Epimerization-suppressed organocatalytic synthesis of poly-L-lactide in supercritical carbon dioxide under plasticizing conditions

Herein, an efficient (>95% yield, >99.0% ee) Bronsted acid-catalyzed synthetic method of poly-L-lactide (PLLA) in supercritical carbon dioxide (scCO(2)) under plasticizing conditions is presented. High-performance liquid chromatography analysis of the PLLA hydrolysis products indicated that, as opposed to the case of organic solvents, the use of a nucleophilic catalyst in scCO(2) suppressed the epimerization. The highly stereochemically pure PLLA prepared by the developed method under metal-free conditions meets the criteria of medicinal/engineering applications. (C) 2019 Elsevier Ltd. All rights reserved.