Angewandte Chemie International Edition

Cover image for Vol. 43 Issue 24

June 14, 2004

Volume 43, Issue 24

Pages 3087–3203

    1. Cover Picture: Al50C120H180: A Pseudofullerene Shell of 60 Carbon Atoms and 60 Methyl Groups Protecting a Cluster Core of 50 Aluminum Atoms (Angew. Chem. Int. Ed. 24/2004) (page 3087)

      Jean Vollet, Jens R. Hartig and Hansgeorg Schnöckel

      Article first published online: 9 JUN 2004 | DOI: 10.1002/anie.200490074

      A model Al50cluster is part of the largest known molecular organometallic compound comprised of metal, carbon, and hydrogen. A central Al8 unit (blue in the picture) is made up of 42 Al atoms (silver), 12 of which carry pentamethylcyclopentadienyl (Cp*) groups. The 60 methyl groups of the Cp* ligands (red pentagons) produce a surface topolgy reminiscent of a football. Further details on this Al50Cpequation image cluster can be found in the Communication by H. Schnöckel et al. on page 3186 ff.

    2. Graphical Abstract: Angew. Chem. Int. Ed. 24/2004 (pages 3090–3096)

      Article first published online: 9 JUN 2004 | DOI: 10.1002/anie.200490075

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      Direct Evidence for Extremely Facile 1,2- and 1,3-Group Migrations in an FeSi2 System (page 3096)

      Hiromi Tobita, Akihisa Matsuda, Hisako Hashimoto, Keiji Ueno and Hiroshi Ogino

      Article first published online: 9 JUN 2004 | DOI: 10.1002/anie.200490076

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      Hydrogen-Bonded Helices in the Layered Aluminophosphate (C2H8N)2[Al2(HPO4)(PO4)2] (page 3096)

      Yu Song, Jihong Yu, Yi Li, Guanghua Li and Ruren Xu

      Article first published online: 9 JUN 2004 | DOI: 10.1002/anie.200490078

    5. Crystallography: Conserving an Endangered Species (page 3098)

      Hans-Beat Bürgi and Thomas Weber

      Article first published online: 9 JUN 2004 | DOI: 10.1002/anie.200460156

    6. Hybrid Inorganic–Organic Mesoporous Materials (pages 3102–3104)

      Guido Kickelbick

      Article first published online: 30 APR 2004 | DOI: 10.1002/anie.200301751

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      Another brick in the wall: Organic groups that contain several alkoxysilane substituents are applied in the synthesis of hybrid inorganic–organic mesoporous materials (see scheme). The resulting materials contain the organic moiety as an integral part of the wall. Depending on the functionality of the organic groups and on the properties of the functionalized porous material a plethora of potential applications can be envisioned.

    7. The Staudinger Ligation—A Gift to Chemical Biology (pages 3106–3116)

      Maja Köhn and Rolf Breinbauer

      Article first published online: 12 MAY 2004 | DOI: 10.1002/anie.200401744

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      Bioconjugation made easy: The Staudinger ligation between azides and acyl-modified phosphanes is probably the mildest and most chemoselective ligation reaction. It has found widespread application in chemical biology and can even be used in the complex environment of a living cell (see scheme).

    8. A Synthetic Antithrombin III Binding Pentasaccharide Is Now a Drug! What Comes Next? (pages 3118–3133)

      Maurice Petitou and Constant A. A. van Boeckel

      Article first published online: 9 JUN 2004 | DOI: 10.1002/anie.200300640

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      Coagulation inhibition: Heparin has been used clinically as an antithrombotic agent since the 1940s. For decades researchers have been working on the development of alternatives with improved pharmacological properties and better-defined modes of action. The picture shows the synthetic pentasaccharide fondaparinux in the conformation it adopts when complexed with antithrombin III.

    9. Thermally and Light-Induced Valence Tautomeric Transition in a Dinuclear Cobalt–Tetraoxolene Complex (pages 3136–3138)

      Chiara Carbonera, Andrea Dei, Jean-François Létard, Claudio Sangregorio and Lorenzo Sorace

      Article first published online: 19 MAY 2004 | DOI: 10.1002/anie.200453944

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      Getting in tune: A material that undergoes valence tautomerism was obtained by tuning the electronic properties of a cobalt–polyoxolene complex (shown schematically) which contains a tripositive metal ion acting as an ancillary counterpart. The tautomerism, which can be thermally or light induced, is quantitative upon irradiation at 617 nm.

    10. Profiling Primary Protease Specificity by Peptide Synthesis on a Solid Support (pages 3138–3141)

      Ron H. P. Doezé, Beatrice A. Maltman, Claire L. Egan, Rein V. Ulijn and Sabine L. Flitsch

      Article first published online: 9 JUN 2004 | DOI: 10.1002/anie.200353367

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      Reverse screening: A greatly simplified primary screening of protease specificity has been achieved by monitoring the fluorescence during the protease-catalyzed coupling of amino acids instead of peptide hydrolysis on a solid support (see picture, AA=amino acid). This approach paves the way for flexible, rapid, high-throughput identification and characterization of proteases without the need for expensively labeled peptide arrays.

    11. A Trinuclear [NiFe] Cluster Exhibiting Structural and Functional Key Features of [NiFe] Hydrogenases (pages 3141–3144)

      Dieter Sellmann, Frank Lauderbach, Franz Geipel, Frank W. Heinemann and Matthias Moll

      Article first published online: 9 JUN 2004 | DOI: 10.1002/anie.200353440

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      Charged but not changed: A trinuclear [NiFe] cluster combining the key structural features and reactivity of [NiFe] hydrogenases has been prepared (structure shown). Protons oxidize this cluster to its cation, which has the same structural parameters as the neutral form and therefore shows an important key feature of many oxidoreductases: structural rigidity during the electron-transfer processes.

    12. Use of Dynamic Combinatorial Chemistry for the Identification of Covalently Appended Residues that Stabilize Oligonucleotide Complexes (pages 3144–3147)

      Anthony Bugaut, Jean-Jacques Toulmé and Bernard Rayner

      Article first published online: 9 JUN 2004 | DOI: 10.1002/anie.200454041

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      Amplification with kissing: Rapid identification of covalently appended residues that stabilize oligonucleotide complexes has been achieved by using a dynamic combinatorial approach that leads to amplification of the best ligand (see schematic representation). Both a DNA duplex and an RNA loop–loop (kissing) complex were investigated. Melting-temperature experiments confirmed that the amplified species stabilize the complexes.

    13. The Binary Group 4 Azides [Ti(N3)4], [P(C6H5)4][Ti(N3)5], and [P(C6H5)4]2[Ti(N3)6] and on Linear Ti[BOND]N[BOND]NN Coordination (pages 3148–3152)

      Ralf Haiges, Jerry A. Boatz, Stefan Schneider, Thorsten Schroer, Muhammed Yousufuddin and Karl O. Christe

      Article first published online: 19 MAY 2004 | DOI: 10.1002/anie.200454156

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      Out of line? Theory predicts that [Ti(N3)4] should exhibit unprecedented linear Ti[BOND]N[BOND]NN bond angles as a consequence of the α-N atoms of the azide groups acting as tridentate donors into the empty tetrahedral d0 orbitals of a (+IV) Group 4 metal atom. The title compounds were prepared and characterized (see structure). They do not possess linear Ti[BOND]N[BOND]NN angles because their coordination numbers exceed four.

    14. Direct Observation of Intramolecular Hydrogen Bonds in Peptide 310 Helices by 3hJN,C′ Scalar Couplings (pages 3152–3155)

      Massimo Bellanda, Mario Rainaldi, Quirinus B. Broxterman, Bernard Kaptein, Fernando Formaggio, Marco Crisma, Stefano Mammi and Claudio Toniolo

      Article first published online: 9 JUN 2004 | DOI: 10.1002/anie.200454224

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      Differentiating helices: The direct observation of hydrogen bonds by 3hJN,C′ scalar couplings (see picture) is not only possible for α-helix and β-sheet peptides and proteins, but for 310-helical peptides as well. The method also provides information on terminal fraying of helices and allows the discrimination between α and 310 helices.

    15. Cationic and Neutral Four-Coordinate Alkylidene Complexes of Vanadium(IV) Containing Short V[DOUBLE BOND]C Bonds (pages 3156–3159)

      Falguni Basuli, Uriah J. Kilgore, Xile Hu, Karsten Meyer, Maren Pink, John C. Huffman and Daniel J. Mindiola

      Article first published online: 9 JUN 2004 | DOI: 10.1002/anie.200353210

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      Kinetically stable, four-coordinate vanadium(IV) neopentylidene complexes such as [(Nacnac)V[DOUBLE BOND]CHtBu(thf)](BPh4) (Nacnac=[Ar]NC(Me)CHC(Me)N[Ar], Ar=2,6-(CHMe2)2C6H3), which was prepared by oxidatively induced α-hydrogen abstraction from [(Nacnac)V(CH2tBu)2] with AgBPh4 in THF (see structure), contain the shortest V[DOUBLE BOND]C bonds known to date.

    16. Small-Interfering-RNA Expression in Cells Based on an Efficiently Constructed Dumbbell-Shaped DNA (pages 3160–3163)

      Masumi Taki, Yoshio Kato, Makoto Miyagishi, Yasuomi Takagi and Kazunari Taira

      Article first published online: 9 JUN 2004 | DOI: 10.1002/anie.200353445

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      A dumbbell-shaped DNA, expected to be useful for gene therapy, was synthesized by using a novel method. The dumbbell-shaped vector (see picture) contains a small interfering RNA (siRNA) coding sequence, and the vector was used to investigate the RNA interference (RNAi) effect inside cells.

    17. Macrocyclic Sugar-Based Surfactants: Block Molecules Combining Self-Aggregation and Complexation Properties (pages 3163–3167)

      Chantal Larpent, Annabelle Laplace and Thomas Zemb

      Article first published online: 9 JUN 2004 | DOI: 10.1002/anie.200353484

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      Each block carries out a designated task: Amphiphilic molecules are obtained by grafting one or several surfactant blocks with a bulky sugar headgroup onto a macrocyclic complexing block. This modular approach allows control of the structure of the aggregates (see scheme) and formation of micelles insensitive to the presence of complexed metal ions.

    18. Concise Total Synthesis and Structure Assignment of TAN-1085 (pages 3167–3171)

      Ken Ohmori, Keiji Mori, Yuji Ishikawa, Hideyuki Tsuruta, Shunsuke Kuwahara, Nobuyuki Harada and Keisuke Suzuki

      Article first published online: 9 JUN 2004 | DOI: 10.1002/anie.200453801

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      Rapid access to the tetracyclic core of TAN-1085 (1) was possible by exploiting three efficient processes: a tandem electrocyclic reaction (A), a pinacol cyclization (B), and a regioselective monobenzoylation of a 1,2-diol (C), which allowed the first total synthesis of 1.

    19. Visualization of Local Valence Structures in Quasi-One-Dimensional Halogen-Bridged Complexes [Ni1−xPdx(chxn)2Br]Br2 by STM (pages 3171–3175)

      Shinya Takaishi, Hitoshi Miyasaka, Ken-ichi Sugiura, Masahiro Yamashita, Hiroyuki Matsuzaki, Hideo Kishida, Hiroshi Okamoto, Hisaaki Tanaka, Kazuhiro Marumoto, Hiroshi Ito, Shin-ichi Kuroda and Tomohide Takami

      Article first published online: 9 JUN 2004 | DOI: 10.1002/anie.200453905

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      State secrets: Mott–Hubbard and charge-density-wave states have been observed in the quasi-1D bromine-bridged Ni and Pd complexes [M(chxn)2Br]Br2, respectively, using STM (see image for the Ni complex, the arrow denotes the direction of the chain). The spin soliton was also visualized in real space in the Ni-Pd mixed-metal complexes for the first time. chxn: (1R,2R)-diaminocyclohexane.

    20. Highly Efficient Total Synthesis of (+)-Citreoviral (pages 3175–3177)

      Yoshihisa Murata, Tomoyuki Kamino, Toshiaki Aoki, Seijiro Hosokawa and Susumu Kobayashi

      Article first published online: 9 JUN 2004 | DOI: 10.1002/anie.200454212

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      Only eight steps were required for the total synthesis of (+)-citreoviral (3) from chiral imide 1 in 18 % overall yield. The key steps included a highly anti-selective aldol reaction, the stereoselective iodolactonization of a γ,δ-unsaturated β-hydroxyimide, and an intramolecular SN2 reaction of a tertiary alcohol to form intermediate 2.

    21. Monitoring Molecular Recognition of the Ribosomal Decoding Site (pages 3177–3182)

      Sarah Shandrick, Qiang Zhao, Qing Han, Benjamin K. Ayida, Masayuki Takahashi, Geoffrey C. Winters, Klaus B. Simonsen, Dionisios Vourloumis and Thomas Hermann

      Article first published online: 9 JUN 2004 | DOI: 10.1002/anie.200454217

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      Adenine flips out: A combination of X-ray crystallography, 2-aminopurine fluorescence labeling, and the use of aminoglycosides as ligands is exploited to demonstrate conformational transitions in the RNA domain that ensures accurate protein synthesis (see picture). The triggering of a conformational change of an adenine unit in the RNA by ligand binding can be used as the basis of a screening method to discover antibiotics.

    22. An Oxygen-Centered Titanium Square Embedded in a Cuboctahedron of Iodine in the Salt K4[{Ti4O}I12] (pages 3183–3185)

      Liesbet Jongen, Anja-Verena Mudring, Angela Möller and Gerd Meyer

      Article first published online: 9 JUN 2004 | DOI: 10.1002/anie.200453739

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      A round peg in a square hole: The unusual bonding situation within the cluster ion [{Ti4O}I12]4− (see picture) arises through the optimization of strong Ti[BOND]Ti and Ti[BOND]O σ bonding as well as to the absence of Ti[BOND]Ti multiple (π) bonding and the avoidance of Ti[BOND]I antibonding interactions.

    23. Al50C120H180: A Pseudofullerene Shell of 60 Carbon Atoms and 60 Methyl Groups Protecting a Cluster Core of 50 Aluminum Atoms (pages 3186–3189)

      Jean Vollet, Jens R. Hartig and Hansgeorg Schnöckel

      Article first published online: 6 MAY 2004 | DOI: 10.1002/anie.200453754

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      The largest organometallic cluster compound consisting of Al, C, and H only (Al50Cpequation image, Cp*=C5Me5) is a fascinatingly simple structure of comparably high symmetry (see structure). The pentamethylcyclopentadienyl ligands form a carbon shell similar to the arrangement found in fullerene structures.

    24. The Polyhedral Gallium Subhalide [Ga24Br22]⋅10 THF: The First Step on the Path to a New Modification of Gallium? (pages 3190–3192)

      Taike Duan, Elke Baum, Ralf Burgert and Hansgeorg Schnöckel

      Article first published online: 9 JUN 2004 | DOI: 10.1002/anie.200453786

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      Shell suits: Two shells of Ga12 icosahedra characterize the arrangement of 24 gallium atoms in the title compound (see structure). The structure indicates connectivity possibilities of Ga12 units that are analogous to the topology of the α-boron modification.

    25. Micelle Formation from Amphiphilic “Cylindrical Brush”—Coil Block Copolymers Prepared by Metallocene Catalysis (pages 3192–3195)

      Michael W. Neiser, Sandra Muth, Ute Kolb, J. Robin Harris, Jun Okuda and Manfred Schmidt

      Article first published online: 9 JUN 2004 | DOI: 10.1002/anie.200353259

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      Giant rod–coil amphiphilic block copolymers were prepared by metallocene-catalyzed polymerization. The hydrophilic coiled block consists of polymethacrylic acid and the rod component of a hydrophobic cylindrical brush polymer. The high solubility of the stiff block results in the micelles being formed with the stiff block forming the solubilizing corona.

    26. Asymmetric Solid-Phase Synthesis of 6,6-Spiroketals (pages 3195–3199)

      Okram Barun, Stefan Sommer and Herbert Waldmann

      Article first published online: 9 JUN 2004 | DOI: 10.1002/anie.200353609

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      Structurally simplified spiroketals derived from natural products often retain the biological activity of the parent compound. An asymmetric solid-phase synthesis with boron-mediated aldol reactions as key stereodifferentiating transformations provides 6,6-spiroketals in just 12 steps in high yield and with high stereoselectivity (see scheme). The procedure is suitable for the creation of compound libraries for use in medicinal chemistry.

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      Preview: Angew. Chem. Int. Ed. 24/2004 (page 3203)

      Article first published online: 9 JUN 2004 | DOI: 10.1002/anie.200490077

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