The Isomeric Composition ofD-ribo-hexos-3-ulose(3-keto-D-glucose) in Aqueous Solution1

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Abstract
1,2:5,6-Di-O-isopropylidene-α-D-ribo-hexofuranos-3-ulose (2) prepared by the phase transfer catalyst promoted ruthenium tetraoxide oxidation of 1,2:5,6-di-O-isopropylidene-α-D-glucofuranose (1), was partially hydrolyzed to give 1,2-O-isopropylidene-α-D-ribo-hexos-3-ulose (3). The title compound (4) was prepared by further acid hydrolysis of 3 or directly from 2. The anomeric region of the 1H NMR spectrum of freshly prepared 4 showed the presence of at least ten isomeric forms with three forms predominating: α-D-ribo-hexofuranos-3-ulose (4a, 44%), β-D-ribo-hexopyranos-3-ulose (4b, 22%) and β-D-ribo-hexopyranos-3-ulose hydrate (4c, 12%). 1H NMR examination of D2O solutions of 4 over time showed that the C-2 protons of the various isomeric forms were being exchanged with deuterium.