Angewandte Chemie International Edition

Cover image for Vol. 42 Issue 21

May 30, 2003

Volume 42, Issue 21

Pages 2319–2431

    1. Cover Picture: Expanding the Functional Group Compatibility of Small-Molecule Microarrays: Discovery of Novel Calmodulin Ligands (Angew. Chem. Int. Ed. 21/2003) (page 2319)

      David Barnes-Seeman, Seung Bum Park, Angela N. Koehler and Stuart L. Schreiber

      Article first published online: 28 MAY 2003 | DOI: 10.1002/anie.200390464

      Small-Molecule Microarrays have provided a robust and scalable means of searching for new small-molecule–protein interactions. The cover picture shows the protein calmodulin binding to a small molecule that was immobilized on a glass surface by using a novel slide/capture method. More about this method and its use is given by S. L. Schreiber et al. on page 2376ff.

    2. Graphical Abstract: Angew. Chem. Int. Ed. 21/2003 (pages 2322–2328)

      Article first published online: 28 MAY 2003 | DOI: 10.1002/anie.200390465

    3. Conformation-Selective Laser Chemistry (pages 2336–2337)

      Martin Goez

      Article first published online: 28 MAY 2003 | DOI: 10.1002/anie.200201626

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      Selection of a conformer by a laser pulse and conformation-specific cleavage by a second laser pulse can be used to control the outcome of a chemical reaction. One of the most recent examples is the selective wavelength-dependent generation of either the 2-propyl cation or corner-protonated cyclopropane from 1-iodopropane (see scheme).

    4. Ketenes in Polymer-Assisted Synthesis (pages 2340–2348)

      Adel Rafai Far

      Article first published online: 28 MAY 2003 | DOI: 10.1002/anie.200201594

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      Ketenes, which are versatile intermediates in organic synthesis, have found a niche of their own in polymer-assisted organic transformations for the preparation of small-molecule libraries. Many of the methods of generating ketenes for such transformations are examined, and the scope of their reactions is discussed.

    5. Higher-Order Organization by Mesoscale Self-Assembly and Transformation of Hybrid Nanostructures (pages 2350–2365)

      Helmut Cölfen and Stephen Mann

      Article first published online: 28 MAY 2003 | DOI: 10.1002/anie.200200562

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      The architecture of organization: By coupling synthesis, self-assembly, and transformation at the mesoscopic scale it should be possible to develop a chemistry of emergent structures based on the time- and scale-dependent coupling of interactive components. This review highlights how the interplay between the aggregation and crystallization of hybrid inorganic–organic building blocks can lead to complex single crystals, organized nanoparticle arrays, and embedded nanostructures with higher-order architecture (see picture).

    6. A Virosome-Mimotope Approach to Synthetic Vaccine Design and Optimization: Synthesis, Conformation, and Immune Recognition of a Potential Malaria-Vaccine Candidate (pages 2368–2371)

      Bernhard Pfeiffer, Elisabetta Peduzzi, Kerstin Moehle, Rinaldo Zurbriggen, Reinhard Glück, Gerd Pluschke and John A. Robinson

      Article first published online: 28 MAY 2003 | DOI: 10.1002/anie.200250348

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      An optimized cyclic peptidomimetic (see picture) of the NPNA-repeat region in the circumsporozoite (CS) protein of P. falciparum was designed. When delivered to the immune system on human-compatible viruslike particles (virosomes), the mimetic effectively elicits sporozoite-binding antibodies. This virosome-mimotope (virotope) approach may be of general value for the design and testing of new synthetic-vaccine candidates.

    7. Magnetically Amplified DNA Assays (MADA): Sensing of Viral DNA and Single-Base Mismatches by Using Nucleic Acid Modified Magnetic Particles (pages 2372–2376)

      Fernando Patolsky, Yossi Weizmann, Eugenii Katz and Itamar Willner

      Article first published online: 28 MAY 2003 | DOI: 10.1002/anie.200250379

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      Taking DNA analysis for a spin: Amplified detection of viral DNA and single-base mutations in nucleic acids is accomplished by the thermally cycled incorporation of biotin labels into DNA replica associated with magnetic particles, by the electrocatalyzed biochemiluminescence transduction of the DNA recognition events, and by the rotation of the magnetic particles on electrode surfaces (see schematic representation).

    8. Expanding the Functional Group Compatibility of Small-Molecule Microarrays: Discovery of Novel Calmodulin Ligands (pages 2376–2379)

      David Barnes-Seeman, Seung Bum Park, Angela N. Koehler and Stuart L. Schreiber

      Article first published online: 28 MAY 2003 | DOI: 10.1002/anie.200351043

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      The importance of the pKa value: Phenols, carboxylic acids, and compounds containing comparably acidic functional groups are covalently captured on a diazobenzylidene-functionalized glass surface. This new covalent slide-capture method has been used to print 6336 diversity-oriented synthesis-derived phenol-containing fused bicycles and tetracycles, from which new calmodulin ligands were identified (see schematic representation).

    9. HR22C16: A Potent Small-Molecule Probe for the Dynamics of Cell Division (pages 2379–2382)

      Srinivas Hotha, Justin C. Yarrow, Janet G. Yang, Sarah Garrett, Kishore V. Renduchintala, Thomas U. Mayer and Tarun M. Kapoor

      Article first published online: 28 MAY 2003 | DOI: 10.1002/anie.200351173

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      A high-throughput, microscopy-based chemical-genetic screen identified HR22C16, which causes a monoastral mitotic block, as a small-molecule probe for cell division (see picture). By using a diastereoselective, traceless solid-phase synthesis and biological assays, a more potent HR22C16 analogue was then identified. A photocaging strategy for HR22C16 was also developed to allow fast temporal control over the function of the target protein Eg5.

    10. Crystallization of an Ordered Mesoporous Nb–Ta Oxide (pages 2382–2385)

      Tokumitsu Katou, Byongjin Lee, Daling Lu, Junko N. Kondo, Michikazu Hara and Kazunari Domen

      Article first published online: 28 MAY 2003 | DOI: 10.1002/anie.200250263

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      The ordered pore structure of 2D hexagonally ordered mesoporous niobium and tantalum mixed oxide has been successfully preserved during crystallization by filling the pores of the precursor with carbon prior to crystallization. Subsequent thermal treatment in an inert atmosphere produces the crystallized product without loss of the ordered mesoporous structure, and the carbon template is removed by calcination in air. Transmission electron microscopy and electron diffraction analyses clarify the preservation of the 2D hexagonally ordered mesoporous structure in single-crystal domains of about 100 nm.

    11. Zwitterionic Relatives to the Classic [(P–P)Rh(solv)2]+ Ions: Neutral Catalysts Active for H[BOND]E Bond Additions to Olefins (E=C, Si, B) (pages 2385–2389)

      Theodore A. Betley and Jonas C. Peters

      Article first published online: 28 MAY 2003 | DOI: 10.1002/anie.200250378

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      Formally zwitterionic bis(phosphanyl)- and bis(amino)borate rhodium(I) complexes (see picture) can catalytically mediate the hydrogenation, hydroacylation, hydroboration, and hydrosilation of double bonds. These neutral systems are shown to be highly active, even under conditions incompatible with their isostructural, but formally cationic, relatives.

    12. Lewis Acid Catalyzed Room-Temperature Michaelis–Arbuzov Rearrangement (pages 2389–2392)

      Pierre-Yves Renard, Philippe Vayron, Eric Leclerc, Alain Valleix and Charles Mioskowski

      Article first published online: 28 MAY 2003 | DOI: 10.1002/anie.200250270

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      The taming of the shrew! For the first time, a broadly applicable efficient room-temperature Arbuzov rearrangement is described. This reaction is accomplished through an atom-economical Lewis acid catalyzed process (see scheme, TMSOTf=trimethylsilyl trifluoromethanesulfonate). The method has been generalized to primary and activated secondary phosphites, phosphinites, and phosphonites.

    13. Insertion of Thiocyanogen into a P[BOND]C Bond and Subsequent Formation of Polysulfide Derivatives (pages 2392–2395)

      Javier Ruiz, Roberto Quesada, Víctor Riera, Marilín Vivanco, Santiago García-Granda and M. Rosario Díaz

      Article first published online: 28 MAY 2003 | DOI: 10.1002/anie.200250621

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      A remarkable lack of cleavage of the S[BOND]S bond characterizes the insertion of thiocyanogen into a P[BOND]C bond of 1 (see scheme) to afford 2. Compound 2 is a valuable reagent for the synthesis of new dimetallic polysulfide derivatives (3 ac, n=2–4). [Mn]=[Mn(CNtBu)(CO)3].

    14. The First X-ray Crystal Structures of Halogenated [70]Fullerene: C70Br10 and C70Br10⋅3 Br2 (pages 2395–2398)

      Sergey I. Troyanov, Alexey A. Popov, Nadezhda I. Denisenko, Olga V. Boltalina, Lev N. Sidorov and Erhard Kemnitz

      Article first published online: 28 MAY 2003 | DOI: 10.1002/anie.200351132

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      C70Br10is the most stable and, apparently, the only product of the C70 bromination in pure bromine and in solution in o-dichlorobenzene. In accordance with the quantum chemical calculations, the ten bromine atoms (orange) form a belt in the equatorial region of the C70 molecule, with nine adjacent pairs of Br atoms located at the 1,4-positions and one pair at the 1,2-position.

    15. Ringing the Changes: A Remarkable Carbene-Free Synthesis of Difluorocyclopropenes (pages 2399–2401)

      Alan K. Brisdon, Ian R. Crossley, Kevin R. Flower, Robin G. Pritchard and John E. Warren

      Article first published online: 28 MAY 2003 | DOI: 10.1002/anie.200250756

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      The end is in sight for the use of difluorocarbene (generated from toxic or inconvenient heavy-metal or gaseous reagents) in the preparation of geminal difluorocyclopropenyl compounds. A series of fluorinated alkynes now serve as precursors to these important small-ring systems (e.g. see picture) through a remarkably facile and convenient transformation initiated by tert-butyllithium.

    16. Parallel Sheet Secondary Structure in β-Peptides (pages 2402–2405)

      Joseph M. Langenhan, Ilia A. Guzei and Samuel H. Gellman

      Article first published online: 28 MAY 2003 | DOI: 10.1002/anie.200350932

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      Diamine-linkedsyn-α,β-dialkyl β-amino acid residues (see picture) have been shown to exhibit parallel sheet secondary structure. Adoption of the parallel hairpin folding pattern is less strongly influenced by linker stereochemistry than for similar parallel hairpins in analogous α-peptide systems.

    17. IPy2BF4-Promoted Intramolecular Addition of Masked and Unmasked Anilines to Alkynes: Direct Assembly of 3-Iodoindole Cores (pages 2406–2409)

      José Barluenga, Mónica Trincado, Eduardo Rubio and José M. González

      Article first published online: 28 MAY 2003 | DOI: 10.1002/anie.200351303

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      All at once! Indoles can be assembled and iodinated in a one-pot process (see scheme) from anilines and their derivatives. This metal-free addition of nitrogen compounds to alkynes is a clean reaction that is promoted by iodonium cations. Such a process provides a general pathway towards utilization of the biologically relevant indole core.

    18. Aqueous Catalytic Pauson–Khand-Type Reactions of Enynes with Formaldehyde: Transfer Carbonylation Involving an Aqueous Decarbonylation and a Micellar Carbonylation (pages 2409–2411)

      Koji Fuji, Tsumoru Morimoto, Ken Tsutsumi and Kiyomi Kakiuchi

      Article first published online: 28 MAY 2003 | DOI: 10.1002/anie.200351384

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      One rhodium(I) complex catalyzes two processes in an overall Pauson–Khand-type reaction of enynes such as 1 with formaldehyde in an aqueous medium to give bicyclic cyclopentenones such as 2 in excellent yields. The use of a water-soluble phosphane ligand in conjunction with a hydrophobic phosphane ligand in the presence of a surfactant promotes the decarbonylation of formaldehyde in the aqueous phase and the carbonylation of enynes in the micellar phase.

    19. Entropically Driven Ring-Opening-Metathesis Polymerization of Macrocyclic Olefins with 21–84 Ring Atoms (pages 2412–2414)

      Philip Hodge and Stephen D. Kamau

      Article first published online: 28 MAY 2003 | DOI: 10.1002/anie.200250842

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      Giant rings make neat monomers: Macrocyclic olefins with up to 84, and possibly even more, ring atoms undergo ring-opening-metathesis polymerization (ROMP) to give high-molecular-weight polymers when the monomer is used neat or at very high concentration (see scheme). This type of ROMP is driven by entropy changes, unlike standard ROMP, which is carried out using strained cyclic monomers and is driven by the enthalpy change of the reaction.

    20. A “Soft-Chemical” Method To Synthesize Lewis Acid Surfaces of Aluminum Oxide (pages 2415–2418)

      A. I. Kozlov, Mayfair C. Kung, W. M. Xue and Harold H. Kung

      Article first published online: 28 MAY 2003 | DOI: 10.1002/anie.200250581

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      Stoichiometric hydrolysis of the monomeric adduct 1 formed from an amine and aluminum tert-butoxide provides aluminum oxide 2 with a high density of Lewis acidic Al surface ions and few hydroxy groups. The amine acts as a protection agent for the coordination site of Al. After the formation of the solid, the amine can be exchanged readily with other Lewis bases, and the surface Al ions that the amine is coordinated to are catalytically active Lewis acid sites.

    21. Determination of the Configuration of an Archaea Membrane Lipid Containing Cyclopentane Rings by Total Synthesis (pages 2419–2421)

      Elvira Montenegro, Bert Gabler, Gesa Paradies, Matthias Seemann and Günter Helmchen

      Article first published online: 28 MAY 2003 | DOI: 10.1002/anie.200250629

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      The fat controller: Thermoacidophilic Archaea possess membranes containing lipids consisting of mixtures of macrocyclic, 72-membered tetraethers composed of saturated isoprenoid chains linked to glycerol or higher sugars. Lipids of this type form highly stable liposomes and, therefore, are of commercial interest. The configurations of lipids containing cyclopentane units have now been determined by total synthesis of the diol 1.

    22. [Ga9(CMe3)9].− —a Persistent Cluster Radical Anion, Boron-Analogous Chemistry with the Heavier Homologue Gallium (pages 2422–2423)

      Werner Uhl, Lars Cuypers, Wolfgang Kaim, Brigitte Schwederski and Rainer Koch

      Article first published online: 28 MAY 2003 | DOI: 10.1002/anie.200351123

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      Family resemblance: While the cluster chemistry of gallium generally proved to be quite different from that of the polyboranes or polyborates, the transfer of one electron to the nonagallium cluster Ga9(CMe3)9 and the formation of its persistent radical anion emphasizes (see formula R=tBu) the close relationship between gallium and boron. The reduction results in a considerable alteration of structural parameters, with the compression of the cluster parallel to its threefold rotation axis.

    23. Site-Directed Alteration of RNA Sequence Mediated by an Engineered Twin Ribozyme (pages 2424–2427)

      Rüdiger Welz, Katrin Bossmann, Christian Klug, Christian Schmidt, Hans-Joachim Fritz and Sabine Müller

      Article first published online: 28 MAY 2003 | DOI: 10.1002/anie.200250611

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      Repair of deletion mutations at the RNA level: A small synthetic twin ribozyme supports the insertion of four additional nucleotides into a predefined site of an arbitrarily chosen substrate RNA (see scheme). This method of RNA repair constitutes a novel approach to the therapy of medically relevant mutations.

    24. Preview: Angew. Chem. Int. Ed. 21/2003 (page 2431)

      Article first published online: 28 MAY 2003 | DOI: 10.1002/anie.200390471

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