SYNTHESIS OF THE MAILLARD REACTION .2. INFLUENCE OF MALONDIALDEHYDE ON THE MAILLARD DEGRADATION OF AMADORI COMPOUNDS

1-Amino-1-deoxy-D-fructose (7), and its N-butyl derivative (8), reacted with malondialdehyde to yield the 1-deoxy-1-(3-oxo-1-propenylamino)-D-fructoses 9 and 10, respectively. Small proportions of 4-methyl-1,4-dihydro-3,5-pyridinedicarbaldehyde (12) and 1-deoxy-1-(3.5-diformyl-4-methyl-1,4-dihydro-pyridin-1-yl)-D-fructose (14) were also formed in the reaction with 7, and of 1-butyl-4-methyl-1,4-dihydro-3,5-pyridinedicarbaldehyde (13) in the reaction with 8. The reaction of 7 with methylmalondialdehyde afforded 1-deoxy-1-(2-methyl-3-oxo-1-propenylamino)-D-fructose (11). The enaminals 9 and 10 cyclised, in neutral or weakly alkaline aqueous solution, into a mixture of 4-(D-arabino-tetritol-1-yl)-3-pyrrolecarbaldehyde pyrrolecarbaldehyde (15 and 17, respectively) and 3-(D-arabino-tetritol-1-yl)-4-pyridone (19 and 21, respectively). Small proportions of 4-(hydroxymethyl)-3-pyrrolecarbaldehyde (16) and 3-(hydroxymethyl)-4-pyridone (20) were also formed in the cyclisation of 9, and of 1-butyl-4-(alpha,beta-D-erythrofuranosyl)-3-pyrrolecarbaldehyde (18-alpha,beta) in the cyclisation of 10. All of the heterocyclic compounds were unstable.