The structure of the estrone related steroid, Equilenin, C18H18O2 (systematic name 3-hydroxy-13-methyl-11,12,13,14,15,16-hexahydro-cyclopenta[a]phenanthren-17-one), has been determined at 100 K. The crystals are orthorhombic, P212121, and the absolute structure of the molecule in the crystal has been determined by resonant scattering [Flack parameter = 0.05 (4)]. The carbon atoms of the A and B rings, are coplanar with an r.m.s. deviation from planarity of 0.0104 A. The C ring has a sofa conformation while the D ring has an envelope conformation with the methine C atom as the flap. The keto oxygen and the methyl group are translated 0.78 A and 0.79 A, respectively, from the equivalent positions on 17β-estrone 3. In the crystal, molecules are linked by O—H・・・O hydrogen bonds forming
14 chains parallel to the c-axis direction
