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41.
Tetra-n-butylammonium hexachloroplatinate (IV) reacts with lithium methyl/lithium iodide in ether to give a solution containing lithium hexamethylplatinate (IV). With lithium methyl/lithium bromide in ether however, tetrabutylammonium hexamethylplatinate (IV) is precipitated together with lithium halides. Solid [Bu4N)2[Pt(Ch3)6] is stable under nitrogen at room temperature, but ether solutions of [Pt(Ch3)6]2- decompose in a few minutes at room temperature in the absence of excess lithium methyl. 相似文献
42.
The linking of pyrimidines to polystyrene supports via either a 2- or 4-thioether provides access to pteridines through solid-phase synthesis. Oxidative cleavage (dimethyldioxirane) followed by nucleophilic substitution by amines, azide, or water completes a traceless synthesis of pteridines. 相似文献
43.
Jensen BP Smith CJ Bailey CJ Rodgers C Wilson ID Nicholson JK 《Rapid communications in mass spectrometry : RCM》2005,19(4):519-524
Inductively coupled plasma mass spectrometry (ICPMS) has been used to determine the rate and routes of excretion of bromine following the intraperitoneal administration (50 mg kg(-1)) of 2-, 3- and 4-bromobenzoic acids to male bile-duct-cannulated rats. Analysis of urine and bile for (79/81)Br using ICPMS showed that all three bromobenzoic acids were rapidly excreted (82-98%) within 48 h of dosing, primarily via the urine. High-performance liquid chromatography/inductively coupled plasma mass spectrometry (HPLC/ICPMS) was then used to obtain metabolite profiles for bile and urine. These profiles revealed that extensive metabolism had taken place, with the unchanged bromobenzoic acids forming a minor part of the total of compound-related material detected. Concomitant MS studies, supplemented by alkaline hydrolysis, enabled the identification of the major metabolite of all three of the bromobenzoic acids as a glycine conjugate. Ester glucuronide conjugates were also identified, but formed only a small proportion of total. 相似文献
44.
Colin Eaborn 《Journal of organometallic chemistry》1985,290(3):c43-c44
Heterobinuclear complexes of formula [LMCl2(pz)M′(tfb)] (M = Ru, L = p-cymene, M′ = Rh; M = Ir, L = C5Me5, M′ = Rh; M = Rh, L = C5Me5, M′ = Ir) and [(C5Me5)IrCl(pz)2Rh(tfb)] (tfb = tetrafluorobenzo[5.6]bicyclo[2.2.2]octan-2,5,7-triene) have been prepared. The molecular structure of [(p-cymene)Ru(μ-Cl)2(μ-pz)Rh(tfb)] has been determined by X-ray diffraction. It consists of two moieties, (p-cymene)Ru and (tfb)Rh, triply-bridged by a pyrazolate group and two chlorine atoms. 相似文献
45.
Geneviéve Cerveau Ernesto Colomer Robert J.P. Corriu J.Colin Young 《Journal of organometallic chemistry》1981,205(1):31-45
We report the chemical behavior of cobalt-stabilized carbenes, R3M(CO)3CoC(OEt)R′, and their parent anions, R3M(CO)3CoC(O?)R′, where M = Si or Ge. The anions where M = Si, R′ = Ph decompose thermally into the corresponding benzoylsilanes; when the silicon atom is chiral (R3 = MePh-1-Np) optically active R3SiCOPh is obtained with complete retention of configuration. 相似文献
46.
The interactions of [Pt(en)Cl(ACRAMTU-S)](NO3)2 (PT-ACRAMTU, en = ethane-1,2-diamine, ACRAMTU = 1-[2-(acridin-9-ylamino)ethyl]-1,3-dimethylthiourea) with adenine in DNA have been studied using a combination of analytical and high-resolution structural methods. For the first time, a cytotoxic platinum(II) complex has been demonstrated to form adducts in the minor groove of DNA through platination of the adenine-N3 endocyclic nitrogen. An acidic depurination assay was developed that allowed the controlled and selective (pH 2, 60 degrees C, 12 h) release of platinum-modified adenine from drug-treated nucleic acid samples. From the digested mixtures, three adducts were isolated by semipreparative reverse phase high-performance liquid chromatography and studied by electrospray ionization mass spectrometry (in-line LC-MS), variable-pH 1H NMR spectroscopy, and, where applicable, X-ray crystallography. The three species were identified as the N7 (A-I), N3 (A-II), and N1 (A-III) linkage isomers of [Pt(en)(ACRAMTU-S)(adenine)]3+ (A). Incubations carried out with the single- and double-stranded model sequences, d(TA)5 and d(TA)15, as well as native DNA indicate that the adduct profiles (A-I:A-II:A-IIIratios) are sensitive to the nature of the nucleic acid template. A-II was found to be a double-strand specific adduct. The crystal structure of this adduct has been determined, providing ultimate evidence for the N3 connectivity of platinum. A-II crystallizes in the triclinic space group P in the form of centrosymmetric dimers, {[Pt(en)(ACRAMTU-S)(adenine-N3)]2}6+. The cations are stabilized by a combination of adenine-adenine base pairing (N6...N1 2.945(5) A) and mutual acridine-adenine base stacking. Tandem mass spectra and 1H chemical shift anomalies indicate that this type of self-association is not merely a crystal packing effect but persists in solution. The monofunctional platination of adenine at its N7, N3, and N1 positions in a significant fraction of adducts breaks a longstanding paradigm in platinum-DNA chemistry, the requirement for nucleophilic attack of guanine-N7 as the principal step in cross-link formation. The biological consequences and potential therapeutic applications of the unique base and groove recognition of PT-ACRAMTU are discussed. 相似文献
47.
Emmanuelle A. BugnetTracy D. Nixon Colin A. KilnerRobert Greatrex Terence P. Kee 《Tetrahedron letters》2003,44(29):5491-5494
Molecular clips derived from 2,4,6,8-tetraazabicyclo[3.3.1]nonane-3,7-dione promote increased regioselectivity in the SO2Cl2-mediated electrophilic aromatic chlorination of ortho-cresol leading to para/ortho ratios (Rp/o) <25; approximately six times larger than in the absence of the clip. Specific recognition events involving hydrogen-bond, π-π and dative covalent interactions are implicated. 相似文献
48.
Conventional figures of merit such as limits of detection, signal to background ratio or repeatability, are used to determine the performance of pneumatic and ultrasonic sample introduction systems in an ultra-clean environment with an axially viewed inductively coupled plasma-atomic emission spectrometry and multichannel detection. We observed that the ultrasonic nebuliser offered a large improvement of signal intensity (10-133 greater) compared to a cyclone chamber coupled with a pneumatic Meinhard nebuliser. This improvement is associated with an average increase of signal to background ratio by a factor 86 and an average decrease of detection limits by a factor 6. The improvement factors generally depend on the element and for the same element on spectral lines. Typically, the observed values of detection limits in this work are lower than those published and obtained in non-ultra-clean conditions. The results emphasize that the environmental conditions of cleaning and analysis are essential to avoid and control cross contamination of the samples and hence to obtain low detection limits. 相似文献
49.
Martin Proudmore Ji-Feng Ding Richard H. Mobbs Stephen G. Yeates Colin Price Colin Booth 《Journal of polymer science. Part A, Polymer chemistry》1995,33(10):1615-1625
Poly(hexafluoropropylene oxide), poly(HFPO), networks were prepared from functional polymers by end linking via urethane groups. The prepolymers were characterized by NMR spectroscopy and GPC. The networks were characterized by determination of the number of network chains from the shear modulus, and were snown to contain both trifunctional crosslinks and difunctional links. The properties of the networks were investigated by a range of techniques. Compared with fully-fluorinated networks formed via triazine cross-links, investigated previously, the urethane-linked networks were more readily prepared but were poorer elastomers, were less thermally stable, and were less resistant to swelling by common polar solvents. © 1995 John Wiley & Sons, Inc. 相似文献
50.
Tsai P Ichikawa K Mailer C Pou S Halpern HJ Robinson BH Nielsen R Rosen GM 《The Journal of organic chemistry》2003,68(20):7811-7817
Apparent rate constants, at acidic pH and neutral pH for the reaction of a family of ester-containing 5-carboxyl-5-methyl-1-pyrroline N-oxides with superoxide (O2*-) were estimated, using ferricytochrome c as a competitive inhibitor. It was of interest to note that the rate constants were similar among the different nitrones and not that significantly different from that found for 5-(diethoxyphosphoryl)-5-dimethyl-1-pyrroline N-oxide. At acidic pH, the rate constant for spin trapping O2*- was 3-fold greater than that at physiological pH. Subsequent experiments determined the half-life of aminoxyls, derived from the reaction of these nitrones with O2*-. The EPR spectra were modeled by using a global analysis method. The results clearly demonstrated that EPR spectra of all the aminoxyls were inconsistent with a model that included a single gamma-hydrogen splitting. A better interpretation modeled them as two diastereomers with identical nitrogen splittings and slightly different beta-hydrogen splittings. Detailed line width analyses slightly favored an equal line width-unequal population ratio for the two diastereomers. 相似文献