Angewandte Chemie International Edition

Cover image for Vol. 42 Issue 5

February 3, 2003

Volume 42, Issue 5

Pages 475–587

    1. Cover Picture: One Century of Aryne Chemistry (Angew. Chem. Int. Ed. 5/2003) (page 475)

      Hans Henning Wenk, Michael Winkler and Wolfram Sander

      Article first published online: 30 JAN 2003 | DOI: 10.1002/anie.200390144

      A century of aryne chemistry has not dampened the interest in this class of reactive intermediates. The cover picture shows the structure of a calicheamicin–DNA complex, the “warhead” of which is a cyclic enediyne unit (highlighted). The biological activity of the enediyne cytostatics is based on the depicted Bergman cyclization of the enediyne to a didehydrobenzene biradical. More about these short-lived species is given by Sander et al. on pp. 502 ff.

    2. Enzymatic Catalysis of the Peptidyl–Prolyl Bond Rotation: Are Transition State Formation and Enzyme Dynamics Directly Linked? (pages 490–492)

      Jörg Fanghänel

      Article first published online: 30 JAN 2003 | DOI: 10.1002/anie.200390149

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      The search for the answer to the question posed in the title has been helped by results by Eisenmesser et al. on the cyclophilin 18-catalyzed peptidyl–prolyl cis/trans isomerization. Here their results are discussed in connection with previously published data about the catalytic mechanism of this enzyme class. For several of the amino acid side chains (see picture) present in the active center of the enzyme it could be shown that they are involved in substrate binding or in formation of the transition state.

    3. Recent Developments in Protein Microarray Technology (pages 494–500)

      David S. Wilson and Steffen Nock

      Article first published online: 30 JAN 2003 | DOI: 10.1002/anie.200390150

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      Small and fast: The miniaturization and parallelization of protein microarrays has made it possible to measure simultaneously the interactions between proteins and numerous analytes in a small biological sample. These microarrays consist of numerous, about 50–200 μm, spots with surface-bound proteins (see picture). This will enable the throughput of proteomic analysis to be increased dramatically.

    4. One Century of Aryne Chemistry (pages 502–528)

      Hans Henning Wenk, Michael Winkler and Wolfram Sander

      Article first published online: 30 JAN 2003 | DOI: 10.1002/anie.200390151

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      One century the after postulation of the first aryne (didehydrobenzofuran 1) as a reactive intermediate, research activities in this area are more prevalent than ever before. The discovery of the endiyne cytostatics in particular has promoted a renaissance of aryne chemistry. Despite considerable progress during the last few years many questions still remain unanswered and, therefore, interest in aryne chemistry—parent systems 24—is expected to continue far into the future.

    5. A Hexanuclear Iridium Chain (pages 529–532)

      Cristina Tejel, Miguel A. Ciriano, B. Eva Villarroya, José A. López, Fernando J. Lahoz and Luis A. Oro

      Article first published online: 30 JAN 2003 | DOI: 10.1002/anie.200390152

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      Electrons in chains: A novel metallic chain made up of six iridium atoms (see picture) with an average oxidation state of +1.33 has been found in the complex HH,HT,HH-[Ir6(μ-OPy)6(I)2(CO)12] (Opy=2-pyridonate, H=head, T=tail). This complex provides a new link in the electronic sequence connecting dinuclear IrI and IrII complexes.

    6. Nanoporous Lanthanide–Copper(II) Coordination Polymers: Syntheses and Crystal Structures of [{M2(Cu3(iminodiacetate)6)}⋅8 H2O]n (M=La, Nd, Eu) (pages 532–535)

      Yan-Ping Ren, La-Sheng Long, Bing-Wei Mao, You-Zhu Yuan, Rong-Bin Huang and Lan-Sun Zheng

      Article first published online: 30 JAN 2003 | DOI: 10.1002/anie.200390153

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      Water shortage: The structures of the three-dimensional coordination polymers [{M2(Cu3(iminodiacetate)6)}⋅8 H2O]n (M=La (1), Nd (2), and Eu (3)) contain water molecules that are located within channels throughout the lattice structure (see picture). Investigation of their thermal stability shows that the frameworks remained intact when the guest water molecules were removed. Rehydration of the La and Eu species leads to polymers with only five lattice water molecules per polymer unit, which corresponds to a change in the bonding characteristics of the water molecules.

    7. Design and Application of an α-Helix-Mimetic Scaffold Based on an Oligoamide-Foldamer Strategy: Antagonism of the Bak BH3/Bcl-xL Complex (pages 535–539)

      Justin T. Ernst, Jorge Becerril, Hyung Soon Park, Hang Yin and Andrew D. Hamilton

      Article first published online: 30 JAN 2003 | DOI: 10.1002/anie.200390154

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      The prevention of cell death by the antiapoptotic protein Bcl-xL has been linked to a number of cancers. Bcl-xl binds to the BH3 domain of the proapoptotic protein Bak, thus preventing programmed cell death. A competitive assay and docking studies have shown that the polyamide scaffold 1, which was synthesized based on a rational structure-based design, interferes with the Bak BH3/Bcl-xl complexation.

    8. Stabilization of Tricoordinate Pyramidal Boron: Theoretical Studies on CBSiH5, BSi2H5, CBGeH5, and CBSnH5 (pages 539–542)

      Kalathingal T. Giju, Ashwini Kumar Phukan and Eluvathingal D. Jemmis

      Article first published online: 30 JAN 2003 | DOI: 10.1002/anie.200390155

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      Discovery of new pyramids: Theoretical studies have characterized CBSiH5, BSi2H5, CBGeH5, and CBSnH5, all of which have a tricoordinate pyramidal boron atom as minima on their respective potential energy surfaces (see picture). The extent of pyramidalization, as well as the energy for inversion through the planar structure, is dependent on the substituents of the boron atom.

    9. ℝPM-1: A Recyclable Nanoporous Material Suitable for Ship-In-Bottle Synthesis and Large Hydrocarbon Sorption (pages 542–546)

      Long Pan, Haiming Liu, Xuegong Lei, Xiaoying Huang, David H. Olson, Nicholas J. Turro and Jing Li

      Article first published online: 30 JAN 2003 | DOI: 10.1002/anie.200390156

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      Narrow windows and large supercavities comprise the novel nanoporous coordination organometallic structure ℝPM-1, which has a two-fold interpenetrating 3D network containing unique open channels (see picture). ℝPM-1 exhibits a high sorption capacity for large hydrocarbons and superior size/shape selectivity for the photolysis of ortho-methyl dibenzyl ketone (o-MeDBK; 100 % cage effect). A completely reversible structural transformation takes place between ℝPM-1 and a nonporous 1D compound, which allows a full recovery of the o-MeDBK derived products (100 % mass balance).

    10. The Preparation of a Double Metallahelicate Containing 28 Copper Atoms (pages 546–549)

      James A. Johnson, Jeff W. Kampf and Vincent L. Pecoraro

      Article first published online: 30 JAN 2003 | DOI: 10.1002/anie.200390157

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      Both L- or D-norvaline hydroxamic acids undergo one-step reactions with acetate, chloride, and CuII ions to form self-assembled metallahelicates that contain 20 chiral carbon and four chiral metal centers. Enantiopure complexes of over three nanometers in length, and composed of either P- or M-type double-stranded helical oligomers (see scheme), have been isolated.

    11. Total Synthesis of (±)-Photodeoxytridachione through a Lewis Acid Catalyzed Cyclization (pages 549–552)

      Aubry K. Miller and Dirk Trauner

      Article first published online: 30 JAN 2003 | DOI: 10.1002/anie.200390158

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      Concerted or stepwise: The concise total synthesis of the molluscan polypropionate photodeoxytridachione (3) features a Lewis acid catalyzed cyclization of tetraenoic ester 1 to form bicylo[3.1.0]hexene 2 as a key step. The stereochemistry of the cyclization can be rationalized in terms of a stepwise or a concerted mechanism.

    12. [{N(PPh3)2}2{Os18Pd36-C)2(CO)42}]: An Osmium–Palladium Mixed-Metal High-Nuclearity Carbonyl Cluster (pages 553–555)

      Ka-Fu Yung and Wing-Tak Wong

      Article first published online: 30 JAN 2003 | DOI: 10.1002/anie.200390159

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      Palladium-filled sandwiches: The reaction between the [Os106-C)(CO)24]2− ion and [Pd(NCMe)4](BF4)2 yields the osmium–palladium mixed-metal cluster, [{N(PPh3)2}2{Os18Pd36-C)2(CO)42}], which has the highest nuclearity known for such clusters, and has been shown by single-crystal X-ray analysis to be a “metal sandwich” with two Os9 units connected by a triangular Pd3 subcluster (see picture); five reversible cathodic waves have been observed through cyclic voltammetry.

    13. Exact Replication of Biological Structures by Chemical Vapor Deposition of Silica (pages 557–559)

      Gary Cook, Peter L. Timms and Christine Göltner-Spickermann

      Article first published online: 30 JAN 2003 | DOI: 10.1002/anie.200390160

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      Silica coats for butterfly wings: The oxidation of silane with hydrogen peroxide is conducted on the surface of delicately structured biological specimens (templates), to produce a thin silica coating that leaves the underlying structure unharmed. Removal of the template by calcination leaves a precise replica of the original specimen (see SEM image of a silica replica obtained from a fly wing). The method is also proposed as a novel means of conservation for sensitive archaeological specimens.

    14. Surface-Initiated Polymerization on Self-Assembled Monolayers: Amplification of Patterns on the Micrometer and Nanometer Scale (pages 559–563)

      Ursula Schmelmer, Rainer Jordan, Wolfgang Geyer, Wolfgang Eck, Armin Gölzhäuser, Michael Grunze and Abraham Ulman

      Article first published online: 30 JAN 2003 | DOI: 10.1002/anie.200390161

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      Patterned polymer brushes can be produced on the micrometer and nanometer scale by a combination of self-assembly and lithography. Self-assembled monolayers of biphenyl thiols were structured by chemical lithography. The patterns were amplified by surface-initiated polymerization.

    15. Coordinated o-Dithio- and o-Iminothiobenzosemiquinonate(1−) π Radicals in [MII(bpy)(L.)](PF6) Complexes (pages 563–567)

      Prasanta Ghosh, Ameerunisha Begum, Diran Herebian, Eberhard Bothe, Knut Hildenbrand, Thomas Weyhermüller and Karl Wieghardt

      Article first published online: 30 JAN 2003 | DOI: 10.1002/anie.200390162

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      Reversible ligand-centered one-electron oxidation of square-planar neutral complexes of palladium(II) and platinum(II) [M(bpy)(L)] (bpy=bipyridine, L: see picture) leads to the paramagnetic complexes [M(bpy)(L.)]+. Thus, the existence of S,S-coordinated o-dithiobenzosemiquinonate(1−) π radical ions has been proven unequivocally.

    16. [2.2]Paracyclophanes with Defined Substitution Pattern—Key Compounds for the Mechanistic Understanding of the Gilch Reaction to Poly(p-phenylene vinylene)s (pages 567–570)

      Jens Wiesecke and Matthias Rehahn

      Article first published online: 30 JAN 2003 | DOI: 10.1002/anie.200390163

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      Radical reassessment: [2.2]Paracyclophanes D and E have been identified as the main side-products of the Gilch reaction leading to poly(p-phenylene vinylene)s (PPV B). The constitution of the cyclic dimers allows the conclusion to be drawn that the PPV formation occurs by free-radical polymerization of C, initiated by diradicals A. Anionic chain growth, often discussed as an alternative to the radical process, can be excluded.

    17. The Surprising Structures of B8F12 and B10F12 (pages 571–573)

      Jennifer A. J. Pardoe, Nicholas C. Norman, Peter L. Timms, Simon Parsons, Iain Mackie, Colin R. Pulham and David W. H. Rankin

      Article first published online: 30 JAN 2003 | DOI: 10.1002/anie.200390164

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      Unstable, reactive, and yellow: Compound B8F12, assumed for 30 years to have a diborane-like structure B2(BF2)6, has now been shown also to contain a short, central B[BOND]B bond. Across the B[BOND]B bond are two bridging BF2 groups, which are bent out of the plane by long-range, intramolecular F⋅⋅⋅B interactions. The B-(μ-BF2) bonds are long and, surprisingly, asymmetric, but calculations confirm that this structure is intrinsic to the molecule.

    18. DIBAH-Mediated Amide/Hydride Transformation in ansa-Lanthanidocene(III) Complexes (pages 574–577)

      Michael G. Klimpel, Peter Sirsch, Wolfgang Scherer and Reiner Anwander

      Article first published online: 30 JAN 2003 | DOI: 10.1002/anie.200390165

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      Unsolvated hydride derivatives [Me2Si(2-Me-C9H5)2LnH] (Ln=Y, Ho) are available from ansa-lanthanidocene complexes rac-[{Me2Si(2-Me-C9H5)2}Ln{N(SiHMe2)2}] by utilizing a novel [N(SiHMe2)2]/[H] transformation inititated by diisobutylaluminumhydride (DIBAH; see scheme; R=SiHMe2). The molecular structure of the THF adduct reveals a “flyover” dimer of composition [{Y(thf)}22-[(η5-2-Me-C9H5)SiMe25-2-Me-C9H5)]}22-H)2].

    19. An Efficient and Selective Photocatalytic System for the Oxidation of Sulfides to Sulfoxides (pages 577–579)

      Jyh-Myng Zen, Shiou-Ling Liou, Annamalai Senthil Kumar and Mung-Seng Hsia

      Article first published online: 30 JAN 2003 | DOI: 10.1002/anie.200390166

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      A heterogenous nafion membrane containing lead ruthenate pyrochlore (Pyc) and [Ru(bpy)3]2+ (designated as |NPycxRu(bpy)|) photochemically catalyzes the selective oxidation of organic sulfide to sulfoxide in the presence of O2 through formation of H2O2 as an intermediate (see scheme, R=Ph, PhCOCH3, PhOCH3).

    20. Highly Stereoselective N-Terminal Functionalization of Small Peptides by Chiral Phase-Transfer Catalysis (pages 579–582)

      Takashi Ooi, Eiji Tayama and Keiji Maruoka

      Article first published online: 30 JAN 2003 | DOI: 10.1002/anie.200390167

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      Virtually complete chirality transfer has been realized in the N-terminal alkylation of small, Schiff-base activated peptides under mild phase-transfer conditions, in which finely tuned chiral quaternary ammonium salts are used as catalysts. Repeated extension and alkylation of the N-terminal position can lead selectively to nonnatural oligopeptides (see picture).

    21. Preview: Angew. Chem. Int. Ed. 5/2003 (page 587)

      Article first published online: 30 JAN 2003 | DOI: 10.1002/anie.200390168