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241.
Two further aporphine alcaloids, N-methyllaurotetanine and boldine, were used to the synthesis of aristolochic acid analogs. By means of their destruction and nitration of the reaction products two new nitrophenanthrene acids were obtained and their chemical structures were proved. 相似文献
242.
Postema MH Piper JL Betts RL Valeriote FA Pietraszkewicz H 《The Journal of organic chemistry》2005,70(3):829-836
The synthesis of a number of biologically relevant C-glycosides has been carried out through the use of an esterification-ring-closing metathesis (RCM) strategy. The required acid precursors were readily prepared via a number of standard chemical transformations followed by dehydrative coupling of these acids with several olefin alcohols 1 to yield the precursor esters 3 in excellent yield. Methylenation of the esters 3 was followed by RCM and in situ hydroboration-oxidation of the formed glycals to furnish the protected beta-C-glycosides 6 in good overall yield. Several examples were converted to the corresponding C-glycoglycerolipids 17 and subsequently screened against solid-tumor cell lines for in vitro differential cytotoxicity. 相似文献
243.
Halina Kaczmarek Krzysztof Bajer Barbara Kotnowska 《Polymer Degradation and Stability》2007,92(11):2058-2069
Blends of two biodegradable polymers: natural pectin and synthetic poly(ethylene oxide) at different weight-ratios were obtained by physical mixing in aqueous solutions, and evaporation of the solvent. The macromolecular order in the composites was investigated by applying X-ray diffraction, while the surface morphology was observed using atomic force microscopy. The photooxidative degradation of the blends was studied by viscometry, FTIR spectroscopy and UV-vis spectroscopy. It has been found that the susceptibility of the studied composites to UV radiation depends on an appropriate ratio of components, and the most sensitive to UV-irradiation among the samples studied was the equal weight-ratio blend of poly(ethylene oxide)/pectin. 相似文献
244.
Mushroom reference material has been prepared and characterized for use in proficiency test exercises within the frame of
an IAEA Interregional Technical Cooperation Project. Laboratories from 14 countries provided results for homogeneity testing
and the assignment of property values. The contents of 11 elements have been assigned. The material was used for conducting
a proficiency test in Poland and the results obtained by Polish laboratories are presented and discussed. 相似文献
245.
Leszek Czuchajowski Jan Habdas Halina Niedbala Vinay Wandrekar 《Journal of heterocyclic chemistry》1992,29(2):479-486
Several porphyrinyl-nucleosides were prepared in the reaction of the OH group of one, two or four meso-p-hydroxyphenyl substituents of porphyrin with 5′-O-tosylates of 2′,3′-O-isopropylidene-adenosine or -uridine, or 5′-O-tosylthymidine; the remaining porphyrin meso-substituents were p-tolyl, p-hydroxyphenyl or 4-pyridyl. The following porphyrinyl-nucleosides were obtained with 8–17% yield: meso-di(p-tolyl)di(p-phenylene-5′-O-2′,3′-O-isopropylidene-adenosine) (or -uridine)porphyrins 1,2 , the respective meso-tetranucleosideporphyrins 3,4 -meso-mono(p-phenylene-5′-O-thymidine)porphyrins 5–7 , meso-di(p-tolyl)di(p-phenylene-5′-O-thymidine)porphyrins 8,9 and the meso-di(p-hydroxyphenyl)di(p-phenylene-5′-O-thymidine)porphyrins 10. Other compounds prepared belonged to the series: meso(4-pyridyl)4?n(p-phenylene-5′-O-2′,3′-O-isopropylideneuridine)nporphyrin, n = 1, 2 or 4, 11–13. N-Methylation gave the water soluble iodide salts: (N-methyl-4-pyridinium)44?n(p-phenylene-5′-O-2′,3′-isopropylideneuridine)nporphyrins, n = 1, 2 or 4, 14–16. The ms fab showed in most cases stepwise detachment of the CH2(5′)-nucleoside fragments. The porphyrins meso disubstituted by thymidine represent a convenient substrate for the build-up of both nucleoside units into the oligo/polynucleotide chains. 相似文献
246.
The kinetics of solventless transesterification of methyl methacrylate with ethylene glycol has been studied to establish the optimal conditions for ethylene glycol monomethacrylate synthesis. The kinetic data presented show strong dependence of kinetic parameters on initial reagents ratio.
Qj . .相似文献
247.
Warner JH Rubinsztein-Dunlop H Tilley RD 《The journal of physical chemistry. B》2005,109(41):19064-19067
Monodisperse 1-2 nm silicon nanocrystals are synthesized in reverse micelles and have their surfaces capped with either allylamine or 1-heptene to produce either hydrophilic or hydrophobic silicon nanocrystals. Optical characterization (absorption, PL, and time-resolved PL) is performed on colloidal solutions with the two types of surface-capped silicon nanocrystals with identical size distributions. Direct evidence is obtained for the modification of the optical properties of silicon nanocrystals by the surface-capping molecule. The two different surface-capped silicon nanocrystals show remarkably different optical properties. 相似文献
248.
Timo A. Nieminen Theodor Asavei Vincent L.Y. Loke Norman R. Heckenberg Halina Rubinsztein-Dunlop 《Journal of Quantitative Spectroscopy & Radiative Transfer》2009,110(14-16):1472-1482
A key element in the generation of optical torque in optical traps, which occurs when electromagnetic angular momentum is transferred from the trapping beam to the trapped particle by scattering, is the symmetries of the scattering particle and the trapping beam. We discuss the effect of such symmetries on the generation and measurement of optical torque in optical tweezers, and some consequent general principles for the design of optically driven micromachines. 相似文献
249.
250.