Upgraded Bioelectrocatalytic N Fixation: From N to Chiral Amine Intermediates.

Enantiomerically pure chiral amines are of increasing value in the preparation of bioactive compounds, pharmaceuticals, and agrochemicals. ω-Transaminase (ω-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 ω-TA to the side of the amine product, an upgraded N fixation system based on bioelectrocatalysis was developed to realize the conversion from N to chiral amine intermediates. The produced NH was in situ reacted with l-alanine dehydrogenase to generate alanine with NADH as a coenzyme. ω-TA transferred the amino group from alanine to ketone substrates and finally produced the desired chiral amine intermediates. The cathode of the upgraded N fixation system supplied enough reducing power to synchronously realize the regeneration of reduced methyl viologen (MV) 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). Because of the wide substrate scope and excellent enantioselectivity of ω-TA, the upgraded N fixation system has great potential to produce a variety of chiral amine intermediates for pharmaceuticals and other applications.