A partial synthesis of 13‐ethyl‐11‐methylene‐18,19‐dinor‐17α‐pregn‐4‐en‐20‐yn‐17‐ol (desogestrel) based upon intramolecular oxidation of an 11β‐hydroxy‐19‐norsteroid to the 18 → 11β‐lactone

Abstract

Abstract A partial synthesis of the 13‐ethyl‐18‐norsteroid desogestrel is reported. The key step in this synthesis is the intramolecular oxidation of 11β‐hydroxyestr‐5‐ene‐3,17‐dione cyclic bis‐(1,2‐ethanediyl acetal) 3 with Pb(OAc) 4 and iodine to 3,3:17,17‐bis[1,2‐ethanediylbis(oxy)]‐11β‐hydroxyestr‐5‐en‐18‐oic acid γ‐lactone 2 . The 13‐COOH group was then converted into a 13‐ethyl group by a Grignard reaction with methyl‐magnesium bromide followed by Wolff‐Kishner reduction of the 13‐acetyl group thus formed.