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The methylation of sugar mercaptals

University of British Columbia

Sugar mercaptals were partially methylated with Purdie's reagents in tetrahydrofuran as a solvent, and the relative reactivity of hydroxyl groups was determined by estimation of the ratio of mono-0̲-methyl ethers. The highest reactivity of the 2-hydroxyl group, followed by that of the 3-hydroxyl group, was accounted for by the inductive effect of the mercaptal group and the variation of the ratios among the sugar mercaptals was further explained by the intramolecular hydrogen bonding in the zig-zag conformation of sugar mercaptals. The exceptionally high reactivity of the 3-hydroxyl group of D̳-galactose diethyl mercaptal was also shown to be explicable in terms of the hydrogen bonding. An appreciable reactivity of the primary hydroxyl groups was noted and attributed to the least steric hindrance at this position. A mechanism for the Purdie methylation was proposed. Mg values of various mono-0̲-methyl sugars were recorded and some modifications in the separation of mono-0̲-methyl sugars were also described. 5-0̲-Methyl-L̳-arabinose and two crystalline derivatives were synthesized for the first time, and 2-0̲-methyl-L̳-arabonolactone, hitherto known as a sirup, was crystallized.

Text

2011-11-18

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http://hdl.handle.net/2429/39157

Chemistry

University of British Columbia

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