Angewandte Chemie International Edition

Cover image for Vol. 46 Issue 15

April 2, 2007

Volume 46, Issue 15

Pages 2545–2725

  1. Cover Picture

    1. Top of page
    2. Cover Picture
    3. Inside Cover
    4. Graphical Abstract
    5. Corrigendum
    6. News
    7. Book Reviews
    8. Highlights
    9. Review
    10. Communications
    11. Preview
    1. Cover Picture: Formation of Gels and Liquid Crystals Induced by Pt⋅⋅⋅Pt and π–π* Interactions in Luminescent σ-Alkynyl Platinum(II) Terpyridine Complexes (Angew. Chem. Int. Ed. 15/2007) (page 2545)

      Franck Camerel, Raymond Ziessel, Bertrand Donnio, Cyril Bourgogne, Daniel Guillon, Marc Schmutz, Cristian Iacovita and Jean-Pierre Bucher

      Version of Record online: 23 MAR 2007 | DOI: 10.1002/anie.200790056

      Platinum soft wires can be created by linking amphiphilic alkyne platforms to planar PtII terpyridine units. The cover picture shows fibers formed from the stacking of such complexes through Pt⋅⋅⋅Pt and π–π interactions that give rise to deep-green gels and liquid-crystalline materials with near-IR phosphorescence. In their Communication on page 2659 ff., R. Ziessel and co-workers describe how the fibers are organized on highly ordered pyrolytic graphite substrates (observed by AFM; background).

  2. Inside Cover

    1. Top of page
    2. Cover Picture
    3. Inside Cover
    4. Graphical Abstract
    5. Corrigendum
    6. News
    7. Book Reviews
    8. Highlights
    9. Review
    10. Communications
    11. Preview
    1. Inside Cover: A Nucleoside That Contains a Rigid Nitroxide Spin Label: A Fluorophore in Disguise (Angew. Chem. Int. Ed. 15/2007) (page 2546)

      Nivrutti Barhate, Pavol Cekan, Archna P. Massey and Snorri Th. Sigurdsson

      Version of Record online: 23 MAR 2007 | DOI: 10.1002/anie.200790057

      A single nucleoside acts as a probe for two complementary spectroscopic techniques. In their Communication on page 2655 ff., S. Th. Sigurdsson and co-workers describe the synthesis of DNA with a rigid nitroxide spin label. The modified nucleoside forms a stable base pair with guanine and projects the spin label into the major groove of the duplex. The rigidity of the nitroxide enables more accurate measurements of distance and motion in nucleic acids (left), while its reduction yields a fluorescent probe DNA (right).

  3. Graphical Abstract

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

    1. Top of page
    2. Cover Picture
    3. Inside Cover
    4. Graphical Abstract
    5. Corrigendum
    6. News
    7. Book Reviews
    8. Highlights
    9. Review
    10. Communications
    11. Preview
    1. You have free access to this content
  5. News

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

    1. Top of page
    2. Cover Picture
    3. Inside Cover
    4. Graphical Abstract
    5. Corrigendum
    6. News
    7. Book Reviews
    8. Highlights
    9. Review
    10. Communications
    11. Preview
    1. Sequence-specific DNA Binding Agents. Edited by Michael Waring. (pages 2566–2567)

      Maxim Frank-Kamenetskii

      Version of Record online: 23 MAR 2007 | DOI: 10.1002/anie.200685487

  7. Highlights

    1. Top of page
    2. Cover Picture
    3. Inside Cover
    4. Graphical Abstract
    5. Corrigendum
    6. News
    7. Book Reviews
    8. Highlights
    9. Review
    10. Communications
    11. Preview
    1. Reformatsky Reactions Meet Catalysis and Stereoselectivity (pages 2568–2571)

      Pier Giorgio Cozzi

      Version of Record online: 20 FEB 2007 | DOI: 10.1002/anie.200604344

      Thumbnail image of graphical abstract

      Classics reformed: The condensation reaction between aldehydes and ketones and α-halocarbonyl compounds, known as the Reformatsky reaction, has undergone enormous development in recent times, including stereoselective and catalytic variants (see scheme, X=halide), The reliable, practical reaction makes it ideal for synthetic preparations on an industrial scale.

      Corrected by:

      Corrigendum: Reformatsky Reactions Meet Catalysis and Stereoselectivity

      Vol. 46, Issue 37, 6948, Version of Record online: 11 SEP 2007

    2. Germanium(cF136): A New Crystalline Modification of Germanium with the Porous Clathrate-II Structure (pages 2572–2575)

      Thomas F. Fässler

      Version of Record online: 27 FEB 2007 | DOI: 10.1002/anie.200604586

      Thumbnail image of graphical abstract

      Homoatomic Zintl ions (for example, [Ge9]4−; see picture, left) have long been discussed as precursors for the formation of more complicated structures. The characterization of “□24Ge136” with the (unfilled) clathrate-II structure (right; orange, gray, yellow: pentagonal dodecahedra, pink: hexakaidecahedra) and other porous germanium-based materials supports this hypothesis.

  8. Review

    1. Top of page
    2. Cover Picture
    3. Inside Cover
    4. Graphical Abstract
    5. Corrigendum
    6. News
    7. Book Reviews
    8. Highlights
    9. Review
    10. Communications
    11. Preview
    1. The σ-CAM Mechanism: σ Complexes as the Basis of σ-Bond Metathesis at Late-Transition-Metal Centers (pages 2578–2592)

      Robin N. Perutz and Sylviane Sabo-Etienne

      Version of Record online: 23 MAR 2007 | DOI: 10.1002/anie.200603224

      Thumbnail image of graphical abstract

      Dynamic processes provide the clue that it is possible to interconvert σ ligands in complexes of the form [ME′(η2-E-H)] (E, E′=H, B, Si, C) without a change in oxidation state (see scheme). This σ-complex-assisted metathesis (σ-CAM) is distinct from the familiar σ-bond metathesis and from oxidative addition/reductive elimination mechanisms. σ-CAM mechanisms are significant in catalytic and stoichiometric reactions.

  9. Communications

    1. Top of page
    2. Cover Picture
    3. Inside Cover
    4. Graphical Abstract
    5. Corrigendum
    6. News
    7. Book Reviews
    8. Highlights
    9. Review
    10. Communications
    11. Preview
    1. Pentavalent Arsenic Can Bind to Biomolecules (pages 2594–2597)

      Andrea Raab, Stephen H. Wright, Marcel Jaspars, Andrew A. Meharg and Jörg Feldmann

      Version of Record online: 13 MAR 2007 | DOI: 10.1002/anie.200604805

      Thumbnail image of graphical abstract

      As biomolecules go: By identifying the dimethylarsinothioyl glutathione complex in arsenic-exposed cabbage, it was shown that pentavalent arsenic can bind to biomolecules when it is activated by sulfide (see picture; AsV purple, S yellow, O red, N blue). The result highlights that sulfide reactions may play a role in the reactivity of arsenic intermediates and the metabolic pathway of arsenic in organisms.

    2. Synthesis of 1,2-Disubstituted Benzimidazoles by a Cu-Catalyzed Cascade Aryl Amination/Condensation Process (pages 2598–2601)

      Benli Zou, Qiliang Yuan and Dawei Ma

      Version of Record online: 9 MAR 2007 | DOI: 10.1002/anie.200700071

      Thumbnail image of graphical abstract

      Helpful neighbors: A wide range of 1,2-disubstituted benzimidazoles can be assembled from 2-haloanilides and primary amines by using a copper-catalyzed amination reaction promoted by an ortho-substituent effect of an NHCOR group (see scheme, DMSO=dimethyl sulfoxide). The strategy also permits a broad array of substituents X at different positions of the benzimidazole phenyl ring.

    3. The Activation of Hydrogen by Li Atoms To Form [(LiH)2] (pages 2602–2606)

      Xuefeng Wang and Lester Andrews

      Version of Record online: 2 MAR 2007 | DOI: 10.1002/anie.200605211

      Thumbnail image of graphical abstract

      Dimers are a girl's best friend: The rhombic dimer [(LiH)2] (see calculated structure) is the major product of the reaction of laser-ablated lithium atoms in solid H2 upon annealing or irradiation with visible light. Irradiation also produces the higher clusters [(LiH)n] (n=3,4). Like the more stable lithium halide dimers, the rhombic dimer [(LiH)2] is highly ionic.

    4. Synthesis of Cyclohexanol Derivatives by Zirconocene-Mediated Ring-Contraction Reactions of Seven-Membered Cyclic Enol Ethers (pages 2607–2609)

      José Barluenga, Lucía Álvarez-Rodrigo, Félix Rodríguez, Francisco J. Fañanás, Tomás L. Sordo and Pablo Campomanes

      Version of Record online: 20 FEB 2007 | DOI: 10.1002/anie.200605172

      Thumbnail image of graphical abstract

      Shrinking the circle: Complex cyclohexanol derivatives with up to four new stereogenic centers are easily obtained by simple one-pot, three-component, zirconium-mediated coupling of an alkyllithium or Grignard reagent, a seven-membered cyclic enol ether, and an electrophile (E, see scheme).

    5. Chromium(0) Alkynylcarbene Complexes as Cβ-Electrophilic Carbene Equivalents: Regioselective Access to Dienynes and Dienediynes (pages 2610–2612)

      José Barluenga, Patricia García-García, Diana de Sáa, Manuel A. Fernández-Rodríguez, Ramón Bernardo de la Rúa, Alfredo Ballesteros, Enrique Aguilar and Miguel Tomás

      Version of Record online: 19 FEB 2007 | DOI: 10.1002/anie.200605197

      Thumbnail image of graphical abstract

      Just one step is all that is needed for a direct, selective, and easy synthesis of different conjugated enyne frameworks from simple chromium alkynylcarbene complexes and commercially available 2-methoxyfuran (see scheme).

    6. Ruthenium Complexes Carrying Hydride, Dihydrogen, and Phosphine Ligands: Reversible Hydrogen Release (pages 2613–2615)

      Mary Grellier, Laure Vendier and Sylviane Sabo-Etienne

      Version of Record online: 6 MAR 2007 | DOI: 10.1002/anie.200605038

      Thumbnail image of graphical abstract

      If it's meant to be, set it free: The bis(dihydrogen) complex 1, which is stabilized by two tricyclopentylphosphine ligands (PCyp3), can release up to ten hydrogen atoms, ultimately forming the new zerovalent ruthenium complex 2. This facile hydrogen release is totally reversible. The first step of the dehydrogenation process leads to various dihydride isomers of formula [RuH2{(PCyp22-C5H7)}2].

    7. Enantioselective Synthesis of Tertiary Alcohols by the Desymmetrizing Benzoylation of 2-Substituted Glycerols (pages 2616–2618)

      Byunghyuck Jung, Mi Sook Hong and Sung Ho Kang

      Version of Record online: 2 MAR 2007 | DOI: 10.1002/anie.200604977

      Thumbnail image of graphical abstract

      Complementary catalysts have been found for the enantioselective desymmetrization of 2-substituted glycerols by monobenzoylation with benzoyl chloride and Et3N to give chiral tertiary alcohols with 80 to 94 % ee (see Scheme; Bn=benzyl, Bz=benzoyl). The dibenzylbisoxazoline–CuCl2 complex 1 is remarkably effective for substrates with an alkyl substituent in the 2-position, the iminooxazoline–CuCl2 complex 2 for those with vinyl, phenyl, and benzyl substituents.

    8. 1,4-Dichloro- and 1,4-Dibromo-2-butenes as Substrates for Cu-Catalyzed Asymmetric Allylic Substitution (pages 2619–2622)

      Caroline A. Falciola and Alexandre Alexakis

      Version of Record online: 9 MAR 2007 | DOI: 10.1002/anie.200604963

      Thumbnail image of graphical abstract

      Cu at the AAA meeting: Difunctionalized allylic substrates can undergo Cu-catalyzed asymmetric allylic alkylation (AAA) reactions with high enantioselectivities. The products have a functional group that remains for further transformation through substitution with a nucleophile (Nu) or electrophile (E) with conservation of optical purity (see scheme; TC=thiophene carboxylate).

    9. Rh-Catalyzed Highly Enantioselective Synthesis of 3-Arylbutanoic Acids (pages 2623–2626)

      Xianfeng Sun, Le Zhou, Chun-Jiang Wang and Xumu Zhang

      Version of Record online: 6 MAR 2007 | DOI: 10.1002/anie.200604810

      Thumbnail image of graphical abstract

      It's in the mix: The reaction conditions—catalyst, additive, and solvent—have been optimized for the asymmetric hydrogenation of 3-aryl-3-butenoic acids. The rigid, chiral bisphospholane ligand (Sp,Rc)-DuanPhos is crucial to achieving high enantioselectivity.

    10. Zwitterionic Polymerization of Lactide to Cyclic Poly(Lactide) by Using N-Heterocyclic Carbene Organocatalysts (pages 2627–2630)

      Darcy A. Culkin, Wonhee Jeong, Szilárd Csihony, Enrique D. Gomez, Nitash P. Balsara, James L. Hedrick and Robert M. Waymouth

      Version of Record online: 2 MAR 2007 | DOI: 10.1002/anie.200604740

      Thumbnail image of graphical abstract

      Closing the loop: The zwitterionic ring-opening polymerization of lactide in the presence of N-heterocyclic carbenes generates well-defined cyclic poly(lactide) (see scheme). The polymerization is rapid and produces macrocyclic polymers with high purity and exceptional control of molecular weight and polydispersity.

    11. Sulfone-Mediated Total Synthesis of (±)-Lepadiformine (pages 2631–2634)

      John J. Caldwell and Donald Craig

      Version of Record online: 2 MAR 2007 | DOI: 10.1002/anie.200604670

      Thumbnail image of graphical abstract

      Key steps in the total synthesis of the marine alkaloid (±)-lepadiformine (1) include regioselective opening of a spirocyclic aziridine ring with a sulfone-stabilized carbanion, cyclocondensation of the N,C dianion of the resulting γ-sulfonamidosulfone with an aldehyde, and highly stereoselective alkynylation by nucleophilic substitution of an aminal. SES=2-(trimethylsilyl)ethylsulfonyl.

    12. A Solid-State 17O NMR Study of Local Order and Crystallinity in Amine-Templated Mesoporous Nb Oxide (pages 2635–2638)

      Boris O. Skadtchenko, Yuxiang Rao, Tom F. Kemp, Prodipta Bhattacharya, Pamela A. Thomas, Michel Trudeau, Mark E. Smith and Dave M. Antonelli

      Version of Record online: 2 MAR 2007 | DOI: 10.1002/anie.200604602

      Thumbnail image of graphical abstract

      Order locally: 17O magic-angle-spinning NMR spectroscopy of bulk sol–gel-prepared Nb2O5 and mesoporous, template-free Nb2O5 (see picture) shows very high local order in the mesoporous sample. The oxygen atoms are coordinated only as ONb2 in contrast with bulk phases in which the oxygen atoms are always present in a mixture of ONb2 and ONb3 coordination environments.

    13. Robust Deconvolution of Complex Mixtures by Covariance TOCSY Spectroscopy (pages 2639–2642)

      Fengli Zhang and Rafael Brüschweiler

      Version of Record online: 5 MAR 2007 | DOI: 10.1002/anie.200604599

      Thumbnail image of graphical abstract

      Reliable analysis of complex mixtures has been achieved with a new analytical method, dubbed DemixC, for the deconvolution of the NMR spectrum of a mixture into individual components (see scheme). The method, which is based on covariance total correlation spectroscopy (TOCSY) spectra, identifies traces with minimal spectral overlap with other spin systems that can be scanned against an NMR database.

    14. Palladium-Catalyzed 2-Pyridylmethyl Transfer from 2-(2-Pyridyl)ethanol Derivatives to Organic Halides by Chelation-Assisted Cleavage of Unstrained Cmath image[BOND]Cmath image Bonds (pages 2643–2645)

      Takashi Niwa, Hideki Yorimitsu and Koichiro Oshima

      Version of Record online: 2 MAR 2007 | DOI: 10.1002/anie.200604472

      Thumbnail image of graphical abstract

      Making a break for it: Treatment of 2-(2-pyridyl)ethanol derivatives with aryl chlorides in the presence of a palladium catalyst results in the transfer of the pyridylmethyl moiety of the alcohol to yield the corresponding (2-pyridylmethyl)arene. The reaction proceeds by chelation-assisted cleavage of an Cmath image[BOND]Cmath image bond (see scheme) followed by formation of a carbon–carbon bond.

    15. The I-Tetraplex Building Block: Rational Design and Controlled Fabrication of Robust 1D DNA Scaffolds through Non-Watson–Crick Interactions (pages 2646–2649)

      Harshad B. Ghodke, Ramya Krishnan, Kasinath Vignesh, G. V. Pavan Kumar, Chandrabhas Narayana and Yamuna Krishnan

      Version of Record online: 2 MAR 2007 | DOI: 10.1002/anie.200604461

      Thumbnail image of graphical abstract

      All wired up: Robust 1D scaffolds have been designed based on the i tetraplex by a strategy of inducing bidirectional growth on “slipped” tetraplexes. The growth propagates through non-Watson–Crick base-pairing and leads to nanowires more than 3 μm long. These nanowires have been characterized by microscopy (AFM and TEM, see picture), surface-enhanced Raman spectroscopy, and circular dichroism spectroscopy.

    16. Single-Crystal Organic Nanowires of Copper–Tetracyanoquinodimethane: Synthesis, Patterning, Characterization, and Device Applications (pages 2650–2654)

      Kai Xiao, Jing Tao, Zhengwei Pan, Alex A. Puretzky, Ilia N. Ivanov, Stephen J. Pennycook and David B. Geohegan

      Version of Record online: 2 MAR 2007 | DOI: 10.1002/anie.200604397

      Thumbnail image of graphical abstract

      Current events: Nanowires of the organic semiconductor copper–tetracyanoquinodimethane (Cu–TCNQ) have been synthesized in a controlled manner and patterned on a variety of substrates by chemical vapor deposition. A cross-point memory device based on a network of Cu–TCNQ nanowires (see picture) has been constructed that repeatedly switches electrically between two states with a conductivity difference of more than two orders of magnitude.

    17. A Nucleoside That Contains a Rigid Nitroxide Spin Label: A Fluorophore in Disguise (pages 2655–2658)

      Nivrutti Barhate, Pavol Cekan, Archna P. Massey and Snorri Th. Sigurdsson

      Version of Record online: 19 FEB 2007 | DOI: 10.1002/anie.200603993

      Thumbnail image of graphical abstract

      Take a spin: The nucleoside Ç (C-spin), which contains a rigid nitroxide spin label, allows the structure and dynamics of nucleic acids into which it is incorporated to be studied by EPR spectroscopy (left spectrum). Reduction of the nitroxide with a mild reducing agent renders the nucleoside fluorescent (right spectrum). Thus, the same nucleic acid can be studied with two complementary spectroscopic techniques.

    18. Formation of Gels and Liquid Crystals Induced by Pt⋅⋅⋅Pt and π–π* Interactions in Luminescent σ-Alkynyl Platinum(II) Terpyridine Complexes (pages 2659–2662)

      Franck Camerel, Raymond Ziessel, Bertrand Donnio, Cyril Bourgogne, Daniel Guillon, Marc Schmutz, Cristian Iacovita and Jean-Pierre Bucher

      Version of Record online: 15 DEC 2006 | DOI: 10.1002/anie.200604012

      Thumbnail image of graphical abstract

      Well organized! A new class of phosphorescent materials was obtained by the coupling of trialkylgallate-functionalized alkynes to a planar PtII terpyridine unit. Pt⋅⋅⋅Pt interactions in these complexes lead to the formation of highly colored organogels and columnar liquid crystals (see picture). Amide groups linking the gallate and alkyne units provide additional stabilization of the structures through hydrogen bonding.

    19. A Metallocavitand Functioning as a Container for Anions: Formation of Noncovalent Linear Assemblies Mediated by a Cyclodextrin-Entrapped NO3 Ion (pages 2663–2665)

      Laurent Poorters, Dominique Armspach, Dominique Matt, Loïc Toupet and Peter G. Jones

      Version of Record online: 9 MAR 2007 | DOI: 10.1002/anie.200604564

      Thumbnail image of graphical abstract

      Containing the negativity: A cyclodextrin-based complex substituted with two phosphine groups is able to fully embrace medium sized anions such as BF4 (see picture), NO3, AcO, or X (X=Cl, Br, I). Besides conventional electrostatic cation⋅⋅⋅anion interactions, complex formation has been shown to involve weak interactions with the lipophilic host environment.

    20. The “Bond-Stretched Invertomer” of Hexafluorocyclopropane—a New Type of Reactive Intermediate (pages 2666–2668)

      Haiyan Wei, David A Hrovat, William R. Dolbier Jr., Bruce E. Smart and Weston Thatcher Borden

      Version of Record online: 5 MAR 2007 | DOI: 10.1002/anie.200604574

      Thumbnail image of graphical abstract

      It all adds up: Calculations show the “bond-stretched invertomer” of hexafluorocyclopropane to be an energy minimum with a barrier to ring closure of 9.8 kcal mol−1 (see potential-energy surface). The bond-stretched invertomer is a likely intermediate in the reactions of hexafluorocyclopropane with halogens to form 1,3-dihalo-1,1,2,2,3,3-hexafluoropropanes.

    21. Beryllium Displacement of H+ from Strong Hydrogen Bonds (pages 2669–2671)

      T. Mark McCleskey, Deborah S. Ehler, Timothy S. Keizer, Dilip N. Asthagiri, Lawrence R. Pratt, Ryszard Michalczyk and Brian L. Scott

      Version of Record online: 9 MAR 2007 | DOI: 10.1002/anie.200604623

      Thumbnail image of graphical abstract

      It's bound to Be: The binding of beryllium to the iron transport protein transferrin proceeds by displacement of H+ from strong hydrogen bonds in the protein (see picture). This new view of beryllium binding, in which beryllium as a “tetrahedral proton” is thermodynamically preferred, provides insight into the transport mechanism of beryllium in chronic beryllium disease.

    22. Intramolecular Carbostannylation of Alkynes Catalyzed by Silver(I) Species (pages 2672–2676)

      Susana Porcel and Antonio M. Echavarren

      Version of Record online: 6 MAR 2007 | DOI: 10.1002/anie.200605041

      Thumbnail image of graphical abstract

      Joined at the hip: The intramolecular carbostannylation of alkynes catalyzed by silver(I) stereoselectively gives E-alkenylstannanes as single isomers (see scheme, Z=C(CO2Me)2, C(SO2Ph)2, C(CH2OR)2). The mechanism of the reaction appears to be similar to that of the reaction of enynes with other electrophilic transition-metal complexes.

    23. Exploiting the Directionality of DNA: Controlled Shrinkage of Engineered Oligonucleotide Capsules (pages 2677–2680)

      Angus P. R. Johnston and Frank Caruso

      Version of Record online: 2 MAR 2007 | DOI: 10.1002/anie.200605135

      Thumbnail image of graphical abstract

      Shrinking capsules: Using the directionality of DNA hybridization, DNA capsules with controllable shrinkage properties are formed (see picture). The degree of shrinkage ranges from 35–90 % of the original particle volume, depending on the oligonucleotide sequences used to assemble the capsules. These capsules could find use in drug delivery and diagnostic applications.

    24. Disruption of Amyloid-Derived Peptide Assemblies through the Controlled Induction of a β-Sheet to α-Helix Transformation: Application of the Switch Concept (pages 2681–2684)

      Richard Mimna, Marie-Stéphanie Camus, Adrian Schmid, Gabriele Tuchscherer, Hilal A. Lashuel and Manfred Mutter

      Version of Record online: 2 MAR 2007 | DOI: 10.1002/anie.200603681

      Thumbnail image of graphical abstract

      Most problems are soluble: Reversal of amyloid formation through a controlled induced transformation from β-sheet to soluble α-helix structures through the use of a switch element S (see scheme, σ is a helix-inducing template) could have an important consequences understanding the mechanisms of amyloid formation and clearance.

    25. Catalytic Enantio- and Diastereoselective Formation of β-Sultones: Ring-Strained Precursors for Enantioenriched β-Hydroxysulfonyl Derivatives (pages 2685–2689)

      Florian M. Koch and René Peters

      Version of Record online: 2 MAR 2007 | DOI: 10.1002/anie.200604796

      Thumbnail image of graphical abstract

      Sultones swing! Sulfenes, the highly reactive sulfonyl equivalents of ketenes, were used for the first time as substrates in asymmetric catalysis. A [2+2] cyclocondensation reaction catalyzed by a tertiary amine enabled the asymmetric synthesis of β-sultones, which are convenient precursors of β-hydroxysulfonyl derivatives (EWG: electron-withdrawing group; Tf: triflate, (DHQ)2PYR: dihydroquinine-2,5-diphenyl-4,6-pyrimidinediyl diether, Nu: nucleophile).

    26. A Diels–Alder Approach to (−)-Ovalicin (pages 2690–2693)

      Konrad Tiefenbacher, Vladimir B. Arion and Johann Mulzer

      Version of Record online: 1 MAR 2007 | DOI: 10.1002/anie.200604781

      Thumbnail image of graphical abstract

      A round at the Oval: The antiangiogenic activity of the natural product ovalicin has sparked significant interest. A highly efficient enantio- and diastereoselective total synthesis of ovalicin proved successful in which the key step involved an endo selective Diels–Alder reaction (see scheme, PG=protecting group).

    27. Direct Translation of Chiral Recognition into Mechanical Motion (pages 2694–2696)

      Hans-Jörg Schneider and Kazuaki Kato

      Version of Record online: 2 MAR 2007 | DOI: 10.1002/anie.200604664

      Thumbnail image of graphical abstract

      Small cause, large effect: The D and L enantiomers of diphenyltartaric acid incur different interactions with chitosan hydrogels and lead to a chemomechanical effect (see scheme), which is expressed through clear differences in the volume of the polymer particles. Increased sensitivity is possible by reducing the size of the polymer particles.

    28. Stabilization of Unsymmetrically Annelated Imidazol-2-ylidenes with Respect to Their Higher Group 14 Homologues by n-/π-HOMO Inversion (pages 2697–2700)

      Farman Ullah, Gabor Bajor, Tamas Veszprémi, Peter G. Jones and Joachim W. Heinicke

      Version of Record online: 2 MAR 2007 | DOI: 10.1002/anie.200604516

      Thumbnail image of graphical abstract

      From annelation to an elation: The surprising stability of pyridoannelated imidazol-2-ylidenes (see scheme) in comparison with the heavier Group 14 homologues suggests broad tuning potential and control of the reactivity by the lone pair of electrons at the carbon atom. The asymmetric distribution of π-electron density, which destabilizes the heavier homologues, does not markedly diminish the kinetic stability of the N-heterocyclic carbenes (NHCs).

    29. Peptide-Embedded Heterocycles by Mild Single and Multiple Aza-Wittig Ring Closures (pages 2701–2703)

      Matthias Riedrich, Surendra Harkal and Hans-Dieter Arndt

      Version of Record online: 5 MAR 2007 | DOI: 10.1002/anie.200604507

      Thumbnail image of graphical abstract

      Ring a ring o'azoles: The aza-Wittig cyclization of amino acids and peptides is extremely mild, selective, and versatile. The reaction of amino acid esters and amino acid thioester azides delivers peptidic 1,3-azolines and 1,3-azoles with unsurpassed functional-group tolerance. This method allows multiple ring closures and tolerates aqueous solvents.

    30. DNA-Controlled Reversible Switching of Peptide Conformation and Bioactivity (pages 2704–2707)

      Lars Röglin, Mohammad R. Ahmadian and Oliver Seitz

      Version of Record online: 2 MAR 2007 | DOI: 10.1002/anie.200603889

      Thumbnail image of graphical abstract

      A DNA switch: Hybridization with DNA controls the conformation of a peptide nucleic acid (PNA)–peptide conjugate. This reversible process can activate (see scheme) or deactivate the binding propensity of the peptide for a protein target involved in cellular signal transduction.

    31. Cyclodextrin Complexes of Polymers Bearing Adamantyl Groups: Host–Guest Interactions and the Effect of Spacers on Water Solubility (pages 2708–2711)

      Oliver Kretschmann, Christopher Steffens and Helmut Ritter

      Version of Record online: 1 MAR 2007 | DOI: 10.1002/anie.200603753

      Thumbnail image of graphical abstract

      Thermoresponsive polymer inclusion complexes were prepared by radical polymerization in water of acrylamides bearing adamantyl groups by the use of randomly methylated β-cyclodextrin (Me-β-CD). Aqueous solutions of the resulting polymer complexes show a temperature-dependent transparency arising from a reversible dissociation above a critical temperature. The rate of the process strongly depends on the distance between the adamantyl groups and the polymer main chain.

    32. A Type II Polyketide Synthase from the Gram-Negative Bacterium Stigmatella aurantiaca Is Involved in Aurachin Alkaloid Biosynthesis (pages 2712–2716)

      Axel Sandmann, Jeroen Dickschat, Holger Jenke-Kodama, Brigitte Kunze, Elke Dittmann and Rolf Müller

      Version of Record online: 5 MAR 2007 | DOI: 10.1002/anie.200603513

      Thumbnail image of graphical abstract

      A closer look: The path for the biosynthesis of aurachin alkaloids (aurachin A is shown) has been deduced by molecular biological methods, including the cloning and sequencing of the biosynthetic gene cluster in the bacterium Stigmatella aurantiaca. The gene cluster encodes a type II polyketide synthase, which was discovered in this form for the first time in a Gram-negative bacterium.

    33. Metal-Free Activation of CO2 by Mesoporous Graphitic Carbon Nitride (pages 2717–2720)

      Frédéric Goettmann, Arne Thomas and Markus Antonietti

      Version of Record online: 2 MAR 2007 | DOI: 10.1002/anie.200603478

      Thumbnail image of graphical abstract

      Doubly useful: The use of a mesoporous graphitic carbon nitride (mpg-C3N4) as a heterogeneous, metal-free catalyst enabled the direct activation of CO2 and the oxidation of benzene to phenol (see picture). The formed CO can be used in situ for subsequent reactions, as is shown for a Pauson–Khand reaction.

  10. Preview

    1. Top of page
    2. Cover Picture
    3. Inside Cover
    4. Graphical Abstract
    5. Corrigendum
    6. News
    7. Book Reviews
    8. Highlights
    9. Review
    10. Communications
    11. Preview
    1. You have free access to this content

SEARCH

SEARCH BY CITATION