Fucose methyl ethers

The glycosyl-linkage compositions of our three RG-II preparations were similar (Table 2) and corresponded to the relative sugar molar ratios obtained from compositional (TMS derivatives) analyses indicating that methylation was complete. Almost all the methyl ethers obtained could be attributed to known residues of the RG-II molecule (Figure 1) and our data were in accordance to that previously reported for RG-II from different plant origins [3,8,12,20,26]. The relative molar ratios of these "characteristic" methyl ethers (calculated on the basis of 1 residue of 3,4-linked fucose) were almost all in stoichiometric amounts (Table 3), confirming thus that our three preparations corresponded to the accepted model for RG-II. 

Relative molar ratios (calculated on the basis of 1 residue of 3,4-linked fucose) of methyl ethers characteristic for RG-II in the preparations isolated from fruit-derived products... 

Maher, George G., The Methyl Ethers of the Aldopentoses and of Rhamnose and Fucose, X, 257-272 Maher, George G., The Methyl Ethers of D-Galactose, X, 273-282 McColloch, R. J. See Kertesz, Z. I. McDonald, Emma J., The Polyfructo-sans and Difructose Anhydrides, II, 253-277... 

The presence of fucose or of methyl ethers of fucose has been reported in many polysaccharides, but the configuration of the sugar has not always been established, as identification has often been based solely on chromatographic data. Great advances have been made with the introduction of new techniques for the elucidation of structures of... 

Apart from their intrinsic interest the methyl ethers of certain of the pentoses, especially those of L-arabinose and D-xylose, are of great importance in structural studies of the naturally occurring pentosans, and of plant gums and mucilages.1 This also applies to the methyl ethers of L-rhamnose and L-fucose. 

Methyl-D-fucose has been prepared by two methods.68 In the first, methyl a-D-galactopyranoside was converted into the 6-tosyl derivative, from which by condensation with acetone methyl 3,4-isopropylidene-6-tosyl-a-D-galactopyranoside (LXIV) was obtained. Methylation gave the corresponding 2-methyl ether which was converted into the 6-deoxy iodide (LXV) by heating with sodium iodide in acetone solution at 140°. Reduction with Raney nickel gave sirupy methyl 2-methyl-3,4-isopro-pylidene-a-D-fucopyranoside (LXVI) from which 2-methyl-D-fucose was obtained on hydrolysis. 

Of the methyl ethers of L-fucose, only the 3-methyl, 2,3-dimethyl and 2,3,4-trimethyl ethers have been isolated so far by the hydrolysis of methylated polysaccharides. 2-Methyl- and 3,4-dimethyl-L-fucose have been prepared synthetically. 

Maher, Georce G., The Methyl Ethers of the Aldopentoses and of Rhamnose and Fucose, 10, 257-272... 

The following revised set of tables of the physical characteristics of the methyl ethers of the aldopentoses and rhamnose and fucose (and their derivatives) replaces those of R. A. Laidlaw and E. G. V. Percival, Advances in Carbohydrate Chem., 7, 1 (1952), and brings the subject up to date. 

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