Glycosides methylation

Methylation of X with silver oxide and methyl iodide gave the lactone of methyl 2,5-dimethyl-j8-D-glucofururonoside (XIII) which was characterized by its conversion to the crystalline amide (XIV). Further methylation of XIII, form, with methyl sulfate and sodium hydroxide gave methyl 2,3,5-trimethyl-/3-D-glucofururonoside (XVI) from which by hydrolysis of the glycosidic methyl group and subsequent oxidation with bromine, there was obtained 2,3,5-trimethyl-D-glucosaccharolactone (XVII) characterized by the formation of its crystalline methyl ester. 

Normal human fibroblasts grown in media with 12% fetal calf serum were treated with or without galactose oxidase and then subjected to reduction with potassium borotritiide. GSLg were isolated and subjected to acid-catalyzed methanolysis (62) (see Materials and Methods). Methyl glycosides, methyl sphingosine, and fatty acid methyl esters were isolated by extraction of the total hydrolysate with solvents as described previously (62). Radioactivity was measured in triplicate in aliquots of these extracts. 

Wintergreen Gaultheria procumbens (Ericacae) or Betula lenta (Betulaceae) leaves bark 0.7-1.5 0.2-0.6 methyl salicylate (98%) flavour, antiseptic, antirheumatic prior to distillation, plant material is macerated with water to allow enzymic hydrolysis of glycosides methyl salicylate is now produced synthetically... 

The structure of the uronic acid was established as follows (a) periodate oxidation, followed by bromine oxidation, gave 2-hydroxy-3-methoxy-L-erj/f/tro-succinic acid 1413 (b) reduction of the methyl glycoside methyl ester with lithium aluminum hydride, followed by hydrolysis, gave 4-0-methyl-D-glucose.13... 

The methyl a-glycoside methyl ester of this sugar was prepared by the methylation of methyl (methyl 2,5-di-0-methyl-a-D-glucosid)uronate with dimethyl sulfate and sodium hydroxide, followed by esterification with diazomethane. The constitution follows from the method of synthesis. 

Ault, Haworth and Hirst47 first synthesized the methyl a-D-glycoside methyl ester of 2,3,4-tri-O-methyl-D-mannuronic acid by successive treatment of potassium (methyl a-D-mannopyranosid)uronate with dimethyl sulfate and sodium hydroxide, and then methyl iodide and silver oxide. Although no crystalline derivatives were isolated, there is little doubt about its structure, since the authors48 subsequently proved the presence of a pyranose ring in the starting material for the synthesis, methyl 2,3-O-isopropylidene-a-D-mannoside. The uronic acid has also been synthesized by Smith, Stacey and Wilson,28 who oxidized methyl... 

Proof of the structure of the uronic acid was obtained by Hirst, Jones and Jones,46 who isolated the methyl glycoside methyl ester by methyla-tion of the products from the graded methanolysis of alginic acid. The tri-O-methyl-D-mannuronic acid was converted to the diamide of 2,3,4-tri-O-methyl-D-mannaric acid, which had previously been prepared from... 

The easily prepared 3,4-isopropylidene derivatives of the a and j3 methyl-D-galactopyranosides form the starting points of the synthesis.7,9 Methylation of either substance, followed by hydrolytic removal of first the isopropylidene and then the glycosidic methyl radicals leads to crystalline 2,6-dimethyl-D-galactose. Since the above mentioned syn-... 

Glucose is converted to a pentamethyl derivative by treatment with excess methyl iodide and silver oxide (Section 23-12). The five methyl groups are not the same, however. Four are methyl ethers, but one is the glycosidic methyl group of an acetal. 

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