bluuebunny/crossref_metadata_2025_split huggingface dataset:
A New Entry to Bis‐Tröger’s Bases
Authors: Mas Thierry , Pardo Carmen , Salort Francisca , Elguero José , Torres M. Rosario 
Published: February 2004

AbstractThis paper reports the use of p‐phenylenediamine to prepare bis‐Tröger’s bases. The methyl,nitro‐substituted bis‐Tröger’s base 5, already previously prepared by another procedure, was obtained in fewer steps, although with no improvement in the yield of the desired syn isomer. The symmetric dinitro‐substituted bis‐Tröger’s base 17, which cannot be prepared by the older method, was then synthesized. Its structure was determined by mass spectrometry, 2D NMR spectroscopy, and, in the case of the syn isomer, by X‐ray crystallography. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
Red‐ and Blue‐Shifts in Oligo(1,4‐phenyleneethynylene)s Having Terminal Donor−Acceptor Substitutions
Authors: Meier Herbert , Mühling Bastian , Kolshorn Heinz 
Published: February 2004

AbstractFour series of oligo(1,4‐phenyleneethynylene)s (OPEs), 1−4 (a−d), each having a terminal dialkylamino group as their electron donor, were prepared by applying Sonogashira−Hagihara reactions and a protecting group strategy. To study the influence that the push−pull effect has on the long‐wavelength absorption, three of the four series of OPEs contain terminal acceptor groups (CN, CHO, NO2). Extending the conjugation (increasing the number of repeat units, n) lowers the energy E(n) of the electron transition in the purely donor‐substituted series 1a−4a (bathochromic shift). This effect is superimposed in the push−pull series 1−4 (b−d) by the effect of the intramolecular charge transfer (ICT), which decreases with increasing the distance between the donor and acceptor groups. In the case of the relatively weak acceptor CN, both effects annihilate one another, whereas the reduction of the ICT predominates in the CHO and NO2 series. Therefore, E(n) is virtually independent of n in the CN series 1b−4b and shows a hypsochromic effect in the CHO and NO2 series (1c−4c and 1d−4d, respectively). We rationalize these results based on AM1−INDO/S calculations. The results of the commonly used intuitive VB model having electroneutral and zwitterionic resonance structures are compared with those of a more appropriate MO model having dipole segments at both chain ends. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
Highly Regio‐ and Diastereoselective Chromium(0)‐Catalysed Cyclopropanation of 1‐Alkoxy‐1,3‐dienes with Diazo Compounds
Authors: Hahn Norbert D. , Nieger Martin , Dötz Karl Heinz 
Published: February 2004

AbstractPentacarbonyl(η2‐cis‐cyclooctene)chromium(0) (1) is an efficient catalyst for diazo decomposition and selective [2+1]‐cycloaddition reactions of the resulting carbene intermediates with electron‐rich dienes. The cyclopropanation of 1‐alkoxy‐1,3‐butadienes 4−8 with 9‐diazo‐9H‐fluorene (2) yields vinylspirocyclopropanes 9−13 in good to excellent yields, as single regioisomers arising from carbene transfer to the less substituted C=C bond. The pentacarbonylchromium‐catalysed cyclopropanation with ethyl α‐diazophenylacetate (3) gives the corresponding vinylcyclopropanecarboxylates 16−20 in very good yields and with exceptionally high trans stereoselectivities (> 95%). (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
Total Syntheses and Biological Assessment of Macrocyclic Glycolipids
Authors: Fürstner Alois 
Published: February 2004

AbstractNovel strategies for the synthesis of structurally complex macrocyclic glycolipids are outlined which have opened concise and highly flexible entries into various resin glycosides and sugar‐based macrodiolides. The key design elements consist of either a ring‐closing alkene (RCM) or alkyne metathesis (RCAM) event or a newly developed template‐directed dilactonization reaction. The performance and excellent application profile of these transformations are illustrated by the total syntheses of tricolorin A and G, woodrosin I, sophorolipid lactone, cycloviracin B1, glucolipsin A, and various analogues thereof. A brief survey of the biological activities exerted by these amphiphilic natural products is provided. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
Fluorinated Heterocyclic Compounds − The First Example of an Irreversible Ring‐Degenerate Rearrangement on Five‐Membered Heterocycles by Attack of an External Bidentate Nucleophile
Authors: Buscemi Silvestre , Pace Andrea , Pibiri Ivana , Vivona Nicolò , Lanza Camilla Zaira , Spinelli Domenico 
Published: February 2004

AbstractThe reactions of 5‐perfluoroalkyl‐1,2,4‐oxadiazoles 3 with hydroxylamine in DMF give the regioisomeric 3‐perfluoroalkyl‐1,2,4‐oxadiazoles 4 in excellent yields. This process is the first example of ring‐degenerate rearrangement (RDR) occurring on five‐membered heterocycles by attack of an external bidentate nucleophile, which replaces two heteroatoms of the ring. We suggest that an ANRORC‐like mechanism occurs in which the addition of the nucleophilic nitrogen atom (NH2OH) on the C(5) atom of 3 is followed by ring opening and irreversible ring‐degenerate closure by attack of the nucleophilic oxygen atom (=NOH) on the C(3) atom of the original ring, realizing an elegant and efficient synthesis of 4 by a C(3)−C(5) annular switch. Ab initio computations on the starting materials and final products, as well as on the proposed intermediates, support the mechanism and shed light on the features of the reaction. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
Asymmetric Synthesis of β‐Amino Acid and Amide Derivatives by Catalytic Conjugate Addition of Aromatic Amines to N‐Alkenoylcarbamates
Authors: Li Kelin , Cheng Xiaohui , Hii King Kuok (Mimi) 
Published: February 2004

AbstractWe report a highly active palladium catalyst for the enantioselective conjugate addition of primary aromatic amines to N‐alkenoylcarbamates, furnishing β‐amino N‐Boc‐amides in extremely high yields (>99 %) and unprecedented optical purity (>99 % ee) with just 2 mol % catalyst loading. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
Cover Picture: Total Syntheses and Biological Assessment of Macrocyclic Glycolipids (Eur. J. Org. Chem. 5/2004)
Authors: Fürstner Alois 
Published: February 2004

AbstractThe cover picture shows the dried calyx of Ipomoea tuberosa L. (Merremia tuberosa) which gives this plant its descriptive common name “woodrose”. One of its bioactive metabolites is the resin glycoside “woodrosin I” shown in the inset, the first total synthesis of which is summarized as part of the Microreview by A. Fürstner on the chemistry and biology of complex glycolipids on p. 943 ff.
Development of an Amperometric Biosensor for β‐N‐Oxalyl‐L‐α,β‐Diaminopropionic Acid (β‐ODAP)
Authors: Beyene Negussie W. , Moderegger Helmut , Kalcher Kurt 
Published: February 2004

AbstractAn amperometric method for the determination of the neurotoxic amino acid β‐N‐oxalyl‐L‐α,β‐diaminopropionic acid (β‐ODAP) using a screen printed carbon electrode (SPCE) is reported. The electrode material was bulk‐modified with manganese dioxide and used as a detector in flow injection analysis (FIA). The enzyme glutamate oxidase (GlOx) was immobilized in a Nafion‐film on the electrode surface. The performance of the biosensor was optimized using glutamate as an analyte. Optimum parameters were found as: operational potential 440 mV (vs. Ag/AgCl), flow rate 0.2 mL min−1, and carrier composition 0.1 mol L−1 phosphate buffer (pH 7.75). The same conditions were used for the determination of β‐ODAP. The signal was linear within the concentration range 53–855 μmol L−1 glutamate and 195–1950 μmol L−1 β‐ODAP. Detection limits (as 3σ value) for both analytes were 9.12 and 111.0 μmol L−1, respectively, with corresponding relative standard deviations of 3.3 and 4.5%. The biosensor retained more than 73% of its activity after 40 days of on‐line use.
An Investigation into Outer‐Surface Biofouling and Electrode Passivation Effects on Gold Electrodes Modified with Calix[4]resorcinarenetetrathiol and a PEG Derivative on Exposure to Whole Human Blood
Authors: Collyer Stuart , Davis Frank , Lucke Andrew , Stirling Charles J. M. , Higson Séamus P. J. 
Published: February 2004

AbstractAn investigation into the hemo‐biocompatibility of calix[4]resorcinarenetetrathiol and calix‐PEG derivative coatings on gold electrodes is reported, with respect to the detection of the ascorbate ion in aqueous solution. The electrochemical behavior of the ascorbate ion at calix‐modified electrodes is also discussed. Findings show that a facilitated adsorption of ascorbate from solution is seen at calix‐modified gold electrodes. Following exposure to whole human blood, calix‐PEG derivative coatings were seen to offer some protection against both outer‐surface biofouling and electrode passivation effects in comparison to calix[4]resorcinarenetetrathiol counterparts. The individual effects of outer surface biofouling and electrode passivation on exposure to whole blood have been investigated. Our findings suggest that PEG moieties help prevent sorption of the biofouling film, thus possibly minimizing the release of a number of low molecular weight solutes which are thought to be involved with the passivation of electrode responses within clinical bio‐ and chemical sensors.
New Macrocyclic Diamides as Neutral Ionophores for Highly Selective and Sensitive PVC‐Membrane Electrodes for Be2+ Ion
Authors: Shamsipur Mojtaba , Soleymanpour Ahmad , Akhond Morteza , Sharghi Hashem 
Published: February 2004

AbstractFive recently synthesized macrocyclic diamides were investigated to characterize their ability as beryllium ion carriers in potentiometric PVC‐membrane electrodes. The electrodes based on 1,15‐diaza‐3,4;12,13‐dibenzo‐5,8,11‐trioxabicyclo[13,2,2] heptadecane‐2,14‐dione exhibited a Nernstian response for Be2+ ion over wide concentration ranges (from 3.0×10−6 to 3.0×10−2 M for polymeric membrane electrode, PME, and from 5.0×10−7 to 2.0×10−2 M for coated glassy carbon electrode, CGCE) and very low detection limits (2.0 ×10−6 M for PME and 4.0×10−7 M for (CGCE). The electrodes possess low resistances, fast responses, satisfactory reproducibilities and, most importantly, good selectivities relative to a variety of other common cations. The potentiometric response of the electrodes is independent of pH of test solution in the pH range of 4.0–7.5. The proposed sensors were used to determine beryllium ion in water samples.
Novel Dicyanoargentate Polymeric Membrane Sensors for Selective Determination of Cyanide Ions
Authors: Hassan Saad S. M. , Marzouk S. A. M. , Mohamed Ayman H. K. , Badawy N. M. 
Published: February 2004

AbstractThe construction and general performance characteristics of three novel potentiometric PVC membrane sensors responsive to dicyanoargentate anion are described. The sensors are based on the use of magnesium(II)‐ and iron(II)‐phthalocyanines as neutral ionophores and iron(II)‐bathophenanthroline dicyanoargentate ion‐pair complex as an ion exchanger in plasticized PVC matrices. These sensors exhibit fast, stable and near‐Nernstian response (54–59 mV/decade) for the singly charged dicyanoargentate anion over the concentration range 1×10−2–5.8×10−6 M. Potentiometric responses of sensors based on metal phthalocyanines and iron(II)‐bathophenanthroline are stable over the pH ranges 5–7 and 5–12, respectively. The selectivity of the sensors are fairly good over most common anions. Use of the sensors for potentiometric determination of microgram quantities of cyanide ion after conversion into dicyanoargentate anions shows an average recovery of 99.5% and a mean standard deviation of ±0.5%. Determination of cyanide ions in some exhausted electroplating bath samples gives results that compare favourably well with data obtained using the solid‐state cyanide electrode.
Validation of Some Procedures for Quantifying Platinum at sub‐μg/L Level in Some Real Matrices by Catalytic Adsorptive Stripping Voltammetry
Authors: Desimoni Elio , Brunetti Barbara , Cattaneo Raffaella 
Published: February 2004

AbstractThe potential toxicological properties of platinum group elements, usually present in real matrices at sub‐ng/g level, explain the increasing interest in developing specific and sensitive analytical methods. In this work, a validation study was performed in order to ensure the fitness‐for‐purposes of procedures developed for quantifying platinum in tap water, beer and lettuce using an extremely sensitive method based on catalytic adsorptive stripping voltammetry. The work involved the estimation of selectivity, detection and quantitation limits, range, accuracy (trueness plus precision), uncertainty of measurement (UOM), robustness and recovery. The results are discussed in the light of the most recent literature findings.
Multiresidue Analysis of Pesticides in Environmental Waters by Capillary Electrophoresis Using Simultaneous UV and Electrochemical Detection
Authors: Chicharro M. , Zapardiel A. , Bermejo E. , Sánchez A. , González R. 
Published: February 2004

AbstractA rapid multiresidue method has been developed for the analysis of eight pesticides (triazines, triazinones and ureas) in environmental waters. A simple end‐column electrochemical detector was used in combination with an available commercial capillary electrophoresis instrument with UV detection. The determination of these pesticides using micellar electrokinetic capillary chromatography (MEKC) with dual electrochemical and UV detection is the first time reported. In both detection systems, a linear range was obtained for the eight pesticides, concentrations lower than 5.0×10−5 mol L−1, in 0.020 mol L−1 boric acid at pH 8.3 and containing 0.025 mol L−1 of sodium dodecylsulfate, to obtain selectivity in the additional separation by micellar distribution process. Under these conditions a lower detection limit than 2.0×10−6 mol L−1 (0.15 pmol of pesticide) was achieved for the most of them. The eight pesticides are resolved in less than 14 min.
Differential Pulse Voltammetric Determination of Local Anesthetics Heptacaine, Carbisocaine and Pentacaine at DNA Modified Screen‐Printed Electrode
Authors: Vaníčková M. , Jakubková E. , Bučková M. , Čižmárik J. , Labuda J. 
Published: February 2004

AbstractA procedure for the differential pulse voltammetric determination of three local anesthetics (Heptacaine, Carbisocaine and Pentacaine) at a screen‐printed electrode surface modified with the dsDNA layer is described. The detection limits obtained after 120 s drug accumulation from 0.01 M phosphate buffer solution pH 6.96 are 0.02 μM (Pentacaine) and 0.03 μM (Carbisocaine and Heptacaine). The method was applied to the determination of Carbisocaine in spiked serum.
Polymorphisms in the vitamin D receptor gene, ultraviolet radiation, and susceptibility to prostate cancer
Authors: Bodiwala Dhaval , Luscombe Christopher J. , French Michael E. , Liu Samson , Saxby Mark F. , Jones Peter W. , Fryer Anthony A. , Strange Richard C. 
Published: February 2004

AbstractUltraviolet radiation (UVR) exposure may protect against prostate cancer development via a mechanism involving vitamin D. The vitamin D receptor (VDR) gene is therefore a candidate susceptibility factor for prostate cancer. This possibility has been previously investigated with conflicting results. We examined the association of VDR genotypes (variants at the CDX‐2, Fok1, and Taq1 sites), haplotypes, and genotype combinations with risk by studying 368 prostate cancer and 243 benign prostatic hypertrophy (BPH) patients. CDX‐2, Fok1, and Taq1 genotype and haplotype frequencies were not significantly different in cancer and BPH patients. As the impact of VDR polymorphisms may depend on UVR exposure, we studied associations of variants with risk in men stratified into low (below median) and high (above median) cumulative exposure/year groups. In men with UVR exposure above the median (1,100 hr/year), CDX‐2 GA and AA (odds ratios [OR] = 2.11 and 2.02, respectively) and Fok1 ff (OR = 2.91) were associated with increased prostate cancer risk. No associations were observed for Taq1 genotypes. Of the genotype combinations, relative to all other CDX‐2 and Taq1 and combinations, GGTT (P = 0.022, OR = 0.30), and relative to all other Fok1 and Taq1 combinations, FFTT (P = 0.026, OR = 0.35) were associated with reduced prostate cancer risk in the presence of the main effects. None of the other two‐ or three‐genotype combinations was associated with risk. These data indicate that VDR variants influence prostate cancer risk and that this association is dependent on the extent of UVR exposure. Environ. Mol. Mutagen. 43:121–127, 2004. © 2004 Wiley‐Liss, Inc.
Proteomic analysis of cellular responses to low concentration N‐methyl‐N′‐nitro‐N‐nitrosoguanidine in human amnion FL cells
Authors: Jin Jinghua , Yang Jun , Gao Zhihua , Yu Yingnian 
Published: February 2004

AbstractWe have shown previously that exposure to a low concentration of N‐methyl‐N′‐nitro‐N‐nitrosoguanidine (MNNG) induces comprehensive changes in the protein expression profile of human amnion FL cells, including the induction, suppression, upregulation, and downregulation of various proteins. In addition, by proteomic analysis combining two‐dimensional gel electrophoresis (2‐DE) and mass spectrometry, some of the induced and suppressed proteins were identified. In this study, we identified an additional 18 proteins among those that were either up‐ or downregulated by MNNG treatment. The proteins identified were a heterogeneous group that included several zinc finger proteins, proteins involved in signal transduction, cytoskeletal proteins, cell‐cycle regulation proteins, and proteins with unknown functions. The involvement of these proteins in the cellular responses to alkylating agents has not been reported before and their physiological relevance is not clear. Therefore, our findings may help better understand the global cellular stress responses to chemical carcinogens, and may lead to new studies on the functions of these MNNG‐responsive proteins. Furthermore, some of these proteins may serve as biomarkers for detecting exposure of human populations to environmental carcinogens. Environ. Mol. Mutagen. 43:93–99, 2004. © 2004 Wiley‐Liss, Inc.
Characterization ofHprtmutations in cDNA and genomic DNA of T‐cell mutants from control and 1,3‐butadiene‐exposed male B6C3F1 mice and F344 rats
Authors: Meng Quanxin , Walker Dale M. , Scott Bobby R. , Seilkop Steve K. , Aden James K. , Walker Vernon E. 
Published: February 2004

AbstractA multiplex PCR procedure for analysis of genomic DNA mutations in the mouse hypoxanthine‐guanine phosphoribosyltransferase (Hprt) gene was developed and then used with other established methods for the coincident identification of large‐ and small‐scale genetic alterations in theHprtgene of mutant T‐cell isolates propagated from sham‐ and 1,3‐butadiene (BD)‐exposed mice and rats. The spectra data for RT‐PCR/cDNA analysis and multiplex PCR of genomic DNA fromHprtmutants were combined, and statistical analyses of the mutant fractions for the classes of mutations identified in control versus exposed animals were conducted. Under the assumption that the mutant fractions are distributed as Poisson variates, BD exposure of mice significantly increased the frequencies of (1) nearly all types of base substitutions; (2) single‐base deletions and insertions; and (3) all subcategories of deletions. Significantly elevated fractions of G:C→C:G and A:T→T:A transversions in theHprtgene of BD‐exposed mice were consistent with the occurrence of these substitutions as the predominantrasgene mutations in multiple tumor types increased in incidence in carcinogenicity studies of BD in mice. BD exposure of rats produced significant increases in (1) base substitutions only at A:T base pairs; (2) single‐base insertions; (3) complex mutations; and (4) deletions (mainly 5′ partial and complete gene deletions). Future coincident analyses of large‐ and small‐scale mutations in rodents exposed to specific BD metabolites should help identify species differences in the sources of deletion mutations and other types of mutations induced by BD exposures in mice versus rats. Environ. Mol. Mutagen. 43:75–92, 2004. © 2004 Wiley‐Liss, Inc.
Genetic polymorphisms and susceptibility to childhood acute lymphoblastic leukemia
Authors: Canalle Renata , Burim Regislaine V. , Tone Luiz G. , Takahashi Catarina S. 
Published: February 2004

AbstractAcute lymphoblastic leukemia (ALL) is the most common form of pediatric cancer. Although exposure to environmental agents appears to predispose individuals to this disease, little attention has been paid to the role of genetic susceptibility to environmental exposures in the etiology of childhood ALL. The enzymes GSTM1, GSTT1, GSTP1, CYP1A1, and CYP2E1 are involved in the bioactivation and detoxification of a variety of xenobiotics present in food, organic solvents, tobacco smoke, drugs, alcoholic drinks, pesticides, and environmental pollutants. Polymorphisms in the genes coding for these enzymes have been associated with increased susceptibility to different cancers, including hematologic malignancies. To investigate whether these polymorphisms represent risk‐modifying factors for childhood ALL, a study was conducted involving 113 Brazilian patients of childhood ALL and 221 controls with similar ethnic backgrounds. The data revealed that carriers of the rare GSTP1 Val allele were at higher risk of ALL (odds ratio [OR] = 2.7; 95% confidence interval [CI] = 1.1–6.8; P = 0.04). No difference was found in the prevalence of the GSTM1 and GSTT1 null genotypes between ALL patients and the controls, and no association was found between CYP1A1*2 and CYP2E1*3 variants and ALL. However, when the mutant CYP1A1 and CYP2E1 alleles were considered together with the GSTM1 and GSTP1 risk‐elevating genotypes, the risk of ALL was increased further (OR = 10.3; 95% CI = 1.0–111.8; P = 0.05), suggesting a combined effect. These results imply that genetic variants of xenobiotic metabolizing genes influence the risk of developing childhood ALL. Environ. Mol. Mutagen. 43:100–109, 2004. © 2004 Wiley‐Liss, Inc.