Direct conversion of 13β-alkylgonatetraenes into 13β-alkylgon-4-en-3-ones

Birch reduction of 8, 9-didehydroestradiol-17β 3-methyl ether 1 or 9(11)-didehydroestradiol-17β 3-methyl ether 2 followed by acid hydrolysis results in a mixture of 19-nortestosterone 8 and 19-nor-9β, 10α-testosterone 9 in varying amounts. However, reduction of their acetates with sodium or lithium, tert-butyl alcohol in liquid ammonia and in the presence of aniline affords exclusively 19-nortestosterone. Similarly, 18a-homo-19-nortestosterone 12 is prepared from the acetate of 18a-homoestradiol-17β 3-methyl ether, 10.