Enantioselective Diels–Alder reactions with left-handed G-quadruplex DNA-based catalysts

Abstract Since the discovery of left-handed G-quadruplex (L-G4) structure formed by natural DNA, there has been a growing interest in its potential functions. This study utilised it to catalyse enantioselective Diels-Alder reactions, considering its different optical rotation compared to an ordinary G4. It was determined that when L-G4 was used with a combination of copper (II) ions, there was a good enantioselectivity (−52 % ee) without further addition of ligands. When further consideration was given by adding G4 ligands, G4 was further stabilised, even obtaining a better enantioselectivity (up to −80 % ee). Moreover, when using ligands that have regulatory effects on G4, the ee value can be adjusted. In this work, a minimal left-handed G4 was reported. A follow-up study was also conducted, which recovers that the minimal left-handed G4 remains its catalytic effect and enantioselectivity, but is not so effective as the former case. This indicates that a complete G4 structure is relatively conducive to chiral catalysis.