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121.
122.
Fiorentino A D'Abrosca B Pacifico S Izzo A D'Angelo G Monaco P 《Natural product communications》2010,5(10):1539-1542
Two new clerodane diterpenes were isolated from roots of Carex distachya Desf., a perennial plant widely distributed in the coastal area of the Mediterranean basin. Chemical characterization of the metabolites was carried out mainly by 1D and 2D NMR spectroscopy. The isolated compounds influenced either positively or negatively the plant growth (root and shoot elongation) of three coexisting herbaceous species. 相似文献
123.
Francesca Di Gaudio Sergio Indelicato Roberto Monastero Grazia Ida Altieri Francesca Fayer Ornella Palesano Manuela Fontana Angelo B. Cefalu Massimiliano Greco David Bongiorno Serena Indelicato Angela Aronica Davide Noto Maurizio R. Averna 《Analytical and bioanalytical chemistry》2016,408(9):2373-2373
124.
The mean diffusion coefficient of 233Pa has been measured simultaneously with those of 22Na and 152Eu in 0.5 M (Na, H)ClO4 solutions with the pH ranging from 0.3 to 13, by the open-end capillary method optimized in order to obtain reproducible and reliable D values at T = 25°C. In the case of Eu(III), the results tend to give higher 13 and 14 hydrolysis constants than the values generally acccepted, but these data are probably affected by the formation of polynuclear or colloidal species as soon as the hydrolysis process is involved. For Pa(V), results are in agreement with the existence of the following two equilibria (I = 0.5 M, T = 25°C):
However, unusual behavior is observed at a pH value around 1.3. A third equilibrium in basic media leads to the formation of a negatively charged species (log K
h4 = –9.03 ± 0.1 at I = 0.5 M). Finally, the presence of chloride in solution (0.1 M; pH = 1 and 4) and carbonate-bicarbonate ions (0.1 M; pH = 9.4 and 11.0), which cannot be neglected in most of the natural waters, decreases the measured values for the diffusion coefficient of Pa(V) appreciably compared to noncomplexing media. 相似文献
125.
Assfeld X García J García JI Mayoral JA Proietti MG Ruiz-López MF Sánchez MC 《The Journal of organic chemistry》1996,61(5):1636-1642
Extended X-ray absorption fine structure (EXAFS) and X-ray absorption near edge structure (XANES) techniques, in combination with (13)C-NMR spectroscopy, have been used to study the complexation of methyl acrylate (1), N-acryloylbenzylamine (2), O-acryloyl-(R)-pantolactone (3), methyl N-acryloyl-(S)-prolinate (4), and methyl N-acryloyl-(S)-phenylalaninate (5) with excess TiCl(4) in solution. The results obtained show that TiCl(4) has a great tendency to coordinate with two ester ligands, but this tendency is not so marked with amides, which is related to the greater basicity of the latter. Complexation increases the Ti-Cl bond distance, in comparison with TiCl(4), which is clearly shown by the EXAFS spectra. Chelate complexes are formed with bidentate ligands, but comparison between the EXAFS spectra, obtained with different TiCl(4)/dienophile ratios, shows that chelation is more difficult with methyl N-acryloyl-(S)-phenylalaninate (5). 相似文献
126.
127.
The title homoazasugar, also referred as (2R,5S)-bis(hydroxymethyl)-(3R,4R)-dihydroxypyrrolidine, has been synthesized by addition of 2-lithiothiazole to the 2,3,5-tri-O-benzyl-d-arabinofuranose-derived nitrone---hydroxylamine mixture followed by reductive N-dehydroxylation and conversion of the thiazole ring into the hydroxymethyl group. 相似文献
128.
Salvatore Cabiddu Enzo Cadoni Stefana Melis Gioanna Gelli Maria Grazia Cabiddu Claudia Fattuoni Stefania De Montis Sandra Ianelli 《Tetrahedron》2001,57(52):10365-10375
The reaction of benzoxathiole-3-oxide with LDA in THF or THF/hexane or THF/HMPA gave a carbanion which was reacted with methyl iodide, aromatic aldehydes or carbon dioxide. The conformational stability (-diastereoselectivity) of the carbanion and the asymmetric induction due to the prochiral electrophiles (β-diastereoselectivity) was studied. The temperature and the solvent effects on the - and β-diastereoselectivity are discussed. 相似文献
129.
We study ball-homogeneity, curvature homogeneity, natural reductivity, conformal flatness and ϕ-symmetry for three-dimensional
contact metric manifolds. Several classification results are given.
Member of G.N.S.A.G.A.
Supported by funds of the M.U.R.S.T. 相似文献
130.
Beam width measurements of multi-mode asymmetric laser beams delivered by a XeCl laser, have been carried out in the focal plane of a lens, by the knife-edge and the variable rectangular aperture technique, respectively to determine beam divergence. It is shown that both methods provide beam width measurements in satisfactory agreement within experimental errors by properly choosing the clip levels. The analytical treatment for the clip level selection is also reported. 相似文献