Angewandte Chemie International Edition
Copyright © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Upcoming Hot Papers
Hot Papers are chosen by the Editors for their importance in a rapidly evolving field of high current interest. Many of the "Very Important Papers" (VIPs) would certainly qualify to be included here, but such a duplication is avoided.
Hot-Electron-Transfer Enhancement for the Efficient Energy Conversion of Visible Light
Sungju Yu, Yong Hwa Kim, Su Young Lee, Hyeon Don Song and Prof. Jongheop Yi
A core–shell nanostructure with three distinct components enables the efficient production of H2 from water and significant electron harvesting under visible-light irradiation because of enhanced hot-electron injection, the formation of a Schottky junction, and high-performance electron filtering. The electron transfer pathway is elucidated through steady-state and time-resolved photoluminescence spectroscopy.
Anion–π and Cation–π Interactions on the Same Surface
Dr. Kaori Fujisawa, Dr. César Beuchat, Marie Humbert-Droz, Dr. Adam Wilson, Prof. Tomasz A. Wesolowski, Dr. Jiri Mareda, Dr. Naomi Sakai and Prof. Stefan Matile
It takes two to tango: Theoretical and experimental evidence shows that anion–π and cation–π interactions can occur simultaneously on the same aromatic surface. The resulting ion pair–π interactions shift the absorption of push–pull chromophores to the red.
Formic Acid Dehydrogenation
Hydrogen from Formic Acid through Its Selective Disproportionation over Sodium Germanate—A Non-Transition-Metal Catalysis System
Dr. Ruth I. J. Amos, Dr. Falk Heinroth, Dr. Bun Chan, Sisi Zheng, Prof. Brian S. Haynes, Prof. Christopher J. Easton, Prof. Anthony F. Masters, Prof. Leo Radom and Prof. Thomas Maschmeyer
From models to reality: A robust catalyst for the selective dehydrogenation of formic acid to liberate hydrogen gas has been designed computationally, and also demonstrated experimentally. This catalyst represents an important step towards the use of renewable formic acid as a hydrogen-storage and transport vector in fuel and energy applications.
The optimally performing Fischer–Tropsch catalyst
Ivo A. W. Filot, Prof. Dr. Rutger A. van Santen and Prof. Dr. Emiel J. M. Hensen
State-of-the-art quantum-chemical reaction data were used in a microkinetics simulations study to elucidate the different fundamental kinetic regimes underlying Fischer–Tropsch activity and selectivity. Based on the nature of the rate-controlling steps, three regimes were identified: I) monomer formation, II) chain-growth termination, and III) water formation.
Dialdehydes Lead to Exceptionally Fast Bioconjugations at Neutral pH by Virtue of a Cyclic Intermediate
Pascal Schmidt, Dr. Linna Zhou, Kiril Tishinov, Kaspar Zimmermann and Prof. Dr. Dennis Gillingham
For aldehydes, 1+1=500: Dialdehydes react with O-alkylhydroxylamines at rates of 500 M−1 s−1 at neutral pH values in the absence of catalysts. The key to these conjugations is an unusually stable cyclic intermediate, which ultimately undergoes dehydration to yield an oxime. The application of this method in bioconjugations and a mechanistic interpretation are outlined.
Ruthenium Pincer Complexes
Direct Catalytic Olefination of Alcohols with Sulfones
Dr. Dipankar Srimani, Dr. Gregory Leitus, Yehoshoa Ben-David and Prof. Dr. David Milstein
The one-step olefination of alcohols with sulfones for the direct synthesis of terminal and internal olefins is catalyzed by ruthenium pincer complexes. Furthermore, performing the reaction with dimethyl sulfone under mild hydrogen pressure provides a one-step method for the replacement of alcohol hydroxy groups by methyl groups.
Super-Resolution Imaging of Plasma Membrane Glycans
Sebastian Letschert, Dr. Antonia Göhler, Christian Franke, Nadja Bertleff-Zieschang, Elisabeth Memmel, Priv.-Doz. Dr. Sören Doose, Prof. Dr. Jürgen Seibel and Prof. Dr. Markus Sauer
Glycan spotting: Click chemistry and super-resolution imaging was used to visualize and quantify ManNAc-, GalNAc-, and O-GlcNAc-modified glycans in the plasma membrane of mammalian cells with single-molecule sensitivity (see image). The data demonstrate that a single cell may easily contain more than ten million glycans, which are homogeneously distributed and do not form clusters or nanodomains.
Controlling Selectivity in the Chlorine Evolution Reaction over RuO2-Based Catalysts
Kai S. Exner, Josef Anton, Timo Jacob and Herbert Over
Being selective: The selectivity in the industrially important Chlor-Alkali process has been elucidated on the microscopic level through a combination of DFT calculations and volcano plots. A single layer of TiO2(110) grown on RuO2(110) increases the selectivity between the chlorine and oxygen evolution reactions (CER and OER, respectively) by several orders of magnitude, while keeping the high activity for CER practically constant.
Aldehyde-Assisted Ruthenium(II)-Catalyzed CH Oxygenations
M. Sc. Fanzhi Yang, Karsten Rauch, M. Sc. Katharina Kettelhoit and Prof. Dr. Lutz Ackermann
The weakest link: Challenging aryl CH oxygenations with very weakly coordinating aldehydes proceed chemoselectively in the presence of versatile ruthenium(II) catalysts under mild reaction conditions. This transformation features an ample substrate scope and excellent positional selectivity.
Ruthenium-Catalyzed Reductive Methylation of Imines Using Carbon Dioxide and Molecular Hydrogen
Dr. Kassem Beydoun, Ghazi Ghattas, Katharina Thenert, Prof. Dr. Jürgen Klankermayer and Prof. Dr. Walter Leitner
Tertiary N-methyl amines were obtained in good to excellent yields through the reductive methylation of imines (used as such or formed in situ from amines and aldehydes, see scheme). Apart from the well-defined [Ru(triphos)(tmm)] catalyst, CO2 was used as C1 source, and H2 as reducing agent. This method enabled the preparation of the antifungal agent butenafine in one step with no apparent waste, thus increasing the atom efficiency of its synthesis.
Vanadium-Catalyzed Solvent-Free Synthesis of Quaternary α-Trifluoromethyl Nitriles by Electrophilic Trifluoromethylation
Natalja Früh and Prof. Dr. Antonio Togni
Not only copper! Oxovanadium(IV) complexes catalyze the trifluoromethylation of silyl ketene imines with hypervalent iodine reagents to form quaternary α-trifluoromethyl nitriles under solvent-free conditions. The products, formed in up to 93 % yield, may be further transformed into useful synthetic building blocks for organofluorine chemistry.
Unexpected Synergy between Magnetic Iron Chains and Stacked B6 Rings in Nb6Fe1−xIr6+xB8
Dipl.-Chem. Mohammed Mbarki, M.Sc. Rachid St. Touzani and Priv.-Doz. Dr. Boniface P. T. Fokwa
A mutual dependency between ferromagnetic iron chains and stacked B6 rings (see picture) is found in the new ferromagnetic material, Nb6Fe1−xIr6+xB8 (TC=350 K) by combining experiment and density functional theory (DFT). The strong magnetic Fe–Fe interactions found in the iron chains induce an unexpected strengthening of the B–B interactions in the B6 rings.
Planet–Satellite Nanostructures Made To Order by RAFT Star Polymers
Christian Rossner and Prof. Dr. Philipp Vana
Small world: Gold nanoparticles decorated with RAFT star polymers of different molecular weights can be used as scaffolds for the attachment of functional units at defined distances from the central core. This approach can result in planet–satellite nanostructures.
Phosphonated Near-Infrared Fluorophores for Biomedical Imaging of Bone
Dr. Hoon Hyun, Dr. Hideyuki Wada, Dr. Kai Bao, Dr. Julien Gravier, Dr. Yogesh Yadav, Dr. Matt Laramie, Dr. Maged Henary, Dr. John V. Frangioni and Dr. Hak Soo Choi
Bifunctional molecules with high-affinity binding to bone minerals as well as bright near-infrared fluorescence were obtained by attaching low-affinity pendant groups to the non-delocalized backbone of polymethines. These agents enable the noninvasive assessment of bone development over the course of weeks in living animals.
Harvesting Solar Light with Crystalline Carbon Nitrides for Efficient Photocatalytic Hydrogen Evolution
Dr. Manas K. Bhunia, Dr. Kazuo Yamauchi and Prof. Kazuhiro Takanabe
Trying out triazine: Crystalline carbon nitrides are synthesized by employing supramolecular aggregation and ionic melt polycondensation. The triazine-based carbon nitride exhibits the excellent hydrogen evolution reaction rate at visible light and apparent quantum yield reaches approximately 7 % at 420 nm.
Oxygen Reduction Reaction
Oxygen Reduction Reaction in a Droplet on Graphite: Direct Evidence that the Edge is More Active than the Basal Plane
Anli Shen, Yuqin Zou, Prof. Qiang Wang, Prof. Robert A. W. Dryfe, Prof. Xiaobing Huang, Shuo Dou, Prof. Liming Dai and Prof. Shuangyin Wang
On the cutting edge: To study the oxygen reduction reaction (ORR), an air-saturated electrolyte solution droplet with a diameter of approximately 15 μm was deposited at a specified position on the edge (see picture) or on the basal plane of highly oriented pyrolytic graphite. Electrochemical measurements suggest that the edge sites are catalytically more active than basal-plane sites towards the ORR.
One-Pot Enzymatic Synthesis of Merochlorin A and B
Dr. Robin Teufel, Dr. Leonard Kaysser, Matthew T. Villaume, Dr. Stefan Diethelm, Mary K. Carbullido, Prof. Dr. Phil S. Baran and Prof. Dr. Bradley S. Moore
Assembly line: The biosynthetic pathway to merochlorins A and B was fully reconstituted in vitro and involves only four enzymes. The assembly route starts from the common metabolites dimethylallyl diphosphate, geranyl diphosphate, and malonyl CoA, which are transformed into an unusual polyketide-terpene hybrid intermediate. Oxidative chlorination and terpene cyclization complete the remarkably short pathway to the merochlorins.
Metal-Free Hydrogenation Catalyzed by an Air-Stable Borane: Use of Solvent as a Frustrated Lewis Base
Daniel J. Scott, Dr. Matthew J. Fuchter and Dr. Andrew E. Ashley
Reduced frustration: THF solutions of the boranes B(C6Cl5)x(C6F5)3−x (x=0–3) activate H2 and effect catalytic hydrogenation of unsaturated substrates through a mechanism in which the solvent acts as a “frustrated” Lewis base. In particular, weakly basic substrates, such as N-tosyl imines, and pyrrole and furan derivatives (a new substrate family for frustrated Lewis pair (FLP) hydrogenations), are reduced under relatively mild conditions using air-stable B(C6Cl5)(C6F5)2.
Visualizing an Ultra-Weak Protein–Protein Interaction in Phosphorylation Signaling
Qiong Xing, Peng Huang, Ju Yang, Jian-Qiang Sun, Dr. Zhou Gong, Dr. Xu Dong, Dr. Da-Chuan Guo, Shao-Min Chen, Yu-Hong Yang, Yan Wang, Prof. Ming-Hui Yang, Dr. Ming Yi, Prof. Yi-Ming Ding, Prof. Mai-Li Liu, Prof. Wei-Ping Zhang and Prof. Chun Tang
Phosphorylation signaling takes place between two bacterial enzymes EI and EIIAGlc that has a binding affinity of only 25 mM (see picture). The structure of the ultra-weak fleeting complex was determined to atomic resolution by novel paramagnetic NMR technique, and it shows that electrostatic repulsion largely accounts for the low affinity between the two proteins.
Temporary Protecting Groups
Carbon Dioxide as a Protecting Group: Highly Efficient and Selective Catalytic Access to Cyclic cis-Diol Scaffolds
Victor Laserna, Dr. Giulia Fiorani, Dr. Christopher J. Whiteoak, Dr. Eddy Martin, Eduardo Escudero-Adán and Prof. Dr. Arjan W. Kleij
Protective Carbon: Aminotriphenolate complexes of FeIII and AlIII are highly efficient and selective catalysts for the conversion of functional (multi)cyclic oxiranes into the corresponding cis carbonates. Basic hydrolysis of the latter provides a series of useful cyclic cis-diol scaffolds in high yield. In this process, CO2 acts as both a temporary protecting group and an oxygen donor.
N-Heterocyclic Carbene Catalyzed Formal [3+2] Annulation Reaction of Enals: An Efficient Enantioselective Access to Spiro-Heterocycles
Dr. Chang Guo, Michael Schedler, Constantin G. Daniliuc and Prof. Dr. Frank Glorius
Ring, ring: A highly enantioselective formal [3+2] annulation of α,β-unsaturated aldehydes with azaaurones or aurone is catalyzed by an N-heterocyclic carbene (NHC) and generates spiroheterocycles. The protocol represents a unique NHC activation-based approach to access spiro-heterocyclic derivatives bearing a quaternary stereogenic center with high optical purity.
Mononuclear and Terminal Zirconium and Hafnium Methylidenes
Dr. Masahiro Kamitani, Balazs Pinter, Dr. Chun-Hsing Chen, Dr. Maren Pink and Prof. Dr. Daniel J. Mindiola
The photolysis of zirconium or hafnium complexes with one aryloxide and two methyl ligands induces α-hydrogen abstraction and results in the formation of mononuclear complexes with terminal methylidene ligands. These unique systems have been fully characterized, including the determination of the solid-state structure in the case of the zirconium complex.
A New Class of Organocatalysts: Sulfenate Anions
Mengnan Zhang, Tiezheng Jia, Haolin Yin, Patrick J. Carroll, Prof. Eric J. Schelter and Prof. Patrick J. Walsh
Sulfenates take center stage: Sulfenate anions are known as highly reactive species in the organic arena. Now they premiere as organocatalysts: A sulfoxide/sulfenate (1–10 mol %) promotes the transformation of benzyl halides into trans-stilbenes under basic conditions (up to 99 % yield). CPME=cyclopentyl methyl ether.
Iron-Catalyzed C(sp2)H Alkylation of Carboxamides with Primary Electrophiles
Brendan M. Monks, Erin R. Fruchey and Prof. Silas P. Cook
The direct ortho alkylation of 8-aminoquinoline-based aryl amides was achieved with primary alkyl bromides in high yields in the presence of an iron catalyst, 1,2-bis(diphenylphosphino)ethane (dppe), and PhMgBr in 2-MeTHF.
Sulfuryl-Based Click Chemistry
SuFEx-Based Synthesis of Polysulfates
Jiajia Dong, K. Barry Sharpless, Luke Kwisnek, James S. Oakdale and Valery V. Fokin
High-molecular-weight polysulfates are readily formed from aromatic bis(silyl ethers) and bis(fluorosulfates) in the presence of a base catalyst. The polymers were obtained in nearly quantitative yield under neat conditions, they are more resistant to chemical degradation than their polycarbonate analogues and exhibit excellent mechanical, optical, and oxygen-barrier properties. BPA=bisphenol A.
Sequential Gene Silencing Using Wavelength-Selective Caged Morpholino Oligonucleotides
Dr. Sayumi Yamazoe, Qingyang Liu, Dr. Lindsey E. McQuade, Prof. Dr. Alexander Deiters and Prof. Dr. James K. Chen
Not on the same wavelength: Sequential gene silencing in zebrafish embryos has been achieved using caged morpholino oligonucleotides with spectrally distinct triggers (see picture). These optochemical tools have allowed the examination of genetic interactions that dynamically regulate mesoderm patterning.
Ultra-Low-Field NMR Relaxation and Diffusion Measurements Using an Optical Magnetometer
Paul J. Ganssle, Hyun D. Shin, Dr. Scott J. Seltzer, Dr. Vikram S. Bajaj, Dr. Micah P. Ledbetter, Prof. Dmitry Budker, Dr. Svenja Knappe, Dr. John Kitching and Prof. Alexander Pines
Portable NMR: NMR relaxometry and diffusometry can be highly effective in applications where high-resolution NMR spectroscopy is unnecessary or impractical, as is the case in the emerging field of portable chemical characterization. A proof-of-concept experiment is presented demonstrating the use of high-sensitivity optical magnetometers as detectors for ultra-low-field NMR relaxation and diffusion measurements.
Visualizing the Golgi Apparatus
Super-Resolution Imaging of the Golgi in Live Cells with a Bioorthogonal Ceramide Probe
Dr. Roman S. Erdmann, Dr. Hideo Takakura, Alexander D. Thompson, Felix Rivera-Molina, Dr. Edward S. Allgeyer, Prof. Dr. Joerg Bewersdorf, Prof. Dr. Derek Toomre and Prof. Dr. Alanna Schepartz
Seeing is believing: A new lipid-based strategy to visualize Golgi structure and dynamics at super-resolution in live cells is presented. The method is based on two reagents: a trans-cyclooctene-containing ceramide lipid and a highly reactive, tetrazine-tagged, near-IR dye. These reagents assemble to give Cer-SiR, which enables prolonged live-cell imaging of the Golgi apparatus by 3D confocal and stimulated emission depletion (STED) microscopy.
Tumor-Targeting of EGFR Inhibitors by Hypoxia-Mediated Activation
M. Sc. Claudia Karnthaler-Benbakka, M. Sc. Diana Groza, Mag. Kushtrim Kryeziu, Dr. Verena Pichler, Dipl.-Ing. Alexander Roller, Prof. Dr. Walter Berger, Dr. Petra Heffeter and Dr. Christian R. Kowol
Targeted attack: Receptor tyrosine-kinase inhibitors are essential cancer therapeutics, but therapy is limited by strong adverse effects. A tumor-targeting strategy for epidermal growth factor receptor (EGFR) inhibitors through hypoxia-mediated activation has now been developed. The CoIII-based prodrug showed selective hypoxic activation with release of the active EGFR inhibitor and potent anticancer activity in human xenograft models.
Paenilamicin: Structure and Biosynthesis of a Hybrid Nonribosomal Peptide/Polyketide Antibiotic from the Bee Pathogen Paenibacillus larvae
Sebastian Müller, Dr. Eva Garcia-Gonzalez, Dr. Andi Mainz, Gillian Hertlein, Nina C. Heid, Eva Mösker, Hans van den Elst, Prof. Dr. Herman S. Overkleeft, Priv.-Doz. Dr. Elke Genersch and Prof.Dr. Roderich D. Süssmuth
The bee all and end all? American Foulbrood, which is caused by the bacterium Paenibacillus larvae, is a widespread and devastating disease of the honey bee brood. Through the isolation and structure elucidation of the antibacterial and antifungal paenilamicins, we deciphered a fascinating nonribosomal biosynthesis. The study of the secondary metabolites of P. larvae sheds light on the virulence mechanisms of this serious disease.
Chemical Vapor Detection Using a Reconstituted Insect Olfactory Receptor Complex
Dr. Koji Sato and Prof. Shoji Takeuchi
Gas sensing by ion channels: Insect olfactory receptors consist of ligand-gated ion channels. Using cell assembly and extracellular field potential recording techniques, olfactory receptor-expressing cell spheroids were formed (see picture). The spheroids electrically responded to chemical vapors at biologically relevant concentrations.
Mapping Polyamide–DNA Interactions in Human Cells Reveals a New Design Strategy for Effective Targeting of Genomic Sites
Graham S. Erwin, Devesh Bhimsaria, Asuka Eguchi and Prof. Aseem Z. Ansari
Siteseeing: The first mapping of pyrrole/imidazole polyamides across several genomic sites with distinct chromatin characteristics in live cells is reported. Bioinformatic analysis of the data shows that clustered binding sites best predict binding in cells. The results point to a new design principle to deploy polyamides and perhaps other synthetic molecules to effectively target desired genomic sites in vivo.
Cell-Penetrating, Dimeric α-Helical Peptides: Nanomolar Inhibitors of HIV-1 Transcription
Sangmok Jang, Dr. Soonsil Hyun, Seoyeon Kim, Seonju Lee, Prof. Dr. Im-Soon Lee, Prof. Dr. Masanori Baba, Prof. Dr. Yan Lee and Prof. Dr. Jaehoon Yu
Going viral: Nearly quantitative penetration into eukaryotic cells and effective inhibition of the elongation of the short hairpin RNA transcript TAR at low nanomolar concentrations has been achieved by using dimeric α-helical peptide bundles based on leucine (L) and lysine (K). The effective inhibition of HIV-1 replication strongly suggests that these dimers have strong potential as anti-HIV-1 drugs.
Local Transient Unfolding of Native State PAI-1 Associated with Serpin Metastability
Dr. Morten B. Trelle, Dr. Jeppe B. Madsen, Prof. Peter A. Andreasen and Prof. Dr. Thomas J. D. Jørgensen
Serpin proteins are prone to pathological conformational change, for instance by conversion to an inactive, so-called latent form. Using advanced hydrogen/deuterium-exchange mass spectrometry transient unfolding of a serpin is shown under native condition. Based on these observations, a new mechanism (see picture) is proposed.
Perovskite Solar Cells
A Fast Deposition-Crystallization Procedure for Highly Efficient Lead Iodide Perovskite Thin-Film Solar Cells
Manda Xiao, Dr. Fuzhi Huang, Wenchao Huang, Yasmina Dkhissi, Dr. Ye Zhu, Prof. Dr. Joanne Etheridge, Dr. Angus Gray-Weale, Prof. Dr. Udo Bach, Prof. Dr. Yi-Bing Cheng and Prof. Dr. Leone Spiccia
Fast and thin: Flat, uniform thin films of CH3NH3PbI3 perovskites have been produced by a fast, one-step procedure involving spin-coating of a DMF solution of CH3NH3PbI3 and immediate exposure to chlorobenzene to induce crystallization. Planar heterojunction solar cells made with these films gave a maximum power conversion efficiency of 16.2 %.
Unprecedented Role of Hydronaphthoquinone Tautomers in Biosynthesis
Dr. Syed Masood Husain, Dr. Michael A. Schätzle, Dr. Steffen Lüdeke and Prof. Dr. Michael Müller
Breaking the cycle: In studies on the reduction of 2-hydroxynaphthoquinones to the stable 1,4-diketo tautomeric form of hydronaphthoquinones and their further reduction by fungal tetrahydroxynaphthalene reductase, diketo tautomers emerge as true intermediates in biosynthesis. Their formation breaks the (redox) cycle, thus protecting the cell from stress-related redox events.
Coordination-Driven In Situ Self-Assembly Strategy for the Preparation of Metal–Organic-Framework Hybrid Membranes
Rong Zhang, Prof. Shulan Ji, Dr. Naixin Wang, Lin Wang, Prof. Guojun Zhang and Jian-Rong Li
Mopping up the mess: A hybrid membrane composed of the metal–organic framework (MOF) ZIF-8 and poly(sodium 4-styrenesulfonate) was prepared by coordination-driven in situ self-assembly method. The MOF particles were well-dispersed in the polymer in the resulting stable membrane (see picture), which showed excellent performance in the nanofiltration and separation of dyes from water.
“CLASSIC NMR”: An In-Situ NMR Strategy for Mapping the Time-Evolution of Crystallization Processes by Combined Liquid-State and Solid-State Measurements
Dr. Colan E. Hughes, P. Andrew Williams and Prof. Kenneth D. M. Harris
Killing two birds with one stone: A new in-situ NMR strategy (termed CLASSIC NMR) for mapping the evolution of crystallization processes is reported, involving simultaneous measurement of both liquid-state and solid-state NMR spectra as a function of time. This combined strategy allows complementary information to be obtained on the evolution of the solid phase during the crystallization process as well as the corresponding changes in the solution phase.