Chick oviduct progesterone receptor binding of 15 beta, 17-dihydroxyprogesterone and its analogues.

We have tested derivatives of progesterone obtained by fermentation with Aspergillus giganteus for relative binding affinity for the progesterone receptor of chick oviduct. Our studies show that hydroxyl and oxo substitutents at C-11 and C-15 of progesterone significantly decrease the hormone's affinity for the progesterone receptor. The loss in affinity on introduction of a C-15 hydroxyl in 17-hydroxyprogesterone is restored by acetylation to 15 beta-acetoxy-17 hydroxyprogesterone. The latter compound may have some potential as an in vivo agent.