Retroprogesterone, also known as 9β,10α-progesterone or as 9β,10α-pregn-4-ene-3,20-dione, is a progestin which was never marketed.[1][2] It is a stereoisomer of the naturally occurringprogestogenprogesterone, 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.[1][2] In other words, the atom positions at the two carbons have been reversed relative to progesterone, hence the name retroprogesterone. 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.[3] This configuration is ideal for interaction with the progesterone receptor, with retroprogesterone binding with high affinity to this receptor.[4] However, the configuration is not as ideal for binding to other steroid hormone receptors, and as a result, retroprogesterone derivatives have increased selectivity for the progesterone receptor relative to progesterone.[5]
Retroprogesterone 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-hydroxylatedanalogues).[1][2][6][7]
^ abcHorský J (6 December 2012). "Therapy of Anovolution". In Horský J, Presl J (eds.). Ovarian Function and its Disorders: Diagnosis and Therapy. Springer Science & Business Media. pp. 305, 329. ISBN978-94-009-8195-9.
^Rižner TL, Brožič P, Doucette C, Turek-Etienne T, Müller-Vieira U, Sonneveld E, et al. (May 2011). "Selectivity and potency of the retroprogesterone dydrogesterone in vitro". Steroids. 76 (6): 607–615. doi:10.1016/j.steroids.2011.02.043. PMID21376746. S2CID31609405.
^Dixon R, Hudson S, Darragh A (1973). "Pharmacokinetics of the retro-steroid progestogen, 16α-ethylthio-9β,10α-pregna-4, 6-diene-3, 20-dione (Ro 6-3129), in man and the sheep". Contraception. 8 (1): 53–65. doi:10.1016/0010-7824(73)90159-5. ISSN0010-7824.