A novel compound of the formula (I): wherein R1 is alkoxycarbonyl or the like, R2 is alkyl or the like; R3 is hydrogen or the like; R4 is alkylene or the like; R5 is optionally substituted heterocyclic group; R6, R7, R8 and R9 are independently hydrogen; alkyl, alkoxy, or the like; R10 is optionally substituted aromatic ring, or the like; or a pharmaceutically acceptable salt thereof, which has an inhibitory activity against cholesteryl ester transfer protein (CETP).