Angewandte Chemie International Edition

Cover image for Vol. 43 Issue 43

November 5, 2004

Volume 43, Issue 43

Pages 5709–5861

    1. Cover Picture: High-Resolution Soft Lithography: Enabling Materials for Nanotechnologies (Angew. Chem. Int. Ed. 43/2004) (page 5709)

      Jason P. Rolland, Erik C. Hagberg, Ginger M. Denison, Kenneth R. Carter and Joseph M. De Simone

      Version of Record online: 2 NOV 2004 | DOI: 10.1002/anie.200490149

      High-performance imprint lithographic applications are ideally suited for perfluoropolyether-based elastomers. The cover picture shows sub-100-nm sized features replicated by these materials whose successful application comes from their remarkably low surface energy and their high flexibility. The performance of the materials suggests that replication at even smaller sizes may be possible. For more information, see the Communication by J. M. De Simone, K. R. Carter, and co-workers on page 5796 ff.

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      Nanofibers from Functionalized Dendritic Molecules (page 5721)

      Maryna Ornatska, Kathy N. Bergman, Beth Rybak, Sergiy Peleshanko and Vladimir V. Tsukruk

      Version of Record online: 2 NOV 2004 | DOI: 10.1002/anie.200490151

    3. Chiral Metal–Organic Assemblies—A New Approach to Immobilizing Homogeneous Asymmetric Catalysts (pages 5726–5729)

      Li-Xin Dai

      Version of Record online: 25 OCT 2004 | DOI: 10.1002/anie.200460301

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      Beyond classical immobilized catalysts, metal–ligand polymers self-assembled through coordination are easily prepared, have a robust chiral structure, and display a high density of catalytically active units. These heterogeneous catalysts give excellent results for enantioselective reactions and can be recovered and recycled without significant loss of selectivity.

    4. DNA-Based Barcodes, Nanoparticles, and Nanostructures for the Ultrasensitive Detection and Quantification of Proteins (pages 5730–5734)

      Susanne Brakmann

      Version of Record online: 2 NOV 2004 | DOI: 10.1002/anie.200461112

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      Beyond the shadow of a doubt: Detecting antigens, antibodies, pathogens, tumor markers, and potential therapeutics on the femto- to attomolar concentration level is still challenging. Nanostructured materials and the innovative combination of immunoassays with (real-time) PCR and magnetic separation techniques hold promise for the field of ultrasensitive protein analytics.

    5. Sulfatases: Structure, Mechanism, Biological Activity, Inhibition, and Synthetic Utility (pages 5736–5763)

      Sarah R. Hanson, Michael D. Best and Chi-Huey Wong

      Version of Record online: 18 OCT 2004 | DOI: 10.1002/anie.200300632

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      Through the cleavage of sulfate esters sulfatases modulate the activity of a broad range of small molecules and proteoglycans (see picture). These enzymes play critical roles in a number of biological events, including lysosomal degradation, hormone regulation, and signaling processes. The structures of sulfatases, their mechanisms of action, their potential as targets for small-molecule intervention, and applications in synthesis are discussed.

    6. Computational Evidence for the Enamine Mechanism of Intramolecular Aldol Reactions Catalyzed by Proline (pages 5766–5768)

      Fernando R. Clemente and K. N. Houk

      Version of Record online: 14 OCT 2004 | DOI: 10.1002/anie.200460916

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      A comparison of previously proposed models of the C[BOND]C bond-forming step of the title reaction with density functional methods indicate that the most favored one involves an enamine intermediate undergoing a concerted aldol cyclization with proton transfer from the proline carboxylic acid group (see structure). This step is equal in energy to the intramolecular deprotonation leading to the enamine, and both are partially rate-determining steps.

    7. Helix inside a Helix: Encapsulation of Hydrogen-Bonded Water Molecules in a Staircase Coordination Polymer (pages 5769–5772)

      Bellam Sreenivasulu and Jagadese J Vittal

      Version of Record online: 2 NOV 2004 | DOI: 10.1002/anie.200460516

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      A stream of water molecules, held together by hydrogen bonding, forms a left-handed helix within the helical channels of a left-handed staircaselike metal coordination polymer. The result is a novel helix-in-a-helix structure. The water-filled channel can be seen on viewing the coordination polymer along the b axis (see picture; C gray, N blue, Ni green, O red).

    8. Building Molecular Minerals: All Ferric Pieces of Molecular Magnetite (pages 5772–5775)

      Guy W. Powell, Hannah N. Lancashire, Euan K. Brechin, David Collison, Sarah L. Heath, Talal Mallah and Wolfgang Wernsdorfer

      Version of Record online: 2 NOV 2004 | DOI: 10.1002/anie.200460636

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      Mimicking magnetic minerals: Controlled hydrolysis of iron(III) salts leads to all-ferric molecular fragments with the iron and oxygen topology of magnetite and large spin ground states (see structure; yellow Fe, red O, blue N, gray C).

    9. Self-Assembly of Interpenetrating Coordination Nets Formed from Interpenetrating Cationic and Anionic Three-Dimensional Diamondoid Cluster Coordination Polymers (pages 5776–5779)

      Kai Liang, Hegen Zheng, Yinglin Song, Michael F. Lappert, Yizhi Li, Xinquan Xin, Zixiang Huang, Jiutong Chen and Shaofang Lu

      Version of Record online: 2 NOV 2004 | DOI: 10.1002/anie.200460681

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      Tetrathiometalates [WS4]2− are the nodal building blocks in a new kind of heterometallic interpenetrating three-dimensional cluster coordination polymer (see picture) that has interesting nonlinear optical properties. The polymer exhibits optical self-focusing behavior and reverse saturable absorption effects.

    10. Modulation of Compactness and Long-Range Interactions of Unfolded Lysozyme by Single Point Mutations (pages 5780–5785)

      Julia Wirmer, Christian Schlörb, Judith Klein-Seetharaman, Ryoma Hirano, Tadashi Ueda, Taiji Imoto and Harald Schwalbe

      Version of Record online: 2 NOV 2004 | DOI: 10.1002/anie.200460907

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      The non-native states of the model protein hen lysozyme (native state shown in picture) were investigated by using site-directed mutagenesis in combination with high-resolution NMR spectroscopy. The disruptions of the interactions between hydrophobic clusters by single point mutations dramatically alter the overall compactness of the unfolded state: single point mutations can turn a compact unfolded state into an extended state.

    11. Synthesis of a Large-Scale Highly Ordered Porous Carbon Film by Self-Assembly of Block Copolymers (pages 5785–5789)

      Chengdu Liang, Kunlun Hong, Georges A. Guiochon, Jimmy W. Mays and Sheng Dai

      Version of Record online: 2 NOV 2004 | DOI: 10.1002/anie.200461051

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      Made to order: The synthesis of well-defined porous carbon films involves four steps: 1) monomer–block copolymer film casting, 2) structure refining through solvent annealing, 3) polymerization of the carbon precursor, and 4) carbonization. The resulting films, such as that depicted, have potential as separation membranes, chemical sensors, and catalysts.

    12. Coupled Hydrogen-Bonding Networks in Polyhydroxylated Peptides (pages 5789–5791)

      Peter Tremmel and Armin Geyer

      Version of Record online: 25 OCT 2004 | DOI: 10.1002/anie.200461099

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      Information transfer: Crystal structures of bicyclic dipeptide analogues within oligopeptides are described for the first time. The bicyclic dipeptides occupy the i to i+1 positions of either βI or βII turns. The rigidified dipeptides form hydrogen-bonding networks which transfer structural information along chains of ambident proton donors and acceptors over several Å (see structures; arrows: hydrogen bonds, red O, blue N, yellow S).

    13. Asymmetric Double Proton Transfer of Excited 1:1 7-Azaindole/Alcohol Complexes with Anomalously Large and Temperature-Independent Kinetic Isotope Effects (pages 5792–5796)

      Oh-Hoon Kwon, Young-Shin Lee, Han Jung Park, Yongho Kim and Du-Jeon Jang

      Version of Record online: 2 NOV 2004 | DOI: 10.1002/anie.200461102

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      Bridging alcohols, tunneling protons: The intrinsic proton-transfer dynamics of cyclic H-bonded 1:1 7-azaindole/alcohol complexes in n-alkanes has been investigated at the lowest-lying excited singlet state with variation of alcohol, solvent, isotope, and temperature by using static and time-resolved spectroscopy. The proton transfer occurs asymmetrically, and the rate is governed by tunneling although it is assisted by heavy-atom motions.

    14. High-Resolution Soft Lithography: Enabling Materials for Nanotechnologies (pages 5796–5799)

      Jason P. Rolland, Erik C. Hagberg, Ginger M. Denison, Kenneth R. Carter and Joseph M. De Simone

      Version of Record online: 11 OCT 2004 | DOI: 10.1002/anie.200461122

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      Making a good impression: Photocurable, liquid perfluoropolyethers (PFPEs) are ideal materials for high-resolution (<100 nm) pattern transfer and imprint lithographic processes (see pictures). PFPEs possess attributes of both elastomers and rigid materials, exhibit a remarkably low surface energy, mold extremely small features with high fidelity, resist swelling by organic solvents, and endure repetitive molding procedures.

    15. Photocontrol of Smad2, a Multiphosphorylated Cell-Signaling Protein, through Caging of Activating Phosphoserines (pages 5800–5803)

      Michael E. Hahn and Tom W. Muir

      Version of Record online: 2 NOV 2004 | DOI: 10.1002/anie.200461141

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      Expressed-protein ligation has been used for the semisynthetic preparation of a Smad2 protein with caged activating phosphoserine residues. Biochemical and cell biological experiments show that the caged protein is activated upon irradiation with UV light (see scheme). This sets the stage for the detailed kinetic analysis of Smad2 function in living cells.

    16. Self-Assembly of Cyclic Metal–DNA Nanostructures using Ruthenium Tris(bipyridine)-Branched Oligonucleotides (pages 5804–5808)

      Debbie Mitra, Nicolas Di Cesare and Hanadi F. Sleiman

      Version of Record online: 2 NOV 2004 | DOI: 10.1002/anie.200460255

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      A discrete cyclic nanostructure was obtained through the self-assembly of oligonucleotide-branched metal complexes. The picture shows the metal–DNA nanostructure, which contains two DNA double-helical arms and two relatively rigid redox- and photoactive [Ru(bpy)3]2+ vertices.

    17. Ru(II) Tris(bipyridyl) Complexes with Six Oligonucleotide Arms as Precursors for the Generation of Supramolecular Assemblies (pages 5808–5811)

      Kristen M. Stewart, Javier Rojo and Larry W. McLaughlin

      Version of Record online: 2 NOV 2004 | DOI: 10.1002/anie.200460399

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      The 3D starshaped Ru–bpy–DNA complex pictured comprises a ruthenium(II) tris(bipyridyl) center with six DNA 20-mer sequences tethered through linkers at its 4- and 4′-positions. The complexes 1 and 2 hybridize with six complementary 20-mer strands to form duplex arms. Alternatively, the complementary DNA strands in 1 and 2 hybridize with each other to form larger nanoscale assemblies.

    18. The Catalytic Activity of “Naked” Gold Particles (pages 5812–5815)

      Massimiliano Comotti, Cristina Della Pina, Roberto Matarrese and Michele Rossi

      Version of Record online: 2 NOV 2004 | DOI: 10.1002/anie.200460446

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      Reducing size helps to oxidize: Unsupported gold particles behave as an efficient catalyst for the aerobic oxidation of glucose, showing a similar activity to enzymatic systems. The catalytic activity is inversely proportional to the particle diameter (d, see graph). With carbon-supported gold, no gold–support interaction is found; however, the use of a support avoids particle aggregation thus preserving the original activity for longer.

    19. An Aromatic Anion Receptor: Anion–π Interactions do Exist (pages 5815–5817)

      Paul de Hoog, Patrick Gamez, Ilpo Mutikainen, Urho Turpeinen and Jan Reedijk

      Version of Record online: 2 NOV 2004 | DOI: 10.1002/anie.200460486

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      A particularly challenging task is the design of anion receptors, because anions are larger than cations and are pH- and solvent-sensitive. The first host for anionic guests is a dendritic octadentate N ligand, which upon reaction with CuCl2, encapsulates chloride ions (Cl6, see picture) as guests by means of anion–π interactions in an electron-deficient cavity formed by four pyridine rings.

    20. Nanofiber Formation in the Chemical Polymerization of Aniline: A Mechanistic Study (pages 5817–5821)

      Jiaxing Huang and Richard B. Kaner

      Version of Record online: 2 NOV 2004 | DOI: 10.1002/anie.200460616

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      Stirring stuff: The morphological evolution of polyaniline from nanofibers to agglomerates during its chemical polymerization shows that the key to producing pure nanofibers is to suppress secondary growth after formation of the nanofibers. A simple and effective method for the synthesis of nanofibers was thus developed in which the polymerization is carried out in a rapidly mixed single-phase reaction (see scheme).

    21. Total Synthesis of Apicularen A through Transannular Pyran Formation (pages 5821–5823)

      Andreas F. Petri, Alexander Bayer and Martin E. Maier

      Version of Record online: 2 NOV 2004 | DOI: 10.1002/anie.200460760

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      A macrocyclization–transannulation strategy is the crux of an efficient total synthesis of the benzolactone enamide apicularen A (see scheme; Bn=benzyl). Key steps include a four-component coupling, a Stille cross-coupling to introduce the aromatic moiety, and the formation of the enamide from a hemiaminal. The size-selective macrolactonization of the ethoxyvinyl ester shown was followed by transannular etherification in excellent yield.

    22. Unusual Reactivity of a Nickel N-Heterocyclic Carbene Complex: tert-Butyl Group Cleavage and Silicone Grease Activation (pages 5824–5827)

      Stephen Caddick, F. Geoffrey N. Cloke, Peter B. Hitchcock and Alexandra K. de K. Lewis

      Version of Record online: 2 NOV 2004 | DOI: 10.1002/anie.200460955

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      Reaction lubrication? The reaction between [Ni(1,5-cod)2] (cod=cyclooctadiene) and 1,3-bis-tert-butylimidazol-2-ylidene in the presence of silicone grease affords the siloxane bridged dimer [{Ni[C(NtBuCH)2][O(Me2SiOSiMe2)-μ-O]}2]. In a greaseless apparatus, the same reaction yields the dimer 1 (see structure), via two structurally characterized intermediates.

    23. Surface-Confined Metalloporphyrin Oligomers (pages 5827–5830)

      Hal Van Ryswyk, Erin E. Moore, Neel S. Joshi, Rebecca J. Zeni, Todd A. Eberspacher and James P. Collman

      Version of Record online: 2 NOV 2004 | DOI: 10.1002/anie.200460992

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      The modular assembly of metalloporphyrin oligomers through the stepwise addition of Ru–porphyrin units and a bidentate linking ligand (L, see graphic) onto a surface-confined isonicotinate ligand is reported. Electrochemical measurements of the resulting oligomer show that electrons are transported along the length of its backbone.

    24. Arsenic–π Interactions Stabilize a Self-Assembled As2L3 Supramolecular Complex (pages 5831–5833)

      W. Jake Vickaryous, Rainer Herges and Darren W. Johnson

      Version of Record online: 2 NOV 2004 | DOI: 10.1002/anie.200461011

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      An As2L3metallocryptand is the result of a new predictive design strategy for forming self-assembled supramolecular arsenic complexes. The assembly is remarkably stable to a variety of competing metal ions, harsh acid, and excess ligand. X-ray crystallographic studies and density functional calculations suggest that a strong arsenic–π interaction adds stability to the structure.

    25. yDNA: A New Geometry for Size-Expanded Base Pairs (pages 5834–5836)

      Haige Lu, Kaizhang He and Eric T. Kool

      Version of Record online: 2 NOV 2004 | DOI: 10.1002/anie.200461036

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      Room for expansion: Insertion of a benzene ring into the natural adenine heterocycle to generate the analogue yA results in the formation of base pairs that are 2.4 Å wider than natural ones (see structure). Melting temperature and free energy data show that yA⋅T and T⋅yA pairs can self-assemble into cooperative helices that are considerably more stable than natural DNA. Thus, yDNA may be a candidate for a new genetic system.

    26. Phosphine-Promoted Conversion of Oxo(dithiolato)rhenium(V) into Thio(thiolatoalkyl)rhenium(V) Compounds (pages 5837–5839)

      Ming Li, Arkady Ellern and James H. Espenson

      Version of Record online: 2 NOV 2004 | DOI: 10.1002/anie.200461060

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      Rhenium reactions: A reaction under mild conditions between oxo(dithiolato)rhenium(V) complex 1 and triphenylphosphine gives 2. In the reaction a Re[TRIPLE BOND]O bond is cleaved, P[DOUBLE BOND]O and Re[TRIPLE BOND]S bonds are formed at the expense of a CH2S[BOND]Re bond, and a new Re[BOND]C bond is formed converting a six-membered chelate ring into a five-membered one.

    27. Solid-Phase Synthesis of Lipidated Peptides (pages 5839–5842)

      Goran Kragol, Maria Lumbierres, Jose M. Palomo and Herbert Waldmann

      Version of Record online: 2 NOV 2004 | DOI: 10.1002/anie.200461150

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      Blockers, anchors, and reporters: A solid-phase method for the synthesis of lipidated peptides (see scheme) relies on the base-labile Fmoc group to block the N-terminus, an oxidation-labile hydrazide linker for anchoring to the solid support, and lipidated amino acid building blocks incorporating labels or photoactivatable groups.

    28. Analysis of Poly(carbon suboxide) by Small-Angle X-ray Scattering (pages 5843–5846)

      Matthias Ballauff, Li Li, Sabine Rosenfeldt, Nico Dingenouts, Johannes Beck and Petra Krieger-Beck

      Version of Record online: 2 NOV 2004 | DOI: 10.1002/anie.200460263

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      Band substances: The polymerization of C3O2 (see picture left, at −10 °C) into a red-brown, solid polymer (right) having identical composition has been known for almost 100 years. However, the constitution of the polymer remained unknown. Small-angle X-ray scattering studies of the dissolved polymer show that it forms a stiff bandlike molecule with approximately 40 monomeric units, thus confirming the predicted bandlike structure with condensed α-pyrone rings.

    29. Synthesis of Beltenes by Reactions of 5,6,11,12-Tetradehydrodibenzo[a,e]cyclooctene with [CpCo(CO)2] Derivatives (pages 5846–5849)

      Björn Hellbach, Frank Rominger and Rolf Gleiter

      Version of Record online: 2 NOV 2004 | DOI: 10.1002/anie.200460772

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      Cobalt studs the beltenes shown (R=H, CO2Me, SiMe3, 5 Me), which consist of annelated, conjugated four- and eight-membered rings. These strained molecules were synthesized in a one-pot reaction by a template supported trimerization of 5,6,11,12-tetradehydrodibenzo[a,e]cyclooctene.

    30. Hydrogen Bond Mediated Enantioselectivity of Radical Reactions (pages 5849–5851)

      Tobias Aechtner, Martina Dressel and Thorsten Bach

      Version of Record online: 2 NOV 2004 | DOI: 10.1002/anie.200461222

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      The chiral complexing reagent 1 used in the reductive cyclization of 3-(ω-iodoalkylidene)piperidin-2-ones in the presence of Bu3SnH and with BEt3 as the initiator (see scheme) leads to good enantioselectivities thanks to its hydrogen bond mediated association with the radical intermediate. As this example shows, high stereoselectivities are possible for radical reactions proceeding through H-bonded intermediates.

    31. Synthesis and Photophysics of a Neutral Organic Mixed-Valence Compound (pages 5851–5856)

      Alexander Heckmann, Christoph Lambert, Mark Goebel and Rüdiger Wortmann

      Version of Record online: 2 NOV 2004 | DOI: 10.1002/anie.200460495

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      Maintaining neutrality: A perchlorinated triarylmethyl radical and a triarylamine redox center were combined in the design of a neutral organic mixed-valence compound (see picture). The neutral character of this compound facilitated a detailed study of its solvatochromic behavior and the direct determination of the electronic coupling and the dipole moments in the ground and excited state by electroptical absorption measurements.

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