Crystal and Molecular Structures of Modified Progestagens (I). 17α‐Cyanomethyl‐17β‐hydroxy‐estr‐4‐en‐3‐one, C 20 H 27 NO 2

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 2 1 2 1 2 1 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, OH… N hydrogen bonds link the molecules into chains parallel to α.