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611.
The reaction of epoxides with chiral nonracemic lithium amide bases, designed and prepared from (R)-phenylglycine, has been studied in detail. A maximum of 80% ee was obtained for conversion of cyclohexene oxide to (S)-2-cyclohexen-1-ol. Enantioselective deprotonation of a variety of other epoxides was studied. A cyclopentanoid core unit for prostaglandin synthesis was synthesized in 97% ee. 相似文献
612.
The notion ofB *-continuous andB c * -continuous maps is introduced. The problem of epireflection of Banaschewski-Fomin-Shanin extension for a general Hausdorff space is investigated with the help ofp B * andP B c * -continuous maps. 相似文献
613.
We use spectrally‐resolved room temperature single molecule spectroscopy to yield insights into the occurrence and dynamics of spectral forms of single tetramers of DsRed and its variants DsRed2, Fluorescent Timer, DsRed_N42H and AG4. The red‐emitting chromophore in DsRed and all studied variants readily converts into a high quantum efficiency super‐red emitting form. We propose the existence of two super‐red forms of different quantum efficiencies. The observed emission from the green‐emitting chromophore is consistent with bulk spectroscopy. We further observe distinct new spectral forms from each variant, which we attribute to a photoinduced chemical reaction leading to a truncated form of the red‐emitting chromophore analogous to the chromophore in the visible fluorescent protein zFP538. Our results have implications for the accurate interpretation of biological and biochemical processes illuminated by fluorescent proteins as well as for choosing appropriate experimental configurations. 相似文献
614.
Lourdes Basabe‐Desmonts Dr. Chien‐Ching Wu Kees O. van der Werf Maria Peter Dr. Martin Bennink Dr. Cees Otto Dr. Aldrik H. Velders Dr. David N. Reinhoudt Prof Dr. Vinod Subramaniam Prof. Dr. Mercedes Crego‐Calama Dr. 《Chemphyschem》2008,9(12):1680-1687
Fluorescent self‐assembled monolayers (SAMs) are used as dip‐pen nanolithography (DPN) substrates for the fabrication of patterns of Ca2+ and Cu2+ ions. The driving force for the transfer of these ions from an atomic force microscopy (AFM) tip to the surface is their complexation to organic ligands on the monolayer. By means of fluorescent surfaces, the patterns can be visualized under a fluorescence microscope. We use a custom‐built atomic force fluorescence microscope (AFFM), a combination of atomic force and confocal fluorescence microscopes, to deposit the metal ions onto the sensing SAMs by DPN and to subsequently visualize modulations of fluorescence intensity in a sequential write–read mode. 相似文献
615.
[Co(P1)], which was designed on the basis of potential hydrogen-bonding interactions in the metal-nitrene intermediate, is a highly active aziridination catalyst with azides. [Co(P1)] can effectively aziridinate various aromatic olefins with arylsulfonyl azides under mild conditions, forming sulfonylated aziridines in excellent yields. The Co-based system enjoys several attributes associated with the relatively low cost of cobalt and the wide accessibility of arylsulfonyl azides. Furthermore, it generates stable dinitrogen as the only byproduct. 相似文献
616.
Yashawantha K. Marigowda Vinod A. Venu 《Journal of Thermal Analysis and Calorimetry》2021,145(2):609-630
Journal of Thermal Analysis and Calorimetry - In this study, ethylene glycol (EG)–water (35:65 %v)-based nanofluids have been prepared to study enhancement in thermal conductivity.... 相似文献
617.
Adsorption studies on the removal of Vertigo Blue 49 and Orange DNA13 from aqueous solutions using carbon slurry developed from a waste material 总被引:12,自引:0,他引:12
Waste material (carbon slurry), from fuel oil-based generators, was used as adsorbent for the removal of two reactive dyes from synthetic textile wastewater. The study describes the results of batch experiments on removal of Vertigo Blue 49 and Orange DNA13 from synthetic textile wastewater onto activated carbon slurry. The utility of waste material in adsorbing reactive dyes from aqueous solutions has been studied as a function of contact time, temperature, pH, and initial dye concentrations by batch experiments. pH 7.0 was found suitable for maximum removal of Vertigo Blue 49 and Orange DNA13. Dye adsorption capacities of carbon slurry for the Vertigo Blue 49 and the Orange DNA13 were 11.57 and 4.54 mg g(-1) adsorbent, respectively. The adsorption isotherms for both dyes were better described by the Langmuir isotherm. Thermodynamic treatment of adsorption data showed an exothermic nature of adsorption with both dyes. The dye uptake process was found to follow second-order kinetics. 相似文献
618.
A chiral diamine was found to catalyze enantioselective addition of ketones to nitroolefins in aqueous/saline/organic media. The products were obtained with excellent diastereoselectivities (syn/anti = 99:1) and enantioselectivities up to 99%. The reaction could be facilitated using a mild acid. [reaction: see text] 相似文献
619.
620.
A simple, fast and sensitive RP-HPTLC method is developed for simultaneous quantitative determination of vanillin and related phenolic compounds in ethanolic extracts of Vanilla planifolia pods. In addition to this, the applicability of accelerated solvent extraction (ASE) as an alternative to microwave-assisted extraction (MAE), ultrasound-assisted extraction (UAE) and Soxhlet extraction was also explored for the rapid extraction of phenolic compounds in vanilla pods. Good separation was achieved on aluminium plates precoated with silica gel RP-18 F(254S) in the mobile phase of methanol/water/isopropanol/acetic acid (30:65:2:3, by volume). The method showed good linearity, high precision and good recovery of compounds of interest. ASE showed good extraction efficiency in less time as compared to other techniques for all the phenolic compounds. The present method would be useful for analytical research and for routine analysis of vanilla extracts for their quality control. 相似文献