Simple, Catalytic Enantioselective Syntheses of Estrone and Desogestrel

Highly enantioselective and very short syntheses of the bioactive forms of estrone (3) and desogestrel (4) are described using a chiral oxazaborolidinium catalyst (2) in the key initial step. Enantiomerically pure estrone was synthesized in eight steps from the readily available starting materials diene 5 and α,β-enal 6 via intermediates 8 and 9. Desogestrel was synthesized using a similar strategy from diene 5 and α,β-enal 11 via intermediates 12−17. The efficient syntheses of the chiral catalyst 2 and its enantiomer are also presented.