Compounds represented by the following general formula (I) or salts thereof: ##STR00001## wherein R.sup.1 represents hydrogen atom, hydroxyl group, or an alkoxy group; R.sup.2 represents hydroxyl group or an alkoxy group which may be substituted; R.sup.3 represents hydrogen atom or an alkyl group which may be substituted; Y represents --CH.dbd.CH-- or --CH.sub.2--; n represents 0 or 1; Ar represents an aryl group which may be substituted or a heteroaryl group which may be substituted, which are useful as inhibitors against the abscisic acid biosynthesis and plant growth regulators.