The anionic cyclopolymerization of 1,2:5,6-dianhydro-3,4- di-O-methyl-L-iditol (3) was carried out using t-BuOK and KOH. The resulting polymer 4 consisted of 2,5-anhydro-3,4-di-O-methyl-D-glucitol as a five-membered repeating unit, which was identical with that of polymer 2 obtained from 1,2:5,6-dianhydro-3,4-di-O-methyl-D-mannitol (1). The copolymerization of 1 with 3 produced a random copolymer consisting of (1-->6)-, (6-->1)-, (1-->1)-, and (6-->6)-linked 2,5-anhydro-3,4-di-O-methyl-D-glucitol. These facts elucidated the presence of two Linkages during the homopolymerization of 1 and 3, i.e., the (1-->6) and (6-->1)-bonded 2,5-anhydro-3,4-di-O-methyl-D-glucitol units in polymers 2 and 4, respectively.