Optimization of Fe/SiO<Subscript>2</Subscript> based metal oxides as selective oxidation catalyst of propane with combinatorial approach

A combinatorial optimization with genetic algorism was performed on the five generations of 0.05 atm% Fe/SiO₂ added multi-metal oxides to be used as catalytic materials for the selective oxidation of propane to give aldehydes at 623-773 K. The loaded multi-metal oxides consist of some elements selected from seven elements with various atomic charges or redox properties. For the best materials, selectivity toward aldehydes from 35% at 1st generation to 45% at 4th generation were achieved at 5% propane conversion. Further rational optimization of the best performance catalyst also improves the selectivity up to 49.5%.     

Solid phase extraction of lead by Chelest Fiber Iry (aminopolycarboxylic acid-type cellulose)

Aminopolycarboxylic acid-type cellulose (Chelest Fiber Iry) has been studied for its sorption efficiencies with respect to lead from acidic solution. The influence pH and other properties related to sorption kinetic, isotherm, maximum capacity, stability and the mechanism of the sorption were discussed.Lead was quantitatively retained on the proposed adsorbent in the pH range of 2.5-5.5 (studied pH range 1.5-5.5). The maximum sorption capacity was found to be 0.86±0.06 mmol/g adsorbent. The decline in the efficiency of the adsorbent was not observed for repeated adsorption-desorption cycles. It was found that the preconcentration factor of 200 can be achieved. The limit of determination was found to be about 1 μg Pb/2 l. The method was applied to the determination of lead in water samples.     

Aurisides A and B, Cytotoxic Macrolide Glycosides from the Japanese Sea Hare Dolabella auricularia

Bioassay-guided fractionation of the cytotoxic constituents of the Japanese sea hare Dolabella auricularia led to the isolation of two novel cytotoxic compounds, aurisides A (1) and B (2). Their gross structures were established by spectroscopic analysis including the 2D NMR technique. On the basis of the NOESY spectral analysis and the degradation experiments, their absolute stereostructures were determined to be 14-membered macrolide glycosides that contain a bromine-substituted conjugated diene structure, a cyclic hemiacetal moiety, and a 2,4-di-O-methyl-L-rhamnopyranoside part. Aurisides A (1) and B (2) show cytotoxicity against HeLa S(3) cells with IC(50) values of 0.17 and 1.2 &mgr;g/mL, respectively.     

Preparation of sterically protected 3,4-bis[(2,4,6-tri-tert-butylphenyl)phosphinidene]cyclobutene derivatives having ring-fused structures

[reaction: see text] Sterically protected 3,4-diphosphinidenecyclobutenes, having ring-fused structures, were prepared. Structures of 8,9-bis[(2,4,6-tri-tert-butylphenyl)phosphinidene]bicyclo[5.2.0]non-1(7)-ene and its dichloropalladium(II) complex were analyzed by X-ray crystallography. A geometrical change induced by the complex formation was exhibited by X-ray crystallographic analysis. The geometrical change in solution was also suggested by (1)H NMR spectroscopy in CDCl(3).     

Synthesis of optically active β-alkyl aspartate via [3,3] sigmatropic rearrangement of α-acyloxytrialkylsilane

The synthesis of four types of optically active β-carbon-substituted analogs of threo-β-hydroxy aspartate (THA) and a β-carbon-substituted analog of threo-β-benzyloxy aspartate (TBOA), which are potent blockers of excitatory amino acid transporters in the mammalian central nervous system, via the chirality-transferring ester-enolate Claisen rearrangement of α-acyloxytrialkylsilane is described.     

Neutron activation analysis of6Li isotopic abundance using a low background liquid scintillation counter

A neutron activation method based on the measurement of tritium radioactivity produced by⁶Li (n,)³H reaction was applied to determine the isotopic abundance of⁶Li in aqueous solution with known lithium concentration. Tritium radioactivity was measured with a low background liquid scintillation counter over a period of 2000 min. The present method demonstrated a good linearity between the isotopic abundance of⁶Li and tritium radioactivity produced per unit amount of lithium in a wide range of lithium concentration. A comparison of the present data with those from mass spectrometry showed agreement, though our method was 10 times less sensitive, than mass spectrometry. The present new approach should thus prove quite useful for determining the isotopic abundance of⁶Li.     

Successive Jahn-Teller transitions and the canted pseudospin state in K2PbCu(NO2)6

The successive phase transitions in K₂PbCu(NO₂)₆ has been studied by precise X-ray measurements. The unit cell in Phase III is doubled along each of the cubic principal axes. The experimental results can be interpreted as sequencial cooperative Jahn-Teller transitions where the higher transition is due to the coupling with the uniform distortion, while the lower transition is caused by the coupling with the uniform distortion, while the lower transition is caused by the coupling with the zone boundary phonon mode with $\text{k}{}_0\text{= (}\text{1}\text{2}\text{,}\text{1}\text{2}\text{,}\text{1}\text{2}$. The electronic state in Phase III is characterized as the “canted pseudospin” state.