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

Abstract

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.