Synthesis of a new 2-amino-glycan, poly-(1?6)-a-D-mannosamine, by ring-opening polymerization of 1,6-anhydro-mannosamine derivatives

A stereoregular 2-amino-glycan composed of a mannosamine residue was prepared by ring-opening polymerization of anhydro sugars. Two different monomers, 1,6-anhydro-2-azido-mannose derivative (3) and 1,6-anhydro-2-(N, N-dibenzylamino)-mannose derivative (6), were synthesized and polymerized. Although 3 gave merely oligomers, 6 was promptly polymerized into high polymers of the number-average molecular weight (Mn) of 2.3 x 104 to 2.9 x 104 with 1,6-alpha stereoregularity. The differences of polymerizability of 3 and 6 from those of the corresponding glucose homologs were discussed. It was found that an N-benzyl group is exceedingly suitable for protecting an amino group in the polymerization of anhydro sugars of a mannosamine type. The simultaneous removal of O- and N-benzyl groups of the resulting polymers was achieved by using sodium in liquid ammonia to produce the first 2-amino-glycan, poly-(1?6)-alpha-D-mannosamine, having high molecular weight through ring-opening polymerization of anhydro sugars.(c) 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012