SYNTHESIS OF ENANTIOPURE ESTRONE VIA A DOUBLE HECK REACTION

An novel efficient catalytic approach to steroids by a double Heck rea ction of the vinyl bromides 2 and the CB-building block 3 is presented . The new estrogen analogues la and 1b are formed via 23a and 23b in a highly regio- and stereoselective manner in good yields. They contain a cis-BC ring junction and two double bonds in the 6,7- and the ll,12 -positions which can be functionalized in a selective way. Inter alia, homogeneous hydrogenation with (PPh3)(3)RhCl to give 28 followed by h ydrogenation with 1,4-cyclohexadiene in the presence of palladium affo rds the known estradiol derivative 29a in 76% yield which can easily b e transformed into estrone 31.