Novel triptycene-based cylindrical macrotricyclic host: synthesis and complexation with paraquat derivatives

[reaction: see text] A novel triptycene-based cylindrical macrotricyclic polyether containing two dibenzo[24]crown-8 cavities has been synthesized and proved to be a highly efficient host for the complexation with paraquat derivatives. Consequently, a new kind of very stable pseudorotaxane-type complex was formed in solution and in the solid state.     

Guest-dependent complexation of triptycene-based macrotricyclic host with paraquat derivatives and secondary ammonium salts: a chemically controlled complexation process

The triptycene-based macrotricyclic host containing two dibenzo-[24]-crown-8 moieties has been found to form stable 1:1 or 1:2 complexes in different complexation modes with different functional paraquat derivatives and secondary ammonium salts in solution and in the solid state. Consequently, the alkyl-substituted paraquat derivatives thread the lateral crown cavities of the host to form 1:1 complexes. It was interestingly found that the paraquat derivatives containing two beta-hydroxyethyl or gamma-hydroxypropyl groups form 1:2 complexes, in which two guests thread the central cavity of the host. Other paraquat derivatives containing terminal hydroxy, methoxy, 9-anthracylmethyl, and amide groups were included in the cavity of the host to form 1:1 complexes. Moreover, the host also forms a 1:2 complex with two 9-anthracylmethylbenzylammonium salts, in which the 9-anthracyl groups were selectively positioned outside the lateral crown cavities. The competition complexation process between the host and two different guests (the propyl-substituted paraquat derivative and a dibenzylammonium salt) could be chemically controlled.     

A triptycene-based bis(crown ether) host: complexation with both paraquat derivatives and dibenzylammonium salts

[reaction: see text] A novel triptycene-based bis(crown ether) host (1) incorporating two dibenzo-24-crown-8 ether moieties has been synthesized. It can form not only a new bis[2]pseudorotaxane with dibenzylammonium salts but also stable clip-shaped complexes with paraquat derivatives. Moreover, the complexation process between 1 and the two classes of guests can be chemically controlled.     

Synthesis of a four-armed cage molecule and its pH-controlled complexation with paraquat

A four-armed cage molecule was synthesized and its pH-controlled host-guest complexation with paraquat was studied. The influences of the location and composition of the arms were also investigated, guiding us to search for more complicate hosts with higher binding affinities.     

Synthesis and structure of a triptycene-based nanosized molecular cage

A triptycene-based nanosized molecular cage was designed and efficiently synthesized by Eglington-Glaser coupling reaction, and its structure was determined by NMR, MS spectrometry and X-ray analysis. Moreover, it was found that the cage molecules could pack into a microporous structure in the solid state and 1,3,5-trimethylbenzene molecules were located in the channels.     

Synthesis of a symmetric cylindrical bis(crown ether) host and its complexation with paraquat

The first cylindrical host for paraquat derivatives was prepared and characterized by X-ray analysis. Its complex with paraquat has 1:2 stoichiometry. The complexation is statistical and strong as shown by proton NMR characterization, electrospray mass spectrometry, and X-ray analysis.     

Synthesis of novel calixcrown derivatives with selective complexation towards cesium ions

A series of novel calix[4]arenecrown-6 derivatives with an alkenyl loop of various sizes 5-8 were synthesized via intramolecular ring closing olefin metathesis and characterized by ~1H NMR,~(13)C NMR and ESI-HRMS.Their complexation property towards cesium ion was studied by ~1H NMR technique.Two-phase extraction of alkali metal ions using UV-vis spectroscopy revealed remarkably different extractabilities.These results indicate that the complexation capacities towards cesium ions can be tuned and controll...     

Synthesis and complexation of molecular clips based on diphenylglycoluril and dibenzocrown ethers with alkali metal cations and paraquat

A new synthetic route to the molecular clip with diphenylglycoluril and dibenzo-18-crown-6 using protection-deprotection protocol is proposed. Yield of desired compound has increased from 10-15% to 41%. Starting from 4,5-dibromobenzene-1,2-diol 4,5-dibromodibenzo-18-crown-6 and then tetrabromo-substituted molecular clip were obtained. The target molecular clip was obtained by bromine cleavage by hydrogenolysis. Stability constants were determined by spectrophotometric titration with alkali metal cations and paraquat. Quantum-chemical calculations confirm the assumption of additional stabilization of complex with K⁺ by π–π stacking between the terminal aromatic fragments with formation of a “pseudocryptand” type structure. The structures of complexes of the molecular clips with paraquat were determined by X-ray crystallography.     

Synthesis and complexation of a novel cyclophane

A novel cyclophane, 17, 17, 40, 40-tetramethyl-7, 30-dinitro-1, 10, 24, 33-tetraoxa[2.2.1.2.2.1] metaparaparametaparaparacyclophane, was synthesized by 2:2 cyclization of 3,5-bis(bromomethyl)nitrobenzene, derived from 3,5-dimethylnitrobenzene, and bisphenol A. The cyclophane was found to form 1:1 complex with benzene.     

Synthesis of a water-soluble molecular tweezer and a recognition study in an aqueous media

Synthesis of a 1,10-diphenanthryl all-trans fused perhydrophenanthrene derivative and a recognition study in an aqueous media were carried out. A water-soluble derivative recognized certain benzene derivatives with 10⁴-10⁵ M⁻¹ of binding constant.     

Synthesis and complexation of a novel soluble vic-dioxime with hydroxyethyl pendant arms

A new soluble vic-dioxime ligand namely 1,4-bis(2′-hydroxyethyl)-2,3-bis(hydroxyimino)-5,6-diphenylpiperazine, (LH₂) containing optically active centers has been prepared as a mixture of isomers from (CNO)₂ and N,N-bis(2-hydroxyethyl)stilbendiamine (1) which has been made by the reduction of the condensation of the product of benzaldehyde and 2-aminoethanol in the presence of aluminum amalgam. N,N-coordinated planar metal complexes of this ligand have been synthesized with Ni^II, Cu^II, Co^II, Pd^II and U^VIO₂. Oxidation of (LH)₂Co in the presence of a base, such as pyridine, leads to an octahedral complex (LH)₂CopyCl containing pyridine and chloride as axial ligands in addition to vic-dioxime ligands. The structures of the ligand and its complexes are proposed on the basis of elemental analysis, ¹H-n.m.r., mass, i.r. and u.v.–vis. spectral data. This revised version was published online in June 2006 with corrections to the Cover Date.     

A new cryptand: synthesis and complexation with paraquat

[formula: see text] Inspired by folded, nonpseudorotaxane complexes of bis(m-phenylene)-32-crown-10 systems, we synthesized a new bicyclic crown ether containing two 1,3,5-phenylene units linked by three tetra(ethyleneoxy) units. The new cryptand forms a "pseudorotaxane-like" inclusion complex with N,N'-dimethyl-4,4'-bipyridinium bis(hexafluorophosphate) with association constant Ka = 6.1 x 10(4) M-1, 100-fold greater than that of an analogous simple crown ether.     

Synthesis of strapped zinc chlorophyll derivatives and their complexation with a single axial ligand

Zinc chlorins having a bridged moiety between 3- or 8- and 17-positions were designed as protected chlorophylls at one of π-faces, aiming at the investigation of asymmetric coordination ability towards the central metal. These strapped chlorins were synthesized by the cyclization of the dihydroxylated chlorins with dicarboxylic acid dichlorides under highly diluted conditions. The synthetic zinc chlorins complexed with pyridine as an axial ligand in benzene to form 5-coordinated species. The 1:1 binding constants determined by UV-vis titration method were smaller than those of the corresponding acyclic (unstrapped) compounds.     

Synthesis and antitumor activity of novel phenylhydrazonopyrazolone derivatives and molecular dynamics simulations

SHP2 is a new promising target for anti-cancer drug discovery. A series of novel phenylhydrazonopyrazolone derivatives was synthesized by a more convenient method, and their chemical structures were characterized by various spectroscopic methods. The inhibitory effects of these compounds on SHP2 enzyme and SHP2-dependent cancer cell H1975 were evaluated. The compound 11f with IC₅₀ value of 3.38 μmol/L exhibited more potent antitumor activity against H1975 cell than GS-493 (IC₅₀?=?20.92 μmol/L). Molecular dynamics simulation of compound 11f displayed a possible mode of interaction between this compound and SHP2 enzyme.     

Synthesis of cyclic bis- and trismelamine derivatives and their complexation properties with barbiturates

Cyclic bis- and trismelamine derivatives were prepared from cyanuric chloride by stepwise substitutions with appropriate amines. The complexation abilities of these melamine derivatives with barbituric acid derivatives were evaluated by UV-vis spectroscopy and (1)H NMR. The structure was also confirmed by X-ray crystallography. Both the acyclic and the cyclic bismelamine derivatives formed a 1 : 1 complex via six hydrogen bonds with barbituric acid derivatives. van't Hoff analyses on the complexation of the bismelamines with the barbituric acid derivative revealed that the complexation of the cyclic bismelamine was entropically favored and enthalpically less favored process than those of the acyclic bismelamine. X-Ray crystallographic analysis and (1)H NMR studies revealed that the cyclic trismelamine bound one barbituric acid derivative into the cavity via six hydrogen bonds by two melamine moieties and another barbituric acid via three hydrogen bonds by the residual melamine moiety.     

Synthesis,biological evaluation and molecular docking studies of novel benzimidazole derivatives

A novel series of N-substituted-benzimidazolyl linked para substituted benzylidene based molecules containing three pharmacologically potent hydrogen bonding parts namely; 2,4-thiazolidinedione (TZD: a 2,4-dicarbonyl), diethyl malonate (DEM: a 1,3-diester and an isooxazolidinedione analog) and methyl acetoacetate (MAA: a β-ketoester) (6a–11b) were synthesized and evaluated for in vitro α-glucosidase inhibition. The structure of the novel synthesized compounds was confirmed through the spectral studies (LC–MS, ¹H NMR, ¹³C NMR, FT-IR). Comparative evaluation of these compounds revealed that the compound 9b showed maximum inhibitory potential against α-amylase and α-glucosidase giving an IC₅₀ value of 0.54 ± 0.01 μM. Furthermore, binding affinities in terms of G score values and hydrogen bond interactions between all the synthesized compounds and the AA residues in the active site of the protein (PDB code: 3TOP) to that of Acarbose (standard drug) were explored with the help of molecular docking studies. Compound 9b was considered as promising candidate of this series.     

A molecular tweezer for lysine and arginine

Lysine and arginine play a key role in numerous biological recognition processes controlling, inter alia, gene regulation, glycoprotein targeting and vesicle transport. They are also found in signaling peptide sequences responsible, e.g. for bacterial cell wall biosynthesis, Alzheimer peptide aggregation and skin regeneration. Almost none of all artificial receptor structures reported to date are selective and efficient for lysine residues in peptides or proteins. An artificial molecular tweezer is introduced which displays an exceptionally high affinity for lysine (K(a) approximately 5000 in neutral phosphate buffer). It features an electron-rich torus-shaped cavity adorned with two peripheral anionic phosphonate groups. Exquisite selectivity for arginine and lysine is achieved by threading the whole amino acid side chain through the cavity and subsequent locking by formation of a phosphonate-ammonium/guanidinium salt bridge. This pseudorotaxane-like geometry is also formed in small basic signaling peptides, which can be bound with unprecedented affinity in buffered aqueous solution. NMR titrations, NOESY and VT experiments as well as ITC measurements and Monte Carlo simulations unanimously point to an enthalpy-driven process utilizing a combination of van der Waals interactions and substantial electrostatic contributions for a conformational lock. Since DMSO and acetonitrile compete with the amino acid guest inside the cavity, a simple change in the cosolvent composition renders the whole complexation process reversible.     

Synthesis and complexation properties of novel triazoyl-based ferrocenyl ligands

Two new ligand derivatives of ferrocene, namely N-4-[3,5-di-(2-pyridyl)-1,2,4-triazoyl]ferrocene carbimine (L1) and N-4-[3,5-di-(2-pyridyl)-1,2,4-triazoyl]ferrocene carbamide (L2), were synthesised in good yields by reacting the known compound 3,5-di-pyridine-2-yl-[1,2,4]triazol-4-ylamine (1) with ferrocenecarbaldehyde and chlorocarbonyl ferrocene, respectively. The structures of L1 and L2 were determined by X-ray crystallography. The complexation of L1 and L2 with Cu^I, Ag^I, Zn^II and Cd^II was studied by NMR and UV-vis spectroscopies, as well as by electrochemistry, with titrations used to determine metal:ligand stoichiometries. The cyclic voltammograms of L1 and L2 and their respective complexes indicated reversible one-electron transfers corresponding to the Fc^0/+ redox couple (Fc = ferrocene), with formal electrode potentials shifting to more positive values upon metal complexation.