Development of hydrophilic fluorogenic derivatization reagents for thiols: 4-(N-acetylaminosulfonyl)-7-fluoro-2,1,3-benzoxadiazole and 4-(N-trichloroacetylaminosulfonyl)-7-fluoro-2,1,3-benzoxadiazole

Sensitive, reactive, and hydrophilic fluorogenic reagents for thiols with the benzofurazan skeleton, 4-(N-acetylaminosulfonyl)-7-fluoro-2,1,3-benzoxadiazole (AcABD-F) and 4-(N-trichloroacetylaminosulfonyl)-7-fluoro-2,1,3-benzoxadiazole (TCAcABD-F) have been developed. These reagents reacted with thiols within 10 min at 60 degrees C. AcABD-F and TCAcABD-F themselves do not fluoresce but are strongly fluorescent after the reaction with thiol compounds. The generated derivatives were highly water-soluble, since they dissociated a proton and ionized in the neutral pH region. The derivatives with four biologically important thiol compounds were separated on a reversed-phase HPLC column and detected fluorometrically at 504 nm with excitation at 388 nm. The detection limit attained for homocysteine with AcABD-F was 25 fmol on column (11 nM) (signal-to-noise ratio = 3), and that for glutathione with TCAcABD-F was 45 fmol on column (20 nM).     

Epoxidation of alpha,beta-unsaturated ketones using hydrogen peroxide in the presence of basic hydrotalcite catalysts

The basic layered hydrotalcites have been used as catalysts for the epoxidation of alpha,beta-unsaturated ketones in heterogeneous reaction media using hydrogen peroxide as an oxidant. A wide variety of alpha,beta-unsaturated ketones were oxidized to the corresponding epoxyketones in excellent yields under mild reaction conditions. For example, 2-cyclohexen-1-one gave 2,3-epoxycyclohexanone in 91% yield at 40 degrees C for 5 h with high efficiency in hydrogen peroxide. The catalytic activity of the hydrotalcites increased as the basicity of their surfaces increased. In the case of the epoxidation of less reactive substrates, adding a cationic surfactant such as n-dodecyltrimethylammonium bromide (DTMAB) to the above oxidation system accelerated the epoxidation reaction. These hydrotalcite catalysts were easily separated from the reaction mixture and were reusable.     

A new memory effect: smectic liquid crystalline memory having both conductive and optical memory

In order to compensate for light leakage in the oblique viewing directions of the dark state of the horizontal-switching mode such as the in-plane switching and fringe field switching modes. The viewing angle performance of the horizontal-switching mode with an compensation film has been evaluated on a case by case basis according to the retardation values of the films. Consequently, we found that a much better dark state can be achieved by using an optimised compensation film.     

Catalyst design of hydrotalcite compounds for efficient oxidations

Various Mg-Al type hydrotalcites were examined as catalysts for the epoxidation of olefins and N-oxidation of pyridines using hydrogen peroxide. The catalytic activity of hydrotalcites increased with increasing the basicity of their surface. Adding cationic surfactants, e.g., n-dodecyltrimethylammonium bromide, to the above system remarkably accelerated the reaction rate. The hydrotalcites, into which were introduced both Ru and Co cations in the Brucite layers, were found to be good catalysts for the oxidation of various alcohols in the presence of molecular oxygen. Moreover, these hydrotalcites could smoothly catalyze also the oxygenation of diphenylmethane, fluorene, and xanthene at benzylic position with excellent yields. The hydrotalcite catalysts could be easily separated from the reaction mixture and reused with retention of their high catalytic performance for the above oxidations.     

Role of base in the formation of silver nanoparticles synthesized using sodium acrylate as a dual reducing and encapsulating agent

The formation mechanism of Ag nanoparticles (NPs) synthesized with a wet-chemical reduction method using sodium acrylate as a dual reducing and capping agent was investigated with various analytical techniques. The time course of the state of the reaction solution was investigated using UV-vis and XAFS spectroscopies which showed that the NP formation rate increased with increasing concentration of sodium hydroxide (NaOH). The detailed kinetic analyses reveal that both the reduction rate of Ag ions and the nucleation rate of Ag NPs are dramatically increased with increasing NaOH concentration. XANES analyses imply that another reaction pathway via alternative Ag(+) species, such as Ag(OH)(x), was developed in the presence of NaOH. Consequently, NaOH is found to play an important role not only in creating specific intermediates in the reduction of Ag(+) to Ag(0), but also in accelerating the reduction and nucleation rates by enhancing the oxidation of sodium acrylate, thereby increasing the rate of formation of the Ag NPs.     

Total synthesis of TT-1 (rasfonin), an α-pyrone-containing natural product from a fungus Trichurus terrophilus

Total synthesis of TT-1 (1=rasfonin), an α-pyrone-containing natural product from a Fungi Imperfecti Trichurus terrophilus culture was achieved by a stereoselective method in optically active form, which further provided evidence for the whole structure of TT-1 (1) including the absolute stereochemistry.     

An acidic layered clay is combined with a basic layered clay for one-pot sequential reactions

A Ti4+-exchanged montmorillonite (Ti4+-mont) and a hydrotalcite (HT) are strong solid Br?nsted acid and base, and these two clay catalysts could be used in a single reactor without neutralization of active sites. Because the Ti4+-mont have active acid site in the narrow interlayers, the base sites of large HT particles show no interaction with the acid sites. A variety of acid and base reactions, such as esterification, acetalization, deacetalization, aldol reaction, Michael reaction, and epoxidation, proceeded using both the Ti4+-mont and the HT in a single reactor.