Biocatalytic Asymmetric Synthesis of Optically Pure Aromatic Propargylic Amines Employing ω-Transaminases

The asymmetric reductive bio-amination of prochiral aromatic propargyl ketones led to the corresponding amines in optically pure form (ee>99%). The (R)- as well as the (S)-enantiomers of the propargylic amines were obtained, employing either (R)-selective omega-transaminases (omega-TAs) originating from Arthrobacter sp. and Aspergillus terreus or an (S)-selective omega-TA from Chromobacterium violaceum. The product propargylic amines were obtained with high conversions (up to 99%). To simplify product isolation, protection of the free amino group to the corresponding acetamides or benzamides was performed without loss of optical puritiy. The final products were isolated in moderate to good yields (33-67% over two steps) in optical pure form without additional purification steps. Although propargyl ketones are described in the literature to be irreversible inhibitors for aminotransferases, suitable omega-transaminases were identified for the amination of these compounds.