ANIONIC RING-OPENING POLYMERIZATION OF A NOVEL OPTICALLY-ACTIVE BICYCLIC LACTAM SYNTHESIZED FROM AN ACIDIC SACCHARIDE

A new optically active bicyclic lactam, (1S,4S,5R)-4-(benzyloxy)-8-oxa-6-azabicyclo[3.2.1]oct-2-en-7-one (2), was synthesized from the most common acidic monosaccharide, D-glucuronic acid (1) in 12% total yield. Anionic ring-opening polymerization of 2 proceeded at -60 to +25-degrees-C in various solvents to give acetone-insoluble polymers. From the spectroscopic analyses, the polymer precipitated from the tetrahydrofuran solution during the polymerization at -40-degrees-C was found to have a repeating unit containing a 5,6-dihydro-2H-pyran ring (3) and that obtained in the NN-dimethylformamide homogeneous solution to have another unit with a 5,6-dihydro-4H-pyran ring (4), which was isomerized from 3. The double bond in 3 rearranges through a polymeric anion formed by a proton abstraction in the later stage of the polymerization in the homogeneous solution.