Structure of 5 beta-dihydrotestosterone

Abstract

17 beta-Hydroxy-5 beta-androstan-3-one, C19H30O2, Mr = 290.45, orthorhombic, P2(1)2(1)2(1), a = 11.7821 (6), b = 21.2184 (8), c = 6.5322 (2) A, V = 1633.0 (2) A3, Z = 4, D chi = 1.181 Mg m-3, lambda(Cu K alpha) = 1.54178 A, mu = 0.58 mm-1, F(000) = 640, T = 293 K, R = 0.033 for 1849 unique observed reflections. The molecular conformation of 5 beta-dihydrotestosterone shows the strong bending typical of 5 beta-steroids: the bowing angle of the A ring, relative to the remainder of the steroid, is 65.1 degrees. Bowing shortens the distance between the terminal O atoms, O(3) and O(17), to 9.824 (2) A which is ca 1 A shorter than was observed in 5 alpha-dihydrotestosterone and testosterone. The effects of both the bowing and the shorter separation between O(3) and O(17) may explain a difference in the affinity of 5 beta-dihydrotestosterone for the dexamethasone binding site on membranes compared to that of the other two compounds. A unique conformational feature of 5 beta-dihydrotestosterone is the flattening of the A ring on the side containing the C(3)--C(4) bond; this may be due to the combination of the 3-oxo substitution and the 5 beta-configuration.