Cloprostenol is a synthetic derivative of prostaglandin F2α that is used in veterinary medicine as a luteolytic agent for the induction of estrus and in the treatment of reproductive disorders in cattle, swine, and horses. (+)-5-trans Cloprostenol is a minor impurity produced in the synthesis of (+)-cloprostenol. The (+)-5-trans isomer is 20-fold less active than the 5-cis form in terminating pregnancy in the hamster.