Search results for "Halogenation"
showing 10 items of 111 documents
Development and Scale-Up of the Electrochemical Dehalogenation for the Synthesis of a Key Intermediate for NS5A Inhibitors
2015
The electrochemical 2-fold dehalogenation of a spirocyclopropane-proline derivative at leaded bronze was scaled-up in a divided batch-type electrolysis cell in good yield and excellent selectivity. The upscaling via a flow electrolysis cell was also successful. Conditions were elaborated employing a single cell passage for complete conversion. The keys here are the direct cooling of the cathode and ensuring a good laminar flow.
Cysteine-Specific Radioiodination of Proteins with Fluorescein Maleimide
1997
A protocol is described for coupling of carrier-free iodine to protein sulfhydryl groups via fluorescein maleimide. 125I is first coupled to fluorescein maleimide in the presence of chloramine T. Iodination is stopped with sodium thiosulfate, and the iodine-substituted fluorescein maleimide is reacted with free cysteines of the protein. Excess label is then removed by gel-permeation chromatography. The procedure avoids exposition of the protein to oxidative conditions and does not require purification of the labeled carrier reagent. Suitability of the method for a given protein can be evaluated spectrophotometrically without employing radioactivity. It can be applied under denaturing condit…
First principles investigations of Pd-on-Au nanostructures for trichloroethene catalytic removal from groundwater
2010
Catalytic groundwater remediation from chlorinated organic solvents like trichloroethene (TCE) has been found to be more effective and sustainable than traditional non-destructive methods. Among the experimentally studied catalyst materials, Pd-decorated Au nanoparticles show the highest activity and selectivity combined with the best resistance towards poisoning by chemicals present in groundwater. In this study the thermochemistry and adsorption geometries of TCE and its hydrodechlorination products are investigated via density functional theory calculations. Various model systems for Pd-supported Au nanoparticles are addressed. The adsorption of TCE is endothermic on bare Au(111), almost…
Mechanisms of covalent dimerization on a bulk insulating surface
2017
Combining density functional theory and high resolution NC-AFM experiments, we have studied the on surface reaction mechanisms' responsible for the covalent dimerization of 4-iodobenzoic acid (IBA) organic molecules on the calcite (10.4), insulating surface. When annealed at 580 K, the Molecules assemble in one-dimensional chains of covalently bound dimers: The chains have a unique orientation and result from a complex set of processes, including a nominally rather. costly double dehalogenation reaction followed by dimerization. First, focusing on the latter two processes and using the nudged elastic band method, we analyze a number of possible mechanisms involving one and two molecules, an…
Site-specific near-infrared fluorescent labelling of proteins on cysteine residues with meso -chloro-substituted heptamethine cyanine dyes
2018
International audience; Near-infrared (NIR) fluorescence imaging is a promising new medical imaging modality. Associated with a targeting molecule, NIR fluorophores can accumulate selectively in tissues of interest and become valuable tools for the diagnosis and therapy of various pathologies. To facilitate the design of targeted NIR imaging agents, it is important to identify simple and affordable fluorescent probes, allowing rapid labelling of biovectors such as proteins, ideally in a site-specific manner. Here, we demonstrate that heptamethine cyanine based fluorophores, such as IR-783, that contain a chloro-cyclohexyl moiety within their polymethine chain can react selectively, at neutr…
ChemInform Abstract: 2-Aryl-Substituted, Benzo-Anellated 5-Membered Heterocyclic Compounds as Potentially Active Substances for the Cardiovascular Sy…
2010
In the course of investigations on structure-activity relationships of calcium antagonists analogous to fostedil, a series of 2-aryl- and 2-arylvinyl-substituted 1,3-henzothiazoles and 1,3-benzoxazoles bearing a phosphonate group on the phenyl ring has been synthesized by cyclization, bromination, and subsequent Michaelis-Arbuzow reaction. Pharmacological investigations on isolated organs from guinea pigs revealed both negative inotropic effects and a relaxing action on smooth musculature; these activities were particularly pronounced in the 1,3-benzothiazole compound group.
2-Aryl-substituted, benzo-anellated 5-membered heterocyclic compounds as potentially active substances for the cardiovascular system: 1,3-Benzothiazo…
1992
In the course of investigations on structure-activity relationships of calcium antagonists analogous to fostedil, a series of 2-aryl- and 2-arylvinyl-substituted 1,3-henzothiazoles and 1,3-benzoxazoles bearing a phosphonate group on the phenyl ring has been synthesized by cyclization, bromination, and subsequent Michaelis-Arbuzow reaction. Pharmacological investigations on isolated organs from guinea pigs revealed both negative inotropic effects and a relaxing action on smooth musculature; these activities were particularly pronounced in the 1,3-benzothiazole compound group.
Electrochemically reduced titanocene dichloride as a catalyst of reductive dehalogenation of organic halides
2006
Abstract We have studied a reaction between the reduced form of titanocene dichloride (Cp 2 TiCl 2 ) and a group of organic halides: benzyl derivatives (4-X C 6 H 4 CH 2 Cl, X = H, NO 2 , CH 3 ; 4-X C 6 H 4 CH 2 Br, X = H, NO 2 , PhC(O); 4-X C 6 H 4 CH 2 SCN, X = H, NO 2 ) as well as three aryl halides (4-NO 2 C 6 H 4 Hal, Hal = Cl, Br; 4-CH 3 O-C 6 H 4 Cl). It has been shown that the electrochemical reduction of Cp 2 TiCl 2 in the presence of these benzyl halides leads to a catalytic cycle resulting in the reductive dehalogenation of these organic substrates to yield mostly corresponding toluene derivatives as the main product. No dehalogenation has been observed for aryl derivatives. Base…
Fluorinated glycosyl amino acids for mucin-like glycopeptide antigen analogues.
2010
The aberrant glycosylation profiles of mucin glycoproteins on epithelial tumour cells represent attractive target structures for the development of immunotherapy against cancer. Mucin-type glycopeptides have been successfully investigated as molecularly defined vaccine prototypes for triggering humoral immunity but are susceptible to rapid in vivo degradation. As a potential means to enhance the bioavailabilities of the antigenic structures, hydrolysis-resistant carbohydrate analogues with fluorine substituents at positions C6, C2' and C6' were synthesised and incorporated into the tandem repeat sequence of the mucin MUC1. The resulting pseudo-glycopeptides can be used to elucidate the effe…
A Novel Cathode Material for Cathodic Dehalogenation of 1,1-Dibromo Cyclopropane Derivatives.
2015
Leaded bronze turned out to be an excellent cathode material for the dehalogenation reaction of cyclopropanes without affecting the strained molecular entity. With this particular alloy, beneficial properties of lead cathodes are conserved, whereas the corrosion of cathode is efficiently suppressed. The solvent in the electrolyte determines whether a complete debromination reaction is achieved or if the process can be selectively stopped at the monobromo cyclopropane intermediate. The electroorganic conversion tolerates a variety of functional groups and can be conducted at rather complex substrates like cyclosporine A. This approach allows the sustainable preparation of cyclopropane deriva…