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11.
12.
Edgardo Laborde John S. Kiely Lawrence E. Lesheski Mel C. Schroeder 《Journal of heterocyclic chemistry》1991,28(1):191-198
A convergent synthesis of 1,8-naphthyridine antibacterials bearing a carbon-carbon bonded, acyclic or cyclic vinyl substituent at the C-7 position has been achieved. The synthetic methodology is based upon the palladium-catalyzed cross coupling of a 7-chloro-1,8-naphthyridine with an appropriately substituted organotin reagent. 相似文献
13.
14.
Frański R Schroeder G Rybachenko V Szwajka OP 《Rapid communications in mass spectrometry : RCM》2002,16(5):390-395
The fragmentation pattern of some protonated 2,5-diaryl-1,3,4-oxadiazoles is discussed. An unusual decomposition consisting of elimination of the isocyanic acid molecule from the internal oxadiazole ring was found. This fragmentation pathway was deduced on the basis of B/E linked scan mass spectra of metastable ions with liquid secondary ion mass spectrometry as the ionization method and also of low-energy CID mass spectra where electrospray was used as the ionization technique. High resolution measurements were also performed. 相似文献
15.
Schroeder G. Rybachenko V. I. Chotii K. Yu. Kovalenko V. V. Grebenyuk L. V. Lenska B. Eitner K. 《Russian Journal of General Chemistry》2003,73(3):455-462
Dimethylcarbamoyl transfer from N-acyloxypyridinium salts to pyridine N-oxides in acetonitrile occurs in one stage by the forced concerted SN2 mechanism. The rate and equilibrium of the reaction are fairly described by the Brönsted equation. The Marcus equation provides a much higher quality of reactivity predictions. 相似文献
16.
The microchromatographic procedure for the quantitative analysis of the hemoglobin components in a hemolysate uses columns of DEAE-cellulose in a plastic drinking straw with a glycine-KCN-NaCl developer. Not only may the method be used for the quantitative analysis of Hb-F but also for the analysis of the varied components in mixtures of hemoglobins. 相似文献
17.
Grzegorz Schroeder Bogumi
Brzezinski Dariusz Pod
bski Eugeniusz Grech 《Journal of Molecular Structure》1997,416(1-3):11-19
Deprotonation of 5,10,15,20-tetrakis(pentafluorophenyl)-21-H, 23-H-porphyrin (PhF5PorH2) by various bases has been studied by 1H NMR and kinetic methods. The kinetic parameters in acetonitrile were defined for proton transfer reactions yielding [NH]+ protonated bases and [NHN]− anions with intramolecular hydrogen-bonded chains. 相似文献
18.
The crystal structures of the apatites Ba10(PO4)6F2(I), Ba6La2Na2(PO4)6F2(II) and Ba4Nd3Na3(PO4)6F2 (III) have been determined by single-crystal X-ray diffraction. All three compounds crystallize in a hexagonal apatite-like structure. The unit cells and space groups are: I, a = 10.153(2), c = 7.733(1)Å, Å, ; III, a = 9.786(2), c = 7.281(1)Å, . The structures were refined by normal full-matrix crystallographic least squares techniques. The final values of the refinement indicators Rw and R are: I, Rw = 0.026, R = 0.027, 613 observed reflections; II, Rw = 0.081, R = 0.074, 579 observed reflections; III, Rw = 0.062, R = 0.044, 1262 observed reflections.In I, the Ba(1) atoms located in columns on threefold axes, are coordinated to nine oxygen atoms; the Ba(2) sites form triangles about the F site and are coordinated to six oxygen atoms and one fluoride ion. The fluoride ions are statistically displaced ~0.25 Å from the Ba(2) triangles. This displacement of the F ions is analogous to the displacement of OH ion in Ca10(PO4)6(OH)2.The structures of II and III contain disordered cations. In II there is disorder between La and Na in the column cation sites as well as triangle sites. In III, Nd and Na ions are ordered in the column sites, but there is disorder among Ba and the remaining Nd and Na ions in the triangle sites to give an average site population of . The coordination of the rare earth ions and Na ions in the ordered column sites are nine and six oxygens, respectively, in accord with the greater charge of the rare earth ions as compared with Na. The F ions in both II and III suffer from considerable disorder in position, and their locations are not precisely known. 相似文献
19.
Experiments were undertaken to verify a method for complete amino acid analysis of plant and animal tissues and waste products from a single hydrolysis and high-performance liquid chromatographic run. Using methanesulfonic acid, hydrolysis of cytochrome c at 115 degrees C for 22 h yielded recoveries equal to or higher than hydrolysis at 115 degrees C for 70 h or at 150 degrees C for 22 h. Triple evacuation of the hydrolysis tube alternated with nitrogen flush gave recovery improvements over single evacuation. Refrigerated storage of samples under vacuum for up to 4 days between hydrolysis and further analysis was not different from immediate analysis. However, recoveries of several amino acids were reduced by refrigerated storage in air. Recoveries of individual amino acids were determined by hydrolysis of biological samples with and without added cytochrome c. Although recoveries from biological samples were lower for several amino acids, precision was sufficient to allow quantitation after correction for incomplete recoveries. Derivatization with 9-fluorenylmethylchloroformate (FMOC) was chosen because derivatives are formed with both primary and secondary amino acids, derivatives are quite stable, and detection may be either UV absorbance or fluorescence. Derivative yield is sensitive to the pH of the reaction mixture. A pH of 8.0 gave reproducible derivative yield for all physiological amino acids. Solvent extraction of excess FMOC, when compared to addition of amantadine to react with excess FMOC, gave both higher recoveries and greater precision. Following derivatization, samples could be kept at 4 degrees C for at least 24 h before high-performance liquid chromatographic analysis without loss of response. Derivative yield and detector response were constant across a wide range of molar ratio of FMOC to total amino acids. Gradient elution was required to separate FMOC derivatives on a reversed-phase column. The capability of the pumping system to produce exponential gradients permitted rapid and easy fine-tuning of the gradient. 相似文献
20.
Rybachenko V. I. Schroeder G. Chotii K. Yu. Titov E. V. Kovalenko V. V. Leska B. Grebenyuk L. V. 《Russian Journal of General Chemistry》2001,71(10):1608-1615
Forty-three (including eight identical) reactions of acetyl transfer from N-acetyloxypyridinium salts to pyridine N-oxides in acetonitrile solutions were studied. The rate constants k
2 vary in the range 107-10-
1 l mol-
1 s-
1; the equilibrium constants K, in the range 107-10-
7; the activation enthalpy H
, in the range 17-30 kJ mol-
1; the activation entropy -S
, in the range 60-85 J mol-
1 K-
1; and the heat of reaction -H
0, within ±50 kJ mol-
1. All reactions occur in a single stage by the concerted SN2 mechanism with a low degree of bond cleavage in the transition state. The rate and equilibrium of the acetyl exchange are satisfactorily described by the Brönsted equation. The quality of predicting the reactivity is substantially improved by introducing into the correlation equation a second parameter, the rates of identical reactions. 相似文献