Masaki Kamata

Photosensitized oxygenation reactions of 1,3-dithianes through cooperative single electron transfer pathway and singlet oxygen pathway

Abstract Photosensitized oxygenation reactions of 2-( p -methylphenyl)-1,3-dithiane 1a , and 2,2-di-( p -methylphenyl)-1,3-dithiane 1b afforded carbony compounds, sulfoxides, and sulfones at the various ratios through cooperative single electron transfer (SET) pathway and singlet oxygen pathway.

Photoinduced single electron transfer reactions of 1,3-dithianes and 1,3-dithiolanes sensitized by triphenylpyrylium salt in the presence of molecular oxygen

Abstract Triphenylpyrylium salt sensitized photoreactions of several dithianes and dithiolanes produced carbonyl compounds in good yields in the presence of molecular oxygen. Molecular oxygen trapping of carbon radical intermediates generated through selective CS bond cleavage of dithiane and dithiolane cation radicals is proposed.

Deprotection of 1,3-dithianes by antimony pentachloride via single electron transfer processes

Abstract A variety of 1,3-dithianes was converted to the corresponding carbonyl compounds in good yields when those substances were treated with antimony pentachloride in methylene chloride. Single electron transfer from dithianes to antimony pentachloride was proposed as an initiation step of the reaction.

Toxoplasma gondii: a simple high-throughput assay for drug screening in vitro.

Toxoplasma gondii is the etiologic agent of toxoplasmosis. Although the combination of sulfadiazine and pyrimethamine is used as therapy for this disease, these drugs can have serious side effects and its use is limited in pregnancy. Therefore there is a need for new anti-T. gondii drugs in the clinic. Some systems for T. gondii drug screening have been described, but these have limitations and can be difficult. In order to solve these problems, we established a system to screen drugs in vitro that involved using cell viability methods to calculate drug selectivities, which are Trypan blue, [3-(4,5-dimethylthiazol-zyl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazoliuzolium, inner salt] (MTS) method and lactate dehydrogenase (LDH) assay. These assays were simple to establish and perform. The IC(50) values calculated from the morphological assay were not significantly different from the EC(50) values calculated using the other three methods. In particular, the results of the morphological assay showed a distinct association with the MTS assay (R=0.9841). These assays could be used for a wide range of applications in the screening of new drugs and may provide an alternative to the techniques currently used to screen for candidate anti-T. gondii compounds in vitro. In this study, we also tested many compounds and identified some that had a good anti-T. gondii effect in vitro based on the MTS assay. This simple and fast system allowed us to determine which compounds to investigate further using in vivo experiments.

Pyrylium salt sensitized photochemical deprotections of dithioacetals and ketals

Abstract Photoreactions of various dithioacetals and ketals using tris(p-chlorophenyl)pyrylium perchlorate as a sensitizer were studied. Irradiation (λ&>360 nm) of dichloromethane solutions containing dithioacetals or ketals and pyrylium salt afforded the corresponding carbonyl compounds in good to excellent yields in the presence of molecular oxygen.

Aminium radical salt catalyzed desulphurization of thiiranes: An efficient preparation of arylsubstituted olefins

Abstract Arylsubstituted olefins are obtained from corresponding thiiranes in high yields under mild conditions by using catalytic amount of tris-(p-bromophenyl)aminium hexachloroantimonate (1) as a single electron transfer (SET) oxidant.

Aminium salt promoted catalytic substitution reactions of acetals with silylated nucleophiles

Abstract A catalytic amount of tris( p -bromophenyl)aminium hexachloroantimonate promoted the substitution reactions of dimethylacetals with various silylated nucleophiles through an electron transfer mechanism. Silyl compounds include silyl enol ether, ketene silyl acetal, and allylsilane. One methoxy group of the substrates was effectively substituted by nucleophiles to form carbon-carbon bonds.

Pyrylium salt promoted substitution reactions of acetals with various silylated nucleophiles

Abstract Catalytic amounts of triarylpyrylium salts photochemically and thermally promoted the substitution reactions of dimethyl acetals with silylated nucleophiles.

Photoinduced electron-transfer oxygenation of arylalkanes. Generation and oxygenation pathways of benzylic-type free radicals from the cation radical deprotonation

Abstract 2,4,6-Triphenylpyrylium tetrafluoroborate(TPP + )-sensitized oxygenation has been carried out for several arylalkanes in dichloromethane. Direct evidence for deprotonation of a cation radical was obtained, and interesting structural effects on the deprotonation efficiency was observed.

The photochemical [3 + 2]cycloaddition reaction of 2,2,3,3-tetra-arylthiiranes and tetracyanoethylene through electron donor–acceptor complexes

Upon irradiation of the electron donor–acceptor complexes of 2,2,3,3-tetra-arylthiiranes and tetracyanoethylene (TCNE), the [3 + 2]cycloadditions occurred efficiently without the desulphurisation of thiiranes.