Disaccharides periodate oxidation

The D-galactosyl residues are the same as in disaccharide 33, and the fact that ribitol is substituted at 0-2 was evident from the methyl-ation analysis. Finally, a nonreducing tetrasaccharide was obtained, containing D-galactose, 2-acetamido-2-deoxy-D-galactose, and ribitol residues in the proportions 2 1 1. From these results, and periodate-oxidation studies, structure 36 was proposed for the neutral hexa-saccharide. 

On deamination, C-substance that had been treated with alkali and phosphatase yielded the disaccharide 2-0-(2-acetamido-2-deoxy-D-galactosyl)-D-ribitol. Periodate oxidation of C-substance had revealed that the ribitol residue is substituted at 0-2 and 0-5. 

Actually, on oxidation of the carbohydrate with sodium periodate, three moles of periodate are consumed and one mole of formic acid is formed. These data agree with the assumption that the disaccharide contains a pyranose and a furanose ring. The possibility that the disaccharide is made up of glucofuranose and sorbopyranose can also be eliminated on the basis of the periodate oxidation data. Glucofuranose would contain two pairs of adjacent hydroxyls, on carbon atoms 2 and 3 and on 5 and 6, and the sorbopyranose would have three adjacent hydroxyls, on carbon atoms 3, 4 and 5. In oxidizing such a disaccharide, a total of four moles of periodate would thus be used, giving rise to one mole of formic acid. This is inconsistent with the experimental data. 

Trifluoroacetic acid is volatile, and thus readily removed. This acid was used by Albersheim and coworkers for the hydrolysis of plant cell-walls,39 and has since been employed for cell walls,40-43 plant mucilages,44 blood-group oligosaccharides,45 peptidogalactoman-nans,46 heparin,47 and disaccharides in blood and urine.48,49 It has also been suggested as an alternative to 6 M hydrochloric acid in the determination of amino sugars,50 and for the hydrolysis of polyalcohols produced by periodate oxidation of polysaccharides.503 Lee... 

A disaccharide derivative (42) of more conventional structure has also been isolated from hen oviduct.177 Its structure was confirmed by its conversion into L-fucose and uridine 5 -(2-acetamido-2-deoxy-a-D-glucopyranosyl pyrophosphate) after treatment with a-L-fucosi-dase. Mild, acidic hydrolysis of the ester 42 produces a disaccharide whose structure was confirmed by periodate oxidation. Human milk and colostrum,178 or milk and colostrum of pig,128 are also sources of... 

The disaccharide nigerose is a-D-Glup-(l — 3)-D-glu. Write out its structure. How would you prove this structure using methylation, periodate oxidation, and other methods. 

The structures of the disaccharides and higher saccharides (obtained by partial hydrolysis of polysaccharides) can be examined by periodate or lead tetraacetate oxidation. Ahlborg studied the periodate oxidation of disaccharides and starch dextrins in 0.5 N sulfuric acid. Since the intermediate formate esters were hydrolyzed, these conditions were favorable for overoxidation. The (1 — 4)- and (1 —> 6)-linkages in the starch dextrins were each found to be associated with a characteristic consumption of oxidant. Neumtiller and Vasseur studied periodate oxidation in solutions of various acidities, from strongly acid to neutral, and showed that there were differences between different types of disaccharides. 

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