclylcarbonyl, heterocyclyloxycarbonyl, heterocyclylalkanoyl, heterocyclylalkoxycarbonyl, heteroaralkanoyl, heteroaralkoxycarbonyl, heteroaryloxycarbonyl, heteroaroyl, alkyl, alkenyl, alkynyl, cycloalkyl, aryl, aralkyl, aryloxyalkyl, heteroaryloxyalkyl, hydroxyalkyl, aminocarbonyl, aminoalkanoyl, or mono- or disubstituted aminocarbonyl or mono- or disubstituted aminoalkanoyl radical, wherein the substituents are selected from the group consisting of alkyl, aryl, aralkyl, cycloalkyl, cycloalkylalkyl, heteroaryl, heteroaralkyl, heterocycloalkyl and heterocycloalkyalkyl radicals; or wherein said aminocarbonyl or aminoalkanoyl radicals are disubstituted, said substituents along with the nitrogen atom to which they are attached form a heterocycloalkyl or heteroaryl radical;
 R′ is a radical as defined for R 3  or R″SO 2 —, wherein R″ is a radical as defined for R 3 ; or R and R′ together with the nitrogen to which they are attached form a heterocycloalkyl or heteroaryl radical; 
 R 1  is a hydrogen, —CO 2 CH 3 , —CH 2 CO 2 CH 3 , —CO 2 H, —CH 2 CO 2 H, —CH 2 CH 2 CONH 2 , —CH 2 CONH 2 , —CONH 2 , —CH 2 C(O)NHCH 3 , —CH 2 C(O)N(CH 3 ) 2 , —CONHCH 3 , —CONH(CH 3 ) 2 , —CH 2 SO 2 NH 2 , —CH 2 CH 2 SO 2 NH 2 , —CH 2 S[O]CH 3 , —CH 2 S[O] 2 CH 3 , —C(CH 3 ) 2 (SCH 3 ), —C(CH 3 ) 2 (S[O]CH 3 ), —C(CH 3 ) 2 (S[O] 2 CH 3 ), alkyl, hydroxyalkyl, cyanoalkyl, haloalkyl, alkenyl, alkynyl, cycloalkyl, cycloalkylalkyl, alkylthioalkyl, aralkyl, heteroaralkyl, aminoalkyl or mono- or disubstituted aminoalkyl radical, wherein said substituents are selected from the group consisting of alkyl, aryl, aralkyl, cycloalkyl, cycloalkylalkyl, heteroaryl, heteroaralkyl, heterocycloalkyl and heterocycloalkylalkyl radicals; or where said aminoalkyl radical is disubstituted, said substituents along with the nitrogen atom to which they are attached, form a heterocycloalkyl or a heteroaryl radical; and 
 each of R 1 ′ and R 1 ″ are independently a radical as defined for R 1 ; or one of R 1 ′ and R 1 ″ together with R 1  and the carbon atoms to which R 1 , R 1 ′ and R 1 ″ are attached, form a cycloalkyl radical; and 
 
       wherein alkyl, alone or in combination, is a straight-chain or branched-chain hydrocarbon radical containing from 1 to 8 carbon atoms; alkenyl, alone or in combination, is a straight-chain or branched-chain hydrocarbon radical having at least one double bond and containing from 2 to 8 carbon atoms; alkynyl. alone or in combination. is a straight-chain or branched-chain hydrocarbon radical having at least one triple bond and containing from 2 to 10 carbon atoms; cycloalkyl, alone or in combination, is a hydrocarbon ring containing from 3 to 8 carbon atoms; aryl, alone or in combination, means a phenyl or naphthyl radical which optionally carries one or more alkyl, alkoxy, halogen, hydroxy, amino, nitro, cyano, haloalkyl, carboxy, alkoxycarbonyl, cycloalkyl, heterocycloalkyl, amido, alkylamino, dialkylamino, alkylamido or dialkylamido radicals; heterocyclyl and heterocycloalkyl, alone or in combination, mean a saturated or partially unsaturated monocyclic, bicyclic or tricyclic heterocycle having 3 to 12 ring members, which contains at least one nitrogen, oxygen, sulfur, sulfone, sulfoxide or N-oxide of a tertiary nitrogen heteroatom ring member, and which is optionally substituted on one or more carbon atoms by halogen, alkyl, alkoxy, hydroxy, oxo or aryl, or on a secondary nitrogen atom by hydroxy, alkyl, aralkoxycarbonyl, alkanoyl, phenyl or phenylalkyl; and heteroaryl, alone or in combination, means an aromatic monocyclic, bicyclic, or tricyclic heterocycloalkyl radical which is optionally substituted as defined above with respect to the definitions of aryl and heterocycloalkyl. 
     
     
       2. The compound of  claim 1  or a pharmaceutically acceptable salt, prodrug or ester thereof, wherein
 R 2  is an alkyl, aryl, cycloalkyl, cycloalkylalkyl or aralkyl radical, which radical is optionally substituted with a radical selected from the group consisting of alkyl, halo and —OR 9 , wherein R 9  is a radical selected from the group consisting of hydrogen and alkyl; 
 R 3  is a hydrogen, alkyl, haloalkyl, alkenyl, alkynyl, hydroxyalkyl, alkoxyalkyl, alkylthioalkyl, alkylsulfonylalkyl, cycloalkyl, cycloalkylalkyl, heterocycloalkyl, heteroaryl, heterocycloalkylalkyl, aryl, aralkyl, heteroaralkyl, aminoalkyl or mono- or disubstituted aminoalkyl radicals, wherein said substituents are selected from the group consisting of alkyl, aralkyl, cycloalkyl and cycloalkylalkyl radicals; or where said aminoalkyl radical is disubstituted, said substituents along with the nitrogen atom to which they are attached, form a heterocycloalkyl or a heteroaryl radical; 
 R 4  is an alkyl, haloalkyl, alkenyl, alkynyl, hydroxyalkyl, alkoxyalkyl, cycloalkyl, cycloalkylalkyl, heterocycloalkyl, heteroaryl, heterocycloalkylalkyl, aryl, aralkyl, aralkenyl or heteroaralkyl radical; 
 R 6  is a hydrogen or alkyl radical; 
 x is 1 or 2; 
 t is 0 or 1; and 
 Y is O or S; and 
 A is an alkoxy, alkenoxy, aralkoxy, alkyl, cycloalkyl, cycloalkylalkoxy, cycloalkylalkyl, aralkyl, aryl, aryloxy, heterocycloalkyl, heterocycloalkoxy, heterocycloalkylalkyl, heterocycloalkylalkoxy, heteroaralkyl, heteroaralkoxy, heteroaryloxy, heteroaryl, hydroxyalkyl, amino, or mono- or disubstituted amino radical, wherein the substituents are selected from the group consisting of alkyl, aralkyl, heteroaryl, heteroaralkyl, heterocycloalkyl and heterocycloalkyalkyl radicals; or where said amino radical is disubstituted, said substituents along with the nitrogen atom to which they are attached form a heterocycloalkyl radical; or is represented by the formula 
 
       
         
           
           
               
               
           
         
       
       wherein R is a hydrogen, alkoxycarbonyl, aralkoxycarbonyl, alkylcarbonyl, carboxyalkanoyl, alkanoyl, aralkanoyl, aroyl, heterocyclylcarbonyl, heterocyclyloxycarbonyl, heterocyclylalkanoyl, heterocyclylalkoxycarbonyl, heteroaralkanoyl, heteroaralkoxycarbonyl, heteroaryloxycarbonyl, heteroaroyl, alkyl, cycloalkyl, aralkyl, hydroxyalkyl, aminocarbonyl, aminoalkanoyl, or mono- or disubstituted aminocarbonyl or mono- or disubstituted aminoalkanoyl radical, wherein the substituents are selected from the group consisting of alkyl, aralkyl, heteroaryl, heteroaralkyl, heterocycloalkyl and heterocycloalkyalkyl radicals; or wherein said aminocarbonyl or aminoalkanoyl radicals are disubstituted, said substituents along with the nitrogen atom to which they are attached form a heterocycloalkyl or heteroaryl radical;
 R′ is a hydrogen, alkyl or aralkyl radical or R″SO 2 —, wherein R″ is a radical as defined for R 3 ; or R and R′ together with the nitrogen to which they are attached form a heterocycloalkyl or heteroaryl radical; 
 R 1  is a hydrogen, —CO 2 CH 3 , —CH 2 CO 2 CH 3 , —CO 2 H, —CH 2 CO 2 H, —CH 2 CH 2 CONH 2 , —CH 2 CONH 2 , —CONH 2 , —CH 2 C(O)NHCH 3 , —CH 2 C(O)N(CH 3 ) 2 , —CONHCH 3 , —CONH(CH 3 ) 2 , —CH 2 SO 2 NH 2 , —CH 2 CH 2 SO 2 NH 2 , —CH 2 S[O]CH 3 , —CH 2 S[O] 2 CH 3 , —C(CH 3 )2(SCH 3 ), —C(CH 3 ) 2 (S[O]CH 3 ), —C(CH 3 ) 2 (S[O] 2 CH 3 ), alkyl, hydroxyalkyl, cyanoalkyl, haloalkyl, alkenyl, alkynyl, cycloalkyl, cycloalkylalkyl, alkylthioalkyl, aralkyl, heteroaralkyl, aminoalkyl or mono- or disubstituted aminoalkyl radical, wherein said substituents are selected from the group consisting of alkyl, aralkyl, heteroaryl, heteroaralkyl, heterocycloalkyl and heterocycloalkylalkyl radicals; or where said aminoalkyl radical is disubstituted, said substituents along with the nitrogen atom to which they are attached, form a heterocycloalkyl or a heteroaryl radical; and 
 
       each of R 1 ′ and R 1 ″ are independently a radical as defined for R 1 ; or one of R 1 ′ and R 1 ″ together with R 1  and the carbon atoms to which R 1 , R 1 ′ and R 1 ″ are attached, form a cycloalkyl radical. 
     
     
       3. The compound of  claim 2  or a pharmaceutically acceptable salt or ester thereof, wherein
 R 2  is an alkyl, aryl, cycloalkyl, cycloalkylalkyl or aralkyl radical, which radical is optionally substituted with a radical selected from the group consisting of alkyl, halo and —OR 9 , wherein R 9  is a radical selected from the group consisting of hydrogen and alkyl; 
 R 3  is a hydrogen, alkyl, haloalkyl, alkenyl, alkynyl, hydroxyalkyl, alkoxyalkyl, alkylthioalkyl, alkylsulfonylalkyl, cycloalkyl, cycloalkylalkyl, heterocycloalkyl, heteroaryl, heterocycloalkylalkyl, aryl, aralkyl, heteroaralkyl, aminoalkyl or mono- or dialkyl substituted aminoalkyl radical; 
 R 4  is an alkyl, haloalkyl, alkenyl, alkynyl, hydroxyalkyl, alkoxyalkyl, cycloalkyl, cycloalkylalkyl, heterocycloalkyl, heteroaryl, heterocycloalkylalkyl, aryl, aralkyl, aralkenyl or heteroaralkyl radical; 
 R 6  is a hydrogen or alkyl radical; 
 x is 1 or 2; 
 t is 0 or 1; and 
 Y is O or S; and 
 A is an alkoxy, alkenoxy, aralkoxy, alkyl, cycloalkyl, aryl, heterocycloalkyl, heterocycloalkoxy, heterocycloalkylalkyl, heteroaralkoxy, heteroaryl, amino, or mono- or disubstituted amino radical, wherein the substituents are selected from the group consisting of alkyl and aralkyl radicals; or is represented by the formula 
 
       
         
           
           
               
               
           
         
       
       wherein R is a hydrogen, alkoxycarbonyl, aralkoxycarbonyl, alkylcarbonyl, carboxyalkanoyl, alkanoyl, aroyl, heteroaroyl, alkyl, aralkyl, aminocarbonyl, aminoalkanoyl, or mono- or disubstituted aminocarbonyl or mono- or disubstituted aminoalkanoyl radical, wherein the substituents are selected from the group consisting of alkyl and aralkyl radicals;
 R′ is a hydrogen, alkyl or aralkyl radical or R″SO 2 —, wherein R″ is a radical as defined for R 3 ; or R and R′ together with the nitrogen to which they are attached form a heterocycloalkyl or heteroaryl radical; 
 R 1  is a hydrogen, —CO 2 CH 3 , —CH 2 CO 2 CH 3 , —CO 2 H, —CH 2 CO 2 H, —CH 2 CH 2 CONH 2 , —CH 2 CONH 2 , —CONH 2 , —CH 2 C(O)NHCH 3 , —CH 2 C(O)N(CH 3 ) 2 , —CONHCH 3 , —CONH(CH 3 ) 2 , —CH 2 SO 2 NH 2 , —CH 2 CH 2 SO 2 NH 2 , —CH 2 S[O]CH 3 , —CH 2 S[O] 2 CH 3 , —C(CH 3 ) 2 (SCH 3 ), —C(CH 3 ) 2 (S[O]CH 3 ), —C(CH 3 ) 2 (S[O] 2 CH 3 ), alkyl, hydroxyalkyl, cyanoalkyl, haloalkyl, alkenyl, alkynyl, cycloalkyl, cycloalkylalkyl, alkylthioalkyl, aralkyl, heteroaralkyl, aminoalkyl or mono- or disubstituted aminoalkyl radical, wherein said substituents are selected from the group consisting of alkyl and aralkyl radicals; and 
 R 1 ′ is a hydrogen, alkyl or aralkyl; and R 1 ″ is a hydrogen, alkyl, —CO 2 CH 3  or —CONH 2 ; or one of R 1 ′ and R 1 ″ together with R 1  and the carbon atoms to which R 1 , R 1 ′ and R 1 ″ are attached, form a cycloalkyl radical. 
 
     
     
       4. The compound of  claim 3  or a pharmaceutically acceptable salt or ester thereof, wherein
 R 2  is an alkyl, cycloalkylalkyl or aralkyl radical, which radical is optionally substituted with a radical selected from the group consisting of alkyl, halo and —OR 9 , wherein R 9  is a radical selected from the group consisting of hydrogen and alkyl; 
 R 3  is a hydrogen, alkyl, alkenyl, alkynyl, hydroxyalkyl, alkoxyalkyl, alkylthioalkyl, alkylsulfonylalkyl, cycloalkyl, cycloalkylalkyl, heterocycloalkylalkyl, aryl, aralkyl, heteroaralkyl, aminoalkyl or mono- or dialkyl substituted aminoalkyl radical; 
 R 4  is an alkyl, haloalkyl, alkenyl, alkynyl, hydroxyalkyl, alkoxyalkyl, cycloalkyl, cycloalkylalkyl, heterocycloalkyl, heteroaryl, heterocycloalkylalkyl, aryl, aralkyl, aralkenyl or heteroaralkyl radical; 
 R 6  is a hydrogen or alkyl radical; 
 x is 1 or 2; 
 t is 0 or 1; and 
 Y is O or S; and 
 A is an alkoxy, alkenoxy, aralkoxy, alkyl, cycloalkyl, aryl, heterocycloalkyl, heterocycloalkoxy, heterocycloalkylalkyl, heteroaralkoxy, heteroaryl, amino, or mono- or disubstituted amino radical, wherein the substituents are selected from the group consisting of alkyl and aralkyl radicals; or is represented by the formula 
 
       
         
           
           
               
               
           
         
       
       wherein R is a hydrogen, alkoxycarbonyl, aralkoxycarbonyl, alkylcarbonyl, carboxyalkanoyl, alkanoyl, aroyl, heteroaroyl, alkyl, aralkyl, aminocarbonyl, aminoalkanoyl, or mono- or disubstituted aminocarbonyl or mono- or disubstituted aminoalkanoyl radical, wherein the substituents are selected from the group consisting of alkyl and aralkyl radicals;
 R′ is a hydrogen, alkyl or aralkyl radical or R″SO 2 —, wherein R″ is a radical as defined for R 3 ; or R and R′ together with the nitrogen to which they are attached form a heterocycloalkyl or heteroaryl radical; 
 R 1  is a hydrogen, —CO 2 H, —CH 2 CO 2 H, —CH 2 CH 2 CONH 2 , —CH 2 CONH 2 , —CONH 2 , —CH 2 C(O)NHCH 3 , —CH 2 C(O)N(CH 3 ) 2 , —CONHCH 3 , —CONH(CH 3 ) 2 , —CH 2 SO 2 NH 2 , —CH 2 CH 2 SO 2 NH 2 , alkyl, hydroxyalkyl, cyanoalkyl, alkynyl, cycloalkylalkyl, alkylthioalkyl, aralkyl or heteroaralkyl radical; and 
 R 1 ′ is a hydrogen, alkyl or aralkyl; and R 1 ″ is a hydrogen, alkyl, —CO 2 CH 3  or —CONH 2 ; or one of R 1  and R 1 ″ together with R 1  and the carbon atoms to which R 1 , R 1 ′ and R 1 ″ are attached, form a cycloalkyl radical. 
 
     
     
       5. The compound of  claim 4  or a pharmaceutically acceptable salt or ester thereof, wherein
 R 2  is an alkyl, cycloalkylalkyl or aralkyl radical, which radical is optionally substituted with a radical selected from the group consisting of alkyl, halo and —OR 9 , wherein R 9  is a radical selected from the group consisting of hydrogen and alkyl; 
 R 3  is a hydrogen, alkyl, alkenyl, alkynyl, hydroxyalkyl, alkoxyalkyl, alkylthioalkyl, alkylsulfonylalkyl, cycloalkyl, cycloalkylalkyl, heterocycloalkylalkyl, aryl, aralkyl, heteroaralkyl, aminoalkyl or mono- or dialkyl substituted aminoalkyl radical; 
 R 4  is an alkyl, haloalkyl, alkenyl, alkynyl, hydroxyalkyl, alkoxyalkyl, cycloalkyl, cycloalkylalkyl, heterocycloalkyl, heteroaryl, heterocycloalkylalkyl, aryl, aralkyl, aralkenyl or heteroaralkyl radical; 
 R 6  is a hydrogen or alkyl radical; 
 x is 1 or 2; 
 t is 0 or 1; and 
 Y is O or S; and 
 A is an alkoxy, alkenoxy, aralkoxy, alkyl, cycloalkyl, aryl, heterocycloalkyl, heterocycloalkoxy, heterocycloalkylalkyl, heteroaralkoxy, heteroaryl, amino, or mono- or disubstituted amino radical, wherein the substituents are selected from the group consisting of alkyl and aralkyl radicals; or is represented by the formula 
 
       
         
           
           
               
               
           
         
       
       wherein R is a hydrogen, alkoxycarbonyl, aralkoxycarbonyl, alkylcarbonyl, carboxyalkanoyl, alkanoyl, aroyl, heteroaroyl, alkyl, aralkyl, aminocarbonyl, aminoalkanoyl, or mono- or disubstituted aminocarbonyl or mono- or disubstituted aminoalkanoyl radical, wherein the substituents are selected from the group consisting of alkyl and aralkyl radicals;
 R′ is a hydrogen, alkyl or aralkyl radical or R″SO 2 —, wherein R″ is a radical as defined for R 3 ; or R and R′ together with the nitrogen to which they are attached form a heterocycloalkyl or heteroaryl radical; 
 R 1  is a hydrogen, —CO 2 H, —CH 2 CO 2 H, —CH 2 CH 2 CONH 2 , —CH 2 CONH 2 , —CONH 2 , —CH 2 C(O)NHCH 3 , —CH 2 C(O)N(CH 3 ) 2 , —CONHCH 3 , —CONH(CH 3 ) 2 , —CH 2 SO 2 NH 2 , —CH 2 CH 2 SO 2 NH 2 , alkyl, hydroxyalkyl, cyanoalkyl, alkynyl, cycloalkylalkyl, alkylthioalkyl, aralkyl or heteroaralkyl radical; and 
 R 1 ′ is a hydrogen, alkyl or aralkyl; and R 1 ″ is a hydrogen, alkyl, —CO 2 CH 3  or —CONH 2 ; or one of R 1 ′ and R 1 ″ together with R 1  and the carbon atoms to which R 1 , R 1 ′ and R 1 ″ are attached, form a cycloalkyl radical; 
 
       with the proviso that alkyl, alone or in combination, is a straight-chain or branched-chain hydrocarbon radical containing from one to five carbon atoms; alkenyl, alone or in combination, is a straight-chain or branched-chain hydrocarbon radical having at least one double bond and containing from two to five carbon atoms; alkynyl, alone or in combination, is a straight-chain or branched-chain hydrocarbon radical having at least one triple bond and containing from two to five carbon atoms; and cycloalkyl, alone or in combination, is a hydrocarbon ring containing from three to eight carbon atoms; and 
       with the proviso that when R 2  is cycloalkylalkyl and t is 0, R′ is a group other than alkoxycarbonyl. 
     
     
       6. The compound of  claim 5  or a pharmaceutically acceptable salt or ester thereof, wherein
 R 2  is butyl, cyclohexylmethyl, benzyl, 4-fluorobenzyl or naphthylmethyl; 
 R 3  is methyl, ethyl, propyl, butyl, pentyl, hexyl, iso-butyl, iso-amyl, 3-methoxypropyl, 3-methylthiopropyl, 4-methylthiobutyl, 4-methylsulfonylbutyl, 2-dimethylaminoethyl, 2-(1-morpholino)ethyl, 4-hydroxybutyl, allyl, propargyl, cyclohexylmethyl, cyclopropylmethyl, phenyl, benzyl, 4-fluorobenzyl, 4-methoxybenzyl, 1-phenylethyl, 2-phenylethyl, naphthylmethyl, 3-pyridylmethyl or 4-pyridylmethyl; 
 R 4  is methyl, ethyl, propyl, butyl, ethenyl, chloromethyl, cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, phenyl, naphthyl, chlorophenyl, fluorophenyl, hydroxyphenyl, methylphenyl, methoxyphenyl, ethoxyphenyl, methylthiophenyl, methylsulfoxyphenyl, methylsulfonylphenyl, acetamidophenyl, methoxycarbonylphenyl, dimethylaminophenyl, nitrophenyl, trifluoromethylphenyl, benzyl, 2-phenylethenyl or thienyl; 
 R 6  is hydrogen; 
 x is 2; 
 t is or 1; and 
 Y is O; and 
 A is methyl, cyclohexyl, cyclopentyl, cycloheptyl, 1,2,3,4-tetrahydronaphthyl, naphthyl, quinolinyl, indolyl, pyridyl, methylpyridyl, furanyl, thiophenyl, oxazolyl, thiazolyl, phenyl, methylphenyl, ethylphenyl, dimethylphenyl, iso-propylphenyl, chlorophenyl, hydroxyphenyl, methoxyphenyl, methylsulfonylphenyl, methylsulfonylmethylphenyl, carboxyphenyl, aminocarbonylphenyl, methylhydroxyphenyl, methylnitrophenyl, methylaminophenyl, methyl-N,N-dimethylaminophenyl, t-butoxy, benzyloxy, pyridylmethoxy, 3-propenoxy, hydroxypyridylmethoxy, aminopyridylmethoxy, pyrimidinylmethoxy, N-oxo-pyrimidinylmethoxy, thiazolylmethoxy, tetrahydrothiophenoxy, 1,1-dioxotetrahydrothiophenoxy, tetrahydrofuranoxy, methylamino, benzylamino or isopropylamino; or is represented by the formula 
 
       
         
           
           
               
               
           
         
       
       wherein R is hydrogen, acetyl, phenoxyacetyl, methoxyacetyl, naphthaloxyacetyl, succinoyl, 2-methylpropionoyl, 2-hydroxypropionoyl, t-butoxycarbonyl, benzyloxycarbonyl, methoxybenzyloxycarbonyl, aminocarbonyl, quinolinylcarbonyl, N-methylglycinyl or N,N-dimethylglycinyl;
 R′ is hydrogen, benzyl or methyl; or R and R′ together with the nitrogen to which they are attached form pyrrolyl; 
 R 1  is hydrogen, —CO 2 H, —CH 2 CO 2 H, —CH 2 CH 2 CONH 2 , —CH 2 CONH 2 , —CONH 2 , —CH 2 C(O)NHCH 3 , —CH 2 C(O)N(CH 3 ) 2 , —CONHCH 3 , —CONH(CH 3 ) 2 , —CH 2 SO 2 NH 2 , —CH 2 CH 2 SO 2 NH 2 , methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, tert-butyl, 3-methylbutyl, cyclohexylmethyl, benzyl, hydroxybenzyl, imidazoyl, imidazoylmethyl, cyanomethyl, methylthiomethyl, propargyl or hydroxyethyl; and 
 R 1 ′ is hydrogen, methyl, ethyl, propyl, isopropyl, butyl, isobutyl, benzyl, phenylethyl, phenylpropyl, phenylbutyl or 4,4-diphenylbutyl; and R 1 ″ is hydrogen, methyl, —CO 2 CH 3  or —CONH 2 ; or one of R 1 ′ and R 1 ″ together with R 1  and the carbon atoms to which R 1 , R 1 ′ and R 1 ″ are attached, form cyclobutyl, cyclopentyl or cyclohexyl; 
 
       with the proviso that when R 2  is cyclohexylmethyl and t is 0, R′ is a group other than t-butoxycarbonyl. 
     
     
       7. The compound of  claim 1  which is: 
       Phenylmethyl[2R-hydroxy-3-[(3-methylbutyl)(methylsulfonyl)amino]-1S-(phenylmethyl)propyl]carbamate; 
       Phenylmethyl[2R-hydroxy-3-[(3-methylbutyl)(phenylsulfonyl)amino]-1S-(phenylmethyl)propyl]carbamate; 
       N1-[2R-hydroxy-3-[(3-methylbutyl)(methylsulfonyl)amino]-1S-(phenylmethyl)propyl]-2S-[(2-quinolinylcarbonyl)amino] butanediamide; 
       N1-[2R-hydroxy-3-[(3-methylbutyl)(methylsulfonyl)amino]-1S-(phenylmethyl)propyl]-2S-[(phenylmethyloxycarbonyl) amino] butanediamide; 
       N1-[2R-hydroxy-3[(3-methylbutyl)(phenylsulfonyl)amino]-1S-(phenylmethyl)propyl]-2S-[(2-quinolinylcarbonyl)amino] butanediamide; 
       N1-[2R-hydroxy-3[(3-methylbutyl)(phenylsulfonyl)amino]-1S-(phenylmethyl)propyl]-2S-[(phenylmethyloxycarbonyl) amino]butanediamide; 
       2S-[[(dimethylamino)acetyl]amino]-N-[2R-hydroxy-3-[(3-methyl-butyl)(phenylsulfonyl)amino]-1S-(phenylmethyl)propyl]-3,3-dimethylbutaneamide; 
       2S-[[(methylamino)acetyl]amino]-N-[2R-hydroxy-3-[(3-methyl-butyl)(phenylsulfonyl)amino]-1S-(phenylmethyl)propyl]-3,3-dimethylbutaneamide; 
       N1-[2R-hydroxy-3-[(3-methylbutyl)(phenyl-sulfonyl)amino]-N4-methyl-1S-(phenylmethyl)propyl]-2S-[(2-quinolinylcarbonyl)amino]butanediamide; 
       [3-[[2-hydroxy-3[N-(3-methylbutyl)-N-(phenylsufonyl)amino]-1-(phenylmethyl)propyl]amino]-2-methyl-3-oxopropyl]-, (4-methoxyphenyl)methyl ester, [1S-[1R*(S*),2S*]]-; 
       Carbamic acid, [2R-hydroxy-3-[(4-hydroxyphenylsulfonyl)(2-methylpropyl)amino]-1S-(phenylmethyl)propyl-, 3(S)-1,1-dioxotetrahydrothiophen-3-yl-ester; 
       Carbamic acid, [2R-hydroxy-3-[(4-methoxyphenylsulfonyl)(2-methylpropyl)amino]-1S-(phenylmethyl)propyl-, 3(S)-1,1-dioxotetrahydrothiophen-3-yl-ester; 
       Carbamic acid, [2R-hydroxy-3-[(4-methoxyyphenylsulfonyl) (2-methylpropyl)amino]-1S-(phenylmethyl)propyl-, 3-S-tetrahydrothiophen-3-yl-ester; 
       Carbamic acid, [2R-hydroxy-3-[(4-hydroxyphenylsulfonyl)(2-methylpropyl)amino]-1S-(phenylmethyl)propyl-, 3-S-tetrahydrothiophen-3-yl-ester; 
       Carbamic acid, [2R-hydroxy-3-[(4-hydroxyphenylsulfonyl)(2-methylpropyl)amino]-1S-(phenylmethyl)propyl-, 3-S-tetrahydrofuran-3-yl-ester; 
       Carbamic acid, [2R-hydroxy-3-[(4-methoxyphenylsulfonyl)(2-methylpropyl)amino]-1S-(phenylmethyl)propyl-, 3-S-tetrahydrofuran-3-yl-ester; 
       Carbamic acid, [2R-hydroxy-3-[[(4-methoxyphenyl)sulfonyl](2-methylpropyl)amino]-1S-(phenylmethyl)propyl]-, 5-(thiazolyl)methyl ester; 
       Carbamic acid, [2R-hydroxy-3-[[(4-hydroxyphenyl)sulfonyl](2-methylpropyl)amino]-1S-(phenylmethyl)propyl]-, 5-(thiazolyl)methyl ester; 
       Benzamide, N-[2R-hydroxy-3-[[(4-hydroxyphenyl)sulfonyl](2-methylpropyl)amino]-1S-(phenylmethyl)propyl]-2-methyl; 
       Carbamic acid, [2R-hydroxy-3-[[(4-methoxyphenyl)sulfonyl](2-methylpropyl)amino]-1S-(phenylmethyl)propyl]-, 3-(6-aminopyridyl)methyl ester; 
       Carbamic acid, [2R-hydroxy-3-[[(4-hydroxyphenyl)sulfonyl](2-methylpropyl)amino]-1S-(phenylmethyl)propyl]-, 3-(6-aminopyridyl)methyl ester; 
       Carbamic acid, [2R-hydroxy-3-[[(4-methoxyphenyl)sulfonyl] (2-methylpropyl)amino]-1S-(phenylmethyl)propyl]-, 3-(6-hydroxypyridyl)methyl ester; 
       Carbamic acid, [2R-hydroxy-3-[[(4-hydroxyphenyl)sulfonyl] (2-methylpropyl)amino]-1S-(phenylmethyl)propyl]-, 5-pyrimidylmethyl ester; or 
       Benzamide, N-[2R-hydroxy-3-[[(4-methoxyphenyl)sulfonyl] (2-methylpropyl)amino]-1S-(phenylmethyl)propyll-2-methyl. 
     
     
       8. A pharmaceutical composition comprising a compound of  claim 1  and a pharmaceutically acceptable carrier. 
     
     
       9. Method of treating a retroviral infection comprising administering an effective amount of a composition of  claim 8 . 
     
     
       10. Method of inhibiting a retroviral protease comprising administering an effective amount of a compound of  claim 1 . 
     
     
       11. Method of inhibiting replication of a retrovirus comprising administering an effective amount of a compound of  claim 1 . 
     
     
       12. A compound represented by the formula: 
       
         
           
           
               
               
           
         
       
       or a pharmaceutically acceptable salt[, prodrug] or ester thereof, wherein
 each of P 1  and P 2  independently represent hydrogen, alkoxycarbonyl, aralkoxycarbonyl, alkylcarbonyl, cycloalkylcarbonyl, cycloalkylalkoxycarbonyl, cycloalkylalkanoyl, alkanoyl, aralkanoyl, aroyl, aryloxycarbonyl, aryloxycarbonylalkyl, aryloxyalkanoyl, heterocyclylcarbonyl, heterocyclyloxycarbonyl, heterocyclylalkanoyl, heterocyclylalkoxycarbonyl, heteroaralkanoyl, heteroaralkoxycarbonyl, heteroaryloxycarbonyl, heteroaroyl, alkyl, alkenyl, cycloalkyl, aryl, aralkyl, aryloxyalkyl, heteroaryloxyalkyl, hydroxyalkyl, aminocarbonyl, aminoalkanoyl, or mono- or disubstituted aminocarbonyl or mono- or disubstituted aminoalkanoyl radical, wherein the substituents are selected from the group consisting of alkyl, aryl, aralkyl, cycloalkyl, cycloalkylalkyl, heteroaryl, heteroaralkyl, heterocycloalkyl and heterocycloalkyalkyl radicals; or where said aminoalkanoyl radical is disubstituted, said substituents along with the nitrogen atom to which they are attached form a heterocycloalkyl or heteroaryl radical; 
 R 2  is an alkyl, aryl, cycloalkyl, cycloalkylalkyl or aralkyl radical, which radicals are optionally substituted with a group selected from alkyl and halogen radicals, nitro, cyano, CF 3 , —OR 9 , —SR 9 , wherein R 9  is a hydrogen or alkyl radical; 
 
       R 3  is a hydrogen, alkyl, haloalkyl, alkenyl, alkynyl, hydroxyalkyl, alkoxyalkyl, cycloalkyl, cycloalkylalkyl, heterocycloalkyl, heteroaryl, heterocycloalkylalkyl, aryl, aralkyl, heteroaralkyl, aminoalkyl or mono- or disubstituted aminoalkyl radical, wherein said substituents are selected from the group consisting of alkyl, aryl, aralkyl, cycloalkyl, cycloalkylalkyl, heteroaryl, heteroaralkyl, heterocycloalkyl and heterocycloalkylalkyl radicals; or where the aminoalkyl radical is disubstituted, said substituents along with the nitrogen atom to which they are attached, form a heterocycloalkyl or a heteroaryl radical; and
 R 4  is a radical as defined by R 3  except for hydrogen; and 
 wherein alkyl, alone or in combination. is a straight-chain or branched-chain hydrocarbon radical containing from 1 to 8 carbon atoms; alkenyl, alone or in combination, is a straight-chain or branched-chain hydrocarbon radical having at least one double bond and containing from 2 to 8 carbon atoms; alkynyl, alone or in combination, is a straight-chain or branched-chain hydrocarbon radical having at least one triple bond and containing from 2 to 10 carbon atoms; cycloalkyl, alone or in combination, is a hydrocarbon ring containing from 3 to 8 carbon atoms; aryl, alone or in combination, means a phenyl or naphthyl radical which optionally carries one or more alkyl, alkoxy, halogen, hydroxy, amino, nitro, cyano, haloalkyl, carboxy, alkoxycarbonyl, cycloalkyl, heterocycloalkyl, amido, alkylamino, dialkylamino, alkylamido or dialkylamido radicals; heterocyclyl and heterocycloalkyl, alone or in combination, mean a saturated or partially unsaturated monocyclic, bicyclic or tricyclic heterocycle having 3 to 12 ring members, which contains at least one nitrogen, oxygen, sulphur, sulfone, sulfoxide or N-oxide of a tertiary nitrogen heteroatom ring member, and which is optionally substituted on one or more carbon atoms by halogen, alkyl, alkoxy, hydroxy, oxo or aryl, or on a secondary nitrogen atom by hydroxy, alkyl, aralkoxycarbonyl, alkanoyl, phenyl or phenylalkyl; and heteroaryl, alone or in combination, means an aromatic monocyclic, bicyclic, or tricyclic heterocycloalkyl radical which is optionally substituted as defined above with respect to the definitions of aryl and heterocycloalkyl. 
 
     
     
       13. The compound of  claim 12 , wherein each of P 1  and P 2  independently represent a hydrogen, alkoxycarbonyl, aralkyloxycarbonyl, heteroaralkoxycarbonyl, aroyl, heteroaroyl, alkanoyl or cycloalkanoyl radical;
 R 2  is a cycloalkylalkyl, aralkyl or alkyl radical;   R 3  is an alkyl, cycloalkyl or cycloalkylalkyl radical; and   R 4  is an aryl, alkyl, heteroaryl or aryl radical.   
     
     
       14. The compound of  claim 13 , wherein P 1  and P 2  independently represent hydrogen, 3-pyridylmethyloxycarbonyl, 3-pyridylmethyloxycarbonyl N-oxide, 4-pyridylmethyloxycarbonyl, 4-pyridylmethyloxycarbonyl N-oxide, 5-pyrimidylmethyloxycarbonyl, tert-butyloxycarbonyl, allyloxycarbonyl, 2-propyloxycarbonyl, benzyloxycarbonyl, cycloheptylcarbonyl, cyclohexylcarbonyl, cyclopentylcarbonyl, benzoyl, 4-pyridylcarbonyl, 2-methylbenzoyl, 3-methylbenzoyl, 4-methylbenzoyl, 2-chlorobenzoyl, 2-ethylbenzoyl, 2,6-dimethylbenzoyl, 2,3-dimethylbenzoyl, 2,4-dimethylbenzoyl or 2,5-dimethylbenzoyl;
 R 2  is benzyl, cyclohexylmethyl, 2-naphthylmethyl, para-fluorobenzyl, para-methoxybenzyl, isobutyl or n-butyl;   R 3  is isobutyl, isoamyl, cyclohexyl, cyclohexylmethyl, n-butyl or n-propyl; and   R 4  is phenyl, para-methoxyphenyl, para-cyanophenyl, para-chlorophenyl, para-hydroxyphenyl, para-nitrophenyl, para-fluorophenyl, 2-naphthyl, 3-pyridyl, 3-pyridyl N-oxide, 4-pyridyl or 4-pyridyl N-oxide;   
       with the proviso that when R 2  is cyclohexylmethyl, each of P 1  and P 2  independently represent a group other than tert-butyloxycarbonyl. 
     
     
       15. A compound of  claim 12  which is: 
       Phenylmethyl[2R-hydroxy-3-[(2-methylpropyl)(phenylsulfonyl)amino]-1S-(phenylmethyl)propyl]carbamate; 
       Phenylmethyl[2R-hydroxy-3-[(2-methylpropyl)(4-methoxyphenylsulfonyl)amino]-1S-(phenylmethyl)propyl]carbamate; 
       Phenylmethyl[2R-hydroxy-3-[(2-methylpropyl)(4-fluorophenylsulfonyl)amino]-1S-(phenylmethyl) propyl]carbamate; 
       Phenylmethyl[2R-hydroxy-3-[(2-methylpropyl)(4-nitrophenylsulfonyl)amino]-1S-(phenylmethyl)propyl]carbamate; 
       Phenylmethyl[2R-hydroxy-3-[(2-methylpropyl)(4-chlorophenylsulfonyl)amino]-1S-(phenylmethyl) propyl]carbamate; 
       Phenylmethyl[2R-hydroxy-3-[(2-methylpropyl)(4-acetamidophenylsulfonyl)amino]-1S-(phenylmethyl)propyl]carbamate; 
       Phenylmethyl[2R-hydroxy-3-[(2-methylpropyl)(4-aminophenylsulfonyl)ano]-1S-(phenylmethyl) -propyl]carbamate; 
       Phenylmethyl[2R-hydroxy-3-[(3-methylbutyl)(4-methoxyphenylsulfonyl)amino]-1S-(phenylmethyl)propyl]carbamate; 
       Phenylmethyl[2R-hydroxy-3-[(3-methylbutyl)(4-fluorophenyl sulfonyl)amino]-1S-(phenylmethyl)propyl]carbamate; 
       Phenylmethyl[2R-hydroxy-3-[(3-methylbutyl)(4-nitrophenyl sulfonyl)amino]-1S-(phenylmethyl)propyl]carbamate; 
       Phenylmethyl[2R-hydroxy-3-[(3-methylbutyl)(4-chlorophenyl sulfonyl)amino]-1S-(phenylmethyl)propyl]carbamate; 
       Phenylmethyl[2R-hydroxy-3-[(2-methylpropyl)(4-methoxyphenyl sulfonyl)amino]-1S-(4-fluorophenylmethyl) propyl]carbamate; 
       Phenylmethyl[2R-hydroxy-3-[(2-methylpropyl)(4-fluorophenylsulfonyl)amino]-1S-(4-fluorophenylmethyl)propyl]carbamate; 
       Phenylmethyl[2R-hydroxy-3-[(butyl)(phenylsulfonyl)amino]-1S-(phenylmethyl)propyl]carbamate; 
       Phenylmethyl[2R-hydroxy-3-[(cyclohexylmethyl)(phenyl sulfonyl)amino]-1S-(phenylmethyl)propyl]carbamate; 
       Phenylmethyl[2R-hydroxy-3-[(cyclohexyl)(phenylsulfonyl)amino]-1S-(phenylmethyl)propyl]carbamate; 
       Phenylmethyl[2R-hydroxy-3-[(propyl)(phenylsulfonyl)amino]-1S-(phenylmethyl)propyl]carbamate; 
       Pentanamide, 2S-[[(dimethylamino)acetyl]amino]-N-2R-hydroxy-3-[(3-methylpropyl)(4-methoxyphenylsulfonyl)amino]-1S-(phenylmethyl)propyl]-3S-methyl; 
       Pentanamide, 2S-[[(methylamino)acetyl]amino]-N-2R-hydroxy-3-[(4-methylbutyl)(phenylsulfonyl)amino]-1S-(phenylmethyl)propyl]-3S-methyl; 
       Pentanamide, 2S-[[(dimethylamino)acetyl]amino]-N-2R-hydroxy-3-[(4-methylbutyl)(phenylsulfonyl)amino]-1S-(phenylmethyl)propyl]-3S-methyl; 
       [2R-hydroxy-3-[[(4-methoxyphenyl)sulfonyl](2-methylpropyl)amino]-1S-(phenylmethyl)propylamine; 
       2R-hydroxy-3-[(2-methylpropyl)(4-hydroxyphenyl)sulfonyl] amino-1S-(phenylmethyl)propylamine; 
       [2R-hydroxy-3-[(phenylsulfonyl)(3-methylbutyl)amino]-1S-(phenylmethyl)propylamine; 
       [2R-hydroxy-3-[(phenylsulfonyl)(2-methylpropyl)amino]-1S-(phenylmethyl)propylamine; 
       [2R-hydroxy-3-[(phenylsulfonyl)(cyclohexylmethyl)amino]-1S-(phenylmethyl)propylamine; 
       [2R-hydroxy-3-[(phenylsulfonyl)(cyclohexyl)amino]-1S-(phenylmethyl)propylamine; 
       4-Pyridinecarboxamide, N-[2R-hydroxy-3-[[(4-methoxyphenyl)sulfonyl](2-methylpropyl)amino]-1S-(phenylmethyl)propyl]; 
       Benzamide, N-[2R-hydroxy-3-[[(4-methoxyphenyl)sulfonyl] (2-methylpropyl)amino]-1S-(phenylmethyl)propyl]-2,6-dimethyl; 
       Benzamide, N-[2R-hydroxy-3-[[(4-methoxyphenyl)sulfonyl] (2-methylpropyl)amino]-1S-(phenylmethyl)propyl]-2-methyl; 
       Benzamide, N-[2R-hydroxy-3-[[(4-methoxyphenyl)sulfonyl] (2-methylpropyl)amino]-1S-(phenylmethyl)propyl]-2-ethyl; 
       Benzamide, N-[2R-hydroxy-3-[[(4-methoxyphenyl)sulfonyl] (2-methylpropyl)amino]-1S-(phenylmethyl)propyl]-2-chloro; 
       Carbamic acid, [2R-hydroxy-3-[[(4-methoxyphenyl)sulfonyl] (2-methylpropyl)amino]-1S-(phenylmethyl)propyl]-, 3-pyridylmethyl ester; 
       Carbamic acid, [2R-hydroxy-3-[[(4-methoxyphenyl)sulfonyl] (2-methylpropyl)amino]-1S-(phenylmethyl)propyl]-, 3-pyridylmethyl ester, N-oxide; 
       Carbamic acid, [2R-hydroxy-3-[[phenylsulfonyl](2-methylpropyl)amino]-1S-(phenylmethyl)propyl]-, 3-pyridylmethyl ester; 
       Carbamic acid, [2R-hydroxy-3-[[(4-methoxyphenyl)sulfonyl] (2-methylpropyl)amino]-1S-(phenylmethyl)propyl]-, 4-pyridylmethyl ester; 
       Carbamic acid, [2R-hydroxy-3-[[(4-methoxyphenyl)sulfonyl] (2-methylpropyl)amino]-1S-(phenylmethyl)propyl]-, 4-pyridylmethyl ester, N-oxide; 
       Carbamic acid, [2R-hydroxy-3-[[(4-chlorophenyl)sulfonyl] (2-methylpropyl)amino]-1S-(phenylmethyl)propyl]-, 3-pyridylmethyl ester; 
       Carbamic acid, [2R-hydroxy-3-[[(4-nitrophenyl)sulfonyl] (2-methylpropyl)amino]-1S-(phenylmethyl)propyl]-, 3-pyridylmethyl ester; 
       Carbamic acid, [2R-hydroxy-3-[[(4-fluorophenyl)sulfonyl] (2-methylpropyl)amino]-1S-(phenylmethyl)propyl]-, 3-pyridylmethyl ester; 
       Carbamic acid, [2R-hydroxy-3-[[(4-hydroxyphenyl)sulfonyl] (2-methylpropyl)amino]-1S-(phenylmethyl)propyl]-, 3-pyridylmethyl ester; or 
       Carbamic acid, [2R-hydroxy-3-[[(4-methoxyphenyl)sulfonyl] (2-methylpropyl)amino]-1S-(phenylmethyl)propyl]-, 5-pyrimidylmethyl ester. 
     
     
       16. A compound of  claim 12  which is: 
       Carbamic acid, [2R-hydroxy-3-[[(4-methoxyphenyl)sulfonyl] (methylpropyl)amino]-1S-(phenylmethyl)propyl]-, 5-thiazolylmethyl ester; 
       Carbamic acid, [2R-hydroxy-3-[[(4-hydroxyphenyl)sulfonyl] (2-methylpropyl)amino]-1S-(phenylmethyl)propyl-, 5-thiazolylmethyl ester; 
       Carbamic acid, [2R-hydroxy-3-[[(4-methoxyphenyl)sulfonyl] (2-methylpropyl)amino]-1S-(phenylmethyl)propyl-, 3-furanylmethyl ester; 
       Benzamide, N-[2R-hydroxy-3-[[(4-methoxyphenyl)sulfonyl] (2-methylpropyl)amino]-1S-(phenylmethyl)propyl]-3-hydroxy-2-methyl; 
       2R-hydroxy-3-[[(4-aminophenyl)sulfonyl](2-methylpropyl)amino]-1S-(phenylmethyl)propylamine; 
       Carbamic acid, 2R-hydroxy-3-[[(4-aminophenyl)sulfonyl] (2-methylpropyl)amino]-1S-(phenylmethyl)propyl-, 3-furanylmethyl ester; 
       Carbamic acid, 2R-hydroxy-3-[[(4-aminophenyl)sulfonyl] (2-methylpropyl)amino]-1S-(phenylmethyl)propyl-, 5-thiazolylmethyl ester; 
       Benzamide, N-[2R-hydroxy-3-[[(4-aminophenyl)sulfonyl] (2-methylpropyl)amino]-1S-(phenylmethyl)propyl]-2-methyl; 
       Benzamide, N-[2R-hydroxy-3-[[(4-aminophenyl)sulfonyl] (2-methylpropyl)amino]-1S-(phenylmethyl)propyl]-3-hydroxy-2-methyl; 
       Carbamic acid, 2R-hydroxy-3-[[(2-aminobenzothiazol-6-yl)sulfonyl](2-methylpropyl)amino]-1S-(phenylmethyl)propyl-, phenylmethyl ester; 
       Carbamic acid, 2R-hydroxy-3-[[(benzothiazol-6-yl)sulfonyl](2-methylpropyl)amino]-1S-(phenylmethyl)propyl-, phenylmethyl ester; 
       2R-hydroxy-3-[[(3-aminophenyl)sulfonyl](2-methylpropyl)amino]-1S-(phenylmethyl)propylamine; 
       Carbamic acid, 2R-hydroxy-3-[[(3-aminophenyl)sulfonyl] (2-methylpropyl)amino]-1S-(phenylmethyl)propyl-, 5-thiazolylmethyl ester; 
       Benzamide, N-[2R-hydroxy-3-[[(3-aminophenyl)sulfonyl] (2-methylpropyl)amino]-1S-(phenylmethyl)propyl]-3-hydroxy-2-methyl; 
       Carbamic acid, 2R-hydroxy-3-[[(2-amino benzothiazol-5-yl) sulfonyl](2-methylpropyl)amino]-1S-(phenylmethyl)propyl-, phenylmethyl ester; 
       Carbamic acid, 2R-hydroxy-3-[[(2-aminobenzothiazol-7-yl)sulfonyl] (2-methylpropyl)amino]-1S-(phenylmethyl)propyl-, phenylmethyl ester; 
       2R-hydroxy-3-[[(2,3-dihydrobenzofuran-5-yl)sulfonyl](2-methylpropyl)amino]-1S-(phenylmethyl) propylamine; 
       Carbamic acid, [2R-hydroxy-3-[[(2,3-dihydrobenzofuran-5-yl)sulfonyl](2-methylpropyl)amino]-1S-(phenylmethyl)propyl-, 3-pyridylmethyl ester; 
       Carbamic acid, [2R-hydroxy-3-[[(2,3-dihydrobenzofuran-5-yl)sulfonyl](2-methylpropyl)amino]-1S-(phenylmethyl)propyl-, 5-thiazolylmethyl ester; 
       Benzamide, N-[2R-hydroxy-3-[[(2,3-dihydrobenzofuran-5-yl) sulfonyl](2-methylpropyl)amino]-1S-(phenylmethyl)propyl]-3-amino-2-methyl-; 
       2R-hydroxy-3-[[(1,3-benzodioxol-5-yl)sulfonyl](2-methylpropyl)amino]-1S-(phenylmethyl) propylamine; 
       Carbamic acid, 2R-hydroxy-3-[[(1,3-benzodioxol-5-yl)sulfonyl](2-methylpropyl)amino]-1S-(phenylmethyl)propyl-, 3-pyridylmethyl ester; 
       Carbamic acid, 2R-hydroxy-3-[[(1,3-benzodioxol-5-yl)sulfonyl](2-methylpropyl)amino]-1S-(phenylmethyl)propyl-, 5-thiazolylmethyl ester; 
       Benzamide, N-[2R-hydroxy-3-[[(1,3-benzodioxol-5-yl)sulfonyl](2-methylpropyl)amino]-1S-(phenylmethyl)propyl]-3-amino-2-methyl; 
       Benzamide, N-[2R-hydroxy-3-[[(1,3-benzodioxol-5-yl)sulfonyl](2-methylpropyl)amino]-1S-(phenylmethyl)propyl]-4-hydroxy-2-methyl; 
       Benzamide, N-[2R-hydroxy-3-[[(1,3-benzodioxol-5-yl)sulfonyl](2-methylpropyl)amino]-1S-(phenylmethyl)propyl]-3-hydroxy-2-methyl; 
       N-[2R-hydroxy-3-[[(4-methoxyphenyl) sulfonyl](2-methylpropyl)amino]-1S-(phenylmethyl)propyl]-(2,6-dimethylphenoxy)acetamide; 
       N-[2R-hydroxy-3-[[(4-methoxyphenyl)sulfonyl](2-methylpropyl)amino]-1S-(phenylmethyl)propyl]-(2-methylphenoxy)acetamide; 
       N-[2R-hydroxy-3-[[(4-methoxyphenyl) sulfonyl](2-methylpropypamino]-1S-(phenylmethyl)propyl]-2-(2,6-dimethylphenylamino)acetamide; or 
       N-[2R-hydroxy-3-[[(4-methoxyphenyl) sulfonyl](2-methylpropyl)amino]-1S-(phenylmethyl)propyl]-2-aminobenzothiazole-6-carboxamide. 
     
     
       17. A compound represented by the formula: 
       
         
           
           
               
               
           
         
       
       or a pharmaceutically acceptable salt or ester thereof, wherein
 R 2  is an alkyl, aryl, cycloalkyl, cycloalkylalkyl or aralkyl radical, which radical is optionally substituted with a radical selected from the group consisting of alkyl, halo, nitro, cyano, CF 3 , —OR 9 , and —SR 9 , wherein R 9  is a radical selected from the group consisting of hydrogen and alkyl; 
 R 3  is a hydrogen, alkyl, haloalkyl, alkenyl, alkynyl, hydroxyalkyl, alkoxyalkyl, alkylthioalkyl, alkylsulfonylalkyl, cycloalkyl, cycloalkylalkyl, aryl, aralkyl, aminoalkyl or mono- or disubstituted aminoalkyl radical, wherein said substituents are selected from the group consisting of alkyl, aryl, aralkyl, cycloalkyl, and cycloalkylalkyl radicals; 
 R 4  is an alkyl, haloalkyl, alkenyl, alkynyl, hydroxyalkyl, alkoxyalkyl, cycloalkyl, cycloalkylalkyl, aryl, aralkyl, aralkenyl, aminoalkyl, mono- or disubstituted aminoalkyl radical, wherein said substituents are selected from the group consisting of alkyl, aryl, aralkyl, cycloalkyl, and cylcloalkylalkyl; and a saturated or partially unsaturated monocyclic, bicyclic or tricyclic heterocycle having 3 to 12 ring members, which contains at least one nitrogen, oxygen, sulphur, sulfone, sulfoxide or N-oxide or a tertiary nitrogen heteroatom ring member, and which is optionally substituted on one or more carbon atoms by halogen, alkyl, alkoxy, hydroxy, oxo or aryl, or on a secondary nitrogen atom by hydroxy, alkyl, aralkoxycarbonyl, alkanoyl, phenyl or phenylalkyl; or an aromatic monocyclic, bicyclic, or tricyclic heterocycloalkyl radical which is optionally substituted with one or more alkyl, alkoxy, halogen, hydroxy, amino nitro, cyano, haloalkyl, carboxy, alkoxycarbonyl, cycloalkyl, amido, alkylamino, dialkylamino, alkylamido or dialkylamido radicals; 
 R 6  is a hydrogen or alkyl radical; 
 x is 2; 
 t is 0 or 1; 
 Y is O; and 
 A is an alkoxy, alkenoxy, aralkoxy, alkyl, cycloalkyl, cycloalkylalkoxy, cycloalkylalkyl, aralkyl, aryl, aryloxy, alkenyl, aryloxyalkyl, hydroxyalkyl, amino, or mono- or disubstituted amino radical, wherein the substituents are selected from the group consisting of alkyl, aryl, aralkyl, cycloalkyl, and cycloalkylalkyl radicals, or is represented by the formula 
 
       
         
           
           
               
               
           
         
       
       wherein R is a hydrogen, alkoxycarbonyl, aralkoxycarbonyl, alkylcarbonyl, cycloalkylcarbonyl, cycloalkylalkoxycarbonyl, cycloalkylalkanoyl, carboxyalkanoyl, alkanoyl, aralkanoyl, aroyl, aryloxycarbonyl, aryloxycarbonylalkyl, aryloxyalkanoyl, alkyl, alkenyl, alkynyl, cycloalkyl, aryl, aralkyl, aryloxyalkyl, hydroxyalkyl, aminocarbonyl, aminoalkanoyl, or mono- or disubstituted aminocarbonyl or mono- or disubstituted aminoalkanoyl radical, wherein the substituents are selected from the group consisting of alkyl, aryl, aralkyl, cycloalkyl, and cycloalkylalkyl radicals;
 R 1  is a radical as defined for R 3  or R″SO 2 —, wherein R″ is a radical as defined for R 3 ; 
 R 1  is a hydrogen, —CO 2 CH 3 , —CH 2 CO 2 CH 3 , —CO 2 H, —CH 2 CO 2 H, —CH 2 CH 2 CONH 2 , —CH 2 CONH 2 , —CONH 2 , —CH 2 (O)NHCH 3 , —CH 2 CH 2 SO 2 NH 2 , —CH 2 S[O]CH 3 , CH 2 S[O] 2 CH 3 , —C(CH 3 ) 2 (SCH 3 ), —C(CH 3 ) 2 (S[O]CH 3 ), —C(CH 3 ) 2 (S[O] 2 CH 3 ), alkyl, hydroxyalkyl, cyanoalkyl, haloalkyl, alkenyl, alkynyl, cycloalkyl, cycloalkylalkyl, alkylthioalkyl, aralkyl, aminoalkyl or mono- or disubstituted animoalkyl radical, wherein said substituents are selected from the group consisting of alkyl, aryal, aralkyl, cycloalkyl, and cycloalkylalkyl radicals; and 
 each of R 1 ′ and R 1 ″ are independently a radical as defined for R 1 ; or one of R 1 ′ and R 1 ″ together with R 1  and the carbon atoms to which R 1 , R 1 ′ and R 1 ″ are attached, form a cycloalkyl radical; and 
 wherein alkyl, alone or in combination, is a straight-chain or branched-chain hydrocarbon radical containing from 1 to 8 carbon atoms; alkenyl, alone or in combination, is a straight-chain or branched-chain hydrocarbon radical having at least one double bond and containing form 2 to 8 carbon atoms; alkynyl, alone or in combination, is a straight-chain or branched-chain hydrocarbon radical having at least one triple bond and containing form 2 to 10 carbon atoms; cycloalkyl, alone or in combination, is a hydrocarbon ring containing from 3 to 8 carbon atoms; aryl, alone or in combination, means a phenyl or napthyl radical which optionally carries one or more alkyl, alkoxy, halogen, hydroxy, amino, nitro, cyano, haloalkyl, carboxy, alkoxycarbonyl, cycloalkyl, amido, alkylamino, dialkylamino, alkylamido or dialkylamido radicals; a saturated or partially unsaturated monocyclic, bicyclic or tricyclic heterocycle having 3 to 12 ring members, which contains at least one nitrogen, oxygen, sulphur, sulfone, sulfoxide or N-oxide or a tertiary nitrogen heteroatom ring member, and which is optionally substituted on one or more carbon atoms by halogen alkyl, alkoxy, hydroxy, oxo or aryl, or on a secondary nitrogen atom by hydroxy, alkyl, aralkoxycarbonyl, alkanoyl, phenyl or phenylalkyl; or an aromatic monocyclic, bicyclic, or tricyclic heterocycloalkyl radical which is optionally substituted with one or more alkyl, alkoxy, halogen, hydroxy, amino nitro, cytano, haloalkyl, carboxy, alkoxycarbonyl, cycloalkyl, amido, alkylamino, dialkylamino, alkylamido or dialkylarnido radicals. 
 
     
     
       18. The compound of  claim 17  or a pharmaceutically acceptable salt or ester thereof, wherein
 R 2  is an aralkyl radical, which is optionally substituted with a radical selected from the group consisting of alkyl, halo and —OR 9 , wherein R 9  is a radical selected from the group consisting of hydrogen and alkyl; 
 R 3  is a hydrogen, alkyl, aryl, or aralkyl radical; 
 R 4  is an alkyl, haloalkyl, alkenyl, alkynyl, hydroxyalkyl, alkoxyalkyl, cycloalkyl, cycloalkylalkyl, aryl, aralkyl, aralkenyl, a saturated or partially unsaturated monocyclic, bicyclic or tricyclic heterocycle having 3 to 12 ring members, which contains at least one nitrogen, oxygen, sulphur, sulfone, sulfoxide or N-oxide or a tertiary nitrogen heteroatom ring member, and which is optionally substituted on one or more carbon atoms by halogen, alkyl, alkoxy, hydroxy, oxo or aryl, or on a secondary nitrogen atom by hydroxy, alkyl, aralkoxycarbonyl, alkanoyl, phenyl or phenylalkyl; or an aromatic monocyclic, bicyclic, or tricyclic heterocycloalkyl radical which is optionally substituted with one or more alkyl, alkoxy, halogen, hydroxy, amino, nitro, cyano, haloalkyl, carboxy, alkoxycarbonyl, cycloalkyl, amido, alkylamino, dialkylamino, alkylamido or dialkylamido radicals; 
 R 6  is a hydrogen or alkyl radical; 
 t is 0 or 1; and 
 A is an alkoxy, alkenoxy, aralkoxy, alkyl, cycloalkyl, aryl, amino, or mono- or disubstituted amino radical, wherein the substituents are selected from the group consisting of alkyl and aralkyl radicals. 
 
     
     
       19. A compound represented by the formula: 
       
         
           
           
               
               
           
         
       
       or a pharmaceutically acceptable salt or ester thereof, wherein
 A is a phenyl or napthyl radical which is optionally substituted with one or more alkyl, alkoxy, halogen, hydroxy, amino, nitro, cyano, haloalkyl, carboxy, alkoxycarbonyl, cycloalkyl, amido, alkylamino, dialkylamino, alkylamido or dialkylamido radicals; 
 R 2  is an aralkyl radical, which is optionally substituted with a radical selected from the group consisting of alkyl, halo, nitro, cyano, —CF 3 , —OR 9  and —SR 9 , wherein R 9  is a radical selected from the group consisting of hydrogen and alkyl; 
 R 3  is an alkyl, and 
 R 4  is an aromatic monocyclic, bicyclic or tricyclic heterocycle which contains at least one nitrogen, oxygen or sulfur and which is optionally substituted on one or more carbon atoms by halogen, alkyl, alkoxy, hydroxy, oxo or aryl, or on a secondary nitrogen atom by hydroxy, alkyl, aralkoxycarbonyl, alkanoyl, phenyl or phenylalkyl. 
 
     
     
       20. pharmaceutical composition comprising a compound of  claim 19  and a pharmaceutically acceptable carrier. 
     
     
       21. Method of treating a retroviral infection comprising administering an effective amount of a composition of  claim 20 . 
     
     
       22. Method of inhibiting a retroviral protease comprising administering an effective amount of a compound of  claim 19 . 
     
     
       23. Method of inhibiting replication of a retrovirus comprising administering an effective amount of a compound of  claim 19 . 
     
     
       24. A pharmaceutical composition comprising a pharmaceutically acceptable carrier and a compound, or pharmaceutically acceptable salt or ester thereof, of the following formula: 
       
         
           
           
               
               
           
         
       
       
        
       
     
     
       25. A pharmaceutical composition comprising a pharmaceutically acceptable carrier and a compound of the following formula: