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"Chirality."
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Catalytic asymmetric reactions of isocyanides for constructing non-central chirality
Beyond the conventional carbon-centered chirality, catalytic asymmetric transformations of isocyanides have recently emerged as a powerful strategy for the efficient synthesis of structurally diverse scaffolds featuring axial, planar, helical, and inherent chirality. Herein, we summarize the exciting achievements in this rapidly evolving field. These elegant examples have been organized and presented based on the reaction type as well as the resulting chirality form. Additionally, we provide a perspective on the current limitations and future opportunities, aiming to inspire further advances in this area.
Journal Article
Chiral phosphoric acid-catalyzed asymmetric synthesis of helically chiral, planarly chiral and inherently chiral molecules
Chiral molecules, distinguished by nonsuperimposability with their mirror image, play crucial roles across diverse research fields. Molecular chirality is conventionally categorized into the following types: central chirality, axial chirality, planar chirality and helical chirality, along with the more recently introduced inherent chirality. As one of the most prominent chiral organocatalysts, chiral phosphoric acid (CPA) catalysis has proven highly effective in synthesizing centrally and axially chiral molecules. However, its potential in the asymmetric construction of other types of molecular chirality has been investigated comparatively less. This Review provides a comprehensive overview of the recent emerging advancements in asymmetric synthesis of planarly chiral, helically chiral and inherently chiral molecules using CPA catalysis, while offering insights into future developments within this domain.
Journal Article
Gigantic vortical differential scattering as a monochromatic probe for multiscale chiral structures
Spin angular momentum of light is vital to investigate enantiomers characterized by circular dichroism (CD), widely adopted in biology, chemistry, and material science. However, to discriminate chiral materials with multiscale features, CD spectroscopy normally requires wavelength-swept laser sources aswell aswavelength-specific optical accessories. Here, we experimentally demonstrate an orbital-angular-momentum-assisted approach to yield chiroptical signals with monochromatic light. The gigantic vortical differential scattering (VDS) of ∼120% is achieved on intrinsically chiral microstructures fabricated by femtosecond laser. The VDS measurements can robustly generate chiroptical properties on microstructures with varying geometric features (e.g., diameters and helical pitches) and detect chiral molecules with high sensitivity. This VDS scheme lays a paradigm-shift pavement toward efficiently chiroptical discrimination of multiscale chiral structures with photonic orbital angular momentum. It simplifies and complements the conventional CD spectroscopy, opening possibilities for measuring weak optical chirality, especially on mesoscale chiral architectures and macromolecules.
Journal Article
Supramolecular Chiral Binding Affinity‐Achieved Efficient Synergistic Cancer Therapy
Supramolecular chirality‐mediated selective interaction among native assemblies is essential for precise disease diagnosis and treatment. Herein, to fully understand the supramolecular chiral binding affinity‐achieved therapeutic efficiency, supramolecular chiral nanoparticles (WP5⊃D/L‐Arg+DOX+ICG) with the chirality transfer from chiral arginine (D/L‐Arg) to water‐soluble pillar[5]arene (WP5) are developed through non‐covalent interactions, in which an anticancer drug (DOX, doxorubicin hydrochloride) and a photothermal agent (ICG, indocyanine green) are successfully loaded. Interestingly, the WP5⊃D‐Arg nanoparticles show 107 folds stronger binding capability toward phospholipid‐composed liposomes compared with WP5⊃L‐Arg. The enantioselective interaction further triggers the supramolecular chirality‐specific drug accumulation in cancer cells. As a consequence, WP5⊃D‐Arg+DOX+ICG exhibits extremely enhanced chemo‐photothermal synergistic therapeutic efficacy (tumor inhibition rate of 99.4%) than that of WP5⊃L‐Arg+DOX+ICG (tumor inhibition rate of 56.4%) under the same condition. This work reveals the breakthrough that supramolecular chiral assemblies can induce surprisingly large difference in cancer therapy, providing strong support for the significance of supramolecular chirality in bio‐application. Supramolecular chiral nanomaterials with the chirality transfer from D/L‐Arg to WP5 are constructed. In contrast with WP5⊃L‐Arg+DOX+ICG, supramolecular nanoparticles in D‐form show enhanced cellular uptake efficiency and improved chemo‐photothermal synergistic therapy.
Journal Article
Multi-layer 3D chirality: new synthesis, AIE and computational studies
New synthesis of multi-layer 3D chiral molecules has been developed under novel conditions to give better outcomes. The aggregation-induced emission (AIE), UV irradiation/excitation, charge transfer (CT) and local excited (LE) ππ* transitions have been investigated on a representative individual enantiomer of
pseudo C
2
asymmetry which was made possibly by differentiating moieties on phosphorous on N-phosphonyl ring of chiral sandwich framework. Meanwhile, a new tandem C-N/C-C coupling reaction was unexpectedly rendered providing a novel access to special benzo[a]carbazoles.
Journal Article
The Asymmetry is Derived from Mechanical Interlocking of Achiral Axle and Achiral Ring Components –Syntheses and Properties of Optically Pure 2Rotaxanes
Rotaxanes consisting of achiral axle and achiral ring components can possess supramolecular chirality due to their unique geometrical architectures. To synthesize such chiral rotaxanes, we adapted a prerotaxane method based on aminolysis of a metacyclophane type prerotaxane that had planar chirality, which is composed of an achiral stopper unit and a crown ether type ring component. The prerotaxanes were well resolved using chiral HPLC into a pair of enantiomerically pure prerotaxanes, which were transferred into corresponding chiral rotaxanes, respectively. Obtained chiral rotaxanes were revealed to have considerable enantioselectivity.
Journal Article
Quantitative Structure–Activity Relationship (QSAR) Modeling of Chiral CCR2 Antagonists with a Multidimensional Space of Novel Chirality Descriptors
The development of chirality descriptors for quantitative chirality structure–activity relationship (QCSAR) modeling has always attracted attention, owing to the importance of chiral molecules in pharmaceutical, agriculture, food, and fragrance industries, and environmental toxicology. The utility of a multidimensional space of novel relative chirality indices (RCIs) in the QCSAR modeling of twenty CCR2 antagonists is reported upon in this paper. The numerical characterization of chirality by the RCI approach gives a large pool of chirality descriptors with different degrees of mutual correlation (the correlation coefficient among the computed descriptors varied from 0.02 to 0.99). In the present study, the final data set contains 198 chirality descriptors for each of the twenty CCR2 antagonist molecules, providing a multidimensional space for modeling. The data reduction using principal component analysis resulted in the extraction of eight principal components (PCs). The linear regression using the principal component scores (PCSs) resulted in a three-predictor prediction model with good statistics: R2 = 0.823; Adj R2 = 0.790. The regression models were rebuilt using the chirality descriptors (RCIs) that are most correlated with each of the scores (PCSs) of the three principal components. The R2 value for the regression models with three RCIs as the predictors is 0.742 and the five-fold cross validation, Rcv2, is 0.839. The new chirality descriptors, namely, the RCIs calculated using a different weighting scheme, provide a multidimensional space of chirality descriptors for a set of chiral molecules, and such a multidimensional chirality space is a powerful tool to build quantitative chiral structure–activity relationship (QCSAR) models.
Journal Article
Symmetry Breaking in Chiral Gold Nanoclusters by Ansa‐Metallamacrocycles Strain
Chiral nanomaterials have recently stimulated significant interest in both fundamental research and practical applications (e.g., nanoprobes for biomolecular recognition). However, achieving chiral nanoclusters is still a major challenge. Herein, we report an effective strategy that affords achiral diphosphine ligand‐protected, chiral Au 11 nanoclusters. Synchrotron radiation X‐ray diffraction solves the chiral structure of Au 11 (dppp) 5 Cl 3 (dppp = 1,3‐bis(diphenylphosphino)propane) and further reveals that the critical feature of bidentate binding of diphosphine induces the unique ansa‐metallamacrocycle pattern (i.e., the “Au─P─CH 2 CH 2 CH 2 ─P─Au” staple). All the possible ansa‐metallamacrocycle patterns are transferred to the most robust pattern by “ligand confinement,” giving rise to the chiral enantiomers. Using Density Functional Theory (DFT), we show that the chirality can emerge due to the low energy barriers facilitating the transformation of the symmetric Au 11 core into the corresponding asymmetric chiral cluster, driven by a favorable fit of ligand bridges. This new type of chiral nanomaterial holds promise in chiral sensing/recognition and enantioselective applications.
Journal Article
Giant intrinsic chiro-optical activity in planar dielectric nanostructures
The strong optical chirality arising from certain synthetic metamaterials has important and widespread applications in polarization optics, stereochemistry and spintronics. However, these intrinsically chiral metamaterials are restricted to a complicated three-dimensional (3D) geometry, which leads to significant fabrication challenges, particularly at visible wavelengths. Their planar two-dimensional (2D) counterparts are limited by symmetry considerations to operation at oblique angles (extrinsic chirality) and possess significantly weaker chiro-optical responses close to normal incidence. Here, we address the challenge of realizing strong intrinsic chirality from thin, planar dielectric nanostructures. Most notably, we experimentally achieve near-unity circular dichroism with ~90% of the light with the chosen helicity being transmitted at a wavelength of 540 nm. This is the highest value demonstrated to date for any geometry in the visible spectrum. We interpret this result within the charge-current multipole expansion framework and show that the excitation of higher-order multipoles is responsible for the giant circular dichroism. These experimental results enable the realization of high-performance miniaturized chiro-optical components in a scalable manner at optical frequencies.
Journal Article