Search results for "cyclic"

Structure and fluxional behaviour of heptaleneirontricarbonyl and heptalenebis (Irontricarbonyl)

1987

Abstract The synthesis of heptaleneirontricarbonyl ( 4 ) is described. The structures of 4 and of the closely related heptalenebis(irontricarbonyl) ( 3 ) are elucidated by NMR spectroscopy ( 1H and 13C) and by X-ray crystallography. Compounds 3 and 4 are shown by dynamic NMR to undergo an isodynamic 1 ,2-migration of the Fe(CO3)-groups as well as a carbonyl scrambling. The relevant kinetic data allow for a mechanistic discussion of the dynamics and a comparison with other irontricarbonyl complexes.

Synthesis of two natural 8-oxo-β-cyperone derivatives from (−)-santonin.

1993

Abstract This paper reports on the chemical transformations of (−)-santonin into (+)-8-oxo-β-cyperone and (+)-12-hydroxy-8-oxo-β-cyperone involving 8-oxo group introduction and elaboration of the side chain.

Pentakis(dimethylzinn)diphosphid, struktur und kernresonanzspektren eines zinnreichen bicyclus

1979

Abstract Dehydrogenation of dimethylstannane combined with the hydrostannolysis of white phosphorus yields pentakis(dimethyltin) diphosphide, a tin-rich heterocyclic compound, which has the highly symmetric, bicyclic molecular structure of norbornane. Using the X-ray structure data the magnetic resonance spectra are discussed.

Total synthesis of (−)-mintlactone

1991

Abstract The first total, stereodirected synthesis of (—)-mintlactone is described. A stereoselective, radical-mediated ring closure was the key step in the synthesis.

ChemInform Abstract: Rhodium Catalyzed Oxidative Coupling of Salicylaldehydes with Diazabicyclic Olefins: A One-Pot Strategy Involving Aldehyde C-H C…

2013

The title reaction involves the first example of ring opening and ring closing of bicyclic hydrazines (I) via metal catalyzed oxidative coupling reaction.

Capillary electrochromatography analysis of hormonal cyclic and linear peptides.

2001

The retention behavior of linear and cyclic peptides has been studied by capillary electrochromatography (CEC) with a variety of different n-alkyl silica reversed-phase sorbents and also with mixed-mode phases containing both strong cation-exchange (sulfonic acid) and n-alkyl groups bonded onto the silica surface, using eluents ranging from pH 2.0 to pH 5.0. Depending upon the amino acid sequence, electrochromatographic retention of the peptides was strongly affected by the composition of the eluent, its pH value, and the choice of sorbent packed into the capillaries. The dominant separation processes operating with these charged analytes could be modulated inter alia by the content of orga…

Study of peak shape and efficiency in butyl acrylate-based monolithic columns for capillary electrochromatography.

2009

Abstract The study and modelling peak shape of in capillary electrochromatography (CEC), obtained using butyl acrylate (BA)-based monolithic columns, is described in this article. A modified-Gaussian model, which is a function of conventional experimental parameters: retention time (tR), peak height (H0) and standard deviation (σ0) at the peak maximum, and left (A) and right (B) halfwidths, was used to describe the peaks of thiourea and several polyaromatic hydrocarbons compounds, which were eluted under several applied voltages. A mean relative error below 2% in the prediction of peak shape is obtained. Based on peak parameters, an easy and reliable estimation of global chromatographic per…

Calixarenes as Stationary Phases

2006

Dinuclear bis(terpyridine)ruthenium(II) complexes by amide coupling of ruthenium amino acids: Synthesis and properties

2011

Abstract Two redox-asymmetric amide-bridged bis(terpyridine)ruthenium(II) complexes (3a, 3b) have been prepared by amide coupling of a carboxylic acid functionalized complex with an amine substituted complex and they were fully characterized by spectroscopic analyses. They emit at 692 and 750 nm at room temperature in fluid solution with quantum yields larger than 10−3 and 3MLCT lifetimes of 22 ns. Ru···Ru distances were estimated from DFT models as 17.7 and 13.4 A for 3a and 3b, respectively. Cyclic voltammetry gives two oxidation potentials for the differently substituted ruthenium sites with splittings of 0.10 and 0.23 V for 3a and 3b, respectively. Oxidation of 3b with CeIV ions gives t…

C1 Inhibitor-C1¯sComplexes Are Internalized and Degraded by the Low Density Lipoprotein Receptor-related Protein

1997

Like other serpin-enzyme complexes (SECs), proteinase-complexed C1 inhibitor (C1-INH) is rapidly cleared from the circulation and thought to be a neutrophil chemoattractant, suggesting that complex formation causes structural rearrangements exposing a domain which is recognized by specific cell surface receptors. However, the cellular receptor(s) responsible for the catabolism and potential mediation of chemotaxis by C1-INH-protease complexes remained obscure. To determine whether the SEC receptor mediates the binding and potential chemotaxis of C1-INH·C1s, we performed binding assays with HepG2 cells, neutrophils, and monocytes, and the results show that C1-INH·C1s neither bind to these ce…