Upgraded Bioelectrocatalytic N2 Fixation: From N2 to Chiral Amine Intermediates

Enantiomerically pure chiral amines are of increasing value in the preparation of bioactive compounds, pharmaceuticals, and agrochemicals. omega-Transaminase (omega-TA) is an ideal catalyst for asymmetric amination because of its excellent enantioselectivity and wide substrate scope. To shift the equilibrium of reactions catalyzed by omega-TA to the side of the amine product, an upgraded N-2 fixation system based on bioelectrocatalysis was developed to realize the conversion from N-2 to chiral amine intermediates. The produced NH3 was in situ reacted with L-alanine dehydrogenase to generate alanine with NADH as a coenzyme. omega-TA transferred the amino group from alanine to ketone substrates and finally produced the desired chiral amine intermediates. The cathode of the upgraded N-2 fixation system supplied enough reducing power to synchronously realize the regeneration of reduced methyl viologen (MV center dot+) and NADH for the nitrogenase and L-alanine dehydrogenase. The coproduct, pyruvate, was consumed by L-alanine dehydrogenase to regenerate alanine and push the equilibrium to the side of amine. After 10 h of reaction, the concentration of 1-methyl-3-phenylpropylamine achieved 0.54 mM with the 27.6% highest faradaic efficiency and >99% enantiomeric excess (ee(p)). Because of the wide substrate scope and excellent enantioselectivity of omega-TA, the upgraded N-2 fixation system has great potential to produce a variety of chiral amine intermediates for pharmaceuticals and other applications.