Reaction of the steroid derivative (1) and the Grignard reagent 4-(dimethylamino)phenylmagnesium bromide (2) gives (3) by vinylogous addition to the epoxide. Oxidation of the alcohol group in the five-membered ring to a ketone gives compound (4). Irradiation of this material for 16 minutes with a mercury lamp results in the methyl group adjacent to the ketone changing from the beta to the alpha configuration, giving (5). Alkynylation with the anion formed from the acetylene derivative (6) using butyllithium gives (7). Catalytic hydrogenation to convert the alkyne group to an alkyl group, followed by acid treatment to remove the protecting groups yielded onapristone.[11][12]
^Lange CA, Sartorius CA, Abdel-Hafiz H, Spillman MA, Horwitz KB, Jacobsen BM (2008). "Progesterone receptor action: translating studies in breast cancer models to clinical insights". Advances in Experimental Medicine and Biology. Vol. 630. Springer. pp. 94–111. doi:10.1007/978-0-387-78818-0_7. ISBN978-0-387-78817-3. PMID18637487. Onapristone, p. 102, at Google Books
^ ab Pavlik EJ, Nelson K, Srinivasan S, Depriest PD, Kenady DE (1997). "Antiestrogen Resistance in Human Breast Cancer". Estrogens, Progestins, and Their Antagonists. Hormones in Health and Disease. Birkhäuser. pp. 115–160. doi:10.1007/978-1-4612-4096-9_5. ISBN978-1-4612-8650-9. Onapristone, p. 134, at Google Books
^ abRobertson JF, Willsher PC, Winterbottom L, Blamey RW, Thorpe S (February 1999). "Onapristone, a progesterone receptor antagonist, as first-line therapy in primary breast cancer". European Journal of Cancer. 35 (2): 214–218. doi:10.1016/S0959-8049(98)00388-8. PMID10448262.
^Katkam RR, Gopalkrishnan K, Chwalisz K, Schillinger E, Puri CP (September 1995). "Onapristone (ZK 98.299): a potential antiprogestin for endometrial contraception". American Journal of Obstetrics and Gynecology. 173 (3 Pt 1): 779–787. doi:10.1016/0002-9378(95)90341-0. PMID7573244.
^Klijn JG, Setyono-Han B, Foekens JA (2000). "Progesterone antagonists and progesterone receptor modulators in the treatment of breast cancer". Steroids. 65 (10–11): 825–830. doi:10.1016/S0039-128X(00)00195-1. PMID11108894. S2CID25524094.