Crystal and Molecular Structures of Modified Progestagens (I). 17α-Cyanomethyl-17β-hydroxy-estr-4-en-3-one,C20H27NO2

17α-Cyanomethyl-17β-hydroxy-estr-4-en-3-one is the first member in a series of progestagens investigated systematically by X-ray structure analyses. It crystallizes in the orthorhombic space group P 2₁2₁2₁ with cell parameters α = 8.887(6), b = 11.814(7), and c = 16.263(2) A. The structure was solved by MULTAN-82 and refined to R = 0.045 for 1453 observed reflections. The steroid ring A has an 1β-sofa conformation, the rings B and C adopt chair forms, ring D is intermediate between 13β,14α-half chair and 13β-envelope. All rings are trans-fused. In the present structure, O H… N hydrogen bonds link the molecules into chains parallel to α.