NMR identification of an acyl-adenylate intermediate in the aryl-aldehyde oxidoreductase catalyzed reaction

A new one-pot synthesis was designed to prepare benzoyl-AMP under anhydrous conditions in N,N-dimethylformamide. Reaction of benzoic acid with N,N'-carbonyldiimidazole and subsequently with 5'-adenosyl monophosphate gave the mixed anhydride in 76% isolated yield. The structure of benzoyl-AMP was confirmed by mass spectroscopy and 1H-, 31P-, and 13C-NMR. The purity of the preparation was greater than 98% as indicated by 31P- and 13C-NMR. Purified aryl-aldehyde oxidoreductase was incubated in NMR tubes together with either carboxy-13C-benzoyl-AMP or carboxy-13C-benzoic acid to demonstrate that benzoyl-AMP is an active intermediate during the enzymatic reduction of benzoic acid to benzaldehyde.