60-31-1Relevant articles and documents
Catalytic application of zinc complex of oxygen depleted 1,3-bis(pyrazole)-p-tert-butylcalix[4]arene
Sinha, Anshu Kumar,Vigalok, Arkadi,Rawat, Varun
supporting information, p. 796 - 799 (2019/02/14)
In this paper we have described the synthesis and coordination properties of monometallic Zinc complex of oxygen depleted bis(pyrazole)-p-tert-butylcalix[4]arene ligand. We also present the catalytic activity of the Zinc–bis(pyrazole) complex, in acetylation of alcohols and lactide polymerization.
Modular incorporation of 1-benzyltryptophan into dipeptide hosts that bind acetylcholine in pure water
Beshara, Cory S.,Hof, Fraser
experimental part, p. 1009 - 1016 (2011/02/16)
Proteins that recognize and bind quaternary ammonium ions depend on " aromatic-cage " structural motifs that use multiple aromatic residues to engage the side chain's ammonium cation. We introduce herein the use of 1-benzyltryp- tophan (Trp(Bn)) residues as synthetic, unnatural partial analogues of natural aromatic cages. We demonstrate the modular incorporation of these building blocks into simple dipeptide hosts and show that they are capable of binding quaternary ammonium ions in buffered water and in chloroform.
Cavitand templated catalysis of acetylcholine
Zelder, Felix H.,Rebek Jr., Julius
, p. 753 - 754 (2008/02/03)
A Zn-salen-modified cavitand templates the catalytic formation of acetylcholine from choline and acetic anhydride. The Royal Society of Chemistry 2006.
Binding of acetylcholine and tetramethylammonium to flexible cyclophane receptors: Improving on binding ability by optimizing host's geometry
Sarri, Paolo,Venturi, Francesca,Cuda, Francesco,Roelens, Stefano
, p. 3654 - 3661 (2007/10/03)
The structure of a cyclophanic tetraester (1), previously employed for investigations on the cation-π interaction, has been optimized to better accommodate acetylcholine (ACh) and tetramethylammonium (TMA) guests. Following indications from molecular modeling calculations, a flexible cyclophane receptor of significantly improved binding properties has been obtained by removing the four carbonyl groups of the parent host. 2,11,20,29-Tetraoxa[3.3.3.3]paracyclophane (2) was prepared by an improved procedure, which was conveniently devised to avoid the formation of contiguous cyclooligomers that caused serious separation issues. Association of 2 with TMA picrate was measured in CDCl3 at T = 296 K by 1H NMR titrations and compared to binding data obtained for a set of reference hosts, including the parent tetraester 1, the corresponding cyclophanic tetraamine, the open-chain counterpart of 2, and its cyclooligomers from pentamer to octamer. Binding enhancements ranging from 15-fold (with respect to the tetraester and the tetraamine) to over 80-fold (with respect to the open-chain tetraether) were achieved by geometry optimization of the host. Binding of 2 to ACh and TMA was investigated for a variety of counterions. A constant binding free energy increment of nearly 8 kJ mol-1 with respect to 1 was observed, independent from the anion and irrespective of the different structure of the cationic guests. Results showed that the electrostatic inhibiting contribution of the counterion to the cation's binding is a characteristic constant of each anion. The value of -ΔG° = 44.9 kJ mol-1 extrapolated for TMA in the absence of a counterion indicates that 28-34 kJ mol-1 of binding free energy are lost in ion pairing.
Recognition of quaternary ammonium salts with tetrapeptides containing α-aminoisobutyric acid as a conformational constraint
Yanagihara, Ryoji,Katoh, Masaki,Hanyuu, Masayuki,Miyazawa, Toshifumi,Yamada, Takashi
, p. 551 - 556 (2007/10/03)
Tetrapeptides Trp-Aib-Gly-Leu-NH-Ar (Aib:α-aminoisobutyric acid, 2-amino-2-methylpropanoic acid, Ar = phenyl or 3,5-dimethylphenyl) were synthesized. The peptides bound quaternary ammonium salts as guests in CDCl3. For every guest, the binding constant K of the peptide host which has a 3,5-dimethylphenyl group was larger than that of the host which has a phenyl group. ROESY analysis of the complex revealed that the N+-CH3 groups of the guests were close to the aromatic moieties of the host in the complex. The charge in cation guests, the φ-basicity of the host, and the turn conformation of the peptides were important factors for the complexation.