Chemistry - A European Journal

Cover image for Vol. 12 Issue 4

January 23, 2006

Volume 12, Issue 4

Pages 963–1295

    1. Cover Picture: Utilization of Self-Sorting Processes To Generate Dynamic Combinatorial Libraries with New Network Topologies (Chem. Eur. J. 4/2006) (page 963)

      Isabelle Saur, Rosario Scopelliti and Kay Severin

      Version of Record online: 13 JAN 2006 | DOI: 10.1002/chem.200690012

      Dynamic combinatorial libraries can be regarded as adaptive chemical networks, in which the library members are connected by exchange reactions. In the Full Paper by K. Severin et al. on page 1058 ff., a library of metallamacrocyclic ruthenium and iridium complexes with a unique network topology is described.

    2. Synthetic Applications of β-Fluoroalkylated α,β-Unsaturated Carbonyl Compounds (pages 974–979)

      Thierry Billard

      Version of Record online: 1 AUG 2005 | DOI: 10.1002/chem.200500466

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      Efficient fluorinated building blocks are required for the synthesis of complex fluorinated compounds. β-Fluoroalkylated α,β-unsaturated carbonyl compounds constitute efficient units for this purpose. A large diversity of reactions can be envisaged with such molecules.

    3. Mollusk Shell Formation: A Source of New Concepts for Understanding Biomineralization Processes (pages 980–987)

      Lia Addadi, Derk Joester, Fabio Nudelman and Steve Weiner

      Version of Record online: 28 NOV 2005 | DOI: 10.1002/chem.200500980

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      Mollusk shell nacre is full of surprises: Here ideas are presented on how disparate components like a hydrophobic silk gel, highly acidic proteins, and possibly an amorphous, transient mineral precursor phase are assembled within a chitinous scaffold to produce the pearly nacreous layer of a mollusk shell (shown here).

    4. A Starburst-Shaped Heterometallic Compound Incorporating Six Densely Packed Gd3+ Ions (pages 989–1003)

      João Bruno Livramento, Angélique Sour, Alain Borel, André E. Merbach and Éva Tóth

      Version of Record online: 28 NOV 2005 | DOI: 10.1002/chem.200500969

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      A remarkable molar proton relaxivity, particularly at high magnetic fields, is displayed by the metallostar {Fe[Gd2bpy(DTTA)2(H2O)4]3}4− (see picture), which is formed by self-assembly of a heterotritopic, poly(amino carboxylate)-derivatized bipyridine ligand with FeII and GdIII. This behavior originates from a limited flexibility, together with the two inner-sphere water molecules and their near-optimal exchange rate.

    5. Synthesis of Heterobimetallic Ru[BOND]Mn Complexes and the Coupling Reactions of Epoxides with Carbon Dioxide Catalyzed by these Complexes (pages 1004–1015)

      Man Lok Man, King Chung Lam, Wing Nga Sit, Siu Man Ng, Zhongyuan Zhou, Zhenyang Lin and Chak Po Lau

      Version of Record online: 24 OCT 2005 | DOI: 10.1002/chem.200500780

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      Cyclic carbonates can be obtained in CO2/epoxide coupling reactions by using heterobimetallic Ru[BOND]Mn complexes. Density functional calculations were carried out at the B3LYP level of theory in order to understand and compare the structural and energetic aspects of the two possible reaction pathways involved in the catalytic reaction (see scheme), both of which begin with heterolytic metal[BOND]metal bond cleavage.

    6. NMR Investigation of the Dihydrogen-Bonding and Proton-Transfer Equilibria between the Hydrido Carbonyl Anion [HRe2(CO)9] and Fluorinated Alcohols (pages 1016–1025)

      Daniela Donghi, Tiziana Beringhelli, Giuseppe D'Alfonso and Marta Mondini

      Version of Record online: 3 NOV 2005 | DOI: 10.1002/chem.200500920

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      A snapshot of the proton-transfer equilibrium between [HRe2(CO)9] and hexafluoroisopropyl alcohol has been provided by 1H 2D EXSY. A dihydrogen-bonded Re2H⋅⋅⋅HOR adduct has been identified as the intermediate, but the assistance of a stronger, “conventional” RO⋅⋅⋅HOR hydrogen bond is necessary to drive the protonation equilibrium to the right (see scheme).

    7. Columnar and Smectic Liquid Crystals Based on Crown Ethers (pages 1026–1035)

      Nelli Steinke, Wolfgang Frey, Angelika Baro, Sabine Laschat, Christina Drees, Manfred Nimtz, Constanze Hägele and Frank Giesselmann

      Version of Record online: 27 OCT 2005 | DOI: 10.1002/chem.200500903

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      Unsymmetrical benzo[15]crown-5 ethers with one lateral alkyloxy-substituted ortho-terphenyl unit form complexes that exhibit liquid crystalline properties (see picture). Fan-shaped textures typical of columnar mesophases are observed.

    8. Ruthenium Complexes with the Stanna-closo-dodecaborate Ligand: Coexistence of η1(Sn) and η3(B[BOND]H) Coordination (pages 1036–1045)

      Torben Gädt, Beatrice Grau, Klaus Eichele, Ingo Pantenburg and Lars Wesemann

      Version of Record online: 26 OCT 2005 | DOI: 10.1002/chem.200500761

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      Fluxional behavior of the stanna-closo-dodecaborate ligand was investigated by dynamic NMR spectroscopy. In four ruthenium complexes, which were characterized by multinuclear NMR spectroscopy in solution as well as in the solid state, the heteroborate shows a novel ambident coordination mode (see for example the structure of [{Ru(dppb)(SnB11H11)}2]; dppb= bis(diphenylphosphino)butane).

    9. Spectroscopic Studies of Water-Soluble Porphyrins with Protein Encapsulated in Bis(2-ethylhexyl)sulfosuccinate (AOT) Reverse Micelles: Aggregation versus Complexation (pages 1046–1057)

      Suzana M. Andrade and Sílvia M. B. Costa

      Version of Record online: 26 OCT 2005 | DOI: 10.1002/chem.200500047

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      Influence of water uptake on TSPP aggregation inside bis(2-ethylhexyl)sulfosuccinate (AOT) reverse micelles has been investigated by spectroscopic studies, which indicate that monomeric and H-type aggregates of the anionic meso-tetrakis(p-sulfonatophenyl)porphyrin sodium salt (TSPP) prevail at low water contents, but revert to the J-type as the amount of water is increased; the amount of water can also control the aggregate growth (see graphic). Drug-carrier proteins, such as human serum albumin, in the system compete in the binding to the aforementioned porphyrins.

    10. Utilization of Self-Sorting Processes To Generate Dynamic Combinatorial Libraries with New Network Topologies (pages 1058–1066)

      Isabelle Saur, Rosario Scopelliti and Kay Severin

      Version of Record online: 15 AUG 2005 | DOI: 10.1002/chem.200500621

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      Dynamic combinatorial libraries of macrocycles were obtained by assembly of two metal fragments A and B with two ligands X and Y. The assembly process is self-sorting with respect to the ligand composition. Consequently, the libraries show a distinct network topology with two partially orthogonal sub-libraries (see scheme).

    11. Assembly of a Tetrathiafulvalene–Anthracene Dyad on the Surfaces of Gold Nanoparticles: Tuning the Excited-State Properties of the Anthracene Unit in the Dyad (pages 1067–1073)

      Guanxin Zhang, Deqing Zhang, Xiaohui Zhao, Xicheng Ai, Jianping Zhang and Daoben Zhu

      Version of Record online: 20 OCT 2005 | DOI: 10.1002/chem.200500524

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      A photoinduced electron-transfer process is tuned by the assembly of tetrathiafulvalene–anthracene dyad on the surface of gold nanoparticles (see figure). The excited-state property of the anthracene unit is also modulated, leading to both fluorescence enhancement and facilitation of photodimerization of the anthracene unit.

    12. Binding of Acetylcholinesterase to Multiwall Carbon Nanotube-Cross-Linked Chitosan Composite for Flow-Injection Amperometric Detection of an Organophosphorous Insecticide (pages 1074–1080)

      Vivek Babu Kandimalla and Huangxian Ju

      Version of Record online: 20 OCT 2005 | DOI: 10.1002/chem.200500178

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      A novel method for the immobilization of acetylcholinesterase by covalent binding to a cross-linked chitosan–multiwall carbon nanotube composite is presented. In addition, a sensitive, fast, cheap, and automatizable flow injection detection of an organophosphorous insecticide down to nM level was developed (see scheme).

    13. Amplification of Bifunctional Ligands for Calmodulin from a Dynamic Combinatorial Library (pages 1081–1087)

      Lilia Milanesi, Christopher A. Hunter, Svetlana E. Sedelnikova and Jonathan P. Waltho

      Version of Record online: 20 OCT 2005 | DOI: 10.1002/chem.200500357

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      Selection of high affinity bifunctional ligands for a receptor with independently mobile binding sites is described using dynamic combinatorial chemistry. Thiol-to-disulfide linkage generated a small dynamic library of bifunctional ligands in the presence of calmodulin, a protein with two independently mobile domains (see scheme).

    14. Unidirectional Threading Synthesis of Isomer-Free [2]Rotaxanes (pages 1088–1096)

      Qiao-Chun Wang, Xiang Ma, Da-Hui Qu and He Tian

      Version of Record online: 24 OCT 2005 | DOI: 10.1002/chem.200500415

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      Switch to shuttle: [2]Rotaxane-based molecular shuttles were synthesized by two different unidirectional threading approaches of α-cyclodextrin (see scheme). The relative switching processes of these shuttles were also investigated.

    15. Photophysics of a Series of Efficient Fluorescent pH Probes for Dual-Emission-Wavelength Measurements in Aqueous Solutions (pages 1097–1113)

      Sandrine Charier, Odile Ruel, Jean-Bernard Baudin, Damien Alcor, Jean-François Allemand, Adrien Meglio, Ludovic Jullien and Bernard Valeur

      Version of Record online: 25 OCT 2005 | DOI: 10.1002/chem.200500619

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      Excited probes: The synthetically versatile 5-aryl-2-pyridyloxazole platform (see scheme) is evaluated for engineering strongly fluorescent water-soluble pH indicators with tunable acid–base properties. pH probes for dual-emission-wavelength measurements working in the pH 3–8 range as well as pOH-jump molecules can be easily obtained and reliably used after one- or two-photon excitation.

    16. A Photocontrolled β-Hairpin Peptide (pages 1114–1120)

      Shou-Liang Dong, Markus Löweneck, Tobias E. Schrader, Wolfgang J. Schreier, Wolfgang Zinth, Luis Moroder and Christian Renner

      Version of Record online: 18 NOV 2005 | DOI: 10.1002/chem.200500986

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      Lights on! A hairpin model, which incorporated the βI′ turn mimetic [3-(3-aminomethyl)-phenylazo]phenylacetic acid inbetween two peptide strands, resulted in a β-hairpin model in which the folding/unfolding of this structural motif is controlled by the isomeric state of the azobenzene chromophore. Pronounced changes in the CD, IR, and fluorescence spectra enable time-resolved folding studies by ultra-fast spectroscopy upon photoisomerization.

    17. Homochiral Helices of Oligonaphthalenes Inducing Opposite-Handed Cholesteric Phases (pages 1121–1126)

      Silvia Pieraccini, Alberta Ferrarini, Kaoru Fuji, Giovanni Gottarelli, Stefano Lena, Kazunori Tsubaki and Gian Piero Spada

      Version of Record online: 25 OCT 2005 | DOI: 10.1002/chem.200500683

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      Alternating handedness was observed for the cholesteric phase of a series of homochiral (all-S)-oligo-1,1′-naphthalenes. This surprising property was obtained by doping nematic phases and resulted in the alternation from right to left and to right again (see scheme), on passing from tetra- to hexa- to octanaphthalene.

    18. Nucleophilicity—Periodic Trends and Connection to Basicity (pages 1127–1136)

      Einar Uggerud

      Version of Record online: 25 OCT 2005 | DOI: 10.1002/chem.200500639

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      The trends in intrinsic nucleophilicity (only defined for identity reactions) and basicity are opposite, thus the overall nucleophilicity (defined for any reaction) will be determined by the relative contribution of the two factors.

    19. Controlled Nanozeolite-Assembled Electrode: Remarkable Enzyme-Immobilization Ability and High Sensitivity as Biosensor (pages 1137–1143)

      Tao Yu, Yahong Zhang, Chunping You, Jihua Zhuang, Bo Wang, Baohong Liu, Yijin Kang and Yi Tang

      Version of Record online: 26 OCT 2005 | DOI: 10.1002/chem.200500562

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      Nano-LTL-zeolite-assembled electrodes for cytochrome c immobilization display good and controllable electrochemical and biosensor behavior. This behavior can be attributed to the unique surface properties and facile assembly character of nanozeolites (see picture).

    20. Electron-Rich Tetrathiafulvalene–Triarylamine Conjugates: Synthesis and Redox Properties (pages 1144–1155)

      Hongchao Li and Christoph Lambert

      Version of Record online: 27 OCT 2005 | DOI: 10.1002/chem.200500928

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      New electron-donating molecular materials with high HOMO levels (−4.70 eV), which are mainly located on the TTF moiety, are afforded by the combination of TTFs and triarylamines. The redox potential of the triarylamine unit is strongly dependent on the conjugated TTF propeller blades (see picture). The morphology of such conjugates can be tuned from liquid oil through crystalline to amorphous glass by variation of the chemical structure.

    21. DFT-HSAB Prediction of Regioselectivity in 1,3-Dipolar Cycloadditions: Behavior of (4-Substituted)benzonitrile Oxides towards Methyl Propiolate (pages 1156–1161)

      Alessandro Ponti and Giorgio Molteni

      Version of Record online: 31 OCT 2005 | DOI: 10.1002/chem.200500739

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      Just relax! Taking into account the relaxation of the electron density during a reaction is a key factor in determining regioselectivity. This is one of the differences between frontier molecular orbital theory and the DFT approach. To see this difference, look at the Fukui function (pink and ochre surfaces) of 4-chlorobenzonitrile oxide, and its lower-order approximation, the HOMO density (blue); the latter is positive, whereas the Fukui function can be both positive (pink) and negative (ochre).

    22. The Transfer of Tin and Germanium Atoms from N-Heterocyclic Stannylenes and Germylenes to Diazadienes (pages 1162–1173)

      Timo Gans-Eichler, Dietrich Gudat, Kalle Nättinen and Martin Nieger

      Version of Record online: 26 OCT 2005 | DOI: 10.1002/chem.200500576

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      Ring metathesis under formal transfer of a “naked” Group 14 atom forms the basis of the reactions of N-heterocyclic stannylenes and germylenes with diazadienes. The computational results indicate notably different geometric and electronic structures for the intermediates in both reactions and suggest further that involvement of triplet states in the reactions of stannylenes may explain the easily occurring cheletropic fragmentation of these species (see picture).

    23. 5-Aminooxazole as an Internal Traceless Activator of C-Terminal Carboxylic Acid: Rapid Access to Diversely Functionalized Cyclodepsipeptides (pages 1174–1184)

      Carine Bughin, Gang Zhao, Hugues Bienaymé and Jieping Zhu

      Version of Record online: 20 OCT 2005 | DOI: 10.1002/chem.200500703

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      A conceptually novel macrolactonization protocol using 5-aminooxazole as an internal traceless activator of a neighboring carboxylic acid has been developed. Its combination with a three-component synthesis of oxazole leads to a two-step synthesis of complex cyclodepsipeptides from readily accessible starting materials (see scheme).

    24. Total Synthesis of Phorboxazole B (pages 1185–1204)

      De-Run Li, Dong-Hui Zhang, Cai-Yun Sun, Ji-Wen Zhang, Li Yang, Jian Chen, Bo Liu, Ce Su, Wei-Shan Zhou and Guo-Qiang Lin

      Version of Record online: 3 NOV 2005 | DOI: 10.1002/chem.200500892

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      21-Membered macrolides: Ranked among the most cytostatic natural products ever known, phorboxazole B (see scheme) represents a new class of 21-membered macrolides. Herein we report an efficient and convergent total synthesis of this compound.

    25. Catalytic Asymmetric Mannich-Type Reactions Activated by ZnF2 Chiral Diamine in Aqueous Media (pages 1205–1215)

      Tomoaki Hamada, Kei Manabe and Shū Kobayashi

      Version of Record online: 3 NOV 2005 | DOI: 10.1002/chem.200500673

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      Carbon–carbon bond-forming reactions in water: Catalytic asymmetric Mannich-type reactions of an α-hydrazono ester with silicon enolates have been developed in aqueous media (see scheme). This methodology utilizes ZnF2 and chiral diamines as catalysts to achieve high yields and enantioselectivities. Interestingly, these reactions proceeded smoothly only in the presence of water.

    26. Enantioselective Epoxidation of Terminal Alkenes to (R)- and (S)-Epoxides by Engineered Cytochromes P450 BM-3 (pages 1216–1220)

      Takafumi Kubo, Matthew W. Peters, Peter Meinhold and Frances H. Arnold

      Version of Record online: 20 OCT 2005 | DOI: 10.1002/chem.200500584

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      Enzymatic, terminal alkene epoxidation: Cytochrome P450 BM-3 was engineered for enantioselective epoxidation of terminal alkenes. Two variants are described that convert a range of terminal alkenes to either (R)- or (S)-epoxide with high catalytic turnovers and high epoxidation selectivity using an NADPH regeneration system (see scheme).

    27. Domino Reactions of 1,3-Bis-Silyl Enol Ethers with Benzopyrylium Triflates: Efficient Synthesis of Fluorescent 6H-Benzo[c]chromen-6-ones, Dibenzo[c,d]chromen-6-ones, and 2,3-Dihydro-1H-4,6-dioxachrysen-5-ones (pages 1221–1236)

      Bettina Appel, Nehad N. R. Saleh and Peter Langer

      Version of Record online: 7 NOV 2005 | DOI: 10.1002/chem.200501024

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      Retro-Michael–aldol–lactonization reactions: Domino reactions of 1,3-bis-silyl enol ethers with chromones provide an efficient approach to a variety of 7-hydroxy-6H-benzo[c]chromen-6-ones, such as the natural product autumnariol (see scheme).

    28. Aminolysis of 2,4-Dinitrophenyl X-Substituted Benzoates and Y-Substituted Phenyl Benzoates in MeCN: Effect of the Reaction Medium on Rate and Mechanism (pages 1237–1243)

      Ik-Hwan Um, Sang-Eun Jeon and Jin-Ah Seok

      Version of Record online: 3 NOV 2005 | DOI: 10.1002/chem.200500647

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      Consult a different medium! For the aminolysis reactions of 2,4-dinitrophenyl X-substituted benzoates and Y-substituted phenyl benzoates (see equation) a change in the reaction medium from H2O to MeCN appears to force the reaction to proceed concertedly by decreasing the stability of the intermediate (T±) in aprotic solvent.

    29. Fine Tuning of the Electronic Properties of Linear π-Conjugated Oligomers by Covalent Bridging (pages 1244–1255)

      Philippe Blanchard, Patrick Verlhac, Laurent Michaux, Pierre Frère and Jean Roncali

      Version of Record online: 10 NOV 2005 | DOI: 10.1002/chem.200500853

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      Bridge to improved properties: Rigidified oligothienylenevinylenes, such as those depicted with optimized π-electron delocalization, have been synthesized by covalent bridging of ethylene linkages. Cyclic voltammetry, UV/Vis spectroscopy, and theoretical results highlight the influence of the position of the covalent bridge on the electronic properties of the title molecules.

    30. A Mechanistic and Kinetic Study of the Formation of Metal Nanoparticles by Using Synthetic Tyrosine-Based Oligopeptides (pages 1256–1265)

      Satyabrata Si, Rama Ranjan Bhattacharjee, Arindam Banerjee and Tarun K. Mandal

      Version of Record online: 9 NOV 2005 | DOI: 10.1002/chem.200500834

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      Redox-active tyrosine-based peptides have been employed to prepare gold and silver nanoparticles. An electron from the tyrosinate ion of the peptide is transferred to the metal ion at basic pH through the formation of a tyrosyl radical, which is eventually converted to the dityrosine form during the reaction (see graphic) and was confirmed by UV-visible, fluorescence, and EPR spectroscopy. The kinetic studies show that the rate of formation of gold nanoparticles was much faster at higher pH than at lower pH and was also dependent on the number of tyrosine residues present in the peptide.

    31. Synthesis of ansa-[n]Silacyclopentadienyl–Cycloheptatrienyl–Chromium Complexes (n = 1, 2): Novel Precursors for Polymers Bearing Chromium in the Backbone (pages 1266–1273)

      Alexandra Bartole-Scott, Holger Braunschweig, Thomas Kupfer, Matthias Lutz, Ian Manners, Thi-loan Nguyen, Krzysztof Radacki and Fabian Seeler

      Version of Record online: 10 NOV 2005 | DOI: 10.1002/chem.200500689

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      Successful polymerization of a novel [1]silatrochrocenophane was achieved, giving a ring-opened chromium-based polymer. The precursor was obtained by reaction of the [1]silatrochrocenophane bearing the Me2Si-bridged [1]silatrochrocenophane with [Pt(PEt3)4], as shown.

    32. Solid-Phase Oligosaccharide Synthesis of a Small Library of N-Glycans (pages 1274–1290)

      Simon Jonke, Ke-gang Liu and Richard R. Schmidt

      Version of Record online: 7 NOV 2005 | DOI: 10.1002/chem.200500707

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      An efficient solid-phase synthesis of N-glycans based on different types of esters is described: benzoate and acetate groups are employed as linkers and for chain termination; Fmoc and phenoxyacetyl (PA) are used as temporary protecting groups for chain extension and branching (see scheme). O-Benzyl and N-dimethylmaleoyl (DMM) are utilized for permanent protection.

    33. Preview: Chem. Eur. J. 4/2006 (page 1295)

      Version of Record online: 13 JAN 2006 | DOI: 10.1002/chem.200690011

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