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Search for "cation binding" in Full Text gives 17 result(s) in Beilstein Journal of Organic Chemistry.
Switchable molecular tweezers: design and applications
- Pablo Msellem,
- Maksym Dekthiarenko,
- Nihal Hadj Seyd and
- Guillaume Vives
Beilstein J. Org. Chem. 2024, 20, 504–539, doi:10.3762/bjoc.20.45
- flourished since the early 2000s. It is worth mentioning, as stated by Leigh in a comprehensive review [15], that a pioneering example of a molecular machine was the photoswitchable molecular tweezers developed by Shinkai [16] in 1981 for photocontrolled cation binding. This novel class of tweezers
- podand unit adopts a cyclic conformation wrapping around the cation and brings the arms close to each other. The selectivity of the cation binding can be modulated by changing the chain length similarly to a crown ether (Figure 17). The cation can be removed by the addition of a better ligand such as a
Graphical Abstract
Figure 1: Principle of switchable molecular tweezers.
Figure 2: Principle of pH-switchable molecular tweezers 1 [19].
Figure 3: a) pH-Switchable tweezers 2 substituted with alkyl chains as switchable lipids. b) Schematic depict...
Figure 4: Modification of spectral properties of 3 by controlled induction of Pt–Pt interactions.
Figure 5: Conformational switching of di(hydroxyphenyl)pyrimidine-based tweezer 4 upon alkylation or fluoride...
Figure 6: Hydrazone-based pH-responsive tweezers 5 for mesogenic modulation.
Figure 7: pH-Switchable molecular tweezers 6 bearing acridinium moieties.
Figure 8: a) Terpyridine and pyridine-hydrazone-pyridine analogs molecular tweezers and b) extended pyridine ...
Figure 9: Terpyridine-based molecular tweezers with M–salphen arms and their field of application. Figure 9 was adapt...
Figure 10: a) Terpyridine-based molecular tweezers for diphosphate recognition [48]; b) bishelicene chiroptical te...
Figure 11: Terpyridine-based molecular tweezers with allosteric cooperative binding.
Figure 12: Terpyridine-based molecular tweezers presenting closed by default conformation.
Figure 13: Pyridine-pyrimidine-pyridine-based molecular tweezers.
Figure 14: Coordination-responsive molecular tweezers based on nitrogen-containing ligands.
Figure 15: Molecular tweezers exploiting the remote bipyridine or pyridine binding to trigger the conformation...
Figure 16: Bipyridine-based molecular tweezers exploiting the direct s-trans to s-cis-switching for a) anion b...
Figure 17: a) Podand-based molecular tweezers [66,67]. b) Application of tweezers 32 for the catalytic allosteric reg...
Figure 18: Anion-triggered molecular tweezers based on calix[4]pyrrole.
Figure 19: Anion-triggered molecular tweezers.
Figure 20: a) Principle of the weak link approach (WLA) developed by Mirkin and its application to b) symmetri...
Figure 21: Molecular tweezers as allosteric catalyst in asymmetric epoxide opening [80].
Figure 22: Allosteric regulation of catalytic activity in ring-opening polymerization with double tweezers 41.
Figure 23: a) Conformational switching of 42 by intramolecular –S–S– bridge formation. b) Shift of conformatio...
Figure 24: a) Redox-active glycoluril-TTF tweezers 44. b) Mechanism of stepwise oxidation of said tweezers wit...
Figure 25: Mechanism of formation of the mixed-valence dimers of tweezers 45.
Figure 26: Mechanism of carbohydrate liberation upon redox-mediated conformation switching of 46.
Figure 27: a) The encapsulation properties of 47 as well as the DCTNF release process from its host–guest comp...
Figure 28: Redox-active bipyridinium-based tweezers. a) With a ferrocenyl hinge 49, b) with a propyl hinge 50 ...
Figure 29: Redox-active calix[4]arene porphyrin molecular tweezers.
Figure 30: a) Mechanism of the three orthogonal stimuli. b) Cubic scheme showing the eight different states of ...
Figure 31: Redox-controlled molecular gripper based on a diquinone resorcin[4]arene.
Figure 32: a) Shinkai's butterfly tweezers and their different host–guest properties depending on the isomer. ...
Figure 33: Cyclam-tethered tweezers and their different host–guest complexes depending on their configuration.
Figure 34: Azobenzene-based catalytic tweezers.
Figure 35: Photoswitchable PIEZO channel mimic.
Figure 36: Stilbene-based porphyrin tweezers for fullerene recognition.
Figure 37: Stiff-stilbene-based tweezers with urea or thiourea functional units for a) anion binding, b) anion...
Figure 38: Feringa’s photoswitchable organocatalyst (a) and different catalyzed reactions with that system (b)....
Figure 39: a) Irie and Takeshita’s thioindigo-based molecular tweezers. b) Family of hemithioindigo-based mole...
Figure 40: Dithienylethylene crown ether-bearing molecular tweezers reported by Irie and co-workers.
Elucidating the glycan-binding specificity and structure of Cucumis melo agglutinin, a new R-type lectin
- Jon Lundstrøm,
- Emilie Gillon,
- Valérie Chazalet,
- Nicole Kerekes,
- Antonio Di Maio,
- Ten Feizi,
- Yan Liu,
- Annabelle Varrot and
- Daniel Bojar
Beilstein J. Org. Chem. 2024, 20, 306–320, doi:10.3762/bjoc.20.31
- (Val6 to Asp132) could be modelled, and unambiguous electron density permitted us to locate and model four cation binding sites (three in each structure) and one sugar binding site (Figure 4a,b and Figure S4, Supporting Information File 2). The complexed structures allowed us to shed light on the
Graphical Abstract
Figure 1: Characterizing a new lectin from the melon Cucumis melo. (a) Evolutionary relationships of common R...
Figure 2: Characterizing the binding specificity of CMA1. (a, b) Lectin produced in mammalian cells was analy...
Figure 3: Assessing and quantifying in-solution binding of CMA1. (a) Erythrocyte agglutination assay. Using r...
Figure 4: Structural insights into the binding mechanism of CMA1. (a, b) Overall representation of the N-term...
Tying a knot between crown ethers and porphyrins
- Maksym Matviyishyn and
- Bartosz Szyszko
Beilstein J. Org. Chem. 2023, 19, 1630–1650, doi:10.3762/bjoc.19.120
- cationic entity in the crown ether-like cavity and an anion in the region close to the metalloporphyrin core (Figure 7). The studies showed that the cation binding in the hovering crown pockets of 9-Zn and 9-Cu included, but was not limited to, alkali metal cations, transition metal cations, and
Graphical Abstract
Figure 1: Porphyrin and crown ether.
Figure 2: Timeline demonstrating the contributions into the crown ether–porphyrin chemistry.
Figure 3: Tetra-crowned porphyrin 1 and dimer 2 formed upon K+ binding.
Figure 4: meso-Crowned 25-oxasmaragdyrins 3a–c and their boron(III) complexes (3a–c)-BF2.
Scheme 1: CsF ion-pair binding of 4. The molecular structure of 4-CsF is shown on the right [101].
Figure 5: CsF ion pair binding by 5. The molecular structure of 5-CsF is shown on the right [102].
Scheme 2: Ion-pair binding by 6. The molecular structure of (6-CsCl)2 is shown on the right [103].
Scheme 3: Hydrated fluoride binding by 7 [104].
Figure 6: β-Crowned porphyrin 8.
Figure 7: Crown ether-capped porphyrins 9.
Figure 8: The capped porphyrin 10 and complex [10-PQ](PF6)2.
Figure 9: The double-capped porphyrin 11.
Figure 10: Selected examples of iminoporphyrinoids [58,122].
Scheme 4: The synthesis of 13.
Scheme 5: Tripyrrane-based crown ether-embedding porphyrinoid 15.
Figure 11: Macrocycles 16–19 and their coordination compounds.
Scheme 6: The flexibility of 16-Co [66].
Figure 12: Hexagonal wheel composed of six 16-Co(III) monomers [66].
Scheme 7: The synthesis of 16-V [67].
Figure 13: The molecular structure of dimers [16-Mn]2 [67].
Scheme 8: Synthesis of crownphyrins 28–33. Compounds 23a/b and 29a/b were obtained from 4,7,10-trioxa-1,13-tr...
Figure 14: The molecular structures of 22a, 34a·(HCl)2, and 29b [69].
Figure 15: Molecular structures of 22a-Pb and (29b)2-Zn [69].
Scheme 9: Reactivity of 29a/b.
Scheme 10: Synthesis of 36 and 37 [131].
Scheme 11: Synthesis of 40–45.
Figure 16: Potential applications of porphyrin-crown ether hybrids.
Constrained thermoresponsive polymers – new insights into fundamentals and applications
- Patricia Flemming,
- Alexander S. Münch,
- Andreas Fery and
- Petra Uhlmann
Beilstein J. Org. Chem. 2021, 17, 2123–2163, doi:10.3762/bjoc.17.138
Graphical Abstract
Figure 1: (a) Schematic representation of the phase stability of a binary mixture based on the free enthalpy ...
Figure 2: Illustration of the relationship between the type of miscibility gap and the temperature dependence...
Figure 3: Schematically pictured phase diagram of a binary mixture composed of a dissolved polymer with a LCS...
Figure 4: Schematic illustration of a thermo-induced swelling behavior of a star polymer composed of responsi...
Figure 5: Schematic illustration of self-assembly of block copolymer amphiphiles in a polar medium.
Figure 6: Schematic comparison of the size and conformation between free polymer chains (a), grafted polymer ...
Figure 7: Comparison of the possible phase diagrams of a polymer in solution with partially miscibility and t...
Figure 8: Selection of polymers exhibiting UCST behavior due to hydrogen bonding (blue) divided into homo- (a...
Figure 9: Part A shows the molecular structure of PDMAPS stars synthesized by Li et al. (left) demonstrating ...
Figure 10: Part A contains a schematic demonstration of conformational transitions of dual-thermoresponsive bl...
Figure 11: Part A pictures zwitterionic brushes grafted from silicon substrates obtaining a nonassociated, hyd...
Figure 12: Part A pictures the UCST phase transition of zwitterionic polymers grafted on the surface of mesopo...
Anion-driven encapsulation of cationic guests inside pyridine[4]arene dimers
- Anniina Kiesilä,
- Jani O. Moilanen,
- Anneli Kruve,
- Christoph A. Schalley,
- Perdita Barran and
- Elina Kalenius
Beilstein J. Org. Chem. 2019, 15, 2486–2492, doi:10.3762/bjoc.15.241
- in pyridine[4]arene is an anion-driven process. Keywords: cation binding; DFT calculations; ion mobility mass spectrometry; macrocycles; pyridinearenes; resorcinarenes; Introduction Resorcinarenes and their derivatives are known for the molecular recognition properties of their self-assembled
- dimeric resorcin[4]arene and pyridine[4]arene capsules, we highlight here unique host–guest properties of pyridinearene capsules. In marked contrast to the corresponding resorcin[4]arene capsules, cation binding is clearly feasible, when anions bind in an exo-site and support cation encapsulation by
- , cation binding to pyridinearene is clearly not as strong as with resorcin[4]arene, which is known for its excellent cation receptor properties. A comparison of these two macrocyclic hosts reveals significant differences in their binding properties. Pyridine[4]arene appears to have a better affinity
Graphical Abstract
Scheme 1: Structures of tetraisobutylpyridine[4]arene 1 and tetraisobutylresorcin[4]arene 2.
Figure 1: Spectra of 1 + Me4NPF6 1:3 in acetone in a) (+)ESI-MS and b) (−)ESI-MS. Insets showing arrival time...
Figure 2: (+)ESI-MS profile spectrum of the mixture of 1, 2 and TMAPF6 in acetonitrile (20 µM, 1:1:1). Inset ...
Figure 3: Calculated ESP surfaces (in au) superimposed on the total electron density (0.004 au) for 1 and 2: ...
Dynamic light scattering studies of the effects of salts on the diffusivity of cationic and anionic cavitands
- Anthony Wishard and
- Bruce C. Gibb
Beilstein J. Org. Chem. 2018, 14, 2212–2219, doi:10.3762/bjoc.14.195
- . More specifically, both octacarboxylate 1 and positand 2 have a non-polar cavity that can function as an anion (but not to our knowledge a cation) binding site. Anion binding to the cavity of positively charged 2 is stronger than to negatively charged 1 [13][14], but nevertheless anion binding to 1 can
- be as strong as 4.60 kcal mol−1. Host 2 has a second anion binding site in the form of the crown of trimethylammoniums “under” the primary bowl [14], and correspondingly the four chelating carboxylates of the crown of 1 may be a reasonable cation binding site. Furthermore, in addition to these
- , Figure S3), which revealed only trace amounts of host aggregation (≈5%). Furthermore, even at 100 mM salt concentration, 1H NMR spectroscopy failed to show any significant association of Cs+ to the crown of four carboxylates. Thus, although this crown is the most obvious potential cation binding site, we
Graphical Abstract
Figure 1: Chemical structures of octaacid 1 and positand 2 showing the anionic binding sites of the two hosts...
Figure 2: Representative plots of the volume-weighted distribution obtained by DLS for salts titrated into 2....
Figure 3: Representative plots of the volume-weighted distribution obtained by DLS for salts titrated into 2....
Scheme 1: Visualization of the competitive equilibrium between iodide binding to host 2 or associating with i...
Sulfation and amidinohydrolysis in the biosynthesis of giant linear polyenes
- Hui Hong,
- Markiyan Samborskyy,
- Katsiaryna Usachova,
- Katharina Schnatz and
- Peter F. Leadlay
Beilstein J. Org. Chem. 2017, 13, 2408–2415, doi:10.3762/bjoc.13.238
- that it contains the sequence motifs xGGDH, DAHxD, and SxDxDxxDPxxxP (where x = any amino acid), which are conserved in this enzyme superfamily and are implicated in cation binding and catalysis [19][20][21][22]. Our finding that amidinohydrolase encoded by the medi4948 gene acts on both
Graphical Abstract
Scheme 1: The structures of clethramycin, mediomycins and related linear polyenes.
Scheme 2: The biosynthetic gene clusters for mediomycin (med) from Streptomyces mediocidicus and clethramycin...
Figure 1: HPLC–UV–MS analysis of polyenes. A) LC–UV (360 nm) trace of mycelium methanol extract from DSM4137 ...
Figure 2: HPLC–UV–MS analysis of polyenes from DSM4137 wild type and mutants. A) LC–UV (360 nm) trace of myce...
Scheme 3: The parallel pathways for the biosynthesis of mediomycin A.
Figure 3: HPLC–UV–MS analysis of in vitro assays with amidinohydrolase Medi4948 and sulfotransferase Slf from ...
p-tert-Butylthiacalix[4]arenes functionalized by N-(4’-nitrophenyl)acetamide and N,N-diethylacetamide fragments: synthesis and binding of anionic guests
- Alena A. Vavilova and
- Ivan I. Stoikov
Beilstein J. Org. Chem. 2017, 13, 1940–1949, doi:10.3762/bjoc.13.188
- (phenolic fragments) groups can participate in anion binding. To determine the possibility of the tetrabutylammonium cation binding by the synthesized thiacalix[4]arenes, solutions of the compounds 3, 5 and 6 in the presence of a 10-fold excess of n-Bu4NX (X = F−, Cl−, Br−, I−, CH3CO2−, H2PO4−, NO3−) were
Graphical Abstract
Scheme 1: Synthesis of 1,3-di- and tetrasubstituted thiacalix[4]arenes 2 and 3. Conditions: (i) macrocycle 1 ...
Scheme 2: Synthesis of monosubstituted thiacalix[4]arene 4. Conditions: (i) macrocycle 1 (1 equiv), 2-chloro-N...
Scheme 3: Synthesis of tetra- and 1,2-disubstituted thiacalix[4]arenes 5 and 6, respectively. Conditions: (i)...
Figure 1: Investigated hosts 2, 3, 7–10.
Figure 2: UV absorption spectra of the complexation system obtained by titration of the receptor 6 (c(6) = 2....
Synthesis and metal binding properties of N-alkylcarboxyspiropyrans
- Alexis Perry and
- Christina J. Kousseff
Beilstein J. Org. Chem. 2017, 13, 1542–1550, doi:10.3762/bjoc.13.154
- spiropyran-modified agarose gel [14][15] and the creation of light-responsive nanopores through modification of natural channel proteins [16]. Furthermore, addition of an N-alkylcarboxylate moiety is a common tactic used to enhance water solubility of spiropyran derivatives [6]. Spiropyran–metal cation
- binding occurs as a result of stabilisation of the zwitterionic merocyanine isomer via phenoxide–metal complexation [17] (Figure 1). Commonly, merocyanines undergo photoreversion to their corresponding spiropyran under visible light irradiation and metal complexation is usually achieved either in darkness
Graphical Abstract
Figure 1: General uses of N-alkylcarboxyspiropyrans.
Scheme 1: C4SP–C4MC spiropyran-merocyanine equilibrium and M2+ binding.
Scheme 2: General synthesis of N-alkylcarboxyspiropyrans.
Scheme 3: Decarboxylation of N-ethanoic acid indolium salt 3a.
Scheme 4: Lactonisation of 4-bromobutyric acid 2c.
Figure 2: N-methyl spiropyran 9.
Figure 3: Example spectra illustrating binding studies of spiropyrans with M2+. (a) 1H NMR spectrum of C10SP ...
Figure 4: ε for MC–M2+ complexes of C2SP–C12SP and 9: (left) with Zn2+; (right) with Mg2+. Values for ε were ...
Figure 5: [MC] for compounds C2SP–C12SP and 9 in the presence of various metal cations. Solutions of spiropyr...
Figure 6: [MC] for spiropyrans C2SP–C12SP, 9 and 10 (0.1 mM) in CH3CN–H2O (99.9% v/v). Samples were kept in d...
Figure 7: C6 ester derivative 10.
Pd- and Cu-catalyzed approaches in the syntheses of new cholane aminoanthraquinone pincer-like ligands
- Nikolay V. Lukashev,
- Gennadii A. Grabovyi,
- Dmitry A. Erzunov,
- Alexey V. Kazantsev,
- Gennadij V. Latyshev,
- Alexei D. Averin and
- Irina P. Beletskaya.
Beilstein J. Org. Chem. 2017, 13, 564–570, doi:10.3762/bjoc.13.55
- arylaminocholanes and cholane-diaminoanthraquinone derivatives by Pd- and Cu-catalyzed amination. Such compounds not only have cation binding properties, but also might be easily introduced in lipid membranes to form ion channels. Appropriate close location of lipophilic steroid fragments in bis(cholanediamino
Graphical Abstract
Figure 1: A tripodal molecular pocket (a) [12] or jellyfish resembling receptors (b) [11,16].
Scheme 1: Example of Pd-catalyzed amination for modification of bile acid derivatives.
Scheme 2: Synthesis of 24-aminocholanols.
Scheme 3: Synthesis of 24-arylaminocholanols by Cu-catalyzed amination.
Scheme 4: Synthesis of 24-arylaminocholanols by Pd-catalyzed amination.
Figure 2: UV–vis spectra of 5c (50 μM solution in MeCN) before and after the addition of 5 equiv of metal per...
From steroids to aqueous supramolecular chemistry: an autobiographical career review
- Bruce C. Gibb
Beilstein J. Org. Chem. 2016, 12, 684–701, doi:10.3762/bjoc.12.69
Graphical Abstract
Scheme 1: The formation of a 1:1 complex and a 2:1 supramolecular nano-capsule complex from bowl-shaped “cavi...
Scheme 2: Abbreviated synthesis of 7-amino-2-phenyl-6-azaindolizine.
Figure 1: My two favorite compounds for my Ph.D. dissertation, “The Synthesis and Structural Examination of 3...
Scheme 3: An inspiring chlorination from the group of Ronald Breslow.
Scheme 4: The carceplex reaction.
Figure 2: Schematic of a cavitein.
Figure 3: General structure of zinc-TPA complexes.
Scheme 5: Stereoselective bridging of a resorcinarene with benzal halides.
Scheme 6: An eight-fold Ullman ether “weaving” reaction.
Scheme 7: Directed ortho-metallation of the deep-cavity cavitands, showing the mono-endo substituted to tetra-...
Scheme 8: Macrocycle synthesis via resorcinarene covalent templates.
Figure 4: Tris-pyridyl hosts.
Figure 5: (Center) Chemical structure of the octa-acid host. (Left and right) Respective space-filling repres...
Figure 6: Cartoons of the 2:1 host–guest complexes of estradiol (left) and cholesterol (right).
Figure 7: Representative guests for the capsular complexes formed by octa-acid (stoichiometry shown in parent...
Figure 8: A dendrimer-coated cavitand.
Figure 9: Selective oxidation of olefins by singlet oxygen.
Figure 10: a) Preferred packing motifs of methyl, pentyl and octyl guests. b) Product distribution observed fo...
Figure 11: Schematic of the competition of two esters for the capsule formed by octa-acid. The ester that bind...
Figure 12: Schematic of the inter-phase separation of propane and butane; the latter binds more strongly to th...
Figure 13: Structure of tetra-endo-methyl octa-acid (TEMOA).
Figure 14: Assembly properties of TEMOA.
Figure 15: How salts influence the association constant (Ka) for the binding of ClO4– to octa-acid (Figure 4). The ind...
Direct and indirect single electron transfer (SET)-photochemical approaches for the preparation of novel phthalimide and naphthalimide-based lariat-type crown ethers
- Dae Won Cho,
- Patrick S. Mariano and
- Ung Chan Yoon
Beilstein J. Org. Chem. 2014, 10, 514–527, doi:10.3762/bjoc.10.47
- these compounds are crown ethers, whose preparation, and metal and ammonium cation-binding properties were explored thoroughly by Petersen and Lehn [68][69]. Early pioneering efforts by Gokel and coworkers [70][71][72][73] in this area have shown that novel, lariat-type crown ethers display unique
- lariat-type crown ethers that could have potentially interesting metal cation binding properties. As can be seen by inspection of the synthetic sequence shown in Scheme 14, the preparation of lariat-type crown ethers 72–74 by employing this strategy began with the synthesis of the α-silyl ether
- substances that signal guest-binding by interrupting the SET-quenching of the excited states of the fluorophore moieties that are appended to the host (Scheme 15). We expected that metal cation binding to 72–74 would be assisted by the oxygen, nitrogen, and sulfur donors within the pendant side chain. As a
Graphical Abstract
Scheme 1: α-Heterolytic cleavage in ion radicals.
Scheme 2: Photochemical reaction pathways of N-alkylphthalimides.
Scheme 3: Photoreactions of N-methylnaphthalimides 8 and 12 with allylsilane 9.
Scheme 4: Regioselective generation of carbon-centered free radicals through sequential SET-desilylation proc...
Scheme 5: Mechanistic pathway of photochemical reactions of α-silyl n-electron donor-linked imides systems.
Scheme 6: Direct and indirect photochemical approaches for the preparation of lariat-type crown ethers.
Scheme 7: Feasible mechanistic pathways of photochemical reactions of donor atom-linked phthalimides and 2,3-...
Scheme 8: Photoreactions of branched, bis(α-silylether)-terminated phthalimides.
Scheme 9: Photoreactions of the α-silylether-linked bisphthalimide acceptor.
Scheme 10: Photoreactions of branched, silyl- and non-silyl-polyethylenoxy-linked phthalimides.
Scheme 11: Photoreactions of branched, non-silyl ether and silyl-thioether-terminated naphthalimides.
Scheme 12: Photoreactions of phthalimide-containing chiral peptide side chains.
Scheme 13: Photoreactions of bis-donor-linked bisphthalimides.
Scheme 14: Indirect approach to the preparation of lariat-type crown ethers.
Scheme 15: SET-based fluorescence sensing modes according to guest binding.
Scheme 16: Enhancement of the exciplex formation and fluorescence of bis-crown ether 60 with a Mg2+ sandwich-t...
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
- surrounding the sodium ion. It has previously been shown that chemical modifications at the C-25 and/or C-26 hydroxy groups of monensin A lower both cation binding and antibiotic activity [35][36], presumably by the same mechanism. However, not all derivatives at C-26 behave in the same way: both natural and
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...
Similarity analysis, synthesis, and bioassay of antibacterial cyclic peptidomimetics
- Workalemahu M. Berhanu,
- Mohamed A. Ibrahim,
- Girinath G. Pillai,
- Alexander A. Oliferenko,
- Levan Khelashvili,
- Farukh Jabeen,
- Bushra Mirza,
- Farzana Latif Ansari,
- Ihsan ul-Haq,
- Said A. El-Feky and
- Alan R. Katritzky
Beilstein J. Org. Chem. 2012, 8, 1146–1160, doi:10.3762/bjoc.8.128
- direction of the two chains attached to the cysteine residue. For example, one of the early cysteine-containing macrocycles was designed to mimic the cation binding ability of valinomycin [24]. Numerous literature approaches to the synthesis of 17-, 18- and 24-membered rings utilize: (i) acyl chlorides, (ii
Graphical Abstract
Figure 1: Molecular-descriptor-based cluster analysis; single-linkage Euclidean distances. Clustering of comp...
Scheme 1: Preparation of dicarboxylic benzotriazole derivatives.
Scheme 2: Preparation of pyridine-based cysteine-containing macrocycles.
Scheme 3: Preparation of pyridine–cysteine-containing macrocycle 39.
Fifty years of oxacalix[3]arenes: A review
- Kevin Cottet,
- Paula M. Marcos and
- Peter J. Cragg
Beilstein J. Org. Chem. 2012, 8, 201–226, doi:10.3762/bjoc.8.22
Graphical Abstract
Figure 1: Calixarenes and expanded calixarenes: p-tert-Butylcalix[4]arene (1), p-tert-butyldihomooxacalix[4]a...
Figure 2: Conventional nomenclature for oxacalix[n]arenes.
Scheme 1: Synthesis of oxacalix[3]arenes: (i) Formaldehyde (37% aq), NaOH (aq), 1,4-dioxane; glacial acetic a...
Figure 3: p-tert-Butyloctahomotetraoxacalix[4]arene (4a) [16].
Figure 4: X-ray crystal structure of 3a showing phenolic hydrogen bonding (IUCr ID AS0508) [17].
Scheme 2: Stepwise synthesis of asymmetric oxacalix[3]arenes: (i) MOMCl, Adogen®464; (ii) 2,2-dimethoxypropan...
Figure 5: X-ray crystal structure of heptahomotetraoxacalix[3]arene 5 (CCDC ID 166088) [21].
Scheme 3: Oxacalix[3]arene synthesis by reductive coupling: (i) Me3SiOTf, Et3SiH, CH2Cl2; R1, R2 = I, Br, ben...
Scheme 4: Oxacalix[3]naphthalene: (i) HClO4 (aq), wet CHCl3 (R = tert-butyl, 6a, H, 6b) [20].
Figure 6: Conformers of 3a.
Scheme 5: Origin of the 25:75 cone:partial-cone statistical distribution of O-substituted oxacalix[3]arenes (p...
Scheme 6: Synthesis of alkyl ethers 7–10: (i) Alkyl halide, NaH, DMF [24].
Scheme 7: Synthesis of a pyridyl derivative 11a: (i) Picolyl chloride hydrochloride, NaH, DMF [26,27].
Figure 7: X-ray crystal structure of partial-cone 11a (CCDC ID 150580) [26].
Scheme 8: Lower-rim ethyl ester synthesis: (i) Ethyl bromoacetate, NaH, t-BuOK or alkali metal carbonate, THF...
Scheme 9: Forming chiral receptor 13: (i) Ethyl bromoacetate, NaH, THF; (ii) NaOH, H2O/1,4-dioxane; (iii) S-P...
Figure 8: X-ray crystal structure of 16 (IUCr ID PA1110) [32].
Scheme 10: Lower rim N,N-diethylamide 17a: (i) N,N-Diethylchloroacetamide, NaH, t-BuOK or alkali metal carbona...
Scheme 11: Capping the lower rim: (i) N,N-Diethylchloroacetamide, NaH, THF; (ii) NaOH, H2O/1,4-dioxane; (iii) ...
Figure 9: X-ray crystal structure of 18 (CCDC ID 142599) [33].
Scheme 12: Extending the lower rim: (i) Glycine methyl ester, HOBt, dicyclohexycarbodiimide (DCC), CH2Cl2; (ii...
Scheme 13: Synthesis of N-hydroxypyrazinone derivative 23: (i) 1-[3-(Dimethylamino)propyl]-3-ethylcarbodiimide...
Scheme 14: Synthesis of 24: (i) 1-Adamantyl bromomethyl ketone, NaH, THF [39].
Scheme 15: Synthesis of 25 and 26: (i) (Diphenylphosphino)methyl tosylate, NaH, toluene; (ii) phenylsilane, to...
Figure 10: X-ray crystal structure of 27 in the partial-cone conformer (CCDC ID SUP 90399) [41].
Scheme 16: Synthesis of strapped oxacalix[3]arene derivatives 28 and 29: (i) N,N’-Bis(chloroacetyl)-1,2-ethyle...
Figure 11: A chiral oxacalix[3]arene [45].
Figure 12: X-ray crystal structure of asymmetric oxacalix[3]arene 30 incorporating t-Bu, iPr and Et groups (CC...
Scheme 17: Reactions of an oxacalix[3]arene incorporating an upper-rim Br atom with (i) Pd(OAc)2, PPh3, HCO2H,...
Scheme 18: Synthesis of acid 39: (i) NaOH, EtOH/H2O, HCl (aq) [47].
Figure 13: Two forms of dimeric oxacalix[3]arene 40 [47].
Scheme 19: Capping the upper rim: (i) t-BuLi, THF, −78 °C; (ii) NaBH4, THF/EtOH; (iii) 1,3,5-tris(bromomethyl)...
Figure 14: Oxacalix[3]arene capsules 46 and 47 formed through coordination chemistry [52,53].
Figure 15: X-ray crystal structure of the 3b-vanadyl complex (CCDC ID 240185) [57].
Scheme 20: Effect of Ti(IV)/SiO2 on 3a: (i) Ti(OiPr)4, toluene; (ii) triphenylsilanol, toluene; (iii) partiall...
Figure 16: X-ray crystal structures of oxacalix[3]arene complexes with rhenium: 3b∙Re(CO)3 (CCDC ID 620981, le...
Figure 17: X-ray crystal structure of the La2·3a2 complex (CSD ID TIXXUT) [60].
Figure 18: X-ray crystal structures of [3a∙UO2]− with a cavity-bound cation (CCDC ID 135575, left) and without...
Figure 19: X-ray crystal structure of a supramolecule comprising two [3g·UO2]− complexes that encapsulate a di...
Figure 20: X-ray crystal structure of oxacalix[3]arene 49 capable of chiral selectivity (CSD ID HIGMUF) [65].
Figure 21: The structure of derivative 50 incorporating a Reichardt dye [66].
Figure 22: Phosphorylated oxacalix[3]arene complexes with transition metals: (Left to right) 26∙Au, 26∙Mo(CO)3...
Figure 23: X-ray crystal structure of [17a·HgCl2]2 (CCDC ID 168653) [69].
Figure 24: X-ray crystal structures of 3f with C60 (CCDC ID 182801, left) [76] and a 1,4-bis(9-fluorenyl) C60 deri...
Figure 25: X-Ray crystal structure of 3i and 6a encapsulating C60 (CCDC ID 102473 and 166077) [23,79].
Figure 26: A C60 complexing cationic oxacalix[3]arene 51 [81].
Figure 27: An oxacalix[3]arene-C60 self-associating system 53 [87].
Scheme 21: Synthesis of fluorescent pyrene derivative 55: (i) Propargyl bromide, acetone; (ii) CuI, 1-azidomet...
Scheme 22: Synthesis of responsive rhodamine derivative 57: (i) DCC, CH2Cl2 [91].
Scheme 23: Synthesis of nitrobenzyl derivative 58: (i) 1-Bromo-4-nitrobenzyl acetate, K2CO3, refluxing acetone...
Figure 28: X-ray crystal structure of [Na2∙17a](PF6)2 (CCDC ID 116656) [97].
(How) does 1,3,5-triethylbenzene scaffolding work? Analyzing the abilities of 1,3,5-triethylbenzene- and 1,3,5-trimethylbenzene-based scaffolds to preorganize the binding elements of supramolecular hosts and to improve binding of targets
- Xing Wang and
- Fraser Hof
Beilstein J. Org. Chem. 2012, 8, 1–10, doi:10.3762/bjoc.8.1
- conformer, namely uddudd. One can expect a significant effect of the nature of the recognition elements on conformational energies. Many recognition elements that vary in shape, functionality, charge, and chirality have been reported. We picked pyrazole-derived hosts 4 (used for cation binding) [17] and
Graphical Abstract
Figure 1: a) The global minimum-energy conformation for hexaethylbenzene reveals the basis for steric gearing...
Figure 2: Structures of hosts discussed in this manuscript. R = H, Me, or Et.
Figure 3: Generalized structural fragments used for mining the Cambridge Structure Database. R = Me and Et, X...
Figure 4: a) Structures used to calculate energy profiles at the starting geometry. b) An example of an energ...
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
- of the macrocyclic ring may have, compared to the related parent crown ether, enhanced cation-binding. Crown ethers with linear or branched heteroatom-containing podand arms – depending on the connection point either N-pivot or C-pivot lariat ethers – exhibit increased guest specificity [106][114
- selectivity in cation binding. The cavities are more rigid and unable to adapt to bind cations that are too small or too large for the cavity. The large body of published work on crown ether synthesis [119] and crown ether ammonium ion binding [120] cannot be covered comprehensively in this review, and
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...
