A compound represented by the formula (I): ##STR00001## wherein R1 is an oxo group, .dbd.N--R or the like; a group represented by the formula: ##STR00002## is a group represented by the formula: ##STR00003## R2 is a group represented by the formula: ##STR00004## R3 and R4 are each H, or C1-C6 alkyl, C3-C6 cycloalkyl, C1-C6 alkoxy, C1-C6 alkylamino, di(C1-C6)alkylamino or C1-C6 alkylthio, each of which is optionally substituted; and R5 is H, or C1-C6 alkyl, C2-C6 alkenyl, cyclic group, each of which is optionally substituted, --CO--R8 or --O--R8', or a salt thereof. The compound of the present invention is useful as a drug for the prophylaxis or treatment of cardiovascular diseases, metabolic diseases and/or central nervous system diseases.