Croissamide,a proline-rich cyclic peptide with an N-prenylated tryptophan from a marine cyanobacterium Symploca sp.

Croissamide, a proline-rich cyclic peptide that contains an N-prenylated tryptophan, was isolated from a marine cyanobacterium Symploca sp. Its gross structure was determined by spectroscopic analyses, and the absolute configuration was established based on chiral HPLC analyses of acid hydrolysates.     

Chemoselectivity Control in the Asymmetric Hydrogenation of γ‐ and δ‐Keto Esters into Hydroxy Esters or Diols

The asymmetric hydrogenation of aromatic γ‐ and δ‐keto esters into optically active hydroxy esters or diols under the catalysis of a novel DIPSkewphos/3‐AMIQ–Ru^II complex was studied. Under the optimized conditions (8 atm H₂ , Ru complex/t‐C₄H₉OK=1:3.5, 25 °C) the γ‐ and δ‐hydroxy esters (including γ‐lactones) were obtained quantitatively with 97–99 % ee. When the reaction was conducted under somewhat harsh conditions (20 atm H₂ , [t‐C₄H₉OK]=50 mm , 40 °C), the 1,4‐ and 1,5‐diols were obtained predominantly with 95–99 % ee. The reactivity of the ester group was notably dependent on the length of the carbon spacer between the two carbonyl moieties of the substrate. The reaction of β‐ and ?‐keto esters selectively afforded the hydroxy esters regardless of the reaction conditions. This catalyst system was applied to the enantioselective and regioselective (for one of the two ester groups) hydrogenation of a γ‐?‐diketo diester into a trihydroxy ester.     

Benzonorcorrole NiII Complexes: Enhancement of Paratropic Ring Current and Singlet Diradical Character by Benzo‐Fusion

Fused benzene rings to antiaromatic compounds generally improve their stability but attenuate their antiaromaticity. The opposite case is now reported. Ni^II benzonorcorroles were synthesized and the effect of benzo‐fusion on the antiaromaticity was elucidated. The benzo‐fusion resulted in significant decrease of the HOMO–LUMO gaps and enhancement of the paratropic ring current effect. Furthermore, the introduction of the benzo groups induced singlet diradical character in the antiaromatic porphyrinoid.     

Synthesis and conformational analysis of N-aryl-N-(3-thienyl)acetamides

The cis-trans conformational equilibrium of amides is of interest because it can be used to control functional activity. Here, we designed and synthesized a series of N-(3-thienyl)amides in order to study the factors affecting their conformational equilibrium. NMR studies showed that the major conformer of N-methyl-N-(3-thienyl)amide in solution is the E-form (cis form), as is the case for N-methylacetamide. For N-aryl-N-(3-thienyl)amides bearing an N-phenyl moiety, the major conformers differ depending on not only the relative π-electron density of the N-aryl moiety, but also its size. X-ray analysis showed that their solid-state conformational preferences were similar to those in solution.     

Levitation of metallic melt by using the simultaneous imposition of the alternating and the static magnetic fields

This study developed a new levitation method, which used the simultaneous imposition of static and alternating magnetic fields. Dynamic behavior was measured for pure Cu and pure Ni melts levitated by the proposed method. The oscillation due to surface tension and convection in levitated Cu melts were hardly observed at static magnetic fields exceeding 1 T. Only the rotation of this axis parallel to the static magnetic field was observed under high static magnetic fields. The proposed method demonstrated that metallic melt could be statically levitated like a solid sphere. It was also found that stable levitation of paramagnetic Ni melt was rather difficult at static magnetic fields exceeding 5 T, because of the magnetization force.     

Density functional study of lanthanide complexes (η-C5H5)2LnX·OC4H8 (Ln=La-Lu; X=F, Cl, Br and I)

Density functional calculations were performed on a series of mixed-ligand organolanthanide complexes, (η⁵-C₅H₅)₂LnX·OC₄H₈ (η⁵-C₅H₅=Cp; Ln=La-Lu; X=F, Cl, Br and I; OC₄H₈=THF). The calculated geometrical parameters are in reasonable agreement with the experimental data. The distances between Ln and ligands follow linearity along the ionic radius of lanthanide metal, as the same as that observed in experiment. In the mixed-ligand complexes, Ln-Cp and Ln-THF bonds are more covalent compared to Ln-X. The lanthanide contraction of various bond and the metal-ligand interaction energy followed the order of Ln-X>Ln-Cp>Ln-OC₄H₈. The orbital population and dipole moment were also discussed.     

Determination of Drugs in Blood Samples by High Performance Liquid Chromatography Using On-Line Sample Pretreatment Technique

The flow diagram of this on-line sample pretreatment system is shown in Fig. I.     

Coal fly ash decomposes diethyl phthalate

Decomposition of diethyl phthalate (DEP) exposed to a coal fly ash has been investigated in water by measuring UV-VIS spectra and GC-MS. Alkaline constituents eluted from the fly ash in the liquid phase gradually hydrolyzed DEP to produce monoethyl phthalate and/or phthalic acid. These products were adsorbed on the fly ash and decarboxylated into ethyl benzoate and benzoic acid, respectively, followed by decomposition into benzenes and/or the other compounds of lower molecular weight. The fly ash acts as not only an adsorbent but also a decomposer.     

Influence of conformational changes of co(III)–poly-N-vinyl-2-methylimidazole complexes on electron-transfer reactions of the complexes

In order to study the effect of conformational changes in electron-transfer reactions of Co(III)–polymer complexes, cis-[Co(III)(en)₂LCl]Cl₂, where the ligand L is PVI(poly-N-vinyl-2-methylimidazole) or NEI (N-ethylimidazole), was prepared. Electrontransfer reactions with ferrous sulfate or FeEDTA^2? were examined mainly with respect to the effects of the degree of coordination, ionic strength, composition of reaction solvent, in relation to the conformational changes. In the reduction by FeEDTA^2?, an increase in the degree of coordination of Co(III)–PVI brought about an extreme increase in its reactivity, while it was almost unity in the reduction by ferrous sulfate. With an increase in the ionic strength, the reactivity decreased due to the electrostatic shielding in the reduction by FeEDTA^2?. It was noticed that the reaction of Co(III)–PVI was much more enthalpically disadvantageous due to the shrinkage of the polymer chain than that of Co(III)–NEI, when neutral salts were added. In an aqueous alcoholic solvent, an increase in the alcohol concentration accelerated the reaction with FeEDTA^2?, and especially in the reaction of Co(III)-PVI, the maximum and minimum points of the reactivity were observed. On increasing the reaction temperature, the maximum and minimum points shifted to lower alcohol concentration. These phenomena are discussed in regard to the conformational changes of Co(III)–PVI.