期刊
JOURNAL OF MOLECULAR CATALYSIS B-ENZYMATIC
卷 66, 期 1-2, 页码 113-119出版社
ELSEVIER
DOI: 10.1016/j.molcatb.2010.04.003
关键词
(R,S)-Pyrazolides; Lipases; Hydrolysis; Kinetic analysis; Substituent effects
资金
- National Science Council [NSC 97-2221-E-182-018-MY3]
With hydrolysis of (R,S)-azolides in water-saturated methyl tert-butyl ether ( MTBE) via Candida antarctica lipase B (CALB) as the model system, (R,S)-pyrazolides containing a leaving 3-, 4- or 3,4-substituted-pyrazole moiety are selected as the best substrates for preparing various optically pure carboxylic acids containing an a-chiral center. Great improvements of enzyme activity for the (R)-enantiomers with excellent enantioselectivity (V-R/V-S > 100) are obtainable, if (R,S)-pyrazolides containing a leaving 3- or 3,4-substituted-pyrazole moiety are employed for the hydrolysis or alcoholysis by methanol in anhydrous MTBE. A detailed kinetic analysis for (R,S)-N-2-phenylpropionylpyrazoles indicates that a bulky 3-substituent such as 3-(3-bromophenyl) or 3-(2-pyridyl) in the leaving pyrazole moiety has profound effects on decreasing the nucleophilic attack and proton transfer of catalytic serine for the slow-reacting enantiomer in anhydrous MTBE, as well as that and substrate affinity for both enantiomers in water-saturated MTBE. The resolution platform is also successfully applied to the hydrolysis of (R,S)-pyrazolides in water-saturated cyclohexane via Candida rugosa lipase (Lipase MY) having opposite enantioselectivity to CALB. Crown Copyright (C) 2010 Published by Elsevier B.V. All rights reserved.
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