Cellulose, (1f4)--D-glucopyranan, was for the first time synthesized by cationic ring-opening polymerization of 3,6-di-O-benzyl-R-D-glucose 1,2,4-orthopivalate (5) into 3,6-di-O-benzyl-2-O-pivaloyl--D-glucopyranan (6) and subsequent removal of the protective groups. Polymerization of the orthoester 5 by triphenyl carbenium tetrafluoroborate gave 3,6-di-O-benzyl-2-O-pivaloyl--D-glucopyranan with [R] D -37.2°and a number-average molecular weight of 8.3 × 10 3 (DP n ) 19.3). Removal of the pivaloyl and benzyl groups and subsequent acetylation gave acetylated (1f4)--D-glucopyranan which was completely identical with cellulose triacetate (CTA) prepared from low molecular weight cellulose. The synthesized CTA was converted by deacetylation to cellulose, which has the cellulose-II crystal structure.

BioOne Complete (complete.BioOne.org) is a full-text database of 200 subscribed and open-access titles in the biological, ecological, and environmental sciences published by nonprofit societies, associations, museums, institutions, and presses.

To investigate the substituent effects at the 3-O and 6-O positions on ring-opening polymerization, 3,6-di-O-benzyl-α-d-glucopyranose 1,2,4-orthopivalate (1), 3-O-benzyl-6-O-pivaloyl-α-d-glucopyranose 1,2,4-orthopivalate (2), 6-O-benzyl-3-O-pivaloyl-α-d-glucopyranose 1,2,4-orthopivalate (3), and 3,6-di-O-pivaloyl-α-d-glucopyranose 1,2,4-orthopivalate (4) were selected as starting monomers and were polymerized under various reaction conditions. It was concluded from the results of monomer 1 reported previously and from those of monomers 2−4 in our present study that the benzyl group at the 3-O position is indispensable for yielding stereoregular (1→4)-β-d-glucopyranan derivatives, i.e., cellulose derivatives. The mechanisms of ring-opening polymerizations are discussed.

No abstract

The first chemical synthesis of cellulose derivatives, (1→4)-β-d-glucopyranan derivatives has been accomplished by cationic ring-opening polymerization using 3,6-di-O-benzyl-α-d-glucopyranose 1,2,4-orthopivalate (1) as a starting monomer, taking into account substituent effects. Here, three orthoester derivatives as starting materials for the polymerization, 3,6-di-O-benzyl-α-d-glucopyranose 1,2,4-orthopropionate (2), 3,6-di-O-benzyl-α-d-glucopyranose 1,2,4-orthoacetate (3), and 3,6-di-O-benzyl-α-d-glucopyranose 1,2,4-orthobenzoate (4), were selected to investigate the substituent effects of orthoester group on the ring-opening polymerization. These three monomers were polymerized under the same reaction conditions as those of monomer 1, yielding stereoregular (1→4)-β-d-glucopyranan derivatives, previously reported. As the result, monomers 2−4 gave non-regioregular polymers consisting of (1→4)- and (1→2)-β-pyranose units, although they gave high stereoregularity, i.e., β-glucosidic linkage. Thus, it was concluded from the polymerizations of the monomers 1−4 that the orthopivaloyl group of the starting monomer is indispensable for regiospecificity of the polymerization, yielding only the (1→4)-glycosidic bond, not the (1→2)-bond.