bluuebunny/crossref_metadata_2025_split huggingface dataset:
Genetic and Biosynthetic Studies of the Fungal Prenylated Xanthone Shamixanthone and Related Metabolites in Aspergillus spp. Revisited
Authors: Simpson Thomas J. 
Published: June 2012

AbstractBiosynthetic genes for the prenylated xanthone shamixanthone have been identified in the Aspergillus nidulans genome; based on assignment of putative functions from sequence analyses and selected gene deletions, a pathway was proposed leading from the anthraquinone emodin via the benzophenone carboxylic acid monodictyphenone and the xanthone emericellin to shamixanthone. Several aspects of this proposed pathway are inconsistent with previously identified biosynthetic intermediates: the anthraquinone chrysophanol and the benzophenone aldehyde derivatives arugosins F and A/B, isotopic labelling studies and chemical precedents. A new pathway is presented that provides a full rationale for the results of the gene deletion studies and reconciles them with previous biosynthetic results, and is in accord with established chemical and biosynthetic mechanisms. The importance of interpreting genetic information in terms of established biosynthetic events is discussed.
Characterization of the Suillus grevillei Quinone Synthetase GreA Supports a Nonribosomal Code for Aromatic α‐Keto Acids
Authors: Wackler Barbara , Lackner Gerald , Chooi Yit Heng , Hoffmeister Dirk 
Published: June 2012

AbstractThe gene greA was cloned from the genome of the basidiomycete Suillus grevillei. It encodes a monomodular natural product biosynthesis protein composed of three domains for adenylation, thiolation, and thioesterase and, hence, is reminiscent of a nonribosomal peptide synthetase (NRPS). GreA was biochemically characterized in vitro. It was identified as atromentin synthetase and therefore represents one of only a limited number of biochemically characterized NRPS‐like enzymes which accept an aromatic α‐keto acid. Specificity‐conferring amino acid residues—collectively referred to as the nonribosomal code—were predicted for the primary sequence of the GreA adenylation domain and were an unprecedented combination for aromatic α‐keto acids. Plausible support for this new code came from in silico simulation of the adenylation domain structure. According to the model, the predicted residues line the active site and, therefore, very likely contribute to substrate specificity.
Palladium‐Catalyzed Allylic Oxidation of Monoterpenic Alkenes with Molecular Oxygen
Authors: Bueno Aline C. , de Souza Ágatha O. , Gusevskaya Elena V. 
Published: June 2012

AbstractPalladium/p‐benzoquinone‐catalyzed aerobic oxidation of biomass‐based feedstock substrates, that is, limonene and α‐terpineol, has been developed. The system promotes an efficient dioxygen‐coupled catalytic turnover in the absence of auxiliary redox‐active co‐catalysts. Important for flavor and pharmaceutical industries, monoterpenic allylic acetates have been obtained in good to excellent yields. The regioselectivity of the limonene oxidation can be controlled through the appropriate choice of ligands and reaction conditions, which enables the variation of organoleptic properties of the product mixtures. The catalytic system can be applied generally to the allylic oxidation of simple cycloalkenes with molecular oxygen, for example, cyclohexene gives the corresponding allylic acetate in a nearly quantitative yield.
The Effect of Alcohol Structures on the Interaction Mode with the Hexameric Capsule of Resorcin[4]arene
Authors: Slovak Sarit , Cohen Yoram 
Published: June 2012

AbstractAfter more than a century of research on resorcin[4]arenes (1) it is clear that such systems form spontaneously [16(H2O)8]‐type hexameric capsules in wet, non‐polar, organic solvents. However, the interactions of these hexameric capsules with alcohols are far from being solved. Here we provide the results of an extensive study on the interaction of different alcohols with the hexameric capsules of resorcin[4]arene 1 a by focusing on the exchange of magnetization manifested in diffusion NMR measurements of such capsular systems. We found that some alcohols such as 2‐octyl‐1‐dodecanol and 1‐octadecanol do not interact with the hexamers of 1 a, whereas other alcohols such as 3‐ethyl‐3‐pentanol, 2‐ethyl‐1‐butanol and more act as simple guests and are simply encapsulated in the hexamers. Others alcohols such as 3‐pentanol, 2‐methyl‐1‐butanol and others, are part of the hexameric structure where they can exchange magnetization with alcohols in the bulk. The bulkier alcohols, due to an increase of the chain length or in branching, have a higher tendency to be encapsulated rather than being part of the hexameric capsule superstructure. This study demonstrate the unique information that diffusion NMR spectroscopy can provide on supramolecular systems in solution and on the precaution that should be exercised when analyzing diffusion NMR data of such dynamic supramolecular capsules.
Porous, Conductive Metal‐Triazolates and Their Structural Elucidation by the Charge‐Flipping Method
Authors: Gándara Felipe , Uribe‐Romo Fernando J. , Britt David K. , Furukawa Hiroyasu , Lei Liao , Cheng Rui , Duan Xiangfeng , O'Keeffe Michael , Yaghi Omar M. 
Published: June 2012

AbstractA new family of porous crystals was prepared by combining 1H‐1,2,3‐triazole and divalent metal ions (Mg, Mn, Fe, Co, Cu, and Zn) to give six isostructural metal‐triazolates (termed MET‐1 to 6). These materials are prepared as microcrystalline powders, which give intense X‐ray diffraction lines. Without previous knowledge of the expected structure, it was possible to apply the newly developed charge‐flipping method to solve the complex crystal structure of METs: all the metal ions are octahedrally coordinated to the nitrogen atoms of triazolate such that five metal centers are joined through bridging triazolate ions to form super‐tetrahedral units that lie at the vertexes of a diamond‐type structure. The variation in the size of metal ions across the series provides for precise control of pore apertures to a fraction of an Angstrom in the range 4.5 to 6.1 Å. MET frameworks have permanent porosity and display surface areas as high as some of the most porous zeolites, with one member of this family, MET‐3, exhibiting significant electrical conductivity.
Synthesis and Study of Plasmon‐Induced Carrier Behavior at Ag/TiO2 Nanowires
Authors: Li Haiyan , Lu Wenbo , Tian Jingqi , Luo Yonglan , Asiri Abdullah M. , Al‐Youbi Abdulrahman O. , Sun Xuping 
Published: June 2012

AbstractNanocomposites of Ag/TiO2 nanowires with enhanced photoelectrochemical performance have been prepared by a facile solvothermal synthesis of TiO2 nanowires and subsequent photoreduction of Ag+ ions to Ag nanoparticles (AgNPs) on the TiO2 nanowires. The as‐prepared nanocomposites exhibited significantly improved cathodic photocurrent responses under visible‐light illumination, which is attributed to the local electric field enhancement of plasmon resonance effect near the TiO2 surface rather than by the direct transfer of charge between the two materials. The visible‐light‐driven photocatalytic performance of these nanocomposites in the degradation of methylene blue dye was also studied, and the observed improvement in photocatalytic activity is associated with the extended light absorption range and efficient charge separation due to surface plasmon resonance effect of AgNPs.
Theoretical Study of the Oxidation of Histidine by Singlet Oxygen
Authors: Méndez‐Hurtado Jefferson , López Ramón , Suárez Dimas , Menéndez María Isabel 
Published: June 2012

AbstractHerein we present a theoretical study of the reaction of singlet oxygen with histidine performed both in the gas phase and in aqueous solution. The potential energy surface of the reactive system was explored at the B3LYP/cc‐pVTZ level of theory and the electronic energies were refined by means of single‐point CCSD(T)/cc‐pVTZ(‐f) calculations. Solvent effects were taken into account by using a solvent continuum model (COSMO) and by adding explicit water molecules. The results show that the first step in the reaction mechanism corresponds to a nearly symmetric Diels–Alder addition of the singlet oxygen molecule to the imidazole ring to yield an endoperoxide, in agreement with experimental evidence. The intermediate formed can evolve along two different reaction paths leading to two isomeric hydroperoxides and, eventually, to open‐chain or internally cyclised oxidised products. Water plays a significant role in stabilising the reaction structures by solvation and by acting as a bifunctional catalyst in the elimination/addition reaction steps. Our results explain why substituents at the N1‐imidazole ring can hamper the evolution of the initial endoperoxide and result in Gibbs energy barriers in solution similar to those experimentally measured and suggest a likely route to the formation of peptide aggregates during the oxidation of histidine by singlet molecular oxygen.
Chitosan Bio‐Based Organic–Inorganic Hybrid Aerogel Microspheres
Authors: El Kadib Abdelkrim , Bousmina Mosto 
Published: June 2012

AbstractRecently, organic–inorganic hybrid materials have attracted tremendous attention thanks to their outstanding properties, their efficiency, versatility and their promising applications in a broad range of areas at the interface of chemistry and biology. This article deals with a new family of surface‐reactive organic–inorganic hybrid materials built from chitosan microspheres. The gelation of chitosan (a renewable amino carbohydrate obtained by deacetylation of chitin) by pH inversion affords highly dispersed fibrillar networks shaped as self‐standing microspheres. Nanocasting of sol–gel processable monomeric alkoxides inside these natural hydrocolloids and their subsequent CO2 supercritical drying provide high‐surface‐area organic–inorganic hybrid materials. Examples including chitosan–SiO2, chitosan–TiO2, chitosan–redox‐clusters and chitosan–clay‐aerogel microspheres are described and discussed on the basis of their textural and structural properties, thermal and chemical stability and their performance in catalysis and adsorption.
Porous Ni@Pt Core‐Shell Nanotube Array Electrocatalyst with High Activity and Stability for Methanol Oxidation
Authors: Ding Liang‐Xin , Li Gao‐Ren , Wang Zi‐Long , Liu Zhao‐Qing , Liu Hong , Tong Ye‐Xiang 
Published: June 2012

AbstractBimetallic core‐shell nanostructures are emerging as more important materials than monometallic nanostructures, and have much more interesting potential applications in various fields, including catalysis and electronics. In this work, we demonstrate the facile synthesis of core‐shell nanotube array catalysts consisting of Pt thin layers as the shells and Ni nanotubes as the cores. The porous Ni@Pt core‐shell nanotube arrays were fabricated by ZnO nanorod‐array template‐assisted electrodeposition, and they represent a new class of nanostructures with a high electrochemically active surface area of 50.08 m2 (g Pt)−1, which is close to the value of 59.44 m2 (g Pt)−1 for commercial Pt/C catalysts. The porous Ni@Pt core‐shell nanotube arrays also show markedly enhanced electrocatalytic activity and stability for methanol oxidation compared with the commercial Pt/C catalysts. The attractive performances exhibited by these prepared porous Ni@Pt core‐shell nanotube arrays make them promising candidates as future high‐performance catalysts for methanol electrooxidation. The facile method described herein is suitable for large‐scale, low‐cost production, and significantly lowers the Pt loading, and thus, the cost of the catalysts.
Isostructural M2L4 Molecular Capsules with Anthracene Shells: Synthesis, Crystal Structures, and Fluorescent Properties
Authors: Li Zhiou , Kishi Norifumi , Yoza Kenji , Akita Munetaka , Yoshizawa Michito 
Published: June 2012

AbstractAn isostructural series of M2L4 molecular capsules quantitatively self‐assembled from two MII ions (M=Zn, Cu, Pt, Pd, Ni, Co, and Mn) and four bent ligands with embedded anthracene fluorophores. X‐ray crystallographic analysis (for M=Zn, Cu, Ni, and Pd) confirmed the formation of closed‐shell structures in which the large interior cavities inside the molecular capsules (about 1 nm) were shielded by eight anthracene panels. Analysis of the ZnII and CuII structures showed the inclusion of an unusual triad guest cluster; four MeCN molecules, one water molecule, and one CF3SO3− ion were located inside the cavities. Full characterization by NMR spectroscopy and MS (ESI‐TOF) demonstrated that the molecular capsules were quite stable and persist in solution. The fluorescence properties of the isostructural capsules were strongly dependent on the identity of the metal species: the ZnII capsule emitted strong blue fluorescence with a high quantum yield (Φ=0.8), in sharp contrast to the weakly emissive NiII and MnII capsules and the completely non‐emissive PdII, PtII, and CoII capsules. On the other hand, the CuII capsule exhibited solvatochromism and solvent‐dependent emission behavior; blue emission of the capsule was “on” in DMSO but “off” in MeCN.
A Flexible Copper(I)‐Complexed [4]Rotaxane Containing Two Face‐to‐Face Porphyrinic Plates that Behaves as a Distensible Receptor
Authors: Roche Cécile , Sour Angélique , Sauvage Jean‐Pierre 
Published: June 2012

AbstractA new cyclic [4]rotaxane composed of two flexible bis‐macrocycles and two rigid axles is described. Each bis‐macrocycle consists of two rings attached to antipodal meso positions of a central Zn porphyrin through single CC bonds. Each ring incorporates a 2,9‐diphenyl‐1,10‐phenanthroline chelation site. The axles contain two coplanar bidentate sites derived from the 2,2′‐bipyridine motif. The building blocks were assembled by using a one‐pot threading‐and‐stoppering reaction, which afforded the [4]rotaxane in 50 % yield. The “gathering‐and‐threading” effect of copper(I) was utilised in the formation of a [4]pseudorotaxane, which was immediately converted to the corresponding [4]rotaxane by a quadruple CuAAC stoppering reaction. The rotaxane contains two face‐to‐face zinc porphyrins, which allowed the coordination of ditopic guest substrates. The rotaxane host showed remarkable flexibility and was able to adjust its conformation to the guest size. It can be distended and accommodate rod‐like guests of 2.6 to 15.8 Å in length.
C3‐Symmetric Trisimidazoline‐Catalyzed Enantioselective Bromolactonization of Internal Alkenoic Acids
Authors: Murai Kenichi , Nakamura Akira , Matsushita Tomoyo , Shimura Masato , Fujioka Hiromichi 
Published: June 2012

AbstractA method for conducting enantioselective bromolactonization reactions of trisubstituted alkenoic acids, using the C3‐symmetric trisimidazoline 1 and 1,3‐dibromo‐5,5‐dimethyl hydantoin as a bromine source, has been developed. The process generates chiral δ‐lactones that contain a quaternary carbon. The results of studies probing geometrically different olefins show that (Z)‐olefins rather than (E)‐olefins are favorable substrates for the process. The method is not only applicable to acyclic olefin reactants but can also be employed to transform cyclic trisubstituted olefins into chiral spirocyclic lactones. Finally, the synthetic utility of the newly developed process is demonstrated by its application to a concise synthesis of tanikolide, an antifungal marine natural product.
Expanding the Scope of Arylsulfonylacetylenes as Alkynylating Reagents and Mechanistic Insights in the Formation of Csp2Csp and Csp3Csp Bonds from Organolithiums
Authors: García Ruano José Luis , Alemán José , Marzo Leyre , Alvarado Cuauhtémoc , Tortosa Mariola , Díaz‐Tendero Sergio , Fraile Alberto 
Published: June 2012

AbstractWe describe the unexpected behavior of the arylsulfonylacetylenes, which suffer an “anti‐Michael” addition of organolithiums producing their alkynylation under very mild conditions. The broad scope, excellent yields, and simplicity of the experimental procedure are the main features of this methodology. A rational explanation of all these results can be achieved by theoretical calculations, which suggest that the association of the organolithiums to the electrophile is a previous step of their intramolecular attack and is responsible for the unexpected “anti‐Michael” reactions observed for substituted sulfonylacetylenes.
Enhanced Red Emission from GdF3:Yb3+,Er3+ Upconversion Nanocrystals by Li+ Doping and Their Application for Bioimaging
Authors: Yin Wenyan , Zhao Lina , Zhou Liangjun , Gu Zhanjun , Liu Xiaoxiao , Tian Gan , Jin Shan , Yan Liang , Ren Wenlu , Xing Gengmei , Zhao Yuliang 
Published: June 2012

AbstractUnder 980 nm near‐infrared (NIR) excitation, upconversion luminescent (UCL) emission of GdF3:Yb,Er upconversion nanoparticles (UCNPs) synthesized by a simple and green hydrothermal process can be tuned from yellow to red by varying the concentration of dopant Li+ ions. A possible mechanism for enhanced red upconverted radiation is proposed. A layer of silica was coated onto the surface of GdF3:Yb,Er,Li UCNPs to improve their biocompatibility. The silica‐coated GdF3:Yb,Er,Li UCNPs show great advantages in cell labeling and in vivo optical imaging. Moreover, GdF3 UCNPs also exhibited a positive contrast effect in T1‐weighted magnetic resonance imaging (MRI). These results suggest that the GdF3 UCNPs could act as dual‐modality biolabels for optical imaging and MRI.
Metal Ions Induce Growth and Magnetism Alternation of α‐Fe2O3 Crystals Bound by High‐Index Facets
Authors: Liu Rongmei , Jiang Yuanwen , Fan Hao , Lu Qingyi , Du Wei , Gao Feng 
Published: June 2012

AbstractIn this study, quasi‐cubic and hexagonal bipyramid α‐Fe2O3 polyhedrons with high‐index facets exposed were controllably synthesized by applying metal ions Zn2+ or Cu2+ as structure‐directing agents. The growth of the α‐Fe2O3 nanostructures with high‐index facets were induced by metal ions without the addition of any other surfactants. The quasi‐cubic form controlled by Zn2+ looks like a cube but has an angle of approximately 86° bound by (012), (10‐2), and (1‐12) facets, whereas the hexagonal bipyramid form controlled by Cu2+ has a sixfold axis bound by {012} facets. Magnetic measurements confirm that these two kinds of nanocrystals display shape‐ and surface‐dependent magnetic behaviors. The hexagonal bipyramid iron oxide nanocrystals show a lower Morin transition temperature of 240 K and might be spin‐canted ferromagnetically controlled at room temperature, and the ferromagnetism disappears at low temperature. The quasi‐cubic nanocrystals have a splitting between FC curve and ZFC curve from the highest experimental temperature and no Morin transformation occurs; this indicates that they would be defect ferromagnetically controlled at low temperature. The reported metal‐ion‐directing technique could provide a universal method for shape‐ and surface‐controlled synthesis of nanocrystals with high‐index facets exposed.
ChemInform Abstract: Pronounced Site Preference and Mixed Dinuclear Dichalcogenide Anions (SSe)2‐ in Ternary Lanthanum Sulfide Selenides — The Solid Solution LaS1.9—LaSe1.9.
Authors: Bartsch Christian , Doert Thomas 
Published: June 2012

AbstractTernary lanthanum sulfide selenides LaS1.9‐xSex (0 < x < 1.9) are prepared by reaction of the elements in a KBr flux (carbon crucibles, 850 °C, 7 d).
ChemInform Abstract: Ternary Compound CuInTe2: A Promising Thermoelectric Material with Diamond‐Like Structure.
Authors: Liu Ruiheng , Xi Lili , Liu Huili , Shi Xun , Zhang Wenqing , Chen Lidong 
Published: June 2012

AbstractCuInTe2 is synthesized from the elements (evacuated silica tube, 900 °C, 12 h; annealing at 650 °C) and characterized by powder XRD and thermoelectric measurements.
ChemInform Abstract: Gaseous Vanadium Molybdate and Tungstates: Thermodynamic Properties and Structures.
Authors: Gunina Anastasia O. , Lopatin Sergey I. , Shugurov Sergey M. 
Published: June 2012

AbstractThermodynamic properties of gaseous V—Mo—O‐ and V—W—O‐containing species such as the standard formation enthalpies of gaseous VMoO4, VWO3, and VWO4 are determined by high‐temperature mass spectrometry.
ChemInform Abstract: Highly Selective Sorption of Small Polar Molecules by a Nonporous Ionic Crystal of a Lacunary Keggin‐Type Heteropoly Anion and Alkali Metal Cations.
Authors: Miura Yu‐ki , Kamiya Yuichi 
Published: June 2012

AbstractCs6.1K0.9[PW11O39] is synthesized from an aqueous solution of K7PW11O39 and CsCl (room temperature, 1 d, followed by treatment at 473 K for 2 h).
ChemInform Abstract: An Easy Access to Nanocrystalline Alkaline Earth Metal Fluorides — Just by Shaking.
Authors: Dreger M. , Scholz G. , Kemnitz E. 
Published: June 2012

AbstractNanocrystalline alkaline earth metal fluorides MF2 (M: Mg, Ca, Sr, Ba) are mechanochemically synthesized by high energy ball milling of mixtures of the metal sources (acetates, carbonates, hydroxides, alkoxides) and NH4F as fluorinating agent.
ChemInform Abstract: PbPt(IO3)6(H2O): A New Polar Material with Two Types of Stereoactive Lone‐Pairs and a Very Large SHG Response.
Authors: Sun Chuan‐Fu , Hu Chun‐Li , Mao Jiang‐Gao 
Published: June 2012

AbstractThe novel title compound is hydrothermally synthesized from a mixture of PbCl2, Pt(acac)2, I2O5, and H2O (autoclave, 190 °C, 4 d, 80% yield).
ChemInform Abstract: Hydrotrope Induced Catalysis in Water: A Clean and Green Approach for the Synthesis of Medicinally Relevant Bis(indolyl)methanes and 2‐Aryl Benzimidazoles.
Authors: Kamble Santosh , Rashinkar Gajanan , Kumbhar Arjun , Salunkhe Rajashri 
Published: June 2012

AbstractThe reaction is conducted in environmentally benign water, whereas the aqueous phase containing the mediating hydrotrope can be recycled.
ChemInform Abstract: Synthesis and Evaluation of Antitubercular and Antibacterial Activities of New 4‐(2,6‐Dichlorobenzyloxy)phenyl Thiazole, Oxazole and Imidazole Derivatives. Part 2.
Authors: Lu Xiaoyun , Liu Xiaobo , Wan Baojie , Franzblau Scott G. , Chen Lili , Zhou Changlin , You Qidong 
Published: June 2012

AbstractA series of novel 4‐(2,6‐dichlorobenzyloxy)phenyl substituted thiazole, oxazole and imidazole derivatives are synthesized and screened in vitro for their antitubercular (H37Rv) and antibacterial activities.
ChemInform Abstract: Metal‐Free, Visible‐Light Mediated Direct C—H Arylation of Heteroarenes with Aryl Diazonium Salts.
Authors: Hari Durga Prasad , Schroll Peter , Koenig Burkhard 
Published: June 2012

AbstractUnder optimized conditions using eosin Y as a photoredox catalyst and green light LED irradiation, a variety of aryldiazonium salts can be applied to the arylation of furan, thiophenes, an N‐protected pyrrole, and nitrobenzene.
ChemInform Abstract: Dual‐Functional Click‐Triazole: A Metal Chelator and Immobilization Linker for the Construction of a Heterogeneous Palladium Catalyst and Its Application for the Aerobic Oxidation of Alcohols.
Authors: Zhang Guofu , Wang Yong , Wen Xin , Ding Chengrong , Li Ying 
Published: June 2012

AbstractA novel SBA‐15 supported Pd‐catalyst containing a 2‐pyridyl‐1,2,3‐triazole ligand framework is prepared.
ChemInform Abstract: Convenient Chlorination of Some Special Aromatic Compounds Using N‐Chlorosuccinimide.
Authors: Gan Zongjie , Hu Bin , Song Qiao , Xu Yungen 
Published: June 2012

AbstractThe use of NCS in acetonitrile or DMF allows the regioselective synthesis of monochlorinated products from different arenes or N‐heterocycles.
ChemInform Abstract: Practical Synthesis of Aromatic Nitriles via Gallium‐Catalyzed Electrophilic Cyanation of Aromatic C—H Bonds.
Authors: Okamoto Kazuhiro , Watanabe Masahito , Murai Masahito , Hatano Ryo , Ohe Kouichi 
Published: June 2012

AbstractThe cyanation of heteroarenes (I) and arenes (IV) proceeds with very high regioselectivity to afford single products (III) and (V), whilst the reaction of biaryl (VI) affords a mixture of isomers (VII) and (VIII).
ChemInform Abstract: Enantioselective Organocatalytic α‐Alkylation of Ketones by SN1‐Type Reaction of Alcohols.
Authors: Trifonidou Maria , Kokotos Christoforos G. 
Published: June 2012

AbstractThe first examples of a non‐ionic liquid‐type organocatalyst for the “difficult” α‐alkylation of ketones is presented.