Lead tetraacetate polysaccharides

Polysaccharides.—Very few oxidations of polysaccharides have been carried out with lead tetraacetate, a situation in marked contrast to the voluminous literature on polysaccharide oxidations with periodate.22 The main reason for this discrepancy has undoubtedly been the fact that polysaccharides are insoluble in the solvents generally used for lead tetraacetate oxidation. 

Because of the small amount of information available and the inconsistencies found in that reported, it is at present difficult to evaluate lead tetraacetate as a reagent for examining polysaccharides or partially-substituted polysaccharides. 

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. 

Lead tetraacetate has been used little for oxidation of polysaccharides. Its ineffectiveness for this purpose probably stems mainly from the fact that the organic media commonly employed for the reagent are unable to dissolve polysaccharides. However, the use of dimethyl sulfoxide (containing about 10% of acetic acid), a good solvent for many polysaccharides, has permitted satisfactory... 

V. Zitko and C. T. Bishop, Oxidation of polysaccharides by lead tetraacetate in dimethyl sulfoxide. Can. J. Chem., 44 (1966) 1749-1756 C. T. Bishop, Oxidation of polysaccharides with lead tetraacetate in dimethyl sulfoxide. Methods Carbohydr. Chem., 6 (1972) 350. 

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