“…However, we were interested in checking the reactivity of the unprotected hydroxymethyl group under the neutral reaction conditions described, and not in pyridine, where formation of 4,6-cyclic phosphates of carbohydrates from their 6-monophosphorylated precursors has been described. [38] Preliminary results showed mainly the formation of two products, one that possibly contains the 3,4-pyrophosphate, and another that contains the 4,6-cyclic phosphate along with the 2,3-pyrophosphate. We checked the formation of cyclic phosphate by the heteronuclear coupling constant observed for C-6 in 13 C NMR spectra.…”