Structure determination of a novel 3(6H)-pyranone chromophore and clarification of its formation from carbohydrates and primary amino acids

An intensely orange compound, which has recently been evaluated as one of the main colored compounds formed in Maillard reactions of hexoses, could be unequivocally identified as (Z)-2-[(2-furyl) methylidene]-5,6-di(2-furyl)-6H-pyran-3-one (1) by application of several NMR and LC-MS experiments. To clarify its formation, the effectiveness of certain carbohydrate degradation products as precursors of 1 was studied in a quantitative experiment demonstrating hydroxy-2-propanone, furan-2-aldehyde, and 3-deoxy-2-hexosulose as precursors of the colorant. Site-specific labeling experiments with D-1-[¹³C]glucose and D-6-[¹³C]glucose, respectively, were performed to elucidate the formation pathway of 1 involving a cleavage of the hexose skeleton between carbon atoms C(5) and C(6). In addition, pentoses could be shown to generate I via a similar formation pathway involving the 3-deoxy-2-pentosulose.