Angewandte Chemie International Edition

Cover image for Vol. 44 Issue 29

July 18, 2005

Volume 44, Issue 29

Pages 4413–4645

    1. Cover Picture: Palladium-Catalyzed Cross-Coupling Reactions in Total Synthesis / Metathesis Reactions in Total Synthesis (Angew. Chem. Int. Ed. 29/2005) (page 4413)

      K. C. Nicolaou, Paul G. Bulger and David Sarlah

      Version of Record online: 8 JUL 2005 | DOI: 10.1002/anie.200590098

      A powerful combination of two synthetic methods has advanced the art of organic synthesis like few other reactions. In their Reviews on page 4442 ff. and 4490 ff. K. C. Nicolaou and co-workers illustrate how palladium-catalyzed cross-couplings and metathesis-based reactions, respectively, have blossomed into powerful tools for carbon–carbon bond formation in the total synthesis of natural products.

    2. Proteins in Motion (page 4428)

      Dirk Heinz and Wolf-Dieter Schubert

      Version of Record online: 8 JUL 2005 | DOI: 10.1002/anie.200502001

    3. A Timely Reassessment of Early Prediction in the Bioavailability of Orally Administered Drugs (pages 4432–4434)

      Tim Larsen and Andreas Link

      Version of Record online: 28 JUN 2005 | DOI: 10.1002/anie.200462888

      Rule of thumb: Deciding the fate of drug candidates after an estimate of oral bioavailability depends on how heavily the selection parameters are applied. A retrospective analysis of medications on the market has shown that lipophilicity, percent polar surface area, and the number of H-bond donors are properties that have remained relatively constant over the years, and are clearly the most important physicochemical determinants.

    4. Recent Progress in Asymmetric Allylic Substitutions Catalyzed by Chiral Copper Complexes (pages 4435–4439)

      Hideki Yorimitsu and Koichiro Oshima

      Version of Record online: 9 JUN 2005 | DOI: 10.1002/anie.200500653

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      Copper complements palladium as a catalyst of asymmetric allylic substitutions (see scheme). Palladium catalysis requires soft nucleophiles to ensure high stereo- and regioselectivity, whereas hard nucleophiles such as Grignard and organozinc reagents may be used under copper catalysis. Vast progress during the last decade reveals the promising future of copper catalysis in this asymmetric transformation.

    5. Palladium-Catalyzed Cross-Coupling Reactions in Total Synthesis (pages 4442–4489)

      K. C. Nicolaou, Paul G. Bulger and David Sarlah

      Version of Record online: 30 JUN 2005 | DOI: 10.1002/anie.200500368

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      The virtues of the palladium-catalyzed cross-coupling reactions come alive in this stimulating Review article as the authors highlight a number of total syntheses featuring these important carbon–carbon bond-forming reactions.

    6. Metathesis Reactions in Total Synthesis (pages 4490–4527)

      K. C. Nicolaou, Paul G. Bulger and David Sarlah

      Version of Record online: 8 JUL 2005 | DOI: 10.1002/anie.200500369

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      The benefits of metathesis reactions (alkene, enyne, and alkyne) are made apparent in this stimulating Review article. The authors highlight a number of total syntheses featuring these important carbon–carbon bond-forming reactions.

    7. Molecular Recognition and Discrimination of Amines with a Colorimetric Array (pages 4528–4532)

      Neal A. Rakow, Avijit Sen, Michael C. Janzen, Jennifer B. Ponder and Kenneth S. Suslick

      Version of Record online: 8 JUL 2005 | DOI: 10.1002/anie.200500939

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      Seeing smells: Highly selective discrimination between closely related amines has been demonstrated by using an array of chemoresponsive dyes (see picture). Hierarchical classification of amines based on their colorimetric response is successful and matches that expected from qualitative structural and electronic considerations. High sensitivity (ca. 100 ppbv) has been shown for the detection and discrimination of amines.

    8. Dried Foam Films: Self-Standing, Water-Free, Reversed Bilayers of Amphiphilic Compounds (pages 4532–4535)

      Jian Jin, Jianguo Huang and Izumi Ichinose

      Version of Record online: 24 JUN 2005 | DOI: 10.1002/anie.200500036

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      Complete removal of interstitial water molecules from various foam films of amphiphilic compounds results in self-standing bilayer membranes. The dried foam films (DFFs) in the micrometer to submicrometer range (see picture) are stable even under ultrahigh-vacuum conditions and at temperatures higher than 100 °C.

    9. A Recyclable Catalytic System Based on a Temperature-Responsive Catalyst (pages 4536–4538)

      Hiromi Hamamoto, Yachiyo Suzuki, Yoichi M. A. Yamada, Hidetsugu Tabata, Hideyo Takahashi and Shiro Ikegami

      Version of Record online: 21 JUN 2005 | DOI: 10.1002/anie.200500574

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      A new concept for catalytic reactions in aqueous media is demonstrated by using a temperature-responsive polymer support, poly(N-alkylacrylamide), which is converted into a catalyst by assembly with phosphotungstic acid. At high temperature, the catalyst is highly active in the oxidation of alcohols with H2O2 owing to the formation of emulsions, whereas the product and catalyst are easily separated at low temperature (see scheme).

    10. Pt–Cu Core–Shell and Alloy Nanoparticles for Heterogeneous NOx Reduction: Anomalous Stability and Reactivity of a Core–Shell Nanostructure (pages 4539–4543)

      Shenghu Zhou, Bindhu Varughese, Bryan Eichhorn, Greg Jackson and Kevin McIlwrath

      Version of Record online: 8 JUL 2005 | DOI: 10.1002/anie.200500919

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      Cores to celebrate: At 370 °C, Pt@Cu core–shell nanoparticles rapidly alloy but the reciprocal core–shell nanoparticles, Cu@Pt (see STEM images, left: Cu spectral map; middle: Pt spectral map; right: bright-field image), are kinetically stabilized and show high activity and selectivity for NO reduction.

    11. Host–Guest Interactions: Design Strategy and Structure of an Unusual Cobalt Cage That Encapsulates a Tetrafluoroborate Anion (pages 4543–4546)

      Hani Amouri, Lamia Mimassi, Marie Noelle Rager, Brian E. Mann, Carine Guyard-Duhayon and Laurence Raehm

      Version of Record online: 21 JUN 2005 | DOI: 10.1002/anie.200500786

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      Stuck in the middle: Supramolecular host–guest cages of general formula [BF4⊂(RCN)2Co2L4](BF4)3 with L being a di(benzimidazole)-1,4-phenylene derivative (R=Me, Et, Ph) have been prepared. An encapsulated BF4 anion (B yellow, F pale green; see structure) is locked firmly inside the cage and plays a pivotal role as a template around which the CoII ions (gray) and L ligands (ball-and-stick representation) self-assemble.

    12. Molecular-Weight-Tagged Glycopeptide Library: Efficient Construction and Applications (pages 4547–4549)

      Hiromi Ito, Akihiko Kameyama, Takashi Sato, Katsue Kiyohara, Yoshiaki Nakahara and Hisashi Narimatsu

      Version of Record online: 27 JUN 2005 | DOI: 10.1002/anie.200500802

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      Generation of diversity: An oligosaccharide library can be constructed from glycopeptides by repeating incomplete glycosyltransferse (GTs) reactions in a single tube (see picture). Each product has a different molecular weight (MW). Therefore, the structure of each component in the library can be identified immediately by mass spectrometry alone. The differently colored shapes in the picture symbolize different glycosyl residues.

    13. Water-Soluble Photoluminescent Silicon Quantum Dots (pages 4550–4554)

      Jamie H. Warner, Akiyoshi Hoshino, Kenji Yamamoto and Richard. D. Tilley

      Version of Record online: 23 JUN 2005 | DOI: 10.1002/anie.200501256

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      Strong photoluminescence in the blue region of the visible spectrum was observed for a dispersion of allylamine-capped silicon quantum dots in water. Their ease of synthesis and optical properties make them excellent candidates for biomedical applications, as demonstrated by their incorporation inside the cytosol of HeLa cells (see microscopy image, the inset shows the fluorescence from the silicon quantum dots on excitation with UV light).

    14. Electrochemical Control of the Photocurrent Direction in Intercalated DNA/CdS Nanoparticle Systems (pages 4554–4557)

      Ron Gill, Fernando Patolsky, Eugenii Katz and Itamar Willner

      Version of Record online: 23 JUN 2005 | DOI: 10.1002/anie.200500830

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      A change in direction: The photocurrent generated by CdS nanoparticles attached by means of a double-stranded DNA linker to a gold electrode is reversibly switched between the anodic or cathodic direction (see graphic) depending on the redox state of the methylene blue intercalator.

    15. Rare and Diverse Binding Modes Introduced through Mechanical Bonding (pages 4557–4564)

      David A. Leigh, Paul J. Lusby, Alexandra M. Z. Slawin and D. Barney Walker

      Version of Record online: 23 JUN 2005 | DOI: 10.1002/anie.200500004

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      Any which way, but not loose: A range of diverse noncovalent binding interactions are observed with a [2]rotaxane (see structure) and a [2]catenane that are not found with similar but not mechanically interlocked fragments. (C (macrocycle) turquoise, other C atoms yellow, O red, N blue, H gray, F green, S orange.)

    16. Enantio- and Diastereoselective Catalytic Mannich-Type Reaction of a Glycine Schiff Base Using a Chiral Two-Center Phase-Transfer Catalyst (pages 4564–4567)

      Akihiro Okada, Tomoyuki Shibuguchi, Takashi Ohshima, Hyuma Masu, Kentaro Yamaguchi and Masakatsu Shibasaki

      Version of Record online: 14 JUN 2005 | DOI: 10.1002/anie.200500927

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      Optically active α,β-diamino acids are prepared under asymmetric phase-transfer reaction conditions from a glycine Schiff base and N-protected imines with a tartrate-derived diammonium salt (TaDiAS) as the phase-transfer catalyst (see scheme; Boc=tert-butoxycarbonyl). Chemoselective deprotection of the N atoms allows straightforward transformations of the α,β-diamino acid products to be carried out.

    17. An Anomalous Endohedral Structure of Eu@C82 Metallofullerenes (pages 4568–4571)

      Bao-Yun Sun, Toshiki Sugai, Eiji Nishibori, Kenichi Iwata, Makoto Sakata, Masaki Takata and Hisanori Shinohara

      Version of Record online: 27 JUN 2005 | DOI: 10.1002/anie.200500876

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      A question of symmetry: Unlike other mono-metallofullerenes, the cage structures of Eu@C82 (isomers I and III) have been shown to have Cs (no. 6) and C2v symmetry, respectively, by the maximum entropy method using synchrotron X-ray powder diffraction data. In both isomers (see structures) the Eu ion (turquoise) is located near the top of the carbon cage adjacent to a C[BOND]C double bond.

    18. Elucidation of the Reaction Mechanism for the Palladium-Catalyzed Synthesis of Vinyl Acetate (pages 4572–4574)

      Dario Stacchiola, Florencia Calaza, Luke Burkholder, Alan W. Schwabacher, Matthew Neurock and Wilfred T. Tysoe

      Version of Record online: 29 JUN 2005 | DOI: 10.1002/anie.200500782

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      Finding the right pathway: Reaction of isotopomers of ethylene with acetate species (see scheme) adsorbed on a Pd(111) surface in ultrahigh vacuum has shown that vinyl acetate is produced by insertion of ethylene into the acetate species to form an acetoxyethyl intermediate, which decomposes by β-hydride elimination to yield vinyl acetate.

    19. Tweezering the Core of a Dendrimer: A Photophysical and Electrochemical Study (pages 4574–4578)

      Vincenzo Balzani, Paola Ceroni, Carlo Giansante, Veronica Vicinelli, Frank-Gerrit Klärner, Carla Verhaelen, Fritz Vögtle and Uwe Hahn

      Version of Record online: 27 JUN 2005 | DOI: 10.1002/anie.200501025

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      A large guest for a small host: The tweezering process about the bipyridinium core of a dendrimer by a molecular tweezer (see picture) has been studied electrochemically and by fluorescence spectroscopy and is found to be quite similar to the threading/dethreading processes observed with wire-type bipyridinium-based units and ring-shaped molecules.

    20. Locking and Unlocking of Polyelectrolyte Brushes: Toward the Fabrication of Chemically Controlled Nanoactuators (pages 4578–4581)

      Sergio Moya, Omar Azzaroni, Tamer Farhan, Vicky L. Osborne and Wilhelm T. S. Huck

      Version of Record online: 21 JUN 2005 | DOI: 10.1002/anie.200500228

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      Polymer brushwork: The collapse of polyelectrolyte brushes in salt solutions combined with binding interactions and ion-size-exclusion effects is used in the design of smart polymer surfaces that can be switched between permanently collapsed or extended states with different surface properties (see picture)—a step toward the use of surface-confined polyelectrolytes as nanoactuators.

    21. An S-Selective Lipase Was Created by Rational Redesign and the Enantioselectivity Increased with Temperature (pages 4582–4585)

      Anders O. Magnusson, Mohamad Takwa, Anders Hamberg and Karl Hult

      Version of Record online: 23 JUN 2005 | DOI: 10.1002/anie.200500971

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      Higher activity with larger pockets: The figure shows a superposition of intermediates that occur in acyl transfer to (S)-1-phenylethanol catalyzed by Candida antarctica lipase B (CALB). Wild-type CALB cannot accomodate the phenyl group (gray) in the stereospecificity pocket and form all of the catalytically essential H bonds. The Trp 104 Ala mutation liberates the volume in yellow, the S enantiomer is easily fitted, and the specificity constant increases by a factor of 130 000.

    22. Photocatalytic Nanodiodes for Visible-Light Photocatalysis (pages 4585–4589)

      Hyun G. Kim, Pramod H. Borse, Wonyong Choi and Jae S. Lee

      Version of Record online: 27 JUN 2005 | DOI: 10.1002/anie.200500064

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      Oxidative decomposition of toxic pollutants (such as acetaldehyde and isopropyl alcohol), decomposition of water, and photocurrent generation can all be achieved with visible light. Nano-islands of p-type CaFe2O4 interfacing with bulk n-type PbBi2Nb1.9W0.1O9 (shown) form photocatalytic nanodiodes that demonstrate high stability and high activity for such applications.

    23. Thermally Stable Nanocrystalline γ-Alumina Layers with Highly Ordered 3D Mesoporosity (pages 4589–4592)

      Monika Kuemmel, David Grosso, Cédric Boissière, Bernd Smarsly, Torsten Brezesinski, Pierre A. Albouy, Heinz Amenitsch and Clement Sanchez

      Version of Record online: 24 JUN 2005 | DOI: 10.1002/anie.200500037

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      Feature film: Mesoporous alumina thin films synthesized with a polymeric template have more than 50% porosity, a narrow pore-size distribution, high accessibility, and high thermal stability up to 900°C. The inorganic network is composed of sintered nanocrystalline γ-Al2O3 particles, and the pores are ellipsoidal with a face-centered cubic mesostructure (see image).

    24. Triatomic EP2 Triangles (E=Ge, Sn, Pb) as μ233-Bridging Ligands (pages 4592–4596)

      Joshua S. Figueroa and Christopher C. Cummins

      Version of Record online: 30 JUN 2005 | DOI: 10.1002/anie.200500707

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      Divalent Group 14 salts react with the [Na(thf)x]+ derivative of the terminal niobium phosphide anion [P[TRIPLE BOND]Nb{N(Np)Ar}3] (Np=neopentyl, Ar=3,5-Me2C6H3) to give complexes of the form [(μ233-cyclo-EP2){Nb[N(Np)Ar]3}2] (E=Ge, Sn, and Pb; see structure). The bridging {cyclo-EP2} units in these complexes can be considered as neutral 2π-electron three-membered rings that are isolobal to the cyclopropenium ion.

    25. A General Strategy toward S-Linked Glycopeptides (pages 4596–4599)

      Desiree A. Thayer, Henry N. Yu, M. Carmen Galan and Chi-Huey Wong

      Version of Record online: 30 JUN 2005 | DOI: 10.1002/anie.200500090

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      A high-yield one-pot synthesis of S-linked glycosyl amino acids 1 has been developed (see scheme; DMF=dimethyl formamide) and used in the solid-phase synthesis of S-linked glycopeptides. This approach has been shown to be efficient for the synthesis of various S-linked glycosyl amino acid building blocks.

    26. Synthesis of an Optically Active C1-Symmetric Al(salalen) Complex and Its Application to the Catalytic Hydrophosphonylation of Aldehydes (pages 4600–4602)

      Bunnai Saito and Tsutomu Katsuki

      Version of Record online: 27 JUN 2005 | DOI: 10.1002/anie.200501008

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      Quite universally: The chiral trigonal-bipyramidal Al(salalen) complex 1 was synthesized and found to be an efficient catalyst for enantioselective hydrophosphonylation of various aldehydes with dimethyl phosphite (see scheme). This is the first example where a molecular catalyst can be applied to the reactions of both aromatic and aliphatic aldehydes with enantioselectivities greater than 80 % ee.

    27. Mining the Tetraene Manifold: Total Synthesis of Complex Pyrones from Placobranchus ocellatus (pages 4602–4606)

      Aubry K. Miller and Dirk Trauner

      Version of Record online: 27 JUN 2005 | DOI: 10.1002/anie.200500488

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      A natural product anticipated through total synthesis! Ocellapyrone A was obtained in the laboratory several months before the structure of this unusual natural product (see scheme) was reported. An isomerization/8π–6π electrocyclization cascade was used for the formation of the natural product from a polyene precursor. The synthesis of ocellapyrone B from a diastereomer of ocellapyrone A was also performed.

    28. Catalytic Asymmetric Couplings of Ketenes with Aldehydes To Generate Enol Esters (pages 4606–4608)

      Carsten Schaefer and Gregory C. Fu

      Version of Record online: 8 JUL 2005 | DOI: 10.1002/anie.200501434

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      With a little help from the ferrocenyl catalyst ((−)-1), a wide array of α-arylalkanoic acid derivatives can be produced from the catalytic asymmetric coupling of ketenes with aldehydes (see scheme). The enol esters are readily transformed into other useful families of compounds such as carboxylic acids and alcohols.

    29. Synthesis of Seven-Membered-Ring Ketones by Arylative Ring Expansion of Alkyne-Substituted Cyclobutanones (pages 4608–4611)

      Takanori Matsuda, Masaomi Makino and Masahiro Murakami

      Version of Record online: 28 JUN 2005 | DOI: 10.1002/anie.200500799

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      Ever-increasing circles: Seven-membered-ring ketones are constructed by a rhodium(I)-catalyzed arylative ring-expansion reaction of alkyne-substituted aryl cyclobutanones, in which two C[BOND]C bond-forming and one C[BOND]C bond-cleaving events occur consecutively (see scheme).

    30. Chiral Phosphine–Olefin Bidentate Ligands in Asymmetric Catalysis: Rhodium-Catalyzed Asymmetric 1,4-Addition of Aryl Boronic Acids to Maleimides (pages 4611–4614)

      Ryo Shintani, Wei-Liang Duan, Takashi Nagano, Atsushi Okada and Tamio Hayashi

      Version of Record online: 23 JUN 2005 | DOI: 10.1002/anie.200501305

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      Two is better than one: Novel chiral phosphine–olefin ligands 1 a and 1 b act as bidentate ligands with some transition metals and have proved to be highly effective in the rhodium-catalyzed asymmetric 1,4-addition of aryl boronic acids to maleimides with high enantioselectivity (see scheme).

    31. An Unstable Ligand-Unsupported CuI Dimer Stabilized in a Supramolecular Framework (pages 4614–4617)

      Shao-Liang Zheng, Marc Messerschmidt and Philip Coppens

      Version of Record online: 8 JUL 2005 | DOI: 10.1002/anie.200501154

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      A stable environment: A [Cu(NH3)2]22+ dimer with weak cuprophilicity is stabilized in the cavities of a supramolecular framework (see structure). This CuI dimer is otherwise unstable, so stabilization within a supramolecular matrix offers an unprecedented opportunity for systematic studies of the isolated dimeric species, either in the ground state or the excited state.

    32. Zn– and Cd–Metallothionein Recombinant Species from the Most Diverse Phyla May Contain Sulfide (S2−) Ligands (pages 4618–4622)

      Mercè Capdevila, Jordi Domènech, Ayelén Pagani, Laura Tío, Laura Villarreal and Sílvia Atrian

      Version of Record online: 30 JUN 2005 | DOI: 10.1002/anie.200501183

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      A sulfide surprise: The analysis of ZnII–, CdII–, and CuI–MT recombinant preparations of metallothioneins (MTs) from many organisms provides clear evidence that sulfide ions are present in nearly all their physiologically stable ZnII–MT and CdII–MT complexes (see picture), but in none of the CuI–MT species. The features of the MT complexes are in good correlation with those reported for plant and yeast ZnII–or CdII–γ-glutamyl peptides.

    33. Ambident Reactivity of the Nitrite Ion Revisited (pages 4623–4626)

      Alexander A. Tishkov, Uli Schmidhammer, Stefan Roth, Eberhard Riedle and Herbert Mayr

      Version of Record online: 8 JUL 2005 | DOI: 10.1002/anie.200501274

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      Lost control: The rationalization of the ambident reactivity of NO2 by the change between charge control to orbital control has to be revised. SN1-type reactions of carbocations with NO2 give kinetically controlled product mixtures only when these reactions proceed without activation energy (diffusion control). Activation-controlled SN1 alkylations are reversible and lead to the thermodynamically more stable nitro compounds.

    34. Highly Enantioselective Preparation of Tertiary Alcohols and Amines by Copper-Mediated Diastereoselective Allylic SN2′ Substitutions (pages 4627–4631)

      Helena Leuser, Sylvie Perrone, Frédéric Liron, Florian F. Kneisel and Paul Knochel

      Version of Record online: 8 JUL 2005 | DOI: 10.1002/anie.200500672

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      Trisubstituted allylic pentafluorobenzoates react with diorganozinc reagents in the presence of CuCN⋅2 LiCl to provide alkenes bearing a chiral quaternary center in α position (>95 % ee). These alkenes are readily converted into chiral tertiary alcohols or into chiral amino alcohols by a straightforward sequence of ozonolysis followed by Curtius rearrangement (see scheme).

    35. 13C-Labeled Tyrosine Residues as Local IR Probes for Monitoring Conformational Changes in Peptides and Proteins (pages 4631–4635)

      Sandra Tremmel, Michael Beyermann, Hartmut Oschkinat, Michael Bienert, Dieter Naumann and Heinz Fabian

      Version of Record online: 24 JUN 2005 | DOI: 10.1002/anie.200500547

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      Launching a probe: Introducing individual tyrosine residues labeled with 13C at the C4 position of the phenol ring (Y11 and Y19 in the picture) shifts the resulting tyrosine IR band to lower frequencies. This opens the door to the simultaneous monitoring of local conformational changes in different regions of proteins by IR spectroscopy, as demonstrated with a chemically synthesized analogue of a WW domain.

    36. Geometrically Precisely Defined Multinanometer Expansion/Contraction Motions in a Resorcin[4]arene Cavitand Based Molecular Switch (pages 4635–4638)

      Vladimir A. Azov, Anna Schlegel and François Diederich

      Version of Record online: 8 JUL 2005 | DOI: 10.1002/anie.200500970

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      A molecular switch based on a resorcin[4]arene cavitand undergoes reversibly very large, geometrically precisely defined molecular motion (see picture). Controlled switching between the contracted (linear extension ≈7 Å) and the expanded (linear extension ≈7 nm) states is induced by pH or temperature changes and was observed by 1H NMR spectroscopy and fluorescence resonance energy transfer (FRET).

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