Biyouyanagin A, an anti-HIV agent from Hypericum chinense L. var. salicifolium

[structure: see text] A structurally unique hydrophobic compound, biyouyanagin A, was isolated from the MeOH extract of the leaves of Hypericum chinense L. var. salicifolium. The structure of biyouyanagin A was elucidated on the basis of spectroscopic evidence. Biyouyanagin A showed a significant activity against HIV and inhibited cytokine production.     

Preparation of titanated alkoxyallenes from 3-alkoxy-2-propyn-1-yl carbonates and (eta(2)-Propene)Ti(O-i-Pr)(2) as an efficient ester homoaldol equivalent

3-Alkoxy-2-propyn-1-yl carbonates (2) react with a divalent titanium reagent (eta(2)-propene)Ti(O-i-Pr)(2) to afford titanated alkoxyallenes 1 which, in turn, react with aldehydes regiospecifically to provide the corresponding gamma-addition products in good to excellent yields, thus affording a convenient method for synthesizing gamma-hydroxy esters 3 and/or gamma-butyrolactones 4.     

Simultaneous determination of eleven ingredients in ophthalmic solutions by cyclodextrin-modified micellar electrokinetic chromatography with tetrabutylammonium salt

Cyclodextrin-modified micellar electrokinetic chromatography was applied to determine simultaneously 11 active ingredients in ophthalmic solutions. All the ingredients were successfully separated by using the mixed carrier system containing sodium dodecyl sulfate with beta-cyclodextrin and tetrabutylammonium phosphate. The effects of the cyclodextrin type on selectivity were also examined. Excellent separation of the all ingredients was obtained by the use of dimethyl-beta-cyclodextrin. The established method was validated and confirmed to be applicable to the determination of the active ingredients in a commercial ophthalmic solution. These results suggest that capillary electrophoresis can be applied to the quantitative analysis as well as qualitative analysis in pharmaceuticals.     

Local plasmon sensor with gold colloid monolayers deposited upon glass substrates

A new optical sensor that uses local plasmon resonance is proposed. A peak that is due to the local plasmon resonance appears in the absorption spectrum of a gold colloid suspension in the visible region, and its height and wavelength depend on the refractive index of the suspension. These properties are used for optical sensors. We used gold colloid monolayers in which colloidal gold particles a few tens of nanometers in diameter were immobilized upon a glass slide by a functional organic coupling agent. We measured the absorption spectra of the the gold colloid monolayers, which were immersed in liquid samples or coated with thin films. We observed increases of both the resonance wavelength and the absorbance as the refractive indices of the sample liquids or the thickness of the coated films increased. The proportional constants of the resonance wavelength to the film thickness were 3.6 and 5.7 for a 13.9- and a 20.2-nm gold colloid monolayer, respectively.     

A new, highly sensitive time-of-flight mass spectrometer consisting of a flangeon-type conical ion lens system and a proto-type Daly detector for exhaust gas analysis based on the Jet-REMPI technique.

For the analysis of trace amounts of hazardous organic compounds, we developed a new ion detection system for supersonic jet resonance-enhanced multiphoton laser ionization mass spectrometry. High sensitivity and selectivity have been achieved by combining a proto-type Daly detector, a newly designed conical ion lens, and a potential switch that can perform the function of a mass selector. This ion detection system enables us to bring the jet nozzle closer to the ionization point. The detection sensitivity has thus been improved totally by more than 100 times compared with that obtained by the parallel-plate electrodes and micro-channel plate. We succeeded in assembling a flangeon-type ion extraction electrode consisting of a conical ion lens and a potential switch.     

A four-wavelength channel absorbance detector with a light emitting diode-fiber optics assembly for simplifying the flow-injection analysis system.

A four-channel absorbance detector was developed for simplifying the flow-injection analysis (FIA). This detector used four light-emitting-diodes (LEDs) as light sources; their wavelengths were 470, 495, 590 and 635 nm, respectively. Their amplitudes were modulated electronically with different frequencies. The light emissions from them were merged by plastic-core fiber optics, and were detected by a photo-diode (PD). The mixed signal was then sent to and discriminated by a four-channel lock-in amplifier corresponding to each modulation frequency. Neither a monochromator nor an optical filter was used. This detector was conveniently applied to the determination of iron in river water by FIA using 1,10-phenanthroline. Though a noisy peristaltic pump was used to propel the solutions, practical precision and accuracy were obtained by means of on-line dual-wavelength measurements and off-line moving average calculations.     

Numerical solution of integral equations in Chebyshev series

In this paper we discuss the Chebyshev series method with Newton iterations for the numerical solution of nonlinear integral equations. An existence theorem for nonlinear integral equations is given using a functional analytic approach. A method to compute and error bound to an approximate solution is discussed on the basis of the theorem.     

The tricyclopropylcyclopropenium ion

A novel non-benzenoid aromatic cation, tricyclopropylcyclopropenium ion, was synthesized by smooth addition of photochemically generated cyclopropylchlorocarbene to dicyclopropylacetylene, and was shown to have remarkable stability.     

Sorption and transport of carbon dioxide in a polyimide from 3,3′4,4′-biphenyltetracarboxylic dianhydride and 4,4′-diaminodiphenyl sulfone

CO₂ sorption and transport were investigated for the polyimide prepared from 3,3′,4,4′-biphenyltetracarboxylic dianhydride (BPDA) and 4,4′-diaminodiphenyl sulfone (DDS). The morphology of films did not change on annealing above the glass transition temperature and remained amorphous unlike the polyimide prepared from BPDA and 4,4′-oxydianilline (ODA). This seems to be due to the strong hindrance to rotation of the sulfonyl linkage. Sorption and transport data were analyzed according to the dual-mode model. Solubility, diffusion, and permeability coefficients at 20 atm and 80°C for BPDA-DDS polyimide were substantially equal between as-cast and annealed films and were 1.7, 2.2, and 3.7 times greater, respectively, than for the as-cast films of the BPDA-ODA polyimide. The higher solubility was due to larger values of the Henry's law solubility constant k_D, Langmuir capacity constant C, and the Langmuir affinity constant b. The sorption and transport properties were compared with those for amorphous glassy aromatic polymers including other polyimides. The relation of k, C, b, and the diffusion coefficients in the Henry's law population and the Langmuir population (D_D and D_H) with other properties of the polymers were discussed. Values D_D and D_H for BPDA-DDS polyimide were much larger than expected from the estimated free-volume fraction.