An enzymatic biomimetic system: enhancement of catalytic efficiency with new polymeric chiral ionic liquids synthesised by controlled radical polymerisation

Abstract

The controlled radical polymerization of monomeric units containing chiral ionic liquids (CILs) allows the synthesis of intrinsically chiral polymers through a bottom-up design. These polymeric chiral ionic liquids (PCILs) show a well-defined three dimensional structure organized as the result of a complex noncovalent network of hydrogen-bonding contacts driven by the C2 hydrogen atoms of the imidazolium aromatic rings and the OH moieties present in the side functionalities of the main polymeric chain. The exchange of the chloride counter ion by the L-prolinate anion leads to new types of polymeric catalysts, which behave as efficient artificial aldolase biomimetic systems, being highly active and selective for the aldol reaction in water. These new polymeric catalysts are significantly more active than the corresponding monomeric counterpart when the reaction is performed either in water or in the presence of water. The increase in catalytic efficiency can be related to their 3D structure, displaying helical chirality in the polymeric chain as a function of their preparation methodology. Under suitable experimental conditions, these polymers are able to catalyse the consecutive aldol-dehydration process, behaving as synthetic mimics of the aldolase-dehydrogenase enzymatic system. Moderate enantioselectivities can be achieved under suitable conditions.

Bioinspired Polymer-Bound Organocatalysts for Direct Asymmetric Aldol Reaction: Experimental and Computational Studies

“…The polymer matrix should be capable of providing a suitable chain architecture to locate the catalytic units for efficient chiral induction. In view of this, among a variety of polymeric catalysts [6][7][8][9][10][11][12][13][14] for asymmetric organic reactions, the synthetic polypeptides [11][12][13][14] show promise as an ideal scaffold to construct artificial enzymes because their structural components are similar to those of biological macromolecules.…”

Chiral anion-triggered helical poly(ionic liquids)

“…It was reported that, the helical stabilization was due to chirality induction at anionic site as well as at cationic site in vinyl polymers. 76 Montolio et al demonstrated that CPILs bearing chirality at the cationic cite can induce well organize secondary structure. 77 In this current contribution we have demonstrated the induction of chirality as well as helicity in PILs by introducing chiral amino acids at the anionic site.…”

Advances in Organic and Organic-Inorganic Hybrid Polymeric Supports for Catalytic Applications

“…In 2014, Karjalainen et al reported the synthesis and application of new polymeric chiral ionic liquids (PCILs) as artificial aldolase biomimetic systems for the aldol reaction [56]. These polymers were prepared by controlled radical polymerization of monomeric units containing chiral ionic liquids (CILs).…”