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1.
Vladimir A. Khripach Vladimir N. Zhabinskii Vladimir V. Gromak Jaap van der Louw 《Tetrahedron letters》2006,47(38):6715-6718
Treatment of 3β,17β-diacetoxy-5,10-secoandrost-1(10)-en-5-one with BF3·Et2O was shown to proceed with cleavage of the macrocycle and formation of a new compound containing a cyclopentenone ring. Based on DFT calculations, an intramolecular Lewis acid promoted [2+2]cycloaddition, followed by a cycloreversion of the intermediate oxetane, is proposed as a possible reaction mechanism. 相似文献
2.
Nomkoko TE Jackson GE Nakani BS Louw WK Zeevaart JR 《Dalton transactions (Cambridge, England : 2003)》2004,(5):741-749
The thermodynamic equilibria of copper(II), zinc(II), calcium(II) and gadolinium(III) with 3,3,9,9-tetramethyl-4,8-diazaundecane-2,10-dione dioxime (L1) have been studied at 25 degrees C and an ionic strength of 0.15 mol dm(-3). Copper and gadolinium form stable complexes with the ligand while the corresponding zinc species are more than 9 log units less stable. No complexes between calcium and the ligand were detected. The low binding strength of L1 towards zinc is attributed to the square-planar coordination geometry forced on the metal ion by the ligand as revealed by molecular mechanics calculations and molecular dynamics simulations. Speciation calculations, using a computer model of blood plasma, indicate that, despite the high concentration of zinc(II) and calcium(II) in vivo, L1 is able to increase the low-molecular-mass fraction of copper in plasma. Octanol/water partition coefficient of [CuL1H(-1)] indicates that although this species is largely hydrophilic, approximately 6% of the complex goes into the octanol phase and hence may promote dermal absorption of copper by the same amount. The dermal penetration rate is calculated to be 4.0 x 10(-4) mm h(-1). The [CuL1H(-1)] complex, which predominates at pH 7.4, is a poor mimic of native copper-zinc superoxide dismutase. Biodistribution experiments using the 64Cu-labelled [CuL1H(-1)] complex indicate an initial high uptake of this species in the liver followed by redistribution into muscle. Only a small amount is excreted through the urine. 相似文献
3.
Dr. Peter Wick Dr. Anna E. Louw‐Gaume Dr. Melanie Kucki Prof. Harald F. Krug Prof. Kostas Kostarelos Prof. Bengt Fadeel Prof. Kenneth A. Dawson Dr. Anna Salvati Prof. Ester Vázquez Dr. Laura Ballerini Dr. Mauro Tretiach Dr. Fabio Benfenati Dr. Emmanuel Flahaut Dr. Laury Gauthier Prof. Maurizio Prato Dr. Alberto Bianco 《Angewandte Chemie (International ed. in English)》2014,53(30):7714-7718
4.
Stefan Louw Frédéric Lynen Melissa Hanna-Brown Pat Sandra 《Journal of chromatography. A》2010,1217(4):514-521
Recently, hydrophilic interaction chromatography (HILIC) has emerged as a valuable orthogonal tool to reversed-phase liquid chromatography (RP-LC) as it allows for resolution of highly polar ionisable compounds. The relationships between separation efficiency, column length and speed of analysis for 4.6 mm ID × 5 μm silica particle columns in HILIC are demonstrated using kinetic plots. The kinetic plots constructed for conventional pressure systems operating at 350 bar and at 30 °C and 80 °C are confirmed using experimental data for different column lengths. Efficiencies of more than 130,000 theoretical plates could be achieved by connecting up to six columns of 25 cm. As expected, a significant gain in analysis speed without loss of efficiency could be obtained by operating at 80 °C compared to 30 °C. The advantages of using long columns in HILIC in combination with elevated column temperature for the pharmaceutical industry are illustrated using test mixtures comprised of commercially available ionisable compounds (including some containing functional groups with potential genotoxic typical structural alerts) as well as real polar ionisable pharmaceuticals. 相似文献
5.
Phase equilibrium measurements of structure II clathrate hydrates of hydrogen with various promoters
Alondra Torres TruebaLaura J. Rovetto Louw J. FlorusseMaaike C. Kroon Cor J. Peters 《Fluid Phase Equilibria》2011,307(1):6-10
Phase equilibrium measurements of single and mixed organic clathrate hydrates with hydrogen were determined within a pressure range of 2.0-14.0 MPa. The organic compounds studied were furan, 2,5-dihydrofuran, tetrahydropyran, 1,3-dioxolane and cyclopentane. These organic compounds are known to form structure II clathrate hydrates with water. It was found that the addition of hydrogen to form a mixed clathrate hydrate increases the stability compared to the single organic clathrate hydrates. Moreover, the mixed clathrate hydrate also has a much higher stability compared to a pure hydrogen structure II clathrate hydrate. Therefore, the organic compounds act as promoter materials. The stabilities of the single and mixed organic clathrate hydrates with hydrogen showed the following trend in increasing order: 1,3-dioxolane < 2,5-dihydrofuran < tetrahydropyran < furan < cyclopentane, indicating that both size and geometry of the organic compound determine the stability of the clathrate hydrates. 相似文献
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J. R. Zeevaart W. K. A. Louw Z. I. Kolar J. M. Wagener N. V. Jarvis R. A. M. J. Claessens 《Journal of Radioanalytical and Nuclear Chemistry》2003,257(1):83-91
Blood plasma modeling has proved effective in the evaluation of clinical observations recorded for baboon and rat tests with 153Sm- ethylenediaminetetraphosphonic acid (EDTMP) as well as for 166Ho-EDTMP. In the search for a cure for metastatic bone cancer, 117mSn with its conversion electrons of discrete energies shows low bone marrow toxicity, providing the opportunity to increase the administered dose. Selective accumulation in lesions would capitalize on this advantage. The 10-30 kDa fraction of the water-soluble polymer polyethyleneimine, functionalized with methylene phosphonate groups (PEI-MP) and labeled with 99mTc, has shown selective uptake into bone tumours. This paper relates the speciation of Sn(II)-PEI-MP and other known 117mSn(II) containing bone-seeking radiopharmaceuticals in blood plasma. Apparent formation constants for the complexation of SnII with PEI-MP, DTPA, HEDP and other important blood plasma ligands were measured potentiometrically or estimated by linear free energy relationships (LFER). These data were added to the ECCLES database in order to construct a blood plasma model for SnII. From this model it is predicted that SnII will remain bound to the polymer (PEI-MP) in blood plasma and therefore, have only slight reticuloendothelial uptake. Preliminary primate studies indeed proved that the complex between SnII and PEI-MP remains intact in blood plasma, which is consistent with the observation for PEI-MP labeled with 99mTc. From these data, it was also possible to explain in retrospect the lower bone uptake, the slow blood clearance and the liver uptake of the agents 117mSn(II) DTPA and 117mSn(II) HEDP agents as reported in the literature. 相似文献
8.
D. Roeland Boer Huub Kooijman Marinus Groen Jaap van der Louw Jan Kelder Jan Kroon 《Acta Crystallographica. Section C, Structural Chemistry》2001,57(10):1177-1181
The crystal structures of five follicular fluid meiosis-activating sterol-related Δ8,14-sterol compounds are presented. These are 4,4-dimethyl-23-phenyl-24-nor-5α-chola-8,14-dien-3β-ol, C31H44O, 4,4-dimethyl-22-phenyl-23,24-dinor-5α-chola-8,14-dien-3β-ol, C30H42O, (20R)-4,4-dimethyl-22-oxa-5α,20-cholesta-8,14,24-trien-3β-ol, C28H44O2, 4,4-dimethyl-23-phenyl-22-oxa-24-nor-5α-chola-8,14-dien-3β-ol–water (4/1), 4C30H42O2·H2O, and 4,4-dimethyl-5α-cholesta-8,14-dien-3-one, C29H46O. Two of the derivatives are inactive and three are active as agonists. Preliminary structure–activity relationship studies showed that the positions of the double bonds in the skeleton and the structures of the side chains are important determinants for activity. The conformations of the skeletons were compared with double-bond isomers retrieved from the Cambridge Structural Database [Allen & Kennard (1993). Chem. Des. Autom. News, 8 , 1, 31–37]; no significant differences were found. Thus, conformational changes induced by the double bonds are not discriminative with respect to the activity of the compounds. Comparisons of the side-chain conformations of active and inactive structures revealed that the crystal structures were not conclusive as far as correlation of conformation and activity of the side chains were concerned. 相似文献
9.
At elevated temperatures. OH is found to abstract H from benzene derivatives; in air, phenols are then generated via reversible addition of ArOO· to arene. 相似文献
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