The Favored Formation of Threo-3-Pentulose in the Formose Reaction

The “formose reaction” is the generic name for the base-catalyzed condensation of formaldehyde to give “formose” which is a complex mixture of sugars, alditols, organic acids, etc.2 Increasing attention has been recently given to this reaction because of its possible importance in the manufacture of edible carbohydrates from a simple material and its possible role in the prebiotic synthesis of carbohydrates.3 In our recent study4 on the reaction catalyzed by triethylamine (TEA) and thiamine HCl in N,N-dimethylformamide (DMF)-water mixed solvent, the formation of 3-pentulose (GP-11-1 corresponding to GLC peak number 11-1) was suggested. P. Decker et al.5 also reported that at the end of formaldehyde consumption the concentration of 3-pentuloses became smaller because of their higher reactivity (these carbohydrates cannot form stable furanoses or pyranoses) compared to tetroses, pentoses, and hexoses. Although the isolation of 3-pentuloses was not described in that report,5 erythro-3-pentulose and threo-3-pentulose in a formose were identified by comparison of GLC retention times and mass spectra with those of authentic samples.