32 resultados para Paclitaxel -- analogs
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5 1 A 2 3 4 A PTP-1B5 1 18 15 3 A 2 3 D101 8 4 192021226 1 H 4 A A PTP-1B II 5 This dissertation composes of five chapters. The first chapter elaborates the detection and qualification of the triterpenoidal saponins in Anemone raddeana by positive and negative full scan ESI-MSn. This part also reports the special fragmentation pathway of Raddeanin A by ESI-MS/MS. The second and third chapters present the phytochemical investigation of two medicinal plants from Anemone. The fourth part dwells on the structure modification of Raddeanin A and their inhibitory activity against PTP-1B. The last part is a review on the progress in the application of ESI-MSn in the structure identification of saponins. The first chapter reports the application of full scan ESI-MSn for fast analysis of triterpenoid saponins in Anemone raddeana. Eighteen quasi- molecular ion peaks were detected in the positive full scan ESI-MS and fifteen of them were identified by analysis of their tandem mass spectral data in the negative ion mode. Several isomers were differentiated. More interesting, three unreported triterpenoid saponins in this medicinal plant were detected and their structures were deduced according to the dissociation pathway of the known triterpenoidal saponins. This chapter also confirms the special fragmentation pathway of Raddeanin A by its derivative and the mass spectral analysis. The second and third chapters expatiate on the isolation and identification of the chemical constituents from A. raddeana and A. hupehensis. Eight compounds were isolated from the roots and stems of A. raddeana by methanol extraction and repeated column chromatography (including D101 and silica gel), and their structures were determined on the basis of IR, ESI-MS, NMR and chemical methods (including acid hydrolysis and alkaline saponification). Among them, four are new triterpenoid saponins and named as Raddeanoside R19, Raddeanoside R20, Raddeanoside R21 and Raddeanoside R22. Six compounds were isolated from the whole plants of A. hupehensis by the same methods as above, and their structures were also determined with the same way. One of them was confirmed to be new triterpenoid saponins and named as hupehensis saponin H. In the fourth chapter, in order to look for new active compounds, the structure of Raddeanin A and its analogs were modified. It was found that the modified products exhibited obvious inhibitory activity against PTP-1B when several acid groups were introduced. The fifth chapter summarizes the progress on the application of ESI-MSn in the structure identification of saponins.
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The applicability of on-line coupling of reversed-phase high-performance liquid chromatography to atmospheric pressure ionization tandem mass spectrometry for the separation and characterization of hop acids mixture from the crude extract of Humulus lupulus was investigated. The solvent system consisting of acetonitrile-aqueous formic acid was used to give proper separation of the six main hop bitter acids within 30 min. Further structural information about the components was acquired by collision-induced dissociation (CID). On the basis of analyses of the fragmentation patterns of the major alpha- and beta-bitter acids respectively, identification of the minor ones was performed using selected reaction monitoring (SRM) with a group of qualitatively relevant selected precursor-product ion transitions for each bitter acid in a single high performance liquid chromatography (HPLC) run. Using this technique, six minor hop acids, including "adprelupulone" observed for the first time in natural resources, were detected along with the six major acids. This hyphenated techniques provides potency for rapid qualitative determination of analogs and homologs in mixtures. (C) 2004 American Society for Mass Spectrometry.
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In the present study, platinum nanoparticles modified with Prussian blue (PB) have been synthesized by a heterogeneous catalytic reaction. Transmission electronic microscopy (TEM) confirmed the deposition of nanoclusters around the Surfaces of platinum particles, and spectroscopic studies verified that the molecular composition of the nanoclusters was dominantly PB and a minority of platinum ferricyanide. Thus, it was shown that the platinum particles behaved not only as catalysts for the growth of PB, but also as a reactant to generate a PB analogue complex.
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Depending on their size, shape. degree of aggregation and nature of the protecting organic shells on their surface, gold nanoparticles (AuNPs) can appear red, blue and other colors and emit bright resonance light scattering of various wavelengths. Because of this unique optical property. AuNPs have been extensively explored as probes for sensing/imaging a wide range of analytes/targets, such as heavy metallic cations, nucleic acids, proteins, cells, etc. Since their initial discovery, novel synthetic methods have led to precise control over particle size, shape and stability, thus allowing the modification of a wide variety of ligands on the AuNP surfaces to meet different experimental conditions. This review discusses the synthesis and applications of functionalized AuNPs in chemical sensing and imaging.
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The coupling of drugs to macromolecular carriers received an important impetus from Ringsdorf's notion of polymer-drug conjugates. Several water-soluble polymers, poly(ethylene glycol), poly[N-(2-hydroxypropyl) methacrylamidel, poly(L-glutamic acid) and dextran, are studied intensively and have been utilized successfully in clinical research. The promising results arising from clinical trials with polymer-drug conjugates (e.g., paclitaxel, doxorubicin, camptothecins) have provided a firm foundation for other synthetic polymers, especially biodegradable polymers, used as drug delivery vehicles. This review discusses biodegradable polymeric micelles as an alternative drug-conjugate system. Particular focus is on A-B or B-A-B type biodegradable amphiphilic block copolymer such as polylactide, morpholine-2,5-dione derivatives and cyclic carbonates, which can form a core-shell micellar structure, with the hydrophobic drug-binding segment forming the hydrophobic core and the hydrophilic segment as a hydrated outer shell. Polymeric micelles can be designed to avoid uptake by cells of reticuloendothelial system and thus enhance their blood lifetime via the enhanced permeability and retention effect.
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The interaction of daunomycin with sodium dodecyl sulfate and Triton X-100 micelles was investigated as a model for the hydrophobic contribution to the free energy of DNA intercalation reactions. Measurements of visible absorbance, fluorescence lifetime, steady-state fluorescence emission intensity, and fluorescence anisotropy indicate that the anthraquinone ring partitions into the hydrophobic micelle interior. Fluorescence quenching experiments using both steady-state and lifetime measurements demonstrate reduced accessibility of daunomycin in sodium dodecyl sulfate micelles to the anionic quencher iodide and to the neutral quencher acrylamide. Quenching of daunomycin fluorescence by iodide in Triton X-100 micelles was similar to that seen with free daunomycin. Studies of the energetics of the interaction of daunomycin with micelles by fluorescence and absorbance titration methods and by isothermal titration calorimetry in the presence of excess micelles revealed that association with sodium dodecyl sulfate and Triton X-100 micelles is driven by a large negative enthalpy. Association of the drug with both types of micelles also has a favorable entropic contribution, which is larger in magnitude for Triton X-100 micelles than for sodium dodecyl sulfate micelles.
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A new straightforward strategy for synthesis of novel hyperbranched poly (ether amide)s from readily available monomers has been developed. By optimizing the reaction conditions, the AB(2)-type monomers were formed dominantly during the initial reaction stage. Without any purification, the AB(2) intermediate was subjected to further polymerization in the presence (or absence) of an initiator, to prepare the hyperbranched polymer-bearing multihydroxyl end-groups. The influence of monomer, initiator, and solvent on polymerization and the molecular weight (MW) of the resultant polymers was studied thoroughly. The MALDI-TOF MS of the polymers indicated that the polymerization proceeded in the proposed way. Analyses of H-1 NMR and C-13 NMR spectra revealed the branched structures of the polymers obtained. These polymers exhibit high-moderate MWs and broad MW distributions determined by gel permeation chromatography (GPC) in combination with triple detectors, including refractive index, light scattering, and viscosity detectors. In addition, the examination of the solution behavior of these polymers showed that the values of intrinsic viscosity [eta] and the Mark-Houwink exponent a were remarkably lower compared with their linear analogs, because of their branched nature.
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Chemical functionalization of single-walled carbon nanotubes (SWNTs) has constructed plenty of new structures with ample new properties into them. But the modification was often confined to organic molecules, either by covalence or non-covalence. In this report, SWNTs were successfully functionalized with one kind of electroactive inorganic compounds: Prussian blue (PB). And the molecular interactions between them were firstly investigated. Interestedly, pi-pi stacking interaction coupled with ionic interaction was found between SWNTs and PB. The electrochemical properties of SWNTs-PB were also investigated. It would pave a new pathway to manipulate molecular entities of SWNTs by cooperation with functional inorganic electroactive compounds.
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Berlin green FeFe(CN)(6) microcubic crystals have been successfully prepared by a simple hydrothermal process between K-3[Fe(CN)(6)] with Na2S2O3 aqueous solution, free of any surfactant or template. The experimental results clearly show that the molar ratio of K-3[Fe(CN)(6)] to Na2S2O3 and their concentrations are the dominant processing factors in controlling the size, morphology, and composition of the resulting products.
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A series of titanium phosphinimide complexes [Ph2P(2-RO-C6H4)(2)TiCl2 (7, R = CH3; 8, R = CHMe2) and (PhP(2-Me2CHOC6H4)][THF]TiCl3 (9) have been prepared by reaction of TiCl4 with the corresponding phosphinimines under dehalosilylation. The structure of complex 9 has been determined by X-ray crystallography, and a solvent molecule THF was found to be coordinated with the central metal and the Ti-O bond was consistent with the normal Ti-O (donor) bond length. The complexes 7 and 8 displayed inactive to ethylene polymerization, and the complex 9 displayed moderate activity in the presence of modified methylaluminoxane (MMAO) or i-BU3Al/Ph3CB(C6F5)(4), and this should be partly attributed to coordination of THF with titanium and the steric effect of two iso-propoxyl. And catalytic activity up to 32.2 kg-PE/(mol-Ti h bar) was observed.
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Four new organotin complexes, namely [(Bu2Sn)(2)O(EtO)(L1)](2) (1), [(Bu2Sn)(2)O(EtO)(L2)](2) (2), [(Bu2Sn)(2)O(EtO)(L-3)](2) (3) and [Ph3Sn(L4)]center dot 0.5H(2)O (4), were obtained by reactions of Bu2SnO and Ph3SnOH with 4-phenylideneamino-3-methyl-1,2,4-triazole-5-thione (HL1), 4-furfuralideneamino-3-methyl-1,2,4-triazole-5-thione (HL2), 4-(2-thienylideneamino)-3-ethyl-1,2,4-triazole-5-thione (HL3) and 4-(3,5-di-t-butylsalicylideneamino)-3-ethyl-1,2,4-triazole-5-thione (HL4). Compounds 1-4 were characterized by elemental analysis, IR spectra and their structures were determined by single-crystal X-ray diffraction methods. Complexes 1-3 show similar structures containing a Sn4O4 ladder skeleton in which each of the exo tin atoms is bonded to the N atom of a corresponding thione-form deprotonated ligand. Complex 4 shows a mononuclear structure in which the tin atom of triphenyltin group is coordinated by the S atom of a thiol-form L4(-) anion.
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A series of aryl hydroxylactams (2a, 2b, 2d-2g, 2i-2k, 2m, and 2n) was synthesized by partially reducing aryl cyclic imides in moderate to excellent yields with activated zinc dust alone in acetic acid. This method was regiospecific and can be employed as an alternative for reported methods to partially reduce aryl cyclic imides.
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A new polyoxometalate derivative {PW9V3O40[Ag(2,2'-bipy)](2)[Ag-2(2,2'-bipy)(3)](2)} 1 has been hydrothermally synthesized and structurally characterized by the single crystal X-ray diffraction. X-Ray analysis showed that both [Ag(2,2'-bipy)](+) and [Ag-2(2,2'-bipy)(3)](2+) units are supported on the alpha-Keggin polyoxoanion [PW9V3O40](6-) via the surface bridging oxygen atoms. 1 represents the first alpha-Keggin type polyoxoanion coordinated with four transition metal complex moieties, which further acts as a neutral molecular units for the construction of an interesting three-dimensional supramolecular framework.
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Cobalt(II) hexacyanoferrate (CoHCF) was deposited on graphite powder by an in situ chemical deposition procedure and then dispersed into methyltrimethoxysilane-derived gels to prepare a surface-renewable CoHCF-modified electrode. The electrochemical behavior of the modified electrode in different supporting electrolyte solutions was characterized by cyclic voltammetry. In addition, square-wave voltammetry was employed to investigate the pNa-dependent electrochemical behavior of the electrode. The CoHCF-modified electrode showed a high electrocatalytic activity toward thiosulfate oxidation and could thus be used as an amperometric thiosulfate sensor.
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A monomer, 2,3,6,7,10,11-hexakispentyloxy triphenylene (HPT) possesses a triphenylene core as a discotic mesogen. Polymers containing this discotic mesogen have been studied using wide-angle X-ray and electron diffraction. HPT is known to show a discotic liquid crystal phase, noted as D-ho (h for hexagonal bidimensional lattice, o for ordered molecular spacing in each column). In this paper, however, HPT Liquid crystalline phases, heated up from the crystalline state and cooled down from the isotropic state, were characterized in the diameter dimensions. In addition. the diameters of the columns are close to a parameter of two separate crystals. A core orientation was, therefore, proposed in the mesophase obtained by heating the crystalline. In order to distinguish these differences, the D-ho phase was divided to include the D-hcd and D-hco phases. Molecular modeling was performed to help our understanding of the orientation. The D-hcd and D-hco phases were used to characterize the phases of the discotic polymeric analogs by comparing their column diameters to those of the monomers. (C) 1998 Published by Elsevier Science Ltd. All rights reserved.