title: Efficient preparation of steroidal 5,7-dienes of high purity.
abstract: Protected forms of dehydroepiandrosterone, delta 5 cholenic acid, (25R)-26-hydroxycholesterol and diosgenin were converted to the corresponding delta 5,7 dienes by successive treatment with 1,3-dibromo-5,5-dimethylhydantoin (dibromantin), tetrabutylammonium bromide and tetrabutylammonium fluoride. The crude products, which contained the delta 5,7 species contaminated by minor amounts of the delta 5 and delta 4,6 steroids, were purified by silica gel-AgNO3 chromatography to give the following steroids in approximately 99% purity and at least 50% yield: 3 beta-acetoxyandrosta-5,7-dien-17-one, methyl 3 beta-acetoxychola-5,7-dien-24-oate, (25R)-3 beta,26-diacetoxycholesta-5,7-diene and (25R)-3 beta-acetoxyspirosta-5,7-diene. Analogous treatment of acetate derivatives of pregnenolone and stigmasterol gave 3 beta-acetoxypregna-5,7-dien-20-one and 3 beta-acetoxystigmasta-5,7,22-triene in approximately 50% yield but of lower purity. Full 1H and 13C NMR assignments are given for seven delta 5,7 steroid acetates and the corresponding delta 5 starting materials. Coupling constants for rings A, B and C of delta 5,7 steroids are presented and stereochemical assignments have been made for the following 1H NMR signals: the C-11 protons of delta 5,7 steroids, the C-16 protons of sterols and bile acids, the C-22 and C-23 protons of bile acid esters and the C-28 protons of stigmasterol derivatives.
authors: Department of Biochemistry and Cell Biology, Rice University, Houston, Texas 77251-1892.
authors: A U
authors: AU
authors: Siddiqui
authors: W K
authors: WK
authors: Wilson
authors: S
authors: S
authors: Swaminathan
authors: G J
authors: GJ
authors: Schroepfer
mesh_terms: D009682:Magnetic Resonance Spectroscopy; D008722:Methods; D015394:Molecular Structure; D000644:Quaternary Ammonium Compounds; D013237:Stereoisomerism; D013256:Steroids / Q000138:chemical synthesis* / Q000737:chemistry / Q000302:isolation & purification
chemical_list: D000644:Quaternary Ammonium Compounds; D013256:Steroids; C009405:tetrabutylammonium