CRYSTAL-STRUCTURE OF TETRAHYDROCORTISOL

The crystal structure of tetrahydrocortisol (3a,11 beta,17 alpha,21-te trahydroxy-5 beta-pregnan-20-one) C21H34O5, has been determined by X-r ay diffraction using CuK alpha radiation. The crystals are orthorhombi c, P2(1)2(1)2(1) with a = 7.696(5), b = 10.227(2), c = 23.688(5) Angst rom and Z = 4. The structure was solved by direct methods and refined to a final R-value of 0.053 with 1714 observed reflections. The rings A, B, C, D are cis, trans, and trans fused, respectively. The rings, A , B, C, have almost perfect chair conformations and D has a distorted envelope conformation. The steroid skeleton as a whole is somewhat con vex toward the beta-side. The molecules are held together by a three-d imensional network of hydrogen bonds. Despite the similar cell constan ts and common space group of the title compound with cortisone and 17 alpha-hydroxyprogesterone, they are not isostructural.