Asymmetric Reduction of Ethyl 4-Chloro-3-oxobutanoate to Ethyl (S)-4-Chloro-3-hydroxybutanoate Catalyzed by Aureobasidium pullulans in an Aqueous/Ionic Liquid Biphase System

The asymmetric reduction of ethyl 4-chloro-3-oxobutanoate (COBE) to ethyl (S)-4-chloro-3-hydroxybutanoate ((S)-CHBE) catalyzed by Aureobasidium pullulans CGMCC 1244 was performed in an aqueous/ionic liquid biphase system to improve the productivity and optical purity of (S)-CHBE. The influences of reaction parameters such as shaking rate, phase volumetric ratio, reaction temperature, initial substrate concentration, and pH were studied. In the aqueous/[bmim]PF6 biphase system and under the optimum reaction conditions of 30 °C, pH 6.6, rotation speed 180 r/min, and reaction time of 8 h, the conversion of COBE, the enantiomeric excess, and the concentration of (S)-CHBE were 95.6%, 98.5%, and 47.1 g/L, respectively. When the substrate was fed in batches under the condition of pH 6.6, the accumulated product concentration could reach up to 75.1 g/L.