Oxidation of oligosaccharides

Some microorganisms effect the oxidation of oligosaccharides to glycosid-3-uloses this conversion has been reported for maltose, lactose, and their respective aldobionic acids. Conditions for the oxidation of sucrose by the action of Agrobacterium tumefaciens have been improved and optimized on a molar scale, so that 3-ketosucrose can be produced in 40% yield 449... 

With hexoses, except for their derived alditols, formaldehyde is produced from a glycosidically bound, nonreducing, furanosyl residue, but not from a similar pyranosyl residue. In the periodate oxidation of oligosaccharides composed of monosaccharide residues commonly occurring in the pyranoid form, the possibility of liberation of formaldehyde should always be checked. Thus, with a-n-glucopyranosyl a-D-galactofuranoside, the detection of nearly one mole of formaldehyde i>er mole, liberated early in the oxidation, was important evidence that the D-galactose residue occurs in the (unexpected) furanoid form. 

Periodate oxidation of oligosaccharide phenylosazones can also yield useful structural information. o-Glucose phenylosazone is thus oxidized to mesoxalaldehyde l,2-bis(phenylhydrazone) (11). The phenylosazones of... 

W. Chai, M. S. Stoll, G. C. Cashmore, and A. M. Lawson, Specificity of mild periodate oxidation of oligosaccharide-alditols relevance to the analysis of the core-branching pattern of O-linked glycoprotein oligosaccharides, Carbohydr. Res., 239 (1993) 107-115. 

An isotachophoretic method has been developed for the separation and determination of 5-100 nmol quantities of iodate, periodate, and formate ions arising from the periodate oxidation of carbohydrates. The carboxylic acid fragments arising from the periodate oxidation of oligosaccharides, oxidation of the resulting dialdehydes, and total acid hydrolysis, have also been determined by use of this technique. 

Aldehydes formed as the products of the periodate oxidation of oligosaccharides have been determined after separation by g.l.c. of their trimethyl-silyl ethers of the dithioacetals. Data on the types and molar proportions... 

Typical spectra obtained are shown in Fig. 1.2. Moreover, substantial radiolytically-mediated elevations in the concentration of serum formate, arising from the oxidation of carbohydrates present by OH radical, were also detectable. In addition to the above modifications, 7-radiolysis of inflammatory knee-joint synovial fluid generated an oligosaccharide species of low molecular mass derived from the radiolytic fragmentation of hyaluronate as outlined in the previous section dealing with oxidative damage to carbohydrates. The... 

Oxidation of carbohydrates is probably the most efficient heterogeneously-catalyzed process since very high yield and selectivity are reported for reactions over solid catalysts. Despite important recent advances, the conversion of carbohydrates to HMF still requires further investigations. For reactions, in water, the yield of HMF is still too low due to the significant formation of side products. Today, several procedures for the conversion of monosaccharides, disaccharides, oligosaccharides, and starch in water into high value added materials are available. With cellulose, its heterogeneously-catalyzed conversion into useful products... 

Glycoproteins, such as horseradish peroxidase, are coupled selectively to other proteins or NH2-groups bearing molecules via oligosaccharide side chain oxidation. The vicinal OH groups of oligosaccharide residues are oxidized by periodate to aldehyde groups, which react with amines to form imines (Schiff bases). 

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... 

Interpretation of the spectra recorded for solutions of oligosaccharides in deuterium oxide is based on chemical shifts and coupling... 

Silyl ethers of aliphatic alcohols are inert towards strong bases, oxidants (ozone [81], Dess-Martin periodinane [605], iodonium salts [610,611], sulfur trioxide-pyridine complex [398]), and weak acids (e.g., 1 mol/L HC02H in DCM [605]), but can be selectively cleaved by treatment with HF in pyridine or with TBAF (Table 3.32). Phenols can also be linked to insoluble supports as silyl ethers, but these are less stable than alkyl silyl ethers and can even be cleaved by treatment with acyl halides under basic reaction conditions [595], Silyl ether attachment has been successfully used for the solid-phase synthesis of oligosaccharides [600,601,612,613] and peptides [614]. 

Metabolic Strategies 227 Glycolysis, Gluconeogenesis, and the Pentose Phosphate Pathway 242 The Tricarboxylic Acid Cycle 282 Electron Transport and Oxidative Phosphorylation 305 Photosynthesis 330 Structures and Metabolism of Oligosaccharides and Polysaccharides 356... 

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