Glycosides, oxidation tritylation

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. 

Dimethyl-J>arabinose (XXXVI) has been isolated from the products of hydrolysis of methylated araban94 and of methylated damson gum.97 It has been synthesized49 from methyl 5-trityl-L-arabofurano-sides (afi mixture) (XXXV) by methylation with methyl iodide and silver oxide followed by removal of the trityl group by means of hydrogen chloride in chloroform and hydrolysis of the methyl glycosides. ... 

The synthesis of this substance was also effected by F. Smith.2 Methyl 6-trityl-a-D-galactopyranoside, in acetone solution, was treated six times with dimethyl sulphate and sodium hydroxide solution. The imperfectly methylated material thus obtained was then subjected to two treatments with methyl iodide and silver oxide. The necessity for so many treatments with methylating reagents emphasizes the difficulty of etherifying a glycoside substituted by the trityl radical in position 6. Subsequent to removal of the trityl radical, the methyl 2,3,4-trimethyl-(33) J. S. D. Bacon, D. J. Bell and J. Lorber, J. Chem. Soc., 1147 (1940). 

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