RESUMEN
2-(2-Acetoxyethyl)cyclohexanone (4) was converted into the lactone (-)-(5) regio- and enantioselectively using 2-oxo-delta 3-4,5,5-trimethylcyclopentenyl acetyl-CoA monooxygenase, an NADPH-dependent Baeyer-Villiger monooxygenase from camphor grown Pseudomonas putida NCIMB 10007. The lactone (-)-(5) was converted into (R)-(+)-lipoic acid in six steps. In contrast cyclopentanone monooxygenase, an NADPH-dependent Baeyer-Villiger monooxygenase from cyclopentanol-grown Pseudomonas sp. NCIMB 9872 selectively oxidized the (S)-enantiomer of the ketone (4) giving better access to optically enriched, naturally occurring lipoic acid.
Asunto(s)
NADH NADPH Oxidorreductasas/metabolismo , Ácido Tióctico/biosíntesis , Biotransformación , Catálisis , Espectroscopía de Resonancia Magnética , Pseudomonas putida/metabolismo , EstereoisomerismoRESUMEN
The biohydrolysis of differently para-substituted styrene oxide derivatives was studied, using whole cells of the fungi Aspergillus niger or Beauveria sulfurescens. These microorganisms proved to be equipped with epoxide hydrolases which are able to achieve these hydrolyses with high enantioselectivity. This allowed the preparation of the optically active epoxides and of the corresponding vicinal diols which were obtained with good to excellent enantiomeric purity. These two microorganisms proved to be enantiocomplementary. A mechanistic study, carried out using a crude lyophilized enzymatic extract from A.niger, indicated via Hammet coefficient plotting that this hydrolysis is very probably due to a general base-catalyzed process.
RESUMEN
The regio- and stereochemistry of the hydrolysis of styrene oxide 1 by two fungi: Aspergillus niger and Beauveria sulfurescens, were studied using H2(18)O labelling experiments. Also, the kinetic parameters of these hydrolyses were determined. We conclude that the epoxide hydrolases of these two fungi operate via different mechanisms.