Monosaccharides glycosides formation

Fig. 1 also may be used to note some general characteristics of C spectra of carbohydrate polymers ( -11) Chemical shifts of anomeric carbons (C-l), in the region of 100-110 p.p.m., are typically well separated from other signals. As compared with C-l of the related monosaccharides (12-15)j the anomeric carbon is strongly deshielded (commonly by 7-10 p.p.m.) through glycoside formation (9)> i.e., by the change from 0-H to an 0-C bond. 

A disaccharide is formed by coupling the hemiacetalic hydroxide group of a monosaccharide with any hydroxide group of a second sugar molecule. Trisaccharides result from a glycosidic formation between three molecules and, in an analogous manner, tetra-, penta-, and hexasaccharides are formed. 

Show the common reactions of monosaccharides that were presented in this chapter oxidation with nitric acid oxidation with bromine reduction with sodium borohydride esterification glycoside formation and the Kiliani-Fischer synthesis. 

Write reactions for monosaccharide oxidation and glycoside formation. (Section 7.5)... 

Write reactions for monosaccharide oxidation and glycoside formation. 

Synthesis of Monosaccharide Glycosides.- A very useful review has appeared on newer methods for glycoside formation, particularly those based on 0-alkylation and on the use of glycosyl trichloro-acetimidates, sulphonium salts and fluorides. A shorter paper has... 

Glycoside formation (Section 17.5) monosaccharide -i- alcohol acetals or ketals ... 

A more stereospecific course of glycoside formation by reaction of the polymer-bound C-1 bromide with the second monosaccharide hydroxyl component involves the initial formation of a c -l 2-orthoester. This undergoes an acid-catalyzed stereospecific isomerization (Kochetkov et al., 1967) to the corresponding glycoside (disaccharide). 

Synthesis of Monosaccharide Glycosides.- A review with 168 references has appeared (in Japanese) of recent developments in the synthesis of 0 -glycosides. The acid-catalyzed formation of D-fructosides and 2-thio-D-fructosldes in DMSO is believed to proceed by way of the cyclic carbonlum ions, and furanoslde-pyranoside isomerization by way of the bicyclic 2,6-anhydro-3-D-fructofuranose... 

Synthesis of Monosaccharide Glycosides.- A review has been published on the synthesis of glycopeptides which covers aspects of glycoside formation and the linkage between sugars and serine or serine-containing peptides. ... 

Similarly, ketose sugars participate in polysaccharide formation by reaction of their ano-meric carbon with a hydroxyl of another monosaccharide to create a ketal linkage. The acetal and ketal bonds within polysaccharides are termed o-glycosidic linkages. 

Because carbohydrates are so frequently used as substrates in kinetic studies of enzymes and metabolic pathways, we refer the reader to the following topics in Ro-byt s excellent account of chemical reactions used to modify carbohydrates formation of carbohydrate esters, pp. 77-81 sulfonic acid esters, pp. 81-83 ethers [methyl, p. 83 trityl, pp. 83-84 benzyl, pp. 84-85 trialkyl silyl, p. 85] acetals and ketals, pp. 85-92 modifications at C-1 [reduction of aldehydes and ketones, pp. 92-93 reduction of thioacetals, p. 93 oxidation, pp. 93-94 chain elongation, pp. 94-98 chain length reduction, pp. 98-99 substitution at the reducing carbon atom, pp. 99-103 formation of gycosides, pp. 103-105 formation of glycosidic linkages between monosaccharide residues, 105-108] modifications at C-2, pp. 108-113 modifications at C-3, pp. 113-120 modifications at C-4, pp. 121-124 modifications at C-5, pp. 125-128 modifications at C-6 in hexopy-ranoses, pp. 128-134. 

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