Lipase-Catalyzed Enantioselective Copolymerization of Substituted Lactones to Optically Active Polyesters

Enantioselective copolymerization of racemic substituted lactones with achiral lactones has been examined by using Candida antarctica lipase as catalyst. In the copolymerization of racemic β-butyrolactone with 12-dodecanolide, the ( S )-isomer was preferentially reacted to give the ( S )-enriched optically active copolymer with enantiomeric excess of β-butyrolactone unit = 69%, which is much larger than that of the homopolymerization under similar reaction conditions. The absolute configuration of β-butyrolactone unit in the copolymer was confirmed by the acid-catalyzed methanolysis to methyl 3-hydroxybutyrate. δ-Caprolactone was also enantioselectively copolymerized by the lipase catalyst to give the optically active polyester. The highest ee value (76%) was achieved by the copolymerization of δ-caprolactone and 12-dodecanolide in diisopropyl ether.