Sunday, July 29, 2007
P43

The kinetic study on lipase ammonolysis of ethyl 4-chloro-3-hydroxybutanoate in organic media

Jianping Wu1, Yong Jin1, Gang Xu1, Lirong Yang1, and Roger Ruan2. (1) Department of Chemical and Biochemical engineering, Zhejiang University, Zheda Road 38, Hangzhou, China, (2) Department of Bioproducts and Biosystems Engineering, University of Minnesota, 1390 Eckles Ave, Saint paul, MN 55108

Biocatalysis in nonaqueous media is becoming increasingly important in organic synthesis. Lipases are the most used enzyme, especially in transesterification reactions. However, in recent years the ammonolysis reaction catalyzed by lipase has also been shown to be a useful tool for the organic chemists. The preparation of different N-unsubstituted amides, as well as the resolution of esters by means of this methodology have been some of the contributions to this field. In connection with these previous studies, we now present a more detailed research of  the lipase-catalyzed resolution of ethyl 4-chloro-3-hydroxybutanoate (CHBE) by aminolysis to explore the kinetics and mechanism of the reaction. 99% ee value of (R)-CHBE and 57.7% conversion of CHBE could be achieved after reaction for 35h. The kinetics were found to obey the Ping-Pong bi-bi mechanism. The enantiomeric ratio E in enzymatic kinetic resolutions was often temperature dependent. Through the theory of temperature effects on the E, we got the racemic temperature of this reaction is 352K. And it is confrimed by the experiment data.

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