GB748958A - Improvements in or relating to the preparation of steroid substances - Google Patents

Abstract

The invention comprises 3-keto-4-bromo-allosteroids and a process for their preparation by reduction of a 2:4-dibromo-3-keto-allosteroid to remove one atom equivalent of bromine, and separation of the 3-keto-4-bromo compound from the mixture thus obtained. The 3-keto-4-bromo-allosteroids may be subsequently dehydrohalogenated to yield 3-keto-D 4-steroids. Specified reducing agents are chromous salts, titanous chloride, titanous sulphate, hydrogen iodide, zinc-copper couple; and the reaction is preferably effected in a polar organic solvent, e.g. methanol, ethanol, acetone, or acetic acid. The dehydrohalogenation process may be effected using dimethyl formamide, 2:4-dinitrophenylhydrazine, collidine, or semicarbazide, decomposing any carbonyl derivative produced by treatment with a carbonyl exchange reagent, e.g. pyruvic acid. In examples (1) 2:4-dibromo-3-ketocholestane in acetone is treated with aqueous chromous chloride under nitrogen, yielding 4-bromo-3-keto cholestane. (2) 21 - acetoxy - 2:4 - dibromo - 17 a - hydroxy-3:11:20 - triketo allopregnane in cooled acetone-methanol is treated with chromous chloride-hydrochloric acid, yielding 21-acetoxy-4 - bromo - 17a - hydroxy - 3:11:20 - triketo allopregnane on fractional crystallization of the product. (3) Subsequent treatment of the 4-bromoallopregnane with semicarbazide gives cortisone 21-acetate 3-semicarbazone, which is then stirred with pyruvic acid-acetic acid to yield cortisone 21-acetate. (4) 2a :4a -dibromo3-ketocholestane is reduced as in (1) with chromous acetate to 4a -bromo-3-ketocholestane. (5) 21 - acetoxy - 17a - hydroxyallopregnane-3:11:20 - trione - 20 - ethylene ketal (prepared from dihydroallocortisone 21-acetate by hydrolysis of the ester group formation of the 3:20-bisethylene ketal, and re-acetylation and splitting of the 3-ethylene ketal group), is brominated in methylene chloride-ether to give the 2a :4a -dibromo derivative, which is then reduced with chromous chloride to 21-acetoxy-4a - bromo - 17a - hydroxyallopregnane-3:11:20 - trione - 20 - ethylene ketal, which is treated as in (3) to give the 20-ethylene ketal of cortisone 21-acetate. Specifications 746,488 and 748,779 are referred to.