C-13 CP MAS AND HIGH-RESOLUTION H-1, N-15 NMR-STUDY OF UREIDO SUGARS

Ureido sugars with eight various alkyl groups at N-3 were studied by means of H-1, C-13, and N-15 NMR spectroscopy in CDCl3 solution and a C-13 CP MAS technique in the solid state. The analysis of chemical shifts and coupling constants suggests the Z,Z-anti conformation of the ureido part of molecule. Differences of delta between the liquid and solid state are observed for the C-2, C-6, and OMe carbon atoms of the o-glucopyranose moiety, as well as the splitting of the anomeric carbon C-1 and OMe signals. The possibility of various conformations in the solid state are discussed. IR spectra of solid ureido sugars indicate that both NH groups are involved in hydrogen bonding. On the other hand, dilution with CDCl3 followed by H-1 NMR showed that N-1-H forms a stronger bond than N-3-H.