A new anhydro disaccharide monomer, 1,6-anhydro-2,3-di-o-benzyl-4-o(2',3',4',6'-tetra-o-benzyl-beta-D-galact opyranosyl)-beta-D-glucopyranose (benzylated 1,6-anhydro lactose (LSHBE)), was synthesized from D-lactose to investigate the polymerizability and biological activities of the resulting branched polysaccharides. The ring-opening polymerization of LSHBE was carried out with phosphorus pentafluoride as a catalyst under high vacuum to give a stereoregular benzylated (1 -> 6)-alpha-D-lactopyranan. The molecular weights of poly(LSHBE)s increased with an increase in the amount of CH2CI2 solvent, and polymerization temperatures were affected in both molecular weights and yields of the polymers. The copolymerization of LSHBE with benzylated 1,6-anhydro-beta-D-glucopyranose (LGTBE) gave the corresponding copolysacchrides having different proportions of lactose and glucose units in good yields. After debenzylation to recover hydroxyl groups and then sulfation, sulfated homopoly(lactose)s and copoly(lactose and glucose)s were obtained. Sulfated homopoly(lactose)s had moderate anti-HIV (EC50 = 5.9 and 1.3 mu g/mL) and blood anticoagulant activities (AA = 18 and 13 unit/mg), respectively. Sulfated copoly(lactose and glucose) having 15 mol % lactose units gave high anti-HIV and blood anticoagulant activities of 0.3 mu g/mL and 54 unit/mg, respectively. These biological results suggest that the distance between branched units on the main chain plays an important role in the anti-HIV and blood anticoagulant activities. (C) 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 913-924, 2009