Enzymatic kinetic resolution of tropic acid

A new strategy has been developed for the CAL-B catalysed kinetic resolution of tropic acid by which both enantiomers of tropic acid can be obtained in good enantiomeric excess. (R)-Tropic acid was synthesised with 90% ee and (S)-tropic acid butyl ester in 99% ee by the hydrolysis of tropic acid butyl ester. The other enantiomers were available through the enzymatically catalysed reaction of tropic acid lactone with butanol to give (S)-tropic acid lactone and (R)-tropic acid ester in >98% ee.

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(R)-3-Hydroxy-2-phenyl-propionic acid butyl esterC13H18O3[α]D25=+40.0 (c 3.4, CHCl3)

(S)-3-Phenyl-oxetan-2-oneC9H8O2[α]D25=+24.0 (c 4.0, CHCl3)