Synthesis of Di- and Trivalent Carbohydrate Mimetics with Oxepane Substructure by Employing Copper-Catalyzed [3+2] Cycloadditions of Alkynes with Azidooxepanes

A series of enantiopure poly(hydroxy)aminooxepanes was converted into the corresponding azidooxepanes by a safe and efficient copper(II)-catalyzed diazo transfer reaction employing nonafluorobutanesulfonyl azide as nitrogen donor. These azidooxepanes underwent smooth copper(I)-catalyzed [3+2] cycloadditions with alkynes (click reaction) to provide a series of simple triazoles. With dialkynes and a trialkyne, bis- and tristriazoles containing oxepane substructures were prepared. Due to the polyhydroxylated end groups, these compounds are regarded as carbohydrate mimetics with potential biological activities, for example, as selectin inhibitors. In addition, unsymmetrical systems and macrocyclic compounds were prepared, again by employing [3+2] cycloadditions as key steps.