Search results for "ligands"
showing 10 items of 721 documents
Progress in palladium-based catalytic systems for the sustainable synthesis of annulated heterocycles: a focus on indole backbones
2012
BIOVERT+LDJ; A survey highlighting the most recent palladium catalytic systems produced and their performances for progress in direct synthesis of indole backbones by heterocarbocyclization of reactive substrates is provided. The discussion is developed in relation with the principles of sustainable chemistry concerning atom and mass economy. In this respect, the general convergent character of the syntheses is of particular interest (one-pot, domino, cascade or tandem reactions), and the substrates accessibility and reactivity, together with the final waste production, are also important. This critical review clearly indicates that the development of ligand chemistry, mainly phosphines and…
Ultra-Low Catalyst Loading as a Concept in Economical and Sustainable Modern Chemistry: The Contribution of Ferrocenylpolyphosphane Ligands
2007
The challenge of sustainability in modern chemistry will be met with new technologies and processes provided significant progress is made in several key research areas, such as the expansion of chemistry from renewable feedstock, the design of environmentally benign chemicals and solvents, the minimization of depletive resources, and the development of high-performance catalysis. In this prospect, ligand chemistry is a pivotal science that links modern-organic,-inorganic, -organometallic, and -coordination chemistry through a vast number of valuable applications, precisely associated to catalysis. We review in this article our recent work on catalysis promoted by original ferrocenyl tetra-,…
Guanine 6-O-Methylation Pattern within the Dioxin Responsive Element of theCYP1A1 Enhancer Shows Two Critical Guanines for AhR/ARNT Binding
2006
The core-recognition motif for TCDD-liganded AhR/ARNT complex of the dioxin-responsive element (DRE) contains four guanine residues, three on the antisense (5'-T T / A GCGTG-3') and one on the sense (5'-CACGC A / T A-3') strand. It has been reported that, in methylation-protection and methylation-interference assays, the TCDD-liganded AhR/ARNT contacts all four guanine residues. On the other hand, it is known that some anticancer drugs, and various environmental and workplace chemicals, including strongly human carcinogenic nitrosoamines, lead to the highly miscoding 6-O-methylation of guanine. In the present study, we have investigated whether specific methylation of guanine at the 6-O-pos…
Ruthenium-arene complexes bearing naphthyl-substituted 1,3-dioxoindan-2-carboxamides ligands for G-quadruplex DNA recognition.
2019
Quadruplex nucleic acids – DNA/RNA secondary structures formed in guanine rich sequences – proved to have key roles in the biology of cancers and, as such, in recent years they emerged as promising targets for small molecules. Many reports demonstrated that metal complexes can effectively stabilize quadruplex structures, promoting telomerase inhibition, downregulation of the expression of cancer-related genes and ultimately cancer cell death. Although extensively explored as anticancer agents, studies on the ability of ruthenium arene complexes to interact with quadruplex nucleic acids are surprisingly almost unknown. Herein, we report on the synthesis and characterization of four novel Ru(…
The Odd Sibling: Features ofβ3-Adrenoceptor Pharmacology
2014
beta(3)-Adrenoceptor agonists have recently been introduced for the treatment of overactive urinary bladder syndrome. Their target, the beta(3)-adrenoceptor, was discovered much later than beta(1)- and beta(2)-adrenoceptors and exhibits unique properties which make extrapolation of findings from the other two subtypes difficult and the beta(3)-adrenoceptor a less-understood subtype. This article discusses three aspects of beta(3)-adrenoceptor pharmacology. First, the ligand-recognition profile of beta(3)-adrenoceptors differs considerably from that of the other two subtypes, i.e., many antagonists considered as nonselective actually are beta(3)-sparing, including propranolol or nadolol. Man…
Electronic characterisation of the oxidized state of the blue copper protein Rusticyanin by 1 H NMR: Is the axial methionine the dominant influence f…
2001
The oxidized state of rusticyanin, the blue copper protein with the highest redox potential in its class, has been investigated through (1)H nuclear magnetic resonance applied to its cobalt(II) derivative. The assignment of the protons belonging to the coordinated residues has been performed. Many other amino acids situated in the vicinity of the metal ion, including six hydrophobic residues (isoleucine140 and five phenylalanines) have also been identified. The orientation of the main axes of the magnetic susceptibility tensor for the cobalt(II)-rusticyanin as well as its axial, Deltachi(ax), and rhombic, Deltachi(rh), magnetic susceptibility anisotropy components have been determined. A co…
Fluorine Scan of Inhibitors of the Cysteine Protease Human Cathepsin L: Dipolar and Quadrupolar Effects in the π-Stacking of Fluorinated Phenyl Rings…
2016
The π-stacking of fluorinated benzene rings on protein backbone amide groups was investigated, using a dual approach comprising enzyme-ligand binding studies complemented by high-level quantum chemical calculations. In the experimental study, the phenyl substituent of triazine nitrile inhibitors of human cathepsin L (hCatL), which stacks onto the peptide amide bond Gly67-Gly68 at the entrance of the S3 pocket, was systematically fluorinated, and differences in inhibitory potency were measured in a fluorimetric assay. Binding affinity is influenced by lipophilicity (clog P), the dipole and quadrupole moments of the fluorinated rings, but also by additional interactions of the introduced fluo…
Cyanide binding and heme cavity conformational transitions in **Drosophila melanogaster** hexacoordinate hemoglobin
2006
The reason for the presence of hemoglobin-like molecules in insects, such as Drosophila melanogaster, that live in fully aerobic environments has yet to be determined. Heme endogenous hexacoordination (where HisE7 and HisF8 axial ligands to the heme Fe atom are both provided by the protein) is a recently discovered mechanism proposed to modulate O-2 affinity in hemoglobins from different species. Previous results have shown that D. melanogaster hemoglobin 1 (product of the glob1 gene) displays heme endogenous hexacoordination in both the ferrous and ferric states. Here we present kinetic data characterizing the exogenous cyanide ligand binding process, and the three-dimensional structure (a…
Metal-Organic Nanocapsules with Functionalized s-Heptazine Ligands.
2020
A metalloorganic capsule was synthesized where the ligand is a derivative of heptazine with three carboxylic groups that are coordinated to CuII cations, forming paddle-wheel motifs. Each nanocapsule is neutral, with 12 CuII centers and 8 ligands adopting a rhombicuboctahedron shape. It has almost 3 nm diameter, and the main intermolecular interactions in the solid are π··· π stacking between the C6N7 heptazine moieties. The nanocapsules can form monolayers deposited on graphite as observed by atomic force microscopy, which confirms their stability in solution. peerReviewed
Amide functionalized aminobisphenolato MoO2 and WO2 complexes: Synthesis, characterization, and alkene epoxidation catalysis
2023
The use of dioxidomolybdenum(vi) and -tungsten(vi) complexes supported by a variety of structurally different tri- and tetradentate aminobisphenolato ligands as pre-catalysts in the epoxidation of alkenes is well established. However, under the widely used standard 1 mol-% catalyst loadings these types of complexes generally show modest activity only. Recently, amide functionalities in the ligand design of various aminomonophenolato MoO2 complexes have been shown to lead to heightened catalytic activity in alkene epoxidation. In this paper we show that similar ligand amide functionalization can lead to significant enhancement in the alkene epoxidation activity of aminobisphenolato MoO2 comp…