Isorotation Rules glycosides

The negative optical rotation of 5-acetamido-5-deoxy-a-D-xylopyra-nose is in contradiction to its existence as the a-D anomer. As Fig. 2 shows, the methyl D-xylopyranoside that corresponds to the a-D form, according to the Hudson isorotation rule, shows a positive plain curve and the p-D form shows a negative plain curve in optical rotatory dispersion. On the other hand, 5-acylamido-5-deoxy-a-D-xylop)franoses and their glycosides exhibit negative plain curves. Obviously, the... 

If the amide chromophore is removed from methyl 5-[(benzyloxy-carbonyl)amino]-5-deoxy-a-D-xylopyranoside (40), or from its non-glycosidic form (31),a positive plain curve of optical rotatory dispersion is found for 5-amino-5-deoxy-D-xylopyranose (17) and its methyl glycoside (41). Because, at least with the glycoside 41, no reversal of configuration at C-1 is to be expected under these conditions, 5-amino-5-deoxy-D-xylopyranose and its methyl glycoside likewise show a tendency to assume the o-D anomeric form, and show plain curves in agreement with the Hudson isorotation rule. ... 

Ultraviolet, infrared, and x-ray data on compound 45 have been reported,81 and it has been pointed out4 that, in this series, the anomeric pairs of glycosides that have so far been examined conform with Hudson s isorotation rules, unlike some 2,3-unsaturated glycosyl esters.51,91 Features of the nuclear magnetic resonance spectra are... 

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. 

In a similar fashion, application of the Isorotation Rules led to the inference 119) that the biose constituent of the glycoside amygdalin is gentio-... 

One of the primary functions of the rules of isorotation of Hudson127 was the demonstration that two glycosides can be a- and /J-anomers this was applied by Haworth and Porter2 to ethyl a- and /3-D-glucofuranosides the difference in rotation of these two compounds is 184°, whereas that for the ethyl D-glucopyranosides is 183.7°. 

Hudson s rules of isorotation are used for the determination of the configuration at the anomeric centers in oligo- and poly-saccharides and Korytnyk has discussed some extensions of these rules. Reeves has demonstrated that studies of the optical rotation in cuprammonia solution can give valuable information on the types of linkages and also on the conformation of sugar residues in a polysaccharide. Bourne and coworkers have shown that some o- and /S-D-glycosidic linkages display characteristic absorptions in the infrared at 844 and 891 cm, respectively. 

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