The reaction of 4-O-acetyl-1-deoxy-5,6-O-isopropylidene-2,3-D-erythroand (D-threo)-hexodiulose with aminoguanidine (guanylhydrazine) was investigated at pH 7.0 and 37°C. The two dicarbonyl compounds reacted rapidly to give 6-methyl-5-substituted triazine derivatives, which were fully characterized. The compounds were deblocked in a stepwise manner to give, first the de-O-acetylated compounds and then (by removal of the isopropylidene groups) the free triazine derivatives which were fully characterized (GLC/MS, NMR and elemental analyses).