14-Methyl steroids: Pt. 6

The steric energies and conformational properties of 14-methyl-8θ,9θ,14θ-estra-1,3,5(10)-trien-17-ones and some derived ring C functionalized molecules have been calculated (MM2) and compared. In an attempt to synthesize 14α-methyl-9β-estra-1,3,5(10)-triene derivatives potentiated for deformation of ring C, hydroboration of mixtures of rac- 14α-methylestra-1,3,5(10),9(11)- and -1,3,5,(10),8-tetraenes was conducted, to give selective attack upon the Δ9(11)-components. In contrast to the favoured β-face hydrogenation of these systems, hydroboration proceeded almost exclusively on the α-face, to give 11α-alcohols, and hence the derived 11-ketones; the latter compounds favour 9α-configuration under equilibrating conditions. It was shown that ring C of a 9βH-11β-alcohol in this series adopts a twist-boat conformation. The structures of rac-14-methylestra-1,3,5(10)-triene-3,11α, 17β-triol 3-methyl ether and rac- 14-methyl-9β-estra-1,3,5(10)-triene-3,17β-diol have been determined by X-ray crystallography