Conformational deformation of ring C in 14β-estra-1,3,5(10),15-tetraen-17-ones

Article abstract of DOI:10.1016/S0040-4020(01)81470-8

High-field n.m.r. analysis of four 3-methoxy-14β-estra-1,3,5(10),15-tetraen-17-ones provides evidence for conformational deformation of ring C to a twist-boat form in solution. These observations are supported by molecular mechanics (MM2) calculations, which predict that the ring C chair and ring C twist-boat conformers have similar steric energies, slightly favouring the latter. An X-ray crystal structure determination on 3-methoxy-14-methyl-14β-estra-1,3,5(10)-,15-tetraen-17-one revealed that ring C does indeed adopt a twist-boat conformation in the solid state.