6-O-Methyl-D-glucose

The first, satisfactory methylation appears to have been effected by Bourne and his colleagues,48 who prepared 6-O-methyl-D-glucose in high yield from the l,2 3,5-bis(phenylboronate), using diazomethane and boron trifluoride etherate in dichloromethane for methylation, and a final separation on a column of cellulose powder. It is this procedure which the same group used for structural analysis of triol phenylboron-ates43 (see Section 111,1) others80 have attempted to use it, but without success. 

A Convenient Method for the Synthesis of 6-O-Methyl-D-glucose, E. J. Bourne,... 

Partially methylated derivatives of D-glucosone have been prepared by decomposition of the corresponding partially methylated phenylosazones with p-nitrobenzaldehyde osones have been obtained from 5-0-methyl-D-glucose phenylosazone and from 3,4,5-tri-O-methyl-D-glucose phenylosazone in this way.22 Although 6-0-methyl-D-glucose phenylosazone is not altered by heating with benzaldehyde or piperonal in aqueous ethanolic... 

It has recently been reported21 that a mixed osazone of 3,4-di-O-methyl-D-glucose can be converted, by treatment with p-nitrobenzaldehyde, into an osone which reacts with phenylhydrazine to give 3,4-di-O-methyl-D-glucose phenylosazone. Von Lebedev29 claimed to have obtained D-glu-cosone 6-phosphate, isolated as an amorphous lead salt, by the action of hydrochloric acid on the phenylosazone prepared from D-fructose 6-phosphate. 

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. 

The reaction that occurs with Gly-OEt, 3,5,6-tri-O-methyl-D-glucose, p-toluidine, and phenacyl bromide to give 48 (or its regioisomer) represents a particular case (920PP665). 

Tetra-O-methyl-D-glucose Acetal formed first followed by p-septa-(Methanolysis) noside (70%) Emphasises the propensity of carbohydrates to adopt ting structures and the fact that acetals can be formed as intermediates in glycosidation. The isolated glycoside is the only glucosqttanose derivative known 19)... 

Desoxy-D-glucose 6-0-Methyl-D-gluoose 6-Desoxy-6-jod-D-gluoose 6-O-Tosyl-D-glucose D -Glucui-ons auremethylester ... 

Problem 22.39 (u) Give the structure of sucrose (cane and beet sugar) from the following information (1) It is hydrolyzed by maltase or emulsin to a mixture of d-( )-glucose and D-(-)-fructose. (2) It does not reduce Fehling s solution and does not mutarotate. (3) Methylation and hydrolysis gives 2,3,4.6-tetra-O-methyl-D-glucose and a tetramethyl-D-fructose. (b) What structural features are uncertain ... 

Problom 22.43 Methylation and hydrolysis of amylose (Problem 22.42) also gives 0.2-0.4% 2,3,4.6-tetra-O-methyl-D-glucose. Explain the origin of this compound. ... 

Problem 22.44 Amylopectin, the water insoluble fraction of starch, behaves like amylose, except that more 2,3,4,6-tetra-O-methyl-D-glucose (5%), and an equal amount of 2.3-di-O-methyl-D-glucose, is formed. Deduce the structure of amylopectin. 

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