Exploring the Syntheses for Phenolic Acid Esters of Cellulose: Pros and Cons of Methods

Phenolic acid esters of cellulose show antioxidative and antimicrobial properties, which are very interesting for a variety of applications, including packaging and medicine. In contrast to simple mixing or encapsulation of phenolic compounds in polymeric materials, covalent linkage to the polymer backbone enables long-term activity and reduces toxicity because leaching of phenolic moieties is avoided. For the synthesis of such polymers, chemical modification of cellulose by polymer analogous reactions must be performed. Cellulose esters of ferulic-, 4-hydroxybenzoic-, vanillic-, protocatechuic-, and gallic acids are synthesized by two different approaches. On the one hand, transesterification of cellulose with corresponding methyl esters in DMSO/DBU/CO₂ is appropriate to synthesize derivatives possessing only one phenolic hydroxyl group, e.g. hydroxybenzoates and vanillates. On the other, conversion with TBS-protected imidazolides is carried out, which allows the synthesis of cellulose esters possessing multiple phenolic hydroxyl groups such as protocatechuates and gallates.