1H NMR Analyses of Rotameric Distribution of C5-C6 bonds of D-Glucopyranoses in Solution

Abstract
1H NMR signals of H-6proR and H-6proS protons of D-glucoses and their per-O-acylated (acetyl and benzoyl) derivatives were unambiguously assigned by chiral deuteration at the C-6 position. The JH5,H-6proR and JH5,H-6proR values thus obtained enabled us to calculate the rotameric distributions of gg, gt and tg conformers. For the calculations, conventional equations (A and B) and novel equations accounting for possible departure of the three conformers from perfect staggering, were employed. The results showed that D-glucoses irrespective of solvents and protecting groups were predominant in two conformers gg and gt in an approximate ratio of 60 and 40, respectively, with a negligibly low population of the tg conformer. These results were in complete accordance with the statistical study of X-ray data of D-glucoses.

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