Crystal structure and conformation of 17α-ethynyl-17β-hydroxy-6,6-dimethyl-6-sila-5α-estr-1(10)-en-3- one

The crystal and molecular structure of the title compound (I) has been established by X-ray analysis. Crystals are monoclinic, space group P21/c, with a = 12.87(2), b = 6.61(1), c = 23.32(3) Å, β = 97.87(10)°, Z = 4. The structure was solved by direct methods and refined by full-matrix least-squares calculations to R 0.114 over 1729 reflections from photographic data. Ring A adopts a semiplanar conformation, rings B and C are in chair forms, and ring D has a C(13) envelope conformation. The endocyclic C-Si-C angle is 100.1 (3)°. The steroid conformation is significantly modified in the A/B region from that usually found.

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Author Andrew T. McPhail Chemistry