Retroviral protease inhibitors

Compound represented by the formula:

• ##STR386## wherein R' represents hydrogen and radicals as defined for R.sup.3, and aralkoxycarbonylalkyl and aminocarbonylalkyl or aminoalkyl radicals, wherein said amino group may be mono- or disubstituted with substitutents selected from alkyl, aryl, aralkyl, cycloalkyl, cycloalkylalkyl, heteroaryl, heteroaralkyl, hetercycloalkyl and heterocycloalkylalkyl radicals;
• R.sup.1 represents hydrogen, --CH.sub.2 SO.sub.2 NH.sub.2, --CO.sub.2 CH.sub.3, --CH.sub.2 CO.sub.2 CH.sub.3, --CONH.sub.2, --CONHCH.sub.3, CON(CH.sub.3).sub.2, --CH.sub.2 CONHCH.sub.3, --CH.sub.2 CON(CH.sub.3).sub.2, alkyl, alkenyl, alkynyl and cycloalkyl radicals and amino acid side chains selected from asparagine, S-methyl cysteine and the corresponding sulfoxide and sulfone derivatives thereof, glycine, leucine, isoleucine, allo-isoleucine, tert-leucine, phenylalanine, ornithine, alanine, histidine, norleucine, glutamine, valine, threonine, serine, aspartic acid, beta-cyano, alanine and allo-threonine side chains;
• R.sup.2 represents alkyl, aryl, cycloalkyl, cycloalkylalkyl, and aralkyl radicals, which radicals are optionally substituted with a group selected from alkyl radicals, --NO.sub.2, OR.sup.9 and SR.sup.9 wherein R.sup.9 represents hydrogen and alkyl radicals, and halogen radicals;
• R.sup.3 represents alkyl, alkenyl, alkynyl, hydroxyalkyl, alkoxyalkyl, cycloalkyl, cycloalkylalkyl, heterocycloalkyl, heteroaryl, heterocycloalkylalkyl, aryl, aralkyl, heteroaralkyl, aminoalkyl and mono- and disubstituted aminoalkyl radicals where said substitutents are selected from alkyl, aryl, aralkyl, cycloalkyl, cycloalkylalkyl, heteroaryl, heteroalkyl, heterocycloalkyl, and heterocycloalkylalkyl radicals;
• R.sup.4 and R.sup.5, independently represent hydrogen and radicals as defined by R.sup.3, or R.sup.4 and R.sup.5 together with the carbon atom to which they are bonded represent cycloalkyl heterocycloalkyl, heteroaryl and aryl radicals;
• R.sup.20 and R.sup.21 represent radicals as defined for R.sup.1 ;
• and
• X represents O and C(R.sup.17) wherein R.sup.17 represents hydrogen and alkyl radicals, provided that when X is O, R.sup.5 is absent;
• and
• Y and Y' independently represent O and S.