Stereoselective enzymatic oxidation and reduction system for the production of d(−)-pantoyl lactone from a racemic mixture of pantoyl lactone

Abstract

A novel enzymatic process for the synthesis of d(−)-pantoyl lactone from a racemic mixture of pantoyl lactone is described. The process involves the stereospecific oxidation of the l(+)-isomer of pantoyl lactone to ketopantoyl lactone followed by its asymmetric reduction to the d(−)-isomer. The oxidation is carried out with cells of Nocardia asteroides AKU 2103 as the catalyst, which convert only the l(+)-isomer of pantoyl lactone to ketopantoyl lactone without any modification of the remaining d(−)-isomer. With 80 g l −1 dl-pantoyl lactone as the substrate, >90% of the added l(+)-isomer was converted to ketopantoyl lactone under the optimum reaction conditions. The ketopantoyl lactone that accumulated in the reaction mixture was almost specifically converted to the d(−)-isomer of pantoyl lactone on incubation with cells of Candida parapsilosis IFO 0784. Since this process is simple and requires no reracemization step, which is necessary for conventional chemical resolution, it is highly advantageous for the practical synthesis of d(−)-pantoyl lactone.