Angewandte Chemie International Edition

Cover image for Vol. 40 Issue 9

May 4, 2001

Volume 40, Issue 9

Pages 1557–1787

    1. Cover Picture (page 1557)

      Sanjoy K. Das, Jean-Maurice Mallet, Jacques Esnault, Pierre-Alexandre Driguez, Philippe Duchaussoy, Philippe Sizun, Jean-Pascal Hérault, Jean-Marc Herbert, Maurice Petitou and Pierre Sinaÿ

      Article first published online: 3 MAY 2001 | DOI: 10.1002/1521-3773(20010504)40:9<1557::AID-ANIE15570>3.0.CO;2-Q

    2. Graphical Abstract (pages 1559–1573)

      Article first published online: 7 AUG 2001 | DOI: 10.1002/1521-3773(20010504)40:9<1559::AID-ANIE15590>3.0.CO;2-M

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      A Versatile and High-Yield Route to Active and Well-Defined Catalysts [Ru(bisphosphane)(H)(solvent)3](BF4) (page 1573)

      Jason A. Wiles, Steven H. Bergens, Koenraad P. M. Vanhessche, Daniel A. Dobbs and Valentin Rautenstrauch

      Article first published online: 3 MAY 2001 | DOI: 10.1002/1521-3773(20010504)40:9<1573::AID-ANIE15731>3.0.CO;2-J

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      New Synthetic Technology for the Construction of N-Containing Quinones and Derivatives Thereof: Total Synthesis of Epoxyquinomycin B (page 1573)

      K. C. Nicolaou, Kazuyuki Sugita, Phil S. Baran and Yong-Li Zhong

      Article first published online: 3 MAY 2001 | DOI: 10.1002/1521-3773(20010504)40:9<1573::AID-ANIE15732>3.0.CO;2-G

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      Synthesis of the FGHI Ring System of Azaspiracid (page 1573)

      K. C. Nicolaou, Petri M. Pihko, Nicole Diedrichs, Ning Zou and Federico Bernal

      Article first published online: 3 MAY 2001 | DOI: 10.1002/1521-3773(20010504)40:9<1573::AID-ANIE15733>3.0.CO;2-D

    6. Adventures in Carbohydrate Chemistry: New Synthetic Technologies, Chemical Synthesis, Molecular Design, and Chemical Biology (pages 1576–1624)

      K. C. Nicolaou and Helen J. Mitchell

      Article first published online: 3 MAY 2001 | DOI: 10.1002/1521-3773(20010504)40:9<1576::AID-ANIE15760>3.0.CO;2-G

      The teamwork between carbohydrate chemistry and total synthesis is surely one of the most exciting aspects of organic chemistry. In this review the contributions made by the principal author's research group in the areas of chemical synthesis and biological chemistry of carbohydrates are presented. Specifically, the use of carbohydrates as starting materials for total synthesis, the development of new technologies for carbohydrate synthesis, the construction of complex oligosaccharides in solution or on solid support, and the use of carbohydrate templates as scaffolds for peptide mimetics and other interesting compounds are discussed.

    7. Contemporary Advances in the Use of Powder X-Ray Diffraction for Structure Determination (pages 1626–1651)

      Kenneth D. M. Harris, Maryjane Tremayne and Benson M. Kariuki

      Article first published online: 3 MAY 2001 | DOI: 10.1002/1521-3773(20010504)40:9<1626::AID-ANIE16260>3.0.CO;2-7

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      As many materials cannot be prepared in the form of single crystals appropriate for single-crystal X-ray diffraction, structure determination of such materials requires the use of powder X-ray diffraction data. However, the determination of crystal structures directly from powder X-ray diffraction data is associated with a number of intrinsic challenges. In recent years there has been substantial progress in the development of techniques to tackle these challenges. In addition to surveying these advances in methodology, the opportunities that now exist for exploiting powder diffraction in structure determination are highlighted with examples taken from diverse areas across the chemical and materials sciences. The picture shows the β phase from 1,4-diketo-2,5-di-tert-butoxycarbonyl-3,6-diphenylpyrrolo[3,4]pyrrole.

    8. Improving Enantioselective Fluorination Reactions: Chiral N-Fluoroammonium Salts and Transition Metal Catalysts (pages 1653–1656)

      Kilian Muñiz

      Article first published online: 3 MAY 2001 | DOI: 10.1002/1521-3773(20010504)40:9<1653::AID-ANIE16530>3.0.CO;2-W

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      Enantioselective fluorinations made easier! Chiral N-fluoroammonium salts such as A, or chiral catalysts generated from complexes B (L=ligand) broaden the substrate scope for electrophilic fluorination. Starting from prochiral substrates they offer an efficient approach to chiral fluoro derivatives such as C. Additionally, fluorinated stereogenic centers can be generated from nucleophilic, catalytic epoxide opening.

    9. Versatile Scorpionates—New Developments in the Coordination Chemistry of Pyrazolylborate Ligands (pages 1656–1660)

      Frank T. Edelmann

      Article first published online: 3 MAY 2001 | DOI: 10.1002/1521-3773(20010504)40:9<1656::AID-ANIE16560>3.0.CO;2-Q

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      Much more versatile than previously anticipated are the coordination modes of tris(pyrazolyl)borate ligands (scorpionates). Recent contributions in this area not only lead to a new understanding of the electronic effects, but for the first time report unusually high and low hapticities as well as novel coordination modes such as the π coordination of a pyrazolyl ring to potassium (see structure). Potentially useful new ligands have been made available through innovative synthetic routes.

    10. Twelvefold Functionalization of an Icosahedral Surface by Total Esterification of [B12(OH)12]2−: 12(12)-Closomers (pages 1661–1664)

      Andreas Maderna, Carolyn B. Knobler and M. Frederick Hawthorne

      Article first published online: 3 MAY 2001 | DOI: 10.1002/1521-3773(20010504)40:9<1661::AID-ANIE16610>3.0.CO;2-U

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      Esterified B12icosahedra with totally organoderivatized surfaces are obtained from the reaction of [closo-B12(OH)12]2− with acetic anhydride or benzoyl chloride. The resulting “closomers”, in which each cluster vertex is substituted with an organic ester moiety, can provide camouflaged modules of variable size, shape, charge, hydrophobicity, etc. and represent the first examples of this structural motif known in chemistry. The figure displays, in a space-filling representation, the result of an X-ray analysis performed with the dodecabenzoate ester derivative.

    11. Dodeca(benzyloxy)dodecaborane, B12(OCH2Ph)12: A Stable Derivative of hypercloso-B12H12 (pages 1664–1667)

      Toralf Peymann, Carolyn B. Knobler, Saeed I. Khan and M. Frederick Hawthorne

      Article first published online: 3 MAY 2001 | DOI: 10.1002/1521-3773(20010504)40:9<1664::AID-ANIE16640>3.0.CO;2-O

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      Per-O-benzylation of [closo-B12(OH)12]2− (12−) using benzyl chloride followed by oxidation with two equivalents of FeIII gave compound 2, the per(benzyloxy) derivative of hypercloso-B12H12 (see scheme). Species 2 is characterized by 11B NMR and electronic spectroscopy, mass spectrometry, cyclic voltammetry, and X-ray crystallography.

    12. Parity Violation in Fluorooxirane (pages 1667–1670)

      Robert Berger, Martin Quack and Jürgen Stohner

      Article first published online: 3 MAY 2001 | DOI: 10.1002/1521-3773(20010504)40:9<1667::AID-ANIE16670>3.0.CO;2-I

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      In contrast to what has been accepted, electroweak quantum chemistry predicts the heats of formation, the structures, the microwave and infrared spectra of enantiomers of chiral molecules to be different. The R enantiomer of fluoroxirane is calculated to be more stable than the S enantiomer by the minute amount of 2×10−12 J mol−1, and the relative IR frequency shifts are ≤10−18 (see scheme). Nevertheless, this recently synthesized compound may prove useful for fundamental experimental tests and calculations of parity violation in chiral molecules because of its particularly simple rovibrational spectrum and its rigid cyclic structure composed of light atoms.

    13. Synthesis of Conformationally Locked Carbohydrates: A Skew-Boat Conformation of L-Iduronic Acid Governs the Antithrombotic Activity of Heparin (pages 1670–1673)

      Sanjoy K. Das, Jean-Maurice Mallet, Jacques Esnault, Pierre-Alexandre Driguez, Philippe Duchaussoy, Philippe Sizun, Jean-Pascal Hérault, Jean-Marc Herbert, Maurice Petitou and Pierre Sinaÿ

      Article first published online: 3 MAY 2001 | DOI: 10.1002/1521-3773(20010504)40:9<1670::AID-ANIE16700>3.0.CO;2-Q

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      Conformational flexibility of L-iduronic acid is a key feature of this typical component of heparin. Three pentasaccharides have now been synthesized, which are analogues of the active site of heparin and in which the single L-iduronic acid is conformationally locked in either the 1C4, 4C1, or 2S0 form. Only the 2S0 variant 1 was able to fully activate antithrombin inhibition of the blood coagulation factor Xa.

    14. Tetrakis(trimethylsilyl)cyclobutadiene and Tetrakis(trimethylsilyl)tetrahedrane (pages 1674–1675)

      Günther Maier, Jörg Neudert and Oliver Wolf

      Article first published online: 3 MAY 2001 | DOI: 10.1002/1521-3773(20010504)40:9<1674::AID-ANIE16740>3.0.CO;2-I

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      A route to unsubstituted tetrahedrane? One option is offered by the tetrakis(trimethylsilyl) derivative, which is generated upon irradiation of the corresponding cyclobutadiene (see scheme). Tetrahedrane itself could also possibly be accessed from the tetralithiotetrahedrane by this route.

    15. From a Cyclobutadiene Dianion to a Cyclobutadiene: Synthesis and Structural Characterization of Tetrasilyl-Substituted Cyclobutadiene (pages 1675–1677)

      Akira Sekiguchi, Masanobu Tanaka, Tsukasa Matsuo and Hidetoshi Watanabe

      Article first published online: 3 MAY 2001 | DOI: 10.1002/1521-3773(20010504)40:9<1675::AID-ANIE16750>3.0.CO;2-G

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      In less than one minute dianion 1 can be oxidized with 1,2-dibromoethane to give pure tetrakis(trimethylsilyl)cyclobutadiene (2, see scheme). The bridged cyclobutadiene derivative 6 was also similarly synthesized and characterized by X-ray crystallography; it exhibits a planar rectangular structure with localized C=C bonds.

    16. Water Exchange Controls the Complex-Formation Mechanism of Water-Soluble Iron(III) Porphyrins: Conclusive Evidence for Dissociative Water Exchange from a High-Pressure 17O NMR Study (pages 1678–1680)

      Thorsten Schneppensieper, Achim Zahl and Rudi van Eldik

      Article first published online: 3 MAY 2001 | DOI: 10.1002/1521-3773(20010504)40:9<1678::AID-ANIE16780>3.0.CO;2-A

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      The water-exchange reactions of three modified iron(III) porphyrins were studied in acidic medium as a function of temperature and pressure using 17O NMR spectroscopic techniques. The positive activation entropies and activation volumes support a dissociative mechanism (see scheme showing the transition state; L=nucleophile, H2O, NO). A comparison with available literature data reveals that the rate and mechanism of complex-formation reactions of such metal porphyrins are controlled by the water-exchange process.

    17. Controlling the Lability of Square-Planar PtII Complexes through Electronic Communication between π-Acceptor Ligands (pages 1680–1683)

      Deogratius Jaganyi, Andreas Hofmann and Rudi van Eldik

      Article first published online: 3 MAY 2001 | DOI: 10.1002/1521-3773(20010504)40:9<1680::AID-ANIE16800>3.0.CO;2-K

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      By a factor of 104–105 that is how much the reactivity of PtII(terpyridine) complexes exceeds the reactivity of the corresponding PtII(diene) complexes in nucleophilic substitution reactions. A systematic π-acceptor study was performed on a series of aqua complexes (see scheme) to elucidate that the source of this unusual acceleration is π conjugation!

    18. Electrokinetics in Fixed Beds: Experimental Demonstration of Electroosmotic Perfusion (pages 1684–1687)

      Ulrich Tallarek, Erdmann Rapp, Henk Van As and Ernst Bayer

      Article first published online: 3 MAY 2001 | DOI: 10.1002/1521-3773(20010504)40:9<1684::AID-ANIE16840>3.0.CO;2-C

      Diffusion or perfusionthis is no longer the question for electroosmotic flow (EOF) through capillaries with fixed beds. The intraparticle EOF in capillary electrochromatography has been shown by using special NMR techniques and forms the basis for a further improvement in separation efficiency, mass sensitivity, and analysis speed. Electroosmotic perfusion phenomena in porous materials also play an important role in other areas, such as in the dewatering of waste sludge and the removal of contaminants from soil.

    19. First, Atropo-Enantioselective Total Synthesis of the Axially Chiral Phenylanthraquinone Natural Products Knipholone and 6′-O-Methylknipholone (pages 1687–1690)

      Gerhard Bringmann and Dirk Menche

      Article first published online: 3 MAY 2001 | DOI: 10.1002/1521-3773(20010504)40:9<1687::AID-ANIE16870>3.0.CO;2-6

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      The first stereoselective access to an axially chiral arylanthraquinone, the antimalarial natural product knipholone (3), was achieved by application of the “lactone concept”. Key steps were the intramolecular coupling of the bromoester 1, to give the configurationally unstable biaryl lactone 2, and the enantioselective ring cleavage to form 3.

    20. High-Temperature Synthesis of an Open-Framework Compound, Na2Cs2Cu3(P2O7)2Cl2 (CU-4), by Molten-Salt Methods (pages 1690–1693)

      Qun Huang, Shiou-Jyh Hwu and Xunhua Mo

      Article first published online: 3 MAY 2001 | DOI: 10.1002/1521-3773(20010504)40:9<1690::AID-ANIE16900>3.0.CO;2-E

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      8-Ring and 16-ring channels with 5.3×5.3 Å and 4.9×17.2 Å windows, respectively, are contained in the new CU-4 phase. The larger channel exhibits an elliptical pore structure templated by an alkali metal chloride salt. CU-4 is structurally related to CU-2 (see picture), and can be chemically modified to CU-2 by an ion-exchange reaction at 600°C.

    21. The Biosynthesis of Vancomycin-Type Glycopeptide Antibiotics—New Insights into the Cyclization Steps (pages 1693–1696)

      Daniel Bischoff, Stefan Pelzer, Alexandra Höltzel, Graeme J. Nicholson, Sigrid Stockert, Wolfgang Wohlleben, Günther Jung and Roderich D. Süssmuth

      Article first published online: 3 MAY 2001 | DOI: 10.1002/1521-3773(20010504)40:9<1693::AID-ANIE16930>3.0.CO;2-8

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      A new oxyA gene replacement mutant of Amycolatopsis mediterranei enabled us to isolate two peptides, SP-1132 (1) and SP-1294 (2), which only have one diaryl ether bridge. These vancomycin-type structures provide further insight into the oxidative ring-bridging steps in their biosynthesis.

    22. New Phosphorus Ligands for the Rhodium-Catalyzed Isomerization/Hydroformylation of Internal Octenes (pages 1696–1698)

      Detlef Selent, Dieter Hess, Klaus-Diether Wiese, Dirk Röttger, Christine Kunze and Armin Börner

      Article first published online: 3 MAY 2001 | DOI: 10.1002/1521-3773(20010504)40:9<1696::AID-ANIE16960>3.0.CO;2-2

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      Going up!n-Selectivity and activity can be increased simultaneously in hydroformylation by the use of novel hybrid ligands such as 1 containing O-acylphosphite groups. For the first time these ligands deliver impressively n-selective rhodium-catalyzed hydroformylation of internal octenes, and this with an industrial relevant catalytic activity.

    23. A Sol–Gel Route to B4C (pages 1698–1700)

      Edwin Kroke, Karl W. Völger, Alexander Klonczynski and Ralf Riedel

      Article first published online: 3 MAY 2001 | DOI: 10.1002/1521-3773(20010504)40:9<1698::AID-ANIE16980>3.0.CO;2-Z

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      B-trichloroborazene reacts with bis(trimethylsilyl)carbodiimide to form non-oxide gels (see scheme). The xerogels consist of a polymeric network of borazine rings linked by carbodiimide groups. Pyrolysis at 1200°C provides amorphous ceramics with the composition BC0.23N1.1Si0.05H0.09 ≈ B4CN4. At 2000°C pure B4C is formed.

    24. Metallacoronates or One-Dimensional Polymers through Self-Assembly—Influence of Templates and Hydrogen Bonding on Product Formation (pages 1700–1703)

      Rolf W. Saalfrank, Ingo Bernt and Frank Hampel

      Article first published online: 3 MAY 2001 | DOI: 10.1002/1521-3773(20010504)40:9<1700::AID-ANIE17000>3.0.CO;2-T

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      Template effect versus hydogen bonding in self-assembly: As predicted, the scaffold of molecular gyroscope [(NaBr)2∩Cu6{(2,5-Me2C6H3CH2)N(CH2CH2O)2}6] (1) is generated from N-substituted diethanolamine together with a copper(II) salt and sodium bromide. However, we did not predict the one-dimensional coordination polymer equation image[Cu4{H[HN(CH2CH2O)2]}4(OAc)4] (2) generated with an unsubstituted diethanolamine. The formation of 2 is a further impressive example of nature's virtuosity in using hydrogen bonds.

    25. Stephanosporin, a “Traceless” Precursor of 2-Chloro-4-nitrophenol in the Gasteromycete Stephanospora caroticolor (pages 1704–1705)

      Martin Lang, Peter Spiteller, Veronika Hellwig and Wolfgang Steglich

      Article first published online: 3 MAY 2001 | DOI: 10.1002/1521-3773(20010504)40:9<1704::AID-ANIE17040>3.0.CO;2-L

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      More like an industrial fungicide than a natural product is the title compound, which occurs as the potassium salt in the carrot truffle, Stephanospora caroticolor, and is responsible for its orange color (see picture). On injury of the fruit body, 1 is transformed into the toxic 2-chloro-4-nitrophenolate (2) by loss of the side chain.

    26. pH-Responsive Polymer Microspheres: Rapid Release of Encapsulated Material within the Range of Intracellular pH (pages 1707–1710)

      David M. Lynn, Mansoor M. Amiji and Robert Langer

      Article first published online: 3 MAY 2001 | DOI: 10.1002/1521-3773(20010504)40:9<1707::AID-ANIE17070>3.0.CO;2-F

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      Microspheres formed from a new poly(β-amino ester) degrade slowly at pH 7.4 (left fluorescence microscopy image) but dissolve quickly at pH values below 6.5 (right), to release encapsulated material rapidly and quantitatively. As the pH/solubility transition occurs within the intracellular pH range, these tiny spheres hold promise as intracellular drug delivery vehicles.

    27. Merging of Hard Spheres by Phototriggered Micromanipulation (pages 1710–1714)

      Georg C. Dol, Kenji Tsuda, Jan-Willem Weener, Marcel J. Bartels, Theodor Asavei, Thomas Gensch, Johan Hofkens, Loredana Latterini, Albert P. H. J. Schenning, Bert W. Meijer and Frans C. De Schryver

      Article first published online: 3 MAY 2001 | DOI: 10.1002/1521-3773(20010504)40:9<1710::AID-ANIE17100>3.0.CO;2-N

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      Micrometer-level billiards or rod-formation: The careful design of poly(propyleneimine) dendrimers enables the physical properties of self-assembled vesicular structures to be tuned so that they behave as hard spheres that either undergo collision in a billiardlike manner or merge (see picture).

    28. Computer-Guided Design in Molecular Recognition: Design and Synthesis of a Glucopyranose Receptor (pages 1714–1718)

      Wei Yang, Huan He and Dale G. Drueckhammer

      Article first published online: 3 MAY 2001 | DOI: 10.1002/1521-3773(20010504)40:9<1714::AID-ANIE17140>3.0.CO;2-F

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      Greater than 400-fold selectivity for glucose over galactose, mannose, and fructose has been achieved with a receptor designed by the computer program CAVEAT. The receptor has precisely positioned boronic acid groups for cyclic boronate formation with the 1,2- and 4,6-hydroxy groups of α-D-glucopyranose (see picture) and exhibits a 50 % decrease in fluorescence upon glucose binding.

    29. A Porphyrin Prism: Structural Switching Triggered by Guest Inclusion (pages 1718–1721)

      Norifumi Fujita, Kumar Biradha, Makoto Fujita, Shigeru Sakamoto and Kentaro Yamaguchi

      Article first published online: 3 MAY 2001 | DOI: 10.1002/1521-3773(20010504)40:9<1718::AID-ANIE17180>3.0.CO;2-7

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      A prismlike hollow structure was assembled when three pyridyl-substituted porphyrin panels were linked by six PdII ions. A dramatic D3hC2 structural change of the prism (see scheme) was triggered by complexation of pyrene.

    30. Preparation and Properties of Polymer-Wrapped Single-Walled Carbon Nanotubes (pages 1721–1725)

      Alexander Star, J. Fraser Stoddart, David Steuerman, Mike Diehl, Akram Boukai, Eric W. Wong, Xin Yang, Sung-Wook Chung, Hyeon Choi and James R. Heath

      Article first published online: 3 MAY 2001 | DOI: 10.1002/1521-3773(20010504)40:9<1721::AID-ANIE17210>3.0.CO;2-F

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      Intimate electrical contact occurs between a substituted poly(metaphenylenevinylene) (PmPV) and bundles of single-walled nanotubes (SWNT) as evidenced by atomic force microscopy, optical, and electronic measurements carried out on single, isolated SWNT/PmPV structures (see picture). PmPV may provide a useful route toward “functionalizing” the SWNT without destroying their electrical character.

    31. Th-Symmetric Nanoporous Network Built of Hexameric Metallamacrocycles with Disparate Cavities for Guest Inclusion (pages 1725–1728)

      Cheng-Yong Su, Xiao-Ping Yang, Bei-Sheng Kang and Thomas C. W. Mak

      Article first published online: 3 MAY 2001 | DOI: 10.1002/1521-3773(20010504)40:9<1725::AID-ANIE17250>3.0.CO;2-7

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      A hexanuclear flying saucer, [Cu6(Acntb)6]6+ (see structure), is obtained by the reaction of Cu(ClO4)2⋅6 H2O with the sodium salt of the tripodal ligand Acntb. Intermolecular hydrogen bonding generates an open three-dimensional nanoporous network containing intra- and intermolecular cavities of different polarity for guest inclusion. HAcntb=N-[N′-(carboxymethyl)benzimidazol-2-ylmethyl]-N,N-bis(benzimidazol-2-ylmethyl)amine.

    32. Toward Fully Synthetic Homogeneous Glycoproteins: A High Mannose Core Containing Glycopeptide Carrying Full H-Type 2 Human Blood Group Specificity (pages 1728–1732)

      Zhi-Guang Wang, Xufang Zhang, Michael Visser, David Live, Andrzej Zatorski, Ulrich Iserloh, Kenneth O. Lloyd and Samuel J. Danishefsky

      Article first published online: 3 MAY 2001 | DOI: 10.1002/1521-3773(20010504)40:9<1728::AID-ANIE17280>3.0.CO;2-1

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      Blood typing with the ABO classification is based on cell-surface glycoproteins. In a significant step toward the synthesis of these compounds, the laboratory synthesis of a fully functional N-linked glycopeptide featuring H-type blood group determinants 1 is described.

    33. Enhanced Physical Properties in a Pentacene Polymorph (pages 1732–1736)

      Theo Siegrist, Christian Kloc, Jan H. Schön, Bertram Batlogg, Robert C. Haddon, Steffen Berg and Gordon A. Thomas

      Article first published online: 3 MAY 2001 | DOI: 10.1002/1521-3773(20010504)40:9<1732::AID-ANIE17320>3.0.CO;2-7

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      A low temperature mobility up to 10 000 cm2 V−1 s−1 at 1.7 K was observed for a new polymorphic form of pentacene (C22H14, see picture). Optical measurements show a band gap of the order of 2 eV, and transport measurements revealed a mobility above 3 cm2 V−1 s−1 at room temperature.

    34. Total Synthesis of Azinomycin A (pages 1736–1739)

      Robert S. Coleman, Jing Li and Antonio Navarro

      Article first published online: 3 MAY 2001 | DOI: 10.1002/1521-3773(20010504)40:9<1736::AID-ANIE17360>3.0.CO;2-#

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      A most elusive of synthetic targets, azinomycin A 1 has now been synthesized for the first time. Using a modular synthetic approach, and after considerable developmental effort, this antitumor agent has been synthesized in a stereocontrolled manner using a convergent series of fragment couplings and a final cyclization to form the structurally unique aziridino[1,2-a]pyrrolidine ring system.

    35. Immunosensing by a Synthetic Ligand-Gated Ion Channel (pages 1740–1743)

      Samuel Terrettaz, Wolf-Peter Ulrich, Remo Guerrini, Antonio Verdini and Horst Vogel

      Article first published online: 3 MAY 2001 | DOI: 10.1002/1521-3773(20010504)40:9<1740::AID-ANIE17400>3.0.CO;2-5

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      Specific binding of an antibody to its antigen at subnanomolar concentrations has been detected electrically by impedance spectroscopy through changes in the ion-conductance of a synthetic ligand-gated ion channel (SLIC) in a supported lipid bilayer on a gold electrode (see picture).

    36. Super-“Amphiphobic” Aligned Carbon Nanotube Films (pages 1743–1746)

      Huanjun Li, Xianbao Wang, Yanlin Song, Yunqi Liu, Qianshu Li, Lei Jiang and Daoben Zhu

      Article first published online: 3 MAY 2001 | DOI: 10.1002/1521-3773(20010504)40:9<1743::AID-ANIE17430>3.0.CO;2-#

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      Fluoroalkylsilane treatment of super-hydrophobic, aligned carbon nanotube films (see electron micrograph) prepared by pyrolysis of metal phthalocyanines results in the films having both super-hydrophobic and super-lipophobic properties, namely they are super-“amphiphobic” surfaces.

    37. Specific Binding and Separation of Dinucleotides by Ferrocene-Modified Artificial Receptors (pages 1746–1748)

      Masahiko Inouye and Masayoshi Takase

      Article first published online: 3 MAY 2001 | DOI: 10.1002/1521-3773(20010504)40:9<1746::AID-ANIE17460>3.0.CO;2-U

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      The multipoint hydrogen-bonded complex 1 (R=alkanoyl) is readily formed between a ferrocene-modified artificial receptor and a dinucleotide. This principle can be used effectively in highly selective, large-scale separations of dinucleotides from mixtures of mono- and oligonucleotides. The process is economically viable and environmentally friendly.

    38. Rectification by a Monolayer of Hexadecylquinolinium Tricyanoquinodimethanide between Gold Electrodes (pages 1749–1752)

      Tao Xu, Ian R. Peterson, M. V. Lakshmikantham and Robert M. Metzger

      Article first published online: 3 MAY 2001 | DOI: 10.1002/1521-3773(20010504)40:9<1749::AID-ANIE17490>3.0.CO;2-O

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      45 000 electrons per molecule per second: such currents and a rectification ratio of 5.38 at 2.2 V were detected between oxide-free Au electrodes for a Langmuir–Blodgett monolayer of the D+–π–A molecule 1.

    39. Nondestructive Data Processing Based on Chiroptical 1,2-Dithienylethene Photochromes (pages 1752–1755)

      Elisa Murguly, Tyler B. Norsten and Neil R. Branda

      Article first published online: 3 MAY 2001 | DOI: 10.1002/1521-3773(20010504)40:9<1752::AID-ANIE17520>3.0.CO;2-W

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      Diastereoselectivities as high as 98 % were the result of the photochemical ring-closure of stereochemically pure copper(I) helicates of a chiral oxazoline-substituted 1,2-dithienylethene photochrome (see scheme). The variations in optical rotation that accompany the photochromic event provide a means to read stored information in a nondestructive manner.

    40. Synthesis and Stability of Phosphatidylcholines Bearing Polyenoic Acid Hydroperoxides at the sn-2 Position (pages 1755–1757)

      Arnold N. Onyango, Takafumi Inoue, Shuhei Nakajima, Naomichi Baba, Takao Kaneko, Mitsuyoshi Matsuo and Sakayu Shimizu

      Article first published online: 3 MAY 2001 | DOI: 10.1002/1521-3773(20010504)40:9<1755::AID-ANIE17550>3.0.CO;2-Q

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      The antitumor and antimalarial activity of fish oils may involve the action of phospholipid hydroperoxides. Two such phosphatidylcholines, 1 and 2, bearing the hydroperoxides of docosahexaenoic and eicosapentaenoic acids—the two major fatty acids in fish oils—have been synthesized. In spite of its high degree of unsaturation, 1 is sufficiently stable to permit its use in biological studies.

    41. Gel-Phase MAS NMR Spectroscopy of a Polymer-Supported Pseudorotaxane and Rotaxane: Receptor Binding to an “Inert” Polyethylene Glycol Spacer (pages 1757–1760)

      Yiu-Fai Ng, Jean-Christophe Meillon, Theo Ryan, Andrew P. Dominey, Anthony P. Davis and Jeremy K. M. Sanders

      Article first published online: 3 MAY 2001 | DOI: 10.1002/1521-3773(20010504)40:9<1757::AID-ANIE17570>3.0.CO;2-M

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      A tricyclic polyamide receptor threads onto the polyethylene glycol chain of a carbohydrate-attached resin, as shown by gel-phase MAS NMR spectroscopy. This observation led to syntheses of a polymer-supported pseudorotaxane and a porphyrin-stoppered rotaxane (see picture).

    42. Cobalt(II)-Nitronyl Nitroxide Chains as Molecular Magnetic Nanowires (pages 1760–1763)

      Andrea Caneschi, Dante Gatteschi, Nikolia Lalioti, Claudio Sangregorio, Roberta Sessoli, Giovanni Venturi, Alessandro Vindigni, Angelo Rettori, Maria G. Pini and Miguel A. Novak

      Article first published online: 3 MAY 2001 | DOI: 10.1002/1521-3773(20010504)40:9<1760::AID-ANIE17600>3.0.CO;2-U

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      Slow magnetic relaxation and hysteresis effects of dynamic origin have been observed above liquid helium temperature in a chain compound (see picture), comprising CoII centers and organic radicals, without any evidence of phase transition to three-dimensional magnetic order. These results are the first evidence of the slow dynamics predicted for one-dimensional magnetic systems with Ising anisotropy, and they open the possibility of storing information in a single magnetic nanowire.

    43. A Novel Polynuclear Gold–Sulfur Cube with an Unusually Large Stokes Shift (pages 1763–1765)

      Vivian W.-W. Yam, Eddie C.-C. Cheng and Nianyong Zhu

      Article first published online: 3 MAY 2001 | DOI: 10.1002/1521-3773(20010504)40:9<1763::AID-ANIE17630>3.0.CO;2-O

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      A 1.87-eV energy gap between the lowest energy excitation maximum and the emission maximum in solution was found for the novel hexanuclear gold(I) sulfido complex 1 (Ar=p-CH3C6H4), which has a heterocubane-type structure. Besides this abnormally large Stokes shift of around 15 000 cm−1, 1 exhibits intense orange luminescence in the solid state.

    44. First Diastereomerically Controlled Aggregation of L-Cysteinato Cobalt(III) Octahedra, Assisted by Silver(I) Ions (pages 1765–1768)

      Takumi Konno, Takashi Yoshimura, Kazumi Aoki, Ken-ichi Okamoto and Masakazu Hirotsu

      Article first published online: 3 MAY 2001 | DOI: 10.1002/1521-3773(20010504)40:9<1765::AID-ANIE17650>3.0.CO;2-K

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      Sheetlike and helical coordination polymers, {ΛL-[Ag{Co(L-cys-N,S)(en)2}](NO3)2} (1) and {ΔL-[Ag{Co(L-cys-N,S)(en)2}](NO3)2} (2), were obtained by treating ΛL- and ΔL-[Co(L-cys-N,S)(en)2]+ (L-cys=L-cysteinate, en=H2NCH2CH2NH2) with AgNO3 in water, respectively. Their structures are comparable to those of the β-sheet and α-helix forms of proteins. Compound 2 undergoes reversible conversion into a third compound on changing the pH of the solution.

    45. Diiron Azadithiolates as Models for the Iron-Only Hydrogenase Active Site: Synthesis, Structure, and Stereoelectronics (pages 1768–1771)

      Joshua D. Lawrence, Hongxiang Li, Thomas B. Rauchfuss, Marc Bénard and Marie-Madeleine Rohmer

      Article first published online: 3 MAY 2001 | DOI: 10.1002/1521-3773(20010504)40:9<1768::AID-ANIE17680>3.0.CO;2-E

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      Most hydrogenase enzymes have organometallic active sites with CO and CN as ligands and metal–metal bonds. Recent evidence points to a novel 2-aza-1,3-propanedithiolate cofactor that directly participates in the heterolytic processing of dihydrogen. A close analogue of this cofactor and its organometallic subunit has been synthesized (see picture); spectroscopic, structural, and theoretical analysis of this model provides detailed insights into the properties of the proposed enzyme active site.

    46. An Enzyme Assay Using pM (pages 1771–1773)

      Gérard Klein and Jean-Louis Reymond

      Article first published online: 3 MAY 2001 | DOI: 10.1002/1521-3773(20010504)40:9<1771::AID-ANIE17710>3.0.CO;2-M

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      A high-throughput fluorescence assay for amidases is demonstrated. It illustrates a new principle in enzyme assays, whereby changes in the pM value during the reaction are recorded (pM=−lg[M], M=free metal ions). An orange fluorescent quinacridone-based ligand 1 is the pM sensor (shown chelated to a reporter metal ion, M2+=Cu2+ or Ni2+) that is used to monitor the release of metal-chelating amino acids by the enzymes acylase I and aminopeptidase.

    47. Using an Enzyme's Active Site To Template Inhibitors (pages 1774–1776)

      Régis Nguyen and Ivan Huc

      Article first published online: 3 MAY 2001 | DOI: 10.1002/1521-3773(20010504)40:9<1774::AID-ANIE17740>3.0.CO;2-G

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      The irreversible formation of carbonic anhydrase inhibitors from competing building block precursors is templated by the active site of the enzyme itself. The reagents are brought into close proximity of each other in a ternary complex with the enzyme (see scheme).

    48. Nonhazardous Direct Oxidation of Hydrogen to Hydrogen Peroxide Using a Novel Membrane Catalyst (pages 1776–1779)

      Vasant R. Choudhary, Abaji G. Gaikwad and Subhash D. Sansare

      Article first published online: 3 MAY 2001 | DOI: 10.1002/1521-3773(20010504)40:9<1776::AID-ANIE17760>3.0.CO;2-C

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      Nonhazardous and highly selective H2O2production! An H2-permselective membrane (2) has been developed which consists of thin films of Pd–Ag alloy (2b) and oxidized Pd (2c), and a hydrophobic polymer membrane (2d) supported on a tubular membrane (2a) within a reactor wall (1). Hydrogen atoms permeate through the membrane and react with molecular O2 in a liquid medium (LM; 2 M H2SO4).

    49. Crystal Structure of Potassium Croconate Dihydrate, after 175 Years (pages 1779–1780)

      Jack D. Dunitz, Paul Seiler and Werngard Czechtizky

      Article first published online: 3 MAY 2001 | DOI: 10.1002/1521-3773(20010504)40:9<1779::AID-ANIE17790>3.0.CO;2-6

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      Stacks of croconate dianions separated by K+ ions and H2O molecules: the crystal structure of potassium croconate dihydrate, K2(C5O5)⋅2 H2O, isolated and described by Leopold Gmelin more than 170 years ago, has now been established by X-ray analysis (see picture). Since the anions have a formal charge of −2 and an interplanar separation of only 3.30 Å, the structure is not easily explained in terms of a simple ionic model.

    50. Book Review: Handbook of Ceramic Hard Materials. Vols. 1 + 2. Edited by Ralf Riedel. (pages 1781–1782)

      Hubert Huppertz

      Article first published online: 7 AUG 2001 | DOI: 10.1002/1521-3773(20010504)40:9<1781::AID-ANIE17810>3.0.CO;2-G

    51. Book Review: X-Ray Characterization of Materials. Edited by Eric Lifshin. (page 1782)

      Peter Dürichen

      Article first published online: 7 AUG 2001 | DOI: 10.1002/1521-3773(20010504)40:9<1782::AID-ANIE17820>3.0.CO;2-E

    52. Book Review: Phosphorus 2000. Chemistry, Biochemistry and Technology. By Derek E. C. Corbridge. (page 1783)

      Norbert W. Mitzel

      Article first published online: 7 AUG 2001 | DOI: 10.1002/1521-3773(20010504)40:9<1783::AID-ANIE17830>3.0.CO;2-C

    53. Book Review: Catalysis from A to Z. A Concise Encyclopedia. Edited by Boy Cornils, W. A. Herrmann, R. Schlögl and Ch.-H. Wong. (page 1785)

      Lothar Heinrich

      Article first published online: 7 AUG 2001 | DOI: 10.1002/1521-3773(20010504)40:9<1785::AID-ANIE17851>3.0.CO;2-5

    54. Book Review: Rhodium Catalyzed Hydroformylation. Edited by Piet W. N. M. van Leeuwen and Carmen Claver. (pages 1785–1786)

      Boy Cornils

      Article first published online: 7 AUG 2001 | DOI: 10.1002/1521-3773(20010504)40:9<1785::AID-ANIE17852>3.0.CO;2-2

    55. Book Review: Iron Metabolism. Inorganic Biochemistry and Regulatory Mechanisms. Edited by Glória C. Ferreira, José J. G. Moura, and Ricardo Franco. (pages 1786–1787)

      Aimin Liu and Lawrence Que, Jr.

      Article first published online: 7 AUG 2001 | DOI: 10.1002/1521-3773(20010504)40:9<1786::AID-ANIE17860>3.0.CO;2-6

    56. Web Site: The Sol—Gel Gateway (page 1787)

      Nicola Hüsing

      Article first published online: 7 AUG 2001 | DOI: 10.1002/1521-3773(20010504)40:9<1787::AID-ANIE17870>3.0.CO;2-4

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