Cation induced changes to the structure of cryptophane cages.

Here the monocation complexes of seven -cryptophanes are examined with high-resolution ion-mobility mass spectrometry. The relative size of the [cation + cryptophane] complexes were compared based on their measured mobilities and derived collisional cross sections. A paradoxical trend of structural contraction was observed for complexes of increasing cation size.

A Water-Soluble Cryptophane Decorated with Aromatic Amine Groups Shows High Affinity for Cesium and Thallium(I).

An -cryptophane decorated with three aromatic amine and three phenol groups shows a high affinity for the cesium and thallium cations in LiOH/HO (0.1 M). The formation of the complexes was studied by Cs NMR and by Tl NMR spectroscopy at different temperatures.

Understanding the surrounding effects on Raman optical activity signatures of a chiral cage system: Cryptophane-PP-111.

Cryptophane molecules are cage-like structures consisting in two hemispheres, each made of three benzene rings. These hemispheres are bound together with three O(CH)Olinkers of various lengths giving rise to a plethora of cryptophane derivatives. Moreover, they are able to encapsulate neutral guests: CHCl, CHCl, …; and charged species: Cs, Tl, ….

Synthesis and Chiroptical Properties of a Chiral Isotopologue of -Cryptophane-B.

We report the synthesis and absolute configuration (AC) of a chiral isotopologue of -cryptophane-B. Low chiral signatures were measured by polarimetry and electronic circular dichroism, whereas most significant chiroptical effects were observed by vibrational circular dichroism (VCD) and Raman optical activity (ROA). The comparison of experimental VCD and ROA spectra with those predicted by DFT calculations allows the determination of the AC of the two enantiomers as (-)--- and (+)---.

Impact of the / Relative Configuration of Cryptophane-222 on the Binding Affinity of Cesium and Thallium.

We report in this article the synthesis, the X-ray crystal structure of compound -, and its binding properties with cesium and thallium in aqueous solution under basic conditions. Compound - is the diastereomeric compound of - that shows very high affinity for cesium and thallium in aqueous solution under the same conditions. Despite the close structural similarities that exist between the - and - compounds, they show large discrepancy in their ability to bind cesium and thallium cations in the same conditions.

-Cryptophanes: macrocyclic compounds with optimized characteristics for the design of Xe NMR-based biosensors.

A new water-soluble xenon host system with great promise for the Xe NMR-based biosensing approach is presented: the -cryptophane-222-hexacarboxylate. It compares favorably with its already known diastereomer, on the one hand, and with cucurbit[6]uril, on the other hand, in particular in terms of xenon binding constant and xenon in-out exchange, a key parameter for the efficiency of the most sensitive HyperCEST method.

Chiroptical and potential in vitro anti-inflammatory properties of viniferin stereoisomers from grapevine (Vitis vinifera L.).

Determination of stereochemistry and enantiomeric excess in chiral natural molecules is a research of great interest because enantiomers can exhibit different biological activities. Viniferin stilbene dimers are natural molecules present in grape berries and wine but also, in larger amount, in stalks of grapevine. Four stereoisomers of viniferin stilbene dimers (7aS,8aS)-E-ε-viniferin (1a), (7aR,8aR)-E-ε-viniferin (1b), (7aS,8aR)-E-ω-viniferin (2a), and (7aR,8aS)-E-ω-viniferin (2b) were isolated from grapevine stalks of Cabernet Sauvignon, Merlot and Sauvignon Blanc, using a combination of centrifugal partition chromatography (CPC), preparative and chiral HPLC.

Access to the diastereomers of cryptophane cages using HFIP.

Cryptophane cages can adopt either an or configuration that present different recognition properties. While the synthesis of -cryptophanes is well reported, the synthesis of -cryptophanes remains a challenge. Herein, we demonstrate that the use of HFIP as a co-solvent during the second ring closure reaction significantly affects the regioselectivity, providing easier access to the -cryptophane stereomers.

Study of and Xenon-Cryptophanes Complexes Decorated with Aromatic Amine Groups: Chemical Platforms for Accessing New Cryptophanes.

We report the synthesis of -symmetric cryptophanes decorated with three aromatic amine groups on the same CTB cap and their interaction with xenon. The relative stereochemistry of these two stereoisomers and was assessed thanks to the determination of the X-ray structure of an intermediate compound. As previously observed with the tris-aza-cryptophanes analogs - and - (.

Enantiopure cryptophane derivatives: Synthesis and chiroptical properties.

This review addresses the synthesis of enantiopure cryptophane and the study of their chiroptical properties. Cryptophane derivatives represent an important class of macrocyclic compounds that can bind a large range of species in solution under different conditions. The overwhelming majority of these host molecules is chiral, and their chiroptical properties have been thoroughly investigated.

Thermodynamic Contribution of Water in Cryptophane Host-Guest Binding Reaction.

A detailed examination of binding thermodynamics is undertaken for the interaction between rubidium ion and a water-soluble cryptophane molecule using isothermal titration calorimetry. The equilibrium-binding quotient for this host-guest pair decreases with increasing product formation. When analyzed with a thermodynamic framework that considers water explicitly in the governing equation, the shift in equilibrium is ascribed to an unfavorable change in the free energy of solvation upon formation of the inclusion complex.

Selective Capture of Thallium and Cesium by a Cryptophane Soluble at Neutral pH.

We report in this article the synthesis of an asymmetrical cryptophane derivative (possessing only -symmetry) bearing three phenol groups and three other carboxylic acid functions, each of these groups on the aromatic rings. Thanks to isothermal titration calorimetry experiments, we show that this compound binds large monovalent cations, such as Cs and Tl, with a binding constant significantly lower than its congeners bearing a larger number of phenol groups grafted on the benzene rings. However, higher selectivity for Cs and Tl was observed with this compound since it does not show any affinity for other alkali cations.

Synthesis of Cryptophane-223-Type Derivatives with Dual Functionalization.

In this article, we present the synthesis of new cryptophane-type hosts capable of binding xenon in aqueous media and that may be useful for the development of xenon-based magnetic resonance imaging derivatives. The synthetic route proposed was chosen to facilitate both the introduction of water-solubilizing substituents and the functionalization of the host with a single arm showing recognition properties that constitute two crucial steps. This was made possible by preparing new cryptophane-223 derivatives bearing two different chemical functions that can be easily modified at a later stage.

Chiroptical study of cryptophanes subjected to self-encapsulation.

In 1,1,2,2-tetrachloroethane-d , the Xe NMR spectrum of the Xe@cryptophane-223 complex bearing seven acetate groups (Xe@1 complex) shows an unusually broad signal compared with that of its congeners (Chapellet, LL. et al. J.

Bioinspired Oxidation of Methane in the Confined Spaces of Molecular Cages.

Non-heme iron, vanadium, and copper complexes bearing hemicryptophane cavities were evaluated in the oxidation of methane in water by hydrogen peroxide. According to H nuclear magnetic resonance studies, a hydrophobic hemicryptophane cage accommodates a methane molecule in the proximity of the oxidizing site, leading to an improvement in the efficiency and selectivity for CHOH and CHOOH compared to those of the analogous complexes devoid of a hemicryptophane cage. While copper complexes showed low catalytic efficiency, their vanadium and iron counterparts exhibited higher turnover numbers, ≤13.

Enantiopure [Cs/Xe⊂Cryptophane]⊂FeL Hierarchical Superstructures.

Hierarchically nested hosts offer new opportunities to control the guest binding of the inner host, functionalize the cavity of the outer host, and investigate communication between different layers. Here we report a self-assembled triazatruxene-based FeL capsule, which was able to encapsulate a covalent cage, cryptophane-111 (CRY). The resulting cage-in-cage complex was capable of accommodating a cesium cation or xenon atom with altered guest binding behavior compared to the CRY alone.

Bimodal Detection of Proteins by Xe NMR and Fluorescence Spectroscopy.

A full understanding of biological phenomena involves sensitive and noninvasive detection. Herein, we report the optimization of a probe for intracellular proteins that combines the advantages of fluorescence and hyperpolarized Xe NMR spectroscopy detection. The fluorescence detection part is composed of six residues containing a tetracysteine tag (-CCXXCC-) genetically incorporated into the protein of interest and of a small organic molecule, CrAsH.

Synthesis of Cryptophane-B: Crystal Structure and Study of Its Complex with Xenon.

Whereas the synthesis of the anti-cryptophane-A (1) derivative has been known for nearly 40 years, the preparation of its diastereomer (cryptophane-B according to Collet's nomenclature) has never been reported. Thus, the synthesis of the cryptophane-B derivative represents a real challenge for chemists interested in the preparation of these hollow molecules. Herein, we describe a synthetic route that allows us to prepare cryptophane-B (2), albeit in a low yield.

Accurate pH Sensing using Hyperpolarized Xe NMR Spectroscopy.

In the search for powerful non-invasive methods for pH measurement, NMR usually suffers from biases, especially for heterogeneous samples or tissues. In this Communication, using the signals of hyperpolarized Xe encapsulated in a pair of water-soluble cryptophanes, we show that a differential pH measurement can be achieved, free from most of these biases, by monitoring the difference between their chemical shifts.

Unsaturated cryptophanes: Toward dual PHIP/hyperpolarised xenon sensors.

Cryptophanes, cage-molecules constituted of aromatic bowls, are now well recognised as powerful xenon hosts in Xe NMR-based biosensing. In the quest of a dual probe that can be addressed only by NMR, we have studied three cryptophanes bearing a tether with an unsaturated bond. The idea behind this is to build probes that can be detected both via hyperpolarised Xe NMR and para-hydrogen induced polarisation H NMR.

Bimodal fluorescence/Xe NMR probe for molecular imaging and biological inhibition of EGFR in Non-Small Cell Lung Cancer.

Although Non-Small Cell Lung Cancer (NSCLC) is one of the main causes of cancer death, very little improvement has been made in the last decades regarding diagnosis and outcomes. In this study, a bimodal fluorescence/Xe NMR probe containing a xenon host, a fluorescent moiety and a therapeutic antibody has been designed to target the Epidermal Growth Factor Receptors (EGFR) overexpressed in cancer cells. This biosensor shows high selectivity for the EGFR, and a biological activity similar to that of the antibody.

Chiroptical properties of cryptophane-111.

The two enantiomers of cryptophane-111 (1), which possesses the most simplified chemical structure of cryptophane derivatives and exhibits the highest binding constant for xenon encapsulation in organic solution, were separated by HPLC using chiral stationary phases. The chiroptical properties of [CD(+)]-1 and [CD(-)]-1 were determined in CHCl and CHCl solutions by polarimetry, electronic circular dichroism (ECD), vibrational circular dichroism (VCD), and Raman optical activity (ROA) experiments and were compared to those of cryptophane-222 (2) derivative. Synchroton Radiation Circular Dichroism (SRCD) spectra were also recorded for the two enantiomers of 1 to investigate low-lying excited states in the B region.