The para acetate ester azlactone of vanillin 2 was synthesized from vanillin 1 and hydrolyzed with sodium hydroxide. The yielded product 3 was investigated with X-ray Crystallographic and nuclear magnetic resonance techniques. Compound 3 crystallized in the orthorhombic Pbca space group (Z = 8) and with cell dimensions a = 14.732(2), b = 12.756(3), c = 12.747(6)Å revealing the enolate tautomer and not the keto form of 3-methoxy-4-hydroxyphenylpyruvic acid as the acetate ester. The structure exhibited the pyruvic acid side chain in the trans extended conformation. A single proton on the benzylic carbon atom further suggested the existence of the enolate tautomer form of 3 in solution. The chemical shift values and peak integration in the NMR spectra add additional support to this finding.