Compounds of the formula ##STR1## or a pharmaceutically acceptable salt or ester thereof, wherein R.sup.1 is selected from the group consisting of hydrogen and C.sub.1-10 alkyl; R.sup.2 is selected from the group consisting of hydrogen and C.sub.1-10 alkyl; R.sup.3 is selected from the group consisting of C.sub.1-10 alkoxyl, C.sub.1-10 alkyl and cyano; R.sup.4 is selected from the group consisting of C.sub.1-10 alkenyloxyl, C.sub.1-10 alkoxyl, C.sub.1-10 alkyl, C.sub.1-10 alkylcarbamic, C.sub.1-10 alkylcarbonyloxyl, carbonyl, hydroxyl, and --NHR.sup.5, and R.sup.5 is selected from the group consisting of hydrogen and C.sub.1-10 alkylcarbonyl. Such compounds are useful as selective antagonists of testosterone 5.alpha.-reductase 1.