Stereoselective polycondensation of levoglucosenone leading to water-degradable biopolymers

Abstract

Highly stereochemically controlled polymers were successfully synthesized from levoglucosenone (LGO), derived from cellulose. Since its discovery in the 1970s, the reactivity of LGO has been widely studied in organic chemistry, owing to its diverse functional groups that serve as linkages for polymer formation. However, most of the previous methods for synthesizing polymers from LGO lacked precise control over regio- and stereochemistry, making stereoselective polymerization from LGO a persistent challenge. Although the ketone moiety in LGO is typically reduced before polymerization, a new LGO polymer was designed, containing a CN bond obtained by condensation with dicarboxylic dihydrazide. NMR measurements revealed that condensation occurred with high stereoselectivity to produce the E-isomer. This selectivity extended from the model compound to polymer synthesis, achieving high E/Z selectivity. The resulting polymer exhibited optical rotation (up to +89), indicating its potential as a chiral polymer. In spite of these polymers showing high tolerance toward many solvents, they were degradable in water with a simple chemical treatment. The proposed approach facilitates the development of sustainable, high-performance materials that can address both environmental and industrial needs.