bluuebunny/crossref_metadata_2025_split huggingface dataset:
Synthesis of Secondary, Tertiary and Quaternary 1,3,5‐Triazapenta‐1,3‐dienes and Their CoII, ZnII, PdII, CuII and BF2 Coordination Compounds
Authors: Häger Ina , Fröhlich Roland , Würthwein Ernst‐Ulrich 
Published: April 2009

AbstractThe secondary and tertiary 1,3,5‐triazapenta‐1,3‐dienes 2 and 3 are easily obtained by the reaction of N‐imidoyl chlorides with amidines or from ethyl N‐imidoylimidoates 5 and primary amines. In a new synthetic pathway the compounds 5 were prepared by the reaction of imidoates in their protonated or free form with N‐imidoyl chlorides. A quaternary 1,3,5‐triazapenta‐1,3‐diene 4a is obtained by the reaction of the imidoate 5b with pyrrolidine. X‐ray diffraction studies of the tertiary 1,3,5‐triazapenta‐1,3‐diene 3c and its protonated form 3c·HCl allow the comparison of different patterns of intermolecular hydrogen bonding in the solid state. Two equivalents of a secondary 1,3,5‐triazapenta‐1,3‐diene 2 were treated at room temperature after deprotonation with potassium tert‐butoxide with CuCl2, Ni(ClO4)2 or with Pd(ac)2 (without deprotonation) to give the corresponding neutral 2:1 chelate complexes (2a)2·Cu, (2a)2·Ni and (2b)2·Pd, respectively. A fluorescent boron complex 2b·BF2 was obtained by reacting 2b with boron trifluoride–diethyl ether. From the tertiary triazapentadiene 3c and CoCl2 or ZnCl2 the six‐membered 1:1 chelate complexes 3c·CoCl2 and 3c·ZnCl2, respectively, were obtained. In these cases a proton shift from the terminal nitrogen atom of the free ligand to the central nitrogen atom of the complex was observed. Two equivalents of 3c reacted at room temperature with Cu(ac)2 or Pd(ac)2 to form the neutral 2:1 chelate complexes (3c)2·Cu and (3c)2·Pd, respectively. A fluorescent 1:1 boron complex 3c·BF2 was obtained from 3c and boron trifluoride–diethyl ether. In all cases the triazapentadienes act as neutral or anionic bidentate ligands to form six‐membered chelates with the metal ion or the boron centre. Most of the complexes were completely characterized, which included X‐ray crystallography.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)
Supramolecular Architectures and Magnetic Properties of Self‐Assembled Windmill‐Like Dinuclear Copper(II) Complexes with Purine Ligands
Authors: Cepeda Javier , Castillo Oscar , García‐Terán Juan P. , Luque Antonio , Pérez‐Yáñez Sonia , Román Pascual 
Published: April 2009

AbstractThree new CuII compounds, [Cu2(μ‐ade)4(H2O)2]·(bpa)·8H2O (1), [Cu2(μ‐Hade)4(H2O)2](NO3)4·2[Cu(pic)2(H2O)]·6H2O (2) and [Cu2(μ‐6Clpur)4(H2O)2]·~6H2O (3) [in which ade = adeninate anion, Hade = 7H‐adenine, 6Clpur = 6‐chloropurinate anion, bpa = 1,2‐bis(4‐pyridyl)ethane, pic = 2‐pyridinecarboxylate anion], are reported. Their crystal structures consist of dinuclear copper(II) units, in which four ligands arranged in a windmill‐like fashion bridge the metal ions through a nonlinear NCN group. Supramolecular crystal building of compound 1 is essentially maintained by an extensive network of hydrogen‐bonding interactions that involves direct contacts between the nucleobases. In contrast, in compound 2 there is no evidence for direct interactions between the nucleobases, but the hydrogen bonds among the nucleobases and nitrate counteranions are especially relevant. Compound 3 is mainly built up from T‐shaped noncovalent Cl···N interactions and hydrogen‐bonding interactions involving the crystallization solvent molecules. Magnetic susceptibility measurements indicate the presence of strong intradimeric antiferromagnetic interactions with large singlet–triplet splittings of –222 (for 1), –288 (for 2) and –255 (for 3) cm–1. DFT calculations were carried out to evaluate the dependence of the magnetic coupling value as a function of some key structural parameters: the Cu–N basal plane distance, the axial Cu–Ow distance and the Cu···Cu distance. DFT calculations also revealed that the nature of the bridging ligand is a crucial factor. In this way, the strength to transmit the magnetic interaction of the different bridging ligands is explained on the basis of the number of electron lone pairs.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)
The development of a two‐leveled two cross interface for on‐line coupling solid‐phase extraction and capillary electrophoresis‐mass spectrometry
Authors: Lee Wei‐Han , Her Guor‐Rong 
Published: April 2009

AbstractA two‐leveled, two cross PDMS‐based interface for on‐line coupling of SPE with CE‐MS was proposed. In this interface, the SPE column and the CE separation column were positioned orthogonally and two crosses were fabricated on the interface. With the two cross design, the operation of SPE could be performed independently without unexpected flow through leakage into the separation column. The performance of the interface was optimized using a peptide mixture. The position of the SPE column related to the CE separation channel was found to be critical to the performance of the system. Under the optimal position, the separation efficiency was similar to a CE‐MS experiment without SPE. The peptide signals were enhanced 50‐ to 100‐fold and the repeatability was within 4% RSD for migration time and 10% RSD for peak area. A tryptic digest of cytochrome c was used to demonstrate the feasibility of the interface in protein identification at a level of 1 ng/μL.
Multiresidue determination of penicillins in environmental waters and chicken muscle samples by means of capillary electrophoresis‐tandem mass spectrometry
Authors: Bailón‐Pérez M. Isabel , García‐Campaña Ana M. , del Olmo Iruela Monsalud , Cruces‐Blanco Carmen , Gracia Laura Gámiz 
Published: April 2009

AbstractA new analytical method based on CZE coupled with tandem MS detection (CE‐MS/MS) has been developed for the simultaneous determination of nine penicillins of human and veterinary use (nafcillin, dicloxacillin, cloxacillin, oxacillin, ampicillin, penicillin G, amoxicillin, penicillin V and piperacillin), whose levels are regulated by the EU Council regulation No. 2377/90 in animal edible tissues. CE separation conditions, sheath liquid composition and electrospray parameters have been carefully optimized to reach high sensitivity and precision. Separation was carried out in a 96 cm total length fused‐silica capillary (50 μm id, 360 μm od) using 60 mM ammonium acetate at pH 6.0 as running buffer. Lomefloxacin was used as internal standard. MS/MS experiments were carried out using an IT as analyzer operating in multiple reaction monitoring mode to achieve the minimum number of identification points established by the 2002/657/EC European Decision. The use of an SPE procedure in two steps, combining Oasis hydrophilic–liphophilic balance and Alumina N cartridges provide a satisfactory preconcentration and clean up treatment for meat samples after extraction of the compounds with ACN. Only Oasis hydrophilic–liphophilic balance cartridges were necessary in water samples to obtain adequate recoveries. The method has been characterized for its use in meat and water samples, using matrix‐matched calibrations. For chicken muscle samples, LODs between 8 and 12 μg/kg have been obtained, in all cases lower than the maximum residue limits permitted. For water samples LODs from 0.18 to 0.26 μg/L could ensure its satisfactory application in aquatic samples.
Development and characterization of cIEF‐MALDI‐TOF MS for protein analysis
Authors: Silvertand Linda H. H. , Toraño Javier Sastre , de Jong Gerhardus J. , van Bennekom Wouter P. 
Published: April 2009

AbstractThis paper describes the hyphenation of cIEF and MALDI‐TOF MS via a fractionation or spotting device. After focusing in cIEF the compounds are hydrodynamically mobilized and deposited on a MALDI target plate using a sheath liquid interface, which provides the catholyte solution and the electrical ground. From previous experiments, sample conditions that resulted in a high resolution in cIEF and acceptable protein signal intensity in MS were selected [Silvertand et al., Electrophoresis, 2008, 29, 1985–1996]. Besides the mixture of test proteins, the sample solution contains 1% Pharmalyte, 0.3% hydroxyethyl cellulose and 0.1% Tween 20 and is used for both optimization as well as characterization of the cIEF‐MALDI‐TOF MS system. Hyphenation problems encountered are mainly due to transfer of the liquid from the needle to the MALDI target plate and are solved by choosing the proper sheath catholyte (200 mM NH4OH in 50% methanol with 0.1% Tween20). MS electropherograms were reconstructed by plotting the intensities of the m/z values corresponding to the proteins versus migration time (related to spot number). Reproducibility, peak width and signal intensity for different focusing and spotting (fractionation) times were calculated using these reconstructed MS electropherograms as well as the UV electropherograms. The best results were obtained with focusing time of 75 min (no under‐ or overfocusing) and a spotting time of 5 s (highest protein signal intensity in MS). The applicability of the system is demonstrated by the analysis of a biopharmaceutical (glucagon) and its deamidation product.
Full operator algorithm for hybrid simulation
Authors: Hung Chung‐Chan , El‐Tawil Sherif 
Published: April 2009

AbstractOne of the weaknesses of the operator splitting method (OSM) is that its corrector step employs the approximation that incremental forces are linearly related to the tested structure's initial stiffness matrix. This paper presents a new predictor–corrector technique in which the assumptions about the tested structure's response are shifted to the predictor step, which results in an enhancement in overall simulation accuracy, especially for nonlinear structures. Unlike OSM, which splits the displacement and velocity operators into explicit and implicit terms, the new method uses predicted accelerations to compute fully explicit displacement and velocity values in the predictor step. Another advantage of the proposed technique, termed the full operator method (FOM) is that its formulation makes it suitable for both quasi‐static and real‐time hybrid simulation. The effectiveness of FOM is first evaluated by investigating error propagation in an undamped single degree‐of‐freedom model. It is shown that the corrector step in FOM is able to significantly suppress aberrant simulation results caused by incorrect estimation of the structure's stiffness matrix. The performance of FOM is demonstrated by exercising two additional models, which exhibit significant inelastic behavior under the prescribed excitation. The simulation results show that the proposed FOM algorithm is capable of producing accurate solutions and that the corrector step is influential in effectively reducing simulation errors. It is also shown that FOM suppresses actuator displacement control errors because of its reliance on measured quantities in the corrector step. Copyright © 2009 John Wiley & Sons, Ltd.
Aroma‐active compounds of Beijing roast duck
Authors: Chen Gengjun , Song Huanlu , Ma Changwei 
Published: April 2009

AbstractThe aroma‐active compounds of Beijing roast duck were investigated by using aroma extract dilution analysis (AEDA), dynamic headspace dilution analysis (DHDA), gas chromatography–olfactometry–mass spectrometry (GC–O–MS) and odour activity values (OAVs; ratio of concentration to odour threshold). The following volatile components are the predominant odorants of Beijing roast duck: 3‐methylbutanal, hexanal, dimethyl trisulphide, methional, 2‐methylbutanal, octanal, heptanal, 2‐methyl‐3‐furanthiol, 2‐furfurylthiol, 2‐ethyl‐3,5‐dimethylpyrazine, (E,E)‐2,4‐nonadienal, 1‐octen‐3‐ol, nonanal, decanal, (E)‐2‐decenal, (E,E)‐2,4‐decadienal, (E)‐2‐nonenal, (E,Z)‐2,6‐nonadienal, (E,E)‐2,4‐octadienal (fatty, fried), etc. Due to abundant flavour precursors of Beijing crammed duck (raw material of Beijing roast duck), such as amino acids, esters, vitamins and carbohydrates, and the special process (e.g. roasting, drying, etc.), the identified compounds above were likely derived from different kinds of reactions, such as degradation of fatty acids and amino acids, Maillard/Strecker and other associated reactions, which were considered to account for the typical aroma of Beijing roast duck. Copyright © 2009 John Wiley & Sons, Ltd.
Effects of surface waves on hydrodynamic pressures on rigid dams with arbitrary upstream face
Authors: Avilés Javier , Suárez Martha 
Published: April 2009

AbstractThe effects of surface gravity waves on earthquake‐induced hydrodynamic pressures on rigid dams with nonvertical upstream face are examined, taking the compressibility and viscosity of water into account. A simple closed‐form solution is obtained by using the Trefftz numerical method. The boundary under study is reduced to the upstream face only and the degrees of freedom of the problem are restricted to the number of trial functions used for analysis. For harmonic base excitation, a number of numerical examples for various geometries of the upstream face are presented. The hydrodynamic pressure distribution, the resultant lateral force and its effective height of application are evaluated. The results are strongly influenced by the upstream shape and, in a lesser degree, by the consideration of surface waves. Copyright © 2009 John Wiley & Sons, Ltd.
Both DNA damage and mitochondrial dysfunction are involved in novel oxadiazolo[3,4‐d]pyrimidine nucleoside derivatives‐induced cancer cell death
Authors: Liu Hai‐liang , Xu Jing‐jing , Dai Xiao‐min , Shi Jing‐Bo , Xu Song , Gao Jing , Yao Qi‐zheng , Liu Feng 
Published: April 2009

AbstractEight novel oxdiazolo[3,4‐d]pyrimidine nucleoside derivatives (I‐VIII) were synthesized to investigate their anti‐tumor effects and possible mechanisms. Four human cancer cell lines including Hela, ECA109, HepG2 and A459 cells were used. Compounds VI and VIII showed significant inhibition on cancer cell proliferation by MTT assay and IC50 values were around 30–70 µmol l−1. Both compounds could release nitric oxide (NO), led to a significant intracellular free Ca2+ overloading and resulted in mitochondrial dysfunction, showing a decrease in mitochondrial membrane potential in HepG2 cells in a dose‐dependent manner. Furthermore, compound VIII induced obvious DNA damage on HepG2 cells. These data indicate that compounds VI and VIII are two active antitumor compounds, and both DNA damage and mitochondrial dysfunction are involved in the mechanisms underlying oxadiazolo[3,4‐d]pyrimidine nucleoside derivative‐induced cancer cell death, which might also be related to the released NO. Copyright © 2009 John Wiley & Sons, Ltd.
Differential developmental toxicities of di‐n‐hexyl phthalate and dicyclohexyl phthalate administered orally to rats
Authors: Saillenfait Anne‐Marie , Gallissot Frédéric , Sabaté Jean‐Philippe 
Published: April 2009

AbstractThe objective of this study was to evaluate the developmental toxic potential of di‐n‐hexyl phthalate (DnHP) and dicyclohexyl phthalate (DCHP) in rats. Pregnant Sprague–Dawley rats were exposed to DnHP or DCHP at doses of 0 (olive oil), 250, 500 and 750 mg kg–1 per day, by gavage, on gestational days (GD) 6–20. Maternal food consumption and body weight gain were significantly reduced at 750 mg kg–1 per day of DnHP and at the two high doses of DCHP. Slight changes in liver weight associated with peroxisomal enzyme induction were seen in dams treated with DnHP or DCHP. DnHP caused dose‐related developmental toxic effects, including marked embryo mortality at 750 mg kg–1 per day, and presence of malformations (mainly cleft palate, eye defects and axial skeleton abnormalities) and significant decreases in fetal weight at 500 and 750 mg kg–1 per day. Significant delay of ossification and increase in the incidence of skeletal variants (e.g. supernumerary lumbar ribs) also appeared at 250 mg kg–1 per day. DCHP produced fetal growth retardation at 750 mg kg–1 per day, as evidenced by significant reduction of fetal weight. DnHP and DCHP induced a significant and dose‐related decrease in the anogenital distance of male fetuses at all doses, and there was a significant increase in the incidence of male fetuses with undescended testis at 500 and 750 mg kg–1 per day of DnHP. In conclusion, DnHP showed clear embryolethality and teratogenicity, but not DCHP. There was evidence that both phthalates could alter the development of the male reproductive system after in utero exposure, DnHP being much more potent than DCHP. Copyright © 2009 John Wiley & Sons, Ltd.
S‐allylcysteine attenuates renal injury by altering the expressions of iNOS and matrix metallo proteinase‐2 during cyclosporine‐induced nephrotoxicity in Wistar rats
Authors: Magendiramani Vinayagam , Umesalma Syed , Kalayarasan Srinivasan , Nagendraprabhu Ponnuraj , Arunkumar Jagadeesan , Sudhandiran Ganapasam 
Published: April 2009

AbstractCyclosporine A (CsA) is the first choice immunosuppressant used for the prevention of allograft rejection in solid organ transplantation and immune‐mediated diseases. Reactive oxygen species‐induced oxidative stress and lipid peroxidation are implicated in the pathophysiology of CsA‐induced renal injury. In this work, we have studied the effect of a garlic‐derived compound, S‐allylcysteine (SAC) on CsA‐induced nephrotoxicity. CsA‐induced nephrotoxicity was assessed in terms of increased activities of serum marker enzymes and levels of kidney markers. CsA administration induced significant elevation in lipid peroxidation along with abnormal levels of enzymic and non‐enzymic antioxidants in the kidneys of the rats. SAC administration improved renal function by bringing about a significant decrease in peroxidative levels and increase in antioxidant status. Elevated expressions of inducible nitric oxide synthase (iNOS) and nuclear factor kappa B (NF‐κB) due to CsA administration were reduced by SAC treatment. An increase in the expression of matrix metalloproteinase‐2 (MMP‐2) was evident in CsA‐induced groups of rats, which was moderately reduced in SAC treated rats. An increase in the levels of serum constituent's urea, uric acid and creatinine was observed in the CsA‐induced rats, which was reduced upon treatment with SAC. These results indicate that SAC has a protective action against CsA‐induced nephrotoxicity which is also supported by histopathological studies. A comparative study of the antioxidant vitamin C and SAC is more valuable to assess the efficacy of the drug that can be used for the treatment of nephrotoxicity. Copyright © 2009 John Wiley & Sons, Ltd.
Kauren‐19‐oic acid induces DNA damage followed by apoptosis in human leukemia cells
Authors: Cavalcanti Bruno C. , Bezerra Daniel P. , Magalhães Hemerson I. F. , Moraes Manoel O. , Lima Mary Anne S. , Silveira Edilberto R. , Câmara Cláudio A. G. , Rao Vietla S. , Pessoa Cláudia , Costa‐Lotufo Letícia V. 
Published: April 2009

AbstractThis study evaluated the potential cytotoxicity of the natural diterpenoids kauren‐19‐oic acid (KA), 14‐hydroxy‐kaurane (1) and xylopic acid (2), and semi‐synthetic derivatives of KA (3–5) towards human cancer cell lines (K562, HL60, MDA‐MB435 and SF295) and lymphocytes. Mouse erythrocytes were used to verify a possible hemolytic activity Cytotoxicity mechanisms were investigated in HL60 cells. KA showed a moderate antiproliferative effect in MTT assay towards all cancer cells (IC50, 9.1–14.3 µg ml−1). However, KA appeared not selective to cancer cells, since it also inhibited the lymphocytes proliferation (IC50, 12.6 µg ml−1). Unlike KA, compounds 1–5 displayed no cytotoxicity and were also free from antiproliferative and hemolytic effects, suggesting that the exocyclic double bond (C16) unit may be the active pharmacophore of KA cytotoxicity. KA‐treated HL60 cells displayed decreased proliferation (5‐bromo‐2';‐deoxyuridine incorporation assay) and topoisomerase I activity (DNA relaxation assay). These assays revealed that KA primarily intercalates with DNA and not with topoisomerase I. Fluorescence microscopy using AO/EB (acridine orange/ethidium bromide) staining indicated that KA can induce both apoptosis and necrosis in HL‐60 cell cultures, which corroborate the findings with MTT. From these findings, we conclude that KA, although demonstrating cytotoxic potential, may have a limited or poor therapeutic potential due to lack of selectivity to tumor cells. Further studies on the structure modification of KA and the mechanism of the new derivatives are currently in progress. Copyright © 2009 John Wiley & Sons, Ltd.
Quantum chemical predictions concerning two unknown “mesoionic” compounds
Authors: Paoloni Leonello , Ciampi Antonio 
Published: April 2009

AbstractThe Pariser‐Parr‐Pople approximation was used to predict the properties of compounds I, 3‐oxo‐2H‐1,2,3‐triazolo[3,4‐a]pyridine, and II, 3‐oxoisoxazolo[2,3‐a]pyridine, originated by joining a pyridine ring to two sydnone‐like heterocyclic systems not yet reported in the literature. A parallel computation was carried out for two known compounds of similar structure, to give the predictions a better reliability through the comparison with observed spectral data and chemical behaviour. Compound I is expected to be stable, with an absorption spectrum similar to III, 2‐oxo‐1,3,4‐oxadiazolo[4,5‐a]pyridine, and chemical properties analogous to IV, 1‐methyl‐3‐oxo‐1,2,4‐triazolo‐[4,3‐a]pyridine. A reaction path is suggested for obtaining from I the unknown isomeric structure V, 3‐oxo‐1H‐1,2,3‐triazolo[3,4‐a]pyridine. Compound II is predicted as an unstable orange‐red substance which should be handled and kept at low temperatures.
The syntheses and thermal rearrangement of some methiodides of s‐triazolo[4,3‐a]pyridines
Authors: Paudler William W. , Brumbaugh Richard J. 
Published: April 2009

AbstractIt has been shown that the N‐methylation, with methyl iodide, of s‐triazolo[4,3‐a]pyridines affords a mixture of the N‐1 and the N‐2 methiodides. The N‐2 methiodides can be thermally rearranged to the N‐1 methiodides. The 8‐methyl N‐1 methiodides exhibit peri interaction between the two methyl groups. This interaction is reflected in greater stability of the N‐2 methiodide vs. the N‐1 compound.
2‐Isoxazoline derivatives. Part I. A base‐promoted fragmentation of 2‐isoxazolines
Authors: Bianchi Giorgio , Gandolfi Remo , Grünanger Paolo 
Published: April 2009

AbstractThe action of bases on 3‐aryl (or alkyl)‐5‐acyl‐2‐isoxazolines has been shown to give rise to the corresponding aromatic (or aliphatic) nitriles and α‐diketones by cleavage of the O‐N and C3C4 bonds of the heterocyclic ring. This fragmentation reaction has been extended to other 2‐isoxazolines substituted in the 5‐position with electron‐attracting groups.
The synthesis of pyridazino[4,5‐d] pyridazines, pyrazino [2,3‐d] pyridazines and a pyrimido [4,5‐d] pyridazine
Authors: DiStefano Lorraine , Castle Raymond N. 
Published: April 2009

AbstractThe synthetic chemistry of the relatively unknown pyridazino [4,5‐d]pyridazine ring system has been extended. 1,4‐Diaminopyridazino [4,5‐d]pyridazine (VIII) has been prepared by two routes, the most interesting of these being the one‐step conversion of 4,5‐dicyanopyridazine into VIII with hydrazine. Upon nitration VIII gave only the mononitramine (X). Attempts to prepare 1,4‐dichloropyridazino [4,5‐d]pyridazine gave only 4‐chloro‐2H‐pyridazino [4,5‐d]pyridazin‐1‐one (XII). Pyrimido [4,5‐d]pyridazine‐1,3‐dione (XIV) was prepared from pyridazine‐4,5‐dicarboxamide (IV). The hydrolysis of 5,8‐dichloropyrazino [2,3‐d]pyridazine (XV) gave 5‐chloropyrazino [2,3‐d]pyridazin‐8‐one (XVII) and likewise the ammonolysis of XV gave 5‐amino‐8‐chloropyrazino [2,3‐d]pyridazine (XX). As expected the hydrolysis of 5,8‐dibromo‐pyrazino [2,3‐d]pyridazine (XXI) gave 5‐bromopyrazino [2,3‐d]pyridazin‐8‐one (XXII). Attempted catalytic dechlorination of 5‐chloropyrazino [2,3‐d]pyridazin‐8‐one (XVII) gave 1,2,3,4‐tetrahydropyrazino [2,3‐d]pyridazin‐5‐one (XIX).
The mass spectra of 1,2,4‐oxadiazolines
Authors: Srivastava R. M. , Clapp Leallyn B. 
Published: April 2009

AbstractThe fragmentation patterns of seven oxadiazolines (compounds I‐VII) were obtained from mass spectral data. Fragmentations a and b (Figure 1) are more important than c. Some of the novel cracking pathways are discussed.