Crystal and molecular structure of (23R)-23-hydroxy-3α,5α-cycloergost-7-en-6-one

Abstract

The title compound (III) crystallises in the monoclinic space group P2₁, with cell dimensions a= 8·048, b= 20·122, c= 7·641 Å, β= 93·92°, and Z= 2. The structure has been solved by direct methods, and refined to R 0·0845 for 1777 significant reflections, measured on a diffractometer. The configuration at C(23) is R, thus confirming the previous assignment. The conformation of the steroid nucleus is of some interest; whereas the BC and CD ring junctions are trans, AB is cis due to the C(3)–C(4)–C(5) cyclopropane ring. Rings A and B, and to a small extent, C, are subject to steric strains due to both the bicyclo[3.1.0]hexane ring A and the enone group in ring B. This is reflected in abnormal values for some bond lengths, angles, and dihedral angles.