Substituent effect on ring-opening polymerization of regioselectively acylated 1,4-anhydro-alpha-D-glucopyranose derivatives

To investigate the substituent effects at the 2-O, 6-O, and 3-O positions on ring-opening polymerization, 1,4-anhydro-2,3-di-O-benzyl-6-O-pivaloyl-alpha-D-glucopyranose (1), 1,4-anhydro-3,6-di-O-benzyl-2-O-pivaloyl-alpha-D-glucopyranose (2), 1,4-anhydro-3-O-benzyl-2,6-di-O-pivaloyl-alpha-D-glucopyranose (3), and 1,4-anhydro-6-O-benzyl-2,3-di-O-pivaloyl-alpha-D-glucopyranose (4) were selected as starting monomers and were polymerized under various reaction conditions. It was concluded from the results of monomers 1 and 2 reported previously and from those of monomers 3 and 4 in our present study that both the pivaloyl group at the 2-O position and the benzyl group at the 3-O position are indispensable for yielding stereoregular (1-->5)-beta-D-glucofuranan derivatives with high molecular weights and theta substituent group at the 6-O position hardly affects stereoregularity or polymerizability. The 1,4-anhydro-alpha-D-glucopyranose skeleton is not suitable for yielding a (1-->4)-beta-D-glucopyranan i.e., cellulose.