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111.
Alfredo E. Bruno Ronald P. Steer Paul G. Mezey 《Journal of computational chemistry》1983,4(1):104-109
Approximate minimum energy reaction paths have been calculated for two thioketone–enethiol tautomeric systems using an ab initio SCF–MO method. The calculations indicate nearly equal stabil ties of the isolated tautomers in both systems and an energy barrier of ca. 85 kcal/mol for their interconversion. This barrier is expected to be significantly lower in solution as a result of solvent–solute interactions. 相似文献
112.
Corona G Casetta B Sandron S Vaccher E Toffoli G 《Rapid communications in mass spectrometry : RCM》2008,22(4):519-525
A simple and rapid method has been developed and validated for the quantitation of vincristine in human plasma by liquid chromatography/tandem mass spectrometry (LC/MS/MS) with atmospheric pressure chemical ionization using on-line solid-phase extraction. The method uses vinblastine as internal standard and the sample preparation is limited just to a plasma protein precipitation step. Further sample clean-up is carried out on-line through a perfusion column preceding an analytical phenyl LC column, the latter directly connected to the mass spectrometer. Quantitation is performed in multiple reaction monitoring mode using the transitions of m/z 825.3 --> 765.3 and 811.3 --> 751.3 for vincristine and vinblastine respectively. The assay was linear (r2 > or =0.99) in a concentration range from 0.1 to 500 ng/mL. Carry-over, measured on the experimental set-up, was less than 0.04%. Recovery for vincristine and the internal standard was within 90-95%. The intra-day and inter-day assay precision ranged from 1.2% to 6.8% RSD while mean percentage deviation from nominal value ranged from 0.01% to 6.1%. The proposed assay was found suitable for pharmacokinetics investigations and clinical therapeutic drug monitoring especially in pediatric cancer patients. 相似文献
113.
Guido D. Frey Rian D. Dewhurst Shazia Kousar Bruno Donnadieu Guy Bertrand 《Journal of organometallic chemistry》2008,693(8-9):1674-1682
A series of mono- and dicarbene gold(I) complexes of types Au(CAAC)(Cl) [CAAC = cyclic (alkyl)(amino)carbene] (1) and [Au(CAAC)2]+[X]? (X = Cl, AuCl2) (2) have been prepared through reaction of AuCl(SMe2) with free carbenes a–e, and structurally characterized by single X-ray diffraction studies (1a, 1b, 2d, 2e). In addition two new free cyclic (alkyl)(amino)carbenes (c and e) have been synthesized. 相似文献
114.
Thyreostatic compounds could be illegally administered to animals in order to obtain a weight gain due to a higher retention of water in the edible tissue and the gastro-intestinal tract. In the European Union their use for animal production is banned since 1981. Recently a highly sensitive method exploiting the determination of thyreostats with 3-iodobenzylbromide prior to purification to determine thyreostats in urine and other matrices was reported. For the first time, the UPLC instrumentation was used to separate the 3-iodobenzyl derivatives of various thyreostats. The deuterated internal standards tapazole-d3 and propylthiouracil-d5 were for the first time used for the quantification of tapazole, thiouracil, methylthiouracil, propylthiouracil, phenylthiouracil and mercaptobenzimidazole. The confirmative quantitative liquid chromatographic tandem mass spectrometric (LC–MS/MS) method was validated according to Commission Decision 2002/657/EC. The decision limit (CCα) and the detection capability (CCβ) were found to be for all compounds below the recommended value of 10 μg kg−1. 相似文献
115.
Bruno Bernet Zeena Johar Anne Ritter Bernhard Jaun Andrea Vasella 《Helvetica chimica acta》2009,92(12):2596-2630
The tritylated and silylated self‐complementary A*[s]U*[s]A*[s]U* and U*[s]A*[s]U*[s]A* tetramers 18 and 24 , linked by thiomethylene groups (abbreviated as [s]) between a nucleobase and C(5′) of the neighbouring nucleoside unit were prepared by a linear synthesis based on S‐alkylation of 5′‐thionucleosides by 6‐(chloromethyl)uridines, 7 or 10 , or 8‐(chloromethyl)adenosines, 12 or 15 . The tetramers 18 and 24 were detritylated to the monoalcohols 19 and 25 , and these were desilylated to the diols 20 and 26 , respectively. The association of the tetramers 18 – 21 and 24 – 26 in CDCl3 or in CDCl3/(D6)DMSO 95 : 5 was investigated by the concentration dependence of the chemical shifts for H? N(3) or H2N? C(6). The formation of cyclic duplexes connected by four base pairs is favoured by the presence of one and especially of two OH groups. The diol 20 with the AUAU sequence prefers reverse‐Hoogsteen, and diol 26 with the UAUA sequence Watson–Crick base pairing. The structure of the cyclic duplex of 26 in CDCl3 at 2° was derived by a combination of AMBER* modeling and simulated annealing with NMR‐derived distance and torsion‐angle restraints resulting in a Watson–Crick base‐paired right‐handed antiparallel helix showing large roll angles, especially between the centre base pairs, leading to a bent helix axis. 相似文献
116.
Valli L Casilli S Giotta L Pignataro B Conoci S Borovkov VV Inoue Y Sortino S 《The journal of physical chemistry. B》2006,110(10):4691-4698
This work reports on the structural and spectroscopic properties of ethane-bridged Zn porphyrin dimers (1) in Langmuir-Sch?fer (LS) thin films by combining scanning force microscopy (SFM) with film balance, UV-vis absorption, fluorescence, and nanosecond laser flash photolysis measurements. Results show that depending on the surface pressure the Langmuir films of pure 1 can be arranged in two different condensed phases, whereas SFM of the LS films shows characteristic fractal networks constituted by nanoscopic aggregates. The spectral findings agree with a picture in which 1 is apparently present in the anti conformation but aggregated in a sort of H-type structure whose optical features resemble those of the syn conformer. This type of structure is not responsive to light stimuli. By diluting 1 in arachidic acid the porphyrin aggregation is significantly minimized with 1 exhibiting almost exclusively the anti conformation. As a result the LS films become photoresponsive, showing fluorescence emission and triplet-triplet transient absorption. 相似文献
117.
Bénisvy L Halut S Donnadieu B Tuchagues JP Chottard JC Li Y 《Inorganic chemistry》2006,45(6):2403-2405
Using the multidentate ligand bis(N-methylimidazol-2-yl)-3-methylthiopropanol (L), the mononuclear iron(II) hydroxo and iron(III) dihydroxo complexes [Fe(II)(L)2(OH)](BF4) (1) and [Fe(III)(L)2(OH)2](BF4) (2) have been synthesized and characterized by X-ray diffraction and spectroscopic methods. The X-ray data suggest that the remarkable stability of the Fe-OH bond(s) in both compounds results from intermolecular hydrogen-bonding interactions between the hydroxo ligand(s) and the tertiary hydroxyl of the L ligands, which prevent further intermolecular reactions. 相似文献
118.
An efficient synthetic method for 3-aryl-5-dichloromethyl-2-isoxazolines has been established. Reactions between anhydrous chloral and acetophenones in hot acetic acid lead to 1-aryl-4,4,4-trichloro-3-hydroxybutan-1-ones (chloralacetophenones), which provided 1-aryl-4,4-dichlorobut-3-en-1-ones (2,2-dichlorovinylacetophenones) by dehydration and subsequent electrochemical reduction. These β,γ-unsaturated enones reacted with hydroxylamine yielding oxime intermediates whose treatment with aqueous sodium hydroxide gave novel 3-aryl-5-dichloromethyl-2-isoxazolines in fair to high yields. The molecular structure of a member of this family of compounds, 5-dichoromethy1-3-(4-methoxyphenyl)-2-isoxazoline, was determined by X-ray crystallography. 相似文献
119.
Mohamed Fatnassi Corine Tourné-Péteilh Pradial Peralta Thomas Cacciaguerra Philippe Dieudonné Jean-Marie Devoisselle Bruno Alonso 《Journal of Sol-Gel Science and Technology》2013,68(2):307-316
Two model drugs of different physico-chemical and pharmaceutical properties (ibuprofen, acetaminophen) have been incorporated together or separately in silica-based microspheres using sol–gel and spray-drying processes. A variable amount of a neutral surfactant Brij-56© has also been added. The properties of the microspheres vary significantly depending on their composition. Three kinds of texture are identified: (1) silica containing spheroid nano-domains (formed by ibuprofen; diameters between 20 and 100 nm), (2) silica containing worm-like mesophases (formed by Brij-56© and both model drugs, typical correlation distances ~6 nm), (3) silica intimately mixed with the drug (acetaminophen) without visible phase-separation. The kinetics of drug release in simulated intestinal fluid strongly depend on these textures. The association of ibuprofen and acetaminophen in a single type of microsphere and without surfactant favours a concomitant release. Possible mechanisms of materials’ formation are discussed. 相似文献
120.
Alberto Palazzolo Sophie Feuillastre Viktor Pfeifer Sbastien Garcia‐Argote Donia Bouzouita Simon Tricard Cline Chollet Elodie Marcon David‐Alexandre Buisson Sophie Cholet Franois Fenaille Guy Lippens Bruno Chaudret Grgory Pieters 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(15):4945-4949
A general approach for the efficient hydrogen‐isotope exchange of nucleobase derivatives is described. Catalyzed by ruthenium nanoparticles, using mild reaction conditions, and involving either D2 or T2 as isotopic sources, this reaction possesses a wide substrate scope and a high solvent tolerability. This novel method facilitates the access to essential diagnostic tools in drug discovery and development: tritiated pharmaceuticals with high specific activities and deuterated oligonucleotides suitable for use as internal standards during LC‐MS quantification. 相似文献