Angewandte Chemie International Edition

Cover image for Angewandte Chemie International Edition

August 25, 2008

Volume 47, Issue 36

Pages 6727–6923

  1. Cover Picture

    1. Top of page
    2. Cover Picture
    3. Inside Cover
    4. Graphical Abstract
    5. News
    6. Book Review
    7. Highlights
    8. Essay
    9. Review
    10. Communications
    11. Preview
    1. Cover Picture: Reversible Redox Reactions in an Extended Polyoxometalate Framework Solid (Angew. Chem. Int. Ed. 36/2008) (page 6727)

      Chris Ritchie, Carsten Streb, Johannes Thiel, Scott G. Mitchell, Haralampos N. Miras, De-Liang Long, Thomas Boyd, Robert D. Peacock, Thomas McGlone and Leroy Cronin

      Article first published online: 20 AUG 2008 | DOI: 10.1002/anie.200890175

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      Like a revolving door that can easily open, close, and return to the start, the first framework material that can undergo reversible electron-transfer reactions is described by L. Cronin et al. in their Communication on page 6881 ff. The solid contains large pockets in which the redox reagents can reside; the manganese(II)/(III)-containing framework is able to move between these oxidation states and is the first in a new class of redox solids.

  2. Inside Cover

    1. Top of page
    2. Cover Picture
    3. Inside Cover
    4. Graphical Abstract
    5. News
    6. Book Review
    7. Highlights
    8. Essay
    9. Review
    10. Communications
    11. Preview
    1. Inside Cover: Asymmetric Suzuki–Miyaura Coupling Reactions Catalyzed by Chiral Palladium Nanoparticles at Room Temperature (Angew. Chem. Int. Ed. 36/2008) (page 6728)

      Koji Sawai, Ryouta Tatumi, Tsukasa Nakahodo and Hisashi Fujihara

      Article first published online: 20 AUG 2008 | DOI: 10.1002/anie.200890176

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      Chiral metal nanoparticles and their nanointerface have received little attention, but their properties are of great interest. In their Communication on page 6917 ff., H. Fujihara and co-workers describe that palladium nanoparticles [(1.6±0.2) nm] stabilized with chiral 2,2′-bis(diphenylphosphino)-1,1′-binaphthene (binap) ligands can efficiently catalyze asymmetric Suzuki–Miyaura cross-coupling reactions of naphthyl halides with naphthylboronic acid at room temperature with short reaction times.

  3. Graphical Abstract

    1. Top of page
    2. Cover Picture
    3. Inside Cover
    4. Graphical Abstract
    5. News
    6. Book Review
    7. Highlights
    8. Essay
    9. Review
    10. Communications
    11. Preview
    1. Graphical Abstract: Angew. Chem. Int. Ed. 36/2008 (pages 6731–6742)

      Article first published online: 20 AUG 2008 | DOI: 10.1002/anie.200890177

  4. News

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

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

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

      Super Robust Nanoparticles for Biology and Biomedicine (pages 6750–6753)

      Rongchao Jin

      Article first published online: 4 AUG 2008 | DOI: 10.1002/anie.200801301

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      The preparation of nanoparticles with sufficient chemical and thermal stability for bio-related applications has long been a major issue in nanobiotechnology. New types of highly stable Au, CdSe/ZnS, and F3O4 nanoparticles have been stabilized with Tween derivatives through coordination to the particle surface as well as van der Waals interaction with the primary ligands on the nanoparticle surface. The Au nanoparticles are more stable than the corresponding Au nanoparticles functionalized with thiolated DNA.

    2. Gold Catalysis

      “High Noon” in Gold Catalysis: Carbene versus Carbocation Intermediates (pages 6754–6756)

      A. Stephen K. Hashmi

      Article first published online: 5 AUG 2008 | DOI: 10.1002/anie.200802517

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      What is the nature of the gold–carbon bond—double, single? The structure of a crucial intermediate of many gold-catalyzed reactions has become a matter of debate. A current study demonstrates that the carbocationic form determines the outcome of many cycloisomerizations.

  7. Essay

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

      Electron Transfer and Electronic Conduction through an Intervening Medium (pages 6758–6765)

      Peter P. Edwards, Harry B. Gray, Matthew T. J. Lodge and Robert J. P. Williams

      Article first published online: 24 JUL 2008 | DOI: 10.1002/anie.200703177

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      A new vision for ET: Electron-transfer (ET) processes in biological and synthetic materials (such as proteins and semiconductors, respectively) are of immense importance. A unified approach to describe these processes is useful in understanding, and controlling the various facets of electron transfer in condensed matter. The diagram shows a plot of the decay constant for the electron-tunneling process against the effective tunneling barrier in different materials.

  8. Review

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

      Hydrogen Storage in Microporous Metal–Organic Frameworks with Exposed Metal Sites (pages 6766–6779)

      Mircea Dincă and Jeffrey R. Long

      Article first published online: 8 AUG 2008 | DOI: 10.1002/anie.200801163

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      Getting a grip on hydrogen: Hydrogen typically adsorbs very weakly in physisorptive systems. In microporous materials, however, coordinatively unsaturated metal centers can contribute to an increase in the enthalpy of H2 adsorption. Strategies to incorporate such metal sites in metal–organic frameworks have led to remarkable results within a short period, thus promising to deliver new materials with improved H2 affinity in the near future.

  9. Communications

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

      Enzymatic Synthesis of Multiple Spin-Labeled DNA (pages 6782–6785)

      Samra Obeid, Maxim Yulikov, Gunnar Jeschke and Andreas Marx

      Article first published online: 31 JUL 2008 | DOI: 10.1002/anie.200802314

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      Multi-spinning: The use of modified triphosphates and DNA polymerases has resulted in the multiple spin-labeling of DNA (see picture). A DNA helix entirely labeled with paramagnetic centers has been generated in this way and investigated by EPR spectroscopy.

    2. Polymer Nanostructures

      Fabrication of a Full-Coverage Polymer Nanobrush on an Electron-Beam-Activated Template (pages 6786–6789)

      Soeren Schilp, Nirmalya Ballav and Michael Zharnikov

      Article first published online: 24 JUL 2008 | DOI: 10.1002/anie.200801858

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      Smart writing by electrons: A new technique enables the fabrication of full-coverage polymer brush patterns of variable shape on a nanometer length scale. The key to this technique is electron-beam activation of amino groups, which serve as the nucleation centers for surface-initiated polymerization. The technique untangles chemistry and morphology, and it is possible to monitor only morphology effects on chemically homogeneous surfaces and interfaces.

    3. Germanium Modifications

      A 3D Network of Four-Bonded Germanium: A Link between Open and Dense (pages 6790–6793)

      Ulrich Schwarz, Aron Wosylus, Bodo Böhme, Michael Baitinger, Michael Hanfland and Yuri Grin

      Article first published online: 31 JUL 2008 | DOI: 10.1002/anie.200800914

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      Under pressure: The new modification Ge(hR8) is obtained upon pressurization of clathrate-type Ge(cF136) or controlled decompression of a Ge(tI4)-type high-pressure phase. The atomic arrangement comprises four-bonded germanium atoms with a topological organization bearing remarkable similarity to high-pressure host–guest assemblies of other main-group elements.

    4. Helical Structures

      Heterobimetallic Triple-Stranded Helicates with Directional Benzene-o-dithiol/Catechol Ligands (pages 6794–6797)

      F. Ekkehardt Hahn, Martin Offermann, Christian Schulze Isfort, Tania Pape and Roland Fröhlich

      Article first published online: 24 JUL 2008 | DOI: 10.1002/anie.200801172

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      It takes two to tango: When ligand H4-1 (see scheme) reacts with MoIV and TiIV, the different binding preferences of the O–O and S–S donor groups lead to the formation of the helicate [TiMo(1)3]4− with a parallel orientation of the ligand strands. With different cations, the supramolecular complexes {Λ,Λ-[TiMo(1)3]-(PNP)-Δ,Δ-[TiMo(1)3]}7− and {Δ,Δ-[TiMo(1)3]-Na-Δ,Δ-[TiMo(1)3]}7− can be crystallized. PNP=bis(triphenylphosphoranylidene)ammonium.

    5. Asymmetric Synthesis (2)

      Highly Enantioselective Organocatalytic Carbonyl-Ene Reaction with Strongly Acidic, Chiral Brønsted Acids as Efficient Catalysts (pages 6798–6801)

      Magnus Rueping, Thomas Theissmann, Alexander Kuenkel and René M. Koenigs

      Article first published online: 24 JUL 2008 | DOI: 10.1002/anie.200802139

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      You can count on the counterion in ion-pair intermediates to induce high levels of asymmetry in the title reaction. The efficient transformation proceeds under mild reaction conditions in the presence of an air-stable N-triflylphosphoramide in a low catalyst loading of just 1 mol % to give substituted α-hydroxyesters in good yields and with excellent ee values (see scheme; R=aryl).

    6. Grignard Reagents

      Convenient Preparation of Polyfunctional Aryl Magnesium Reagents by a Direct Magnesium Insertion in the Presence of LiCl (pages 6802–6806)

      Fabian M. Piller, Prasad Appukkuttan, Andrei Gavryushin, Matthew Helm and Paul Knochel

      Article first published online: 28 JUL 2008 | DOI: 10.1002/anie.200801968

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      In the footsteps of Victor Grignard: The simple LiCl-mediated insertion of magnesium into aryl chlorides and bromides at moderate temperatures leads to functionalized organomagnesium reagents (see scheme). An unprecedented range of functional groups may be present in the substrates (e.g. CN, CO2R, OTs, OBoc; Ts=p-toluenesulfonyl, Boc=tert-butylcarbonyloxy).

    7. Peptide Ligation without Cysteine

      Native Chemical Ligation at Valine (pages 6807–6810)

      Christian Haase, Heike Rohde and Oliver Seitz

      Article first published online: 14 JUL 2008 | DOI: 10.1002/anie.200801590

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      Peptide ligation at hydrophobic sites is possible with a ligation–desulfurization strategy in which penicillamine serves as a precursor of valine. The β,β-dimethylcysteine peptides reacted surprisingly fast in native chemical ligation reactions. Even the sterically crowded and unpolar Leu–Val bond can be formed in high yield.

    8. Synthetic Methods

      Cobalt-Catalyzed [2+2] Cycloaddition (pages 6811–6813)

      Jonas Treutwein and Gerhard Hilt

      Article first published online: 20 AUG 2008 | DOI: 10.1002/anie.200801778

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      Three's a charm, but four's not half bad either: A simple cobalt–diphosphine complex facilitates the synthesis of cyclobutene derivatives through the chemoselective transformation of strained five-membered unsaturated rings with internal alkynes (see scheme). This atom-efficient, intermolecular reaction generates polycyclic products in excellent yields and with excellent exo selectivity. dppp=1,3-bis(diphenylphosphanyl)propane.

    9. Acid Anhydrides

      Tetrakis[2,4-bis(trifluoromethyl)phenyl]diphosphoxane: An Anhydride of a Phosphinous Acid (pages 6814–6816)

      Berthold Hoge and Boris Kurscheid

      Article first published online: 25 JUL 2008 | DOI: 10.1002/anie.200801025

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      Steric and electronic characteristics of the bulky, strongly electron-withdrawing 2,4-(CF3)2C6H3 group are ideally suited to stabilize the unusual form of a diphosphoxane, R2POPR2, the anhydride of a phosphinous acid. The high-yield synthesis and first structural characterization of a tetraorganyl diphosphoxane are described (see structure; C gray, H white, O red, F yellow, P green).

    10. Microfluidics

      Droplet-Based Microreactors for the Synthesis of Magnetic Iron Oxide Nanoparticles (pages 6817–6820)

      Lucas Frenz, Abdeslam El Harrak, Matthias Pauly, Sylvie Bégin-Colin, Andrew D. Griffiths and Jean-Christophe Baret

      Article first published online: 21 JUL 2008 | DOI: 10.1002/anie.200801360

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      Microdroplets for nanoparticles: An extremely reliable method to create droplet pairs, based on hydrodynamic coupling of two spatially separated nozzles, has been developed. Droplets containing the reagents for the precipitation of iron oxide are electrocoalesced to synthesize iron oxide nanoparticles in a very fast (millisecond-scale) and reproducible reaction (see picture).

    11. Natural Products

      Synthetic Access to the Chlorocyclopentane Cores of the Proposed Original and Revised Structures of Palau′amine (pages 6821–6824)

      Michael S. Bultman, Jun Ma and David Y. Gin

      Article first published online: 24 JUL 2008 | DOI: 10.1002/anie.200801969

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      Core knowledge: The synthesis of the functionalized cores of both the originally proposed and revised structures of palau′amine have been achieved (see structures). A Diels–Alder/[3,3]-sigmatropic rearrangement sequence and a Beckmann rearrangement enable the stereocontrolled formation of the highly congested cores.

    12. Asymmetric Catalysis

      Enantioselective C[BOND]H Amination Using Cationic Ruthenium(II)–pybox Catalysts (pages 6825–6828)

      Erika Milczek, Nadège Boudet and Simon Blakey

      Article first published online: 18 JUL 2008 | DOI: 10.1002/anie.200801445

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      The whole “pybox” and dice: Highly enantioselective amination reactions of both allylic and benzylic C[BOND]H bonds are catalyzed by cationic ruthenium(II)–pybox complexes (see structure). A novel mode of stereocontrol, which is induced by the versatile pybox ligand, is proposed to account for the excellent enantioselectivity in these reactions. Boc=tert-butoxycarbonyl, pybox=pyridine bisoxazoline.

    13. Natural Product Synthesis

      Total Synthesis of (±)-Trichodermamide B and of a Putative Biosynthetic Precursor to Aspergillazine A Using an Oxaza-Cope Rearrangement (pages 6829–6831)

      Chong-Dao Lu and Armen Zakarian

      Article first published online: 24 JUL 2008 | DOI: 10.1002/anie.200801652

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      Coping with tandem reactions: The total synthesis of marine fungal metabolite, trichodermamide B, is accomplished using a tandem nitrosation/oxaza-Cope rearrangement as the key step to establish the characteristic heterocyclic ring system of the natural product. Preparation of the putative biosynthetic precursor of aspergillazine A provides further insight into the possible biosynthetic pathway to aspergillazines.

    14. Asymmetric Autocatalysis

      Unraveling the Mechanism of the Soai Asymmetric Autocatalytic Reaction by First-Principles Calculations: Induction and Amplification of Chirality by Self-Assembly of Hexamolecular Complexes (pages 6832–6835)

      Luca Schiaffino and Gianfranco Ercolani

      Article first published online: 24 JUL 2008 | DOI: 10.1002/anie.200802450

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      Soai, so good: The Soai reaction is the sole reported case of amplifying asymmetric autocatalysis. A mechanism is proposed for this reaction, supported by first-principle calculations, clarifying not only the reasons for the detected chiral induction and amplification, but also the roles performed by isopropyl groups, γ-pyridinic nitrogen atoms, and the δ-substituent.

    15. Asymmetric Synthesis

      Configurational Control of Benzyl Carbanion–Copper Complexes by Sulfinyl Groups: Synthesis of Optically Pure Allenes with Central and Axial Chirality (pages 6836–6839)

      José Luis García Ruano, Vanesa Marcos and José Alemán

      Article first published online: 25 JUL 2008 | DOI: 10.1002/anie.200802158

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      Lean, mean, chiral allene: Optically pure complexes 2 react with propargyl bromides and mesylates 1 to afford the title products (see scheme; LG=leaving group). The regioselectivity and the configuration of the chiral axis are completely controlled, and the stereoselectivity at the benzylic position is high. Kinetic resolution of racemic propargyl mesylates can also be achieved with these reagents.

    16. Natural Products Synthesis

      Total Synthesis of Cyclotheonamide C using a Tandem Backbone-Extension–Coupling Methodology (pages 6840–6842)

      Stéphane P. Roche, Sophie Faure and David J. Aitken

      Article first published online: 25 JUL 2008 | DOI: 10.1002/anie.200802005

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      Mastering unusual amino acids: The first total synthesis of the potent protease inhibitor cyclotheonamide C (see structure representation) has been achieved. The key features of the synthesis are a three-component tandem procedure to create a masked α-keto-β-arginine within a peptide chain, and the control of the extended conjugation of a vinylogous α,β-dehydrotyrosine.

    17. Synthetic Methods

      Overall “Pseudocationic” Trifluoromethylation of Dihydropyridines with Triflic Anhydride (pages 6843–6846)

      Henri Rudler, Andrée Parlier, Cesar Sandoval-Chavez, Patrick Herson and Jean-Claude Daran

      Article first published online: 30 JUL 2008 | DOI: 10.1002/anie.200801879

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      A triflic reaction: The role of triflic anhydride is not limited to the transfer of a triflyl group to the nitrogen atom during the interaction of pyridine with bis(trimethylsilyl)ketene acetals: it can also provide an electrophilic CF3 group able to transform the formed dihydropyridines substituted with trimethylsilyl ester groups into α-trifluoromethyllactones (see scheme).

    18. Chiral γ-Amino Amide Synthesis by Heterobimetallic Lanthanum/Lithium/Pybox-Catalyzed Direct Asymmetric Mannich-Type Reactions of α-Keto Anilides (pages 6847–6850)

      Gang Lu, Hiroyuki Morimoto, Shigeki Matsunaga and Masakatsu Shibasaki

      Article first published online: 24 JUL 2008 | DOI: 10.1002/anie.200801564

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      Not so Mannich now: A heterobimetallic La/Li/pybox complex was key in direct catalytic asymmetric Mannich-type reactions, using α-keto anilides as synthetic homoenolate equivalents to afford γ-amino amide products in up to >99 % yield, 95 % ee, and >97:3 syn-selectivity. Stereoselective reduction of the α-keto moiety afforded the β-alkyl-γ-amino-α-hydroxy amide with three contiguous stereocenters (PG=protecting group).

    19. Peptide Ligation

      An Efficient Fmoc-SPPS Approach for the Generation of Thioester Peptide Precursors for Use in Native Chemical Ligation (pages 6851–6855)

      Juan B. Blanco-Canosa and Philip E. Dawson

      Article first published online: 24 JUL 2008 | DOI: 10.1002/anie.200705471

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      Intramolecular activation of C-terminal peptides: Mildly activated N-acylurea peptides are readily formed on the solid support following chain assembly, avoiding over-activation of the C-terminus. The utility of these peptides is demonstrated by the native chemical ligation of unprotected peptides (see scheme; R=amino acid side chain).

    20. Host–Guest Chemistry

      Diphosphinite AgI and PdII Dinuclear Complexes as Adaptable Anion Receptors: An Unprecedented Bridging Mode for the PF6 Ion (pages 6856–6859)

      Changxiu Li, Roberto Pattacini, Roland Graff and Pierre Braunstein

      Article first published online: 25 JUL 2008 | DOI: 10.1002/anie.200801850

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      The special guest: In the host–guest chemistry of dinuclear complexes that contain the 9H-fluorene-9,9′-dimethanediphenylphosphinite ligand the synergy between the phenyl groups and the axial fluorene moiety leads to the formation of molecular cavities that have selective steric affinity for the anions BF4 or PF6 (see picture). An unprecedented M⋅⋅⋅F(PF5)⋅⋅⋅M bridging coordination mode of PF6 has now been established.

    21. Homogeneous Catalysis

      Iron-Catalyst-Switched Selective Conjugate Addition of Grignard Reagents: α,β,γ,δ-Unsaturated Amides as Versatile Templates for Asymmetric Three-Component Coupling Processes (pages 6860–6864)

      Satoshi Okada, Kyohei Arayama, Ryuji Murayama, Takumi Ishizuka, Keiichi Hara, Naoki Hirone, Takeshi Hata and Hirokazu Urabe

      Article first published online: 29 JUL 2008 | DOI: 10.1002/anie.200801928

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      Diene for conjugate addition: Iron(II) chloride switches the reaction course of the three-component coupling of a Grignard reagent, an alkyl halide, and a dienamide, thus making the amide a simple yet versatile chiral template.

    22. Synthetic Methods

      Convergent Preparation of Enantiomerically Pure Polyalkylated Cyclopropane Derivatives (pages 6865–6868)

      Adi Abramovitch, Louis Fensterbank, Max Malacria and Ilan Marek

      Article first published online: 25 JUL 2008 | DOI: 10.1002/anie.200802093

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      Crossroads: Selective sulfoxide/lithium exchange reactions lead to the unique preparation of diastereo- and enantiomerically pure polyalkylated cyclopropanes (see scheme). This reaction allows the independent formation of both diastereoisomers from a common starting material.

    23. Asymmetric Synthesis (1)

      Asymmetric Synthesis of Natural Product Inspired Tricyclic Benzopyrones by an Organocatalyzed Annulation Reaction (pages 6869–6872)

      Herbert Waldmann, Vivek Khedkar, Heiko Dückert, Markus Schürmann, Iris M. Oppel and Kamal Kumar

      Article first published online: 25 JUL 2008 | DOI: 10.1002/anie.200802413

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      Going back to nature: Electron-deficient oxadienes and electron-poor acetylene carboxylates react in the presence of an organocatalyst to give natural product inspired tricyclic benzopyrones efficiently (up to 99 % yield) and stereoselectively (up to 87 % ee; see scheme). This efficient and operationally simple asymmetric annulation involves the generation of zwitterions from acetylene carboxylates.

    24. Stereoselective Catalysis

      Catalytic Enantioselective Alkylation of Substituted Dioxanone Enol Ethers: Ready Access to C(α)-Tetrasubstituted Hydroxyketones, Acids, and Esters (pages 6873–6876)

      Masaki Seto, Jennifer L. Roizen and Brian M. Stoltz

      Article first published online: 24 JUL 2008 | DOI: 10.1002/anie.200801424

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      Adaptive Alkylation: Palladium-catalyzed asymmetric alkylation enables access to fully substituted enantioenriched oxygenated stereocenters, which can be transformed easily to α-hydroxyketones, esters, and acids, providing a catalytic, enantioselective synthesis for natural products.

    25. Natural Product Synthesis

      Dynamic Stereochemistry Transfer in a Transannular Aldol Reaction: Total Synthesis of Hypocrellin A (pages 6877–6880)

      Erin M. O'Brien, Barbara J. Morgan and Marisa C. Kozlowski

      Article first published online: 27 MAY 2008 | DOI: 10.1002/anie.200800734

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      A dynamic approach: The key step in the total synthesis of hypocrellin A involves a potentially biomimetic 1,8-diketone aldol reaction, which constructs the seven-membered ring. The helical configuration is established first from an axially chiral biaryl unit and is then used in a dynamic stereochemical transfer process to form the remaining stereocenters in the intramolecular aldol reaction (see scheme).

    26. Polyoxometalates

      Reversible Redox Reactions in an Extended Polyoxometalate Framework Solid (pages 6881–6884)

      Chris Ritchie, Carsten Streb, Johannes Thiel, Scott G. Mitchell, Haralampos N. Miras, De-Liang Long, Thomas Boyd, Robert D. Peacock, Thomas McGlone and Leroy Cronin

      Article first published online: 31 JUL 2008 | DOI: 10.1002/anie.200802594

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      Back and forth: A concerted reversible redox reaction occurs in a pure metal oxide extended polyoxometalate framework when the accessible pockets are filled with a suitable redox agent (see picture). Direct control over the framework properties is demonstrated by repeated reversible switching between an expanded and a contracted structure. Successive recrystallizations from hot water repeatedly destroys and regenerates the framework.

    27. Spin-Crossover Magnets

      Observation of an Iron(II) Spin-Crossover in an Iron Octacyanoniobate-Based Magnet (pages 6885–6887)

      Michio Arai, Wataru Kosaka, Tomoyuki Matsuda and Shin-ichi Ohkoshi

      Article first published online: 5 AUG 2008 | DOI: 10.1002/anie.200802266

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      A spin-crossover from FeII(S=2)-NbIV(S=1/2)-FeII(S=2) to FeII(S=0)-NbIV(S=1/2)-FeII(S=2) occurs in Fe2[Nb(CN)8]⋅(3-pyCH2OH)8⋅4.6 H2O (3-py=3-pyridyl) with decreasing temperature (see picture; red Fe, blue Nb). The low-temperature phase shows ferrimagnetism with a Curie temperature of 12 K owing to an antiferromagnetic interaction between the remaining FeII (S=2) and the NbIV (S=1/2) centers.

    28. Peptide Design

      Cyclic Peptides Bearing a Side-Chain Tail: A Tool to Model the Structure and Reactivity of Protein Zinc Sites (pages 6888–6891)

      Olivier Sénèque, Emilie Bourlès, Vincent Lebrun, Estelle Bonnet, Pascal Dumy and Jean-Marc Latour

      Article first published online: 24 JUL 2008 | DOI: 10.1002/anie.200800677

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      A near-perfect model: The design of short peptides with cyclic and linear components allows mimicking of the structure and reactivity of protein tetracysteinate zinc sites, as illustrated by the superposition of the Zn(Cys)4 site of Hsp33 (blue) and its 20 amino acid model (green).

    29. Liquid Crystals

      Bent-Core Mesogens with Branched Carbosilane Termini: Flipping Suprastructural Chirality without Reversing Polarity (pages 6892–6896)

      Yongqiang Zhang, Michael J. O'Callaghan, Ute Baumeister and Carsten Tschierske

      Article first published online: 22 JUL 2008 | DOI: 10.1002/anie.200800814

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      Back flip: Field-induced transformations between the two homogeneously chiral enantiomers of a bent-core mesogen (see picture) take place by two different mechanisms (A and B). Their combination leads to an unexpected field-induced chirality flipping (C) between the oppositely tilted structures without polarity reversal.

    30. Light-induced spin transitions

      Light-Induced Excited Spin State Trapping in an Exchange-Coupled Nitroxide-Copper(II)-Nitroxide Cluster (pages 6897–6899)

      Matvey Fedin, Victor Ovcharenko, Renad Sagdeev, Edward Reijerse, Wolfgang Lubitz and Elena Bagryanskaya

      Article first published online: 28 JUL 2008 | DOI: 10.1002/anie.200801400

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      Beyond the classics: An exchange-coupled three-spin cluster of copper(II) with nitroxides can be converted by light from a strongly to a weakly coupled spin state (see picture), the latter being metastable at low temperatures. This kind of magnetic photoswitching is very similar to the LIESST effect in spin-crossover complexes of iron. Such compounds form a new class of systems capable of optical switching of their magnetic properties.

    31. Protein Engineering

      You have full text access to this OnlineOpen article
      An Effective Strategy for the Design of Proteins with Enhanced Mechanical Stability (pages 6900–6903)

      Alessandro Borgia, Annette Steward and Jane Clarke

      Article first published online: 29 JUL 2008 | DOI: 10.1002/anie.200801761

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      Titinic strength: The mechanical resistance of titin domain I27 (see picture, left) was increased by substituting residues from a stronger homologue in regions of the protein important for mechanical strength (red). The unfolding profile of I27st (see picture, right) shows that the mechanical strength is significantly increased compared to wild-type I27 (black arrow).

    32. Polyoxometalate Clusters

      Hybrid Organic–Inorganic Polyoxometalates: Functionalization of VIV/VV Nanosized Clusters to Produce Molecular Capsules (pages 6904–6908)

      John M. Breen and Wolfgang Schmitt

      Article first published online: 24 JUL 2008 | DOI: 10.1002/anie.200801770

      Thumbnail image of graphical abstract

      Functionalization of polyoxovanadate clusters using phosphonate and arsonate ligands results in molecular capsules (see structure; green V, purple P, red O, black C). Through the use of extended homologous ligands, these hybrid organic-inorganic capsules can be successively elongated into tubular molecules.

    33. Water Chemistry

      Lewis Acid Catalysis in Water with a Hydrophilic Substrate: Scandium-Catalyzed Hydroxymethylation with Aqueous Formaldehyde in Water (pages 6909–6911)

      Masaya Kokubo, Chikako Ogawa and Shū Kobayashi

      Article first published online: 29 JUL 2008 | DOI: 10.1002/anie.200801849

      Thumbnail image of graphical abstract

      Synthesis in deep water: For the title reaction, which proceeds with high selectivities, acid–base interactions between the Sc catalyst and HCHO are important. The reaction was used in the synthesis of an odorant to demonstrate its utility (see scheme; ligand DS not shown; PI-Pd=polymer-incarcerated palladium; BTF=benzotrifluoride).

    34. Click chemistry

      Dendronized Polymer Organogels from Click Chemistry: A Remarkable Gelation Property Owing to Synergistic Functional-Group Binding and Dendritic Size Effects (pages 6912–6916)

      Kwun-Ngai Lau, Hak-Fun Chow, Man-Chor Chan and Ka-Wai Wong

      Article first published online: 24 JUL 2008 | DOI: 10.1002/anie.200801870

      Thumbnail image of graphical abstract

      Click together and gel: Non-gelating AB-type heterobifunctional macromonomers “click” together to form polytriazole-containing dendronized polymers. These polymers form interchain hydrogen bonds, the extent of which is influenced by the size of the dendritic appendage.

    35. Asymmetric Catalysis

      Asymmetric Suzuki–Miyaura Coupling Reactions Catalyzed by Chiral Palladium Nanoparticles at Room Temperature (pages 6917–6919)

      Koji Sawai, Ryouta Tatumi, Tsukasa Nakahodo and Hisashi Fujihara

      Article first published online: 1 AUG 2008 | DOI: 10.1002/anie.200802174

      Thumbnail image of graphical abstract

      Similar but different: Chiral mono- and bisphosphine ligands have been used to prepare chiral stabilized palladium nanoparticles (Pd NPs). Despite the chiral Pd NPs having similar diameters of 1.2–1.7 nm, they show very different catalytic activities and enantioselectivities in the room-temperature asymmetric Suzuki–Miyaura cross-coupling reactions of aryl halides with aryl boronic acids (see picture).

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      Article first published online: 20 AUG 2008 | DOI: 10.1002/anie.200890179

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