Structure of 19-nor-17α-pregna-4,15-dien-20-yn-17β-ol

Abstract

C20H260 , Mr=282.42, monoclinic, P2~, a = 7.152 (3), b = 10.955 (6), c= 10.295 (4) A, //= 93.24 (3) °, V= 805.3 (6) A 3, Z= 2, Dx= 1.165 (1) g cm -3, 2(Cu Kct) = 1.5418 A, /t = 5 cm -I, F(000) = 308, T= 293 K, R = 0-067 for 1540 observations. The crystal structure is isomorphous to that of lynestrenol (19-nor- 17ct-pregn-4-en-20-yn- 17//- ol) (Rohrer, Lauffenburger, Duax & Zeelen (1976). Cryst. Struct. Commun. 5, 539-542); a least-squares fit of the steroid backbones IC(1)-C(18)1 gave a mean deviation of the fitted atoms of 0.05 A. The D ring has an ideal 13fl-envelope conformation {ACsIC(13)I= 2-3 (5) ° }, imposed by the A ~s unsaturation. All inter- molecular contacts are at normal van der Waals separations. Initial phases were obtained from the coordinates of the isomorphous crystal structure of lynestrenol and were used to initiate the tangent refinement of SHELXS86 (Sheldrick, 1986). H atoms were placed at calculated positions and were refined riding on their bonded atoms, except the hydroxyl-group H atom and the H atom bonded to the ethynyl group, which were located on a difference map and refined positionally. 198 parameters refined on F with full-matrix least squares using SHELX76 (Sheldrick, 1976); all non-H atoms refined anisotropically and for H atoms an overall isotropic thermal parameter was varied I U = 0.070 (3) A2); convergence reached at R = 0.067 and wR=0.083, where w= I/a2(F) and S=0.35; A/o= 0.01 (1) (av.) and 0.06 (max.) for non-H-atom