(15) ##STR13## in which each of X and Y is a hydrogen atom, an alkyl group, an acylamino group, an alkoxy group or a halogen atom; each of R1, R2 and R3 is a hydrogen atom, a substituted or unsubstituted alkyl group, an aryl group, a heterocyclic ring or cyclohexyl group having 1-20 carbon atoms; and A is --NHCO-- or --CONH--.