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91.
A liquid chromatographic chiral stationary phase based on (+)‐(18‐crown‐6)‐2,3,11,12‐tetracarboxylic acid was applied to the resolution of 15 analytes, including racemic rasagiline, a chiral drug for the treatment of Parkinson's disease, and its analogues. The composition of mobile phase was optimized to be ethanol/acetonitrile/acetic acid/triethylamine (80:20:0.2:0.3, v/v/v/v) by evaluating the chromatographic results for the resolution of five selected analytes under various mobile phase conditions. Under the optimized mobile phase conditions, racemic rasagiline was resolved quite well with a separation factor of 1.48 and resolution of 2.71 and its 14 analogues were also resolved reasonably well with separation factors of 1.06–1.54 and resolutions of 0.54–2.11. Among 15 analytes, racemic rasagiline was resolved best except for just one analyte. The analyte structure–enantioselectivity relationship indicated that racemic rasagiline has the most appropriate structural characteristics for resolution on the chiral stationary phase. 相似文献
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93.
Tse-Lok Ho 《合成通讯》2013,43(9):761-764
4-Acetyl-2-carene obtained from 3-carene undergoes methylation, ozonolysis, and lead tetraacetate oxidation resulting in cis-dihydrochrysanthemolactone. 相似文献
94.
An efficient and simple amine‐catatalyzed azide conjugate addition to α,β‐unsaturated aldehydes has been developed. In the presence of a catalytic amount of tertiary amine with a 1:1 mixture of NaN3 and 37% HCl in CH2Cl2, α,β‐unsaturated aldehydes provided β‐azido aldehydes, which could be transformed into 1,3‐amino alcohols. 相似文献
95.
Mainly through the extensive investigations of Nakagawa and coworkers, nickel peroxide has emerged as a powerful oxidant for organic compounds. For example, it has been used for the oxidation of alcohols to aldehydes or carboxylic acids,2,3 allylic hydroxyl (selectively) to the carbonyl group,4 α-ketols to α-diketones,5 α-glycols, α-ketols, α-hydroxyl and α-keto acids to cleavage products,6 aldehydes to amides or nitriles in the presence of ammonia,7 phenols to quinones,8,9 certain Schiff bases to benzoxazoles,10 amines to azo compounds or nitriles,11,12 diarylamines to hydrazines,13 carbazoles to dimers and trimers,14 hydrazones to diazo compounds,15,16 1-aminobenzotriazole to benzyne,17 N-substituted hydroxylamines to azoxy compounds,18 phenylacetonitrile to dimeric products,19 a thiouracil to a uracil derivative,20 thiols to disulfides and sulfides to sulfones,21 N-substituted phenothiazines to sulfoxides and sulfones,21 haloforms to hexahaloethanes.23 相似文献
96.
András Kovács Zoltán Patai András Guttman János Kádas László Takács István Kurucz 《Electrophoresis》2013,34(20-21):3064-3071
Immunization with complex mixtures, like the human plasma resulted in the generation of cloned mAb libraries (PlasmaScan? and QuantiPlasma? libraries, with >1000 individual mAbs) reacting with a nonredundant set of antigenic epitopes. mAb proteomics refers to quasi‐hypothesis‐free profiling of plasma samples with nascent or cloned mAb libraries for the discovery of disease‐specific biomarkers. Once mAbs with biomarker potential have been identified, the next task is the determination of cognate antigens recognized by the respective mAbs. To determine the cognate protein antigen corresponding to each individual mAbs in the cloned mAb libraries, we have separated human plasma by consecutive steps of desalting and various chromatography procedures. The process resulted in 783 fractions, which we termed “Analyte Library” (AL). The AL represents the human plasma proteome in relatively low‐protein complexity fractions. Here, to determine the utility of the AL, we selected ten plasma proteins and checked for their presence in the fractions. Among the ten cases, the distribution of four selected plasma proteins matched expectations, as these proteins were present only in a few fractions corresponding to their physical, chemical, and biochemical properties. However, in six cases, we observed “smear” ‐like distribution or complete absence of the proteins, suggesting that protein–protein interactions or protein variants may alter the observed plasma distribution profiles. Nevertheless, we conclude that the AL is an efficient, high throughput tool to complement the mAb biomarker discovery process with cognate protein antigen identification for each mAbs. 相似文献
97.
Oxidative stress plays a key role in the pathophysiology of many diseases. Hydroxyl radical is the oxidative species most commonly causing damage to cells. The aim of this work was to optimize the method for antioxidant activity determination on a model lipophilic geranylated flavanone, diplacone. This method uses protection of plasmid DNA from oxidation by a hydroxyl radical generated by the Fenton reaction involving oxidation of metal ions using H2O2 and ascorbate. The method was optimized for lipophilic compounds using several solvents and co-solvents. It was found that (2-hydroxypropyl)-β-cyclodextrin (0.1 mass % aq. sol.) is the best co-solvent for our model lipophilic compound to measure the antioxidant activity by the method presented. Other solvents, namely dimethyl sulfoxide, Cremophor EL® (0.1 mass % aq. sol.), ethanol, and methanol, were not suitable for the determination of the antioxidant activity by the method described. Tween 80 (0.1 mass % aq. sol.) and a mixture of 10 vol. % ethanol and 9 mass % bovine serum albumin (aq. sol.) significantly decreased the antioxidant activity of the model lipophilic compound and thus were not suitable for this method. 相似文献
98.
99.
100.
Lavini C de Jonge MC van de Sande MG Tak PP Nederveen AJ Maas M 《Magnetic resonance imaging》2007,25(5):604-612
Dynamic contrast enhanced (DCE) MRI is a widespread method that has found broad application in the imaging of the musculoskeletal (MSK) system. A common way of analyzing DCE MRI images is to look at the shape of the time-intensity curve (TIC) in pixels selected after drawing an ROI in a highly enhanced area. Although often applied to a number of MSK affections, shape analysis has so far not led to a unanimous correlation between these TIC patterns and pathology. We hypothesize that this might be a result of the subjective ROI approach. To overcome the shortcomings of the ROI approach (sampling error and interuser variability, among others), we created a method for a fast and simple classification of DCE MRI where time-curve enhancement shapes are classified pixel by pixel according to their shape. The result of the analysis is rendered in multislice, 2D color-coded images. With this approach, we show not only that differences on a short distance range of the TIC patterns are significant and cannot be appreciated with a conventional ROI analysis but also that the information that shape maps and conventional standard DCE MRI parameter maps convey are substantially different. 相似文献