A compound of the formula: whereinQ is an optionally substituted carbon atom or N(O)p wherein p is 0 or 1;Y is an optionally substituted methylene group, S(O)q wherein q is an integer of 0 to 2, or an optionally substituted imino group;Z.sup.1 is a C.sub.1-3 alkylene group which may have an oxo group or a thioxo group and may contain etherified oxygen or sulfur within the carbon chain;Z.sup.2 is an optionally substituted C.sub.1-3 alkylene group;Ar is an optionally substituted carbocyclic group or an optionally substituted heterocyclic group;one of R.sup.1 and R.sup.2 is a hydrogen atom, a halogen atom, a hydroxyl group, an optionally substituted lower alkyl group, or an optionally substituted lower alkoxy group;the other is a halogen atom, a hydroxyl group, an optionally substituted lower alkyl group, or an optionally substituted lower alkoxy group; orR.sup.1 and R.sup.2 taken together with adjacent --c.dbd.c-- form a ring; andring A is a benzene ring which may be substituted in addition to R.sup.1 and R.sup.2 ; or a salt thereof.