Glycine reaction with glucose

In a less straightforward way, D-glucose (393) underwent a Maillard-type reaction with an excess of glycine (394) under microwave irradiation to afford 5-hydroxy-l,3-dimethyl-2(l/f)-quinoxahnone (395) as a major product, Repetition with labeled reactants suggested that the product contained six carbon atoms from the sugar and four from the amino acid on this evidence, a detailed mechanism has been postulated. 

The reaction of glycine and D-glucose at 300° was investigated in buffered acid. The results concerning the formation of pyrazines are presented in Table 1. The additional glycine, in the molar ratio of 2 1 with D-glucose, provided a higher proportion of pyrazines compared with stoichiometric reactions of the two components. This is particularly evident for the formation of trimethylpyrazine. Other components identified in these reaction mixtures were 5, 11, 17, and 23. 

The glucose-glycine reaction has therefore been reinvestigated using glucose labelled with 90 % at C-1. The behavior of a few potential intermediates under similar reaction conditions has also been studied. 

After refluxing creatinine, glycine and D-glucose in diethyleneglycol water 6 1 (v/v) for 20 h, IQ was isolated from the reaction mixture in 2.6 per cent yield (7.6 mg calculated on glucose) and found to be identical (EI-MS, H-NMR, HPLC) with a synthetic sample given by T. Sugimura and also with IQ synthe-... 

Figure 1.2. Differential thermal analysis for the humic acid fraction isolated in NaOH from a sapric histosol (1), from the acid precipitate isolated from products of the reaction of meth-ylglyoxal with glycine (2), and from the acid precipitate formed from the reaction of glucose with glycine (3), alkali lignin (4), casein (5), lignin-casein 3 1 complex (6), and lignin-casein 6 1 complex (7).

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