Glycosyl Azides as Building Blocks in Convergent Syntheses of Oligomeric Lactosamine and Lewis Saccharides

Article abstract of DOI:10.1016/S0968-0896(96)00209-X

Oligosaccharides containing type 2 lactosamine repeating units, e.g. neo-lacto-octaose and trimeric Lewis derivatives, are constructed using neo-lactosamine azide building blocks.The azido group provides a favorable protection of the anomeric position which is stable to versatile protecting group manipulations and glycosylation reactions.On the other hand, glycosyl azides can be converted into glycosyl fluorides via a 1,3-dipolar cycloaddition with di-tert-butyl-acetylenedicarboxylate and subsequent treatment of the resulting N-glycosyl triazoles with hydrogen fluoride-pyridine complex.Activation of the lactosamine fluorides with Lewis acids affords the possibility to extend the oligosaccharide chain with disaccharide units.Suitable protecting group combinations within the galactose and the glucosamine portion of the lactosamine unit enable selective deprotection reactions and subsequently, chain extension or branching, e.g. to yield Lewis structures. - Keywords: glycosyl azides; glycosyl fluorides; oligosaccharide synthesis; trimeric Lewis; oligomeric lactosamines.