Angewandte Chemie International Edition

Cover image for Vol. 44 Issue 34

August 26, 2005

Volume 44, Issue 34

Pages 5349–5533

    1. Cover Picture: A Microfabricated Gas–Liquid Segmented Flow Reactor for High-Temperature Synthesis: The Case of CdSe Quantum Dots (Angew. Chem. Int. Ed. 34/2005) (page 5349)

      Brian K. H. Yen, Axel Günther, Martin A. Schmidt, Klavs F. Jensen and Moungi G. Bawendi

      Version of Record online: 22 AUG 2005 | DOI: 10.1002/anie.200590114

      The two-phase flow of the gas–liquid segmented flow reactor with multiple temperature zones shown in the cover picture makes it possible to realize both rapid mixing of reagents and narrow residence-time distributions. The reactor design allows the preparation of colloidal CdSe quantum dots (bottom right) with excellent size distributions at high temperature. For more details, see the Communication by K. F. Jensen, M. G. Bawendi, and co-workers on page 5447 ff. (The authors thank Jane Rempel for assistance with the cover picture.)

    2. Joint Meeting on Medicinal Chemistry in Vienna (pages 5364–5366)

      Rainer E. Martin, Peter Mohr, Wylie Palmer and Henri Stalder

      Version of Record online: 22 AUG 2005 | DOI: 10.1002/anie.200502439

    3. Molecules with Exceptionally Small HOMO–LUMO Gaps (pages 5370–5373)

      Dmitrii F. Perepichka and Martin R. Bryce

      Version of Record online: 20 JUL 2005 | DOI: 10.1002/anie.200500413

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      Mind the gap: HOMO–LUMO gaps less than 0.5 eV have been recently engineered in small organic molecules through extended conjugation and donor–acceptor covalent coupling approaches (see picture). Such compounds reveal a number of unusual electronic properties such as thermo-excited intramolecular electron transfer (in solution) and metallic conductivity (in the solid state).

    4. Hydrogen-Bonding Motifs in Fullerene Chemistry (pages 5374–5382)

      Luis Sánchez, Nazario Martín and Dirk M. Guldi

      Version of Record online: 5 JUL 2005 | DOI: 10.1002/anie.200500321

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      Supramolecular chemistry of C60 is leading the way for the use of C60 as a unique photo- and electroactive building block. Arrays of hydrogen bonds ensure a high degree of order on the nanometer scale, a feature that will be critical in the application of the resulting noncovalently bound ensembles as molecular materials or supramolecular catalysts (see scheme; eT=electron transfer, ET=energy transfer).

    5. Atroposelective Synthesis of Axially Chiral Biaryl Compounds (pages 5384–5427)

      Gerhard Bringmann, Anne J. Price Mortimer, Paul A. Keller, Mary J. Gresser, James Garner and Matthias Breuning

      Version of Record online: 22 AUG 2005 | DOI: 10.1002/anie.200462661

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      Not only classic, atroposelective biaryl couplings lead to stereochemically pure, axially chiral biaryl compounds (see scheme); recently, novel, highly original strategies have also emerged. The authors present a discussion of the structural preconditions of axial chirality and the most successful and innovative of these strategies.

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      Reversible Expansion and Contraction of a 1,2-Diborylated Ferrocene Dimer Promoted by Redox Chemistry and Nucleophile Binding (pages 5428–5433)

      Krishnan Venkatasubbaiah, Lev N. Zakharov, W. Scott Kassel, Arnold L. Rheingold and Frieder Jäkle

      Version of Record online: 12 AUG 2005 | DOI: 10.1002/anie.200502148

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      Two Bs in a pod: The first 1,2-diborylated ferrocene (see structure) was obtained upon reaction of PhBCl2 with 1,1′-bis(trimethylstannyl)ferrocene. Conformational changes in this highly rigid species are triggered either through redox chemistry or the binding of nucleophiles, to render the complex an interesting candidate for the design of new types of molecular machines.

    7. Total Synthesis of Spongistatin 1: A Synthetic Strategy Exploiting Its Latent Pseudo-Symmetry (pages 5433–5438)

      Matthew Ball, Matthew J. Gaunt, David F. Hook, Alan S. Jessiman, Shigeru Kawahara, Paolo Orsini, Alessandra Scolaro, Adam C. Talbot, Huw R. Tanner, Shigeo Yamanoi and Steven V. Ley

      Version of Record online: 1 AUG 2005 | DOI: 10.1002/anie.200502008

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      The challenging structure and potent growth inhibition properties against a variety of human cancer cell lines make Spongistatin 1 (1) an exciting target for total synthesis. Enantioselective total synthesis has been achieved by exploiting a latent element of pseudo-symmetry (- - - - - =pseudo-C2 axis) within the ABCD bis(spiroketal) fragment (red substructure).

    8. Extension of the Applicable Range of Fluorescein: A Fluorescein-Based Probe for Western Blot Analysis (pages 5439–5441)

      Mako Kamiya, Yasuteru Urano, Nobuyoshi Ebata, Masami Yamamoto, Jyunichi Kosuge and Tetsuo Nagano

      Version of Record online: 26 JUL 2005 | DOI: 10.1002/anie.200501542

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      The new star of Westerns: A highly sensitive fluorescence probe for alkaline phosphatase (ALP) based on a fluorescein derivative has been prepared and found to be suitable for use in Western blot analysis. The probe 1 is nonfluorescent but undergoes hydrolysis in the presence of ALP to yield a green-fluorescent derivative 2 and may be used in multicolor labeling in combination with other probes.

    9. Small-Molecule-Induced Folding of a Synthetic Polymer (pages 5441–5447)

      Suhrit Ghosh and S. Ramakrishnan

      Version of Record online: 29 JUL 2005 | DOI: 10.1002/anie.200501448

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      Stack 'em high: A polyimide with pyromellitic diimide units linked by hexaoxyethylene segments can be made to fold by cooperative two-point interactions on addition of a folding agent (see scheme). The ammonium group of the folding agent forms complexes with the oxyethylene spacer which greatly facilitates the formation of charge-transfer complexes between the aromatic units of the two components.

    10. A Microfabricated Gas–Liquid Segmented Flow Reactor for High-Temperature Synthesis: The Case of CdSe Quantum Dots (pages 5447–5451)

      Brian K. H. Yen, Axel Günther, Martin A. Schmidt, Klavs F. Jensen and Moungi G. Bawendi

      Version of Record online: 20 JUN 2005 | DOI: 10.1002/anie.200500792

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      Monodisperse CdSe quantum dots (QDs) with excellent optical properties can be prepared with a gas–liquid segmented flow microreactor with multiple temperature zones (see picture; red=heated; blue=cooled quench zone). The enhanced mixing and narrow residence time distributions of segmented flow produce QDs superior to those prepared in single-phase operations.

    11. In Vivo Optical Imaging of Amyloid Aggregates in Brain: Design of Fluorescent Markers (pages 5452–5456)

      Evgueni E. Nesterov, Jesse Skoch, Bradley T. Hyman, William E. Klunk, Brian J. Bacskai and Timothy M. Swager

      Version of Record online: 1 AUG 2005 | DOI: 10.1002/anie.200500845

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      Routine diagnostics and studies of Alzheimer's disease might benefit form the noninvasive optical imaging of amyloid-β plaques in the brain. A rational design strategy for in vivo amyloid-imaging agents that enter the brain and selectively stain amyloid plaques is presented (see picture), and properties of a promising lead biomarker candidate are reported.

    12. Label-Free Electronic Detection of Thrombin in Blood Serum by Using an Aptamer-Based Sensor (pages 5456–5459)

      Yi Xiao, Arica A. Lubin, Alan J. Heeger and Kevin W. Plaxco

      Version of Record online: 26 JUL 2005 | DOI: 10.1002/anie.200500989

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      Blue, gold, and DNA: A methylene blue (MB) tagged, thrombin-binding DNA aptamer immobilized on a gold surface undergoes a large conformational change upon target binding (see schematic representation; eT: electron transfer). This folding produces a large, readily measurable change in redox current and allows the electrochemical detection of thrombin in blood serum.

    13. Paramagnetic Platinum–Rhodium Octamers Bridged by Halogen Ions To Afford a Quasi-1D System (pages 5459–5464)

      Kazuhiro Uemura, Kôichi Fukui, Hiroyuki Nishikawa, Saiko Arai, Kazuko Matsumoto and Hiroki Oshio

      Version of Record online: 25 JUL 2005 | DOI: 10.1002/anie.200501049

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      Down to the wire: A new class of 1D chain, [-Pt-Rh-Pt4-Rh-Pt-Cl-]n, composed of Pt–Pt and Pt–Rh dimeric complexes linked through metal–metal bonds has been prepared (see structure). This chain of mixed-valent metals (PtII/PtIII and RhII/RhIII) contains one unpaired electron in each octameric segment, leading to unique electrical and magnetic properties.

    14. A DNA–Protein Nanoengine for “On-Demand” Release and Precise Delivery of Molecules (pages 5464–5467)

      Razvan Nutiu and Yingfu Li

      Version of Record online: 25 JUL 2005 | DOI: 10.1002/anie.200501214

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      A DNA aptamer (green in the scheme), an antisense DNA strand (purple), and an enzyme (blue) form a nanoengine that responds to a small-molecule input (red) and dispatches a DNA output. The addition of the input promotes the first stroke of the nanoengine, the action of the enzyme the second stroke. Joint exploration of all components could lead to bionanodevices that can detect a biological malfunction and initiate a repair.

    15. On the Importance of Leaving Group Ability in Reactions of Ammonium, Oxonium, Phosphonium, and Sulfonium Ylides (pages 5468–5471)

      Varinder K. Aggarwal, Jeremy N. Harvey and Raphaël Robiette

      Version of Record online: 1 AUG 2005 | DOI: 10.1002/anie.200501526

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      What controls reactivity of ylides? Computational data show that reactivity in the reactions shown in the scheme is mainly determined by the leaving group ability of the onium group, and this decreases for both intrinsic and thermochemical reasons in the order O>S>N>P. The results are consistent with experimental observations and account for the dearth of examples of phosphorus ylides in these reactions.

    16. Cu2+-Mediated Dehydrogenative Coupling and Hydroxylation of an N-Heterocyclic Ligand: From Generation of a New Tetratopic Ligand to the Designed Assembly of Three-Dimensional Copper(I) Coordination Polymers (pages 5471–5475)

      Sheng Hu, Jing-Cai Chen, Ming-Liang Tong, Bo Wang, Yun-Xin Yan and Stuart R. Batten

      Version of Record online: 29 JUL 2005 | DOI: 10.1002/anie.200501753

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      The hydrothermal reaction of 1,3-di(4-pyridyl)propane with Cu(OH)2 in the presence of 1,4-cyclohexanedicarboxylic acid and dilute HCl generates an unprecedented tetratopic ligand (chtpy) and a family of interesting coordination networks in situ (see scheme). The topological diversification of the CuI–chtpy nets can be controlled simply by changing the molar ratio of the starting materials.

    17. Mimicking the Function of Eggshell Matrix Proteins: The Role of Multiplets of Charged Amino Acid Residues and Self-Assembly of Peptides in Biomineralization (pages 5476–5479)

      Parayil Kumaran Ajikumar, Subramanian Vivekanandan, Rajamani Lakshminarayanan, Seetharama D. S. Jois, R. Manjunatha Kini and Suresh Valiyaveettil

      Version of Record online: 1 AUG 2005 | DOI: 10.1002/anie.200500261

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      An eggshell finish: Designed peptides can be used as a tool to unravel the structure–activity relationships of eggshell matrix proteins. The ordered arrangement of doublets of charged residues on the peptide and its self-assembling characteristics play a key role in the biomimetic nucleation of polycrystalline calcite crystal aggregates (see picture), which models that initiated by the goose eggshell matrix protein, ansocalcin.

    18. Label-Free Detection of Protein–Protein Interactions on Biochips (pages 5480–5483)

      Woon-Seok Yeo, Dal-Hee Min, Robert W. Hsieh, Geoffrey L. Greene and Milan Mrksich

      Version of Record online: 29 JUL 2005 | DOI: 10.1002/anie.200501363

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      Eliminating the middle-man: The combination of MALDI-TOF mass spectrometry and self-assembled monolayers on gold (SAMDI) offers a new detection method for protein–ligand (shown) and protein–protein interactions. Proteins and protein complexes are selectively bound to biochips and then directly analyzed by MALDI-TOF MS without the need for labels.

    19. The “Noncoordinating” Anion Tf2N Coordinates to Yb2+: A Structurally Characterized Tf2N Complex from the Ionic Liquid [mppyr][Tf2N] (pages 5485–5488)

      Anja-Verena Mudring, Arash Babai, Sven Arenz and Ralf Giernoth

      Version of Record online: 26 JUL 2005 | DOI: 10.1002/anie.200501297

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      Not as innocent as it looks: The first anionic Tf2N complex, [Yb(Tf2N)4]2−, has been prepared in the ionic liquid [mppyr][Tf2N] (see crystal structure; blue: N, yellow: S, gray: C, green: F, orange: Yb, red: O; mppyr=1-methyl-1-propyl-pyrrolidinium, Tf=trifloromethanesulfonyl). The coordination of the presumed noncoordinating (“innocent”) Tf2N2− ion could have a decisive influence on reactions in ionic liquids.

    20. Hierarchically Structured Carbon: Synthesis of Carbon Nanofibers Nested inside or Immobilized onto Modified Activated Carbon (pages 5488–5492)

      Dang Sheng Su, Xiaowei Chen, Gisela Weinberg, Achim Klein-Hofmann, Olaf Timpe, Sharifah Bee Abd. Hamid and Robert Schlögl

      Version of Record online: 25 JUL 2005 | DOI: 10.1002/anie.200500685

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      Filling in the gaps of activated carbon by chemical vapor decomposition of ethylene results in hierarchically structured carbon with carbon nanofibers (CNFs) nested inside and immobilized on the surface (see picture). The adsorption experiments show that this nanostructuring of carbon creates novel functions on the surface of activated carbon.

    21. Solid-State Structure and Enantioselective Reactions of a Complex of a 1-Thio-Substituted Propargyllithium and (−)-Sparteine (pages 5492–5496)

      Ralf Otte, Roland Fröhlich, Birgit Wibbeling and Dieter Hoppe

      Version of Record online: 26 JUL 2005 | DOI: 10.1002/anie.200501142

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      A useful transformation in enantioselective synthesis: (−)-Sparteine-assisted lithiation of the propargylic 1-thiocarbamate 1 (Cb=CONiPr2) forms the enantiomerically and diastereomerically pure lithium (−)-sparteine complex 2. Its solid-state structure and application in the asymmetric synthesis of highly enantioenriched 1-thioallenes 3 were investigated.

    22. Dimerization of a Cyclo-1σ4,3σ2,4σ2-Triphosphapentadienyl Radical: Evidence for Phosphorus–Phosphorus Odd-Electron Bonds (pages 5497–5500)

      Tsuyoshi Kato, Heinz Gornitzka, Wolfgang W. Schoeller, Antoine Baceiredo and Guy Bertrand

      Version of Record online: 29 JUL 2005 | DOI: 10.1002/anie.200501369

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      How odd! The title radical can be represented by resonance structures A and B. From A, dimerization refers to a [π22] reaction and results in the formation of two inter-ring P[BOND]P single bonds, whereas from B, only one unpaired electron is supplied from each radical unit, which leads to two inter-ring P[BOND]P one-electron bonds. As a consequence, the isolated dimer features “short” P[BOND]P half-bonds.

    23. Alzheimer's Disease Related Copper(II)- β-Amyloid Peptide Exhibits Phenol Monooxygenase and Catechol Oxidase Activities (pages 5501–5504)

      Giordano F. Z. da Silva and Li-June Ming

      Version of Record online: 29 JUL 2005 | DOI: 10.1002/anie.200501013

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      A gray area in gray matter: The CuII complex of a truncated β-amyloid, CuAβ1–20, catalyzes the oxidation of catechol and the hydroxylation and oxidation of phenol (see picture) with dramatic rate accelerations (≈105–106-fold increases). The Cu–oxygen chemistry of CuAβ may offer both a better understanding of the chemical effect in the brains of patients who suffer from Alzheimer's disease as well as possible treatment strategies of this disease.

    24. Electrografting of Poly(ethylene glycol) Acrylate: A One-Step Strategy for the Synthesis of Protein-Repellent Surfaces (pages 5505–5509)

      Sabine Gabriel, Peter Dubruel, Etienne Schacht, Alain M. Jonas, Bernard Gilbert, Robert Jérôme and Christine Jérôme

      Version of Record online: 29 JUL 2005 | DOI: 10.1002/anie.200500639

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      Hydrophilic adherent coatings: Electrografting of acrylate end-capped poly(ethylene glycol) (PEG) is an important technique for the one-step coating of electroconductive substrates by an adherent hydrophilic coating (see figure). This technique is very efficient for the production of new protein-repellent surfaces.

    25. Formation of an Unsymmetrical Dinuclear Ruthenium Complex with μ-H, μ-OH, and μ-κ2-CO2 Bridges and Multiple Reactive Sites (pages 5509–5513)

      Yasuhiro Arikawa, Shuichi Nagae, Jun-ichi Morishita, Katsuma Hiraki and Masayoshi Onishi

      Version of Record online: 26 JUL 2005 | DOI: 10.1002/anie.200501335

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      Holding on to hydrido: The reactivity of the asymmetric dinuclear ruthenium species 1, which is bridged by three different ligands, is studied. It undergoes ligand-exchange reactions, dehydration with protic acids, and decarboxylation by oxidative addition. Only the bridging hydrido ligand remains intact during all these reactions.

    26. Highly Sensitive MRI Chemical Exchange Saturation Transfer Agents Using Liposomes (pages 5513–5515)

      Silvio Aime, Daniela Delli Castelli and Enzo Terreno

      Version of Record online: 29 JUL 2005 | DOI: 10.1002/anie.200501473

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      Contrasting views: Entrapment of a paramagnetic shift reagent for water protons inside liposomes dramatically improves the sensitivity of chemical exchange saturation transfer agents. The chemical shift of the water entrapped within the liposomes, relative to bulk water, depends upon the nature and concentration of the shift reagent as well as on the permeability of the liposome membrane (see picture; SR=shift reagent, Ln=lanthanide ion).

    27. Enantioselective α-Arylation of Cyclohexanones with Diaryl Iodonium Salts: Application to the Synthesis of (−)-Epibatidine (pages 5516–5519)

      Varinder K. Aggarwal and Berit Olofsson

      Version of Record online: 29 JUL 2005 | DOI: 10.1002/anie.200501745

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      Short cut: Direct asymmetric α-arylation of prochiral ketones has been effected using chiral lithium amide bases and diaryl iodonium salts. The methodology has been employed in a short total synthesis of the alkaloid (−)-epibatidine (see scheme).

    28. Highly Efficient NaNO2-Catalyzed Destruction of Trichlorophenol Using Molecular Oxygen (pages 5520–5523)

      Xinmiao Liang, Dongmei Fu, Renhua Liu, Qing Zhang, Tony Y. Zhang and Xinquan Hu

      Version of Record online: 29 JUL 2005 | DOI: 10.1002/anie.200501470

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      Cleaning up: NaNO2, a simple, inexpensive and biodegradable inorganic compound, acts as a catalyst to activate molecular oxygen for the destruction of polychlorinated phenols. The NaNO2/O2 system efficiently oxidizes the recalcitrant trichlorophenol into CO2 and/or CO and a small fraction of biodegradable organic products with a high rate of conversion (see ion chromatogram).

    29. Asymmetric Photocycloaddition in Solution of a Chiral Crystallized Naphthamide (pages 5523–5526)

      Masami Sakamoto, Atsushi Unosawa, Shuichiro Kobaru, Ayako Saito, Takashi Mino and Tsutomu Fujita

      Version of Record online: 29 JUL 2005 | DOI: 10.1002/anie.200501156

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      Frozen chirality: Achiral naphthamide 1 can be crystallized to give chiral 1*, whose chiral molecular conformation is retained (“frozen”) after the crystals are dissolved in cold THF. Asymmetric photocycloaddition of 1* with 9-cyanoanthracene (9-CNAN) in solution gives cycloadduct 2 with high enantioselectivity.

    30. Direct Mannich and Nitro-Mannich Reactions with Non-Activated Imines: AgOTf-Catalyzed Addition of Pronucleophiles to ortho-Alkynylaryl Aldimines Leading to 1,2-Dihydroisoquinolines (pages 5526–5528)

      Naoki Asao, Salprima Yudha S., Tsutomu Nogami and Yoshinori Yamamoto

      Version of Record online: 26 JUL 2005 | DOI: 10.1002/anie.200500795

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      A variety of 1,2-dihydroisoquinoline derivatives 3 have been prepared in good to high yields by the AgOTf-catalyzed reaction of ortho-alkynylaryl aldimines 1 with various pronucleophiles 2 (see scheme). Treatment of 1 with a stoichiometric amount of AgOTf followed by protonation with TfOH produced 4, which suggests the formation of an isoquinolinium intermediate in the present direct addition reaction. Tf=trifluoromethanesulfonyl.

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      Preview: Angew. Chem. Int. Ed. 34/2005 (page 5533)

      Version of Record online: 22 AUG 2005 | DOI: 10.1002/anie.200590116