Angewandte Chemie International Edition

Cover image for Angewandte Chemie International Edition

November 19, 2007

Volume 46, Issue 45

Pages 8521–8717

  1. Cover Picture

    1. Top of page
    2. Cover Picture
    3. Inside Cover
    4. Graphical Abstract
    5. Corrigendum
    6. News
    7. Book Review
    8. Highlights
    9. Review
    10. Communications
    11. Preview
    1. Cover Picture: Colorless Tetrapyrrolic Chlorophyll Catabolites Found in Ripening Fruit Are Effective Antioxidants (Angew. Chem. Int. Ed. 45/2007) (page 8521)

      Thomas Müller, Markus Ulrich, Karl-Hans Ongania and Bernhard Kräutler

      Article first published online: 8 NOV 2007 | DOI: 10.1002/anie.200790227

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      The ripening of fruit … is accompanied by a loss of green color (degreening) and by the typical appearance of appealing colors. In their Communication on page 8699 ff., B. Kräutler and co-workers describe the identification of chlorophyll catabolites in ripening fruit and degreened leaves from fruit trees. The availability of chlorophyll catabolites in plant-derived food and also their antioxidant activity call for attention to be paid as to their possible physiological relevance to humans and animals.

  2. Inside Cover

    1. Top of page
    2. Cover Picture
    3. Inside Cover
    4. Graphical Abstract
    5. Corrigendum
    6. News
    7. Book Review
    8. Highlights
    9. Review
    10. Communications
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    1. Inside Cover: Guest and Ligand Behavior in Zinc-Seamed Pyrogallol[4]arene Molecular Capsules (Angew. Chem. Int. Ed. 45/2007) (page 8522)

      Nicholas P. Power, Scott J. Dalgarno and Jerry L. Atwood

      Article first published online: 8 NOV 2007 | DOI: 10.1002/anie.200790228

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      A guest of choice confined within an octanuclear zinc-seamed pyrogallol[4]arene capsule (light green Zn, red O, black C) can act as a reporter for electronic communication between the exterior and interior of the capsule. As Atwood and co-workers report in their Communication on page 8601 ff., by interchanging ligands (represented by blue and dark green balls) and concomitantly varying electron donation to the metal centers, a C[BOND]H⋅⋅⋅π interaction between the guest and the capsule is either enhanced or diminished (represented by the color of the guest).

  3. Graphical Abstract

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    3. Inside Cover
    4. Graphical Abstract
    5. Corrigendum
    6. News
    7. Book Review
    8. Highlights
    9. Review
    10. Communications
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  4. Corrigendum

    1. Top of page
    2. Cover Picture
    3. Inside Cover
    4. Graphical Abstract
    5. Corrigendum
    6. News
    7. Book Review
    8. Highlights
    9. Review
    10. Communications
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    1. You have free access to this content
      Fluorescence-Lifetime Imaging of DNA–Dye Interactions within Continuous-Flow Microfluidic Systems (page 8536)

      Richard K. P. Benninger, Oliver Hofmann, Björn Önfelt, Ian Munro, Chris Dunsby, Daniel M. Davis, Mark A. A. Neil, Paul M. W. French and Andrew J. de Mello

      Article first published online: 8 NOV 2007 | DOI: 10.1002/anie.200790230

      This article corrects:

      Fluorescence-Lifetime Imaging of DNA–Dye Interactions within Continuous-Flow Microfluidic Systems1

      Vol. 46, Issue 13, 2228–2231, Article first published online: 23 JAN 2007

  5. News

    1. Top of page
    2. Cover Picture
    3. Inside Cover
    4. Graphical Abstract
    5. Corrigendum
    6. News
    7. Book Review
    8. Highlights
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    10. Communications
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  6. Book Review

    1. Top of page
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    4. Graphical Abstract
    5. Corrigendum
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    7. Book Review
    8. Highlights
    9. Review
    10. Communications
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  7. Highlights

    1. Top of page
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    1. Total Syntheses of Lysobactin (Katanosin B) (pages 8548–8552)

      Jean-Marc Campagne

      Article first published online: 17 OCT 2007 | DOI: 10.1002/anie.200702687

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      Catching up with the bugs: Lysobactin (1) is a natural cyclodepsipeptide with potent antibiotic activity against vancomycin-resistant enterococci and methicillin-resistant Staphylococcus aureus. Two total syntheses of 1 have been published recently which should enable further chemical modifications of the lysobactin structure and a better understanding of its mode of action.

    2. Structural “Snapshots” along Reaction Pathways of Non-Heme Iron Enzymes (pages 8553–8556)

      Joseph P. Emerson, Erik R. Farquhar and Lawrence Que Jr.

      Article first published online: 8 OCT 2007 | DOI: 10.1002/anie.200703057

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      Recent X-ray crystallography studies on two non-heme iron enzymes (see picture, orange Fe, red O, blue N) involved in oxygen activation and superoxide detoxification have provided unique structural insights into intermediates in their individual reaction pathways. The results of these studies and their mechanistic significance are discussed.

  8. Review

    1. Top of page
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    1. Organic Transformations on σ-Aryl Organometallic Complexes (pages 8558–8573)

      Marcella Gagliardo, Dennis J. M. Snelders, Preston A. Chase, Robertus J. M. Klein Gebbink, Gerard P. M. van Klink and Gerard van Koten

      Article first published online: 12 OCT 2007 | DOI: 10.1002/anie.200604290

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      In a pinch: A literature survey is presented which describes organic transformations performed on σ-aryl organometallic complexes. Emphasis has been put on the developments of the synthetic protocols that allow easy modification of accessible organometallic compounds. These protocols can be divided into two main categories: electrophilic aromatic substitution and metal-mediated C[BOND]C coupling reactions (see examples in scheme).

  9. Communications

    1. Top of page
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    4. Graphical Abstract
    5. Corrigendum
    6. News
    7. Book Review
    8. Highlights
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    10. Communications
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    1. Conjugated Microporous Poly(aryleneethynylene) Networks (pages 8574–8578)

      Jia-Xing Jiang, Fabing Su, Abbie Trewin, Colin D. Wood, Neil L. Campbell, Hongjun Niu, Calum Dickinson, Alexey Y. Ganin, Matthew J. Rosseinsky, Yaroslav Z. Khimyak and Andrew I. Cooper

      Article first published online: 26 SEP 2007 | DOI: 10.1002/anie.200701595

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      Rigid wiry nets: Conjugated microporous polymer networks are formed by Sonogashira–Hagihara coupling. Although these materials are amorphous, the micropore size and surface area can be controlled by varying the length of the phenyleneethynylene struts (see picture; the network is shown in blue, and one 1,3,5-substituted benzene node and three connected struts are highlighted with C gray and H white).

    2. Siliceous Nanopods from a Compromised Dual-Templating Approach (pages 8579–8582)

      Sui Yang, Xufeng Zhou, Pei Yuan, Meihua Yu, Songhai Xie, Jin Zou, Gao Qing Lu and Chengzhong Yu

      Article first published online: 10 OCT 2007 | DOI: 10.1002/anie.200703628

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      Like a silkworm cocoon: Siliceous nanostructures that resemble silkworm cocoons with inner multishells and outer well-oriented nanochannels have been synthesized by simultaneous compromised vesicle templating and liquid-crystal templating methods (see picture). CTA+=cetyltrimethylammonium; PFO=perfluorooctanoate.

    3. Transition-Metal Complexes Featuring Z-Type Ligands: Agreement or Discrepancy between Geometry and dn Configuration? (pages 8583–8586)

      Marie Sircoglou, Sébastien Bontemps, Maxime Mercy, Nathalie Saffon, Masashi Takahashi, Ghenwa Bouhadir, Laurent Maron and Didier Bourissou

      Article first published online: 8 OCT 2007 | DOI: 10.1002/anie.200703518

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      The value of gold: The coordination of ambiphilic diphosphanylborane ligands to AuCl provides unusual square-planar gold(I) complexes. Insight is gained on the nature of the gold[RIGHTWARDS ARROW]borane interactions in these complexes through natural bond orbital (NBO) analysis and 197Au Mössbauer spectroscopy.

    4. Catalytic Deprotection of Acetals in Basic Solution with a Self-Assembled Supramolecular “Nanozyme” (pages 8587–8589)

      Michael D. Pluth, Robert G. Bergman and Kenneth N. Raymond

      Article first published online: 9 OCT 2007 | DOI: 10.1002/anie.200703371

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      Changing on the inside: Acetals are a commonly used protecting groups for aldehydes and ketones in organic synthesis because of their ease of installation and resistance to cleavage in neutral or basic solution. A self-assembled supramolecular assembly has been shown to catalyze the hydrolysis of acetals and ketals in basic solution (see scheme).

    5. Templated Encapsulation of Pyridyl-Bian Palladium Complexes: Tunable Catalysts for CO/4-tert-Butylstyrene Copolymerization (pages 8590–8592)

      Jitte Flapper and Joost N. H. Reek

      Article first published online: 10 OCT 2007 | DOI: 10.1002/anie.200703294

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      Tuning with zinc: Palladium complexes of 3-pyridyl-bian (see scheme, blue) provide active catalysts for the copolymerization of CO and 4-tert-butylstyrene, but only after encapsulation by two zinc salphen building blocks (red). The catalyst properties depend on the salphen units, giving rise to novel tools for catalyst tuning.

    6. High-Activity, Single-Site Mesoporous Pd/Al2O3 Catalysts for Selective Aerobic Oxidation of Allylic Alcohols (pages 8593–8596)

      Simon F. J. Hackett, Rik M. Brydson, Mhairi H. Gass, Ian Harvey, Andrew D. Newman, Karen Wilson and Adam F. Lee

      Article first published online: 5 OCT 2007 | DOI: 10.1002/anie.200702534

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      Pd does it alone: Tailored heterogeneous catalysts offer exciting, alternative, clean technologies for regioselective molecular transformations. A mesoporous alumina support stabilizes atomically dispersed PdII surface sites (see picture, C light gray, O red, Pd dark gray, Al purple, H white), thereby dramatically enhancing catalytic performance in the aerobic selective oxidation of alcohols.

    7. Alternate-Site Enzyme Promiscuity (pages 8597–8600)

      Andreas Taglieber, Horst Höbenreich, J. Daniel Carballeira, Régis J. G. Mondière and Manfred T. Reetz

      Article first published online: 2 OCT 2007 | DOI: 10.1002/anie.200702751

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      Promiscuous reactions get around: It is shown that promiscuous enzyme-catalyzed reactions (i.e., the catalysis of distinctly different chemical transformations) can also take place at sites other than where the natural reaction occurs.

    8. Guest and Ligand Behavior in Zinc-Seamed Pyrogallol[4]arene Molecular Capsules (pages 8601–8604)

      Nicholas P. Power, Scott J. Dalgarno and Jerry L. Atwood

      Article first published online: 20 SEP 2007 | DOI: 10.1002/anie.200702941

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      Not just an inside job: Encapsulated and confined in an octanuclear zinc-seamed pyrogallol[4]arene molecular capsule, a guest of choice can act as a reporter for electronic communication between the exterior and the interior of the capsule through ligand exchange (see structure of capsule, Zn light blue, O red, S yellow).

    9. A Binuclear Manganese Cluster That Catalyzes Radical-Mediated N-Oxygenation (pages 8605–8608)

      Robert Winkler, Georg Zocher, Ingrid Richter, Thorsten Friedrich, Georg E. Schulz and Christian Hertweck

      Article first published online: 9 OCT 2007 | DOI: 10.1002/anie.200703089

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      Site-directed mutagenesis was used to explore the ligand sphere and geometry of a novel binuclear manganese biocatalyst (see picture; Mn green, C gray, O red, N blue) that oxidizes amino to nitro groups with high specificity. The involvement of Mn in catalysis and radical formation was unequivocally proven by ESR spectroscopy.

    10. Insight into Solid-State Entropy from Diffraction Data (pages 8609–8613)

      Anders Østergaard Madsen and Sine Larsen

      Article first published online: 5 OCT 2007 | DOI: 10.1002/anie.200702423

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      Molecules in motion: The two diastereomeric pentoses ribitol and xylitol differ in that the higher melting isomer, ribitol (see picture, red O, white H) is less dense. Accurate high-resolution diffraction data is used to show that this is an entropy effect caused by a difference between them in the librational motion L1. Their solid-state entropies, calculated from the rigid-body vibrations, are in agreement with calorimetric results.

    11. Benzoylurea Oligomers: Synthetic Foldamers That Mimic Extended α Helices (pages 8614–8617)

      Johanna M. Rodriguez and Andrew D. Hamilton

      Article first published online: 5 OCT 2007 | DOI: 10.1002/anie.200701869

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      Not-so-short and curlies: A new benzoylurea-based foldamer scaffold favors a linear conformation governed by intramolecular hydrogen bonding (see picture, left). The functional groups R are in a staggered arrangement analogous to an α helix. Iterative synthesis and diversification of the functional groups leads to structures with lengths similar to those of naturally occurring α helices (right).

    12. “Dissolution” of Indium(I) Iodide: Synthesis and Structural Characterization of the Neutral Indium Sub-Halide Cluster Complex [In6I8(tmeda)4] (pages 8618–8621)

      Shaun P. Green, Cameron Jones and Andreas Stasch

      Article first published online: 4 OCT 2007 | DOI: 10.1002/anie.200703809

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      The “In” crowd: “Dissolution” of the widely used synthetic reagent indium(I) iodide in tmeda/toluene mixtures (tmeda=N,N,N′,N′-tetramethylethylenediamine) gives [In6I8(tmeda)4]. Its stability and significant solubility in toluene makes it an alternative reagent for synthetic methodologies employing InI. DFT studies (see picture) suggest that its deep red-orange color arises from metal-based σ[RIGHTWARDS ARROW]σ* electronic transitions.

    13. Formation of Polyamide Nanofibers by Directional Crystallization in Aqueous Solution (pages 8622–8624)

      A. Levent Demirel, Matthias Meyer and Helmut Schlaad

      Article first published online: 1 OCT 2007 | DOI: 10.1002/anie.200703486

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      Great balls of fiber! Annealing of a dilute aqueous solution of poly(2-isopropyl-2-oxazoline) above its cloud point leads to the formation of a coagulate in the form of crystalline nanofibers (see microscopy image). Directional crystallization, which occurs below the glass transition temperature of the polymer at 65 °C, is driven by hydrophobic and dipolar interactions in combination with a solvation effect.

    14. Total Synthesis of (−)-Decarbamoyloxysaxitoxin (pages 8625–8628)

      Osamu Iwamoto, Hiroyuki Koshino, Daisuke Hashizume and Kazuo Nagasawa

      Article first published online: 10 OCT 2007 | DOI: 10.1002/anie.200703326

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      A facile and general synthetic strategy for saxitoxin derivatives has been developed, as exemplified by the efficient synthesis of (−)-decarbamoyloxysaxitoxin ((−)-doSTX), the putative enantiomer of the natural product, in 17 steps and in 10 % overall yield. The synthesis features a diastereoselective 1,3-dipolar cycloaddition and a direct oxidation with o-iodoxybenzoic acid (IBX; see scheme, Cbz=benzyloxycarbonyl).

    15. “Oxidationless” Promotion of Rapid Palladium Redispersion by Oxygen during Redox CO/(NO+O2) Cycling (pages 8629–8631)

      Mark A. Newton, Carolina Belver-Coldeira, Arturo Martínez-Arias and Marcos Fernández-García

      Article first published online: 1 OCT 2007 | DOI: 10.1002/anie.200702134

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      The rapid and reversible dispersion of palladium nanoparticles is considerably enhanced if oxygen gas is present in the oxidizing step of the redox cycle. At 673 K oxidation of the Pd nanoparticles is too slow to compete with this dispersion and only occurs after the Pd particles undergo significant size/morphological alteration. Thus, catalyst dispersion and sintering could be controlled by dynamic feedstock management.

    16. Encapsulated N-Heterocyclic Carbenes in Silicones without Reactivity Modification (pages 8632–8635)

      Fabien Bonnette, Tsuyoshi Kato, Mathias Destarac, Gérard Mignani, Fernando P. Cossío and Antoine Baceiredo

      Article first published online: 2 OCT 2007 | DOI: 10.1002/anie.200702288

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      Let them off the leash! Silicone protecting media allow the manipulation and storage of air- and moisture-sensitive N-heterocyclic carbenes (NHCs). Calculations show that a weak carbene–Lewis acid interaction minimizes decomposition of NHCs but does not inhibit NHC reactivity.

    17. Synthesis and Enantioselectivity of P-Chiral Phosphine Ligands with Alkynyl Groups (pages 8636–8639)

      Tsuneo Imamoto, Youichi Saitoh, Aya Koide, Tomokazu Ogura and Kazuhiro Yoshida

      Article first published online: 5 OCT 2007 | DOI: 10.1002/anie.200702513

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      A range of asymmetric transformations are catalyzed by transition-metal complexes of the title ligands with excellent enantioselectivities. The ligands, which were applied successively in Rh-catalyzed hydrogenation and Rh- or Pd-catalyzed C[BOND]C bond-forming reactions, were synthesized by nucleophilic substitution of (R)-(bromo(tert-butyl)methylphosphanyl)borane (see scheme).

    18. An Extensive Class of Solids Full of Holes Large Enough To Enclose over 200 Molecules of H2O (pages 8640–8643)

      Brendan F. Abrahams, Nicholas J. FitzGerald and Richard Robson

      Article first published online: 4 OCT 2007 | DOI: 10.1002/anie.200702656

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      Swiss cheese, Gromit! A new class of solids of widely variable composition has essentially the same crystal structure reminiscent of Emmental cheese (see picture). The presence of the roughly spherical holes in the structure, which are large enough to enclose around 200 water molecules, is a consequence of the edge-to-face agglomeration of 12 fluorene units into pseudospherical clusters.

    19. “Homeopathic” Catalytic Activity and Atom-Leaching Mechanism in Miyaura–Suzuki Reactions under Ambient Conditions with Precise Dendrimer-Stabilized Pd Nanoparticles (pages 8644–8648)

      Abdou Khadri Diallo, Cátia Ornelas, Lionel Salmon, Jaime Ruiz Aranzaes and Didier Astruc

      Article first published online: 11 OCT 2007 | DOI: 10.1002/anie.200703067

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      What generation gap? Three generations (G0, G1, G2) of dendrimer-stabilized Pd nanoparticles (PdNPs) synthesized by click chemistry catalyze Suzuki reactions of PhX (X=I or Br) at 25 °C with increasing catalytic activity as their concentration is decreased: A turnover number of 540 000 was observed for the G0 catalyst at 1 ppm in Pd atoms. Extraction of the PdNPs with alkanethiols yields robust Suzuki catalysts for PhI only (see scheme).

    20. Synergistic Effects of TiO2 and Palladium-Based Cocatalysts on the Selective Oxidation of Ethene to Acetic Acid on Mo–V–Nb Oxide Domains (pages 8649–8652)

      Xuebing Li and Enrique Iglesia

      Article first published online: 9 OCT 2007 | DOI: 10.1002/anie.200700593

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      A great show at the Palladium: Precipitation of Mo–V–Nb oxides in the presence of colloidal TiO2 leads to more dispersed active structures and much higher rates of ethene oxidation to acetic acid. The presence of trace amounts of palladium as supported clusters in physical mixtures (<0.05 % w/w) catalyzes the formation of acetaldehyde intermediates and leads to unprecedented rates and selectivities in the synthesis of acetic acid from ethene and O2.

    21. Unusual Nanoparticle Structures from the Silica Sol–Gel-Mediated Self-Assembly of a Prussian-Blue Analogue and the Formation of Templated Graphite Regions (pages 8653–8655)

      Joshua G. Moore, Eric J. Lochner and Albert E. Stiegman

      Article first published online: 5 OCT 2007 | DOI: 10.1002/anie.200701344

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      A carbon copy that's in a glass of its own: Nanoparticle structures are formed from the gelation of a silica sol–gel solution and the precipitation of a KIXNiIIY[FeIII(CN)6] Prussian-blue analogue in the sol–gel solution. Calcination of the resulting nanoparticle glass destroys the complex, leaves imprints in the silica, and deposits graphite crystals oriented along the long dimension of the void.

    22. A Sydnone Cycloaddition Route to Pyrazole Boronic Esters (pages 8656–8658)

      Duncan L. Browne, Matthew D. Helm, Andrew Plant and Joseph P. A. Harrity

      Article first published online: 4 OCT 2007 | DOI: 10.1002/anie.200703767

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      From dipole to diazole! A direct and regioselective route to functionalized pyrazole boronic esters is developed that employs the cycloaddition of alkynylboronates with sydnones. Functionalization of these products by Suzuki coupling and N-deprotection processes highlight the potential synthetic utility of these species.

    23. Straightforward Synthesis of CF3-Substituted Triarylethenes by Stereoselective Threefold Cross-Coupling Reactions (pages 8659–8661)

      Youhei Takeda, Masaki Shimizu and Tamejiro Hiyama

      Article first published online: 8 OCT 2007 | DOI: 10.1002/anie.200703759

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      Any way round: The palladium-catalyzed threefold cross-coupling reaction of 1,1-dibromo-3,3,3-trifluoro-2-tosyloxypropene with aryl boronic acids provides a versatile route to CF3-substituted triarylethenes (see scheme). The CF3 group is essential for the high Z selectivity in the first coupling reaction, which is the key step in the process. Any of the ethene stereoisomers can be prepared simply by changing the order of the aryl boronic acids.

    24. Tandem Catalysis for a One-Pot Regioselective Protection of Carbohydrates: The Example of Glucose (pages 8662–8665)

      Antoine Français, Dominique Urban and Jean-Marie Beau

      Article first published online: 2 OCT 2007 | DOI: 10.1002/anie.200703437

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      Fine-tuning the conditions for a tandem reaction using a single catalyst in a single reaction vessel leads to carbohydrate building blocks displaying different patterns of protecting groups (see picture). This process greatly simplifies the access to oligomers, as illustrated by the rapid assembly of a trisaccharide.

    25. Cinchona-Alkaloid-Catalyzed Enantioselective Direct Aldol-Type Reaction of Oxindoles with Ethyl Trifluoropyruvate (pages 8666–8669)

      Shinichi Ogawa, Norio Shibata, Junji Inagaki, Shuichi Nakamura, Takeshi Toru and Motoo Shiro

      Article first published online: 2 OCT 2007 | DOI: 10.1002/anie.200703317

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      One or t'other: Pseudoenantiomeric cinchona alkaloids can be used as organocatalysts to access both enantiomeric products of the title reaction selectively in high yields with high diastereo- and enantioselectivities (up to 99 % ee; see scheme). One of the two contiguous quaternary stereogenic carbon centers that are constructed simultaneously is a pharmaceutically significant tertiary α-trifluoromethyl alcohol center. R1=alkyl; R2=H, Me.

    26. Reagent Directing Group Controlled Organic Synthesis: Total Synthesis of (R,R,R)-α-Tocopherol (pages 8670–8673)

      Christian Rein, Peter Demel, Robert A. Outten, Thomas Netscher and Bernhard Breit

      Article first published online: 12 OCT 2007 | DOI: 10.1002/anie.200703268

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      The direct approach: The efficient use of substrate control has served as the basis for the enantioselective total synthesis of (R,R,R)-α-tocopherol. A single reagent directing group (ortho-diphenylphosphanyl benzoate, o-DPPB) served to control the stereoselectivity of a rhodium-catalyzed hydroformylation reaction and the directed allylic substitution as the fragment-coupling step (see picture).

    27. Palladium Fluoro Complexes: Useful Tools To Access Organometallic Metallamacrocycles (pages 8674–8678)

      Andreas Steffen, Thomas Braun, Beate Neumann and Hans-Georg Stammler

      Article first published online: 8 OCT 2007 | DOI: 10.1002/anie.200703393

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      Fluorine's the key: Fluoropalladium complexes open up a new route to metallamacrocycles. Treatment of 1 with 1-trimethylsilylated derivatives of imidazole, 2-phenylimidazole, or purine (see scheme) gives neutral molecules such as the bowl-shaped compound 2 (see structure, iPr groups have been omitted for clarity). All compounds represent rare examples of neutral organometallic macrocycles and do not undergo reductive elimination of a C[BOND]N bond.

    28. An R-Selective Hydroxynitrile Lyase from Arabidopsis thaliana with an α/β-Hydrolase Fold (pages 8679–8681)

      Jennifer Andexer, Jan von Langermann, Annett Mell, Marco Bocola, Udo Kragl, Thorsten Eggert and Martina Pohl

      Article first published online: 1 OCT 2007 | DOI: 10.1002/anie.200701455

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      Folding and selectivity: The noncyanogenic plant Arabidopsis thaliana contains a new hydroxynitrile lyase, which was cloned and characterized. This enzyme is readily available form a recombinant source, has a broad range of substrates, and enantioselectively transforms aliphatic and aromatic aldehydes as well as ketones into the corresponding R-cyanohydrins.

    29. From 2,4-Diphospha-3-Thia- and -3-Selenapentadienes [(Me3Si)2C[DOUBLE BOND]P]2E to Heteronorbornane Cage Compounds (pages 8682–8685)

      Wolf-W. du Mont, Thorsten Gust, Jens Mahnke, Roxana M. Birzoi, Lisa Barra, Delia Bugnariu, Frank Ruthe, Cathleen Wismach, Peter G. Jones, Konstantin Karaghiosoff, László Nyulászi and Zoltán Benkõ

      Article first published online: 2 OCT 2007 | DOI: 10.1002/anie.200703000

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      Cagey characters: Heteronorbornanes (R2CP)2E3 unexpectedly form when selenium or sulfur react with 2,4-diphosphapentadiene derivatives (R2C[DOUBLE BOND]P)2E (R=Me3Si, E=S, Se; see picture). Calculations on model compounds (R=H3Si, E=S), and synthesized counterparts suggest that the (R2CP)2S3 cage forms after a sequence of C[BOND]S and P[BOND]S bond cleavage and formation steps involving S[DOUBLE BOND]PIII-CR2-S-PV([DOUBLE BOND]S)[DOUBLE BOND]CR2 as an open-chain intermediate.

    30. The Binary Selenium(IV) Azides Se(N3)4, [Se(N3)5], and [Se(N3)6]2− (pages 8686–8690)

      Thomas M. Klapötke, Burkhard Krumm, Matthias Scherr, Ralf Haiges and Karl O. Christe

      Article first published online: 12 OCT 2007 | DOI: 10.1002/anie.200702758

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      Black, red, gold: The reaction of SeF4 with Me3SiN3 at low temperatures results in the formation of the first binary selenium(IV) azide Se(N3)4. The decomposition in an NMR tube shows the colors of gray selenium, red selenium, and the desired yellow selenium tetraazide (see picture). The reactions of [SeF5] and [SeF6]2− with Me3SiN3 furnish the corresponding polyazidoselenites [Se(N3)5] and [Se(N3)6]2−. All materials are extremely temperature-sensitive.

    31. Gas-Phase Infrared Spectroscopy and Multidimensional Quantum Calculations of the Protonated Ammonia Dimer N2H7+ (pages 8691–8694)

      Knut R. Asmis, Yonggang Yang, Gabriele Santambrogio, Mathias Brümmer, J. Robert Roscioli, Laura R. McCunn, Mark A. Johnson and Oliver Kühn

      Article first published online: 5 OCT 2007 | DOI: 10.1002/anie.200702607

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      Zero-point energy matters: In strong, low-barrier hydrogen bonds, quantum effects cause a structural symmetrization (see picture). Together with the pronounced anharmonicity of vibrational motion, this situation gives rise to peculiar infrared (IR) spectral signatures in the region below 2000 cm−1. For the shared proton in N2H7+, the IR spectrum is elucidated by combining two experimental techniques with anharmonic quantum calculations.

    32. C(NHC)2: Divalent Carbon(0) Compounds with N-Heterocyclic Carbene Ligands—Theoretical Evidence for a Class of Molecules with Promising Chemical Properties (pages 8695–8698)

      Ralf Tonner and Gernot Frenking

      Article first published online: 8 OCT 2007 | DOI: 10.1002/anie.200701632

      Thumbnail image of graphical abstract

      Future targets: Quantum-chemical calculations predict that the experimentally still unknown carbodicarbenes C(NHC)2 (NHC=N-heterocyclic carbene; see picture for example) are a synthetically accessible class of divalent carbon(0) compounds which are very strong nucleophiles and bases that may be useful ligands for transition-metal complexes.

    33. Colorless Tetrapyrrolic Chlorophyll Catabolites Found in Ripening Fruit Are Effective Antioxidants (pages 8699–8702)

      Thomas Müller, Markus Ulrich, Karl-Hans Ongania and Bernhard Kräutler

      Article first published online: 17 OCT 2007 | DOI: 10.1002/anie.200703587

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      An apple a day keeps the doctor away: This old saying may obtain a new meaning. The degradation of chlorophyll in ripe apples and pears gives rise to so-called nonfluorescent catabolites of chlorophyll (NCCs), which are identical to NCCs from leaves. The NCCs from fruit prove to be effective natural antioxidants.

    34. Palladium Monomers, Dimers, and Trimers on the MgO(001) Surface Viewed Individually (pages 8703–8706)

      Martin Sterrer, Thomas Risse, Livia Giordano, Markus Heyde, Niklas Nilius, Hans-Peter Rust, Gianfranco Pacchioni and Hans-Joachim Freund

      Article first published online: 8 OCT 2007 | DOI: 10.1002/anie.200702444

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      Atom by atom: The formation of palladium dimers and trimers from single palladium atoms adsorbed on the surface of a thin MgO(100) film has been observed with a low-temperature scanning tunneling microscope. Combining experimental results and DFT calculations allows the adsorption sites, the geometry, and the electronic properties of the palladium particles to be determined. These are found to have the structures predicted to be most stable on the MgO surface.

    35. Total Synthesis, Configuration, and Biological Evaluation of Anguinomycin C (pages 8707–8710)

      Simone Bonazzi, Stephan Güttinger, Ivo Zemp, Ulrike Kutay and Karl Gademann

      Article first published online: 4 OCT 2007 | DOI: 10.1002/anie.200703134

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      Against nuclear export! Immunofluorescence assays indicate that anguinomycin C is a potent inhibitor of protein export from the nucleus. Key features in the total synthesis of this antitumor natural product include a Cr-catalyzed enantioselective hetero-Diels–Alder reaction, a Negishi reaction with stereoinversion, and application of the DIOZ auxiliary.

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      Preview: Angew. Chem. Int. Ed. 46/2007 (page 8717)

      Article first published online: 8 NOV 2007 | DOI: 10.1002/anie.200790232

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