Short-chain, Primary Derivatives of Polysaccharides

Miscellaneous, Short-chain, Primary Derivatives OF Polysaccharides 

The reaction of polysaccharides ivith aldehydes to give cross-linked products has been known and exploited industrially for some time. Starch acetals may also be prepared by a method that does not give rise to cross-links and involves treatment of starch with a cyclic vinyl ether, 3,4-dihydro-2H-pyran, to give a tetrahydropyran-2-yl derivative (16). At low levels of substitution, the acetals are water-soluble, at 

Complex side-reactions, including overoxidation, are likely to occur in the oxidations, and information on the mechanism of periodate oxidation and the periodate-oxidation products of starch, cellulose, xylan, and other polysaccharides have been discussed. Thus, the limit of periodate oxidation is not always that expected, and the formation of interresidue hemiacetal structures during the oxidation can cause an early halt. - It is not until these structures have been reduced that oxidation can proceed once more. Other oxidants, such as dichromate-sulfuric acid, dichromate-oxalic acid, and sodium hypochlorite (which cause more extensive reactions), have been investigated with respect to cellulose and periodate-oxidized cellulose. Further oxidation of 2,3-dialdehydocel-lulose with halogen peroxy acids gives 2,3-dicarboxycellulose.  

Oxo derivatives of dextrans result from the oxidation of dextran or dex-tran 2,4-benzeneboronate with methyl sulfoxide-acetic anhydride.  

Most of the carbonyl groups involve C-3, and reduction of the oxidized dextrans gives modified polysaccharides containing n-allose, n-mannose, and D-galactose residues. Oxidation of 6-O-tritylamylose with methyl sulfoxide-acetic anhydride gives keto groups mainly at C-2. Similar oxidation of cellulose has been described.  

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IV. Miscellaneous, Short-chain, Primary Derivatives of Polysaccharides. 339... 

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