Angewandte Chemie International Edition

Cover image for Vol. 44 Issue 24

June 13, 2005

Volume 44, Issue 24

Pages 3635–3785

    1. Cover Picture: Pyrromethene Dialkynyl Borane Complexes for “Cascatelle” Energy Transfer and Protein Labeling (Angew. Chem. Int. Ed. 24/2005) (page 3635)

      Gilles Ulrich, Christine Goze, Massimo Guardigli, Aldo Roda and Raymond Ziessel

      Article first published online: 6 JUN 2005 | DOI: 10.1002/anie.200590080

      An energy-cascade device is created by linking ethynylpyrene fragments to boron centers. The cover picture shows such a Bodipyrene dye in which irradiation of the pyrene moiety gives a virtual Stokes shift of 10 000 cm−1. The background shows a 3D plot of a fluorescence well containing femtomolar amounts of labeled biomaterial. In their Communication on page 3694 ff., G. Ulrich, R. Ziessel, and co-workers describe how biomolecules can be labeled with these dyes, which are very promising for fluorescence imaging.

    2. Chemical Genealogy: Lessons from History (page 3648)

      Pedro Cintas

      Article first published online: 6 JUN 2005 | DOI: 10.1002/anie.200501585

    3. Very Large Container Molecules (pages 3652–3654)

      Kari Rissanen

      Article first published online: 11 MAY 2005 | DOI: 10.1002/anie.200500714

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      Welcome to the superbowl! The coupling of five resorcinarene-based compounds affords the covalent bowl-shaped analogues of hydrogen-bonded hexameric capsular assemblies (see picture). Such molecules offer stability, solubility, and functionality beyond those of their noncovalent cousins, and provide interesting insight into intracavity reactions, molecular transport, and complexation processes.

    4. Hypervalent Iodine Chemistry in Synthesis: Scope and New Directions (pages 3656–3665)

      Thomas Wirth

      Article first published online: 12 APR 2005 | DOI: 10.1002/anie.200500115

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      New reagents and reactions show the potential of hypervalent iodine compounds in organic synthesis: The understanding of the structures and reactivities of iodine(III) and iodine(V) compounds forms the basis for novel synthetic strategies and their application in the synthesis of complex natural products.

    5. Friedel–Crafts-Type Mechanism for the Enzymatic Elimination of Ammonia from Histidine and Phenylalanine (pages 3668–3688)

      László Poppe and János Rétey

      Article first published online: 20 MAY 2005 | DOI: 10.1002/anie.200461377

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      In the enzymatic superelectrophile 5-methylene-3,4-dihydroimidazol-4-one (MIO), delocalization of the lone pair of electrons on the nitrogen atom into the Michael system is prohibited for stereoelectronic reasons, and nucleophilic attack at the exocyclic double bond makes the ring aromatic. The MIO group in histidine and phenylalanine ammonia-lyases activates a β hydrogen atom of the corresponding amino acid and facilitates the elimination of ammonia (see scheme).

    6. Structures of Nonheme Oxoiron(IV) Complexes from X-ray Crystallography, NMR Spectroscopy, and DFT Calculations (pages 3690–3694)

      Eric J. Klinker, József Kaizer, William W. Brennessel, Nathaniel L. Woodrum, Christopher J. Cramer and Lawrence Que Jr.

      Article first published online: 25 MAY 2005 | DOI: 10.1002/anie.200500485

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      Stabilizing the oxoiron(IV) unit: From a combination of X-ray crystallography, NMR spectroscopy, and DFT calculations, the relative thermal stabilities of two oxoiron(IV) complexes with pentaaza ligands, such as that shown in the picture, can be ascribed to the number of pyridine rings that are oriented parallel to the Fe[DOUBLE BOND]O bond. (Fe pink, N blue, O red, C black.)

    7. Pyrromethene Dialkynyl Borane Complexes for “Cascatelle” Energy Transfer and Protein Labeling (pages 3694–3698)

      Gilles Ulrich, Christine Goze, Massimo Guardigli, Aldo Roda and Raymond Ziessel

      Article first published online: 25 MAY 2005 | DOI: 10.1002/anie.200500808

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      All aglow: A new class of highly luminescent dyes is built by the attachment of a pyrene fragment to the boron center of a boradiazaindacene moiety through an ethynyl unit (see scheme). Very efficient energy transfer from the pyrene to the indacene center produces virtual large Stokes shifts, which are maintained, along with strong luminescence (Φ=32–45 %) when the dyes are attached to proteins such as bovine serum albumin.

    8. Control of Biomineralization Dynamics by Interfacial Energies (pages 3698–3702)

      Ruikang Tang, Molly Darragh, Christine A. Orme, Xiangying Guan, John R. Hoyer and George H. Nancollas

      Article first published online: 6 MAY 2005 | DOI: 10.1002/anie.200500153

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      The critical length and density of the steps, rather than step morphology and velocity of deposition, are useful for understanding the effectiveness of the additive molecules in modifying the crystallization kinetics in biomineralization. This biological control stems from a change in solid–solution interfacial energies, which delays the formation of active steps on the growing crystal face (see picture).

    9. Enantioselective Formation of Stereogenic Carbon–Fluorine Centers by a Simple Catalytic Method (pages 3703–3706)

      Mauro Marigo, Doris Fielenbach, Alan Braunton, Anne Kjærsgaard and Karl Anker Jørgensen

      Article first published online: 28 APR 2005 | DOI: 10.1002/anie.200500395

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      An easy protocol has been developed for the formation of stereogenic carbon–fluorine centers by the organocatalytic asymmetric α-fluorination of aldehydes 1. The 2-fluoroaldehydes 4 are formed with 2 as the fluorinating agent and only 1 mol % of a sterically demanding silylated prolinol 3 as catalyst. The 2-fluoroaldehydes are subsequently reduced to the corresponding alcohols 5 without loss of enantiomeric excess.

    10. Direct Asymmetric α-Fluorination of Aldehydes (pages 3706–3710)

      Derek D. Steiner, Nobuyuki Mase and Carlos F. Barbas III

      Article first published online: 13 MAY 2005 | DOI: 10.1002/anie.200500571

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      Linear and branched aldehydes are asymmetrically α-fluorinated with L-proline- and pyrrolidine-based organocatalysts (see scheme; NFSi: N-fluorobenzenesulfonamide). In the first case, yields and enantioselectivities were high; in the second, the yields remained high and the enantioselectivities were moderate. Significantly, linear aldehydes were only monofluorinated.

    11. A Dendritic Tetra(bisphosphonic acid) for Improved Targeting of Proteins to Bone (pages 3710–3714)

      Geeti Bansal, Jennifer E. I. Wright, Cezary Kucharski and Hasan Uludaǧ

      Article first published online: 6 MAY 2005 | DOI: 10.1002/anie.200500350

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      Close to the bone: A dendritic molecule that contains four bone-seeking bisphosphonic acid groups (see picture) has been prepared for targeting proteins to bone tissue. The tetra(bisphosphonic acid) molecule provides a high density of bisphosphonic acid groups per attachment site at the protein and will aid the design of bone-seeking proteins with minimal modification.

    12. A Remarkable Ring Contraction En Route to the Chartelline Alkaloids (pages 3714–3717)

      Phil S. Baran, Ryan A. Shenvi and Christos A. Mitsos

      Article first published online: 18 MAY 2005 | DOI: 10.1002/anie.200500522

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      One-of-a-kind. A bromine-induced rearrangement has been designed for the formation of the spiro-β-lactam ring present in the structurally unique chartelline alkaloids (see picture of chartelline A). This method is used in combination with others to provide rapid access to the carbocyclic skeletons of the chartelline, securine, and securamine alkaloids.

    13. Telluradistibirane and Telluradibismirane: Three-Membered Heterocycles of Heavier Main Group Elements (pages 3717–3720)

      Takahiro Sasamori, Eiko Mieda, Nobuhiro Takeda and Norihiro Tokitoh

      Article first published online: 20 MAY 2005 | DOI: 10.1002/anie.200462122

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      Metal triangles: The first stable telluradistibirane and telluradibismirane derivatives (see structure) have been successfully synthesized by the reaction of an overcrowded distibene (BbtSb[DOUBLE BOND]SbBbt) and dibismuthene (BbtBi[DOUBLE BOND]BiBbt) with nBu3P[DOUBLE BOND]Te, respectively. (C cyan, Si red).

    14. Radical Mechanism of a Place-Exchange Reaction of Au Nanoparticles (pages 3720–3722)

      Petre Ionita, Bruce C. Gilbert and Victor Chechik

      Article first published online: 4 MAY 2005 | DOI: 10.1002/anie.200500518

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      Spin-trapping experiments show the formation of sulfur-centered radicals during a ligand-exchange reaction between Ph3P-protected Au nanoparticles and alkanethiols in air (see picture). Oxidation of the alkanethiols by molecular O2 adsorbed on the nanoparticles is proposed as the key step. The feasibility of such a process is demonstrated by the Au-nanoparticle-catalyzed oxidation of BH4 and tBuOOH with air.

    15. Aqueous Foams Stabilized Solely by Silica Nanoparticles (pages 3722–3725)

      Bernard P. Binks and Tommy S. Horozov

      Article first published online: 11 MAY 2005 | DOI: 10.1002/anie.200462470

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      Foamability and foam stability: By using a novel dispersion method, suitably hydrophobic silica particles can be dispersed in water to form very stable foams through adsorption of particle aggregates at the surfaces of micrometer-sized bubbles. The optical microscope image shows air bubbles in pure water stabilized solely by partially hydrophobic silica nanoparticles (scale bar: 50 μm).

    16. Dicopper and Disilver Complexes of Octaphyrin( Reversible Hydrolytic Cleavage of the Pyrrolic Ring to a Keto–Imine (pages 3726–3729)

      Soji Shimizu, Yasuo Tanaka, Katsuyuki Youfu and Atsuhiro Osuka

      Article first published online: 11 MAY 2005 | DOI: 10.1002/anie.200500676

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      Metallooctaphyrin complexes: Dimetalation of perfluorinated [36]octaphyrin with copper(II) results in the hydrolytic ring opening of one of the pyrrole rings (see structure), whereas with silver ions perfluorinated [36]octaphyrin and meso-pentafluorophenyl-substituted [36]octaphyrin gave disilver(I) complexes of [34]octaphyrin.

    17. An Electrochemically Driven and Electrochemically Regenerated NOx Trap (pages 3730–3732)

      Norman MacLeod, Federico J. Williams, Mintcho S. Tikhov and Richard M. Lambert

      Article first published online: 11 MAY 2005 | DOI: 10.1002/anie.200500393

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      Fort NOx: The principle of an NOx trap based on the use of solid alkali-metal-ion conductors is demonstrated. The trap efficiently stores NOx and subsequently releases mainly NO2 under isothermal conditions (see scheme); this is relevant to the abatement of nitrogen oxides in the exhaust gases of fuel-efficient automotive engines.

    18. Synthesis of cis,cis,cis,cis-[]-1-Azafenestrane with Discovery of an Unexpected Dyotropic Rearrangement (pages 3732–3736)

      Scott E. Denmark and Justin I. Montgomery

      Article first published online: 11 MAY 2005 | DOI: 10.1002/anie.200500367

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      An unprecedented skeletal reorganization initially hindered a concise route based on a tandem [4+2]/[3+2] nitroalkene cycloaddition for the synthesis of the strained title compound. Conditions to suppress the observed dyotropic rearrangement were developed, and X-ray crystallographic analysis of the BF3 derivative (see picture) of the azafenestrane revealed significant planarization around the central carbon atom.

    19. Construction of Substituted N-Hydroxyindoles: Synthesis of a Nocathiacin I Model System (pages 3736–3740)

      K. C. Nicolaou, Sang Hyup Lee, Anthony A. Estrada and Mark Zak

      Article first published online: 13 MAY 2005 | DOI: 10.1002/anie.200500724

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      Generation (1[RIGHTWARDS ARROW]2) and trapping (2[RIGHTWARDS ARROW]3) of the fleeting α,β-unsaturated nitrone system 2 leads to the rare, biologically important N-hydroxyindole 3 in synthetically useful yields. This structural motif is found within the molecule of the antibiotic nocathiacin I.

    20. Drastic Effect of a Single Base Difference between Human and Tetrahymena Telomere Sequences on Their Structures under Molecular Crowding Conditions (pages 3740–3744)

      Daisuke Miyoshi, Hisae Karimata and Naoki Sugimoto

      Article first published online: 29 APR 2005 | DOI: 10.1002/anie.200462667

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      Making a difference: Tetrahymena telomere sequences form well-ordered G-wires in the presence of cosolutes, whereas human telomere sequences remain as compact G-quadruplexes (see picture). A single base difference in telomere sequences therefore can affect telomere function under cell-like conditions. The G-wire structure may be useful in the design of DNA nanomaterials.

    21. Size-Selective and Reversible Encapsulation of Single Small Hydrocarbon Molecules by a Cavitand–Porphyrin Species (pages 3744–3746)

      Jun Nakazawa, Jun Hagiwara, Maki Mizuki, Yuichi Shimazaki, Fumito Tani and Yoshinori Naruta

      Article first published online: 4 MAY 2005 | DOI: 10.1002/anie.200500732

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      An accommodating host: A new capsule-shaped host molecule, the cavitand–porphyrin shown, reversibly encapsulates single hydrocarbon molecules smaller than propane (see picture). With the exception of acetylene, the binding affinities are inversely correlated with the size of the guest hydrocarbons.

    22. Trapping of Proteins under Physiological Conditions in a Nanopipette (pages 3747–3750)

      Richard W. Clarke, Samuel S. White, Dejian Zhou, Liming Ying and David Klenerman

      Article first published online: 10 MAY 2005 | DOI: 10.1002/anie.200500196

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      Caught in a trap and on camera: A nanopipette is used for electrodeless dielectrophoresis and clear evidence is shown, by using wide-field fluorescence imaging (see image), for the reversible trapping of Alexa-488-labeled proteins (protein G and immunoglobulin G) and also of the fluorophore alone. The dielectrophoretic concentration is enhanced by at least a factor of 300 for these fluorophore-labeled proteins.

    23. Ultrastable Rhodamine with Cucurbituril (pages 3750–3754)

      Jyotirmayee Mohanty and Werner M. Nau

      Article first published online: 11 MAY 2005 | DOI: 10.1002/anie.200500502

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      Exceptionally stable aqueous dye solutions, resistant towards aggregation as well as unspecific adsorption to material surfaces, and with improved photostability, in particular at high levels of irradiation, are obtained when the supramolecular host cucurbit[7]uril (CB7) is added to a rhodamine 6G solution. Complexation by CB7 (see picture) increases the fluorescence lifetime because of the low polarizability inside the cucurbituril cavity.

    24. Tetraphosphacyclopentadienyl and Triphosphaallyl Ligands in Iron Complexes (pages 3755–3758)

      Manfred Scheer, Shining Deng, Otto J. Scherer and Marek Sierka

      Article first published online: 11 MAY 2005 | DOI: 10.1002/anie.200500194

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      Different faces of phosphorus chemistry: The reaction of the bicyclotetraphosphine complex 1 with tBuC[TRIPLE BOND]P leads to the first 1,2,3,4-tetraphosphaferrocene complex 2 and an allylic P3-bridged complex 3. Cp′′′=η5-C5H2tBu3.

    25. Template Synthesis of a Coordinated Tetracarbene Ligand with Crown Ether Topology (pages 3759–3763)

      F. Ekkehardt Hahn, Volker Langenhahn, Thomas Lügger, Tania Pape and Duc Le Van

      Article first published online: 11 MAY 2005 | DOI: 10.1002/anie.200462690

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      A template-controlled reaction cascade starting from [Pt(PMe3)4](CF3SO3)2 and 2-azidophenyl isocyanide yields the tetracarbene complex [1](CF3SO3)2. The four NH,NH-stabilized carbene ligands in [1]2+ can be bridged at the metal template by reaction with N,N-dimethylformamide (DMF) and diphosgene to give the coordinated cyclic tetracarbene ligand with crown ether topology in complex [2](Cl)2.

    26. Terminal Borylene Complexes Stabilized by a Transition-Metal Base (pages 3763–3766)

      Holger Braunschweig, Daniela Rais and Katharina Uttinger

      Article first published online: 11 MAY 2005 | DOI: 10.1002/anie.200500302

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      The heat is on: In the first instance of thermal reactivity of the terminal borylenes [(OC)5M[DOUBLE BOND]B[DOUBLE BOND]N(SiMe3)2] (M=Cr, W), the new heterodinuclear complexes [(OC)4M(μ-CO){μ-BN(SiMe3)2}Pd(PCy3)] (see structure; M=Cr) are synthesized. The compounds feature a semibridging borylene ligand and, by virtue of the dative Pd[BOND]B bonding interaction, represent the only examples of terminal borylene species stabilized by a transition-metal base.

    27. Asymmetric Synthesis of the 1-epi Aglycon of the Cripowellins A and B (pages 3766–3769)

      Dieter Enders, Achim Lenzen and Gerhard Raabe

      Article first published online: 13 MAY 2005 | DOI: 10.1002/anie.200500556

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      The unusual [5.3.2]bicyclic structure of the insecticidal Amaryllidaceae alkaloids cripowellins A and B has been synthesized for the first time by a sequence of Sharpless dihydroxylation, ring-closing metathesis (RCM), and intramolecular Heck reaction (see scheme). The asymmetric synthesis of the 1-epi aglycon proceeds with virtually complete diastereo- and enantioselectivity (≥98 % de, ≥98 % ee) in 13 steps and an overall yield of 5.6 %.

    28. Exploring Polymorphism: The Case of Benzene (pages 3769–3773)

      Paolo Raiteri, Roman Martoňák and Michele Parrinello

      Article first published online: 11 MAY 2005 | DOI: 10.1002/anie.200462760

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      Gazing into the crystal ball: The prediction of crystal structures is one of the most challenging problems in theoretical chemistry. In the metadynamics approach described, the search for stable polymorphs is guided by the Gibbs free energy and takes the role of temperature and pressure fully into account. This method was used to predict the polymorphs of benzene (see picture) and solve many contradictions and uncertainties about its phase diagram.

    29. The Ball-Shaped Heteropolytungstates [{Sn(CH3)2(H2O)}24{Sn(CH3)2}12(A-XW9O34)12]36− (pages 3773–3777)

      Ulrich Kortz, Firasat Hussain and Markus Reicke

      Article first published online: 11 MAY 2005 | DOI: 10.1002/anie.200500548

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      Great balls of tungsten: Two polyoxotungstates with spectacular size (almost 1000 atoms), molar mass (approximately 33 000 g mol−1), and spherical symmetry have been synthesized. The dimethyltin-substituted [{Sn(CH3)2(H2O)}24{Sn(CH3)2}12(A-XW9O34)12]36− ions (see polyhedral representation; X=P, As; red octahedra WO6, yellow tetrahedra XO4) consist of 12 (A-XW9O34) Keggin moieties linked by 36 dimethyltin groups resulting in a spherical structure with a cavity 8 Å in diameter.

    30. The Wheel-Shaped Cu20 Tungstophosphate [Cu20Cl(OH)24(H2O)12(P8W48O184)]25− Ion (pages 3777–3780)

      Sib Sankar Mal and Ulrich Kortz

      Article first published online: 11 MAY 2005 | DOI: 10.1002/anie.200500682

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      Anions get wheely big: A Cu20-containing polyoxotungstate of large size and high symmetry was synthesized by making use of the template effect. The wheel-shaped [Cu20Cl(OH)24(H2O)12(P8W48O184)]25− ion (see picture; black W, turquoise Cu, yellow P, violet Cl, red O) is the first transition-metal-substituted derivative of [H7P8W48O184]33− and incorporates more paramagnetic 3d metal ions than any other polyoxotungstate to date.

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      Preview: Angew. Chem. Int. Ed. 24/2005 (page 3785)

      Article first published online: 6 JUN 2005 | DOI: 10.1002/anie.200590082