Microbiological transformations. 47. A step toward a green chemistry preparation of enantiopure (S)-2-, -3-, and -4-pyridyloxirane via an epoxide hydrolase catalyzed kinetic resolution

The biocatalyzed hydrolytic kinetic resolution of 2-, 3-, and 4-pyridyloxir ane by the Aspergillus niger epoxide hydrolase (EH) has been explored. This was used to perform a gram scale preparation of these epoxides of (S) abso lute configuration using a process performed at a concentration as high as 10 g/L (82 mM). All three epoxides have been obtained in a nearly enantiopu re form (ee > 98%). Interestingly, it was shown that this biotransformation could be achieved using plain water instead of buffer solution, an importa nt improvement as far as downstream processing of an eventual industrial pr ocess is concerned. Neither of these substrates could be obtained in reason able enantiomeric purity and yield using the nowadays most efficient metal- based catalysts.