Toshifumi Satoh, Tomoko Imai, Norihiko Sugie, Hisaho Hashimoto and Toyoji Kakuchi
The polymerizations of 1,2:5,6-diepithio-3,4-di-O-methyl-D-mannitol (1a), 1,2:5,6-diepithio-3,4-di-O-methyl-L-iditol (1b), and 1,2:5,6-diepithio-3,4-di-O-methyl-allitol (1c) were carried out with zinc complexes. The polymerization of 1a using the ZnEt2/H2O (1/1) catalyst in tetrahydrofuran proceeded through a regio- and stereoselective cyclopolymerization mechanism to produce thiosugar polymers mainly consisting of 2,5-anhydro-1,5-dithio-3,4-di-O-methyl-D-glucitol units. The polymers obtained from 1b and 1c with ZnEt2/H2O exhibited lower stereoregularities than that from 1a. On the other hand, the polymerization of 1c using ZnEt2/(R or S)-BN asymmetrically proceeded, and optically active polymers consisting of desulfurized acyclic units were obtained. When ZnEt2/(R)-BN (1/1) in toluene was used, the polymer with [α]D23 = +56.9° was obtained.