Methylglyoxal reduction

While the mechanism for the formation of (35) has not been determined, an internal oxidation-reduction of the ribityl group (similar to that catalyzed by methylglyoxal synthetase) to afford the free diketone (38) which reacts with a second molecule of (32), appears plausible. In support of this it has been shown (82JA3754) that label from [1-3C]ribose is incorporated at the C-5 of riboflavin (corresponding to the 6-methyl of 33) and not at C-8. 

Two dehydration reactions, one preceding the first electron uptake and the other interposed between the first and second electron uptake, are also involved in polarographic reduction of aliphatic a-dicarbonyl compounds 86), such as diacetyl (R = CHs) or methylglyoxal (R = H). 

In the presence of metallic zinc and a catalytic amount of BiCl3, the reductive coupling between a-diketones and aldehydes takes place to yield a,/3-dihydroxyketones with moderate //-selectivity (Equation (48)).83 The reaction proceeds even in aqueous media. Phenylglyoxal and methylglyoxal can be converted to the corresponding coupling products. The reductive coupling of aldimines to vicinal diamines can also be accomplished by the action of Bi-KOH in methanol at room temperature.84... 

The three-carbon compound methylglyoxal is the byproduct of fermentation processes and of the Maillard reaction. Products of its reduction, namely acetol (hydroxyacetone), (f )-propane-l,2-diol (D-propane-l,2-diol) and (J )-lactaldehyde (n-lactic acid aldehyde or D-lactaldehyde) are relatively common compounds present in... 

Misra, K., Baneqee, A.B., Ray, S., et al., 1996. Reduction of methylglyoxal in Escherichia coli K12 by an aldehyde reductase and alcohol dehydrogenase. Molecular and Cellular Biochemistry 156,117-124. 

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