Ring-C aromatic steroids. Part 5. C-17 Hydroxylation and side-chain degradation of 18-nor-17α(H)- and -17β(H)-pregna-4,8,11,13-tetraene-3,20-dione. X-Ray structure of 17β-hydroxy-18-nor-17β(H)-pregna-4,8,11,13-tetraene-3,20-dione

Abstract

The procedure for 17-hydroxylation of pregnan-20-ones using oxygen, butoxide, and triethyl phosphite was extended to steroid analogues with aromatic C-rings, viz. 18-nor-17α(H)- and -17β(H)-pregna-4,8,11,13-tetraene-3,20-dione (and to 1-acetylindan). At temperatures higher than that we adopted (–50 °C), side-chain cleavage to give the 17-ketone (or equivalent) became prominent. Results of an X-ray crystallographic study on one of the two 17-epimeric C-aromatic products, 17β-hydroxy-18-nor-17β(H)-pregna-4,8,11,13-tetraene-3,20-dione, are presented. The crystals are orthorhombic, space group P2₁2₁2₁, with four molecules in a cell of dimensions a= 9.643(3), b= 17.043(4), c= 10.015(3)Å. The structure was solved by direct methods and refined by full-matrix least-squares calculations; R= 0.059 for 1 219 observed reflections. Ring A has a 1α,2β-half -chair conformation, ring B is in a 5α,6β-half-chair conformation, aromatic ring C is planar, and ring D is a C(16)β-envelope. Molecules are linked to form infinite chains by intermolecular O–H ⋯ O hydrogen bonds [O ⋯ O 2.801 (4)Å].