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Search for "ionophores" in Full Text gives 7 result(s) in Beilstein Journal of Organic Chemistry.
Cholyl 1,3,4-oxadiazole hybrid compounds: design, synthesis and antimicrobial assessment
- Anas J. Rasras,
- Mohamed El-Naggar,
- Nesreen A. Safwat and
- Raed A. Al-Qawasmeh
Beilstein J. Org. Chem. 2022, 18, 631–638, doi:10.3762/bjoc.18.63
- [27][28][29], and were used for ischemic stroke treatment [30], to decrease the cytotoxicity of anticancer drugs [31], and as amphiphilic copolymers as artificial ionophores [32]. Result and Discussion The synthetic strategy for the synthesis of the desired compounds 4a–v commenced from commercially
Graphical Abstract
Figure 1: Biologically active cholic acid hybridized with different heterocyclic scaffolds.
Scheme 1: Synthesis of cholyl 1,3,4-oxadiazole-2-thiol 2.
Scheme 2: Synthesis of cholyl 2-(propargylthio)-1,3,4-oxadiazole 3.
Scheme 3: Synthesis of target compounds 4a–v.
Figure 2: Structures of target compounds 4a–v.
Design, synthesis and application of carbazole macrocycles in anion sensors
- Alo Rüütel,
- Ville Yrjänä,
- Sandip A. Kadam,
- Indrek Saar,
- Mihkel Ilisson,
- Astrid Darnell,
- Kristjan Haav,
- Tõiv Haljasorg,
- Lauri Toom,
- Johan Bobacka and
- Ivo Leito
Beilstein J. Org. Chem. 2020, 16, 1901–1914, doi:10.3762/bjoc.16.157
- titrations were used to quantify binding in DMSO-d6/H2O solvent systems of two proportions – 99.5%:0.5% m/m and 90.0%:10.0% m/m, suggesting initial selectivity towards acetate. Three ionophores were selected for successful sensor prototype development and characterization. The constructed ion-selective
- sensor development, the results obtained in this work emphasize the importance of evaluating the binding behavior of receptors in real sensor membranes. Keywords: anion sensors; carboxylates; ionophores; macrocycles; sensor prototype; Introduction In 2013, Otto S. Wolfbeis asked the supramolecular
- electrodes are commercially available. This is largely due to the challenges associated with the selectivity of ionophores towards anions [20][21]. In this work, potentiometric solid-contact ion-selective electrodes (SC-ISEs) were chosen as the sensor type for several reasons. Potentiometric ISEs possess
Graphical Abstract
Figure 1: The biscarbazolylurea moiety.
Figure 2: The structure of the solid-contact ion-selective electrode (sensor): a) glassy carbon as the electr...
Figure 3: Studied receptor molecules.
Figure 4: MC001 and MC003 lowest energy conformers (COSMO-RS) showing intramolecular bonds. Color coding: whi...
Figure 5: a) Complex of MC008 with acetate; b) complex of MC006 with formate; c) complex of MC007 with lactat...
Scheme 1: The synthetic pathway to receptors CZ016 and MC001–MC014. The reaction yield for 2–3a/3b is given a...
Figure 6: Binding affinities of the studied receptors towards different carboxylates in DMSO-d6/H2O (99.5%:0....
Figure 7: Impedance spectra of sensors with each of the membranes. The spectra were recorded in 0.1 M sodium ...
Figure 8: Calibration curves for each of the membranes. The calibrations were performed by diluting 0.1 M sod...
Figure 9: The influence of solution pH on the potential responses of the sensor prototypes (three sensors for...
Figure 10: Potentiometric selectivity coefficients of interfering anions (relative to acetate) determined usin...
Tautomerism as primary signaling mechanism in metal sensing: the case of amide group
- Vera Deneva,
- Georgi Dobrikov,
- Aurelien Crochet,
- Daniela Nedeltcheva,
- Katharina M. Fromm and
- Liudmil Antonov
Beilstein J. Org. Chem. 2019, 15, 1898–1906, doi:10.3762/bjoc.15.185
- stability constants upon complexation, the selectivity is rather low, which can be attributed to the crown ether complexation features in general. Developing the system further, leads to modification of the ionophore part by replacing the crown ether with other ionophores, such as done in the case of 4 and
Graphical Abstract
Scheme 1: Conceptual idea for tautomeric metal sensing.
Scheme 2: 4-(Phenyldiazenyl)naphthalen-1-ol (1) and tautomeric ligands based on it.
Figure 1: The most stable tautomeric form of 6 in neutral state (left) and upon complexation with Mg(ClO4)2 (...
Figure 2: Absorption spectra of compounds 1 (a) and 6 (b) in acetonitrile (—), chloroform (− · −), dichlorome...
Figure 3: Left: Theoretically predicted structure of 6K (blue), overlaid with the X-ray structure (red). Righ...
Figure 4: Left: Absorption spectra of 6 with stepwise addition of Mg(ClO4)2 in acetonitrile (1 – neutral liga...
Figure 5: Normalized spectra of the free ligand 6 (c = 5 × 10−5 M) and its complexes obtained with Ba(ClO4)2,...
Scheme 3: Synthetic route of 6.
Bridgehead vicinal diallylation of norbornene derivatives and extension to propellane derivatives via ring-closing metathesis
- Sambasivarao Kotha and
- Rama Gunta
Beilstein J. Org. Chem. 2016, 12, 1877–1883, doi:10.3762/bjoc.12.177
- property is useful to design norbornene-based ionophores [12]. Due to the strained nature of norbornene systems they are useful precursors for ring-rearrangement metathesis (RRM) [13][14][15][16][17][18][19][20][21] to generate intricate polycyclics involving non-traditional retrosynthetic routes. Recently
Graphical Abstract
Figure 1: Retrosynthetic approach to propellane derivatives.
Scheme 1: Synthesis of the propellane derivative 1a via RCM.
Scheme 2: Garratts work on alkylation of norbornene with retention of configuration.
Figure 2: The molecular structure of 1a, with displacement ellipsoids drawn at the 50% probability level.
Scheme 3: Control experiment carried out to probe the configuration of 2a.
Figure 3: Crystal structure of compound 15 showing 50% displacement ellipsoids.
Scheme 4: RCM of the compound 2aa'.
Scheme 5: RCM approach to the propellane derivative 1b.
Figure 4: The molecular structures of the compounds 2b (left) and 1b (right) showing 30% displacement ellipso...
Scheme 6: Construction of the propellane derivative 1bb' using RCM.
Intermediates in monensin biosynthesis: A late step in biosynthesis of the polyether ionophore monensin is crucial for the integrity of cation binding
- Wolfgang Hüttel,
- Jonathan B. Spencer and
- Peter F. Leadlay
Beilstein J. Org. Chem. 2014, 10, 361–368, doi:10.3762/bjoc.10.34
- important and extensive group of natural products including a large number of antibiotic ionophores [1][2][3][4][5] as well as remarkable marine toxins such as the brevetoxins [6][7]. The antibiotic polyethers adopt a characteristic conformation in which multiple oxygen atoms provide ligands for a centrally
- for the key role of late-stage hydroxylation at C-26 of the monensin molecule. Like other polyether ionophores, monensin is assembled by the polyketide biosynthetic pathway on a modular polyketide synthase (PKS) multienzyme [14]. A model has been proposed [14] for monensin biosynthesis in which an
- hydrogen bonds for the stability of the complex is underlined by the conservation of this feature in the crystal structures of the polyether ionophores nigericin [30][31] and dianemycin (nanchangmycin) [32], where a carboxylic acid oxygen atom likewise form hydrogen bonds to the distal hydroxy groups
Graphical Abstract
Scheme 1: The proposed pathway for monensin biosynthesis in Streptomyces cinnamonensis. The polyketide syntha...
Figure 1: LC–MS-analysis of purified monensin-related metabolites. Monensin B derivatives (peaks marked with ...
Figure 2: (a) Crystal structure of sodium demethylmonensin A (4) (ellipsoid probability = 50%); (b) overlay o...
Molecular recognition of organic ammonium ions in solution using synthetic receptors
- Andreas Späth and
- Burkhard König
Beilstein J. Org. Chem. 2010, 6, No. 32, doi:10.3762/bjoc.6.32
Graphical Abstract
Figure 1: Biologically important amines and quaternary ammonium salts: histamine (1), dopamine (2) and acetyl...
Figure 2: Crown ether 18-crown-6.
Figure 3: Conformations of 18-crown-6 (4) in solvents of different polarity.
Figure 4: Binding topologies of the ammonium ion depending on the crown ring size.
Figure 5: A “pseudorotaxane” structure consisting of 24-crown-8 and a secondary ammonium ion (5); R = Ph.
Figure 6: Typical examples of azacrown ethers, cryptands and related aza macrocycles.
Figure 7: Binding of ammonium to azacrown ethers and cryptands [111-113].
Figure 8: A 19-crown-6-ether with decalino blocking groups (11) and a thiazole-dibenzo-18-crown-6-ether (12).
Figure 9: 1,3-Bis(6-oxopyridazin-1-yl)propane derivatives 13 and 14 by Campayo et al.
Figure 10: Fluorescent azacrown-PET-sensors based on coumarin.
Figure 11: Two different pyridino-cryptands (17 and 18) compared to a pyridino-crown (19); chiral ammonium ion...
Figure 12: Pyridino-18-crown-6 ligand (21), a similar acridino-18-crown-6 ligand (22) and a structurally relat...
Figure 13: Ciral pyridine-azacrown ether receptors 24.
Figure 14: Chiral 15-crown-5 receptors 26 and an analogue 18-crown-6 ligand 27 derived from amino alcohols.
Figure 15: C2-symmetric chiral 18-crown-6 amino alcohol derivatives 28 and related macrocycles.
Figure 16: Macrocycles with diamide-diester groups (30).
Figure 17: C2-symmetric chiral aza-18-crown-6 ethers (31) with phenethylamine residues.
Figure 18: Chiral C-pivot p-methoxy-phenoxy-lariat ethers.
Figure 19: Chiral lariat crown ether 34.
Figure 20: Sucrose-based chiral crown ether receptors 36.
Figure 21: Permethylated fructooligosaccharide 37 showing induced-fit chiral recognition.
Figure 22: Biphenanthryl-18-crown-6 derivative 38.
Figure 23: Chiral lariat crown ethers derived from binol by Fuji et al.
Figure 24: Chiral phenolic crown ether 41 with “aryl chiral barriers” and guest amines.
Figure 25: Chiral bis-crown receptor 43 with a meso-ternaphthalene backbone.
Figure 26: Chromogenic pH-dependent bis-crown chemosensor 44 for diamines.
Figure 27: Triamine guests for binding to receptor 44.
Figure 28: Chiral bis-crown phenolphthalein chemosensors 46.
Figure 29: Crown ether amino acid 47.
Figure 30: Luminescent receptor 48 for bis-alkylammonium guests.
Figure 31: Luminescent CEAA (49a), a bis-CEAA receptor for amino acids (49b) and the structure of lysine bindi...
Figure 32: Luminescent CEAA tripeptide for binding small peptides.
Figure 33: Bis crown ether 51a self assembles co-operatively with C60-ammonium ion 51b.
Figure 34: Triptycene-based macrotricyclic dibenzo-[24]-crown-8 ether host 52 and guests.
Figure 35: Copper imido diacetic acid azacrown receptor 53a and the suggested His-Lys binding motif; a copper ...
Figure 36: Urea (54) and thiourea (55) benzo crown receptor for transport and extraction of amino acids.
Figure 37: Crown pyryliums ion receptors 56 for amino acids.
Figure 38: Ditopic sulfonamide bridged crown ether receptor 57.
Figure 39: Luminescent peptide receptor 58.
Figure 40: Luminescent receptor 59 for the detection of D-glucosamine hydrochloride in water/ethanol and lumin...
Figure 41: Guanidinium azacrown receptor 61 for simple amino acids and ditopic receptor 62 with crown ether an...
Figure 42: Chiral bicyclic guanidinium azacrown receptor 63 and similar receptor 64 for the enantioselective t...
Figure 43: Receptors for zwitterionic species based on luminescent CEAAs.
Figure 44: 1,10-Azacrown ethers with sugar podand arms and the anticancer agent busulfan.
Figure 45: Benzo-18-crown-6 modified β-cyclodextrin 69 and β-cyclodextrin functionalized with diaza-18-crown-6...
Figure 46: Receptors for colorimetric detection of primary and secondary ammonium ions.
Figure 47: Porphyrine-crown-receptors 72.
Figure 48: Porphyrin-crown ether conjugate 73 and fullerene-ammonium ion guest 74.
Figure 49: Calix[4]arene (75a), homooxocalix[4]arene (75b) and resorcin[4]arene (75c) compared (R = H, alkyl c...
Figure 50: Calix[4]arene and ammonium ion guest (R = H, alkyl, OAcyl etc.), possible binding sites; A: co-ordi...
Figure 51: Typical guests for studies with calixarenes and related molecules.
Figure 52: Lower rim modified p-tert-butylcalix[5]arenes 82.
Figure 53: The first example of a water soluble calixarene.
Figure 54: Sulfonated water soluble calix[n]arenes that bind ammonium ions.
Figure 55: Displacement assay for acetylcholine (3) with a sulfonato-calix[6]arene (84b).
Figure 56: Amino acid inclusion in p-sulfonatocalix[4]arene (84a).
Figure 57: Calixarene receptor family 86 with upper and lower rim functionalization.
Figure 58: Calix[6]arenes 87 with one carboxylic acid functionality.
Figure 59: Sulfonated calix[n]arenes with mono-substitution at the lower rim systematically studied on their r...
Figure 60: Cyclotetrachromotropylene host (91) and its binding to lysine (81c).
Figure 61: Calixarenes 92 and 93 with phosphonic acids groups.
Figure 62: Calix[4]arene tetraphosphonic acid (94a) and a double bridged analogue (94b).
Figure 63: Calix[4]arene tetraphosphonic acid ester (92c) for surface recognition experiments.
Figure 64: Calixarene receptors 95 with α-aminophosphonate groups.
Figure 65: A bridged homocalix[3]arene 95 and a distally bridged homocalix[4]crown 96.
Figure 66: Homocalix[3]arene ammonium ion receptor 97a and the Reichardt’s dye (97b) for colorimetric assays.
Figure 67: Chromogenic diazo-bridged calix[4]arene 98.
Figure 68: Calixarene receptor 99 by Huang et al.
Figure 69: Calixarenes 100 reported by Parisi et al.
Figure 70: Guest molecules for inclusion in calixarenes 100: DAP × 2 HCl (101a), APA (101b) and Lys-OMe × 2 HC...
Figure 71: Different N-linked peptido-calixarenes open and with glycol chain bridges.
Figure 72: (S)-1,1′-Bi-2-naphthol calixarene derivative 104 published by Kubo et al.
Figure 73: A chiral ammonium-ion receptor 105 based on the calix[4]arene skeleton.
Figure 74: R-/S-phenylalaninol functionalized calix[6]arenes 106a and 106b.
Figure 75: Capped homocalix[3]arene ammonium ion receptor 107.
Figure 76: Two C3 symmetric capped calix[6]arenes 108 and 109.
Figure 77: Phosphorous-containing rigidified calix[6]arene 110.
Figure 78: Calix[6]azacryptand 111.
Figure 79: Further substituted calix[6]azacryptands 112.
Figure 80: Resorcin[4]arene (75c) and the cavitands (113).
Figure 81: Tetrasulfonatomethylcalix[4]resorcinarene (114).
Figure 82: Resorcin[4]arenes (115a/b) and pyrogallo[4]arenes (115c, 116).
Figure 83: Displacement assay for acetylcholine (3) with tetracyanoresorcin[4]arene (117).
Figure 84: Tetramethoxy resorcinarene mono-crown-5 (118).
Figure 85: Components of a resorcinarene based displacement assay for ammonium ions.
Figure 86: Chiral basket resorcin[4]arenas 121.
Figure 87: Resorcinarenes with deeper cavitand structure (122).
Figure 88: Resorcinarene with partially open deeper cavitand structure (123).
Figure 89: Water-stabilized deep cavitands with partially structure (124, 125).
Figure 90: Charged cavitands 126 for tetralkylammonium ions.
Figure 91: Ditopic calix[4]arene receptor 127 capped with glycol chains.
Figure 92: A calix[5]arene dimer for diammonium salt recognition.
Figure 93: Calixarene parts 92c and 129 for the formation molecular capsules.
Figure 94: Encapsulation of a quaternary ammonium cation by two resorcin[4]arene molecules (NMe4+@[75c]2 × Cl−...
Figure 95: Encapsulation of a quaternary ammonium cation by six resorcin[4]arene molecules (NMe3D+@[130]6 × Cl−...
Figure 96: Structure and schematic of cucurbit[6]uril (CB[6], 131a).
Figure 97: Cyclohexanocucurbit[6]uril (CB′[6], 132) and the guest molecule spermine (133).
Figure 98: α,α,δ,δ-Tetramethylcucurbit[6]uril (134).
Figure 99: Structure of the cucurbituril-phthalhydrazide analogue 135.
Figure 100: Organic cavities for the displacement assay for amine differentiation.
Figure 101: Displacement assay methodology for diammonium- and related guests involving cucurbiturils and some ...
Figure 102: Nor-seco-Cucurbituril (±)-bis-ns-CB[6] (140) and guest molecules.
Figure 103: The cucurbit[6]uril based complexes 141 for chiral discrimination.
Figure 104: Cucurbit[7]uril (131c) and its ferrocene guests (142) opposed.
Figure 105: Cucurbit[7]uril (131c) guest inclusion and representative guests.
Figure 106: Cucurbit[7]uril (131c) binding to succinylcholine (145) and different bis-ammonium and bis-phosphon...
Figure 107: Paraquat-cucurbit[8]uril complex 149.
Figure 108: Gluconuril-based ammonium receptors 150.
Figure 109: Examples of clefts (151a), tweezers (151b, 151c, 151d) and clips (151e).
Figure 110: Kemp’s triacid (152a), on example of Rebek’s receptors (152b) and guests.
Figure 111: Amino acid receptor (154) by Rebek et al.
Figure 112: Hexagonal lattice designed hosts by Bell et al.
Figure 113: Bell’s amidinium receptor (156) and the amidinium ion (157).
Figure 114: Aromatic phosphonic acids.
Figure 115: Xylene phosphonates 159 and 160a/b for recognition of amines and amino alcohols.
Figure 116: Bisphosphonate recognition motif 161 for a colorimetric assay with alizarin complexone (163) for ca...
Figure 117: Bisphosphonate/phosphate clip 164 and bisphosphonate cleft 165.
Figure 118: N-Methylpyrazine 166a, N-methylnicotinamide iodide (166b) and NAD+ (166c).
Figure 119: Bisphosphate cavitands.
Figure 120: Bisphosphonate 167 of Schrader and Finocchiaro.
Figure 121: Tweezer 168 for noradrenaline (80b).
Figure 122: Different tripods and heparin (170).
Figure 123: Squaramide based receptors 172.
Figure 124: Cage like NH4+ receptor 173 of Kim et al.
Figure 125: Ammonium receptors 174 of Chin et al.
Figure 126: 2-Oxazolin-based ammonium receptors 175a–d and 176 by Ahn et al.
Figure 127: Racemic guest molecules 177.
Figure 128: Tripods based on a imidazole containing macrocycle (178) and the guest molecules employed in the st...
Figure 129: Ammonium ion receptor 180.
Figure 130: Tetraoxa[3.3.3.3]paracyclophanes 181 and a cyclophanic tetraester (182).
Figure 131: Peptidic bridged paraquat-cyclophane.
Figure 132: Shape-selective noradrenaline host.
Figure 133: Receptor 185 for binding of noradrenaline on surface layers from Schrader et al.
Figure 134: Tetraphosphonate receptor for binding of noradrenaline.
Figure 135: Tetraphosphonate 187 of Schrader and Finocchiaro.
Figure 136: Zinc-Porphyrin ammonium-ion receptors 188 and 189 of Mizutani et al.
Figure 137: Zinc porphyrin receptor 190.
Figure 138: Zinc porphyrin receptors 191 capable of amino acid binding.
Figure 139: Zinc-porphyrins with amino acid side chains for stereoinduction.
Figure 140: Bis-zinc-bis-porphyrin based on Tröger’s base 193.
Figure 141: BINAP-zinc-prophyrin derivative 194 and it’s guests.
Figure 142: Bisaryl-linked-zinc-porphyrin receptors.
Figure 143: Bis-zinc-porphyrin 199 for diamine recognition and guests.
Figure 144: Bis-zinc-porphyrin crown ether 201.
Figure 145: Bis-zinc-porphyrin 202 for stereodiscrimination (L = large substituent; S = small substituent).
Figure 146: Bis-zinc-porphyrin[3]rotaxane and its copper complex and guests.
Figure 147: Dien-bipyridyl ligand 206 for co-ordination of two metal atoms.
Figure 148: The ligand and corresponding tetradentate co-complex 207 serving as enantioselective receptor for a...
Figure 149: Bis(oxazoline)–copper(II) complex 208 for the recognition of amino acids in aqueous solution.
Figure 150: Zinc-salen-complexes 209 for the recognition tertiary amines.
Figure 151: Bis(oxazoline)–copper(II) 211 for the recognition of amino acids in aqueous solution.
Figure 152: Zn(II)-complex of a C2 terpyridine crown ether.
Figure 153: Displacement assay and receptor for aspartate over glutamate.
Figure 154: Chiral complex 214 for a colorimetric displacement assay for amino acids.
Figure 155: Metal complex receptor 215 with tripeptide side arms.
Figure 156: A sandwich complex 216 and its displaceable dye 217.
Figure 157: Lanthanide complexes 218–220 for amino acid recognition.
Figure 158: Nonactin (221), valinomycin (222) and vancomycin (223).
Figure 159: Monesin (224a) and a chiral analogue for enantiodiscrimination of ammonium guests (224b).
Figure 160: Chiral podands (226) compared to pentaglyme-dimethylether (225) and 18-crown-6 (4).
Figure 161: Lasalocid A (228).
Figure 162: Lasalocid derivatives (230) of Sessler et al.
Figure 163: The Coporphyrin I tetraanion (231).
Figure 164: Linear and cyclic peptides for ammonium ion recognition.
Figure 165: Cyclic and bicyclic depsipeptides for ammonium ion recognition.
Figure 166: α-Cyclodextrin (136a) and novocaine (236).
Figure 167: Helical diol receptor 237 by Reetz and Sostmann.
Figure 168: Ammonium binding spherand by Cram et al. (238a) and the cyclic[6]metaphenylacetylene 238b in compar...
Figure 169: Receptor for peptide backbone and ammonium binding (239).
Figure 170: Anion sensor principle with 3-hydroxy-2-naphthanilide of Jiang et al.
Figure 171: 7-bromo-3-hydroxy-N-(2-hydroxyphenyl)naphthalene 2-carboxamide (241) and its amine binding.
Figure 172: Naturally occurring catechins with affinity to quaternary ammonium ions.
Figure 173: Spiropyran (244) and merocyanine form (244a) of the amino acid receptors of Fuji et al.
Figure 174: Coumarin aldehyde (245) and its iminium species with amino acid bound (245a) by Glass et al.
Figure 175: Coumarin aldehyde appended with boronic acid.
Figure 176: Quinolone aldehyde dimers by Glass et al.
Figure 177: Chromogenic ammonium ion receptors with trifluoroacetophenone recognition motifs.
Figure 178: Chromogenic ammonium ion receptor with trifluoroacetophenone recognition motif bound on different m...
Synthesis and properties of calix[4]arene telluropodant ethers as Ag+ selective sensors and Ag+, Hg2+ extractants
- Yang Lu,
- Yuanyuan Li,
- Song He,
- Yan Lu,
- Changying Liu,
- Xianshun Zeng and
- Langxing Chen
Beilstein J. Org. Chem. 2009, 5, No. 59, doi:10.3762/bjoc.5.59
- +-selective ionophores in ion-selective electrodes evaluated by electromotive force measurements of polymer membrane electrodes. The tweezer-like ionophores 6–8 showed excellent extraction ability towards Ag+ and Hg2+. Keywords: calix[4]arenes; extractants; mercury; sensors; silver; telluropodant ether
- -selective electrodes (ISEs) in our group and by our co-workers [50][51][52][53]. To continue our interest in the development of new ionophores, herein we describe the design and synthesis of three novel tweezer-like 25,27-dihydroxy-26,28-bis(phenyltelluroalkoxy)calix[4]arenes 6–8 composed of two tellurium
- saturated carbons attached to tellurium were detected at 4.06 ppm and 3.54 ppm, respectively. Ion selectivity For assessment of Ag+ ion selective behaviour of phenyltelluroalkoxyl modified calix[4]arenes derivatives (6–8, 10 and 12), ISEs based on 6–8, 10 and 12 as ionophores were prepared and their
Graphical Abstract
Scheme 1: Synthesis and structures of calix[4]arenes 6–8; 3, 6: n = 2; 4, 7: n = 3; 5, 8: n = 5.
Scheme 2: Synthesis of calix[4]arene 10 and 12.
