High Resolution1H and13C NMR Resonance Assignments, Conformation and Solution Behavior ofN-Phenyl (N-Phenyl-β-D-Glucopyranosylamine) Uronamide in DMSO

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Abstract
N-phenyl (N-phenyl-β-D-glucopyranosylamine) uronamide (1) and N-phenyl(N-phenyl-D-galactopyranosylamine) uronamide (2) spontaneously formed and precipitated (pH = 4.75 [aq]) in the presence of aniline upon C6 activation with a carbodiimide reagent. In the presence of H2O, 1 and 2 were hydrolyzed to N-phenyl-D-glucopyranuronamide (3) and N-phenyl-D-galacto-pyranuronamide (4), respectively, with a rate constant proportional to the concentration of H2O, with compound 2 degrading 2-4 times faster than 1. We have unequivocally assigned both the 1H and 13C NMR spectra for 1 using a combination of 1H-1H and 13C-1H Chemical Shift-Correlation Spectroscopy as well as 2D nuclear Overhauser enhancement (nOe) and natural abundance 2D Double Quantum Transfer experiments. Scalar coupling constants for the directly-bonded pyranose protons of compounds 1 and 2, 2D nOe data as well as conformational energy minimization calculations indicated the sugar existed almost exclusively in DMSO as the 4C1 conformer.