The crystal and molecular structure of 9α-bromo-17β-hydroxy-17α-methylandrost-4-ene-3,11-dione

Abstract

Enhancement of activity of biologically-active steroids may often be obtained by 9α- or 12α-halogenation of the steroid. The crystal and molecular structure of the activated anabolic agent, 9α-bromo-17β-hydroxy-17α-methylandrost-4-ene-3,11-dione(C₂₀H₂₇O₃Br), has been determined by X-ray methods. The crystals occur in space group P2₁ with a= 7·042, b= 20·429, c= 6·481 Å, β= 104·30°, Z= 2. Compared to the structures of 9α-H steroids, 9α-halogenation has had the effect of flattening the B and C rings and of further lowering the functional 11-oxo group to a more equatorial configuration where it is less shielded by the hydrogen atoms on the β-surface of the steroid. In the steroid nucleus, the cyclohexenone A ring is not puckered about the Δ⁴-bond, as is commonly supposed, but has atom C(1) lying almost in the plane of atoms C(3), C(4), C(5), C(6), and (C10), with the puckering mainly at C(2). This implies that the conjugated Δ⁴-3-one system is not planar.