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本文报道用CuBr_2作溴化剂,以甲醇作溶剂使3β-羟基-5-孕甾烯-20-酮类的21-位直接溴化的方法。该试剂不影响△~5-双键。所得溴化物经碱水解,生成21-羟基-20-酮的边链结构。3β-羟基孕甾-5-烯-20-酮(1)以3摩尔CuBr_2和3摩尔吡啶进行溴化得到21-溴代物(2a),收率71％。若不加入吡啶则生成物为17-甲氧基化合物(3a),收率65％。若用6摩尔CuBr_2进行溴化,则得到21-溴-17-甲氧基化合物(3b),收率54％。2a在67％DMF中用1.2摩尔NaOH水解,得到21-羟基物(2b),收率95％。
This paper reports the direct bromination of 3-hydroxy-5-pregnen-20-ones by CuBr 2 as a brominating agent and methanol as a solvent. This reagent does not affect △ ~ 5-double bond. The resulting bromide is base-hydrolyzed to yield a side chain structure of 21-hydroxy-20-keto. 3β-hydroxypregna-5-en-20-one (1) Bromination with 3 moles of CuBr 2 and 3 moles of pyridine gave 21-bromo (2a) in 71% yield. Without the addition of pyridine, the product was 17-methoxy compound (3a) in a yield of 65%. Bromination with 6 moles of CuBr 2 gave 21-bromo-17-methoxy (3b) in 54% yield. 2a was hydrolyzed with 1.2 molar NaOH in 67% DMF to give 21-hydroxy (2b) in 95% yield.