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41.
Katritzky AR Abo-Dya NE Abdelmajeid A Tala SR Amine MS El-Feky SA 《Organic & biomolecular chemistry》2011,9(2):596-599
The transprotection of N-Fmoc-cysteine containing di- and tripeptides possessing a free SH group to produce the corresponding S-Fm-cysteine di- and tripeptides bearing a free amino group is accomplished efficiently with DBU in dry THF. The N-Fmoc to S-Fm transformation mechanism is discussed. S-Fm-Cysteine di- and tripeptides readily form amide bonds on coupling with N-(Pg-α-aminoacyl)benzotriazoles and N-(Pg-α-dipeptidoyl)benzotriazoles to give larger peptides. 相似文献
42.
Radiation exposure and effective dose received through two routes of exposure, viz. external and internal, via inhalation, by residents of 10 villages belonging to Natural High Background Radiation Areas (NHBRA) of coastal regions of Kanyakumari District and Tamil Nadu in India were studied. While the indoor gamma radiation levels were monitored using Thermo Luminescent Dosimeters (TLDs), the indoor radon and thoron gas concentrations were measured using twin chamber dosimeters employing Solid State Nuclear Track Detectors (SSNTDs, LR-115-II). The average total annual effective dose was estimated and found to be varying from 2.59 to 8.76 mSv. 相似文献
43.
Velu Manikandan Palanivel Velmurugan Palaniyappan Jayanthi Jung-Hee Park Woo-Suk Chang Yool-Jin Park Min Cho Byung-Taek Oh 《Research on Chemical Intermediates》2018,44(4):2489-2502
Green synthesis of TiO2 nanoparticles (NPs) from Prunus × yedoensis leaf extract (PYLE), and their application for removal of phosphate and their antibacterial activity, were studied for the first time. NPs were obtained using a green chemistry approach from 0.1 M TiO2 and PYLE at ratio of 1:1 (v/w). Initial confirmation of production of TiO2 NPs was provided by a color change from white to light yellow, then calcination was performed at 500 °C for 1 h. The TiO2 NPs were characterized using various analytical techniques such as ultraviolet–visible (UV–Vis) spectroscopy, X-ray diffraction analysis, Fourier-transform infrared spectroscopy, Raman spectroscopy, UV–Vis diffuse reflectance spectroscopy, X-ray photoelectron spectroscopy, and high-resolution transmission electron microscopy. The results indicated that the optimal amount of TiO2 NPs for removal of phosphate was 10 mg/l (10 ppm) with duration of 25 min. Furthermore, the antibacterial activity of TiO2 NPs was also investigated using two different bacteria (Gram-positive Staphylococcus aureus and Gram-negative Escherichia coli) in aqueous medium. The results revealed highly efficient sunlight-driven photocatalytic and antibacterial activity of TiO2 NPs. 相似文献
44.
Cladosporin, a secondary metabolite isolated from fungal sources like Cladosporium cladosporioides and Aspergillus flavus was found to exhibit selective nano-molar activity against malarial parasite Plasmodium falciparum by inhibiting parasitic protein biosynthesis. In addition, this natural product has a broad range of bioactivities including, antiparasitic, antifungal, antibacterial as well as plant growth inhibition. However, it has limited availability from the natural sources for further development. Herein, we report a modified and improved synthetic route which led us to produce this potent natural product in a gram scale. Conversion of the undesired diastereomer to desired one via Mitsunobu inversion of secondary alcohol and carbon monoxide insertion reaction towards the construction of isocoumarin unit are the key features of the present synthesis. 相似文献
45.
46.
Jayabharathi J Thanikachalam V Srinivasan N Perumal MV Jayamoorthy K 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2011,79(1):137-147
A series of substituted imidazoles have been synthesized in very good yield under solvent free condition by grinding 1,2-diketone, arylaldehyde, arylamine and ammonium acetate in the presence of molecular iodine as the catalyst. The short reaction time, good yield and easy workup make this protocol practically and economically attractive and the imidazoles are characterized by NMR spectra, X-ray, mass and CHN analysis. The push-pull character of series of imidazoles have been analyzed by the quotient of the occupations of the bonding (π) and anti-bonding (π*) orbitals of the central linking -N=C-C=C- unit. Excellent correlation of the push-pull parameter with the corresponding bond lengths d(CN) and d(CC) strongly recommend both the occupation quotients (π*/π) and the corresponding bond lengths are reasonable sensors for quantifying the push-pull character and for the molecular hyperpolarizability ?(0) of these compounds. To support the experimental results, theoretical calculations (heat of formation, NLO, NBO and vibrational analysis) were also made. Within this context, reasonable conclusions concerning the steric hindrance in the chromospheres, push-pull character, hyperpolarizability of the imidazoles and their application as NLO materials will be drawn. 相似文献
47.
开发了一种由金和钯催化π-活化由炔醇合成呋喃衍生物的集成方法.该合成策略是最显著的特点适用于带环辛基的底物,其适用范围比之前报道的有很大扩展.在Sonogashira反应条件下,由相应底物可直接得到环辛基呋喃.Pd在这些反应中起到2个重要作用:底物发生偶联反应的关键催化剂;通过π-活化促进炔醇中间体成环反应.该方法在一步合成3-碘呋喃反应中作用很突出,使通过偶联法进一步官能团化成为可能.我们还将AuBr_3用于多米诺成环/C-H键活化反应和无环前体的成环反应.本文结果表明,在该类成环反应中金和钯催化剂相辅相成. 相似文献
48.
Raghoottama S. Pandurangl Srinivasa R. Karra Robert R. Kuntz Wynn A. Volkert 《Photochemistry and photobiology》1996,64(1):100-105
Abstract— A mild and efficient method of linking a dihydroflavin to the C-17 carboxylic acid side chain of protochlorophyllide, without degradation of the sensitive E ring or loss of magnesium, is described. The appended dihydroflavin was shown to quench the fluorescence of protochlorophyllide. In contrast, a dihydronicotinamide moiety was unable to effect fluorescence quenching. The relevance of these findings to a possible mechanism of action of the enzyme protochlorophyllide reductase is discussed. 相似文献
49.
The 4-hydroxy buteneolide terminus 3, applicable to mucocin 1 and related annonaceous acetogenins, was prepared in an expeditious manner from the selenocarbonate 2 via an intramolecular acyl radical cyclization followed by an enantioselective Lewis-acid catalyzed Keck-allylation reaction. 相似文献
50.
A. K. Jain Bhattacharjee V. Kolandai Velu 《Reaction Kinetics and Catalysis Letters》1984,26(3-4):235-243
A modification in the reaction mechanism of 0-(2,4-dinitrophenyl)cyclohexanone Oxime with OH– in 30% aqueous methanol is suggested. The cationic micelles of cetyltrimethyl ammonium bromide enhance the reaction by a factor ofca. 3. The pseudo first order rate constant at the micellar surface was found to be 10.9×10–4 s–1 at 35±0.1°C. Anionic and nonionic micelles inhibit the rate of the reaction. Bromide ion inhibits the catalysis, which indicates that catalysis is partially due to a concentration effect. The catalytic efficiency increases with decreasing [OH–), which implies that the efficiency of the surfactant could be related to some standard parameter(s).
0-(2,4-)-- OH– 30%- . . 3. - 10.9·10–4 –1 35±0.1°C. . . , - . - [OH–], , - - .相似文献