2.3.4.6- Tetra-O-methyl-D-galactose

A methylation analysis of S14, performed in the authors laboratory,44 gave 2,3,4,6-tetra-O-methyl-D-galactose, 2,4,6-tri-O-methyl-D-galactose, and 2,3,6-tri-O-methyl-D-glucose in the proportions 1 1 1. Although these are the same components as previously reported, the proportions are different. In addition to these sugars, 2-deoxy-3-0-methyl-2-(methylamino)-D-glucose was also obtained. 

As part of his monumental study20 on stachyose, Onuki converted manninotrionic acid into its completely methylated derivative, which he hydrolyzed, to obtain methylated D-galactoses and methylated D-gluconic acid. These products were isolated and identified by Onuki as 2,3,4,6-tetra-O-methyl-D-galactose, 2,3,4-tri-O-methyl-D-galactose and 2,3,5,6-tetra-O-methyl-D-gluconic acid. From these findings, Onuki proposed that manninotriose is... 

Methylation of stachyose and subsequent hydrolysis, by Onuki,20 gave 2,3,4,6-tetra-O-methyl-D-galactose (identified as the crystalline anilide), a tri-O-methyl-D-galactose and a tri-O-methyl-D-glucose (which were converted into the 2,3,4,6-tetra-O-methyl derivatives, and characterized as the crystalline anilides), and 1,3,4,6-tetra-O-methyl-D-fructose, a sirup which agreed in properties with the authentic material. 

Complete structural analysis of galactinol by the methylation method was reported66 by Kabat and associates in 1953. On hydrolysis, completely methylated galactinol gives 2,3,4,6-tetra-O-methyl-D-galactose (identified as the anilide) and 2,3,4,5,6-penta-O-methyl-D-myo-inositol (identified by oxidation to the penta-O-methylinosose, reduction, and demethylation, to give mpo-inositol and L-inositol). 

Recently, Putman and Hassid have confirmed93 the structural formula given by Colin and Gueguen. Methylation of floridoside, followed by hydrolysis, gave 2,3,4,6-tetra-O-methyl-D-galactose and 1,3-di-O-methyl-glyceritol (identified by its lack of optical rotation, and by mixed melting point of its p-nitrobenzoate with the authentic ester). Periodate-oxidation studies on floridoside also confirmed the earlier formula. 

The powdered-cellulose, chromatographic assay of the hydrolyzate of methylated stachyose has furnished important structural data. 1,3,4,6-Tetra-O-methyl-D-fructose, 2,3,4,6-tetra-O-methyl-D-galactose, 2,3,4-tri-0-methyl-D-galactose, and 2,3,4-tri-O-methyl-D-glucose were recovered in approximately equimolar quantities the glycosidic 1- 6 bond for the D-glucose residue and for one of the o-galactose residues in stachyose is clearly indicated. 

Methylation of raffinose, followed by hydrolysis, gives 1,3,4,6-tetra-O-methyl-D-fructose, 2,3,4,6-tetra-O-methyl-D-galactose, and 2,3,4-tri-O-mcthyl-D-glucose. 

All values in mole per cent. Small amount. Large amount. 2,3,4,6-Tetra-O-methyl-D-galactose + 2,3, tii-0-melLyl-ii-arabinose. 4. ... 

Methylation of the polysaccharide with subsequent hydrolysis and separation of products leads to the isolation (1) of 2,3,4,6-tetra-O-methyl-D-galactose, 2,3,6-tri-0-methyl-l>-mannose, and 2,3-di-0-methyl-l>-mannose. These results, confirmed by others (11) f show that D-galactopyranose units occur as nonreducing terminal units. Since the branches must be short, the most likely structure of guaran, based on evidence to this point, is that shown. 

S O-a B-Galdctopyranosyl-L-arabinose. Amorphous, [a] +152° (water) phenylosazone, m.p. 240°C. obtained by partial hydrolysis of Acacia cyanophylla gum 119). Hydrolysis of the methylated disaccharide gives 2,3,4,6-tetra-O-methyl-D-galactose and 2,4-di-O-methyl-L-arabinose. 

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