反应详情

The synthetic protocols to be followed for preparing the preferred side chain derivatized cholest-8(14)-en-15-one compounds are known to those of skill in the art. For example, 3β-acetoxy-24-hydroxy-5α-chol-8(14)-en-15-one is converted to 3β-acetoxy-15-keto-5α-chol-8(14)-en-24-oic acid by oxidation of the alcohol with Jones reagent and subsequent hydrolysis of the C-3 acetate. Compounds such as 3β,24-dihydroxy-5α-cholest-8(14)-en-15-one, 3β,25-dihydroxy-5α-cholest-8(14)-en-15-one and 3β-hydroxy-5α-cholesta-8(14),24-dien-15-one arise from a common intermiediate, viz., 3β-acetoxy-15-keto-5α-chol-8(14)en-24-al. The C-24 aldehyde is readily prepared from 3β-acetoxy-24-hydroxy-5α-chol-8(14)-en-15-one by oxidation with periodinane according to the method of Dess and Martin. Wittig olefination of 3β-acetoxy-15-keto-5α-chol-8(14)en-24-al yields a 24-olefin, 3β-acetoxy-5α-cholesta-8(14),24-dien-15-one which may be hydrolyzed to 362 -hydroxy-5α-cholesta-8(14),24-dien-15-one. Hydration of the 3β-acetoxy-5α-cholesta-8(14),24-dien-15-one and hydrolysis of the ester yields either 3β,24-dihydroxy-5α -cholest-8(14)-en-15-one or 3β,25-dihydroxy-5α-cholest-8(14)-en-15-one, depending upon the reaction conditions selected. For example, oxymercuration of the 24-olefin will result in 3β,25-dihydroxy-5α-cholest-8(14)-en-15-one, while hydroboration will give 3β,24-dihydroxy-5α-cholest-8(14)-en-15-one. The 3β-acetoxy-24-hydroxy-5α-chol-8(14)-en-15-one is converted to 3β-acetoxy-5α-chola-8(14),23-dien-15-one by treatment with ortho-nitrophenyl selenocyanate, followed by hydrogen peroxide. Reaction of this 23-olefin with 2-iodoheptafluoropropane produces 3β-acetoxy-23ξ-iodo-25,26,26,26,27,27,27-heptafluoro-5α-cholest-8(14)-en-15-one. Subsequent reduction with tributyl tin hydride and deprotection of the C-3 alcohol yields the F7 analog of the starting sterol, viz., 3β-hydroxy-25,26,26,26,27,27,27-heptafluoro-5α-cholest-8(14)-en-15-one. Alternatively, the free hydroxy in 3β-acetoxy-24-hydroxy-5α-chol-8(14)-en-15-one may be converted to a leaving group and replaced by nucleophilic substitution. Transformation of 3β-acetoxy-24-hydroxy-5α-chol-8(14)-en-15-one to the C-24 tosylate followed by reaction with dimethylamine and saponification gives the 25-aza analog of the cholest-8(14)-en-15-one, 3β-hydroxy-24-dimethylamino-5α-cholest-8(14)-en-15-one.