Glucopyranoside catalytic

Catalytic Constants and Activation Parameters for the Enzymic Hydrolysis of /i-D-Glucopyranosides ... 

Catalytic reduction and methanolysis of the methylated capsular polysaccharide of Type III pneumococcus gives a mixture of methyl 2,3,6-trimethyl- and 2,4-dimethyl-a/3-D-glucopyranosides. The latter, which arises from glucuronic acid units in the polysaccharide, can be separated into crystalline a- and 6-isomers identical with synthetic specimens.84,88... 

The electron-donating effect of pyridine substituents becomes especially evident with 4-dimethylaminopyridine. Methyl a-D-glucopyranoside reacts with 1.1 molar equiv. of trityl chloride, 1.5 molar equiv. of triethylamine, and a catalytic amount of 4-dimethylaminopyridine in DMF to give 88% of the 6-trityl ether after only several hours at room temperature [326], With the classical method, the yield was 61 % and some difficulties with the formation of addition complexes of the product with pyridine were encountered [326]. Surprisingly, pyridine still remains frequently used as a solvent in combination with this effective catalyst [327, 328]. Of the two secondary hydroxyl groups of methyl 4,6-O-benzyl-a-D-mannopyranoside [119] or methyl 4-0-benzyl-a-L-rhamnopyranoside [122], the equatorial OH-3 was protected first. Tritylation of methyl 2-0-benzyl-a-L-fucopyranoside (46) proceeded readily to give (47) in 70% yield [109]. 

Ballou, Roseman and Link43 have reported that, on catalytic hydro-genolysis, the 0-acetylated benzyl D-glucopyranoside, D-xylopyranoside,... 

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