Olefin cross-metathesis as a source of polysaccharide derivatives: cellulose ω-carboxyalkanoates.

Cross-metathesis has been shown for the first time to be a useful method for the synthesis of polysaccharide derivatives, focusing herein on preparation of cellulose ω-carboxyalkanoates. Commercially available cellulose esters were first acylated with 10-undecenoyl chloride, providing esters with olefin-terminated side chains. Subsequent cross-metathesis of these terminal olefin moieties with acrylic acid was performed in solvents including acrylic acid, THF, and CH2Cl2. Complete conversion to discrete, soluble cross-metathesis products was achieved by using the Hoveyda-Grubbs second generation ruthenium catalyst and an excess of acrylic acid. Oligomerization during storage, caused by a free radical mechanism, was observed and successfully suppressed by the addition of a free radical scavenger (BHT). Furthermore, the cross-metathesis products exhibited glass transition temperatures (Tg) that were at least 50 °C higher than ambient temperature, supporting the potential for application of these polymers as amorphous solid dispersion matrices for enhancing drug aqueous solubility.