Identification of a Chromogen in the Assay of Hippuric Acid with Acetic Anhydride, Pyridine, and 4-(Dimethylamino)benzaldehyde

Article abstract of DOI:10.1021/ac00236a032

A yellow chromogen, formed in the assay system for hippuric acid which consists of acetic anhydride, pyridine, and 4-(dimethylamino)benzaldehyde, was isolated, and the structure was determined to be 4-(1-acetyl-4(1H)-pyridylidene)-2-phenyl-2-oxazolin-5-one.The structure was confirmed by the chemical conversion to known compounds as well as by NMR spectra.The conversion was accomplished by hydrolysis of the chromogen to 4-((benzoylamino)methyl)pyridine, 4-(aminomethyl)pyridine, and benzoic acid via 5-hydroxy-2-phenyl-4-(4-pyridyl)oxazole. 4-(Dimethylamino)benzaldehyde included in the assay system increased the production of the chromogen.The formation mechanism of the chromogen via an intermediate susceptible to oxidation was proposed.