A medicament for preventive and/or therapeutic treatment of neurodegenerative diseases such as Alzheimer's disease or the like which comprises as an active ingredient a substance selected from the group consisting of a compound represented by the following general formula (I) and a pharmacologically acceptable salt thereof, and a hydrate thereof and a solvate thereof: wherein A represents hydrogen atom or acetyl group, E represents a 2,5-di-substituted or a 3,5-di-substituted phenyl group, or a monocyclic or a fused polycyclic heteroaryl group which may be substituted, provided that the compound wherein said heteroaryl group is {circle around (1)} a fused polycyclic heteroaryl group wherein the ring which binds directly to --CONH-- group in the formula (I) is a benzene ring, {circle around (2)} unsubstituted thiazol-2-yl group, or {circle around (3)} unsubstituted benzothiazol-2-yl group is excluded, ring Z represents an arene which may have one or more substituents in addition to the group represented by formula --O-A wherein A has the same meaning as that defined above and the group represented by formula --CONH-E wherein E has the same meaning as that defined above, or a heteroarene which may have one or more substituents in addition to the group represented by formula --O-A wherein A has the same meaning as that defined above and the group represented by formula --CONH-E wherein E has the same meaning as that defined above.