TOTAL SYNTHESIS OF RETROPROGESTERONES

The first total syntheses (by three different routes) of 9β, 10α-progesterones are described: (1) previously prepared tricyclic keto alcohol I was converted into retroprogesterone VI by a sequence involving the Wittig reaction, hydroboration, and A-ring annelation; (2) the Δ17(20)-olefin intermediate (IV) was converted into 16-dehydroretroprogesterone (IX) by another sequence consisting of A-ring annelation and photosensitized oxygenation as the key steps; (3) compound I was converted into 16-dehydroretroprogesterone by A-ring annelation, the Wittig reaction, and photosensitized oxygenation. © 1968, American Chemical Society. All rights reserved.