Crystal and molecular structure of 3-methoxy-7α,8α-methylene-1,3,5(10)-oestratrien-17β-yl bromoacetate

Abstract

The observed oestrogenic activity of 7α,8α-methylene-1,3,5(10)-oestratrien-3,17β-diol diacetate is suprising on account of its unnatural cis junction between the B and C rings. The crystal and molecular structure of the 3-methyl ether 17-bromoacetate derivative of this steriod has been determined by X-ray analysis in order to confirm the configuration of the B–C juncture. The crystals are orthorhombic, space group P2₁2₁2₁ with cell dimensions a= 14·134, b= 22·944, and c= 6·147 Å. The B ring has a configuration which is closer to an ideal boat than any configuration previously observed in steroid crystal structures, and the C ring has the normally observed chair conformation. The presence of the cyclopropane ring causes enlargement of the valency angles about C(7) and C(8).