Elucidation of the Mechanism of Pyrazinone Formation in Glycine Model Systems Using Labeled Sugars and Amino Acids

Abstract

Model studies using d-[13C]glucoses and a series of C2, C3, and C4 dicarbonyl compounds with labeled [15N/13C]glycines have indicated that methyl-substituted pyrazines and pyrazinones formed in these model systems have a common intermediate. The labeling studies have also helped to identify a new chemical transformation of α-dicarbonyls, affected by the amino acid, that lead to the addition of the C-2 atom of the amino acid to the α-dicarbonyl compounds, instead of the amino group as in the case of the Strecker-type interaction between the two reactants. Thus, glyoxal and pyruvaldehyde can be transformed into pyruvaldehyde and 2,3-butanedione, respectively, by the amino acid. Two pathways of formation of pyrazinones were distinguished on the basis of the labeling experiments, one involving the reaction of 3 mol of glycine and the other the interaction of the dipeptide glycylglycine with an α-dicarbonyl compound. Keywords: Amadori; decomposition mechanisms; Maillard reaction; 13C-labeled glucose; [15N]- an...