The purpose is to provide selective PDE IV inhibitors which have a potent anti-asthmatic profile with excellent safety. A compound of the formula (1): ##STR00001## wherein A is methylene, lower alkylmethylene, carbonyl, etc., Y is a 5- or 6-membered heteroaryl group containing one or two heteroatoms selected from nitrogen, sulfur and oxygen, Z is i) a fused ring in which any of 5- or 6-membered heteroaryl groups is fused to a benzene ring, or ii) a phenyl group which may be unsubstituted or optionally substituted with one or more members selected from the group consisting of nitro, amino, an amino nitrogen-containing group, etc., provided that when A is methylene, Y is a 5- or 6-membered heteroaryl group selected from the group consisting of pyrrolyl, pyridyl, etc., and Z is a phenyl group which may be unsubstituted or substituted, the substituent on said phenyl group is amino, or an amino nitrogen-containing group; or a pharmaceutically acceptable salt thereof, possesses excellent PDE IV inhibition and is useful as a pharmaceutical drug, preferably an anti-asthmatic, etc.