bluuebunny/crossref_metadata_2025_split huggingface dataset:
Synthesis of Highly Substituted Benzofuran–containing Natural Products via Rh–catalyzed Carbonylative Benzannulation
Authors: Liu Ji‐tian , Simmons Christopher J. , Xie Haibo , Yang Fan , Zhao Xian‐liang , Tang Yu , Tang Weiping 
Published: December 2016

AbstractWe recently developed a novel Rh‐catalyzed carbonylative benzannulation for the synthesis of indoles, benzofurans, and many related heterocycles. In this update, we demonstrated the utility of this method for the synthesis of several highly substituted benzofuran‐containing natural products. The scope and limitation of the Rh‐catalyzed carbonylative benzannulation was investigated in the context of natural product synthesis for the first time. This study also revealed the site‐selectivity for Pd‐catalyzed cross‐coupling of substituted benzofurans. Two one‐pot sequential cross‐couplings were realized based on the observed site‐selectivity. The strategy of preparing bicyclic heterocycles such as benzofurans by de novo synthesis of the benzene ring will find applications in many other related bioactive heterocycles.magnified image
A Chiral Nitrogen Ligand for Enantioselective, Iridium‐Catalyzed Silylation of Aromatic C−H Bonds
Authors: Su Bo , Zhou Tai‐Gang , Li Xian‐Wei , Shao Xiao‐Ru , Xu Pei‐Lin , Wu Wen‐Lian , Hartwig John F. , Shi Zhang‐Jie 
Published: December 2016

AbstractIridium catalysts containing dative nitrogen ligands are highly active for the borylation and silylation of C−H bonds, but chiral analogs of these catalysts for enantioselective silylation reactions have not been developed. We report a new chiral pyridinyloxazoline ligand for enantioselective, intramolecular silylation of symmetrical diarylmethoxy diethylsilanes. Regioselective and enantioselective silylation of unsymmetrical substrates was also achieved in the presence of this newly developed system. Preliminary mechanistic studies imply that C−H bond cleavage is irreversible, but not the rate‐determining step.
High‐Throughput Screening of Catalytic H2 Production
Authors: Koo Jamin , Schnabel Tim , Liong Sylvie , Evitt Niklaus H. , Swartz James R. 
Published: December 2016

AbstractHydrogenases, ferredoxins, and ferredoxin‐NADP+ reductases (FNR) are redox proteins that mediate electron metabolism in vivo, and are also potential components for biological H2 production technologies. A high‐throughput H2 production assay device (H2PAD) is presented that enables simultaneous evaluation of 96 individual H2 production reactions to identify components that improve performance. Using a CCD camera and image analysis software, H2PAD senses the chemo‐optical response of Pd/WO3 thin films to the H2 produced. H2PAD‐enabled discovery of hydrogenase and FNR mutants that enhance biological H2 production is reported. From a library of 10 080 randomly mutated Clostridium pasteurianum [FeFe] hydrogenases, we found a mutant with nearly 3‐fold higher H2 production specific activity. From a library of 400 semi‐randomly mutated Oryza sativa FNR, the top hit enabled a 60 % increase in NADPH‐driven H2 production rates. H2PAD can also facilitate elucidation of fundamental biochemical mechanisms within these systems.
Die Kristallstruktur von RosB: Einblicke in den Reaktionsmechanismus des ersten Mitglieds einer flavodoxinähnlichen Enzymfamilie
Authors: Konjik Valentino , Brünle Steffen , Demmer Ulrike , Vanselow Amanda , Sandhoff Roger , Ermler Ulrich , Mack Matthias 
Published: December 2016

AbstractDie 8‐Demethyl‐8‐aminoriboflavin‐5′‐phosphat(AFP)‐Synthase RosB katalysiert die Schlüsselreaktion der Roseoflavinbiosynthese, die Bildung von AFP aus Riboflavin‐5′‐phosphat (RP) und Glutamat. Zwischenprodukte dieser enzymatischen Reaktion sind 8‐Demethyl‐8‐formylriboflavin‐5′‐phosphat (OHC‐RP) und 8‐Demethyl‐8‐carboxylriboflavin‐5′‐phosphat (HO2C‐RP). Um den schwierigen Austausch einer Methylgruppe am Aromaten gegen eine Aminogruppe zu verstehen, haben wir die Struktur von RosB im Komplex mit OHC‐RP (2.0 Å) und im Komplex mit AFP (1.7 Å) gelöst. RosB ist als Homotetramer aktiv und wurde im Verlauf der Evolution mit spezifischen Domänen und einem einzigartigen C‐terminalen Arm ausgestattet. Wir glauben, dass RosB dabei aus einem einfachen Elektronen‐ oder Hydrid‐übertragenden Flavoprotein zu einem komplexen mehrstufigen Enzym “entwickelt” wurde. Im Gegensatz zu anderen Flavoenzymen nutzt RosB RP als Substrat und nicht als Kofaktor. Die strukturelle Analyse des aktiven Zentrums von RosB wurde durch Mutagenesestudien und isotopenbasierte massenspektrometrische Untersuchungen ergänzt. Auf Grundlage dieser Ergebnisse schlagen wir einen Reaktionsmechanismus auf atomarer Ebene vor.
Development of Gold‐catalyzed [4+1] and [2+2+1]/[4+2] Annulations between Propiolate Derivatives and Isoxazoles
Authors: Sahani Rajkumar Lalji , Liu Rai‐Shung 
Published: December 2016

AbstractTwo new gold‐catalyzed annulations of isoxazoles with propiolates have been developed. Most isoxazoles follow an initial O attack on the alkyne to afford a [4+1] annulation product. This process results in a remarkable alkyne cleavage of initial propiolates. Unsubstituted isoxazoles proceed through an N attack step to yield formal [2+2+1]/[4+2] annulation products. These two annulation products arise initially from two seven‐membered heterocyclic intermediates, which then lead to products.
A Stereoconvergent Cyclopropanation Reaction of Styrenes
Authors: del Hoyo Ana M. , Herraiz Ana G. , Suero Marcos G. 
Published: December 2016

AbstractThe first stereoconvergent cyclopropanation reaction by means of photoredox catalysis using diiodomethane as the methylene source is described. This transformation exhibits broad functional group tolerance and it is characterized by an excellent stereocontrol en route to trans‐cyclopropanes regardless of whether E‐ or Z‐styrene substrates were utilized.
Azaindoles as Zinc‐Binding Small‐Molecule Inhibitors of the JAMM Protease CSN5
Authors: Altmann Eva , Erbel Paul , Renatus Martin , Schaefer Michael , Schlierf Anita , Druet Adelaide , Kieffer Laurence , Sorge Mickael , Pfister Keith , Hassiepen Ulrich , Jones Matthew , Ruedisser Simon , Ostermeier Daniela , Martoglio Bruno , Jefferson Anne B. , Quancard Jean 
Published: December 2016

AbstractCSN5 is the zinc metalloprotease subunit of the COP9 signalosome (CSN), which is an important regulator of cullin‐RING E3 ubiquitin ligases (CRLs). CSN5 is responsible for the cleavage of NEDD8 from CRLs, and blocking deconjugation of NEDD8 traps the CRLs in a hyperactive state, thereby leading to auto‐ubiquitination and ultimately degradation of the substrate recognition subunits. Herein, we describe the discovery of azaindoles as a new class of CSN5 inhibitors, which interact with the active‐site zinc ion of CSN5 through an unprecedented binding mode. The best compounds inhibited CSN5 with nanomolar potency, led to degradation of the substrate recognition subunit Skp2 in cells, and reduced the viability of HCT116 cells.
Nickel‐Catalyzed Barton Decarboxylation and Giese Reactions: A Practical Take on Classic Transforms
Authors: Qin Tian , Malins Lara R. , Edwards Jacob T. , Merchant Rohan R. , Novak Alexander J. E. , Zhong Jacob Z. , Mills Riley B. , Yan Ming , Yuan Changxia , Eastgate Martin D. , Baran Phil S. 
Published: December 2016

AbstractTwo named reactions of fundamental importance and paramount utility in organic synthesis have been reinvestigated, the Barton decarboxylation and Giese radical conjugate addition. N‐hydroxyphthalimide (NHPI) based redox‐active esters were found to be convenient starting materials for simple, thermal, Ni‐catalyzed radical formation and subsequent trapping with either a hydrogen atom source (PhSiH3) or an electron‐deficient olefin. These reactions feature operational simplicity, inexpensive reagents, and enhanced scope as evidenced by examples in the realm of peptide chemistry.
The Crystal Structure of RosB: Insights into the Reaction Mechanism of the First Member of a Family of Flavodoxin‐like Enzymes
Authors: Konjik Valentino , Brünle Steffen , Demmer Ulrike , Vanselow Amanda , Sandhoff Roger , Ermler Ulrich , Mack Matthias 
Published: December 2016

Abstract8‐demethyl‐8‐aminoriboflavin‐5′‐phosphate (AFP) synthase (RosB) catalyzes the key reaction of roseoflavin biosynthesis by forming AFP from riboflavin‐5′‐phosphate (RP) and glutamate via the intermediates 8‐demethyl‐8‐formylriboflavin‐5′‐phosphate (OHC‐RP) and 8‐demethyl‐8‐carboxylriboflavin‐5′‐phosphate (HO2C‐RP). To understand this reaction in which a methyl substituent of an aromatic ring is replaced by an amine we structurally characterized RosB in complex with OHC‐RP (2.0 Å) and AFP (1.7 Å). RosB is composed of four flavodoxin‐like subunits which have been upgraded with specific extensions and a unique C‐terminal arm. It appears that RosB has evolved from an electron‐ or hydride‐transferring flavoprotein to a sophisticated multi‐step enzyme which uses RP as a substrate (and not as a cofactor). Structure‐based active site analysis was complemented by mutational and isotope‐based mass‐spectrometric data to propose an enzymatic mechanism on an atomic basis.
Skull Anatomy and Ontogeny of Legless Lizard Pseudopus apodus (Pallas, 1775): Heterochronic Influences on Form
Authors: Klembara Jozef , Dobiašová Karolína , Hain Miroslav , Yaryhin Oleksandr 
Published: December 2016

ABSTRACTPseudopus apodus (Pallas, 1775) is the largest extant legless species of the subfamily Anguinae (Anguimorpha, Anguidae) living mostly in the sub‐arid territories ranging from the Balkan area in Europe to Kazakhstan in Asia. The species of other two genera live in North America, South‐East Asia and North Africa (Ophisaurus) and Europe and South‐West Asia (Anguis). The interrelationships of Anguinae are unresolved; this is in part the consequence of the insufficient knowledge of the cranial, postcranial and integumentary anatomy of the individual anguine species. The aim of this article is to fulfill this gap in our knowledge of the anguine anatomy. Now, in the first part of the project, the individual bones of the exocranium and visceral endocranium of the anguine legless lizard P. apodus are described in detail. In the present study, P. apodus is revealed to have autoapomorphic features of the skull which clearly distinguish it from Anguis and Ophisaurus. In addition, the study of posthatchling ontogeny of exocranium of P. apodus revealed some features, such as a nasal process of premaxilla being slightly widened in about its mid‐length, that are also typical for adults of the Ophisaurus and Anguis species as well as extinct species of Pseudopus. This strongly indicates that peramorphic heterochronic process played role in the evolution of the P. apodus skull. Anat Rec, 2017. © 2017 Wiley Periodicals, Inc. Anat Rec, 300:460–502, 2017. © 2016 Wiley Periodicals, Inc.
High‐Throughput Synthetic Chemistry Enabled by Organic Solvent Disintegrating Tablet
Authors: Li Tingting , Xu Lei , Xing Yanjun , Xu Bo 
Published: December 2016

AbstractSynthetic chemistry remains a time‐ and labor‐intensive process of inherent hazardous nature. Our organic solvent disintegrating tablet (O‐Tab) technology has shown potential to make industrial/synthetic chemistry more efficient. As is the case with pharmaceutical tablets, our reagent‐containing O‐Tabs are mechanically strong, but disintegrate rapidly when in contact with reaction media (organic solvents). For O‐Tabs containing sensitive chemicals, they can be further coated to insulate them from air and moisture.
Identification of lanthanum‐specific peptides for future recycling of rare earth elements from compact fluorescent lamps
Authors: Lederer Franziska L. , Curtis Susan B. , Bachmann Stefanie , Dunbar W.Scott , MacGillivray Ross T.A. 
Published: December 2016

ABSTRACTAs components of electronic scrap, rare earth minerals are an interesting but little used source of raw materials that are highly important for the recycling industry. Currently, there exists no cost‐efficient technology to separate rare earth minerals from an electronic scrap mixture. In this study, phage surface display has been used as a key method to develop peptides with high specificity for particular inorganic targets in electronic scrap. Lanthanum phosphate doped with cerium and terbium as part of the fluorescent phosphors of spent compact fluorescent lamps (CFL) was used as a target material of economic interest to test the suitability of the phage display method to the separation of rare earth minerals. One random pVIII phage library was screened for peptide sequences that bind specifically to the fluorescent phosphor LaPO4:Ce3+,Tb3+ (LAP). The library contained at least 100 binding pVIII peptides per phage particle with a diversity of 1 × 109 different phage per library. After three rounds of enrichment, a phage clone containing the surface peptide loop RCQYPLCS was found to bind specifically to LAP. Specificity and affinity of the identified phage bound peptide was confirmed by using binding and competition assays, immunofluorescence assays, and zeta potential measurements. Binding and immunofluorescence assays identified the peptide's affinity for the fluorescent phosphor components CAT (CeMgAl11O19:Tb3+) and BAM (BaMgAl10O17:Eu2+). No affinity was found for other fluorescent phosphor components such as YOX (Y2O3:Eu3+). The binding specificity of the RCQYPLCS peptide loop was improved 3–51‐fold by using alanine scanning mutagenesis. The identification of peptides with high specificity and affinity for special components in the fluorescent phosphor in CFLs provides a potentially new strategic approach to rare earth recycling. Biotechnol. Bioeng. 2017;114: 1016–1024. © 2016 Wiley Periodicals, Inc.
Skin‐derived precursors possess the ability of differentiation into the epidermal progeny and accelerate burn wound healing
Authors: Bayati Vahid , Abbaspour Mohammad Reza , Neisi Niloofar , Hashemitabar Mahmoud 
Published: December 2016

AbstractSkin‐derived precursors (SKPs) are remnants of the embryonic neural crest stem cells that reside in the dermis until adulthood. Although they possess a wide range of differentiation potentials, their differentiation into keratinocyte‐like cells and their roles in skin wound healing are obscure. The present study aimed to investigate the differentiation of SKPs into keratinocyte‐like cells and evaluate their role in healing of third degree burn wounds. To this aim, SKPs were differentiated into keratinocyte‐like cells on tissue culture plate and collagen–chitosan scaffold prepared by freeze‐drying. Their differentiation capability was detected by real‐time RT‐PCR and immunofluorescence. Thereafter, they were cultured on scaffold and implanted in a rat model of burn wound. Histopathological and immunohistochemical analyses were employed to examine the reconstituted skin. The research findings revealed that SKPs were able to differentiate along the epidermal lineage and this ability can be enhanced on a suitable scaffold. Additionally, the results indicated that SKPs apparently promoted wound healing process and accelerate its transition from proliferating stage to maturational phase, especially if they were differentiated into keratinocyte‐like cells. Regarding the results, it is concluded that SKPs are able to differentiate into keratinocyte‐like cells, particularly when they are cultured on collagen–chitosan scaffold. Moreover, they can regenerate epidermal and dermal layers including thick collagen bundles, possibly through differentiation into keratinocyte‐like cells.
Remarkable Acceleration of Benzimidazole Synthesis and Cyanosilylation Reactions in a Supramolecular Solid Catalyst
Authors: Rojas‐Buzo Sergio , García‐García Pilar , Corma Avelino 
Published: December 2016

AbstractA solid metal–organic catalyst with hydrophobic pockets and Lewis acid centers strongly accelerates the reaction rate for organic reactions. This is exemplified for the cyanosilylation of ketones and for the synthesis of benzimidazoles, for which very high selectivities are obtained. The solid can be recovered and reused and its behavior approaches that of a functional enzyme mimic.
Selective Catalytic Hydrocarboxylation and Deuterocarboxylation of Allyl Cyanide to Cyanobutanoic Acids with Monodentate and Bidentate Phosphines
Authors: Vallcorba Oriol , Polo Alfonso , Real Julio 
Published: December 2016

AbstractThe hydrocarboxylation of allyl cyanide with monodentate phosphine systems (Pd/triphenylphosphine and protic acid cocatalyst) gave branched 3‐cyano‐2‐methylpropanoic acid chemo‐ and regioselectively, whereas with bidentate systems (Pd/bis[(2‐diphenylphosphino)phenyl] ether and protic acid cocatalyst) it gave linear 4‐cyanobutanoic acid chemo‐ and regioselectively. 3‐Cyano‐2‐methylpropanoic acid and 4‐cyanobutanoic acid were isolated in high yields as carboxylic acids and purified as benzyl esters. No isomerization of allyl cyanide to crotononitrile or its carbonylated derivatives was observed in any case. In parallel experiments, deuterocarboxylation under the same conditions gave the corresponding deuterated products, which were analyzed by MS and 2H NMR spectroscopy: only d0, d1, and d2 products were detected. Deuterium entered the β and γ‐CN positions of the products but never the α position.
Asymmetric Cation‐Binding Catalysis
Authors: Oliveira Maria Teresa , Lee Ji‐Woong 
Published: December 2016

AbstractThe employment of metal salts is quite limited in asymmetric catalysis, although it would provide an additional arsenal of safe and inexpensive reagents to create molecular functions with high optical purity. Cation chelation by polyethers increases the salts’ solubility in conventional organic solvents, thus increasing their applicability in synthesis. The expansion of this concept to chiral polyethers led to the emergence of asymmetric cation‐binding catalysis, where chiral counter anions are generated from metal salts, particularly using BINOL‐based polyethers. Alkali metal salts, namely KF and KCN, are selectively bound to the catalyst, providing exceptionally high enantioselectivities for kinetic resolutions, elimination reactions (fluoride base), and Strecker synthesis (cyanide nucleophile). Asymmetric cation‐binding catalysis was recently expanded to silicon‐based reagents, enabling highly enantioselective silylation reactions in polyether‐generated chiral environments, and leading to a record‐high turnover in asymmetric organocatalysis. This can lead to further applications by the asymmetric use of other inorganic salts in various organic transformations.
Electrocatalytic Activity and Stability Enhancement through Preferential Deposition of Phosphide on Carbide
Authors: Regmi Yagya N. , Roy Asa , Goenaga Gabriel A. , McBride James R. , Rogers Bridget. R. , Zawodzinski Thomas A. , Labbé Nicole , Chmely Stephen C. 
Published: December 2016

AbstractPhosphides and carbides are among the most promising families of materials based on earth‐abundant elements for renewable energy conversion and storage technologies such as electrochemical water splitting, batteries, and capacitors. Nickel phosphide and molybdenum carbide in particular have been extensively investigated for electrochemical water splitting. However, a composite of the two compounds has not been explored. Here, we demonstrate preferential deposition of nickel phosphide on molybdenum carbide in the presence of carbon by using a hydrothermal synthesis method. We employ the hydrogen evolution reaction in acid and base to analyze the catalytic activity of phosphide‐deposited carbide. The composite material also shows superior electrochemical stability in comparison to unsupported phosphide. We anticipate that the enhanced electrochemical activity and stability of carbide deposited with phosphide will stimulate investigations into the preparation of other carbide–phosphide composite materials.
Csp3−H Activation without Chelation Assistance in an Iridium Pincer Complex Forming Cyclometallated Products
Authors: Ahlstrand David A. , Polukeev Alexey V. , Marcos Rocío , Ahlquist Mårten S. G. , Wendt Ola F. 
Published: December 2016

AbstractCyclometallation of 8‐methylquinoline and 2‐(dimethylamino)‐pyridine in an iridium‐based pincer complex is described. The C−H activation of 2‐(dimethylamino)pyridine is not chelation assisted, which has not been described before for Csp3−H bonds in cyclometallation reactions. The mechanism of the cyclometallation of 2‐(dimethylamino)pyridine was studied by DFT calculations and kinetic measurements.
New Conjugated meso‐Tetrafluorenylporphyrin‐Cored Derivatives as Fluorescent Two‐Photon Photosensitizers for Singlet Oxygen Generation
Authors: Yao Dandan , Zhang Xu , Triadon Amédée , Richy Nicolas , Mongin Olivier , Blanchard‐Desce Mireille , Paul Frédéric , Paul‐Roth Christine O. 
Published: December 2016

AbstractA series of three conjugated meso‐porphyrin dendrimers containing conjugated dendrons featuring 2,7‐fluorenyl groups, incorporating overall 8, 12, or 28 fluorenyl units have been synthesized and characterized. The photophysical properties of these new compounds were studied in the context of photodynamic therapy. The relevant linear and nonlinear optical properties were measured in organic media and useful structure–properties relationships were derived.
Crystal Structure of the DFNKF Segment of Human Calcitonin Unveils Aromatic Interactions between Phenylalanines
Authors: Bertolani Arianna , Pizzi Andrea , Pirrie Lisa , Gazzera Lara , Morra Giulia , Meli Massimiliano , Colombo Giorgio , Genoni Alessandro , Cavallo Gabriella , Terraneo Giancarlo , Metrangolo Pierangelo 
Published: December 2016

AbstractInvited for the cover of this issue is the group of Pierangelo Metrangolo at the Politecnico di Milano. The image depicts the steric zipper formed by the amyloidogenic peptide, DFNKF. Read the full text of the article at 10.1002/chem.201604639.
Functionalization of Hydrogenated Chemical Vapour Deposition‐Grown Graphene by On‐Surface Chemical Reactions
Authors: Drogowska Karolina , Kovaříček Petr , Kalbáč Martin 
Published: December 2016

AbstractThe reactivity of hydrogenated graphene when treated with oxidising agents, KMnO4 and KIO4, as well as alkylated with benzyl bromide (BnBr) was studied. The probed reactions are strictly limited to the partly hydrogenated form of graphene in which most of the hydrogen atoms are located in activated benzylic/allylic positions. This, in turn, clearly demonstrates the presence of hydrogen attached to the graphene lattice. Attachment of the benzyl group was also unequivocally demonstrated by characteristic vibrations recorded in the surface‐enhanced Raman spectra, and all reactions were shown to proceed solely on hydrogenated graphene as evidenced by the comparison with pristine chemical vapour deposition‐grown graphene.
Zuverlässigkeit in der Nanosicherheitsforschung
Authors: Krug Harald Friedrich , Nau Katja 
Published: December 2016

AbstractAuch nach 15 Jahren intensiver Risikoforschung zu Nanomaterialien gestaltet sich die Beurteilung einzelner Materialien noch schwierig. Je länger geforscht wird, umso mehr Studien werden publiziert, die kritische Effekte der Nanomaterialien beobachten. Dabei sollte aber beachtet werden, dass die meisten Studien keine verwertbaren toxikologischen Inhalte haben, auch wenn sie vielfach als solche zitiert und von der Tagespresse aufgegriffen werden. Es mangelt an Verlässlichkeit in der wissenschaftlichen Praxis, insb. in der Nanosicherheitsforschung. Hier wird diese Aussage anhand von Beispielen belegt und Lösungsvorschläge werden aufgezeigt.