Structure of 1 alpha,3 alpha-trimethylene-2',5-epoxyandrostane-3 beta, 17 beta-diol 17-propionate methanol solvate (1/0.5).

C25H38O4.0.5CH4O, Mr = 418.6, monoclinic, P2(1), a = 19.8504 (20), b = 7.3909 (4), c = 15.7998 (18) A, beta = 93.09 (2) degrees, V = 2314.7 (8) A3, Z = 4, D chi = 1.201 Mg m-3, lambda(Cu K alpha) = 1.54184 A, mu = 0.604 mm-1, F(000) = 916, T = 295 K, R = 0.056 for 4946 unique observed reflections. The crystallographic asymmetric unit contains two steroid molecules and a molecule of methanol. All six-membered rings for both molecules have chair conformations. The D ring has a 13 beta-envelope conformation in molecule 1 and a 13 beta, 14 alpha-half-chair conformation in molecule 2. The most significant differences between the crystallographically independent steroids are in the orientation of the H atoms of the C(3) hydroxyl groups and the conformations of the propionate side chains. When the crystallographically observed molecules are subjected to energy minimization their respective hydroxyl H-atom orientations are retained, but the D rings of both molecules refine to a common 13 beta,14 alpha-half-chair conformation and a significantly different orientation of the C(17) propionate side chain is generated. A comparison with other C(17)-ester-bearing steroids suggests that the energy minimization fails to simulate fully all intramolecular interactions.