Insight into the mechanochemistry of the Maillard reaction: degradation of Schiff bases via 5-oxazolidinone intermediate

摘要

With the emergence of mechanochemistry as a fast and efficient synthetic methodology, we reported earlier that ball milling of glucose with histidine leads to the formation of reaction mixtures rich in Schiff bases. Upon subsequent thermal treatments,these mixtures exhibited enhanced reactivity generating more browning and pyrazine-rich volatiles, compared to non-milled samples. To rationalize these observations, we further investigated the mechanochemistry of the Maillard reaction using glycolaldehyde and histidine or phenylalanine as model systems. The conversion of Schiff bases into reactive 5-oxazolidi-none in these model systems was proposed as the basis of the observed enhanced reactivity. Furthermore, the formation of 5-oxazolidinone in theball-milled samples was verified through direct spectroscopic observation of its characteristic FTIR absorption band between 1780 cm-1 and 1810 cm-1 and through the identification of its specific degradation products. The important role of the carboxylicacid moiety in enabling the formation of reactive 5-oxazolidinone intermediate that facilitates its subsequent decarboxylation and formation of downstream degradation products such as dihydropyrazines and Strecker aldehydes were elucidated.