Retroviral protease inhibitors

A compound represented by the formula:

• ##STR208## wherein A represents radicals represented by formula:
• ##STR209## wherein R.sup.2 represents alkyl, aryl, cycloalkyl, cycloalkylalkyl and aralkyl radicals, which radicals are optionally substituted with a group selected from --OR.sup.9, --SR.sup.9, and halogen radicals,
• wherein R.sup.9 represents hydrogen and alkyl radicals;
• R.sup.3 represents alkyl, alkenyl, alkynyl, hydoxyalkyl, 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;
• X' represents O, C(R.sup.17) where R.sup.17 represents hydrogen and alkyl radicals, and N provided that when X' is O, R.sup.12 is absent;
• Y and Y' independents represent O,S and NR.sup.15 wherein R.sup.15 represents radicals as defined for R.sup.3 ;
• R.sup.4, R.sup.5, R.sup.11 and R.sup.12 independently represent hydrogen and radicals as defined by R.sup.3, or R.sup.4 and R.sup.5, and/or R.sup.11 and R.sup.12 together with the nitrogen atom to which they are bonded represent heterocycloalkyl and heteroaryl radicals, or R.sup.11 and R.sup.12 together with a carbon atom to which they are attached represent cycloalkyl and aryl radicals;
• B represents R.sup.5 and radicals represented by the formula:
• ##STR210## wherein:
• R.sup.7 and R.sup.7 ' represent radicals as defined for R.sup.3 and amino acid side chains selected from valine, isoleuceine, glycine, alaninc, allo-isoleucine, asparagine, leucine, glutamine and t-butylglycine;
• and R.sup.8 represents an amide derivative of an amino acid;
• and R.sup.6 represents hydrogen and alkyl radicals.