(438d) 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. ω-transaminase (ω-TA) is an ideal catalyst for the asymmetric amination as its excellent enantioselectivity and wide substrate scope. In order to shift the equilibrium of reactions catalyzed by ω-TA to the side of amine product, an upgraded N₂ fixation system based on bioelectrocatalysis was developed to realize the conversion from N₂ to chiral amine intermediates. The produced NH₃ was in situ reacted by L-alanine dehydrogenase to perform the alanine generation with NADH as a coenzyme. ω-TA transferred the amino group from alanine to ketone substrates and finally produced desired chiral amine intermediates. The cathode of the upgraded N₂ 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 co-product, pyruvate, was consumed by L-alanine dehydrogenase to regenerate alanine and push the equilibrium to the side of amine. After 10 hours 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). Due to the wide substrate scope and excellent enantioselectivity of ω-TA, the upgraded N₂ fixation system has great potential to produce a variety of chiral amine intermediates for pharmaceuticals and other applications.