Angewandte Chemie International Edition

Cover image for Vol. 43 Issue 4

January 16, 2004

Volume 43, Issue 4

Pages 381–529

    1. Cover Picture: Chemistry in Microstructured Reactors (Angew. Chem. Int. Ed. 4/2004) (page 381)

      Klaus Jähnisch, Volker Hessel, Holger Löwe and Manfred Baerns

      Article first published online: 14 JAN 2004 | DOI: 10.1002/anie.200490000

      Microstructured reactors such as the SuperFocus Interdigital micromixer offer an alternative to conventional large-scale techniques. Flow patterns with reduced layer thicknesses lead to enlarged reactive surfaces that result in short mixing times, and thus high-throughput reactions can be achieved. In their review on page 406 ff. K. Jähnisch, V. Hessel, et al. examine the potential of this new and powerful technology.

    2. Do Heavy Nuclei See Light at the End of the Tunnel? (pages 398–401)

      Robert Berger

      Article first published online: 14 JAN 2004 | DOI: 10.1002/anie.200301675

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      The direct route. Low-temperature experiments and calculations on the ring expansion of (1-methylcyclobutyl)fluorocarbene, which involves considerable movement of the heavy nuclei, indicate that tunneling through the barrier is more favorable than the classical route over the “mountain pass” (see picture).

    3. Stable, Self-Assembling, Equilibrating Catalysts for Green Chemistry (pages 402–404)

      Craig L. Hill

      Article first published online: 14 JAN 2004 | DOI: 10.1002/anie.200301701

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      Increased stability of oxidation catalysts results from the self-assembly of the catalysts under near-turnover conditions from oxidatively resistant precursors. The described polyoxometalate epoxidation catalyst uses a green oxidant (H2O2), solvent, and separation conditions and is fast, selective, and safe. This self-assembling system is an important step towards truly green catalysis (see scheme).

    4. Chemistry in Microstructured Reactors (pages 406–446)

      Klaus Jähnisch, Volker Hessel, Holger Löwe and Manfred Baerns

      Article first published online: 14 JAN 2004 | DOI: 10.1002/anie.200300577

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      Good things come in small packages: The reduced dimensions of microstructured reactors offer many advantages in chemistry, particularly with respect to enhanced conversion, selectivity, and safety. This Review presents a discussion of the process parameters and the design of such reactors, which are crucial to their development and optimization.

    5. Metal-Mediated Cross-Linking in the Generation of a Marine-Mussel Adhesive (pages 448–450)

      Mary J. Sever, Jaime T. Weisser, Jennifer Monahan, Shalini Srinivasan and Jonathan J. Wilker

      Article first published online: 18 DEC 2003 | DOI: 10.1002/anie.200352759

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      Iron muscles into mussels: Marine mussels adhere to rocks with a protein-based glue. An iron complex is the key curing agent in this adhesive, and the iron center is coordinated by three DOPA residues (see picture). These studies present the first identified case in which a transition-metal center is integral to forming a noncrystalline biological material.

    6. Identification of Potent Ras Signaling Inhibitors by Pathway-Selective Phenotype-Based Screening (pages 450–454)

      Oliver Müller, Eleni Gourzoulidou, Mercedes Carpintero, Ioanna-Maria Karaguni, Anette Langerak, Christian Herrmann, Tarik Möröy, Ludger Klein-Hitpaß and Herbert Waldmann

      Article first published online: 14 JAN 2004 | DOI: 10.1002/anie.200352587

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      Blocking the path to cancer: Application of efficient strategy for a phenotype-based screening of compound libraries to a library of sulindac-derived compounds (see scheme) yielded new inhibitors of the tumor-relevant Ras signal transduction pathway with high fidelity (as shown by microscopy). The results underline the advantage of using biologically prevalidated compound classes in chemical biology research.

    7. Sulindac-Derived Ras Pathway Inhibitors Target the Ras–Raf Interaction and Downstream Effectors in the Ras Pathway (pages 454–458)

      Herbert Waldmann, Ioanna-Maria Karaguni, Mercedes Carpintero, Eleni Gourzoulidou, Christian Herrmann, Christoph Brockmann, Hartmut Oschkinat and Oliver Müller

      Article first published online: 14 JAN 2004 | DOI: 10.1002/anie.200353089

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      Tracking down the target: The biological targets of eight new Ras-pathway inhibitors were investigated. Several of the compounds were shown to inhibit the RasGTP–Raf interaction (see example shown) and NMR data strongly suggest that this inhibition is the result of direct interaction between the inhibitors and the Ras protein. An inhibitor with a target probably downstream of MAP kinase was also found.

    8. Spontaneous Assembly of a Monolayer of Charged Gold Nanocrystals at the Water/Oil Interface (pages 458–462)

      Francois Reincke, Stephen G. Hickey, Willem K. Kegel and Daniel Vanmaekelbergh

      Article first published online: 14 JAN 2004 | DOI: 10.1002/anie.200352339

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      Charge control as a tool for assembly: Dense layers of individual, charged nanocrystals are formed at the aqueous/organic interface upon a slight reduction of the surface charge. The layers are remarkably robust, they creep up the glass (see picture). This method should be widely applicable to a broad range of charged colloids and will lead to the production of new materials.

    9. X-ray Absorption Spectroscopic and Electrochemical Studies of Tris(catecholato(2−))chromate(V/IV/III) Complexes (pages 462–465)

      Aviva Levina, Garry J. Foran, David I. Pattison and Peter A. Lay

      Article first published online: 14 JAN 2004 | DOI: 10.1002/anie.200352418

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      Contrary to popular belief, the redox chemistry of Cr–catecholato complexes [CrIII(cat)3]3− has been shown by X-ray absorption spectroscopic data to be predominantly metal-based and not ligand-based. The observed increase in the energies of the edge and pre-edge features of the spectra (see picture) and the decrease in the Cr[BOND]O bond lengths on oxidation are consistent with the formation of [CrIV(cat)3]2− and [CrV(cat)3], both with a strong electron delocalization between the metal ion and the ligands.

    10. Helical Superstructure of Conductive Polymers as Created by Electrochemical Polymerization by Using Synthetic Lipid Assemblies as a Template (pages 465–469)

      Tsukasa Hatano, Ah-Hyun Bae, Masayuki Takeuchi, Norifumi Fujita, Kenji Kaneko, Hirotaka Ihara, Makoto Takafuji and Seiji Shinkai

      Article first published online: 14 JAN 2004 | DOI: 10.1002/anie.200351749

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      A templating method is used to create conductive polymers that have a helical superstructure. The driving force is an electrostatic interaction between the negative charge in a synthetic lipid and the cationic charge generated in the polymers during oxidative electrochemical polymerization of ethylenedioxythiophene (EDOT) and a pyrrole (see picture; CV=cyclic voltammetry).

    11. Pressure-Induced Hydration Effects in the Zeolite Laumontite (pages 469–472)

      Catherine L. I. M. White, A. Rabdel Ruiz-Salvador and Dewi W. Lewis

      Article first published online: 14 JAN 2004 | DOI: 10.1002/anie.200352364

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      Computer modeling methods predict that the natural zeolite laumontite will undergo pressure-induced hydration. Specifically, the water-poor analogue “leonhardite” transforms to the fully hydrated laumontite structure (see picture), a transformation with significant geochemical impact. The models and methodologies employed are also capable of replicating the observed dehydration behavior of laumontite.

    12. One-Dimensional Magnetism in Anhydrous Iron and Cobalt Ternary Oxalates with Rare Trigonal-Prismatic Metal Coordination Environment (pages 472–475)

      Michael B. Hursthouse, Mark E. Light and Daniel J. Price

      Article first published online: 14 JAN 2004 | DOI: 10.1002/anie.200352406

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      Imprismed metals: Hydrothermal crystallization of Fe and Co oxalates from extremely concentrated KBr solutions yield a coordination network where the paramagnetic metal ions are in rare coordination geometries (see structure). Both materials show a strong 1D magnetic character and for the FeII derivative no long-range order is seen above 2 K, making it a candidate for a Spin 2 quasi-1D quantum antiferromagnet.

    13. Heterobimetallic C3 Complexes through Silylpropargylidyne Desilylation (pages 476–478)

      Rian D. Dewhurst, Anthony F. Hill and Matthew K. Smith

      Article first published online: 14 JAN 2004 | DOI: 10.1002/anie.200352693

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      Odd compounds: The study of bimetallic complexes spanned by linear carbon chains was mainly restricted to even-numbered chains. The fluorodesilylation of silylated propargylidynes now provides a range of C3-spanned heterobimetallic complexes based on Ru and either Mo or W (e.g. see picture).

    14. An Efficient Synthesis of Bicyclic Amidines by Intramolecular Cyclization (pages 478–482)

      Naoya Kumagai, Shigeki Matsunaga and Masakatsu Shibasaki

      Article first published online: 14 JAN 2004 | DOI: 10.1002/anie.200352750

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      A real step-saver! In a one-step procedure for the synthesis of bicyclic amidines, the azido group is used directly as the nucleophile in the ring-forming reaction. Many functionalized and chiral bicyclic amidines were synthesized in good yield under mild reaction conditions.

    15. Polymer-Supported Ionic Liquids: Imidazolium Salts as Catalysts for Nucleophilic Substitution Reactions Including Fluorinations (pages 483–485)

      Dong Wook Kim and Dae Yoon Chi

      Article first published online: 18 DEC 2003 | DOI: 10.1002/anie.200352760

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      Ionic liquids obtain firm support: Polymer-supported imidazolium salts are shown to be highly efficient catalysts for fluorination and other nucleophilic substitution reactions. The polystyrene-based ionic materials catalyze fluorination reactions (such as that shown in the scheme; X=BF4, OTf) in very high yield, and can be reused for many such reactions.

    16. Facile Oxidative Rearrangement of Dispiro-Porphodimethenes to Nonplanar and Sheetlike Porphyrins with Intense Absorptions in the Near-IR Region (pages 485–490)

      Hubert S. Gill, Michael Harmjanz, Javier Santamaría, Isaac Finger and Michael J. Scott

      Article first published online: 14 JAN 2004 | DOI: 10.1002/anie.200352762

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      Exceedingly large, planar porphyrin systems composed of 49 non-hydrogen nuclei in highly delocalized π systems display exceptionally low-energy transitions in UV/Vis/NIR spectroscopy and in cyclic voltammetry. The spectra shown are for cis palladium complex depicted and the corresponding trans isomer

    17. Stereoselective Construction of Acyclic Carbon Chains by a One-Pot Coupling Process Based on Alkenyloxazoline–Titanium Complexes (pages 490–492)

      Kazuhisa Mitsui, Takayuki Sato, Hirokazu Urabe and Fumie Sato

      Article first published online: 14 JAN 2004 | DOI: 10.1002/anie.200352769

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      A versatile organometallic intermediate, an alkenyloxazoline–titanium complex, has been developed that enables one-pot multicomponent diastereoselective and asymmetric coupling processes to be achieved in a remarkably efficient manner (see scheme).

    18. Peptidyl Thiophenols as Substrates for Nonribosomal Peptide Cyclases (pages 493–498)

      Stephan A. Sieber, Junhua Tao, Christopher T. Walsh and Mohamed A. Marahiel

      Article first published online: 14 JAN 2004 | DOI: 10.1002/anie.200352787

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      Activity-based enzyme acylation: Although small peptides are specifically cyclized by nonribosomal peptide cyclases (thioesterases, TEs) in nature, artificial N-acetylcysteamine thioester (SNAC) mimics have often failed to act as substrates for these enzymes in vitro. However, new reactive peptidyl aromatic thioesters solve this problem by selective acylation of the enzyme active site (see scheme).

    19. An Integrated Approach to a Portable and Low-Cost Immunoassay for Resource-Poor Settings (pages 498–502)

      Samuel K. Sia, Vincent Linder, Babak Amir Parviz, Adam Siegel and George M. Whitesides

      Article first published online: 14 JAN 2004 | DOI: 10.1002/anie.200353016

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      An integrated approach for detecting proteins that is low-cost, portable, battery-operated, and works under field conditions such as direct sunlight has been developed. The “POCKET immunoassay” uses commercially available components, and exhibits an analytical performance approaching that of established bench-top techniques. It may be appropriate for the diagnosis of infectious diseases, such as HIV/AIDS, in developing countries (see picture).

    20. Stable Cubic Phosphorus-Containing Radicals (pages 502–505)

      Andrea Armstrong, Tristram Chivers, Masood Parvez and Rene T. Boeré

      Article first published online: 18 DEC 2003 | DOI: 10.1002/anie.200353108

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      Stable, deep-blue neutral radicals [(Me3SiN)P(μ3-NtBu)33-Li(thf)}3X] (X=Br, I) with distorted cubic structures are obtained by the oxidation of [{Li3[P(NtBu)3(NSiMe3)]}2] with halogens in THF (see picture). The cubes comprise the radical dianion [P(NtBu)3(NSiMe3)].2−, two Li+ ions, and a molecule of LiX. Solvation in very dilute THF solution releases (thf)3LiX and generates the cyclic radical monoanion [(Me3SiN)(tBuN)P(μ-NtBu)2Li(thf)2].−.

    21. Two Helical Conformations from a Single Foldamer Backbone: “Split Personality” in Short α/β-Peptides (pages 505–510)

      Ahlke Hayen, Margaret A. Schmitt, Felix N. Ngassa, Kathryn A. Thomasson and Samuel H. Gellman

      Article first published online: 14 JAN 2004 | DOI: 10.1002/anie.200352125

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      Oligopeptides with heterogeneous backbones, i.e., oligopeptides containing more than one monomer type, may be a fruitful source of new foldamers. This conclusion was suggested by studies on oligomers comprising L-α-amino acid and cyclic β-amino acid residues in a sequentially alternating pattern, which are shown to display helical secondary structure in solution.

    22. Surprisingly Stable Helical Conformations in α/β-Peptides by Incorporation of cis-β-Aminocyclopropane Carboxylic Acids (pages 511–514)

      Silvia De Pol, Chiara Zorn, Christian D. Klein, Oliver Zerbe and Oliver Reiser

      Article first published online: 14 JAN 2004 | DOI: 10.1002/anie.200352267

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      With as few as seven residues, acyclic α/β-peptides, which consist of alternating units of (L)-alanine and of cis-β-aminocyclopropanecarboxylic acids (cis-β-ACCs, see structure), form stable 313-helix turns in solution. The configuration of the cis-β-ACCs was found to be crucial for the helical structure of this new class of foldamers.

    23. Titanium(IV)-Catalyzed Dynamic Kinetic Asymmetric Transformation of Alcohols, Silyl Ethers, and Acetals under Carbon Allylation (pages 514–517)

      Manfred Braun and Wolfgang Kotter

      Article first published online: 14 JAN 2004 | DOI: 10.1002/anie.200352128

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      High yields and enantioselectivities are obtained in a dynamic kinetic asymmetric transformation in which the C[BOND]O bond of alcohols, silyl ethers, and acetals are substituted by a C[BOND]C bond. For example, the racemic indanyl silyl ether 1 is converted into (S)-2 in the presence of the chiral Lewis acidic TiIV complex 3.

    24. Structural Changes in Nanoparticle Catalysts as Monitored by Their Magnetic Properties (pages 517–520)

      Thomas Risse, Mohsen Mozaffari-Afshar, Heiko Hamann and Hans-Joachim Freund

      Article first published online: 14 JAN 2004 | DOI: 10.1002/anie.200352107

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      Interfaces of supported metal nanoparticles, in particular the metal–support interface, are still very difficult to characterize. Since magnetic properties are strongly correlated to structural properties, ferromagnetic resonance spectroscopy can be used (see picture). The high sensitivity of the method is demonstrated for processes at both the particle–gas and the particle–support interface.

    25. Facile Route to Ultraflat SAM-Protected Gold Surfaces by “Amphiphile Splitting” (pages 520–523)

      Pooja Gupta, Katja Loos, Alexander Korniakov, Chiara Spagnoli, Mary Cowman and Abraham Ulman

      Article first published online: 14 JAN 2004 | DOI: 10.1002/anie.200352249

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      Self-assembled monolayers of both aliphatic and aromatic thiols can be produced with no apparent contact-angle hysteresis by a modified “template-stripping” method. Organothiol solutions serve as splitting reagents for the removal of the mica from the gold surface. These new ultrasmooth SAM surfaces (see the AFM image) provide new information on interfacial properties including wetting and adhesion.

    26. Preview: Angew. Chem. Int. Ed. 4/2004 (page 529)

      Article first published online: 14 JAN 2004 | DOI: 10.1002/anie.200490003