Acid-Catalyzed\nTransformation of Pyranosides into\nFuranosides as a Tool for Preparation of Furanoside Synthetic Blocks

The importance of natural glycoconjugates containing\nfuranoside\nresidues causes a continued demand for the development of efficient\nmethods for the synthesis of corresponding oligosaccharide derivatives\nto be used as molecular probes in glycobiological studies. Currently,\nthe chemical synthesis of furanose-containing oligosaccharides often\nrepresents a significant challenge because of the lack of short, efficient,\nand reliable methods for the preparation of selectively substituted\nfuranoside blocks. Herein, we report an easy protocol toward galactofuranose-containing\nmolecules based on the unusual equilibrium between pyranoside and\nfuranoside forms observed for a series of substituted galactosides.\nThe method’s utility is illustrated by the syntheses of furanoside-containing\noligosaccharides related to the antigenic polysaccharides of <i>Aspergillus fumigatus</i> and <i>Klebsiella pneumoniae</i> O2ac.