Angewandte Chemie International Edition in English

Cover image for Vol. 36 Issue 20

November 3, 1997

Volume 36, Issue 20

Pages 2139–2253

Currently known as: Angewandte Chemie International Edition

    1. Cover Picture (Angew. Chem. Int. Ed. Engl. 20/1997)

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199721371

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      The cover picture shows a model for the selective incorporation and localization of lipopeptides and lipid-modified proteins in the plasma membrane of cells. The lipopeptides were introduced into the cell by microinjection or membrane fusion. According to this model, peptides and proteins which contain S-farnesylated cysteine residues can diffuse freely between different subcellular membranes until they are additionally S-acylated in a membrane compartment. The now doubly lipid-modified peptide/protein can no longer be transferred between different membranes and is localized in the membrane where S-acylation takes place, here the plasma membrane. More on this proposed mechanism and how it was approached by a combination of techniques from organic synthesis, biophysics, and cell biology can be found on pages 2238 ff in the contribution from the groups of Waldmann, Wittinghofer, and Silvius.

  1. Reviews

    1. Top of page
    2. Reviews
    3. Highlights
    4. Communications
    5. Book Reviews
    1. Chemistry and Molecular Biology in the Search for New LHRH Antagonists (pages 2148–2161)

      Prof. Bernhard Kutscher, Dr. Michael Bernd, Dr. Thomas Beckers, Dr. Emmanuel E. Polymeropoulos and Prof. Jürgen Engel

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199721481

      The first growth factors revealed to be involuntary helpers of cancer were hormones. Synthetic modification of the decapeptide hormone LHRH gave about 5000 analogues, which are superagonists or antagonists. After the sequence determination of the human LHRH receptor and models derived from it, characterization of the substances and a search for new lead structures by high-throughput screening have become possible. The first peptidomimetics and the growing understanding of the three-dimensional structure of the receptor raises hopes of a new generation of clinically active LHRH antagonists.

    2. N-Heterocyclic Carbenes (pages 2162–2187)

      Prof. Dr. Wolfgang A. Herrmann and Dr. Christian Köcher

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199721621

      An important role in organometallic chemistry is predicted for N-heterocyclic carbenes, which are no longer laboratory curiosites but have developed into an industrially interesting class of compounds. They are readily accessible from azolium salts, can combine with a large variety of metals in different oxidations states, and form highly active and stable catalysts.

  2. Highlights

    1. Top of page
    2. Reviews
    3. Highlights
    4. Communications
    5. Book Reviews
    1. The Direct Synthesis of a closo-Borate from Elemental Boron (pages 2189–2190)

      Priv.-Doz. Dr. Lars Wesemann

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199721891

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      Among the diverse range of polyhedra seen for structure of boron clusters, the icosahedron is of particular imporatnce. An unusual icosahedral boron cluster, in which both closo-borate and selenoborate substructure are present, was recently synthesized by Krebs et al. from cesium selnide, boron, and selenium (see schematic representation on the right, ˆ = B, • = Se).

    2. Biosynthesis of Taxol (pages 2190–2195)

      Prof. Dr. Jürgen Rohr

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199721901

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      Taxol, a true “evergreen” in natural product chemistry! Owing to the limited supply of this successful antitumor agent in the bark of yew trees, alternative sources are being sought. Crucial information on its unusual and complex biosynthesis (shown below) has been obtained, and some enzymes responsible have been identified. The long-term goal is the efficient, biotechnology production of taxol (1) by fungi or plant tissue cultures.

  3. Communications

    1. Top of page
    2. Reviews
    3. Highlights
    4. Communications
    5. Book Reviews
    1. Immobilization of Platinated and Iodinated Oligonucleotides on Carbon Nanotubes (pages 2198–2200)

      Dr. Shik Chi Tsang, Dr. Zijian Guo, Yao Kuan Chen, Prof. Dr. Malcolm L. H. Green, Prof. Dr. H. Allen O. Hill, Dr. Trevor W. Hambley and Prof. Dr. Peter J. Sadler

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199721981

      Thumbnail image of graphical abstract

      A combination of biotechnology and material science enables the immobilization of DNA on carbon nanotubes. After labeling with the heavy atoms platinum and iodine, the double-stranded DNA can be visualized by high-resolution transmission electron microscopy. In the picture the arrow highlights the DNA layer.

    2. Beltlike Aromatic Hydrocarbons by Metathesis Reaction with Tetradehydrodianthracene (pages 2200–2202)

      Dr. Stefan Kammermeier, Prof. Dr. Peter G. Jones and Prof. Dr. Rainer Herges

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199722001

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      A substructure of a (5,5)-armchair nanotube was obtained by metathesis reactions with tetradehydrodianthracene. The C[BOND]C bonds in the product are all unsaturated and form a fully conjugated, beltlike system. A set of molecular building blocks can be used to synthesize other sections of nanotubes as well.

    3. Organic-Soluble Neutral and Ionic Indium Siloxane Cages: Potential Precursors for Indium-Containing Silicates (pages 2203–2205)

      Dr. Andreas Voigt, Mrinalini G. Walawalkar, Dr. Ramaswamy Murugavel, Prof. Dr. Herbert W. Roesky, Dr. Emilio Parisini and Dr. Paolo Lubini

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199722031

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      Small variations in the reaction conditions and the choice of starting materials lead to a diverse range of novel indium siloxane structures. These compounds can serve as model compounds for zeolites. The framework of one of the indium siloxanes is depicted on the right.

    4. The Distortive Tendency of Benzene π Electrons: How Is It Related to Structural Observables? (pages 2205–2208)

      Avital Shurki and Prof. Sason Shaik

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199722051

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      Why does the benzene nucleus have a structure similar to cyclohexatriene in the ground state 1, and a virtually D6h-symmetrical structure in the π [RIGHTWARDS ARROW] π* excited state 2? A simple model based on the distortive propensity of the π electrons in the ground state and their opposite tendency in the excited state predicts this behavior, and more.

    5. Anaerobic Copper-Catalyzed Oxidation of Alcohols to Aldehydes and Ketones (pages 2208–2210)

      Prof. István E. Markó, Dr. Masao Tsukazaki, Dr. Paul R. Giles, Dr. Stephen M. Brown and Dr. Christopher J. Urch

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199722081

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      The aerobic copper-catalyzed oxidation of alcohols such as 1 [Eq. (1)] functions even in the absence of oxygen. Non-benzylic and secondary alcohols are further suitable substrates. A key role in this reaction is played by azocarboxylates, which not only serve as complex ligands but also as hydride acceptors; bulky R groups such as tert-butyl are particularly suitable.

    6. Electron-Density Relaxation and Oppositely Signed Reaction Constants in Dual Substituent Parameter Relationships in Dediazoniation Reactions (pages 2210–2213)

      Prof. Dr. Rainer Glaser, Dr. Christopher J. Horan and Prof. Dr. Heinrich Zollinger

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199722101

      Why are there so few exceptions to the fact that ρRF = λ is positive? A straightforward theoretical basis is provided for the interpretation of the dediazoniation of benzenediazonium ions, one of the most prominent examples of the few reactions for which the reaction constants ρR and ρF [Eq. (1)] have opposite signs. The results support the model that describes C[BOND]N bonding as synergistic N [RIGHTWARDS ARROW] C σ dative and C [RIGHTWARDS ARROW] N π backdative bonding. The analysis furnishes details about the electronic structure that cannot be deduced from physical–organic studies alone.

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    7. Hexavinylogous Porphyrins with Aromatic 30 π-Electron Systems (pages 2213–2215)

      Dr. Christian Eickmeier and Prof. Dr. Burchard Franck

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199722131

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      The incorporation of pyrrole units was the key to stabilizing the largest annulene from Sondheimer et al., [30]annulene. Of the new aromatic [30]porphyrins 1–3, the 16-phenyl derivative 2 is the most stable.

    8. The Crystal Structure of Aziridine (pages 2215–2216)

      Dr. Norbert W. Mitzel, Jürgen Riede and Christoph Kiener

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199722151

      Thumbnail image of graphical abstract

      The simplest nitrogen heterocycle, aziridine, a very toxic and potentially explosive liquid at room temperature, forms endless chains with an ABCABC motif by hydrogen bonding in the solid state. The results of the crystal structure analysis at 145 K do not suggest any deformations of the molecular skeleton on going from the gas phase to the solid state.

    9. The Chiral S[BOND]N Axis in Sulfenamides: Enantiomeric Resolution, Direct Demonstration of Optical Activity, and Kinetics of Interconversion (pages 2216–2219)

      Merav Ben-David Blanca, Eric Maimon and Prof. Dr. Daniel Kost

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199722161

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      Optically activity due only to restricted rotation about the S[BOND]N bond in a sulfenamide is demonstrated for the first time. Selective inversion recovery experiments were utilized to measure the rate of interconversion of the enantiomers (shown below) that were seperated by using HPLC.

    10. Synthesis of a Triiodide-Like Pentamesityl-tritellurium Cation by Addition of Dimesityltelluride to the Remarkably Electrophilic Trimesitylditelluronium Ion (pages 2219–2221)

      Dipl-Chem. Jörg Jeske, Prof. Dr. Wolf-Walther du Mont and Prof. Dr. Peter G. Jones

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199722191

      Thumbnail image of graphical abstract

      The first stable derivative of the hypothetical Temath image ion—the triiodide-analogous [Mes5Te3]+ ion (partial structure depicted on the right; Mes = 2,4,6-trimethylphenyl)—is obtained by addition of the nucleophile Mes2Te to the iodine-like electrophilic ion [Mes3Te2]+. This reaction provides the first experimental proof of the close relationship between the formation of hypervalent nonclassical Te3 units and that of triiodide from I2 and I.

    11. The First Di-μ3-hydroxo-Bridged Tetramanganese(II) Complex (pages 2221–2222)

      Dr. Lutz Stelzig, Bruno Donnadieu and Prof. Jean-Pierre Tuchagues

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199722211

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      Two molecules of water inserted between two dinuclear Mnmath image species as μ3-hydroxo bridges are evident in the manganese–oxygen core of [{Mnmath image(L)(OH)(thf)}2]·2THF (structure shown on the right). This discrete complex is thus an appealing functional model of the Mn4 core of the oxygen-evolving center in photosystem II at early S state. LH3 = 1,5-bis(3,5-dinitosalicylideneamino)pentan-3-ol; solid unmarked ellipsoids: N; open unmarked ellipsoids: O.

    12. Isolation and X-ray Crystallographic Analysis of a Stable Selenenic Acid (pages 2223–2224)

      Dr. Toshiyuki Saiki, Dr. Kei Goto and Prof. Dr. Renji Okazaki

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199722231

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      The deep cavity in the calix[6]arene framework provides a sterically shielded environment for the SeOH group of the selenenic acid 1. Thanks to this shielding the compound is extraordinarily stable—no decomposition was observed even after heating at 120°C for 5 h in CDCl2CDCl2—although the functional group is still reactive.

    13. Anti-Markovnikov Functionalization of Olefins: Rhodium-Catalyzed Oxidative Aminations of Styrenes (pages 2225–2227)

      Prof. Dr. Matthias Beller, Dipl.-Chem. Martin Eichberger and Dipl.-Chem. Harald Trauthwein

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199722251

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      Not the Markovnikov product 4, but the anti-Markovnikov product 3 is obtained by the oxidative amination of styrenes 1 with secondary amines 2. The oxidant in this rhodium-catalyzed reaction is the olefin itself, which is reduced to the ethylarene 5. Ar = aryl, R = alkyl, aryl.

    14. [Ru20H4Cu6Cl2(CO)48]4− : A New High Nuclearity Copper–Ruthenium Cluster (pages 2227–2228)

      Dr. Michael A. Beswick, Prof. The Lord Jack Lewis, Dr. Paul R. Raithby and Dr. M. Carmen Ramirez de Arellano

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199722271

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      A precursor for Cu/Ru mixed-metal catalysts? This is one of the potential applications of the title cluster (structure of the Ru20Cu6Cl2 framework shown below), which can be isolated as the nBu4N+ salt from the reaction of [(Ph3P)2N]2[Ru10H2(CO)25] with nBu4NOH/H2O,[Cu(MeCN)4], and (Ph3P)2NCl.

    15. Cationic Metallatricarbadecaboranyl Analogues of Metallocene Antitumor Agents: Synthesis, Structure, and Antineoplastic Activity of [1-(η5-C5H5)Fe-2-Me-2,3,4-C3B7H9]+[X] Salts (X = AsFmath image, SbFmath image) (pages 2228–2230)

      Michael D. Wasczcak, Christian C. Lee, Prof. Iris H. Hall, Dr. Patrick J. Carroll and Prof. Larry G. Sneddon

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199722281

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      A cationic ferratricarbadecaboranyl analogue of the ferrocenium cation was synthesized and structurally characterized (structure shown on the right). Cytotoxicity and topoisomerase II inhibition studies of the AsFmath image and SbFmath image salts strongly suggest that tricarbadecaboranyl analogues of other metallocene antitumor agents will exhibit significant and selective anticancer activities.

    16. Enhanced α-CH Acidity and Reactivity of Lewis Acid–Base Complexes in the Gas Phase (pages 2230–2232)

      Jianhua Ren, Dr. Derek B. Workman and Prof. Robert R. Squires

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199722301

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      Borane complexation at the heteroatom increases the gas-phase C[BOND]H acidities of dimethyl sulfide, trimethylamine, and trimethylphosphane by up to 20 kcal mol−1. Deprotonation of the volatile Lewis acid–base complexes in the gas phase produces dipole-stabilized carbanions (see below) that do not rearrange to the more stable borate isomers. The complexation also enhances the reactivity of pendant methyl and ethyl groups toward substitution and elimination reactions.

    17. Cyclopropenylidene Adducts of Divalent Germanium, Tin, and Lead (pages 2232–2234)

      Prof. Dr. Herbert Schumann, Dr. Mario Glanz, Dipl.-Chem. Frank Girgsdies, Prof. Dr. F. Ekkehardt Hahn, Dr. Matthias Tamm and Dipl.-Chem. Alexander Grzegorzewski

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199722321

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      Not germa-, stanna-, and plumbaethenes, but ylidic carbene adducts (depicted on the right) are obtained with bis(diisopropylamino)cyclopropenylidenes. The first main group metal complexes with this nucleophilic carbene are interesting alternatives to the intensively studied imidazol-2-ylidenes.

    18. On the Mechanism of the McMurry Reaction (pages 2234–2237)

      Dr. Martin Stahl, Dr. Ulrich Pidun and Prof. Dr. Gernot Frenking

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199722341

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      A nucleophilic rather than a radical mechanism was recently proposed for the McMurry reaction. Quantum chemical density functional calculations support this hypothesis. An intramolecular and an intermolecular pathway for the C[BOND]C coupling step are discussed, and the pinacolate complexes 1 and 2 are identified as central intermediates.

    19. Sb8R4, R = (Me3Si)2 CH[BOND]A Polycyclic Organostibane (pages 2237–2238)

      Prof. Dr. Hans Joachim Breunig, Roland Rösler and Dr. Enno Lork

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199722371

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      The reaction of RSbCl2 with magnesium in tetrahydrofuran provides, in addition to Sb4R4 and Sb3R3, the title compound 1. The X-ray structure analysis of the yellow crystals of 1 shows that the Sb8 cage corresponds to the P8 section of the structure of Hittorf's phosphorus and is structurally related to realgar (As4S4).

    20. Chemoenzymatic Synthesis of Fluorescent N-Ras Lipopeptides and Their Use in Membrane Localization Studies in Vivo (pages 2238–2241)

      Prof. Dr. Herbert Waldmann, Dr. Michael Schelhaas, Dr. Edgar Nägele, Dr. Jürgen Kuhlmann, Prof. Dr. Alfred Wittinghofer, Hans Schroeder and Prof. John R. Silvius

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199722381

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      Very small regions determine where lipoproteins accumulate in the cell. S-Farnesylated and S-palmitoylated N-Ras lipopeptides 1 accumulate specifically in the plasma membrane, as determined by investigations on fibroblast cells with fluorescence microscopy. (In the structure below the shaded circle symbolizes a fluorescent label). Peptides that were only S-farnesylated do not accumulate in the plasma membrane.

    21. Bimetallic Nanoparticle Catalysts Anchored Inside Mesoporous Silica (pages 2242–2245)

      Dr. Douglas S. Shephard, Dr. Thomas Maschmeyer, Prof. Brian F. G. Johnson, Prof. Sir John Meurig Thomas, Dr. Gopinathan Sankar, Dr. Dogan Ozkaya, Dr. Wuzong Zhou, Dr. Richard D. Oldroyd and Robert G. Bell

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199722421

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      A new hydrogenation catalyst is formed by thermolysis of the anionic carbonyl cluster [Ag3Ru10C2(CO)28Cl]2− anchored to the mesoporous silicate MCM-41. The cluster was isolated and characterized in MCM-41 both before and after thermal treatment. The picture on the right shows a model, based in particular on EXAFS analysis, of the active bimetallic particle. The distribution of the Ag/Ru particles in the MCM-41 cavities was determined by electron microscopy.

  4. Book Reviews

    1. Top of page
    2. Reviews
    3. Highlights
    4. Communications
    5. Book Reviews

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