Helical Polymers Showing Inverse Helicity and Synergistic Effect in Chiral Catalysis: Catalytic Functionality Determining Enantioconfiguration and Helical Frameworks Providing Asymmetric Microenvironment
Haiyang Zhang, Jianping Deng
Macromolecule Chemistry and Physics
This article reports optically active helical polymers showing inverse helicity, which is controlled by copolymer composition. L-Proline-derived monomer and an achiral monomer have been copolymerized, affording copolymers with optical activity and remarkable catalytic ability. By adjusting relative content of the two monomers, a series of copolymers with varied optical activity has been obtained. More notably, the handedness of the macromolecular helices inverses at specific monomer feed ratios. Copolymers with opposite helicity have been applied as chiral catalysts for asymmetric aldol reaction to investigate the exact role of helical structures in catalysis. The variation in the stereoselectivity of product has demonstrated an intriguing synergistic effect occurring between the helical macromolecular frameworks and pendent prolineamide groups. The macromolecular helices provide asymmetric microenvironment for the reaction while enantioconfiguration of the product is determined by the specific catalytic functionality. This study opens up new opportunities for manufacturing macromolecules as mimetic enzymes catalyzing asymmetric reactions.
Circular dichroism, Secondary structure, Polymers, Stereochemistry,