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Abstract

Chromatographic separation of penta-O-acetylsucrose fraction from deacetylation of octa-O-acetylsucrose by treatment with aluminium oxide impregnated by potassium carbonate gave 1',3,4,6,6'-penta-O-acetylsucrose (XII), 1,2,3,4,6-penta-O-acetylsucrose (XIII), and the prevailing 2,3,4,6,6'-penta-O-acetylsucrose (XIV). Reaction of compound XIV with two equivalents of p-toluenesulfonyl chloride in pyridine produced besides the 1'-O-p-toluenesulfonyl derivative XXI and 1',3',4'-tri-O-tosyl derivative XXII also 1',3'-di-O-tosyl derivative XXIII and 1',4'-di-O-tosyl derivative XX. 1',2-anhydro-(3,4,6-tri-O-acetyl-α-D-glucopyranosyl 6'-O-acetyl-3',4'-anhydro-β-D-ribo-hexulofuranoside) (X) and 2,3,4,6-tetra-O-acetyl-α-D-glucopyranosyl 1,6-di-O-acetyl-3,4-anhydro-β-D-ribo-hexulofuranoside (VIII) were prepared from compound XXIII by two minutes boiling with 1M sodium methoxide, evaporation of the reaction mixture, and acetylation (method A). Compound XX gives under reaction conditions of method A 2,3,4,6-tetra-O-acetyl-α-D-glucopyranosyl 1,6-di-O-acetyl-3,4-anhydro-β-D-lyxo-hexulofuranoside (IX) only. However, upon 24h boiling with 1M sodium methoxide, neutralization, evaporation, and acetylation of the reaction mixture (method B), we obtained 3,3',4,6,6'-penta-O-acetyl-1',2-anhydro-4'-O-methylsucrose (XXIV), 1',2,3,3',4,6,6'-hepta-O-acetyl-4'-O-methylsucrose (XXV), and 1',2-anhydro-(3,4,6-tri-O-acetyl-α-D-glucopyranosyl 3',4',6'-tri-O-acetyl-β-D-xylo-hexulofuranoside) (XXVI). Compounds XXV and XXVI are also formed by reaction of epoxide IX with sodium methoxide according to method B. Compound XXVI can be prepared by hydrolysis of the dianhydro derivative X followed by acetylation. A reaction mechanism for compound XXVI formation from the epoxide IX is proposed. It assumes an intramolecular opening of the oxirane ring in compound IX under formation of α-D-glucopyranosyl 1,3-anhydro-β-D-xylo-hexulofuranoside (XLVI). The 1'-O-tosyl derivative XXI reacts with sodium methoxide according to method B to give 3,3',4,4',6,6'-hexa-O-acetyl-1',2-anhydrosucrose (XXVIII), octa-O-acetylsucrose, and 2,3,3',4,6,6'-hexa-O-acetyl-1',4'-anhydrosucrose XL.