Chiral calix[4]arenes bearing α-hydroxy amide units as membrane carriers for amino acid methyl esters

Novel chiral calix[4]arene derivatives functionalized at the lower rim have been prepared from the reaction of p-tert-butylcalix[4]arene diamine or acylhydrazine derivative with mandelic acid or hydroxyisovaleric acid. The structures of these receptors were characterized by FTIR, ¹H, ¹³C and 2D COSY NMR spectroscopy and elemental analysis. The transport of amino acid derivatives (phenylalanine, phenylglycine and tryptophan methyl ester hydrochlorides) was studied through bulk liquid membrane in the presence of chiral calix[4]arene derivatives. The receptors have been found to act as carriers for transport of aromatic amino acid methylesters from the aqueous source phase to the aqueous receiving phase. The transport rate and L/D selectivity of amino acid esters studied depend strongly upon the structure of the chiral receptors and guests. The best enantioselectivity was obtained in the case of phenylglycine methyl ester for all chiral carriers.     

A multichannel thiacalix[4]arene-based fluorescent chemosensor for Zn2+, F− ions and imaging of living cells

Abstract

The fluorescent sensor (3) based on the 1,3-alternate conformation of the thiacalix[4]arene bearing the coumarin fluorophore, appended via an imino group, has been synthesised. Sensing properties were evaluated in terms of a colorimetric and fluorescence sensor for Zn²⁺ and F^?. High selectivity and excellent sensitivity were exhibited, and ‘off-on’ optical behaviour in different media was observed. All changes were visible to the naked eye, whilst the presence of the Zn²⁺ and F^? induces fluorescence enhancement and the formation of a 1:1 complex with 3. In addition, 3 exhibits low cytotoxicity and good cell permeability and can readily be employed for assessing the change of intracellular levels of Zn²⁺ and F^?.     

Metal complexes of anthranilic acid derivatives: A new class of noncompetitive α-glucosidase inhibitors

Metal complexes of anthranilic acid derivatives that constitute a novel class of non-sugar-type aglucosidase inhibitors were synthesized and assessed in vitro for inhibitory activity. All of the Ag(I)complexes(9–16) inhibited a-glucosidase at the nanomolar scale, while 3,5-dichloroanthranilic acid silver(I)(9) was the most potent(IC_(50)= 3.21 nmol/L). Analysis of the kinetics of enzyme inhibition indicated that the mechanism of the newly prepared silver complexes was noncompetitive. The structure-activity relationships were also analyzed, and they are discussed in this report.     

Ionic Liquid [bmim][BF4] as a Green Medium for Passerini Reaction

The Passerini reaction, a three-component condensation reaction of carboxylic acid, aldehyde and isocyanide constructing an α-acyloxycarboxamide in a single step, was first discovered by Passerini about 80 years ago1. Since then, this reaction has been w…     

Aminoalkylated Calix[4]resorcinarenes as pH Sensitive “hosts” for Charged Metallocomplexes

On the basis of RCA, pH-potentiometry and EPR-spectroscopy data aminoalkylated derivatives were proved to bind metal ion complexes both in alkaline and in acidic media. Outer-sphere coordination is the only interaction mode in these host-guest complexes.     

A water-soluble calix[4]resorcinarene with α-methyl-L-prolinylmethyl groups as a chiral NMR solvating agent

A water-soluble calix[4]resorcinarene containing α-methyl-L-prolinylmethyl groups is synthesized and evaluated as a chiral NMR solvating agent. Aryl-containing substrates with substituted amines are studied.     

Design and synthesis of novel α-aminoamides derivatives as Nav1.7 inhibitors for antinociception

Three novel series of α-aminoamides derivatives were designed and synthesized based on ralfinamide,and their Nav1.7 inhibitory activities were evaluated using manual patch clamp electrophysiology. Active compounds inhibited Nav1.7 with half maximal inhibitory concentration(IC50) values ranging from2.9 μmol/L to 21.4 μmol/L. Among them, the most potent compound 19h exhibited about 12-fold potency better than ralfinamide. The investigation of their structure-activity relationship gives a strategy ...     

Chiral dihydrobenzo[1,4]oxazines as catalysts for the asymmetric transfer-hydrogenation of α,β-unsaturated aldehydes

A new class of organocatalysts based on the structure of 2,3-dihydrobenzo[1,4]oxazine was prepared and applied in the enantioselective transfer-hydrogenation of α,β-unsaturated aldehydes with Hantzsch ester as hydride donor. These catalysts proved to be particularly effective for the conjugate reduction of β,β-diaryl-substituted acrylaldehydes leading to saturated aldehydes bearing a stereogenic center with two different aryl groups with enantioselectivities of up to 91% ee.     

Novel redox receptors for ion-pair and α-amino acid: synthesis and complexation properties of calix[4]arene derivatives bearing large conjugated ferrocene groups

By reacting calix[4]arene 1,3-bi-hydrazide derivative (2) with formacylferrocene in “1?+?2” condensation mode, novel calix[4]arene derivative bearing two conjugated ferrocene groups (3) was obtained in yield of 88%. By reacting 1,3-bi-substituted [2-(p-formylphenyloxy)ethyloxy]-p-tert-butylcalix[4]arene (5) with 1,1′-diacetylferrocene hydrazone (4) in “1?+?1” condensation mode, novel calix[4]arene derivative with 1,3-substituted large conjugated ferrocene bridge (6) was synthesized in yield of 83%. The structures and conformations of new compounds were confirmed by elemental analyses, IR spectra, ESI-MS, ¹H NMR, etc. The electrochemical cyclic voltammetry experiments revealed that compounds 3 and 6 possessed excellent reversible electrochemical properties. The ¹H NMR titration study showed that compound 6 possessed excellent complexation abilities for NaH₂PO₄ and glycine in 1:1 host–guest complex with the association constants of 3,850 and 2,460?M^?1, respectively.     

Tetraviologen calix[4]resorcine as a mediator of the electrochemical reduction of [PdCl4]2– for the production of Pd0 nanoparticles

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Graphene oxide as an enzyme inhibitor: modulation of activity of α-chymotrypsin

We have investigated the efficacy of graphene oxide (GO) in modulating enzymatic activity. Specifically, we have shown that GO can act as an artificial receptor and inhibit the activity of α-chymotrypsin (ChT), a serine protease. Most significantly, our data demonstrate that GO exhibits the highest inhibition dose response (by weight) for ChT inhibition compared with all other reported artificial inhibitors. Through fluorescence spectroscopy and circular dichroism studies, we have shown that this protein-receptor interaction is highly biocompatible and conserves the protein's secondary structure over extended periods (>24 h). We have also explored GO-enzyme interactions by controlling the ionic strength of the medium, which attenuates the host-guest electrostatic interactions. These findings suggest a new generation of enzymatic inhibitors that can be applied to other complex proteins by systematic modification of the GO functionality.     

Calix[4]arene-Based New Neutral Sensors for Fluoride

The development of new receptors which can recognize neutral and charged species has attracted considerable interest in the recent past.[1] Anions such as fluoride, chloride, phosphate and carboxylate play crucial roles in a range of biological phenomena and are implicated in many disease states.[2] Investigations on molecular and/or ionic recognition by calixarenes and their derivatives as synthetic receptors have attracted increasing attention in supramolecular chemistry because of their modifiable structure.[3] However, calix[4]arenes-based neutral receptors containing thiourea and amide groups are still rare. In this paper, we report fluoride selective optical chemosensors 4 and 5, based on calix[4]arene thiourea and amide derivatives, which only show a remarkable absorption change in the presence of fluoride ions, while have no any change upon addition of other anions (Cl- Br-, I-, AcO- and H2PO4-). The association constants are 947 and 2883 mol·L-1, respectively. The synthesis of calix[4]arene derivatives 4 and 5 is outlined in the following Scheme 1.     

High Stereoselective Glycosylation of Calix[4]arenes with α-Acetobromoglucopyranoside

Ithasbeenevidencedthatcthehydratesp1ayamajorroleinnature,etwallyasrecoghtiondeterminantsuchasinh0st-pathogeninteractionsorincell-cellintendions.Moreover,dramaticchangesinthestruct-Uresofcarbohydratemoiety0fglycocojugaesoftenareassociatedwithcogeniceventsWhichaIlowtousesomeofthemastumormarkersusefu1f0rdiagnosticpurp0ses.'Inordertobetterundersbodtheseinteractionandtodeve1opbio1ogicalaCtivecomPOundsbased0nm0lecularrecoghtion,stereoc0ntrolledgJycoSylationhasbecome0neofthemostimPOrtanttopicinor…     

Functioned Calix[4]arenes as Artificial Enzymes Catalyze Aldol Condensation

Aldolcondensationcanbegenerallycatalyzedbymeansofbasesoracids.Usually,itiseasytoobtainα,β-unsaturatedketonesderivedfromthedehydrationofthealdol-typeproducts(β-hydroxyketones).Watanabeetal'successfullydevelopedthemethodtodepressthedehydrationbyusingmetal(Ⅱ)complexesofα-aminoacidesterswithcyclodextrin.Later,ZhaoHua-mingetal.2．3studiedthefunctionedcyclodextrinsasaldolasetomimicthecondensationofp-nitrobenzaldehydewithacetoneandobtainedtheaIdol-typeproductingoodyield.Recentyears,studiesonca…     

Calix [ 4 ] arene Polyaza Derivatives： Novel Effective Neutral Receptors for Cations and α-Amino Acids

IntroductionCalixarenes are one of the most important supra-molecular building blocks, which can be modified byintroducing different functional and/or structural groupsto create a specific interaction between the host and thetarget molecules, such as meta…     

Biological evaluation of 9-(1H-Indol-3-yl) xanthen-4-(9H)-ones derivatives as noncompetitive α-glucosidase inhibitors: kinetics and molecular mechanisms

Structural Chemistry - The α-Glucosidase plays a key role in attenuation of postprandial hyperglycemia in diabetic patients. In this study, a class of 9-(1H-Indol-3-yl) xanthen-4-(9H)-ones...     

Complementary α-alkylation approaches for a sterically hindered spiro[pyrazolopyranpiperidine]ketone

Complementary α-alkylation methods are used to derivatize a sterically hindered spiro[pyrazolopyranpiperidine]ketone. More specifically, enolate alkylations in the presence of DMPU and aldol condensations are employed to deliver these compounds.     

Synthesis and anion recognition of neutral receptors based on multiamide calyx[4]arene

~~Synthesis and anion recognition of neutral receptors based on multiamide calyx[4]arene~~     

Ionic liquid [bmim][BF4] acts as solvent and promoter for synthesis of halo-containing N-arylphthalimides

A new synthetic process of N-arylphthalimide and halo-containing N-arylphthalimides through the reaction between phthalic anhydride and aromatic amines bearing halo groups in[bmim][BF_4]was described,ionic liquid[bmim][BF_4]acted as the dual role of solvent and promoter.     

Synthetic receptors based on calix[4]arene functionalized at the lower rim in molecular recognition of dicarboxylic, α-hydroxycarboxylic,and α-amino acids

New calix[4]arenes, di- and tetrasubstituted at the lower rim, with different functional groups were synthesized. They were studied as carriers of a series of dicarboxylic and -hydroxycarboxylic acids through a liquid impregnated membrane. The calix[4]arenes under study are capable of molecular recognition of oxalic acid in the series of structurally similar dicarboxylic and -hydroxycarboxylic acids. The regularities found make it possible to change purposefully the receptor ability of 1,3-disubstituted calix[4]arenes by variation of the nature of substituents.