Heterocyclic derivatives of antivirally active azahexane.

In the present invention compounds of formula (I *) DESCRIBED IN R 1 is lower alkoxycarbonyl, R2 is lower alkyl secondary or tertiary or lower alkylthio lower alkyl, R.sup.3 is phenyl which is OR NOT Susti tuted by one or MAS RADICAL lower alkoxy, or cycloalkyl C 4 - C 8, R 4 is phenyl or cyclohexyl, each of which is substituted in position 4 heterocyclyl UNSATURATED linked through a carbon atom in ring having 5 TO 8 ring atoms, containing 1 to 4 HETERO - atoms selected from the nitrogen, oxygen, sulfur, sulfinyl (- SO -) and sulfonyl (- SO 2 -) AND IS Susti tuted or substituted by lower alkyl or phenyl - loweralkyl, R 5, HOWEVER R 2, has one of the meanings given for R 2 YR 6, HOWEVER R 1, ES lower alkoxycarbonyl, or salts thereof, provided that is present at least one group forming YOU GO OUT. The compounds are inhibitors of retroviral aspartate protease and be used, for example, in the treatment of AIDS. These compounds have excellent pharmacodynamic properties.