Based upon Periodate Oxidation

The periodate oxidation of carbohydrates, an important analytical technique, has been reviewed earlier in this Series.73 The dialdehydes obtained on periodate oxidation of polysaccharides have also been discussed.74 The requisite for the degradations to be discussed here is that part of the sugar residues in a polysaccharide are not oxidized by periodate and can be obtained separated from the oxidized residues as mono-, oligo-, or poly-saccharide derivatives after some chemical treatment. Characterization of these products may then give significant structural information. 

It is essential that the oxidation of the glycol groupings in the polysaccharide be complete, and that no overoxidation occurs. The latter is excluded by performing the reaction with the exclusion of light, at low temperature, and at a pH of 3-3.5, as described by Bobbitt.73 The use of oxygen-free water and the addition of propyl alcohol, as a radical scavenger, also lessen radical-induced depolymerization during oxidation.75 

Painter and coworkers demonstrated that inter-residue hemiacetals may be formed during the periodate oxidation of polysaccharides, 

Periodate oxidation is generally performed in aqueous solution, but Yu and Bishop studied oxidation with periodic acid in dimethyl sulfoxide.81 They observed limited oxidation, probably attributable to rapid formation of hemiacetals. Concentrated solutions of periodic acid in dimethyl sulfoxide may explode 82 therefore, only dilute solute) T. Painter and B. Larsen, A eta Chem. Scand., 24, 2366-2378 (1970). 

In a modification of the Barry degradation,91,82 A/,A/-dimethylhydra-zine is used instead of phenylhydrazine. The advantages of the modified procedure were not actually stated, but it is conceivable that the milder conditions employed and less discoloration produced result in an improved yield of the degraded product. In one application, the glycerol glycoside 25 of a tetrasaccharide obtained on limited per- 

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Based upon its position on the periodic table, what are the highest and lowest oxidation numbers for phosphorus ... 

Whereas the development of crystalline, open-frameworks based upon silicates, phosphates and related materials has progressed at an ever increasing pace, the synthesis of simple binary oxides with periodic open stmctures has been less sue-... 

Alternatively, the starting compound could be L-arabinose, which upon isopropylidenation and then benzoylation gave 125. Glycosylations were effected by various procedures, which, except for the guanine and cytosine series, did not require prior protection of the heterocyclic bases to give 126. Removal of the isopropylidene and subsequent periodate oxidation, reduction, and then debenzoylation gave the acyclonucleosides 127 [92JCS(P1)1943],... 

D. Volz, P. E. Reid, C. M. Park, D. A. Owen, and W. L. Dunn, Histochemical procedures for the simultaneous visualization of neutral sugars and either sialic acid and its side chain O-acyl variants or O-sulfate ester. I. Methods based upon the selective periodate oxidation of sialic acids, Histochem. J., 19 (1987) 249-256 Histochemical procedures for the simultaneous visualization of neutral sugars and either sialic acid and its O-acyl variants or O-sulfate ester. II. Methods based upon the periodic acid-phenylhydrazine-Schiff reaction, Histochem. J., 19 (1987) 257-263. 

Storage and reduction catalysts (NSR) offer the possibility of controlling NOx emissions from automobile sources while permitting operation under predominantly lean-burn conditions. °" The concept is based upon the storage of NO under lean conditions on an alkaline-earth oxide component, such as baria, which is then released during intermittent rich/stoichiometric periods where the stored NO is released and reduced by Hg, CO or HC over the noble metal component (Fig. 10.9). 

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