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排序方式: 共有273条查询结果,搜索用时 31 毫秒
51.
Vakhid A. Mamedov Dina F. Saifina Aidar T. Gubaidullin Alina F. Saifina Il’dar Kh. Rizvanov 《Tetrahedron letters》2008,49(43):6231-6233
A highly efficient one-step and versatile method for the synthesis of 2-(indolizin-2-yl)benzimidazoles has been developed on the basis of the novel ring contraction of 3-arylchloromethyl- and alkylchloromethylquinoxalin-2-ones with α-picoline. 相似文献
52.
Dichloro- and phenylchlorocarbene (CCl2 and PhCCl) add to cyclooctyne via a barrierless process (MP2/6-311+G*, B3LYP/6-311+G*, B3LYP/6-31G*) to yield the expected corresponding cyclopropene adducts. A three-dimensional potential energy surface (PES) for CCl2 addition to cyclooctyne (B3LYP/6-31G*) shows the formation of the cyclopropene product and also possible formation of a vinylcarbene. Residing in a shallow energy well, the vinylcarbene easily rearranges to the cyclopropene product, or to an exocyclic vinyl bicyclo[3.3.0]octane. Although the calculated three-dimensional PES indicates possible dynamic control of the cyclooctyne-chlorocarbene system through the putative formation of a vinylcarbene (in addition to the expected cyclopropene), additional calculations and preliminary experimental work show paths through the vinylcarbene to be unlikely. If the additions of chlorocarbenes to cyclooctyne are controlled by reaction dynamics, we predict that the vast majority of the reactions proceed via traditional carbene cycloaddition with only a very minor amount of products formed from the alternative pathway. 相似文献
53.
Wilton-Ely JD Solanki D Knight ER Holt KB Thompson AL Hogarth G 《Inorganic chemistry》2008,47(20):9642-9653
Treatment of cis-[RuCl2(dppm)2] (dppm = bis(diphenylphosphino)methane) with dithiocarbamates, NaS2CNR2 (R = Me, Et) and [H2NC5H10][S2CNC5H10], yields cations [Ru(S2CNR2)2(dppm)2](+) and [Ru(S2CNC5H10)2(dppm)2](+), respectively. The zwitterions S2CNC4H8NHR (R = Me, Et) react with the same metal complex in the presence of base to yield [Ru(S2CNC4H8NR)(dppm)2](+). Piperazine or 2,6-dimethylpiperazine reacts with carbon disulfide to give the zwitterionic dithiocarbamate salts H2NC4H6(R2-3,5)NCS2 (R = H; R = Me), which form the complexes [Ru(S2CNC4H6(R2-3,5)NH2)(dppm)2](2+) on reaction with cis-[RuCl2(dppm)2]. Sequential treatment of [Ru(S2CNC4H8NH2)(dppm)2](2+) with triethylamine and carbon disulfide forms the versatile metalla-dithiocarbamate complex [Ru(S2CNC4H8NCS2)(dppm)2] which reacts readily with cis-[RuCl2(dppm)2] to yield [{Ru(dppm)2}2(S2CNC4H8NCS2)]. Reaction of [Ru(S2CNC4H8NCS2)(dppm)2] with [Os(CH=CHC6H4Me-4)Cl(CO)(BTD)(PPh3)2] (BTD = 2,1,3-benzothiadiazole), [Pd(C6H4CH2NMe2)Cl]2, [PtCl2(PEt3)2], and [NiCl2(dppp)] (dppp = 1,3-bis(diphenylphosphino)propane) results in the heterobimetallic complexes [(dppm)2Ru(S2CNC4H8NCS2)ML(n))](m+) (ML(n) = Os(CH=CHC6H4Me-4)(CO)(PPh3)2](+), m = 1; ML(n) = Pd(C,N-C6H4CH2NMe2), m = 1; ML(n) = Pt(PEt3)2, m = 2; ML(n) = Ni(dppp), m = 2). Reaction of [NiCl2(dppp)] with H2NC4H8NCS2 yields the structurally characterized compound, [Ni(S2CNC4H8NH2)(dppp)](2+), which reacts with base, CS2, and cis-[RuCl2(dppm)2] to provide an alternative route to [(dppm)2Ru(S2CNC4H8NCS2)Ni(dppp)](+). A further metalla-dithiocarbamate based on cobalt, [CpCo(S2CNC4H8NH2)(PPh3)](2+), is formed by treatment of CpCoI2(CO) with S2CNC4H8NH2 followed by PPh3. Further reaction with NEt3, CS2, and cis-[RuCl2(dppm)2] yields [(Ph3P)CpCo(S2CNC4H8NCS2)Ru(dppm)2](2+). Heterotrimetallic species of the form [{(dppm)2Ru(S2CNC4H8NCS2)}2M](2+) result from the reaction of [Ru(S2CNC4H8NCS2)(dppm)2] and M(OAc)2 (where M = Ni, Cu, Zn). Reaction of [Ru(S2CNC4H8NCS2)(dppm)2] with Co(acac)3 and LaCl3 results in the formation of the compounds [{(dppm)2Ru(S2CNC4H8NCS2)}3Co](3+) and [{(dppm)2Ru(S2CNC4H8NCS2)}3La](3+), respectively. The electrochemical behavior of selected examples is also reported. 相似文献
54.
Justes DR Talaty N Cotte-Rodriguez I Cooks RG 《Chemical communications (Cambridge, England)》2007,(21):2142-2144
Single nanogram amounts of the explosives TNT, RDX, HMX, PETN and their mixtures were detected and identified in a few seconds on the surface of human skin without any sample preparation by desorption electrospray ionization (DESI) using a spray solution of methanol-water doped with sodium chloride to form the chloride adducts with RDX, HMX, and PETN while TNT was examined as the radical anion and tandem mass spectrometry was used to confirm the identifications. 相似文献
55.
Spectrophotometric, spectrofluorometric and HPLC determination of desloratadine in dosage forms and human plasma 总被引:1,自引:0,他引:1
Four sensitive, simple and specific methods were developed for the determination of desloratadine (DSL), a new antihistaminic drug in pharmaceutical preparations and biological fluids. Methods I and II are based on coupling DSL with 4-chloro-7-nitrobenzo-2-oxa-1,3-diazole (NBD-Cl) in borate buffer of pH 7.6 where a yellow colored reaction product was obtained and measured spectrophotometrically at 485 nm (Method I). The same product could be measured spectrofluorometrically at 538 nm after excitation at 480 nm (Method II). Methods III and IV, on the other hand, involved derivatization of DSL with 2,4-dinitrofluorobenzene (DNFB) in borate buffer of pH 9.0 producing a yellow colored product that absorbs maximally at 375 nm (Method III). The same derivative was determined after separation adopting HPLC (Method IV). The separation was performed on a column packed with cyanopropyl bonded stationary phase equilibrated with a mobile phase composed of acetonitrile-water (60 : 40, v/v) at a flow rate of 1.0 ml min(-1) with UV detection at 375 nm. The calibration curves were linear over the concentration ranges of 0.5-6, 0.02-0.4, 1-10 and 1-30 microg ml(-1) for Methods I, II, III and IV, respectively. The lower detection limits (LOD) were 0.112, 0.004, 0.172 and 0.290 microg ml(-1), respectively, for the four methods. The limits of quantification (LOQ) were 0.340, 0.012, 0.522 and 0.890 microg ml(-1) for Methods I, II, III and IV, respectively. The proposed methods were applied to the determination of desloratadine in its tablets and the results were in agreement with those obtained using a reference method. Furthermore, the spectrofluorometric method (Method II) was extended to the in-vitro determination of the drug in spiked human plasma, with a mean percentage recovery (n=4) of 99.7+/-3.54. Interference arising from endogenous amino acids has been overcome using solid phase extraction. The proposed methods are highly specific for determination of DSL in the presence of the parent drug loratadine. A proposal for the reaction pathways is postulated. 相似文献
56.
Ali Badiee Mahmoud R. Jaafari Ali Khamesipour Afshin Samiei Dina Soroush Masoumeh Tavassoti Kheiri Farzaneh Barkhordari W. Robert McMaster Fereidoun Mahboudi 《Colloids and surfaces. B, Biointerfaces》2009,74(1):37-44
Development of new generation vaccines requires adjuvants to elicit the type and intensity of immune response needed for protection. Liposomes have been shown to be an effective adjuvant formulation. In this study, the role of liposome bilayer composition with different phase transition temperature (Tc) to induce a T helper 1 (Th1) type of immune response and protection against leishmaniasis in BALB/c mice was assessed. Liposome formulations with different bilayer compositions consisting of egg phosphatidylcholine (EPC, Tc < 0 °C), dipalmitoylphosphatidylcholine (DPPC, Tc 41 °C), or distearoylphosphatidylcholine (DSPC, Tc 54 °C) were prepared. All liposomes were contained rgp63 as a recombinant antigen and used to immunize mice subcutaneously 3 times in 3-week intervals. Evaluation of lesion development and splenic parasite burden after challenge with L. major, evaluation of Th1 cytokine (IFN-γ) and Th2 cytokine (IL-4), and titration of IgG isotypes were carried out to assess the type of generated immune response and extent of protection. The results indicated the generated immune response in mice was influenced by the bilayer composition of liposomes, so that mice immunized with liposomes consisting of EPC induced a Th2 type of immune response while liposome consisting of DPPC or DSPC induced Th1 type of immune response. It seems that liposomes prepared with higher Tm phospholipids are suitable formulation to induce Th1 type of immune response and protection, and so might be used for further investigations to develop an effective vaccine against leishmaniasis. 相似文献
57.
David M. Good Craig D. Wenger Graeme C. McAlister Dina L. Bai Donald F. Hunt Joshua J. Coon 《Journal of the American Society for Mass Spectrometry》2009,20(8):1435-1440
Tandem mass spectra (MS/MS) produced using electron transfer dissociation (ETD) differ from those derived from collision-activated
dissociation (CAD) in several important ways. Foremost, the predominant fragment ion series are different: c- and z
·-type ions are favored in ETD spectra while b- and y-type ions comprise the bulk of the fragments in CAD spectra. Additionally, ETD spectra possess charge-reduced precursors
and unique neutral losses. Most database search algorithms were designed to analyze CAD spectra, and have only recently been
adapted to accommodate c- and z
·-type ions; therefore, inclusion of these additional spectral features can hinder identification, leading to lower confidence
scores and decreased sensitivity. Because of this, it is important to pre-process spectral data before submission to a database
search to remove those features that cause complications. Here, we demonstrate the effects of removing these features on the
number of unique peptide identifications at a 1% false discovery rate (FDR) using the open mass spectrometry search algorithm
(OMSSA). When analyzing two biologic replicates of a yeast protein extract in three total analyses, the number of unique identifications
with a ∼1% FDR increased from 4611 to 5931 upon spectral pre-processing—an increase of ∼28. 6%. We outline the most effective
pre-processing methods, and provide free software containing these algorithms. 相似文献
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60.
Majumder Ratan Kumar Das Sudeb Chandra Rasul Md. Golam Khalil Mohammad Ibrahim Dina Nafisa Tamannaya Kabir Mohammad Zafrul Deeba Farah Rajib Mohammad 《Journal of Radioanalytical and Nuclear Chemistry》2021,329(1):265-277
Journal of Radioanalytical and Nuclear Chemistry - The study investigates the measurement of radon concentration in soils and rocks as a natural tracer for exploring uranium mineralization, first... 相似文献