Highly stereoselective synthesis of imino-C-di- and trisaccharides as hydrolytically stable glycomimetics

A new straightforward route to glycomimetics containing a piperidine unit is reported. The key step of the methodology is the intramolecular 1,3-dipolar cycloaddition of easily accessible glycosyl alkenyl nitrones. The reaction takes place in most cases with a complete selectivity in favor of the exo–exo adduct, which facilitates the synthesis of all-cis piperidines bearing the glycosyl units. The direct transformation of adducts into the final imino-C-di and trisaccharide analogues is achieved in one step using simple reagents. Inhibition properties against two glycosidases have been tested but no positive results have been found.