Synthesis of 3,5-Dihydroxy-2-methylpyran-4-one (5-Hydroxymaltol)

We recently described the synthesis of the dihydropyranone 1 from aldohexoses and secondary amine salts¹: in addition to 1, Trace amounts of 5-hydroxyml to 1, 11, were formed. Compound 11 was isolated by preparative gas chromstography and identified by i.r., n.m.r., and mass spectrometric analysis.     

PMR investigation into the structure of some n-substituted 1-amino-1-deoxy-D-fructoses (amadori rearrangement products) : Evidence for a preferential conformation in solution

The PMR spectra at 220 MHz of some Amadori rearrangement products deduced from D-glucose with p-toluidine (1), N-methylphenylamine (2), di-butylamine (4), piperdine (5), and morpholine (6) have been studied in detail.Compounds 1-6 appear to exist in solution predominantly as an equilibrium mixture of the furanose and pyranose ring. The pyranose ring occurs exclusively in the β(D)-²C₅-conformation (corresponds to Reeves 1C-conformation). The furanose ring probably exists as a mixture of both the β- and α-anomer, in which the β-anomer is favoured.