Crystal and molecular structures of (20R)-20-aminopregn-5-en-3β-ol and (20S)-20-aminopregn-5-en-3β-ol hydrochloride

Abstract

Two epimers of 20-aminopregn-5-en-3β-ol differing in configuration at C(20) have been synthesized and their structures have been determined by single crystal X-ray diffraction methods. The (20R)-epimer (1) crystallized in the orthorhombic system, space group P212121, with a = 9.0432(5) A, b = 13.3446(7) A, c = 15.1086(8) A, and Z = 4. The (20S)-epimer hydrochloride hydrate (2 hydrate) crystallized in the monoclinic system, space group C2, with a = 31.0501(3) A, b = 11.8221(1) A, c = 11.9703(2) A, β = 98.5140(10)°, and Z = 8. The absolute configurations at the C(20) chiral centers for the title compounds were unequivocally established for the first time. The asymmetric unit cell of 2 hydrate contained two steroid molecules, A and B, two hydrochloride molecules, and two molecules of water. The crystal packing for both diastereomers was strongly influenced by the presence of intermolecular hydrogen bonding. The molecules of 1 were linked in a head-to-tail fashion via hydrogen bonds between the hydroxyl group of the ring A and the amino group of the side chain of the ring D. The two molecules A and B of 2 hydrate were held together in head-to-head and head-to-tail fashions by a three-dimensional network of hydrogen bonds involving chlorine ions, disordered water molecules, and hydroxyl–amino groups interactions.