Angewandte Chemie International Edition

Cover image for Vol. 42 Issue 38

October 6, 2003

Volume 42, Issue 38

Pages 4555–4707

    1. Cover Picture: Molybdenum and Tungsten Imido Alkylidene Complexes as Efficient Olefin-Metathesis Catalysts (Angew. Chem. Int. Ed. 38/2003) (page 4555)

      Richard R. Schrock and Amir H. Hoveyda

      Version of Record online: 1 OCT 2003 | DOI: 10.1002/anie.200390586

      Molybdenum imido alkylidenes along with the corresponding tungsten complexes have played a critical role in the emergence of catalytic olefin metathesis as one of the key transformations in chemical synthesis. R. R. Schrock and A. H. Hoveyda recount on page 4592 ff the journey that began with the discovery of tantalum alkylidenes and eventually led to the development of highly effective chiral catalysts, and even supported chiral catalysts (shown in the vials), for asymmetric metathesis.

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    3. Web Site: The A to Z of Materials—for Chemists? (page 4568)

      Edwin Kroke

      Version of Record online: 1 OCT 2003 | DOI: 10.1002/anie.200390589

    4. Metal-Ion-Binding Peptides: From Catalysis to Protein Tagging (pages 4572–4575)

      Giulia Licini and Paolo Scrimin

      Version of Record online: 1 OCT 2003 | DOI: 10.1002/anie.200301668

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      Natural selection: Peptide-based ligands for metal ions (see schematic representation) have a diverse range of applications that extends from stereoselective catalysis to the sensing of proteins. The possibility to screen large libraries of ligands for the selection of the best systems and their coexpression with proteins make peptide-based ligands powerful tools for bridging the gap between chemistry and biology.

    5. Magnetic Control of Electrocatalytic and Bioelectrocatalytic Processes (pages 4576–4588)

      Itamar Willner and Eugenii Katz

      Version of Record online: 1 OCT 2003 | DOI: 10.1002/anie.200201602

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      Going for a spin: Circular rotation of an external magnet enhances the bioelectrocatalytic oxidation of a substrate such as glucose when magnetic particles are functionalized with a redox-relay group such as ferrocene (see scheme). This example of a magneto-controlled electrocatalytic reaction may find application in sensor technology.

    6. Molybdenum and Tungsten Imido Alkylidene Complexes as Efficient Olefin-Metathesis Catalysts (pages 4592–4633)

      Richard R. Schrock and Amir H. Hoveyda

      Version of Record online: 1 OCT 2003 | DOI: 10.1002/anie.200300576

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      25 years on: Molybdenum alkylidene complexes (see picture) have played a crucial role in the emergence of olefin metathesis as a powerful method in modern chemical synthesis. This review highlights the 25-year journey from the first high-oxidation-state tantalum alkylidene complex to chiral molybdenum catalysts for asymmetric olefin metathesis.

    7. A Covalent Tetrathiafulvalene–Tetracyanoquinodimethane Diad: Extremely Low HOMO–LUMO Gap, Thermoexcited Electron Transfer, and High-Quality Langmuir–Blodgett Films (pages 4636–4639)

      Dmitrii F. Perepichka, Martin R. Bryce, Christopher Pearson, Michael C. Petty, Eric J. L. McInnes and Jing P. Zhao

      Version of Record online: 11 SEP 2003 | DOI: 10.1002/anie.200351876

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      Nearly 30 years after theoretical prediction, a stable and well-characterized compound that covalently links tetrathiafulvalene and tetracyanoquinodimethane fragments has been synthesized (1, see scheme). The extremely low HOMO–LUMO gap of 1 (0.17 eV) allows the first observation of thermoexcited electron transfer in a donor–acceptor diad. Langmuir–Blodgett films of 1 are not electrically conducting.

    8. Design of Environment-Sensitive Supramolecular Assemblies for Intracellular Drug Delivery: Polymeric Micelles that are Responsive to Intracellular pH Change (pages 4640–4643)

      Younsoo Bae, Shigeto Fukushima, Atsushi Harada and Kazunori Kataoka

      Version of Record online: 1 OCT 2003 | DOI: 10.1002/anie.200250653

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      Drug smuggling: Micelles made up of block copolymers and the anticancer drug adriamycin (ADR), which is linked to the polymer by a pH-sensitive linker, have been prepared (see picture). Treatment of cancer cells with the micelles shows that the micelles are transported into the cell by endocytosis, thus bypassing the cell-membrane transporters. In the cell, the decrease in pH value triggers the release of the ADR, which retains its cytotoxic effect. The released ADR fluoresces which allows its localization within the cells to be detected.

    9. First Structurally Authenticated Zinc Alkylperoxide: A Model System for the Epoxidation of Enones (pages 4643–4646)

      Janusz Lewiński, Zbigniew Ochal, Emil Bojarski, Ewa Tratkiewicz, Iwona Justyniak and Janusz Lipkowski

      Version of Record online: 1 OCT 2003 | DOI: 10.1002/anie.200351940

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      β-Ketoimine ligands stabilize zinc compounds: The dimeric zinc alkylperoxide [{(LL)ZnOOEt}2] (where LL=HC{(CMe)(2,6-iPr2C6H3N)}2) has been prepared and structurally characterized (see picture, Zn green, N blue, O red, C gray). This compound, which is formed by the insertion of dioxygen into the Zn[BOND]Et bond, is very active in the epoxidation of enones.

    10. Terpenoid-Derived Sulfides as Ultimate Organic Sulfur Compounds in Extensively Desulfurized Fuels (pages 4646–4649)

      Armelle Charrié-Duhaut, Christine Schaeffer, Pierre Adam, Pascal Manuelli, Pierre Scherrer and Pierre Albrecht

      Version of Record online: 1 OCT 2003 | DOI: 10.1002/anie.200351426

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      Extremely hydrodesulfurization-resistant organosulfur compounds of biological origin are present in trace amounts in highly desulfurized fuels. A series of these compounds (see picture; left) was characterized by mass spectrometry and NMR spectroscopic structural elucidation of the corresponding sulfones (right), which were isolated after selective oxidation.

    11. One-Pot Synthesis of Hierarchically Ordered Porous-Silica Materials with Three Orders of Length Scale (pages 4649–4653)

      Tapas Sen, Gordon J. T. Tiddy, John L. Casci and Michael W. Anderson

      Version of Record online: 1 OCT 2003 | DOI: 10.1002/anie.200351479

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      An entirely synthetic method is used to produce hierarchically ordered porous silica materials in a one-pot synthesis, with ordering on three different scales; that is, macropores (200–800 nm), interconnecting windows (70–130 nm), ordered mesoporous walls (80 nm) with narrow micropores (<2 nm) in the presence of multiple templates (see picture). At the macro- and mesoscale both ordering and size is controlled whilst at the microscale the interconnectivity is controlled.

    12. Synthesis and Characterization of a Cobalt(II) Single-Molecule Magnet (pages 4653–4656)

      Mark Murrie, Simon J. Teat, Helen Stœckli-Evans and Hans U. Güdel

      Version of Record online: 1 OCT 2003 | DOI: 10.1002/anie.200351753

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      Small and attractive: The proligand citric acid has been used to assemble a new anionic hexanuclear cobalt(II) cluster (see picture). The complex displays single-molecule magnet (SMM) behavior, with an energy barrier to the reorientation of magnetization of 26 K, the highest value to have been recorded for a non-manganese based SMM.

    13. A Programmable One-Pot Oligosaccharide Synthesis for Diversifying the Sugar Domains of Natural Products: A Case Study of Vancomycin (pages 4657–4660)

      Thomas K. Ritter, Kwok-Kong T. Mong, Haitian Liu, Takuji Nakatani and Chi-Huey Wong

      Version of Record online: 1 OCT 2003 | DOI: 10.1002/anie.200351534

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      The notoriously difficult glycosylation of vancomycin was tackled in a one-pot procedure. A number of oligosaccharides were synthesized and attached to the vancomycin aglycon to create a library of derivatives (see formula) to probe the effect of glycosylation on the antibiotic activity.

    14. Rapid Diversity-Oriented Synthesis in Microtiter Plates for In Situ Screening: Discovery of Potent and Selective α-Fucosidase Inhibitors (pages 4661–4664)

      Chung-Yi Wu, Chuan-Fa Chang, Jenny Szu-Yu Chen, Chi-Huey Wong and Chun-Hung Lin

      Version of Record online: 1 OCT 2003 | DOI: 10.1002/anie.200351823

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      An efficient and simple method has been developed to identify potent and selective inhibitors against α-fucosidases based on the amide-forming reaction in a microtiter plate of a fuconojirimycin core with various carboxylic acids, followed by a direct inhibition assay without product isolation. The structures of the two most potent inhibitors are shown.

    15. Dormant States of Rhodium Hydroformylation Catalysts: Carboalkoxyrhodium Complex Formed from Enones in the Alkene Feed (pages 4665–4669)

      Edyta B. Walczuk, Paul C. J. Kamer and Piet W. N. M. van Leeuwen

      Version of Record online: 1 OCT 2003 | DOI: 10.1002/anie.200351884

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      Catalysts get food poisoning: Conversion of the active 1-alkene hydroformylation catalyst 1 with reactive impurities in the feed, such as dienes and enones, into unreactive rhodium intermediates leads to deactivation of 1. For example, 2 is much more reactive towards 1 than the substrate and transforms it temporarily into 4 blocking the hydroformylation activity.

    16. Measuring Reaction Kinetics by Using Multiple Microcoil NMR Spectroscopy (pages 4669–4672)

      Luisa Ciobanu, Dimuthu A. Jayawickrama, Xiaozhong Zhang, Andrew G. Webb and Jonathan V. Sweedler

      Version of Record online: 1 OCT 2003 | DOI: 10.1002/anie.200351901

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      The technique of continuous reactant flow is combined with multiple microcoil NMR detection in a new and efficient approach to obtain kinetic information on reactions that take place on timescales between seconds and minutes. As a model system, xylose–borate reaction kinetics are studied (see picture).

    17. Rhodium-Catalyzed Mizoroki–Heck-Type Arylation of Alkenes with Aroyl Chlorides under Phosphane- and Base-Free Conditions (pages 4672–4674)

      Toru Sugihara, Tetsuya Satoh, Masahiro Miura and Masakatsu Nomura

      Version of Record online: 1 OCT 2003 | DOI: 10.1002/anie.200351905

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      Simple but effective! Even without the addition of any phosphane ligand and base, alkenes efficiently undergo Mizoroki–Heck-type arylation upon treatment with aroyl chlorides in the presence of a rhodium catalyst (see scheme). The products were isolated by a very simple procedure.

    18. A Practical Solid-Phase Synthesis of Glycosylphosphatidylinositol Precursors (pages 4674–4677)

      Niels-Christian Reichardt and Manuel Martín-Lomas

      Version of Record online: 1 OCT 2003 | DOI: 10.1002/anie.200351950

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      The conserved pseudo-pentasaccharide structure common to all known GPI-anchors (GPI=glycosylphosphatidylinositol) was assembled on a solid support by using a novel attachment procedure and a optimized deprotection/glycosylation protocol. Orthogonal protection for the main branching points allows access to a variety of GPI-glycan structures from the same precursor molecule.

    19. Transition-Metal Variation as a Probe of the Origins of Hypoelectronic Metallaboranes: Eight- and Ten-Vertex Open Ruthenaboranes (pages 4678–4680)

      Sundargopal Ghosh, Alicia M. Beatty and Thomas P. Fehlner

      Version of Record online: 1 OCT 2003 | DOI: 10.1002/anie.200352101

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      Finding skeletons in metallaboranes' closets: Reaction of [(Cp*Ru)2B4H8] (Cp*=C5Me5) with BH3⋅THF leads to the formation of 10 skeletal electron pair (sep) compound [(Cp*RuH2)2B6H8] and 11 sep, hypoelectronic [(Cp*Ru)2B8H12] (1). Compound 1 has the framework of the 12 sep cluster B10H14 but modified by a single diamond-square-diamond rearrangement that permits a Ru–Ru interaction (green) between the five-connected (blue) and six-connected (red) {Cp*Ru} fragments which generates an additional unavailable orbital in the ruthenium “t2g” set.

    20. Sequential Wittig Olefination–Catalytic Asymmetric Epoxidation with Reuse of Waste Ph3P(O): Application of α,β-Unsaturated N-Acyl Pyrroles as Ester Surrogates (pages 4680–4684)

      Tomofumi Kinoshita, Shigemitsu Okada, Sun-Ryung Park, Shigeki Matsunaga and Masakatsu Shibasaki

      Version of Record online: 11 SEP 2003 | DOI: 10.1002/anie.200352509

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      Waste not, want not: Efficient one-pot access to optically active epoxides with 96 to 99.5 % ee from a variety of aldehydes is described. In a sequential process, the Ph3P(O) by-product of a Wittig reaction acts as a modulator for the samarium catalyst in the asymmetric epoxidation of the conjugated N-acyl pyrrole Wittig product (see scheme). The N-acyl pyrrole functionality is key to the high reactivity and selectivity observed. R=alkyl, aryl, vinyl.

    21. Total Synthesis of (+)-Wailupemycin B (pages 4685–4687)

      Stefan Kirsch and Thorsten Bach

      Version of Record online: 1 OCT 2003 | DOI: 10.1002/anie.200351455

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      A high functional-group density necessitated the careful choice of protection/deprotection strategy for the successful stereoselective total synthesis of the marine polyketide (+)-wailupemycin B (1) from (S)-carvone in 6 % overall yield. Key to the success of the synthesis was the manipulation of orthogonal protecting groups, two stereoselective additions to highly functionalized cyclohexanones, and mild reliable methods for the oxidation of alcohols.

    22. Poly(methylene amine): A Polymer with the Maximum Possible Number of Amino Groups on a Polymer Backbone (pages 4687–4690)

      Markus Klapper, Corneliu Hamciuc, Rainer Dyllick-Brenzinger and Klaus Müllen

      Version of Record online: 1 OCT 2003 | DOI: 10.1002/anie.200351500

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      Taken to the limit: The synthesis of a new amino-functionalized polymer containing one amino group on each carbon of the backbone, is presented. This compound, poly(methylene amine), can be considered as the polymer with the highest content of amino functions known.

    23. The Trifluoromethyltrioxy Radical, CF3OOO (pages 4690–4693)

      Stefan von Ahsen, Helge Willner and Joseph S. Francisco

      Version of Record online: 1 OCT 2003 | DOI: 10.1002/anie.200351909

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      Tic-tac-toe, three O's in a row: The trifluoromethyltrioxy radical, CF3OOO (structure shown), is generated by vacuum flash thermolysis of CF3OC(O)OOC(O)OCF3 or CF3OC(O)OOCF3 in an excess of O2. The reaction products are quenched as a matrix at low temperatures.

    24. From Particle-Assisted Wetting to Thin Free-Standing Porous Membranes (pages 4694–4696)

      Hui Xu and Werner A. Goedel

      Version of Record online: 1 OCT 2003 | DOI: 10.1002/anie.200351427

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      Puncturing polymer membranes: Non-wetting organic liquids (see scheme; red) can form a mesoscopic wetting layer on a water surface (light blue), if they are mixed with suitable particles (dark blue). Photochemical cross-linking of the liquid in the mixed layer and transfer to metal grids or porous supports produces composite membranes. Subsequent removal of the particles yields free-standing porous membranes with uniform pore size and high porosity (see scheme).

    25. Mesoscopic Rings by Controlled Wetting of Particle Imprinted Templates (pages 4696–4700)

      Hui Xu and Werner A. Goedel

      Version of Record online: 8 SEP 2003 | DOI: 10.1002/anie.200351428

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      Rings and a few other things: A method for the preparation of uniform mesoscopic titanium dioxide rings that are bound in a periodic array on a substrate, linked to a free-standing membrane, or are dispersed as individual particles (see SEM image) is presented. The technique is based on the selective wetting of the inner surface of a porous membrane.

    26. Investigation of Reactive Intermediates of Chemical Reactions in Solution by Electrospray Ionization Mass Spectrometry: Radical Cation Chain Reactions (pages 4700–4703)

      Sven Meyer, Rainer Koch and Jürgen O. Metzger

      Version of Record online: 1 OCT 2003 | DOI: 10.1002/anie.200352044

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      Transient radicals tracked down: An electrospray ionization mass spectrometer coupled on-line to a microreactor system is useful for investigating reactions in solution and for directly detecting reactive intermediates. The transient radical cations 1.+ and 2.+ formed in the radical cation chain dimerization of trans-anethole were detected unambiguously by MS/MS methods.