Deracemization carboxylic acids

Although decarboxylation reaction seems to be a simple one-carbon removing reaction, it is demonstrated that this reaction is a unique and useful reaction in the preparation of optically active carboxylic acids. If the starting material is a racemic carboxylic acid, the optically active compound can be obtained via symmetrization by chemical carboxylation followed by asymmetrization via enzymatic reaction. Accordingly, the whole process can be said as chemicoenzymatic deracemization (Fig. 24). 

The final example constitutes one of the few deracemizations of carboxylic acids... 

Kato, D., Mitsuda, S., and Ohta, H. 2002. Microbial deracemization of a-substituted carboxylic acids. Org. Lett., 4, 371-373.107. 

Enantioenriched a-substituted carboxylic acids have been prepared using the growing cell system of Nocardia diaphanozonaria JCM3208. Racemic 2-aryl and 2-aryloxypropanoic acid could be deracemized leading to the recovery of the (R)-enantiomer in high yield (>50%) and 69% ee (Scheme 4.44). A new biocatalytic... 

K. and Ohta H., Microbial deracemization of a-substituted carboxylic acids control of the reaction path. Tetrahedron Asymmetry, 2004, 15, 2965-2973 (h) Kato, D., Mitsuda S. and Ohta, H., Microbial deracemization of a-substituted carboxylic acids substrate specificity and mechanistic investigation, /. Org. Chem., 2003, 68, 7234-7242 (i) Mitsukura, K., Yoshida, T. and Nagasawa T., Synthesis of (R)-2-phenylpropanoic acid from its racemate through an isomerase-involving reaction by Nocardia diaphanozonaria, Biotechnol Lett., 2002, 24, 1615-1621. 

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