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

Model studies using d -[ 13 C]glucoses and a series of C 2, C 3, and C 4 dicarbonyl compounds with labeled [ 15 N/ 13 C]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.