Angewandte Chemie International Edition

Cover image for Vol. 44 Issue 2

December 27, 2004

Volume 44, Issue 2

Pages 167–341

    1. Cover Picture: Palladium-Catalyzed Enantioselective Domino Reaction for the Efficient Synthesis of Vitamin E (Angew. Chem. Int. Ed. 2/2005) (page 167)

      Lutz F. Tietze, Konrad M. Sommer, Julia Zinngrebe and Florian Stecker

      Article first published online: 21 DEC 2004 | DOI: 10.1002/anie.200590003

      A domino reaction consists of several consecutive transformations in which the functions required for one reaction are generated in the preceding bond-formation or fragmentation step. L. F. Tietze et al. applied this concept to the synthesis of vitamin E described on page 257 ff. They developed an enantioselective palladium-catalyzed process for the construction of the chiral chroman framework with 96 % ee and concomitant introduction of part of the side chain.

    2. Graphical Abstract: Angew. Chem. Int. Ed. 2/2005 (page 170)

      Article first published online: 21 DEC 2004 | DOI: 10.1002/anie.200590004

    3. Protecting Groups. By Philip J. Kocieński. (page 183)

      Christian Vogel

      Article first published online: 21 DEC 2004 | DOI: 10.1002/anie.200485226

    4. Nucleic Acids. By Shawn Doonan. (pages 184–185)

      Richard Cosstick

      Article first published online: 21 DEC 2004 | DOI: 10.1002/anie.200385219

    5. Recent Developments in the Transfer of Chirality within Enolate Alkylation Reactions (pages 186–189)

      Jason Eames and Michael J. Suggate

      Article first published online: 21 DEC 2004 | DOI: 10.1002/anie.200461617

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      Remarkable asymmetric induction is observed in the alkylation of enolates derived from enantiomerically pure amides, even though these enolates seem to have no apparent chirality (see scheme). The proposed origin and mechanism for this transfer of chirality is discussed. LTMP=lithium tetramethylpiperidide.

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      Selectfluor: Mechanistic Insight and Applications (pages 192–212)

      Paul T. Nyffeler, Sergio Gonzalez Durón, Michael D. Burkart, Stéphane P. Vincent and Chi-Huey Wong

      Article first published online: 1 DEC 2004 | DOI: 10.1002/anie.200400648

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      A versatile reagent: The search for more efficient and readily available sources of electrophilic fluorine culminated in the development of selectfluor (see scheme), which is both highly reactive and safe to handle. This Review presents the myriad of applications of selectfluor and discusses possible reaction mechanisms. The perspectives for fluorinated compounds in medicine and biology are also investigated.

    7. Modern Synthetic Methods for Fluorine-Substituted Target Molecules (pages 214–231)

      Masaki Shimizu and Tamejiro Hiyama

      Article first published online: 21 DEC 2004 | DOI: 10.1002/anie.200460441

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      The incorporation of fluorine into organic molecules is a powerful strategy for the discovery of potent biologically active agents and versatile materials that exhibit unique functions (see scheme). The availability of such fluorinated compounds is critically dependent on synthetic fluorine chemistry. Novel synthetic methods for the preparation of a variety of organofluorine target molecules are described.

    8. Synthesis and Structure of the Highly Chlorinated [60]Fullerene C60Cl30 with a Drum-Shaped Carbon Cage (pages 234–237)

      Pavel A. Troshin, Rimma N. Lyubovskaya, Ilya N. Ioffe, Natalia B. Shustova, Erhard Kemnitz and Sergey I. Troyanov

      Article first published online: 12 NOV 2004 | DOI: 10.1002/anie.200461531

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      Chlorination of C60 with SbCl5, ICl, or ICl3 at 220–250 °C gives the highly chlorinated fullerene C60Cl30. The carbon cage of the C60Cl30 molecule has a unique cylindrical shape (see picture), composed of two aromatic six-membered rings located opposite each other and one equatorial aromatic 18π trannulene belt. DFT calculations suggest that C60Cl30 is the final product of [60]fullerene chlorination.

    9. Transition-Metal-Catalyzed Benzylation of Arenes and Heteroarenes (pages 238–242)

      Kristin Mertins, Irina Iovel, Jette Kischel, Alexander Zapf and Matthias Beller

      Article first published online: 21 DEC 2004 | DOI: 10.1002/anie.200460666

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      Friedel–Crafts-type benzylation of various aromatic and heteroaromatic compounds with benzylic acetates, alcohols, and carbonates was promoted under mild reaction conditions by a series of Rh, Ir, Pd, and Pt catalysts (see scheme; R1=H, Me; R2=H, Cl, MeO; R3=H, Ac, CO2Me). The desired products were obtained in high yields and with high selectivities.

    10. Helical Chirality in Pentacoordinate Zinc Complexes—Selective Access to Both Pseudoenantiomers with One Ligand Configuration (pages 242–245)

      Michael Seitz, Sabine Stempfhuber, Manfred Zabel, Martin Schütz and Oliver Reiser

      Article first published online: 21 DEC 2004 | DOI: 10.1002/anie.200460843

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      Δ2or Λ2, that is the question! Depending on the heteroatom X, the pentadentate bis(oxazoline) ligand will fold around a zinc(II) ion exclusively in the Δ2 or Λ2 configuration, both in solution and in the solid state.

    11. From a Monomeric Bismuth Silanolate to a Molecular Bismuth Oxo Cluster: [Bi22O26(OSiMe2tBu)14] (pages 245–249)

      Dirk Mansfeld, Michael Mehring and Markus Schürmann

      Article first published online: 21 DEC 2004 | DOI: 10.1002/anie.200461476

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      The high-nuclearity bismuth oxo cluster [Bi22O26(OSiMe2tBu)14] (see structure) was obtained by partial hydrolysis of Bi(OSiMe2tBu)3. A hydrophobic layer of silanolate groups covers the bismuth oxo core, the structure of which is closely related to that of β-Bi2O3. Both the bismuth oxo cluster and the bismuth silanolate precursor decompose to give the sillenite-type compound Bi12SiO20.

    12. Perylene Bisimide Based Macrocycles: Effective Probes for the Assessment of Conformational Effects on Optical Properties (pages 250–253)

      Peter Osswald, Dirk Leusser, Dietmar Stalke and Frank Würthner

      Article first published online: 21 DEC 2004 | DOI: 10.1002/anie.200461585

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      Conformation-dependent tuning of color: Starting from aryloxy-substituted perylene bisimides two isomeric diagonally (A) and laterally (B) bridged macrocycles were synthesized (see picture) for three different bridge lengths. These isomers comprise different conformational features and can, therefore, be used as molecular probes to deduce the conformational influence on the optical properties of this important class of fluorophores in solution.

    13. The SF5Ox Radicals, x=0–3 (pages 253–257)

      Marc Kronberg, Stefan von Ahsen, Helge Willner and Joseph S. Francisco

      Article first published online: 21 DEC 2004 | DOI: 10.1002/anie.200461235

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      No longer up in the air: The radicals SF5Ox (x=0–3) were isolated in a matrix and characterized by IR and UV spectroscopy, photolysis experiments, and quantum chemical calculations. They are probably involved in the atmospheric oxidation of SF6, a gas commonly used in the electricpower industry.

    14. Palladium-Catalyzed Enantioselective Domino Reaction for the Efficient Synthesis of Vitamin E (pages 257–259)

      Lutz F. Tietze, Konrad M. Sommer, Julia Zinngrebe and Florian Stecker

      Article first published online: 26 NOV 2004 | DOI: 10.1002/anie.200461629

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      A new route to vitamin E: The palladium-catalyzed enantioselective domino reaction of the unsaturated phenol derivative 1 with acrylate provides efficient access to the chiral chroman 2 with 96 % ee and in 84 % yield (see scheme). Intermediate 2 can then be converted into vitamin E in a few steps.

    15. Formation of Ir[BOND]Rh and Ir[BOND]Mo Bonds by Using an Ancillary ortho-Carborane-1,2-diselenolato Ligand (pages 259–262)

      Guo-Xin Jin, Jian-Qiang Wang, Chen Zhang, Lin-Hong Weng and Max Herberhold

      Article first published online: 21 DEC 2004 | DOI: 10.1002/anie.200461348

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      Trinuclear clusters containing heteronuclear Ir[BOND]M bonds, for example [{Cp*Ir[Se2C2(B10H10)]}2Rh] (1), were obtained from the reactions of the 16-electron complex [Cp*Ir{Se2C2(B10H10)}] and characterized by X-ray crystallography. Compound 1 is thermally converted into 2 by generation of an additional Ir[BOND]B bond (see picture: Ir yellow; Rh red; Se magenta; C black; B white). Cp*=η5-C5Me5.

    16. VS2 Nanotubes Containing Organic-Amine Templates from the NT-VOx Precursors and Reversible Copper Intercalation in NT-VS2 (pages 262–265)

      Helen Annal Therese, Frank Rocker, Andreas Reiber, Jixue Li, Michael Stepputat, Gunnar Glasser, Ute Kolb and Wolfgang Tremel

      Article first published online: 21 DEC 2004 | DOI: 10.1002/anie.200461326

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      Softly, softly: VS2 nanotubes (see electron micrograph, layer separation 1.6 nm) are prepared from vanadium oxide nanotubes by a “chimie douce” process. The VS2 nanotubes are remarkably stable; the corresponding bulk compound is unstable unless it is intercalated with alkali-metal atoms. The nanotubes reversibly intercalate copper with high capacity and thus could serve as precursors for conductors or contacts in electronic circuitry.

    17. Mass Spectrometric Investigations of the Dissociation of [C@W6Cl17] Ions in the Gas Phase (pages 265–269)

      Ralf Burgert, Katharina Koch, Hansgeorg Schnöckel, Martina Weisser, Hans-Jürgen Meyer and Hans Georg von Schnering

      Article first published online: 21 DEC 2004 | DOI: 10.1002/anie.200460972

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      A clean break: A carbon-centered tungsten cluster [C@W6Cl18]2− (see picture: C orange, Cl green, W blue) was examined by mass spectrometry and its decomposition studied by collisionally activated dissociation experiments. A retrosynthesis-type dissociation sequence which gives indications about the mechanism of formation is observed. The bonding of the carbon atoms in the center of the tungsten framework shows parallels to the bonding in tungsten carbide.

    18. Three-Dimensional Mesoporous Chromium Oxide: A Highly Efficient Material for the Elimination of Volatile Organic Compounds (pages 271–273)

      Anil K. Sinha and Kenichirou Suzuki

      Article first published online: 21 DEC 2004 | DOI: 10.1002/anie.200461284

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      An exceptionally high capacity for the elimination of volatile organic compounds (VOCs) is displayed by a three-dimensional mesoporous chromium oxide (see picture). Under ambient conditions the material acts as a selective sorbent for VOCs (e.g., toluene), whereas at higher temperatures it is an effective and selective deep oxidation catalyst for these compounds.

    19. Germanium-Catalyzed Growth of Zinc Oxide Nanowires: A Semiconductor Catalyst for Nanowire Synthesis (pages 274–278)

      Zheng Wei Pan, Sheng Dai, Christopher M. Rouleau and Douglas H. Lowndes

      Article first published online: 21 DEC 2004 | DOI: 10.1002/anie.200460043

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      Green fields of nanowires: Germanium, a Group IV semiconductor, can act as an efficient catalyst for high-rate (up to 400 μm h−1) growth of very long (up to 200 μm), extremely straight, and quasi-aligned arrays of single-crystalline ZnO nanowires (see picture). The diameter of the Ge particles (0.5–4 μm) is about 5–15 times that of the associated nanowires (50–400 nm). The patterned growth of ZnO nanorods was achieved on photolithographically prepared Ge-dot patterns.

    20. Selective Synthesis of Two Constitutionally Isomeric Oriented Calix[6]arene-Based Rotaxanes (pages 278–281)

      Arturo Arduini, Flavio Ciesa, Marcello Fragassi, Andrea Pochini and Andrea Secchi

      Article first published online: 21 DEC 2004 | DOI: 10.1002/anie.200461336

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      Only in apolar media is the calix[6]arene wheel threaded from its upper rim by asymmetric bipyridinium axles. This leads to the formation of oriented pseudorotaxanes. Their stoppering with a different stopper yields rotaxanes characterized by the unequivocal orientation of the wheel rims with respect to the two different stoppers (see picture, R1=CHPh2/CHCy2, R2=CHCy2/CHPh2, Cy=cyclohexyl, Ts=toluene-4-sulfonyl).

    21. The Formal Conversion of SiOH Protons into Hydrides by Germanium(II) Species Leads to the Formation of the Germanium(IV) Hydride Cluster [(RSiO3GeH)4] (pages 281–284)

      Umesh N. Nehete, Vadapalli Chandrasekhar, Herbert W. Roesky and Jörg Magull

      Article first published online: 21 DEC 2004 | DOI: 10.1002/anie.200460849

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      Germanium cubed: Addition of [Ge{N(SiMe3)2}2] to a suspension of RSi(OH)3 (R=(2,6-iPr2C6H3)N(SiMe3)) in hexane/THF affords the germanium siloxane 1 with terminal Ge[BOND]H units in good yield. Compound 1 contains a Ge4O12Si4 cubic polyhedron core in which the corners of the cube are alternately occupied by germanium and silicon atoms. Each of the twelve edges of the cube contains one bridging oxygen atom.

    22. Tri- and Tetracarbanionic Initiators by a Lithium/Halide Exchange Reaction: Application to Star-Polymer Synthesis (pages 284–287)

      Rachid Matmour, Arnaud Lebreton, Constantinos Tsitsilianis, Ioannis Kallitsis, Valérie Héroguez and Yves Gnanou

      Article first published online: 21 DEC 2004 | DOI: 10.1002/anie.200461056

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      A family of polycarbanionic initiators: Bis-, tris-, and tetrakisaryl lithium compounds (see scheme) were synthesized from the corresponding aryl halides by simple halogen/lithium exchange reactions. These polylithiated species were used to prepare telechelic and three- and four-armed star polystyrene and polybutadiene homopolymers, as well as poly(styrene-block-butadiene-block-methyl methacrylate) star block terpolymers.

    23. Generalized Fluorocarbon-Surfactant-Mediated Synthesis of Nanoparticles with Various Mesoporous Structures (pages 288–292)

      Yu Han and Jackie Y. Ying

      Article first published online: 21 DEC 2004 | DOI: 10.1002/anie.200460892

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      Tunable mesostructures and ultrafine particle sizes were achieved by means of triblock-copolymer and fluorocarbon surfactants, respectively, in the hydrothermal synthesis of mesoporous silica nanoparticles. The TEM image shows one such nanoparticle with a diameter of approximately 300 nm.

    24. The First Proton-Conducting Metallic Ion-Radical Salts (pages 292–295)

      Akane Akutsu-Sato, Hiroki Akutsu, Scott S. Turner, Peter Day, Michael R. Probert, Judith A. K. Howard, Tomoyuki Akutagawa, Sadamu Takeda, Takayoshi Nakamura and Takehiko Mori

      Article first published online: 21 DEC 2004 | DOI: 10.1002/anie.200461686

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      Any old ion? Two bis(ethylenedithio)tetrathiafulvalene (BEDT-TTF) radical salts with ion channels of stacked [18]crown-6 and Cat/H2O molecules (Cat=H3O+ or NH4+) are described. The structures contain alternating BEDT-TTF layers, [(Cat)M(C2O4)3]2− (M=Ga, Cr) layers, and the [18]crown-6 ion channels (see picture). The salts are metallic electrical conductors, and they show high protonic conductivity.

    25. 1D Saturation Transfer Difference NMR Experiments on Living Cells: The DC-SIGN/Oligomannose Interaction (pages 296–298)

      Silvia Mari, Diego Serrano-Gómez, F. Javier Cañada, Angel L. Corbí and Jesús Jiménez-Barbero

      Article first published online: 21 DEC 2004 | DOI: 10.1002/anie.200461574

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      SIGN of the times: Receptor–ligand interactions in which integral membrane proteins are involved can be detected directly by 1D saturation transfer difference (STD) NMR experiments on living cells (see 1H NMR (a) and STD (b) spectra of mannan with K562-CD209 cells). The technique can be used for molecular recognition in drug-screening processes and is demonstrated for the DC-SIGN receptor.

    26. Carbohydrate Recognition in Water by a Tricyclic Polyamide Receptor (pages 298–302)

      Emmanuel Klein, Matthew P. Crump and Anthony P. Davis

      Article first published online: 21 DEC 2004 | DOI: 10.1002/anie.200461409

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      A sweet center: Most carbohydrates are supremely comfortable in water. Can they be tempted to leave? Yes, if their new home satisfies all their needs. The water-soluble receptor 1 (R=polycarboxylate) provides hydrophobic surfaces (purple) for CH groups and amide groups (red) for polar substituents. Equatorial substitution is especially well accommodated, and the system duly favors β-glucosyl (2).

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      Renewable Olefins from Biodiesel by Autothermal Reforming (pages 302–305)

      Ramanathan Subramanian and Lanny D. Schmidt

      Article first published online: 21 DEC 2004 | DOI: 10.1002/anie.200460790

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      Not just a fuel: Renewable olefins, olefinic esters, and hydrogen are synthesized by the partial oxidation of biodiesel (methyl esters derived from vegetable oils) with air on a Rh–Ce catalyst in an autothermal reactor (see scheme). The availability and prices of vegetable oils suggest that this process could replace much of chemical production from fossil fuels.

    28. A Spin-Admixed Ruthenium Complex (pages 305–307)

      M. Carmen Barral, Santiago Herrero, Reyes Jiménez-Aparicio, M. Rosario Torres and Francisco A. Urbanos

      Article first published online: 21 DEC 2004 | DOI: 10.1002/anie.200461463

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      The unusual magnetic behavior of [Ru2(μ-O2CMe)(μ-DPhF)3(H2O)]BF4⋅0.5 CH2Cl2 (1; DPhF=N,N′-diphenylformamidinate), which is intermediate between that of compounds with spin states S=1/2 and S=3/2, is attributed to a quantum mechanical spin admixture. This phenomenon results from a multiple bond between the metal atoms which permits an appropriate disposition of molecular orbitals.

    29. Palladium-Catalyzed Asymmetric Allylation of Prochiral Nucleophiles: Synthesis of 3-Allyl-3-Aryl Oxindoles (pages 308–310)

      Barry M. Trost and Mathias U. Frederiksen

      Article first published online: 21 DEC 2004 | DOI: 10.1002/anie.200460335

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      Excellent yields and enantioselectivies are attained in the synthesis of 3-alkyl-3-aryl oxindoles based on the Pd-catalyzed asymmetric allylic alkylation (AAA) reaction. This approach utilizes a nonbasic hydroxylic additive in the transformation of 3-aryl oxindoles into complex, synthetically valuable oxindoles (see scheme).

    30. Bromide-Assisted Oxidation of Substituted Phenols with Hydrogen Peroxide to the Corresponding p-Quinol and p-Quinol Ethers over WO42−-Exchanged Layered Double Hydroxides (pages 310–313)

      B. F. Sels, D. E. De Vos and P. A. Jacobs

      Article first published online: 21 DEC 2004 | DOI: 10.1002/anie.200461555

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      A simple and efficient one-pot synthesis of p-quinols and their ethers occurs over tungstate-exchanged layered double hydroxides (WO42−-LDHs), which catalyze the bromide-assisted oxidation of substituted phenols to the corresponding 4-alkoxy- and 4-hydroxycyclohexa-2,5-dienones in high yields (see scheme).

    31. Rapid I/I3 Diffusion in a Molecular-Plastic-Crystal Electrolyte for Potential Application in Solid-State Photoelectrochemical Cells (pages 313–316)

      Qing Dai, Douglas R. MacFarlane, Patrick C. Howlett and Maria Forsyth

      Article first published online: 21 DEC 2004 | DOI: 10.1002/anie.200460871

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      High current-carrying capacity and rapid, liquidlike diffusion were achieved in a dye-sensitized solar cell (DSSC) based on the plastic-crystalline electrolyte succinonitrile and the I/I3 redox couple (see diagram). This could lead to the development of true solid-state DSSCs without conventional organic-liquid electrolytes, which can cause problems with long-term device stability.

    32. A Hexapentaene-Extended Quinocumulene Cyclotrimerized to a Tricyclobutabenzene Derivative (pages 316–319)

      Takeshi Kawase, Yuichiro Minami, Naoki Nishigaki, Satoshi Okano, Hiroyuki Kurata and Masaji Oda

      Article first published online: 21 DEC 2004 | DOI: 10.1002/anie.200461608

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      Rings around rings: Cyclotrimerization of a hexapentaene-extended quinocumulene led to the novel tricyclobutabenzene derivative shown. Its molecular structure reveals a considerably distorted propeller configuration that deviates largely from the ideal C3 symmetry. Moderate bond alternation is evident in the central benzene ring.

    33. Enantiospecific Strategy Towards Oxygen-Bridged Terpenoids: Tandem Transannular-Cyclization and Ring-Contraction Processes (pages 319–322)

      Antonio Rosales, Rosa E. Estévez, Juan M. Cuerva and J. Enrique Oltra

      Article first published online: 21 DEC 2004 | DOI: 10.1002/anie.200461210

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      From conformational flexibility to rigidity: The straightforward synthesis of rigid molecules with a transannular oxygen bridge starting from flexible germacrolides, which are easily obtained from renewable sources, is described (see scheme). Transannular cyclization of medium-sized rings enhances molecular rigidity and structural complexity, two properties often associated with biological activity in small molecules.

    34. Hydrogen Processing by FeIII-Exchanged Montmorillonite: A Unique Geochemical Protocol (pages 322–325)

      Boyapati M. Choudary, Mannepalli L. Kantam, Kalluri V. S. Ranganath and Kottapalli K. Rao

      Article first published online: 21 DEC 2004 | DOI: 10.1002/anie.200461070

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      The production of hydrogen by the relay of electrons from I to H+ in an acidic, aqueous medium and the consumption of hydrogen by reductive N acylation open up enormous opportunities in hydrogen chemistry (see scheme).

    35. Polar Assembly in a Designed Protein Fiber (pages 325–328)

      Andrew M. Smith, Steve F. A. Acquah, Neil Bone, Harold W. Kroto, Maxim G. Ryadnov, Marryat S. P. Stevens, David R. M. Walton and Derek N. Woolfson

      Article first published online: 21 DEC 2004 | DOI: 10.1002/anie.200461599

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      Bioinspiration: Polar assembly (a feature of many natural protein-based fibrous structures, such as actin, microtubules, intermediate filaments, and collagens) is demonstrated in a straightforward, synthetic, peptide-based fiber system of de novo design (see false-color confocal-microscope image of fibers). This finding opens up possibilities for engineering self-assembling soft materials from the bottom up and with nano-to-microscale precision.

    36. Liquid-Crystalline Assembly from Rigid Wedge–Flexible Coil Diblock Molecules (pages 328–332)

      Jung-Keun Kim, Min-Ki Hong, Jong-Hyun Ahn and Myongsoo Lee

      Article first published online: 21 DEC 2004 | DOI: 10.1002/anie.200461623

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      Shape sorting: The incorporation of a flexible coil of variable length into a rigid wedge-shaped building block leads to the spontaneous formation of a rich variety of supramolecular structures. These include a bilayer lamellar structure with in-plane hexagonally ordered perforations (see picture, R=(CH2)13CH3).

    37. Single-Crystal Mesoporous Silica Ribbons (pages 332–336)

      Jianfang Wang, Chia-Kuang Tsung, Ryan C. Hayward, Yiying Wu and Galen D. Stucky

      Article first published online: 21 DEC 2004 | DOI: 10.1002/anie.200461296

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      Take a length of ribbon: Mesoporous silica ribbons that are typically 50–250 nm thick, 0.4–1.5 μm wide, and hundreds of micrometers long were prepared by a one-phase approach with cationic surfactants as templates under acidic conditions, and their cross-sections were studied by SEM and TEM techniques (see picture).

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      Preview: Angew. Chem. Int. Ed. 2/2005 (page 341)

      Article first published online: 21 DEC 2004 | DOI: 10.1002/anie.200590005

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