bluuebunny/crossref_metadata_2025_split huggingface dataset:
Synthesis and Biological Evaluation of Phosphono Analogues of Capsular Polysaccharide Fragments from Neisseria meningitidis A
Authors: Torres‐Sanchez Maria I. , Zaccaria Cristina , Buzzi Benedetta , Miglio Gianluca , Lombardi Grazia , Polito Laura , Russo Giovanni , Lay Luigi 
Published: May 2007

AbstractNeisseria meningitidis type A (MenA) is a Gram‐negative encapsulated bacterium that may cause explosive epidemics of meningitis, especially in the sub‐Saharan region of Africa. The development and manufacture of an efficient glycoconjugate vaccine against Neisseria meningitidis A is greatly hampered by the poor hydrolytic stability of its capsular polysaccharide, which is made up of (1→6)‐linked 2‐acetamido‐2‐deoxy‐α‐D‐mannopyranosyl phosphate repeating units. Since this chemical lability is a product of the inherent instability of the phosphodiester bridges, here we report the synthesis of phosphonoester‐linked oligomers of N‐acetyl mannosamine as candidates for stabilised analogues of the corresponding phosphate‐bridged saccharides. The installation of each interglycosidic phosphonoester linkage was achieved by Mitsunobu coupling of a glycosyl C‐phosphonate building block with the 6‐OH moiety of a mannosaminyl residue. Each of the synthesised compounds contains an O‐linked aminopropyl spacer at its reducing end (α‐ or β‐oriented) to allow for protein conjugation. The relative affinities of the synthetic molecules were investigated by a competitive ELISA assay and showed that a human polyclonal anti‐MenA serum can recognise both the phosphonoester‐bridged fragments 1–3 and their monomeric subunits, glycosides 20 and 21. Moreover, the biological results suggest that the abilities of these compounds to inhibit the binding of a specific antibody to MenA polysaccharide are dependent on the chain lengths of the molecules, but independent on the orientations of the anomeric linkers.
Intramolecular Hydroamination with Homogeneous Zinc Catalysts: Evaluation of Substituent Effects in N,N′‐Disubstituted Aminotroponiminate Zinc Complexes
Authors: Dochnahl Maximilian , Löhnwitz Karolin , Pissarek Jens‐Wolfgang , Biyikal Mustafa , Schulz Sabrina R. , Schön Sebastian , Meyer Nils , Roesky Peter W. , Blechert Siegfried 
Published: May 2007

AbstractA series of symmetrical and unsymmetrical N,N′‐disubstituted aminotroponimines (ATIHs) have been prepared. Substituents ranging from linear to cyclic alkyl groups, chelating ethers, and aryl groups were employed. The corresponding aminotroponiminate zinc complexes were then synthesized and characterized by a number of techniques, including by X‐ray crystallography. Herein we report on the investigations into their activity in the intramolecular hydroamination of nonactivated alkenes. We also demonstrate that complexes bearing ligands with cyclic alkyl groups show superior activity in a number of selected reactions with functionalized aminoalkenes.
Preparation of a Polymer‐Supported Fluorene‐Based Receptor for Quantitative and Efficient Binding of Silver Cations
Authors: Chebny Vincent J. , Banerjee Moloy , Rathore Rajendra 
Published: May 2007

AbstractWe have designed and synthesized a polymer‐supported material in which a versatile fluorene‐p‐xylene‐based receptor is woven onto the backbone of polystyrene. This polymer‐supported receptor adopts a π‐prismand‐like conformation through a simple CC bond rotation that results in the quantitative binding of a single silver cation per receptor site with a remarkable efficiency that exceeds the binding abilities of the well‐known tris[2.2.2]‐p‐cyclophane (or π prismand) by at least a factor of 100. More importantly, the binding event can be readily monitored by 1H NMR spectroscopy, as well as by a more sensitive emission spectroscopic technique in which the quenching of fluorescence of the receptor moiety is quantitatively related to the binding of silver cations.
Hydrolysis of Dinuclear Ruthenium Complexes [{CpRu(PPh3)2}2(μ,η1:1‐L)][CF3SO3]2 (L=P4, P4S3): Simple Access to Metal Complexes of P2H4 and PH2SH
Authors: Barbaro Pierluigi , Di Vaira Massimo , Peruzzini Maurizio , Seniori Costantini Stefano , Stoppioni Piero 
Published: May 2007

AbstractThe reaction of [CpRu(PPh3)2Cl] (1) with half an equivalent of P4 or P4S3 in the presence of AgCF3SO3 as chloride scavenger affords the stable dimetal complexes [{CpRu(PPh3)2}2(μ,η1:1‐P4)][CF3SO3]2⋅ 3 CH2Cl2 (2) and [{CpRu(PPh3)2}2(μ,η1:1‐Papical‐Pbasal‐P4S3)][CF3SO3]2⋅ 0.5 C7H8 (3), in which the tetrahedral P4 and mixed‐cage P4S3 molecules are respectively bound to two CpRu(PPh3)2 fragments through two phosphorus atoms. The coordinated cage molecules, at variance with the free ligands, readily react with an excess of water in THF under mild conditions. Among the hydrolysis products, the new, remarkably stable complexes [{CpRu(PPh3)2}2(μ,η1:1‐P2H4)][CF3SO3]2 (4) and [CpRu(PPh3)2(η1‐PH2SH)]CF3SO3 (8) were isolated. In the former, diphosphane, P2H4, is coordinated to two CpRu(PPh3)2 fragments, and in the latter thiophosphinous acid, H2PSH, is coordinated to the metal centre through the phosphorus atom. All compounds were characterised by elemental analyses and IR and NMR spectroscopy. The crystal structures of 2, 3, 4 and 8 were determined by X‐ray diffraction.
Novel Transition‐Metal‐Free Heterogeneous Epoxidation Catalysts Discovered by Means of High‐Throughput Experimentation
Authors: Pescarmona Paolo P. , Janssen Kris P. F. , Jacobs Pierre A. 
Published: May 2007

AbstractVarious transition‐metal‐free oxides have been studied as catalysts for the epoxidation of cyclooctene with hydrogen peroxide by means of high‐throughput experimentation. Different boron, aluminium, and gallium oxides were prepared according to various synthesis methods. A number of pure aluminium and gallium oxides showed very good catalytic performances, while the results obtained with boron oxides or mixed oxides were less positive. The best results were obtained with a gallium oxide catalyst, which gave an epoxide yield of 71 % and a selectivity of 99 % after reaction for 4 h at 80 °C. Gallium oxides had not been reported previously as active epoxidation catalysts. The use of high‐throughput experimentation proved useful both for discovering new active catalysts and for identifying a number of relationships between the synthesis conditions and the catalytic properties of the transition‐metal‐free oxides.
Copper Halide‐Bridged Ruthenium Telluride Carbonyl Complexes: Discovery of the Semiconducting Cluster Chain Polymer {[PPh4]2[Te2Ru4(CO)10Cu4Br2Cl2]⋅THF}∞
Authors: Shieh Minghuey , Hsu Miao‐Hsing , Sheu Wen‐Shyan , Jang Li‐Fing , Lin Shu‐Fen , Chu Yen‐Yi , Miu Chia‐Yeh , Lai Yun‐Wen , Liu Hsiang‐Lin , Her Jim Long 
Published: May 2007

AbstractA new series of Te–Ru–Cu carbonyl complexes was prepared by the reaction of K2TeO3 with [Ru3(CO)12] in MeOH followed by treatment with PPh4X (X=Br, Cl) and [Cu(MeCN)4]BF4 or CuX (X=Br, Cl) in MeCN. When the reaction mixture of K2TeO3 and [Ru3(CO)12] was first treated with PPh4X followed by the addition of [Cu(MeCN)4]BF4, doubly CuX‐bridged Te2Ru4‐based octahedral clusters [PPh4]2[Te2Ru4(CO)10Cu2X2] (X=Br, [PPh4]2[1]; X=Cl, [PPh4]2[2]) were obtained. When the reaction mixture of K2TeO3 and [Ru3(CO)12] was treated with PPh4X (X=Br, Cl) followed by the addition of CuX (X=Br, Cl), three different types of CuX‐bridged Te–Ru carbonyl clusters were obtained. While the addition of PPh4Br or PPh4Cl followed by CuBr produced the doubly CuBr‐bridged cluster 1, the addition of PPh4Cl followed by CuCl led to the formation of the Cu4Cl2‐bridged bis‐TeRu5‐based octahedral cluster compound [PPh4]2[{TeRu5(CO)14}2Cu4Cl2] ([PPh4]2[3]). On the other hand, when the reaction mixture of K2TeO3 and [Ru3(CO)12] was treated with PPh4Br followed by the addition of CuCl, the Cu(Br)CuCl‐bridged Te2Ru4‐based octahedral cluster chain polymer {[PPh4]2(Te2Ru4(CO)10Cu4Br2Cl2)⋅THF}∞ ({[PPh4]2[4]⋅THF}∞) was produced. The chain polymer {[PPh4]2[4]⋅THF}∞ is the first ternary Te–Ru–Cu cluster and shows semiconducting behavior with a small energy gap of about 0.37 eV. It can be rationalized as resulting from aggregation of doubly CuX‐bridged clusters 1 and 2 with two equivalents of CuCl or CuBr, respectively. The nature of clusters 1–4 and the formation and semiconducting properties of the polymer of 4 were further examined by molecular orbital calculations at the B3LYP level of density functional theory.
On the Mechanism and Stereochemistry of Chiral Lithium‐Carbenoid‐Promoted Cyclopropanation Reactions
Authors: Ke Zhuofeng , Zhou Yubing , Gao Hui , Zhao Cunyuan , Phillips David Lee 
Published: May 2007

AbstractAn investigation into the mechanism and stereochemistry of chiral lithium‐carbenoid‐promoted cyclopropanation reactions by using density functional theory (DFT) methods is reported. Previous work suggested that this type of cyclopropanation reaction may proceed by competition between a methylene‐transfer mechanism and a carbometalation mechanism. In this paper, it is demonstrated that the intramolecular cyclopropanation reactions promoted by chiral carbenoids 1 and 2 proceed by the methylene‐transfer mechanism. The carbometalation mechanism was found to have a much higher reaction barrier and does not appear to compete with the methylene‐transfer mechanism. The Lewis base group does not enhance the carbometalation pathway enough to compete with the methylene‐transfer pathway. The present computational results are consistent with experimental observations for these cyclopropanation reactions. The factors governing the stereochemistry of the intramolecular cyclopropanation reaction by the methylene‐transfer mechanism were examined to help elucidate the origin of the stereoselectivity observed in experiments. Both the directing group and the configuration at the C1 centre were found to play a key role in the stereochemistry. Carbenoid 1 has a chiral C1 centre of R configuration. The Lewis base group directs the cyclization of carbenoid 1 to form a single product. In contrast, the Lewis base group cannot direct the cyclization of carbenoid 2 to furnish a stereoselective product due to the S configuration of the chiral C1 centre in carbenoid 2. This relationship of the stereochemistry to the chiral character of the carbenoid has implications for the design of new efficient carbenoid reagents for stereoselective cyclopropanation.
Microwave‐Assisted Transition‐Metal‐Catalyzed Synthesis of N‐Shifted and Ring‐Expanded Buflavine Analogues
Authors: Appukkuttan Prasad , Dehaen Wim , Van der Eycken Erik 
Published: May 2007

AbstractTwo novel and efficient strategies for the synthesis of hitherto unknown N‐shifted and ring‐expanded buflavine analogues are presented. Construction of the medium‐sized ring system of the title molecules, a difficult task due to the high activation energy needed for the ring‐closure with the additional rigidity imposed by the biaryl skeleton, was achieved by using Suzuki–Miyaura biaryl coupling and a ring‐closing metathesis reaction as the key steps. The combination of a second‐generation Grubbs catalyst and microwave irradiation proved to be highly useful in generating the otherwise difficult to obtain medium‐sized ring system of the buflavine analogues.
Cucurbit[8]uril/Cucurbit[7]uril Controlled Off/On Fluorescence of the Acridizinium and 9‐Aminoacridizinium Cations in Aqueous Solution
Authors: Wang Ruibing , Yuan Lina , Ihmels Heiko , Macartney Donal H. 
Published: May 2007

AbstractThe blue fluorescence of acridizinium bromide (ADZ+) and the green fluorescence of 9‐aminoacridizinium bromide (AADZ+) in aqueous solutions can be almost entirely switched off upon the double inclusion of these guests in the cavity of cucurbit[8]uril (CB[8]) owing to the formation of a nonfluorescent, noncovalent dimer complex, and then fluorescence can be effectively restored by adding cucurbit[7]uril (CB[7]) to the complex because it competitively extracts the fluorophores out of the CB[8] cavity.
Understanding Adsorption and Interactions of Alkane Isomer Mixtures in Isoreticular Metal–Organic Frameworks
Authors: Zhang Li , Wang Qi , Wu Tao , Liu Ying‐Chun 
Published: May 2007

AbstractNovel metal–organic frameworks (MOFs) may lead to advances in adsorption and catalysis owing to their superior properties compared to traditional nanoporous materials. A combination of the grand canonical Monte Carlo method and configurational‐bias Monte Carlo simulation was used to evaluate the adsorption isotherms of C4–C6 alkane isomer mixtures in IRMOF‐1 and IRMOF‐6. The amounts of adsorbed linear and branched alkanes increase with increasing pressure, and the amount of branched alkanes is larger than that of the linear ones. The locations of the alkane isomer reveal that the Zn4O clusters of the IRMOFs are the preferential adsorption sites for the adsorbate molecules. The interaction energy between the Zn4O cluster and the adsorbate is larger than that between the organic linker and the adsorbate. It was further confirmed that the Zn4O cluster plays a much more important role in adsorption by pushing a probe molecule into the pore at positions closer to the Zn4O cluster. It is difficult for branched alkane molecules to approach the Zn4O cluster of IRMOF‐6 closely owing to strong spatial hindrance. In addition, the adsorption selectivity is discussed from the viewpoints of thermodynamics and kinetics, and the diffusion behavior of n‐butane and 2‐methylpropane were investigated to illustrate the relationship between diffusion and adsorption.
A Sol–Gel‐Modified Poly(methyl methacrylate) Electrophoresis Microchip with a Hydrophilic Channel Wall
Authors: Chen Gang , Xu Xuejiao , Lin Yuehe , Wang Joseph 
Published: May 2007

AbstractA sol–gel method was employed to fabricate a poly(methyl methacrylate) (PMMA) electrophoresis microchip that contains a hydrophilic channel wall. To fabricate such a device, tetraethoxysilane (TEOS) was injected into the PMMA channel and was allowed to diffuse into the surface layer for 24 h. After removing the excess TEOS, the channel was filled with an acidic solution for 3 h. Subsequently, the channel was flushed with water and was pretreated in an oven to obtain a sol–gel‐modified PMMA microchip. The water contact angle for the sol–gel‐modified PMMA was ≈27.4° compared with ≈66.3° for the pure PMMA. In addition, the electro‐osmotic flow increased from 2.13×10−4 cm2 V−1 s−1 for the native‐PMMA channel to 4.86×10−4 cm2 V−1 s−1 for the modified one. The analytical performance of the sol–gel‐modified PMMA microchip was demonstrated for the electrophoretic separation of several purines, coupled with amperometric detection. The separation efficiency of uric acid increased to 74 882.3 m−1 compared with 14 730.5 m−1 for native‐PMMA microchips. The result of this simple modification is a significant improvement in the performance of PMMA for microchip electrophoresis and microfluidic applications.
Total Synthesis of Five Thapsigargins: Guaianolide Natural Products Exhibiting Sub‐Nanomolar SERCA Inhibition
Authors: Andrews Stephen P. , Ball Matthew , Wierschem Frank , Cleator Ed , Oliver Steven , Högenauer Klemens , Simic Oliver , Antonello Alessandra , Hünger Udo , Smith Martin D. , Ley Steven V. 
Published: May 2007

AbstractHerein we describe the total synthesis of five guaianolide natural products: thapsigargin, thapsivillosin C, thapsivillosin F, trilobolide and nortrilobolide. Prodrug derivatives of thapsigargin have shown selective in vivo cytotoxicity against prostate tumours and the need for further investigation of this phenomenon highlights the importance of these total syntheses. The first absolute stereochemical assignment of thapsivillosin C is also delineated.
Charge‐Transfer Emission Involving Three‐Coordinate Organoboron: V‐Shape versus U‐Shape and Impact of the Spacer on Dual Emission and Fluorescent Sensing
Authors: Bai Dong‐Ren , Liu Xiang‐Yang , Wang Suning 
Published: May 2007

AbstractNew V‐shaped bifunctional organosilicon compounds that contain an electron acceptor, B(Mes)2, and an electron donor, N(1‐naph)Ph, with the formulae Ph2Si{p‐C6H4B(Mes)2}{p‐C6H4N(1‐naph)ph)} (1), Ph2Si{p‐C6H4(Mes)2}{p‐biphenyl‐N(1‐naph)ph} (2), and Si{p‐C6H4B(Mes)2}2{p‐C6H4N(1‐naph)ph)}2 (3) have been synthesized as model compounds for the investigation of through‐space charge‐transfer emission involving triarylboron and triarylamino centers. The photophysical properties of the new bifunctional organosilicon compounds are compared to two U‐shaped compounds sBN and BN in which the boron acceptor and the amino donor groups are linked together by a rigid 1,10‐naphthyl group. The results of our investigation establish that dual emission pathways, namely through‐space donor‐acceptor charge transfer and π–π* transitions coexist in the V‐shaped molecules 1–3, while charge transfer emission is dominant in the U‐shaped molecules. It is found that depending on the geometry of the linker and the B⋅⋅⋅N separation distance, the compound either displays dual emission bands simultaneously or single emission band. In addition, the dual emission pathways in these molecules can be selectively switched on or off by using fluoride ions. The sensitivity of response to fluoride ions by these molecules is also found to be highly dependent on the geometry of the linker and the B⋅⋅⋅N separation distance. The V‐shaped molecules are found to be “turn‐on” sensors to fluorides with a much higher sensitivity than the U‐shaped molecules.
The Anhydride Route to Group 15/16 Ligands in Oligomeric and Polymeric Environments: From Metal Complexes to Supraionic Chemistry
Authors: Rothenberger Alexander , Shi Weifeng , Shafaei‐Fallah Maryam 
Published: May 2007

AbstractThe aim of this paper is to introduce a synthetic concept suitable for the preparation of a broad variety of compounds. The so‐called anhydride route (in this article the term anhydride is used for compounds derived from corresponding acids by formal loss of H2O, H2S and H2Se) has so far led to a range of unusual Group 15/16 ligands in oligomeric and polymeric environments. Commonly, reactions of neutral precursor molecules, for example, [{RP(S)(μ‐S)}2] (R=4‐anisyl) Lawesson's reagent or [{PhP(Se)(μ‐Se)}2] Woollins's reagent and metal salts are performed to result in novel coordination compounds in which ligands and metal atoms form coordination oligomers and polymers. An attempt is made to relate the outcome of the investigations to the type of metal used. By relating the strength of ionic interactions, which correspond to metal–donor distances, to phenomena observed in the solid‐state structures, an aspect of supraionic chemistry is described. Chemistry of and beyond novel Group 15/16 anions is further discussed using a novel approach in coordination chemistry where the chemical nature of ligands is unknown prior to the experiment despite the use of a range of similar starting materials.
Gold(I)‐Catalyzed 5‐endo Hydroxy‐ and Alkoxycyclization of 1,5‐Enynes: Efficient Access to Functionalized Cyclopentenes.
Authors: Buzas Andrea K. , Istrate Florin M. , Gagosz Fabien 
Published: May 2007

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.
Intramolecular Acylation of α‐Sulfinyl Carbanions with Masked α,β‐Unsaturated Esters: A General Strategy to 5‐Alkylidene‐2‐cyclopentenones.
Authors: Pohmakotr Manat , Thamapipol Sirinporn , Tuchinda Patoomratana , Reutrakul Vichai 
Published: May 2007

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.
A Highly Efficient Carbon—Sulfur Bond Formation Reaction via Microwave‐Assisted Nucleophilic Substitution of Thiols to Polychloroalkanes Without a Transition‐Metal Catalyst.
Authors: Cao Yi‐Ju , Lai Yuan‐Yuan , Cao Hong , Xing Xiao‐Ning , Wang Xiang , Xiao Wen‐Jing 
Published: May 2007

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.
Pd(N,N‐Dimethyl β‐alaninate)2 as a High‐Turnover‐Number, Phosphine‐Free Catalyst for the Suzuki Reaction.
Authors: Cui Xin , Qin Tian , Wang Jia‐Rui , Liu Lei , Guo Qing‐Xiang 
Published: May 2007

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.
Strained 1‐Azabicyclo[1.1.0]butanes in the Synthesis of Azetidinethiocarboxylate Derivatives.
Authors: Woznicka Marta , Urbaniak Katarzyna , Mloston Grzegorz , Heimgartner Heinz 
Published: May 2007

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.
A Novel Propargylation/Cycloisomerization Tandem Process Catalyzed by a Ruthenium(II)/Trifluoroacetic Acid System: One‐Pot Entry to Fully Substituted Furans from Readily Available Secondary Propargylic Alcohols and 1,3‐Dicarbonyl Compounds.
Authors: Cadierno Victorio , Gimeno Jose , Nebra Noel 
Published: May 2007

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.
Highly Enantioselective Vinylogous Addition of 2‐Trimethylsilyloxyfuran to Aldehydes Promoted by the SiCl4/Chiral Lewis Base System.
Authors: Palombi Laura , Acocella Maria R. , Celenta Nicoletta , Massa Antonio , Villano Rosaria , Scettri Arrigo 
Published: May 2007

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.
Palladium‐Catalyzed Direct Arylation of Furans via C—H Functionalization at Low Catalyst Loadings.
Authors: Battace Ahmed , Lemhadri Mhamed , Zair Touriya , Doucet Henri , Santelli Maurice 
Published: May 2007

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.
Butenolide Synthesis by Molybdenum‐Mediated Hetero‐Pauson—Khand Reaction of Alkynyl Aldehydes.
Authors: Adrio Javier , Carretero Juan C. 
Published: May 2007

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.
Synthesis and Antimicrobial Investigation of Some Novel Phenyl Pyrazole, Azetidinone and Diazenyl Ethanone Derivatives of Benzofurans.
Authors: Kumar D. B. Aruna , Prakash G. K. , Kumaraswamy M. N. , Nandeshwarappa B. P. , Sherigara B. S. , Mahadevan K. M. 
Published: May 2007

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.
Regioselective Cross‐Coupling of 1‐Vinylpyrroles with Acylbromoacetylenes on Al2O3: Synthesis of 2‐(2‐Acylethynyl)‐1‐vinylpyrroles.
Authors: Trofimov B. A. , Sobenina L. N. , Stepanova Z. V. , Ushakov I. A. , Petrova O. V. , Tarasova O. A. , Volkova K. A. , Mikhaleva A. I. 
Published: May 2007

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.