PNA as Hybrid Catalyst Scaffold Catalyzed Asymmetric Friedel–Crafts Alkylation

Abstract

Double-stranded DNA can form efficient hybrid catalysts for asymmetric catalysis upon binding of small metal complexes, which has attracted significant interest. Catalytic microenvironment and chiral transfer are still a matter of concern. Here, we introduced peptide nucleic acid (PNA) chains to design oligo-dsPNA and hybrid PNA/DNA as chiral scaffolds to catalyze Friedel–Crafts reaction. Though with the same sequence as DNA control, dsPNA and hybrid duplexes are less suited for use in asymmetric catalysis due to ligand-Cu2+ complex does not form highly active and enantioselective hybrid catalysts with PNA-containing scaffolds. CD and UV titration assays indicated that the complex bound to suitable groove and the resulting preferential conformation are the key to catalytic performance, rather than just binding affinity. The negative charge of backbone and the resulting groove size of DNA are the key to act as a more active and highly selective catalyst than PNA.