The preparation of 2,3-di-O-benzyl ribose and 2,3-di-O-benzyl xylose will be described. These monomeric units contain unprotected hydroxyl groups at the 4 and 5 positions as well as an unprotected anomeric center, therefore they are subject to mutarotation. Equilibria studies, with the use of nuclear magnetic resonance, were performed to determine the relative abundance of the conformers, in solvents of varying polarity, as well as the change in the ratios of the conformers with time. In all cases, the pyranoses dominated. In DMSO the major isomer had a �-pyranose structure. In less polar solvents, the proportion of the furanoses increasedIn the case of 2,3-di-O-benzyl ribose, the crystal structure was elucidated via x-ray crystallography. This revealed that the molecule adopts a �- pyranose chair conformation comprised of two molecules in the unit cell.An iterative approach to the synthesis of oligofuranosides will be discussed that employs a biomimetic activation of the anomeric center. This synthetic approach employs the use of a limited protection protocol where acceptors of 2,3 di-O-benzyl ribose and 2,3-di-O-benzyl xylose are used to form oligomers of the respective sugars which are 1,5- linked and proceed with high �- selectivity.

Synthesis of 2,3-O-dibenzylribo and xylosides, and their equilibriation studies; Application to oligosaccharide synthesis

248th National Meeting (2014)

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