Melezitose methylation

Turanose is readily purified by recrystallization from hot methyl alcohol, in which it is moderately, though slowly, soluble. In preparing the sugar, the first stage of the hydrolysis of melezitose by an acid solution is carried out under well controlled conditions, and is followed by the removal of the D-glucose from its mixture with turanose. This is usually accomplished by a selective fermentation with yeast, but an... 

Revised Interpretation of the Methylation Data concerning Melezitose... 

The presence of the pyranose ring in the two D-glucose units of melezitose was inferred by Zempl6n and Braun from good evidence, and made certain by Miss Leitch29 through the crystallization of the requisite amount of 2,3,4,6-tetramethyl-D-glucose from the scission products of the fully methylated trisaccharide. The revised interpretation of Miss Leitch s experimental data concerns only the structure of the... 

One notices that the data from the oxidation of melezitose by per-iodic acid confirm the pyranose structure of the D-glucose unit in turanose, and therefore also in the case of maltose, in agreement with the original assignments for both of these disaccharides from methylation studies. 

The same holds for substitution at C3 and C5 of the fructofuranose moiety of sucrose neither melezitose (XV)61 nor o-D-glucopyranosyl-/3-D-xyloketofuranoside (XVIc)22 is hydrolyzed by yeast saccharase. As might have been expected from the experience with glycosidases, any change in the configuration of the fructon of sucrose results in stereoisomers unhydrolyzable by /3-fructofuranosidase. Thus, methyl and benzyl a-D-fructofuranosides,62 isosucrose (= /3-D-glucopyranosyl-a-D-fructo-... 

One of the major points advanced by Kuhn and von Grundherr for the substituted-sucrose structure of melezitose was the extreme ease of acid hydrolysis of one of the linkages, which had earlier led Alekhine to the discovery of turanose and the trisaccharide nature of melezitose. For years this feature was accepted as virtual proof of the presence of sucrose in the melezitose molecule. However, the opinion that the ease of hydrolysis was evidence for the furanoid form of the D-fructose ring lost all validity with the discovery by Purves and Hudson1 that methyl D-fructopyranoside is hydrolyzed by acids with the same ease as methyl D-fructofuranoside moreover, the ease of hydrolysis never was evidence concerning the a- or /3-configuration of the D-fructose unit in melezitose. ... 

ZempKin and Braun1 showed that methylation of melezitose followed by hydrolysis gave as one of the products a liquid trimethyl-D-fructose which they claimed to be 1,3,4-trimethyl-D-fructose. They... 

Methylation of melezitose, followed by hydrolysis, gives I,4,6-tri-0-methyl-D-fructosc and two moles of 2,3,4,6-tclra-0-meth>i-i>-glucose. 

The full methylation of melezitose in 1926-1927 by Zempldn and Braun and by Miss Leitch yielded a hendecamethyl-melezitose, the acid hydrolysis of which produced two moles of 2,3,4,6-tetramethyl-D-glucopyranose and one mole of a trimethyl-D-fructose, to which a 1,3,4-trimethyl structure was assigned on evidence that cannot now be regarded as precise, though it seemed reasonable at the time. The selection of a faulty formula for this trimethyl-D-fructose, which must have been 1,4,6-trimethyl-D-fructose as will be shown later, led to much confusion during the following decade. 

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