Biomedical subjects
Publications and source records attributed to Masato Kawamura.
Magnetic nanoparticles-supported quaternary ammonium and phosphonium salts were prepared and evaluated as phase-transfer catalysts. Some of them exhibited good activities that were comparable to that of tetra-n-butylammonium iodide. The catalysts were readily separated using an external magnet and reusable without significant loss of their catalytic efficiency.
Hospital-acquired legionellosis is one of the serious problems in nosocomial infection. For risk assessment of nosocomial Legionella infection, we surveyed samples from bathrooms for public use in three hospitals and two nursing homes to determine whether Legionella pneumophila was present. A total of 70 hot bathwater samples and samples wiped from bathtubs were collected at 1-h intervals. Fifteen shower-water and 15 inner-head samples were obtained at the start of a bath. Water samples were cultured using the Legionella spp. selective medium, and discrimination between L. pneumophila and other Legionella spp. was performed by PCR analysis. L. pneumophila serogroup 7 was detected in 1 bathwater and 1 wiped sample, both of which were collected 1 h after daily use from the same bathtub in a hospital. However, L. pneumophila SG7 was not detected in any other samples. Furthermore, the concentrations of free residual chlorine in most bath- and shower-water samples were lower than 0.1 mg/l. These results suggest that L. pneumophila has become a potential pathogen for nosocomial infections in public-type hospital baths. From the point of view of an infection-control program, it might be advisable to hold the concentration of free residual chlorine at 0.2-0.4 mg/l, which is generally required for public baths in Japan.
Diels-Alder reaction of 2-acryloyloxy-2'-(2-pyridylazo)-1,1'-binaphthyl with cyclopentadiene in the presence of an equimolar amount of tin(IV) chloride showed unusual exo-selectivity with a high degree of diastereofacial differentiation.
Novel photoresponsive axially chiral monophosphine ligands containing azobenzene moiety were prepared and applied to a palladium-catalyzed allylic alkylation. The reaction of rac-1,3-diphenyl-2-propenyl acetate gave the alkylated products with up to 90% enantiomeric excess. The ligand exhibited a trans to cis photoisomerization upon irradiation with UV light.
alpha-Alkylation of 2-phenylacetate ester of 2-alkylamino-2'-hydroxy-1,1'-binaphthyls with various alkyl iodides proceeded with good stereoselectivities. An intramolecular hydrogen bonding between N-H group and the carbonyl oxygen seemed to play an important role for asymmetric induction. The auxiliary was also applicable to Diels-Alder reaction of an acrylate.