Synthesis and crystal and molecular structure of a 1,11-methano-steroid, 3-methoxy-1′β-methyl-1,11α-methano-9β-estra-1,3,5(10)-trien-17β-ol

Abstract

Treatment of 17,17-ethylenedioxy-3-methoxy-11α-vinylestra-1,3,5(10)-trien-11β-ol with various acids afforded 3-methoxy-1′β-methyl-1,11-methanoestra-1,3,5(10),9(11)-tetraen-17-one, and not the isomeric 1,11-ethanosteroid. Birch reduction of this pentacyclic product gave the title compound, the structure of which was established by X-ray single-crystal analysis. Crystals are orthorhombic, space group P2₁2₁2₁, with a= 9.153(5), b= 17.918(10), c= 10.200(5)Å, Z= 4. The structure was solved by direct methods and refined by full-matrix least-squares calculations to R 0.046 over 1474 statistically significant reflections from diffractometer measurements. The steroid skeleton is folded severely to the α-side about the C(8)–C(9) bond. Ring B adopts a distorted half-chair conformation, ring C has a chair form significantly flattened around C(9), and ring D approximates to a C(13)-envelope.