Retroviral protease inhibitors

Compound represented by the formula:

• ##STR209## or a pharmaceutically acceptable salt, prodrug or ester thereof, wherein R.sup.13 represents alkoxycarbonyl, aralkoxycarbonyl, alkylcarbonyl, cycloalkylcarbonyl, aralkanoyl, aroyl, heterocyclylcarbonyl, heteroaralkoxycarbonyl or hetereoaroyl radicals;
• 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, or halogen radicals;
• wherein R.sup.9 represents hydrogen or alkyl radicals;
• R.sup.3 represents alkyl, alkenyl, alkynyl, hydroxyalkyl, alkoxyalkyl, cycloalkyl, cycloalkylalkyl, heterocycloalkyl, heteroaryl, heterocycloalkylalkyl, aryl, aralkyl, heteroaralkyl, aminoalkyl or N-mono- or N,N-disubstituted aminoalkyl radicals where said substitutents are alkyl, aryl, aralkyl, cycloalkyl, cycloalkylalkyl, heteroaryl, heteroaralkyl, heterocycloalkyl or heterocycloalkylalkyl radicals;
• Y represents O or S;
• and
• 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 nitrogen atom to which they are bonded represent heterocycloalkyl radicals;
• wherein alkyl, alone or in combination, has 1 to 8 carbon atoms;
• alkenyls alone or in combination, has 2 to 8 carbon atoms;
• alkynyl, alone or in combinations has 2 to 10 carbon atoms;
• cycloalkyl, alone or in combination, has 3 to 8 carbon atoms;
• aryl, alone or in combination, is a phenyl or naphthyl radical optionally substituted with alkyl, alkoxy, halogen, hydroxy or amino radicals;
• heterocycloalkyls alone or in combination, is a saturated or partially. unsaturated monocyclic, bicyclic or tricyclic heterocycle containing nitrogen, oxygen or sulfur heteroatoms, which is optionally substituted on one or more ring carbon atoms with halogen, alkyl, alkoxy or oxo radicals, or on a secondary ring nitrogen atom with alkyl, aralkoxycarbonyl, alkanoyl, phenyl or phenylalkyl or on a tertiary nitrogen atom with oxido;
• and heteroaryl, alone or in combinations aromatic monocyclic, bicyclic, or tricyclic heterocycle containing nitrogen, oxygen or sulfur heteroatomss which is optionally substituted on one or more ring carbon atoms with halogen, alkyl, alkoxy or oxo radicals, or on a secondary ring nitrogen atom with alkyl, aralkoxycarbonyl, alkanoyl, phenyl or phenylalkyl or on a tertiary nitrogen atom with oxido.