Supramolecular Capsules Derived from Calixpyrrole Scaffolds

This review article describes recent results obtained in the self-assembly of supramolecular capsules derived from calixpyrrole components. Due to their ease of synthesis, calix[4]pyrroles are by far the most typically used units in these systems. A clear conformational and structural analogy exists between calix[4]arenes and calix[4]pyrroles. However, to date, the number of examples in the literature that use calix[4]pyrrole scaffolds instead of calix[4]arenes for the construction of supramolecular capsules is still meager. Four different approaches are considered for the use of calix[4]pyrrole derivatives in the assembly of molecular capsules. Firstly, in an analogous manner to resorcin[4]arenes and pyrogallol[4]arenes, aryl-extended calix[4]pyrroles with hydroxyl groups in their upper rim self-assemble through direct or mediated rim-to-rim interactions into capsular aggregates. Secondly, aryl-extended calix[4]pyrroles having non-complementary hydrogen-bonding groups in their upper rim form dimeric templated capsules with suitable substrates. Thirdly, the elaboration of the upper rim of the calix[4]pyrroles with urea groups affords dimeric capsules with polar functionalized interiors that closely resemble their tetraurea calix[4]arene analogs. Finally, the chemical modification of the pyrrole units of octamethyl calix[4]pyrrole into tetrathiafulvalene derivatives yields dimeric capsules induced by anion coordination that display interesting properties in the binding of electron-poor guests.     

Complex Formation between Cytochrome c and a Tetra-alanino-calix[4]arene

Owing to their remarkable features, calix[n]arenes are being exploited to study different aspects of molecular recognition, including protein complexation. Different complexation modes have been described, depending on the moieties that complement the aromatic cavity, allowing for function regulation and/or controlled assembly of the protein target. Here, a rigid cone calix[4]arene, bearing four anionic alanine units at the upper rim, was tested as a ligand for cytochrome c. Cocrystallization attempts were unfruitful, preventing a solid-state study of the system. Next, the complex was studied using NMR spectroscopy, which revealed the presence of two binding sites at lysine residues with dissociation constants (K_d) in the millimolar range.     

Calix[n]arene-based glycoclusters: bioactivity of thiourea-linked galactose/lactose moieties as inhibitors of binding of medically relevant lectins to a glycoprotein and cell-surface glycoconjugates and selectivity among human adhesion/growth-regulatory galectins

Growing insights into the functionality of lectin-carbohydrate interactions are identifying attractive new targets for drug design. As glycan recognition is regulated by the structure of the sugar epitope and also by topological aspects of its presentation, a suitable arrangement of ligands in synthetic glycoclusters has the potential to enhance their avidity and selectivity. If adequately realized, such compounds might find medical applications. This is why we focused on lectins of clinical interest, acting either as a potent biohazard (a toxin from Viscum album L. akin to ricin) or as a factor in tumor progression (human galectins-1, -3, and -4). Using a set of 14 calix[n]arenes (n=4, 6, and 8) with thiourea-linked galactose or lactose moieties, we first ascertained the lectin-binding properties of the derivatized sugar head groups conjugated to the synthetic macrocycles. Despite their high degree of flexibility, the calix[6,8]arenes proved especially effective for the plant AB-toxin, in the solid-phase model system with a single glycoprotein (asialofetuin) and with human tumor cells in vitro. The bioactivity of the calix[n]arenes was also proven for human galectins. Notably, selectivity for the tested tandem-repeat-type galectin-4 among the three subgroups was determined at the level of solid-phase and cell assays, the large flexible macrocycles again figuring prominently as inhibitors. Alternate and cone versions of calix[4]arene with lactose units distinguished between galectins-1 and -4 versus galectin-3 in cell assays. The results thus revealed bioactivity of galactose-/lactose-presenting calix[n]arenes for medically relevant lectins and selectivity within the family of adhesion/growth-regulatory human galectins.     

Calix[4]arene Polyamine Triazoles: Synthesis,Aggregation and DNA Binding

Artificial gene delivery systems are in great demand from both scientific and practical biomedical points of view. In this paper, we present the synthesis of a new click chemistry calix[4]arene precursor with free lower rim and new water-soluble calixarene triazoles with 12 amino-groups on the upper rim (one with free phenol hydroxyl groups and two another containing four butyl or tetradecyl fragments). Aggregation in the series of amino-triazole calixarenes of different lipophilicity (calixarene with free phenol hydroxyl groups or butyl and tetradecyl fragments on the lower rim) was studied using dynamic light scattering and fluorescent pyrene probe. It was found that calix[4]arene with a free lower rim, like alkyl-substituted butyl calix[4]arene, forms stable submicron aggregates 150–200 nm in size, while the more lipophilic tetradecyl –substituted calix[4]arene forms micellar aggregates19 nm in size. Using UV-Vis spectroscopy, fluorimetry and CD, it was shown that amino-triazole calix[4]arenes bind to calf thymus DNA by classical intercalation. According to DLS and TEM data, all studied macrocycles cause significant DNA compaction, forming stable nanoparticles 50–20 nm in size. Among all studied calix[4]arenes the most lipophilic tetradecyl one proved to be the best for both binding and compaction of DNA.     

Calixarenes 30. Calixquinones

Chlorine dioxide and thallium trifluoroacetate are shown to be useful reagents for the preparation of calixquinones. p-H-Calix[4]arene( 1a ),p-H-calix[5]arene ( 1b ), and p-H-calix[6]arene ( 1c ) are oxidized in modest yields by ClO₂ to the fully quinonoid compounds calix[4]tetraquinone ( 2a ), calix[5]pentaquinone ( 2b ), and calix[6]hexaquinone ( 2c ), respectively. Although Tl(OCOF₃)₃ is less effective for the oxidation of 1a-c , it proves to be the reagent of choice for converting partially etherified or esterified calixarenes carrying p-tert-butyl groups directly to partially quinonoid calixarenes. Thus, monosubstituted calix[4]arenes yield triquinones; disubstituted calix[4]arenes yield diquinones; trisubstituted calix[4]arenes yield monquinones; and tetrasubstituted calix[6]arenes yield diquinones. The structures of the calixquinones have been established by elemental analysis, ¹H NMR spectroscopy, mass spectroscopy, and in the case of 2c by X-ray crystallography. Since the starting materials are readily accessible, the calixquinones become easily available compounds for further study.     

羧基苯偶氮基杯[4]芳烃衍生物的合成、表征及光谱特性

以邻、间、对氨基苯甲酸和杯 [4]芳烃为原料 ,经重氮化 -偶联反应合成了发色邻、间、对羧基苯偶氮基杯 [4]芳烃 ,产物的结构经 IR,1H NMR和元素分析表征 ;研究了它们的生色原理和光谱性能。结果表明它们是一类新型指示剂和具有新型配位空腔的主体分子。     

Novel Upper Rim Functionalizations of Calix[4]arenes using the Tscherniac-Einhorn Amidomethylation Reaction

A variety of novel upper rim functionalized calix-[4]arenes have been synthesized, using the Tscherniac-Einhorn amidomethylation reaction. Partially or fully alkylated calix [4]arenes bearing propyl or ethoxyethyl substituents could be easily condensed with various N-methylol-amides and -imides under mild conditions. The resulting methyl-acetamido- ( 4a , 4b , 7a ), methylchloroacetamido ( 4c , 4d , 7b , 7c , 9 methylphthalimido ( 4e , 4f , 4h )and methylchloroacetamido methylphthalimido functionalized calix[4]arenes ( 5 ) were obtained in yields varying from 30 till 97%. The amidomethylation reactions were proven to be independent of the conformation of the calix[4]arene.     

Synthesis of Water-Soluble Calixarenes Catalyzed One-Pot Mannich-Type Reaction in Aqueous Media

This article demonstrates the synthesis of new water soluble calix[4]arenes (8) based catalyst and application in one-pot, three component Mannich reactions to catalyze reaction between aromatic ketones/aldehyde and amines to acquire β-Amino carbonyl compounds in appreciable yields at room temperature in aqueous media.     

Electrochemical response of ferrocenium filled calix[4]arene capsules in solution and immobilized on gold

Hydrogen-bonded dimers of tetra-urea calix[4]arenes are able to include ferrocenium ions as a guest. Heterodimeric capsules are exclusively formed in 1:1 mixtures of tetra-arylurea calix[4]arene 1 with tetra-tosylurea calix[4]arene 2. Sulfide groups attached via spacers on the urea rim of 1 allow their binding to metal surfaces rendering simultaneously their dissociation more difficult. Thus, the electrochemical response of encapsulated ferrocenium could be studied in a self-assembled monolayer (SAM) in addition to the solution electrochemistry with cyclic voltammetry. The stability of the electrochemically active monolayers was tested after a heat treatment (225 °C for 30 min in N₂ atmosphere) and multiple cycling (up to 1200 cycles), which could be required for a possible application as molecular based information storage.     

氨基硫脲基新型杯[4]芳烃衍生物的合成

通过1,3-环氧丙基杯[4]烃与硫代氨基脲开环反应,合成硫代氨基脲基杯[4]芳烃衍生物,研究了其对阳离子的吸附性能后发现,与其他氨基杯芳烃相比,该衍生物对铜离子的吸附性能较好,并且有很好的选择性。     

含氮杯[4]芳烃的合成

以对叔丁基苯酚为起始原料,经过3步反应,在母体杯芳烃的下沿引入3种不同的含氮基团,得到5种含氮杯[4]芳烃,并通过1HNMR和熔点测定确定了产物结构.实验中发现,当母体杯芳烃下沿引入的溴代烷基变长时,进一步引入含氮基团,只能得到1,3位环化的含氮杯[4]芳烃.     

Sensitive molecular determination of polycyclic aromatic hydrocarbons based on thiolated Calix[4]arene and CdSe quantum dots (QDs)

A novel and sensitive electrochemical sensor based on the cone conformation of the supramolecule 25, 27-(3-thiopropoxy)-p-tert-butyl calix[4]arene has been developed for quantitative determination of polycyclic aromatic hydrocarbons (PAHs). The method works effectively by immobilizing calix[4]arenes on Fe₃O₄ magnetic nanoparticles. CdSe quantum dots were used as electrochemical labels. CdSe quantum dots (QDs) modified PAHs in competition with the sample PAHs were intercalated into calix[4]arenes supramolecules via a host–guest interaction through individual bowl-shaped calix[4]arenes. The stripping analysis of the cadmium dissolved from CdSe nanoparticles provided a sensitive method for the detection of PAHs in the samples. The signal decrease of the QDs was proportional to the increase in the concentration of the PAHs. Under optimal conditions, among the five PAHs, the square wave voltammetry (SWV) response of QDs decreased linearly for anthracene and naphthalene in the range of 2.1 × 10^?7–1.4 × 10^?5 and 1.5 × 10^?6–2.5 × 10^?5 M, respectively. The calculated detection limits (3δ) were 20.1 ng mL^?1 for anthracene and 105.5 ng mL^?1 for naphthalene.     

EXTRACTION OF TRIVALENT LANTHANIDES AND ACTINIDES BY “CMPO-LIKE” CALIXARENES

ABSTRACT

Extractive properties of calix[4]arenes bearing carhamoylmethylphosphine oxide moieties on their upper rim toward trivalent lanthanide and actinide cations were investigated. The study revealed that these molecules selectively extract light lanthanides and actinides from heavy lanthanides. All parameters present in the extraction system were varied to determine the origin of the selectivity. It was found that this selectivity requires a calix[4]arene platform and acetamidophosphine oxide groups containing phenyl substituents on the four phosphorus atoms.     

Coordination and Organometallic Polymers and Oligomers of Upper-Rim Functionalized Calix[4]arenes by Transition Metals

This short review focuses on recent advances in the syntheses, characterization and structures of coordination and organometallic complexes of upper-rim functionalized calix[4]arenes that form either small oligomers or polymers. This field is very limited, presumably due to the lack of X-ray data or reliable characterization that demonstrates the presence of oligomers or polymers. Nonetheless, the few published works already clearly demonstrate the immense versatility of the calix[4]arene macrocycle as it forms polymeric materials via coordination bondings with transition metals.     

Calix[4]arene‐tetranitrone as crosslinker in dental composite materials

The synthesis of a functionalized calix[4]arene bearing 1,3‐dipolaric nitrone groups ( 5 ) has been carried out. The reaction of N‐methylhydroxylamine or N‐propylhydroxylamine with the carbonyl group of 5,11,7,23‐tetraformyl‐25,26,27,28‐tetraalkoxycalix[4]arene leads to calix[4]arenes bearing a nitrone function at each of the four para‐positions. Via 1,3‐dipolar cyclo‐addition of acrylic acid methyl ester with the nitrone functions of 5 , subsequently an upper rim‐substituted tetraisoxalidinecalix[4]arene is quantitatively synthesized. Further, the minimization of shrinkage of a dental filling depending on the amount of calix[4]arene‐tetranitrone is discussed. Copyright © 2011 Society of Chemical Industry     

基于杯[4]芳烃的选择性识别二酸的化学传感器

设计、合成了以杯[4]芳烃为平台,以氨基吡啶基团为双识别位点的新型化学传感器,并用红外光谱、质谱、核磁共振和元素分析方法对其进行了表征。紫外和荧光光谱研究结果表明,该受体分子在二氯甲烷溶液中能选择性识别脂肪二酸,络合常数可达103~104L/mol,络合能力大小顺序为:丙二酸>草酸>丁二酸>戊二酸>已二酸。     

对叔丁基杯[n](n=6,8)芳烃O-烃基化衍生物的微波辐射合成

在微波辐射条件下,以对叔丁基杯[6]、杯[8]芳烃为原料,采用氯化苄、碘代正丁烷、溴代正戊烷为烃基化试剂,PEG..400为催化剂,制备了标题化合物,通过IR、1HNMR光谱对产物的结构进行表征.微波辐射约5 min,即可得到收率中等(40％ ～66％)的对叔丁基杯芳烃O-烃基化衍生物.结果表明微波辐射法操作简单、反应...     

Synthesis,extraction, and adsorption properties of calix[4]arene‐poly(ethylene‐glycol) crosslinked polymer

Novel calix[4]arene‐poly(ethylene glycol) crosslinked polymer (CCP) has been synthesized by the polycondensation reaction between a p‐tert‐butylcalix[4]arene derivative and dihydroxyl capped poly(ethylene glycol) (DHPEG, M_n = 1000) catalyzed by neodymium tosylate. The hydrogel, consisted of 66.9% water and 33.1% CCP, can selectively extract aromatic organic molecules from aqueous solution according to the diameter of the guest molecules, which infers that the diameter of the calix[4]arene cavity is about 5.4 Å and the conformation of calix[4]arene units altered from cone conformation to 1,3‐alternate conformation during the polycondensation reaction. Furthermore, CCP can also adsorb naphthalene from gas phase, showing much higher capacity than active carbon does, which may have some potential applications in the field of separation and environment protection. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

杯芳烃／聚丙烯共混体系耐热氧性能的研究

合成了对叔丁基杯[4]、杯[6]、杯[8]芳烃,并用热重法和烘箱老化评价了共混体系的耐热氧性能。结果表明,杯芳烃能明显提高聚丙烯的耐热氧性能,其耐热氧能力为：对叔丁基杯[6]芳烃＞对叔丁基杯[4]＜2,6－二叔丁基－4－甲基苯酚。     

Synthesis of Oligomeric Calix[4]arene-Crowns as Novel Ionophores for Alkali and Transition Metals

Two different oligomeric calix[4]arene-crowns ( 2b and 3b ) were synthesized ( via ) the condensation reaction of p- tert -butylcalix[4]arene-oxacrown-4 ( 2a ) and p- tert -butylcalix[4]arene-thiacrown-4 ( 3a )(calix[4]arene-crown monomers) with 1,5-dibromopentane. In these oligomerization reactions, it has been found that only three or four calix[4]arene-crowns-4 units have been linked together through alkyl bridges. Their comparative complexing properties with selected alkali and transition metals are reported here. It has been deduced that the selectivity of monomer 2a toward alkali metals has not been reserved, but a pronounced increase in its complexing ability was observed after the oligomerization. However, the selectivity of the monomer 3a toward Cu 2+ , Hg 2+ , and Pb 2+ has also been lost after oligomerization, and it has been found that oligomer 3b is an efficient extractant for the transition metal cations employed in the two-phase extraction systems.