Methyl /8-D-fructoside

When the original methyl D-fructofuranoside sirup was fermented with yeast, the unstable beta isomer was selectively eliminated and the residue yielded a crystalline methyl D-fructoside melting at 81° and with [a] D +93° in water. The ring structure of this new isomer was proved to be furan by methylation to the liquid tetramethyl derivative, of [a] °D +129.4°, and subsequent hydrolysis to 1,3,4,6-tetramethyl-D-fructofuranose (structure IX) with the correct specific rotation of +29.8° in water. Both the methyl D-fructoside and its fully methylated derivative were therefore of the alpha configuration, since the latter was more dextrorotatory than the tetramethyl-D-fructose and also since the former was more dextrorotatory than the isomer, of [a] D —51°, unstable to invertase. Similar work with the benzyl D-fructofuranoside sirup produced the crystalline alpha isomer, melting point 89°, [a] D +45.7° in water, the liquid tetramethyl derivative, [a] D +83.3° in chloroform and, after acid hydrolysis of the latter, 1,3,4,6-tetramethyl-D-fructofuranose. 

A simple preparation of pure methyl /3-D-fructofuranoside has been described earlier syntheses had given a,/3 mixtures of unknown composition. A solution of sucrose (0.2 M) in anhydrous methanol was refluxed for 1 hour in the presence of dry Dowex-50 (H+), with constant stirring. After evaporation of the solution under vacuum, the resulting sirup was purified on a Dowex-1 (borate) column, and the chromatographicaUy pure methyl D-fructoside showed Cq ]d — 60 3° (in water) this value agrees with the value of —52° predicted by Purves and Hudson. ... 

Gee and Walker reported the separation of such methylated glucose and fructose derivatives, mainly tetra- and tri-methyl ethers, as would arise from methylated sucrose derivatives. At the same time, they showed that fully methylated di- and tri-saccharides could be separated by gas chromatography. In a study on sucrose lactate, Percival and Young showed that the isomeric methyl 1,3,4-, 1,3,6-, and 1,4,6-tri-O-methyl-D-fructosides have similar retention times on 15% butanediol succinate, but are resolved on IM polyphenyl ether or 10 ethylene glycol adipate. 

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