The structure and conformations of methyl 3,4,6-tri-O-acetyl-2-deoxy-2-(3′,3′-dicyclohexylureido)-β-D-glucopyranoside

The title compound was studied by H-1 and C-13 NMR in CD2Cl2 solution and by C-13 CPMAS NMR and X-ray diffraction in the solid phase. Low-temperature NMR spectra showed separate signals for the two cyclohexyl rings, located E and Z with respect to C2'=O. Distinct resonances of cyclohexyl carbons are also present in the solid state 13 C NMR spectrum. The barrier to rotation around C-2'-N-3' bond is 41.5 kJ/mol. Separate signals for H-1, H-2 and H-3 of the sugar unit indicate also that rotation around C-2-N-1' is hindered; the barrier height is 39.5 kJ/mol. The Z conformation is preferred (4: 1) over E at 193 K. In the crystals the glucopyranose ring is located Z with respect to C2'=O, and the molecules are linked by the N1'H...O=C (acetyl group at C-6) hydrogen bond.