Highly chemoselective lipase from Candida sp. 99-125 catalyzed ring-opening polymerization for direct synthesis of thiol-terminated poly(ɛ-caprolactone)

Lipase from Candida sp. 99-125 catalyzed ring-opening polymerization of ɛ-caprolactone in the presence of 6-mercapto-1-hexanol was presented as a new metal-free approach for direct synthesis of well-defined thiol-terminated poly(ɛ-caprolactone). Remarkably, high chemoselectivity of lipase from Candida sp. 99-125 toward hydroxyl and thiol was exhibited and quantitative thiol fidelity over 90% was achieved. The tedious protecting/deprotecting steps for thiol and metal residue were avoided. The polymerizations with around 70% monomer conversion were conducted in bulk and toluene at relative low temperature of 40 °C. Number–average molecular weight of resulted polymers ranged from 3000 to 4700 Da by changing the feed ratio between monomer and initiator. The structures of obtained thiol-terminated poly(ɛ-caprolactone) were demonstrated by combining NMR and SEC analyses.

Graphical abstractHigh chemoselectivity of lipase from Candida sp. 99-125 toward hydroxyl and thiol was exhibited. Well-defined thiol-terminated poly(ɛ-caprolactone) with over 90% thiol fidelity was directly obtained under mild conditions.Figure optionsDownload full-size imageDownload as PowerPoint slide