Diinsertion of fluorenylidene into a sulfur-sulfur bond of diaryl disulfides

Upon irradiation (>340 nm) of a benzene solution of diazofluorene with di-p-tolyl- or di-p-anisyl disulfide, the corresponding 9,9′-bis(arylmercapto)bifluorenyl was afforded in moderate to good yield accompanied by formation of 9,9′-bis(arylmercapto)fluorene. The major reaction pathway is considered to be a disulfur ylide formation followed by two times of successive Stevens rearrangement or by concerted electron redistribution via [2,3]sigmatropic rearrangement.     

Determination of plasma protein binding of propafenone in rats, dogs and humans by highly sensitive gas chromatography-mass spectrometry

A highly sensitive method for the determination of propafenone in plasma has been established using gas chromatography-mass spectrometry with the deuterium-labelled compound as an internal standard. Plasma levels as low as 1 ng/ml were measured using 0.5-ml plasma samples. Plasma protein binding of the drug in rats, dogs and humans in vitro and in vivo was determined by the proposed method. About 90% of the drug was bound to the plasma protein in all species in vitro (20-500 ng/ml) and 69-88% in rats, 90-95% in dogs and 77-89% in humans after oral administration of the drug at doses of 50 mg/kg, 5 mg/kg and 200 mg per person, respectively.     

XPS study on valence band structures of transition-metal trisulfides,TiS3, NbS3, and TaS3

Transition-metal trisulfides, TiS₃, NbS₃, and TaS₃, with a quasi-one-dimensional structure are investigated by X-ray photoelectron spectroscopic (XPS) measurements to obtain information on the valence band structures. The band structures at the Fermi level of these compounds correspond well to their transport properties. A shoulder is observed at the top of the valence band in NbS₃ and TaS₃, suggesting that this band is made up of the metal d_z² electrons. The d_z² band is occupied in NbS₃ and TaS₂ and empty in TiS₃. The characteristic features at the top of the valence band in NbS₃ imply the occurrence of d_z² band separation, which leads to a semiconducting nature.     

Chemoenzymatic synthesis of (+)-totarol, (+)-podototarin, (+)-sempervirol, and (+)-jolkinolides E and D

The enzymatic resolution products [(1R,4aR,8aR)-1,2,3,4,4a,5,6,7,8,8a-decahydro-5,5,8a-trimethyl-2-oxo-trans-naphthalene-1-methanol-2-ethylene acetal (8aR)-7 (98% ee) and {acetate of (1S,4aS,8aS)-1,2,3,4,4a,5,6,7,8,8a-decahydro-5,5,8a-trimethyl-2-oxo-trans-naphthalene-1-methanol-2-ethylene acetal} (8aS)-9 (>99% ee)] obtained by the lipase-catalyzed enantioselective acetylation of (±)-7 in the presence of vinyl acetate as an acyl donor were converted to the ,β-unsaturated ketones (8aR)-6 and (8aS)-6, respectively. Concise syntheses of (+)-totarol 1, (+)-podototarin 2 and (+)-sempervirol 3 were achieved based on Michael reactions between (8aS)-6 and the appropriate β-keto ester followed by aldol condensation. The first chiral syntheses of (+)-jolkinolides E 4 and D 5 were achieved from (5R,10R,12R)-12-hydroxypodocarpa-8(14)-en-13-one 15 derived from (8aR)-6.     

Determination of ammonium ion in a flow-injection system with a gas-diffusion membrane : Selection of Optimal Conditions for the pH Indicator

The spectrophotometric determination of ammonium ion in water by flow-injection analysis with a membrane-separator and a pH indicator for detection is studied in detail. The relations derived facilitate the selection of appropriate solution compositions or the prediction of sensitivity. It is shown that 1.5×10^?5 M bromocresol purple (pH 6.8) as acceptor solution gives the maximal sensitivity in the flow system with a laboratory-made separation unit. Application of ultrasonic radiation in the separation step and the use of different flow rates for the donor and acceptor streams may result in increased permeation of ammonia and a correspondingly high sensitivity. By modifying the acceptor solution so that the sensitivity is decreased, more concentrated samples such as urine can be analyzed by direct injection without prior dilution. In this procedure, the sample rate was 60 h^?1 for ammonium concentration of more than 10^?5 M and 30–40 h^?1 for concentrations in the range 3×10^?7?10^?5 M. The detection limit was about 3×10^?7 M.     

Isolation,Diversity and Characterization of Ulvan-Degrading Bacteria Isolated from Marine Environments

In this study, we aimed to isolate bacteria capable of degrading the polysaccharide ulvan from the green algae Ulva sp. (Chlorophyta, Ulvales, Ulvaceae) in marine environments. We isolated 13 ulvan-degrading bacteria and observed high diversity at the genus level. Further, the genera Paraglaciecola, Vibrio, Echinicola, and Algibacter, which can degrade ulvan, were successfully isolated for the first time from marine environments. Among the 13 isolates, only one isolate (Echinicola sp.) showed the ability not only to produce externally expressed ulvan lyase, but also to be periplasmic or on the cell surface. From the results of the full-genome analysis, lyase was presumed to be a member of the PL25 (BNR4) family of ulvan lyases, and the bacterium also contained the sequence for glycoside hydrolase (GH43, GH78 and GH88), which is characteristic of other ulvan-degrading bacteria. Notably, this bacterium has a unique ulvan lyase gene not previously reported.     

Effect of an electric field on defects in a nematic liquid crystal with variable surface anchoring

We report experimental studies on defects in a nematic liquid crystal with negative dielectric anisotropy mounted in a cell with perfluoropolymer-coated surfaces. The sample exhibits a discontinuous anchoring transition from planar to homeotropic on cooling at zero or a small electric field, and above a cross-over voltage a continuous ‘inverse Freedericksz transition’, at which the director starts tilting in opposite directions at the two surfaces. Defects of strength ±1/2 are either annihilated or expelled when the director tilts. On the other hand, disclination lines of ±1 which end in partial point defects (boojums) at the surfaces in the planar alignment regime acquire point defects of strength ±1 at the midplane of the cell when the director tilts. At a low enough temperature, the homeotropic anchoring becomes strong, and an electric field above the Freedericksz threshold generates the usual umbilic defects, which follow the dynamic scaling laws found in earlier studies.     

Enantioselective copper-catalyzed 1,4-addition of dialkylzincs to enones using a novel N,N,P–Cu(II) complex

Enantioselective copper-catalyzed 1,4-additions of dialkylzincs to enones were carried out in the presence of 1 mol % of Cu(OTf)₂ and 2.5 mol % of an N,N,P-ligand possessing a tert-butyl group at the adjacent position of the nitrogen of pyridine to afford the corresponding 1,4-adducts in up to 98% ee.     

Heat of Terpolymerization

Abstract

A novel correlation for predicting the heat of terpolymerization from the binary data is proposed. This correlation is applicable to the ternary system with monomers which obey the Q-e scheme. The heat of terpolymerization for the ternary system methyl methacrylate-styrene-acrylonitrile is calculated from binary data.