Chemo-enzymatic D-enantiomerization of DL-lactate.
We investigated the total conversion of racemic lactate, L-lactate, and pyruvate into D-lactate, which is very useful as a starting material for the synthesis of chiral compounds and much more valuable than the L-enantiomer by means of coupling of L-specific oxidation of the racemate with L-lactate oxidase and non-enantiospecific reduction of pyruvate to DL-lactate with sodium borohydride. In this one-pot system, L-lactate was enantiospecifically oxidized to an achiral product, pyruvate, which was chemically reduced to DL-lactate leading to a turnover. Consequently, either DL-lactate, L-lactate, or pyruvate was fully converted to the D-enantiomer. We optimized the reaction conditions: DL-lactate was converted to D-lactate in 99% of the theoretical yield and with more than 99% enantiomeric excess. DL-alpha-Hydroxybutyrate and alpha-ketobutyrate were converted also to D-alpha-hydroxybutyrate in the same way, though slowly.
Department of Biotechnology, Faculty of Engineering, Kansai University, Suita-Shi, Osaka-Fu 564-8680, Japan. oikawa@ipcku.kansai-u.ac.jp
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D001894:Borohydrides / Q000378:metabolism; D019344:Lactic Acid / Q000737:chemistry* / Q000302:isolation & purification / Q000378:metabolism*; D006899:Mixed Function Oxygenases / Q000378:metabolism*; D008968:Molecular Conformation; D010084:Oxidation-Reduction; D019289:Pyruvic Acid / Q000378:metabolism; D013237:Stereoisomerism; D013997:Time Factors
D001894:Borohydrides; D019344:Lactic Acid; D019289:Pyruvic Acid; C025364:sodium borohydride; D006899:Mixed Function Oxygenases; C021497:lactate 2-monooxygenase