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-pyridyloxirane by the Aspergillus niger epoxide hydrolase (EH) has been explored. This was used to perform a gram scale preparation of these epoxides of (S) absolute 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 enantiopure form (ee > 98%). Interestingly, it was shown that this biotransformation could be achieved using plain water instead of buffer solution, an important improvement as far as downstream processing of an eventual industrial process is concerned. Neither of these substrates could be obtained in reasonable enantiomeric purity and yield using the nowadays most efficient metal-based catalysts.