Routes to 18-nor and 19-nor steroids

Abstract

17-Oxo-18-nor-5α,13β-androstan-3β-yl acetate (6) and the 13α-epimer (7) have been synthesized by two routes, both of which involve initially an ?abnormal? Beckmann rearrangement of the oxime of 17-oxo-5α-androstan- 3β-yl acetate to the 13,17-seco nitrile (4). In the shorter but lower- yielding sequence, the mixture of epimeric epoxides obtained from (4) was converted into a mixture of (6) and (7) in 25% yield with boron trifluoride in refluxing toluene. A higher yield was achieved by a Dieckmann condensation of the nitrile esters (9) and (10), readily prepared from the above epoxides via the aldehydes.     The latter method was also found to be useful for the synthesis of 1-oxo-19-nor-5α,10β-androstan-17β-yl acetate (22) from 1-oxo-5α- androstan-17β-yl acetate.