Glucopyranose dimethyl sulfate

Methylation with dimethyl sulfate in basic solution followed by acid hydrolysis gives 2,3,4,6-tetra-O-methyl-D-glucopyranose and 2,3,6-tri-O-methyl-D-glucose. 

The selectivity of alkylation of 1,6-anhydrohexopyranoses is lower than drat of acylations. The relative rate-constants for the three hydroxyl groups in 1,6-anhydro-jS-D-glucopyranose (6) during methyla-tion with dimethyl sulfate in 19% sodium hydroxide solution689 are k2 ks k4 = 2.5 1 1.8, so that the formation of pure monomethyl or dimethyl ethers of 6 by this method is of little preparative value (compare Refs. 224 and 671). l,6-Anhydro-/3-D-galactopyranose (12) affords mostly the 2,4-di-O-methyl derivative,690 and 2-acetamido-l,6-anhy-dro-2-deoxy-/3-D-galactopyranose is mainly methylated at 0-4 by the... 

Repeated methylation of SII with dimethyl sulfate and sodium hydroxide afforded a product containing only 42% of methoxyl group, which represented a slight improvement on the methylated SII (OMe, 38.2%) obtained by Kent. Sequential methanolysis, acidic hydrolysis, and fractionation of the hydrolysate on ion-exchange resins led to identification and characterization of 2,4-di-O-methyl-L-rhamnopyranose (7 parts) 2,3-di-O-methyl-D-glucopyranose (1 part) 2,3,4-tri-O-methyl-D-glucuronic acid (1 part) and 2,3-di-O-methyl-D-glucuronic acid (2 parts). 2,4-Di-O-methyl-L-rhamnopyranose had previously been characterized as a com-... 

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