No abstract

The composition, sequence, length, and type of glycosidic linkages of polysaccharides profoundly affect their biological and physical properties. However, investigation of the structure-function relationship of polysaccharides is hampered by accessing well-defined polysaccharides in sufficient quantities. Here, we report a chemical approach to precision polysaccharides with native glycosidic linkages via living cationic ring-opening polymerization of 1,6-anhydrosugars. We synthesized well-defined polysaccharides with tunable molecular weight, low dispersity, and excellent regio- and stereoselectivity using a boron trifluoride etherate catalyst and glycosyl fluoride initiators. Computational studies revealed that the reaction propagated through the monomer alpha-addition to the oxocarbenium and was controlled by the reversible deactivation of the propagating oxocarbenium to form the glycosyl fluoride dormant species. Our method afforded a facile and scalable pathway to multiple biologically relevant precision polysaccharides, including D-glucan, D-mannan, and an unusual L-glucan. We demonstrated that catalytic depolymerization of precision polysaccharides efficiently regenerated monomers, suggesting their utility as a class of chemically recyclable materials with tailored thermal and mechanical properties.