Angewandte Chemie International Edition

Cover image for Vol. 46 Issue 27

July 2, 2007

Volume 46, Issue 27

Pages 5033–5245

  1. Cover Picture

    1. Top of page
    2. Cover Picture
    3. Inside Cover
    4. Graphical Abstract
    5. Corrigenda
    6. News
    7. Obituary
    8. Book Reviews
    9. Highlight
    10. Reviews
    11. Communications
    12. Preview
    1. Cover Picture: Phloroglucinol Derivatives Guttiferone G, Aristoforin, and Hyperforin: Inhibitors of Human Sirtuins SIRT1 and SIRT2 (Angew. Chem. Int. Ed. 27/2007) (page 5033)

      Claudia Gey, Sergiy Kyrylenko, Lothar Hennig, Lien-Hoa D. Nguyen, Anita Büttner, Hung D. Pham and Athanassios Giannis

      Version of Record online: 22 JUN 2007 | DOI: 10.1002/anie.200790122

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      Hippocrates (the father of medicine) described the healing properties of St. John's wort 2500 years ago and prescribed it for the treatment of depression. Hyperforin, which is considered to be responsible for this activity, also has anticancer, antibacterial, and wound-healing activity. A. Giannis et al. describe in their Communication on page 5219 ff. that hyperforin and two related compounds are inhibitors of sirtuins SIRT1 and SIRT2. This property could explain some of the pharmacological properties of hyperforin.

  2. Inside Cover

    1. Top of page
    2. Cover Picture
    3. Inside Cover
    4. Graphical Abstract
    5. Corrigenda
    6. News
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    8. Book Reviews
    9. Highlight
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    1. Inside Cover: Regio- and Stereoselective Synthesis of Enamides and Dienamides by Ruthenium-Catalyzed Co-Oligomerization of N-Vinylamides with Alkenes or Alkynes (Angew. Chem. Int. Ed. 27/2007) (page 5034)

      Hiroshi Tsujita, Yasuyuki Ura, Shingo Matsuki, Kenji Wada, Take-aki Mitsudo and Teruyuki Kondo

      Version of Record online: 22 JUN 2007 | DOI: 10.1002/anie.200790123

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      Just as with the Chimera, a creature from Greek mythology that has the head of a lion, a goat, and a snake, three distinct monomers can be combined to make one molecule. In their Communication on page 5160 ff., T. Kondo, Y. Ura, and co-workers describe a series of ruthenium-catalyzed co-oligomerization reactions, including the cotrimerization of N-vinylamides with acrylates and ethylene, as a route to biologically and synthetically important enamides and dienamides.

  3. Graphical Abstract

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    2. Cover Picture
    3. Inside Cover
    4. Graphical Abstract
    5. Corrigenda
    6. News
    7. Obituary
    8. Book Reviews
    9. Highlight
    10. Reviews
    11. Communications
    12. Preview
  4. Corrigenda

    1. Top of page
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    3. Inside Cover
    4. Graphical Abstract
    5. Corrigenda
    6. News
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    8. Book Reviews
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    1. You have free access to this content
      Highly Asymmetric Michael Addition to α,β-Unsaturated Ketones Catalyzed by 9-Amino-9-deoxyepiquinine (page 5049)

      Jian-Wu Xie, Wei Chen, Rui Li, Mi Zeng, Wei Du, Lei Yue, Ying-Chen Chen, Yong Wu, Jin Zhu and Jin-Gen Deng

      Version of Record online: 22 JUN 2007 | DOI: 10.1002/anie.200790125

      This article corrects:
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      Control of Magnetic Properties through External Stimuli (page 5049)

      Osamu Sato, Jun Tao and Yuan-Zhu Zhang

      Version of Record online: 22 JUN 2007 | DOI: 10.1002/anie.200790128

      This article corrects:

      Control of Magnetic Properties through External Stimuli

      Vol. 46, Issue 13, 2152–2187, Version of Record online: 9 MAR 2007

    3. You have free access to this content
      Direct Monitoring of Formation and Dissociation of Individual Metal Complexes by Single-Molecule Fluorescence Spectroscopy (page 5049)

      Alexander Kiel, Janos Kovacs, Andriy Mokhir, Roland Krämer and Dirk-Peter Herten

      Version of Record online: 22 JUN 2007 | DOI: 10.1002/anie.200790129

      This article corrects:
  5. News

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  6. Obituary

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    1. Nils Wiberg (1934–2007) (page 5052)

      Heinrich Nöth and Peter Paetzold

      Version of Record online: 22 JUN 2007 | DOI: 10.1002/anie.200702371

  7. Book Reviews

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    4. Graphical Abstract
    5. Corrigenda
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  8. Highlight

    1. Top of page
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    5. Corrigenda
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    1. Production of Platform Chemicals and Synthesis Gas from Biomass (pages 5056–5058)

      B. Kamm

      Version of Record online: 14 JUN 2007 | DOI: 10.1002/anie.200604514

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      Sugar rush: The development of biorefinery technology and the use of renewable resources is gaining importance in the chemical industry. The emphasis of current research lies in the production of platform chemicals and synthesis gas (syngas) from biomass (lignocellulosic feedstock). Examples include the two-phase conversion reaction of fructose to 5-hydroxymethylfurfural (HMF; see scheme) as well as the production of syngas from glycerol using Pt-Al2O3.

  9. Reviews

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    1. Strained Metallocenophanes and Related Organometallic Rings Containing π-Hydrocarbon Ligands and Transition-Metal Centers (pages 5060–5081)

      David E. Herbert, Ulrich F. J. Mayer and Ian Manners

      Version of Record online: 22 JUN 2007 | DOI: 10.1002/anie.200604409

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      Tension you can cut without a knife: Over the past 40 years, metallocenophanes and related species have emerged as the first broad class of strained organometallic rings to be systematically developed and studied (for examples, see scheme; Mes=2,4,6-trimethylphenyl). This Review focuses on the synthesis, structures, and reactivities of these interesting species based on π-hydrocarbon ligands and transition-metal centers.

    2. Polyferrocenylsilane-Based Polymer Systems (pages 5082–5104)

      Vasilios Bellas and Matthias Rehahn

      Version of Record online: 22 JUN 2007 | DOI: 10.1002/anie.200604420

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      No longer in its infancy: Polyferrocenylsilane (PFS) chemistry already occupies a leading role in the field of organometallic polymers. Ring-opening polymerization (ROP) of strained ferrocenophanes (see scheme) has enabled access to a plethora of PFS-based materials with distinctive physical properties and functions. Self-assembly of PFS block copolymers and fabrication of nanostructures by various patterning techniques are also discussed.

  10. Communications

    1. Top of page
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    1. A Concise Synthesis of Enantioenriched Fluorinated Carbocycles (pages 5106–5110)

      Yu-hong Lam, Carla Bobbio, Ian R. Cooper and Véronique Gouverneur

      Version of Record online: 5 JUN 2007 | DOI: 10.1002/anie.200701365

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      A “reverse” cycloaddition–fluorination strategy has been validated to access enantioenriched fluorinated compounds featuring up to five stereogenic centers, one of which is fluorinated. This highly convergent process features a mild and high-yielding fluorination, for which the sense and level of stereocontrol have been probed.

    2. Assembly of Nanoparticle–Protein Binding Complexes: From Monomers to Ordered Arrays (pages 5111–5114)

      Minghui Hu, Luping Qian, Raymond P. Briñas, Elena S. Lymar and James F. Hainfeld

      Version of Record online: 30 MAY 2007 | DOI: 10.1002/anie.200701180

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      Tag it: Well-defined monomers, dimers, trimers, three-dimensional spherical shells, and two-dimensional ordered arrays of genetically engineered proteins were constructed by using functionalized gold nanoparticles. Nanoparticle size, functionality, and protein genetic motif contribute to the unique geometry, precise stoichiometry, given orientation, and high specificity of these nanoparticle–protein hybrid structures.

    3. Boron Nitride Nanomesh: Functionality from a Corrugated Monolayer (pages 5115–5119)

      Simon Berner, Martina Corso, Roland Widmer, Oliver Groening, Robert Laskowski, Peter Blaha, Karlheinz Schwarz, Andrii Goriachko, Herbert Over, Stefan Gsell, Matthias Schreck, Hermann Sachdev, Thomas Greber and Jürg Osterwalder

      Version of Record online: 30 MAY 2007 | DOI: 10.1002/anie.200700234

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      A nanotemplate surface that functions as a regular array of traps for molecules such as naphthalocyanine (see picture) is provided by a nanomesh of hexagonal BN on Rh(111), which has now been identified as a single, complete monolayer. The 2-nm-sized pores form at regions where the layer binds strongly to the underlying metal, while the regular network of mesh wires corresponds to regions where the layer is not bonded to the substrate.

    4. Bismuth and Lead Hanging-Carboxylate Porphyrins: An Unexpected Homobimetallic Lead(II) Complex (pages 5120–5124)

      Zakaria Halime, Mohammed Lachkar, Thierry Roisnel, Eric Furet, Jean-François Halet and Bernard Boitrel

      Version of Record online: 30 MAY 2007 | DOI: 10.1002/anie.200700543

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      Strapped in: Insertion of PbII into a porphyrin bearing 5,15 straps with a pendant carboxylate group led to the first homobimetallic porphyrin complex of a divalent metal ion, which belongs to class III/type M in Buchler's classification of metalloporphyrins (see picture). Since the ligand also readily coordinates the isoelectronic BiIII ion, it is of potential interest as a chelator for 212Pb/212Bi isotope generators.

    5. Synthesis of Doubly β-to-β 1,3-Butadiyne-Bridged Diporphyrins: Enforced Planar Structures and Large Two-Photon Absorption Cross Sections (pages 5125–5128)

      Ichiro Hisaki, Satoru Hiroto, Kil Suk Kim, Su Bum Noh, Dongho Kim, Hiroshi Shinokubo and Atsuhiro Osuka

      Version of Record online: 5 JUN 2007 | DOI: 10.1002/anie.200700550

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      Plane and simple! Doubly β-to-β 1,3-butadiyne-bridged diporphyrins have been synthesized efficiently through metal-catalyzed reactions. The double bridges enforce the two porphyrins in a perfectly planar conformation (see picture), which leads to almost a 100 % increase in the two-photon absorption cross section.

    6. Rapid and Highly Selective Copper-Free Sonogashira Coupling in High-Pressure, High-Temperature Water in a Microfluidic System (pages 5129–5132)

      Hajime Kawanami, Keiichiro Matsushima, Masahiro Sato and Yutaka Ikushima

      Version of Record online: 6 JUN 2007 | DOI: 10.1002/anie.200700611

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      All in a whirl: A reaction system based on “step-by-step rapid mixing and heating” with high-pressure, high-temperature water has been applied to an extremely efficient Sonogashira coupling (see picture). No organic solvents or ligands for the Pd catalyst were required. R=Me, OMe, NH2, OH, CF3.

    7. Switching the Interior Hydrophobicity of a Self-Assembled Spherical Complex through the Photoisomerization of Confined Azobenzene Chromophores (pages 5133–5136)

      Takashi Murase, Sota Sato and Makoto Fujita

      Version of Record online: 30 MAY 2007 | DOI: 10.1002/anie.200700793

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      Synergy effect: A discrete highly cationic spherical Pd12L24 complex was prepared that concentrates 24 photoresponsive azobenzene units internally (see picture; shell blue, N dark blue, Pd yellow, O red, C gray, H white; azobenzene units shown as CPK models). The concentrated azobenzenes provide a hydrophobic environment in the sphere, and the degree of hydrophobicity is reversibly changed by the isomerization of the azobenzenes.

    8. The Emitting State of Tryptophan in Proteins with Highly Blue-Shifted Fluorescence (pages 5137–5139)

      Jaap Broos, Karina Tveen-Jensen, Ellen de Waal, Ben H. Hesp, J. Baz Jackson, Gerard W. Canters and Patrik R. Callis

      Version of Record online: 31 MAY 2007 | DOI: 10.1002/anie.200700839

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      Kind of blue: Tryptophan residues embedded in rigid and hydrophobic protein matrices, like azurin and domain 1 of a transhydrogenase (dI), yield blue-shifted emission spectra with vibrational fine structure. These features are typical for emission from the 1Lb state of indole, and not the 1La state. Nevertheless, these proteins are found to emit from 1La, except for a mutant of domain 1 (dI.M97V), which features the most blue-shifted protein emission ever reported.

    9. Nitroxylcob(III)alamin: Synthesis and X-ray Structural Characterization (pages 5140–5143)

      Luciana Hannibal, Clyde A. Smith, Donald W. Jacobsen and Nicola E. Brasch

      Version of Record online: 1 JUN 2007 | DOI: 10.1002/anie.200701131

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      Mystery solved: The long-elusive crystal structure of nitrosylcobalamin (NOCbl) reveals that the Co-N-O angle is 117.4–121.4°; hence, NOCbl is best described as nitroxylcob(III)alamin in the solid state (see picture: Co purple, N blue, O red, P orange, C gray, H white). The length of the Co[BOND]N bond trans to the NO ligand is typical of those seen when strong β-axial ligands are positioned trans to the 5,6-dimethylbenzimidazole group.

    10. A Chemical-Responsive Supramolecular Hydrogel from Modified Cyclodextrins (pages 5144–5147)

      Wei Deng, Hiroyasu Yamaguchi, Yoshinori Takashima and Akira Harada

      Version of Record online: 25 MAY 2007 | DOI: 10.1002/anie.200701272

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      No backbone required: A supramolecular hydrogel has been synthesized from a guest-modified cyclodextrin (CD) without a polymer backbone. The β-CD forms supramolecular fibrils through host–guest interactions, and then hydrogen bonds between the CDs cross-link the fibrils to give a hydrogel. Gel-to-sol transitions can be effected by adding a competitive guest or a denaturing reagent (see example).

    11. Double C[BOND]H Activation of an N-Heterocyclic Carbene Ligand in a Ruthenium Olefin Metathesis Catalyst (pages 5148–5151)

      Soon Hyeok Hong, Anatoly Chlenov, Michael W. Day and Robert H. Grubbs

      Version of Record online: 5 JUN 2007 | DOI: 10.1002/anie.200701234

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      Having a breakdown: Decomposition of the olefin metathesis catalyst [(biph)(PCy3)Cl2Ru[DOUBLE BOND]C(H)Ph] (biph= N,N′-diphenylbenzimidazol-2-ylidene, Cy=cyclohexyl) results in benzylidene insertion into an ortho C[BOND]H bond of an N-phenyl group of the biph ligand. The ruthenium center further inserts into another ortho C[BOND]H bond of the other N-phenyl ring to give a new Ru[BOND]C bond as a part of a five-membered metallacycle (see scheme).

    12. Small-Molecule N-Heterocyclic-Carbene-Containing Olefin-Metathesis Catalysts for Use in Water (pages 5152–5155)

      Jason P. Jordan and Robert H. Grubbs

      Version of Record online: 5 JUN 2007 | DOI: 10.1002/anie.200701258

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      ROMPing around in water: Two well-defined, small-molecule olefin-metathesis catalysts (1 and 2) are introduced. While they are insufficiently stable to mediate most cross-metathesis reactions in water, these catalysts competently mediate ring-opening metathesis polymerization (ROMP) and ring-closing metathesis reactions in an aqueous environment.

    13. Gold-Catalyzed Intramolecular Redox Reaction of Sulfinyl Alkynes: Efficient Generation of α-Oxo Gold Carbenoids and Application in Insertion into R[BOND]CO Bonds (pages 5156–5159)

      Guotao Li and Liming Zhang

      Version of Record online: 1 JUN 2007 | DOI: 10.1002/anie.200701449

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      Golden touch: α-Oxo Au carbenoids are efficiently generated by Au-catalyzed intramolecular redox reactions of sulfinyl alkynes. Besides cyclization to form benzo-fused sulfur-containing rings, these intermediates can participate in subsequent pinacol-type rearrangements, leading to a two-step insertion of a latent vinylcarbonylmethylene group into aldehydes or ketones (see scheme for second step).

    14. Regio- and Stereoselective Synthesis of Enamides and Dienamides by Ruthenium-Catalyzed Co-Oligomerization of N-Vinylamides with Alkenes or Alkynes (pages 5160–5163)

      Hiroshi Tsujita, Yasuyuki Ura, Shingo Matsuki, Kenji Wada, Take-aki Mitsudo and Teruyuki Kondo

      Version of Record online: 25 MAY 2007 | DOI: 10.1002/anie.200701356

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      The zero-valent ruthenium complex6-1,3,5-cyclooctatriene)bis(η2-dimethyl fumarate)ruthenium effectively catalyzes the highly selective codimerization of N-vinylamides with alkenes or alkynes and was successfully applied in the cotrimerization of N-vinylamides with ethyl acrylate and ethylene (see scheme). These reactions offer a rapid and atom-economical synthesis of biologically and synthetically important enamides and dienamides.

    15. Nucleophilic Addition of Organometallic Reagents to Cinchona Alkaloids: Simple Access to Diverse Architectures (pages 5164–5167)

      Lukas Hintermann, Marco Schmitz and Ulli Englert

      Version of Record online: 30 MAY 2007 | DOI: 10.1002/anie.200701341

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      Aminal pharm: Grignard reagents undergo a surprising nucleophilic aromatic addition reaction to cinchona alkaloids to stereoselectively produce cyclic aminals. Structurally diverse alkaloid derivatives with rigid cores that bear reactive functional groups (see examples) can be readily synthesized by this simple nucleophilic alkylation protocol.

    16. Organocatalytic Enantioselective [3+2] Cycloaddition of Azomethine Ylides and α,β-Unsaturated Aldehydes (pages 5168–5170)

      Jose L. Vicario, Silvia Reboredo, Dolores Badía and Luisa Carrillo

      Version of Record online: 30 MAY 2007 | DOI: 10.1002/anie.200700988

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      One out of a possible 16: Commercially available α,α-diphenylprolinol catalyzes the [3+2] cycloaddition of α,β-unsaturated aldehydes with azomethine ylides derived from imines to produce pyrrolidines as single regioisomers with excellent diastereo- and enantioselectivities (see scheme; R1=aryl; R2=alkyl, aryl, 2-furyl). A fourth stereocenter can be introduced subsequently with complete stereoselectivity.

    17. Intramolecular [3+2] Annulation of 5-Aryl-, 20-Ethynyl-Substituted [26]Hexaphyrin(1.1.1.1.1.1) Triggered by Molecular Compression through a Dynamic Conformational Change (pages 5171–5174)

      Masaaki Suzuki and Atsuhiro Osuka

      Version of Record online: 5 JUN 2007 | DOI: 10.1002/anie.200700958

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      Across the great divide: Substituents located opposite one another in meso positions on a [26]hexaphyrin scaffold are forced into close contact through a dynamic conformational change. A simple aryl group and an ethynyl group in these positions undergo a [3+2] annulation reaction either upon thermal activation or spontaneously to provide indenylene-bridged macrocycles that can serve as ligands for mixed-valence complexes (see structures).

    18. Roof-Shaped Pyrazaboles as a Structural Motif for Bent-Core Liquid Crystals (pages 5175–5177)

      Emma Cavero, Donocadh P. Lydon, Santiago Uriel, M. Rosario de la Fuente, José Luis Serrano and Raquel Giménez

      Version of Record online: 30 MAY 2007 | DOI: 10.1002/anie.200700820

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      Boron coordination compounds with a roof-shaped morphology (see structure) exhibit unusual liquid-crystalline behavior with a transition (represented by the red arrow) from a nematic mesophase with similar characteristics to those of some bent-core liquid crystals to a compact lamellar phase with a chiral organization (see microphotographs of the two phases).

    19. The Generation of Aryl Anions by Double Electron Transfer to Aryl Iodides from a Neutral Ground-State Organic Super-Electron Donor (pages 5178–5183)

      John A. Murphy, Sheng-ze Zhou, Douglas W. Thomson, Franziska Schoenebeck, Mohan Mahesh, Stuart R. Park, Tell Tuttle and Leonard E. A. Berlouis

      Version of Record online: 4 JUN 2007 | DOI: 10.1002/anie.200700554

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      It takes two to cyclize: Aryl halides are reduced to aryl anions by double electron transfer from the neutral ground-state electron donor 1 (see scheme), as shown by the formation of a cyclic ketone (2). The reduced compound (3) is also formed. Calculations show that the loss of two electrons from 1 is both thermodynamically and kinetically viable and generates a more planar resonance-stabilized structure.

    20. Silver-Catalyzed Intermolecular Amination of C[BOND]H Groups (pages 5184–5186)

      Zigang Li, D. A. Capretto, R. Rahaman and Chuan He

      Version of Record online: 30 MAY 2007 | DOI: 10.1002/anie.200700760

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      Teamwork: The dinuclear silver complex [Ag2(OTf)2(bp)2] (OTf=trifluoromethanesulfonate, bp=bathophenanthroline) catalyzes the intermolecular amination of saturated C[BOND]H bonds by using PhI[DOUBLE BOND]NNs (Ns=p-nitrosulfonyl) as the nitrene precursor (see scheme). Preliminary investigations suggest that the dinuclear structural motif is crucial to catalytic performance.

    21. A General Approach to Chemo- and Regioselective Cyclotrimerization Reactions (pages 5187–5190)

      Douglas D. Young and Alexander Deiters

      Version of Record online: 25 MAY 2007 | DOI: 10.1002/anie.200700802

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      Microwave-ready heterocycles: Cobalt-catalyzed [2+2+2] cyclotrimerization of nitrile derivatives with diynes anchored to a solid support under microwave irradiation provides a universal approach to pyridine, pyridone, and iminopyridine products. The reaction is completely chemo- and regioselective, and the products are obtained in excellent yield and high purity.

    22. Structural Studies on a Lithium Organo-Amidocuprate in the Solid State and in Solution (pages 5191–5194)

      Robert P. Davies, Stefan Hornauer and Peter B. Hitchcock

      Version of Record online: 25 MAY 2007 | DOI: 10.1002/anie.200700822

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      Head-to-tail or head-to-head? A lithium amidocuprate complex has been characterized in the solid state and shown to adopt a head-to-tail conformation (see picture). 2D NMR spectroscopic studies show the presence of several structural isomers in solution, including a head-to-head isomer, resulting from Schlenk equilibrium. The presence of these isomers is postulated to have a significant influence on heterocuprate reactivity.

    23. Metal-Catalyzed [1,2]-Alkyl Shift in Allenyl Ketones: Synthesis of Multisubstituted Furans (pages 5195–5197)

      Alexander S. Dudnik and Vladimir Gevorgyan

      Version of Record online: 25 MAY 2007 | DOI: 10.1002/anie.200701128

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      Even fused furans can be prepared by cycloisomerization of substituted allenyl ketones. The cascade reaction involves a [1,2]-migration of alkyl or aryl groups in allenyl ketones as the key step. Facile reaction in the presence of cationic complexes, as well as migratory aptitude in the cycloisomerization of unsymmetrically substituted allenes, strongly supports an electrophilic mechanism for this transformation.

    24. The Geometric and Electronic Structure of a One-Electron-Oxidized Nickel(II) Bis(salicylidene)diamine Complex (pages 5198–5201)

      Tim Storr, Erik C. Wasinger, Russell C. Pratt and T. Daniel P. Stack

      Version of Record online: 1 JUN 2007 | DOI: 10.1002/anie.200701194

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      Class III delocalization? The isolation and analysis of the ligand-radical title complex has allowed description of the changes in bonding from the reduced form as well as the extent of delocalization. The intense low-energy absorption of the oxidized complex can be described as a ligand-radical transition of a highly delocalized class III mixed-valence compound.

    25. A One-Pot Synthesis of Primary Amides from Aldoximes or Aldehydes in Water in the Presence of a Supported Rhodium Catalyst (pages 5202–5205)

      Hiroshi Fujiwara, Yoshiyuki Ogasawara, Kazuya Yamaguchi and Noritaka Mizuno

      Version of Record online: 30 MAY 2007 | DOI: 10.1002/anie.200701273

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      Dehydration/Rehydration in Water: Supported rhodium hydroxide (Rh(OH)x/Al2O3) is an effective heterogeneous catalyst for the synthesis of primary amides from aldoximes and aldehydes in water in a reaction that is entirely free of hazardous and carcinogenic organic solvents (see scheme).

    26. De Novo Asymmetric Synthesis of the Anthrax Tetrasaccharide by a Palladium-Catalyzed Glycosylation Reaction (pages 5206–5208)

      Haibing Guo and George A. O'Doherty

      Version of Record online: 30 MAY 2007 | DOI: 10.1002/anie.200701354

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      Choose your poison: In the de novo asymmetric synthesis of the anthrax tetrasaccharide 1 (25 steps from acetylfuran), the absolute configurations of three L sugars and one D sugar were set by the Noyori reduction of acetylfuran with the S,S and the R,R reagent, respectively. The configuration of the remaining carbohydrate unit was set by highly diastereoselective palladium-catalyzed glycosylation and post-glycosylation transformations.

    27. Total Synthesis of Cruentaren A (pages 5209–5211)

      Viktor V. Vintonyak and Martin E. Maier

      Version of Record online: 24 MAY 2007 | DOI: 10.1002/anie.200701423

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      A triple bypass: The triple bond in the macrolactone ring of 2 served as a lock to prevent the unwanted translactonization to the δ-lactone during the formation of the side chain of the macrolide cruentaren A (1). Subsequent cleavage of the methyl ether and the silicon protecting groups (PG) followed by a Lindlar reduction of the two triple bonds completed the synthesis (see scheme).

    28. Stepwise Intermetal Borylene Transfer: Synthesis and Structure of Mono- and Dinuclear Cobalt–Borylene Complexes (pages 5212–5214)

      Holger Braunschweig, Melanie Forster, Krzysztof Radacki, Fabian Seeler and George R. Whittell

      Version of Record online: 1 JUN 2007 | DOI: 10.1002/anie.200701142

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      Step by step: Stepwise transmetalation of the borylene ligand BN(SiMe3)2 from [(OC)5W[DOUBLE BOND]B[DOUBLE BOND]N(SiMe3)2] to [(η5-C5H5)Co(CO)2] gives access to the first mono- and dinuclear cobalt borylene species and provides convincing evidence that the intermetal borylene transfer proceeds by an associative process with a heterodimetallic intermediate (see structure) without generation of an intermediate free borylene species.

    29. Synthesis and Electronic Structure of a Ferroborirene (pages 5215–5218)

      Holger Braunschweig, Israel Fernández, Gernot Frenking, Krzysztof Radacki and Fabian Seeler

      Version of Record online: 30 MAY 2007 | DOI: 10.1002/anie.200700382

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      The photochemically induced transfer of a ferroborylene yielded the first metal-bound borirene (see scheme and product structure, in which the methyl substituents are omitted). Experimental and theoretical data suggest significant π delocalization in the three-membered BC2 ring.

    30. Phloroglucinol Derivatives Guttiferone G, Aristoforin, and Hyperforin: Inhibitors of Human Sirtuins SIRT1 and SIRT2 (pages 5219–5222)

      Claudia Gey, Sergiy Kyrylenko, Lothar Hennig, Lien-Hoa D. Nguyen, Anita Büttner, Hung D. Pham and Athanassios Giannis

      Version of Record online: 22 MAY 2007 | DOI: 10.1002/anie.200605207

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      Preventative medicine: The natural products guttiferone G and hyperforin (1) as well as the synthetic aristoforin (2) are inhibitors of human SIRT1 and SIRT2. Guttiferone G and 2 are less toxic but stronger inhibitors of cell proliferation than 1. These compounds may be valuable tools for epigenetics and for the elucidation of the biological role of sirtuins in processes such as cancer, ageing, neurodegenerative diseases, adipositas, and diabetes.

    31. Triplex Molecular Beacons as Modular Probes for DNA Detection (pages 5223–5225)

      Tom N. Grossmann, Lars Röglin and Oliver Seitz

      Version of Record online: 30 MAY 2007 | DOI: 10.1002/anie.200700289

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      Reporting live: Triplex formation is used to construct a stem–loop probe, which is opened upon binding of the DNA target (red). The triplex molecular beacon is composed of a single DNA strand (blue), a stem-forming oligomer (black), and is labeled with a fluorophore and a quencher (red and blue circles). This concept facilitates the introduction of further functionalities such as additional quenchers in the assembly of “superquenched” beacons.

    32. Synthetic Vaccines of Tumor-Associated Glycopeptide Antigens by Immune-Compatible Thioether Linkage to Bovine Serum Albumin (pages 5226–5230)

      Sven Wittrock, Torsten Becker and Horst Kunz

      Version of Record online: 4 JUN 2007 | DOI: 10.1002/anie.200700964

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      Immunologically noninterfering thioether linkages between a carrier protein (bovine serum albumin) and synthetic tumor-associated glycopeptide antigens from MUC1 (as in A) are important prerequisites for the development of synthetic vaccines useful for active immunization. These thioether linkages are formed by photochemically induced addition of thiol to vinyl groups. None of the sensitive structural elements are affected.

    33. Site-Selective Surface-Initiated Polymerization by Langmuir–Blodgett Lithography (pages 5231–5233)

      Marion K. Brinks, Michael Hirtz, Lifeng Chi, Harald Fuchs and Armido Studer

      Version of Record online: 29 MAY 2007 | DOI: 10.1002/anie.200605020

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      Brushing the surface: Structured polymer brushes are readily prepared by site-selective immobilization of initiators in a self-assembly process by Langmuir–Blodgett lithography with subsequent polymerization. The AFM images show a DPPC/alkoxy amine LB film before and after surface-initiated controlled nitroxide-mediated radical polymerization. Large surface areas (several cm2) can readily be structured with this method.

    34. Regioselective Cysteine Bioconjugation by Appending a Labeled Cystein Tag to a Protein by Using Protein Splicing in trans (pages 5234–5237)

      Thomas Kurpiers and Henning D. Mootz

      Version of Record online: 30 MAY 2007 | DOI: 10.1002/anie.200700719

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      Orthogonal cysteines: The chemical modification of cysteine residues is one of the most important methods for the chemoselective bioconjugation of proteins; however, it lacks regioselectivity. By assembling the protein from two pieces using protein trans-splicing, regioselectivity can be achieved. This reaction can even be performed in complex mixtures such as cell extracts.

    35. Influence of Functional Groups on the Site-Selective Dissociation of Adenine upon Low-Energy Electron Attachment (pages 5238–5241)

      Stephan Denifl, Philipp Sulzer, Dieter Huber, Fabio Zappa, Michael Probst, Tilmann D. Märk, Paul Scheier, Natcha Injan, Jumras Limtrakul, Robert Abouaf and Henri Dunet

      Version of Record online: 1 JUN 2007 | DOI: 10.1002/anie.200700032

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      The butterfly effect (a small change can have large repercussions): Dissociative electron attachment (DEA) was used to probe the reactivities of purine derivatives. A change of the substituent at the C6 position of adenine strongly affects the ion yield of the closed-shell dehydrogenated anion (see picture), although the hydrogen loss can be ascribed exclusively to the diametric N9 position.

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