Glycosides conformational isomerism

Several comprehensive studies have been made of the anomeriza-tion and isomerization reactions of methyl glycosides under a wide variety of conditions, and the reaction rates have been correlated with configurations and conformations. The work is not discussed here, because it has been covered in several excellent reviews.100,264-267... 

After methylation of compounds (50, R = Me) and (51, R=Me) with methyl sulfate, four isomeric pyranosides were isolated by gas-liquid chromatography by detailed nuclear magnetic resonance studies, these were shown to exist in the H° conformation.103 Unlike related esters (see p. 221), but like other 2,3-unsaturated glycosides (see p. 237), these anomeric pairs of glycosides were found to conform with Hudson s isorotation rules. In dilute acid, they are degraded to methyl 3,4-dideoxy-6-0-methyl-a- and /3-D-g/ycero-hex-3-enopyrano-sidulose (52) these also were characterized configurationally and conformationally by nuclear magnetic resonance methods. 

---