Angewandte Chemie International Edition

Cover image for Vol. 43 Issue 33

August 20, 2004

Volume 43, Issue 33

Pages 4239–4377

    1. Cover Picture: Structural Revision and Total Synthesis of Azaspiracid-1, Part 1: Intelligence Gathering and Tentative Proposal (Angew. Chem. Int. Ed. 33/2004) (page 4239)

      K. C. Nicolaou, Stepan Vyskocil, Theocharis V. Koftis, Yoichi M. A. Yamada, Taotao Ling, David Y.-K. Chen, Wenjun Tang, Goran Petrovic, Michael O. Frederick, Yiwei Li and Masayuki Satake

      Version of Record online: 13 AUG 2004 | DOI: 10.1002/anie.200490111

      The mussel toxin azaspiracid-1, which was isolated from Mytilus edulis, has baffled chemists for quite some time, as the originally proposed structure was incorrect. In their Communications on pages 4312 ff. and 4318 ff., Nicolaou and co-workers describe how they determined the structure and absolute configuration of the molecule through degradation studies and total synthesis. The synthesis should render this valuable, but scarce, substance available for much-needed biotoxin assays and biological investigations.

    2. Paul Ehrlich: The Founder of Chemotherapy (pages 4254–4261)

      Fritz Stern

      Version of Record online: 13 AUG 2004 | DOI: 10.1002/anie.200460632

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      150 years of Ehrlich: He was the founder of chemotherapy and established the basis for modern immunology. This year sees the 150th anniversary of Paul Ehrlich's birth. Prize-winning writer Fritz Stern sketches a portrait of a man born into a world of progress, a brilliant researcher, who through his achievements, became a target for hostility.

    3. Potassium Channels and the Atomic Basis of Selective Ion Conduction (Nobel Lecture) (pages 4265–4277)

      Roderick MacKinnon

      Version of Record online: 13 AUG 2004 | DOI: 10.1002/anie.200400662

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      Closing in on the facts: The key to understanding the transport of K+ ions through the cell membrane lay in the structure elucidation of a K+ ion channel (see picture). The studies of Roderick MacKinnon and co-workers have contributed significantly to the understanding of this research area. In his Nobel Lecture, he describes the structural characteristics of K+ ion channels as well as a possible mechanism for ion conduction.

    4. Aquaporin Water Channels (Nobel Lecture) (pages 4278–4290)

      Peter Agre

      Version of Record online: 13 AUG 2004 | DOI: 10.1002/anie.200460804

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      Water is the most important component of all organisms and is the basis of all life. That water can pass through cell membranes has long been known—but how is the selective transport of water molecules achieved without concommitent diffusion of H3O+ ions? Peter Agre received the 2003 Nobel Prize in Chemistry for the discovery and investigation of the membrane proteins responsible, namely, the aquaproteins.

    5. Host–Guest Compounds in the Family of Tellurium–Nickel Oxohalogenides (pages 4292–4295)

      Mats Johnsson, Sven Lidin, Karl W. Törnroos, Hans-Beat Bürgi and Patrice Millet

      Version of Record online: 23 JUN 2004 | DOI: 10.1002/anie.200460001

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      The peeling of an onion: Embedded in the voids of an infinite cationic [Te32Ni30X3O90]5+ network lies an icosahedral [Ni4X13]5− anionic guest cluster (ochre). It may be considered wrapped and trapped in a successive series of concentric skins made from the lone pairs of Te atoms (blue), the Te (yellow), O (red), and Ni atoms (light blue polyhedra). But are there any other guests?

    6. Strain-Induced Formation of Subsurface Species in Transition Metals (pages 4296–4300)

      Jeff Greeley, William P. Krekelberg and Manos Mavrikakis

      Version of Record online: 13 AUG 2004 | DOI: 10.1002/anie.200454062

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      Expansive surface strain facilitates the formation of subsurface heteroatoms in transition metals. Density functional calculations show that subsurface hydrogen atoms form more rapidly, as depicted schematically in the picture, and are thermodynamically stable at much lower pressures and higher temperatures in stretched (as opposed to unstretched) nickel surfaces.

    7. Highly Selective Oligonucleotide-Based Sensor for Mercury(II) in Aqueous Solutions (pages 4300–4302)

      Akira Ono and Humika Togashi

      Version of Record online: 13 AUG 2004 | DOI: 10.1002/anie.200454172

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      Mercury gauge: An oligodeoxyribonucleotide(ODN)-based sensor, which carries energy-donor and -acceptor moieties (fluorescein, F, and dabcyl, D, respectively), selectively detects HgII ions in aqueous solution. Upon binding HgII ions, the ODN takes on a hairpin structure (see picture); this results in a decrease in the fluorescence emission through enhanced FRET (fluorescence resonance energy transfer) from F to D.

    8. Nanoengineering of a Magnetically Separable Hydrogenation Catalyst (pages 4303–4306)

      An-Hui Lu, Wolfgang Schmidt, Nina Matoussevitch, Helmut Bönnemann, Bernd Spliethoff, Bernd Tesche, Eckhard Bill, Wolfgang Kiefer and Ferdi Schüth

      Version of Record online: 13 AUG 2004 | DOI: 10.1002/anie.200454222

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      Magnetic, highly porous ordered carbon of the CMK-3 and CMK-5 type and with pure carbon or carbon–nitrogen framework were nanoengineered by a sequence of bulk manipulation steps. The materials can be used as efficient magnetic adsorbents (see picture) or catalysts, but applications going far beyond these can be envisaged.

    9. Binding Mode Determination of Benzimidazole Inhibitors of the Hepatitis C Virus RNA Polymerase by a Structure and Dynamics Strategy (pages 4306–4311)

      Steven R. LaPlante, Araz Jakalian, Norman Aubry, Yves Bousquet, Jean-Marie Ferland, James Gillard, Sylvain Lefebvre, Martin Poirier, Youla S. Tsantrizos, George Kukolj and Pierre L. Beaulieu

      Version of Record online: 13 AUG 2004 | DOI: 10.1002/anie.200460326

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      A novel strategy involving NMR, medicinal chemistry, and molecular modeling is described for determining the binding mode of ligands and the binding roles of their substituents. The first solution structure of an inhibitor bound to hepatitis C virus (HCV) polymerase (see picture) provides practical information for the rational design of potential therapeutics against HCV infections.

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      Structural Revision and Total Synthesis of Azaspiracid-1, Part 1: Intelligence Gathering and Tentative Proposal (pages 4312–4318)

      K. C. Nicolaou, Stepan Vyskocil, Theocharis V. Koftis, Yoichi M. A. Yamada, Taotao Ling, David Y.-K. Chen, Wenjun Tang, Goran Petrovic, Michael O. Frederick, Yiwei Li and Masayuki Satake

      Version of Record online: 25 JUN 2004 | DOI: 10.1002/anie.200460695

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      Phantom molecules from Nature: Degradation studies of azaspiracid-1 (see originally proposed, incorrect structure), the notorious marine neurotoxin isolated from contaminated mussels, revealed that the double bond of ring A was located at C7–C8 and not at C8–C9 and also provided further information on the overall stereochemistry of the molecule.

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      Structural Revision and Total Synthesis of Azaspiracid-1, Part 2: Definition of the ABCD Domain and Total Synthesis (pages 4318–4324)

      K. C. Nicolaou, Theocharis V. Koftis, Stepan Vyskocil, Goran Petrovic, Taotao Ling, Yoichi M. A. Yamada, Wenjun Tang and Michael O. Frederick

      Version of Record online: 29 JUN 2004 | DOI: 10.1002/anie.200460696

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      The chase for the structure of azaspiracid-1 has ended with a revised structure (see picture). The total synthesis of this challenging target has closed another chapter in this intriguing chemical detective story and allowed the assignment of the relative and absolute configuration of the molecule.

    12. 23-Oxa-Analogues of OSW-1: Efficient Synthesis and Extremely Potent Antitumor Activity (pages 4324–4327)

      Bingfeng Shi, Hao Wu, Biao Yu and Jiarui Wu

      Version of Record online: 13 AUG 2004 | DOI: 10.1002/anie.200454237

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      An aldol condensation is the key to the eight-step linear synthesis of 23-oxa analogues of OSW-1 (e.g. 2) in more than 20 % overall yield from the industrially produced steroid 1. Compound 2 is up to 2000 times more potent than cisplatin as an inhibitor of tumor cell growth.

    13. Stereocontrolled Total Synthesis of (+)-Streptazolin by a Palladium-Catalyzed Reductive Diyne Cyclization (pages 4327–4329)

      Barry M. Trost, Cheol K. Chung and Anthony B. Pinkerton

      Version of Record online: 13 AUG 2004 | DOI: 10.1002/anie.200460058

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      (+)-Streptazolin synthesis revisited: The key reaction in the 11-step total synthesis of (+)-streptazolin (3), which starts from D-mannitol diacetonide, is the palladium-catalyzed reductive cyclization of two alkyne arms in 1 to provide the desired 1,3-diene 2 with the correct defined geometry. TBS=tert-butyldimethylsilyl.

    14. Probing the Mechanism of the Baylis–Hillman Reaction by Electrospray Ionization Mass and Tandem Mass Spectrometry (pages 4330–4333)

      Leonardo Silva Santos, Cesar Henrique Pavam, Wanda P. Almeida, Fernando Coelho and Marcos N. Eberlin

      Version of Record online: 13 AUG 2004 | DOI: 10.1002/anie.200460059

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      Ion fishing”: Protonated intermediates in the catalytic cycle of the Baylis–Hillman reaction between an activated alkene and an electrophile have been intercepted and characterized by electrospray ionization tandem mass spectrometry. This approach provides direct evidence for the currently accepted mechanism (see scheme).

    15. Synthesis and Stereoselective Lithiation of Enantiopure 2-(1-Aminoalkyl)aziridine–Borane Complexes (pages 4333–4336)

      José M. Concellón, José Ramón Suárez, Santiago García-Granda and M. Rosario Díaz

      Version of Record online: 13 AUG 2004 | DOI: 10.1002/anie.200460120

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      Two alternative methodologies can be used to obtain enantiopure aziridine–borane complexes 2: successive treatment of 2-(1-aminoalkyl)aziridines 1 with BF3⋅Et2O and LiAlH4 or by direct reaction with BH3⋅THF (see scheme, Bn=benzyl). The complexes 2 can be deuterated or silylated highly stereoselectively at C3 by reaction with sBuLi and subsequent treatment with D2O or ClSiMe3, respectively.

    16. Fully Stereocontrolled Total Syntheses of (−)-Cylindricine C and (−)-2-Epicylindricine C: A Departure in Sulfonamide Chemistry (pages 4336–4338)

      Sylvain Canesi, Denis Bouchu and Marco A. Ciufolini

      Version of Record online: 13 AUG 2004 | DOI: 10.1002/anie.200460178

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      A common intermediate was used in the total syntheses of (−)-cylindricine C and (−)-2-epicylindricine C (see picture) in a process that involves the initial oxidative spirocyclization of a phenolic sulfonamide. The remainder of the molecules is constructed through interesting sulfonamide chemistry.

    17. A Lotus-Leaf-like Superhydrophobic Surface: A Porous Microsphere/Nanofiber Composite Film Prepared by Electrohydrodynamics (pages 4338–4341)

      Lei Jiang, Yong Zhao and Jin Zhai

      Version of Record online: 13 AUG 2004 | DOI: 10.1002/anie.200460333

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      A hierarchical micro/nanostructure and low surface energy result in superhydrophobicity in a polystyrene film prepared by the electrohydrodynamics method. The composite film consists of porous microspheres, which contribute to superhydrophobicity by increasing the surface roughness, and interwoven nanofibers, which reinforce the film (see the SEM image). A water droplet resides on the film with a contact angle of about 160° (see inset).

    18. Stereoselective Total Synthesis of the Ionophore Antibiotic Zincophorin (pages 4341–4345)

      Kei Komatsu, Keiji Tanino and Masaaki Miyashita

      Version of Record online: 13 AUG 2004 | DOI: 10.1002/anie.200460434

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      Acyclic stereocontrol is the basis of an original strategy adopted for the first, highly stereoselective total synthesis of the free acid zincophorin (1), a unique ionophore antibiotic. The stereoselective synthesis of the trisubstituted tetrahydropyran moiety and the construction of the eight contiguous stereogenic centers were key challenges in the synthesis.

    19. Nonaqueous Synthesis of Nanocrystalline Semiconducting Metal Oxides for Gas Sensing (pages 4345–4349)

      Nicola Pinna, Giovanni Neri, Markus Antonietti and Markus Niederberger

      Version of Record online: 28 JUL 2004 | DOI: 10.1002/anie.200460610

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      Superior crystallinity and good yields are found for SnO2 and In2O3 (see HRTEM image) semi-conducting metal oxide nanocrystals prepared by a non-aqueous approach involving the reaction of a metal alkoxide with benzyl alcohol. The sensor devices fabricated just by deposition of the as-synthesized nanoparticles showed the high sensitivity and good recovery time required for technological applications.

    20. Rh-Catalyzed Amination of Ethereal Cα[BOND]H Bonds: A Versatile Strategy for the Synthesis of Complex Amines (pages 4349–4352)

      Kristin Williams Fiori, James J. Fleming and Justin Du Bois

      Version of Record online: 13 AUG 2004 | DOI: 10.1002/anie.200460791

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      Intramolecular C[BOND]H insertion with sulfamates catalyzed by rhodium complexes offers an effective method for the preparation of N,O-acetals, which function as iminium ion precursors and undergo smooth diastereoselective coupling with nucleophiles under Lewis acidic conditions (see scheme). These findings advance the versatility of catalytic C[BOND]H amination for the assembly of structurally complex nitrogen-containing products. Tf=trifluoromethanesulfonyl.

    21. Synthesis of Dimeric Terpenoyl Glycoside Side Chains from Cytotoxic Saponins (pages 4353–4357)

      Sabine Reicheneder and Carlo Unverzagt

      Version of Record online: 13 AUG 2004 | DOI: 10.1002/anie.200352895

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      A bottleneck in the synthesis of the model compound 1, which bears a dimeric terpenoyl glycoside side chain from cytotoxic saponins, was overcome by the stepwise construction of the terpene part by regioselective acylation of the sugar with a functionalized phosphonate followed by a Horner–Wadsworth–Emmons olefination.

    22. Electroactive Cytochrome c Multilayers within a Polyelectrolyte Assembly (pages 4357–4360)

      Moritz K. Beissenhirtz, Frieder W. Scheller, Walter F. M. Stöcklein, Dirk G. Kurth, Helmuth Möhwald and Fred Lisdat

      Version of Record online: 13 AUG 2004 | DOI: 10.1002/anie.200352804

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      Strata pack: Electroactive cytochrome c multilayer assemblies were constructed within a polyelectrolyte network on a gold electrode. Up to 15 layers were electroactive, with a linear increase in redoxactive protein per layer. Evidence for a protein–protein electron transfer through the assembly was found (pathway marked by arrows in the picture).

    23. Combined Spectroscopic and Theoretical Evidence for a Persistent End-On Copper Superoxo Complex (pages 4360–4363)

      Markus Schatz, Volker Raab, Simon P. Foxon, Georg Brehm, Siegfried Schneider, Markus Reiher, Max C. Holthausen, Jörg Sundermeyer and Siegfried Schindler

      Version of Record online: 13 AUG 2004 | DOI: 10.1002/anie.200454125

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      A tale of two modes: An end-on copper superoxo complex was identified in a combined experimental and theoretical study. Theory clearly discloses the presence of an end-on complex (see picture, O red, Cu pink, N green) with a minute isotopic resonance Raman splitting below experimental resolution. The results cast doubts on the uncritical use of 16O,18O isotopic-labeling Raman experiments to discriminate end-on from side-on bonding modes in M(O2) complexes.

    24. Preparation of Polyfunctional Arynes via 2-Magnesiated Diaryl Sulfonates (pages 4364–4366)

      Ioannis Sapountzis, Wenwei Lin, Markus Fischer and Paul Knochel

      Version of Record online: 13 AUG 2004 | DOI: 10.1002/anie.200460417

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      The synthetic potential of arynes can be exploited through a new method for their generation from functionalized aryl magnesium reagents and controlled reaction. Arynes with functional groups such as ester, nitrile, ketone, or nitro groups, or with a quinolyl skeleton, can be formed from polyfunctionalized 2-iodo aryl 4-chlorobenezenesulfonates and trapped in 68–93 % yield with furan (see scheme).

    25. Synthesis and Biochemical Properties of Reversible Inhibitors of UDP-N-Acetylglucosamine 2-Epimerase (pages 4366–4370)

      Samy Al-Rawi, Stephan Hinderlich, Werner Reutter and Athanassios Giannis

      Version of Record online: 13 AUG 2004 | DOI: 10.1002/anie.200453863

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      Sialic acids have important biochemical functions in healthy organisms, for example, in embryogenesis, as well as in the spread of diseases like influenza. A key step in the biosynthesis of the sialic acid N-acetylneuraminic acid is the epimerization of 1 to give 2 (see scheme, UDP=uridine diphosphate). Transition-state analogues (e.g. 4) of this enzyme-catalyzed reaction were made and tested for their inhibitory action.

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      Preview: Angew. Chem. Int. Ed. 33/2004 (page 4377)

      Version of Record online: 13 AUG 2004 | DOI: 10.1002/anie.200490113

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