Relative biological activity of certain prostaglandins and their enantiomers

A series of mirror image (ent) forms of prostaglandins F2 and E2 have been compared for potency in a hamster antifertility test. In the PGF2 series, ent-compounds surveyed had less potency than corresponding natural structures. For the PGE2 series, 11alpha-(15S)-ent-PGE2 methyl ester was 10-fold more potent than PGE2. Altering the C-9 hydroxy configuration in the PGF2 series from the natural alpha to beta decreased potency dramatically for compounds tested.