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薯蓣皂苷元经甲基化、开环反应得(25R)-3β-甲氧基胆甾-5-烯-16β,26-二醇,用叔丁基二甲基氯硅烷选择性保护26-位羟基后,依次经磺酰化、氢化铝锂还原得(25R)-26-叔丁基二甲硅氧基-3β-甲氧基胆甾-5-烯,经四丁基氟化铵脱保护、Jones氧化得(25R)-3β-甲氧基胆甾-5-烯-26-酸,再将3-位甲氧基转变为乙酰氧基后,经氢氧化钾皂化制得(25R)-胆固醇酸,总收率26.8%。
Diosgenin was methylated to give (25R) -3β-methoxycholest-5-ene-16β, 26-diol by ring-opening reaction and protected by tert- butyldimethylchlorosilane Hydroxy group followed by sulfonylation and reduction with lithium aluminum hydride to give (25R) -26-tert-butyldimethylsilyloxy-3β-methoxycholest-5-ene and deprotection with tetrabutylammonium fluoride , Jones oxidation of (25R) -3β-methoxycholest-5-ene-26-acid, and then 3-position methoxy into acetoxy group, the saponification of potassium hydroxide (25R) - Cholesteric acid, the total yield of 26.8%.