Disclosed is a compound represented by the formula (I) below, a pharmaceutically acceptable salt thereof, or a solvate of any of them. (I) In the formula, R represents an optionally substituted lower alkyl group； Y represents -S(O)- (wherein n is 1 or 2) or -CO-； R represents a hydrogen or a lower alkyl； R represents a hydrogen or a lower alkyl； X represents a lower alkylene, a lower alkenylene, an arylene, a cycloalkylene or the like； and Z represents a lower alkyl, an optionally substituted hydrocarbon ring group, an optionally substituted heterocyclic group or the like.
