Abstract: This invention encompasses prostaglandins of the formula I ##STR1## wherein R represents hydrogen or lower alkyl containing 1 to 6 carbon atoms;X represents --CH.sub.2 --, --CH.dbd.CH--, --C.tbd.C--, --CH.sub.2 --C.tbd.C--, --CH.sub.2 --CH.dbd.CH-- --CH.sub.2 --CH.sub.2 --CH.sub.2, --CH.dbd.CH--CH.sub.2 --, --C.tbd.C--CH.sub.2 --; andR.sub.1 represents cyclopropyl, cyclobutyl, cyclopentyl, 1-methylcyclopropyl or 1-methylcyclobutyl or XR.sub.1 together represent 1-methyl-1-cyclopropylethyl or 1-methyl-1-cyclobutylethyl; and R.sub.2 is lower alkyl having 1 to 4 carbon atoms or vinyl or ethynyl; the wavy line represents optional R or S sterochemistryThese compounds are potent antisecretory agents.