排序方式: 共有53条查询结果,搜索用时 15 毫秒
41.
Nicolaou KC Li Y Sugita K Monenschein H Guntupalli P Mitchell HJ Fylaktakidou KC Vourloumis D Giannakakou P O'Brate A 《Journal of the American Chemical Society》2003,125(50):15443-15454
The total synthesis of apoptolidin (1) is reported together with the design, synthesis, and biological evaluation of a number of analogues. The assembly of key fragments 6 and 7 to vinyl iodide 3 via dithiane coupling technology was supplemented by a second generation route to this advanced intermediate involving a Horner-Wadsworth-Emmons coupling of fragments 22 and 25. The final stages of the synthesis featured a Stille coupling between vinyl iodide 3 and vinylstannane 2, a Yamaguchi lactonization, a number of glycosidations, and final deprotection. The developed synthetic technology was applied to the construction of several analogues including 74, 75, and 77 which exhibit significant bioactivity against tumor cells. 相似文献
42.
Nicolaou KC Zak M Rahimipour S Estrada AA Lee SH O'Brate A Giannakakou P Ghadiri MR 《Journal of the American Chemical Society》2005,127(43):15042-15044
Design, synthesis, and biological evaluation of several domains of the thiopeptide antibiotic thiostrepton led to the discovery of a biologically active fragment. The biological properties of this novel small organic molecule include antibiotic activity against methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant Enterococcus faecalis (VREF) bacterial strains, as well as cytotoxic action against a number of cancer cell lines. 相似文献
43.
Thermal rearrangement of (±)-spiro{naphthalene-1(2H),4′-(naphtho-[2′,1′:2,3]pyrano[4,5-c]furazan)}-2-one-11′-oxides in DMF or acetic anhydride at 140 °C gave an isomeric mixture of (±)-spiro{naphthalene-1(2H),1′-(5′-hydroxyphenalene[1,2-c]furazan)}-2-one-2′-oxides and 4′-oxides. The rearranged structure was confirmed from X-ray analysis and was consistent with the through space NOE data. The rearrangement is suggested to be an overall tandem isomerization process. Using variable temperature 1H NMR spectroscopy the lower limit for the isomerisation barrier for a pair of tautomers was calculated to be 22 kcal mol−1 at 423 K. The isomerisation equilibrium for a pair of isomers was studied by variable temperature 1H NMR. The lower limit for the isomerisation barrier was calculated to be 22 kcal mol−1 at 423 K. This low value may be indicative of the difficulty encountered in separating the isomers by chromatography. Semi-empirical AM1 and molecular mechanics calculations suggest that the (±)-spiro{naphthalene-1(2H),1′-(5′-hydroxyphenalene[1,2-c]furazan)}-2-one-2′-oxides are more stable than their 4′-oxide counterparts, in accordance to the X-ray structure. The lower population of the 4′-oxide isomers relative to that of the 2′-oxide isomers was explained in terms of an unfavourable intramolecular steric interaction found in the low energy structure of the former. 相似文献
44.
Nikolaos Mitrou Georgia‐Paraskevi Nikoleli Dimitrios P. Nikolelis Nikolas Psaroudakis Michael Scoullos 《Electroanalysis》2014,26(5):919-923
This article describes the development of a calcium solid minisensor based on lipid films on ZnO nanorods. The lipid film was composed from dipalmitoylphosphatidylcholine (DPPC) and dipalmitoylphosphatidylcic acid (DPPA). The calibration graph was logarithmically related to the concentration of calcium ions in the range from 10?6 to 10?3 M. The response times of the electrode were less than 5 s. No memory effects were observed for this electrode. The reproducibility of the electrode was less than 5 %. The electrode has shown good stability for a period of 1 month. The influence of a wide range of metals and anions as potential interferences was checked. The method was applied to the rapid detection of calcium ions in mineral waters. 相似文献
45.
Paraskevi Driva Hermis Iatrou David J. Lohse Nikos Hadjichristidis 《Journal of polymer science. Part A, Polymer chemistry》2005,43(18):4070-4078
The synthesis of model linear and star double‐comb polybutadienes, as well as molecular double‐brush polybutadienes, with two tails emanating from each branch point, is presented. The synthetic approach involves (1) the selective reaction of living polybutadienes with the two chlorines of 4‐(dichloromethylsilyl)styrene to make double‐tailed macromonomers and (2) the homopolymerization or copolymerization of the double‐tailed macromonomer, in situ without isolation, to produce the double brushes and double combs, respectively. The star double comb was synthesized by the reaction of living double‐comb polybutadiene with trichloromethylsilane. Characterization carried out by size exclusion chromatography, with differential refractometer and light scattering detectors, indicated that the synthesized polybutadienes had a high degree of molecular and structural homogeneity. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 4070–4078, 2005 相似文献
46.
A short and efficient synthesis of new isoxazolinyl nucleosides bearing the nucleobase at the 3-position is reported. The synthetic approach relies upon the 1,3-dipolar cycloaddition of bromonitrile oxide to allyl benzoate and subsequent substitution of the bromine by the nucleobase. 相似文献
47.
Electrochemical Biosensor for Naphthalene Acetic Acid in Fruits and Vegetables Based on Lipid Films with Incorporated Auxin‐binding Protein Receptor Using Graphene Electrodes
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Spyridoula Bratakou Georgia‐Paraskevi Nikoleli Christina G. Siontorou Stephanos Karapetis Dimitrios P. Nikolelis Nikolaos Tzamtzis 《Electroanalysis》2016,28(9):2171-2177
The present work describes a miniaturized potentiometric naphthalene acetic acid (NAA) sensor on graphene nanosheets with incorporated lipid films. Auxin‐binding protein 1 receptor immobilized on the stabilized lipid films provided adequate selectivity for detection over a wide range of hormone concentrations, fast response time of ca. 5 min, and detection limit of 10 nM. The proposed sensor is easy to construct and exhibits good reproducibility, reusability, selectivity, long shelf life and high sensitivity of ca. 56 mV/decade of hormone concentration. The reliability of the biosensor was successfully evaluated using a wide range of NAA‐spiked fruits and vegetables. 相似文献
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49.
Statistical copolymers of 2-vinylpyridine (VP) with oligo(ethylene glycol) methyl ether methacrylates of two different molecular weights (300 g/mol (OEGMA300) and 1100 g/mol (OEGMA1100)), were prepared by free radical polymerization. The reactivity ratios of these two sets of monomers were estimated using the Finemann–Ross, the inverted Finemann–Ross and the Kelen–Tüdos graphical methods. Structural parameters of the copolymers were obtained by calculating the dyad monomer sequence fractions and the mean sequence length. The effect of the length of the oligo(ethylene glycol) group on the copolymer structure is discussed. The glass-transition temperature (Tg) values of the VP copolymers with OEGMA300 were measured and examined in the frame of several theoretical equations, allowing the prediction of these Tg values. The copolymers of VP with OEGMA1100 exhibited the characteristic melting endotherm, due to the crystallinity of the methacrylate sequences and glass transition temperatures attributed to the PVP sequences. 相似文献
50.
Nikolaos Tzamtzis Vasillios N. Psychoyios Georgia‐Paraskevi Nikoleli Dimitrios P. Nikolelis Nikolas Psaroudakis Magnus Willander Muhammad Qadir Israr 《Electroanalysis》2012,24(8):1719-1725
A novel potentiometric uric acid biosensor was fabricated by immobilization of uricase into stabilized lipid films using zinc oxide (ZnO) nanowires as measuring electrode. Uricase was incorporated into the lipid film prior polymerization on the surface of well aligned ZnO nanowires resulting in a sensitive, selective, stable and reproducible uric acid biosensor. The potentiometric response was twice as large from previously reported values due to the presence of a cationic lipid in the lipid film. The sensor response had no interferences by normal concentrations of ascorbic acid, glucose, urea, proteins and lipids. 相似文献