bluuebunny/crossref_metadata_2025_split huggingface dataset:
Transannular Cyclization in Cyclodecenes: The Case Study of Melampolides
Authors: Neukirch Hannes , Guerriero Antonio , D’Ambrosio Michele 
Published: October 2003

AbstractThe structures of products formed by electrophilic transannular cyclization (ETC) in medium‐ring compounds are affected by several parameters. The melampolides, (cis,trans)‐cyclodeca‐1(10),5‐diene terpenes, undergo ring closure only under Lewis acid conditions. The transannular distance proves to be a key factor. Molecular mechanics calculations suggest that the cis ring junction of products is formed through a less populated conformer. ETC has chemical significance because it may play an important role in the pharmacological action of sesquiterpene lactones. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
Copper(II)‐Catalyzed Oxidation of Alcohols to Carbonyl Compounds with Hydrogen Peroxide
Authors: Velusamy Subbarayan , Punniyamurthy Tharmalingam 
Published: October 2003

AbstractCopper(II) complex 1 efficiently catalyses the oxidation of alcohols to the corresponding carboxylic acid analogues and ketones in the presence of H2O2 in high yields. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
Efficient Synthesis of Differently Protected Lanthionines via β‐Bromoalanine Derivatives
Authors: Zhu Xiangming , Schmidt Richard R. 
Published: October 2003

AbstractLanthionines, thioether‐linked alanines, are readily available from differently protected β‐bromoalanine and cysteine derivatives under phase‐transfer conditions at pH 8.5. Racemisation or elimination of starting materials or products was not observed. Also base‐sensitive protecting groups, such as, for instance, the Fmoc group, were compatible with this procedure, thus conveniently permitting the synthesis of orthogonally protected lanthionines. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
Asymmetric Synthesis of α,γ‐Substituted γ‐Sultones via Allylation of Chiral Lithiated Sulfonates
Authors: Enders Dieter , Harnying Wacharee , Vignola Nicola 
Published: October 2003

AbstractThe first auxiliary controlled asymmetric synthesis of enantiopure α,γ‐substituted γ‐sultones via α‐allylation of lithiated sulfonates by using 1,2:5,6‐di‐O‐isopropylidene‐α‐D‐allofuranose as chiral auxiliary is described. The high asymmetric inductions of the α‐allylations were reached in good to excellent yields. Successive epimerization‐free cleavage of the auxiliary and diastereoselective ring closure of the sulfonic acid intermediates in a one‐pot procedure led to the title compounds in good to excellent yields and diastereo‐ and enantiomeric excesses (de, ee ≥ 98%). (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
Chemistry of Tonghaosu Analogs: Novel Acid‐Catalyzed Nucleophilic Addition to the Dienyl Acetal System
Authors: Yin Biao‐Lin , Wu Wen‐Min , Hu Tai‐Shan , Wu Yu‐Lin 
Published: October 2003

AbstractThe acid‐catalyzed nucleophilic addition reaction of spiroketal enol ether‐containing tonghaosu analogs 2 was explored. Soft nucleophiles, such as mercaptans, alcohols and heteroaromatic compounds, gave rise exclusively to 1,6‐adducts, while harder nucleophiles, such as Grignard reagents, afforded mixtures of 1,2‐ and 1,6‐adducts. The reaction with cysteine and glutathione, which might be related to the mode of action of insect antifeeding, also took place smoothly. Friedel−Crafts dimerization reactions of 10 and 11 gave the dimers 12 and 13 respectively. By comparison of 1H NMR spectroscopic data, we also suggest that the structure of compound 9 reported in the literature for a natural product is revised to that of compound 13. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
A Mild and Versatile Method for Palladium‐Catalyzed Cross‐Coupling of Aryl Halides in Water and Surfactants
Authors: Arcadi Antonio , Cerichelli Giorgio , Chiarini Marco , Correa Mariano , Zorzan Daniel 
Published: October 2003

AbstractVarious aqueous surfactants proved to be excellent media for carrying out palladium‐catalyzed Suzuki−Miyaura cross‐coupling reactions under mild conditions. The dehalogenation side reaction, which is usually a drawback with the aqueous protocol, was not observed. The concentration of the surfactant in water played a pivotal role for the reaction outcome. Smooth cross‐coupling of iodoanisole and a variety of aryl bromides, including electron‐rich derivatives, with aryl boronic acids occurred at room temperature in high yields either with [Pd(PPh3)4] or Pd/C as catalyst. The water‐surfactant Pd/C system combines high activity under ambient conditions (air), easy separation and recyclability. Palladium acetate was found to be effective in cross‐coupling of the less reactive aryl chlorides at 100 °C. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
The First Crystal Structure of a Halogenated Higher Fullerene, C78Br18, Obtained by Bromination of a Fullerene Mixture
Authors: Troyanov Sergey I. , Kemnitz Erhard 
Published: October 2003

AbstractSimple bromination of a fullerene mixture allowed the separation of C78 from other fullerenes in form of crystalline C78Br18. The first X‐ray single‐crystal structure of a halogenated higher fullerene, C78Br18, revealed that the addition pattern of 18 bromine atoms on the C78 cage corresponds to a partial retention of the conjugated double bond systems and the formation of isolated C−C double bonds. Evidently, even a separation of the C2v and D3 isomers of C78 occurred in the course of bromination and precipitation. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
Synthesis of Theophylline and 6‐Thiotheophylline 7‐Ribosyl Nucleosides
Authors: Rico‐Gómez Rodrigo , Rodríguez‐González Angel , Ríos‐Ruíz Josefa , Nájera Francisco , López‐Romero J. Manuel 
Published: October 2003

AbstractThe syntheses of theophylline and thiotheophylline 7‐ribopyranose and 7‐ribofuranose nucleosides, both by direct coupling of the base and the sugar and by construction of the imidazole ring, are reported. The conformational syn/anti equilibrium of the peracetyl derivatives was studied by molecular mechanics and by the low‐temperature line‐shape/1H NMR method. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
Vicarious Nucleophilic Substitution of (Chloroalkyl)oxazolines with Nitroarenes: Synthesis of (Nitrobenzyl)oxazolines
Authors: Florio Saverio , Lorusso Patrizia , Granito Catia , Ronzini Ludovico , Troisi Luigino 
Published: October 2003

Abstract2‐Chloroalkyloxazolines 1a and 1b react with nitroarenes in the presence of tBuOK in DMSO to give, upon acidic quenching, substituted nitroaryloxazolines 2a, 2b, 3a, 9, 10, 11a−d, 12−19, and 21−22, probably by vicarious nucleophilic substitution (VNS). The reaction of 1a is poorly regioselective, while that of 1b is completely para regioselective, thus showing that the coupling is sterically controlled. Trapping of the carbanionic intermediate B of the VNS reaction with electrophiles furnished α,α‐disubstituted (nitrobenzyl)oxazolines 4−7. Attempts to trap B with PhCHO failed: the [(p‐nitrophenyl)oxazolinyl]ethanol 8 was obtained. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
Stereocontrol of the Intramolecular Diels−Alder Reaction by Internal Hydrogen Bonding
Authors: Cayzer Tory N. , Paddon‐Row Michael N. , Sherburn Michael S. 
Published: October 2003

AbstractA novel approach for exo/endo stereocontrol of intramolecular Diels−Alder reactions is described. Substrates carrying a hydroxymethyl group attached to the diene and an ester group attached to the dienophile participate in hydrogen bonding in the transition state. This non‐covalent interaction causes either a significant enhancement or diminution in the observed kinetic endo/exo product ratio. Thus, the parent pentadienyl maleate 12 undergoes intramolecular Diels−Alder reaction to give an approx. 5:1 mixture of trans‐ and cis‐fused bicyclic cycloadducts, whereas the C2‐hydroxymethyl analogue 1 delivers a 1:1 ratio of products. In contrast, the parent pentadienyl fumarate 13 gives a 3:2 trans:cis ratio, which is improved to 9:1 in the C2‐hydroxymethyl analogue 4. These stereoselectivities are accurately predicted from transition structure populations calculated using B3LYP/6‐31+G(d) theory. The presence of an intramolecular H‐bond confers a transannular Diels−Alder‐like appearance upon the transition states of these reactions. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
Construction of Consecutive Chiral Non‐Racemic Quaternary and Tertiary Carbon Centers: A Short Synthetic Route to (−)‐Acetomycin
Authors: Uenishi Jun′ichi , Kawatsura Motoi , Ikeda Daiji , Muraoka Nobuhiro 
Published: October 2003

AbstractRegio‐ and diastereoselective nucleophilic substitution of 2‐methylacetoacetate with a chiral non‐racemic π‐allyl Pd complex creates consecutive chiral non‐racemic quaternary and tertiary carbon centers. σ‐Bond formation between the re‐face of the π‐allyl Pd complex and the re‐face of the enol acetoacetate was controlled by the o‐(diphenylphosphanyl)arylcarboxylic acid ligand selectively. (−)‐Acetomycin was synthesized in seven steps using this key approach. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
Cover Picture: Recent Advances in the Synthesis of Spermine and Spermidine Analogs of the Shark Aminosterol Squalamine (Eur. J. Org. Chem. 20/2003)
Authors: Brunel Jean Michel , Letourneux Yves 
Published: October 2003

AbstractThe cover picture shows, the dogfish shark Squalus Acanthias from which the aminosterol squalamine has been isolated. Squalamine has been characterized as a water‐soluble cationic steroid exhibiting potent antimicrobial activity against fungi, protozoa fungi, protozoa and both Gram‐negative and Gram‐positive bacteria. Details on the different series of spermine and spermidine analogs synthesized as well as comparison of their pharmacological properties are discussed in the Microreview by J. M. Brunel and Y. Letourneux on p. 3897 ff.
Evaluation of mutagenic activity in an extract of pepper tree stem bark (Schinus terebinthifolius Raddi)
Authors: de Carvalho Maria Cleide Ribeiro Dantas , Barca Francisco Napoleão Túlio Varela , Agnez‐Lima Lucymara Fassarella , de Medeiros Sílvia Regina Batistuzzo 
Published: October 2003

AbstractAn extract (decoction) from pepper tree stem bark (Schinus terebinthifolius Raddi) is widely used in Brazil as a topical antiinflammatory agent and to cicatrize wounds. The extract contains catechin, tannins, terpenes, flavonoids, and saponins; of these components, both mutagenic potential and antioxidant properties have been ascribed to flavonoids. The mutagenicity of some flavonoids is believed to be associated with the formation of reactive oxygen species and seems to depend on the number and position of hydroxyl groups. In the present study, we evaluated an extract of S. terebinthifolius in a series of cell‐free and bacterial assays in order to determine its genotoxic potential. The extract was negative in a cell‐free plasmid DNA test, indicating that it did not directly break DNA. Positive results, however, were obtained in the SOS chromotest, in a forward mutagenesis assay employing CC104 and CC104mutMmutY strains of Escherichia coli, and in the Salmonella reversion assay, using strains TA97, TA98, TA100, and TA102. All the bacterial tests were performed without exogenous metabolic activation due to the topical use of this preparation. The results indicate that pepper tree stem bark extract produces DNA damage and mutation in bacteria, and that oxidative damage may be responsible for the genotoxicity. Environ. Mol. Mutagen. 42:185–191, 2003. © 2003 Wiley‐Liss, Inc.
Structure–activity relationships for the mutagenicity and carcinogenicity of simple and α‐β unsaturated aldehydes
Authors: Benigni Romualdo , Passerini Laura , Rodomonte Andrea 
Published: October 2003

AbstractAldehydes are important industrial compounds that are used for the synthesis of chemicals and pharmaceuticals and as solvents, food additives, and disinfectants. Because of their reactivity, aldehydes are able to interact with electron‐rich biological macromolecules and adverse health effects have been reported, including general toxicity, allergenic reactions, mutagenicity, and carcinogenicity. The cost, time, and number of animals necessary to adequately screen these chemicals places serious limitations on the number of aldehydes whose health potential can be studied and points to the need of using alternative methods for assessing, at least in a preliminary way, the risks associated with the use of aldehydes. A method of choice is the study of quantitative structure–activity relationships (QSARs). In the present work, we present QSAR models for the mutagenicity and carcinogenicity of simple aldehydes and α‐β unsaturated aldehydes. The models point to the role of electrophilicity, bulkiness, and hydrophobicity in the genotoxic activity of the aldehydes and lend themselves to the prediction of the activity of other untested chemicals of the same class. Environ. Mol. Mutagen. 42:136–143, 2003. © 2003 Wiley‐Liss, Inc.
Methylated trivalent arsenicals as candidate ultimate genotoxic forms of arsenic: Induction of chromosomal mutations but not gene mutations
Authors: Kligerman Andrew D. , Doerr Carolyn L. , Tennant Alan H. , Harrington‐Brock Karen , Allen James W. , Winkfield Ernest , Poorman‐Allen Patricia , Kundu Bijit , Funasaka Kunihiro , Roop Barbara C. , Mass Marc J. , DeMarini David M. 
Published: October 2003

AbstractArsenic is a prevalent human carcinogen whose mutagenicity has not been characterized fully. Exposure to either form of inorganic arsenic, AsIII or AsV, can result in the formation of at least four organic metabolites: monomethylarsonic acid, monomethylarsonous acid (MMAIII), dimethylarsinic acid, and dimethylarsinous acid (DMAIII). The methylated trivalent species, as well as some of the other species, have not been evaluated previously for the induction of chromosome aberrations, sister chromatid exchanges (SCE), or toxicity in cultured human peripheral blood lymphocytes; for mutagenicity in L5178Y/Tk+/‐ mouse lymphoma cells or in the Salmonella reversion assay; or for prophage‐induction in Escherichia coli. Here we evaluated the arsenicals in these assays and found that MMAIII and DMAIII were the most potent clastogens of the six arsenicals in human lymphocytes and the most potent mutagens of the six arsenicals at the Tk+/‐ locus in mouse lymphoma cells. The dimethylated arsenicals were also spindle poisons, suggesting that they may be ultimate forms of arsenic that induce aneuploidy. Although the arsenicals were potent clastogens, none were potent SCE inducers, similar to clastogens that act via reactive oxygen species. None of the six arsenicals were gene mutagens in Salmonella TA98, TA100, or TA104; and neither MMAIII nor DMAIII induced prophage. Our results show that both methylated AsV compounds were less cytotoxic and genotoxic than AsV, whereas both methylated AsIII compounds were more cytotoxic and genotoxic than AsIII. Our data support the view that MMAIII and DMAIII are candidate ultimate genotoxic forms of arsenic and that they are clastogens and not gene mutagens. We suggest that the clastogenicity of the other arsenicals is due to their metabolism by cells to MMAIII or DMAIII. Environ. Mol. Mutagen. 42:192–205, 2003. Published 2003 Wiley‐Liss, Inc.
Computation of moving boundaries and interfaces and stabilization parameters
Authors: Tezduyar Tayfun E. 
Published: October 2003

AbstractThe interface‐tracking and interface‐capturing techniques we developed in recent years for computation of flow problems with moving boundaries and interfaces rely on stabilized formulations such as the streamline‐upwind/Petrov–Galerkin (SUPG) and pressure‐stabilizing/Petrov–Galerkin (PSPG) methods. The interface‐tracking techniques are based on the deforming‐spatial‐domain/stabilized space–time formulation, where the mesh moves to track the interface. The interface‐capturing techniques, typically used with non‐moving meshes, are based on a stabilized semi‐discrete formulation of the Navier–Stokes equations, combined with a stabilized formulation of the advection equation governing the time‐evolution of an interface function marking the interface location. We provide an overview of the interface‐tracking and interface‐capturing techniques, and highlight how we determine the stabilization parameters used in the stabilized formulations. Copyright © 2003 John Wiley & Sons, Ltd.
Fast preconditioned multigrid solution of the Euler and Navier–Stokes equations for steady, compressible flows
Authors: Caughey David A. , Jameson Antony 
Published: October 2003

AbstractNew versions of implicit algorithms are developed for the efficient solution of the Euler and Navier–Stokes equations of compressible flow. The methods are based on a preconditioned, lower‐upper (LU) implementation of a non‐linear, symmetric Gauss‐Seidel (SGS) algorithm for use as a smoothing algorithm in a multigrid method. Previously, this method had been implemented for flows in quasi‐one‐dimensional ducts and for two‐dimensional flows past airfoils on boundary‐conforming ‘O’‐type grids for a variety of symmetric limited positive (SLIP) spatial approximations, including the scalar dissipation and convective upwind split pressure (CUSP) schemes. Here results are presented for both inviscid and viscous (laminar) flows past airfoils on boundary‐conforming ‘C’‐type grids. The method is significantly faster than earlier explicit or implicit methods for inviscid problems, allowing solution of these problems to the level of truncation error in three to five multigrid cycles. Viscous solutions still require as many as twenty multigrid cycles. Copyright © 2003 John Wiley & Sons, Ltd.
The distinctive CFD challenges of computational rheology
Authors: Walters K. , Webster M. F. 
Published: October 2003

AbstractIn this general lecture, we shall first outline the way computationalnon‐Newtonian fluid mechanics differs from conventional computational fluid dynamics (CFD). We do this by briefly outlining the major historical developments in this relatively new field of science, which is conveniently called Computational Rheology. To illustrate essential features, we limit the discussion to the Oldroyd B, UCM and Phan‐Thien/Tanner constitutive models. In order to provide a serious challenge to existing numerical codes, we describe some recent unpublished experimental results on flow through a contraction of constant viscosity (Boger) and also shear‐thinning elastic liquids. Both planar and axisymmetric contractions are of interest, and pressure drops and observed flow structures provide the relevant points of contact between experiment and numerical prediction. Numerical codes developed at UWS involving a hybrid finite‐element/finite‐volume scheme for Oldroyd B and Phan‐Thien/Tanner constitutive models are applied to the contraction‐flow problems and an encouraging agreement is demonstrated between theory and experiment. Specifically, the dramatic experimental differences between flow in planar and axisymmetric contractions and between constant viscosity and shear‐thinning polymer solutions are mirrored in the numerical predictions, at least in a qualitative sense. Notwithstanding these encouraging developments, the review ends with a realistic assessment of the challenges still awaiting computational rheologists, with particular reference to the choice of constitutive model and the possibility of further refinements to the numerical techniques. Copyright © 2003 John Wiley & Sons, Ltd.
A multigrid accelerated time‐accurate inviscid compressible fluid flow solution algorithm employing mesh movement and local remeshing
Authors: Sørensen K. A. , Hassan O. , Morgan K. , Weatherill N. P. 
Published: October 2003

AbstractAn implicit scheme for the time accurate solution of three dimensional compressible fluid flow problems with moving boundaries on unstructured tetrahedral meshes is described. The numerical scheme is nominally second order accurate in both space and time and satisfies a geometric conservation law. For improved computational performance, the implicit equation system is solved by explicit iteration with multigrid acceleration. For the multigrid implementation, the coarse meshes are automatically generated by an agglomeration technique. The change in the solution domain geometry with time is handled by moving the mesh using a spring analogy scheme, with local remeshing performed in regions of reduced mesh quality. Copyright © 2003 John Wiley & Sons, Ltd.
Numerical modelling of free‐surface flows in ship hydrodynamics
Authors: Bulgarelli U. P. , Lugni C. , Landrini M. 
Published: October 2003

AbstractCurrent trends in the investigation of ship hydrodynamics are reviewed with emphasis on the problem of wave‐body interaction. This includes the classical seakeeping problem and as a special case, the problem of prediction for the drag encountered by a ship advancing in calm water. Specific issues related to the numerical treatment of the air–water interface are examined, with emphasis on the modelling of wave breaking. The discussion on the large‐scale modelling of the flow around ships is focused on the prediction of wave loads, ship motions and resistance in calm water. Copyright © 2003 John Wiley & Sons, Ltd.
Evapotranspiration and runoff in a forest watershed, western Japan
Authors: Shimizu A. , Shimizu T. , Miyabuchi Y. , Ogawa Y. 
Published: October 2003

AbstractA Note has been published for this article in Hydrological Processes 18(4) 2004, 825.
Both water and heat balances were studied in a conifer plantation watershed in south‐west Japan, within the warm‐temperate East Asia monsoon area. Forest cover in the watershed consists mainly of Japanese cedar (Cryptomeria japonica) and Japanese cypress (Chamaecyparis obtusa) plantations. Precipitation and runoff have been observed since 1991, so evapotranspiration can be compared with the water balance. Two meteorological observation towers were built to monitor evapotranspiration in the watershed. The annual average precipitation, amount of runoff and losses were 2166, 1243 and 923 mm, respectively. The evapotranspiration (latent heat flux) agreed well with the water balance losses. The average annual evapotranspiration at the tower built in the centre of the watershed was 902 mm; evapotranspiration at the other tower, further upslope, was 875 mm. The observed evapotranspiration was 39% to 40% of the average precipitation (2166 mm). The mean net radiation was c. 2·6 GJ m−2 year−1, and is considered a representative value of the net radiation (Rn) in coniferous plantations in this region. This region is classified in the humid zone based on the ratio of net radiation (Rn) to the energy required to evaporate the rainfall (λR). The mean annual evaporation of canopy‐intercepted water was 356 mm or about 15% of the average precipitation. Copyright © 2003 John Wiley & Sons, Ltd.