The coupling constant of anomeric hydrogen for mannopyranosyl 7c was 4.0 Hz in both the anomers. Finally the synthesis of glycopyranosides was supported by one of the crystal structure for a-anomer, O-(2,3,4,6-tetra-O-acetyl-a-D-mannopyranosyl)(4R,5R)-2,2-dimethyl-1,3-dioxolane-4,5-dicarboxylate 7c by X-ray crystallography (Figure 1).
Utille, "Coupure selective par l'hydrazine des groupements acetyles anomeres de residus glycosyles acetyles," Carbohydrate Research, vol.
The two conformations of glucose are called anomers. There is the alpha ([alpha]) anomer and the beta ([beta]) anomer, and the difference between them has tremendous significance in animal nutrition.
These linkages may be made between [alpha] glucose anomers or [beta] glucose anomers.
Use the following terms in a description of the structural and nutritional differences between starch and cellulose: monosaccharide, glycosidic bond, alpha anomer, beta anomer.
represented by the following formula A or formula B: ##STR1## wherein R is selected from the group consisting of C.sub.1-6 alkyl and C.sub.6-15 aryl and Bz is benzoyl.
Con A preferentially binds the alpha anomer
and the two anomers
were bound in different conformations.
The peaks at 2.03 and 2.05 ppm were assigned to the N-acetyl protons of the [alpha] and [beta] anomers of sialic acid, respectively.
For the fifth sample, we have concluded that the NMR result is the more correct one for the following reasons: (a) the peak assigned to the [beta] resonance (the largest component) is at the appropriate frequency; (b) the sum of peak areas of the carbon-3 proton resources at 1.84 and 2.24 ppm is in the appropriate ratio to that of the [beta] peak (~1:3); (c) the ratio of [beta]/[alpha] anomers is 6.52, which is well within the range of values for this ratio in the other samples (Table 1); and (d) the colorimetric assay for this sample demonstrated considerable interference, so it is possible that some sialate was not detected.