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61.
Scheuermann JE Sibbons KF Benoit DM Motevalli M Watkinson M 《Organic & biomolecular chemistry》2004,2(18):2664-2670
A number of chiral unsymmetrically N-substituted 1,4,7-triazacyclononane ligands have been prepared by modular methods. The key step in the synthesis centres on the macrocyclisation of three tertiary amide precursors under standard Richman-Atkins conditions which allows for subsequent N-functionalisation. 相似文献
62.
Carrier solutions for stripping voltammetry in flow systems are deoxygenated by reaction with glucose added to the carrier. The reaction was catalyzed by glocuse oxidase and catalase co-immobilized in an enzyme reactor which was inserted before the injector. The oxygenated was removed at least as efficiently as with nitrogen purging and the voltametric behaviour of cadmium(II), lead(II) and zinc(II) was unaffected by the glucose/gluconic acid system. A particular advantage is the rapid start-up compared to the lengthy purging of carrier solution when nitrogen degassing is used. The enzyme reactor made from porous glass was effective for several months. 相似文献
63.
A field theoretical formulation is given for the method of different orbitals for different spins (DODS ). For an infinite system DODS describes an antiferromagnetic state and to account for this spin ordering a Gorkov-type of factorization is introduced. A corresponding gap equation is derived, where a non-zero solution indicates the presence of long-range order in the system. Actually the formulation given is general enough as to render DODS as a special case. As shown, we may also obtain a ferrimagnetic as well as a density wave state solution depending on the special characteristics of the system at hand. A related type of antiferromagnetism is described by the Overhauser spin density wave (SDW ) state and also this theory is formulated in a field theoretical language. The similarities and differences between DODS and SDW are discussed. The energy expressions for the two states are given within the Hartree-Fock approximation. It is proposed that the SDW state could be used to partly account for the correlation problem in molecules, as well as the method of DODS which has previously been employed for that purpose. 相似文献
64.
Erik Larsen Abdel Aleem H. Abdel Aleem Erik B. Pedersen 《Journal of heterocyclic chemistry》1995,32(5):1645-1646
α-Thymidine (4) was synthesized from thymidine (1) in 3 steps in 36% overall yield without using chro-matography and with the possibility of increasing the yield to 85% by reusing the remaining α,β-mixture. 1-(2-Deoxy-3,5-di-O-p-toluoyl-α-D-erythro-pentofuranosyl)thymine (3) was further converted to 1-(2-deoxy-α-D-erythro-pentofuranosyl)-5-methylcytosine (5) . 相似文献
65.
Thapper A Behrens A Fryxelius J Johansson MH Prestopino F Czaun M Rehder D Nordlander E 《Dalton transactions (Cambridge, England : 2003)》2005,(21):3566-3571
Reaction of the tetradentate ligand N-(2-hydroxybenzyl)-N,N-bis(2-pyridylmethyl)amine (L-OH) with MoO2Cl2 in methanol in the presence of NaOMe and PF6- results in the formation of [MoO2(L-O)]PF6. Similarly, the reaction of N-(2-mercaptobenzyl)-N,N-bis(2-pyridylmethyl)amine (L-SH) with MoO2(acac)2 leads to the formation of [MoO2(L-S)]+. The dioxo-molybdenum complex [MoO2(L-O)]+ reacts with phosphines in methanol to afford phosphine oxides and an air-sensitive molybdenum complex, tentatively identified as [Mo(IV)O(L-O)(OCH3)]. The latter complex is capable of reducing biological oxygen donors such as DMSO or nitrate, thereby mimicking the activity of DMSO reductase and nitrate reductase. Reaction of [MoO2(L-O)]PF6 with PPh3 in other solvents than methanol leads to the formation of the Mo(V) dimer [(L-O)OMo(micro-O)MoO(L-O)](PF6)2. The crystal structures of [MoO2(L-O)]PF6 and the micro-oxo bridged dimer are presented. 相似文献
66.
Blanco JM Caamaño O Fernández F Rodríguez-Borges JE Balzarini J de Clercq E 《Chemical & pharmaceutical bulletin》2003,51(9):1060-1063
Six new carbocyclic nucleosides were prepared by constructing a purine base (in compounds 9-11) or pyrimidine base (in 6-8) on the amino groups of (+/-)-(1 beta,2 alpha,4 beta)-4-amino-1,2-cyclopentanedimethanol (4) and (+/-)-(1 beta,3 alpha,4 beta)-4-amino-1,3-cyclopentanedimethanol (5), and their activities against a variety of viruses and tumour cell lines were determined. 相似文献
67.
Determination of noscapine in plasma by liquid chromatography 总被引:1,自引:0,他引:1
A liquid chromatographic method has been developed for the determination of noscapine in plasma. Noscapine and the internal standard, papaverine, were extracted into methylene chloride by column extraction. The separation was performed on a straight-phase liquid chromatographic system using a mobile phase of hexane--methanol--chloroform--diethylamine. A high detection selectivity was obtained by UV detection at 310 nm. The precision of the method was 3.8% (standard deviation) at a level of 89 ng/ml and 9.5% (standard deviation) at 5.9 ng/ml. The selectivity of the analytical method was evaluated by comparing analytical results after isolation of extracts of plasma samples on reversed- and straight-phase liquid chromatographic systems. 相似文献
68.
GROMACS: fast, flexible, and free 总被引:37,自引:0,他引:37
Van Der Spoel D Lindahl E Hess B Groenhof G Mark AE Berendsen HJ 《Journal of computational chemistry》2005,26(16):1701-1718
This article describes the software suite GROMACS (Groningen MAchine for Chemical Simulation) that was developed at the University of Groningen, The Netherlands, in the early 1990s. The software, written in ANSI C, originates from a parallel hardware project, and is well suited for parallelization on processor clusters. By careful optimization of neighbor searching and of inner loop performance, GROMACS is a very fast program for molecular dynamics simulation. It does not have a force field of its own, but is compatible with GROMOS, OPLS, AMBER, and ENCAD force fields. In addition, it can handle polarizable shell models and flexible constraints. The program is versatile, as force routines can be added by the user, tabulated functions can be specified, and analyses can be easily customized. Nonequilibrium dynamics and free energy determinations are incorporated. Interfaces with popular quantum-chemical packages (MOPAC, GAMES-UK, GAUSSIAN) are provided to perform mixed MM/QM simulations. The package includes about 100 utility and analysis programs. GROMACS is in the public domain and distributed (with source code and documentation) under the GNU General Public License. It is maintained by a group of developers from the Universities of Groningen, Uppsala, and Stockholm, and the Max Planck Institute for Polymer Research in Mainz. Its Web site is http://www.gromacs.org. 相似文献
69.
70.
We have calculated the self-consistent Green's function for a number of atoms and diatomic molecules. This Green's function is obtained from a conserving self-energy approximation, which implies that the observables calculated from the Green's functions agree with the macroscopic conservation laws for particle number, momentum, and energy. As a further consequence, the kinetic and potential energies agree with the virial theorem, and the many possible methods for calculating the total energy all give the same result. In these calculations we use the finite temperature formalism and calculate the Green's function on the imaginary time axis. This allows for a simple extension to nonequilibrium systems. We have compared the energies from self-consistent Green's functions to those of nonselfconsistent schemes and also calculated ionization potentials from the Green's functions by using the extended Koopmans' theorem. 相似文献