Effects of catechins on superoxide and hydroxyl radical

Superoxide (O2-.) was reduced by the addition of superoxide dismutase (SOD: O2-. scavenger) and catechins. In competitive reactions utilizing different concentrations of spin-trap agent, the IC50 values of each sample were changed. With regard to the Cu2+/H2O2 and Fe2+/H2O2 reaction systems, metal chelater, hydroxyl radical (.OH) scavenger and catechins eliminated the levels of .OH. For the Cu2+/H2O2 reaction systems, the IC50 for .OH scavenger changed, but that for metal chelater and catechins did not. However, for the Fe2+/H2O2 reaction system, the IC50 for .OH scavenger and catechins changed, whereas that for metal chelater did not. The ESR signal for free Cu2+ was changed by addition of metal chelater and catechins. In the spectrophotometer experiments, it was confirmed that the CuCl2 spectrum was changed by addition of metal chelater and catechins but not by .OH scavenger. Conversely, the FeSO4 spectrum was not changed by addition of .OH scavenger or catechins, but was altered by metal chelater. Lipid peroxidation was inhibited by catechins in a concentration-dependent manner. Therefore, it was suggested that the catechins did not scavenge directly the generated .OH from the Cu2+/H2O2 reaction system, but inhibited the generation of .OH by acting on the Cu2+/H2O2 reaction system. On the other hand, with respect to the .OH generated from the Fe2+/H2O2 reaction system, it was suggested that the catechins had a direct scavenging capacity of the .OH, but had little chelating activity of iron. It was confirmed that catechins have the ability to scavenge for O2-. as well as .OH and to inhibit the generation of .OH by chelation with metal ions.     

The preparation and the nucleophilic reaction of 3,3-di(1-azolyl)-2-alken-1-ones,precursor of acetylketene derivatives

2-Alken-1-ones, 3,3-di-(1-azolyl)-2-alken-1-ones and related compounds were prepared by two methods. These compounds were found to be the useful precursors for acylketene derivatives such as ketene dithioacetals and diaminals by treatment with various nucleophiles.     

Ozonolysis of five-membered heterocycles

The relative reaction rate of five-membered heterocycles with ozone was evaluated. These relative rates were correlated to the highest bond order value in the corresponding ring, calculated by the convenient HMO method. From this correlation, the reactivity of heterocycles with ozone was able to be predicted. Also it was concluded that the predominant product in the ozonolysis of five-membered heterocycles containing an oxygen atom was the corresponding carboxylic acid, while nitrogen heterocycles gave the corresponding amide.     

Regioselective synthesis of 3-hydroxyisoxazoles and 5-isoxazolones from β-amino α,β-unsaturated esters

The regioselective synthesis of 3-hydroxyisoxazoles and 5-isoxazolones is accomplished by the reaction of β-amino α,β-unsaturated esters with hydroxylamine hydrochloride in the presence of appropriate bases. The total yield of isoxazole derivatives is sensitively influenced on the β-substituent group of the esters.     

Conjugate addition of grignard reagents to N-(α,β-unsaturated)acylpyrazoles. Diastereoselective β-alkylation using 3-phenyl-l-menthopyrazole

The conjugate additions of N-(α,β-unsaturated)acylpyrazoles were carried out by the treatment with Grignard reagents in the presence of cuprous halides. The reaction of 2-(α,β-unsaturated)acyl-3-phenyl-l-menthopyrazoles 3a-h occurred in higher chemical yields and with asymmetric inductions on β-position, where the addition of magnesium bromide as a Lewis acid influenced to the yields and the diastereoselectivities. In the case of α-methylated 2-(α,β-unsaturated)acyl-3-phenyl-l-menthopyrazoles 3i-n , the excellent asymmetric induction on the α-position was also observed through the diastereofacial protonation.     

Syntheses and structures of mono-, di- and tetranuclear rhodium or iridium complexes of thiacalix[4]arene derivatives

The reactions of [Cp*MCl2]2(Cp*=eta5-C5Me5, M = Rh, Ir) with thiacalix[4]arene (TC4A(OH)4) and tetramercaptothiacalix[4]arene (TC4A(SH)4) gave the mononuclear complexes [(Cp*M){eta3-TC4A(OH)2(O)2}] and the dinuclear complexes [(Cp*M)2{eta3eta3-TC4A(S)4}] respectively, while the analogous reactions with dimercaptothiacalix[4]arene (TC4A(OH)2(SH)2) produced the tetranuclear complexes [(Cp*M)2(Cp*MCl2)2-{eta3eta3eta1eta1-TC4A(O)2(S)2}].     

Flexible taper-shaped liquid crystal trimer exhibiting a modulated smectic phase

We prepared some taper-shaped liquid-crystalline trimers in which two phenylpyrimidine units and a 1,4-diphenyl-2,3-difluorobenzene unit are connected to 2,4-dihdroxy benzoic acid via flexible spacers. We then investigated their liquid-crystalline properties using polarised optical microscopy, differential scanning microscopy and X-ray diffraction. 6-[4–(5-Octylpyrimidin-2-yl)phenyloxy]hexyl 2-{7-{4-[4–(4-hexylphenyl)-2,3-difluorophenyl]phenyloxy}heptanoyloxy}-4-{6-[4–(5-octylpyrimidin-2-yl)phenyloxy]hexyloxy}benzoate (1) was found to exhibit a phase sequence of isotropic liquid – nematic – intercalated smectic A – intercalated anticlinic smectic C – modulated smectic C. The structure–property relation in the taper-shaped trimers reveals that the modulated phase is induced by competition between an intercalated structure stabilised by dipole–dipole interaction and a monolayer structure by packing entropy effects. Conformational change of compound 1 induced by intermolecular interactions plays an important role in the phase transition behaviour.