Method for preparing 13,14-dihydro-17-phenyl analogues of PGF2α or PGE2 comprising the step of hydrogenating the double bond in an intermediate compound (I) without deoxygenation of the allylic alcohol to give one of the intermediate compounds (II, III) wherein R is hydrogen or one or more halogen, hydroxyl, cyanide, alkyl (preferably 1-4 carbon atoms), hydroxyalkyl, trifluoromethyl or aromatic or heteroaromatic substituents on the aromatic ring R1 and R2 are each hydrogen, alkyl (preferably 1-4 carbon atoms), hydroxyl, halogen or hydroxyalkyl substituents, R3 is O-alkyl or N(alkyl), P is a protecting group.