X-Ray crystallographic determination of the structure of the p-bromophenylboronate ester of 17α,20β,21-trihydroxypregn-4-en-3-one

Abstract

The p-bromophenylboronate ester formed by 17α, 20β,21-trihydroxypregn-4-en-3-one has been shown by X-ray crystallography to have a six-membered ring structure involving the 17- and 21-hydroxy-groups. The dioxaborinane ring has an envelope-like conformation in which C(20) is the out-of-plane atom. The hydroxy-group at C(20) is not co-ordinated to boron, O ⋯ B being 3.05 Å. Crystals of 20β-hydroxy-3-oxopregn-4-ene-17α, 21-diyl p-bromophenylboronate are orthorhombic, space group P2₁2₁2₁, with a= 16.85(3), b= 13.29(2), c= 11.08(1)Å, Z= 4. The structure was determined from diffractometer data by Patterson and tangent-formula procedures, and least-squares refinement converged at R 9.6% over 699 reflections.