Retroviral protease inhibitors

A compound represented by the formula

• wherein
• R′ represents a radical selected from the group consisting of a hydrogen radical, alkenyl, alkynyl, haloalkyl, hydroxyalkyl, alkoxyalkyl, cycloalkyl, cycloalkylalkyl, heterocycloalkyl, heteroaryl, heterocycloalkylalkyl, and heteroaralkyl;
• t is 0 or 1;
• R1 represents a radical selected from the group consisting of a hydrogen radical, —CH2SO2NH2, —CO2CH3, —CH2CO2CH3, —C(O)NH2, —C(O)NHCH3, —C(O)N(CH3)2, —CH2C(O)NHCH3, —CH2C(O)N(CH3)2, alkyl, alkylthioalkyl, thioalkyl, the corresponding sulfoxide and sulfone derivatives of alkylthioalkyl and thioalkyl, alkenyl, alkynyl, alkoxyalkyl, haloalkyl, cycloalkyl, and amino acid side chains selected from the group consisting of asparagine, S-methyl cysteine and the corresponding sulfoxide and sulfone derivatives of S-methyl cysteine, glycine, leucine, isoleucine, allo-isoleucine, tert-leucine, alanine, phenylalanine, ornithine, histidine, norleucine, glutamine, valine, threonine, allo-threonine, serine, aspartic acid and beta-cyano alanine;
• Y′ represents O, S, and NR3, wherein R3 represents a radical selected from the group consisting of a hydrogen radical, alkyl, alkenyl, alkynyl, haloalkyl, hydroxyalkyl, alkoxyalkyl, cycloalkyl, cycloalkylalkyl, heterocycloalkyl, heteroaryl, heterocycloalkylalkyl, aryl, aralkyl, and heteroaralkyl radicals;
• R6 represents a hydrogen radical or an alkyl radical;
• and
• R20 and R21 independently represent radicals as defined for R1.