Pollen suppressants of the formula ##STR1## wherein X represents a group of the formula OR.sup.1 or NR.sup.1 R.sup.2 wherein R.sup.1 represents a C.sub.1 -C.sub.4 alkyl (optionally substituted with a C.sub.1 -C.sub.4 alkoxy group, 1 to 3 halogen atoms, or a carboxy or C.sub.1 -C.sub.4 alkylcarbonyl group), alkenyl (optionally substituted with 1 to 3 halogen atoms), or alkynyl group and R.sup.2 represents H or CH.sub.3, with the proviso that when R.sup.1 is CH.sub.3 , R.sup.2 is CH.sub.3 ; Y is hydrogen, C.sub.1 -C.sub.22 linear alkyl or alkenyl containing up to four C.dbd.C double bonds C.sub.3 -C.sub.6 branched alkyl or alkenyl, C.sub.2 -C.sub.4 alkoxyalkyl, cyclohexylmethyl, halogenated C.sub.1 -C.sub.4 alkyl, phenyl, benzyl, --(CH.sub.2 CH.sub.2 O).sub.m CH.sub.2 CH.sub.3 in which m is an integer from 1 to 5, or --CH(CH.sub.2 OR.sup.4)CH.sub.2 OR.sup.5 or --CH.sub.2 CHOR.sup.4 CH.sub.2 OR.sup.5 in which either R.sup. 4 or R.sup.5 but not both represent a C.sub.1 -C.sub.22 linear alkyl- or alkenyl-carbonyl group containing up to four C-C double bonds; and R represents C.sub.1 -C.sub.4 alkyl, phenyl, naphthyl, or phenyl or naphthyl substituted with one to three substituents selected from the group consisting of halogen, trihalomethyl, C.sub.1 -C.sub.4 alkoxy, C.sub.1 -C.sub.4 alkyl, and cyano; and salts thereof are disclosed along with methods of producing these compounds and of using them to produce hybrid seed in self-fertilizing plants.