Angewandte Chemie International Edition

Cover image for Vol. 43 Issue 19

May 3, 2004

Volume 43, Issue 19

Pages 2455–2583

    1. Cover Picture: A Droplet-Based, Composite PDMS/Glass Capillary Microfluidic System for Evaluating Protein Crystallization Conditions by Microbatch and Vapor-Diffusion Methods with On-Chip X-Ray Diffraction (Angew. Chem. Int. Ed. 19/2004) (page 2455)

      Bo Zheng, Joshua D. Tice, L. Spencer Roach and Rustem F. Ismagilov

      Version of Record online: 28 APR 2004 | DOI: 10.1002/anie.200490056

      Protein crystals can be grown inside nanoliter droplets in a composite polydimethylsiloxane/glass microfluidic device. R. F. Ismagilov and co-workers describe in their Communication on page 2508 ff. how this approach can be used to screen conditions for protein crystallization by both microbatch and vapor-diffusion methods. The quality of the crystals grown in the device was evaluated directly from the X-ray diffraction pattern shown in the background.

    2. You have free access to this content
      The One-Stop Site for Organic Chemistry (page 2468)

      Kilian Muñiz

      Version of Record online: 28 APR 2004 | DOI: 10.1002/anie.200483068

    3. Peptides and Proteins. By Shawn Doonan. (page 2470)

      Annette G. Beck-Sickinger

      Version of Record online: 28 APR 2004 | DOI: 10.1002/anie.200385020

    4. Polyamides as Artificial Transcription Factors: Novel Tools for Molecular Medicine? (pages 2472–2475)

      Katja Schmitz and Ute Schepers

      Version of Record online: 28 APR 2004 | DOI: 10.1002/anie.200301745

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      Misregulation of gene expression often leads to severe defects in the development of an organism or to uncontrolled cell growth. Artificial transcription factors can control the expression of the genes concerned to restore normal cell regulation. Dervan and co-workers have synthesized several DNA-binding polyamides (see picture: TALE (yellow) is a class of homeobox protein) that show potential for the treatment of diseases such as cancer.

    5. Electrochemistry/Mass Spectrometry (EC/MS)—A New Tool To Study Drug Metabolism and Reaction Mechanisms (pages 2476–2478)

      Uwe Karst

      Version of Record online: 28 APR 2004 | DOI: 10.1002/anie.200301763

      A great combination: The coupling of electrochemistry and mass spectrometry (EC/MS) opens up new possibilities in analytics—not only in biochemistry for the investigation of natural products and metabolites, but also in the screening of combinatorial libraries and the characterization of transition-metal complexes. The mode of operation, range of application, and perspectives of the current EC/MS methods are the themes of this Highlight.

    6. Nanolithography and Nanochemistry: Probe-Related Patterning Techniques and Chemical Modification for Nanometer-Sized Devices (pages 2480–2495)

      Daan Wouters and Ulrich S. Schubert

      Version of Record online: 28 APR 2004 | DOI: 10.1002/anie.200300609

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      Nanometer-sized devices: Scanning probe based techniques will form the basis for the future production of small devices. This Review describes how oxidative scanning probe lithography can be a versatile platform for creating nanopatterns with (chemical) functionality.

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      Screening of Chiral Catalysts and Catalyst Mixtures by Mass Spectrometric Monitoring of Catalytic Intermediates (pages 2498–2500)

      Christian Markert and Andreas Pfaltz

      Version of Record online: 19 MAR 2004 | DOI: 10.1002/anie.200453844

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      The enantioselectivity of chiral palladium catalysts in the kinetic resolution of allylic esters can be determined by mass spectrometric monitoring of allyl–Pd intermediates A and B, which are derived from pseudoenantiomeric substrates 1 a and 1 b. In contrast to conventional screening methods, which are based on product analysis, simultaneous screening of catalyst mixtures in homogeneous solution is possible.

    8. Remarkable 4,4′-Substituent Effects on Binap: Highly Enantioselective Ru Catalysts for Asymmetric Hydrogenation of β-Aryl Ketoesters and Their Immobilization in Room-Temperature Ionic Liquids (pages 2501–2504)

      Aiguo Hu, Helen L. Ngo and Wenbin Lin

      Version of Record online: 28 APR 2004 | DOI: 10.1002/anie.200353415

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      A family of chiral diphosphanes with systematically tunable electronic and steric properties have been used in the asymmetric hydrogenation of β-aryl ketoesters with excellent ee values (up to 99.8 %) by taking advantage of remarkable 4,4′-substituent effects on binap. These highly enantioselective Ru catalysts have also been effectively immobilized in room-temperature ionic liquids (RTIL).

    9. Semisynthesis of a Functional K+ Channel (pages 2504–2507)

      Francis I. Valiyaveetil, Matthew Sekedat, Tom W. Muir and Roderick MacKinnon

      Version of Record online: 28 APR 2004 | DOI: 10.1002/anie.200453849

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      Selective ion-conduction properties in lipid membranes have been found for a semisynthetic KcsA K+ channel containing a mutation (A98G) that allows the channel to open. Thus, it is now possible to study ion conduction in a K+ channel with chemical modification of the main-chain atoms of the selectivity filter. The picture shows the single-channel responses of the semisynthetic K+ channel and its structure.

    10. A Droplet-Based, Composite PDMS/Glass Capillary Microfluidic System for Evaluating Protein Crystallization Conditions by Microbatch and Vapor-Diffusion Methods with On-Chip X-Ray Diffraction (pages 2508–2511)

      Bo Zheng, Joshua D. Tice, L. Spencer Roach and Rustem F. Ismagilov

      Version of Record online: 13 APR 2004 | DOI: 10.1002/anie.200453974

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      On-chip protein crystallization and diffraction: Proteins can be crystallized in nanoliter volumes by using both microbatch and vapor-diffusion techniques inside composite PDMS/glass microfluidic devices (PDMS=polydimethylsiloxane). The quality of crystals can be assessed directly by on-chip X-ray diffraction (see picture).

    11. Visual Observations of SERRS from Single Silver-Coated Silica Microparticles within Optical Tweezers (pages 2512–2514)

      Graeme McNay, Frances T. Docherty, Duncan Graham, W. Ewen Smith, Pamela Jordan, Miles Padgett, Jonathan Leach, Gavin Sinclair, Paul B. Monaghan and Jonathan M. Cooper

      Version of Record online: 28 APR 2004 | DOI: 10.1002/anie.200352999

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      Surface-enhanced resonance Raman scattering (SERRS) is considerably more efficient than Raman spectroscopy, thereby enabling the detection of single molecules. Strong and short-lived SERRS emissions (<100 ms) from single, partially silver-coated, dye-adsorbed microparticles have been detected within optical tweezers (see picture). Full spectra, recorded from single particles, clearly show that the emission is due to SERRS.

    12. Probing the Mechanism of the Heck Reaction with Arene Diazonium Salts by Electrospray Mass and Tandem Mass Spectrometry (pages 2514–2518)

      Adão A. Sabino, Angelo H. L. Machado, Carlos Roque D. Correia and Marcos N. Eberlin

      Version of Record online: 28 APR 2004 | DOI: 10.1002/anie.200353076

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      Key ionic intermediates of the Heck reaction of arene diazonium salts have been intercepted and structurally characterized by ESI-MS/MS. The use of electrospray ionization enables the ionic species to be transferred smoothly to the gas phase. A catalytic cycle for this reaction involving all the Pd cationic species intercepted has been proposed (see scheme).

    13. Glycosidation Reactions of Silyl Ethers with Conformationally Inverted Donors Derived from Glucuronic Acid: Stereoselective Synthesis of Glycosides and 2-Deoxyglycosides (pages 2518–2521)

      Monika Poláková, Nigel Pitt, Manuela Tosin and Paul V. Murphy

      Version of Record online: 28 APR 2004 | DOI: 10.1002/anie.200353196

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      The donor makes the difference: The tin(IV) chloride catalyzed coupling of silyl ethers to donors derived from glucuronic acid has shown that the silyl ethers (see scheme) are significantly better acceptors than the corresponding alcohols or phenol. The reactions are highly stereoselective and dependant on the donor structure. They provide 1,2-trans- and 1,2-cis-(deoxy)glycosides in moderate to excellent yields.

    14. A Monomeric Organolithium Compound Containing a Free Pyramidal Carbanion in Solution and in the Solid State (pages 2521–2524)

      Frank Breher, Jörg Grunenberg, Sally C. Lawrence, Philip Mountford and Heinz Rüegger

      Version of Record online: 28 APR 2004 | DOI: 10.1002/anie.200353308

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      A suitable bridle, created by intramolecular chelation of the Li cation, and lack of π delocalization, yielded the first monomeric lithium organyl compound containing an unassociated tetrahedral carbanionic center (see picture). The zwitterionic structure found in the solid state is preserved in solution. Only weak electrostatic Li+⋅⋅⋅C interactions are apparent; there is no Li–C contact and therefore no “classical” aggregation.

    15. A Mild Method for the Preparation of γ-Hydroxy-α,β-Acetylenic Esters (pages 2525–2527)

      Shatrughan P. Shahi and Kazunori Koide

      Version of Record online: 28 APR 2004 | DOI: 10.1002/anie.200353400

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      The beauty of silver has been demonstrated in the alkynylation of functionalized aldehydes and ketones. Silver acetylides of alkynyl propiolates undergo addition to carbonyl compounds in the presence of [Cp2ZrCl2] and AgOTf (see scheme) in a reaction that is compatible with both base-sensitive and acid-sensitive functional groups. Tf=trifluoromethanesulfonyl.

    16. Size-Selective Olefin Hydrogenation by a Pd Nanocluster Provided in an Apo-Ferritin Cage (pages 2527–2530)

      Takafumi Ueno, Masako Suzuki, Toshiaki Goto, Tomoharu Matsumoto, Kuniaki Nagayama and Yoshihito Watanabe

      Version of Record online: 28 APR 2004 | DOI: 10.1002/anie.200353436

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      Deep penetration by substrates through the size-restricted channels of an apo-ferritin cage results in size-selective olefin hydrogenation at the Pd nanocluster core (see picture). The encapsulated zero-valent cluster is synthesized in situ by chemical reduction of PdII ions in the apo-ferritin cage.

    17. Reaction-Temperature-Dependent Supramolecular Isomerism of Coordination Networks Based on the Organometallic Building Block [CuI22-BQ)(μ2-OAc)2] (pages 2530–2534)

      Shigeyuki Masaoka, Daisuke Tanaka, Yasunori Nakanishi and Susumu Kitagawa

      Version of Record online: 28 APR 2004 | DOI: 10.1002/anie.200353463

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      Three supramolecular isomers, [Cuequation image4-BQ)(μ2-OAc)2]n (α phase), [Cuequation image3-BQ)(μ2-OAc)(μ3-OAc)]n (β phase), and [Cuequation image2-BQ)(μ3-OAc)2]n (γ phase), were crystallized by using the organometallic building block shown, which has two types of supramolecular synthon. Interestingly, these three supramolecular isomers were crystallized from the same solvent. BQ=benzoquinone.

    18. A One-Pot Total Synthesis of Crambin (pages 2534–2538)

      Duhee Bang and Stephen B. H. Kent

      Version of Record online: 28 APR 2004 | DOI: 10.1002/anie.200353540

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      Making up for lost time: The one-pot synthesis of crambin (see structure) with only a single final purification step gave the target protein of exceptional purity in only two days with an overall yield of ≈40 %. Three unprotected peptide segments were linked by native chemical ligation, and the polypeptide chain assumed its 3D structure without intermediate purification steps.

    19. Nanocrystalline CeO2 Increases the Activity of Au for CO Oxidation by Two Orders of Magnitude (pages 2538–2540)

      Silvio Carrettin, Patricia Concepción, Avelino Corma, José M. López Nieto and Victor F. Puntes

      Version of Record online: 13 APR 2004 | DOI: 10.1002/anie.200353570

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      The smaller the better: Depositing gold on nanocrystalline particles of cerium oxide, instead of a regular cerium oxide support, increases the activity of the resulting catalyst by two orders of magnitude for the selective oxidation of CO to CO2, even in the presence of H2 (shown schematically).

    20. Sb8(GaCl4)2: Isolation of a Homopolyatomic Antimony Cation (pages 2540–2543)

      Martin Lindsjö, Andreas Fischer and Lars Kloo

      Version of Record online: 28 APR 2004 | DOI: 10.1002/anie.200353578

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      An almost perfect square-antiprismatic geometry is observed for Sb82+ (see picture), as predicted by the Wade rules. The title compound, which was synthesized in benzene at room temperature, represents the first homopolyatomic antimony cation and has Sb[BOND]Sb bond lengths of 285–300 pm.

    21. Highly Enantioselective Construction of Fused Pyrrolidine Systems That Contain a Quaternary Stereocenter: Concise Formal Synthesis of (+)-Conessine (pages 2543–2546)

      Biao Jiang and Min Xu

      Version of Record online: 28 APR 2004 | DOI: 10.1002/anie.200353583

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      No protecting groups were required in a concise and atom-economical synthesis of the optically active tetracyclic pyrrolidine 3 under mild conditions. A highly diastereoselective Pauson–Khand reaction (1[RIGHTWARDS ARROW]2) was used to construct the compact tetracycle with its quaternary stereocenter. The stereoselectivity of the cycloaddition was affected by the substituent on the propargylic moiety.

    22. The Cofactor of the Iron–Sulfur Cluster Free Hydrogenase Hmd: Structure of the Light-Inactivation Product (pages 2547–2551)

      Seigo Shima, Erica J. Lyon, Melanie Sordel-Klippert, Manuela Kauß, Jörg Kahnt, Rudolf K. Thauer, Klaus Steinbach, Xiulan Xie, Laurent Verdier and Christian Griesinger

      Version of Record online: 5 APR 2004 | DOI: 10.1002/anie.200353763

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      A combination of NMR spectroscopy and mass spectrometry has been crucial in determining the structure of the relatively stable light-inactivated form of the cofactor of the hydrogenase Hmd (see scheme). These studies have shown that the chromophore bound to GMP through a phosphoester linkage is a pyridone derivative.

    23. Isolation and Characterization of Pre-rapamycin, the First Macrocyclic Intermediate in the Biosynthesis of the Immunosuppressant Rapamycin by S. hygroscopicus (pages 2551–2553)

      Matthew A. Gregory, Sabine Gaisser, Rachel E. Lill, Hui Hong, Rose M. Sheridan, Barrie Wilkinson, Hrvoje Petkovic, Alison J. Weston, Isabelle Carletti, Huai-Lo Lee, James Staunton and Peter F. Leadlay

      Version of Record online: 2 APR 2004 | DOI: 10.1002/anie.200453764

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      It's arap: A double recombination strategy has been utilized to uncover the biosynthetic route to the key intermediate in the formation of rapamycin. Removal of a section of the rapamycin gene cluster from Streptomyces hygroscopicus produced a strain that generated no rapamycin. Gene complementation proved, surprisingly, that the accumulation of this previously elusive intermediate pre-rapamycin (1) depended on the presence of the gene rapK.

    24. Significant Interactions between Uranium and Noble-Gas Atoms: Coordination of the UO2+ Cation by Ne, Ar, Kr, and Xe Atoms (pages 2554–2557)

      Xuefeng Wang, Lester Andrews, Jun Li and Bruce E. Bursten

      Version of Record online: 28 APR 2004 | DOI: 10.1002/anie.200453790

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      A noble gas and an ignoble cation: A laser-ablated uranium cation reacts with O2 to give UO2+, which is found to form [UO2(Ng)n]+ (Ng=Ne, Ar, Kr, Xe) complexes on condensation with excess noble gas. Experiments with mixtures of noble gases lead to five new absorptions for the mixed [UO2+(Ng)x(Ng′)y] complexes and show that the coordination number is five for Ng=Ar, Kr, and Xe (see picture).

    25. In Pursuit of Carbohydrate-Based HIV Vaccines, Part 1: The Total Synthesis of Hybrid-Type gp120 Fragments (pages 2557–2561)

      Mihirbaran Mandal, Vadim Y. Dudkin, Xudong Geng and Samuel J. Danishefsky

      Version of Record online: 28 APR 2004 | DOI: 10.1002/anie.200353625

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      Key features in the successful synthesis of hybrid-type gp-120 fragments (see picture) include β-mannosylations to construct the core trisaccharide and a fragment-coupling strategy to install the “upper” high-mannose domain.

    26. In Pursuit of Carbohydrate-Based HIV Vaccines, Part 2: The Total Synthesis of High-Mannose-Type gp120 Fragments—Evaluation of Strategies Directed to Maximal Convergence (pages 2562–2565)

      Xudong Geng, Vadim Y. Dudkin, Mihirbaran Mandal and Samuel J. Danishefsky

      Version of Record online: 28 APR 2004 | DOI: 10.1002/anie.200353626

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      A “layered approach” and a “block approach” were used to assemble the high-mannose glycan of gp120 glycopeptide fragments (e.g. high-mannose-type conjugates gp120316–3351). The glycan was then conjugated with the gp120 peptide segments through direct aspartylation.

    27. Stereochemical Control of the Redox Potential of Tetracoordinate Rhodium Complexes (pages 2567–2570)

      Cécile Laporte, Frank Breher, Jens Geier, Jeffrey Harmer, Arthur Schweiger and Hansjörg Grützmacher

      Version of Record online: 28 APR 2004 | DOI: 10.1002/anie.200353027

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      An apitite for reduction: The diastereoisomers of the tetrachelating ligand 1,3-bis[(5H-dibenzo[a,d]cyclohepten-5-yl)phenylphosphanyl propane, bis(troppPh)propane, can be used to control the redox potentials of 16-electron rhodium(I) complexes. Whereas the R,S-isomer of the ligand enforces a more planar complex which is difficult to reduce, the R,R(S,S)-isomer favors a tetrahedrally distorted structure which is easily reduced to give a stable rhodium(0) complex (see structure, Rh silver, P yellow, C black, H white).

    28. Highly Resolved Spin-Density Distribution in the Prussian-Blue Precursors Cs2K[Fe(CN)6] and Cs2K[Mn(CN)6] (pages 2571–2573)

      Frank H. Köhler and Rodrigue Lescouëzec

      Version of Record online: 28 APR 2004 | DOI: 10.1002/anie.200453726

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      In magnetic materials of the Prussian-blue type, what proportion of the unpaired electrons in the simple hexacyanometalate moves from the metal (red) to the carbon (gray) and nitrogen (green) atoms? Based on the solid-state 13C and 15N NMR spectra, the amount, the sign, and the shape of the spin densities can be distinguished for axial and equatorial CN ligands. There is surprisingly little spin on the N atoms.

    29. Abyssomicin C—A Polycyclic Antibiotic from a Marine Verrucosispora Strain as an Inhibitor of the p-Aminobenzoic Acid/Tetrahydrofolate Biosynthesis Pathway (pages 2574–2576)

      Bojan Bister, Daniel Bischoff, Markus Ströbele, Julia Riedlinger, Andreas Reicke, Falko Wolter, Alan T. Bull, Hans Zähner, Hans-Peter Fiedler and Roderich D. Süssmuth

      Version of Record online: 28 APR 2004 | DOI: 10.1002/anie.200353160

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      Plumbing the depths: Abyssomicin C (structure shown) from ocean floor sediment is a novel antibiotic that inhibits the biosynthesis steps between chorismate and p-aminobenzoic acid. Its activity may be explained by the irreversible trapping of the targeted enzymes by a Michael addition. Blocking the biosynthesis of p-aminobenzoic acid may be one approach to developing new antibiotics.

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      Preview: Angew. Chem. Int. Ed. 19/2004 (page 2583)

      Version of Record online: 28 APR 2004 | DOI: 10.1002/anie.200490058

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