bluuebunny/crossref_metadata_2025 huggingface dataset:
Establishing reference laboratories in laboratory medicine
Authors: Siekmann Lothar
Published: August 2005

The concept of measurement traceability provides probably the most important strategy to achieve standardization in laboratory medicine aimed at comparable measurement results regardless of the method, the measurement procedure (test kit) and of the laboratory where analyses are carried out. Establishing networks of reference laboratories is - in addition to reference measurement procedures and reference materials - one of the biggest challenges in implementing the concept of measurement traceability. With respect to these requirements, the Joint Committee on Traceability in Laboratory Medicine (JCTLM), established by the BIPM, the IFCC and the ILAC, has launched two projects in its working groups. WG-1 has to date published tables of reference materials and reference procedures on the BIPM web-sites, whereas WG-2 is identifying reference measurement laboratories. There is general agreement now that reference laboratories should be identified - according to the metrological level of the procedures applied where the principle of measurement is the most important criterion, - on the basis of accreditation or at least compliance with ISO 15195 or ISO 17025 as calibration laboratory, and - on the basis of their ability to demonstrate performance in regular inter - laboratory comparisons (ring trials). To date, a data base on candidate reference laboratories has been collected containing information on the laboratory identity, the metrological level of the procedures and on the status of accreditation and the participation in networks or ring trials. The data base currently contains the addresses of about 60 laboratories. On average, each of the laboratories reported measurement capabilities for six different measurands resulting in about 360 entries. The IFCC has recently launched a ring trial program for reference laboratories for some thirty different measurands. Ring trial results not only demonstrate the competence of individual laboratories, but also reveal the equivalence or bias of different reference procedures. .
The stability of emulsions in the presence of additives
Authors: Gasic S. , Jovanovic Bratislav , Jovanovic S.
Published: August 2005

The influence of different additives on the effectiveHLBvalues of non-ionic emulsifiers was studied by the method of the determination of the phenol index values and by the determination of the emulsion inversion point in the system with xylene as the oil phase. Ethanol, glycerol and ethylene glycol were investigated as additives. The method of the determination of the phenol index value was applied on two homologous series of non-ionic emulsifiers: nonylphenolpolyglycolethers with 10, 15, 23 and 30 moles of bound ethylene oxide and polyglycolethers of fatty alcohols (C16?C18) with 15, 20 and 23 moles of bound ethylene oxide. The additives were applied in the concentration of 5, 10, 15 and 20 %. The results showed that ethanol and ethylene glycol increased the phenol index value. The influence of ethanol was more pronounced. On the contrary, glycerol reduces the phenol index value. There were small differences in the influence of these additives on certain members of both homologous series, but the general trend is presented here. The influence of the same additives on the values of the emulsion inversion point was investigated in the system with xylene and nonylphenolpolyglycolethers with 10 moles of bound ethylene oxide. Ethanol and ethylene glycol were applied in the concentrations of 1, 5, 10 and 15 % and glycerol in 5,7.5,10 and 15 %. The results showed that ethanol and ethylene glycol reduce the emulsion inversion points, while glycerol increases them. On the basis of these investigations it can be concluded that ethanol and ethylene glycol could contribute to an increase in the stability of emulsions, glycerol has the opposite effect. The results of both applied methods are in accordance.
Extraction and separation studies of zinc(II) and copper(II) with D2EHPA and PC-88A from perchlorate media
Authors: Singh Rajeev , Dhadke Purshottam
Published: August 2005

The extraction behaviors of Zn(II) and Cu(II) from perchlorate media have been investigated using bis-2-ethylhexyl phosphoric acid (D2EHPA) and 2-ethylhexyl phosphoric acid mono-2-ethylhexyl ester, (PC-88A) in toluene. The extraction of Zn(II) was found to be quantitative in the pH range 2.5 to 3.0 and 3.0 to 4.0 using 1.0 x 10-1 moldm-3 D2EHPAand 1.0x10-2 mol dm-3 PC-88Ain toluene, respectively, while Cu(II) was extracted quantitatively in the pH range 6.0 to 8.0 and 5.5 to 7.0 with 1.0x10-2 mol dm-3 and 1.0 x 10-3 mol dm-3 D2EHPA and PC-88A in toluene, respectively. Zn(II) was stripped with 4.0 moldm-3 HCl, while Cu(II) with 2.0 moldm-3H2SO4 and 3.0 moldm-3 HNO3 from the organic phase containing D2EHPAand PC-88A respectively. The probable extracted species were ascertained by log D vs. log [HR] plot to be ZnR2.2HR and CuR2.2HR for both the reagents. These methods were used for the determination of Zn(II) and Cu(II) in real samples. The separation of Zn(II) and Cu(II) were carried out from each other and with associated metals.
Inverse gas chromatrography of chromia. Part II. Finite surface coverage
Authors: Onjia Antonije , Milonjic Slobodan , Rajakovic Ljubinka
Published: August 2005

The interactions of n-hexane, benzene, chloroform, and tetrahydrofuran with dried (amorphous) chromia (I) and chromia heated at 1073 K (crystalline) (II), both obtained from a colloidal dispersion, and a commercially available chromia (III) were studied by inverse gas chromatography (IGC) under finite surface coverage conditions. The isotherms, in the temperature range 383 ? 423 K, were used to estimate the surface area, the adsorption energy distribution, the isosteric heat of adsorption, and the spreading pressure on the surfaces of the solids. The uniformly reduced adsorption ability of the heated chromia was attributed to the dehydroxylation of the surface at the higher temperatures. Both solids showed an increased affinity toward chloroform molecules, as a result of strong acid-base interaction.
Thermodynamics of complexation of isatin-3-thiosemicarbazone (HIT) and other related derivatives with some metal ions
Authors: Seleem H.S.M. , El-Behairy M. , Masshaly M.M. , Mena H.H.
Published: August 2005

Proton-ligand formation constants of isatin-3-thiosemicarbazone (HIT) N-acetylisatin-3-thiosemicarbazone (HAIT) and 5-(p-nitrobenzoyl)-1,2,4-triazino[5,6-b]indole- 3-thione (HBITr) ligands and their corresponding metal-ligand formation constants with Mn2+, Fe3+, Co2 Ni2+, Cu2+, Zn2+, Cd2+, UO22+ and Th4+ ions were determined pH-metrically at 10, 20, 30 and 40 ?C in 75 %(v/v) ethanol?water. The thermodynamic parameters (?G, ?H and ?S) were also evaluated. It was found that both log K1 and ??H1, for HIT and HAIT-complexes are somewhat larger than log K2 and ??H2, indicating a change in the dentate character of these ligands from tridentate (ONN-donors) in 1:1 chelates to bidentate (ON-donors) in 1:2; M:L chelates. In contrast, the values of logK2 and ??H2 for HBITr-complexes are somewhat larger than logK1 and ??H1, indicating a strong trans-effect for the second coordination. The dissociation process is non-spontaneous endothermic and entropically unfavorable while the complexation process is spontaneous, exothermic and entropically favorable. The thermodynamic parameters were separated into their electrostatic (el) and non-electrostatic (non) constituents.
Comparison of the influence of nitrate ions on the electrochemical behaviour of iron and carbon steels in sulphate solutions
Authors: Ma Houy , Chen Shenhao , Yang Chao , Luo Jingli
Published: August 2005

The effect of nitrate ions on the electrochemical behaviour of iron (ferrite) and two carbon steels (martensite and pearlite) in sulphate solutions of different pH values was investigated by cyclic voltammetry polarization and electrochemical impedance spectroscopy. The pitting inhibiting effect of nitrate ions on ferrite in sulphate media is pH dependent. Nitrate ions were unable to inhibit the pitting on ferrite in neutral sulphate solutions, but did effectively protect passivated ferrite from pitting in acidic sulphate solutions. No pitting occurred on the surface of the martensite and pearlite specimens in sulphate solutions regardless of the pH of the solutions. At the open-circuit corrosion potentials, the three materials underwent general corrosion. The impedance spectra for the three materials measured in neutral sulphate solutions containing nitrates and chlorides at the corrosion potentials all showed a capacitive loop, while in acidic sulphate solutions their impedance spectra were greatly reduced in size and displayed at least a low frequency impedance loop (inductive or capacitive loop) besides the well-known high frequency capacitive loop. The variation of the impedance behaviour with pH is explained.
Antimalarial peroxides: The first intramolecular 1,2,4,5-tetraoxane
Authors: Opsenica Dejan , Pocsfalvi Gabriella , Milhous Wilburk , Solaja Bogdan
Published: August 2005

An intramolecular steroidal 1,2,4,5-tetraoxane has been synthesised in six steps starting from methyl3-oxo-7?,12?-diacetoxy-5?-cholan-24-oate. The synthesised 1,2,4,5-tetraoxane has moderate in vitro antimalarial activity against P. falciparum strains (IC50 (D6) = 0.35 ?g/mL; IC50 (W2) = 0.29 ?g/mL).
Computational study of the chromatographic enantioseparation of tris(acetylacetonato)cobalt(III) complexes on an arginine complex of cobalt(III) acting as a chiral selector
Authors: Cuckovic Ljiljana , Hodzic Ismet , Niketic Svetozar
Published: August 2005

Acomputational procedure for the modelling of chromatographic separation of neutral tris(acetylacetonato)cobalt(III) into enantiomers on a dinitrobis(arginine)cobalt(III) complex as a chiral selector is described. Predicted elution order calculated from the differences in total energy of interaction for ? and ? selectands is in agreement with the experimental results. Predictive power of the method and its possible practical applications in designing efficient chiral stationary phases is demonstrated.
Spectrophotometric determination of phosphorus in coal and coal ash using bismuth-phosphomobybdate complex
Authors: Mihajlovic Randjel , Ignjatovic Natasa , Todorovic Marija , Holclajtner-Antunovic Ivanka , Kaljevic Vesna
Published: August 2005

A modified spectrophotometric method using the bismuth phosphomolybdate complex for the determination of phosphorus in coal and coal ash is suggested. Bismuth together with phosphate and molybdate forms a very stable complex in acid medium which turns blue ("molibdenum blue") by reduction with ascorbic acid. The apparent molar absorptivity of PBiMo is 1.66x104 dm3 mol-1cm-1 at 720 nm and 2.10x104 dm3 mol-1cm-1 at 670 nm isobutyl methyl ketone (MIBK). Interference caused by the ions present are within the tolerance limits (?2 %). Beer?s law is obeyed in the for concentration range to 0.6 ?g/mL (aqueous solution) and to 1.2 ?g/mL P (MIBK). The sensitivity of the proposed method is 0.0078 ?g/mL (aqueous solution) and 0.0066 ?g/mL (MIBK).
Excitation and analytical characteristics of an ethanol loaded U-shaped arc
Authors: Raskovic Marija , Holclajtner-Antunovic Ivanka , Tripkovic Mirjana , Markovic Dragan
Published: August 2005

The effect of the ethanol load on the discharge and analytical parameters of an argon stabilized U-shaped DC arc has been recorded. Measurements of the radial distribution of the apparent temperatures and the electron number density of the DC plasma showed that ethanol addition causes a decrease in both plasma parameters. The changes in the plasma characteristics, as well as in transport and atomisation processes of the analyte cause a general change in the spectral line intensities, which depends on the physical characteristics of the analyte and the quantity of ethanol loaded into the plasma. Improved detection limits were obtained for V and Mn when a 10%(v/v) water?ethanol solution was nebulized into the plasma.
Kinetic determination of ultramicro amounts of As(III) in solution
Authors: Igov Aleksandar , Simonovic Ranko , Igov Rangel
Published: August 2005

A new catalytic reaction is proposed and a kinetic method developed for the determination of ultramicro amounts of As(III) on the basis of its catalytic activity in the oxidation of ethylenediamine-N,N?-diacetic-N,N? dipropionic acid (EAP) by KMnO4 in the presence of hydrochloric acid. Under optimal conditions, the sensitivity of the method is 20 ng/cm3. The probable relative error is 7.6 ? 14.5 % for the concentration range 50 ? 200 ng/cm3 As(III). The effect of certain foreign ions upon the reaction rate were determined for the assessment of the selectivity of the method. The method has relatively good selectivity. Kinetic equations were proposed for the investigated process.
A comparative study on the sterol composition of some brown algae from the Black Sea
Authors: Kamenarska Zotnitsa , Dimitrova-Konaklieva Stefka , Stefanov Ljubomirov , Popov Simonov
Published: August 2005

The sterol composition of the brown algae Stilophora rhizodes (Turner) J. Agardh, Punctaria latifolia Grev. and Punctaria plantaginea (Roth) Grev. from the Black Sea was investigated. Fifteen sterols were identified in the sterol fractions. The main ones were cholesterol and 24-methylenecholesterol. Characteristic for brown algae, fucosterol was present in low concentrations. The results obtained were compared with recent data for the sterol composition of other Black Sea brown algae. Some conclusions concerning the evolutionary position of brown algae are made.
Lignans from the plant species Achillea lingulata
Authors: Trifunovic Snezana , Vajs Vlatka , Tesevic Vele , Djokovic Dejan , Milosavljevic Slobodan
Published: August 2005

Five lignans with a 2,6-diaryl-3,7-dioxabicycloS3.3.0Coctane skeleton epieudesmin, kobusin, pinoresinol, fargesin and sesartemin, were isolated from the aerial parts and roots of Achillea lingulata. Their structures were identified by comparison of their 1H-NMR and MS data to those in the literature. Fargesin and pinoresinol have not been isolated previously from any species of the genus Achillea.
The critical apparent density for the free flow of copper powder
Authors: Popov Konstantin , Krstic Snezana , Pavlovic Miomir
Published: August 2005

A method for the determination of the critical apparent density, which permits the free flow of electrodeposited copper powder is discussed. It was found that powders the apparent density of which were larger than 2.3 g/cm3 exhibit free flow. This is in good agreement with the literature data.
Aspects of solid state 13C CPMAS NMR spectroscopy in coals from the Balkan peninsula
Authors: Georgakopoulos Andreas
Published: August 2005

The cross-polarized magic-angle-spinning NMR (CPMAS-NMR) technique was used in this work to assess the carbon distribution in coals of different rank (peat, lignite, xylite, sub-bituminous coal) from important deposits in Greece and Bulgaria. The technique is assumed to be only semiquantitative due to a number of interferences, such as spinning side bands (SSB) in the spectra, paramagnetic species in the samples, and low or remote protonation of aromatic carbons. The Bulgarian sub-bituminous coal shows the greatest amounts of aromatic structures. The lignite sample from the Drama basin Northern Greece, is relatively unaltered and largely unlettered, and shows the greatest amounts of aliphatic groups. The 13C-NMR spectra of Pliocene lignites from endemic areas in Serbia and Montenegro and Bosnia, taken from published papers, show significantly more intense resonance's for methoxyl phenolic, and polysaccharide moieties compared to the Drama lignite NMR spectrum. Xylite reveals high contents of carbohydrates.
Synthesis, crystal structure and antiaromatase activity of 17-halo-16,17-seco-5-androstene derivatives
Authors: Penov-Gasi Katarina , Stojanovic Srdjan , Sakac Marija , Djurendic Evgenija , Jovanovic-Santa Suzana , Stankovic S. , Andric Nebojsa , Popsavin Mirjana
Published: August 2005

Starting from 3?-acetoxy-15-cyano-17-oxo-16,17-seco-5-androstene (2) and 3?-acetoxy- 15-cyano-17-hydroxy-17-methyl-16,17-seco-5-androstene (11), new 17-halo-derivatives (5?10 and 13) were obtained. The fluoro derivative 5 was obtained from 17-tosylate 4 in reaction with tetrabutylammonium fluoride. The structure of the 17-iodo-devitive 10 was unambiguously proved by the appropriate X-ray structural analysis. Compounds5?10, as well as 12 and 13 were tested for possible anti-aromatase activity, whereby only compound 9 with bromine as the C-17 substituent, induced 19.4 % inhibition of aromatase activity compared to the control.
The effect of the particle shape and structure on the flowability of electrolytic copper powder I: Modeling of a representative powder particle
Authors: Popov Konstantin , Krstic Snezana , Obradovic Milutin , Pavlovic Miomir , Pavlovic Ljubica , Ivanovic Evica
Published: August 2005

One of the most important properties of copper powder is its flow ability which depends on the shape and the structure of the powder particles. A procedure for the determination of a representative powder particle permitting the free flow of copper powder is proposed.
Synthesis of copper nanorods using electrochemical methods
Authors: Yang Xuegeng , Chen Shenhao , Zhao Shiyong , Li Degang , Ma Houyi
Published: August 2005

Copper nanorods were synthesized using controlled-current electrochemical methods. The surfactants in the electrolyte served as both a templates and stabilizers during the synthesis procedure. TEM images show that the products consist mainly of nanosized rod-like structures. The current density applied during the electrodeposition was found to have an effect on the shape and yield of the copper nanorods.
Stereoselective synthesis of (E)-vinyl alkyl sulfides via hydrozirconation of terminal alkynes
Authors: Ping Zhong , Xian Huang
Published: August 2005

Terminal alkynes react with Cp2Zr(H)Cl (Cp = ?5-C5H5) to give organozirconium complexes, which are trapped with alkylsulfenyl chlorides to afford (E)-vinyl alkyl sulfides in good yield.
Selective liquid-liquid extraction of antimony(III) from hydrochloric acid media by N-n-octylaniline in xylene
Authors: Sargar B.M. , Rajmane M.M. , Anuse M.A.
Published: August 2005

N-n-Octylaniline in xylene was used for the extraction separation of antimony( III) from hydrochloric acid media. Antimony(III) was extracted quantitatively with 10 mL4%N-n-octylaniline in xylene. It was stripped from the organic phase with 0.5 M ammonia and estimated photometrically by the iodide method. The effect of metal ion, acid, reagent concentration and various foreign ions was investigated. The method affords binary and ternary separation of antimony(III) from tellurium(IV), selenium( IV), lead(II) bismuth(III), tin(IV), germanium(IV), copper(II), gold(III), iron(III) and zinc(II). The method is applicable for the analysis of synthetic mixtures alloys and semiconductor thin films. It is fast, accurate and precise.
Sorption-spectrophotometric method for the determination of Pd(II) in aqueous solutions
Authors: Vasic Vesna , Savic Jasmina , Vukelic Nikola
Published: August 2005

The reaction of Pd(II) with 1,8-dihydroxy-2-(pyrazol-5-ylazo)-naphthalene 3-6-disulphonic acid (PACA) sorbed onto Dowex 1-X8 ion-exchange resin was investigated with the aim of developing an absorption-spectrophotometric analytical method for the determination of low Pd(II) concentrations in water. The immobilized reagent formed a 1:1 complex with Pd(II) having an absorption maximum at 650 nm. Parameters, such as pH, wavelength and contact time were optimised for a given amount of the sorbed reagent. The linearity range of absorbance vs. Pd(II) concentration extended from 5x10-6 ? 5x10-5 M 5x10-7 ? 5x10-6 and 2.5x10-8 ? 2.5x10-7 M when using 10, 100 and 200 ml of sample solution, respectively. With a 200 ml sample, the detection limit was 2.5x10-7 M Pd(II). Most metals, except Cu(II), did not interfere when present in up to 100 times the concentration of Pd(II).
The influence of the solvent on organic reactivity. Part II. Hydroxylic solvent effects on the reaction rates of diazodiphenylmethane with 2-(2-substituted cyclohex-1-enyl)acetic and 2-(2-substituted
Authors: Nikolic Jasmina , Uscumlic Gordana , Krstic Vera
Published: August 2005

The rate constants for the reaction of diazodiphenylmethane with 2-(2-substituted cyclohex-1-enyl)acetic acids and 2-(2-substituted phenyl)acetic acids, previously determined in seven hydroxylic solvents, were correlated using the total solvatochromic equation, of the form logk = logk0 + s?*+ a? + b?, the two-parameter model, logk=logk0 + s?*+ a? and a single parameter model logk = logk0 + b?, where ?*is a measure of the solvent polarity, ? represents the scale of solvent hydrogen bond acceptor basicities and ? represents the scale of solvent hydrogen bond donor acidities. The correlations of the kinetic data were carried out by means of multiple linear regression analysis and the solvent effects on the reaction rates were analyzed in terms of initial state and transition state contributions.
Synthesis and characterization of zinc(II), palladium(II) and platinum(II) complexes with 2’-[1-(2-pyridinyl)- ethylidene]oxamohydrazide: The crystal structure of biss2'-[1-(2-pyridinyl)ethylidene]oxa
Authors: Andjelkovic Katarina , Jakovljevic Gordana , Zlatovic Mario , Tesic Zivoslav , Sladic Dusan , Howing Jonas , Tellgren Roland
Published: August 2005

Complexes of Zn(II), Pd(II) and Pt(II) with 2?-[1-(2-pyridinyl)ethylidene ]oxamohydrazide (Hapsox) were synthesized and their structures were determined. All the complexes are of a neutral type with two apsox ligands coordinated to Zn(II) and one apsox ligand coordinated to Pd(II) or Pt(II). In each case, the polydentate was coordinated via pyridine and hydrazone nitrogens and ?-oxyazine oxygen, forming an octahedral geometry around Zn(II), and a square planar one around Pd(II) and Pt(II). The structure determination was performed by IR, 1H-NMR and 13C-NMR spectroscopy, and for the Zn(II) complex by X-ray structure analysis.
Influence of the irradiation conditions on the effect of radiation on polyethylene
Authors: Kacarevic-Popovic Zorica , Kostoski Dusan , Novakovic Ljiljana , Miljevic Nada , Secerov Bojana
Published: August 2005

Two types of polyethylene, low density (LDPE) and high density (HDPE), as well as low density polyethylene containing an antioxidant were subjected to ?-irradiation in the presence of air and in water. The irradiated polymers were studied using IR spectrophotometric analysis. The radiation induced oxidative degradation was followed through the formation of oxygen containing groups by the development of bands in the 1850?1650 cm-1 region and double bonds formation by the development of bands in the 1050?850 cm-1 region. The crosslinking efficiency was determined by measuring the gel content by extraction with xylene. The radiation induced changes in the molecular structure, evolution of oxygen containing species and formation, of vinyl double bonds as well as of the crosslinking efficiency are discussed in terms of the properties of the polymers in an electric field of low strength.
Styrene-divinylbenzene copolymer grafted with phosphonic acid dialkyl esters
Authors: Ilia Gheorghe , Fagadar-Cosma Eugenia , Popa Adriana , Iliesku Smaranda
Published: August 2005

The functionalization of a crosslinked chloromethylated polystyrene 8% divinylbenzene copolymer with phosphonic ester groups is detailed. The reacton conditions were studied in order to determine the optimal conditions for obtaining only diesters. Astatistical method for the calculation of the fraction of repetive units for the inited and final resin is proposed.
Determination of intrinsic equilibrium constants at alumina/electrolyte interface
Authors: Todorovic Zaklina , Milonjic Slobodan
Published: August 2005

Intrinsic ionization and complexation constants at an alumina/electrolyte interface were studied by the site binding model, while the sorption of alkali cations from aqueous solutions was interpreted by the triple-layer model. The surface properties of alumina were investigated by the potentiometric acid-base titrationmethod. The point of zero charge (pHpzc) of alumina obtained by thismethod was found to be 7.2. The obtained mean values of the intrinsic protonation and ionization constants of the surface hydroxyl groups and the intrinsic surface complexation constant, in different electrolytes, are pKinta1 = 4.4, pKinta2 = 9.6 and pKintM+ = 9.5 respectively.
Influence of temperature on the volumetric properties of ethanol + water + 1-pentanol
Authors: Resa J.M. , Gonzáles C. , Goenaga J.M. , Iglesias M.
Published: August 2005

Knowledge of physical properties and phase equilibria is necessary for the design and optimization of the equipment for the production of distilled alcoholic beverages. In this paper the temperature dependence of the excess molar volumes of the ternary system ethanol + water + 1-pentanol in the temperature range 228.15 ? 323.15 K and atmospheric pressure, are presented due to the importance of 1-pentanol among the flavour compounds contained in this type of beverages. The excess molar volumes are negative over the whole homogeneous composition range, but tend to positive values towards the binaries ethanol + 1-pentanol and water + 1-pentanol. Because the design of current processes is strongly computer oriented, consideration was also given to how accurate the predictions of the SRK equations of state are. Different derived properties were computed due to their importance in the study of specific molecular interactions.
Reduction of Ribonucleosides to 2′‐Deoxyribonucleosides
Authors: Robins Morris J. , Wnuk Stanislaw F.
Published: August 2005

Ribonucleosides are converted into 2′‐deoxyribonucleosides in good yields by a four‐step procedure. Selective protection of the 3′‐ and 5′‐hydroxyl groups with 1,3‐dichloro‐1,1,3,3‐tetraisopropyl‐1,3‐disiloxane is followed by functionalization of the 2′‐hydroxyl group with phenoxythiocarbonyl chloride. Free radical–mediated reductive C2′–O2′ bond cleavage of these 3′,5′‐O‐TPDS‐2′‐O‐PTC‐nucleoside derivatives with tributyltin hydride, followed by removal of the silyl protecting group with tetrabutylammonium fluoride, provides the 2′‐deoxyribonucleosides. Adenosine, cytidine, guanosine, and uridine are converted into dA, dC, dG, and dU in overall yields of 60% to 80%. Use of tributyltin deuteride in the reductive cleavage step gives 2′‐deuterio‐2′‐deoxyadenosine in 81% yield from adenosine with >85% retention of configuration at C2′. Application of this four‐step protocol with nucleoside analogs is straightforward.
A low‐temperature heteronuclear NMR study of two exchanging conformations of metal‐bound pyoverdin PaA from Pseudomonas aeruginosa
Authors: Tzou Der‐Lii , Wasielewski Emeric , Abdallah Mohamed A. , Kieffer Bruno , Atkinson R. Andrew
Published: August 2005

Under iron‐deficient conditions, the Gram‐negative bacterium Pseudomonas aeruginosa ATCC 15692 secretes a peptidic siderophore, pyoverdin PaA, composed of an aromatic chromophore derived from 2,3‐diamino‐6,7‐dihydroxyquinoline and a partially cyclized octapeptide, D‐Ser–L‐Arg–D‐Ser–L‐FoOHOrn–(L‐Lys–L‐FoOHOrn–L‐Thr–L‐Thr) (FoOHOrn: δN‐formyl‐δN‐hydroxyornithine), in which the C‐terminal carboxyl group forms a peptidic bond with the primary amine of the L‐Lys side chain. Ferric iron is chelated by the catechol group on the chromophore and the two hydroxyornithine side chains. In aqueous solution, the 1H‐NMR spectrum of pyoverdin PaA–Ga(III), in which Ga(III) is used instead of Fe(III) for spectroscopic purposes, showed clear evidence of exchange broadening, preventing further structural characterization. The use of cryo‐solvents allowed measurements to be made at temperatures as low as 253 K where two distinct conformations with roughly equivalent populations could be observed. 13C and 15N labeling of pyoverdin PaA enabled complete assignment of both forms of pyoverdin PaA–Ga(III) at 253 and 267 K, using triple‐resonance multidimensional NMR experiments commonly applied to doubly labeled proteins. © 2005 Wiley Periodicals, Inc. Biopolymers 79: 139–149, 2005

This article was originally published online as an accepted preprint. The “Published Online” date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com
Development of a Novel Environmentally Friendly Electrolytic System by Using Recyclable Solid‐Supported Bases for In Situ Generation of a Supporting Electrolyte from Methanol as a Solvent: Application for Anodic Methoxylation of Organic Compounds
Authors: Tajima Toshiki , Fuchigami Toshio
Published: August 2005

We have successfully developed a novel environmentally friendly electrolytic system using recyclable solid‐supported bases for in situ generation of a supporting electrolyte from methanol as a solvent. It was found that solid‐supported bases are electrochemically inactive at an electrode surface. It was also found that solid‐supported bases dissociate methanol into methoxide anions and protons. Therefore, in the presence of solid‐supported bases, it was clarified that methanol serves as both a solvent and a supporting electrolyte generated in situ. Anodic methoxylation of various compounds with solid‐supported bases was carried out to provide the corresponding methoxylated products in good to excellent yields with a few exceptions. The methoxylated products and the solid‐supported bases were easily separated by only filtration, and the desired pure methoxylated products were readily isolated simply by concentration of the filtrates. The separated and recovered solid‐supported bases were recyclable for several times.
Asymmetric Total Synthesis of Fredericamycin A: An Intramolecular Cycloaddition Pathway
Authors: Akai Shuji , Tsujino Toshiaki , Fukuda Nobuhisa , Iio Kiyosei , Takeda Yoshifumi , Kawaguchi Ken‐ichi , Naka Tadaatsu , Higuchi Kazuhiro , Akiyama Emi , Fujioka Hiromichi , Kita Yasuyuki
Published: August 2005

The asymmetric total synthesis of the potent antitumor antibiotic fredericamycin A ((S)‐1) was achieved by the intramolecular [4+2] cycloaddition of the silylene‐protected styrene derivative (S)‐7 followed by the aromatic Pummerer‐type reaction of the sulfoxide (S)‐5. Although we had already succeeded in the total synthesis of racemic 1 by the same approach, synthesis of its asymmetric version was more complicated than we had expected due to the difficulties involved in constructing the quaternary carbon center and the tendency of this center to undergo facile racemization. Racemization of this center during the installation of the acetylene moiety on the dione (R)‐8 was the most serious aspect. Systematic studies of its DE‐ring analogue (R)‐25 revealed that racemization of the quaternary carbon center proceeded by a retro‐aldol–aldol reaction of the initial adduct, (1R)‐39 a‐Li, and that the degree of racemization was dependent on the reaction temperature. The racemization process could be completely depressed by keeping the reaction temperature at −78 °C. The construction of the stereogenic quaternary carbon center was achieved by the lipase‐catalyzed desymmetrization of the prochiral 1,3‐diol 9 a bearing the DEF‐ring moiety. These studies enabled us to attain the asymmetric total synthesis of (S)‐1 while completely retaining the chiral integrity created by the enzymatic reactions.
Configurational Stability of Bisindolylmaleimide Cyclophanes: From Conformers to the First Configurationally Stable, Atropisomeric Bisindolylmaleimides
Authors: Barrett Simon , Bartlett Stephen , Bolt Amanda , Ironmonger Alan , Joce Catherine , Nelson Adam , Woodhall Thomas
Published: August 2005

The bisindolylmaleimides are selective protein kinase inhibitors that can adopt two limiting diastereomeric (syn and anti) conformations. The configurational stability of a range of substituted and macrocyclic bisindolylmaleimides was investigated by using appropriate techniques. With unconstrained bisindolylmaleimides, the size of the 2‐indolyl substituents was found to affect configurational stability, though not sufficiently to allow atropisomeric bisindolylmaleimides to be obtained. However, with a tether between the two indole nitrogen atoms in place, the steric effect of 2‐indolyl substituents was greatly exaggerated, leading to large differences in configurational stability. The rate of interconversion of the syn and anti conformers varied by over twenty orders of magnitude through substitution of a bisindolylmaleimide ring system, which was constrained within a macrocyclic ring. Indeed, the first examples of configurationally stable atropisomeric bisindolylmaleimides are reported; the half‐life for epimerisation of these compounds at room temperature was estimated to be >107 years.
The para‐Siletanylbenzyl (PSB) Ether: A Peroxide‐Cleavable Protecting Group for Alcohols and Phenols.
Authors: Lam Hubert , House Sarah E. , Dudley Gregory B.
Published: August 2005

For Abstract see ChemInform Abstract in Full Text.
Regioselective Allylgallation of Terminal Alkynes.
Authors: Lee Phil Ho , Heo Yunkiu , Seomoon Dong , Kim Sundae , Lee Kooyeon
Published: August 2005

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Efficient Enantioselective Synthesis of Cyclopropanes from Sulfonylpyrazolines
Authors: Garcia Ruano Jose L. , Martin Castro Ana M. , Torrente Esther
Published: August 2005

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Palladium‐Catalyzed Suzuki—Miyaura Coupling Reactions Involving β,β‐Dihaloenamides: Application to the Synthesis of Disubstituted Ynamides.
Authors: Couty Sylvain , Barbazanges Marion , Meyer Christophe , Cossy Janine
Published: August 2005

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One‐Pot Synthesis of Substituted Catechols from the Corresponding Phenols.
Authors: Hansen Trond Vidar , Skatteboel Lars
Published: August 2005

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Synthesis of New 3‐Phenoxypropan‐2‐ols with Various Heterocyclic Substituents.
Authors: Mesropyan E. G. , Ambartsumyan G. B. , Avetisyan A. A. , Galstyan A. S. , Arutyunova I. R.
Published: August 2005

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Reaction of α‐Methylstyrene with Arylsulfonyl Chlorides: Spontaneous Dehydrochlorination Against the Zaitsev Rule.
Authors: Ermolaeva Valentina V. , Gerasimova Nina P. , Nozhnin Nikolai A. , Moskvichev Yuri A. , Alov Eugeni M. , Danilova Angelina S. , Shutova Irina V. , Kozlova Olga S.
Published: August 2005

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Catalytic Metathesis of Carbon Dioxide with Heterocumulenes Mediated by Titanium Isopropoxide.
Authors: Ghosh Rajshekhar , Samuelson Ashoka G.
Published: August 2005

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A Convenient Synthesis of Fluoroalkylated γ‐Butyrolactones from Polyfluoroalkyl Iodides and 4‐Pentenoic Acid Catalyzed by Pd(PPh3)4.
Authors: Xiao Fanhua , Wu Fanhong , Yang Xueyan , Shen Yongjia , Shi Xinmei
Published: August 2005

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Efficient and Versatile Single‐Pot Alternative Approach to Dipyrromethanes.
Authors: Singh Kamaljit , Behal Sonia , Deb Prasant K.
Published: August 2005

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Reactivity of Amidinium Salts′ Access to Benzo[4,5]imidazo[2,1‐b]thiazoles
Authors: Sissouma D. , Adjou A. , Toure S. A. , Zoakouma S. , Gnon Baba , Tea G. C.
Published: August 2005

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Synthesis and Fungicidal Activity of Fluorine‐Containing Phenylimino‐thiazolidines Derivatives.
Authors: Xu Xiaoyong , Qian Xuhong , Li Zhong , Song Gonghua , Chen Weidong
Published: August 2005

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Microwave‐Assisted Preparation of 2‐Substituted Benzothiazoles
Authors: Rostamizadeh Shahnaz , Housaini S. A. Gh.
Published: August 2005

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Preparation of 1,5‐Fused Tetrazoles under Solvent‐Free Conditions.
Authors: Eshghi Hossein , Hassankhani Asadollah
Published: August 2005

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Chemistry of 3‐Hetarylcoumarins. Part 2. 3‐(2‐Thiazolyl)coumarins.
Authors: Khilya O. V. , Shablykina O. V. , Frasinyuk M. S. , Turov A. V. , Ishchenko V. V. , Khilya V. P.
Published: August 2005

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Synthesis and Herbicidal Activity of 2‐Cyano‐3‐(2‐fluoro‐5‐pyridyl)methylaminoacrylates.
Authors: Liu Yuxiu , Zhao Qiqi , Wang Qingmin , Li Heng , Huang Runqiu , Li Yonghong
Published: August 2005

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Efficient Route to Substituted 2‐Aminoquinoline.
Authors: Dyachenko V. D. , Kudryavtseva A. G.
Published: August 2005

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Synthesis of 2‐R‐4,5,7‐Trimethyl‐1‐vinyl‐4,5,6,7‐tetrahydropyrrolo[3,2‐c]pyridines
Authors: Borisova T. N. , Bonifas Nsabimana , Voskresenskii L. G. , Chernyshev A. I. , Varlamov A. V. , Krapivko A. P.
Published: August 2005

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Optimization of Purine Based PDE1/PDE5 Inhibitors to a Potent and Selective PDE5 Inhibitor for the Treatment of Male ED.
Authors: Boyle Craig D. , et al. et al.
Published: August 2005

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Quinoxaline Synthesis from α‐Hydroxy Ketones via a Tandem Oxidation Process Using Catalyzed Aerobic Oxidation.
Authors: Robinson Ross S. , Taylor Richard J. K.
Published: August 2005

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Ring Fission of Chiral Cyclic Acetals Plus Intramolecular [4 + 2] Cycloaddition: A Sequential Access to Medium‐Size Lactones. Application to the Synthesis of Carbasugars.
Authors: Lemiegre Loic , Stevens Richard L. , Combret Jean‐Claude , Maddaluno Jacques
Published: August 2005

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Synthesis of Multisubstituted 1,3‐Butadienes Using the Ruthenium‐Catalyzed Double Addition of Trimethylsilyldiazomethane to Alkynylboronates.
Authors: Morita Ryotaro , Shirakawa Eiji , Tsuchimoto Teruhisa , Kawakami Yusuke
Published: August 2005

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Lathyranoic Acid A: First Secolathyrane Diterpenoid in Nature from Euphorbia lathyris.
Authors: Liao Shang‐Gao , Zhan Zha‐Jun , Yang Sheng‐Ping , Yue Jian‐Min
Published: August 2005

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The Synthesis of Various of 1,6‐Disulfide‐Bridged D‐Hexopyranoses.
Authors: Goddard‐Borger Ethan D. , Stick Robert V.
Published: August 2005

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Synthesis of Pyrazine Alkaloids (I) from Botryllus leachi
Authors: Buron Frederic , Ple Nelly , Turck Alain , Queguiner Guy
Published: August 2005

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Formal Synthesis of Linderone and Lucidone Based on One‐Pot Cyclizations of 1,3‐Bis‐silyl Enol Ethers with Oxalyl Chloride.
Authors: Bose Gopal , Langer Peter
Published: August 2005

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Trivalent Atom Contribution on Solid—Solid Transformation of Ga13 Polycation Intercalated Clay into Sodalite Investigated by X‐Ray Absorption Spectroscopy.
Authors: Lee Sung‐Reol , Park Man , Han Yang‐Su , Hwang Sung‐Ho , Choy Jin‐Ho
Published: August 2005

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Photophysical Processes Related to Photoadsorption and Photocatalysis on Wide Band Gap Solids: A Review
Authors: Ryabchuk Vladimir
Published: August 2005

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Homoleptic, Mononuclear Transition Metal Complexes of 1,2‐Dithiolenes: Updating Their Electrochemical‐to‐Structural Properties
Authors: Zanello Piero , Grigiotti Emanuela
Published: August 2005

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Cyclizations to New Azolopyridazines and Related Ring Systems
Authors: Hajos Gyoergy , Riedl Zsuzsanna , Matyus Peter , Maes Bert U. W. , Lemiere Guy L. F.
Published: August 2005

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Nonionic Tenside Ligands and Its Application in Biphasic Catalysis
Authors: Jin Zilin , Feng Cuilan , Wang Yanhua
Published: August 2005

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Side Effects, Solvents, and Co‐Solvents
Authors: Hanson Brian E.
Published: August 2005

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Indium Compounds
Authors: Loh T.‐P.
Published: August 2005

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Novel at the Library
Authors: Yaffe Michael B.
Published: August 2005

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Macrocyclic and Supramolecular Coordination Chemistry
Authors: Cronin Leroy
Published: August 2005

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Odor and (Bio)diversity: Single Enantiomers of Chiral Fragrant Substances
Authors: Abate Agnese , Brenna Elisabetta , Fuganti Claudio , Gatti Francesco G. , Serra Stefano
Published: August 2005

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Conformationally Constrained PNA Analogues: Structural Evolution Toward DNA/RNA Binding Selectivity
Authors: Kumar Vaijayanti A. , Ganesh Krishna N.
Published: August 2005

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Total Synthesis of Macrosphelides
Authors: Kobayashi Yuichi
Published: August 2005

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Catalytic Properties and the Role of Copper in Bovine and Lentil Seedling Copper/Quinone‐Containing Amine Oxidases: Controversial Opinions
Authors: Agostinelli Enzo , Belli Francesca , Dalla Vedova Laura , Longu Silvia , Mura Anna , Floris Giovanni
Published: August 2005

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Order—Disorder Conformational Transitions of Carbohydrate Polymers: The Calorimetry Contribution to Understand Polysaccharide Solution Properties
Authors: Cesaro A. , Sussich L. F. , Navarini L.
Published: August 2005

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A Chiral Copper Complex Forms Supramolecular Homochiral Helices viaO–H···Cl–Cu Interactions
Authors: Pradeep Chullikkattil P. , Zacharias Panthapally S. , Das Samar K.
Published: August 2005

An enantiopure ligand H2L [Schiff base prepared from (S)‐(+)‐2‐phenylglycinol and 2‐hydroxy‐5‐nitrobenzaldehyde] reacts with CuCl2·2H2O to yield a chiral copper complex [Cu(HL)Cl] (1) that forms right‐handed supramolecular helices via O–H···Cl–Cu hydrogen bonds. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)
Conformational Analysis of Chiral Ferrocene–Peptides
Authors: Heinze Katja , Beckmann Manuela
Published: August 2005

Ferrocene‐containing dipeptides Ac‐Fca‐AA‐OMe (AA = L‐Val, L‐Ile) with the artificial amino acid 1'‐aminoferrocene‐1‐carboxylic acid (Fca) and chiral α‐amino acid building blocks display hydrogen‐bonded structures that result in organised helical ferrocene units in solution, as evidenced by spectroscopic and theoretical investigations. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)
4f‐ansa‐Metallocenes—Dinuclear Complexes where the ansa‐Dicyclopentadienyl Ligands Simultaneously Act in a Chelating and Bridging Mode — Crystal Structure of (LY)2(μ‐L) [L = 2,6‐Pyridinediylbis(methylcyclopentadienyl)]
Authors: Paolucci G. , Vignola M. , Formenti S. , Massa W.
Published: August 2005

The reaction between [LNYX]2 [X = Cl, OTf; LN = 2,6‐pyridinediylbis(methylcyclopentadienyl] and L'Na2 [L' = LN = 2,6‐pyridinediylbis(methylcyclopentadienyl; LSi = dimethylsilanediylbis(cylopentadienyl); LO = 2,5‐furanediylbis(methylcyclopentadienyl)] in a 2:1 molar ratio affords dinuclear complexes of formula (LY)2(μ‐L'), in which the ansa‐bis(cyclopentadienyl) ligands simultaneously act both in a chelating and bridging mode. The X‐ray crystal structure of (LNY)2(μ‐LN), determined at 193 K shows an arrangement close to trigonal planar of the centroids Cg of the three Cp ligands around the Y atoms. The reactivity of the (LNLn)2(μ‐L') species containing different bridging ansa‐bis(cyclopentadienyl) groups with an additional free donor atom was tested to verify the possibility of coordination of a third lanthanide ion. The rearrangement reactions that occur, finally leading to the formation of the only [LNLnX]2 species, are likely to depend on the presence of the further coordinating atom in the ligand bridging the two metal ions. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)
A Tetraphosphane Imine Ligand Which Enforces Square‐Pyramidal Coordination
Authors: Zimmermann Christopher , Heinemann Frank W. , Grohmann Andreas
Published: August 2005

The tetrapodal pentadentate NP4 ligand 2,6‐C5H3N[CMe(CH2PPh2)2]2, which is readily prepared from the reaction of the corresponding tetrabromide with KPPh2, forms mononuclear complexes with nickel(II) and cobalt(II). In the case of nickel(II), the coordination mode adopted by the ligand is sensitive to the nature of the counterion: Use of NiCl2 gives a chloro complex as one of the products, which, as determined by X‐ray crystallography, has a central ion coordinated by three phosphane and one chloro substituent in a distorted square planar fashion; by contrast, the reaction with Ni(BF4)2 gives a complex of approximate square‐pyramidal geometry as the only product, in which all five atoms of the NP4 set are coordinated to the nickel ion, despite the steric bulk of the eight phenyl substituents. The same type of complex is obtained with Co(BF4)2 and Co(ClO4)2. Attempts to increase the coordination number of either complex beyond 5 have been unsuccessful. In particular, the cobalt(II) complex (17 valence electrons) is practically inert to reagents such as O2, NO, NO+, I2, Cl2 or H2. Full spectroscopic details for the complexes, as well as X‐ray structure analyses, are reported. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)
Unprecedented Coordination Mode Variation of Group 13 Metal–Alkyl Compounds Derived from Methyl Thiosalicylate
Authors: Lewiński Janusz , Bury Wojciech , Kopeć Tomasz , Tratkiewicz Ewa , Justyniak Iwona , Lipkowski Janusz
Published: August 2005

The X‐ray structure analysis of the alkylaluminum and‐indium compounds derived from methyl thiosalicylate,Me2Al(SC6H4‐2‐CO2Me) and [Me2In(μ‐SC6H4‐2‐CO2Me)]2, revealed that the intermolecular S···C(π) interaction between the Al–S thiolate units and the ester π‐surface can effectively compete with the hypercoordinate sulfur–metal dative bond. The former compound exists as the noncovalently bonded dimer involving the thiolate sulfur atom and the electrophilic carbon atom of the ester functionality, whereas the indium complex is a five‐coordinate dimer with the In2(μ‐S)2 central core. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)
Desymmetrizing Hydroformylation of Diallylcarbinols with the Aid of a Planar‐Chiral, Catalyst‐Directing Group
Authors: Breit Bernhard , Breuninger Daniel
Published: August 2005

The desymmetrizing hydroformylation of diallylcarbinols has been achieved by employing a planar‐chiral, substrate‐bound catalyst‐directing group — the ortho‐(diphenylphosphanyl)ferrocenylcarbonyl group (o‐DPPF). The method allows the simultaneous construction of two stereogenic centers in a 1,3‐relative position with high levels of stereocontrol. The diastereoselectivity was investigated as a function of substrate structure. Determination of the relative and absolute configuration of the product aldehydes (chemical derivatization and X‐ray crystallographic studies), as well as the conditions for removal and recovery of the catalyst‐directing o‐DPPF group, are described. Furthermore, a model is suggested that rationalizes the experimentally observed stereochemical result based on the minimization of syn‐pentane interactions. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)
Efficient Preparation of 4‐Iodofuran‐2(5H)‐ones by Iodolactonisation of 2,3‐Allenoates with I2
Authors: Fu Chunling , Ma Shengming
Published: August 2005

4‐Iodofuran‐2(5H)‐ones were prepared, in moderate to high yields, by the facile iodolactonisation of ethyl 2,3‐allenoates with I2 in aqueous MeCN by the direct participation of the carbonyl oxygen atom in the regioselective electrophilic addition of the allene moiety. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)