Abnormal Beckmann fragmentation/ring closing metathesis route for preparation of 18-nor-Δ 13(17)-androgens and their 18-nor-13,17-epoxide derivatives

The synthesis of 18-nor-Delta(13(17))-androgens and the structurally related 13,17-epoxides is described. The synthetic route involves the cleavage of 17-ketosteroids by an abnormal Beckmann rearrangement, modification of the D-ring cleavage product to obtain an intermediate tricyclic diene and ring closing metathesis of the diene to the 18-nor-Delta(13(17)) -androgen. (3 alpha,5 alpha)-18-Norandrost-13(17)-en-3-ol and the derivative 13 alpha,17 alpha- and 13 beta,17 beta-epoxides were prepared by this route. (c) 2006 Elsevier Ltd. All rights reserved.