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Selective substitution of sucrose McKeown, George Gordon

Abstract

Detritylation of tri-O-trityl-penta-O-acetyl sucrose with catalytic bydrogenolysis or graded hydrolysis with aqueous acetic acid gave in yields up to 60% a new crystal line penta-O-acetyl sucrose derivative. Methylation of the pentaacetate with the Purdie reagents, followed by deacetylation and chromatographic purification gave a sirupy tri-O-methyl sucrose which was shown to be 1’, 4, 6' -tri-O-methyl sucrose by periodate oxidation and by hydrolysis to equal parts of 4-O-methyl-D-glucose and 1, 6-di-O-methyl-D-fructose. The glucose derivative was identified by paper chromatography, specific rotation and by conversion to the known, crystalline osazone, and the structure of the new sirupy 1, 6-di-O-raethyl-D-fruetose was established by analysis, periodate oxidation, paper chromatographic behavior and the specific rotation. Deacetylation of tri-0-trityl-penta-O-acetyl sucrose gave an amorphous tri-O-trityl sucrose and methylation of this compound with the Purdie reagents, followed by detritylation with aqueous acetic acid gave a sirupy penta-O-methyl sucrose derivative, which was identified as 2, 3, 3', 4, 4’ -penta-O-methyl sucrose by hydrolysis to equal parts of the known 2, 3, k -tri-O-methyl-D-glueose and 3, 4 -di-O-methyl-D-fructose. It was therefore established that the trityl groups in the original tri-O-trityl-penta-O-acetyl sucrose occupied the three primary positions (1’, 6 and 6’) in the sucrose molecule and that acetyl migration from C4 to C6 in the glucose moiety had occurred during the synthesis of the tri-O-methyl sucrose. Vinylation of 1: 2-3: 4-di-O-isopropylidene-D-galactose with vinyl acetate after the method of Adelraan gave after catalytic hydrogenation followed by removal of the acetone groups a 0.7% yield of sirupy 6-O-ethyl-D-galactose. The new galactose derivative was identified by comparison with an authentic sample synthesized by direct ethylation of 1; 2 -3: 4 -di-O-iaopropylidene-D-galactose. Preliminary studies of the vinylation of the new crystalline penta-O-acetyl sucrose are reported. The action of Dowex I on several acetates of non-reducing carbohydrates was found to result in deacetylation in nearly quantitative yields.

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