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.     

Synthesis and xanthine oxidase inhibitory activity of 4,6-disubstituted 1-p-chlorophenylpyrazolo[3,4-d]pyrimidines

Several 4,6-disubstituted 1-p-chlorophenylpyrazolo[3,4-d]pyrimidines were prepared from 4,6-dichloro-1-p-chlorophenylpyrazolo[3,4-d]pyrimidine and their xanthine oxidase inhibitory activity were tested in vitro.     

Diastereoselective amidoallylation of glyoxylic acid with chiral tert-butanesulfinamide and allylboronic acid pinacol esters: efficient synthesis of optically active γ,δ-unsaturated α-amino acids

A convenient synthesis of δ,γ-unsaturated amino acids has been developed. After a mixture of (R)-tert-butanesulfinamide and glyoxylic acid with molecular sieves in CH₂Cl₂ was stirred for 42 h at room temperature, allylboronic acid pinacol ester was added to the mixture to give (R)-2-((R)-tert-butanesulfinamido)pent-4-enoic acid with high diastereoselectivity. The corresponding reaction of (Z)-crotylboronic acid pinacol ester produced no product; however, that of (E)-crotylboronic acid pinacol ester produced (2R,3S)-2-((R)-tert-butylsulfinamido)-3-methylpent-4-enoic acid with excellent diastereoselectivity.     

Water-soluble NIR fluorescent probes based on squaraine and their application for protein labeling.

Water-soluble near-infrared (NIR) fluorescent labeling probes, named KSQ-3 and -4, which are based on a squaraine backbone, were synthesized and applied to biological labeling. The presented results demonstrate that the large, planar and hydrophobic squaraine dye becomes fully soluble in aqueous solution by the introduction of several sulfo group terminated alkyl substituents. Especially KSQ-4, which is substituted with four sulfo groups, exhibited perfect water solubility and significant fluorescence emission at the NIR region (817 nm) in the presence of bovine serum albumin (BSA). BSA was covalently labeled with KSQ-4, and the conjugate showed a strong absorption peak at 787 nm, which indicates compatibility with commercially available NIR laser diodes used for exciting the fluorophore. Furthermore, strong fluorescence emission was observed at 812 nm (phi = 0.08).     

Non-enzymatic diastereoselective asymmetric desymmetrization of 2-benzylserinols giving optically active 4-benzyl-4-hydroxymethyl-2-oxazolidinones: asymmetric syntheses of α-(hydroxymethyl)phenylalanine,N-Boc-α-methylphenylalanine,cericlamine and BIRT-377

A reaction of (S)-2-benzyl-2-(α-methylbenzyl)amino-1,3-propanediol (S)-4a and 2-chloroethyl chloroformate, and the subsequent addition of DBU gave (4R,αS)-4-benzyl-4-hydroxymethyl-3-(α-methylbenzyl)-2-oxazolidinone (4R)-5a (92% de) via a diastereoselective asymmetric desymmetrization process. Debenzylation of (4R)-5a using trifluoromethanesulfonic acid and anisole in MeNO₂ gave (R)-4-benzyl-4-hydroxymethyl-2-oxazolidinone (R)-15a, which was converted into (R)-(α-hydroxymethyl)phenylalanine (7) in two steps. N-Boc-α-methylphenylalanine (8), cericlami0ne (9) and BIRT-377 (10) were also synthesized using these asymmetric desymmetrization and debenzylation.     

Effect of Al2O3 addition on the formation of perovskite-type NaNbO3 nanocrystals in silicate-based glasses

The crystallization behavior of 30Na₂O–25Nb₂O₅–(45 ? x) SiO₂–xAlO_1.5 (x = 0, 2.5, and 5) (mol%) glasses was examined and the effect of Al₂O₃ addition on the formation of perovskite-type NaNbO₃ crystals was clarified. It is found from X-ray diffraction analyses and transmission electron microscope observations that NaNbO₃ nanocrystals are formed in all glasses and the size of NaNbO₃ crystals decreases with the substitution of Al₂O₃ for SiO₂. A crystallized (heat-treated at 684 °C for 5 h) glass with x = 5, which contains NaNbO₃ nanocrystals with an average size of 50 nm, shows good optical transparency in the wavelength region of 500–2000 nm and a small hysteresis loop in the polarization–electric field curve. The lines containing NaNbO₃ crystals were patterned on the surface of NiO-doped glass with x = 5 by irradiations (power: 1.3–1.4 W, scanning speed: 10 μm/s) of Yb:YVO₄ fiber laser (wavelength: 1080 nm). The formation mechanism of NaNbO₃ nanocrystals in aluminosilicate glasses was also discussed.     

Ferrocenyl D-π-A conjugated polyenes with 3-dicyanomethylidene-1-indanone and 1,3-bis(dicyanomethylidene)indane acceptor groups: Synthesis, linear and second-order nonlinear optical properties and electrochemistry

Second-order nonlinear optical chromophores incorporating the ferrocenyl group as an electron donor and 3-dicyanomethylidene-1-indanone and 1,3-bis(dicyanomethylidene)indane acceptor groups, connected by a conjugated polyenic bridge of varied length (2[n] and 3[n], respectively) have been synthesized. The electronic absorption spectra of these compounds display in the visible region bands attributable to π-π* and metal-to ligand charge transfer (MLCT) transitions. The energies of these transitions are close to those reported earlier for ferrocenyl D-π-A chromophores with the strongest acceptor groups, e.g., with the 3-dicyanomethylidene-2,3-dihydrobenzothiophene-1,1-dioxide group (1[n]) [V. Alain, M. Blanchard-Desce, C.-T. Chen, S.R. Marder, A. Fort, M. Barzoukas, Synt. Met. 81 (1996) 133]. The solid-state structure of 2[3], determined by X-ray diffraction shows a significant reduction of the bond length alternation (BLA), 0.05 Å, suggesting high first hyperpolarizability. However, a centrosymmetrical packing of molecules of this compound in the crystal excludes its second harmonic generation ability. The μβ values of 2[n] and 3[n], determined by the EFISH technique at 1907 nm are high and increase with the increasing length of the conjugated π-bridge. The highest value of μβ (8720 × 10⁻⁴⁸ esu) was determined for 3[4], which is close to that reported for 1[4] (11 200 × 10⁻⁴⁸ esu), the highest value found for a ferrocenyl D-π-A chromophore until now.     

The Earth effects on the supernova neutrino spectra

The Earth effects on the energy spectra of supernova neutrinos are studied. We analyze numerically the time-integrated energy spectra of neutrino in a mantle–core–mantle step function model of the Earth's matter density profile. We consider a realistic frame-work in which there are three active neutrinos whose mass squared differences and mixings are constrained by the present understanding of solar and atmospheric neutrinos. We find that the energy spectra change for some allowed mixing parameters. Especially, the expected number of events at SNO shows characteristic behavior with respect to energy, i.e., a great dip and peak. We show that observations of the Earth effect allow us to identify the solar neutrino solution and to probe the mixing angle θ₂.     

Numerical study on three-dimensional C-J detonation waves: detailed propagating mechanism and existence of OH radical

An unsteady three-dimensional simulation is performed for a hydrogen/air C–J detonation in a rectangular tube, where a detailed chemical reaction model is used to reveal the C–J detonation structure. In this simulation, detailed propagating detonation structures for a diagonal mode are described in three-dimensions. The detonation front structures, the line of triple points, and the strong explosions at the corners of the rectangular tube are revealed by using a three-dimensional numerical visualization. From the spatial isosurface profiles of H₂ mass fraction, it is confirmed that the triple point lines have a role of “shutter” to generate unburned gas pockets and become of a ring shape behind the detonation front due to its explosion. The explosion process and its influence on an induction delay are observed by visualizing the spatial isosurface profiles of OH mass fraction. Moreover, a high “peninsula-shaped” OH mass fraction area, which has been experimentally reported, is reproduced on the side wall of the rectangular tube.