bluuebunny/crossref_metadata_2025_split huggingface dataset:
Isolation and Neuroprotective Activities of Acylated Iridoids from Valeriana jatamansi
Authors: Xu Jing , Guo Yuanqiang , Xie Chunfeng , Jin Da‐Qing , Gao Jie , Gui Liping 
Published: July 2012

AbstractThree new iridoids, jatairidoids A–C (1–3, resp.), have been isolated from the roots of Valeriana jatamansi (V. wallichii). Their structures were elucidated by spectroscopic methods (IR, ESI‐MS, HR‐ESI‐MS, 1D‐ and 2D‐NMR). Compounds 1 and 2 are C(3)‐epimers. The three compounds were evaluated for their neuroprotective effects against MPP+‐induced neuronal cell death in human dopaminergic neuroblastoma SH‐SY5Y cells. All the isolates exhibited moderate neuroprotective effects.
Jiangxienone, a New Compound with Potent Cytotoxicity against Tumor Cells from Traditional Chinese Medicinal Mushroom Cordyceps jiangxiensis
Authors: Xiao Jian‐Hui , Sun Zhong‐Hua , Pan Wei‐Dong , Lü Yu‐Hong , Chen Dai‐Xiong , Zhong Jian‐Jiang 
Published: July 2012

AbstractA new compound, named jiangxienone, has been isolated from a culture of the traditional Chinese medicinal mushroom Cordyceps jiangxiensis, and its chemical structure was established on the basis of spectroscopic and chemical techniques. Jiangxienone showed potent cytotoxic effects against human gastric adenocarcinoma SGC‐7901 cell and human lung carcinoma A549 cell with IC50 values ranging from 1.38 to 2.93 μM, i.e., with at least approximately six‐fold stronger cytotoxicity than cisplatin, a first‐line chemotherapy drug for cancer patients.
Volatile Secondary Metabolites of Micromeria dalmaticaBenth. (Lamiaceae): Biosynthetical and Chemotaxonomical Aspects
Authors: Radulović Niko S. , Blagojević Polina D. 
Published: July 2012

AbstractAnalysis by GC and GC/MS of the essential oil obtained from above‐ground parts of Micromeria dalmatica Benth. allowed the identification of 116 components, comprising 93.6% of the total oil composition. The major compounds are 3‐oxygenated p‐menthane monoterpenes and were identified as pulegone (29.6%), menthone (11.7%), and piperitenone (10.8%). The chemical composition of this and additional 30 oils obtained from selected Micromeria Benth. taxa were compared by using multivariate statistical analysis (agglomerative hierarchical cluster analysis and principal component analysis (PCA)). The results of statistical analyses, as well as the domination of different concurrent p‐menthane‐skeleton‐type monoterpene biosynthetical sub‐branches in the compared M. dalmatica samples, implied the occurrence of at least two different chemotypes of the mentioned species.
Carbohydrate Chelation in Neutral Aqueous Solution: The threo‐Tetritolato‐Pd4 Butterfly Motif
Authors: Allscher Thorsten , Klüfers Peter 
Published: July 2012

AbstractAlditols (“sugar alcohols”, “glycitols”) form palladium(II) complexes in neutral aqueous solution if they can provide the threitol partial structure. This requirement excludes erythritol, ribitol, and allitol when applied to the common tetritols, pentitols, and hexitols. The remaining alditols are able to arrange their threo‐tetraol‐O4 pattern to an almost planar rhomb, to which four PdIIN2 (N2=bidentate nitrogen ligand) centres bind in a butterfly‐shaped Pd4 motif. Bridging is the exclusive bonding mode of the four alkoxido donors. In contrast to the butterfly complexes, all alditols are able to form a species at a pH intermediate between neutrality and the stronger alkaline conditions of non‐bridging diolato‐palladium(II) binding, namely, the μ‐triolato bonding mode. A Pd2(μ‐triolato) unit shows the middle O atom of a propanetriolato fragment as a bridging ligator, with the lateral O atoms binding in the terminal mode.
Organocatalytic Kinetic Resolution Cascade Reactions: New Mechanistic and Stereochemical Manifold in Diphenyl Prolinol Silyl Ether Catalysis
Authors: McGarraugh Patrick G. , Johnston Ryne C. , Martínez‐Muñoz Aurora , Cheong Paul Ha‐Yeon , Brenner‐Moyer Stacey E. 
Published: July 2012

AbstractA new cascade reaction involving an iminium‐catalyzed intramolecular oxa‐Michael addition followed by an enamine‐catalyzed intermolecular Michael addition is reported herein. This cascade reaction generates enantiopure, highly functionalized tetrahydropyrans and tetrahydrofurans in a one‐pot reaction and in up to 89 % combined yield and up to 99 % ee. This cascade reaction is catalyzed by diaryl prolinol silyl ethers, which are a privileged class of catalysts. The stereochemical outcome of these cascade reactions is unprecedented. Computational studies indicate that this stereochemical outcome arises from nonclassical hydrogen‐bonding interactions between the electrophile and the substrate, and from entropic considerations of preorganization. The unprecedented configurations of the cascade products, combined with the computational models, reveal for the first time that asymmetric induction by diaryl prolinol silyl ether catalysts is not always exclusively reagent controlled. The stereochemical outcome also arises from a kinetic resolution or dynamic kinetic resolution of the β‐stereocenter through an enamine‐catalyzed intermolecular reaction. This unprecedented organocascade reaction mechanism may be adaptable to diaryl prolinol silyl ether‐catalyzed cascade reactions, in which both the iminium‐ and enamine‐catalyzed steps are intermolecular, an underdeveloped type of cascade reaction.
The Role of the Alcohol and Carboxylic Acid in Directed Ruthenium‐Catalyzed C(sp3)H α‐Alkylation of Cyclic Amines
Authors: Bergman Sheba D. , Storr Thomas E. , Prokopcová Hana , Aelvoet Karel , Diels Gaston , Meerpoel Lieven , Maes Bert U. W. 
Published: July 2012

AbstractA general directed Ru‐catalyzed C(sp3)H α‐alkylation protocol for piperidines (less‐reactive substrates than the corresponding five‐membered cyclic amines) has been developed. The use of a hindered alcohol (2,4‐dimethyl‐3‐pentanol) as the solvent and catalyst activator, and a catalytic amount of trans‐1,2‐cyclohexanedicarboxylic acid is necessary to achieve a high conversion to product. This protocol was used to effectively synthesize a number of 2‐hexyl‐ and 2,6‐dihexyl piperidines, as well as the alkaloid (±)‐solenopsin A. Kinetic studies have revealed that the carboxylic acid additive has a significant effect on catalyst initiation, catalyst longevity, and reverses the reaction selectivity compared with the acid‐free reaction (promotes alkylation versus competing alkene reduction).
Highly Strained Heterometallacycles of Group 4 Metallocenes with Bis(diphenylphosphino)amide Ligands
Authors: Haehnel Martin , Hansen Sven , Spannenberg Anke , Arndt Perdita , Beweries Torsten , Rosenthal Uwe 
Published: July 2012

AbstractA study regarding coordination chemistry of the bis(diphenylphosphino)amide ligand Ph2P‐N‐PPh2 at Group 4 metallocenes is presented herein. Coordination of N,N‐bis(diphenylphosphino)amine (1) to [(Cp2TiCl)2] (Cp=η5‐cyclopentadienyl) generated [Cp2Ti(Cl)P(Ph2)N(H)PPh2] (2). The heterometallacyclic complex [Cp2Ti(κ2‐P,P‐Ph2P‐N‐PPh2)] (3 Ti) can be prepared by reaction of 2 with n‐butyllithium as well as from the reaction of the known titanocene–alkyne complex [Cp2Ti(η2‐Me3SiC2SiMe3)] with the amine 1. Reactions of the lithium amide [(thf)3Li{N(PPh2)2}] with [Cp2MCl2] (M=Zr, Hf) yielded the corresponding zirconocene and hafnocene complexes [Cp2M(Cl){κ2‐N,P‐N(PPh2)2}] (4 Zr and 4 Hf). Reduction of 4 Zr with magnesium gave the highly strained heterometallacycle [Cp2Zr(κ2‐P,P‐Ph2P‐N‐PPh2)] (3 Zr). Complexes 2, 3 Ti, 4 Hf, and 3 Zr were characterized by X‐ray crystallography. The structures and bondings of all complexes were investigated by DFT calculations.
Combined Light‐ and Radio Wave Emission during Cracking of Particles
Authors: Aman Sergej , Tomas Jürgen 
Published: July 2012

AbstractDer Zusammenhang zwischen den Licht‐ und Radioimpulsen, die während der Beanspruchung von Glaspartikeln entstehen, wurde untersucht. Dazu wurden die einzelnen Partikel und Partikelschichten zwischen zwei metallischen Platten, die unter angelegter Hochspannung stehen, mechanisch beansprucht. Die Lichtemission beginnt während der Entstehung der ersten Risse in den Glaspartikeln. Danach, mit einer Verzögerung von wenigen Mikrosekunden, wird die Radiowellenemission aus der neu entstandenen Schicht des zerkleinerten Glases registriert. Die Verzögerung zwischen dem Beginn der Lichtemission und die Entstehung der Radioimpulse stellt eine charakteristische Zerkleinerungszeit dar.
Construction of a Miniplant for the Catalytic Aerobic Cleavage of Methyl 9,10‐Dihydroxystearate
Authors: Behr Arno , Tenhumberg Nils 
Published: July 2012

AbstractDie Entwicklung neuer Katalysatoren zur Oxidation chemischer Verbindungen unter Verwendung von Sauerstoff als kostengünstiges und umweltfreundliches Oxidationsmittel ist eine wichtige Aufgabe der aktuellen Forschung. Aufgrund der Gefahr der Bildung explosionsfähiger Gasgemische müssen bei diesen Oxidationen wirksame Maßnahmen zum Explosionsschutz getroffen werden. Es wird ein Sicherheitskonzept für den Explosionsschutz aerober Oxidationsreaktionen und der Aufbau einer Versuchsanlage vorgestellt. Als Modellreaktion wurde die oxidative Spaltung des 9,10‐Dihydroxystearinsäuremethylesters zum Azelainsäuremethylester und zur Nonansäure untersucht.
A Novel Method for One‐pot Synthesis of Furo[3,2‐c]coumarin Derivatives from 4‐Hydroxycoumarin and Arylglyoxal under Microwave Irradiation
Authors: Chen Zhiwei , Bi Jianhao , Su Weike 
Published: July 2012

AbstractA novel one‐pot synthesis of furo[3,2‐c]coumarins has been developed from readily available starting materials 4‐hydroxycoumarin and arylglyoxal. This method is simple, rapid and good yielding.
Synthesis and Properties of Novel Aromatic Azo Compounds from Hydroxyazobenzene and Cyanuric Chloride
Authors: Li Weiwei , Xu Dongmei , Zhang Zhilan , Xu Ying 
Published: July 2012

AbstractA new series of aromatic azo compounds with one, two, three and five azobenzene units were facilely constructed by dehydrochlorination reaction between p‐hydroxyazobenzene, 4,4′‐dihydroxyazobenzene and cyanuric chloride under very mild conditions. Their solubility, crystallinity, thermostability, UV‐vis absorption properties and photoisomerization behaviors were carefully examined. When the number of azobenzene unit grew, the solubility of the synthesized compounds basically decreased, the crystallinity of the synthesized compounds firstly rose then dropped, while the thermostability and UV‐vis absorption ability of the synthesized compounds greatly improved. All the aromatic azo compounds exhibited typical reversible photoisomerization behaviors and were expected to be applied in photosensitive material areas.
Aqueous‐mediated Michael Addition of Active Methylene Compounds with Nitroalkenes
Authors: Dong Wenkai , Xu Dongcheng , Xie Jianwu 
Published: July 2012

AbstractA simple, atom economical and highly efficient green protocol has been developed for the synthesis of Michael adducts of nitroalkenes and 2‐amino‐2‐chromene derivatives by Michael addition of active methylene compounds (such as malononitrile and ethyl cyanoacetate) to nitroalkenes under aqueous‐mediated conditions. This green approach provided the desired products in high yields and the reaction scope proved to be quite broad.
Efficient Synthesis of 3‐Methyl‐Flavanones and Evaluation of Their Anti‐Bacterial Activity
Authors: Nawghare Beena , Funde Sharad , Raheem Abdul , Lokhande Pradeep 
Published: July 2012

AbstractA series of 2‐phenyl‐2,3‐dihydrochromon‐4‐one derivatives (flavanone derivatives) were synthesized by silica gel assisted isomerization of several α‐methyl‐2′‐hydroxy chalcones in 74%–88% yield. These flavanones were further oxidized to 3‐methyl flavones by using iodine in dimethyl sulphoxide at 60°C in presence of acid. The newly synthesized derivatives were evaluated for in vitro study against Staphylococcus aureus, Micrococcus luteus and Staphylococcus epidermis.
A Highly Copper‐Selective Ratiometric Fluorescent Sensor Based on BODIPY
Authors: Huang Jinlong , Wang Bo , Ye Jianguo , Liu Bin , Qiu Huayu , Yin Shouchun 
Published: July 2012

AbstractA new ratiometric fluorescent sensor (1) for Cu2+ based on 4,4‐difluoro‐4‐bora‐3a,4a‐diaza‐s‐indacene (BODIPY) with di(2‐picolyl)amine (DPA) as ion recognition subunit has been synthesized and investigated in this work. The binding abilities of 1 towards different metal ions such as alkali and alkaline earth metal ions (Na+, K+, Mg2+, Ca2+) and other metal ions ( Ba2+, Zn2+, Cd2+, Fe2+, Fe3+, Pb2+, Ni2+, Co2+, Hg2+, Ag+) have been examined by UV‐vis and fluorescence spectroscopies. 1 displays high selectivity for Cu2+ among all test metal ions and a ∼10‐fold fluorescence enhancement in I582/I558 upon excitation at visible excitation wavelength. The binding mode of 1 and Cu2+ is a 1:1 stoichiometry determined via studies of Job plot, the nonlinear fitting of the fluorometric titration and ESI mass.
Mechanism of Imidazole‐Promoted Ligation of Peptide Phenyl Esters
Authors: Wang Chen , Liu Lei 
Published: July 2012

AbstractImidazole‐promoted ligation of peptide phenyl esters was recently found to be a complementary method for protein chemical synthesis. Theoretical calculations have been carried out to understand the detailed mechanism of this particular ligation process. It is found that both the reaction of the phenyl ester with imidazole and the reaction of the acyl imidazole intermediate with cysteine proceed through an addition‐elimination mechanism. The cleavage of the CO bond in the reaction between the phenyl ester and imidazole is the rate‐limiting step of the overall ligation process. Interestingly, although the imidazole‐promoted phenyl ester ligation has a higher free energy barrier than the conventional thiophenol‐promoted native chemical ligation for a sterically less hindered C‐terminal amino acid (e.g. gylcine), for a sterically hindered C‐terminal amino acid (e.g. proline) the imidazole‐promoted phenyl ester ligation is calculated to be more favorable than the conventional thiophenol‐promoted native chemical ligation.
A Facile Method to Form a Densely Grafted PEO‐b‐P4VP Brush on Gold Surface
Authors: Yang Qian , Zhou Changming , Chen Wang , Fang Jiajie , Chen Daoyong 
Published: July 2012

AbstractHere we report a facile method for the preparation of a PEO113‐b‐P4VP93 brush on gold surface with a grafting density as high as 1.32 chains/nm2; the P4VP blocks were physically adsorbed on gold surface forming an inner layer while the PEO blocks stretched towards the solution forming PEO brush. PEO113‐b‐P4VP93 micelles with P4VP core and PEO shell formed in methanol/water mixed solvents were used as the precursor. By adsorbing PEO113‐b‐P4VP93 micelles from pure water, in which the density of the micelles is the largest, maximum amount of the micelles was adsorbed onto gold surface, and the adsorbed micelles existed as individual domains on the surface. To prepare the polymer brush with a density as high as possible, we annealed the adsorbed micelles by methanol/water mixed solvent at the volume fraction of methanol (VF) of 20%, which was the proper proportion at which the core‐forming P4VP chains began to be flexible but the integrity of the micelles was remained. At this volume fraction, almost all the adsorbed micelles originally existing as individual domains were transformed into a dense polymer brush.
Growth, interaction, and positioning of microtubule asters in extremely large vertebrate embryo cells
Authors: Mitchison Timothy , Wühr Martin , Nguyen Phuong , Ishihara Keisuke , Groen Aaron , Field Christine M. 
Published: July 2012

AbstractRay Rappaport spent many years studying microtubule asters, and how they induce cleavage furrows. Here, we review recent progress on aster structure and dynamics in zygotes and early blastomeres of Xenopus laevis and Zebrafish, where cells are extremely large. Mitotic and interphase asters differ markedly in size, and only interphase asters span the cell. Growth of interphase asters occurs by a mechanism that allows microtubule density at the aster periphery to remain approximately constant as radius increases. We discuss models for aster growth, and favor a branching nucleation process. Neighboring asters that grow into each other interact to block further growth at the shared boundary. We compare the morphology of interaction zones formed between pairs of asters that grow out from the poles of the same mitotic spindle (sister asters) and between pairs not related by mitosis (non‐sister asters) that meet following polyspermic fertilization. We argue growing asters recognize each other by interaction between antiparallel microtubules at the mutual boundary, and discuss models for molecular organization of interaction zones. Finally, we discuss models for how asters, and the centrosomes within them, are positioned by dynein‐mediated pulling forces so as to generate stereotyped cleavage patterns. Studying these problems in extremely large cells is starting to reveal how general principles of cell organization scale with cell size. © 2012 Wiley Periodicals, Inc
In vitro Percutaneous Absorption of 14C‐Labeled β‐Lactone Promises Topical Delivery of New Bacterial Virulence Inhibitors
Authors: Lorenz‐Baath Katrin , Korotkov Vadim S. , Lierse von Gostomski Christoph , Sieber Stephan A. 
Published: July 2012

AbstractBacterial infections of skin and soft tissue represent a major health threat, especially if they are caused by multidrug‐resistant strains such as MRSA. Novel treatment options for topical application are urgently needed, and even if new drug candidates are identified, their properties must match the specific physical requirements of the skin in order to penetrate and reach the site of bacterial infection. β‐Lactones have been shown to eliminate bacterial virulence, but knowledge about their potential in topical treatments had thus far been lacking. Herein we present the synthesis and in‐depth investigations of skin permeation and skin distribution of a radioactive 14C‐labeled tool compound that was formulated with various basic ointments and applied to pig skin samples. Our results show that skin penetration depends highly on the nature of the formulation base. Vaseline is the most efficient ointment and is best suited for effecting maximal drug delivery within and through the stratum corneum, an important entrance barrier, and meets the required quantities for eliciting anti‐virulence effects. We are confident that the nature of these new β‐lactone virulence inhibitors confers applicability and potency for topical treatment, and will translate into a new formulation of this highly potent drug candidate for the treatment of skin and soft tissue infections.
An Efficient Synthesis of a Hydroxyethylamine (HEA) Isostere and Its α‐Aminophosphonate and Phosphoramidate Derivatives as Potential Anti‐HIV Agents
Authors: Bhattacharya Asish K. , Rana Kalpeshkumar C. , Pannecouque Christophe , De Clercq Eric 
Published: July 2012

AbstractHIV protease is a promising drug target for AIDS therapy, and several potent HIV‐1 protease inhibitors have been reported to date. Although existing inhibitors exhibit high selectivity, they have also been associated with severe side effects and the possible emergence of therapeutic resistance. As HIV protease cleaves the peptide bond via a tetrahedral intermediate, various transition‐state models such as hydroxyethylamine (HEA) have been designed. We therefore pursued an efficient synthesis of an HEA isostere; this was performed with a novel one‐pot reduction–transimination–reduction reaction sequence as a key step. α‐Aminophosphonate and phosphoramidate derivatives of the HEA isostere were designed and synthesized, and all of the synthesized derivatives were assayed for their anti‐HIV activities against wild‐type and mutant HIV strains. Phosphoramidate derivative 15 a was found to be the most active of all synthesized compounds against the IIIB and RES056 strains. As phosphonates are known to exhibit physiological stability, good cell permeability, and other promising pharmacokinetic characteristics, our newly synthesized compounds have the potential as alternatives to existing therapeutics and diagnostics.
Preferences for outcomes associated with decisions to undergo or forgo genetic testing for Lynch syndrome
Authors: Kuppermann Miriam , Wang Grace , Wong Shirley , Blanco Amie , Conrad Peggy , Nakagawa Sanae , Terdiman Jonathan , Ladabaum Uri 
Published: July 2012

AbstractBACKGROUND:Current guidelines recommend offering genetic testing for Lynch syndrome to individuals whose tumors suggest this condition and to relatives of affected individuals. Little is known, however, regarding how patients view the prospect of such testing. In addition, data on preferences (utilities) for the potential outcomes of testing decisions for use in cost‐effectiveness analyses are lacking.METHODS:Time tradeoff utilities were elicited for 10 potential outcomes of Lynch syndrome testing decisions and 3 associated cancers from 70 participants, representing a range of knowledge about and experiences with Lynch syndrome.RESULTS:Highest mean utilities were assigned to scenarios in which only the assessor's sibling had Lynch‐associated colorectal cancer (ranging from 0.669 ± 0.231 to 0.760 ± 0.220). Utilities assigned to scenarios in which the assessor had Lynch‐associated colorectal cancer ranged from 0.605 ± 0.252 to 0.682 ± 0.246, whereas the lowest mean utilities were assigned to 2 of the general cancer states (0.601 ± 0.238 and 0.593 ± 0.272 for colorectal and ovarian cancer respectively). Only 43% of the sample assigned higher values to undergoing Lynch testing and receiving negative results versus forgoing Lynch testing, whereas 50% assigned higher values to undergoing rather than forgoing surgery to prevent a subsequent cancer.CONCLUSIONS:Genetic testing for Lynch syndrome, regardless of results, can have profound effects on quality of life; the utilities we collected can be used to incorporate these effects into cost‐effectiveness analyses. Importantly, preferences for the potential outcomes of testing vary substantially, calling into question the extent to which patients would avail themselves of such testing if it were offered to them. Cancer 2013. © 2012 American Cancer Society