Angewandte Chemie International Edition

Cover image for Vol. 43 Issue 20

May 10, 2004

Volume 43, Issue 20

Pages 2585–2725

    1. Cover Picture: Ultrafast Electron Crystallography of Surface Structural Dynamics with Atomic-Scale Resolution (Angew. Chem. Int. Ed. 20/2004) (page 2585)

      Franco Vigliotti, Songye Chen, Chong-Yu Ruan, Vladimir A. Lobastov and Ahmed H. Zewail

      Version of Record online: 5 MAY 2004 | DOI: 10.1002/anie.200490059

      Surface structural dynamics are determined with unprecedented spatial and temporal resolution by ultrafast electron crystallography. The dynamics are initiated by a femtosecond laser pulse, and transient surface structures are imaged by an ultrashort electron pulse: A diffraction snapshot is obtained at a given time, δt, and allows the real-time observation of surface structural dynamics with atomic-scale resolution. For more details see the Communication by A. H. Zewail and co-workers on page 2705 ff.

    2. EPA Environmental Science Database: Not Only for Americans (page 2597)

      Kristian W. Fried and Dieter Lenoir

      Version of Record online: 5 MAY 2004 | DOI: 10.1002/anie.200460015

    3. Threading the Needle: Mimicking Natural Toroidal Catalysts (pages 2602–2605)

      Paul R. Carlier

      Version of Record online: 5 MAY 2004 | DOI: 10.1002/anie.200301731

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      Can a hollow catalyst process a polymeric substrate by “threading the needle?” Nature's DNA-processing enzymes effortlessly use this pseudorotaxane mechanism, but until recently this topology has not been realized in a synthetic supramolecular system. However, there is now compelling evidence that a toroidal metallopophyrin does just that in the epoxidation of polybutadiene (see picture).

    4. Ultrafast Electron Crystallography: The Dawn of a New Era (pages 2606–2610)

      John Meurig Thomas

      Version of Record online: 5 MAY 2004 | DOI: 10.1002/anie.200301746

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      Submonolayer sensitivity, spatial resolutions of 0.02 Å, and time resolutions of less than 1 ps are key features of the latest developments in electron crystallography, a method that allows the determination of the structures of solid surfaces (see picture). The road to this powerful technique and a comparison with complementary structure-determination techniques are discussed.

    5. Controversy in Chemistry: What Counts as Evidence?—Two Studies in Molecular Structure (pages 2612–2619)

      Jay A. Labinger and Steve J. Weininger

      Version of Record online: 28 APR 2004 | DOI: 10.1002/anie.200330055

      Hindsight is a wonderful thing: Controversies are always difficult to characterize while they are in progress; however, as shown for the cases of stereochemistry and bond-stretch isomerization, it is much easier once all the evidence has been amassed. These two examples have demonstrated how important it is to consider all the experimental results before coming to a conclusion. The second example shows above all that some evidence is more equal than others—crystal-structure analysis was considered at all stages to be the most reliable.

    6. Superfluid Helium Droplets: A Uniquely Cold Nanomatrix for Molecules and Molecular Complexes (pages 2622–2648)

      J. Peter Toennies and Andrey F. Vilesov

      Version of Record online: 5 MAY 2004 | DOI: 10.1002/anie.200300611

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      Helium droplets as a matrix: Helium droplets (see picture) have unusual properties that are very useful in spectroscopy and in the study of chemical reactions of molecules and complexes. Single molecules (e.g. OSC; S yellow, C black, O red) can be embedded, and homo- and heteronuclear clusters can be formed in their interiors. This unique matrix technique opens the way for a variety of new possible applications in chemistry and physics.

    7. A Molecular Mechanism of Hysteresis in Clay Swelling (pages 2650–2652)

      Tim J. Tambach, Peter G. Bolhuis and Berend Smit

      Version of Record online: 5 MAY 2004 | DOI: 10.1002/anie.200353612

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      Feats of clay: Molecular simulations are used to study the mechanism of clay-swelling hysteresis. A free-energy barrier separating stable layered hydrates is found to be the origin of this hysteresis. The simulations are also used to predict that changing the external pressure on a clay mineral layer can induce hysteresis (see picture).

    8. Catalytic Asymmetric Acylation of (Silyloxy)nitrile Anions (pages 2652–2655)

      David A. Nicewicz, Christopher M. Yates and Jeffrey S. Johnson

      Version of Record online: 5 MAY 2004 | DOI: 10.1002/anie.200353354

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      An enantiopure (salen)aluminum alkoxide complex catalyzes the asymmetric coupling of acylsilanes and cyanoformate esters [Eq. (1) , R=Bn, Et]. The reactions afford unsymmetrical, fully protected malonic acid derivatives that may be elaborated to nonnatural β-amino acid derivatives, and represent the first asymmetric catalytic reactions involving protected cyanohydrin anions.

    9. Synthesis and Characterization of a Quasi-One-Coordinate Lead Cation (pages 2655–2658)

      Shirley Hino, Marcin Brynda, Andrew D. Phillips and Philip P. Power

      Version of Record online: 5 MAY 2004 | DOI: 10.1002/anie.200353365

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      Easily lead: The demethylation of [PbMe(2,6-Trip2C6H3)] (Trip=2,4,6-iPr3C6H2) with tris(perfluorophenyl)borane in toluene affords [Pb(2,6-Trip2C6H3)⋅(η2-MeC6H5)][B(Me)(C6F5)3] (see picture), in which the lead center is singly bound to the 2,6-Trip2C6H3 moiety and also weakly solvated by toluene.

    10. Total Synthesis of (−)-Galanthamine by Remote Asymmetric Induction (pages 2659–2661)

      Sumiaki Kodama, Yoshio Hamashima, Kiyoharu Nishide and Manabu Node

      Version of Record online: 5 MAY 2004 | DOI: 10.1002/anie.200353636

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      A pivotal intramolecular Michael addition to form a fused 5,7,5 ring system and the skeleton of (−)-galanthamine (1) was completely controlled by a remote chiral imidazolidinone auxiliary derived from D-phenylalanine (see scheme). This total synthesis of the allylic alcohol 1 avoids the corresponding enone narwedine, a highly allergenic intermediate in previous syntheses of 1.

    11. A Lockable Light-Driven Molecular Shuttle with a Fluorescent Signal (pages 2661–2665)

      Qiao-Chun Wang, Da-Hui Qu, Jun Ren, Kongchang Chen and He Tian

      Version of Record online: 5 MAY 2004 | DOI: 10.1002/anie.200453708

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      A turn on! A lockable photodriven molecular shuttle is based on a [2]rotaxane that consists of an α-cyclodextrin threaded by a stilbene derivative. The fluorescent signals originate from the naphthalimide stopper and indicate the position of the shuttle. Once unlocked, the device can be turned on by irradiation at 335 nm and turned off by irradiation at 280 nm. The shuttle can be locked or unlocked by the addition acid or alkali, respectively (see picture).

    12. A New Dirhodium(II) Carboxamidate Complex as a Chiral Lewis Acid Catalyst for Enantioselective Hetero-Diels–Alder Reactions (pages 2665–2668)

      Masahiro Anada, Takuya Washio, Naoyuki Shimada, Shinji Kitagaki, Makoto Nakajima, Motoo Shiro and Shunichi Hashimoto

      Version of Record online: 5 MAY 2004 | DOI: 10.1002/anie.200453821

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      Excellent enantioselectivities (up to 99 % ee) and turnover numbers (up to 48 000) were attained in the hetero-Diels–Alder reaction of a diverse range of aldehydes and activated dienes catalyzed by [Rh2(S-bptpi)4] (see scheme).

    13. Formal [3+2] Addition of Acceptor-Substituted Cyclopropylmethylsilanes with Aryl Acetylenes (pages 2669–2671)

      Veejendra K. Yadav and Vardhineedi Sriramurthy

      Version of Record online: 5 MAY 2004 | DOI: 10.1002/anie.200453823

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      Push–pull substitution of cyclopropanes can make these compounds synthetic equivalents of 1,3-dipolar synthons 2, suitable for formal [3+2] addition reactions with aryl acetylenes. Upon treatment with TiCl4, tert-butyldiphenylsilylmethyl-substituted cyclopropyl ketones 1 reacted with aryl acetylenes to furnish cyclopentene derivatives 3 regio- and stereoselectively. R=nBu, tBu, Ph.

    14. High-Content Peptide Microarrays for Deciphering Kinase Specificity and Biology (pages 2671–2674)

      Mike Schutkowski, Ulf Reimer, Sören Panse, Liying Dong, Jose M. Lizcano, Dario R. Alessi and Jens Schneider-Mergener

      Version of Record online: 5 MAY 2004 | DOI: 10.1002/anie.200453900

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      Thousands of kinase assays at one stroke are possible by using high-content peptide microarrays. Such experiments deliver information regarding peptidic kinase substrates and accelerate the development of high-throughput screening assays. Moreover, knowledge-based selection of human sequences allows the reliable detection of downstream targets of protein kinases, as demonstrated for 3-phosphoinositide-dependent protein kinase.

    15. Sceptrin as a Potential Biosynthetic Precursor to Complex Pyrrole–Imidazole Alkaloids: The Total Synthesis of Ageliferin (pages 2674–2677)

      Phil S. Baran, Daniel P. O'Malley and Alexandros L. Zografos

      Version of Record online: 5 MAY 2004 | DOI: 10.1002/anie.200453937

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      Microwave-induced magic: There is a widely held conviction that the antiviral marine alkaloid ageliferin 1 arises biosynthetically from a Diels–Alder reaction which, although possible, has yet to materialize in the laboratory. A total synthesis of 1 from sceptrin is now reported that has led to a new hypothesis for how 1 and other dimeric pyrrole-imidazole alkaloids might be formed in nature.

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      Au32: A 24-Carat Golden Fullerene (pages 2678–2681)

      Mikael P. Johansson, Dage Sundholm and Juha Vaara

      Version of Record online: 22 APR 2004 | DOI: 10.1002/anie.200453986

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      Golden balls! Relativistic quantum chemical theory suggests the existence of an interesting and surprising gold cluster. The all-gold fullerene Au32 (see picture) is structurally very similar to the familiar buckminsterfullerene C60, as it is approximately the same size and hollow. Au32 is stabilized by relativistic effects and spherical aromaticity; the magnetic shielding at the center of the fullerene has the highest predicted value.

    17. An Intramolecular Organocatalytic Cyclopropanation Reaction (pages 2681–2684)

      Nadine Bremeyer, Stephen C. Smith, Steven V. Ley and Matthew J. Gaunt

      Version of Record online: 28 APR 2004 | DOI: 10.1002/anie.200454007

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      Nucleophilic tertiary amines catalyze an intramolecular cyclopropanation reaction to give [n.1.0]bicycloalkanes in good yield (see scheme). The reaction is tolerant of a wide range of functional groups and is highly diastereoselective. Furthermore, when a catalytic amount of a chiral cinchona alkaloid derivative is used the reaction produces cyclopropanes with enantiomeric excess of 94 %. EWG=electron withdrawing group.

    18. Immobilization of a Metallo Schiff Base into a Microporous Coordination Polymer (pages 2684–2687)

      Ryo Kitaura, Goro Onoyama, Hirotoshi Sakamoto, Ryotaro Matsuda, Sin-ichiro Noro and Susumu Kitagawa

      Version of Record online: 5 MAY 2004 | DOI: 10.1002/anie.200352596

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      Wall decoration: Coordinatively unsaturated metal centers (CuII, CoII, and NiII) can be embedded in the pore wall of a microporous coordination polymer containing Schiff base type metalloligands [M(salphdc)]2− (H4salphdc=N,N′-o-phenylenebis(salicylideneimine-5,5′-dicarboxylic acid)). These coordination polymers possess large 1D channels with dimensions of approximately 14×14 Å2 (see structure).

    19. Consecutive Cyclic Pentapeptide Modules Form Short α-Helices that are Very Stable to Water and Denaturants (pages 2687–2690)

      Nicholas E. Shepherd, Giovanni Abbenante and David P. Fairlie

      Version of Record online: 5 MAY 2004 | DOI: 10.1002/anie.200352659

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      A generic approach to mimicking α-helices has been achieved by using sequences of consecutive macrocyclic pentapeptides (for example, cyclo(1[RIGHTWARDS ARROW]5)-Ac-[KARAD]n-NH2) to form 3-turn (see picture) and 4-turn α-helices, which have high conformational stability in water and are resistant to protein-denaturing conditions (65 °C, 8 M guanidine⋅HCl, trypsin digestion).

    20. Water-Soluble Supramolecular Fullerene Assembly Mediated by Metallobridged β-Cyclodextrins (pages 2690–2694)

      Yu Liu, Hao Wang, Peng Liang and Heng-Yi Zhang

      Version of Record online: 5 MAY 2004 | DOI: 10.1002/anie.200352973

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      A coordinated metal center aids water solubility of a supramolecular fullerene assembly. Two cyclodextrins rings are bridged back-to-back in one unit, and these units form an end-to-end intermolecular inclusion complex with fullerene to produce an intermolecular polyfullerene (see picture). Under the right conditions the assembly acts as an efficient photodriven DNA-cleavage reagent.

    21. Direct Evidence for a Furtive State in the Degradation of Carbasalatum Calcicum (pages 2694–2697)

      Philippe Ochsenbein, Michel Bonin, Olivier Masson, Denis Loyaux, Gervais Chapuis and Kurt J. Schenk

      Version of Record online: 5 MAY 2004 | DOI: 10.1002/anie.200353007

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      Blink and you will miss it! The structure of carbasalatum calcicum (CC) has been determined by synchrotron powder diffractometry. By scrutinizing crystal dissolution and nucleation, it was found that the degradation of CC in water involves acetylsalicylatum calcicum (AC) as a furtive species that quickly exchanges its acetylsalicylic acid (ASA) ligands with water (see scheme). The crystal structure of AC is also reported.

    22. Dissolution at the Nanoscale: Self-Preservation of Biominerals (pages 2697–2701)

      Ruikang Tang, Lijun Wang, Christine A. Orme, Tammy Bonstein, Peter J. Bush and George H. Nancollas

      Version of Record online: 5 MAY 2004 | DOI: 10.1002/anie.200353652

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      Dissolution of nanosized crystallites may be inhibited and even suppressed due to their small size. Nanoparticles with size distribution similar to that of critical dissolution pits (see picture) can be kinetically stabilized against further dissolution even in undersaturated solutions. In biological systems, this behavior confers remarkable self-preservation on biominerals in the fluctuating milieu.

    23. Porous Organic–Inorganic Assemblies Constructed from Keggin Polyoxometalate Anions and Calix[4]arene–Na+ Complexes: Structures and Guest-Sorption Profiles (pages 2702–2705)

      Yusuke Ishii, Yasumasa Takenaka and Katsuaki Konishi

      Version of Record online: 5 MAY 2004 | DOI: 10.1002/anie.200453693

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      Amphiphilic pore walls facilitate reversible sorption of short-chain alcohols by the 1D microporous organic–inorganic hybrid [1-Na]3[PW12O40] assembled from calix[4]arene–Na+ complex 1-Na+ (R1=R2=H) and the polyoxotungstate anion [PW12O40]3−. The analogous assembly formed with 2-Na+ (R1=tBu, R2=CH2CO2Et) has a 3D microporous architecture.

    24. Ultrafast Electron Crystallography of Surface Structural Dynamics with Atomic-Scale Resolution (pages 2705–2709)

      Franco Vigliotti, Songye Chen, Chong-Yu Ruan, Vladimir A. Lobastov and Ahmed H. Zewail

      Version of Record online: 23 MAR 2004 | DOI: 10.1002/anie.200453983

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      A formidable contender to X-ray diffraction is ultrafast electron crystallography. Whereas the former is more suited to investigate the bulk of the substrate, the time, length, and sensitivity scales of electron crystallography provide powerful and complementary information on atomic-scale structural dynamics at the surface (see diffraction image of GaAs crystal).

    25. Synthesis and Application of Fluorescence-Labeled Ras-Proteins for Live-Cell Imaging (pages 2711–2714)

      Reinhard Reents, Melanie Wagner, Jürgen Kuhlmann and Herbert Waldmann

      Version of Record online: 5 MAY 2004 | DOI: 10.1002/anie.200353265

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      Seeing is believing! Semisynthetic Ras-proteins with a fluorophore introduced at an appropriate site have been developed as probes for live-cell imaging experiments. They are processed by the cellular machinery, and their intracellular location can then be determined by confocal laser fluorescence microscopy.

    26. The Chemistry of CaII and YbII: Astoundingly Similar But Not Equal! (pages 2714–2718)

      Sjoerd Harder

      Version of Record online: 5 MAY 2004 | DOI: 10.1002/anie.200353557

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      Not a red/green stereographic, but a plot showing the striking similarity between a Ca and Yb complex. The molecular structures, and the NMR and IR spectra of these Ca/Yb benzyl complexes are nearly identical. However, their reactivity in styrene polymerization is completely different: an internally coordinated dibenzylytterbium(II) complex produces polystyrene of high syndiotacticity (r=94.9 %, rr=90.0 %).

    27. A Simple Approach to Nonspherical Electron Densities by Using Invarioms (pages 2718–2721)

      Birger Dittrich, Tibor Koritsánszky and Peter Luger

      Version of Record online: 5 MAY 2004 | DOI: 10.1002/anie.200353596

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      The transfer of multipole parameters from theoretically calculated pseudoatoms (invarioms) allows the derivation of nonspherical electron densities and related properties even from low-resolution X-ray data, the electrostatic potential of tri(L-valine) is obtained in this way (see picture).

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