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11.
12.
Erich Metzger Roland Aeschimann Martin Egli Gaby Suter Ren Dohner Daniel Ammann Max Dobler Wilhelm Simon 《Helvetica chimica acta》1986,69(8):1821-1828
Lipophilic neutral carriers were synthesized which show Li+/Na+ selectivities of up to ca. 80 in highly lipophilic liquid membranes. The sensor membranes exhibit improved response times and increased lifetimes as compared to systems described earlier. They allow reliable measurements of Li+ in blood serum within the clinical concentration range. A 1:1 Li+/ionophore complex of one representative (N,N,N′,N′-tetracyclohexyl-5,5-dimethyl-3,7-dioxaazelaamide) has been prepared, and its structure was elucidated by X-ray analysis. 相似文献
13.
J. L. Gascón M. Rodríguez J. A. Suárez Del Rey 《Journal of Radioanalytical and Nuclear Chemistry》1996,207(1):63-69
The determination of Am and Cm in typical waste streams from nuclear power plants using anion exchange chromatography has some drawbacks like the contamination by Pu and Po. This improved procedure solves these problems, and it has been applied with success to the analysis of Am and Cm in nuclear waste samples: ion exchange resins, ion exchange resins solidified with cement and evaporator concentrates. 相似文献
14.
Gerhard Laus Johannes Schütz Herwig Schottenberger Max Andre Klaus Wurst Mariana Spetea Karl‐Hans Ongania AdrianG. Müller Helmut Schmidhammer 《Helvetica chimica acta》2003,86(10):3274-3280
The two diastereoisomeric ferrocenyl‐substituted orvinols 2 and 3 were prepared. The modified alkaloids are still able to interact with opioid receptors (see Table). The ferrocene moiety allows highly selective and sensitive electrochemical detection. The X‐ray crystal structure of the major isomer 2 was determined. The combination of a metallocene and a morphinan alkaloid holds promise for useful antitumor activity. 相似文献
15.
Starting with 5-formyl-6,7-dimethyl-5,6,7,8-tetrahydropterine (II), a new synthesis of 5,6,7-trimethyl-5,6,7,8-tetrahydropterine (III) is described. Thereby the chemical behaviour of the 5-formyl group in II is investigated, in order to enable the unequivocal differentiation between formylation at position 5 and at position 10 in folic and tetrahydrofolic acid derivatives. 13C-NMR. spectra of II and III are discussed. 相似文献
16.
Ab initio Hartree–Fock band structure and molecular calculations have been performed to study the electronic structure of LiN3 in a monoclinic C 2/m crystal structure. The total energy, band structure, density of states, and charge densities are computed. The calculated lattice energy (energy to separate the ions infinitely apart) of 8.6 eV agrees very well with 8.45 eV deduced from Madelung and London polarizability energies. The calculated split of the N 1s core bands of 5.0 eV compares favorably with the experimental X-ray photoelectron value of 4.4 eV. This good agreement is not contributed to crystalline environment effects as proposed in earlier MO studies of N where the best values obtained were 5.1, 5.8, and 6.3 eV, but to the quality of the nitrogen core basis set. The calculated valence density of states supports one of two competing interpretations that peak III observed in the X-ray photoelectron spectrum arises from contaminations or other extrinsic states. 相似文献
17.
Roger Kalbermatten Werner Stdeli Jost H. Bieri Max Viscontini 《Helvetica chimica acta》1981,64(8):2627-2635
13C- and 15N-NMR.-Spectroscopic Studies on (6RS)-5, 10-Methylene-5, 6, 7, 8-tetrahydro-L -folic Acid; Unequivocal Proof of thier Structure The existence of a 5, 10-methylene bridge in the title compound has been established with the help of 15N-NMR, and 13C-NMR. spectroscopy. The simultaneous coupling of 13C(11) with 15N(5) and 15N(10) proves that C(11) must be bound as a methylene bridge to both N-atoms. Some other aspects of the NMR. spectra of the compound are discussed. Synthesis of the title product with the label 15N is described. 相似文献
18.
The purpose of this communication is to describe the preparation and some properties of the first two synthetic peptides containing D - and L -γ-carboxyglutamic acid. Use was made of N-protected γ,γ′-di-t-butyl-γ-carboxyglutamic acids (D , L , and DL ) described earlier [1 a]. Preliminary 1H-NMR. data (360 MHz) indicate a restricted rotation of the Gla side chain in the free amino acid as well as in the C-terminal Gla of Gla-Gla in H2O solution at acid pH. The proton dissociation from Gla and Gla-Gla was studied by potentiometric titration and NMR. methods. The pH titration in the presence of Ca2+ ions shows that Gla-Gla has a much higher association constant for this cation than Gla. It is almost as great as that of prothrombin (pCa2+ = 3.2 vs. 3.5). 相似文献
19.
Selected [2+2]-cycloadditions of three alkylvinylketenes 2 to one mono- and seven dialkyl-olefins 3 yielded eleven 2-alkyl-2-vinylcyclobutanones 4 (Tables 1 and 2). Three methods were compared, all involving in situ generation of the ketenes 2 by HCl-elimination from α,β-unsaturated acid chlorides 1 ; the most effective employed a large excess of olefin 3 and a high reaction temperature. The [2+2]-cycloadditions were fully regio- and stereoselective with respect to the olefin 3 , but less so with respect to the ketene 2 , so that - where possible - two stereoisomers of 4 resulted, namely A and B , whose configurations were determined from their 1H-NMR, spectra, mechanistic considerations and, in one case, 4f , by chemical correlation with a previously known cycloadduct 8 . 相似文献
20.
The crystal structure of 5,6,7-trimethyl-5,6,7,8-tetrahydropterine-dihydrochloride-monohydrate The crystal structure of the title compound has been determined by X-ray analysis (direct methods) and refined with 947 structure amplitudes to R = 0.026. The crystal system is orthorhombic, space group Pna21, with unit cell dimensions a = 14.081, b = 14.623, c = 6.773 Å. The molecule is protonated at the N(1)- and N(5)-position. The tetrahydropyrazine ring exists in a conformation in which C(6) deviates markedly from the mean plane of the other five atoms. The CH3-groups at N(5) and C(6) possess a trans configuration with a pseudoaxial and an axial conformation respectively. The CH3-groups at C(6) and C(7) in return possess the cis configuration, whereby the CH3-group at C(7) occupies an equatorial conformation. 相似文献