Reducing sugar ball Au (III)Au (0) A hyperbranched glycopolymer arranged with numerous reducing D-glucose units on the peripheries of the polymer, i.e., "reducing sugar ball", possessed a higher reducing ability than D-glucose because of the glyco-cluster effect or the multivalent effect of the D-glucose units.2Abstract. The ring-opening polymerization of 5,6-anhydro-1,2-O-isopropylidene--D-glucofuranose (1) as a latent cyclic AB 2 -type monomer was carried out using potassium tert-butoxide (t-BuOK) or boron trifluoride diethyletherate (BF 3 ·OEt 2 ) as an initiator in order to synthesize a novel hyperbranched glycopolymer. The anionic and cationic polymerizations proceeded via the proton-transfer reaction mechanism to produce the hyperbranched poly(5,6-anhydro-1,2-O-isopropylidene--D-glucofuranose) (2). In particular, the cationic polymerization with the slow-monomer-addition strategy is a facile method leading to the hyperbranched glycopolymers with high molecular weights and highly branched