The thiamine-dependent enzyme(1R,2S,5S,6S)-2-succinyl-5-enolpyruvyl-6-hydroxyl-3-cyclohexene-1-carboxylate(SEPHCHC) synthase,also known as MenD,catalyzes a Stetter-like reaction in the biosynthesis of vitamin K.It is found to catalyze a novel reductive C N bond ligation reaction between nitroarenes and-ketoacids to form N-hydroxamates.This reaction likely proceeds through an enzyme-mediated,slow two-electron reduction of the nitroalkanes to form a nitroso intermediate,which serves as the electrophilic acceptor of the ketoacid-derived acyl anion.The involvement of the nitroso intermediate is supported by the fact that similar N-hydroxamates are readily formed at a much higher rate when nitroso compounds replace the nitro substrates in the chemoenzymatic reactions.These results demonstrate that the thiamine-dependent enzyme is able to catalyze novel,nonnative reactions that may find new chemoenzymatic applications. The thiamine-dependent enzyme (1R, 2S, 5S, 6S) -2-succinyl-5-enolpyruvyl-6-hydroxyl-3-cyclohexene- 1-carboxylate (SEPHCHC) synthase, also known as MenD, catalyzes a Stetter-like reaction in the biosynthesis of vitamin K. It is found to catalyze a novel reductive CN bond ligation reaction between nitroarenes and-ketoacids to form N-hydroxamates. This reaction likely proceeds through an enzyme-mediated, slow two-electron reduction of the nitroalkanes to form a nitroso intermediate, which serves as the electrophilic acceptor of the ketoacid-derived acyl anion. The involvement of the nitroso intermediate is supported by the fact that similar N-hydroxamates are readily formed at a much higher rate when nitroso compounds replace the nitro substrates in the chemoenzymatic reactions.These results demonstrate that the thiamine-dependent enzyme is able to catalyze novel, nonnative reactions that may find new chemoenzymatic applications.