【摘要】 利用活性酵母细胞催化 4 氯乙酰乙酸乙酯 (COBE)的不对称还原可以直接合成具有光学活性的 4 氯 3 羟基丁酸乙酯(CHBE) .实验发现 ,在水相体系中主要生成 D (S) 型产物 ,COBE的转化率及CHBE的收率和光学选择性都比较高 .考察了底物和产物的浓度、辅助底物的种类和浓度、体系的pH和温度以及菌体培养条件等因素对反应的影响 .结果表明 ,在较低COBE浓度下R型产物占优 ,在高浓度下主要是S型产物 ;较高的反应温度有利于S型产物的生成 ,pH≈ 8 0时可获得较高的S型产物选择性 ;产物CHBE对COBE的还原反应具有一定的抑制作用 .在酵母催化COBE还原的同时需要一定的辅助底物来再生辅酶NAD(P)H ,利用乙醇、异丙醇和仲丁醇作辅助底物可获得较高的立体选择性 .对数生长期和厌氧条件培养的细胞对生成S型产物较有利更多还原

【Abstract】 The asymmetric reduction of ethyl 4-chloro-3-oxobutanoate (COBE) to optically active ethyl 4-chloro-3-hydroxybutanoate (CHBE) catalyzed by yeast cells in aqueous phase was investigated. The reduction was conducted in Tris-HCl buffer, and the concentrations of COBE and CHBE and the optical purity of product were determined by capillary GC and HPLC equipped with a chiralcel OB column, respectively. The product was mainly D-(S)-CHBE. Both the yield and the stereo-selectivity of CHBE were higher for the reaction. However, the product was mainly R-CHBE when the initial concentration of COBE was low, and the product was mainly S-CHBE when the initial concentration of COBE was higher. The CHBE had a few of inhibition effects on the reaction. In the COBE reduction, a co-substrate was required to regenerate the NAD(P)H. Ethanol, isopropanol and secondary butyl alcohol as the co-substrate were advantageous to the stereo-selectivity of S-CHBE, but glucose as the co-substrate could achieve higher yield. The higher temperature and pH 8 0 were favorable to the production of S-CHBE. The cells in logarithmic growth phase and cultured under anaerobic condition were also favorable to the stereo-selectivity of S-CHBE. 92% for yield and 90% for ee of S-CHBE were obtained respectively under appropriate reaction conditions.更多还原