Chemo-Enzymatic Synthesis of Pyrazines and Pyrroles.

Abstract

Herein we report the biocatalytic synthesis of substituted pyrazines and pyrroles using a transaminase (ATA) to mediate the key amination step of the ketone precursors. Treatment of α‐diketones with ATA‐113 in the presence of a suitable amine donor yielded the corresponding α‐amino ketones which underwent oxidative dimerization to the pyrazines. Selective amination of α‐diketones in the presence of β‐keto esters afforded substituted pyrroles in a biocatalytic equivalent of the classical Knorr pyrrole synthesis. Finally we have shown that pyrroles can be prepared by internal amine transfer catalyzed by a transaminase in which no external amine donor is required.