A highly efficient synthetic strategy for polymeric support synthesis of Le^x, Le^y, and H-type 2 oligosaccharides

The O-protecting groups Levulinoyl (Lev) and 9-fluroenylmethoxycarbonyl (Fmoc) offer an attractive set of orthogonal protecting groups which are compatible with base sensitive N-trichloroethoxylcarbonyl (Troc) group. By exploiting these orthogonal protecting groups and a novel phenolic ester linker, a series of oligosaccharide of biological importance, Le^x, H-type 2, and Le^y, were synthesized on the x polytheylene glycol resin MPEG (M_w 5000). The products bearing a p-hydroxybenzyl group could be easily converted into glycosyl donors for further synthesis. Using this strategy, a spacer containing tumor antigen Le^y-Lac hexasaccharide was described. The artificial spacer at the reducing end provides an opportunity for selective conjugation to an appropriate carrier protein for immunlogical studies.