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.     

Recognition of amino acids by functionalized calixarenes

The calixarenic receptors exhibit remarkable host-guest properties towards biologically relevant guests. Aspects of complex formation reactions between both native and derivatized amino acids, di-and tripeptides with calixarenic (chiral or not) receptors are summarized in this critical review. Thus, the discussions emphasize the parameters that affect the molecular binding selectivity and efficiency of functionalized calix[n]arenes towards these substrates. A brief survey on their application in separation of amino acids is also considered (123 references).     

Calix[4]azacrowns as ionophores for liquid?Cliquid extraction and facilitated transport of biological supramolecular complexes

The native and methyl ester amino acids have been extracted by calix[4]azacrowns 1 (1,3-[ethylene-bis-aminocarbonylmethoxy)]-p-tert-butylcalix[4]arene) and 2 (1,3-[propylene-bis-aminocarbonylmethoxy)]-p-tert-butyl-calix[4]arene) from an aqueous phase into a chloroform phase and transported through a chloroform liquid membrane as ion pairs in the presence of picrate or tropaeolin 00 as counter ions aiming their separation. The amino acids under study exhibited good extractability by calix[4]azacrowns 1 and 2. Both receptors 1 and 2 showed good extractability towards amino acids under study. The results are discussed in term of correlation of structural properties of amino acids and calix[4]azacrowns involved in experiments. In this respect, the influence of chain length of receptors upon extraction and transport of amino acids, and the nature of anions used as counter ions are evaluated.     

Synthesis and Extraction Properties of 1,3,5-O-trimethyl-2,4,6-tri-O-hydroxamic Acid p-tert-butyl Calix[6]arene

A calix[6]arene bearing three hydroxamic acid groups arranged in aC₃ symmetry has been synthesized. Extraction properties towards transition metal ions are presented and compared with other proton-ionizable related calix[6]arenes and with a monomeric hydroxamic acid analog.     

Novel calix[4]cryptands: “Mappemonde II” and “Mill II”

Two novel calix[4]cryptands were synthesized from 1,3‐alternate calix[4]bis‐azacrown. “Mappemonde II” consists of one 1,3‐calix[4]bis‐azacrown wrapped by a benzo‐crown ether loop. “Mill II” is composed of two 1,3‐calix[4]bis‐azacrowns linked by two benzo‐crown ether strands.     

p‐Methyl­tetrahomodioxacalix­[4]­arene

The title compound, 7,13,21,27‐tetramethyl‐3,17‐dioxapenta­cyclo­[23.3.1.1^5,9.1^11,15.1^9,23]ditriaconta‐1(29),5,7,­9(30),­11(31),‐12,­14,19(32),20,22,25,27‐dodecaene‐29,30,31,32‐tetraol, C₃₄H₃₆O₆, assumes in the solid state a very distorted cone‐like conformation stabilized by intramolecular simple and bifurcated hydrogen bonds involving both phenolic and ether O atoms. One part of the mol­ecule, comprising an ether link, is included in the cavity of an adjacent calixarene related by a screw axis, giving rise to a one‐dimensional self‐inclusion polymer.     

Synthesis of a Calix[4]arene Containing 'Hard' and 'Soft' Metal Ion Binding Sites

Co-receptor 1,3-calix[4]-di(aza-benzo)crown-crown-6 (1-H) designed with one calix[4]arene in a 1,3-alternate conformation and hard and soft metal ion binding sites has been prepared according to three pathways (A-C). Pathway B, consisting of two different 1 + 1 condensations with ditosylate derivatives, was shown to be the most efficient.     

Cation Recognition by Picolyl-Armed Calix[4]crown-5-azacrown-5s

A series of N-pivot calix[4]crown-5-azacrown-5 ethers substituted by 2-picolyl, 3-picolyl and benzyl groups respectively were synthesized. The nitrogen atom of the 2-picolyl group is found to participate in the silver ion complexation through three dimensional encapsulation.