Synthesis of oligosaccharide dendrimers

Abstract

Two β-D-glucopyranoside-based dendrimers, one incorporating three tetra- and the other three heptasaccharide wedges attached to a central trisfunctionalized nonsaccharide core component, have been synthesized. Branching at designated saccharide units of the tetra- and of the heptasaccharide wedges arises from (1→2)/ (1→3)/(1→6) and from (1→3)/(1→6) intersaccharide linkages, respectively, with the 1,2-trans configuration at all anomeric centers. Both oligosaccharide wedges were constructed by stepwise glycosylation strategies and have reactive primary amino groups at their focal points located at the termini of spacer arms connected to the reducing glucose residues. Amide bond formation between these amino groups and appropriate core components carrying three carboxylic acid functions afforded two dendrimers incorporating a total of 12 and 21 monosaccharide units when the tetra- and the heptasaccharide wedges were employed, respectively. These nanosized highly branched macromolecules possess molecular diameters of 5-6 nm and molecular weights of 6195 and 10008 Daltons for the 12-mer and 21-mer, respectively. The wedges and dendrimers were characterized and the intersaccharide connectivity elucidated by extensive mono- and bidimensional 1H and 13C NMR spectroscopic investigations. In addition, LSIMS and MAL-DI-TOFMS investigations were also performed and revealed molecular ion peaks generally as H, Na, or K adducts for all oligosaccharides.