Highly enantioselective catalytic carbon dioxide incorporation reaction: nickel-catalyzed asymmetric carboxylative cyclization of bis-1,3-dienes

A method for nickel-catalyzed asymmetric carbon dioxide (CO2) incorporation via carbon-carbon bond formation was developed. In the presence of a catalytic amount of Ni(acac)2 and MeO-MOP, various bis-1,3-dienes reacted with CO2 (1 atm) and a diorganozinc reagent (Me2Zn or Ph2Zn) to afford cyclic carboxylic acids in good yields (71-100%) and with high enantioselectivities (90-96% ee).     

Observation of vacuum-ultraviolet Ar2* radiation gain at 126 nm produced by an ultrashort high-intensity laser pulse propagating in a hollow fiber

We observed a small-signal gain of Ar2* emission at 126 nm by use of a hollow fiber to guide the high-intensity laser propagation in high-pressure Ar. The small-signal gain coefficient was measured to be 0.05 cm(-1) at 126 nm. Kinetic analysis revealed that the electrons produced by the high-intensity laser through an optical-field-induced ionization process initiated the Ar2* production processes. The increase in the emission intensity was measured to be exp(2.5), with an increase in the fiber length.     

Efficient synthesis of optically active α-substituted glutamate analogs possessing α-hydroxymethyl and α-alkoxymethyl groups

Highly enantioselective synthesis of (2R)-α-(hydroxymethyl)glutamate (1), a selective agonist of mGluR2 and 3, was achieved in short steps using an asymmetric version of the Strecker synthesis. This was converted into its α-methoxymethyl- and α-benzyloxymethyl derivatives 2 and 3, possible ligands as tools to investigate glutamate receptors, via protection of the sterically hindered amino group by means of phase transfer catalyst.     

Synthesis and evaluation of 6-nitro-7-(1-piperazino)quinazolines: dual-acting compounds with inhibitory activities toward both tumor necrosis factor-alpha (TNF-alpha) production and T cell proliferation

We investigated the chemical modifications of the nitroquinazoline derivative (1) through the replacement of the NH group at the C(4)-position with several N-alkyl groups to increase the lipophilicity at the C(4)-position. Among them, we found that the N-methyl analogue (5a) showed a 2-fold loss in the inhibitory activity toward tumor necrosis factor-alpha (TNF-alpha) production in vitro as compared with the NH analogue (1); however, 5a exhibited an oral inhibitory activity on TNF-alpha production with an ED50 value of 26 mg/kg, whereas 1 did not. Moreover, the oral bioavailability of 5a was higher than that of 1 (1, F=1%; 5a, F=21%), and the calculated ClogP value for 5a was higher than that for 1. These results suggest that the improved lipophilicity of 5a compared with that of 1 reflects its greater inhibitory activity on TNF-alpha production in vivo as well as oral bioavailability.     

Formation,structure, and structural properties of a new filamentary tubular form: hollow conical-helix of graphitic boron nitride

A novel tubular form of graphitic boron nitride (BN) displaying a hollow conical-helix was discovered. It was generated via wrapping a single beltlike filament according to the geometry of an Archimedes spiral. Cone apex angles of helical-conical nanotubes (HCNTs) were found to exhibit specific values, each of which refers to a certain coincidence site lattice. A unique structural property of HCNTs was observed, displaying the transformation of apex angles during the annealing process. The observed apex angles were reduced with decreasing annealing temperature, which is in accordance with an estimated HCNT strain energy decrease for a given tubular radius. It is suggested that the curvature and apex angle of a HCNT are determined by a sole dynamic element, that is, enthalpy (DeltaH), whereas the HCNT disclination configuration changes through helical sliding of the filament.     

Solubilization of C60 by micellization with a thermoresponsive block copolymer in water: Characterization,singlet oxygen generation,and DNA photocleavage

Water‐soluble diblock copolymer, poly(N‐isopropylacrylamide)‐block‐poly(N‐vinyl‐2‐pyrroridone) (PNIPAM_m‐b‐PNVP_n), was found to associate with fullerene (C₆₀), and thus C₆₀ can be solubilized in water. The 63C₆₀/PNIPAM_m‐b‐PNVP_n micelle formed a core‐shell micelle‐like aggregate comprising a C₆₀/PNVP hydrophobic core and a thermoresponsive PNIPAM shell. The C₆₀‐containing polymer micelle formation and its thermoresponsive behavior were characterized using light scattering and ¹H NMR techniques. The hydrodynamic radius (R_h) of the C₆₀‐bound polymer micelle increased with increasing temperature, which was ascribed to the hydrophobic association between dehydrated PNIPAM shells above lower critical solution temperature (LCST). ¹H NMR data suggest that the motion of the PNIPAM block is restricted above LCST due to the dehydration of the PNIPAM shell in water. The generation of singlet oxygen by photosensitization by the C₆₀‐bound polymer micelle was confirmed from photooxidation of 9,10‐anthracenedipropionic acid. Furthermore, DNA was found to be cleaved by visible light irradiation in the presence of the C₆₀‐bound polymer micelle. Therefore, there may be a hope for a pharmaceutical application of the C₆₀‐bound polymer micelle to cancer photodynamic therapy. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011.     

Synthesis and isomerization of conjugated oligomers containing azoimidazole unit

The Suzuki (for O1 – O3 ) and Stille (for O4 ) coupling polymerization of 2‐(phenylazo)imidazole bearing the benzyl protecting group at the 1‐position gave conjugated oligomers. The transformation from the neutral imidazole in the conjugated oligomer O2 , consisted of the alternating 2,5‐didecyl‐1,4‐phenylene unit, to the cationic imidazolium salt O2S was performed. Depending on the chemical structure of coupling partners, the absorption maximum of conjugated oligomers showed red shift or blue shift from that of the model compound M with the benzene ring at the 4,5‐positions. The absorption maximum wavelength of the cationic conjugated oligomer O2S showed a blue shift from that of the neutral conjugated oligomer O2 . The trans‐to‐cis photoisomerization of the azoimidazole unit in conjugated oligomers was observed by irradiating the light at 436 nm, and the conversion degree to the cis structure had a rough correlation with the maximum absorption wavelength of materials. The trans‐to‐cis photoisomerization in the film state was sluggish. On the other hand, the cis‐to‐trans thermal isomerization of the azoimidazole unit was confirmed and the absorbance returned to the initial state before the photoisomerization. The trans‐to‐cis photoisomerization of the cationic conjugated oligomer O2S required large energy, and the prolonged light irradiation might decompose the azoimidazole unit. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011.     

Wave propagation in saturated ground using the volume fractions

The purpose of this paper is to study the dynamic behavior of soft ground including a porous layer by considering the porosity change. In order to take the porosity change into account, the concept of the volume fraction, which has been proposed in continuum mechanics, is introduced. The constitutive equations presented by Bowen are applied to the analysis of the porous media. According to Bowen's theory, the porosity is considered as a variable called the volume fraction and has its own constitutive equation. The constitutive equation of the volume fraction has thermoelastic equation coefficients and is determined by the strains of the solid and the fluid. This means that the compressibilities of the solid and the fluid are considered. When the special condition is assumed, Bowen's theory can contain Biots's theory, which has been applied in earthquake engineering. The wave propagation in the ground including a porous layer, modeled by Bowen's theory, is studied and compared with that of Biot's theory. One-dimensional attenuation and surface amplitude are calculated. The effect of the volume fraction is discussed with respect to the compressibilities of the solid and the fluid.     

Influences of Si pillar geometry on SiN-stressor induced local strain

The local strains in Si pillars induced by SiN stressors were quantitatively investigated as a function of geometry by micro-Raman scattering spectroscopy. Raman shifts of a cantilever microstructure were twice as large as those of a bridge microstructure. This difference was due to the different dimensions of the strains, i.e., biaxial strains in the cantilever type and uniaxial strains in bridge type. The thermal stability of the SiN stressor was also investigated. The results showed induced strains were stable after post-annealing at high temperature (∼1000 °C).