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Synthesis of partially methylated tetroses

University of British Columbia

It is well established that various partially methylated tetroses and pentoses occur in periodate oxidation products of methylated polysaccharides. To provide reference compounds as a means of identifying some of these sugars 2,3 di-O-methyi-L-threose, 2,3 di-O-methyi-D-erythrose, and 3,4 di-O-methyl-L-xylose have been synthesized. The threose and xylose were synthesized from ∝-methyl-D-glucoside by benzylidene condensation, methyiation, hydrolysis, reduction and periodate oxidation, whereas the erythrose was obtained from D-mannose by a similar sequence of reactions. The sugars were obtained as syrups and were characterized by the preparation of crystalline derivatives. ii. Black Spruce hemicelluloses:- By using different concentrations of alkali three different hemiceiluloses were extracted from black spruce holocellulose. Of these two fractions, the xylan and the glucomannan were purified by fractional precipitation using barium hydroxide solution and Fehling's solution. Previous workers have observed that the xylan fraction was always contaminated by small amounts of galactose. This was also true in the present instance if barium hydroxide alone was used for purification, but when this was followed by two treatments with Fehling's solution the galactose was completely eliminated. This is believed to be the first case of the isolation of such a xylan in a pure state from the hemicelluloses of a coniferous wood. The third fraction - the galactoglucomannan was found to be quite difficult to re-dissolve in alkali and as a result its purification is not quite complete.

Text

2011-12-02

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http://hdl.handle.net/2429/39473

Chemistry

University of British Columbia

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