Organocatalyzed Ring-Opening Polymerization of Cyclic Lysine Derivative: Sustainable Access to Cationic Poly(ε-lysine) Mimics

Poly(ε-lysine) has broad applications and is dominantly produced via fermentation. Our group successfully realized the chemosynthesis of poly(ε-lysine) through ring-opening polymerization (ROP) of a 2,5-dimethylpyrrole-protected cyclic lysine monomer, but the complete removal of the protecting group suffers from a prolonged time and low yield. Herein, we have developed organocatalyzed ROP of a dimethyl-protected cyclic lysine that avoids the tedious deprotection procedures to prepare cationic poly(ε-lysine) mimics with quaternary ammonium groups in high yields. Such poly(ε-lysine) mimics not only exhibit potent antimicrobial activities but also demonstrate good biocompatibility and have no significant hemolytic activities. The antimicrobial activities of poly(ε-lysine) mimics were ∼80.0% at a concentration of 100 μg/mL in comparison to 76.0% of the poly(ε-lysine) control. In brief, our research provides a novel class of functional mimics of poly(ε-lysine) and opens up new avenues for designing and furnishing poly(amino acid) mimetics for biological functions and applications.