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The hemicelluloses of sitka spruce Hunt, Kenneth

Abstract

The hemicellulose of sitka spruce obtained by alkaline extraction from the holocellulose was acetylated and a fractionation attempted by precipitation with petroleum ether from a chloroform solution of the acetate. Acid hydrolysis yielded neutral sugars and a uronic acid fraction. Separation of the neutral sugars was attempted on a cellulose column and xylose, mannose, glucose and galactose were characterized as well known derivatives. L-Arabinose and L-rhamnose were shown to be present by paper chromatography. Chromatographic separations of the uronic acid fraction showed at least seven components, only one, the aldobiouronic acid was studied. Reduction of its methyl glycoside methyl ester with lithium aluminum hydride followed by hydrolysis yielded D-xylose and a monomethyl glucose which was not characterized. Methanolysis of aldobiouronic acid followed by treatment with methanolic ammonia yielded the amide of 4-O-methyl-D-glucuronic acid and D-xylose. Reduction with lithium aluminum hydride followed by methylation and hydrolysis yielded 2,3,4,6 tetra-O-methyl-D-glucose and a dimethyl-D-xylose. The evidences points to the 3,4 isomer in which case the aldobiouronic acid would be 2-O-(4-O-methyl-α-D-glucuronopyranosyl)-D-xylose. A synthesis of 3-O-methyl-D-xylose was carried out.

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