Angewandte Chemie International Edition

Cover image for Vol. 45 Issue 21

May 19, 2006

Volume 45, Issue 21

Pages 3383–3553

    1. Cover Picture: Multidimensional Large-Amplitude Motion: Revealing Concurrent Tunneling Pathways in Molecules with Several Internal Rotors / The Glycine–Water Complex (Angew. Chem. Int. Ed. 21/2006) (page 3383)

      Melanie Schnell, Jens-Uwe Grabow, José L. Alonso, Emilio J. Cocinero, Alberto Lesarri, M. Eugenia Sanz and Juan C. López

      Article first published online: 10 MAY 2006 | DOI: 10.1002/anie.200690073

      Microsolvation of glycine has been studied by combining impulse supersonic-jet Fourier-transform microwave spectroscopy with laser ablation and the structure of the monohydrated complex derived from rotational spectra. Combining this method with theoretical considerations enables the internal dynamics of multiple large-amplitude motions, such as in (CH3)3XCl (X=Si, Ge, Sn), to be revealed. For more details, see the Communications by J.-U. Grabow and J. L. Alonso and co-workers on pages 3465 and 3471 ff.

    2. Graphical Abstract: Angew. Chem. Int. Ed. 21/2006 (pages 3386–3396)

      Article first published online: 10 MAY 2006 | DOI: 10.1002/anie.200690074

    3. The Puzzling Properties of Supercooled and Glassy Water (pages 3402–3405)

      Ralf Ludwig

      Article first published online: 28 APR 2006 | DOI: 10.1002/anie.200601053

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      Cold as ice: The anomalies in the properties of water arise from a transformation between two major liquid forms of water in the deeply supercooled region which are proposed to meet at a liquid–liquid critical point. Recent studies of glassy and supercooled water give insight into water's unusual phase-transition behavior.

    4. “Design” in Chemical Synthesis—An Illusion? (pages 3406–3412)

      Martin Jansen and J. Christian Schön

      Article first published online: 10 MAY 2006 | DOI: 10.1002/anie.200504510

      The power of words: According to its generally accepted definition, the process of “design” is the creation of a form that fulfills a given function as well as possible and is also considered aesthetically pleasing. This implies a type of creativity that does not exist in the synthesis of new chemical compounds. This essay discusses the implications of the term “design” in the context of chemistry.

    5. Shape Control of Semiconductor and Metal Oxide Nanocrystals through Nonhydrolytic Colloidal Routes (pages 3414–3439)

      Young-wook Jun, Jin-sil Choi and Jinwoo Cheon

      Article first published online: 27 APR 2006 | DOI: 10.1002/anie.200503821

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      Nanocrystals get into shape: Recent developments in the shape control of semiconductor and metal oxide nanocrystals have yielded many structurally unprecedented nanocrystals including polyhedrons, rods, wires, plates, prisms, and other complex shapes (see picture). Such specially shaped nanocrystals exhibit novel properties and can be further utilized as key building blocks for the fabrication of nanosystems.

    6. Chirality-Induced Switch in Hydrogen-Bond Topology: Tetrameric Methyl Lactate Clusters in the Gas Phase (pages 3440–3445)

      Thomas B. Adler, Nicole Borho, Markus Reiher and Martin A. Suhm

      Article first published online: 3 MAY 2006 | DOI: 10.1002/anie.200600380

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      Supersonic jet expansions of racemic methyl lactate show a prominent OH-stretching infrared absorption at 3401 cm−1 which is not present in the enantiopure compound. Experimental results and quantum chemical calculations show that the underlying tetrameric cluster has 2:2 stoichiometry of the R and S isomers and S4 symmetry (see picture; C orange, O red, H gray).

    7. Catalytic Epoxidation and 1,2-Dihydroxylation of Olefins with Bispidine–Iron(II)/H2O2 Systems (pages 3446–3449)

      Michael R. Bukowski, Peter Comba, Achim Lienke, Christian Limberg, Carlos Lopez de Laorden, Rubén Mas-Ballesté, Michael Merz and Lawrence Que Jr.

      Article first published online: 25 APR 2006 | DOI: 10.1002/anie.200504357

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      Going ferryl: FeII complexes with two isomeric bispidine ligands catalyze the oxidation of cyclooctene with H2O2 in MeCN under aerobic conditions with high selectivity for the epoxide (see scheme; L=bispidine ligand). An {FeIV[DOUBLE BOND]O} complex is postulated to be the oxidant, formed by the homolytic cleavage of the O[BOND]O bond of an {FeIII-OOH} intermediate. Performing the reaction under argon gives a mixture of cis and trans diols as well as the epoxide.

    8. A General Approach for the Identification of Site-Specific RNA Binders by 19F NMR Spectroscopy: Proof of Concept (pages 3450–3453)

      Christoph Kreutz, Hanspeter Kählig, Robert Konrat and Ronald Micura

      Article first published online: 19 APR 2006 | DOI: 10.1002/anie.200504174

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      Bound to succeed: Noncovalent binding of ligands to RNA can be analyzed easily by 19F NMR spectroscopy through site-specific fluorine-labeling of the target RNA (see picture; B=adenine, cytosine, guanine, uracil). The proof of concept is provided by RNA aptamer–ligand interactions. The speed and the robustness of this simple approach present major advantages over methods relying on 1H NMR spectroscopy.

    9. A Biocatalytic Henry Reaction—The Hydroxynitrile Lyase from Hevea brasiliensis Also Catalyzes Nitroaldol Reactions (pages 3454–3456)

      Thomas Purkarthofer, Karl Gruber, Mandana Gruber-Khadjawi, Kerstin Waich, Wolfgang Skranc, Daniel Mink and Herfried Griengl

      Article first published online: 24 APR 2006 | DOI: 10.1002/anie.200504230

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      Novel enzyme activity: Biocatalytic Henry reactions with nitromethane and nitroethane yielded the corresponding nitroalcohols with good enantio- and diastereocontrol in the presence of the hydroxynitrile lyase from the tropical rubber tree Hevea brasiliensis. Molecular modeling and deuterated starting materials were used in mechanistic investigations.

    10. Space Filling Versus Symmetry: Two Consecutive Crystal-to-Crystal Phase Transitions in a 2D Network (pages 3457–3459)

      Chunhua Hu and Ulli Englert

      Article first published online: 19 APR 2006 | DOI: 10.1002/anie.200504460

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      Three structures for the price of one: The room-temperature phase of the 2D network [Pb(μ-Cl)2(μ-bipy)] (bipy=4,4′-bipyridine) undergoes crystal-to-crystal transformations both upon cooling (see picture; Pb pink, Cl green, N blue, C gray, H white) and upon heating. With increasing temperature, decreased packing efficiency is traded for higher symmetry.

    11. The Zintl Ion [Pb10]2−: A Rare Example of a Homoatomic closo Cluster (pages 3459–3462)

      Annette Spiekermann, Stephan D. Hoffmann and Thomas F. Fässler

      Article first published online: 19 APR 2006 | DOI: 10.1002/anie.200503916

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      Closed encounters: A closed deltahedral homoatomic cluster, [Pb10]2−, is structurally characterized. When this “empty” cluster is considered together with the recently published filled cluster [Ni@Pb10]2−, a striking parallel to the fullerenes emerges: Zintl ions form polyhedral cages that can enclose a central atom without any major structural alterations.

    12. Chemoselective Benzylic C[BOND]H Activations for the Preparation of Condensed N-Heterocycles (pages 3462–3465)

      Hongjun Ren and Paul Knochel

      Article first published online: 25 APR 2006 | DOI: 10.1002/anie.200600111

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      Buttoning up: A chemoselective domino reaction including one or two successive C[BOND]H activations serves to convert a range of readily available N-arylpyrroles into complex polycondensed N-heterocycles. The reaction is catalyzed by Pd(OAc)2 (5 mol %), and p-Tol3P (10 mol %) is added as the ligand (see scheme; Tol=tolyl).

    13. Multidimensional Large-Amplitude Motion: Revealing Concurrent Tunneling Pathways in Molecules with Several Internal Rotors (pages 3465–3470)

      Melanie Schnell and Jens-Uwe Grabow

      Article first published online: 10 MAY 2006 | DOI: 10.1002/anie.200600201

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      Light at the end of the tunnel: Knowledge of the feasible tunneling pathways of a molecule can shed light on the interaction mechanisms that govern its internal dynamics. A combination of rotational spectroscopy, permutation inversion group theory, and multidimensional tunneling formalism has shown that in the series (CH3)3XCl (X=Si, Ge, Sn), electrostatic repulsion is gradually reduced and the chemical bond gains importance.

    14. The Glycine–Water Complex (pages 3471–3474)

      José L. Alonso, Emilio J. Cocinero, Alberto Lesarri, M. Eugenia Sanz and Juan C. López

      Article first published online: 3 MAY 2006 | DOI: 10.1002/anie.200600342

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      Expanding the possibilities: The hydration of glycine has been observed in a supersonic jet by using laser ablation in combination with Fourier transform microwave spectroscopy. The rotational spectrum reveals that water binds to glycine through two hydrogen bonds, which bridge the carboxylic acid group in a closed planar structure. In the complex, glycine retains the most stable conformer of the parent unhydrated molecule.

    15. Rational Design of a Well-Defined Soluble Calcium Hydride Complex (pages 3474–3478)

      Sjoerd Harder and Julie Brettar

      Article first published online: 25 APR 2006 | DOI: 10.1002/anie.200601013

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      A surprisingly simple approach led to the synthesis of a molecular calcium hydride. Reaction of a calcium amide with phenylsilane gives clean conversion into the hydride that crystallizes as a dimer (see structure).

    16. Titanium–Salan-Catalyzed Asymmetric Epoxidation with Aqueous Hydrogen Peroxide as the Oxidant (pages 3478–3480)

      Yuji Sawada, Kazuhiro Matsumoto, Shoichi Kondo, Hisayuki Watanabe, Tomoyuki Ozawa, Kenji Suzuki, Bunnai Saito and Tsutomu Katsuki

      Article first published online: 24 APR 2006 | DOI: 10.1002/anie.200600636

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      Keep it simple: A titanium complex with a salan ligand bearing phenyl groups at C3 and C3′ is an efficient catalyst for the enantioselective epoxidation of unfunctionalized olefins with aqueous hydrogen peroxide (see scheme); furthermore, the epoxidation was stereospecific. The C3 and C3′ substituents stabilize this complex and enhance the asymmetric induction.

    17. Lithiation/Electrophilic Quench of [(η5-Cyclohexadienyl)Mn(CO)3]: Versatile Functionalization and Resolution of Planar Chirality in the Organomanganese Series (pages 3481–3484)

      Béatrice Jacques, Murielle Chavarot, Françoise Rose-Munch and Eric Rose

      Article first published online: 26 APR 2006 | DOI: 10.1002/anie.200600689

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      Easy does it: A lithiation/electrophilic quench sequence gives efficient access to a large variety of unprecedented complexes. One such complex (1; see scheme) can be successfully used in the synthesis of the first enantiopure formyl-substituted [(η5-cyclohexadienyl)Mn(CO)3] derivatives.

    18. A Highly Active Catalyst for Suzuki–Miyaura Cross-Coupling Reactions of Heteroaryl Compounds (pages 3484–3488)

      Kelvin L. Billingsley, Kevin W. Anderson and Stephen L. Buchwald

      Article first published online: 26 APR 2006 | DOI: 10.1002/anie.200600493

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      Unprecedented activity: Catalysts derived from Pd and bulky dialkylphosphinobiaryl ligands are shown to be highly stable and active in Suzuki–Miyaura reactions of heteroaryl halides and heteroaryl boronic acids/esters (e.g., 3- or 4-pyridine, indole, and N-protected pyrrole derivatives). Furthermore, this catalyst system is not inhibited by the presence of highly basic aminopyridines or aminopyrimidines.

    19. CO Fixation to Stable Acyclic and Cyclic Alkyl Amino Carbenes: Stable Amino Ketenes with a Small HOMO–LUMO Gap (pages 3488–3491)

      Vincent Lavallo, Yves Canac, Bruno Donnadieu, Wolfgang W. Schoeller and Guy Bertrand

      Article first published online: 25 APR 2006 | DOI: 10.1002/anie.200600987

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      A quick fix: In contrast to cyclic diamino carbenes, stable alkyl amino carbenes react with CO to give stable ketenes (see scheme, top). Contrary to the acyclic versions, cyclic amino ketenes cannot escape from the destabilizing n–π donation of the nitrogen lone pair, which induces a diradical character and unusual optical (see scheme, bottom and photographs of crystals) and NMR spectroscopic properties.

    20. Catalytic Enantioselective Crossed Aldehyde–Ketone Benzoin Cyclization (pages 3492–3494)

      Hiroshi Takikawa, Yoshifumi Hachisu, Jeffrey W. Bode and Keisuke Suzuki

      Article first published online: 25 APR 2006 | DOI: 10.1002/anie.200600268

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      Joining together: The catalytic, asymmetric benzoin cyclization of a wide variety ketoaldehydes using chiral triazolium salts of type 1 has been carried out (see scheme). The corresponding cyclized products were prepared in high yields and with excellent enantioselectivities.

    21. Alcohols in Isonitrile-Based Multicomponent Reaction: Passerini Reaction of Alcohols in the Presence of O-Iodoxybenzoic Acid (pages 3495–3497)

      Tifelle Ngouansavanh and Jieping Zhu

      Article first published online: 25 APR 2006 | DOI: 10.1002/anie.200600588

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      High proof: An alcohol instead of an aldehyde is an effective reaction partner in the Passerini reaction (P-3CR) in the presence of O-iodoxybenzoic acid (IBX). Thus, by simply heating a solution of an alcohol, a carboxylic acid, an isonitrile, and IBX at 40 °C, an oxidation/P-3CR sequence occurred smoothly to afford the α-acyloxy carboxamide in good-to-excellent yield.

    22. Hydrothermal Chemistry of the Copper–Triazolate System: A Microporous Metal–Organic Framework Constructed from Magnetic {Cu33-OH)(triazolate)3}2+ Building Blocks, and Related Materials (pages 3497–3500)

      Wayne Ouellette, Ming Hui Yu, Charles J. O'Connor, Douglas Hagrman and Jon Zubieta

      Article first published online: 20 APR 2006 | DOI: 10.1002/anie.200504128

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      Networking with triazolate: Three new compounds containing networks of CuI or CuII ions linked by 1,2,4-triazolate (trz) ligands were prepared by hydrothermal synthesis. The microporous metal–organic framework {Cu33-OH)(trz)3(OH)2(H2O)4}n, which is built up from magnetic triangles, forms 17×13×13 Å3 cavities (see picture; Cu dark blue, O red, N light blue, C black).

    23. Facilitated Hydrogen Storage in NaAlH4 Supported on Carbon Nanofibers (pages 3501–3503)

      Cornelis P. Baldé, Bart P. C. Hereijgers, Johannes H. Bitter and Krijn P. de Jong

      Article first published online: 24 APR 2006 | DOI: 10.1002/anie.200504202

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      The ins and outs of hydrogen: The hydrogen desorption from and absorption to sodium alanate (NaAlH4) supported on carbon nanofibers are significantly facilitated if its particle size is reduced from the micrometer to the nanometer range (see graph). This improvement is tentatively attributed to the minimization of the solid-state diffusion path length during loading and desorption of hydrogen.

    24. Introduction of 2,2,2-Trichloroethyl-Protected Sulfates into Monosaccharides with a Sulfuryl Imidazolium Salt and Application to the Synthesis of Sulfated Carbohydrates (pages 3503–3506)

      Laura J. Ingram and Scott D. Taylor

      Article first published online: 24 APR 2006 | DOI: 10.1002/anie.200600153

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      Sweet sulfur: Sulfuryl imidazolium salt 1 represents a new class of highly potent sulfating agents and is very effective for introducing trichloroethyl-protected sulfates into monosaccharides for the synthesis of sulfated oligosaccharides (see scheme; NMI=N-methylimidazole, OTf=triflate, PG=protecting group, TCE=2,2,2-trichloroethyl).

    25. Biosynthesis of Thiamin Thiazole: Determination of the Regiochemistry of the S/O Acyl Shift by Using 1,4-Dideoxy-D-xylulose-5-phosphate (pages 3507–3510)

      Abhishek Chatterjee, Xuemei Han, Fred W. McLafferty and Tadhg P. Begley

      Article first published online: 20 APR 2006 | DOI: 10.1002/anie.200504614

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      ThiS and that: An alternative substrate for thiazole synthase, namely 1,4-dideoxy-D-xylulose-5-phosphate, was synthesized and used as a mechanistic probe to determine the regiochemistry of the acyl-shift reaction that occurs as an intermediate step in the biosynthesis of thiamin thiazole in B. subtilis (see scheme; ThiS protein (blue); ThiG protein (red); OP=phosphate group).

    26. A New Class of Biochemically Degradable, Stimulus-Responsive Triblock Copolymer Gelators (pages 3510–3513)

      Chengming Li, Jeppe Madsen, Steven P. Armes and Andrew L. Lewis

      Article first published online: 24 APR 2006 | DOI: 10.1002/anie.200600324

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      To rub gel into the wound: A thermoresponsive ABA triblock copolymer gelator with A=N-isopropylacrylamide and B=2-(methacryloyloxy)ethyl phosphorylcholine has been synthesized by atom transfer radical polymerization by using a bifunctional disulfide-based initiator. This triblock copolymer forms free-standing peptide-degradable micellar gels under physiologically relevant conditions.

    27. Cationic Terminal Borylene Complexes: Interconversion of Amino and Alkoxy Borylenes by an Unprecedented Meerwein–Ponndorf Hydride Transfer (pages 3513–3516)

      Deborah L. Kays (née Coombs), Joanna K. Day, Simon Aldridge, Ross W. Harrington and William Clegg

      Article first published online: 24 APR 2006 | DOI: 10.1002/anie.200600714

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      It's all new to B: In the reaction of borylene complex 1 with benzophenone, a Meerwein–Ponndorf β-hydride transfer from the aminoborylene ligand to the coordinated ketone generates 2 (see structure), the first example of an imine-donor-stabilized borylene complex, and the first cationic alkoxyborylene system.

    28. A Deep, Water-Soluble Cavitand Acts as a Phase-Transfer Catalyst for Hydrophobic Species (pages 3517–3519)

      Richard J. Hooley, Shannon M. Biros and Julius Rebek Jr.

      Article first published online: 20 APR 2006 | DOI: 10.1002/anie.200600405

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      Overcoming inhibition: A deep, water-soluble cavitand has been shown to extract various N-substituted maleimides into aqueous solution through the hydrophobic effect. These complexes react with a water-soluble thiol to confer water solubility to the product, thus leading to a drastic reduction in binding affinity and allowing this system to function as a phase-transfer catalyst.

    29. Reversible Sulfurization–Desulfurization of Tungsten Bis(dithiolene) Complexes (pages 3520–3522)

      Hideki Sugimoto, Reiko Tajima, Takashi Sakurai, Hiromi Ohi, Hiroyuki Miyake, Shinobu Itoh and Hiroshi Tsukube

      Article first published online: 24 APR 2006 | DOI: 10.1002/anie.200600640

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      Easy come, easy go: Tungsten bis(dithiolene) complexes undergo reversible sulfurization–desulfurization in which the metal center changes between {WVI(S2)} and {WV}. The process is effectively controlled by the solution temperature, the solvent, and the electron-donating properties of the dithiolene ligands and results in a distinct color change (see scheme).

    30. Controlling RNA Digestion by RNase H with a Light-Activated DNA Hairpin (pages 3523–3526)

      XinJing Tang and Ivan J. Dmochowski

      Article first published online: 24 APR 2006 | DOI: 10.1002/anie.200600954

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      Making sense: A DNA hairpin was synthesized by attaching a 20-mer antisense oligodeoxynucleotide (asODN) to a sense ODN through a bifunctional photocleavable linker. This conjugate became much less stable upon UV photoactivation (ΔTm=−29 K, ΔΔG=4.6 kcal mol−1), which facilitated binding of the asODN to the complementary RNA. By this strategy, photomodulation of RNase H activity towards a variety of RNA targets was performed.

    31. Ultrastable Particle-Stabilized Foams (pages 3526–3530)

      Urs T. Gonzenbach, André R. Studart, Elena Tervoort and Ludwig J. Gauckler

      Article first published online: 26 APR 2006 | DOI: 10.1002/anie.200503676

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      Pump up the volume: Wet foams prepared with surfactants are thermodynamically unstable systems that undergo rapid disproportionation, drainage, and coalescence. Ultrastable foams have now been prepared using colloidal particles as stabilizers (left picture). The stabilization results from the irreversible adsorption at the air–water interface of particles surface-modified with short-chain amphiphiles (right picture).

    32. Tetraarylporphyrin as a Selective Molecular Cap for Non-Watson–Crick Guanine–Adenine Base-Pair Sequences (pages 3530–3533)

      Milan Balaz, Benjamin C. Li, Steffen Jockusch, George A. Ellestad and Nina Berova

      Article first published online: 20 APR 2006 | DOI: 10.1002/anie.200504431

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      Well protected: Porphyrins act as a molecular cap (see picture) to selectively stabilize a non-self-complementary non-Watson–Crick DNA structure through additional hydrophobic interactions. At the same time, these porphyrins serve as an efficient internal sensor of the newly formed secondary structure.

    33. Regioselective Glucosylation of Aromatic Compounds: Screening of a Recombinant Glycosyltransferase Library to Identify Biocatalysts (pages 3534–3538)

      Markus Weis, Eng-Kiat Lim, Neil Bruce and Dianna Bowles

      Article first published online: 24 APR 2006 | DOI: 10.1002/anie.200504505

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      A novel whole-cell screen for the identification of new glucosyltransferase (GT) biocatalysts within a recombinant enzyme library was developed. Following biotransformation, levels of D-glucose were used as a measure of biocatalysis. Twenty five enzymes that transfer D-glucose to trans-resveratrol were identified that have the regioselectivity shown in the picture.

    34. Multivalent Dendrons for High-Affinity Adhesion of Proteins to DNA (pages 3538–3542)

      Mauri A. Kostiainen, Géza R. Szilvay, David K. Smith, Markus B. Linder and Olli Ikkala

      Article first published online: 26 APR 2006 | DOI: 10.1002/anie.200504540

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      Strength in numbers: Multivalent dendrons that have an N-maleimido group at the focal point can be used to construct monodisperse one-to-one protein–dendron conjugates. The second generation polyamine dendron with spermine surface groups clearly imparts its high-affinity DNA binding to a protein of choice.

    35. A Self-Regulatory Host in an Oscillatory Guest Motion: Complexation of Fullerenes with a Short-Spaced Cyclic Dimer of an Organorhodium Porphyrin (pages 3542–3546)

      Ayako Ouchi, Kentaro Tashiro, Kentaro Yamaguchi, Takahiro Tsuchiya, Takeshi Akasaka and Takuzo Aida

      Article first published online: 20 APR 2006 | DOI: 10.1002/anie.200600478

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      Shake, rattle, and roll: As a guest within a short-spaced cyclic dimer of an organorhodium porphyrin 1, fullerenes such as C60 and C70 start to oscillate by slipping through the host cavity. This dynamic motion is substantially prohibited by another molecule of 1 through the formation of capsule-type inclusion complexes. In contrast, a larger fullerene such as C76 can hardly slip through the host cavity but is simply encapsulated by two molecules of 1.

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      Article first published online: 10 MAY 2006 | DOI: 10.1002/anie.200690075