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  • Rewiring chemical networks based on dynamic dithioacetal and disulfide bonds
    Chem. Eur. J. (IF 5.317) Pub Date : 2018-01-18
    Gaston Orrillo, Agustina La-Venia, Escalante Andrea, Ricardo L.E. Furlan

    The control of the connectivity between nodes of synthetic networks is still largely unexplored. To address this point we take advantage of a simple dynamic chemical system with two exchange levels that are mutually connected and can be activated simultaneously or sequentially. Dithioacetals and disulfides can be exchanged simultaneously under UV light in the presence of a sensitizer. Crossover reactions between both exchange processes produce a fully connected chemical network. On the other hand, the use of acid, base or UV light connects different nodes allowing network rewiring.

    更新日期:2018-01-18
  • Versatile Modes of Cooperative B-H Bond Activation Reactions in Ruthenium Carbene Complexes: Addition, Ring-opening and Insertion
    Chem. Eur. J. (IF 5.317) Pub Date : 2018-01-18
    Scharf T. Lennart, Julia Weismann, Kai-Stephan Feichtner, Felix Lindl, Viktoria H. Gessner

    Cooperative B-H bond activation reactions with thio- and iminophosphoryl tethered ruthenium carbene complexes are reported. The complexes show surprisingly different reactivities towards the commonly employed boranes CatBH, PinBH and BH3∙LB as a result of different modes of metal ligand cooperation. While the iminophosphoryl system allows for selective 1,2-addition of the B-H bond across the Ru=C double bond, the sulfur analogue only delivers the 1,2-addition product for CatBH, while activation of BH3 and PinBH lead to further insertion reactions in one or more sides of the Ru-C-P-S-ring. The different reactivities can be explained by the differences in the electronics of the carbene complexes and the phosphoryl tether and by the Lewis acidities of the boranes. DFT calculations show that the mechanism of the reactions either proceeds via an addition across the Ru=C bond with different regioselectivities or across the Ru-S linkage.

    更新日期:2018-01-18
  • Remote C-H Activation of Various N-Heterocycles Using a Single Template
    Chem. Eur. J. (IF 5.317) Pub Date : 2018-01-18
    Guoqiang Yang, Dajian Zhu, Peng Wang, Ri-Yuan Tang, Jin-Quan Yu

    A single simple ortho-sulfonyl benzonitrile template was developed to achieve remote C-H olefination of six different classes of N-heterocycles. We demonstrate that, by varying precatalysts and conditions, the same template can be applied to the remote C-H activation of six structurally distinct heterocyclic scaffolds, and the site-selectivity can be predicted based on distance and geometry. Furthermore, this new development shows that template-directed remote C-H activation are possible via macrocyclopalladation processes with smaller ring sizes.

    更新日期:2018-01-18
  • Integration of open metal sites and Lewis basic sites for construction of a Cu MOF with rare chiral Oh type of cage for high performance of methane purification
    Chem. Eur. J. (IF 5.317) Pub Date : 2018-01-18
    Zhan Shi, Lingkun Meng, Ziyuan Niu, Chen Liang, XingLong Dong, Kang Liu, Guanghua Li, Chunguang Li, Yu Han, Shouhua Feng

    A Cu MOF [Cu4(PMTD)2(H2O)3]·20H2O, 1, (Where PMTD is (1,4-phenylenebis(5-methyl-4H-1,2,4-triazole-3,4-diyl)bis(5-carboxylato-3,1-phenylene)bis(hydroperoxymethanide) with rare chiral Oh type of cage and dual functionalities of open metal sites and Lewis basic sites based on a designed U-shaped ligand was synthesized by hydrothermal method. It exhibits high-capacity of CO2, C2 and C3 hydrocarbon storage capacity under atmospheric pressure as well as high H2 (1.96% wt) adsorption capacity at 77K. Methane purification capacity was tested and verified step by step. Isosteric heats (Qst) study reveals that CH4 has the weakest van der Waals host- guest interactions among the seven gases at 298K. Ideal adsorbed solution theory (IAST) calculation reveals that compound 1 is more selective toward CO2, C2H6 and C3H8 over CH4 in further calculating its separation capacity, as exemplified for CO2/CH4 (50:50, 5:95), C2H6/CH4 (50:50, 5:95) or C3H8/CH4 (50:50, 5:95) binary gas mixtures. Breakthrough experiments show that 1 has a significantly higher adsorption capacity for CO2, C2H6 and C3H8 than CH4. The selective adsorption properties of 1 make it a promising candidate for methane purification.

    更新日期:2018-01-18
  • Oxidation of Methylalumoxane Oligomers
    Chem. Eur. J. (IF 5.317) Pub Date : 2018-01-17
    Harmen Zijlstra, Scott Collins, Jason Scott McIndoe

    The anions formed from methylalumoxane (MAO) and suitable donors (e.g. octamethyltrisiloxane) are amenable to mass spectrometric (MS) analysis. Their composition as deduced from this data allows direct insight into the chemical transformations of their neutral precursors. One such process is oxidation, which is well-known to be facile for MAO without any clear idea of what actually occurs at a molecular level. Addition of O2 to MAO results in immediate gelation, but MS analysis reveals no corresponding change to the composition of the principal oligomeric anions. A slow (hours) reaction does occur that involves net incorporation of Me2AlOMe into the oligomeric anions, and the identities of the OMe-containing anions were confirmed by 1H NMR, MS/MS analysis, and addition of an authentic sample of Me2AlOMe to MAO. The result tallies with the fact that addition of O2 to MAO produces Me2AlOMe from free Me3Al which eventually leads to formation of oxidized MAO oligomers and changes in ion abundance. Aging of the oxygenated MAO results in further growth of the oligomers similar to that of the non-oxidized species. Mass spectrometric analysis therefore reveals useful insights into the environmental history of a given MAO batch.

    更新日期:2018-01-18
  • Mixed Fluorotryptophan Substitutions at the Same Residue Expand the Versatility of ¹⁹F Protein NMR Spectroscopy
    Chem. Eur. J. (IF 5.317) Pub Date : 2018-01-17
    Calem Kenward, Kyungsoo Shin, Jan Rainey

    The strategy of applying fluorine NMR to characterize ligand binding to a membrane protein prepared with mixtures of tryptophans substituted with F at different positions on the indole ring was tested. The ¹⁹F NMR behavior of 4-, 5-, 6-, and 7-fluorotryptophan were directly compared as a function of both micellar environment and fragment size for two overlapping apelin receptor (AR/APJ) segments - one with a single transmembrane (TM) helix and two tryptophan residues, the other with three TM helices and two additional tryptophan residues. Chemical shifts, peak patterns, and nuclear spin relaxation rates were observed to vary as a function of micellar conditions and F substitution position in the indole ring, with the exposure of a given residue to micelle or solvent being the primary differentiating factor. Titration of the 3-TM AR segment biosynthetically prepared with mixtures of 5- and 7-fluorotryptophan by two distinct peptide ligands - apelin-36 and apela-32 - demonstrated site-specific ¹⁹F peak intensity changes for one ligand but not the other. In contrast, both ligands perturbed ¹H-¹⁵N heteronuclear single quantum coherence experiment peak patterns to a similar degree. Characterization of fluorotryptophan mixtures for a given set of tryptophan residues, thus, significantly augments the potential to apply ¹⁹F NMR to track otherwise obscure modulation of protein conformation and dynamics without an explicit requirement for mutagenesis or chemical modification.

    更新日期:2018-01-18
  • Twisted charge-transfer antennas for ultra-bright terbium(III) and dysprosium(III) bioprobes.
    Chem. Eur. J. (IF 5.317) Pub Date : 2018-01-17
    Anh Thy Bui, Amandine Roux, Alexei Grichine, Alain Duperray, Chantal Andraud, Olivier Maury

    The design of original twisted charge transfer antennas where a non planar geometry is enforced thanks to one or two bulky ortho-Me substituents allows us to prepare the corresponding ultra-bright Tb(III) and Dy(III) bioprobes. The brightness of the Tb(III) derivative compares well with that of the benchmark Tb-Lumi4 complex. The first bio-imaging experiments with a Dy(III) luminescent bioprobe are also reported

    更新日期:2018-01-18
  • Title Synthesis of α-L-fucopyranoside-presenting glycoclusters and investigation of their interaction with recombinant Photorhabdus asymbiotica lectin (PHL)
    Chem. Eur. J. (IF 5.317) Pub Date : 2018-01-17
    Jančaříková Gita, Mihály Herczeg, Eva Fujdiarová, Josef Houser, Katalin E. Kövér, Anikó Borbás, Michaela Wimmerová, Magdolna Csávás

    Photorhabdus asymbiotica is a gram-negative bacterium that is not only as effective an insect pathogen as other members of the genus, but it also causes serious diseases in humans. The recently identified lectin PHL from P. asymbiotica verifiably modulates an immune response of humans and insects, which supports the idea that the lectin might play an important role in the host-pathogen interaction. Dimeric PHL contains up to seven L-fucose specific binding sites per monomer, and in order to target multiple binding sites of PHL, α-L-fucoside-containing di-, tri- and tetravalent glycoclusters were synthesized. Methyl gallate and pentaerythritol were chosen as multivalent scaffolds, and the fucoclusters were built from the above-mentioned cores by coupling with different oligoethylene bridges and propargyl α-L-fucosides using 1,3-dipolar azide-alkyne cycloaddition. The interaction between fucoside derivates and PHL was investigated by several biophysical and biological methods, ITC and SPR measurements, hemagglutination inhibition assay and an investigation of bacterial aggregation properties were carried out. Moreover, details of the interaction between PHL and propargyl α-L-fucoside as a monomer unit were revealed using X-ray crystallography. Besides this, the interaction with multivalent compounds was studied by NMR techniques. The newly synthesized multivalent fucoclusters proved to be up to several orders of magnitude better ligands than the natural ligand, L-fucose.

    更新日期:2018-01-18
  • Enantioselective Synthesis of Aminodiols by Sequential Rh-Catalysed Oxyamination/Kinetic Resolution. Expanding the Substrate Scope of Amidine-Based Catalysis
    Chem. Eur. J. (IF 5.317) Pub Date : 2018-01-17
    Joan Guasch, Irene Giménez, Ignacio Funes-Ardoiz, Isabel Matheu, Feliu Maseras, Sergio Castillón, Yolanda Díaz, Miguel Bernús

    Regio- and stereoselective oxyamination of dienes through a tandem rhodium catalysed aziridination-nucleophilic opening affords racemic oxazolidinone derivatives, which undergo a kinetic resolution acylation process using ABCs (amidine-based catalysts) achieving s values up to 117. This protocol was applied to the enantioselective synthesis of sphingosine.

    更新日期:2018-01-17
  • Brønsted Base-Catalyzed Umpolung Intramolecular Cyclization of Alkynyl Imines
    Chem. Eur. J. (IF 5.317) Pub Date : 2018-01-17
    Azusa Kondoh, Masahiro Terada

    A novel "umpolung" intramolecular cyclization of alkynyl imines, in which the electrophilic imine sp2-carbon formally serves as a nucleophilic site, was developed under Brønsted base catalysis. The reaction involves the unprecedented catalytic generation of α-aminoester enolates from α-iminoesters via the 1,2-addition of the anion of a secondary phosphite to an imine moiety followed by the [1,2]-rearrangement of a dialkoxyphosphoryl moiety from carbon to nitrogen, which is a formal umpolung process, and the intramolecular addition to an alkyne. This is a rare example of a [1,2]-rearrangement of a dialkoxyphosphoryl moiety from carbon to nitrogen to generate an α-amino carbanion and the first catalytic carbon-carbon bond forming reaction utilizing the resulting carbanion as a nucleophile.

    更新日期:2018-01-17
  • Ligand- and Metal-Based Reactivity of a Neutral Ruthenium Diolefin Diazadiene Complex; The Innocent, the Guilty, and the Suspicious
    Chem. Eur. J. (IF 5.317) Pub Date : 2018-01-17
    Vivek Sinha, Bruno Pribanic, Bas de Bruin, Monica Trincado, Hansjörg Grützmacher

    Coordination of the diazadiene diolefin ligand trop2dad to ruthenium leads to various complexes of composition [Ru(trop2dad)(L)]. DFT studies indicate that the closed-shell singlet (CSS), open-shell singlet (OSS) and triplet electronic structures of this species are close in energy, with the OSS state being the lowest in energy for all tested functionals. Singlet state CASSCF calculations reveal a significant multireference character for these complexes. The closed-shell singlet wavefunction dominates, but these complexes have a significant (~8-16%) open-shell singlet [d7 Ru(I)(L)(trop2dad●-] contribution mixed into the ground state. In agreement with their ambivalent electronic structure, these complexes reveal both metal and ligand centered reactivity. Most notably are the reactions with AdN3, diazomethane, and a phosphaalkyne leading to scission of the C-C bond of the diazadiene moiety of the trop2dad ligand, resulting in net (formal) nitrene, carbene or P-C insertion in the dad C-C bond, respectively. Supporting DFT studies reveal that several of the ligand-based reactions proceed via low barrier radical-type pathways, involving the dad●- ligand radical character of the OSS or triplet species.

    更新日期:2018-01-17
  • Fluorescence redox blinking adaptable to structural analysis of nucleic acids
    Chem. Eur. J. (IF 5.317) Pub Date : 2018-01-17
    Takafumi Miyata, Naohiko Shimada, Atsushi Maruyama, Kiyohiko Kawai

    The phenomenon of "blinking" is unique to single-molecule fluorescence measurements. By designing a fluorophore with an appropriate dark state lifetime (τoff), we have devised a kinetic analysis based on the control of fluorescence blinking (KACB) to investigate the dynamics of biomolecules. By controlling the redox reaction based blinking (rKACB), we have previously investigated conformational dynamics of RNA at the single-molecule level. However, there have been little knowledge about suitable fluorescent molecules for rKACB, and the application of rKACB has been limited to the analysis of hairpins and duplex structures of nucleic acids. In this paper, we evaluated various fluorescent molecules, including ATTO 655, ATTO 647N, TAMRA, R6G, and Alexa 488, for rKACB. rKACB was adapted to the discrimination of DNA/DNA and DNA/RNA nucleic acid duplexes and investigation of antigen-antibody interactions. Further, by changing the size of the oxidant, we were able to determine the solvent accessibility of the target domain of the biomolecules analysed.

    更新日期:2018-01-17
  • 2,2'-Bipyridine Equipped with a Disulfide/Dithiol Switch for Coupled Two Electron and Proton Transfer
    Chem. Eur. J. (IF 5.317) Pub Date : 2018-01-17
    Mauricio Cattaneo, Christine Schiewer, Anne Schober, Sebastian Dechert, Inke Siewert, Franc Meyer

    [1,2]dithiino[4,3-b:5,6-b']dipyridine (1) and its protonated open form 3,3'-dithiol-2,2'-bipyridine (2) were synthesised and their interconversion investigated. The X-ray structure of 2 revealed an anti orientation of the two pyridine units and a zwitterionic form. In depth electrochemical studies in combination with DFT calculations lead to a comprehensive picture of the redox chemistry of 1 in the absence and presence of protons. Initial one electron reduction at E1 = −1.97 V results in the formation of the radical anion 1red with much elongated S-S bond, which readily undergoes further reduction at E2 = −2.15 V. Water triggers a potential inversion (E ≥ −1.9 V for the second reduction) as the radical anion 1red is protonated at its basic N atom. DFT studies revealed that S−S bond breaking and twisting of the pyridine units generally occurs after the second reduction step while the potential inversion induced by protonation is a result of charge compensation. The CV data were simulated to derive rate constants for the individual chemical and electrochemical reactions for both scenarios in the absence and presence of protons.

    更新日期:2018-01-17
  • The Pentagonal-Pyramidal Hexamethylbenzene Dication: The Many Shades of Coordination Chemistry at Carbon
    Chem. Eur. J. (IF 5.317) Pub Date : 2018-01-17
    Johannes E. M. N. Klein, Remco W. A. Havenith, Gerald Knizia

    A recent report of the crystal structure of the pentagonal-pyramidal hexamethylbenzene dication C6(CH3)62+ by Malischewski and Seppelt [Angew. Chem. Int. Ed. 2017, 56, 368.] confirmed the structural proposal made in the first report of this compound in 1973 by Hogeveen and Kwant [Tetrahedron Lett. 1973, 14, 1665]. The widespread attention that this compound quickly gained led us to reinvestigate its electronic structure. Based on intrinsic bond orbital analysis, effective oxidation state analysis, ring current analysis and comparison to well established coordination complexes, we demonstrate that the central carbon atom behaves like a transition metal. The central (apical) carbon atom, although best described as a highly Lewis-acidic carbon atom coordinated with an anionic cyclopentadienyl ligand, is also capable to act as an electron pair donor to a formal CH3+ group. The different roles of coordination chemistry are discussed.

    更新日期:2018-01-17
  • One-Pot Synthesis of Functionalized Fused Furans via a BODIPY Catalyzed Domino Photooxygenation
    Chem. Eur. J. (IF 5.317) Pub Date : 2018-01-17
    Audrey Mauger, Jonathan Farjon, Pierrick Nun, Vincent Coeffard

    Six-membered ring fused furans containing a tetrasubstituted tertiary carbon were prepared via an unprecedented one-pot BODIPY-catalyzed domino photooxygenation/reduction process. A series of functionalized furans was synthesized from readily available 2-alkenylphenols and mechanistic studies were performed to account for the domino photosensitized oxygenation.

    更新日期:2018-01-17
  • Plasmid-Templated Control of DNA-Cyclodextrin Nanoparticle Morphology Through Molecular Vector Design for Effective Gene Delivery
    Chem. Eur. J. (IF 5.317) Pub Date : 2018-01-17
    Laura Gallego-Yerga, Juan M Benito, Laura Blanco-Fernández, María Martínez-Negro, Itziar Vélaz, Emilio Aicart, Elena Junquera, Carmen Ortiz Mellet, Conchita Tros de Ilarduya, Jose M. Garcia Fernandez

    Engineering self-assembled superstructures through complexation of plasmid DNA (pDNA) and single-isomer nanometric size macromolecules (molecular nanoparticles) is a promising strategy for gene delivery. Notably, the functionality and overall architecture of the vector can be precisely moulded at the atomic level by chemical tailoring, enabling unprecedented opportunities for structure/self-assembling/pDNA delivery relationship studies. Beyond this notion, by judiciously preorganizing the functional elements in cyclodextrin (CD)-based molecular nanoparticles through covalent dimerization, here we demonstrate that the morphology of the resulting nanocomplexes (CDplexes) can be tuned, from spherical to ellipsoidal, rod-type or worm-like nanoparticles, which makes it possible to gain understanding of their shape-dependent transfection properties. The experimental findings are in agreement with a shift from chelate to cross-linking interactions on going from primary face- to secondary face-linked CD dimers, the pDNA partner acting as an active payload and as a template. Most interestingly, transfection efficiency in different cells was shown to be differently impacted by modifications on CDplex morphology, which has led to the identification of an optimal prototype for tissue-selective DNA delivery to the spleen in vivo.

    更新日期:2018-01-17
  • Circularly Polarized Luminescence Appeared from Complete Inorganic Materials Encapsulating Guest Lanthanide Oxides in Host Chiral Silica
    Chem. Eur. J. (IF 5.317) Pub Date : 2018-01-17
    Ren-Hua Jin

    Recently, circularly polarized luminescence (CPL)-active systems have become a very hot and interesting subject in chirality- and optics-related areas. The CPL-active systems are usually available by two approaches: combining covalently a luminescent centre to chiral motif or associating the guest of luminescent probe to a chiral host. However, all the chiral components in CPL materials were organics although the parts of luminescent were alternative as organics or inorganics. Herein, we proposed the first totally inorganic CPL-active system by "luminescent guest - chiral host" strategy. Typically, luminescent sub-10 nm lanthanide oxides (Eu2O3 or Tb2O3) nanoparticles ("guest") were encapsulated on chiral non-helical SiO2 nanofibres ("host") via the calcination (at 900 oC) of chiral SiO2 hybrids nanofibres of trapping Eu3+ (or Tb3+). These lanthanide oxides showed circular dichroism (CD) optical activity in the ultraviolet wavelength and CPL signals around at 615 nm for Eu3+ or 545 nm for Tb3+. This work would be very instructive to design inorganics-based CPL-active systems by incorporation of various luminescent guests in chiral inorganic hosts.

    更新日期:2018-01-17
  • Synthesis, Crystal Analysis and Optoelectronic Properties of Diazole-functionalized Acenes and Azaacenes
    Chem. Eur. J. (IF 5.317) Pub Date : 2018-01-17
    Jinchong Xiao, Huahang Pan, Tingting Song, Xiaomeng Yin, Pengcheng Jin

    Doping heteroatoms into the skeletons of parent acenes can provide more chances to construct novel thermally and photo-stable organic π-conjugated semiconductors. Herein, a family of diazole-decorated acenes (APyS and APySe) and azaacenes (PyP, PyTh, PyPy, PyPh and PyAP) have been successfully synthesized through the classical reactions. Single crystal X-ray analyses showed that these as-formed diazole-modified derivatives adopted twisted topology configuration, whereas the azaacenes display reclining-chair architectures, besides twisted structure. All these compounds displayed yellow or red light in solution. Moreover, their electrochemical behaviors were also examined. We also found that the azaacenes exhibited positive spectroscopic response to acid.

    更新日期:2018-01-17
  • Chemical and Enzymatic Strategies for Bacterial and Mammalian Cell Surface Engineering
    Chem. Eur. J. (IF 5.317) Pub Date : 2018-01-17
    Xiaobao Bi, Juan Yin, Ashley Chen Guanbang, Chuan-Fa Liu

    Cell surface serves important functions such as the regulation of cell-cell and cell-environment interactions. The understanding and manipulation of the cell surface is important for a wide range of fundamental studies of cellular behavior and for biotechnological and medical applications. With the rapid advance of biology, chemistry and materials science, many strategies have been developed for the functionalization of bacterial and mammalian cell surfaces. Here, we review the recent development of chemical and enzymatic approaches to cell surface engineering with particular emphasis on discussing the advantages and limitations of each of these strategies.

    更新日期:2018-01-17
  • Brønsted Acid-Catalyzed Tandem Cyclizations of Tryptamine-Ynamides Yielding 1H-Pyrrolo[2,3-d]carbazole Derivatives
    Chem. Eur. J. (IF 5.317) Pub Date : 2018-01-17
    Yanshi Wang, Jingsheng Lin, Xiaoyu Wang, Guanghui Wang, Xinhang Zhang, Bo Yao, Yuandong Zhao, Pengfei Yu, Bin Lin, Yongxiang Liu, Maosheng Cheng
    更新日期:2018-01-17
  • Tsuji–Trost Reaction of Non-Derivatized Allylic Alcohols
    Chem. Eur. J. (IF 5.317) Pub Date : 2018-01-17
    Sunisa Akkarasamiyo, Supaporn Sawadjoon, Andreas Orthaber, Joseph S. M. Samec
    更新日期:2018-01-17
  • Structural factors affecting binding of platinum anticancer agents with phospholipids. Influence of charge and phosphate clamp formation
    Chem. Eur. J. (IF 5.317) Pub Date : 2018-01-17
    Anil Kumar Gorle, Junyong Zhang, Qin Liu, Susan J. Berners-Price, Nicholas P Farrell

    We report a detailed NMR and DFT study of the interaction of polynuclear platinum anticancer agents (PPCs) with negatively charged phospholipids as a mechanism for their cellular uptake. The reactions of fully 15N-labelled [{trans-PtCl(NH3)2}2(-trans-Pt(NH3)2{NH2(CH2)6NH2}2)]4+ (15N-1, 1,0,1/t,t,t) and the dinuclear [{trans-PtCl(NH3)2}2{-H2N(CH2)6NH2}]2+ (15N-2, 1,1/t,t) with the sodium salt of 1,2-dihexanoyl-sn-glycero-3-phosphate (DHPA) were studied at 298 K, pH ~5.4, by [1H,15N] HSQC 2D NMR spectroscopy. Both 15N-1 and -2 form an initial mono-adduct in which the DHPA is coordinated via the phosphate O atom. For the dinuclear 15N-2, coordination of a second DHPA, in two different orientations, leads to two conformers of the bifunctional adduct. For 15N-1, coordination of the second DHPA allows the central {PtN4} coordination unit to bind electrostatically to two additional DHPA molecules via phosphate clamp interactions, in an extended network. For both 1,0,1/t,t,t (1) and 1,1/t,t (2), equilibrium conditions are obtained more slowly (> 35 h) than in the presence of phosphate (12 h) and in each case the rate constant for the first step of DHPA binding (kL) is about 8 times higher than that for phosphate, whereas the rate constants for the reverse reactions are quite similar. Reaction of 15N-1 with the sodium salt of 1,2-dihexanoyl-sn-glycero-3-[phosphatidyl-L-serine] (DHPS) showed only minor adduct formation via coordination to the N-donor atom of the phosphoserine group

    更新日期:2018-01-17
  • Controlling selectivity in aliphatic C-H oxidation via supramolecular recognition
    Chem. Eur. J. (IF 5.317) Pub Date : 2018-01-16
    Diego Vidal, Giorgio Olivo, Miquel Costas

    Aliphatic C-H oxidation is the most attractive approach to functionalize hydrocarbon skeletons. The main challenge of this reaction is the control of regioselectivity since organic molecules contain multiple C-H bonds. This control is perfectly achieved in natural enzymes by means of a web of interactions that orient the substrate in a specific geometry and override intrinsic reactivity patterns. Replication of this control by combination of molecular catalysts and supramolecular recognition is highly desirable in this regard. This strategy would unlock hydroxylation of C-H bonds that are not accessible with conventional methodologies, in which the selectivity dictated by the geometry of the substrate-receptor adduct. Herein, we review the reports of recognition-driven C-H oxidations and highlight the key design principles that inspired these works.

    更新日期:2018-01-17
  • Fixing the conformation of calix[4arenes:when are three carbons not enough?
    Chem. Eur. J. (IF 5.317) Pub Date : 2018-01-16
    Susan Matthews, Samy Cecioni, John E O’Brien, Colin J MacDonald, David L Hughes, Garth A Jones, Stephen H. Ashworth, Sébastien Vidal

    Calix[4]arenes are unique macrocycles that through judicious functionalisation at the lower-rim can be either fixed in one of four conformations or remain conformationally flexible. Introduction of propynyl or propenyl groups unexpectedly provides a new possibility; a unidirectional conformational switch, with the 1,3-alternate and 1,2-alternate conformers switching to the partial cone conformation, whilst the cone conformation is unchanged, under standard experimental conditions. Using 1H NMR kinetic studies, rates of switching have been shown to be dependent on the starting conformation, upper-rim substituent, where reduction in bulk enables faster switching, solvent and temperature with 1,2-alternate conformations switching fastest. Ab initio calculations (DFT) confirmed the relative stabilities of the conformations and point towards the partial cone conformer being the most stable of the four. The potential impact on synthesis through the 'click' reaction has been investigated and found not to be significant.

    更新日期:2018-01-16
  • Organotin dyes bearing anionic boron clusters as cell-staining fluorescent probes.
    Chem. Eur. J. (IF 5.317) Pub Date : 2018-01-16
    Rosario Nuñez, Blanca M. Muñoz Flores, Justo Cabrera-González, Clara Viñas, Arturo Chávez-Reyes, H. V. Rasika Dias, Victor Manuel Jiménez Pérez

    Herein, the design of novel fluorescent organotin compounds derived from 4-hydroxy-N'-((2-hydroxynaphthalen-1-yl)methylene)benzohydrazidato and their cytoplasm and nucleoli staining in vitro (B16F10 cells) are described. Tin compounds were prepared to bear an aliphatic carbon chain (-C12H25) and an electrodonor group (-OH), being also the latest derivatised to contain boron cluster anions, [B12H12]2- and [3,3′-Co(1,2-C2B9H11)2]- (COSAN). All the conjugates have been fully characterised and their luminescence properties assessed. They show in general good quantum yields in solution (24% - 49%), being lower for COSAN derivatives. Remarkably, the linking of [B12H12]2- and COSAN into the complexes made them more soluble without loosing their luminescence properties. Living B16F10 cells were treated with all the compounds to determine their staining fluorescent properties; the compounds bearing the aliphatic chain showed a reduced staining capacity with the formation of aggregates. Noticeable, the presence of each boron cluster in the complexes structure produces a different staining effect; those bearing [B12H12]2- produce extraordinary nucleoli and cytoplasmic staining, while the COSAN-containing dyes are only detected in the cytoplasm. The remarkable fluorescence staining properties showed by theses organotin compounds make them excellent candidates for fluorescent bioimaging in vitro.

    更新日期:2018-01-16
  • Synthesis of multifunctional spirocyclic azetidines, and their application in drug discovery.
    Chem. Eur. J. (IF 5.317) Pub Date : 2018-01-16
    Alexander Kirichok, Irina Shton, Irina Pishel, Sergey Zozulya, Petro Borysko, Vladimir Kubyshkin, Olha Zaporozhets, Andrei Tolmachev, Pavel Mykhailiuk

    Spirocyclic polyfunctional azetidines have been synthesized and validated in drug discovery. Spirocyclic analogue of the anesthetic drug Bupivacaine with 5-times smaller toxicity was developed.

    更新日期:2018-01-16
  • Mechanochromic Polymers that Turn Green upon the Dissociation of Diarylbibenzothiophenonyl: The Missing Piece toward Rainbow Mechanochromism
    Chem. Eur. J. (IF 5.317) Pub Date : 2018-01-16
    Kuniaki Ishizuki, Hironori Oka, Daisuke Aoki, Raita Goseki, Hideyuki Otsuka

    Mechanochromic polymers, i.e., polymers sensitive to mechanical impact, promise great potential for applications in damage sensors. In particular, radical-type mechanochromic polymers, which produce colored radical species in response to mechanical stress, may enable not only the visualization of mechanical stress, but also its quantitative evaluation by electron paramagnetic resonance analysis. In this work, a radical-type mechanochromic polymer that exhibits a color change from white to green upon dissociation of a diarylbibenzothiophenonyl moiety at the mid-point of a polystyrene chain is presented, and its mechanochromic behavior examined. Mechanochromic materials that show a variety of colors ('rainbow colors') in response to mechanical stress were prepared by simply mixing radical-type mechanochromic polymers of primary colors.

    更新日期:2018-01-16
  • Interrogating Protein Phosphatases with Chemical Activity Probes
    Chem. Eur. J. (IF 5.317) Pub Date : 2018-01-16
    Garrett Casey, Cliff Stains

    Protein phosphatases, while long overlooked, have recently become appreciated as drivers of both normal- and disease-associated signaling events. As a result, the spotlight is now turning torwards this enzyme family and efforts geared towards the development of modern chemical tools for studying these enzymes are well underway. This minireview focuses on the evolution of chemical activity probes, both optical and covalent, for the study of protein phosphatases. Small-molecule probes, global monitoring of phosphatase activity through the use of covalent modifiers, and targeted fluorescence-based activity probes are discussed. We conclude with an overview of open questions in the field and highlight the potential impact of chemical tools for studying protein phosphatases.

    更新日期:2018-01-16
  • Reactions of an Al/P Frustrated Lewis Pair with α,β-Unsaturated Carbonyl Compounds - FLPs as Efficient 2e Reductants with the Formation of Enolates, a cis-Enediolate and an Allene
    Chem. Eur. J. (IF 5.317) Pub Date : 2018-01-16
    Werner Uhl, Merten Lange, Jonas C. Tendyck, Philipp Wegener, Alexander Hepp, Ernst Ulrich Würthwein

    The Al/P based FLP Mes2P-C(AltBu)2=C(H)Ph (1) reacted as an efficient 2e reductant with benzil to afford a cis-enediolate which is coordinated to the FLP via P-O and Al-O bonds and formation of a seven-membered heterocycle (2). The P atom is oxidised from +III to +V. Similar heterocycles (3a to 3f) were formed when 1 was treated with various enones (acroleine, acrylate, acrylamide). The resulting enolates are bound to the FLP via P-C and Al-O bonds. Cyclopropenone gave an adduct (4) with the C=O bond coordinated by P and Al. Ynones gave a fascinating variety of different structures. 1,3-Diphenylprop-2-yn-1-one afforded a remarkable allene type moiety with two cumulated C=C bonds (5), 3-hexyn-2-one yielded a ligand with two conjugated C=C bonds by C-H bond activation at the carbonyl methyl group (7), and 4-(trimethylsilyl)-3-butyn-2-one reacted by C-H bond cleavage, formation of an enolate group with a terminal C=C bond and shift of the proton to the P atom (8). The C≡C bond was not affected. The allene compound 5 rearranged at elevated temperature and day-light by formation of a tricyclic compound via C-H bond activation and C-C bond formation. DFT calculations on this unusual rearrangement suggest insertion of the central allene C atom into the C-H bond of a methyl group and the intermediate formation of a three-membered C3 ring.

    更新日期:2018-01-16
  • A Combined Photochemical and Multi-Component Reaction Approach to Precision Oligomers
    Chem. Eur. J. (IF 5.317) Pub Date : 2018-01-16
    Waldemar Konrad, Fabian Raphael Blößer, Katharina Wetzel, Andreas Boukis, Michael Meier, Christopher Barner-Kowollik

    We introduce an avenue for the convergent synthesis of linear monodisperse sequence-defined oligomers via a unique approach, combining the Passerini three-component reaction (P 3CR) and a Diels-Alder reaction based on photo-caged dienes. Based on a Passerini linker unit carrying an isocyano group for chain extension via P 3CR and a maleimide moiety for photo-enol conjugation enabling a modular approach for chain extension. Monodisperse oligomers are accessible in a stepwise fashion by switching between both reaction types. Employing sebacic acid as a core unit allows for the synthesis of a library of symmetric sequence-defined oligomers. Consisting of alternating P-3CR and photo-blocks with molecular weights up to 3532.16 g mol-1, the oligomers demonstrate the successful switching from P-3CR to photo-enol conjugation. In depth characterization is carried out including SEC, high resolution mass spectrometry (ESI-MS) and NMR, evidencing the monodisperse nature of the precision oligomers.

    更新日期:2018-01-16
  • 9,9'-Bifluorenylidene Cored Perylene Diimide Acceptors for As-cast Non-fullerene Organic Solar Cells: the Isomeric Effect on Optoelectronic Properties
    Chem. Eur. J. (IF 5.317) Pub Date : 2018-01-16
    Yuan Zhao, Huan Wang, Shengpeng Xia, Feng Zhou, Zhenghui Luo, Jiajia Luo, Feng He, Chuluo Yang

    Two different non-fullerene small molecule acceptors, named m-PIB and p-PIB based on 9,9'-bifluorenylidene (BF) and perylene diimide (PDI) were designed and synthesized. Four β-substituted PDIs were linked to 9,9'-bifluorenylidene in different positions. Based on the analysis of density function theory (DFT), p-PIB exhibited reduced intramolecular twisting between the perylene diimide moieties, more delocalized wave function and sufficiently wider π-electron delocalization compared to m-PIB. The absorption ability of p-PIB was enhanced due to the increased intermolecular interaction. By blending p-PIB with PTB7-Th, organic solar cells (OSCs) based on p-PIB obtained a maximum PCE of 5.95% without any treatments. Due to the improved and balanced hole and electron mobilities, the short-circuit current and fill factor of OSCs based on PTB7-Th and p-PIB were significantly increased. The AFM and TEM results revealed that the PTB7-Th: p-PIB film had favorable nanoscale phase separation and formed bicontinuous interpenetrating network.

    更新日期:2018-01-16
  • N-terminal Cu Binding Motifs Xxx-Zzz-His (ATCUN) and Xxx-His and their derivatives: Chemistry, Biology and Medicinal Applications.
    Chem. Eur. J. (IF 5.317) Pub Date : 2018-01-16
    Peter Faller, Paulina Gonzalez, Karolina Bossak, Ewelina Stefaniak, Christelle Hureau, Laurent Raibaut, Wojciech Bal

    Peptides and proteins with N-terminal amino acid sequences NH2-Xxx-His (XH) and NH2-Xxx-Zzz-His (XZH) form well established high affinity CuII-complexes. Key examples are Asp-Ala-His (in serum albumin) and Gly-His-Lys, the wound healing factor. This opens a straightforward way to add a high affinity CuII-binding site to almost any peptide or protein, by chemical or recombinant approaches. Thus, these motifs, NH2-Xxx-Zzz-His in particular, have been used to equip peptides and proteins with a multitude of functions based on the redox activity of Cu, including nuclease, protease, glycosidase, or oxygen activation, useful in anticancer or antimicrobial drugs. More recent research suggest novel biological function, mainly based on the redox inertness of CuII in XZH, like PET imaging (with 64Cu), chelation therapies (for instance in Alzheimer's disease and other types of neurodegeneration), antioxidant units, Cu transporters and activation of biological functions by strong CuII binding. This review gives an overview on the chemical properties of Cu-XH and -XZH motifs and discusses the pros and cons for the vast and different biological applications, and how they could be improved depending on the application.

    更新日期:2018-01-16
  • Hierarchy of Asymmetry at Work: Chain-Dependent Helix-to-Helix Interactions in Supramolecular Polymers
    Chem. Eur. J. (IF 5.317) Pub Date : 2018-01-16
    Sandra Díaz-Cabrera, Yeray Dorca, Joaquín Calbo, Juan Aragó, Rafael Gómez, Enrique Ortí, Luis - Sanchez

    A detailed investigation of the hierarchy of asymmetry operating in the self-assembly of achiral (1) and chiral ((S)-2 and (R)-3) 1,3,5-triphenylbenzenetricarboxamides (TPBAs) is reported. The aggregation of these TPBAs is conditioned by the point chirality at the peripheral side chains for (S)-2 and (R)-3. An efficient helix-to-helix interaction that goes further in the organization of fibrillar bundles has been experimentally detected and theoretically supported only for the achiral TPBA 1. The effective interdigitation of the achiral aliphatic side chains produces a social self-sorting to form preferentially heterochiral macromolecular aggregates

    更新日期:2018-01-16
  • New stretching method for aligning gels. Its application to the measurement Residual Chemical Shift Anisotropies (RCSAs) without the need for isotropic shift correction
    Chem. Eur. J. (IF 5.317) Pub Date : 2018-01-16
    Roberto Ricardo Gil, Erich Hellemann

    An existing gel stretching device is modified, permitting the use of organic solvents for the study of small molecules. Different from the original device, gels are stretched into 4-mm open-ended NMR tubes and then inserted into regular 5-mm NMR tubes. No open-ended tubes are inserted in the NMR probe avoiding the risk of sample leaking. It is also shown that Residual Chemical Shift Anisotropies (RCSAs) measured with the device are free of isotropic shift interferences and corrections for them are not needed during the post-acquisition data analysis. Three internal references for chemical shift were evaluated (CCl4, CBr4 and TMS), being CCl4 the most convenient one to measure RCSAs in CDCl3. RCSAs measured with the modified stretching device using CCl4 as the internal chemical shift reference were enough to determine the relative configuration of three small molecules with an excellent degree of configuration discrimination.

    更新日期:2018-01-16
  • Hierarchical N-Rich Carbon Sponge with Excellent Cycling Performance for Lithium-Sulfur Battery at High Rates
    Chem. Eur. J. (IF 5.317) Pub Date : 2018-01-15
    Cheng Wang, Mengmeng Zhen, Juan Wang, Xin Wang

    Lithium-sulfur batteries (LSBs) are receiving extensive attention because of their high theoretical energy density. However, practical applications of LSBs are still hindered by the rapid capacity decay and short cycle life, especially at high rates. Herein, a highly N-doped (~13.42 at%) hierarchical carbon sponge (HNCS) having strong chemical adsorptions toward lithium polysulfide was fabricated by a simple sol-gel route followed with carbonization. When using the HCNS as the sulfur host material in cathode and HNCS-coated separator as separator, the battery delivers an excellent cycling stability with high specific capacities of 424/326 mAh g−1, low capacity fading rates of 0.033%/0.030% per cycle after 1000 cycles under high rates of 5 and 10 C, respectively, which are superior to other reported carbonaceous materials. These impressive cycling performances indicate that such battery could promote the practical application prospect of LSBs.

    更新日期:2018-01-16
  • 更新日期:2018-01-16
  • Synthesis and X-Ray Crystallographic Characterisation of Frustum-Shaped Ligated [Cu18H16(DPPE)6]2+ and [Cu16H14(DPPA)6]2+ Nanoclusters and Studies on Their H2 Evolution Reactions
    Chem. Eur. J. (IF 5.317) Pub Date : 2018-01-16
    Jiaye Li, Howard Z. Ma, Gavin E. Reid, Alison J. Edwards, Yuning Hong, Jonathan M. White, Roger J. Mulder, Richard A. J. O'Hair
    更新日期:2018-01-16
  • Recent Advances in Micro-/Nanostructured Metal–Organic Frameworks towards Photonic and Electronic Applications
    Chem. Eur. J. (IF 5.317) Pub Date : 2018-01-16
    Xiaogang Yang, Xianqing Lin, Yong Sheng Zhao, Dongpeng Yan
    更新日期:2018-01-16
  • Brønsted Acid-Catalyzed Tandem Cyclizations of Tryptamine-Ynamides Yielding 1H-Pyrrolo[2,3-d]carbazole Derivatives
    Chem. Eur. J. (IF 5.317) Pub Date : 2018-01-16
    Yanshi Wang, Jingsheng Lin, Xiaoyu Wang, Guanghui Wang, Xinhang Zhang, Bo Yao, Yuandong Zhao, Pengfei Yu, Bin Lin, Yongxiang Liu, Maosheng Cheng
    更新日期:2018-01-16
  • Microsphere Assemblies via Phosphonate Monoester Coordination Chemistry
    Chem. Eur. J. (IF 5.317) Pub Date : 2018-01-16
    Kamila J. Bladek, Margaret E. Reid, Hirotomo Nishihara, Farid Akhtar, Benjamin S. Gelfand, George K. H. Shimizu
    更新日期:2018-01-16
  • Biomass-Derived N-Doped Carbons with Silica Supported Ultrasmall ZnO Nanoparticles: Robust Catalysts for the Green Synthesis of Benzimidazoles
    Chem. Eur. J. (IF 5.317) Pub Date : 2018-01-16
    Bo Chen, Chan Zhang, Libo Niu, Xiaozhen Shi, Huiling Zhang, Xingwang Lan, Guoyi Bai
    更新日期:2018-01-16
  • Selective Transformation of Well-defined Alkenyllithiums to Alkenylmagnesiums via Transmetalation
    Chem. Eur. J. (IF 5.317) Pub Date : 2018-01-16
    Miaomiao Zhu, Liang Liu, Yongliang Zhang, Hai-Tao Yu, Wen-Xiong Zhang, Zhenfeng Xi
    更新日期:2018-01-16
  • Molecular Wire Effects in Phenyleneethynylene Oligomers: Surprising Insights
    Chem. Eur. J. (IF 5.317) Pub Date : 2018-01-15
    Uwe Heiko Bunz, Marcel Hergert, Markus Bender, Kai Seehafer

    We report the synthesis and quenching behavior of a series of water soluble, carboxylate-carrying phenyleneethynylene oligomers - monomer to tetramer - and their polymers and investigate their quenching behavior with different test analytes (paraquat, lead salts, mercury salts, picric acid, methylpyridinium iodide) in water and compare the results to that of the conjugated polymer. We find significant but analyte-dependent enhancement effects. For monovalent quenchers only the molecular wire effect applies but for divalent quenchers multivalency effects are also important.

    更新日期:2018-01-16
  • A metallo pro-drug to target Cu(II) in the context of Alzheimer's disease
    Chem. Eur. J. (IF 5.317) Pub Date : 2018-01-15
    Amandine Conte-Daban, Vinita Ambike, Régis Guillot, Nicolas Delsuc, Clotilde Policar, Christelle Hureau

    Alzheimer's disease and oxidative stress are connected. In the present communication, we report the use of a Mn(II)-based superoxide dismutase mimic ([MnII(L)]+, 1+) as a pro-drug candidate to target Cu(II) associated events, i.e. Cu(II)-induced formation of reactive oxygen species (ROS) and modulation of the amyloid-beta (Abeta) peptide aggregation. Complex 1+ is able to remove Cu(II) from Abeta, stop ROS and prevent alteration of Abeta aggregation as would do the corresponding free ligand LH. Using 1+ instead of LH in further biological applications would have the double advantage to avoid the cell toxicity of LH and to benefit from its proved SOD-like activity.

    更新日期:2018-01-15
  • Selective Binding and Precipitation of Cesium Ions from Aqueous Solutions: A Size-Driven Supramolecular Reaction
    Chem. Eur. J. (IF 5.317) Pub Date : 2018-01-15
    Ravell Bengiat, Benny Bogoslavsky, Daniel Mandler, Joseph Almog

    The nuclear disasters of Chernobyl and Fukushima presented an urgent need for finding solutions to treatment of radioactive wastes. Among the by-products of nuclear fission is the radioactive 137Cs, which evokes an environmental hazard due to its long half-life (>30 years) and high solubility in water. In this work, a water-soluble organic ligand, readily obtained from alloxan and 1,3,5-benzenetriol, has been found to selectively bind and precipitate Cs+ ions from aqueous solutions. The special rigid structure of the ligand, which consists of a "tripodal" carbonyl base above and below an aromatic plane, contributes to the size-driven selectivity towards the large Cs+ ions and the formation of a giant, insoluble supramolecular complex. In addition to the ligand's low costs, high yields and effectiveness in precipitating Cs+ ions, the Cs-complex revealed a high endurance to continuous doses of gamma-radiation, increasing its potential to act as a precipitating agent for 137Cs.

    更新日期:2018-01-15
  • Features of Auxiliaries that Enable Native Chemical Ligation beyond Glycine and Cleavage via Radical Fragmentation
    Chem. Eur. J. (IF 5.317) Pub Date : 2018-01-15
    Simon Ferdinand Loibl, Andre Dallmann, Kathleen Hennig, Carmen Juds, Oliver Seitz

    The native chemical ligation (NCL) is an invaluable tool in the total chemical synthesis of proteins. Ligation auxiliaries overcome the requirement for cysteine. However, the reported auxiliaries remained limited to glycine-containing ligation sites and the acidic conditions applied for cleavage of the typically applied N-benzyl-type linkages promote side reactions. With the aim to improve upon both ligation and cleavage, we systematically investigated alternative ligation scaffolds that challenge the N-benzyl dogma. The study revealed that auxiliary-mediated peptide couplings are fastest when the ligation proceeds via 5-membered rather than 6-membered rings. Substituents in α-position of the amine shall be avoided. We observed, perhaps surprisingly, that additional β-substituents accelerated the ligation conferred by the β-mercaptoethyl scaffold. We also describe a potentially general means to remove ligation auxiliaries by treatment with an aqueous solution of triscarboxyethylphosphine (TCEP) and morpholine at pH 8.5. NMR analysis of a 13C-labeled auxiliary showed that cleavage most likely proceeds through a radical-triggered oxidative fragmentation. High ligation rates provided by β-substituted 2-mercaptoethyl scaffolds, their facile introduction as well as the mildness of the cleavage reaction are attractive features for protein synthesis beyond cysteine and glycine ligation sites.

    更新日期:2018-01-15
  • Copper-catalyzed regioselective cleavage of C-X bond and C-H bond: A strategy for sulfur dioxide fixation
    Chem. Eur. J. (IF 5.317) Pub Date : 2018-01-15
    Daoshan Yang, Pengfei Sun, Wei Wei, Fengjuan Liu, Hui Zhang, Hua Wang

    The first example of direct fixation of sulfur dioxide between heteroaryls and aryl halides has been developed via copper-catalyzed regioselective cleavage of C-X and C-H bonds under base-free and ligand-free conditions by using DABSO as a solid and bench-stable sulfur dioxide surrogate. This mild protocol results in double C-S bond-forming reactions from simple precursors in the absence of prefunctionalized organometallic reagents, arenediazonium salts, and iodonium salts which extends the still limited number of sulfur dioxide fixation strategies.

    更新日期:2018-01-15
  • Nickel-Catalyzed C-S Bond Formation via Decarbonylative Thioetherification of Esters, Amides and Intramolecular Recombination Fragment Coupling of Thioesters
    Chem. Eur. J. (IF 5.317) Pub Date : 2018-01-15
    Shao-Chi Lee, Hsuan-Hung Liao, Adisak Chatupheeraphat, Magnus Rueping

    A nickel catalyzed cross-coupling protocol for the straightforward C-S bond formation has been developed. Various mercaptans and a wide range of ester and amide substrates bearing various substituents were tolerated in this process which afforded products in good to excellent yields. Furthermore, an intramolecular protocol for the synthesis of thioethers starting from thioesters has been developed. The utility of this protocol has been demonstrated in the synthesis of benzothiophene on the bench top.

    更新日期:2018-01-15
  • A gold(III) pincer ligand scaffold for the synthesis of binuclear and bioconjugated complexes: synthesis and anticancer potential.
    Chem. Eur. J. (IF 5.317) Pub Date : 2018-01-15
    Bertrand Benoît, Maria A. O'Connell, Zöe A. E. Waller, Manfred Bochmann

    Cyclometalated (C^N^C)Au(III) complexes bearing functionalized N-heterocyclic carbene (NHC) ligands provide a high-yielding, modular route to bioconjugated and binuclear complexes. That methodology has been applied to the synthesis of bioconjugated complexes presenting biotin and 17α-ethynylestradiol vectors, as well as to the synthesis of bimetallic Au(III)/Au(I) complexes. The in vitro antiproliferative activities of these compounds against various cancer cells lines depend on the linker length, with the longer linker being the most potent. The estradiol conjugate AuC6Estra proved to be more toxic against the estrogen receptors positive (ER+) cancer cells than against the ER- cancer cells and non-cancer cells. The bimetallic complex AuC6Au was more selective for breast cancer cells with respect to a healthy cell standard than the monometallic complex AuNHC. The metal uptake study on cells expressing or not biotin and estrogen receptors revealed an improved and targeted delivery of gold for both the bioconjugated complexes AuC6Biot and AuC6Estra compared to the non-vectorised analogue AuNHC. The investigations of the interaction of the bioconjugates and bimetallic complexes with human telomeric G-quadruplex DNA using FRET-melting techniques revealed a reduced ability to stabilize this DNA structure with respect to the non-vectorised analogue AuNHC.

    更新日期:2018-01-15
  • Heterobimetallic complexes for theranostic applications
    Chem. Eur. J. (IF 5.317) Pub Date : 2018-01-15
    M. Concepción Gimeno, Vanesa Fernández-Moreira

    The design of more efficient anticancer drugs requires a deeper understanding of their biodistribution and mechanism of action. Cell imaging agents could help to gain insight into biological processes and, consequently, the best strategy for attaining suitable scaffolds in which both, biological and imaging properties are maximized. A new concept arises in this field which is the combination of two metal fragments as collaborative partners to provide the precise emissive properties to visualize the cell as well as the optimum cytotoxic activity to build more potent and selective chemotherapeutic agents.

    更新日期:2018-01-15
  • Isomerically Pure Star-Shaped Triphenylene-Perylene Hybrids Involving Highly Extended π Conjugation
    Chem. Eur. J. (IF 5.317) Pub Date : 2018-01-15
    Edurne Nuin, Vicent Lloret, Konstantin Amsharov, Frank Hauke, Gonzalo Abellán, Andreas Hirsch

    The synthesis and characterization of a new type of a highly conjugated heterocyclic π-chromophore, consisting of a central triphenylene core fused with three perylene-monoimide units (star-shaped molecule) is described. By judicious bay-functionalization with tert-butylphenoxy substituents, aggregation was completely prevented in common organic solvents, allowing for a straightforward purification and, for the very first time, the complete separation of the constitutional isomers by HPLC. Both isomers can be easily distinguished by means of several conventional spectroscopic techniques. Furthermore, we have illustrated the absence of supramolecular aggregates and enhanced processability by noncovalent functionalization of graphene substrates, showing an outstanding homogeneity and observing a different doping behavior in both isomers, being possible to distinguished by Raman spectroscopy.

    更新日期:2018-01-15
  • K3Li3Gd7(BO3)9: A New Gadolinium-Rich Orthoborate for Cryogenic Magnetic Cooling
    Chem. Eur. J. (IF 5.317) Pub Date : 2018-01-15
    Mingjun Xia, Shipeng Shen, Jun Lu, Young Sun, R.K. Li

    Magnetic cooling technology based on magnetocaloric effect (MCE) has attracted great interest in obtaining extreme low temperature, e. g. for space exploration. Here we grew a new gadolinium-rich orthoborate K3Li3Gd7(BO3)9 (1) as a promising cryogenic magnetic coolant. It exhibits complicated three dimensional framework constructed from BO3 groups and gadolinium-oxygen chains. The Gd-O chain consists of two types of clusters of Gd3O20 and Gd3O19 interconncetion by Gd(4)O8 polyhydron. Thanks to its high gadolinium concentration, a large -Sm for 1 was obtained as 56.6 J kg-1 K-1 at 2 K and H = 7 T, much larger than that of commercial benchmark Gd3Ga5O12 (GGG) crystal (38.4 J kg-1 K-1), suggesting it to be an excellent MCE material.

    更新日期:2018-01-15
  • Syntheses of Amino-Substituted Iridabenzofurans and Subsequent Selective N-Functionalisation
    Chem. Eur. J. (IF 5.317) Pub Date : 2018-01-15
    Benjamin J. Frogley, Lakshika C. Perera, L. James Wright
    更新日期:2018-01-15
  • Syntheses of Amino-Substituted Iridabenzofurans and Subsequent Selective N-Functionalisation
    Chem. Eur. J. (IF 5.317) Pub Date : 2018-01-15
    Benjamin J. Frogley, Lakshika C. Perera, L. James Wright
    更新日期:2018-01-15
  • Re(bpy)(CO)3Cl Immobilized on Bipyridine-Periodic Mesoporous Organosilica for Photocatalytic CO2 reduction
    Chem. Eur. J. (IF 5.317) Pub Date : 2018-01-14
    Minoru Waki, Ken-ichi Yamanaka, Soichi Shirai, Yoshifumi Maegawa, Yasutomo Goto, Yuri Yamada, Shinji Inagaki

    This paper describes the physicochemical properties of a rhenium (Re) complex [Re(bpy)(CO)3Cl] immobilized on a bipyridine-periodic mesoporous organosilica (BPy-PMO) acting as a solid support. The immobilized Re complex generated a metal-to-ligand charge transfer absorption band at 400 nm. This wavelength is longer than that exhibited by Re(bpy)(CO)3Cl in the polar solvent acetonitrile (371 nm) and is almost equal to that in nonpolar toluene (403 nm). The photocatalytic activity of this heterogeneous Re complex was lower than that of a homogeneous Re complex due to the reduced phosphorescence lifetime resulting from immobilization. However, the catalytic activity was enhanced by the co-immobilization of the ruthenium (Ru) photosensitizer [Ru(bpy)3]2+ on the PMO pore surfaces. Quantum chemical calculations suggest that electron transfer between the Ru and Re complexes occurs via interactions between the molecular orbitals in the pore walls. These results should have applications to the design of efficient heterogeneous CO2 reduction photocatalysis systems.

    更新日期:2018-01-15
  • Identification of the minimal glycotope of Streptococcus pneumoniae 7F capsular polysaccharide using synthetic oligosaccharides
    Chem. Eur. J. (IF 5.317) Pub Date : 2018-01-14
    Petra Menova, Mauro Sella, Katrin Sellrie, Claney Pereira, Peter H. Seeberger

    Streptococcus pneumoniae causes life-threatening diseases including meningitis, pneumonia and sepsis. Existing glycoconjugate vaccines based on purified capsular polysaccharides are widely used and help to prevent millions of deaths every year. Here, we report total synthesis of oligosaccharides resembling portions of the S. pneumoniae serotype 7F (ST7F) capsular polysaccharide repeating unit. To define minimal glycan epitopes, glycan microarrays containing the synthetic oligosaccharides were used to screen human reference serum and revealed that both side chains of the ST7F play a key role in antigen recognition. The identification of protective minimal epitopes is vital to design efficient semi- and fully-synthetic glycoconjugate vaccines.

    更新日期:2018-01-15
  • Cobaltocenylidene, a mesoionic metalloceno carbene, stabilized in a gold(III) complex
    Chem. Eur. J. (IF 5.317) Pub Date : 2018-01-12
    Benno Bildstein, Stefan Vanicek, Maren Podewitz, Christopher Hassenrück, Michael Pittracher, Holger Kopacka, Klaus Wurst, Thomas Müller, Klaus R. Liedl, Rainer F. Winter

    Oxidative addition of cobaltoceniumdiazonium bis(hexafluoridophosphate) with (pseudo)halide aurates afforded gold(III) complexes containing zwitterionic cobaltoceniumide as a ligand. Its selenium derivative, cobaltoceniumselenolate, was obtained by an electrophilic aromatic substitution reaction of iodocobaltocenium iodide with Na2Se. Spectroscopic and structural data in combination with DFT calculations show that this cobaltocenylidene species is a mesoionic carbene quite different from common N-heterocyclic carbenes. Its ligand properties (TEP, singlet-triplet gap, nucleophilicity, π-acidity, Brønsted basicity) are in part comparable to those of cyclic (amino)(alkyl/aryl)carbenes. Electrochemistry shows that the mesoionic cobaltoceniumides are more electron-rich than their parent ferrocenes. The reversible reduction of the tricyanido gold complex appears 50 mV negative of the cobaltocenium/cobaltocene couple while that of the selenide derivative is shifted cathodically by 550 mV.

    更新日期:2018-01-12
  • Fusing Planar Group to a pi-Bowl: Electronic and Molecular Structure, Aromaticity and Solid State Packing of Naphthocorannulene and its Anions
    Chem. Eur. J. (IF 5.317) Pub Date : 2018-01-12
    Zheng Zhou, Sarah Spisak, Qi Xu, Andrey Rogachev, Zheng Wei, Massimo Marcaccio, Marina A. Petrukhina

    Molecular and electronic structure, reduction and coordination abilities of a PAH having a planar naphtho-group fused to the corannulene bowl have been investigated for the first time using a combination of theoretical and experimental tools. A direct comparison of naphtho[2,3-a]corannulene (C28H14, 1) with parent corannulene (C20H10, 2) revealed the effect of framework topology change on electronic properties and aromaticity of 1. Two reversible one-electron reduction processes with the formal reduction potentials at -2.30 V and -2.77 V vs. Fc+/0 were detected by CV measurements, demonstrating accessibility of the corresponding mono- and dianionic states of 1. The products of the mono- and doubly-reduced napththocorannulene were prepared using chemical reduction with Group 1 metals and isolated as sodium and rubidium salts. Their X-ray diffraction study revealed the formation of "naked" mono- and dianions crystallized as solvent-separated ion products with one or two sodium ions as [Na+(18-crown-6)(THF)2][C28H14-] and [Na+(18-crown-6)(THF)2]2[C28H142-] (3·THF and 4·THF, respectively). The dianion of 1 was also isolated as a contact-ion complex with two rubidium countercations, [{Rb+(18-crown-6)}2(C28H142-)] (5·THF). The structural consequences of adding one and two electrons to the carbon framework of 1 are compared for 3, 4 and 5. Changes in aromaticity and charge distribution stemming from the stepwise electron acquisition are discussed based on DFT computational study.

    更新日期:2018-01-12
  • Deracemization of a Racemic Compound Using Tailor-Made Additives
    Chem. Eur. J. (IF 5.317) Pub Date : 2018-01-12
    Ton Engwerda, Pim van Schayik, Henjo Jagtenberg, Hugo Meekes, Floris P. J. T. Rutjes, Elias Vlieg

    Viedma ripening is a process that combines abrasive grinding of a slurry of crystals with solution phase racemization, resulting in solid phase deracemization. One of the major disadvantages of Viedma ripening is that the desired compound needs to crystallize as a racemic conglomerate, accounting for only 5-10% of all chiral molecules. In this work, we show that use of a chiral additive causes deracemization under conditions in which the compound normally crystallizes as a racemic compound. Although this concerns a single example, it is envisioned that through this new approach the scope of Viedma ripening can be significantly expanded.

    更新日期:2018-01-12
  • Electrophile-Directed Diastereoselective Oxonitrile Alkylations
    Chem. Eur. J. (IF 5.317) Pub Date : 2018-01-12
    Fraser Fergusson Fleming, Sergiy Chepyshev, Bhaskar Reddy Pitta, Saidi Reddy Vangala, J. Armando Lujan-Montelongo, Omar Steward

    Diastereoselective alkylation of prochiral oxonitrile dianions with secondary alkyl halides efficiently installs two contiguous stereogenic centers. The confluence of nucleophilic trajectory and the electrophile chirality causes distinct steric differences that allow efficient discrimination for one of the six possible conformers. Numerous oxonitrile-derived dianions efficiently displace secondary alkyl halides propagating the electrophile chirality to efficiently install two contiguous tertiary centers. The prevalence of chiral, secondary electrophiles makes the interdigitated alkylation of chiral electrophiles a particularly attractive route because the resulting oxonitriles are readily transformed into bioactive heterocycles.

    更新日期:2018-01-12
Some contents have been Reproduced with permission of the American Chemical Society.
Some contents have been Reproduced by permission of The Royal Society of Chemistry.
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