Angewandte Chemie International Edition

Cover image for Vol. 46 Issue 41

October 15, 2007

Volume 46, Issue 41

Pages 7715–7901

  1. Cover Picture

    1. Top of page
    2. Cover Picture
    3. Inside Cover
    4. Graphical Abstract
    5. Corrigenda
    6. News
    7. Book Review
    8. Highlights
    9. Review
    10. Communications
    11. Preview
    1. Cover Picture: Rational Design of a Fluorescence-Turn-On Sensor Array for Phosphates in Blood Serum (Angew. Chem. Int. Ed. 41/2007) (page 7715)

      Grigory V. Zyryanov, Manuel A. Palacios and Pavel Anzenbacher Jr.

      Version of Record online: 4 OCT 2007 | DOI: 10.1002/anie.200790203

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      The beauty of symmetry is evident in many different forms, such as in The Star of David, rosette windows, and receptor–substrate complexes. P. Anzenbacher, Jr. et al. show in their Communication on page 7849 ff. how C3-symmetrical receptors with an array of six hydrogen-bond donors replicate the symmetry in the complex of three phosphate anions within the binding cavity. These receptors were converted into fluorescence sensors capable of detecting phosphates, including AMP and ATP, in water and in blood serum.

  2. Inside Cover

    1. Top of page
    2. Cover Picture
    3. Inside Cover
    4. Graphical Abstract
    5. Corrigenda
    6. News
    7. Book Review
    8. Highlights
    9. Review
    10. Communications
    11. Preview
    1. Inside Cover: Expanded Porphyrin with a Split Personality: A Hückel–Möbius Aromaticity Switch (Angew. Chem. Int. Ed. 41/2007) (page 7716)

      Marcin Stępień, Lechosław Latos-Grażyński, Natasza Sprutta, Paulina Chwalisz and Ludmiła Szterenberg

      Version of Record online: 4 OCT 2007 | DOI: 10.1002/anie.200790204

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      The two complementary worlds of π aromaticity meet in one molecule. Di-p-benzihexaphyrin, described by Latos-Grażyński et al. in their Communication on page 7869 ff., contains two phenylene rings, which, when oriented face-to-face, define an antiaromatic macrocycle with an orientable (Hückel) π system. With a 90° twist of one phenylene ring, the molecule transforms into a remarkable edge-to-face conformer with a Möbius topology. The different colors of the two forms show the effect of topology switching on the π conjugation.

  3. Graphical Abstract

    1. Top of page
    2. Cover Picture
    3. Inside Cover
    4. Graphical Abstract
    5. Corrigenda
    6. News
    7. Book Review
    8. Highlights
    9. Review
    10. Communications
    11. Preview
  4. Corrigenda

    1. Top of page
    2. Cover Picture
    3. Inside Cover
    4. Graphical Abstract
    5. Corrigenda
    6. News
    7. Book Review
    8. Highlights
    9. Review
    10. Communications
    11. Preview
    1. You have free access to this content
      A DMSO-Compatible Orienting Medium: Towards the Investigation of the Stereochemistry of Natural Products (page 7730)

      Peter Haberz, Jonathan Farjon and Christian Griesinger

      Version of Record online: 4 OCT 2007 | DOI: 10.1002/anie.200790206

      This article corrects:
    2. You have free access to this content
      Suzuki–Miyaura Coupling Reaction by PdII-Catalyzed Aromatic C[BOND]H Bond Activation Directed by an N-Alkyl Acetamino Group (page 7730)

      Zhangjie Shi, Bijie Li, Xiaobing Wan, Jiang Cheng, Zhao Fang, Bin Cao, Changming Qin and Yang Wang

      Version of Record online: 4 OCT 2007 | DOI: 10.1002/anie.200790209

      This article corrects:
  5. News

    1. Top of page
    2. Cover Picture
    3. Inside Cover
    4. Graphical Abstract
    5. Corrigenda
    6. News
    7. Book Review
    8. Highlights
    9. Review
    10. Communications
    11. Preview
  6. Book Review

    1. Top of page
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    3. Inside Cover
    4. Graphical Abstract
    5. Corrigenda
    6. News
    7. Book Review
    8. Highlights
    9. Review
    10. Communications
    11. Preview
  7. Highlights

    1. Top of page
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    4. Graphical Abstract
    5. Corrigenda
    6. News
    7. Book Review
    8. Highlights
    9. Review
    10. Communications
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    1. Induced Chirality in Achiral Media—How Theory Unravels Mysterious Solvent Effects (pages 7738–7740)

      Johannes Neugebauer

      Version of Record online: 20 SEP 2007 | DOI: 10.1002/anie.200702858

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      The solvent makes the difference: Quantum chemical investigations show that chiroptical properties can originate mainly from a chiral solvent shell rather than from the chiral solute. By using this approach it is possible to explain, for example, why the optical rotation of (S)-methyloxirane is positive in water, but has a relatively strong negative value in benzene (see picture; red: (S)- or (R)-methyloxirane, blue benzene).

    2. Teaching Bacteria New Tricks—With RNA Switches (pages 7741–7743)

      Jörg S. Hartig

      Version of Record online: 20 SEP 2007 | DOI: 10.1002/anie.200703088

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      A demanding challenge for the genetic modification of organisms that could target pollutants or diseases in future applications will be the recruitment of such entities to the respective sites of action. Topp and Gallivan have used RNA switches to guide bacteria along paths of specific compounds by rewiring their chemosensory system (see picture; the CheZ protein controls the motility).

  8. Review

    1. Top of page
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    4. Graphical Abstract
    5. Corrigenda
    6. News
    7. Book Review
    8. Highlights
    9. Review
    10. Communications
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    1. The Renaissance of H/D Exchange (pages 7744–7765)

      Jens Atzrodt, Volker Derdau, Thorsten Fey and Jochen Zimmermann

      Version of Record online: 21 SEP 2007 | DOI: 10.1002/anie.200700039

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      A favorable exchange: Deuterated organic compounds may be prepared significantly more efficiently and more cost effectively by H/D exchange rather than by classical synthetic procedures. In this Review, the development of methods for the preparative application of the H/D-exchange reaction on a carbon center (see picture) over the last ten years are brought together and discussed.

  9. Communications

    1. Top of page
    2. Cover Picture
    3. Inside Cover
    4. Graphical Abstract
    5. Corrigenda
    6. News
    7. Book Review
    8. Highlights
    9. Review
    10. Communications
    11. Preview
    1. Amide-to-Ester Substitution in Coiled Coils: The Effect of Removing Hydrogen Bonds on Protein Structure (pages 7766–7769)

      Jessica A. Scheike, Carsten Baldauf, Jan Spengler, Fernando Albericio, M. Teresa Pisabarro and Beate Koksch

      Version of Record online: 17 SEP 2007 | DOI: 10.1002/anie.200702218

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      The latest twist: The effect of backbone H-bonding on the stability of proteins was studied by experimental techniques and molecular dynamics simulation. The structure of the coiled-coil model peptide examined (see picture) is affected by interactions in the solvent-exposed regions as well as by interhelical hydrophobic interactions.

    2. A Titanium Disilicide Derived Semiconducting Catalyst for Water Splitting under Solar Radiation—Reversible Storage of Oxygen and Hydrogen (pages 7770–7774)

      Peter Ritterskamp, Andriy Kuklya, Marc-André Wüstkamp, Klaus Kerpen, Claudia Weidenthaler and Martin Demuth

      Version of Record online: 5 SEP 2007 | DOI: 10.1002/anie.200701626

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      Divide and separate: Photocatalytic splitting of water into hydrogen and oxygen is achieved with a catalyst which is formed on the surface of titanium dicilicide (see picture). The two product gases are reversibly physisorbed by the catalyst. Desorption of hydrogen occurs at ambient temperature, but oxygen is entirely stored up to 100 °C in light and can be released upon heating at this temperature in the dark, which allows convenient separation of the gases.

    3. Transformation of Nitrile to Cyanide and Aldehyde Using a Cobalt(II) Complex and Dioxygen (pages 7775–7777)

      Jörg Müller, Christian Würtele, Olaf Walter and Siegfried Schindler

      Version of Record online: 11 SEP 2007 | DOI: 10.1002/anie.200701408

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      Canning a carbon: During oxidation with O2, the cobalt(II) complex [Co(salmdpt)] (salmdptH2=bis[3-(salicylideneimino)-propyl]methylamine) reacts with a nitrile substrate to form the cyanide complex [Co(salmdpt)CN] (see structure) and the corresponding aldehyde, which contains one less carbon atom than the starting nitrile.

    4. Fast Lithium Ion Conduction in Garnet-Type Li7La3Zr2O12 (pages 7778–7781)

      Ramaswamy Murugan, Venkataraman Thangadurai and Werner Weppner

      Version of Record online: 5 SEP 2007 | DOI: 10.1002/anie.200701144

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      Low activation energy and fast lithium ion conduction have been observed for the new compound Li7La3Zr2O12. Relative to previously reported lithium garnets, the solid electrolyte shows a larger cubic lattice constant, higher lithium ion concentration, lower degree of chemical interaction between the Li+ ions and the other lattice constituents, and higher densification.

    5. Interaction between d- and p-Block Metals: Synthesis and Structure of Platinum–Alane Adducts (pages 7782–7784)

      Holger Braunschweig, Katrin Gruss and Krzysztof Radacki

      Version of Record online: 5 SEP 2007 | DOI: 10.1002/anie.200702726

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      You'll never walk alane: An intriguing T-shaped platinum–alane adduct results from the almost quantitive reaction of [Pt(PCy3)2] with AlX3 (X=Cl, Br, I). The compound [(Cy3P)2Pt[BOND]AlCl3] represents the first neutral alane complex displaying an unsupported Pt–Al dative bond.

    6. Synthesis and Electronic Structure of a Terminal Alkylborylene Complex (pages 7785–7787)

      Holger Braunschweig, Michael Burzler, Thomas Kupfer, Krzysztof Radacki and Fabian Seeler

      Version of Record online: 5 SEP 2007 | DOI: 10.1002/anie.200702029

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      Without π stabilization: Phosphine-induced cleavage of a dinuclear precursor yielded the first terminal alkylborylene complex. Experimental and computational data suggest a strong Mn[BOND]B interaction, thus compensating the lack of π stabilization provided by the B-bound alkyl group and accounting for the thermal stability of the title compound and its propensity to undergo controlled derivatization.

    7. Conformational Locking through Allylic Strain as a Device for Stereocontrol—Total Synthesis of Grandisine A (pages 7789–7792)

      David J. Maloney and Samuel J. Danishefsky

      Version of Record online: 17 SEP 2007 | DOI: 10.1002/anie.200703245

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      Controlled fusion: The use of a seco ring D precursor to control both the stereochemistry of a critical cycloaddition with acetaldehyde and the direction of protonation of the resultant silyl enol ether cycloadduct has led to the total synthesis of grandisine A, which shows promising selectivity for binding to the δ-opioid receptor. The D ring is installed in the final stages of the synthesis (see scheme, LA=Lewis acid).

    8. Indium-Catalyzed Retro-Claisen Condensation (pages 7793–7795)

      Atsushi Kawata, Kazumi Takata, Yoichiro Kuninobu and Kazuhiko Takai

      Version of Record online: 4 SEP 2007 | DOI: 10.1002/anie.200702798

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      Retro-aldol reaction: Indium-catalyzed reaction of a 1,3-diketone with an alcohol proceeds under solvent-free conditions by nucleophilic attack of the alcohol on a carbonyl group of the 1,3-diketone and carbon–carbon bond cleavage by a retro-Claisen condensation to give an ester in high yield (see scheme). Using water and an amine as nucleophiles instead of an alcohol gave the corresponding carboxylic acid and amide.

    9. Synthesis and Characterization of Chiral Periodic Mesoporous Organosilicas (pages 7796–7798)

      Xiangju Meng, Toshiyuki Yokoi, Daling Lu and Takashi Tatsumi

      Version of Record online: 11 SEP 2007 | DOI: 10.1002/anie.200702666

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      Keep this handy! Periodic mesoporous organosilica-based compounds with chiral channels are prepared by using an achiral fluorinated surfactant (FC-4911) and cetyltrimethylammonium bromide as structure-directing agents. Spiral samples synthesized from 1,4-bis(triethoxysilyl)benzene exhibit structural periodicity and a crystal-like mesoporous wall (see TEM image).

    10. Regioselectivity of the Rhodium-Catalyzed Hydroboration of Vinyl Arenes: Electronic Twists and Mechanistic Shifts (pages 7799–7802)

      David R. Edwards, Yonek B. Hleba, Christopher J. Lata, Larry A. Calhoun and Cathleen M. Crudden

      Version of Record online: 6 SEP 2007 | DOI: 10.1002/anie.200702563

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      Any substituent does it: The hydroboration of vinyl arenes with pinacol borane (HBPin) and cationic rhodium complexes selectively placed the boron proximal to the aryl rather than phenyl ring, regardless of whether this ring bears electron-donating or electron-withdrawing substituents. In competition experiments between styrene and various vinyl arenes, preferential hydroboration also occured at the substituted arene (see scheme). Hammett plots indicate a break in the mechanism.

    11. Catalytic Asymmetric Michael Reactions with Enamides as Nucleophiles (pages 7803–7805)

      Florian Berthiol, Ryosuke Matsubara, Nobuyuki Kawai and Shū Kobayashi

      Version of Record online: 4 SEP 2007 | DOI: 10.1002/anie.200702517

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      Under its own steam: No external proton source is required for catalytic turnover in the copper-catalyzed title reaction with alkylidenemalonates, as proton transfer occurs rapidly in an intramolecular manner. The desired 1,5-dicarbonyl adducts were formed in moderate to high yield with high enantioselectivity (see scheme). R1=alkyl; R2=alkyl, aryl; Tf=trifluoromethanesulfonyl.

    12. Catalytic Enantioselective α-Acylvinyl Anion Reactions of Silyloxyallenes (pages 7806–7809)

      Troy E. Reynolds and Karl A. Scheidt

      Version of Record online: 11 SEP 2007 | DOI: 10.1002/anie.200702818

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      Alternatives with silicon: The enantioselective Lewis acid catalyzed addition of racemic silyloxyallenes to aldehydes is reported. A {(salen)CrIII} complex efficiently catalyzes the reaction of these α-acylvinyl anion equivalents (see scheme) with excellent enantioselectivity, high yield, and superb control over the configuration of the resulting double bond.

    13. Highly Enantioselective Synthesis of α-Hydroxy Phosphonic Acid Derivatives by Rh-Catalyzed Asymmetric Hydrogenation with Phosphine–Phosphoramidite Ligands (pages 7810–7813)

      Dao-Yong Wang, Xiang-Ping Hu, Jia-Di Huang, Jun Deng, Sai-Bo Yu, Zheng-Chao Duan, Xue-Feng Xu and Zhuo Zheng

      Version of Record online: 11 SEP 2007 | DOI: 10.1002/anie.200702924

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      A class act: Unsymmetrical hybrid phosphine–phosphoramidite ligands with central and axial chirality are applied to the highly enantioselective hydrogenation of various enol ester phosphonates (see scheme; cod=cycloocta-1,5-diene). Enantioselectivities up to 99.9 % ee are obtained for all classes of β-aryl, β-alkoxy, and β-alkyl substrates.

    14. Thermally Stable Gold(I) Ethylene Adducts: [(HB{3,5-(CF3)2Pz}3)Au(CH2[DOUBLE BOND]CH2)] and [(HB{3-(CF3),5-(Ph)Pz}3)Au(CH2[DOUBLE BOND]CH2)] (pages 7814–7816)

      H. V. Rasika Dias and Jiang Wu

      Version of Record online: 4 SEP 2007 | DOI: 10.1002/anie.200703328

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      Captured by scorpionates: Using fluorinated scorpionates, remarkably stable gold(I) complexes containing ethylene are isolated and structurally characterized (see structure of molecule core: yellow Au, blue N, red B, light gray C). These adducts feature κ2-bonded tris(pyrazolyl)borate ligands, and show in the 1H and 13C NMR spectra considerably upfield-shifted ethylene signals.

    15. Asymmetric Synthesis of the Phytopathogen (+)-Fomannosin (pages 7817–7819)

      Leo A. Paquette, Xiaowen Peng and Jiong Yang

      Version of Record online: 6 SEP 2007 | DOI: 10.1002/anie.200702056

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      Three new construction features in one synthesis—for the fused cyclobutene ring, the cyclopentanone, and the functionalized six-membered lactone—characterize the procedure that leads to the natural (+)-enantiomer of the title compound starting with D-glucose. Central to the routing are steps involving organometallic reagents containing ruthenium, osmium, zirconium, and samarium among others.

    16. Gold Nanoparticles and Gold(III) Complexes as General and Selective Hydrosilylation Catalysts (pages 7820–7822)

      Avelino Corma, Camino González-Arellano, Marta Iglesias and Félix Sánchez

      Version of Record online: 11 SEP 2007 | DOI: 10.1002/anie.200702032

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      Worth their weight in gold: Au/CeO2 nanoparticles are a highly active catalyst for the hydrosilylation of a large variety of unsaturated compounds with high chemo- and regioselectivity. To understand the nature of the catalytic active sites, AuI and AuIII phosphine-free stable organogold complexes and their supported counterparts were prepared and their relative activity towards hydrosilylation was elucidated.

    17. Noncovalent Functional-Group–Arene Interactions (pages 7823–7826)

      William B. Motherwell, Joëlle Moïse, Abil E. Aliev, Miloslav Nič, Simon J. Coles, Peter N. Horton, Michael B. Hursthouse, Gianni Chessari, Christopher A. Hunter and Jeremy G. Vinter

      Version of Record online: 24 SEP 2007 | DOI: 10.1002/anie.200701463

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      Hanging in the balance: A series of dibenzobicyclo[3,2,2]nonanes provides a delicate conformational balance for investigating weak interactions, such as O[BOND]H⋅⋅⋅π(Ar) π-hydrogen bonding (see scheme, red O) and solvent–solute interactions. The models are designed to probe the effectiveness of replacing a hydroxy group by fluorine or to compare the arene affinities of sulfur and oxygen.

    18. Formation and Structure of the [(1,2-C6H4P2Sb)2]4− Ion: Implications for an Extended Family of Isoelectronic Main-Group Radicals (pages 7827–7830)

      Felipe García, Robert J. Less, Vesal Naseri, Mary McPartlin, Jeremy M. Rawson and Dominic S. Wright

      Version of Record online: 4 SEP 2007 | DOI: 10.1002/anie.200702603

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      A fine pair: Quadruple deprotonation of 1,2-(PH2)2C6H4 with Sb(NMe2)3/nBuLi gives the 6π-aromatic ion [1,2-C6H4P2Sb], which is converted by one-electron reduction into the radical [1,2-C6H4P2Sb].2− (see picture). DFT calculations reveal that dimerization of the radical is only favored if ionic interactions with cations are considered.

    19. Enantioselective Synthesis of the Complex Rocaglate (−)-Silvestrol (pages 7831–7834)

      Baudouin Gerard, Regina Cencic, Jerry Pelletier and John A. Porco Jr.

      Version of Record online: 5 SEP 2007 | DOI: 10.1002/anie.200702707

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      The total synthesis of the natural product (−)-silvestrol (1) has been accomplished and features enantioselective [3+2] photocycloaddition of a substituted 3-hydroxyflavone and methyl cinnamate promoted by a chiral Brønsted acid. Initial biological studies indicate a 5–10-fold greater activity of silvestrol as an inhibitor of protein synthesis in HeLa cells than its 1′′′′ diastereomer.

    20. Total Synthesis of (−)-Episilvestrol and (−)-Silvestrol (pages 7835–7838)

      Mariana El Sous, Mui Ling Khoo, Georgina Holloway, David Owen, Peter J. Scammells and Mark A. Rizzacasa

      Version of Record online: 6 SEP 2007 | DOI: 10.1002/anie.200702700

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      Sugar and spice… The total synthesis of the rare but potent anticancer natural product (−)-episilvestrol and its 5′′′ epimer (−)-silvestrol was accomplished from D-glucose, naringenin, and methyl cinnamate (see scheme). The key steps of the sequence were inspired by the possible biogenesis of these compounds.

    21. Ionothermal Synthesis of Unusual Choline-Templated Cobalt Aluminophosphates (pages 7839–7843)

      Ewan A. Drylie, David S. Wragg, Emily R. Parnham, Paul S. Wheatley, Alexandra M. Z. Slawin, John E. Warren and Russell E. Morris

      Version of Record online: 6 SEP 2007 | DOI: 10.1002/anie.200702239

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      Into the deep: A deep-eutectic solvent based on choline chloride and one of several carboxylic acids can be used to prepare cobalt aluminophosphate analogues of zeolites. One of the new materials contains unusual ring-opened double-four-ring units, in which a cobalt atom forms a terminal Co[BOND]Cl bond (see picture; Co cyan, Al gray, P purple, O red, Cl green).

    22. [Rh7(PiPr3)6H18][BArF4]2: A Molecular Rh(111) Surface Decorated with 18 Hydrogen Atoms (pages 7844–7848)

      Simon K. Brayshaw, Jennifer C. Green, Ruth Edge, Eric J. L. McInnes, Paul R. Raithby, John E. Warren and Andrew S. Weller

      Version of Record online: 6 SEP 2007 | DOI: 10.1002/anie.200703069

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      Heptarhodium wagon wheel [Rh7(PiPr3)6H18][BArF4]2 (shown), which resembles a planar Rh(111) surface with 18 hydride ligands, was obtained together with [Rh8(PiPr3)6H16][BArF4]2 from the reaction of [Rh(PiPr3)2(nbd)][BArF4] and [Rh(nbd)2][BArF4] with hydrogen (ArF=C6H3(CF3)2, nbd=norbornadiene). Some of the H ligands are located in threefold hollows between Rh centers and thus mimic the orientation of atomic hydrogen adsorbed on Rh(111).

    23. Rational Design of a Fluorescence-Turn-On Sensor Array for Phosphates in Blood Serum (pages 7849–7852)

      Grigory V. Zyryanov, Manuel A. Palacios and Pavel Anzenbacher Jr.

      Version of Record online: 15 AUG 2007 | DOI: 10.1002/anie.200702611

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      Getting turned on: An order-of-magnitude fluorescence amplification of simple tripodal sensors has been observed in the presence of phosphate ions. An X-ray structure analysis of one of the complexes (see picture) shows the binding of three phosphate ions, which closely resembles the anionic part of ATP, by the sensor. The sensors were used to generate cross-reactive arrays that can detect anions in human serum.

    24. Water Dissociation in the Presence of Metal Ions (pages 7853–7855)

      Orkid Coskuner, Emily A. A. Jarvis and Thomas C. Allison

      Version of Record online: 6 SEP 2007 | DOI: 10.1002/anie.200701617

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      With or without the metal: Recently, the Grotthuss mechanism of proton transfer in water has been described in detail. A similar mechanism has been found in the vicinity of transition-metal ions, which leads to the formation of Zundel and Eigen complexes (see picture).

    25. Complex Liquid-Crystalline Superstructure of a π-Conjugated Oligothiophene (pages 7856–7859)

      Marko Prehm, Günther Götz, Peter Bäuerle, Feng Liu, Xiangbing Zeng, Goran Ungar and Carsten Tschierske

      Version of Record online: 4 SEP 2007 | DOI: 10.1002/anie.200701585

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      A good connection: A polyphilic oligothiophene derivative (see formula) forms a complex liquid-crystalline phase, in which the π-conjugated rods are organized in a honeycomb-like network of square cylinders (see picture). This arrangement opens new possibilities for the directed organization of π-conjugated organic materials into complex superstructures and patterns for the design of functional devices by means of liquid-crystal self-assembly.

    26. Homogeneous Biocatalysis in both Fluorous Biphasic and Supercritical Carbon Dioxide Systems (pages 7860–7863)

      Helen R. Hobbs, Helen M. Kirke, Martyn Poliakoff and Neil R. Thomas

      Version of Record online: 6 SEP 2007 | DOI: 10.1002/anie.200701488

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      HIP to be green: Cytochrome c and α-chymotrypsin (CMT) can be solubilized in either fluorous solvents or supercritical CO2 by hydrophobic ion pairing (HIP) with perfluorinated anionic surfactants (Krytox 157 FSL, KDP 4606). A model system for homogeneous fluorous biphasic biocatalysis involving the CMT–KDP complex in hexane/perfluoromethylcyclohexane is reported that simplifies both product separation and recycling of the biocatalyst.

    27. Catalytic Consequences of Composition in Polyoxometalate Clusters with Keggin Structure (pages 7864–7868)

      Josef Macht, Michael J. Janik, Matthew Neurock and Enrique Iglesia

      Version of Record online: 7 SEP 2007 | DOI: 10.1002/anie.200701292

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      Rate constants for acid-catalyzed butanol dehydration on Keggin-type polyoxometalate clusters H8−nXn+W12O40 (X=P, Si, Al, Co) increase as the oxidation state of the central atom increases and the number of cluster protons concurrently decreases (see diagram). These trends reflect the lower deprotonation enthalpies of clusters with high valent central atoms and their stability as the anionic conjugate base in ionic transition states involved in dehydration catalysis.

    28. Expanded Porphyrin with a Split Personality: A Hückel–Möbius Aromaticity Switch (pages 7869–7873)

      Marcin Stępień, Lechosław Latos-Grażyński, Natasza Sprutta, Paulina Chwalisz and Ludmiła Szterenberg

      Version of Record online: 2 JUL 2007 | DOI: 10.1002/anie.200700555

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      Dual identity: It takes a single phenylene twist to reveal the dichotomous nature of a di-para-benzihexaphyrin (see picture; phenylene rings highlighted in red). This expanded porphyrinoid switches between Hückel and Möbius topologies in an unusual solvent- and temperature-dependent equilibrium. Each of the two incarnations of the macrocycle has its own unmistakable spectral signature.

    29. Crossover Site-Selectivity in the Adsorption of the Fullerene Derivative PCBM on Au(111) (pages 7874–7877)

      David Écija, Roberto Otero, Luis Sánchez, José María Gallego, Yang Wang, Manuel Alcamí, Fernando Martín, Nazario Martín and Rodolfo Miranda

      Version of Record online: 7 SEP 2007 | DOI: 10.1002/anie.200702531

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      With increasing coverage, self-assembly of the fullerene derivative phenyl-C61-butyric acid methyl ester (PCBM) on Au(111) undergoes a transition from substrate-controlled to hydrogen-bond-controlled. At low coverages, PCBM nucleates exclusively at the fcc areas of the “herringbone” reconstruction (left image). At higher coverages, double rows of PCBM molecules connected through hydrogen bonds are formed (right image). ML: monolayer.

    30. Mechanisms of Cyaphide (C[TRIPLE BOND]P) Formation (pages 7878–7881)

      Andreas Ehlers, Joseph G. Cordaro, Daniel Stein and Hansjörg Grützmacher

      Version of Record online: 4 SEP 2007 | DOI: 10.1002/anie.200702442

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      Rock 'n' roll cyaphide: Although the kinetic product B is an observable intermediate of nucleophilic attack on the low-coordinate phosphorus atom in A, it is not directly involved in the mechanism leading to cyaphide complex F. Instead, DFT calculations suggest that nucleophilic attack at silicon ([RIGHTWARDS ARROW]C) initiates decomposition via D to F. In contrast to cyanide complexes, isocyaphide E is only a transition state for C[TRIPLE BOND]P-ligand rotation DD′.

    31. Continuous Fluorometric Assays for Acetylcholinesterase Activity and Inhibition with Conjugated Polyelectrolytes (pages 7882–7886)

      Fude Feng, Yanli Tang, Shu Wang, Yuliang Li and Daoben Zhu

      Version of Record online: 4 SEP 2007 | DOI: 10.1002/anie.200701724

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      Quick but sensitive: A super-quenched fluorogenic complex of a cationic acetylcholine (ACh) derivative with an energy-acceptor tag and an anionic water-soluble conjugated polymer forms the basis of a highly effective fluorescence turn-on assay for studying the enzyme kinetics and inhibition of acetylcholinesterase (AChE; see schematic representation of the assay). FRET=fluorescence resonant energy transfer.

    32. Synthesis and Conformation of Multi-Vicinal Fluoroalkane Diastereoisomers (pages 7887–7890)

      Luke Hunter, Alexandra M. Z. Slawin, Peer Kirsch and David O'Hagan

      Version of Record online: 4 SEP 2007 | DOI: 10.1002/anie.200701988

      Thumbnail image of graphical abstract

      Doing the twist: Differences in behavior between isomers of straight-chain alkanes bearing four vicinal fluorine atoms are revealed by conformational analyses (X-ray diffraction, NMR spectroscopy). For example, computational studies show that the all-syn vicinal fluoroalkane (see picture, C gray, F green, H white) adopts a helical conformation, while the anti-syn-anti isomer prefers to be linear.

    33. Forming Aromatic Hemispheres on Transition-Metal Surfaces (pages 7891–7895)

      Kwang Taeg Rim, Mohamed Siaj, Shengxiong Xiao, Matthew Myers, Vincent D. Carpentier, Li Liu, Chaochin Su, Michael L. Steigerwald, Mark S. Hybertsen, Peter H. McBreen, George W. Flynn and Colin Nuckolls

      Version of Record online: 18 SEP 2007 | DOI: 10.1002/anie.200701117

      Thumbnail image of graphical abstract

      Bowled over: Hexabenzocoronene (HBC) binds to the surface of a ruthenium crystal through its “radialene” π bonds. Measurements on the product after heating of the HBC–surface complex are consistent with a bowl-shaped molecular fragment that is strongly bound, rim down, to the metal surface. This structure represents a new type of seed that could be used to grow single-walled carbon nanotubes of specific diameter and chirality.

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