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111.
Summary Enantiomeric separation of (–)-menthyl chloroformate derivatives of some chiral cardioactive drugs, on porous graphitic carbon (PGC), Hypercarb-S, is described. Capacity and separation factors of derivatives of the calcium channel blockers; amlodipine and UK52.829, the -blockers; atenolol, sotalol and propranolol, and mexiletine were studied in different chromatographic systems based on dichloromethane. A high content of a carboxylic acid in the mobile phase was found to decrease the retention and positively affect the stereoselectivity of the derivatives. A mobile phase with dichloromethane, acetonitrile and formic acid gave baseline separation of the enantiomers of amlodipine in less than 8 minutes. Results show that acetic acid and formic acid, may be regarded as strong organic solvents in PGC chromatography with nearly the same elution power as dichloromethane. 相似文献
112.
113.
Michael?Sch?ferlingEmail author Michael?Riepl Petra?Pavlickova Hubert?Paul Dev?Kambhampati Bo?Liedberg 《Mikrochimica acta》2003,142(4):193-203
Two different types of -substituted alkanethiol/disulfide compounds have been used to prepare monolayer architectures on gold serving as platforms for the immobilization of receptor probe molecules – antibodies. These are: (i) carboxylic acid alkanethiols post-reacted with amino biotin to generate streptavidin surfaces, and (ii) N-hydroxysuccinimide-terminated disulfide surfaces. The properties of the monolayers, with and without attached receptor probe molecules, were analysed using infrared spectroscopy, ellipsometry, fluorescence scanning and atomic force microscopy. Several experimental parameters, such as condensation reagents, additives, probe and target concentrations and immobilization time, were systematically varied to determine the dynamic range and to optimize the sensitivity and signal-to-noise ratio of the biochip platforms. Fluorescence screening using Cy5-labelled antigens finally demonstrated that both surfaces could be successfully employed to immobilize the antibodies. The pros and cons of the two approaches are also discussed.Received November 15, 2002; accepted March 25, 2003
Published online July 28, 2003 相似文献
114.
Summary Optically activeMichael adducts were synthesized by addition of 1,3-dicarbonyl compounds to conjugated nitroalkenes. Good chemical yields were obtained for nitroalkenes stabilized by an aromatic substituent without any further substituents at the double bond. Acetylacetone and methyl-2,3-dihydro-1-oxo-1H-indene-2-carboxylate were used asMichael donors and four cinchona alkaloids as chiral base catalysts. Enantiomeric excess determinations were performed by1H NMR spectroscopy in the presence of thePirkle alcohol and by HPLC on chiral stationary phases. A correlation between the relative configuration of the prevailing isomer of theMichael adduct and the catalysts was established.
Asymmetrische Katalyse, 103. Mitt.: EnantioselektiveMichael-Addition von 1,3-Dicarbonylverbindungen an konjugierte Nitroalkene
Zusammenfassung Optisch aktiveMichael-Addukte werden durch die Addition von 1,3-Dicarbonylverbindungen an konjugierte Nitroalkene synthetisiert. Gute chemische Ausbeuten werden für durch aromatische Substituenten stabilisierte Nitroalkene ohne weitere Substituenten an der Doppelbindung erreicht. Acetylaceton und 2,3-Dihydro-1-oxo-1H-inden-2-carbonsäuremethylester werden alsMichael-Donoren und vier Cinchona-Alkaloide als chirale basische Katalysatoren verwendet. Die Bestimmung des Enantiomerenüberschusses wird mittels1H-NMR-Spektroskopie in Gegenwart vonPirkle-Alkohol und HPLC an chiralen stationären Phasen durchgeführt. Eine Korrelation zwischen der relativen Konfiguration der Vorzugsisomeren derMichael-Addukte und den Katalysatoren wurde hergestellt.相似文献
115.
Summary The effect of perchlorate anion as mobile phase modifier on the separation factor, α, forN-(dansyl)-dl-norvaline andN-(dansyl)-dl-tryptophan on a human serum albumin (HSA) column was studied by varying the concentration,c, of the chaotropic agent and the column temperatureT. Gibbs-Helmholtz parameters Δ(ΔH) and Δ(ΔS) between thed andl enantiomers were determined from linear van't Hoff plots of lnα against 1/T. Thermodynamic results indicated that the enhancement of the separation factor observed asc was increased was enthalpically controlled owing to stereoselective H-bonding interactions. Such behavior was used to optimize
the chromatographic conditions for separation ofN-(dansyl)-amino acids on HSA. 相似文献
116.
Hao Li 《Tetrahedron letters》2007,48(12):2209-2211
2,2′-Disubstituted ferrocenecarboxaldehydes are subjected to zinc-mediated allylation to form homoallylic ferrocenyl alcohols. The effects of ortho-substituted functional groups on facial selectivities of planar chiral aldehydes were studied and it was found that the corresponding homoallylic alcohols were obtained as single diastereomers in excellent yields. 相似文献
117.
组合电化学是一种新的电化学研究策略,通过设计和构建大量多样性的电极阵列,并对其进行高通量筛选和表征,快速、高效地实现了体系的电化学研究。本文综述了近年来进行的组合电化学研究,重点介绍了组合光学筛选方法、组合电化学合成方法以及电化学平行筛选方法,并探讨了各种方法的优势和存在的问题。 相似文献
118.
[2+2] Carbonylative cycloaddition of chiral imines to various allyl halides, under CO pressure, in the presence of Et3N, a catalytic amount of Pd(OAc)2 and PPh3 as ligand, are carried out. Separable diastereomeric mixtures of chiral alkenyl-β-lactams are isolated with good yields and high trans diastereoselections. Absolute configurations are assigned by X-ray measurements and 1H NMR spectroscopy. 相似文献
119.
Benjamin Esquivel Lawrence Nicholson Linda Peerey Michael Fazio 《Journal of separation science》1991,14(12):816-823
Factors influencing the stereoisomeric resolution of underivatized dipeptides and a representative tripeptide on Crownpak (CR) columns have been investigated. The elution order and relative retention suggest that a combination of chiral, steric, and hydrophobic interactions effects the extent of chiral recognition and the retention achieved during separations. Some dipeptides whose amine terminus is located three atoms from the asymmetric center (such as dipeptides of D ,L -glycine) were resolved, but the elution order was the opposite of that expected for the type of Crownpak column used (CR(+)). Peptides containing hydrophobic substituents were strongly retained, but their retention times could be significantly reduced, and detectability improved, by use of gradient elution. Analysis of a commercial sample of D ,L -leucine-D ,L -alanine revealed the stereoisomers to be present in an unexpected quantitative ratio and demonstrated the utility of these separations for quality assurance and quantitative analyses. 相似文献
120.
Pengyuan Zhao Aolin Cheng Xinxu Wang Jiguo Ma Guoqing Zhao Yingkun Li Yi Zhang Baoguo Zhao 《中国化学》2020,38(6):565-569
By using a combination of a chiral N‐triflyl phosphoramide and TiCl4 as the catalyst, a new process for asymmetric intramolecular hydroalkoxylation of unactivated alkenes was developed, producing various chiral tetrahydrofuran derivatives in 51%—99% yields with 30%—71% ee's. 相似文献