Oxidation, monosaccharides

Collins PM, Ferrier RJ (1995) Oxidations monosaccharides their chemistry and their role in natural products. Wiley, New York... 

The reaction of phenylhydrazine with oxysucrose was found to be similar to that described for oxidized monosaccharide derivatives above, as only two molecules of the base reacted with the four potential aldehyde groups the product was assigned structure (89). Mester found that this derivative forms an amorphous bis(diphenylformazan) with benzenediazonium chloride, and so he assigned structure (90) to it. Acetylation of the formazan gave an amorphous product, identical with the formazan prepared from... 

In polysaccharides oxidized with periodic acid, one molar proportion of each individual, oxidized monosaccharide reacts with only one mole of... 

Oxidation of secondary hydroxyl groups at C-2 and C-3 leads to acyclic dialde-hydes and dicarboxylic derivatives. Selective oxidation of primary hydroxyl groups is more difficult, but can be achieved by stoichiometric as well as catalytic methods. Nitric acid oxidizes monosaccharides into aldaric acids. Oxidation of cellulose or starch by nitrogen dioxide (N2O4) yields 6-carboxy starch and 6-carboxycellulose respectively. Subsequent hydrolysis under well-controlled conditions (0.5-2 M HCl at 150 °C) of these materials yields o-glucuronic acid (o-GlcAp) [12]. 

What are the main oxidizing agents used to oxidize monosaccharides to carbonic acids ... 

Keywords metal nanoparticles, nanocomposites, hydrogenation, oxidation, monosaccharides... 

Vigorous oxidation of a monosaccharide (e.g., with dUute nitric acid) produces carboxyl groups at both ends of the chain. Thus galactose gives the sparingly soluble mucic acid glucose affords the soluble saccharic acid, which is best isolated as the sparingly soluble acid potassium salt. 

The most general methods for the syntheses of 1,2-difunctional molecules are based on the oxidation of carbon-carbon multiple bonds (p. 117) and the opening of oxiranes by hetero atoms (p. 123fl.). There exist, however, also a few useful reactions in which an a - and a d -synthon or two r -synthons are combined. The classical polar reaction is the addition of cyanide anion to carbonyl groups, which leads to a-hydroxynitriles (cyanohydrins). It is used, for example, in Strecker s synthesis of amino acids and in the homologization of monosaccharides. The ff-hydroxy group of a nitrile can be easily substituted by various nucleophiles, the nitrile can be solvolyzed or reduced. Therefore a large variety of terminal difunctional molecules with one additional carbon atom can be made. Equally versatile are a-methylsulfinyl ketones (H.G. Hauthal, 1971 T. Durst, 1979 O. DeLucchi, 1991), which are available from acid chlorides or esters and the dimsyl anion. Carbanions of these compounds can also be used for the synthesis of 1,4-dicarbonyl compounds (p. 65f.). 

Monosaccharides such as glucose and fmctose are the most suitable as starting materials. When starch is used, it is first hydrolyzed with oxahc acid or sulfuric acid into a monosaccharide, mainly glucose. It is then oxidized with nitric acid in an approximately 50% sulfuric acid solution at 63—85°C in the presence of a mixed catalyst of vanadium pentoxide and iron(III) sulfate. 

Uronic acids are monosaccharides in which the terminal primary alcohol group is oxidized to a carboxyhc acid functional group, eg, D-glucuronic acid [6556-12-3] (11). 

COLLECTION AND IDENTIFICATION OF BIOACTIVE ORGANIC COMPOUNDS OCCURRING IN RIVERS AND LAKES. ADSORPTION SELECTIVITY OF MONOSACCHARIDES ONTO HYDROUS METAL OXIDES... 

As a possible method of concentrating trace amounts of bioactive organic compounds occurring in the hydrosphere, adsorption properties of various compounds have been explored by employing hydrous metal oxides as the adsorbents. To date, a family of organophosphoms compounds and carbonic acids were adsorbed onto hydrous iron oxide, along with the adsoi ption of monosaccharides onto hydrous zirconium oxide. 

Monosaccharides can be oxidized enzymatically at C-6, yielding uronic acids, such as D-glucuronic and L-iduronic acids (Figure 7.10). L-Iduronic acid is similar to D-glucuronic acid, except for having an opposite configuration at C-5. Oxidation at both C-1 and C-6 produces aldaric acids, such as D-glucaric... 

PhB(OH)2, PhH or Pyr. A polymeric version of the phenyl boronate has been developed.Phenyl boronates are stable to the conditions of stannyla-tion and have been used for selective sulfation to produce monosulfated monosaccharides. Phenyl boronates were found to be stable to oxidation with pcc ... 

Much of the chemistry of monosaccharides is the familiar chemistry of alcohols and aldehydes/ketones. Thus, the hydroxyl groups of carbohydrates form esters and ethers. The carbonyl group of a monosaccharide can be reduced with NaBH4 to form an alditol, oxidized with aqueous Br2 to form an aldonic acid, oxidized with HNO3 to form an aldaric acid, oxidized enzymatically to form a uronic acid, or treated with an alcohol in the presence of acid to form a glycoside. Monosaccharides can also be chain-lengthened by the multistep Kiliani-Fischer synthesis and can be chain-shortened by the Wohl degradation. 

The anomeric configurations of the sugar residues were determined by chromium trioxide oxidation [14], Oxidation of the fully acetylated polysaccharide and subsequent monosaccharide analysis by GLC indicated that the D-Xyl units are P-linked (oxidized more rapidly) and that die D-GlcA are a-linked (Table II). 

Scheme 31. Monosaccharide derivatives obtained by oxidation at secondary hydroxyl groups using PCC in the presence of 3A or 4A MS.

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