Angewandte Chemie International Edition in English

Cover image for Vol. 34 Issue 20

November 3, 1995

Volume 34, Issue 20

Pages 2177–2293

Currently known as: Angewandte Chemie International Edition

    1. Cover Picture (Angew. Chem. Int. Ed. Engl. 20/1995)

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199521751

      Thumbnail image of graphical abstract

      The cover picture shows the crucial step of the reaction sequence determined by quantum chemical calculations for the elimination of hydrogen from ethane by an iron cation. This is described in the article by M. C. Holthausen et al on the explanation of the mechanistic details of the C[BOND]C and C[BOND]H bond activations by Fe+ on page 2282 ff. Density functional studies suggest that the H2 elimination does not, as previously proposed, occur via a (dihydrido)iron intermediate, but is concerted. The structure shown in the center of the cover is calculated to be the structure of the saddle point. The computer graphics was produced in collaboration with Dr. T. Steinke at the Konrad-Zuse-Zentrum für Informationstechnik Berlin.

  1. Reviews

    1. Top of page
    2. Reviews
    3. Highlights
    4. Communications
    5. Book Reviews
    1. Volatile Metal Alkoxides according to the Concept of Donor Functionalization (pages 2187–2206)

      Prof. Dr. Wolfgang A. Herrmann, Dr. Norbert W. Huber and Oliver Runte

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199521871

      Strategies for the synthesis of volatile metal alkoxides for the purpose of chemical vapor deposition (CVD) were previously limited to the use of either bulky (for example tris(tert-butyl)methanol) (tritox-H) or chelating (for example perfluorinated β-diketonate) ligands. However, neither of these approaches gave satisfactory results for metals in low oxidation states. A combination of both steric demand and σ-donor functionality now appears as the safest way to metal alkoxides that sublime at reasonable temperature without decomposition. Typical examples are the vanadium alkoxide [V(OCMe2CH2OMe)3] (sublimation: 55 °C/1.5 Torr), one of the most volatile metal alkoxides, and the volatile barium complex [Ba{OCtBu-(CH2OiPr)2}2].

    2. Carbon Dioxide as a Raw Material: The Synthesis of Formic Acid and Its Derivatives from CO2 (pages 2207–2221)

      Priv.-Doz. Dr. Walter Leitner

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199522071

      CO2 is a safe, ecologically and economically interesting raw material that is gaining increasing significance as an alternative, almost unlimited carbon source for the industrial manufacture of chemical products. Formic acid, an important basic chemical, can be obtained by reduction of CO2 either by electron transfer or by direct addition of H2. Both processes are homogeneously catalyzed by transition metal complexes. The most effective catalysts and most suitable reaction conditions, which make the prospect of industrial application of these procedures feasible in the near future, are discussed, and our present understanding of the mechanisms of catalysis in these processes is described.

  2. Highlights

    1. Top of page
    2. Reviews
    3. Highlights
    4. Communications
    5. Book Reviews
    1. Transition Metal Catalyzed Synthesis of Seven-Membered Carbocyclic Rings (pages 2223–2224)

      Prof. Dr. Gerald Dyker

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199522231

      Thumbnail image of graphical abstract

      A variant of the Diels-Alder reaction with a vinylcyclopropane group as “homodiene” component enables a novel access to seven-membered carbocyclic rings [Eq. (a)]. Metallacycles are considered as key intermediates of this rhodium-catalyzed process.

    2. Control of the Reactivity of Double Bonds through Their Fixed Geometrical Arrangement (pages 2225–2226)

      Dr. habil. J. Jens Wolff

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199522251

      Thumbnail image of graphical abstract

      Reactions may proceed selectively if the reactants are arranged in a defined geometrical orientation with respect to each other. Recent success in the application of this concept pertaining to the [2+2]cycloaddition of two preorganized double bonds (shown on the right) is presented.

  3. Communications

    1. Top of page
    2. Reviews
    3. Highlights
    4. Communications
    5. Book Reviews
    1. Selective Syntheses of 1,3-Diphosphacyclobutadiene, Dewar-1,3,5-triphosphabenzene, 1,3,5-Triphosphabenzene, and 1,3,5,7-Tetraphosphabarrelene by Cyclooligomerization of Phosphaalkynes (pages 2227–2230)

      Prof. Dr. Paul Binger, Dipl.-Chem. Jörg Stannek, Barbara Gabor, Dr. Richard Mynott, Dipl.-Min. Joachim Bruckmann, Prof. Dr. Carl Krüger and Dipl.-Chem. Stefan Leininger

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199522271

      Thumbnail image of graphical abstract

      By varying the temperature, tBuC[TRIPLE BOND]P reacts in the presence of η4-butadiene(η8-cyclooctatetraene)hafnium complexes to give different cyclooligomers. Thus, the triphosphabenzene 1 is formed at -78 °C and the dewar-triphosphabenzene 2 at 0 °C. Both compounds are initially bound to the complex and can be liberated with hexachloroethane in a redox reaction. Compounds 1 and 2 are the first compounds of these classes of substances. Cyclodimers or cyclotetramers are obtained at higher temperature.

    2. meso-Tetrakis[4-(diphenylphosphino)-phenyl]porphyrin and a Water-Soluble Octakis-(phosphonium salt) Porphyrin Double-Decker with a Cage Structure (pages 2230–2234)

      Prof. Dr. Gottfried Märkl, Dipl.-Chem. Martin Reiss, Dr. Peter Kreitmeier and Prof. Dr. Heinrich Nöth

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199522301

      Thumbnail image of graphical abstract

      A phosphino-substituted porphyrin was synthesized in its free and metalcontaining (M = 2H, Zn, Co) form for the first time (depicted on the right). The reaction of two porphyrin molecules of this type with α,ω-dihalogen compounds results in a water-soluble, macrocyclic phosphonium ion, in which the porphyrin rings are arranged parallel to each other, and together with the spacers this leads to a large cage. Whether guest molecules can be incorporated in this cavity requires further study.

    3. Tetracarboxylic Bisimide–Lactam Ring Contraction: A Novel Type of Rearrangement (pages 2234–2236)

      Prof. Dr. Heinz Langhals and Dipl.-Chem. Petra von Unold

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199522341

      Thumbnail image of graphical abstract

      A novel type of rearrangement occurs when aromatic bisimides that are usually chemically inert are treated with alkali metal hydroxides in alcohols. With this reaction naphthalene-lactamimides, some with high fluorescent quantum yields and large Stokes-shifts, can be obtained in a single step [Eq. (a); R = aryl].

    4. First Reaction of 1,2-Dimethyl-o-silaborane: Nucleophilic Degradation (pages 2236–2238)

      Dr. Lars Wesemann, Dr. Ulli Englert and Prof. Dr. Dietmar Seyferth

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199522361

      Thumbnail image of graphical abstract

      The novel nido-silaborane 1 is formed surprisingly smoothly in 89% yield by the reaction of 1,2-dimethyl-o-silaborane with NaOH. In contrast to the corresponding reaction with the analogous o-carborane, the nucleophilic attack does not occur at a boron atom but at the heteroatom silicon. The methyl substituent at silicon has been omitted from the structure on the right.

    5. The β-Lactam-Nucleoside Chimera (pages 2238–2239)

      Dr. Alexander Dömling, Dipl.-Chem. Manfred Starnecker and Prof. Dr. Ivar Ugi

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199522381

      Thumbnail image of graphical abstract

      Potential antiviral agents or antibiotics such as 1 are described herein. They consist of a nucleoside portion and a β-lactam portion and can be prepared in a one-pot reaction by the Ugi reaction from a β-amino acid, an aldehyde, and an isocyanide.

    6. A New Method for the Preparation of Nanostructured Metal Clusters (pages 2240–2241)

      Prof. Dr. Manfred T. Reetz and Dipl.-Chem. Stefan A. Quaiser

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199522401

      Thumbnail image of graphical abstract

      Supporting electrolyte, stabilizer, and “chemical disposal unit” at the anode all in one! These three functions (that of stabilizer is visualized on the right) are performed by tetraalkylammonium acetates in the electrolysis of metal salts with the formation of metal clusters in the nanometer range. Furthermore, the particle size can be controlled by the current density. Other advantages include general applicability, good yields, easy isolation, and straightforward heterogenization on solid supports.

    7. A Novel Hexanuclear FeIII-cis-Inositolato Complex as a Model for FeIII–Polyol Interactions in Aqueous Solution (pages 2242–2243)

      Dr. Kaspar Hegetschweiler, Dipl.-Chem. Lorenza Hausherr-Primo, Prof. Dr. Willem H. Koppenol, Dr. Volker Gramlich, Dr. Léon Odier, Dipl.-Phys. Wolfram Meyer, Dr. Heiner Winkler and Prof. Dr. Alfred X. Trautwein

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199522421

      Thumbnail image of graphical abstract

      Corner-sharing, edge-sharing, and face-sharing FeOx polyhedra (x = 5,6) form a cyclic complex anion in K5[OFe6{(ino)6[BOND]21H}]·14.5 H2O (ino = cis-inositol), the first structurally characterized polyolato(oxo)ferrate from aqueous solution. The synthesis is as simple as the structure is complicated (see diagram).

    8. Bis(trifluoromethyl)trioxide: First Structure of a Straight-Chain Trioxide (pages 2244–2245)

      Karina I. Gobbato, Prof. Dr. Heinz Oberhammer, Martin Frank Klapdor, Prof. Dr. Dietrich Mootz, Dr. Wolfgang Poll, Dr. Sonia E. Ulic and Prof. Dr. Helge Willner

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199522441

      Thumbnail image of graphical abstract

      A skew structure with trans orientation of the two CF3 groups and with an O[BOND]O[BOND]O[BOND]C dihedral angle of 96° describes the trioxide CF3OOOCF3 (see picture). The O[BOND]O bond lengths are 1.452(5) (gas phase) and 1.437(2) Å (crystal).

    9. Electronically Tuned trans Labilization Controls the Substitution Behavior of Rhodoximes (pages 2245–2247)

      Dipl.-Chem. Carlos Dücker-Benfer, Prof. Dr. Rudi van Eldik and Prof. Dr. Renata Dreos

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199522451

      Thumbnail image of graphical abstract

      An unexpected changeover in the mechanism of substitution of the alkyl(aqua)bis(dimethylglyoximato)-rhodium(III) complexes is controlled by the electronic nature of the alkyl group R. The substitution reactions of the CH3 complex follow a dissociative interchange mechanism, those of the CF3CH2 complex an associative interchange mechanism. The transition state of these substitution reactions is shown on the right.

    10. On the Mechanism of Catalysis by a Metal-Free Hydrogenase from Methanogenic Archaea: Enzymatic Transformation of H2 without a Metal and Its Analogy to the Chemistry of Alkanes in Superacidic Solution (pages 2247–2250)

      Prof. Dr. Albrecht Berkessel and Prof. Dr. Rudolf K. Thauer

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199522471

      Thumbnail image of graphical abstract

      Substrate activation by protonation to form a “superelectrophile” could be a new mechanism for enzyme catalysis. The hydrogenation below, catalyzed by an enzyme containing no redox-active transition metal, is very similar to the reaction of carbocations with hydrogen under superacidic conditions. This suggests that in the enzyme-bound state the stable formamidinium ion 1 may also be converted into a highly reactive carbocation, probably through N-protonation and conformational locking.

    11. The Coexistence of the Reactivity–Selectivity Principle and of Linear Free Energy Relationships: A Diffusion Clock for Determining Carbocation Reactivities (pages 2250–2252)

      Dipl.-Ing. Michael Roth and Prof. Dr. Herbert Mayr

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199522501

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      Electrophilicity parameters of reactive carbocations and the rate constants of the reactions of such short-lived species with uncharged nucleophiles can be determined simply by competition experiments [Eq. (a); R = Ar1Ar2CH]. The only prerequisite for this is that suitable pairs of nucleophiles must be chosen so that one of the parallel reactions is diffusion controlled.

    12. Alteration of the Reactivity of a Tellurophene Within a Core-Modified Porphyrin Environment: Synthesis and Oxidation of 21-Telluraporphyrin (pages 2252–2254)

      Prof. Dr. Lechoslaw Latos-Grażyński, Ewa Pacholska, Dr. Piotr J. Chmielewski, Dr. Marilyn M. Olmstead and Prof. Dr. Alan L. Balch

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199522521

      Thumbnail image of graphical abstract

      A pyrrole ring of a porphyrin as an intramolecular proton donor: compound 1 (depicted below), with a deprotonated pyrrole ring, has been isolated as an intermediate in the oxidative transformation of the corresponding air-sensitive 21-telluraporphyrin into 21-oxaporphyrin.

    13. Acyclic 1,4-Diastereoselectivity in γ-Substituted α-Enones: Transmission of Chiral Information through Conjugation (pages 2254–2256)

      Prof. Dr. Tsuneo Sato, Prof. Dr. Junzo Otera and Dr. Masaru Kido

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199522541

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      Because of the high electron-donating power of the Cγ–S-σ bond, the γ-sulfenyl substituent in 1 is arranged orthogonal to the enone group in the ground state. Consequently, nucleophilic attack occurs preferentially from the opposite side of the sulfenyl group, resulting in the diastereoselective formation of the allyl alcohols 2 and 3 in the ratio of 97:3. R1, R2 = alkyl; R3 = Ph, Me.

    14. C59N+ and C69N+: Isoelectronic Heteroanalogues of C60 and C70 (pages 2257–2259)

      Iris Lamparth, Berthold Nuber, Georg Schick, Andreas Skiebe, Thomas Grösser and Prof. Dr. Andreas Hirsch

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199522571

      Thumbnail image of graphical abstract

      Fragmentation reactions in the mass spectrometer were used to generate the first characterized nitrogen heterofullerene ions C59N+ and C69N+ from regioselectively synthesized oligoiminofullerenes. During this process one carbon atom in the fullerene core is removed and replaced with a nitrogen atom. C59N+ (shown on the right) has almost the same structure as the isoelectronic C60.

    15. Synthesis of the Palmitoylated and Farnesylated C-Terminal Lipohexapeptide of the Human N-Ras Protein by Employing an Enzymatically Removable Urethane Protecting Group (pages 2259–2262)

      Prof. Dr. Herbert Waldmann and Dipl.-Chem. Edgar Nägele

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199522591

      Thumbnail image of graphical abstract

      Enzyme-labile urethane protecting groups, which enable the construction of biologically important peptides relevant for cancer research, were used to synthesize characteristic lipidated partial sequences of the human N-Ras protein for the first time. The strategy is sketched below. They are cleaved chemoselectively under very mild conditions (pH 7, 45 °C), and therefore leave extremely sensitive peptide side chains intact.

    16. CsPr9NbBr15N6: A New Type of Interstitially Stabilized Cluster Compound (pages 2262–2264)

      Dr. Michael Lulei and Prof. John D. Corbett

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199522621

      Thumbnail image of graphical abstract

      A [Pr9NbN6] cluster unit with a niobium atom centered in a tricapped trigonal prism of praseodymium atoms (shown on the right) is the important structural feature of the title compound. Nitrogen atoms occupy the tetrahedral cavities in all six Pr3Nb tetrahedra. This is the first example where a transition metal atom has been incorporated into a cluster framework of trivalent rare earth metal atoms.

    17. [{Ti(μ-CH3)5(μ-CH2)}{(tmeda)Li}3] · THF: An Unusual and Highly Fluxional Titanium Organometallic Compound (pages 2264–2266)

      Pietro Berno, Hilary Jenkins, Prof. Sandro Gambarotta, Johan Blixt, Glenn A. Facey and Christian Detellier

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199522641

      Thumbnail image of graphical abstract

      One methylene and five methyl groups are surprisingly the ligands attached to the titanium atom in 1. Compound 1 is formed from the reaction of [{(Me3Si)2N}3Ti] with an excess of (Me3Si)2NLi followed by subsequent treatment with CH2Cl2. Unusual Ti-H-C bridges are present in the highly fluxional compound. Whether the methylene group in 1 stems from the solvent or not is still unclear.

    18. Stereoselective Synthesis of Chiral Zirconocenes from Doubly Substituted, Donor Functionalized Cyclopentadienes via Helical Chelate Complexes (pages 2266–2267)

      Dr. Jens Christoffers and Prof. Dr. Robert G. Bergman

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199522661

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      The combination of planar chirality and helicity gives rise to the novel stereochemical properties of the metallocene 1, which can be synthesized from a disubstituted cyclopentadiene derivative with a donor functionalized side chain. Cleavage of either one or both metal-chelate arms transforms 1 into single diastereomers of 2 and 3, respectively, with complete retention of configuration of the chiral planes.

    19. Detection and Reactions of Radical Cations Generated by Photolysis of Aromatic Compounds with Tetranitromethane in 1,1,1,3,3,3-Hexafluoro-2-propanol at Room Temperature (pages 2268–2269)

      Prof. Lennart Eberson, Ola Persson and Prof. Michael P. Hartshorn

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199522681

      Extremely persistent even at room temperature are the radical cations of aromatic compounds such as dimethoxybenzene and dimethyl- and methoxynaphthalene, when generated photolytically in 1,1,1,3,3,3-hexafluoro-2-propanol (HFP). They can be detected by EPR spectroscopy even in the presence of nucleophiles such as trinitromethanide ion. Their half-lives in HFP often exceed those found in CF3COOH by a factor of more than 100!

    20. Molecular Recognition between Chemically Modified β-Cyclodextrin and Dec-1-ene: New Prospects for Biphasic Hydroformylation of Water-Insoluble Olefins (pages 2269–2271)

      Dr. Eric Monflier, Dipl.-Chem. Georges Fremy, Prof. Dr. Yves Castanet and Prof. Dr. André Mortreux

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199522691

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      A conversion of up to 100% and a selectivity for aldehyde formation of up to 95% is achieved in the Rh-catalyzed hydroformylation of dec-1-ene in the two-phase system water/alkene in the presence of partially methylated β-cyclodextrins [Eq. (a); R = Me; acac = acetylacetonate]. These remarkable results are attributed to the formation of an alkene/cyclodextrin inclusion complex as well as to the solubility of the chemically modified cyclodextrins in both phases.

    21. Facial Diastereoselectivity in the Paternò–Büchi Reaction of Chiral Silyl Enol Ethers (pages 2271–2273)

      Dr. Thorsten Bach, Dipl.-Chem. Kai Jödicke, Dipl.-Chem. Kristian Kather and Dipl.-Chem. Jürgen Hecht

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199522711

      Thumbnail image of graphical abstract

      A single element of chirality determines the configuration of the three newly formed stereogenic centers in the title reaction [Eq. (a)]. In particular, large (R = SiMe2Ph,tBu) and polar (R = OMe) substituents induce good diastereoselectivities. Simple ring-opening reactions facilitate a stereoselective approach to acyclic products.

    22. A Tailor-Made Metallocene for the Copolymerization of Ethene with Bulky Cycloalkenes (pages 2273–2275)

      Prof. Dr. Walter Kaminsky, Dr. Rüdiger Engehausen and Dr. Jürgen Kopf

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199522731

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      Zirconocene/methylaluminoxane catalysts made-to-measure (with zirconocenes such as 1) facilitate statistical incorporation of bulky cycloolefins such as dimethanooctahydronapthalene into a polyethylene chain. The new cycloolefin copolymers are extremely thermally stable and show very promising properties for optoelectronic and technical applications.

    23. Antibody-Catalyzed Phosphate Triester Hydrolysis (pages 2275–2277)

      Jonathan S. Rosenblum, Dr. Lee-Chiang Lo, Dr. Tingyu Li, Prof. Dr. Kim D. Janda and Prof. Dr. Richard A. Lerner

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199522751

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      Not geometric but electrostatic features of the transition state serve as a paradigm for the design of antibodies that catalyze the hydrolysis of phosphate triesters. Thus, an efficient catalytic antibody was obtained with the dipolar amine oxide 1 as hapten. Potential applications of such antibodies include activation of prodrugs, disposal of insecticides, and counteraction of the toxicity of chemical warfare agents.

    24. Diastereo- and Enantioselective Synthesis of Polyfunctional Ketones with Adjacent Quaternary and Tertiary Centers by Asymmetric Carroll Rearrangement (pages 2278–2280)

      Prof. Dr. Dieter Enders, Dipl.-Chem. Monika Knopp, Dr. Jan Runsink and Dr. Gerhard Raabe

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199522781

      Thumbnail image of graphical abstract

      The first asymmetric Carroll rearrangement via dienolate intermediates derived from β-ketoesters 1 provides access to highly functionalized ketones 2 of high diastereo-and enantiomeric purity. The chiral auxiliary in this [3,3]sigmatropic rearrangement is (S)-1-amino-2-methoxymethylpyrrolidine (SAMP). The products 2 with adjacent quaternary and tertiary stereogenic centers show promise as versatile building blocks for natural product and drug synthesis.

    25. Optimization of the Biological Activity of Combinatorial Compound Libraries by a Genetic Algorithm (pages 2280–2282)

      Dr. Lutz Weber, Dr. Sabine Wallbaum, Dr. Clemens Broger and Dr. Klaus Gubernator

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199522801

      Thumbnail image of graphical abstract

      Artificial evolutionary synthesis can be used to find biologically active compounds out of a library of 160000 possible Ugi-type reaction products by using an enzymatic assay (thrombin) as the feedback loop function. Thus, a reaction in generation 18 gave compound 1, which exhibits the structural features of known thrombin inhibitors and inhibits the enzyme effectively (Ki = 0.22 μM).

    26. Mechanism of the Fe+ Mediated C[BOND]C and C[BOND]H Bond Activations in Ethane from a Theoretical Viewpoint (pages 2282–2285)

      Dipl.-Chem. Max C. Holthausen, Dipl.-Chem. Andreas Fiedler, Prof. Dr. Helmut Schwarz and Prof. Dr. Wolfram Koch

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199522821

      An explanation for the absence of H2 and CH4 elimination in the gas phase reaction of Fe+ with ethane is provided by the in-depth analysis of computed stationary points in the system [Fe, C2, H6]+ presented herein. The results of the calculations verify the experimentally observed direct fragmentation processes.

      • equation image
    27. (S)-Selective Retroaldol Reaction and (R)-Selective β-Elimination with an Aldolase Catalytic Antibody (pages 2285–2287)

      Prof. Jean-Louis Reymond

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199522851

      Thumbnail image of graphical abstract

      The artificial aldolase assembled from ArCH2NH2 and antibody 72D4, which was raised against hapten 1, catalyzes the si-selective aldol addition of acetone to aldehydes by an enamine mechanism. In the back reaction, the (4S)-configurated aldols undergo a selective retroaldol reaction [Eq. (a)] and the (4R)-configurated aldols eliminate water [Eq. (b)]. These results can be explained by conformational control of the imine intermediate.

    28. Asymmetrization of meso 1,4-Enediol Ethers by Isomerization with a Chiral binap–RhI Catalyst (pages 2287–2289)

      Prof. Dr. Kou Hiroya, Yuko Kurihara and Prof. Dr. Kunio Ogasawara

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199522871

      Thumbnail image of graphical abstract

      High enantiomeric purities are achieved with the method described here for the transformation of meso 1,4-enediol ethers such as 1 into oxyketones such as 2 in the presence of a chiral RhI catalyst. These products are versatile chiral building blocks in synthesis. TBS = tert-butyldimethylsilyl.

    29. Radiofrequency Encoded Combinatorial Chemistry (pages 2289–2291)

      Prof. Dr. K. C. Nicolaou, Dr. Xiao-Yi Xiao, Dr. Zahra Parandoosh, Dr. Andrew Senyei and Dr. Michael P. Nova

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199522891

      Thumbnail image of graphical abstract

      The combinatorial synthesis of peptides on a support can be traced exactly by the incorporation of semi-conductor memory chips in Microreactors containing polymer beads (see picture on the right). Before each coupling step the chip is encoded with a radiofrequency signal (for example A); the sequence of signals encoding the complete amino acid sequence (for example A-B-A) can be read before or after the oligopeptide is cleaved from the support. This approach was used to construct a 24-member peptide library from 96 Microreactors and could be applicable to the synthesis of small organic molecule libraries as well.

  4. Book Reviews

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

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