A compound of the formula (I): ##STR00001## wherein R.sup.1 is hydrogen or lower alkyl; R.sup.2 is lower alkyl, etc.; R.sup.3 is lower alkoxy, etc.; R.sup.4 is hydroxy, etc.; X is O, S, etc.; Y is CH or N; Z is lower alkylene or lower alkenylene; and m is 0 or 1; or salts thereof, which are useful as a medicament.