Hydrogen bonds methyl glycoside

The catalytic hydrogenation of difluorovinylic compounds affords C-difluoro-methyl glycosides and 2-, 3-, or 5-C-difluoromethyl sugars vide supra) (Figure 6.29). In the a-pyranose series, hydrogenation of the exocyclic double bond occurs on the jS... 

C2 Z = 8 Dx = 1.457 R = 0.032 for 1,535 intensities. The crystals contain two symmetry-independent molecules, both of which have the C4 conformation, but differ in the orientation of the thio-glycosidic bonds. The torsion angle S-5-C-1-S-1-C-6 is 159° in one molecule and 82° in the other. As in methyl jS-D-ribopyranoside, there are intramolecular hydrogen-bonds between O-2-H and O-4-H. The O-H O direction of the hydrogen bonds is opposite in the two molecules. There are small, but possibly significant, differences in the S-C bond lengths. 

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