A novel
dipeptide compound inhibiting the enzymatic activity of HIV
protease, an anti-AIDS
medicine comprising this
dipeptide compound as an effective component. The
dipeptide compound is the compound represented by the formula (I) or a pharmaceutically acceptable salt thereof wherein R1, R2, and R3 independently represent a linear or branched, saturated or unsaturated lower
alkyl group, alkoxyl group,
alkyl amino group, or dialkyl amino group having 1-4 carbon atoms (with a
carbon atom being either replaced by an
oxygen atom or not), a halogeno group, or a
hydrogen atom, provided that all of the R1, R2, and R2 are not a
hydrogen atom at the same time, R2 and R3 may form a ring together, R4 represents a linear or branched lower
alkyl group having 1-4 carbon atoms or a
hydrogen atom; X is a
methylene group or a
sulfur atom; Y represents a five or six member monocyclic or polycyclic
hydrocarbon group, a heterocyclic group having a structure in which one or more
carbon atom in the monocyclic or polycyclic
hydrocarbon group is replaced by a hetero atom, an aryloxy group having 12 or less carbon atoms, in which the aromatic ring may be substituted with an alkyl group,
alkoxy group, halogeno group, amino group or hydroxyl group; and Z represents an
aliphatic hydrocarbon group having 1-6 carbon atoms or an
aromatic hydrocarbon group having 12 or less carbon atoms in which the aromatic ring may be substituted with an alkyl group,
alkoxy group, or halogeno group, or one or more
carbon atom in the
aromatic hydrocarbon group may be replaced by a hetero atom.