bluuebunny/crossref_metadata_2025 huggingface dataset:
A New Synthetic Strategy towards Molecules with Mechanical Bonds: Nonionic Template Synthesis of Amide‐Linked Catenanes and Rotaxanes
Authors: Jäger Ralf , Vögtle Fritz
Published: January 2004

After Sauvage et al. and Stoddart et al. had developed the now commonly used and well‐established catenane and rotaxane synthesis utilizing phenanthroline/Cu+and bipyridinium/crown units, a new way to synthesize mechanical bonds was discovered in 1992—the synthesis of amide‐linked catenanes and rotaxanes around a neutral template. The formation of the template, which leads to the host–guest bond, does not proceed by covalent or ionic interaction, but by weak supramolecular interactions, such as hydrogen bonding, π‐stacking, π‐donor–π‐acceptor interaction, and steric complementarity. The simple synthetic units (arene dicarboxylic acid dichlorides and diamines) can be varied in an astonishing number of ways, few steps are required to obtain the target molecules, and the yields of these syntheses approach those of ordinary organic syntheses. After the preparation of [2]catenanes, it took only a few years to prepare [2]‐, [3]‐, and bis[2]‐rotaxanes of the amide type. The introduction of sulfonamide groups enabled alkylation of the sulfonamide nitrogen atom, and this made chemical reactions with catenanes and rotaxanes feasible. Intra‐ and intermolecular connections of catenanes and rotaxanes were then possible, and a molecule with the topology of a “pretzel” has recently been prepared. This allowed new insights into the molecular recognition processes of neutral guest and host substances, as well as further understanding of these processes in template synthesis, isomerism in catenanes, and the regioselectivity of the formation of catenane isomers. Competitive binding studies of guest molecules in the cavity of concave receptors with more than one binding site can be perfomed. These studies might result in higher synthetic yields of molecules with mechanical bonds and lead to further progress in the development of supramolecular nanostructures and molecular switches.
Enzymes and Transition Metal Complexes in Tandem—A New Concept for Dynamic Kinetic Resolution
Authors: Stürmer Rainer
Published: January 2004

Some enzymes tolerate bases and transition metal catalysts at elevated temperatures—conditions which, for example, Williams et al. and Bäckvall et al. have shown are suitable for racemizing secondary alcohols by Meerwein–Ponndorf reduction/Oppenauer oxidation. Enzyme‐catalyzed acylation under Meerwein‐Pondorf‐Varley conditions facilitates dynamic kinetic resolutions of alcohols.
Effective Low‐Temperature Aromatization of Ethane over H‐Galloaluminosilicate(MFI) Zeolites in the Presence of Higher Alkanes or Olefins
Authors: Choudhary Vasant R. , Kinage Anil K. , Choudhary Tushar V.
Published: January 2004

The high thermodynamic barrier for ethane aromatization at lower temperatures (400–500°C) over a H‐GaAlMFI zeolite can be overcome. Both ethane conversion and the yield of arenes drastically increase (4–80 ×) by carring out the aromatization in the presence of olefins or higher alkanes. The enhanced reactivity results from a change in the reaction mechanism, and a hydrogen‐transfer reaction takes place between ethane and higher olefins.
Superconductivity and Chemistry
Authors: Simon Arndt
Published: January 2004

The microscopic theory of superconductivity worked out by Bardeen, Cooper, and Schrieffer led to a fundamental understanding of the phenomenon. However, this theory does not provide a materials aspect. Starting from the special situation of chemical bonding in carbides and carbide halides of the rare earth metals a general view of the origin of superconductivity is developed, based on a tendency for (pairwise) localization of conduction electrons. This approach is tested in terms of special features in the electronic band structure and compared with existing physical models of electron pairing in real space. Its applicability to high‐temperature superconductors discovered during the last decade is discussed.
2‐Thioxoethen‐1‐one (OCCS)
Authors: Maier Günther , Reisenauer Hans Peter , Ruppel Raimund
Published: January 2004

C2S2can be detected in a matrix, whereas C2O2cannot. What about C2OS?This question has now been answered with the generation of C2OS in an Ar matrix [Eq. (a)] and the characterization with matrix‐isolation spectroscopy. Under matrix conditions C2OS is a stable molecule, which most likely exists in the triplet ground state.equation image
Chemistry and Molecular Biology in the Search for New LHRH Antagonists
Authors: Kutscher Bernhard , Bernd Michael , Beckers Thomas , Polymeropoulos Emmanuel E. , Engel Jürgen
Published: January 2004

Hormones—and in particular, the sex hormones—were the first growth factors discovered to be involuntary helpers of cancer. Female breast cancer and male prostate cancer are the best known examples of tumors acknowledged to be hormone‐dependent. A look at cancer statistics shows that breast cancer is still the most frequent cancer in women; in men, prostate cancer plays a similarly dominant role with increasing age. Shutting down the main production site of the sex hormones estrogen and testosterone either by removing the ovaries or by castration is a well‐known and often effective therapy; however, these procedures can be problematic due to the concomittant psychological stress. Modern hormone therapy for advanced breast cancer and prostate cancer attempts to spare the patient such irreversible operative procedures for as long as possible, by using hormone antagonists, such as the LHRH antagonists, which hinder deployment of the hormone itself and thus its growth‐promoting activity.
Effects of calcium carbonate and its purity on crystallization and melting behavior, mechanical properties, and processability of syndiotactic polypropylene
Authors: Supaphol Pitt , Harnsiri Wipasiri , Junkasem Jirawut
Published: February 2004

Calcium carbonate‐filled syndiotactic poly(propylene) (CaCO3‐filled s‐PP) was prepared in a self‐wiping, co‐rotating twin‐screw extruder. The effects of CaCO3 of varying particle size (1.9, 2.8 and 10.5 μm), content (0–40 wt %), and type of surface modification (uncoated, stearic acid‐coated, and paraffin‐coated) on the crystallization and melting behavior, mechanical properties, and processability of CaCO3‐filled s‐PP were investigated. Non‐isothermal crystallization studies indicate that CaCO3 acts as a good nucleating agent for s‐PP. The nucleating efficiency of CaCO3 for s‐PP was found to depend strongly on its purity, type of surface treatment, and average particle size. Tensile strength was found to decrease, while Young's modulus increased, with increasing CaCO3 content. Both types of surface treatment on CaCO3 particles reduced tensile strength and Young's modulus, but improved impact resistance. Scanning electron microscopy (SEM) observations of the fracture surfaces for selected CaCO3‐filled s‐PP samples revealed an improvement in CaCO3 dispersion as a result of surface treatment. Finally, steady‐state shear viscosity of CaCO3‐filled s‐PP was found to increase with increasing CaCO3 content and decreasing particle size. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 201–212, 2004
Synthesis and characterization of novel aromatic condensation polymers containing rigid benzoxazole pendent groups
Authors: Kim Ji‐Heung , Kim Yong Hwan , Kim Young Jun , Won Jong Chan , Choi Kil‐Young
Published: February 2004

A new aromatic diamine monomer containing benzoxazole substituents was prepared by a multistep synthesis starting from 1,4‐dibromo‐2,5‐difluorobenzene. The diamine was polymerized with commercial aromatic dianhydride or dicarboxylic acid chloride monomers to provide several different poly(amic acid)s and polyamides with their inherent viscosities in the range of 0.24–0.46 dL/g. Thermal properties of these polymers including thermal imidization of poly(amic acid)s into polyimides were investigated by using FTIR, DSC, and TGA. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 178–185, 2004
Polyaniline–nylon 6 composite fabric for ammonia gas sensor
Authors: Hong Kyung Hwa , Oh Kyung Wha , Kang Tae Jin
Published: February 2004

Conducting polymers constitute a new class of sensing materials, which can be prepared by a simple oxidative polymerization method. An ammonia gas sensor was prepared by polymerizing aniline on the surface of nylon 6 fabrics and doped with various acids in this study. The fabricated polyaniline (PANI)–nylon 6 composite fabrics showed high sensitivity and fast response for NH3 gas. In particular, the PANI–nylon 6 composite fabrics doped by monocarboxylic acids (such as formic acid, acrylic acid, and trichloroacetic acid) displayed excellent sensitivity and fast response. Moreover, no significant changes in the Tm and crystallinity were found in these composite fabrics. Hence the PANI–nylon 6 composite fabrics are attractive alternatives for use in sensing applications because of their excellent sensing ability, low cost, and ease of preparation. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 37–42, 2004
Cure properties of methacrylate‐type prepolymer that include cyclohexane moiety
Authors: Kim Whan Gun , Lee Jun Young
Published: February 2004

New methacrylate‐type prepolymers including a cyclohexane moiety, which may be used as binder resins for the color filter resist of liquid crystal display, were synthesized by the reaction with methacrylic acid (MA) and epoxy resins. Their photo‐ and thermal cure properties were investigated using Fourier transform infrared spectroscopy and DSC, respectively. Their photocure reaction rates and the extent of reaction conversion increased with the concentration of photoinitiator and intensity of UV irradiation. An increase of photocure reaction temperature was attributed to the increase of photocure reaction rate and the degree of reaction conversion for EHPE‐3150‐MA prepolymer. Thermal stability was studied by observing changes in the transmittance of the photocured polymer film upon heating. The polymer was extremely stable, showing almost no transmittance change in the visible range even after being heated at 250°C for 1 h. We also investigated thermal cure reaction using a DSC technique. An autocatalytic kinetic reaction occurs in these systems, and the kinetic parameters of all systems were reported in terms of a generalized kinetic equation that considered the diffusion term. It can be shown that the reaction conversion rate of NC‐9110‐MA is faster than that of EHPE‐3150‐MA, regardless of the kind of thermal initiator. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 43–52, 2004
Acetylation of sugarcane bagasse hemicelluloses under mild reaction conditions by using NBS as a catalyst
Authors: Sun Xaio‐Feng , Sun Run‐Cang , Zhao Li , Sun Jing‐Xia
Published: February 2004

Sugarcane bagasse hemicelluloses were partially acetylated with acetic anhydride using N‐bromosuccinimide (NBS) as a catalyst under mild conditions in an almost solvent‐free system. The overall yield and degree of substitution (DS) were varied from 66.2 and 83.5% and between 0.27 and 1.15, respectively, by changing the reaction temperature and duration. It was found that the yield and DS increased with reaction temperature from 18 to 80°C and reaction time between 0.5 and 5.0 h. The results showed that treatment of the native hemicelluloses with acetic anhydride using NBS as a catalyst conveniently provided the corresponding biopolymer esters. The products were characterized by FTIR, 13C‐NMR spectroscopy, and thermal analysis. The new biopolymer acetates were thermally stable to over 200°C but underwent significant and rapid thermal degradation when heated above the onset of thermal degradation. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 53–61, 2004
Chromatographic performance of monodisperse–macroporous particles produced by “modified seeded polymerization.” I: Effect of monomer/seed latex ratio
Authors: Unsal E. , Camli S. T. , Senel S. , Tuncel A.
Published: February 2004

In this study, the monodisperse–macroporous particles produced by a relatively new polymerization protocol, the so‐called, “modified seeded polymerization,” were used as column‐packing material in the reversed phase chromatography (RPC) of proteins. The particles were synthesized in the form of styrene‐divinylbenzene copolymer approximately 7.5 μm in size. In the first stage of the synthesis, the monodisperse polystyrene particles 4.4 μm in size were obtained by dispersion polymerization and used as the “seed latex.” The seed particles were swollen by a low‐molecular‐weight organic agent and then by a monomer mixture. The monodisperse–macroporous particles were obtained by the polymerization of monomer mixture in the seed particles. In the proposed polymerization protocol, the number of successive swelling stages was reduced with respect to the present techniques by the use of sufficiently large particles with an appropriate average molecular weight as the seed latex. A series of particles with different porosity properties was obtained by varying the monomer/seed latex ratio. The separation behavior of HPLC columns including the produced particles as packing material was investigated in the RPC mode using a protein mixture including albumin, lysozyme, cytochrome c, and ribonuclease A. The chromatograms were obtained with different flow rates under an acetonitrile–water gradient. The theoretical plate number increased and chromatograms with higher resolutions were obtained with the particles produced by using a lower monomer/seed latex ratio. The separation ability of the column could be protected over a wide range of flow rates (i.e., 0.5–3 mL/min) with most of the materials tested. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 607–618, 2004
Low electromagnetic field (50 Hz) induces differentiation on primary human oral keratinocytes (HOK)
Authors: Manni Vanessa , Lisi Antonella , Rieti Sabrina , Serafino Annalucia , Ledda Mario , Giuliani Livio , Sacco Donatella , D'Emilia Enrico , Grimaldi Settimio
Published: January 2004

This work concerns the effect of low frequency electromagnetic fields (ELF) on biochemical properties of human oral keratinocytes (HOK). Cells exposed to a 2 mT, 50 Hz, magnetic field, showed by scanning electron microscopy (SEM) modification in shape and morphology; these modifications were also associated with different actin distribution, revealed by phalloidin fluorescence analysis. Moreover, exposed cells had a smaller clonogenic capacity, and decreased cellular growth. Indirect immunofluorescence with fluorescent antibodies against involucrin and β‐catenin, both differentiation and adhesion markers, revealed an increase in involucrin and β‐catenin expression. The advance in differentiation was confirmed by a decrease of expression of epidermal growth factor (EGF) receptor in exposed cells, supporting the idea that exposure to electromagnetic field carries keratinocytes to higher differentiation level. These observations support the hypothesis that 50 Hz electromagnetic fields may modify cell morphology and interfere in differentiation and cellular adhesion of normal keratinocytes. Bioelectromagnetics 25:118–126, 2004. © 2004 Wiley‐Liss, Inc.
Apparent biological effect of strong magnetic field on mosquito egg hatching
Authors: Pan Hongjun , Liu Xianghong
Published: January 2004

Apparent biological effects of strong magnetic fields were observed in the hatching behavior of fresh mosquito eggs in the center of 9.4 and 14.1 T magnets. In the first experiment performed at 20 ± 1 °C, the hatching was delayed 32 h by a 9.4 T magnetic field and 71 h by a 14.1 T magnetic field. In the second experiment performed at 22 ± 1 °C, the hatching was delayed 14 h by a 9.4 T magnetic field and 27 h by a 14.1 T magnetic field. In the magnetic field range of this study, the hatching delay increases nonlinearly with the intensity of the magnetic field. The experimental results also suggest that the biological effects of magnetic fields could be reversible or partially reversible to some extent. Bioelectromagnetics 25:84–91, 2004. © 2004 Wiley‐Liss, Inc.
Corona discharge influences ozone concentrations near rats
Authors: Goheen Steven C. , Gaither Kari , Anantatmula Shantha M. , Mong Gary M. , Sasser Lyle B. , Lessor Delbert
Published: January 2004

Ozone can be produced by corona discharge either in dry air or when one electrode is submerged in water. Since ozone is toxic, we examined whether ozone production by corona near laboratory animals could reach levels of concern. Male rats were exposed to a corona discharge and the concentration of ozone produced was measured. The resulting concentration of ozone ranged from ambient levels to 250 ppb when animals were located 1 cm from a 10 kV source. Similar ozone concentrations were observed when a grounded water source was present. Possible explanations for, as well as concerns regarding, ozone production under these conditions are discussed. Bioelectromagnetics 25:107–113, 2004. © 2004 Wiley‐Liss, Inc.
Apoptosis induced by ultraviolet radiation is enhanced by amplitude modulated radiofrequency radiation in mutant yeast cells
Authors: Markkanen Ari , Penttinen Piia , Naarala Jonne , Pelkonen Jukka , Sihvonen Ari‐Pekka , Juutilainen Jukka
Published: January 2004

The aim of this study was to investigate whether radiofrequency (RF) electromagnetic field (EMF) exposure affects cell death processes of yeast cells. Saccharomyces cerevisiae yeast cells of the strains KFy417 (wild‐type) and KFy437 (cdc48‐mutant) were exposed to 900 or 872 MHz RF fields, with or without exposure to ultraviolet (UV) radiation, and incubated simultaneously with elevated temperature (+37°C) to induce apoptosis in the cdc48‐mutated strain. The RF exposure was carried out in a special waveguide exposure chamber where the temperature of the cell cultures can be precisely controlled. Apoptosis was analyzed using the annexin V–FITC method utilizing flow cytometry. Amplitude modulated (217 pulses per second) RF exposure significantly enhanced UV induced apoptosis in cdc48‐mutated cells, but no effect was observed in cells exposed to unmodulated fields at identical time‐average specfic absorption rates (SAR, 0.4 or 3.0 W/kg). The findings suggest that amplitude modulated RF fields, together with known damaging agents, can affect the cell death process in mutated yeast cells. Bioelectromagnetics 25:127–133, 2004. © 2004 Wiley‐Liss, Inc.
Influence of Threose Nucleoside Units on the Catalytic Activity of a Hammerhead Ribozyme
Authors: Kempeneers Veerle , Froeyen Mattheus , Vastmans Karen , Herdewijn Piet
Published: February 2004

TNA (α‐L‐threose nucleic acids) is potentially a natural nucleic acid, that might have acted as an evolutionary alternative of RNA. We determined the catalytic activity of hammerhead ribozymes containing a threofuranosyl‐modified nucleoside at position U4 and U7, and compared these results with those obtained from HNA (hexitol nucleic acids) insertion into the same ribozyme. Our experiments showed that, although the threofuranosyl‐modified ribozymes still cleave the substrate strand, cleavage activity is highly decreased. It, therefore, seems that TNA can play a functional role in the RNA world, but only to a limited extent.
A Novel Type of Membranes Based on Cholesteryl Phosphate
Authors: Sedaghat Soheila , Désaubry Laurent , Streiff Stéphane , Ribeiro Nigel , Michels Bernard , Nakatani Yoichi , Ourisson Guy
Published: February 2004

Mixtures of the rigid amphiphile disodium cholesteryl phosphate (DCP) with the non‐phosphorylated diacyl amphiphile dimyristoylglycerol (DMG) give self‐organized systems in a wide range of pH, as demonstrated by differential microcalorimetry. These systems can be closed bilayer vesicles, as shown by optical microscopy (Nomarski and confocal). Neither DMG nor DCP, taken alone, give vesicles in these conditions but 10% DMG is enough to lead to the formation of vesicles from pH 5.8 to 9.3. These novel self‐organized systems are akin to the classical eucaryotic ones, built on a phosphorylated diacylglycerol and free cholesterol (or analogues), the only difference being the site of the phosphate head‐group.
The First Chemical Synthesis of a Cyclodextrin Heteroduplex
Authors: Bistri Olivia , Lecourt Thomas , Mallet Jean‐Maurice , Sollogoub Matthieu , Sinaÿ Pierre
Published: February 2004

The synthesis of the first heteroduplex of cyclodextrin (CD) 11, i.e., a compound in which the two primary rims of α‐ and β‐CDs are doubly connected, was achieved. The selected strategy involved a Sonogashira coupling of propargylated β‐CD 6 and iodo‐alkenyl α‐CD 4 to singly connect the two CDs. A ring‐closing metathesis (RCM) of the heterodimer 9 afforded the second bridge, final deprotection and reductions giving acces to 11.
An Inorganic Double Helix Sheathing Alkali Metal Cations: ANb2P2S12 (A=K, Rb, Cs), A Series of Thiophosphates Close to the Metal–Nonmetal Boundary—Chalcogenide Analogues of Transition‐Metal Phosphate Bronzes?
Authors: Gieck Christine , Derstroff Volkmar , Block Thomas , Felser Claudia , Regelsky Guido , Jepsen Ove , Ksenofontov Vadim , Gütlich Philipp , Eckert Hellmut , Tremel Wolfgang
Published: January 2004

The new quaternary niobium thiophosphates ANb2P2S12 (A=K, Rb, Cs) have been prepared and characterized. The title compounds were synthesized by reacting Nb metal, A2S, P2S5, and S at 600–700 °C in evacuated silica tubes. They crystallize as “stuffed” variants of the tetragonal TaPS6 structure type in the tetragonal space group I$\bar 4$2d with eight formula units per unit cell and lattice constants a=15.923(2) and c=13.238(3) Å for CsNb2P2S12, a=15.887(3) and c=13.132(3) Å for RbNb2P2S12, and a=15.850(2) and c=13.119(3) Å for KNb2P2S12. Their structures are based on double helices formed from interpenetrating, noninteracting spiral chains of binuclear [Nb2S12] cluster units and [PS4] thiophosphate groups. The cavities and tunnels, which are formed by the helical chains, are filled with A+ ions. Temperature‐dependent conductivity studies reveal thermally activated electrical transport behavior. This result is consistent with the observation of a temperature‐dependent contribution to the 31P MAS‐NMR shift, suggesting that the delocalized s‐electron spin density increases with increasing temperature. These findings are supported by the results of tight‐binding band structure calculations which reveal that the unusual electrical transport behavior of ANb2P2S12 is a consequence of the structure symmetry. Therefore, CsNb2P2S12 may be considered a chalcogenide analogue of metal phosphate bronzes.
Dendronized Perylenetetracarboxdiimides with Peripheral Triphenylamines for Intramolecular Energy and Electron Transfer
Authors: Qu Jianqiang , Pschirer Neil G. , Liu Daojun , Stefan Alina , De Schryver Frans C. , Müllen Klaus
Published: January 2004

Novel perylene‐3,4,9,10‐tetracarboxdiimides (PDI) dyes functionalized with polyphenylene dendrimers attached at the bay region are reported. Derivatives of PDI bearing polyphenylene dendrimers up to the second generation, substituted with an increasing number of triphenylamine (TPA) moieties at the periphery, as well as a related nondendronized model compound were prepared. Intramolecular energy transfer was demonstrated by the observation of PDI emission on excitation of the triphenylamines, and electron transfer was detected by comparing photoluminescence quenching in solvents of different polarity.
From D‐Glucose to Biologically Potent L‐Hexose Derivatives: Synthesis of α‐L‐Iduronidase Fluorogenic Detector and the Disaccharide Moieties of Bleomycin A2 and Heparan Sulfate
Authors: Lee Jinq‐Chyi , Chang Shu‐Wen , Liao Chih‐Cheng , Chi Fa‐Chen , Chen Chien‐Sheng , Wen Yuh‐Sheng , Wang Cheng‐Chung , Kulkarni Suvarn S. , Puranik Ramachandra , Liu Yi‐Hung , Hung Shang‐Cheng
Published: January 2004

A novel and convenient route for the synthesis of biologically potent and rare L‐hexose derivatives from D‐glucose is described. Conversion of diacetone‐α‐D‐glucose (14) into 1,2:3,5‐di‐O‐isopropylidene‐β‐L‐idofuranose (19) was efficiently carried out in two steps. Orthogonal isopropylidene rearrangement of compound 19 led to 1,2:5,6‐di‐O‐isopropylidene‐β‐L‐idofuranose (27), which underwent regioselective epimerization at the C3 position to give the L‐talo‐ and 3‐functionalized L‐idofuranosyl derivatives. Hydrolysis of compound 19 under acidic conditions furnished 1,6‐anhydro‐β‐L‐idopyranose (35) in excellent yield, which was successfully transformed into the corresponding L‐allo, L‐altro, L‐gulo, and L‐ido derivatives via regioselective benzylation, benzoylation, triflation and nucleophilic substitution as the key steps. Applications of these 1,6‐anhydro‐β‐L‐hexopyranoses as valuable building blocks to the syntheses of 4‐methylcoumarin‐7‐yl‐α‐L‐iduronic acid and the disaccharide moieties of bleomycin A2 as well as heparan sulfate are highlighted.
Syntheses and Reactivities of Stable Halosilylenoids, (Tsi)X2SiLi (Tsi=C(SiMe3)3, X=Br, Cl)
Authors: Lee Myong Euy , Cho Hyeon Mo , Lim Young Mook , Choi Jin Kyong , Park Chang Hee , Jeong Seong Eun , Lee Uk
Published: January 2004

Halosilylenoids, stable at room temperature (Tsi)X2SiLi (Tsi=C(SiMe3)3, X=Br, Cl), were synthesized from the reaction of TsiSiX3 with lithium naphthalenide. Bromosilylenoid reacted with tBuOH and MeI both at −78 °C and at room temperature to give (Tsi)HSiBr2 and (Tsi)MeSiBr2, respectively, in high yields; this clearly shows its nucleophilicity. In the reaction of bromosilylenoid with methanol, 2‐propanol, and 2,3‐dimethyl‐1,3‐butadiene, the corresponding products, (Tsi)HSi(OMe)2, (Tsi)HSi(OiPr)Br, and bromo(Tsi)silacyclopent‐3‐ene, were obtained in high yields; this demonstrates its amphiphilic property, as if bromosilylene would be trapped. Chlorosilylenoid also exhibited both nucleophilic and amphiphilic properties. The 29Si chemical shifts for (Tsi)Br2SiLi, (Tsi)Br2SiK, and (Tsi)Cl2SiLi were 106, 70, and 87 ppm, respectively.
New Chiral Ruthenium(II) Catalysts Containing 2,6‐Bis(4′‐(R)‐phenyloxazolin‐2′‐yl)pyridine (Ph‐pybox) Ligands for Highly Enantioselective Transfer Hydrogenation of Ketones
Authors: Cuervo Darío , Gamasa M. Pilar , Gimeno José
Published: January 2004

Treatment of complex trans‐[RuCl2(η2‐C2H4){κ3‐N,N,N‐(R,R)‐Ph‐pybox}] [(R,R)‐Ph‐pybox = 2,6‐bis{4′‐(R)‐phenyloxazolin‐2′‐yl}pyridine] with phosphines or phosphites in dichloromethane at 50 °C leads to the formation of novel ruthenium(II)‐pybox complexes trans‐[RuCl2(L){κ3‐N,N,N‐(R,R)‐Ph‐pybox}] [L = PPh3 (1 a), PPh2Me (2 a), PPh2(C3H5) (3 a), PPh2(C4H7) (4 a), PMe3 (5 a), PiPr3 (6 a), P(OMe)3 (7 a) and P(OPh)3 (8 a)]. Likewise, reaction of trans‐[RuCl2(η2‐C2H4){κ3‐N,N,N‐(R,R)‐Ph‐pybox}] with PPh3 or PiPr3 in refluxing methanol leads to the complexes cis‐[RuCl2(L)(κ3‐N,N,N‐(R,R)‐Ph‐pybox] [L = PPh3 (1 b), PiPr3 (6 b)]. No trans–cis isomerisation of complexes 1 a–8 a has been observed. Complexes 1 a–8 a, 1 b, 6 b together with the analogous trans‐[RuCl2{P(OMe)3}{κ3‐N,N,N‐(S,S)‐iPr‐pybox}] (10 a) and the previously reported trans‐ and cis‐[RuCl2(PPh3){κ3‐N,N,N‐(S,S)‐iPr‐pybox}] (9 a and 9 b, respectively) are active catalysts for the transfer hydrogenation of acetophenone in 2‐propanol in the presence of NaOH (ketone/cat/NaOH 500:1:6). cis‐Ph‐pybox derivatives are the most active catalysts. In particular, cis complexes 1 b and 6 b led to almost quantitative conversions in less than 5 min with a high enantioselectivity (up to 95 %). A variety of aromatic ketones have also been reduced to the corresponding secondary alcohols with very high TOF and ee up to 94 %. The overall catalytic performance seems to be a subtle combination of the steric and/or electronic properties both the phosphines and the ketones. A high TOF (27 300 h−1) and excellent ee (94 %) have been found for the reduction of 3‐bromoacetophenone with catalyst 6 b. Reductions of alkyl ketones also proceed with high and rapid conversions but low enantioselectivities are achieved.
Uniform Micro‐Sized α‐ and β‐Si3N4 Thin Ribbons Grown by a High‐Temperature Thermal‐Decomposition/Nitridation Route
Authors: Hu Junqing , Bando Yoshio , Liu Zongwen , Xu Fangfang , Sekiguchi Takashi , Zhan Jinhua
Published: January 2004

Uniform micro‐sized α‐ and β‐Si3N4 thin ribbons have been achieved by a high‐temperature thermal‐decomposition/nitridation route. As‐grown ribbons were characterized by using powder X‐ray diffraction, scanning electron microscopy, transmission electron microscopy, energy‐dispersive X‐ray spectroscopy, electron energy loss spectroscopy, and cathodoluminescence. These α‐ and β‐Si3N4 ribbons are structurally uniform micro‐sized single crystals, and have a width of ∼2–3 microns, a thickness of ∼20–60 nm, and a length, that ranges from several hundreds of microns to the order of millimeters. A room‐temperature cathodoluminescence spectrum recorded from these ribbons shows one intensive blue emission peak at ∼433 nm. The growth for the new ribbon form of this material is believed to be dominated by a vapor–solid process.
Self‐Organized Glycoclusters Along DNA: Effect of the Spatial Arrangement of Galactoside Residues on Cooperative Lectin Recognition
Authors: Matsuura Kazunori , Hibino Miki , Ikeda Takayasu , Yamada Yoshinao , Kobayashi Kazukiyo
Published: January 2004

We describe herein the relationship between the spatial arrangement of self‐organized galactose clusters and lectin recognition. β‐Galactose‐modified deoxyuridine phosphoramidite was synthesized and applied to solid‐phase synthesis to provide 18‐, 20‐, and 22‐mers of site‐specifically galactosylated oligodeoxynucleotides (Gal‐ODNs). These Gal‐ODNs were self‐organized through hybridization with the corresponding 18‐, 20‐, and 22‐mers of half‐sliding complementary ODNs (hsc‐ODNs) to give periodic galactoside clusters. The self‐organization of ODNs was confirmed by size exclusion chromatography and gel electrophoresis. The binding of the Gal‐clusters to the FITC‐labeled RCA120lectin was analyzed by monitoring the change in fluorescence intensity. The assembly of 20‐mer Gal‐ODN with the 20‐mer hsc‐ODN was strongly and cooperatively recognized by the lectin. The 18‐mer assembly was bound more weakly and less cooperatively, and the 22‐mer assembly was minimally bound to the lectin. RCA120lectin recognized not only the density of galactoside residues, but also the spatial arrangement. The size of the Gal cluster was estimated from the association constant of Gal‐ODN with hsc‐ODN. The relationship between lectin‐recognition and Gal‐cluster size is also discussed.
Cover Picture: First Structural Characterization of Binary AsIII and SbIII Azides (Chem. Eur. J. 2/2004)
Authors: Haiges Ralf , Vij Ashwani , Boatz Jerry A. , Schneider Stefan , Schroer Thorsten , Gerken Michael , Christe Karl O.
Published: January 2004

The cover picture shows a packing diagram of antimony triazide. Its motif closely resembles the three legged Manx symbol of the Isle of Man. The backdrop shows the harbor of Ramsey on the Isle of Man. For more information on the synthesis and characterization of both antimony and arsenic triazides see the paper by K. O. Christe, R. Haiges, A. Vij, et al. on p. 508 ff.
Wärmeübergang und Druckverlust beim Strömungsverdampfen von CO2 im horizontalen Glattrohr
Authors: Schael A.‐E. , Kind M.
Published: February 2004

No abstracts.
Untersuchungen zur dynamischen Filtration mit dem Centrifugal Disk Filter (CD‐Filter)
Authors: Tonhäuser M. , Woldmann K. , Ripperger S. , Tichy J. W.
Published: February 2004

No abstracts.
Simulation der Scherdynamik kohäsiver Pulver
Authors: Tykhoniuk R. , Tomas J. , Luding S.
Published: February 2004

No abstracts.
Hepatic dendritic cell subsets in the mouse
Authors: Jomantaitė Ieva , Dikopoulos Nektarios , Kröger Andrea , Leithäuser Frank , Hauser Hansjörg , Schirmbeck Reinhold , Reimann Jörg
Published: February 2004

The CD11c+ cell population in the non‐parenchymal cell population of the mouse liver contains dendritic cells (DC), NK cells, B cells and T cells. In the hepatic CD11c+ DC population from immunocompetent or immunodeficient [recombinase‐activating gene‐1 (RAG1)–/–] C57BL/6 mice (rigorously depleted of T cells, B cells and NK cells), we identified a B220+ CD11cint subset of ‘plasmacytoid’ DC, and a B220– CD11c+ DC subset. The latter DC population could be subdivided into a major, immature (CD40lo CD80lo CD86lo MHC class IIlo) CD11cint subset, and a minor, mature (CD40hi CD80hi CD86hi MHC class IIhi) CD11chi subset. Stimulated B220+ but not B220– DC produced type I interferon. NKT cell activation in vivo increased the number of liver B220– DC three‐ to fourfold within 18 h post‐injection, and up‐regulated their surface expression of activation marker, while it contracted the B220+ DC population. Early in virus infection, the hepatic B220+ DC subset expanded, and both, the B220+ as well as B220– DC populations in the liver matured. In vitro, B220– but not B220+ DC primed CD4+ or CD8+T cells. Expression of distinct marker profiles and functions, and distinct early reaction to activation signals hence identify two distinct B220+ and B220– subsets in CD11c+ DC populations freshly isolated from the mouse liver.
The regulation of the cis‐trans isomerase of unsaturated fatty acids in Pseudomonas putida: correlation between cti activity and K+‐uptake systems
Authors: Neumann Grit , Kabelitz Nadja , Heipieper Hermann J.
Published: January 2004

The regulation of an urgent stress adaptive mechanism of Pseudomonas putida, the isomerization of cis‐ to trans‐unsaturated fatty acids, was investigated. By comparing the responses of the cells to a series of stress factors, a direct correlation between the activation of this unique mechanism and the well‐investigated K+‐uptake pumps was observed. Only those stress conditions (osmotic stress caused by glycerol, cold shock, high pH) that are well known not to activate cellular K+‐uptake, showed no effect on the cis‐trans isomerase (cti). On the other hand, organic solvents, osmotic stress caused by NaCl and sucrose, heavy metals, heat shock and membrane‐active antibiotics activated both K+‐uptake and the cti system. This seems to be another indication for an activation of the constitutively present cti by increasing membrane fluidity. The enzyme, which is located in the periplasma, can only reach its substrate, the double bond in the hydrophobic zone of the membrane bilayer, when the membrane fluidity is disturbed by an environmental factor.
Conjugated α‐linolenic acid production from α‐linolenic acid by Lactobacillus plantarum AKU 1009a
Authors: Kishino Shigenobu , Ogawa Jun , Ando Akinori , Shimizu Sakayu
Published: January 2004

Conjugated α‐linolenic acid (CALA) was produced by incubation of α‐linolenic acid with the washed cells of Lactobacillus plantarum AKU 1009a. The washed cells expressing high levels of CALA productivity were obtained by cultivation in a nutrient medium supplemented with 0.01% (wt/vol) α‐linolenic acid as an inducer. Under the optimum reaction conditions with 63 mg/ml α‐linolenic acid as substrate, the washed cells produced 25 mg CALA/ml reaction mixture (40 mol‐% yield) in 72 h. The produced CALA were a mixture of the two isomers, i.e., cis‐9, trans‐11, cis‐15‐octadecatrienoic acid (CALA1, 67% of total CALA) and trans‐9, trans‐11, cis‐15‐octadecatrienoic acid (CALA2, 33% of total CALA), and accounted for 48% of total fatty acid obtained. Almost stoichiometric conversion was attained with 12 mg/ml α‐linolenic acid as the substrate in 48 h reaction time. It resulted in 12 mg CALA/ml reaction mixture consisting of 43% CALA1 and 57% CALA2 accounting for 66% of total fatty acid obtained. The CALA produced was obtained as the free fatty acid.
An assay system for the detection of phospholipase C activity
Authors: Durban Markus , Bornscheuer Uwe
Published: January 2004

Phospholipase C (PLC, EC 3.1.4.3) enzymes specifically hydrolyze the C‐O‐P‐bond in phospholipids, yielding sn‐1, 2(2, 3)‐diglycerides and a phosphate residue bearing the corresponding head group. Biochemical characterization of PLC requires methods for determination of activity. During characterization and purification, proteins are separated by polyacrylamide gel electrophoresis (PAGE). For direct identification and visualization of PLC, a new assay for activity staining in native and renatured SDS‐PAGE is described. Incubation of a gel containing an active PLC in the presence of α‐naphthylphosphorylcholine leads to α‐naphthol formation. This reacts with the diazonium salt Fast Red, forming a red dye which allows clear determination of PLC purity, molecular weight and substrate specificity. The assay was verified using commercially available PC‐PLC and new PC‐PLC‐producing Bacillus cereus strains. The substrate α‐NPC was prepared by chemical synthesis at an overall yield of 12%.
Industrial use of lipases to produce fatty acid esters
Authors: Hills Geoffrey
Published: January 2004

A wide range of fatty acid esters can be synthesised by esterification and transesterification reactions catalysed by lipases in non‐aqueous systems. As well as modifications to the natural substrate triacylglycerol, many other commercially important substances can be produced using this enzyme technology, as lipases have been shown to have broad substrate specificities and can thus catalyse conversions with many other non‐glycerol based compounds. In mild reaction conditions, emollient esters for use in the personal care industry can be made with excellent quality.

Development of economical processes was necessary to commercialise this technology for the manufacture of cosmetic ingredients. Enzymatic production methods had to be established which could compete against standard established chemical synthetic methods. Now relatively simple esters are being produced enzymatically. Extensive purification procedures to clean up products after high temperature reaction steps are not required. Product quality and specifications, such as the acid and hydroxy values of commercial ester products, could be improved. Examples of products manufactured with better purity and yields in economical and ecologically friendly processes are decyl oleate, cetyl ricinoleate, myristyl myristate and decyl cocoate.
Four Novel Nortriterpenoids Isolated from Schisandra henryi var. yunnanensis
Authors: Li Rongtao , Shen Yunheng , Xiang Wei , Sun Handong
Published: February 2004

Four novel nortriterpenoids, henridilactones A−D (1−4), members of a very rare highly oxidized cycloartane skeletal class with a biosynthetically modified eight‐membered ring D, were isolated from the leaves and stems of Schisandra henryi var. yunnanensis. Their structures were elucidated using extensive spectroscopic techniques including 1D and 2D NMR spectra. Eight known triterpenoids were also isolated from the same source. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
Pentakis(phenylethynyl)benzene and Hexakis(phenylethynyl)benzene: A Revision Concerning Two Far Too Similar Prototype Hydrocarbons
Authors: Nierle Jens , Barth Dieter , Kuck Dietmar
Published: February 2004

A previously overlooked hydrodehalogenation reaction occurring during the multiple Pd0‐catalysed C−C coupling reaction between phenylacetylene and hexaiodo‐ and hexabromobenzene was found to give pentakis(phenylethynyl)benzene (“pentatolane”) as the major product, but no hexakis(phenylethynyl)benzene (“hexatolane”) under conditions previously claimed to yield the latter hydrocarbon. As an alternative to a viable route to hexatolane described in the literature, an independent synthesis of this hydrocarbon through sixfold Sonogashira coupling of hexakis(ethynyl)benzene with iodobenzene has been developed. Some physical and spectroscopic properties of hexatolane and of the hitherto unknown pentatolane have been determined after thorough purification by HPLC. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
Thiophenylhydrazonoacetates in heterocyclic synthesis
Authors: Mohareb Rafat M. , Sherif Sherif M. , Gaber Hatem M. , Ghabrial Sami S. , Aziz Susan I.
Published: January 2004

Benzo[b]thiophen‐2‐yl‐hydrazonoesters 4 were synthesized by coupling of 2‐diazo‐4,5,6,7‐tetrahydrobenzo[b]thiophene‐3‐carboxamide (1) with either ethyl cyanoacetate or ethyl acetoacetate. The reactivity of 4 toward a variety of nitrogen nucleophiles was investigated to yield pyrazole, isoxazole, pyrimidine, triazine, pyrazolopyridine, and pyrazolopyrimidine derivatives. © 2003 Wiley Periodicals, Inc. 15:15–20, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/.hc10205
Microwave‐assisted synthesis of 2‐amino and 2‐azetidinonyl 5‐(2‐benzoyl‐phenoxymethyl) 1,3,4‐oxadiazoles
Authors: Khanum Shaukath Ara , Shashikanth S. , Sudha B. S.
Published: January 2004

A simple high yielding method for the integration of heterocyclic rings viz. 1,3,4‐oxadiazole and azetidin‐2‐one at the benzophenone nucleus has been developed starting from substituted 2‐hydroxybenzophenones, and by using mild conditions, wet solid surface, and microwave irradiation. A comparison of this microwave‐accelerated reaction with conventional heating condition is also illustrated. © 2003 Wiley Periodicals, Inc. Heteroatom Chem 15:37–42, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.10210
Palmitoleate (=(9Z)‐Hexadeca‐9‐enoate) Esters of Oleanane Triterpenoids from the Golden Flowers of Tagetes erecta: Isolation and Autoxidation Products
Authors: Faizi Shaheen , Naz Aneela
Published: February 2004

Six oleanane‐type triterpenoid esters were isolated from the golden flowers of Tagetes erecta. Spectral studies characterized their structures as 3‐O‐[(9Z)‐hexadec‐9‐enoyl]erythrodiol (1), 11α,12α:13β,28‐diepoxyoleanan‐3β‐yl (9Z)‐hexadec‐9‐enoate (2), 13β,28‐epoxyolean‐11‐en‐3β‐yl (9Z)‐hexadec‐9‐enoate (3), 28‐hydroxy‐11‐oxoolean‐12‐en‐3β‐yl (9Z)‐hexadec‐9‐enoate (4), 3‐O‐[(9Z‐hexadec‐9‐enoyl]‐β‐amyrin (5), and 11‐oxoolean‐12‐en‐3β‐yl (9Z)‐hexadec‐9‐enoate (6). Compounds 1–4 and 6 are new natural products, while the known 5 was isolated for the first time from the genus Tagetes, from which only one triterpenoid has earlier been obtained. Aerial oxidation (autoxidation) converted amyrin 1 into 2–4 and transformed amyrin 5 into 6. The configuration of 1–6 and an autoxidation mechanism (Scheme) involving the formation of the intermediate 11α‐hydroxyolean‐12‐ene derivatives 1b and 5b on thermal decomposition of the labile 11α‐OOH derivatives 1a and 5a, respectively, under neutral conditions are discussed. For the first time, the reactivity of the allylic HC(11) bond of triterpenoids of type 1 and 5 toward aerial oxidation was observed. The long‐chain ester group at C(3) of 1 and 5 may be responsible for their labile nature, as β‐amyrin (7), erythrodiol (8), and ursolic acid were found to be inert toward autoxidation.
Hyaluronan‐binding peptide can inhibit tumor growth by interacting with Bcl‐2
Authors: Liu Ninfei , Xu Xue‐Ming , Chen Jinguo , Wang Luping , Yang Shanmin , Underhill Charles B. , Zhang Lurong
Published: January 2004

Previous studies have indicated that proteins that bind hyaluronan can also inhibit the growth of tumor cells. To determine if synthetic peptides also possessed these properties, we tested a series of polypeptides containing structural motifs from different proteins for their ability to bind [3H]hyaluronan, and identified one compound termed P4 that had a particularly strong interaction. Further studies revealed that P4 also inhibited the growth of tumor cells in tissue culture as well as on the chorioallantoic membranes of chicken embryos. In addition, expression vectors for P4 caused tumor cells to grow slower in nude mice and reduced their vascularization. The P4 peptide also inhibited VEGF‐induced angiogenesis in the chorioallantoic membranes of chicken embryos. Studies on cultured cells indicated that P4 induced apoptosis, which was blocked by a pan‐caspase inhibitor. Confocal microscopy revealed that shortly after its uptake, P4 became associated with mitochondria. Immunoprecipitation indicated that P4 could bind to Bcl‐2 and Bcl‐xL, which are associated with mitochondria and regulate apoptosis. This was also supported by the fact that P4 induced the release of cytochrome c from preparations of mitochondria. Taken together, these results suggest that P4 binds to Bcl‐2 and related proteins and this activates the apoptotic cascade. © 2003 Wiley‐Liss, Inc.
Antisense abrogation of DENN expression induces apoptosis of leukemia cells in vitro, causes tumor regression in vivo and alters the transcription of genes involved in apoptosis and the cell cycle
Authors: Lim Kah M. , Yeo Wee S. , Chow Vincent T. K.
Published: January 2004

We previously reported that messenger RNA expression of DENN (differentially expressed in normal and neoplastic cells) is considerably higher in cancer cell lines than in normal cells. In our present study, we established that certain cancer cell lines express conspicuously higher levels of the 2 DENN isoforms in contrast to the 2 pro‐apoptotic IG20 isoforms. Antisense DENN oligodeoxynucleotide treatment of K36 cells in vitro induced extensive apoptosis, while antisense DENN silencing of K36 tumor‐bearing mice caused significant tumor regression in vivo. Compared to wild‐type murine embryonic fibroblasts, antisense treatment of NFκB and TNFR1 KO cells resulted in markedly more pronounced cell death, whereas antisense‐treated TNFα and TNFR2 knockouts exhibited less prominent apoptosis. Cell viability and apoptosis were authenticated by flow cytometry, membrane integrity, TUNEL, annexin V assays, histology and electron microscopy. Antisense abrogation of DENN expression culminated in upregulated expression of TNFR2, TRAIL and Fas, but downregulation of TNFα, TNFR1 and cyclin D3. Conversely, DENN overexpression stimulated cell proliferation and led to upregulated TRPM2 and cyclin B1, but diminished expression of Fas, TNFR2, TRAIL and Egr‐1. The participation of TNFα, TNFR1, TNFR2 and Fas in the inhibition of DENN expression was also demonstrated. These data support the anti‐apoptotic and cell survival role of DENN, especially in malignant cells, and its interaction with specific genes and proteins involved in the apoptotic and cell cycle pathways. © 2003 Wiley‐Liss, Inc.
Candidate regions of tumor suppressor locus on chromosome 9q31.1 in gastric cancer
Authors: Kakinuma Naoto , Kohu Kazuyoshi , Sato Masaaki , Yamada Tatsuya , Nakajima Motowo , Akiyama Tetsu , Ohwada Susumu , Shibanaka Yasuhiko
Published: January 2004

Loss of heterozygosity (LOH) is an important event of tumorigenesis. In gastric cancer, we found a novel region of LOH in chromosome 9q having about 800 kb deletions at 9q31.1. The microsatellite marker D9S938 in that region exhibiting the highest LOH frequency, 56.5%. In addition, the LOH at 9q31.1 did not show any relationship to either histologic types or stages of gastric cancers, and several genes were predicted in the remaining allele by in silico methods. These data suggest that the deletion at 9q31.1 would be common in both differentiated‐type and undifferentiated‐type gastric cancers. Furthermore, this deletion was found in the primary tumors of early‐stage gastric cancer, indicating that loss of function of predicted genes appears to be associated with the tumorigenesis of gastric cancer. © 2003 Wiley‐Liss, Inc.