Angewandte Chemie International Edition

Cover image for Vol. 44 Issue 40

October 14, 2005

Volume 44, Issue 40

Pages 6427–6597

    1. Cover Picture: Linking Rings through Diamines and Clusters: Exploring Synthetic Methods for Making Magnetic Quantum Gates (Angew. Chem. Int. Ed. 40/2005) (page 6427)

      Marco Affronte, Ian Casson, Marco Evangelisti, Andrea Candini, Stefano Carretta, Christopher A. Muryn, Simon J. Teat, Grigore A. Timco, Wolfgang Wernsdorfer and Richard E. P. Winpenny

      Version of Record online: 7 OCT 2005 | DOI: 10.1002/anie.200590133

      Linked paramagnetic cage complexes could potentially be used as quantum gates for quantum information processing. The cover picture shows such a supramolecular assembly, which consists of two heterometallic octagons (paramagnetic {Cr7Ni} cages) linked through a metal dimer. The white arrow represents the light input that switches the interaction between the two halves of the quantum gate. For more details see the Communication by M. Affronte, G. A. Timco, R. E. P. Winpenny et al. on page 6496 ff.

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    3. A Feast of Supramolecular Chemistry (pages 6442–6444)

      Daniel-Petru Funeriu

      Version of Record online: 7 OCT 2005 | DOI: 10.1002/anie.200503161

    4. Essential NMR. By Bernhard Blümich. (pages 6445–6446)

      Arne Lützen

      Version of Record online: 7 OCT 2005 | DOI: 10.1002/anie.200585322

    5. Artificial Molecular Double-Stranded Helices (pages 6448–6451)

      Markus Albrecht

      Version of Record online: 26 JUL 2005 | DOI: 10.1002/anie.200501472

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      Not only aesthetically appealing: The motif of the double-stranded helix (see picture) is found in DNA, which is able to store and process “information”. It inspires scientists to search for ways to mimic not only its fascinating structure but also to develop helical systems with different functionalities and properties, with which one day, likewise, information storage and processing could be achieved.

    6. Charge-Transfer Isomers and Mixed-Valence Properties (pages 6452–6454)

      Robert J. Crutchley

      Version of Record online: 30 AUG 2005 | DOI: 10.1002/anie.200501598

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      The unusual suspects: By using a series of ruthenium clusters of the type [{Ru3O(μ-CH3COO)6(CO)L′}(μ-L){Ru3O(μ-CH3COO)6(CO)L′′}] (see picture) it has been possible to identify the existence of charge-transfer isomers and establish them as identifiable chemical entities that exist in dynamic equilibrium.

    7. Single-Site Heterogeneous Catalysts (pages 6456–6482)

      John Meurig Thomas, Robert Raja and Dewi W. Lewis

      Version of Record online: 7 OCT 2005 | DOI: 10.1002/anie.200462473

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      Living in isolation: Single-site heterogeneous catalysts offer a widely applicable strategic principle for the design of new mono- and bifunctional catalysts. They combine the merits of homogeneous and heterogeneous processes and permit the preparation of high activity regio-, shape-, and enantioselective solid catalysts. The picture shows a spatially constrained organometallic, RhI-based enantioselective catalyst.

    8. Two-Step Spin Conversion in a Cyanide-Bridged Ferrous Square (pages 6484–6487)

      Masayuki Nihei, Mayumi Ui, Mizuho Yokota, Lingqin Han, Atsushi Maeda, Hideo Kishida, Hiroshi Okamoto and Hiroki Oshio

      Version of Record online: 7 OCT 2005 | DOI: 10.1002/anie.200502216

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      Spinning out: A cyanide-bridged molecular square (see picture) has been isolated and found to undergo thermally induced, two-step spin crossover. Molecules with more than one spin-crossover site are suitable building blocks for multistepped molecular switches.

    9. A Three-Dimensional Metal–Organic Framework with an Unprecedented Octahedral Building Unit (pages 6488–6491)

      Carine Livage, Nathalie Guillou, Julienne Chaigneau, Pierre Rabu, Marc Drillon and Gérard Férey

      Version of Record online: 15 SEP 2005 | DOI: 10.1002/anie.200502185

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      Unusual octahedral hexamers built up from triangular, corner-linked cobalt trimers (see figure), form the basis of a novel three-dimensional cobalt isophthalate obtained by a solvothermal route. This structure provides a new example of the concept of scale chemistry, in which an {Na6Co6O26} “super octahedron” is connected in a classical ReO3 architecture.

    10. Fabrication of Random Assemblies of Metal Nanobands: A General Method (pages 6491–6496)

      Michael E. Hyde, Trevor J. Davies and Richard G. Compton

      Version of Record online: 20 SEP 2005 | DOI: 10.1002/anie.200502128

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      The unique structure of a highly ordered pyrolytic-graphite (HOPG) surface is employed as a template to fabricate large random arrays of metal-nanoband electrodes. This process is achieved through selective blocking of the basal-plane HOPG (A) with a polymer film (B), followed by metal coating (C) and cleavage of the metal layer from the HOPG substrate (D; see picture).

    11. Linking Rings through Diamines and Clusters: Exploring Synthetic Methods for Making Magnetic Quantum Gates (pages 6496–6500)

      Marco Affronte, Ian Casson, Marco Evangelisti, Andrea Candini, Stefano Carretta, Christopher A. Muryn, Simon J. Teat, Grigore A. Timco, Wolfgang Wernsdorfer and Richard E. P. Winpenny

      Version of Record online: 13 SEP 2005 | DOI: 10.1002/anie.200502505

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      Gates leading from cages: Linked paramagnetic cage complexes could potentially be used as quantum gates for quantum information processing. Experiments demonstrate that it is possible to link octanuclear {Cr7Ni} rings through both organic and metal–organic fragments into supramolecular dimers (see structure; Cr green, Ni light green, Cu orange, F yellow, O red, N blue, C black).

    12. Control of the Coil-to-Globule Transition and Ultrahigh Mechanical Properties of PNIPA in Nanocomposite Hydrogels (pages 6500–6504)

      Kazutoshi Haraguchi and Huan-Jun Li

      Version of Record online: 13 SEP 2005 | DOI: 10.1002/anie.200502004

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      Polymer clay for chemists: High strengths and high fracture energies of polymeric hydrogels have been demonstrated by incorporating a substantial amount of nanodispersed inorganic clay during the in situ free-radical polymerization of N-isopropylacrylamide. By varying the amount of clay used, mechanical properties as well as the swelling and transparency of the nanocomposite (NC) could be controlled (see picture; NC20 contains more clay than NC5).

    13. Synthetic Macrocyclic Peptidomimetics as Tunable pH Probes for the Fluorescence Imaging of Acidic Organelles in Live Cells (pages 6504–6508)

      Francisco Galindo, M. Isabel Burguete, Laura Vigara, Santiago V. Luis, Nurul Kabir, Jelena Gavrilovic and David A. Russell

      Version of Record online: 15 SEP 2005 | DOI: 10.1002/anie.200501920

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      Acid test: Macrocyclic compounds that comprise a 9,10-anthracene subunit linked by a C2-symmetric peptidomimetic chain (see formula) are useful as fluorescent probes in a pH range of biomedical interest. Changes in the size of the macrocycle (n=3,4,6,8) produce a shift in the pKa values. Experiments with live mouse macrophage cells show the selective localization of the probe in the acidic organelles (see differential interference contrast image).

    14. Dielectric Properties of Porous Molecular Crystals That Contain Polar Molecules (pages 6508–6512)

      Heng-Bo Cui, Kazuyuki Takahashi, Yoshinori Okano, Hayao Kobayashi, Zheming Wang and Akiko Kobayashi

      Version of Record online: 15 SEP 2005 | DOI: 10.1002/anie.200501867

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      Simply lowering the temperature changes a polarizable molecular system, which consists of H2O and CH3OH inserted into the porous crystal [Mn3(HCOO)6] (see structure; Mn pink, C gray, O red), into a nonpolarizable one. Although a large drop in the dielectric constant was observed around 120 K, reminiscent of a liquid[LEFT RIGHT ARROW]solid phase transition of the guest molecules, the anisotropy cannot be explained by a simple liquid model of the guest molecules.

    15. Quantitative Spatial Mapping of Mixing in Microfluidic Systems (pages 6512–6516)

      Steven W. Magennis, Emmelyn M. Graham and Anita C. Jones

      Version of Record online: 21 SEP 2005 | DOI: 10.1002/anie.200500558

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      The problem of miniaturizing the mixing process is a barrier to the advance of microfluidic technology. Fluorescence lifetime imaging is a powerful technique for the quantitative mapping of mixing in microfluidic systems, providing information essential to the design and evaluation of next-generation devices. With the use of a pulsed laser (B), mixing in a microfluidic cell (A) can be measured with fluorescence (C); a sample image is shown (right).

    16. The Internal Structure of Helical Pores Self-Assembled from Dendritic Dipeptides is Stereochemically Programmed and Allosterically Regulated (pages 6516–6521)

      Virgil Percec, Andrés E. Dulcey, Mihai Peterca, Monica Ilies, Janine Ladislaw, Brad M. Rosen, Ulrica Edlund and Paul A. Heiney

      Version of Record online: 13 SEP 2005 | DOI: 10.1002/anie.200501331

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      Keeping nature under control: The internal structure of helical porous protein mimics self-assembled from hybrid dendritic dipeptides is programmed by the stereochemistry of the dipeptide and regulated allosterically. This is the first example of a synthetic helical porous supramolecular structure that is stable both in solution and in the solid state, and that is created by a sequence of events related to those encountered in nature.

    17. Straightforward Access to a Structurally Diverse Set of Oxacyclic Scaffolds through a Four-Component Reaction (pages 6521–6525)

      Oscar Jiménez, Guillermo de la Rosa and Rodolfo Lavilla

      Version of Record online: 15 SEP 2005 | DOI: 10.1002/anie.200501548

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      Just add CH3CN and stir! Four building blocks taken in a multicomponent reaction (MCR, see picture; Tf=trifluoromethanesulfonyl) afford a β-aminoacetal adduct, which can be further diversified by post-condensation reactions. The modular character of this approach, the simplicity of the building blocks used, and the structural diversity attained render this process attractive for combinatorial as well as target- and diversity-oriented synthesis.

    18. Enhanced Metabolic Stability and Protein-Binding Properties of Artificial α Helices Derived from a Hydrogen-Bond Surrogate: Application to Bcl-xL (pages 6525–6529)

      Deyun Wang, Wei Liao and Paramjit S. Arora

      Version of Record online: 19 SEP 2005 | DOI: 10.1002/anie.200501603

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      Artificial α helices prepared by the replacement of a hydrogen bond between residues i and i+4 with a carbon–carbon bond can stabilize biologically relevant peptides in helical conformations (1, internal constraint shaded in gray). α Helices based on hydrogen-bond surrogates that mimic Bak BH3 (2, yellow) can bind their expected protein receptor, Bcl-xL (2, green), with high affinity and resist proteolytic degradation.

    19. Saccharide–Peptide Hybrid Copolymers as Biomaterials (pages 6529–6533)

      Mark Metzke, Naphtali O'Connor, Soumen Maiti, Edward Nelson and Zhibin Guan

      Version of Record online: 15 SEP 2005 | DOI: 10.1002/anie.200501944

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      Au natural: A new class of synthesized biomaterials (saccharide–peptide hybrid copolymers shown) are biodegradable, nontoxic, and nonimmunogenic. The cationic saccharide–peptide hybrid copolymers were also shown to be effective in compacting and transferring plasmid DNA into cells.

    20. A Diels–Alder Macrocyclization Enables an Efficient Asymmetric Synthesis of the Antibacterial Natural Product Abyssomicin C (pages 6533–6537)

      Christoph W. Zapf, Bryce A. Harrison, Carmen Drahl and Erik J. Sorensen

      Version of Record online: 15 SEP 2005 | DOI: 10.1002/anie.200502119

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      An efficient and highly diastereoselective intramolecular Diels–Alder reaction is the basis of a concise asymmetric synthesis of the potent antibacterial natural product abyssomicin C (see formula). The complexity of the target structure was reduced to three fragments and required two carbonyl addition reactions to achieve key bond formations.

    21. Oligothiophenes Incorporating Metal–Metal Quadruple Bonds (pages 6537–6540)

      Malcolm H. Chisholm, Arthur J. Epstein, Judith C. Gallucci, Florian Feil and Wesley Pirkle

      Version of Record online: 15 SEP 2005 | DOI: 10.1002/anie.200500138

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      Illuminating quadruple bonds: The polymeric materials [M2(O2CC6H2-2,4,6-Me3)2(O2C-(Thp)n-CO2)]n (M=Mo or W (green); Thp=thiophene (S atoms yellow); DMSO molecules also shown) incorporate metal–metal quadruple bonds and form thin films from THF solutions. These films show electroluminescence when deposited on an indium–tin oxide glass-coated plate followed by vapor deposition of aluminum or calcium.

    22. Linking Centered Manganese Triangles into Larger Clusters: A {Mn32} Truncated Cube (pages 6540–6543)

      Richard T. W. Scott, Simon Parsons, Muralee Murugesu, Wolfgang Wernsdorfer, George Christou and Euan K. Brechin

      Version of Record online: 21 SEP 2005 | DOI: 10.1002/anie.200501881

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      Cutting Corners: Elaborate triangular arrays of Mn ions are stabilized by the tripodal ligand 1,1,1-tris(hydroxymethyl)ethane. The self-assembled {Mn32} truncated cube (see picture) is further stabilized by end-on-bridging azide ligands and acetate groups. Such stabilization could prove to be useful in the preparation of single-molecule magnets.

    23. Highly Enantioselective Pd-Catalyzed Allylic Alkylations of Acyclic Ketones (pages 6544–6546)

      Xiao-Xia Yan, Chun-Gen Liang, Yan Zhang, Wei Hong, Bo-Xun Cao, Li-Xin Dai and Xue-Long Hou

      Version of Record online: 20 SEP 2005 | DOI: 10.1002/anie.200502020

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      Pocket the difference: Highly enantioselective allylic alkylation of simple acyclic ketones is carried out by using a Pd catalyst with a “chiral pocket” ligand 1 (see scheme). The addition of a Lewis acid such as AgBr and the selection of one enolate form over another dramatically affect the enantioselectivity of the reaction.

    24. Unexpected Participation of an Unconjugated Olefin during Nazarov Cyclization of Bridged Bicyclic Dienones (pages 6546–6549)

      Sören Giese, Robert D. Mazzola Jr., Clare M. Amann, Atta M. Arif and F. G. West

      Version of Record online: 19 SEP 2005 | DOI: 10.1002/anie.200501737

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      Surprising rearrangements in a rigid system: A cyclopropyl ring is formed unexpectedly when a trienone substrate is subjected to the Nazarov cyclization (see scheme). The participation of the unconjugated alkene unit present in the substrate might be a consequence of the complete torquoselectivity of the initial electrocyclic closure. A subsequent rearrangement by a homo-1,5-hydrogen shift occurs cleanly to give the final product.

    25. Synthesis of Nanowire and Mesoporous Low-Temperature LiCoO2 by a Post-Templating Reaction (pages 6550–6553)

      Feng Jiao, Kuthanapillil Mani Shaju and Peter G. Bruce

      Version of Record online: 13 SEP 2005 | DOI: 10.1002/anie.200501663

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      Giving in to templation: Lithium-containing nanostructured transition metal oxides have been prepared by a templating route with preservation of the nanostructure. Both one-dimensional nanowire and three-dimensional mesoporous samples of low-temperature (LT)-LiCoO2 with highly crystalline structures (see image) have been obtained, and these perform better than “normal” LT-LiCoO2 as intercalation electrodes in lithium batteries.

    26. The Aromaticity of the Stannole Dianion (pages 6553–6556)

      Masaichi Saito, Ryuta Haga, Michikazu Yoshioka, Kazuya Ishimura and Shigeru Nagase

      Version of Record online: 12 SEP 2005 | DOI: 10.1002/anie.200501632

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      Delocalization in heterocycles: Reaction of hexaphenylstannole with excess lithium gives the dilithium stannole as deep-red crystals. The aromaticity of the dianion was examined by NMR spectroscopy, X-ray analysis (see picture), and calculations. The dianion has considerable aromatic character and is reported to be the first tin-containing carbocyclic aromatic compound.

    27. Tungsten Carbide Microspheres as a Noble-Metal-Economic Electrocatalyst for Methanol Oxidation (pages 6557–6560)

      Raman Ganesan and Jae Sung Lee

      Version of Record online: 11 AUG 2005 | DOI: 10.1002/anie.200501272

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      Thrifty catalysis: Tungsten carbide microspheres with high surface area and CO chemisorption capacity were prepared by heating mixtures of a resorcinol–formaldehyde polymer and ammonium metatungstate. Platinum supported on these microspheres (see electron micrograph) shows higher activity than the commercial catalyst with 20 % Pt–Ru (1:1) on C for the electrooxidation of methanol.

    28. Rapid Synthesis in Ionic Liquids of Room-Temperature-Conducting Solid Microsilica Spheres (pages 6560–6563)

      David S. Jacob, Augustine Joseph, Somashekarappa P. Mallenahalli, Sangaraju Shanmugam, Shirly Makhluf, Jose Calderon-Moreno, Yuri Koltypin and Aharon Gedanken

      Version of Record online: 13 SEP 2005 | DOI: 10.1002/anie.200501446

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      Take the rough with the smooth: Conducting silica microspheres with different morphologies—rough, dotted, and smooth (see picture)—have been rapidly synthesized in an ionic liquid under various experimental conditions. The conducting property of the silica particles is attributed to the presence of entrapped molecules of ionic liquid and water.

    29. Synthesis, Intermolecular Interaction, and Semiconductive Behavior of a Delocalized Singlet Biradical Hydrocarbon (pages 6564–6568)

      Takashi Kubo, Akihiro Shimizu, Maki Sakamoto, Mikio Uruichi, Kyuya Yakushi, Masayoshi Nakano, Daisuke Shiomi, Kazunobu Sato, Takeji Takui, Yasushi Morita and Kazuhiro Nakasuji

      Version of Record online: 13 SEP 2005 | DOI: 10.1002/anie.200502303

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      A phenalenyl-based Kekulé hydrocarbon with singlet biradical character has been isolated and characterized. Strong intra- and intermolecular interactions between the unpaired electrons lead to short π–π contacts and formation of one-dimensional chains (see picture). Thus, wide valence and conduction bands are established, and the compound shows semiconductive behavior.

    30. Borane Mimics of Classic Organometallic Compounds: [(Cp*Ru)B8H14(RuCp*)]0,+, Isoelectronic Analogues of Dinuclear Pentalene Complexes (pages 6568–6571)

      Sundargopal Ghosh, Bruce C. Noll and Thomas P. Fehlner

      Version of Record online: 20 SEP 2005 | DOI: 10.1002/anie.200502212

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      Body doubles: An isolectronic borane analogue of a dinuclear ruthenium–pentalene (C8H6) π complex (see picture) has been prepared and isolated. It is found to be an intermediate in the growth of the borane fragment of a diruthenaborane framework.

    31. The Hierarchical Architecture of Nacre and Its Mimetic Material (pages 6571–6575)

      Yuya Oaki and Hiroaki Imai

      Version of Record online: 15 SEP 2005 | DOI: 10.1002/anie.200500338

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      Mother-of-pearl has a three-level nanoscopic-to-macroscopic hierarchical architecture, which provides storage for organic molecules at the nanoscale. A material that mimics the hierarchical architecture and nanostorage properties of nacre emerges from the simple crystallization of potassium sulfate and poly(acrylic acid) (see picture).

    32. Catalytic Enantioselective Friedel–Crafts Alkylation of Indoles with Nitroalkenes by Using a Simple Thiourea Organocatalyst (pages 6576–6579)

      Raquel P. Herrera, Valentina Sgarzani, Luca Bernardi and Alfredo Ricci

      Version of Record online: 19 SEP 2005 | DOI: 10.1002/anie.200500227

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      A facile access to optically active 2-indolyl-1-nitro derivatives, which can be easily transformed into highly valuable compounds such as tryptamines and 1,2,3,4-tetrahydro-β-carbolines, is provided by the first catalytic enantioselective Friedel–Crafts alkylation of indoles with nitroalkenes (see scheme; e.g. R1=R2=H, R3=Ph).

    33. Valence Isomerization of 2-Phosphabicyclo[1.1.0]butanes (pages 6579–6582)

      J. Chris Slootweg, Steffen Krill, Frans J. J. de Kanter, Marius Schakel, Andreas W. Ehlers, Martin Lutz, Anthony L. Spek and Koop Lammertsma

      Version of Record online: 13 SEP 2005 | DOI: 10.1002/anie.200502248

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      Remarkably stable 2-phosphabicyclo[1.1.0]butanes (see picture; O red, P violet, W turquoise) were synthesized from the complexed phosphinidene Ph[BOND]P[DOUBLE BOND]W(CO)5 and cyclopropenes. These compounds undergo valence isomerization to form 3-phosphacyclobutenes via 1-phosphabutadienes at elevated temperatures.

    34. Uncatalyzed Mukaiyama–Michael Reaction: Rapid Access to Simple and Complex Enantiopure γ-Butenolides (pages 6583–6585)

      José Barluenga, Ana de Prado, Javier Santamaría and Miguel Tomás

      Version of Record online: 19 SEP 2005 | DOI: 10.1002/anie.200501746

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      A simple start: A tungsten carbene 3, 2-trimethylsilyloxyfuran (4), and an enantiopure aldehyde 5 provide easy access to enantiopure butenolides 2. The metal carbene increases the accepting character of the C[DOUBLE BOND]C bond and allows further transformations into butenolide structures such as 1.

    35. Finding Adiabatically Bound Anions of Guanine through a Combinatorial Computational Approach (pages 6585–6588)

      Maciej Harańczyk and Maciej Gutowski

      Version of Record online: 15 SEP 2005 | DOI: 10.1002/anie.200501671

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      Enamine–imine transformations of guanine lead to tautomers that support valence anionic states which are adiabatically bound by as much as 8 kcal mol−1 (see scheme). The valence anions might be formed by dissociative electron attachment followed by attachment of a hydrogen atom to a carbon atom. Such tautomers might affect the structure and properties of DNA and RNA exposed to low-energy electrons.

    36. Chemical Primer Extension: Efficiently Determining Single Nucleotides in DNA (pages 6588–6592)

      Patrizia Hagenbuch, Eric Kervio, Annette Hochgesand, Ulrich Plutowski and Clemens Richert

      Version of Record online: 21 SEP 2005 | DOI: 10.1002/anie.200501794

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      Rapid replication: Non-enzymatic primer extension has previously been studied in the context of prebiotic chemistry, but not for practical applications. Reactions with primers featuring a 3′-amino-2′,3′-dideoxynucleotide can be rapid and selective for all four templating nucleobases (see scheme). On a chip with immobilized capture strands, 500 fmol of template suffice for single-nucleotide determinations within 2.7 h.

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