bluuebunny/crossref_metadata_2025_split huggingface dataset:
Metal‐Dependent Formation of Mononuclear Complexes and M2L2 Mesocates with Schiff‐Base Ligands
Authors: Fielden John , Long De‐Liang , Evans Cameron , Cronin Leroy 
Published: August 2006

AbstractThe coordination chemistry of the tetradentate pyridylN‐donor ligands r‐1‐hydroxy‐t‐3,t‐5‐bis{[(2‐pyridinyl)methylene]amino}cyclohexane (DDOP) and r‐1‐hydroxy‐t‐3,t‐5‐bis{[(E)‐(6‐methyl‐2‐pyridinyl)methylene]amino}cyclohexane(DDMOP) has been investigated with the d10 metal centres silver(I) and cadmium(II). These conformationally flexible ligands offer two coordination modes; either a mononucleating tetradentate coordination pocket or a bridging bis(bidentate) chelate. Hence, reaction with CdII produced six‐coordinate mononuclear complexes whose compositions were determined by X‐ray crystallography as [Cd(DDOP)(NO3)2] (1) and [Cd(DDMOP)(Cl)2]·MeOH (2), while AgI led to the four‐coordinate dinuclear mesocate structures [{Ag(DDOP)}2](CF3SO3)2 (3) and [{Ag(DDMOP)}2](CF3SO3)2·0.5MeOH (4). It is thought that the mononuclear, octahedral complexes in the case of zinc(II) and cadmium(II) result from the energetic stabilisation gained through two extra coordinate bonds, while in the case of silver(I) the lower propensity of the metal centre for six‐coordination causes the ligand to retain its energetically preferred dinucleating conformation and to form the mesocates. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)
Synthesis, Structure and Reactivity of Hydrated and Dehydrated Organotin Cations
Authors: Chandrasekhar Vadapalli , Boomishankar Ramamoorthy , Gopal Kandasamy , Sasikumar Palani , Singh Puja , Steiner Alexander , Zacchini Stefano 
Published: August 2006

AbstractMonomeric organotin dications {[nBu2Sn(H2O)4]2+·2C6H5SO3–} and {[nBu2Sn(H2O)4]2+·1,5‐C10H6(SO3–)2} have been synthesized by the reaction of [nBu2SnO]n and the corresponding arylsulfonic acid. Dodecanuclear organooxotin macrocations {[(nBuSn)12(μ3‐O)14(μ2‐OH)6]2+·2RSO3–} (R = C6H5; 2,5‐Me2C6H3) have been synthesized by the reaction of nBuSn(O)(OH) and the corresponding arylsulfonic acid. The X‐ray crystal structure of one of the dodecanuclear cages is reported. These organotin cations have been shown to be effective catalysts in acetylation and transacetylation reactions. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)
A General and Facile One‐Step Synthesis of Imido–Titanium(IV) Complexes: Application to the Synthesis of Compounds Containing Functionalized or Chiral Imido Ligands and Bimetallic Diimido Architectures
Authors: Lorber Christian , Choukroun Robert , Vendier Laure 
Published: August 2006

AbstractOne‐pot reactions of Ti(NMe2)4 with a wide range of primary alkyl, aryl, and silylamines RNH2 in the presence of excess chlorotrimethylsilane produced the corresponding imido–titanium(IV) complexes [Ti(=NR)Cl2(NHMe2)2] (1a–j), in which R = tBu, 1‐adamantane, Ph3C, Ph3Si, Ph, 2,6‐iPr2–C6H3, 2,6‐Cl2–C6H3, 2,6‐Br2–4‐Me–C6H2, C6F5, and 3,5‐(F3C)2–C6H3. This general synthesis, which starts from commercially available reagents, represents a simple and direct route to imido complexes. Reaction of complexes 1 with pyridine afforded the six‐coordinate tris‐pyridine adducts [Ti(=NR)Cl2(Py)3] (2). Another advantage of this method is its tolerance to other functional groups; complexes that contain halides, ether, dialkylamino, cyano, ethynyl, olefin, and nitro substituents on the imido moiety have been prepared. The use of enantiomerically pure primary amines affords the first group of titanium complexes that contain chiral imido groups, and the use of diamines produces diimido complexes. Alternatively, CH3I has been used as an alkylating agent to generate titanium–imido complexes of the type [Ti(NR)I2(THF)2]2. All compounds were fully characterized by spectroscopic methods (IR, 1H NMR, 13C NMR) and elemental analysis. Some of the compounds were also analyzed by single‐crystal X‐ray diffraction studies. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)
Chelating Phosphane–Boranes as Hemilabile Ligands – Synthesis of[Mn(CO)3(η2‐H3B·dppm)][BArF4] and [Mn(CO)4(η1‐H3B·dppm)][BArF4]
Authors: Merle Nicolas , Frost Christopher G. , Kociok‐Köhn Gabriele , Willis Michael C. , Weller Andrew S. 
Published: August 2006

AbstractManganese complexes bearing the chelating phosphane–borane ligand H3B·dppm [dppm = bis(diphenylphosphanyl)methane] have been prepared. Addition of H3B·dppm to Mn(CO)5Br using Na[BArF4] as a halide‐abstracting reagent affords [Mn(CO)3(η2‐H3B·dppm)][BArF4] (1). This reacts with CO to open the bidentate borane to afford [Mn(CO)4(η1‐H3B·dppm)][BArF4] (2) in which the borane is now bound in a monodentate manner. The CO addition is reversible, and placing 2 under vacuum (hours) regenerates 1 quantitatively, demonstrating that the chelating phosphane–boranes can act as hemilabile ligands. The complexes 1 and 2 have been fully characterised by NMR spectroscopy and X‐ray crystallography. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)
Tetra‐ and Triphosphane Pyridine Podands and Their Cobalt(II) and Nickel(II) Complexes
Authors: Kohl Stephan W. , Heinemann Frank W. , Hummert Markus , Weißhoff Hardy , Grohmann Andreas 
Published: August 2006

AbstractThe reaction of the 2,6‐diethylpyridine‐derived tetraphosphane ligand C5H3N[CMe(CH2PMe2)2]2 (1Me) with nickel(II) or cobalt(II) perchlorate or tetrafluoroborate in methanol produces complexes of approximate square‐pyramidal geometry (NP4 coordination). The nickel complexes are diamagnetic, with NMR spectral features (31P) that reflect a tetrahedral distortion of diametrically opposite phosphorus donors; this is also found in the solid state. In terms of bond lengthsand angles, all complexes differ significantly from theiranalogues containing the phenyl‐substituted ligand C5H3N[CMe(CH2PPh2)2]2. The ligand 1Me is readily and completely oxidised to the corresponding tetrakis(phosphane oxide) upon reaction with NO. Slow oxidation of the cobalt(II) tetrafluoroborate complex of 1Me with aerobic oxygen in acetonitrile produces a trinuclear cobalt complex containing two equivalents of partially oxidised ligand (C2‐symmetrical; donor set: [PMe2]2[P(O)Me2]2). Four phosphane oxide oxygen atoms coordinate the central cobalt(II) ion in tetrahedral fashion, whereas the lateral cobalt(II) ions are in a square‐pyramidal environment provided by two PMe2 donors and three acetonitrile ligands in each case. The reaction of the cobalt(II) perchlorate complex of 1Me with carbonmonoxide gives an octahedral, 19‐valence‐electron dicarbonyl complex in which one of the dimethylphosphanyl groups is uncoordinated. A structural relative of 1Me, C5H3N[CMe(CH2PMe2)2][CMe2(CH2PMe2)] (2), which contains one fewer dimethylphosphanyl donor, can be prepared in a straightforward manner from 2‐ethyl‐6‐isopropylpyridine in a four‐stage process. In a series of mononuclear nickel(II) complexes, 2 employs only its three phosphane donors which, together with a monodentate ligand (acetonitrile, acetamide, or bromide), provide a tetragonal coordination environment for the metal ion which is intermediate between square planar and tetrahedral. The acetamide complex is generated from the acetonitrile complex by slow hydrolysis of the coordinated ligand. Full spectroscopic details for the complexes, as well as X‐ray structure analyses, are reported. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)
An Improved Synthesis of 3,4‐(Aminomethano)proline and Its Incorporation into Small Oligopeptides
Authors: Brackmann Farina , Colombo Noemi , Cabrele Chiara , de Meijere Armin 
Published: August 2006

AbstractStarting from the readily available Garner aldehyde, a new synthesis of diastereomerically and enantiomerically pure 3,4‐(aminomethano)prolinol (2R,1′S,3S,4S)‐17 has been developed using simple and easily scalable transformations. The protected diamino alcohol (2R,1′S,3S,4S)‐17 has been shown to be an appropriate compound for the exchange of protecting groups. Final Jones oxidation furnished the correspondingly protected diamino acids in high yields. The newly synthesized Fmoc/Boc‐protected 3,4‐(aminomethano)proline (Amp) derivatives, which are proline mimics as well as bicyclic γ‐amino acids, depending on the orthogonal protecting group pattern, were employed for solid‐phase peptide synthesis with the Fmoc strategy. Thus, the features of Amp as a γ‐amino acid residue (γ‐Amp) were investigated in the preparation of alternating α/γ‐amino acid sequences. The obtained highly homogeneous products were characterized by circular dichroism spectroscopy. The fact that the dichroic properties of the α/γ‐oligopeptides were independent from the solvent used (water or methanol) suggests the presence of a preferred conformation. These results are encouraging for the development of foldamers based on γ‐Amp units. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)
Activation Parameters for the Epoxidation of Substituted cis/trans Pairs of 1,2‐Dialkylalkenes by Dimethyldioxirane
Authors: Crow Brian S. , Winkeljohn W. Rucks , Navarro‐Eisenstein Angela , Michelena‐Baez Elba , Franklin Paul J. , Vasquez Pedro C. , Baumstark Al 
Published: August 2006

AbstractThe first activation parameter data for the reaction of dimethyldioxirane (1) with five cis/trans pairs of alkenes are reported. The epoxidation of cis‐1,2‐dialkylalkenes (2cis: R1 = Me, R2 = iPr; 3cis: R1 = Me, R2 = tBu; 4cis: R1 = R2 = Et; 5cis: R1 = Et, R2 = iPr; 6cis: R1 = Et, R2 = tBu) and trans‐1,2‐dialkylalkenes (2trans: R1 = Me, R2 = iPr; 3trans: R1 = Me, R2 = tBu; 4trans: R1 = R2 = Et; 5trans: R1 = Et, R2 = iPr; 6trans: R1 = Et, R2 = tBu) by 1 produced the corresponding epoxides, quantitatively and stereospecifically, as the sole observable products. Activation parameters of the epoxidation of the five pairs of alkenes, 2cis–6cis and 2trans–6trans, by 1 were determined using the Arrhenius method. Enhanced selectivity for cis‐ vs. trans‐alkene epoxidation was observed at lower temperatures. In general, the ΔG‡ terms were larger and showed more variability for the reaction of 1 with trans‐alkenes as compared to those for the corresponding cis isomers. The ΔH‡ terms mirrored trends observed in ΔG‡ because ΔS‡ terms for all ten of the compounds were roughly identical. The ΔΔG‡ values, a comparison of the trans to the cis isomer data, yielded positive values of 1.2 to 1.8 kcal/mol for the five sets of data and appeared to be dependent on relative steric interactions. The experimental activation parameter data, consistent with predictions from ab initio calculations based on a spiro transition‐state model, showed that the lower reactivity of trans‐alkenes is due to enthalpy factors. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)
PtCl2‐ and PtCl4‐Catalyzed Cycloisomerization of Polyunsaturated Precursors
Authors: Marco‐Contelles José , Arroyo Nieves , Anjum Shazia , Mainetti Emily , Marion Nicolas , Cariou Kevin , Lemière Gilles , Mouriès Virginie , Fensterbank Louis , Malacria Max 
Published: August 2006

AbstractThe PtCl2‐ and PtCl4‐catalyzed cycloisomerization of polyunsaturated precursors with different O‐protecting groups at the propargylic position is reported. The free hydroxy, O‐(bromomethyl)dimethylsilyl, O‐methyl and O‐propenyl derivatives 1a–f have afforded mixtures of skeletal rearrangement products and/or polycyclic molecules incorporating a cyclopropyl ring system in variable chemical yields. Other parameters such as the variation of the alkenyl chains and the triple‐bond substitution have been examined and gave new mechanistic elements. Very interestingly, for analogous compounds containing an ester moiety, such as the O‐4‐nitrobenzoyl or acetate group (1g–j, and 22) bicyclo[4.1.0]hept‐2‐enyl derivatives were obtained in good yields. These products are formally the result of a 1,2‐migration of an O‐acyl group, coupled to a cyclopropanation step. Related propargylic acetates with a pendant aromatic group (25) or substituted at the terminal acetylenic carbon with a methoxycarbonyl group (24) did not afford this class of rearranged compounds. This type of reaction seems restricted to propargylic derivatives, because the suitably functionalized homopropargylic acetate 24 only afforded 1,3‐dienes. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)
H.264/AVC prediction modules complexity analysis
Authors: Ayed Mohamed Ali Ben , Samet Amine , Masmoudi Nouri 
Published: August 2006

AbstractIn this paper we study the computational complexity of the intra/inter prediction modules for video coding software according to H.264/AVC standard. We analyse separately the complexity of each mode toward an implementation on TMS320C64 platform. Since any real‐time implementation is considered to be time and money consuming, complexity pre‐analysis of any giving video‐coding algorithm is very important to determine not only software bottlenecks, but also the minimum hardware resources and characteristics required for the targeted platform. To estimate the total complexity of the prediction processes (intra/inter), we assume that the encoder tests all modes. The total cycle's account is estimated by multiplying the number of cycles of each mode by the number of macroblocks in the frame. Simulation results indicate that our methodology for the complexity analyses for H.264/AVC prediction modules provides a good approximation with respect to the experimental results. Copyright © 2006 AEIT.
Pterosaur assemblages of the Jehol Biota and their implication for the Early Cretaceous pterosaur radiation
Authors: Xiaolin Wang , Zhonghe Zhou 
Published: August 2006

AbstractThe Early Cretaceous Jehol Biota from northeast China is well known for many beautifully preserved feathered dinosaurs, early birds and angiosperms. A great number of pterosaurs have also been discovered from the same deposits in recent years, representing arguably the best pterosaur assemblage from the Lower Cretaceous. Two pterosaur assemblages are recognized from the Jehol Biota, and represent two major adaptive radiations in the Early Cretaceous. The first radiation was preserved mainly in the Yixian Formation, and shows a strong resemblance to the Upper Jurassic pterosaur radiation in the Solnhofen Limestone of Germany. The second radiation was preserved in the Jiufotang Formation, with many of its taxa much similar to those of the pterosaur assemblages from the Lower Cretaceous Santana Formation of Brazil. Recent biostratigraphic work and radiometric datings of the Yixian and Jiufotang formations have provided a reliable geochronologic framework for the Jehol pterosaur radiations. The two major radiations occurred at about 125 Ma and 120 Ma, respectively. The radiations of the Jehol pterosaurs are characterized by a remarkable taxonomic diversity, great variation in body size, significant dietary differentiation, and occupancy of diverse niches. The appearance of several biological novelties was also critical in the success of the Jehol pterosaur radiations. The adaptive radiation of the Jehol pterosaurs was obviously coupled with the competition or co‐evolution with many other groups of the Jehol Biota. Among the flying animals in the Jehol Biota, pterosaurs were the major competitors for niches and food with birds. Although the Jehol pterosaurs probably fed mainly on fishes, the co‐evolution between plants and pterosaurs in the Jehol Biota might also have played a significant role in the pterosaur radiations, as is the case for plants and insects, birds, mammals and dinosaurs. Copyright © 2006 John Wiley & Sons, Ltd.
An introduction to Ordovician bivalves of southern China, with a discussion of the early evolution of the Bivalvia
Authors: Zong‐Jie Fang 
Published: August 2006

AbstractThis paper introduces the Ordovician bivalves of southern China to non‐Chinese colleagues, and then incorporates them into the global Ordovician bivalve database compiled by Cope (2004). This will provide a firmer basis for the discussion of the initial adaptive radiation of the Bivalvia. A new scenario for the early evolution of the class Bivalvia is advanced herein based on the integration of a wide variety of evidence concerning bivalves, including morphological features, ontogenetic trajectory, benthic environment and lithologic setting, so as to explain reasonably why the initial explosive radiation of bivalves in the Early Ordovician followed a long‐term macroevolutionary lag since their first appearance during the Cambrian explosion. The early evolution of the Bivalvia can be divided into three phases: (a) the origination and macroevolutionary lag phase in the Early and Middle Cambrian; (b) the crisis phase in the Late Cambrian; and (c) the Ordovician radiation phase, which can be subdivided into two radiation pulses or intervals (the Arenig and the Caradoc radiation intervals). It is the Cambrian substrate revolution that caused a transformation of shallow subtidal seafloors from more coherent Neoproterozoic‐style matgrounds to soupier Phanerozoic‐style mixgrounds, thus compelling Cambrian ‘archetype’ bivalves to sink into the infaunal realm and to adapt themselves to the development of the mixed layer in siliciclastic soft substrate environments. As a result, Cambrian ‘archetype’ bivalves entered a tight bottleneck and became extinct while the latest common ancestor of ‘modern‐type’ bivalves originated from a certain founder population somewhere in the Gondwanan shelf seas. The rapidly evolving founder population may be the place of origin of evolutionary novelties and it became the starting point of the evolution of ‘modern‐type’ bivalves. The macroevolutionary lag of the Bivalvia ended in the earliest Ordovician as a result of the successful invasion of the infaunal adaptive zone. The bivalve die of ‘modern‐type’ was cast during the Ordovician, when all principal clades and all four principal life‐habit groups underwent initial development. A series of morphological innovations, especially the evolution of the muscular hydraulic foot with burrowing adaptations, byssus, and feeding gill, are responsible for the initial adaptive radiation. It is these morphological innovations that provide evolutionary access to the new adaptive zone for bivalves. Copyright © 2006 John Wiley & Sons, Ltd.
Molecular determinants of irinotecan efficacy
Authors: Vallböhmer Daniel , Iqbal Syma , Yang Dong Yun , Rhodes Katrin E. , Zhang Wu , Gordon Michael , Fazzone William , Schultheis Anne M. , Sherrod Andy E. , Danenberg Kathleen D. , Lenz Heinz‐Josef 
Published: August 2006

AbstractMolecular markers predicting the efficacy of CPT‐11 based chemotherapies in patients with colorectal cancer (CRC) are unknown. Therefore, we investigated whether mRNA levels of drug targets (Topoisomerase I, TS), enzymes involved in 5‐FU metabolism (DPD), in angiogenesis (EGFR, IL‐8, VEGF) and in DNA‐repair/drug detoxification (ERCC1, GST‐P1) are associated with the clinical outcome of patients with CRC treated with first‐line CPT‐11 based chemotherapy. Thirty three patients with metastatic CRC were included in the study. Intratumoral gene expression levels were assessed from paraffin‐embedded tissue samples, using laser capture microdissection and quantitative Real‐Time PCR. Complete response was observed in 1 patient, partial response in 12 patients, stable disease in 13 patients and progressive disease in 6 patients. Response was inevaluable for 1 patient. Patients with complete response or partial response were classified as responders, while patients with stable disease or progressive disease were classified as nonresponders. High intratumoral mRNA levels of EGFR, ERCC1 and GSPT‐P1 were each significantly associated with response to CPT‐11 based chemotherapy. Recursive partitioning analysis showed that mRNA levels of EGFR and ERCC1 are primarily responsible for delineating responders from nonresponders. Also, the combination of high intratumoral gene expression levels of both EGFR and ERCC1 was significantly associated with progression‐free survival. The mRNA levels of EGFR had a significant correlation with expression levels of ERCC1, GST‐P1 and VEGF. This small retrospective study suggests that gene expression levels of EGFR, ERCC1 and GST‐P1 may be useful in predicting the clinical outcome of patients with metastatic CRC treated with first‐line CPT‐11 based chemotherapy. © 2006 Wiley‐Liss, Inc.
Cellular telephones and non‐Hodgkin lymphoma
Authors: Linet Martha S. , Taggart Theresa , Severson Richard K. , Cerhan James R. , Cozen Wendy , Hartge Patricia , Colt Joanne 
Published: August 2006

AbstractDramatic increase in hand‐held cellular telephone use since the 1980s and excess risk of lymphoproliferative malignancies associated with radio‐frequency radiation (RFR) exposures in epidemiological and experimental studies motivated assessment of cellular telephones within a comprehensive US case–control investigation of non‐Hodgkin lymphoma (NHL). A questionnaire ascertained cellular telephone use in 551 NHL cases and 462 frequency‐matched population controls. Compared to persons who had never used cellular telephones, risks were not increased among individuals whose lifetime use was fewer than 10 (odds ratio (OR) = 0.9, 95% confidence intervals (CI): 0.6, 1.3), 10–100 (OR = 1.0, 95 % CI: 0.7, 1.5) or more than 100 times (e.g., regular users, OR = 0.9, 95% CI: 0.6, 1.4). Among regular users compared to those who had never used hand‐held cellular telephones, risks of NHL were not significantly associated with minutes per week, duration, cumulative lifetime or year of first use, although NHL was non‐significantly higher in men who used cellular telephones for more than 8 years. Little evidence linked use of cellular telephones with total, diffuse large B‐cell lymphoma or follicular NHL. These findings must be interpreted in the context of less than 5% of the population reporting duration of use of 6 or more years or lifetime cumulative use of 200 or more hours. © 2006 Wiley‐Liss, Inc.
Anticancer effects of amooranin in human colon carcinoma cell line in vitro and in nude mice xenografts
Authors: Ramachandran Cheppail , Nair P.K. Raveendran , Alamo Arturo , Cochrane Curtis Bruce , Escalon Enrique , Melnick Steven J. 
Published: August 2006

AbstractAmooranin (AMR), a natural triterpenoid drug isolated and characterized from Amoora rohituka stem bark, is cytotoxic to SW620 human colon carcinoma cell line with an IC50 value of 2.9 μg/ml. This novel compound caused depolarization of mitochondrial membrane and decrease of membrane potential, indicating initial signal of apoptosis induction. The percentage of cells with decreased mitochondrial potential ranged from 7.4% at 1 μg/ml to 60.5% at 100 μg/ml AMR. Flow cytometric analysis of apoptosis using Annexin‐V‐FITC staining showed that the percentage of apoptotic cells ranged from 7.5% at 1 μg/ml to 59.2% at 100 μg/ml AMR. AMR‐induced apoptosis was accompanied by redistribution of cytochrome c from mitochondria to cytosol as well as down regulation of Bcl‐2 and Bcl‐XL proteins in a dose‐dependent manner. SW620 human colon carcinoma xenograft mice treated with AMR showed significant reduction in tumor growth rates compared to saline‐ and doxorubicin‐treated groups. The reduction in tumor growth rate was better in xenografts treated with 2 mg/kg AMR than 5 and 10 mg/kg treated mice. The analysis of global gene expression changes induced by AMR in xenograft tumors by microarray hybridization revealed that several genes involved in energy pathways, transport, apoptosis, immune response, nucleic acid metabolism, protein metabolism, cell growth and/or maintenance, signal transduction and cell communication, were affected by this natural cancer drug. These results suggest that the anticancer properties of AMR in SW620 human colon carcinoma cell line are mediated through its effects on functional genomics, targeting the apoptotic process. © 2006 Wiley‐Liss, Inc.