Angewandte Chemie International Edition in English

Cover image for Vol. 34 Issue 8

May 2, 1995

Volume 34, Issue 8

Pages 837–937

Currently known as: Angewandte Chemie International Edition

    1. Cover Picture (Angew. Chem. Int. Ed. Engl. 8/1995)

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199508351

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      The cover picture shows a space-filling model of a porphyrin quinone model compound (1 b in the article with 2 H instead of Zn), which can be used to simulate and analyze the first step of the charge separation in photosynthesis (shown schematically). Investigations of this kind have allowed the study of the factors contributing to the high efficiency of the charge separation in the photosynthetic reaction centers. More about the recent investigations on porphyrin quinones is reported by H. Kurreck and M. Huber on p. 849ff.

  1. Reviews

    1. Top of page
    2. Reviews
    3. Highlights
    4. Communications
    5. Book Reviews
    1. Model Reactions for Photosynthesis—Photoinduced Charge and Energy Transfer between Covalently Linked Porphyrin and Quinone Units (pages 849–866)

      Prof. Dr. Harry Kurreck and Dr. Martina Huber

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199508491

      The 100% quantum yield in the primary step of photosynthesis, namely the light-induced charge separation, is seen as a challenge by many research groups, whose aim is the complete understanding of its mechanism. Here time-resolved spectroscopic studies of porphyrin quinones, models of the pigments of the photosynthetic reaction center, are presented.

    2. Anticoagulatory Substances of Bloodsucking Animals: From Hirudin to Hirudin Mimetics (pages 867–880)

      Priv.-Doz. Dr. Johannes Dodt

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199508671

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      Highly potent, well-tolerated, and few side effects are the promising characteristics of relatively small peptides that are contained in the salivary gland secretions of bloodsucking animals such as vampire bats and leeches as anticoagulants. Hirudin and its mimetics, for example, interfere with the complex process of blood clotting by directly inhibiting the key enzyme thrombin in a novel mechanism. Several structure-activity relationships of the complex formation could be explained with the aid of the structure of the r-hirudin/thrombin complex (shown on the right).

  2. Highlights

    1. Top of page
    2. Reviews
    3. Highlights
    4. Communications
    5. Book Reviews
    1. Combinatorial Biosynthesis–An Approach in the Near Future? (pages 881–885)

      Priv.-Doz. Dr. Jürgen Rohr

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199508811

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      A gene library has been conceived for the construction of multienzyme complexes from natural and altered building blocks. The first encouraging results have been achieved with polyketide synthases (PKSs): enzyme hybrids were formed by “mixing” genes coding for PKSs, which provide novel polyketides such as 1. The ring frameworks, configurations, and/or functional groups of these novel compounds depend on the manipulated genes.

    2. Control of Ion–Molecule Reactions in the Gas Phase (pages 885–886)

      Dr. Karl-Heinz Gericke

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199508851

      Excitation of a particular stretching vibration in the reagent ion NHmath image influences the course of its reaction with ND3. The extent of charge transfer (a), proton transfer (b), and deuterium abstraction (c) depends on how the unbrella mode and the symmetrical breathing mode are excited. Thanks to the work of Zare et al. discussed here, the goal of controlling the reaction channels of complex molecules is a little closer.

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  3. Communications

    1. Top of page
    2. Reviews
    3. Highlights
    4. Communications
    5. Book Reviews
    1. Octadecanuclearity in Manganese Carboxylate Chemistry: K4[Mn18O16(O2CPh)22(phth)2(H2O)4] (phthH2 = phthalic acid) (pages 887–889)

      Prof. Dr. David N. Hendrickson, Sheila M. J. Aubin, Rachel C. Squire, Dr. Kirsten Folting, Dr. William E. Streib and Prof. Dr. George Christou

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199508871

      Small change—large effect: If some of the carboxylato ligands in the coordination sphere of the anion in 1, which contains the butterfly-like [Mn43-O)2] unit, are replaced by dicarboxylato ligands by treatment with potassium hydrogen phthalate, the title compound 2 containing an Mn18O16 framework in its anion is formed. It is the largest Mn/O aggregate discovered to date.

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    2. A Nickel(II) Azide Cubane: Characterization of the Magnetic Exchange Interactions Mediated by a Triply Bridging Azide Group Bound End-On (pages 889–891)

      Dr. Malcolm A. Halcrow, Dr. John C. Huffman and Prof. Dr. George Christou

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199508891

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      A ferromagnetic exchange interaction that is not influenced by the distortion of the cubane framework of 1 (see picture; only the O atoms of the EtOH and dbm ligands are shown) and is mediated by the end-on-coordinated μ3-azide bridges has been detected for the first time. Although the unusual [M413-N3)4] core is also displayed by a Pt complex, 1 is the first parmagnetic example. (dbmH = dibenzoylmethane).

    3. Complexes with Polar W[BOND]W Multiple Bonds: [W2(OiPr)4L(dmpe)2] (L = (H)2, CO) and [W2(O)4(μ-O){W(CO)(dmpe)2}2] (pages 891–893)

      Prof. Malcolm H. Chisholm, Dr. Keith S. Kramer and Dr. William E. Streib

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199508911

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      An unsupported W[BOND]W multiple bond between centers having different oxidation states is found in the homonuclear complex 1, which is formed from [W2(OiPr)4(iBu)2], a complex containing a W[BOND]W bond. Dimers of this kind with mixed oxidation states arise because tungsten can bind hard as well as soft ligands. Such complexes should display interesting reactivity.

    4. A Multienzyme System for a One-Pot Synthesis of Sialyl T-Antigen (pages 893–895)

      Dr. Vladimír Křen and Prof. Dr. Joachim Thiem

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199508931

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      With a new multienzyme system with cofactor regeneration based on a sequential action of glycosidase and glycosyltransferase, a semipreparative scale synthesis of the cell epitope Neu5Acα(2 [RIGHTWARDS ARROW] 3)Galβ(1 [RIGHTWARDS ARROW] 3)GalNAc 1 was achieved. Although the participating enzymes have maximum activities at very different pH values, a satisfactory optimization of the synthesis was possible.

    5. The Dimerization of (E)-1,3-Diphenyl-1,3-butadiene Proceeds Suprafacially with Respect to Both Components: Evidence for a Concerted [4 + 2] Cycloaddition (pages 895–898)

      Prof. Dr. Johann Mulzer and Dipl.-Chem. Katja Melzer

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199508951

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      Despite the potential stabilization of diradical intermediates through the phenyl groups, the thermal dimerization of (E)-1,3-diphenyl-1,3-butadiene does not follow a diradical mechanism as previously assumed, but a concerted pathway. The case examined here is the dimerization of the deuteriated diene 1 giving 2, which proceeds suprafacially with regard to both diene and dienophile.

    6. Li5Pt2H9, a Complex Hydride Containing Isolated [Pt2H9]5− Ions (pages 898–900)

      Prof. Dr. Welf Bronger and Dipl.-Chem. Lothar à Brassard

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199508981

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      A description as vertex-connected square double pyramid fits the coordination polyhedrons of the two platinum centers in the anion 1 of Li5Pt2H9. The ternary hydride can be synthesized from LiH and Pt sponge under a hydrogen pressure of 1250 bar. The lithium counterions are eight- and sevenfold coordinated.

    7. Aldehyde-Appended Tetraphenylporphyrin: A New Building Block for Porphyrin Arrays (pages 900–902)

      Dr. Anthony K. Burrell, Dr. David L. Officer and David C. W. Reid

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199509001

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      Porphyrin arrays may act as light-harvesting devices which mimic the photosynthetic capture of light. Until now the construction of a variety of arrays has been restricted by the lack of suitable methodology for porphyrin synthesis. A fully conjugated, aldehyde-appended porphyrin building block has been made and its potential demonstrated with the one-step synthesis of dimers and trimer 1.

    8. Radical Additions of Activated Haloalkanes to Alkenes Initiated by Electron Transfer from Copper in Solvent-Free Systems (pages 902–904)

      Prof. Dr. Jürgen O. Metzger and Dr. Ralf Mahler

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199509021

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      Ecologically sound chemistry relies on the development of new, environmentally friendly synthetic methods in which few toxic substances are used. Copper powder was found to be a suitable initiator for the addition in Equation (a) (R1, R2 = H, alkyl, (CH2)nCOOMe). This initiator is not only cheap but also nontoxic, easily removed, and readily recyclable.

    9. Metal-Induced Dispersion of Lipid Aggregates: A Simple, Selective, and Sensitive Fluorescent Metal Ion Sensor (pages 905–907)

      Deborah R. Shnek, Daniel W. Pack, Prof. Frances H. Arnold and Darryl Y. Sasaki

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199509051

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      A new metal ion sensor capable of detecting nanomolar concentrations (< 1 ppb) of Cu2+ is made from mixed vesicles of a novel pyrene-labeled metal-chelating ligand and distearoyl phosphatidylcholine. When copper is added, the fluorescence monomer intensity emitted at 377 nm greatly increases, while the intensity of light emitted at 470 nm decreases. This effect is probably due to the dispersal of the fluorescent lipid throughout the matrix upon metal binding and is depicted schematically below.

    10. Solid-Phase Syntheses of Unnatural Biopolymers Containing Repeating Urea Units (pages 907–909)

      Prof. Kevin Burgess, Hunwoo Shin and Dr. D. Scott Linthicum

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199509071

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      New “oligourea”-based peptidomimetics are the subject of this communication. Two new derivatives of this type, including the Leu-enkephalin analog 1, have been prepared by addition of suitably protected isocyanates to amino acids supported on Rink's amide resin. The chemistry described is designed for solid-phase approaches to combinatorial libraries by split syntheses.

    11. A Highly Stereoselective Synthesis of 1,2-trans-C-Glycosides via Glycosyl Samarium(III) Compounds (pages 909–912)

      Daniel Mazéas, Dr. Troels Skrydstrup and Prof. Dr. Jean-Marie Beau

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199509091

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      Remarkably stable even at room temperature towards elimination are the 1,2-trans-glycosyl samarium(III) species of type 2. The stability of these species, which contrasts sharply with that of glycosyl lithium counterparts, is the decisive factor for the high 1,2-trans selectivity of the synthesis of the C-glycoside 3 by reductive samariation of anomeric sulfones of type 1 in the presence of carbonyl compounds.

    12. Synthesis, Chemical Trapping, and Dimerization of 3,7-Dimethyltricyclo[3.3.0.03, 7]oct-1(5)-ene: [2 + 2] Retrocycloaddition of the Cyclobutane Dimer (pages 912–914)

      Prof. Dr. Pelayo Camps, Dr. Francesc Pérez, Dipl.-Pharm. Santiago Vázquez, Dr. Mercè Font-Bardia and Prof. Dr. Xavier Solans

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199509121

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      Reduction of 1 with sodium or tert-butyllithium yields the diene dimer 3. The key intermediate, the strongly pyramidalized alkene 2, dimerizes to give a cyclobutane dimer, which then leads to 3. Compound 2 can also be trapped as a Diels-Alder adduct with 1,3-dienes.

    13. Synthesis, Structural Investigation, and Ligand Properties of Isocyanoacetonitrile (pages 914–915)

      Priv.-Doz. Dr. Dieter Lentz, Dirk Scharn, Stefan Willemsen, Dr. Jürgen Buschmann, Prof. Dr. Peter Luger and Genivaldo Perpetuo

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199509141

      An [BOND]N[TRIPLE BOND]C and a [BOND]C[TRIPLE BOND]N group bonded to CH2 describes the structure of the title compound 1. The unstable compound 1 was obtained analytically pure for the first time and characterized spectroscopically. The X-ray crystal structure analysis enables a direct comparison of the isomeric nitrile and isocyanide functions. First investigations on complexes of 1 show that low-valent metal complex fragments coordinate preferably to the isocyanide group.

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    14. Unprecedented Mode of Bonding for Olefins on Bimetallic Complexes: An Agostic Interaction of a sp2 C[BOND]H Bond with a Ruthenium Center in Addition to a π bond to a Rhenium Center (pages 916–917)

      Dr. Zhongli He, Laurent Plasseraud, Dr. Isabel Moldes, Dr. Françoise Dahan, Dr. Denis Neibecker, Dr. Michel Etienne and Dr. René Mathieu

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199509161

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      An arrested migration of a hydrido ligand from a ruthenium center to a μ-η12-bound alkenyl group results in the bonding mode in the products 2 of the reaction of terminal alkynes HC[TRIPLE BOND]CR with 1. These products can be considered to represent the last step of the hydrogenation of an alkyne to an alkene at a heterobimetallic center. R = Ph, CH2Ph, CH2OMe, CH2OH.

    15. A Chiral Cyanohydrin Phosphate for Carbonyl Umpolung—Stereoselective Synthesis of Tertiary Cyanohydrins (pages 917–919)

      Dr. Thomas Schrader

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199509171

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      High asymmetric induction is achieved in the diastereoselective alkylation of cyanohydrin carbanion 1 (de = 82–94%). The synthesis of optically active tertiary cyanohydrins demonstrates how P-chiral auxiliaries temporarily linked to the substrate through heteroatoms can be used in asymmetric synthesis.

    16. Synthesis and Structure of Organometallic Compounds with (Al2Si)2 and Al3Sb2 Frameworks (pages 919–920)

      Dr. Stephan Schulz, Dipl.-Chem. Torsten Schoop, Prof. Dr. Herbert W. Roesky, Dipl.-Chem. Ludger Häming, Dr. Alexander Steiner and Dr. Regine Herbst-Irmer

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199509191

      A complex with an eight-membered Al4F4 ring in which pairs of Al atoms are bridged by Ph2Si units is the unexpected product of the reaction of [(Cp*Al)4] with Ph2SiF2[Eq. (a)]. The formation of 1 can be explained in terms of the marked fluorophilicity of [(Cp*Al)4]. Reaction of [(Cp*Al)4] with (tBuSb)4 yields [(Cp*Al)3Sb2], the first organometallic compound to contain an aluminium-antimony bond.

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    17. Lithium Intermediates during the α-Lithiation and Subsequent α-Substitution of Heterocyclic Amines in the Presence of CO2 (pages 921–923)

      Sarah C. Ball, Ian Cragg-Hine, Dr. Matthew G. Davidson, Robert P. Davies, Dr. Andrew J. Edwards, Dr. Isabel Lopez-Solera, Dr. Paul R. Raithby and Dr. Ronald Snaith

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199509211

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      Two interdependent steps appear to be involved in the CO2-mediated electrophilic substitution of cyclic amines in the α position. The key finding is that the lithium carbamate 1 is not lithiated with tBuLi to any extent, but reacts only after addition of electrophiles like Me3SiCl to give the desired α-substitution product 2.

    18. Aminocarbyne Complexes of Chromium in a High Oxidation State—Synthesis, Structure, and Reactivity (pages 924–927)

      Prof. Dr. Alexander C. Filippou, Dipl.-Chem. Bernhard Lungwitz, Dipl.-Chem. Klaus M. A. Wanninger and Dr. Eberhardt Herdtweck

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199509241

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      Oxidation of half-sandwich chromium complexes of type 1 (R = H, Me) with halogens afforded the first carbyne complexes 2 (X = Cl,Br) of chromium in a high oxidation state. With tBuNC or P(OMe)3 these complexes can be converted into thermally stable products, which were structurally and spectroscopically characterized. Counterion: Cl, Br.

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    19. 2-[p(N-tert-butyl-N-oxyamino)phenyl]-4,4,5,5-tetramethyl-4,5-dihydroimidazol-3-oxide-1-oxyl, a Stable Diradical with a Triplet Ground State (pages 927–928)

      Dr. Katsuya Inoue and Prof. Dr. Hiizu Iwamura

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199509271

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      A value of 2.71 μB for the effective magnetic moment between 100 and 300 K is determined for 1. This magnetic moment supports the assumption of a triplet ground state for 1. The bis(nitroxyl) diradical, which melts only at 180 °C with decomposition, could be characterized by X-ray crystallography. It has a distinctly more planar conformation than the analogous monoradicals.

    20. Reaction of 1,1-Dimethylsilene with Formaldehyde (pages 929–931)

      Martin Trommer, Prof. Dr. Wolfram Sander, Carl-Henrik Ottosson and Prof. Dr. Dieter Cremer

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199509291

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      Even at 30 K 1,1-dimethylsilene (1) reacts smoothly with formaldehyde in a thermal transformation to give trimethylsiloxycarbene (2). This singlet carbene is extremely photolabile and rapidly rearranges on irradiation with visible light (λ > 570 nm) in a 1,2 migration of the silyl group to give aldehyde 3. According to CCSD(T)/6-31G(d,p) calculations on the parent silence, reaction takes place via a van der Waals complex and a diradical intermediate.

    21. Strong Electronic Effects on Enantioselectivity in Rhodium-Catalyzed Hydroborations with Novel Pyrazole-Containing Ferrocenyl Ligands (pages 931–933)

      Dipl.-Chem. Anita Schnyder, Lukas Hintermann and Prof. Dr. Antonio Togni

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199509311

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      The highest enantioselectivity yet for a hydroboration (98% ee) was achieved with the ferrocenyl ligand 1, R1 = R3 = Me, R2 = H, Ar = 4[BOND]CF3C6H4, in the Rh-catalyzed reaction of styrene with catecholborane. The influence of the substituents on both the pyrazolyl and phosphano fragments was studied, and the observations tentatively interpreted in terms of the varying electronic asymmetry they engender at the metal center.

  4. Book Reviews

    1. Top of page
    2. Reviews
    3. Highlights
    4. Communications
    5. Book Reviews

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