Synthesis of optically inactive cellulose via cationic ring-opening polymerization

Cellulose, which comprises D-glucose and L-glucose (D,L-cellulose), was synthesized from D-glucose ( 1D ) and L-glucose ( 1L ) via cationic ring-opening polymerization. Specifically, the ring-opening copolymerization of 3- O -benzyl-2,6-di- O -pivaloyl-β-D-glucopyranoside ( 2D ) and 3- O -benzyl-2,6-di- O -pivaloyl-β-D-glucopyranoside ( 2L ), synthesized from compounds 1D and 1L , respectively, in a 1:1 ratio, afforded 3- O -benzyl-2,6-di- O -β-D,L-glucopyranan ( 3DL ) with a degree of polymerization ( DPn ) of 28.5 ( Mw/Mn = 1.90) in quantitative yield. The deprotection of compound 3DL and subsequent acetylation proceeded smoothly to afford acetylated compound 4DL with a DPn of 18.6 ( Mw/Mn = 2.08). The specific rotation of acetylated compound 4DL was + 0.01°, suggesting that acetylated compound 4DL was optically inactive cellulose triacetate. Furthermore, before acetylation, compound 4DL was an optically inactive cellulose comprising an almost racemic mixture of D-glucose and L-glucose. Compound 4DL was an amorphous polymer. This is the first reported synthesis of optically inactive D,L-cellulose.