Conversion of yeast mannan polysaccharide in mannose oligosaccharides with a thiopropargyl linker at the pseudo-reducing end

Polysaccharides are useful sources of preformed glycosyl linkages and therefore convenient building blocks can be prepared from them upon application of a proper degradation and derivatization scheme. Following this idea, the alpha-(1 -> 6) linkages of this polysaccharide were broken applying acetolysis reaction and the pseudo-reducing position of the resulting acetylated mannose oligosaccharides was functionalized with a thiopropargyl appendage through thiourea activation of the related glycosyl iodides. Deacetylation of the final products and optimization of the purification procedures are discussed. The best yields were observed combining size exclusion chromatography and HPLC. Nine different oligosaccharides, from mono-to tetrasaccharides, mainly alpha-configured at the pseudo-reducing terminal, were obtained in pure form, presenting the propargyl appendage, a feature that makes them suitable substrates for successive functionalizations.