| 摘要 |
9(11)-Ene compounds of formula A.3 are converted to 12-keto compounds of formula A.5 via a mixture of compounds of formula, A.4.A. and A.6.A, and optionally A.4:wherein the mixture is formed by compound A.3 undergoing allylic oxidation with an alkyl hydroperoxide in the presence of a co-oxidant, preferably t-butyl hydroperoxide with sodium hypochlorite (NaOC1), and conversion of this A.4.A, A.6.A, and optionally A.4, mixture to A.5 is effected by first reacting these compounds under hydrogenation conditions, for example in the presence of a platinum group metal catalyst e.g. Pd/C or PtO2, and subsequently reacting the product formed under oxidative conditions such as pyridinium chlorochromate (PCC); in each instance Pg is a hydroxyl protecting group; R1is the 17-side chain of a bile acid, as defined in claim 1, with the carboxyl functionality of the side chain optionally being esterified with a C1-6alkyl group, and R2is hydrogen; or R1and R2together with the carbon atom to which they are attached form a keto group or keto protecting group; and R3-R5are C1-3alkyl. Compounds of formula A.4.A are claimed per se as are several other intermediates. Certain alternative forms of the A.3 to A.5 process are also outlined. |
