Chirality Gearing in an Achiral Cage through Adaptive Binding

Abstract

Herein we report an adaptive, achiral trithiourea molecular cage and its conformational and stereodynamics toward tricarboxylate anion binding. The cage was readily synthesized in four steps with a 44% yield for the irreversible cage-forming reaction. It possesses a flexible conformation and strongly binds 1,3,5-benzene tricarboxylate by forming a sandwich-like inclusion complex, with an affinity up to 106 M–1 in acetonitrile. Upon binding, the cage is locked in a twisted helical conformation. By incorporation of three chiral arms on the guest, a gear-like complex dominant in one given helical sense was produced. Due to the steric crowding in the helical grooves, a small change of methyl to ethyl on guest caused a striking difference on binding and chiral induction. The system thus represents a rare example of chiral induction on a flexible, achiral host and provides a decoupled model that the generation of a racemate and following chiral discrimination can be individually probed.

Chiral adaptive recognition with sequence specificity of aromatic dipeptides in aqueous solution by an achiral cage

“…As a result, these achiral hosts can gain a kind of guest-induced conformation chirality in the host-guest complexation to exhibit turn-on chiroptical signals (e.g., CD and CPL), which are distinguished, real-time, and adaptive responses to the different chiral guests and their enantiomers. 47,48 Here, we develop the chiral adaptive recognition (CAR) with sequence specificity of aromatic dipeptides by an achiral TPE-based cage (1) in an aqueous solution. The molecular recognition of 1 for amino acids, dipeptides, tetrapeptides, polypeptides, and even proteins are systematically proposed and investigated.…”

“…, CD and CPL), which are distinguished, real-time, and adaptive responses to the different chiral guests and their enantiomers. 47,48…”

Amino-Ligand-Coordinated Dicopper Active Sites Enable Catechol Oxidase-Like Activity for Chiral Recognition and Catalysis

“…Metal–organic frameworks (MOFs), featuring molecular/atomic-level active sites, precisely tailored scaffolds, and tunable coordination microenvironment, hold great promise in molecularly customizing the active sites of enzymes. − The catalytic units and recognition binding units of enzymes can be mirrored in the structure and composition of MOFs via a vast library of metal–ligand coordination bonds. Lewis acid metal centers assist electron transfer from substrates, and their subsequent activation and conversion, which points out the direction for manipulating enzyme-like catalytic activities and types. , Also, the ligand-induced steric effect dominates the conformational adaptation and the free rotation of the substrate, which sheds light on obtaining high-level catalytic selectivity. , Thus, the conjugation of ligand-binding metal centers can be designed rationally in pursuit of duplicating enzyme-like structure and reactivity. Meanwhile, chiral ligands can be delicately tailored around the catalytic sites for targeted stereoselectivity by transferring the ligand asymmetry to the reactions.…”

“…11,18 Also, the ligand-induced steric effect dominates the conformational adaptation and the free rotation of the substrate, which sheds light on obtaining high-level catalytic selectivity. 19,20 Thus, the conjugation of ligand-binding metal centers can be designed rationally in pursuit of duplicating enzyme-like structure and reactivity. Meanwhile, chiral ligands can be delicately tailored around the catalytic sites for targeted stereoselectivity by transferring the ligand asymmetry to the reactions.…”

Real-time chirality transfer monitoring from statistically random to discrete homochiral nanotubes

“…Compared with polymeric and supramolecular polymeric systems involving chirality transfer, discrete chirality transfer systems are much easier to monitor and analyze because of their simpler structures [15][16][17][18][19] . For example, enantiopure metallocages and organic cages can be synthesized using chirality transfer from chiral guest molecules or chiral auxiliary ligands [25][26][27][28][29][30] . However, these initial studies mainly focused on the chirality transfer in the final stage (equilibrium state), because controlling the chirality transfer rate and trapping the heterochiral assemblies were difficult (Fig.…”