Angewandte Chemie International Edition

Cover image for Vol. 45 Issue 25

June 19, 2006

Volume 45, Issue 25

Pages 4037–4217

    1. Cover Picture: Chiral Borromeates (Angew. Chem. Int. Ed. 25/2006) (page 4037)

      Cari D. Pentecost, Andrea J. Peters, Kelly S. Chichak, Gareth W. V. Cave, Stuart J. Cantrill and J. Fraser Stoddart

      Article first published online: 8 JUN 2006 | DOI: 10.1002/anie.200690086

      Chirality is transferred from 12 stereogenic centers, all of the same chirality, to the six templating zinc(II) ions in each enantiomer of an optically active Borromeate. Recognizing that the three-component Borromean link is topologically achiral, J. F. Stoddart et al. describe in their Communication on page 4099 ff. the dynamic stereospecific synthesis of both all-R and all-S enantiomers of the Borromeate and report the X-ray crystal structure of the all-R enantiomer.

    2. Fundamental Processes in Radiation Damage of DNA (pages 4056–4059)

      Petra Swiderek

      Article first published online: 8 JUN 2006 | DOI: 10.1002/anie.200600614

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      Ionizing radiation (UV, X-rays, etc.) induces DNA damage not merely from the primary impact of high-energy quanta but, to a large extent, from secondary particles. Among these, low-energy electrons (see scheme) play an important role. Gas-phase studies that use crossed-molecular and monochromatic electron beams have provided new fundamental insight into the mechanism of radiation damage in DNA.

    3. Some Experimental Evidence that Zn4O(BO3)2 is Zn6O(OH)(BO3)3 (pages 4060–4062)

      Thibaud Delahaye, Florent Boucher, Michaël Paris, Olivier Joubert, Mayté Caldes and Yves Piffard

      Article first published online: 8 JUN 2006 | DOI: 10.1002/anie.200503999

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      A combination of techniques show that the so-called zincoborate “Zn4O(BO3)2” is in fact a zinc oxyhydroxyborate. The presence of hydrogen in the structure explains the constriction of the O(3)⋅⋅⋅O(3) distance through it being straddled by an O[BOND]H⋅⋅⋅O bridge and rules out the hypothesis of oxygen vacancies in the environment of boron.

    4. Biomolecular Modeling: Goals, Problems, Perspectives (pages 4064–4092)

      Wilfred F. van Gunsteren, Dirk Bakowies, Riccardo Baron, Indira Chandrasekhar, Markus Christen, Xavier Daura, Peter Gee, Daan P. Geerke, Alice Glättli, Philippe H. Hünenberger, Mika A. Kastenholz, Chris Oostenbrink, Merijn Schenk, Daniel Trzesniak, Nico F. A. van der Vegt and Haibo B. Yu

      Article first published online: 8 JUN 2006 | DOI: 10.1002/anie.200502655

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      Present day biomolecular modeling is limited in its application by four main problems: 1) the force-field problem, 2) the search problem, 3) the ensemble problem, and 4) the experimental problem. These four problems are discussed in this Review by using practical examples, and perspectives are outlined for overcoming the limitations of biomolecular modeling.

    5. An Optically Reversible Switching Membrane Surface (pages 4094–4098)

      Arpan Nayak, Hongwei Liu and Georges Belfort

      Article first published online: 16 MAY 2006 | DOI: 10.1002/anie.200600581

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      Lighting the way: Through the combination of a UV-grafting process with the photoresponsive properties of spiropyran molecules, an optically reversible switching membrane surface was developed. This process can be used in preference to inducing physical movement of long-chain SAMs toward an electrode and as a result improve many industrial opportunities including those dependent on surface wettability and molecular adhesion.

    6. Chiral Borromeates (pages 4099–4104)

      Cari D. Pentecost, Andrea J. Peters, Kelly S. Chichak, Gareth W. V. Cave, Stuart J. Cantrill and J. Fraser Stoddart

      Article first published online: 8 JUN 2006 | DOI: 10.1002/anie.200600817

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      The fellowship of the rings: Circular dichroism measurements reveal that chirality is transferred from 12 stereogenic centers to 6 octahedral zinc(II) centers (see picture) in two enantiomeric pairs of chiral Borromeates, one of which has been found to be wholly asymmetric in the solid state by X-ray crystallography.

    7. Chemical Composition and Topology of Poly(lactide-co-glycolide) Revealed by Pushing MALDI-TOF MS to Its Limit (pages 4104–4108)

      Saskia Huijser, Bastiaan B. P. Staal, Juan Huang, Robbert Duchateau and Cor E. Koning

      Article first published online: 26 MAY 2006 | DOI: 10.1002/anie.200600594

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      Software developed in house in combination with a recently developed method of MALDI-TOF MS enable not only the elucidation of individual chain structures of poly(lactide-co-glycolide), a polymer used extensively in the medical sector, but a full characterization of this copolymer including even its chemical composition and topology (random, gradient, block (see figure), or alternating).

    8. Engineering a Polymeric Chiral Catalyst by Using Hydrogen Bonding and Coordination Interactions (pages 4108–4112)

      Lei Shi, Xingwang Wang, Christian A. Sandoval, Mingxing Li, Qiaoyan Qi, Zhanting Li and Kuiling Ding

      Article first published online: 24 MAY 2006 | DOI: 10.1002/anie.200600432

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      Noncovalent interactions are used to generate a polymeric supramolecular chiral catalyst (see picture). This heterogeneous catalyst, which is based on Feringa's MonoPhos/RhI system, is formed by orthogonal self-assembly of recognition motifs through hydrogen bonding and ligand-to-metal coordination interactions. It shows excellent asymmetric induction and reusability in the catalysis of the asymmetric hydrogenation of dehydro-α-amino acid and enamide derivatives.

    9. Nanochannel-Promoted Polymerization of Substituted Acetylenes in Porous Coordination Polymers (pages 4112–4116)

      Takashi Uemura, Ryo Kitaura, Yusuke Ohta, Masataka Nagaoka and Susumu Kitagawa

      Article first published online: 24 MAY 2006 | DOI: 10.1002/anie.200600333

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      Get into the groove: Porous coordination polymers with basic interaction sites catalyze the fast and stereoselective polymerization of acetylene derivatives. The reactions take place in the one-dimensional nanochannels of the coordination polymer (see picture).

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      Building Complex Glycopeptides: Development of a Cysteine-Free Native Chemical Ligation Protocol (pages 4116–4125)

      Bin Wu, Jiehao Chen, J. David Warren, Gong Chen, Zihao Hua and Samuel J. Danishefsky

      Article first published online: 19 MAY 2006 | DOI: 10.1002/anie.200600538

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      The missing link: Reiterative ligations based on non-cysteine and cysteine-based acyl acceptors have been used to prepare synthetic polypeptides and proteins with multiple sites of glycosylation. Highly complex positionally defined glycopolypeptides corresponding to single glycoforms can be formed from simple components.

    11. Mechanism of the Vinylcyclobutane Rearrangement of Sceptrin to Ageliferin and Nagelamide E (pages 4126–4130)

      Brian H. Northrop, Daniel P. O'Malley, Alexandros L. Zografos, Phil S. Baran and K. N. Houk

      Article first published online: 16 MAY 2006 | DOI: 10.1002/anie.200600514

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      Naturally radical: The microwave-induced rearrangement of sceptrin to natural products ageliferin and nagelamide E results in approximately the same ratio as they are isolated from natural sources. Computational investigations show that the vinylcyclobutane–cyclohexene rearrangement occurs via diradical intermediates and support the involvement of this rearrangement in the biosynthesis of the natural products.

    12. Progressive Stabilization of Zwitterionic Structures in [H(Ser)2–8]+ Studied by Infrared Photodissociation Spectroscopy (pages 4130–4134)

      Xianglei Kong, I-An Tsai, Sahadevan Sabu, Chau-Chung Han, Yuan T. Lee, Huan-Cheng Chang, Shih-Yu Tu, A. H. Kung and Chih-Che Wu

      Article first published online: 23 MAY 2006 | DOI: 10.1002/anie.200600597

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      Does (Ser)2have a neutral structure? How does the zwitterion evolve with an increasing cluster size of serine (Ser)? Infrared spectroscopic and mass-spectrometric analysis of [H(Ser)n]+ (n=2–8) shows progressive stabilization of the zwitterion with increasing cluster size, and the results of ab initio calculations based on density functional theory of [H(Ser)2]+ are also given (picture: a neutral structure; red O, blue N, gray C, white H).

    13. High-Nuclearity, High-Symmetry, High-Spin Molecules: A Mixed-Valence Mn10 Cage Possessing Rare T symmetry and an S=22 Ground State (pages 4134–4137)

      Theocharis C. Stamatatos, Khalil A. Abboud, Wolfgang Wernsdorfer and George Christou

      Article first published online: 16 MAY 2006 | DOI: 10.1002/anie.200600691

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      Taking the high road: The unification of azide and hmp (hmpH=2-(hydroxymethyl)pyridine) ligands has provided a route to two salts of a new Mn10 cation with an aesthetically pleasing, high-symmetry structure. The cation (see excerpt of structure; MnII yellow, MnIII blue, O red, N green, C gray) is completely ferromagnetically coupled and possesses an S=22 ground state, one of the highest values ever reported.

    14. Accelerated Discovery of Red-Phosphorescent Emitters through Combinatorial Organometallic Synthesis and Screening (pages 4138–4142)

      Nai-Mu Hsu and Wen-Ren Li

      Article first published online: 30 MAY 2006 | DOI: 10.1002/anie.200600004

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      Seeing red dots: A parallel solid-phase synthetic protocol was developed in the search for red-phosphorescent iridium complexes. Direct screening of resin-bound chloro-bridged dimers and leads was performed and validated (see picture), and two hits were identified. Their electroluminescent devices exhibited very high external quantum efficiencies.

    15. Supramolecular Chirality in Layered Crystals of Achiral Ammonium Salts and Fatty Acids: A Hierarchical Interpretation (pages 4142–4145)

      Akira Tanaka, Katsunari Inoue, Ichiro Hisaki, Norimitsu Tohnai, Mikiji Miyata and Akikazu Matsumoto

      Article first published online: 24 MAY 2006 | DOI: 10.1002/anie.200504424

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      Something out of nothing: Chiral layered crystals are obtained from achiral 4-methylbenzylammonium myristate and pentadecanoate. The molecular chirality within a single molecule in these systems arises from the fixation of the conformation. It then spreads over the 2D layers and finally over the 3D crystal to generate supramolecular chirality by parallel assembly (see picture).

      Corrected by:

      Corrigendum: Supramolecular Chirality in Layered Crystals of Achiral Ammonium Salts and Fatty Acids: A Hierarchical Interpretation

      Vol. 45, Issue 28, 4539, Article first published online: 3 JUL 2006

    16. Self-Supported and Clean One-Step Cathodic Coupling of Activated Olefins with Benzyl Bromide Derivatives in a Micro Flow Reactor (pages 4146–4149)

      Ping He, Paul Watts, Frank Marken and Stephen J. Haswell

      Article first published online: 23 MAY 2006 | DOI: 10.1002/anie.200600951

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      Currently coupled: A clean microreactor-based electrosyntheses in the absence of supporting electrolyte is demonstrated and shown to feature very simple cell geometries. As exemplified for the coupling reaction of various olefins with benzyl bromides, the height of the microfluidic cell and the flow rate are crucial for the minimization of unwanted side products and optimization of yields (see picture).

    17. Biaryl Axis as a Stereochemical Relay for the Enantioselective Synthesis of Antimicrotubule Agents (pages 4149–4152)

      Agnès Joncour, Anne Décor, Sylviane Thoret, Angèle Chiaroni and Olivier Baudoin

      Article first published online: 10 MAY 2006 | DOI: 10.1002/anie.200600451

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      Return to sender: A biaryl configuration that is controlled by a benzylic stereocenter in an atropo-selective Suzuki coupling in turn controls the stereocenter configuration in an SN1-type dehydrative cyclization performed at low temperature. Promising antimicrotubule biaryls of high optical purity are obtained in this manner. TFA=trifluoroacetic acid, pin=pinacolato.

    18. The Heck Reaction of Electron-Rich Olefins with Regiocontrol by Hydrogen-Bond Donors (pages 4152–4157)

      Jun Mo and Jianliang Xiao

      Article first published online: 23 MAY 2006 | DOI: 10.1002/anie.200600799

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      No salt please: Halide scavengers AgOTf and TlOAc are not required for the Heck coupling of electron-rich olefins with aryl bromides and chlorides. Using ammonium additives, these reactions can be carried out in either an imidazolium ionic liquid or a common molecular solvent, thus furnishing 1,1′-disubstituted olefins in high yields with excellent regioselectivities.

    19. [{(tBu2Me)2Si}3Li4]2−: An Aggregated Dianion of a 1,1-Dilithiosilane with a Unique Structural Motif (pages 4157–4159)

      Dmitry Bravo-Zhivotovskii, Ilya Ruderfer, Semyon Melamed, Mark Botoshansky, Asher Schmidt and Yitzhak Apeloig

      Article first published online: 16 MAY 2006 | DOI: 10.1002/anie.200600308

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      An anionic dilithium compound: The dianion [(R2Si)3Li4]2− (R=tBu2MeSi) as salt 2 was synthesized as the first of its kind by dissolving 1 in THF. The structure of 2 was solved by X-ray crystallography and studied by solid-state and solution NMR spectroscopy. Compound 2 reacts as a dilithiosilane.

    20. Radical Photochemistry in Oxygen-Loaded Ices (pages 4159–4163)

      Sandrine Lacombe, Fabrice Bournel, Carine Laffon and Philippe Parent

      Article first published online: 16 MAY 2006 | DOI: 10.1002/anie.200504509

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      Ice to see you all: The photoproducts formed by irradiation of water and molecular oxygen ices are strongly dependent on the chemical composition of the medium. The observation of all the transient species (radicals and molecules, see picture) simultaneously will have applications in different fields such as astrochemistry and radiobiology.

    21. Highly Stereoselective Synthesis of TMS-, Alkyl-, or Aryl-Substituted cis-[3]Cumulenols via α-Alkynylated Zirconacyclopentenes (pages 4163–4167)

      Yuanhong Liu, Hongjun Gao and Shaolin Zhou

      Article first published online: 16 MAY 2006 | DOI: 10.1002/anie.200600520

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      Double bonds come in threes: A highly stereoselective and potentially general method for the synthesis of tetrasubstituted cis-[3]cumulenes through zirconium-mediated coupling of 1,3-butadiynes with aldehydes or ketones is described (see scheme). Remarkably, the reaction occurs with completely different chemoselectivity to that usually observed with alkyl- or aryl-substituted zirconacyclopentenes.

    22. Solid-Phase Oligosaccharide Tagging (SPOT): Validation on Glycolipid-Derived Structures (pages 4167–4172)

      Anders Lohse, Rita Martins, Malene Ryborg Jørgensen and Ole Hindsgaul

      Article first published online: 19 MAY 2006 | DOI: 10.1002/anie.200600642

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      SPOT check: A simple technique for labeling oligosaccharides consists of capturing the sugars on beads functionalized with hydroxylamine groups bearing cleavable linkers. After sequential pipetting in and out of reagents, tagged sugars are released into solution (see picture; PEGA=polyethylene glycol–polyacrylamide resin) for analysis by electrophoresis or mass spectrometry.

    23. Pericyclic Cascade Reactions of (Bicyclo[1.1.0]butylmethyl)amines (pages 4172–4175)

      Peter Wipf and Maciej A. A. Walczak

      Article first published online: 19 MAY 2006 | DOI: 10.1002/anie.200600723

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      Direct access: Phase-transfer N-allylation and N-propargylation of (bicyclo[1.1.0]butylmethyl)amines initiate diastereoselective pericyclic cascade reactions that culminate in novel spirocyclic and tricyclic pyrrolidine heterocycles through formal ene or [2+2] pathways.

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      From Aryl Bromides to Enantioenriched Benzylic Alcohols in a Single Flask: Catalytic Asymmetric Arylation of Aldehydes (pages 4175–4178)

      Jeung Gon Kim and Patrick J. Walsh

      Article first published online: 24 MAY 2006 | DOI: 10.1002/anie.200600741

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      Stop that achiral catalyst! Chiral Lewis acid catalyzed aryl additions to aldehydes that originate from aryl halides generate products with very low ee values (see scheme, left), because the achiral metal halide by-products are much more efficient catalysts than those derived from chiral amino alcohols. A LiCl-selective inhibitor is introduced that enables a highly enantioselective one-pot arylation of aldehydes that begins with aryl bromides (right).

    25. Electrodeposition of Silver Particles and Gold Nanoparticles from Ionic Liquid-Crystal Precursors (pages 4179–4182)

      William Dobbs, Jean-Moïse Suisse, Laurent Douce and Richard Welter

      Article first published online: 24 MAY 2006 | DOI: 10.1002/anie.200600929

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      Precious particles: Dicyanoargentate(I) and dicyanoaurate(I) salts of an imidazolium cation form both crystalline (see structure and enlargement of the cation and anion) and smectic-A phases. Electrodeposition from the ionic liquid crystals provides a novel route to silver particles and gold nanoparticles.

    26. A Snapshot of P4 Tetrahedron Opening: Rh- and Ir-Mediated Activation of White Phosphorus (pages 4182–4185)

      Dmitry Yakhvarov, Pierluigi Barbaro, Luca Gonsalvi, Sonia Mañas Carpio, Stefano Midollini, Annabella Orlandini, Maurizio Peruzzini, Oleg Sinyashin and Fabrizio Zanobini

      Article first published online: 16 MAY 2006 | DOI: 10.1002/anie.200601048

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      P's in a pod: White phosphorus reacts with [M(dppm)2]OTf (M=Rh, Ir; dppm=PPh2CH2PPh2) to give [M(dppm)(Ph2PCH2PPh2PPPP)]OTf whereby a trihapto “P5” ligand is assembled through P[BOND]P bond formation between one dppm PPh2 group and an activated P4 molecule (see scheme; P green, M red, C white, phenyl groups omitted). A bimetallic reaction pathway leading to the final product is proposed, as based on in situ 31P NMR studies.

    27. Adhesion of a Free-Standing Newton Black Film onto a Solid Substrate (pages 4186–4188)

      Jean-Jacques Benattar, Michael Nedyalkov, Fuk Kay Lee and Ophelia K. C. Tsui

      Article first published online: 23 MAY 2006 | DOI: 10.1002/anie.200600367

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      Film transfer: A new method is presented to transfer free-standing Newton black films of surfactant onto a solid substrate (see picture). X-ray reflectivity and atomic force microscopy reveal that the deposited films have a high degree of molecular organization and good adhesion.

    28. The Potential of a cyclo-As3-Ligand Complex in Supramolecular Chemistry (pages 4189–4192)

      Laurence J. Gregoriades, Hannes Krauss, Joachim Wachter, Alexander V. Virovets, Marek Sierka and Manfred Scheer

      Article first published online: 24 MAY 2006 | DOI: 10.1002/anie.200600815

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      As3makes the connection: [Cp*Mo(CO)23-As3)] reacts with Ag[Al{OC(CF3)3}4] to yield a novel dimeric complex featuring the cyclo-As3 ligand in an unusual face-bridging coordination mode. Analytical data and DFT calculations support the existence of a monomer–dimer equilibrium in solution (see scheme). [Cp*Mo(CO)23-As3)] also reacts with CuX (X=Cl, Br, I) to yield insoluble dimers consisting of planar Cu2X2 moieties.

    29. Asymmetric Counteranion-Directed Catalysis (pages 4193–4195)

      Sonja Mayer and Benjamin List

      Article first published online: 24 MAY 2006 | DOI: 10.1002/anie.200600512

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      Exceedingly high enantioselectivity in a catalytic reaction can be realized even when the chirality resides only in the counteranion of the catalyst. A salt (1) composed of an achiral ammonium cation and a chiral phosphate counteranion catalyzes asymmetric transfer hydrogenations of aromatic and aliphatic α,β-unsaturated aldehydes with a Hantzsch ester in excellent enantioselectivities (see scheme).

    30. Formation of Zirconocene Fluoro Complexes: No Deactivation in the Polymerization of Olefins by the Contact-Ion-Pair Catalysts [Cp′2ZrR]+[RB(C6F5)3] (pages 4195–4198)

      Perdita Arndt, Ulrike Jäger-Fiedler, Marcus Klahn, Wolfgang Baumann, Anke Spannenberg, Vladimir V. Burlakov and Uwe Rosenthal

      Article first published online: 16 MAY 2006 | DOI: 10.1002/anie.200600361

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      Not a catalyst killer: In the reaction of 2 with B(C6F5)3, a nucleophilic aromatic substitution with C[BOND]F bond cleavage leads to the unexpected difluoride 1. Although the formation of Zr[BOND]F species during olefin polymerization by [Cp′2ZrR]+[RB(C6F5)3] (Cp′=substituted or unsubstituted η5-cyclopentadienyl; R=Me, H) catalysts is often described as a deactivation, the catalyst precursor 2 can be regenerated from 1 through treatment with iBu2AlH.

    31. Fluorine in a Native Protein Environment—How the Spatial Demand and Polarity of Fluoroalkyl Groups Affect Protein Folding (pages 4198–4203)

      Christian Jäckel, Mario Salwiczek and Beate Koksch

      Article first published online: 11 MAY 2006 | DOI: 10.1002/anie.200504387

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      Give and take: The influence of fluoro substitution of amino acid side chains on their interaction profile in a native polypeptide environment was studied systematically. The fluorination of alkyl groups has opposing electrostatic and steric consequences for the stability of hydrophobic protein cores.

    32. Liquid Crystals from C3-Symmetric Mesogens for Second-Order Nonlinear Optics (pages 4203–4206)

      Gunther Hennrich, Ana Omenat, Inge Asselberghs, Stijn Foerier, Koen Clays, Thierry Verbiest and José Luis Serrano

      Article first published online: 24 MAY 2006 | DOI: 10.1002/anie.200600019

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      Octopolar tris[(phenyl)ethynyl]benzenes with high second-order nonlinear optical (NLO) activity form discotic liquid-crystalline mesophases whose properties depend on the length of the alkoxy chains. The molecules self-organize in a non-centrosymmetric fashion in the bulk phase which enables the construction of a simple, efficient, NLO device (see picture).

    33. DNA-Templated Synthesis in Three Dimensions: Introducing a Micellar Scaffold for Organic Reactions (pages 4206–4210)

      Fikri E. Alemdaroglu, Ke Ding, Rüdiger Berger and Andreas Herrmann

      Article first published online: 17 MAY 2006 | DOI: 10.1002/anie.200600524

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      Blocked up: Amphiphilic DNA-block copolymers were prepared in a fully automated single process by using a DNA synthesizer. These materials formed micelles in aqueous solution which were applied as a scaffold for DNA-templated organic reactions (see picture, red and green balls=reactants, yellow bar=new bond). For a novel fluorogenic reaction, the DNA-templated conversions were detected by fluorescence spectroscopy.

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