<unk> , also known as 9β,10α-progesterone or as 9β,10α-pregn-4-ene-3,20-dione, is a progestin which was never marketed. It is a stereoisomer of the naturally occurring progestogen progesterone, in which the hydrogen atom at the 9th carbon is in the α-position (below the plane) instead of the β-position (above the plane) and the methyl group at the 10th carbon is in the β-position instead of the α-position. In other words, the atom positions at the two carbons have been reversed relative to progesterone, hence the name<unk> . This reversal results in a "bent" configuration in which the plane of rings A and B is orientated at a 60° angle below the rings C and D. This configuration is ideal for interaction with the progesterone receptor, with<unk>  binding with high affinity to this receptor. However, the configuration is not as ideal for binding to other steroid hormone receptors, and as a result,<unk>  derivatives have increased selectivity for the progesterone receptor relative to progesterone.<unk>  is the parent compound of a group of progestins consisting of the marketed progestins dydrogesterone (6-dehydroretroprogesterone) and trengestone (1,6-didehydro-6-chlororetroprogesterone) and the never-marketed progestin Ro 6-3129, as well as the active metabolites of these progestins like 20α-dihydrodydrogesterone and 20α-dihydrotrengestone (i.e., the 20α-hydroxylated analogues).
Retroprogesterone
Haloprogesterone
Bromoketoprogesterone
Hydroxyprogesterone acetate
Vinyltestosterone
Estradiol enantate
Gestodene
Estradiol dienantate