Condensation of vanillin with hippuric acid in presence of acetic anhydride gives a-benzoylamino-3-methoxy-4-acetoxycinnamic acid which, under the conditions of the experiment, loses the elements of water to give the related azlactone. This view of the reaction is supported by the fact that when esters of hippuric acid are used in this condensation lactones are not obtained. The ring may be opened by warming the lactone with 3 N caustic alkali solution. More drastic treatment causes further hydrolysis with the loss of benzoic acid and ammonia, and gives the related pyruvic acid. Similar results were obtained by starting with aceturic instead of hippuric acid. Several substitution products of vanillin were tested
