bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Squaramide‐Catalyzed 1,3‐Dipolar Cycloaddition of Nitroalkenes with N‐2,2,2‐Trifluoroethylisatin Ketimines: An Approach for the Synthesis of 5′‐Trifluoromethyl‐spiro[pyrrolidin‐3,2′‐oxindoles]
Authors: Sun Quantao , Li Xiaoyuan , Su Jinhuan , Zhao Long , Ma Mingxia , Zhu Yuanyuan , Zhao Yanyan , Zhu Ranran , Yan Wenjin , Wang Kairong , Wang Rui 
Published: October 2015

AbstractA Cinchona alkaloid‐derived squaramide‐catalyzed asymmetric cycloaddition of trfluoromethyl‐containing azomethine ylides with β‐nitroalkenes was realized under mild conditions. A series of biologically important 5′‐trifluoromethyl‐ spiro[pyrrolidin‐3,2′‐oxindoles] was synthesized efficiently by this process in excellent yields, enantioseletivities and diastereoselectivities.magnified image
Hemin‐Catalyzed, Cyclodextrin‐Assisted Insertion of Carbenoids into NH Bonds
Authors: Xu Xiaofei , Li Chang , Tao Zhihao , Pan Yuanjiang 
Published: October 2015

AbstractAn aqueous hemin‐catalyzed, cyclodextrin‐assisted NH insertion reaction of α‐diazo ester into aromatic amines is described here. This aqueous catalytic system showed good compatibility with various arylamines, with yields up to 96%. A size‐controlled reaction phenomenon by different cyclodextrins (CDs) was also observed when ethyl diazoacetate (EDA) was used. The reaction mechanism was also preliminarily proposed on the basis of designed control experiments.magnified image
Copper(I) Complexes Bearing Carbenes Beyond Classical N‐Heterocyclic Carbenes: Synthesis and Catalytic Activity in “Click Chemistry”
Authors: Bidal Yannick D. , Lesieur Mathieu , Melaimi Mohand , Nahra Fady , Cordes David B. , Athukorala Arachchige Kasun S. , Slawin Alexandra M. Z. , Bertrand Guy , Cazin Catherine S. J. 
Published: October 2015

AbstractThe synthesis and characterization of abnormal N‐heterocyclic carbene, cyclic (alkyl)(amino)carbene, and mesoionic carbene copper(I) complexes are reported. These organometallic species are obtainedviaa versatile and inexpensive synthetic pathway using readily available reactants, namely copper oxide and iminium salts. The catalytic activity of this series of complexes was evaluated in the [3+2] cycloaddition of alkynes with azides (CuAAC). Outstanding catalytic properties were observed for the abnormal NHC‐ and triazolylidene‐based copper(I) complexes.magnified image
Catalytic Aerobic Oxidation of Arylhydrazides with Iron Phthalocyanine
Authors: Hashimoto Takuma , Hirose Daisuke , Taniguchi Tsuyoshi 
Published: October 2015

AbstractA convenient method for the synthesis of 2‐arylazocarboxylates from 2‐arylhydrazinecarboxylates by aerobic oxidation with iron phthalocyanine is described. The reaction is applicable to oxidative activation of 1‐acyl‐2‐phenylhydrazines. Some preliminary experiments suggest Michaelis–Menten kinetics and participation of radical species in the reaction mechanism.magnified image
Synthesis of O,S‐Containing Polycycles via One‐Pot Michael Addition–Cycloacetalisation Cascade
Authors: Bankar Siddheshwar K. , Shirke Rajendra P. , Ramasastry S. S. V. 
Published: October 2015

AbstractAn efficient diversity‐oriented approach for the synthesis of previously unknown di‐, tri‐, tetra‐ and spirocyclic pyrano‐1,4‐dioxinones, pyrano‐1,4‐dithiinones and pyrano‐1,4‐oxathiinones from readily available starting compounds has been described. Cascade Michael addition–cycloacetalisation of acetoxy‐, alkoxy‐, and aryloxypyranones and 1,2‐dinucleophiles under mild Lewis acidic conditions provides a direct access to oxygen and sulfur‐containing complex heterocycles. Mechanistic aspects of the cascade process were elucidated in light of experimental facts. The methodology described herein shows high promise for the synthesis of several bioactive natural products as well as pharmaceutically important compounds.magnified image
Stannylation and Stille Coupling of Base‐Sensitive Tetrahydroxanthones to Heteromeric Biaryls
Authors: Lindner Stephanie , Nieger Martin , Bräse Stefan 
Published: October 2015

AbstractHerein, the synthesis of heteromeric tetrahydroxanthone biaryls is described, a widespread core structure of many natural products. The development of both stannylation and Stille coupling procedures of base‐sensitive tetrahydroxanthones enabled their coupling with benzene derivatives as well as with xanthenes. These methods provide access to structures that are analogous to parnafungins as well as to dimeric compounds similar to secalonic acids or phomoxanthones.magnified image
Oxidative Alkene Cleavage Catalysed by Manganese‐Dependent Cupin TM1459 from Thermotoga maritima
Authors: Hajnal Ivan , Faber Kurt , Schwab Helmut , Hall Mélanie , Steiner Kerstin 
Published: October 2015

AbstractA novel biocatalytic oxidative alkene cleavage activity was identified in protein TM1459 from Thermotoga maritima, a so far uncharacterised metalloprotein with a cupin fold, which preferentially binds manganese (over iron and zinc). Various styrene derivatives were converted with high chemoselectivity to the corresponding carbonyl compounds by the manganese‐containing protein, using organic hydroperoxide and molecular oxygen as oxidant. 4‐Chloroacetophenone could be obtained in 40% conversion from 4‐chloro‐α‐methylstyrene (50 mM) in a biphasic system using ethyl acetate as organic cosolvent (5% v/v), while 76% conversion was obtained at a lower substrate concentration (10 mM). This novel biocatalyst can be easily over‐expressed in Escherichia coli in exceptionally high yield and purified, and thus may offer a valuable and safer alternative in oxidative CC bond cleavage reactions for synthetic applications.magnified image
Enantioselective Nickel‐Catalyzed Hydrocyanation using Chiral Phosphine‐Phosphite Ligands: Recent Improvements and Insights
Authors: Falk Anna , Cavalieri Alberto , Nichol Gary S. , Vogt Dieter , Schmalz Hans‐Günther 
Published: October 2015

AbstractThe asymmetric hydrocyanation of vinylarenes was investigated using hydrogen cyanide (HCN) in the presence of 5 mol% of a catalyst prepared from a phenol‐derived chiral phosphine‐phosphite ligand and bis(cyclooctadiene)nickel [Ni(cod)2]. The reactions were performed in tetrahydrofuran (THF) at room temperature to give exclusively the branched nitriles with superior enantioselectivities of 88–99% ee for vinylarenes and 74–94% ee for vinylheteroarenes, respectively. Using styrene as a model substrate it was shown that the catalyst loading could be decreased to 0.42 mol% without any loss of selectivity (88% ee). The structure of the pre‐catalyst, i.e., a tetrahedral Ni(0)(P,P‐chelate)(cod) complex, was proven by X‐ray and NMR analysis. Additional insight into the reaction course was gained by monitoring the hydrocyanation of styrene‐d8 by means of 2D NMR spectroscopy.magnified image
Asymmetric Hydrogenation of β‐Secondary Amino Ketones Catalyzed by a Ruthenocenyl Phosphino‐oxazoline‐ruthenium Complex (RuPHOX‐Ru): the Synthesis of γ‐Secondary Amino Alcohols
Authors: Wang Jianxia , Wang Yanzhao , Liu Delong , Zhang Wanbin 
Published: October 2015

AbstractA ruthenocenyl phosphino‐oxazoline‐ruthenium complex (RuPHOX‐Ru) was applied successfully to the asymmetric hydrogenation of β‐secondary amino ketones, directly affording the corresponding chiral γ‐secondary amino alcohols in up to 99% yield and with 99% ee. Reaction with β‐(benzylamino)‐1‐phenylpropan‐1‐one could be performed on a gram‐scale with a relatively low catalyst loading (up to 2000 S/C). The resulting hydrogenated product could be used for the synthesis of synthetically useful compounds.magnified image
Synthesis and Evaluation of Organic–Inorganic Hybrid Molecularly Imprinted Monolith Column for Selective Recognition of Acephate and Phosphamidon in Vegetables
Authors: Wang Qingqing , Zhang Xin , Li Jie , Xu Zhixiang 
Published: October 2015

ABSTRACTIn this study, a molecularly imprinted capillary monolithic column that can recognize the acephate and phosphamidon was synthesized by the molecular imprinting technique combined with a nonhydrolytic sol–gel process using intermediate 4‐(dimethoxyphosphorothioylamino)butanoic acid as the template molecule. The resulting material was characterized by scanning electron microscopy and Fourier transform infrared spectroscopy. The potential of the prepared imprinted monolithic columns used as the stationary phase for capillary electrochromatography (CEC) was evaluated. The effects of operating voltage, pH, and acetonitrile content on the electroosmotic flow of the imprinted monolithic columns were evaluated in CEC. Under optimal conditions, the cucumber and lettuce samples spiked with acephate and phosphamidon were extracted and analyzed by this method with satisfactory recoveries ranging from 79.7 to 94.4%. The relative standard deviation for five replicates of 0.1 mg/L mixed solution of acephate and phosphamidon was in the range of 2.7–4.6%.
Triphenylphosphine/Triethylamine‐Mediated Decarboxylation of α‐Oxocarboxylic Acids and Application in a One‐Pot Synthesis of Deuterated Aldehydes.
Authors: Niu Guang‐Hao , Huang Pei‐Ru , Chuang Gary Jing 
Published: October 2015

AbstractA simple method for synthesizing aldehydes from α‐oxocarboxylic acids via decarboxylation in the presence of PPh3 and Et3N is reported. The decarboxylation can be performed on a wide range of α‐oxocarboxylic acids; electron‐rich/electron‐deficient aryl, heteroaryl, as well as alkyl α‐oxocarboxylic acids. This method also provides a convenient procedure for the synthesis of deuterated aldehydes using D2O as deuterium source in a facile one‐pot process.
Standing on the shoulders of apes: Analyzing the form and function of the hominoid scapula using geometric morphometrics and finite element analysis
Authors: Püschel Thomas A. , Sellers William I. 
Published: October 2015

ABSTRACTObjectiveThe aim was to analyze the relationship between scapular form and function in hominoids by using geometric morphometrics (GM) and finite element analysis (FEA).MethodsFEA was used to analyze the biomechanical performance of different hominoid scapulae by simulating static postural scenarios. GM was used to quantify scapular shape differences and the relationship between form and function was analyzed by applying both multivariate‐multiple regressions and phylogenetic generalized least‐squares regressions (PGLS).ResultsAlthough it has been suggested that primate scapular morphology is mainly a product of function rather than phylogeny, our results showed that shape has a significant phylogenetic signal. There was a significant relationship between scapular shape and its biomechanical performance; hence at least part of the scapular shape variation is due to non‐phylogenetic factors, probably related to functional demands.DiscussionThis study has shown that a combined approach using GM and FEA was able to cast some light regarding the functional and phylogenetic contributions in hominoid scapular morphology, thus contributing to a better insight of the association between scapular form and function. Am J Phys Anthropol 159:325–341, 2016. © 2015 Wiley Periodicals, Inc.
Non‐interacting single‐impurity Anderson model: solution without using the equation‐of‐motion method
Authors: Mahmoud Zakaria M.M. , Gebhard Florian 
Published: October 2015

Ground‐state properties of the non‐interacting symmetric single‐impurity Anderson model (SIAM) are derived from the corresponding eigenenergy equation. Explicit formulae are given for the ground‐state energy, the hybridization, and the momentum distribution that are essential quantities for variational approaches to the interacting model. Various spectral functions, e.g., the total density of states, the phase shift function, and the impurity spectral function, are shown to agree with those obtained from the equation‐of‐motion method (see supplementary material). For a constant hybridization strength and a semi‐elliptic host density of states it is seen that the impurity spectral function builds up weight at the band edges.
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Direkte Modulation von Aktivität und Funktion kleiner GTPasen
Authors: Cromm Philipp M. , Spiegel Jochen , Grossmann Tom N. , Waldmann Herbert 
Published: October 2015

AbstractKleine GTPasen bilden eine Familie von GDP‐/GTP‐bindenden Proteinen, die als biomolekulare Schalter innerhalb von Zellen wirken. Fehlfunktionen oder Fehlregulierungen kleiner GTPasen stehen in Verbindung mit zahlreichen menschlichen Erkrankungen, was diese Proteine zu einem vielversprechenden Ziel der pharmazeutischen Forschung macht. Allerdings werden kleine GTPasen oftmals als pharmakologisch nicht adressierbar klassifiziert, da jahrzehntelange Bemühungen keinerlei klinisch relevante Verbindungen liefern konnten, die die Aktivität kleiner GTPasen direkt modulieren. Die Entdeckung neuer, transienter Bindetaschen an den Proteinoberflächen und die Anwendung neuartiger Techniken haben dem Feld jedoch kürzlich neuen Schwung verliehen. Neben Ras‐Proteinen rücken zudem vermehrt andere kleine GTPasen in den Fokus der Forschung. Dieser Artikel bietet einen Überblick über die relevanten Aspekte der Superfamilie kleiner GTPasen und fasst die jüngsten Fortschritte und Perspektiven für die direkte Modulierung dieser herausfordernden Proteinklasse zusammen.
Funktionelle Synthese des Lichtsammelkomplexes II in Polymermembran‐Architekturen
Authors: Zapf Thomas , Tan Cherng‐Wen Darren , Reinelt Tobias , Huber Christoph , Shaohua Ding , Geifman‐Shochat Susana , Paulsen Harald , Sinner Eva‐Kathrin 
Published: October 2015

AbstractEines der wirkungsvollsten Konzepte der Natur ist die Aufnahme und Umwandlung von Sonnenenergie durch den Lichtsammelkomplex II (LHCII). Dieser Protein‐Pigment‐Komplex mit seinen zugehörigen Pigmenten ist der Hauptsonnenenergiekollektor in Pflanzen. Unser Ziel ist es, ein stabiles, reproduzierbares und ressourcenschonendes LHCII‐Pigment‐Material außerhalb der pflanzlichen Zelle zu generieren, das genauso bereit und in der Lage zur Aufnahme von Sonnenenergie ist. Wir verwendeten dafür ein konventionelles, zellfreies Proteinsynthesesystem aus Weizenkeimen und beobachteten eine cotranslationale Insertion von LHCII‐Proteinen in die Polymermembranen, die als Polymersomen der Synthesemischung zugegeben worden waren. Eine einheitliche Insertionsrichtung der Proteine in den Polymermembranen konnten wir durch einen Protease‐Assay nachweisen. Die Gegenwart des LHCII bewirkte einen Anstieg der Chlorophyllkonzentration in den Polymermembranen, und die Oberflächenplasmonen‐verstärkte Fluoreszenzspektroskopie (SPFS) ermöglichte die Messung des Energietransfers von Chl b nach Chl a, was als Indikator für die native Faltung des LHC‐Proteins gilt.
Ultrafine Molybdenum Carbide Nanoparticles Composited with Carbon as a Highly Active Hydrogen‐Evolution Electrocatalyst
Authors: Ma Ruguang , Zhou Yao , Chen Yongfang , Li Pengxi , Liu Qian , Wang Jiacheng 
Published: October 2015

AbstractThe replacement of platinum with non‐precious‐metal electrocatalysts with high efficiency and superior stability for the hydrogen‐evolution reaction (HER) remains a great challenge. Herein, we report the one‐step synthesis of uniform, ultrafine molybdenum carbide (Mo2C) nanoparticles (NPs) within a carbon matrix from inexpensive starting materials (dicyanamide and ammonium molybdate). The optimized catalyst consisting of Mo2C NPs with sizes lower than 3 nm encapsulated by ultrathin graphene shells (ca. 1–3 layers) showed superior HER activity in acidic media, with a very low onset potential of −6 mV, a small Tafel slope of 41 mV dec−1, and a large exchange current density of 0.179 mA cm−2, as well as good stability during operation for 12 h. These excellent properties are similar to those of state‐of‐the‐art 20 % Pt/C and make the catalyst one of the most active acid‐stable electrocatalysts ever reported for HER.
Entschlüsselung einer repetitiven Amyloidsequenz: Korrelation von Biofilm‐extrahierten und segmental markierten Curli‐Fimbrien mittels Festkörper‐NMR‐Spektroskopie
Authors: Schubeis Tobias , Yuan Puwei , Ahmed Mumdooh , Nagaraj Madhu , van Rossum Barth‐Jan , Ritter Christiane 
Published: October 2015

AbstractCurli sind funktionelle bakterielle Amyloide, die durch eine ausgefeilte Biogenesemaschinerie hergestellt werden. Einblicke in ihre Faltung und Regulierung kann unser Verständnis der Amyloidbildung erweitern. Allerdings ist die Aufklärung hochaufgelöster Strukturen von Amyloiden aufgrund ihrer Tendenz zu strukturellen Polymorphismen weiterhin eine Herausforderung. Hier vergleichen wir qualitativ hochwertige Festkörper‐NMR‐Spektren von Curli, die aus Biofilmen isoliert wurden, mit rekombinant hergestellten Curli, und zeigen so, dass sie eine ähnliche, gut definierte β‐Solenoid‐Struktur annehmen. Curli‐Untereinheiten bestehen aus fünf repetitiven Sequenzwiederholungen, die in den NMR‐Spektren zu einer starken Resonanzüberlagerung führen. Durch die Anwendung segmentaler Isotopenmarkierung ist es gelungen, die Signale einer einzelnen Sequenzwiederholung eindeutig zuzuordnen. Die gewonnenen Sekundärstrukturinformationen zeigen, dass alle Wiederholungen höchstwahrscheinlich strukturell äquivalent sind.
Total Synthesis of the Posttranslationally Modified Polyazole Peptide Antibiotic Plantazolicin A
Authors: Wada Hiroki , Williams Huw E. L. , Moody Christopher J. 
Published: October 2015

AbstractThe power of rhodium–carbene methodology in chemistry is demonstrated by the synthesis of a structurally complex polyazole antibiotic. Plantazolicin A, a novel soil‐bacterium metabolite, comprises a linear array of 10 five‐membered rings in two pentacyclic regions that derive from ribosomal peptide synthesis followed by extensive posttranslational modification. The compound possesses potent antimicrobial activity, and is selectively active against the anthrax‐causing organism. A conceptually different synthesis of plantazolicin A is reported in which the key steps are the use of rhodium(II)‐catalyzed reactions of diazocarbonyl compounds to generate up to six of the seven oxazole rings of the antibiotic. NMR spectroscopic studies and molecular modeling reveal a likely dynamic hairpin conformation with a hinge region around the two isoleucine residues. The compound has modest activity against methicillin‐resistant Staphylococcus aureus (MRSA).
Nanoporous Graphene with Single‐Atom Nickel Dopants: An Efficient and Stable Catalyst for Electrochemical Hydrogen Production
Authors: Qiu H.‐J. , Ito Yoshikazu , Cong Weitao , Tan Yongwen , Liu Pan , Hirata Akihiko , Fujita Takeshi , Tang Zheng , Chen Mingwei 
Published: October 2015

AbstractSingle‐atom nickel dopants anchored to three‐dimensional nanoporous graphene can be used as catalysts of the hydrogen evolution reaction (HER) in acidic solutions. In contrast to conventional nickel‐based catalysts and graphene, this material shows superior HER catalysis with a low overpotential of approximately 50 mV and a Tafel slope of 45 mV dec−1 in 0.5 M H2SO4 solution, together with excellent cycling stability. Experimental and theoretical investigations suggest that the unusual catalytic performance of this catalyst is due to sp–d orbital charge transfer between the Ni dopants and the surrounding carbon atoms. The resultant local structure with empty C–Ni hybrid orbitals is catalytically active and electrochemically stable.
Membrane Disruption and Enhanced Inhibition of Cell‐Wall Biosynthesis: A Synergistic Approach to Tackle Vancomycin‐Resistant Bacteria
Authors: Yarlagadda Venkateswarlu , Samaddar Sandip , Paramanandham Krishnamoorthy , Shome Bibek R. , Haldar Jayanta 
Published: October 2015

AbstractResistance to glycopeptide antibiotics, the drugs of choice for life‐threatening bacterial infections, is on the rise. In order to counter the threat of glycopeptide‐resistant bacteria, we report development of a new class of semi‐synthetic glycopeptide antibiotics, which not only target the bacterial membrane but also display enhanced inhibition of cell‐wall biosynthesis through increased binding affinity to their target peptides. The combined effect of these two mechanisms resulted in improved in vitro activity of two to three orders of magnitude over vancomycin and no propensity to trigger drug resistance in bacteria. In murine model of kidney infection, the optimized compound was able to bring bacterial burden down by about 6 logs at 12 mg kg−1 with no observed toxicity. The results furnished in this report emphasize the potential of this class of compounds as future antibiotics for drug‐resistant Gram‐positive infections.
Meltable Spin Transition Molecular Materials with Tunable Tc and Hysteresis Loop Width
Authors: Romero‐Morcillo Tania , Seredyuk Maksym , Muñoz M. Carmen , Real Jose A. 
Published: October 2015

AbstractHerein, we report a way to achieve abrupt high‐spin to low‐spin transition with controllable transition temperature and hysteresis width, relying not on solid‐state cooperative interactions, but utilizing coherency between phase and spin transitions in neutral FeII meltable complexes.
Metal‐Free Hydrosilylation Polymerization by Borane Catalyst
Authors: Kim Dong Wook , Joung Seewon , Kim Jeung Gon , Chang Sukbok 
Published: October 2015

AbstractThe first example of metal‐free hydrosilylation polymerization between dienes and disilanes is developed by using a borane catalyst, B(C6F5)3to replace precious transition‐metal‐based systems. Under the easy‐to‐handle and mild conditions, a step‐growth polymerization of two readily available diene and disilane units was achieved with high degrees of polymerization. Various combinations of dienes and disilanes produced polycarbosilanes with a broad range of structures and properties.
Facile Synthesis of N‐Carboranyl Amines through an ortho‐Carboryne Intermediate
Authors: Cheng Ruofei , Zhang Jie , Zhang Jiji , Qiu Zaozao , Xie Zuowei 
Published: October 2015

AbstractThe efficient o‐carboryne precursor 1‐Li‐2‐OTf‐o‐C2B10H10 reacts with lithium amides at room temperature to give a series of N‐carboranyl amines in moderate to high isolated yields. This reaction is compatible with a broad substrate scope from primary to secondary, alkyl to aryl amines. The reaction mechanism is also proposed on the basis of experimental results and DFT calculations. This represents the first general and efficient method for the synthesis of 1‐NR1R2‐o‐carboranes.
Cobalt‐katalysierte Alkylierung von aromatischen Aminen durch Alkohole
Authors: Rösler Sina , Ertl Michael , Irrgang Torsten , Kempe Rhett 
Published: October 2015

AbstractDie Implementierung von preiswerten, auf der Erde häufig vorkommenden Metallen in Edelmetall‐vermittelten Reaktionen ist ein zentrales Ziel in der homogenen Katalyse. Eine nachhaltige oder grüne Reaktion, die große Aufmerksamkeit in den letzten Jahren erhalten hat und vorzugsweise durch Ir‐ oder Ru‐Komplexe katalysiert wird, ist die Alkylierung von Aminen durch Alkohole. Sie basiert auf dem “Borrowing‐Hydrogen”‐ oder “Hydrogen‐Auto‐Transfer”‐Konzept. Wir berichten hier über die Co‐vermittelte Alkylierung von aromatischen Aminen durch Alkohole. Die Reaktion läuft unter milden Bedingungen ab und selektiv monoalkylierte Amine werden erhalten. Die beobachtete Selektivität ermöglicht die Synthese von unsymmetrisch substituierten Diaminen. Ein neuartiger PN5P‐Ligand stabilisierter Co‐Komplex katalysiert die Reaktionen am effizientesten.
Direct Trifluoromethylthiolation and Perfluoroalkylthiolation of C(sp2)H Bonds with CF3SO2Na and RfSO2Na
Authors: Jiang Lvqi , Qian Jinlong , Yi Wenbin , Lu Guoping , Cai Chun , Zhang Wei 
Published: October 2015

AbstractA new method for CF3SO2Na‐based direct trifluoromethylthiolation of C(sp2)H bonds has been developed. CF3SSCF3 is generated in situ from cheap and easy‐to‐handle CF3SO2Na, and in the presence of CuCl can be used for electrophilic trifluoromethylthiolation of indoles, pyrroles, and enamines. The method has been extended to perfluoroalkylthiolation reactions using RfSO2Na.