Total syntheses of epothilones B and D: applications of allylstannanes in organic synthesis

Following exploratory studies which culminated in syntheses of the alcohol 16, a total synthesis of epothilones B and D is reported in which the trisubstituted 12,13-double-bond is introduced stereoselectively using the tin(IV) bromide-promoted reaction between the allylstannane 22 and the aldehyde 17. A Barton deoxygenation then gave the C(7)C(15) fragment 25. After development of the thiazole containing side-chain, an aldol condensation with the ethyl ketone 36 gave the adduct 37 which was taken through to epothilone D 2 and then to epothilone B 1.