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排序方式: 共有306条查询结果,搜索用时 15 毫秒
1.
Vinay V. ThakurA. Sudalai 《Tetrahedron letters》2003,44(5):989-992
N-Bromoamides catalyze effectively the aziridination of electron-deficient as well as electron-rich olefins using chloramine-T (N-chloro-N-sodio-p-toluenesulfonamide) as a nitrogen source under ambient conditions to afford the corresponding aziridines in good to excellent yields. 相似文献
2.
K. Vinay Kumar Reddy B. Sreenivasa Reddy M. Sreenath Reddy Ch. Gopal Reddy P. Yadagiri Reddy K. Rama Reddy 《Radiation measurements》2003,36(1-6):419-423
Studies conducted by Atomic Minerals Directorate of Exploration and Research (AMD) of Hyderabad, India had established the presence of higher concentrations of uranium in Lambapur and Peddagattu areas of Nalgonda district, AP, India and it was estimated that it could be a viable source for commercial extraction. The envisaged extraction process involves dispersion of radioactive particulate matter into atmosphere. Environmental radioactive studies in and around proposed mining areas at this point of time will be extremely useful for establishing base line data before a large scale uranium extraction process comes into existence. To this end, Solid State Nuclear Track Detectors were installed to evaluate indoor radon and thoron concentration levels in the dwellings of the area. The geometric means of radon and thoron concentration levels were found to be (7.1±0.2)×101 and (6.7±0.3)×101 Bq/m3, respectively. Simultaneously, natural background radiation measurements were also made and these levels are found to vary from 770 to 3995 μGy/y in the spatial distribution. 相似文献
3.
Kishore K Tiwari Girdhar L Mundhara Manish K Rai Vinay K Gupta 《Analytical sciences》2006,22(2):259-262
The results of a study and application of leucocrystal violet for the determination of antimony in parts per million levels is described here. The proposed method is based on the reaction of antimony(III) with acidified potassium iodate to liberate iodine. The liberated iodine selectively oxidizes leucocrystal violet to crystal violet dye. The formed dye shows maximum absorbance at 590 nm. The color system obeys Beer's law in the concentration range from 0.4 - 3.6 microg antimony per 25 ml of final solution. The molar absorptivity and Sandell's sensitivity were found to be 7.32 x 10(5) l mol(-1) cm(-1) and 0.0016 microg cm(-2), respectively. All variables were studied in order to optimize the reaction. The proposed method is satisfactorily applicable for the analysis of antimony in various environmental and biological samples. The method is simple, highly sensitive, accurate and reliable. 相似文献
4.
Venkatraman S Njoroge FG Girijavallabhan V McPhail AT 《The Journal of organic chemistry》2002,67(8):2686-2688
A novel synthesis of cis and trans substituted 4-tert-butoxycarbonyl cyclohexylglycines via asymmetric aminohydroxylation of vinyl styrene followed by reduction of the aromatic ring and subsequent oxidation is reported. 相似文献
5.
M. S. Raghu K. Basavaiah Sameer A. M. Abdulrahaman K. N. Prashanth K. B. Vinay 《Journal of Analytical Chemistry》2013,68(11):969-976
Two simple, selective and sensitive spectrophotometric methods are described for the determination of pheniramine maleate (PAM) in pure and dosage forms. The method is based on the reaction of PAM with hypochlorite in the presence of Kolthoff buffer (phosphate-borate) of pH 7.0 to form the chloro derivative of PAM, destruction of the excess hypochlorite by nitrite ion (the chloro derivative of drug is unaffected under the optimized conditions) followed by the oxidation of iodide with the chloro derivative of PAM to iodine (I 3 ? which is either measured directly at 355 (method A) or reacted with starch to form a blue chromogen measurable at 590 nm (method B). The optimum conditions that affect the reaction were ascertained, and under these conditions linear relationship was obtained in the concentration ranges of 2–50 and 1–25 μg/mL PAM in methods A and B, respectively. The calculated molar absorptivity values are 7.26 × 103 and 1.28 × 104 L/(mol cm) for method A and method B, respectively. Sandell’s sensitivity values, limits of detection (LOD) and quantification (LOQ) are calculated as per ICH guidelines. The proposed methods were applied successfully to the determination of PAM in tablets and injection with good accuracy and precision and without interferences from common additives. The results obtained by the proposed methods were compared favourably with those of the reference method. The accuracy and reliability of the proposed methods were further checked by recovery studies via standard addition procedure. 相似文献
6.
Qun Dang Zhibo Zhang Bingyu Tang Yang Song Ling Wu Tongqian Chen Stephane Bogen Vinay Girijavallabhan David B. Olsen Peter T. Meinke 《Tetrahedron letters》2014
To discover novel nucleosides as potential antiviral agents, 2′-spirolactam and 2′-spiropyrrolidine-containing nucleoside analogs were envisioned. Efficient synthetic routes were developed with an epoxide opening as the key step to establish the quaternary center at the 2′ position, leading to the design and synthesis of uridine analogs 8 and 21, prodrugs 13–16, and cytidine analog 11. 相似文献
7.
Qun Dang Zhibo Zhang Shuangsheng He Yaohong Liu Tongqian Chen Stephane Bogen Vinay Girijavallabhan David B. Olsen Peter T. Meinke 《Tetrahedron letters》2014
To discover novel nucleosides as potential antiviral agents, 4′-spirocyclic phosphono-nucleosides were designed to mimic the monophosphate of R-1479, a known nucleoside inhibitor of HCV NS5B. Bypassing the first kinase step to nucleoside monophosphate is viewed as advantageous since this phosphorylation is often observed as the rate-limiting transformation to the active NTP for many nucleosides. Efficient synthetic routes were developed with a triphenylphosphine–iodine cyclization reaction as the key step to form the tetrahydrofuran 4′-spirocycle. The desired 4′-spirocyclic phosphono-cytidine analogs 12a, 12b, and 16 were prepared in 11 steps. 相似文献
8.
Quality by design: A systematic and rapid liquid chromatography and mass spectrometry method for eprosartan mesylate and its related impurities using a superficially porous particle column 下载免费PDF全文
Pradipbhai D. Kalariya Murali V. N. Kumar Talluri Vinay D. Gaitonde Prashant S. Devrukhakar Ragampeta Srinivas 《Journal of separation science》2014,37(16):2160-2171
The present work describes the systematic development of a robust, precise, and rapid reversed‐phase liquid chromatography method for the simultaneous determination of eprosartan mesylate and its six impurities using quality‐by‐design principles. The method was developed in two phases, screening and optimization. During the screening phase, the most suitable stationary phase, organic modifier, and pH were identified. The optimization was performed for secondary influential parameters—column temperature, gradient time, and flow rate using eight experiments—to examine multifactorial effects of parameters on the critical resolution and generated design space representing the robust region. A verification experiment was performed within the working design space and the model was found to be accurate. This study also describes other operating features of the column packed with superficially porous particles that allow very fast separations at pressures available in most liquid chromatography instruments. Successful chromatographic separation was achieved in less than 7 min using a fused‐core C18 (100 mm × 2.1 mm, 2.6 μm) column with linear gradient elution of 10 mM ammonium formate (pH 3.0) and acetonitrile as the mobile phase. The method was validated for specificity, linearity, accuracy, precision, and robustness in compliance with the International Conference on Harmonization Q2 (R1) guidelines. The impurities were identified by liquid chromatography with mass spectrometry. 相似文献
9.
Vinay S. Sharma Anuj S. Sharma Upendra H. Jadeja Deepak Suthar 《Molecular Crystals and Liquid Crystals》2018,665(1):64-81
In this study, the synthesis, structural characterization and mesomorphic properties of newly thirteen calamitic shaped compounds derived from allylidene amino chalcone and 4-n-alkoxy benzoyloxy benzoic acid. Comp.H1 to H3 exhibited nonliquid crystalline nature, while comp.H4 to comp.H18 displayed enantiotropical smectic C phase. Phase transition temperatures of present synthesised compounds were determined by optical polarising microscopy (POM), differential scanning calorimetric (DSC) and powder X-ray diffraction (PXRD) techniques. Thermal stabilities of smectic to isotropic phase are 150.0 °C and temperature range of mesophase is in decreasing order from comp.H3 to comp.H18 respectively. The presences of SmC phase are the type of broken fan and needle type in present synthesized series. It is also shown that presence of chalcone amino allylidene central linking group favors a calamitic liquid crystalline behaviour in molecules with lower member to higher member aliphatic side chain in alkoxy group (-OR). 相似文献
10.
Pandya Bhargav Kumar Vinay Matawala Vijay Patel Jatin 《Journal of Thermal Analysis and Calorimetry》2018,133(3):1635-1648
Journal of Thermal Analysis and Calorimetry - This paper presents the comprehensive thermodynamic modelling to compare the performance and optimization of single-stage NH3–H2O-type absorption... 相似文献