Angewandte Chemie International Edition

Cover image for Vol. 44 Issue 6

January 28, 2005

Volume 44, Issue 6

Pages 829–981

    1. Cover Picture: Direct Observation of Hydrogen Molecules Adsorbed onto a Microporous Coordination Polymer (Angew. Chem. Int. Ed. 6/2005) (page 829)

      Yoshiki Kubota, Masaki Takata, Ryotaro Matsuda, Ryo Kitaura, Susumu Kitagawa, Kenichi Kato, Makoto Sakata and Tatsuo C. Kobayashi

      Version of Record online: 25 JAN 2005 | DOI: 10.1002/anie.200590017

      Fundamental structural information on hydrogen molecules adsorbed in nanochannels is required for the rational synthetic design of novel metal–organic porous materials as hydrogen-storage materials. The cover picture shows the charge-density distribution of hydrogen molecules adsorbed in the nanochannels of a copper coordination polymer. The hydrogen molecules are located in the pocket cavities of the suitably sized nanochannels. More details can be found in the Communication by Y. Kubota et al. on page 920 ff.

    2. Developments in Furan Syntheses (pages 850–852)

      Richard C. D. Brown

      Version of Record online: 23 DEC 2004 | DOI: 10.1002/anie.200461668

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      Diversely substituted furans can be prepared from alkynones and alkynoate esters by means of mechanistically novel cycloisomerization and reductive cyclization processes, respectively. Even tetrasubstituted furans can be prepared by cycloisomerization of alkynones, or from allenyl ketones through a Pd-catalyzed cross-coupling-cyclization approach (see scheme; DMA=N,N-dimethylacetamide).

    3. The Quest for Quinine: Those Who Won the Battles and Those Who Won the War (pages 854–885)

      Teodoro S. Kaufman and Edmundo A. Rúveda

      Version of Record online: 25 JAN 2005 | DOI: 10.1002/anie.200400663

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      Tonic for the troops: The year 2004 marks the 60th anniversary of Woodward's total synthesis of quinine (see picture), which for a long time had been the only useful treatment for malaria. Quinine proved to be an attractive and elusive synthetic target since Perkin's attempts in 1856, which gave birth to industrial organic synthesis and the dye industry. This Review highlights the history of the isolation, structural elucidation, and synthesis of quinine.

    4. Magnetic Information Storage on Polymers by Using Patterned Single-Molecule Magnets (pages 888–892)

      Massimiliano Cavallini, Jordi Gomez-Segura, Daniel Ruiz-Molina, Massimiliano Massi, Cristiano Albonetti, Concepció Rovira, Jaume Veciana and Fabio Biscarini

      Version of Record online: 25 JAN 2005 | DOI: 10.1002/anie.200461554

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      An attractive read: Magnetic Mn12 clusters are patterned by molding a dispersion in a polymer matrix onto a structured master (e.g., a DVD). The protrusions of the polymer replica surface disappear on exposure to solvent vapor, and the clusters concentrate on the surface at the positions of the original protrusions. The cluster distribution produces a magnetic contrast, which can be imaged by magnetic force microscopy (see picture).

    5. New Structural Motifs in Manganese Single-Molecule Magnetism from the Use of Triethanolamine Ligands (pages 892–896)

      Muralee Murugesu, Wolfgang Wernsdorfer, Khalil A. Abboud and George Christou

      Version of Record online: 28 DEC 2004 | DOI: 10.1002/anie.200461703

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      Saddle seen: The use of the potentially tetradentate triethanolamine (teaH3) ligand provides a useful route to three new structural types in mixed-valent manganese cluster chemistry, which include near-rectangular and closed-sinusoidal (saddle-shaped; see structure: MnIII purple, MnII yellow, O red, N blue, C gray) topologies. Further, two of these complexes are also new single-molecule magnets (SMMs).

    6. DFT Computational Rationalization of an Unusual Spin Ground State in an Mn12 Single-Molecule Magnet with a Low-Symmetry Loop Structure (pages 897–901)

      Dolos Foguet-Albiol, Ted A. O'Brien, Wolfgang Wernsdorfer, Brian Moulton, Michael J. Zaworotko, Khalil A. Abboud and George Christou

      Version of Record online: 28 DEC 2004 | DOI: 10.1002/anie.200461820

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      Loopy about magnetism: The use of N-methyldiethanolamine (mdaH2) leads to new Mn12 and Mn4 single-molecule magnets (SMMs) with S=7 and S=9 ground-state spins, respectively. The Mn12 species (see structure: MnIII green, MnII orange, O red, N blue, C gray) is a rare example of an SMM with a loop structure. Its unusual S=7 ground state for an MnIII6MnII6 species is rationalized by DFT calculations.

    7. Metal–Organic Rotaxane Frameworks: Three-Dimensional Polyrotaxanes from Lanthanide-Ion Nodes, Pyridinium N-Oxide Axles, and Crown-Ether Wheels (pages 901–904)

      Dennis J. Hoffart and Stephen J. Loeb

      Version of Record online: 28 DEC 2004 | DOI: 10.1002/anie.200461707

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      Circles cubed: The title materials can be prepared by self-assembly and are similar to conventional metal–organic framework materials, but with every linker being a [2]rotaxane made from pyridinium axles and crown-ether wheels (see structures; left: a single “cube” unit of the 3D network with the crown-ether wheels removed, right: the same framework with crown-ether wheels included; Sm ions gold).

    8. Towards a Rational Design of Antibody Catalysts through Computational Chemistry (pages 904–909)

      Sergio Martí, Juan Andrés, Vicent Moliner, Estanislao Silla, Iñaki Tuñón and Juan Bertrán

      Version of Record online: 28 DEC 2004 | DOI: 10.1002/anie.200461325

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      Stabilizing the transition state of a reaction is not the only consideration in the design of catalytic antibodies. The energetics of the substrate–catalyst complex preceding the transition state also play a role. The picture shows such a complex for an oxy-Cope rearrangement in the active site of the antibody catalyst AZ-28 in its germline form.

    9. 1:1 and 2:1 Charge-Transfer Complexes between Aromatic Hydrocarbons and Dry Titanium Dioxide (pages 910–913)

      You Seok Seo, Changhoon Lee, Kee Hag Lee and Kyung Byung Yoon

      Version of Record online: 28 DEC 2004 | DOI: 10.1002/anie.200461972

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      The coloration of TiO2 upon contact with solutions of aromatic hydrocarbons is explained by the formation of 1:1 and 2:1 complexes (see picture) by physical adsorption. UV/Vis spectra and calculations indicate that these complexes are based on a charge-transfer interaction.

    10. Direct Characterization of Enzyme–Substrate Complexes by Using Electrosonic Spray Ionization Mass Spectrometry (pages 913–916)

      Justin M. Wiseman, Zoltán Takáts, Bogdan Gologan, V. J. Davisson and R. Graham Cooks

      Version of Record online: 28 DEC 2004 | DOI: 10.1002/anie.200461672

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      It's a phase it's going through: Electrosonic spray ionization shows better desolvation efficiency than electrospray ionization and usually gives single-charge states when used to ionize noncovalent complexes of large biomolecules. The binary and ternary complexes of imidazole-3-glycerol phosphate synthase (IGPS) with its inhibitors appear to retain their native solution-phase conformations upon transfer into the gas phase (see picture).

    11. Understanding the Structural Deactivation of Ruthenium Catalysts on an Atomic Scale under both Oxidizing and Reducing Conditions (pages 917–920)

      Jens Aßmann, Daniela Crihan, Marcus Knapp, Edvin Lundgren, Elke Löffler, Martin Muhler, Vijay Narkhede, Herbert Over, Michael Schmid, Ari P. Seitsonen and Peter Varga

      Version of Record online: 28 DEC 2004 | DOI: 10.1002/anie.200461805

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      Performance enhancement: The surface-science approach coupled with industrial catalyst research offers a synergistic strategy to improve the performance of industrial catalysts. The poorly understood microscopic processes that determine the structural deactivation of ruthenium-based catalysts during CO oxidation have been elucidated (see scheme). Based on these results measures are proposed to improve the performance of ruthenium catalysts.

    12. Direct Observation of Hydrogen Molecules Adsorbed onto a Microporous Coordination Polymer (pages 920–923)

      Yoshiki Kubota, Masaki Takata, Ryotaro Matsuda, Ryo Kitaura, Susumu Kitagawa, Kenichi Kato, Makoto Sakata and Tatsuo C. Kobayashi

      Version of Record online: 22 NOV 2004 | DOI: 10.1002/anie.200461895

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      Trapped hydrogen molecules in the nanochannels of a copper coordination polymer were successfully observed by the synchrotron powder-diffraction method. The adsorbed molecules are located near one corner of the rectangular nanochannels, and the pockets of the pore walls are suited to the size of the hydrogen molecules (see picture). These results could provide guidelines for the design of hydrogen-storage materials.

    13. Carbohydrate–Metal Interactions Shaped by Supramolecular Assembling (pages 924–927)

      Andreas Geißelmann, Peter Klüfers, Claudia Kropfgans, Peter Mayer and Holger Piotrowski

      Version of Record online: 3 JAN 2005 | DOI: 10.1002/anie.200460079

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      Cyclodextrin ligands: Carbohydrates can be used as framework molecules that provide patterns of metal-binding oxygen atoms. The divalent forms of the biologically important metals iron and manganese can be part of such assemblies (see structure: Fe blue, O red, counterion green, hydrogen bonds between water molecules yellow). The assemblies are stabilized by favorable contributions other than the carbohydrate–metal interaction.

    14. RNA-Selective Modification by a Platinum(II) Complex Conjugated to Amino- and Guanidinoglycosides (pages 927–932)

      Jürgen Boer, Kenneth F. Blount, Nathan W. Luedtke, Lev Elson-Schwab and Yitzhak Tor

      Version of Record online: 3 JAN 2005 | DOI: 10.1002/anie.200461182

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      Revving up the RNA response: Binding of the anticancer drug cisplatin (cis-Pt) to nucleic acids is believed to favor DNA over RNA. To “reverse” the nucleic acid selectivity of cis-Pt, amino- and guanidinoglycoside–PtII conjugates (1 and 2) have been synthesized and evaluated. The conjugates generate site-specific, RNA-selective, covalent cross-links to the HIV-1 Rev response element.

    15. Anthracene-Bridged Z-Shaped [26]Hexaphyrin(1.1.1.1.1.1.1) Dimer from the Regioselective Diels–Alder Reaction of a Hexaphyrin with Bis-o-xylylene Equivalents (pages 932–935)

      Hiroshi Hata, Hiroshi Shinokubo and Atsuhiro Osuka

      Version of Record online: 28 DEC 2004 | DOI: 10.1002/anie.200462231

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      An expanded porphyrin with six pyrrole units, a meso-aryl hexaphyrin, acts as a dienophile in Diels–Alder reactions with o-xylylene. Consecutive double cycloadditions of the hexaphyrin with a bis-o-xylylene equivalent leads to an anthracene-bridged hexaphyrin dimer (see scheme), whose unique Z-shaped structure has been elucidated by X-ray crystallographic analysis.

    16. 1,2,4-Oxadiazolidinones as Configurationally Stable Chiral Building Blocks (pages 936–938)

      Tobias Ritter and Erick M. Carreira

      Version of Record online: 28 DEC 2004 | DOI: 10.1002/anie.200461934

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      An intriguing scaffold for drug development, 1,2,4-oxadiazolidinones are obtained in enantiomerically pure form by a simple reaction and purification protocol (see scheme). These heterocycles, including the previously unknown N2-unsubstituted parent structures, were shown to be configurationally stable under a variety of conditions.

    17. Origins of Stereoselectivity in Strain-Release Allylations (pages 938–941)

      Xiyun Zhang, Kendall N. Houk and James L. Leighton

      Version of Record online: 28 DEC 2004 | DOI: 10.1002/anie.200462130

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      Explaining the experiment: The transition states for a concerted asymmetric allylation (see scheme) were studied by theoretical methods. The apical attack of the aldehyde oxygen atom on Si accompanied by minimization of electrostatic repulsion in the trigonal-bipyramidal transition state leads to high stereoselectivity.

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      The Composition of Ehrlich's Salvarsan: Resolution of a Century-Old Debate (pages 941–944)

      Nicholas C. Lloyd, Hugh W. Morgan, Brian K. Nicholson and Ron S. Ronimus

      Version of Record online: 29 DEC 2004 | DOI: 10.1002/anie.200461471

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      Elusive molecular structure revealed: The primary components of the historically important pharmaceutical compound salvarsan (arsphenamine, Ehrlich 606) have been shown by ESI mass spectrometry to be cyclopolyarsines [RAs]n (see structure; n=3–6 and R=3-amino-4-hydroxyphenyl).

    19. Alkene–Arene meta Photocycloadditions with a Four-Carbon-Atom Tether: Efficient Approach toward the Polycyclic Ring Systems of Aphidicolin and Stemodinone (pages 944–946)

      Joseph W. Boyd, Nicola Greaves, Jason Kettle, Andrew T. Russell and Jonathan W. Steed

      Version of Record online: 5 JAN 2005 | DOI: 10.1002/anie.200461661

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      At the end of its tether! The fusion of a six-membered ring onto the four-carbon-atom tether of substrate 1 provides an efficient approach toward the polycyclic ring systems of the natural products aphidicolin and stemodinone. The reaction represents a unique example of a preference for product formation from an endo exciplex in an intramolecular system (exo:endo2:3=1.0:1.2).

    20. Stereoselective Glycosylation Reactions with Chiral Auxiliaries (pages 947–949)

      Jin-Hwan Kim, Hai Yang and Geert-Jan Boons

      Version of Record online: 3 JAN 2005 | DOI: 10.1002/anie.200461745

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      Good neighbors: A chiral auxiliary is used for the first time to control the anomeric selectivity of glycosylation reactions. In this approach, upon treatment with an activator A+, neighboring-group participation of an (S)-ethoxycarbonylbenzyl auxiliary at C2 leads to the formation of 1,2-cis glycosides, probably via a trans-fused ethyloxonium ion intermediate (see scheme).

    21. Nucleophile-Catalyzed Asymmetric Acylations of Silyl Ketene Imines: Application to the Enantioselective Synthesis of Verapamil (pages 949–952)

      Ara H. Mermerian and Gregory C. Fu

      Version of Record online: 3 JAN 2005 | DOI: 10.1002/anie.200461886

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      All-carbon quaternary stereocenters are generated with good enantioselectivity through a nucleophile-catalyzed acylation reaction of silyl ketene imines (see scheme, TBS=tert-butyldimethylsilyl). The method is applied to the first catalytic asymmetric synthesis of the drug verapamil.

    22. Clean and Highly Selective Oxidation of Alcohols in an Ionic Liquid by Using an Ion-Supported Hypervalent Iodine(III) Reagent (pages 952–955)

      Weixing Qian, Erlei Jin, Weiliang Bao and Yongmin Zhang

      Version of Record online: 3 JAN 2005 | DOI: 10.1002/anie.200461889

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      Alcohol consumption: The PhI(OAc)2-derived hypervalent iodine reagent 1 acts as an oxidant in the conversion of primary and secondary alcohols 2 into carbonyl compounds 3 with good to excellent yields (see scheme). The bromide ion remaining from the preparation of [emim]+[BF4] (emim=1-ethyl-3-methylimidazolium tetrafluoroborate) acts as a catalyst in the reaction. Primary alcohols are oxidized without any detectable overoxidation.

    23. Stretching and Rupturing Individual Supramolecular Polymer Chains by AFM (pages 956–959)

      Shan Zou, Holger Schönherr and G. Julius Vancso

      Version of Record online: 28 DEC 2004 | DOI: 10.1002/anie.200460963

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      Breaking point: The unbinding behavior of single supramolecular polymers formed through quadruple hydrogen bonds between 2-ureido-4(1H)-pyrimidinone (UPy) units was studied by AFM-based single-molecule force spectroscopy. The interactions between individual UPy moieties and the stretching of polyethylene glycol (PEG) spacers in reversible supramolecular polymer chains were unveiled by AFM force-displacement measurements.

    24. Lanthanide–Imido Complexes and Their Reactions with Benzonitrile (pages 959–962)

      Dongmei Cui, Masayoshi Nishiura and Zhaomin Hou

      Version of Record online: 21 DEC 2004 | DOI: 10.1002/anie.200461939

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      Highly reactive imido ligands, even when in a bridging mode as in 1, distinguish lanthanide–imido complexes from their d-block counterparts. For example, imido species 1 can undergo nucleophilic addition to benzonitrile to give 2. Catalytic cyclotrimerization of benzonitrile occurs in the presence of 1 or 2 by a unique combination of C[BOND]N bond-formation, hydrogen-transfer, and C[BOND]N bond-cleavage reactions (see scheme). Cp′ = η5-C5Me4SiMe3

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      Alternating Ethylene–Norbornene Copolymerization Catalyzed by Cationic Half-Sandwich Scandium Complexes (pages 962–965)

      Xiaofang Li, Jens Baldamus and Zhaomin Hou

      Version of Record online: 23 DEC 2004 | DOI: 10.1002/anie.200461971

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      Rare activity of an active rare-earth-metal catalyst is observed in the alternating copolymerization of ethylene and norbornene. The reaction yields exclusively the alternating copolymer in the presence of both monomers and affords poly(ethylene-alt-norbornene)-b-polyethylene block copolymers when a relatively small quantity of norbornene is used under a constant flow of ethylene (see scheme).

    26. Dynamic Combinatorial Chemistry: Lysozyme Selects an Aromatic Motif That Mimics a Carbohydrate Residue (pages 965–969)

      Sandrine Zameo, Boris Vauzeilles and Jean-Marie Beau

      Version of Record online: 11 JAN 2005 | DOI: 10.1002/anie.200462150

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      Lysozyme makes its choice: Hen egg-white lysozyme selects the optimal binder from a collection of aromatic motifs that mimic a carbohydrate unit upon exposure to a dynamic library of potential ligands that are directed towards its active site by a low-affinity scaffold. The structure of one of the selected members 1 is shown.

    27. Linear-to-Turn Conformational Switching Induced by Deprotonation of Unsymmetrically Linked Phenolic Oligoamides (pages 969–972)

      Daisuke Kanamori, Taka-aki Okamura, Hitoshi Yamamoto and Norikazu Ueyama

      Version of Record online: 28 DEC 2004 | DOI: 10.1002/anie.200461842

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      Proton-triggered conformational switching: Unsymmetrically linked phenolic oligoamides fold into a turn conformation from a linear conformation following the deprotonation of the phenol groups (see scheme). Deprotonation induces a rearrangement of the hydrogen-bonding mode within each unit from OH⋅⋅⋅O[DOUBLE BOND]C (linear) to NH⋅⋅⋅O(oxyanion) such that all of the phenolate O atoms are directed toward the inside of the turn.

    28. Synthesis of Fluorodihydroxysulfonium Hexafluoroantimonate [FS(OH)2]+[SbF6] (pages 973–975)

      Andreas Kornath, Raphael Seelbinder and Rolf Minkwitz

      Version of Record online: 28 DEC 2004 | DOI: 10.1002/anie.200461847

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      Audience participation: Fluorosulfinic acid, which is not known in its free state, was isolated in its protonated form as the [FS(OH)2]+[SbF6] salt. It was prepared by addition of SO2 to the superacid HF/SbF5. SO2 has been used as a solvent for HF/SbF5 superacid systems for over 40 years. Only now is it shown that when SO2 is added to HF/SbF5 the [FS(OH)2]+ ion (see structure) is formed in an equilibrium with the SO2SbF5 adduct.

    29. Cyclometalation of Substrates Containing Imine and Pyridyl Anchoring Groups by Iron and Cobalt Complexes (pages 975–977)

      Hans-Friedrich Klein, Sebnem Camadanli, Robert Beck, Diana Leukel and Ulrich Flörke

      Version of Record online: 11 JAN 2005 | DOI: 10.1002/anie.200460978

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      Steric control dictates the cyclometalation of aromatic substrates containing imine anchoring groups upon reaction with basic iron or cobalt complexes. As structural isomers, the azadiene systems 1 and 2 undergo regiospecific activation of the (vinylic or aromatic) C[BOND]H bond of the CH group that has switched places with the N atom.

    30. Preview: Angew. Chem. Int. Ed. 6/2005 (page 981)

      Version of Record online: 25 JAN 2005 | DOI: 10.1002/anie.200590019

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