bluuebunny/crossref_metadata_2025_split huggingface dataset:
Directional Materials—Nanoporous Organosilica Monoliths with Multiple Gradients Prepared Using Click Chemistry
Authors: Schachtschneider Andreas , Wessig Martin , Spitzbarth Martin , Donner Adrian , Fischer Christian , Drescher Malte , Polarz Sebastian 
Published: July 2015

AbstractThe existence of more than one functional entity is fundamental for materials, which are desired of fulfilling complementary or succeeding tasks. Whereas it is feasible to make materials with a homogeneous distribution of two different, functional groups, cases are extremely rare exhibiting a smooth transition from one property to the next along a defined distance. We present a new approach leading to high‐surface area solids with functional gradients at the microstructural level. Periodically ordered mesoporous organosilicas (PMOs) and aerogel‐like monolithic bodies with a maximum density of azide groups were prepared from a novel sol–gel precursor. The controlled and fast conversion of the azide into numerous functions by click chemistry is the prerequisite for the implementation of manifold gradient profiles. Herein we discuss materials with chemical, optical and structural gradients, which are interesting for all applications requiring directionality, for example, chromatography.
Hydrothermal Synthesis of Unique Hollow Hexagonal Prismatic Pencils of Co3V2O8⋅n H2O: A New Anode Material for Lithium‐Ion Batteries
Authors: Wu Fangfang , Xiong Shenglin , Qian Yitai , Yu Shu‐Hong 
Published: July 2015

AbstractHollow structures of transition‐metal oxides, particularly mixed‐metal oxides, could be promising for various applications such as lithium‐ion batteries (LIBs). Compared to the synthesis of metal oxide hollow spheres by the template method, non‐spherical metal oxide hollow hexagonal polyhedra have not been developed to date. Herein, we report the controlled hydrothermal synthesis of a new phase of Co3V2O8⋅n H2O hollow hexagonal prismatic pencils (HHPPs), which is composed of uniform structural units. By varying the amount of NaOH in the presence of NH4+ and without any template or organic surfactant, the hexagonal prismatic pencils gradually transform from solid into hollow structures, with sizes varying from 5 to 20 μm. The structure of pencils can be preserved only in a limited range of the molar ratio of OH−/NH4+. As a new anode material for LIBs, such hollow pencils exhibit impressive lithium storage properties with high capacity, good cycling stability, and superior rate capability.
Ein universeller Zugang zu Nucleobasen‐modifizierten Aptameren
Authors: Tolle Fabian , Brändle Gerhard M. , Matzner Daniel , Mayer Günter 
Published: July 2015

AbstractWir beschreiben eine neue und vielseitige Methode, um die chemische Diversität von Nucleinsäurebibliotheken modular zu erweitern. Dies ermöglicht den Zugang zu Nucleobasen‐modifizierten Aptameren mit einer bisher unerreicht hohen Affinität und Spezifität für ihre Zielstrukturen. Die Wiedereinführung der Modifikation nach der enzymatischen Replikation gewährt dabei einen eleganten Zugang zu einer Vielzahl von chemischen Gruppen. Die breite Anwendbarkeit, die sich nicht auf eine einzige Modifikation beschränkt, wird in Zukunft In‐vitro‐Selektionsprozesse rasant voranbringen und weitere Aptamere für viele bis dato nicht adressierbare Zielstrukturen generieren.
Total Syntheses and Biological Evaluation of Both Enantiomers of Several Hydroxylated Dimeric Nuphar Alkaloids
Authors: Korotkov Alexander , Li Hui , Chapman Charles W. , Xue Haoran , MacMillan John B. , Eastman Alan , Wu Jimmy 
Published: July 2015

AbstractHerein, we describe the first total syntheses of five members of the dimeric nuphar alkaloids: (+)‐6,6′‐dihydroxythiobinupharidine (+)‐1 a, (+)‐6‐hydroxythiobinupharidine (+)‐1 b, (−)‐6,6′‐dihydroxythionuphlutine (−)‐2 a, (−)‐6,6′‐dihydroxyneothiobinupharidine (−)‐3 a, and (+)‐6,6′‐dihydroxyneothionuphlutine (+)‐4 a. The latter two have not been found in nature. We have also made each of their enantiomers (−)‐1 a–b, (+)‐2 a, (+)‐3 a, and (−)‐4 a. The key step in these syntheses was the dimerization of an α‐aminonitrile (a hydrolytically stable surrogate for its corresponding hemiaminal) with chiral Lewis acid complexes. We have also reassigned the literature structures of (+)‐1 a–1 b—for those instances in which the NMR spectra were obtained in CD3OD—to their corresponding CD3O‐adducts. Our efforts provide for the first time apoptosis data for (−)‐3 a, (+)‐4 a, and all five non‐natural enantiomers prepared. The data indicate high apoptotic activity regardless of the enantiomer or relative stereochemical configuration at C7 and C7′.
Palladium‐Catalyzed Hydroamidocarbonylation of Olefins to Imides
Authors: Li Haoquan , Dong Kaiwu , Neumann Helfried , Beller Matthias 
Published: July 2015

AbstractCarbonylation reactions allow the efficient synthesis of all kinds of carbonyl‐containing compounds. Here, we report a straightforward synthesis of various imides from olefins and CO for the first time. The established hydroamidocarbonylation reaction affords imides in good yields (up to 90 %) and with good regioselectivity (up to 99:1) when applying different alkenes and amides. The synthetic potential of the method is highlighted by the synthesis of Aniracetam by intramolecular hydroamidocarbonylation.
Regioselective and 1,2‐cis‐α‐Stereoselective Glycosylation Utilizing Glycosyl‐Acceptor‐Derived Boronic Ester Catalyst
Authors: Nakagawa Akira , Tanaka Masamichi , Hanamura Shun , Takahashi Daisuke , Toshima Kazunobu 
Published: July 2015

AbstractRegioselective and 1,2‐cis‐α‐stereoselective glycosylations using 1α,2α‐anhydro glycosyl donors and diol glycosyl acceptors in the presence of a glycosyl‐acceptor‐derived boronic ester catalyst. The reactions proceed smoothly to give the corresponding 1,2‐cis‐α‐glycosides with high stereo‐ and regioselectivities in high yields without any further additives under mild reaction conditions. In addition, the present glycosylation method was successfully applied to the synthesis of an isoflavone glycoside.
Revealing the Macromolecular Targets of Fragment‐Like Natural Products
Authors: Rodrigues Tiago , Reker Daniel , Kunze Jens , Schneider Petra , Schneider Gisbert 
Published: July 2015

AbstractFragment‐like natural products were identified as ligand‐efficient chemical matter for hit‐to‐lead development and chemical‐probe discovery. Relying on a computational method using a topological pharmacophore descriptor and a drug database, several macromolecular targets from distinct protein families were expeditiously retrieved for structurally unrelated chemotypes. The selected fragments feature structural dissimilarity to the reference compounds and suitable target affinity, and they offer opportunities for chemical optimization. Experimental confirmation of hitherto unknown macromolecular targets for the selected molecules corroborate the usefulness of the computational approach and suggests broad applicability to chemical biology and molecular medicine.
Herstellung von festen, substituierten Allylzinkreagentien und deren Reaktionen mit Elektrophilen
Authors: Ellwart Mario , Knochel Paul 
Published: July 2015

AbstractDie Reaktion von verschiedenen allylischen Chloriden und Bromiden mit Zinkstaub in der Gegenwart von Lithiumchlorid und Magnesiumpivalat (Mg(OCOtBu)2) in THF führt zu allylischen Zinkreagentien, welche nach Entfernen des Lösungsmittels als feste Zinkreagentien erhalten werden, die eine exzellente thermische Stabilität aufweisen. Diese allylischen Reagentien können sowohl in Pd‐katalysierten Kreuzkupplungen mit PEPPSI‐IPent, als auch in regio‐ und stereoselektiven Additionen an aromatische Ketone und Aldehyde verwendet werden. Acylierungen mit verschiedenen Säurechloriden führen regioselektiv zu den entsprechenden homoallylischen Ketonen, wobei die neue C‐C‐Bindung immer an der sterisch stärker gehinderten Seite gebildet wird.
Amphiphilic Nanoparticles Control the Growth and Stability of Lipid Bilayers with Open Edges
Authors: Shin Sun Hae Ra , Lee Hee‐Young , Bishop Kyle J. M. 
Published: July 2015

AbstractMolecular amphiphiles self‐assemble in polar media to form ordered structures such as micelles and vesicles essential to a broad range of industrial and biological processes. Some of these architectures such as bilayer sheets, helical ribbons, and hollow tubules are potentially useful but inherently unstable owing to the presence of open edges that expose the hydrophobic bilayer core. Here, we describe a strategy to stabilize open bilayer structures using amphiphilic nanoparticle surfactants that present mixtures of hydrophilic and hydrophobic ligands on their surface. We observe that these particles bind selectively to the open edge of bilayer membranes to stabilize otherwise transient amphiphile assemblies. We show how such particles can precisely control the size of lipid tubules, how they can inhibit the formation of undesirable assemblies such as gallstone precursors, and how they can stabilize free‐floating lipid microdiscs.
A Small‐Molecule Probe for Selective Profiling and Imaging of Monoamine Oxidase B Activities in Models of Parkinson’s Disease
Authors: Li Lin , Zhang Cheng‐Wu , Ge Jingyan , Qian Linghui , Chai Bing‐Han , Zhu Qing , Lee Jun‐Seok , Lim Kah‐Leong , Yao Shao Q. 
Published: July 2015

AbstractThe design of the first dual‐purpose activity‐based probe of monoamine oxidase B (MAO‐B) is reported. This probe is highly selective towards MAO‐B, even at high MAO‐A expression levels, and could sensitively report endogenous MAO‐B activities by both in situ proteome profiling and live‐cell bioimaging. With a built‐in imaging module as part of the probe design, the probe was able to accomplish what all previously reported MAO‐B imaging probes failed to do thus far: the live‐cell imaging of MAO‐B activities without encountering diffusion problems.
A Single Stereodynamic Center Modulates the Rate of Self‐Assembly in a Biomolecular System
Authors: Zhang Yitao , Malamakal Roy M. , Chenoweth David M. 
Published: July 2015

AbstractChirality is a property of asymmetry important to both physical and abstract systems. Understanding how molecular systems respond to perturbations in their chiral building blocks can provide insight into diverse areas such as biomolecular self‐assembly, protein folding, drug design, materials, and catalysis. Despite the fundamental importance of stereochemical preorganization in nature and designed materials, the ramifications of replacing chiral centers with stereodynamic atomic mimics in the context of biomolecular systems is unknown. Herein, we demonstrate that replacement of a single amino acid stereocenter with a stereodynamic nitrogen atom has profound consequences on the self‐assembly of a biomolecular system. Our results provide insight into how the fundamental biopolymers of life would behave if their chiral centers were not configurationally stable, highlighting the vital importance of stereochemistry as a pre‐organizing element in biomolecular folding and assembly events.
A Single Enzyme Transforms a Carboxylic Acid into a Nitrile through an Amide Intermediate
Authors: Nelp Micah T. , Bandarian Vahe 
Published: July 2015

AbstractThe biosynthesis of nitriles is known to occur through specialized pathways involving multiple enzymes; however, in bacterial and archeal biosynthesis of 7‐deazapurines, a single enzyme, ToyM, catalyzes the conversion of the carboxylic acid containing 7‐carboxy‐7‐deazaguanine (CDG) into its corresponding nitrile, 7‐cyano‐7‐deazaguanine (preQ0). The mechanism of this unusual direct transformation was shown to proceed via the adenylation of CDG, which activates it to form the newly discovered amide intermediate 7‐amido‐7‐deazaguanine (ADG). This is subsequently dehydrated to form the nitrile in a process that consumes a second equivalent of ATP. The authentic amide intermediate is shown to be chemically and kinetically competent. The ability of ToyM to activate two different substrates, an acid and an amide, accounts for this unprecedented one‐enzyme catalysis of nitrile synthesis, and the differential rates of these two half reactions suggest that this catalytic ability is derived from an amide synthetase that gained a new function.
White‐Light Emission from an Integrated Upconversion Nanostructure: Toward Multicolor Displays Modulated by Laser Power
Authors: Zhang Cheng , Yang Liang , Zhao Jun , Liu Bianhua , Han Ming‐Yong , Zhang Zhongping 
Published: July 2015

AbstractThe white backlight in displays is generated by optimizing the proportions of individual emitters with different wavelengths by variations in materials composition, phase, and structure. Color pixels usually result from the separation of white light or the excitation with multiwavelength or multipulse sources. However, it is a challenge to develop a material that comprises a single structure and emits over the full visible spectrum, but where the emission wavelengths can be controlled by a simple excitation source. Herein, we report an upconversion nanostructure that incorporates several lanthanide ions in the same core@shell@shell structure. The combination of multiple narrow spectral bands results in the emission of white light. The emission colors can be tuned by changing the excitation power density, which manipulates the photon transfer pathways. Applications such as flat‐panel displays and imaging have been demonstrated.
Synthesis of 3,4,5‐Trisubstituted Isoxazoles from Morita–Baylis–Hillman Acetates by an NaNO2/I2‐Mediated Domino Reaction
Authors: Dighe Shashikant U. , Mukhopadhyay Sushobhan , Kolle Shivalinga , Kanojiya Sanjeev , Batra Sanjay 
Published: July 2015

AbstractAn efficient NaNO2/I2‐mediated one‐pot transformation of Morita–Baylis–Hillman (MBH) acetates into alkyl 3‐nitro‐5‐(aryl/alkyl)isoxazole‐4‐carboxylates is described. In a cascade event, initial Michael addition of NaNO2 to the MBH acetate furnishes the allylnitro intermediate which undergoes I2‐catalyzed oxidative α‐CH nitration of the nitromethyl subunit followed by [3+2] cycloaddition to afford the title compounds. Structural elaborations of these highly substituted isoxazoles by SNAr reactions and hydrogenolysis allows access to useful products.
X‐ray Radiation‐Controlled NO‐Release for On‐Demand Depth‐Independent Hypoxic Radiosensitization
Authors: Fan Wenpei , Bu Wenbo , Zhang Zhen , Shen Bo , Zhang Hui , He Qianjun , Ni Dalong , Cui Zhaowen , Zhao Kuaile , Bu Jiwen , Du Jiulin , Liu Jianan , Shi Jianlin 
Published: July 2015

AbstractMultifunctional stimuli‐responsive nanotheranostic systems are highly desirable for realizing simultaneous biomedical imaging and on‐demand therapy with minimized adverse effects. Herein, we present the construction of an intelligent X‐ray‐controlled NO‐releasing upconversion nanotheranostic system (termed as PEG‐USMSs‐SNO) by engineering UCNPs with S‐nitrosothiol (R‐SNO)‐grafted mesoporous silica. The PEG‐USMSs‐SNO is designed to respond sensitively to X‐ray radiation for breaking down the SN bond of SNO to release NO, which leads to X‐ray dose‐controlled NO release for on‐demand hypoxic radiosensitization besides upconversion luminescent imaging through UCNPs in vitro and in vivo. Thanks to the high live‐body permeability of X‐ray, our developed PEG‐USMSs‐SNO may provide a new technique for achieving depth‐independent controlled NO release and positioned radiotherapy enhancement against deep‐seated solid tumors.
An Enantioselective Synthesis of Spirobilactams through Copper‐Catalyzed Intramolecular Double N‐Arylation and Phase Separation
Authors: Liu Jianguang , Tian Yingying , Shi Jialing , Zhang Shasha , Cai Qian 
Published: July 2015

AbstractSpirobicyclic structures are versatile building blocks for functional chiral molecules. An enantioselective synthesis of chiral spirobilactams via a copper‐catalyzed double N‐arylation was developed. Amplification of solution ee by in situ precipitation of the racemate was observed with this method and enantioenriched spirobilactams were obtained with excellent ee values through simple solid–solution phase separation.
Switchable Lipids: Conformational Change for Fast pH‐Triggered Cytoplasmic Delivery
Authors: Viricel Warren , Mbarek Amira , Leblond Jeanne 
Published: July 2015

AbstractWe report the use of switchable lipids to improve the endosomal escape and cytosolic delivery of cell‐impermeable compounds. The system is based on a conformational reorganization of the lipid structure upon acidification, as demonstrated by NMR spectroscopic studies. When incorporated in a liposome formulation, the switchable lipids triggered bilayer destabilization through fusion even in the presence of poly(ethylene glycol). We observed 88 % release of sulforhodamine B in 15 min at pH 5, and the liposome formulations demonstrated high stability at pH 7.4 for several months. By using sulforhodamine B as a model of a highly polar drug, we demonstrated fast cytosolic delivery mediated by endosomal escape in HeLa cells, and no toxicity.
Rattling in the Quadruple Perovskite CuCu3V4O12
Authors: Akizuki Yasuhide , Yamada Ikuya , Fujita Koji , Taga Kazuya , Kawakami Takateru , Mizumaki Masaichiro , Tanaka Katsuhisa 
Published: July 2015

AbstractOf particular interest is a peculiar motion of guest atoms or ions confined to nanospace in cage compounds, called rattling. While rattling provides unexplored physical properties through the guest–host interactions, it has only been observed in a very limited class of materials. Herein, we introduce an A‐site‐ordered quadruple perovskite, CuCu3V4O12, as a new family of cage compounds. This novel AA′3B4O12‐type perovskite has been obtained by a high‐pressure synthesis technique and structurally characterized to have cubic Im$\bar 3$ symmetry with an ionic model of Cu2+Cu2+3V4+4O12. The thermal displacement parameter of the A‐site Cu2+ ion is as large as Uiso≈0.045 Å2 at 300 K, indicating its large‐amplitude thermal oscillations in the oversized icosahedral cages. Remarkably, the presence of localized phonon modes associated with rattling of the A‐site Cu2+ ion manifests itself in the low‐temperature specific heat data. This work sheds new light on the structure–property relations in perovskites.
Waterproof Alkyl Phosphate Coated Fluoride Phosphors for Optoelectronic Materials
Authors: Nguyen Hoang‐Duy , Lin Chun Che , Liu Ru‐Shi 
Published: July 2015

AbstractA facile approach for coating red fluoride phosphors with a moisture‐resistant alkyl phosphate layer with a thickness of 50–100 nm is reported. K2SiF6:Mn4+ particles were prepared by co‐precipitation and then coated by esterification of P2O5 with alcohols (methanol, ethanol, and isopropanol). This route was adopted to encapsulate the prepared phosphors using transition‐metal ions as cross‐linkers between the alkyl phosphate moieties. The coated phosphor particles exhibited a high water tolerance and retained approximately 87 % of their initial external quantum efficiency after aging under high‐humidity (85 %) and high‐temperature (85 °C) conditions for one month. Warm white‐light‐emitting diodes that consisted of blue InGaN chips, the prepared K2SiF6:Mn4+ phosphors, and either yellow Y3Al5O12:Ce3+ phosphors or green β‐SiAlON: Eu2+ phosphors showed excellent color rendition.
Frustration Sculpts the Early Stages of Protein Folding
Authors: Di Silvio Eva , Brunori Maurizio , Gianni Stefano 
Published: July 2015

AbstractThe funneled energy landscape theory implies that protein structures are minimally frustrated. Yet, because of the divergent demands between folding and function, regions of frustrated patterns are present at the active site of proteins. To understand the effects of such local frustration in dictating the energy landscape of proteins, here we compare the folding mechanisms of the two alternative spliced forms of a PDZ domain (PDZ2 and PDZ2as) that share a nearly identical sequence and structure, while displaying different frustration patterns. The analysis, based on the kinetic characterization of a large number of site‐directed mutants, reveals that although the late stages for folding are very robust and biased by native topology, the early stages are more malleable and dominated by local frustration. The results are briefly discussed in the context of the energy‐landscape theory.
Stabilisierung von anorganischem Acetylen, HBNH, mithilfe flankierender koordinativer Wechselwirkungen
Authors: Swarnakar Anindya K. , Hering‐Junghans Christian , Nagata Koichi , Ferguson Michael J. , McDonald Robert , Tokitoh Norihiro , Rivard Eric 
Published: July 2015

AbstractEin stabiler Donor‐Akzeptor‐Koordinationskomplex des schwer greifbaren Stamm‐Iminoborans HBNH (ein strukturelles Analog von Acetylen) wird beschrieben. Diese Spezies wurde durch eine thermisch induzierte N2‐Eliminierung/1,2‐H‐Migration generiert, ausgehend von einem Hydrido(azido)boran‐Addukt NHC⋅BH2N3 (NHC=N‐heterocyclisches Carben) in der Gegenwart eines fluorierten Triarylborans. Der Mechanismus dieses Prozesses wurde mithilfe von Berechnungen und Isotopenmarkierungsstudien untersucht. Diese Umwandlung stellt eine neue und potentiell modulare Route zu ungesättigten anorganischen Baueinheiten für fortgeschrittene Materialien dar.
Catalytic Synthesis of N‐Unprotected Piperazines, Morpholines, and Thiomorpholines from Aldehydes and SnAP Reagents
Authors: Luescher Michael U. , Bode Jeffrey W. 
Published: July 2015

AbstractCommercially available SnAP (stannyl amine protocol) reagents allow the transformation of aldehydes and ketones into a variety of N‐unprotected heterocycles. By identifying new ligands and reaction conditions, a robust catalytic variant that expands the substrate scope to previously inaccessible heteroaromatic substrates and new substitution patterns was realized. It also establishes the basis for a catalytic enantioselective process through the use of chiral ligands.
Self‐Pillared, Single‐Unit‐Cell Sn‐MFI Zeolite Nanosheets and Their Use for Glucose and Lactose Isomerization
Authors: Ren Limin , Guo Qiang , Kumar Prashant , Orazov Marat , Xu Dandan , Alhassan Saeed M. , Mkhoyan K. Andre , Davis Mark E. , Tsapatsis Michael 
Published: July 2015

AbstractSingle‐unit‐cell Sn‐MFI, with the detectable Sn uniformly distributed and exclusively located at framework sites, is reported for the first time. The direct, single‐step, synthesis is based on repetitive branching caused by rotational intergrowths of single‐unit‐cell lamellae. The self‐pillared, meso‐ and microporous zeolite is an active and selective catalyst for sugar isomerization. High yields for the conversion of glucose into fructose and lactose to lactulose are demonstrated.
Pushing the Limits of Neutral Organic Electron Donors: A Tetra(iminophosphorano)‐Substituted Bispyridinylidene
Authors: Hanson Samuel S. , Doni Eswararao , Traboulsee Kyle T. , Coulthard Graeme , Murphy John A. , Dyker C. Adam 
Published: July 2015

AbstractA new ground‐state organic electron donor has been prepared that features four strongly π‐donating iminophosphorano substituents on a bispyridinylidene skeleton. Cyclic voltammetry reveals a record redox potential of −1.70 V vs. saturated calomel electrode (SCE) for the couple involving the neutral organic donor and its dication. This highly reducing organic compound can be isolated (44 %) or more conveniently generated in situ by a deprotonation reaction involving its readily prepared pyridinium ion precursor. This donor is able to reduce a variety of aryl halides, and, owing to its redox potential, was found to be the first organic donor to be effective in the thermally induced reductive SN bond cleavage of N,N‐dialkylsulfonamides, and reductive hydrodecyanation of malonitriles.