Polysaccharides methylated, partial acid hydrolysis

Structural studies on the oligosaccharide derivatives obtained by partial, acid hydrolysis of fully methylated polysaccharides often furnish valuable information on the positions at which the oligosaccharides were linked in the original polysaccharide. When the folly methylated Klebsiella O group 9 lipopolysaccharide,27 which contains D-galactopyranose and D-galactoforanose residues, was subjected to mild, acid hydrolysis, and the product reduced with lithium aluminum deuteride and remethylated with trideuteriomethyl iodide, a good yield of the disaccharide derivative 10 was obtained. 

In 1951, Whistler and Durso reported68 the isolation of epimelibiose by partial, acid hydrolysis of the polysaccharide guaran, followed by charcoal-column fractionation of the products. ThA material was obtained in anhydrous crystalline form from a mixture of methyl and butyl alcohols it had m.p. 201°, [a]26D + 120.9° — +124.6° in 36 hr. (c 2, in water). The yield was 2.2% of the weight of guaran used. Epimelibiose has also been produced72" in crystalline form following the ammonia-catalyzed alkaline isomerization of melibiose. 

B. Partial Acid Hydrolysis of Neutral Methylated Polysaccharides... 

B. PARTIAL ACID HYDROLYSIS OF NEUTRAL METHYLATED POLYSACCHARIDES... 

An L-arabino-D-galactan, in 2% yield, has been isolated from the fruits of Dillenia indica. From the results of partial acid hydrolysis and methylation analyses, when 2,6-di-O-methyl-D-galactose, 2,3,6-tri-O-methyl-D-galactose, 2,3,4,6-tetra-(9-methyl-D-galactose, and 2,3,5-tri-O-methyl-L-arabinose residues in the molar ratio 7 3 1 8 were identified, it was concluded that the polysaccharide was a (1- 4)-j3-D-galactan that contained L-arabinofuranose residues linked at 0-3 of some of the D-galactose residues in the main chain. 

Partial acid hydrolysis of paniculatan, the mucous polysaccharide from the inner bark of Hydrangea paniculata, led to the isolation of five acidic oligosaccharides. The structure of each oligosaccharide was established by methylation analysis although each has previously been isolated from other sources. A possible structure of the polysaccharide was proposed. The polysaccharide had a molecular weight of 5.46 X There were O-acetyl groups present on... 

The occurrence in many polyglycosiduronic acids of relatively resistant linkages, usually those between uronic acid residues and adjacent residues, has resulted in the isolation of several aldobiouronic acids on graded hydrolysis of acidic polysaccharides. The isolation of such aldobiouronic acids, and subsequent conversion to their fully methylated derivatives, has become a standard procedure in structural studies on polyglycosiduronic acids, especially those of plant gums and mucilages.1 In other cases, partially methylated aldobiouronic acids have been isolated from the hydrolyzates of methylated polysaccharides. The sources and methods of isolation of the methyl ethers of aldobiouronic acids so far examined are given in Table I. Some properties of derivatives are recorded in Table Y. 

A, Hydrolysis of naturally-occurring polysaccharide B, inethylation of aldobiouronio acid isolated after graded hydrolysis of polysaccharide C, hydrolysis of methylated polysaccharide D, methylation of partially methylated aldobiouronic acid isolated by method C. 

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