Revised structure of kasarin, an antibacterial pyrazinone compound from the marine microorganism Hyphomycetes sp.

Kasarin is an antibacterial marine alkaloid that was isolated from the microorganism Hyphomycetes sp. Its structure was previously reported to be an azetinone compound 1. However, detailed spectroscopic analysis of the natural compound and its related synthetic analogs revealed that the structure of kasarin should be revised to be a novel 5-malonyloxy-1-methoxy-pyrazin-2(1H)-one derivative 2.     

Fabrication of ultrathin color filters for three primary colors using guided-mode resonance in silicon subwavelength gratings

We fabricate reflection color filters for three primary colors using silicon two-dimensional triangular-lattice subwavelength gratings on the same quartz substrate. The grating periods are 480, 390, and 300 nm for red, green, and blue filters, respectively. All of the color filters have the same thickness of 100 nm, which enables the simple fabrication of a color filter array. Maximum reflectances of 75 and 46% are obtained at wavelengths of 647.1 and 522.1 nm for the red and green filters, respectively. The blue filter has a double-peaked spectrum with a reflectance of 30% at the peak wavelengths of 450.0 and 502.7 nm. By rigorous coupled-wave analysis, the dimensions of each color filter are designed, and the calculated theoretical reflectance is compared with the measured one.     

Infrared diode laser spectroscopy of N212C18O2

The high-resolution infrared spectrum of N₂¹²C¹⁸O₂ has been observed in the ν₃ band (2314 cm^?1) region of ¹²C¹⁸O₂ with diode laser absorption spectroscopy of pulsed molecular beam. The geometry of N₂¹²C¹⁸O₂ is similar to N₂¹²C¹⁶O₂, a T-shaped structure with the nitrogen molecular axis pointing towards the carbon atom. The geometrical parameters of the T-shaped ground-state structure are determined as R_NcmC = 3.7285(5) Å and (90?Θ_NcmCO) = 6.85(3)°. The vibrational band origin of N₂¹²C¹⁸O₂ corresponding to the ν₃ mode of ¹²C¹⁸O₂ shows a shift of 0.52499(10) cm^?1 with respect to that of ¹²C¹⁸O₂.     

Enantioselective synthesis induced by chiral crystal composed of DL-serine in conjunction with asymmetric autocatalysis

Asymmetric autocatalysis initiated by chiral crystals containing racemic DL-serine was achieved. P- and M-crystals of DL-serine acted as the source of chirality of asymmetric autocatalysis to afford highly enantioenriched (>99.5% ee) (S)- and (R)-pyrimidylalkanols after the amplification of ee. This is the first example of the usage of the crystal, which contains the same number of D- and L-enantiomers as an origin of chirality in enantioselective synthesis.     

On-chip magnetically actuated robot with ultrasonic vibration for single cell manipulations

This paper presents an innovative driving method for an on-chip robot actuated by permanent magnets in a microfluidic chip. A piezoelectric ceramic is applied to induce ultrasonic vibration to the microfluidic chip and the high-frequency vibration reduces the effective friction on the MMT significantly. As a result, we achieved 1.1 micrometre positioning accuracy of the microrobot, which is 100 times higher accuracy than without vibration. The response speed is also improved and the microrobot can be actuated with a speed of 5.5 mm s(-1) in 3 degrees of freedom. The novelty of the ultrasonic vibration appears in the output force as well. Contrary to the reduction of friction on the microrobot, the output force increased twice as much by the ultrasonic vibration. Using this high accuracy, high speed, and high power microrobot, swine oocyte manipulations are presented in a microfluidic chip.     

Photoexcited chemical wave in the ruthenium-catalyzed Belousov-Zhabotinsky reaction

The excitation of the photosensitive Belousov-Zhabotinsky (BZ) reaction induced by light stimulation was systematically investigated. A stepwise increase in the light intensity induced the excitation, whereas a stepwise decrease did not induce the excitation. The threshold values for the excitation were found to be a function of the initial and final light intensities, time variation in light intensity, and the concentration of NaBrO(3). The experimental results were qualitatively reproduced by a theoretical calculation based on a three-variable Oregonator model modified for the photosensitive BZ reaction. These results suggest that although the steady light irradiation is known to inhibit oscillation and chemical waves in the BZ system under almost all conditions, the stepwise increase in the light irradiation leads to the rapid production of an activator, resulting in the photoexcitation.     

Solvent dependence of absorption intensities and wavenumbers of the fundamental and first overtone of NH stretching vibration of pyrrole studied by near-infrared/infrared spectroscopy and DFT calculations

Near-infrared (NIR) and IR spectra were measured for pyrrole in CCl(4), CHCl(3), and CH(2)Cl(2) to study solvent dependence of absorption intensities and wavenumbers of the fundamental and first overtone of NH stretching vibration. It was found that the wavenumbers of the NH fundamental and its first overtone decrease in the order of CCl(4), CHCl(3), and CH(2)Cl(2), which is the increasing order for of the dielectric constant of the solvents. Their absorption intensities increase in the same order, and the intensity increase is more significant for the fundamental than the overtone. These results for the solvent dependence of the wavenumbers and absorption intensities of NH stretching bands of pyrrole are quite different from those due to the formation of hydrogen bonds. Quantum chemical calculations of the wavenumbers and absorption intensities of NH stretching bands by using the 1D Schr?dinger equation based on the self-consistent reaction field (SCRF)/isodensity surface polarized continuum model (IPCM) suggest that the decreases in the wavenumbers of both the fundamental and the overtone of the NH stretching mode with the increase in the dielectric constant of the solvents arise from the anharmonicity of vibrational potential and their intensity increases come from the gradual increase in the slope of the dipole moment function.     

Second harmonic generation in ferroelectric liquid crystals and their mixtures

Abstract

The second harmonic generation (SHG) in the ferroelectric liquid crystal (FLC) state has been studied as functions of electric field strength, rotating angle, temperature and molecular structure. It has been confirmed that a sharp angularly phase-matching curve of the SHG controlled by an electric field is observed even in the liquid crystal. The temperature dependences of the phase-matched SHG and Maker fringe in the ferroelectric phase have also been studied, and temperature dependences of non-linear optical coefficients obtained. The SHG in several kinds of FLC and dye doped FLC have also been measured, and the enhancement of SHG realized by means of doping the FLC with several kinds of dye.     

Magnitude and direction of the spontaneous polarization of ferroelectric liquid crystals with several bond moments

The magnitude and direction of the spontaneous polarization in most ferroelectric liquid crystals have been confirmed to be determined by the location and magnitude of the bond moment around the chiral carbon and the core. In compounds with several bond moments their relative orientation is very important for obtaining a large spontaneous polarization. Compounds with benzene rings in the core substituted with OH also have a large spontaneous polarization, perhaps due to the formation of hydrogen bonds. Reversal of the direction of the spontaneous polarization with temperature has been found for EFPPOPB. This anomalous behaviour has been explained tentatively in terms of a conformation change due to the existence of a flexible -CH₂- unit between the chiral carbon and the dipole moment.     

Mild Deprotection of Methyl,Benzyl, Methoxymethyl,Methylthiomethyl, Methoxyethoxymethyl,and β-(Trimethylsilyl)-ethoxymethyl Esters with AlCl3-N,N-dimethylaniline

Methyl, benzyl, methoxymethyl, methylthiomethyl, methoxyethoxymethyl, and β-(trimethylsilyl)ethoxymethyl esters could be cleaved readily under mild conditions on treatment with AlCl₃-N,N-dimethylaniline in CH₂Cl₂ to give parent carboxylic acids in high yields.