Search results for "deriva"
showing 10 items of 1423 documents
Synthesis of (E)- and (Z)-29-methylidyne-2,3-oxidosqualene derivatives as inhibitors of liver and yeast oxidosqualene cyclase
2002
The synthesis of (E)- and (Z)-29-methylidyne-2,3-oxidosqualene derivatives is described starting from the C22 and C17 squalene aldehyde monobromohydrins. The conversion was achieved by means of a Wittig reaction, followed by desilylation of the terminal acetylene. For trisubstituted 1,3-enynes, preliminary alkylation with a suitable allyl bromide was performed. A new procedure for the synthesis of squalene aldehyde C27, C22 and C17 monobromohydrins is also described. Some of the new compounds behaved as inhibitors of pig liver and yeast oxidosqualene cyclase and were time-dependent inhibitors of the animal enzyme.
Extraction of dansylated amino acids using the supported liquid membrane technique
1997
Extraction using the supported liquid membrane (SLM) technique demands conditions where the extracted compounds can be made uncharged allowing them to pass through the membrane. For amino acids, being bifunctional, such conditions can not be obtained directly. One way to overcome this problem is to block one of the functionalities by derivatization, utilising the other group for the transport. The SLM extraction of dansylated amino acids was investigated and optimized. It was possible to obtain high extraction efficiencies (>90%) for most amino acids. For amino acids with polar side chains, such high extraction efficiencies were only obtained at low analyte concentrations ( 10 nmol 1-l). Fo…
Kinetic and Mechanistic Aspects of a Poly(o-toluidine)-Modified Gold Electrode. 1. Simultaneous Cyclic Spectroelectrochemistry and Electrogravimetry …
2012
International audience; Electrodeposited poly(o-toluidine) (POT) on gold electrodes was investigated in a 0.5 M H2SO4 aqueous solution using cyclic electrogravimetry with in situ vis-NIR spectroscopy. This coupling of different techniques allows the electrical, color, and mass changes during the electrochemical reactions of these polymers to be correlated. Therefore, this is a powerful tool to obtain valuable information on the physical models of polymer films and their electrochemical properties. The accurate analysis of the results from these techniques showed the contribution of three different redox transitions (leucoemeraldine-polaron transition, polaron-bipolaron transition, and bipol…
A detailed MSn study for the molecular identification of a dimer formed from oxidation of pinene
2016
Abstract Dimeric products formed in the oxidation of α- and β-pinene have been frequently observed in laboratory and field studies of biogenic SOA formation. While their existence is undoubted, their exact chemical structures remain unclear. This study uses a combined two step approach aiming on the molecular identification of the most important of the various dimers that have been observed in biogenic secondary organic aerosol formation, a dimer with the molecular weight 358 g mol−1. The first step is the application of a functional group derivatization technique (esterification) to quantify the number of carboxylic acid groups in the target molecule. Based on the detailed interpretation o…
3'-Arylazido-beta-alanyl-2-azido ATP, a cross-linking photoaffinity label for F1ATPases.
1989
Abstract The synthesis of the 3′-arylazido-2-azido ATP derivative 3′-O-{3-[N-(4-azido-2-nitrophenyl)-amino]propionyl}2-azido-adenosine 5′-triphosphate (2,3′-DiN3ATP) is described. The bifunc tional photoreactive ATP analog is characterized spectroscopically. Photoaffinity labeling of F, ATPase from Micrococcus luteus by this analog results in the inactivation of the enzyme and in the formation of higher molecular weight cross-links,
Deprotonation of Fluoro Aromatics Using Lithium Magnesates.
2004
Abstract 3-Fluoropyridine was deprotonated on treatment with 1/3 equiv of Bu 3 MgLi in THF at −10 °C. The lithium arylmagnesate formed was either trapped with electrophiles or involved in a palladium-catalyzed cross-coupling reaction with 2-bromopyridine. The use of a less nucleophilic lithium-magnesium-dialkylamide, (TMP) 3 MgLi, allowed the reaction of 3-fluoroquinoline, giving the 2,2′-dimeric derivative. 2-Fluoropyridine and 2,6-difluoropyridine were deprotonated using 1/3 equiv of the highly coordinated magnesate Bu 4 MgLi 2 in THF at −10 °C in the presence of a substoichiometric amount of 2,2,6,6-tetramethylpiperidine. 1,3-Difluorobenzene reacted similarly when treated with Bu 3 MgLi;…
Stereoselektive c-glycosidsynthese durch titan-(iv)-katalysierte addition von silylenolethern an 2-acyloxy-3-keto-glycale
1984
Abstract C-Glycosides are stereoselectively formed by the titan-(IV)-catalysed addition of silyl enolethers 2 to 2,4,6-tri-O-acyl-1-deoxy-D-erythro-hex-1-enopyran-3-uloses 1 followed by elimination of the 4-acyloxy substituent. Cyclohexenyl silylether 2a reacts with 2-acetoxy-3-keto-glycal derivative la forming only one product 3a . Thus, the reaction seems to be diastereospecific with respect to both new chiral centers of the product.
Differential reactivity of fluorinated homopropargylic amino esters vs gold(I) salts. The role of the nitrogen protecting group
2015
The reaction of several homopropargyl amino esters 4, bearing aromatic substituents and a benzyl group as nitrogen substituents, with gold(I) salts gave rise to fluorinated quinolines 6 in a tandem hydroarylation-isomerization process. On the other hand, homopropargyl amino esters 7 containing a carbamate group underwent the carbonyl addition over the triple bond in the presence of gold(I) salts, rendering fluorinated oxazines 8. The use of chiral sulfoxides allowed us to develop the asymmetric version of this protocol. This two processes complete the differential reactivity showed by these types of susbtrates, depending on the nature of the nitrogen protecting group. (C) 2014 Elsevier B.V.…
Crystal structure of the chalcone (E)-3-(furan-2-yl)-1-phenylprop-2-en-1-one
2015
The crystal packing of the compound is described by an intermolecular arrangement with the molecules as interlaced layers in a zigzag fashion, denoting interacting self-complementary dimers mainly by the localization of weak hydrogen bonds in a head-to-tail arrangement.
A missing member in the family of chalcogenophene-substituted 2,2′:6′,2″-terpyridine: 4′-(tellurophen-2-yl)-2,2′:6′,2″-terpyridine, its Ru(II) comple…
2019
Abstract The new terpyridine derivative 4’-(tellurophen-2-yl)-2,2′:6′,2″-terpyridine and its homoleptic Ru(II) complex have been prepared and characterized by different techniques (NMR, UV–Vis, mass spectrometry). Additionally, a thin polymer film was obtained through electrochemical oxidation and coupling of tellurophene moieties. The obtained organic coating showed very interesting electrochemical and electrochromic properties, thanks to its Ru(terpy)2 groups.