TRIHYDROXYCHOLESTA-5,7-DIENES

摘要

1508043 1,3,24 - Trihydroxy - cholesta - 5,7- dienes and their derivatives TEIJIN Ltd 4 June 1975 [18 June 1974 9 Dec 1974 (3) 27 Dec 1974 (4)] 44013/76 Divided out of 1508042 Heading C2U Novel steroids of the formula (wherein R 1 , R 2 and R 3 are each H or a protective group removable without changing the structure of the rest of the molecule), including the individual 24-epimers and their mixtures, are prepared by allylic bromination and dehydrobromination of the corresponding 7,8- saturated steroids, in turn prepared by reacting 1α,2α - epoxy - 24 - keto - cholesta - 4,6 - dien- 3-one with an alkali metal and a proton donor in the presence of C.NH 3 or a liquid amine and, when required, protecting one or more of the OH groups. Product ols of the above formula may also be protected, or protecting groups may be removed from products containing protected OH groups. Preferably the #5-triols (epimeric mixture) are protected before bromination, particularly by benzoylation (the benzene ring being optionally substituted) in the 3- and 24- positions with optional protection in the 1-position, and are also separated by chromatography using a carrier at least containing SiO 2 into the 24(R)- and 24(S)-epimers after protection but before bromination. Following dehydrobromination and hydrolysis of any protecting groups, the 1α,3#,24(S)- or 1α,3#,24(R)-trihydroxycholesta-5,7-diene or a mixture of the epimers may be recovered by contacting the product as a solution in an inert organic solvent with a carrier containing SiO 2 and having adsorbed thereon non-metallic silver. This serves to separate the required #5,7-compound from any contaminant #4,6-isomer. 1α,2α - Epoxy - 24 - ketocholesta - 4,6 - dien - 3- one is prepared from fucosterol via 24-ketocholesterol and 24 - keto - cholesta - 1,4,6 - trien- 3-one.