Mechanism of gold adsorption by persimmon tannin gel.

Gold adsorption by persimmon tannin (PT) gel from a solution containing hydrogen tetrachloroaurate(III) was examined. A flow-rate examination in a column system indicated the reduction of Au(III) ion to Au(0). XRD patterns clarified the existence of Au(0) on the gel which adsorbed gold. The gel could also adsorb colloidal Au(0) prepared independently. A model consisting of ligand exchange, Au(III) reduction to Au(0), and resulting Au(0) adsorption by PT gel was presented for the gold adsorption mechanism.     

Chromium- and tungsten-triggered valence isomerism of cis-1-acyl-2-ethynylcyclopropanes via [3,3]sigmatropy of (2-acylcyclopropyl)vinylidene-metal intermediates.

The reaction of cis vicinal acetylethynylcyclopropanes 1 with a catalytic amount of M(CO)5(THF) (M = Cr or W) in the presence of Et3N at room temperature gave ortho-substituted phenols 7 in good yields as valence isomerized products. In the absence of Et3N the reactions did not work at all. The reaction of a cyclopropane having an ester or an amide instead of an acetyl moiety with M(CO)5(THF) did not take place, whereas an ethynylvinylcyclopropane gave a mixture of 1- and 2-substituted 1,3,5-cycloheptatrienes. These valence isomerization reactions are assumed to proceed via the formation of vinylidene-metal intermediates 2 from terminal alkynyl moieties followed by [3,3]sigmatropy of 2 to give seven-membered carbene complexes 3.     

Highly Selective Asymmetric Intramolecular Selenocyclisation

Asymmetric intramolecular selenocyclisation of alkenoic acids, alkenols and alkenyl urethanes using chiral ferrocenylselenenyl cations proceeds smoothly to give the corresponding lactones, cyclic ethers and N-heterocyclic compounds, respectively, in moderate yields with very high diastereoselectivities.     

Chiral Bis(oxazoline)-copper Catalyzed Enantioselective Imidation of Sulfides

Prochiral sulfides reacted with Phl=NTs in the presence of a catalytic amount of Cu(I) salt together with a chiral 4,4′-disubstituted bis(oxazoline) ligand to afford the corresponding chiral sulfimides.     

A direct identification method for current dipoles from electromagnetic fields

We discuss the identification problem for current dipoles in a spherically symmetric conductor. This mathematical model is used for a biomedical inverse problem such as the source current identification for the human brain activity. We have already proposed a direct identification method for this inverse source problem using observations of the magnetic fields outside of the conductor. One of the difficulties of current dipole identification using the magnetic fields is caused by the fact that magnetic field does not include any information about the radial component of dipole moments. In this paper, we consider an improvement of the direct method to identify both radial and tangential components of current dipole moments by combining electric and magnetic observation data. Furthermore, our approach is effective in the case where the number of dipoles is unknown.     

Near-infrared BODIPY dyes modulated with spirofluorene moieties

New structurally constrained BODIPY dyes having electron-donating substituents were synthesized. As the key compounds for the construction of the BODIPY dyes, 1′H-spiro-[fluorene-9,4′-indeno[1,2-b]pyrrole] (sp-FIP) derivatives with electron-donating groups, such as OMe and NMe₂ at its 6′-position, were prepared using palladium-catalyzed intramolecular direct C-H arylation of a pyrrole moiety. The resulting BODIPY dyes showed bathochromic shift in absorption and fluorescence spectra in comparison to the unsubstituted analogs. Furthermore, pH-dependent reversible spectrum changes of the BODIPY dye were observed with the addition of trifluoroacetic acid (TFA) and subsequent addition of i-Pr₂NEt.     

Virtual screening for ligands of the insect molting hormone receptor

Insect growth is regulated by the orchestrated event of ecdysteroids and their receptor proteins. Agonists/antagonists of ecdysteroid receptor are predicted to disrupt normal growth, providing good candidates of new insecticides. A database of over 2 million compounds was subjected to a shape-based virtual screening cascade to identify novel nonsteroidal hits similar to the known EcR ligand ponasterone A. Testing revealed micromolar hits against two strains of insect cells. Docking experiments against EcR were used to support the predicted binding mode of these ligands based on their overlay to ponasterone A.     

Sorption and diffusion behaviours of strontium in sodium-type bentonite bed

Sorption and diffusion of Sr were examined using a typical Japanese bentonite. The experimental results showed that Sr sorption on the bentonite had linear relationship between the equilibrium Sr concentration and Sr sorption amount, i.e., Henry’s type of sorption, in wide initial Sr concentration from 1.1×10⁻⁹ to 1.1×10⁻⁴ mol L⁻¹ at pH 10. The Sr sorption also indicated pH dependence in pH range between 2 and 12. Sorption modelling calculation indicated that cation-exchange reactions contributed to Sr sorption in the pH range studied and a surface complexation reaction was predominant above pH 8. Diffusion of Sr in loosely compacted bentonite bed was described by pore and surface diffusion and surface complexation of Sr. Chemical-transport calculations reproduce the diffusion data at pH 5 using the cation-exchange parameters obtained in the analysis of the batch sorption experiment.