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Tushar van der Wijst Célia Fonseca Guerra Dr. Marcel Swart Dr. F. Matthias Bickelhaupt Prof. Dr. Bernhard Lippert Prof. Dr. 《Angewandte Chemie (International ed. in English)》2009,48(18):3285-3287
Pass the salt, please! State‐of‐the‐art computations indicate that the stacking complex of a guanine quartet and an adenine quartet (G4A4) can function as a potent ditopic receptor for NaCl in aqueous solution (see picture; Na+, Cl? yellow, O red, N blue, C black, H white).
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Dorothea Richter Dipl.‐Chem. Herbert Mayr Prof. Dr. 《Angewandte Chemie (International ed. in English)》2009,48(11):1958-1961
How are dihydropyridines like indoles? Both groups of compounds have similar nucleophilicity parameters N and are therefore suitable substrates for iminium‐catalyzed reactions of α,β‐unsaturated aldehydes. The N parameters of 1,4‐dihydropyridines were derived from the rates of hydride transfer reactions to benzhydrylium ions (see scheme).
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Playing the sax : The enantioselective total syntheses of (?)‐ and (+)‐decarbamoyloxysaxitoxin (doSTX) and (+)‐saxitoxin (STX) are reported. A new methodology was developed for the synthesis of STXs, featuring discriminative reduction of the nitro group and N? O bond in nitroisoxazolidine.
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Katharina Baumann Dr. Danuta Kowalczyk Tobias Gutjahr Dipl.‐Chem. Markus Pieczyk Claire Jones Dr. Martin K. Wild Priv.‐Doz. Dr. Dietmar Vestweber Prof. Dr. Horst Kunz Prof. Dr. 《Angewandte Chemie (International ed. in English)》2009,48(17):3174-3178
Total synthesis through block glycosylation and selective chemical O‐sulfation of tyrosine residues yielded the glycopeptide recognition domain A (X=SO3?) of the P‐selectin glycoprotein ligand 1, in which the terminal sialic acid of the complex hexasaccharide side chain was replaced by (S)‐cyclohexyl lactic acid. In binding assays the O‐sulfated structure A showed high affinity towards P‐selectin, the non‐sulfated towards E‐selectin.
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Three attractions in one cage : Various magnetic networks are formed in the three polymorphs of an organic magnet, BBTDA(=benzo[1,2‐d:4,5‐d′]bis[1,3,2]dithiazole)?GaBr4. The three phases show quite different magnetic behaviors in spite of having the same chemical formula. Their magnetic differences originate from the relative configuration of the neighboring organic radical molecules in their crystals.
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Farhan R. Bou‐Hamdan Dr. James L. Leighton Prof. Dr. 《Angewandte Chemie (International ed. in English)》2009,48(13):2403-2406
“ Quat's” the story? N‐Aryl amides are effective directing/activating groups for chlorosilane Lewis acids. This aspect has been exploited for the development of the first simple and general method for the highly enantioselective Pictet–Spengler reaction of ketimines derived from α‐ketoamides leading to quaternary α‐amino acid derivatives (see scheme).
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The synthesis of cationic mono‐(6‐O‐(1‐vinylimidazolium))‐ß‐cyclodextrin with toluenesulfonate as the corresponding anion is described. Free‐radical copolymerization of the resulting host–guest complex with N‐isopropylacrylamide or N,N‐diethylacrylamide yielded copolymers showing a temperature‐controlled solubility window in water. The impact of different anionic guests and salt concentrations on solubility behavior was investigated via turbidity measurements.
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Kathrin Prantz Mag. Johann Mulzer Prof. 《Angewandte Chemie (International ed. in English)》2009,48(27):5030-5033
Discriminating elimination : A new method for the synthesis of methyl‐branched trisubstituted Z olefins, a structural motif in many polyketides with anticancer activity, relies on an ?OH‐induced decarboxylative Grob‐type fragmentation (see scheme; Ms=mesyl). The starting materials are β‐mesyloxy lactones with a quaternary α center, which are prepared by aldol reactions in a diastereo‐ and enantioselective manner.
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Lin Li Yu‐Peng Tian Jia‐Xiang Yang Ping‐Ping Sun Jie‐Ying Wu Hong‐Ping Zhou Sheng‐Yi Zhang Bao‐Kang Jin Xiao‐Juan Xing Chuan‐Kui Wang Ming Li Guang‐Hua Cheng Huo‐Hong Tang Wen‐Hao Huang Xu‐Tang Tao Min‐Hua Jiang 《化学:亚洲杂志》2009,4(5):668-680
Mark us bent! The synthesis, structure, and single‐ and two‐photon spectroscopic properties of a series of pyrimidine‐based (bent‐shaped) molecules are reported. These allow structure‐property relationships and guidelines for both the development and application of TPA compounds to be derived.
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Bjrn Kusebauch Benjamin Busch Kirstin Scherlach Martin Roth Christian Hertweck 《Angewandte Chemie (International ed. in English)》2009,48(27):4869-4869
The fungus Rhizopus microsporus …? ; shown in the micrograph on the cover picture, harbors the endosymbiotic bacteria Burkholderia rhizoxinica that produces the antimitotic polyketide macrolide rhizoxin (see structure). In their Communication on page 5001 ff. , C. Hertweck and co‐workers show that the enzyme rhizoxin polyketide synthase is uniquely capable of introducing a β branch (highlighted by the magnifying glass) by a Michael‐type addition of a malonyl unit to an acryloyl intermediate.
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Synergy in synthesis : Strategic consideration of metathesis and Suzuki–Miyaura (SM) cross‐coupling for C? C bond‐formation processes has opened up new and “green” synthetic routes to various complex targets. The use of this synergistic combination for the synthesis of supramolecular ligands, polyaromatic compounds, and complex natural products is covered in this Focus Review.
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Da‐Yu Wu Dr. Osamu Sato Prof. Yasuaki Einaga Prof. Chun‐Ying Duan Dr. 《Angewandte Chemie (International ed. in English)》2009,48(8):1475-1478
How low can you go? An FeII4 square was prepared by self‐assembly and exhibits both thermally induced and photoinduced spin crossover from a system with four high‐spin (HS) centers to one with two high‐spin and two low‐spin (LS) centers. The spin‐crossover sites are located on the same side of the square, and the spin transition and magnetic interactions (see picture) are synergistically coupled.
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Amaruka Hazari Véronique Gouverneur Prof. John M. Brown Dr. 《Angewandte Chemie (International ed. in English)》2009,48(7):1296-1299
As unusual substrates for the Tsuji–Trost allylation reaction, allylic fluorides are responsive to palladium‐catalyzed substitution. Their activity towards this reaction fits in the series OCO2Me>OBz? F ?OAc. The classic stereoretention mechanism that involves sequential inversions does not operate in this case. Several distinct cases are considered.
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Anthony S. R. Chesman David R. Turner Dr. Glen B. Deacon Prof. Stuart R. Batten Assoc. Prof. 《化学:亚洲杂志》2009,4(5):761-769
Additional cyclization : Dicyanonitrosomethanide, [C(CN)2(NO)]? undergoes nucleophilic addition and cyclization of 1,2‐diaminoethane and 1,3‐diaminopropane on the nitrile groups to form imidazolinyl and 1,4,5,6‐tetrahydropyrimidinyl groups, respectively. Ethanolamine has lower reactivity and fails to cyclize.
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Synthesis and Characterization of Novel Glycerol‐Derived Polycarbonates with Pendant Hydroxyl Groups
Hujie Mei Zhenlin Zhong Feifu Long Renxi Zhuo 《Macromolecular rapid communications》2006,27(22):1894-1899
Summary: A novel type of glycerol‐derived, water‐soluble polycarbonate with pendant, primary hydroxyl groups was prepared from 2‐(2‐benzyloxyethoxy)trimethylene carbonate (BETC). Ring‐opening polymerization of BETC and 2,2‐dimethyltrimethylene carbonate (DTC) gave narrow distribution of homopolymers or random copolymers with high molecular weights. The protecting benzyl groups were removed by catalyzed hydrogenation at atmosphere H2 pressure to give hydroxyl polycarbonates without observable changes on the polymer backbone and molecular weight distribution. The hydrophilicity of the copolymers increases with the increase in the hydrophilic glycerol‐derived carbonate content.
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Zhixin Tian Steven R. Kass Prof. 《Angewandte Chemie (International ed. in English)》2009,48(7):1321-1323
Preferred protonation : Does electrospray ionization mass spectrometry produce gas‐phase or liquid‐phase structures? The preferred protonation site in p‐aminobenzoic acid depends upon the medium, and the structure of its conjugate acid varies with the solvent used during spraying.