Abstract: EPR and ¹³C NMR techniques were used systematically to study the products formed by the reaction of sugar with amino acid. The characteristic hyperfine structure of EPR spectra of the products depended mainly upon the structure of amino acids. The chemical shifts of ¹³C NMR spectra of the products showed that the principal structure would be 2,5-piperazine dione. The results lead to the assumption of the identity as l,4-disubstituted-2,5-piperazme dione. The EPR spectral analyses and the assumed structures were strongly supported by the close agreement between the observed spectra and those simulated on ASPECT 2000 computer. The proposed probable mechanism of the reaction of sugar with amino acid is presented in this paper.

Key words: EPR, ¹³C NMR, Sugar, Amino acid, l,4-disubstituted-2,5-piperazine dione