Preparation and evaluation of a deoxycholic‐calix[4]arene hybrid‐type receptor as a chiral stationary phase for HPLC

We report the synthesis and enantioseparation characteristics of two novel covalently immobilized deoxycholic acid derivatives as chiral stationary phases for high‐performance liquid chromatography. In the structure of the first stationary phase, the 3‐position of deoxycholic acid is substituted with a 3,5‐dinitrophenylcarbamoyl group and the second one has an additional calix[4]arene attached to the carboxylic group of the deoxycholic acid. The chromatographic performance of the stationary phases was evaluated with enantioseparation of N‐(3,5‐dinitrobenzoyl)‐dl ‐leucine, N‐(3,5‐dinitrobenzoyl)‐dl ‐valine, omeprazole, diclofop‐methyl, dl ‐mandelic acid and (RS)‐pregabalin. Comparison of the performance characteristics of the prepared chiral stationary phases provided evidence for the active involvement of the calix[4]arene unit in the chiral recognition process. Both stationary phases are chemically bonded to the silica and can be used in both normal‐phase and reversed‐phase modes.     

Anion‐binding properties of two calix[4]arene derivatives containing two ferrocene imine or ferrocene amine units at the upper rim

Calix[4]arene derivatives containing ferrocene units at the upper rim have been synthesized and their anion‐binding and sensing investigated towards anions such as chloride, bromide and hydrogen sulfate by cyclic voltammetry. Electrochemical studies show that these redox‐active ligands electrochemically recognize chloride and bromide anions. These compounds have excellent selectivity for chloride and bromide ions, in the comparison with hydrogen sulfate anion. With ferrocenyl Schiff base calix[4]arene 1 an anodic shift as large as 302 mV is observed on addition of four equivalents of Cl⁻ anion. Also electrochemical and UV–vis spectroscopic titrations ferrocenyl calix[4]arene derivatives 1 with chloride and bromide ions and 2 (only with Cl⁻) indicate a 1:1 binding‐stiochiometry. Copyright © 2011 John Wiley & Sons, Ltd.     

Preparation and chromatographic characteristics of calix[4]arene polysiloxane as stationary phases for capillary gas chromatography

Summary Two new kinds of calix[4]arene derivatives, 5, 11, 17, 23-tetra-tert-butyl-25,27-bis(isopropylcarbamoyl-methoxy)-26,28-diundecenyloxy calix[4]arene (C[4]A) and 25,27-dibutoxy-5, 11, 17, 23-tetra-tert-butyl-26,28-diundecenyloxy calix[4]arene (C[4]B0, are prepared and then are polymized by two different processes. Three calix[4]arene polysiloxane stationary phases for capillary gas chromatography are obtained. Their chromatographic characteristics, including column efficiency, polarity, selectivity, glass-transition temperature and thermal stability are studied. Retention mechanisms are also discussed.     

量化计算辅助解析杯[4]芳烃固定相对萘胺和苯二胺的保留机制

杯芳烃对客体具有优异的识别作用,可作为液相色谱的固定相．本文以萘胺（NA）、苯二胺（BDA）位置异构体为溶质探针,考察其在杯[4]芳烃（Cx4）固定相上的色谱分离,用量子化学计算辅助研究了其在Cx4芳烃固定相上的保留机制．结果表明,用DFT-B3LYP／STO-3G＊＊量化计算方法,获得了质子化溶质与Cx4形成的Cx4．HBDA＋、Cx4-HNA＋超分子结构,直观地观察到了HBDA＋、HNA＋与Cx4的作用主要是π-π疏水作用和氢键作用．超分子Cx4-HBDA＋和Cx4-HNA＋的ΔG数值、稳定性与其色谱保留行为一致．     

New preorganized calix[4]arenes. Part I. A doubly-crowned calix and a double-calixcrown derived from 4,6,10,12,16,18,22,24,25,26,27,28-Dodecamethyl-5,11,17,23-tetrahydroxycalix[4] arene

A doubly-crowned calix and a double-calixcrown derived from 4,6,10,12,16,18,22,24,25,26,27, 28-dodecamethyl-5,11,17, 23-tetrahydroxycalix[4]arene (1) have been prepared by reaction of appropriate oligoethylene glycol ditosylates with (1) in acetonitrile in the presence of potassium carbonate. A potassium template effect is observed during one of the double cyclizations.     

Anion influence on extraction and transport of amino acid methyl esters by functionalised calix[4]arene

The liquid–liquid extraction of a series of amino acid methyl esters has been carried out with functionalised calix[4]arene (5,11,17,23-tetrakis(N-methylpiperazino)-25,26,27,28-tetrahydroxycalix[4]arene) from an aqueous phase into a chloroform phase as ion pairs in the presence of picrate ion or tropaeolin 00 as counter ion in order to study the molecular recognition properties of this receptor. The active transport assisted by pH gradient of amino acids as ion pairs through liquid membrane employing the functionalised calix[4]arene as carrier has been investigated. The results showed that the receptor exhibits good extractability towards amino acids and it can also act as carrier through liquid membrane aiming to the separation of amino acids. It was highlighted that the anion nature used as counter ion, the structure of calix[4]arene, and the structure of amino acids are responsible for the experimental results obtained. High yields in both amino acids extraction and transport were obtained for picrate ion used as counter ion.     

Syntheses of Chiral Calix [4] arene Derivatives Bearing Amino Acid Residue

The syntheses of chirai calix[4]arene derivatives bearing amino acid residue at the lower rim or upper rim by three different methods were reported.     

对-叔丁基杯［6］芳烃键合固定相的制备和评价

合成了对-叔丁基杯［6］芳烃高效液相色谱键合固定相,考察了多环芳烃、硝基苯胺位置异构体、邻苯二甲酸酯及苯的单官能团取代化合物的反相液相色谱保留行为。发现该键合相具有明显的反相特征,对位置异构体的分离优于C18柱,并讨论了可能的分离机理。     

Polymeric membrane sodium-selective electrodes based on calix[4]arene ionophores

Six kinds of tetra alkylester type calix[4]arene derivatives, (R₁=R₂=CH₃1, C₂H₅2, C₃H₇3,n-C₄H₉4,t-C₄H₉5,n-C₁₀H₂₁6), a diethyl-didecyl mixed ester type (R₁=C₂H₅, R₂ =C₁₀H₂₁7), and three kinds of lower rim bridged types (R₁=C₂H₅, R₂–R₂=(CH₂)₁₀8, (CH₂)₁₂9, (CH₂)₂(OCH₂CH₂)₃10) were characterized by electrochemical measurement to elucidate the effect of the length of the alkyl group of alkoxycarbonyl substituents on Na⁺ selectivity. To obtain excellent Na⁺ selective ionophores, introduction of short chain alkyl groups rather than long chain ones, such as a decyl group, and maintenance of sufficient solubility of the calix[4]arene derivatives in the membrane solvent are required concurrently. Among the calix[4]arenes tested, 25,26,27,28-tetrakis[(ethoxycarbonyl)methoxy]-p-tert-butylcalix[4]arene2, and the diethyl-didecyl mixed ester type derivative7 are the best ionophores for a Na⁺ selective electrode. On the other hand, sodium selectivity of the bridged type derivative9 is comparable or even superior to that of the known bis(12-crown-4).This paper is dedicated to the commemorative issue on the 50th anniversary of calixarenes.     

Isolation and X-ray crystal structure of a stable calix[4]arene monohemiketal

The formation of a stable calix[4]arene monohemiketal is described. X-ray crystallographic data provide conclusive evidence for the presence of a stabilizing hydrogen bond. Supplementary Data. Lists of H-atom parameters and bond lengths and angles involving hydrogens have been deposited with the British Library Document Supply Centre as Supplementary Publication No. SUP 82159 (5 pp.).     

Synthesis and cationic selectivity studies of novel calix[4]arene derivatives containing heteroatom at the lower rim

A series of calixarene derivatives 2―5 containing heteroatom at the lower rim have been synthesized. 1H NMR studies and crystallographic structures demonstrated that the calix[4]arene derivatives adopted cone conformations. Their cationic binding abilities and selectivities towards heavy and tran- sition metal ions have been evaluated by solvent extraction of aqueous metal picrates. The obtained results indicated that the introduction of nitrogen, sulfur, and/or phosphor atoms to the calix[4]arene framework could effectively enhance their binding ability and selectivity for heavy and transition metal ions, such as Pb2 or Ag .     

Inherently chiral calix[4]arene-based bifunctional organocatalysts for enantioselective aldol reactions

Two optical pure m-dimethylamino substituted inherently chiral calix[4]arene derivatives 8a and 8b bearing an l-prolinamido group have been synthesized by two routes, and structurally studied by the usual spectroscopic methods and X-ray crystallographic analysis. It was found that both of 8a and 8b could be utilized as bifunctional organocatalysts to efficiently promote the aldol reactions between aromatic aldehydes and ketones in the presence of acetic acid. Especially, with 8a as the catalyst, the reaction between 4-nitrobenzaldehyde and cyclopentanone at −20 °C gave the anti-aldol product up to 94% ee, while the anti-aldol product in up to 94:6 dr and 79% ee was obtained when 4-cyanobenzaldehyde was used as the aldol donor. Moreover, it was also demonstrated that the inherently chiral calixarene skeleton with (cS)-conformation in 8a was identified as the matched configuration of the stereogenic elements, and the inherently chiral moiety might play an important role in helping to stereocontrol the reaction.     

基于杯[4]芳烃的手性识别*

手性杯芳烃是一类重要的主体化合物,在手性识别、对映体分离和不对称催化等方面有着广泛的用途。[4]芳烃引其稳定的构象和易于修饰的特点,成为研究最为广泛的杯芳烃分子,其中大量的文献报道了能够用于对映体识别和检测的手性[4]芳烃。在手性识别的研究中,荧光、紫外和核磁是3中最常见的研究方法,本文根据这3种方法进行分类,综述了近年来以杯[4]芳烃为分子骨架的手性受体的合成及其在手性识别中的应用。最后对手性[4]芳烃的发展前景作了展望。     

Separation and identification of chiralN-acylcalix[4]arene amino acid derivatives by use of reversed-phase HPLC

Summary This work focuses on the separation and identification of p-tert butyl calix[4]arene derivatives. An isocratic mixture of 65% (v/v) acetonitrile and 35% (v/v) water with 0.1% (v/v) phosphoric acid was used as the mobile phase. A Bio-Rad Bio-Sil ODS-5S (250 mm×4 mm) column was used as the stationary phase with UV detection of the analytes at 274 nm. The reversed-phase high performance liquid chromatographic method which was developed provided baseline separation of five p-tertbutyl calix[4]arene derivatives in twenty minutes.     

High-performance Liquid Chromatography Study of the Nitration Course of Tetrabutoxycalix[4]arene at the Upper Rim:Determination of the Optimum Conditions for the Preparation of 5,11,17-Trinitro-25,26,27,28-tetrabutoxycalix[4]arene

A selective nitration of calix[4]arene at the upper rim in one pot process was described by monitoring the time dependence of the distribution of products by high‐performance liquid chromatography (HPLC). The discrimination of five nitrated products was accomplished by molecular symmetry considerations and ¹H NMR analysis. As a result, unusual 5,11,17‐trinitrocalix[4]arene ( 2d ) was obtained in 57% isolated yield. 5,11‐Dinitro‐calix[4]arene ( 2b ) and 5,11,17‐trinitrocalix[4]arene ( 2d ) with tetranitrocalix[4]arene 2e were further characterized by crystal X‐ray diffraction analysis. Furthermore, as an example of potential application, trinitrocalix[4]arene 2d could be converted to triaminocalix[4]arene 3d conveniently.     

一种新型杯[4]芳烃的合成

本文通过对特丁基杯[4]芳烃的酚羟基烷基化和苯环特丁基位上的IPSO-硝化制备了一系列对硝基杯[4]芳烃烷基醚,烷基分别是n-C~4H~9(3a)、n-C~8H~1~7(3b)、n-C~1~2H~2~5(3c)和n-C~1~6H~3~3(3d)。^1HNMR表明所有新的杯[4]芳烃都具有锥形(cone)构象。     

Highly selective fluorescent recognition of amino alcohol based on chiral calix[4]arenes bearing L-tryptophan unit

Four two-armed chiral calix[4]arenes (1a–1d) functionalised at the lower ring with amino acid units have been synthesised and the structures of these compounds were characterised by IR, MS, ¹H NMR, ¹³C NMR spectra and elemental analysis. Their molecular recognition abilities towards amino alcohol were examined by fluorescence titration experiment in three kinds of solution. The results indicated that these receptors exhibited excellent fluorescent response to phenylglycinol and could distinguish phenylglycinol from phenylalaninol rapidly through the obvious difference in the fluorescent response. Solvent comparative experiments also indicated that acetonitrile was the best solvent to detect these phenomena.     

新型杯[4]芳烃衍生物的合成及其氨基酸萃取性能

杯[4]-1,3-二乙酸乙酯衍生物(1)与水合肼反应生成杯[4]芳烃酰肼衍生物(2),化合物(2)与异硫氰酸苯酯反应得到含酰胺和硫脲单元的新型杯[4]芳烃衍生物(3).总产率达70%.系列氨基酸萃取实验表明化合物(3)对异亮氨酸有较好的选择性萃取能力.     

Synthesis and amino acid extraction abilities of chiral calix[4]arene triamides containing amino alcohol units

Herein the synthesis and extraction abilities of new d-/l-phenylalaninol substituted p-tert-butylcalix[4]arene triamide derivatives (3 and 4) towards amino acids are reported. These compounds (3 and 4) have been easily synthesized via aminolysis of p-tert-butylcalix[4]arene trimethylester (2) with d-/l-phenylalaninol in methanol-toluen solvent system at one step. The extraction properties of the prepared chiral calix[4]arene triamide derivatives (3 and 4) towards some selected amino acid methylesters are studied by liquid–liquid extraction. Results show that these chiral calix[4]arene triamide derivatives (3 and 4) exhibited a good affinity towards all amino acid species without any remarkably discrimination.     

Synthesis of upper rim calix[4]arene divalent glycoclusters via amide bond conjugation

Synthetic routes for linking two sugar units at the upper rim of cone calix[4]arenes, through the formation of amide bonds, have been explored. Steric effects prevent the coupling of calix[4]arene dicarboxylic acid with simple aminoglycosides, whereas the corresponding reaction with carbohydrates bearing a two or three carbon atoms spacer, terminating with a primary amino group, allows the synthesis of several difunctionalized calix[4]arene neoglycoconjugates, attractive in chemical glycobiology and supramolecular chemistry.