bluuebunny/crossref_metadata_2025_split huggingface dataset:
Remarkably Slow Rotation about a Single Bond between an sp3‐Hybridised Carbon Atom and an Aromatic Ring without ortho Substituents
Authors: Murrison Sarah , Glowacki David , Einzinger Christian , Titchmarsh James , Bartlett Stephen , McKeever‐Abbas Ben , Warriner Stuart , Nelson Adam 
Published: January 2009

AbstractLook, no ortho substituents! A series of polycycles were prepared by using a three‐component Joullié–Ugi reaction. The rate of rotation about the bond between a highly hindered bridgehead and a phenyl ring with no ortho substituents was measured, and was highly dependent on the substitution. Rotamer half‐lives of up to 21 h at 298 K were observed (see figure). Rotamers resulting from this restricted rotation were isolated for the first time.magnified imageA series of polycycles was prepared by using a three‐component Joullié–Ugi reaction. The rate of rotation about the bond between a highly hindered bridgehead and a phenyl ring with no ortho substituents was measured by using, in general, variable‐temperature HPLC. The rate of rotation was highly dependent on substitution and rotamer half‐lives of up to 21 h at 298 K were observed. Insights into the effect of substitution on the rate of rotation were gleaned through electronic structure calculations on closely related derivatives. Rotamers resulting from restricted rotation about a bond between an sp3‐hybridised carbon atom and a phenyl ring with no ortho substituents were isolated for the first time, and the equilibration of the separated rotamers was followed by using analytical HPLC. It was demonstrated, for the first time, that a highly hindered environment for the sp3‐hybridised atom is sufficient for slow bond rotation about a single bond between sp3‐ and sp2‐hybridised carbon atoms.
para‐Functionalized Aryl‐di‐tert‐butylfluorosilanes as Potential Labeling Synthons for 18F Radiopharmaceuticals
Authors: Iovkova Ljuba , Wängler Björn , Schirrmacher Esther , Schirrmacher Ralf , Quandt Gabriele , Boening Guido , Schürmann Markus , Jurkschat Klaus 
Published: January 2009

AbstractBroad spectrum: Novel para‐functionalized aryl‐di‐tert‐butylfluorosilanes, p‐(tBu2FSi)C6H4X (X=functional group), have been made available and broaden the spectrum of silicon‐based 18F acceptors (SiFAs) for potential PET applications. For example, the [18F]maleimido derivative 1 has been employed for the synthesis of [18F]1‐ labeled rat serum albumin (RSA), the applicability of which for PET has been verified by in vivo experiments.magnified imageThe syntheses of the functionalized triorganofluorosilanes tBu2(p‐XC6H4)SiF (3 a, X=SH; 4 a, X=NCS; 4 b, X=NCO; 5, X=NC4H2O2; 7, X=COOH; 8 a, X=COONC4H4O2; 8 b, X=COOC6F5) are reported. These compounds display potential as silicon‐based fluoride acceptors (SiFAs). The molecular structures of compounds 5, 7, and 8 a have been determined by single‐crystal X‐ray diffraction studies. With the exception of compounds 8 a and 8 b, all of the compounds could be 18F‐labeled by isotopic exchange in good to high radiochemical yields (RCY) with good to excellent specific activities. As proof of applicability, the maleimido‐functionalized SiFA derivative 5, which is specific for thiol groups, has been used for the labeling of rat serum albumin (RSA) that had been derivatized with 2‐iminothiolane. The incorporation of [18F]5 into the derivatized RSA reached a maximum yield after 30 min at ambient temperature. After purification, the [18F]RSA was evaluated in a healthy rat by means of μPET and displayed an expedient in vivo stability over 180 min.
Organische Synthese im Mikroreaktor – Heterogen katalysierte Epoxidierung von 1,3‐Butadien
Authors: Otto T. , Pfeifer P. , Pitter S. , Powietzka B. 
Published: January 2009

AbstractDiese Arbeit untersucht die Machbarkeit der Ag‐katalysierten Epoxidierung von 1,3‐Butadien (1,3‐BD) zu 3,4‐Epoxy‐1‐buten (EpB) in einem am Forschungszentrum Karlsruhe entwickelten Mikroreaktor (MR) [1]. Für Vorversuche kommt ein Rohrreaktor (RR) zum Einsatz. Als Katalysator wird ein α‐Al2O3‐Träger eingesetzt, auf dem die Aktivkomponenten aufgebracht sind. Die Epoxidierung erfolgt im Bereich von 180 °C bis 320 °C und Raumgeschwindigkeiten (RG) von 2950 h–1 bis 17 701 h–1 bei Umgebungsdruck in einem Katalysatorteststand. Die höchste EpB‐Selektivität von 52 % wird bei einem 1,3‐BD‐Umsatz von 2,1 % und einer RG von 8851 h–1 mit mikrostrukturierten Ti‐Folien bei 240 °C erreicht.
A Novel MALDI Matrix for Analyzing Peptides and Proteins: Paraffin Wax Immobilized Matrix
Authors: WEI Yuanlong , MEI Yuan , XU Zhe , WANG Cuihong , GUO Yinlong , DU Yiping , ZHANG Weibing 
Published: January 2009

AbstractA new kind of MALDI matrix, termed paraffin wax immobilized matrix, was used to study peptide mixtures and proteins. During the preparation process, the paraffin wax was heated and coated on the stainless‐steel target plate, and then 2,5‐dihydrobenzoic acid (DHB) was deposited on the paraffin layer and stainless‐steel target plate to obtain different kinds of matrix spots. The morphology of matrices on different supports and peptide‐matrix co‐crystallization were observed by a high resolution digital‐video microscopy system. Peptide mixtures and bovine serum albumin (BSA) digests were used to investigate the performance of the immobilized matrices on the paraffin target. The MALDI‐FTMS analysis results also showed that the detection sensitivity of matrices immobilized in the paraffin sample support was better than that on other sample supports.
Probing the Subunit‐Subunit Interaction of the Tetramer of E. coli KDO8P Synthase by Electrospray Ionization Mass Spectrometry
Authors: LI Zhili , SAU Apurba Kumar 
Published: January 2009

AbstractEscherichia coli 3‐Deoxy‐D‐manno‐octulosonate 8‐phosphate (KDO8P) synthase catalyzes the condensation reaction between D‐arabinose 5‐phosphate (A5P) and phosphoenolpyruvate (PEP) to form KDO8P and inorganic phosphate (Pi). This enzyme exists as a tetramer in solution, which is important for catalysis. Two different states of the enzyme were obtained: i) PEP‐bound and ii) PEP‐unbound. The effect of the substrates and products on the overall structure of KDO8P synthase in both PEP‐bound and unbound states was examined using electrospray ionization mass spectrometry. The analysis of our data showed that the complexes of the PEP‐unbound enzyme with PEP (or Pi) favored the formation of monomers, while the complexes with A5P (or KDO8P) mainly favored dimers. The PEP‐bound enzyme was found to exist in the monomer and dimer with a small amount of the tetramer, whereas the PEP‐unbound form primarily exists in the monomer and dimer, and no tetramer was observed, suggesting that the bound PEP have a role in stabilization of the tetrameric structure. Taken together, the results imply that the addition of the substrates or products to the unbound enzyme may alter the subunit‐subunit interactions and/or conformational change of the protein at the active site, and this study also demonstrates that the electrospray ionization mass spectrometric method may be a powerful tool in probing the subunit‐subunit interactions and/or conformational change of multi‐subunit protein upon binding to ligand.
Dynamic Covalent Self‐Assembly of Mono‐, Bi‐ and Trimacrocycles from Hydrogen Bonded Preorganized Templates
Authors: LIN Jianbin , WU Jing , JIANG Xikui , LI Zhanting 
Published: January 2009

AbstractThis paper describes the dynamic covalent assembly of three mono‐, bi‐ and trimacrocycles by utilizing hydrogen bonding‐driven zigzag anthranilamides as "leading" components. The monomacrocycle, a tetraamino molecule, was prepared from the [2+2] coupling reaction of a "U"‐shaped dialdehyde and a porphyrin diamine, followed by the reduction of the macrocyclic tetraimine by NaBH3CN, while the bi‐ and trimacrocycles were obtained through two six‐component coupling reactions with rigid tri‐ and tetraamino‐appended oligomers as templates.
Synthesis and Absolute Configuration of the Diynediol from Psathyrella scobinacea
Authors: WU Jianzhong , WU Yikang , JIAN Yajun , ZHANG Yihua 
Published: January 2009

AbstractAll the four isomers of Scobidiynediol (hepta‐4,6‐diyne‐2,3‐diol), a natural product isolated from white‐rot fungus Psathyrella scobinacea, were synthesized using either (R)‐ or (S)‐lactate as the source of chirality. The relative configurations of the diols were established by NOE experiments performed on the cyclic acetonides. The relative as well as absolute configurations of the natural Scobidiynediol was assigned as (2S,3S) through comparison of the optical rotation and 1H NMR data.
Synthesis of Tonghaosu Analogues
Authors: SUN Hai , LIN Yingjie , WU Yulin , WU Yikang 
Published: January 2009

AbstractSeveral new analogues of natural antifeedant tonghaosu were synthesized via m‐CPBA (m‐chloroperoxybenzoic acid) oxidation of corresponding 3‐(α‐furyl)propanols, Luche reduction of the resulting enone, epoxidation, acid‐ mediated spiroketalization, and radical mediated dehydration.
KF‐Montmorillonite‐catalyzed Michael Addition Reaction of Malononitrile to α,β‐Unsaturated Ketones
Authors: SHI Daqing , WU Nan , ZHUANG Qiya 
Published: January 2009

AbstractThe Michael addition reaction of α,β‐unsaturated ketones with malononitrile catalyzed by KF‐montmorillonite was investigated. It was interesting to note that at different reaction temperatures the addition and cycloaddition reaction products were obtained. This method has the advantages of good yields, mild reaction conditions, easy work‐up and inexpensive reagents over the existing procedures.
Improvement of Hydrophobicity of Ionic Liquids by Partial Chlorination and Fluorination of the Cation
Authors: TAN Kuilong , LI Chunxi , MENG Hong , WANG Zihao 
Published: January 2009

AbstractTwo novel hydrophobic ionic liquids (IL) with partial substitution of chlorine and fluorine in the 1‐butyl‐3‐methylimidazolium cation (noted as [BMIM] or [C8H15N2] hereafter), viz. [C8H12.28Cl0.96F1.76N2]Cl and [C8H12.75Cl1.58F0.67N2][PF6], were reported, which were prepared from the precursors [BMIM]Cl and [BMIM][PF6], respectively through chlorination with chlorine gas and fluorination with potassium fluoride. The position of the chlorine substitution in the resulting IL was identified using proton nuclear magnetic resonance (1H NMR). The results showed that chlorination mainly took place in the imidazolium ring and partly in the methyl of butyl group. Moreover, the physico‐chemical properties of the resulting IL were measured experimentally including thermal stability, viscosity, and mutual solubility with water. It is showed that the hydrophobic property and viscosity of the IL [C8H12.28Cl0.96F1.76N2]Cl and [C8H12.75Cl1.58F0.67N2][PF6] increased greatly while the decomposition temperature decreased to some extent compared to their corresponding non‐modified IL [C8H15N2]Cl and [C8H15N2][PF6]. This study proposed an alternative and cost‐effective approach for tuning the hydrophobic property of IL.
A Concise Synthesis of (−)‐Indolizidines 209D and 209B
Authors: WU Hao , YU Menglong , ZHANG Yazhu , ZHAO Gang 
Published: January 2009

AbstractA general stereoselective synthetic route to 5‐substituted and 5,8‐disubstituted indolizidine alkaloids has been developed starting from commercially available L‐proline. (−)‐Indolizidines 209D and 209B were efficiently synthesized in 9.8% and 14.8% overall yields in seven and five‐step reactions from readily available aldehyde 3 and ketone 10, respectively. The key steps of this synthesis involve a substrate‐induced asymmetric addition of ethyl lithiopropiolate to aldehyde 3 or methyl ketone 10, and a two‐step one‐pot hydrogenation/cyclization sequence to construct the bicyclic skeleton.
Synthesis of Small Peptides and Their Use as Bifunctional Chelating Agents in Diagnostic Radiopharmaceuticals
Authors: TANG Chongzhi , LI Longjin , PANG Zhen , YUAN Zhibin 
Published: January 2009

AbstractThree linear mercaptoacetyl tetrapeptides, MAG3‐Leu‐OH, MAG3‐Phe‐OH and MAG3‐Tyr‐OH, were synthesized via a liquid phase synthetic approach with high yields and high purities without using preparative HPLC technique. The obtained products could be radiolabeled easily with 99mTc under a mild condition and showed high stability in vitro and in vivo conditions. The scintigrams of the tested rabbit after injection of the radiolabeled products via mainline showed a normal biodistribution, which is definitely different from that of 99mTc‐MAG3, indicating different routes of metabolization between these two radiochemicals.
Selective Colorimetric Fluoride Sensor: A Heteroditopic Receptor Combining Pyrrolic Amide with Urea
Authors: YIN Zhenming , LIU Shangyuan 
Published: January 2009

AbstractA heteroditopic anion receptor, bearing one pyrrolic amide site and a urea site, has been synthesized. UV‐Vis spectrum studies in CH3CN solution revealed that the receptor had higher anion binding ability than the homoditopic one. A naked‐eye detectable color change, from colorless to yellow, of the receptor solution took place when fluoride was added, which indicates that the receptor has potential application to selective colorimetric fluoride sensing.
Theoretical Study on Mechanism of Hydroformylation of Ethene Catalyzed by a Heterobimetallic Rh(I)‐Cr Complex
Authors: TANG Dianyong , ZHANG Yuanqin , HU Changwei 
Published: January 2009

Abstract The mechanism of ethene hydroformylation catalyzed by a heterobimetallic complex HRh(CO)(PH3)(µ‐PH2)2‐ Cr(CO)4 was investigated by density functional theory (DFT). Both the associative and dissociative mechanisms were studied, and the results were compared. It was found that the introduction of Cr(CO)4 moiety did not remodel the mechanism of hydroformylation of simple alkenes. The dissociative mechanism is predominant. The carbonyl insertion is the rate‐limiting step for the whole catalytic cycle with a free energy barrier of 91.15 kJ/mol at 298.15 K and 101.325 kPa. The aldehyde elimination step was predicted to be irreversible. These results are in good agreement with the previous theoretical and experimental studies.
Salicylate‐selective Potential Response of an Electrode Based on a Copper(II)‐phthalocyanine Derivative as an Ionophore
Authors: XU Wenju , YUAN Ruo , CHAI Yaqin 
Published: January 2009

Abstract Selectivity properties were established for salicylate‐selective electrodes prepared by incorporating 2,9,16,23‐copper(II)‐tetranitrophthalocyanine (Cu(II)TNPc) and 2,9,16,23‐copper(II)‐tetraaminophthalocyanine (Cu(II)TAPc) into plasticized poly(vinyl chloride) (PVC) membranes. The effect of nature of plasticizer, concentrations of ionophore and anionic and cationic additives on the potential response of the electrode was investigated. The PVC membrane electrode based on Cu(II)TNPc exhibited preferential selectivity for salicylate (Sal−) over other tested anions. The best potential response characteristics of a wide working concentration range 1.0×10−1–9.0×10−7 mol·L−1 and a limit of detection of 7.2×10−7 mol·L−1 with a slope of (−59.8±0.5) mV/decade were observed for the membrane containing (w/w) 3.0% Cu(II)TNPc, 67.0% o‐NPOE, 29.5% PVC, and 0.5% NaTPB. The proposed electrode with good stability and fast response could be used over a pH range of 3.0–7.0. And it was successfully applied to the determination of salicylate in actual samples with satisfactory results.
Auf malerischem Weg zur Chemie
Authors: Tomcin Romy , Reiners Christiane S. 
Published: January 2009

AbstractDas Methodenwerkzeug Chemie‐Foto‐Storys ist eine alternative Form des Versuchsprotokolls, das im Chemieanfangsunterricht eingesetzt und erprobt wurde. In diesem Beitrag sollen die Ergebnisse einer Fallstudie vorgestellt und mögliche Vorteile gegenüber dem üblichen Versuchsprotokoll diskutiert werden.
Experimentierkastensystem „NAWIlino‐Box”︁
Authors: Bröll Leena , Friedrich Jens , Oetken Marco 
Published: January 2009

AbstractSeit der Lehrplanreform im Jahr 2004 wird im Bildungsplan für Grundschulen in Baden‐Württemberg zur Stärkung naturwissenschaftlicher Themenfelder explizit die Erarbeitung bestimmter naturwissenschaftlicher Inhalte gefordert. Ähnliche Forderungen finden sich auch in den Bildungsplänen anderer Bundesländer.Untersuchungen [z. B. 1, 2, 3, 4] haben gezeigt, dass diese Forderungen nur bedingt in die Realität umgesetzt werden können; neben einer im Grundschullehramt häufig nur unzureichend stattfindenden naturwissenschaftlichen Ausbildung und einer häufig nicht zufrieden stellenden materiellen Ausstattung der Grundschulen mangelt es vor allem an einem hinreichenden Fortbildungsangebot für naturwissenschaftliche Aus‐ und Weiterbildung im Primarbereich.Hinsichtlich dieser Defizite wurde in der Abteilung Chemie der Pädagogischen Hochschule Freiburg im Rahmen der Aktivitäten um das Schülerlabor NAWIlino ein Experimentierkastensystem entwickelt, mit dem sich knapp 100 Experimente zu verschiedenen naturwissenschaftlichen Themenbereichen durchführen lassen. Im Rahmen von mehrtägigen Lehrerfortbildungen setzen sich die Lehrkräfte anhand des Experimentierkastensystems mit verschiedenen naturwissenschaftlichen Themenfeldern in Theorie und Praxis intensiv auseinander und bekommen im Anschluss die Experimentierbox für den weiteren Einsatz im Unterricht ausgehändigt.Sowohl die Effektivität des Experimentierkastensystems als auch das angebotene Lehrerfortbildungskonzept werden in einer umfangreichen Langzeitstudie empirisch untersucht.
Die Untersuchung von Olivenöl im Chemieunterricht
Authors: Zimmermann Johannes , Teuscher Markus , Woest Volker 
Published: January 2009

AbstractOlivenöl wird rein mechanisch ohne weitere Zusatzstoffe aus dem Fruchtfleisch der Olivensteinfrucht gewonnen und muss folglich nicht nachraffiniert werden. Es ist fruchtig, hat eine gewisse Schärfe, darf aber auch bitter sein und schmeckt zuweilen, je nach Klima, Boden und Reifegrad der Oliven, würzig oder mild, rassig oder fein, manchmal sogar mandelbitter [1].Der Sektor Olivenöl wird in der EU durch eine Vielzahl von Verordnungen zur Produktion, zum Export und zur Vermarktung geregelt und ist zu einem der wichtigen Wirtschaftszweige für Europa geworden. Olivenöl wird außer als Nahrungsmittel auch für die Herstellung von Seifen und allgemein Kosmetika sowie für pharmazeutische Produkte verwendet [2, S. 29].Zur qualitativen Charakterisierung von Olivenöl dienten früher chemische Kennzahlen, die durch moderne apparative Analysemethoden allerdings in den Hintergrund gedrängt wurden. Die aktuellen chemischen und sensorischen Prüfverfahren sind auf der Internetseite des Internationalen Olivenölrates (IOOC) http://www.internationaloliveoil.org zu finden. Aufgrund ihrer einfachen Durchführbarkeit bieten die wenig material‐ und arbeitsaufwändigen Untersuchungsmethoden der chemischen Kennzahlen aber eine gute Möglichkeit, mit dem Lebensmittel Olivenöl das Gebiet der Fette und fetten Öle im Chemieunterricht experimentell und analytisch beispielhaft zu behandeln.
Efficient Synthesis of Highly Active Phospha‐Isosteres of the Influenza Neuraminidase Inhibitor Oseltamivir
Authors: Carbain Benoit , Collins Patrick J. , Callum Lori , Martin Stephen R. , Hay Alan J. , McCauley John , Streicher Hansjörg 
Published: January 2009

AbstractWith a Hunsdiecker–Barton iododecarboxylation strategy, we converted the carboxylate group of the oseltamivir precursor into exemplary phosphonate monoesters. In all cases, Ki values towards influenza virus sialidase remained in the sub‐nanomolar range. We have thus made valuable structural space available for the design of novel oseltamivir‐based tools for influenza virus research.magnified image
Diversity of participants in clinical trials in an academic medical center
Authors: Joseph Galen , Dohan Daniel 
Published: January 2009

AbstractBACKGROUND:Only 2.5% of adults and even fewer minorities participate in cancer therapeutic trials. Researchers have concluded that many barriers to participation stem from how recruitment is performed by clinician investigators. The objective of the current research was to document specifically how these barriers impede recruitment in the clinical setting.METHODS:The authors conducted a case study of recruitment in an academic medical center using ethnographic research methods (direct observation of provider‐patient interactions and in‐depth interviews with providers) to collect data. Qualitative data analysis was used to identify themes related to the provider's role in the recruitment processes.RESULTS:In the clinics that were studied, the authors observed that providers subjectively assessed which patients seemed to be ‘good study patients’ to target for recruitment. ‘Good study patients’ were identified as those who were able to adhere to complex trial protocols, thus helping clinician researchers to complete studies in a timely and efficient manner. These patients were perceived as meticulous, proactive, and compliant; they were considered good communicators; and they were embedded in the kinds of strong social support networks that facilitated their trials participation.CONCLUSIONS:The providers that were studied sought ‘good study patients’ for therapeutic trials because they wanted to perform studies in a timely and efficient manner. Future research should examine whether providers in other settings also target their recruitment efforts for this or other reasons. Further research also should consider whether differentially recruiting ‘good patients’ can impact the ethnic/racial diversity or other characteristics of trial participants in ways that may bias the outcomes or conclusions of therapeutic trials. Cancer 2009. © 2009 American Cancer Society.
Computed tomography scan‐driven selection of treatment for retroperitoneal liposarcoma histologic subtypes
Authors: Lahat Guy , Madewell John E. , Anaya Daniel A. , Qiao Wei , Tuvin Daniel , Benjamin Robert S. , Lev Dina C. , Pollock Ralphael E. 
Published: January 2009

AbstractBACKGROUND:Well differentiated (WD) and dedifferentiated (DD) retroperitoneal liposarcoma (RPLS) have distinct biologic behaviors. Consequently, the therapeutic approaches for these tumors differ and mandate an accurate preoperative diagnosis. The authors of this report evaluated whether computed tomography (CT) can be used to differentiate between WD and DD RPLS.METHODS:Imaging studies (CT, magnetic resonance imaging, and positron emission tomography‐CT) from 78 patients with RPLS who underwent surgery at the University of Texas M. D. Anderson Cancer Center (UTMDACC) between 2001 and 2007 were reviewed by a senior bone and soft tissue sarcoma radiologist who was blinded to the final histopathologic diagnosis. A focal nodular/water density area within an RPLS was interpreted as a marker suggestive of DD. Correlations between imaging diagnosis, histology, and clinical outcome were analyzed.RESULTS:The study radiologist identified 60 RPLS as DD and 17 RPLS as WD. A radiologic diagnosis of a WD was correlated with preoperative biopsy and postoperative histology in all patients (100%). Focal nodular/water density was a very sensitive marker of DD (97.8%); however, it had relatively low specificity (51.5%). Sixteen WD RPLS (48.5%) contained focal nodular/water density areas, leading to their misdiagnosis as DD; half of those tumors had hypercellular WD. Of 78 preoperative biopsies, 22 (28.2%) were performed at UTMDACC under CT guidance. Preoperative histologic diagnoses obtained from 12 biopsies derived from focal nodular/water density areas were confirmed as unchanged on final pathology; whereas, in 50% of biopsies that were not taken from a suspicious area, DD histology was misdiagnosed as WD.CONCLUSIONS:When CT features are suggestive of WD, no further diagnostic tests are needed for tumor characterization. Moreover, CT can accurately identify most DD, thereby rendering their under‐treatment unlikely; however, a CT‐guided biopsy is needed to differentiate between DD and WD RPLS that contain focal nodular/water density areas, thereby avoiding their over treatment. Cancer 2009. © 2009 American Cancer Society.