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51.
Aryl-substituted 5-(3-indolyl)oxazoles are readily synthesized in a novel one-pot three-component synthesis consisting of a microwave assisted sequence of Sonogashira coupling, an acid-catalyzed cycloisomerization, and a concluding Fischer indole synthesis. All title compounds are intensely blue-luminescent with large Stokes shifts upon UV-irradiation. The experimental absorption spectra are rationalized by ZINDO-CI computations based upon DFT geometry optimization. 相似文献
52.
A new rapid, sensitive and validated HPLC method has been developed for the determination of methylxanthines and their metabolites in asthmatic patients. The method was initiated by using spiked urine samples on a silica monolithic column as a novel packing material. The mobile phase consisted of 10 mM potassium dihydrogen phosphate buffer/methanol (87.5:12.5 v/v), at a flow rate 1 mL/min. Detection was set at 274 nm. The LOQ for all the compounds ranged from 14 to 41 ng/mL. Excellent linearity was achieved over the studied range of concentration with correlation coefficients 0.9991–0.9998 (n = 6). The developed method was validated by precision and accuracy with RSD <2.55%. On extraction of the drugs and metabolites from the urine samples high recoveries were achieved ranging from 82.06 to 98.34% w/w on RP18 cartridges and methanol/chloroform (20:80 v/v) as the extraction solvent. This method has advantages over other methods using conventional C18 packings. 相似文献
53.
The sequence of orthogonal polynomials
is said to be classical if
is also orthogonal. The aim of this paper is to find the sequences
which have the property that
is also orthogonal. We prove that sequences, with this property have to be, classical and belong either to the set of Laguerre or Jacobi polynomials, where in the Laguerre case c has to be zero and in the Jacobi case c = ±1. 相似文献
54.
In this paper, we deal with some linear functionals on the vector space of polynomials whose moments are, in certain normalization, classical orthogonal polynomials (Hermite, Laguerre and Gegenbauer). We show that these linear functionals are semiclassical of class, at most, three. We give the coefficients in the three-term recurrence relations that the corresponding monic orthogonal polynomial sequences satisfy. 相似文献