Showing papers by "Masahiro Murakami published in 1995"

Hydrocarbon composition of newly isolated strains of the green microalga Botryococcus braunii

Abstract: Four new strains of Botryococcus braunii were isolated from Japanese waters and cultured under defined conditions. Their hydrocarbon content and composition were analyzed and compared with those of the Darwin and Berkeley strains. The Yamanaka strain produced only alkadienes characteristic of the A race, whereas the others, the Yayoi, Kawaguchi-1 and -2 strains as well as the Darwin and Berkeley strains, produced botryococcenes peculiar to the B race. The hydrocarbon content of the Yamanaka strain was 16.1 % dry weight and that of the B race strains ranged from 9.7 to 37.9%. Botryococcene composition of the Japanese strains differed from each other as well as from the Darwin and Berkeley strains. More than 50% of the hydrocarbons in the Yayoi, Darwin, and Berkeley strains were composed of C34H58, but the main components were different from one another as isomers. The Kawaguchi-1 and -2 strains did not have a high level of C34 botryococcenes, C32 ones being the main components. In these strains significant amounts of squalene-related compounds were detected.

Generation of (α-aminoalkyl)samarium(III) by a new method of metalation and its carbon–carbon bond-forming reactions

Abstract: (α-Aminoalkyl)samarium(III) is generated on treatment of a tertiary amine having a pendant o-iodobenzyl group on the nitrogen atom with samarium(II) iodide (SmI 2 ) in tetrahydropyran containing hexamethylphosphoramide. Deuterium incorporation experiments demonstrate that the reaction proceeds via a delivery of a radical center from the pendant benzyl group to the α-position of nitrogen and the following one-electron transfer from SmI 2 to the delivered radical. Subsequent nucleophilic addition of (α-aminoalkyl)samarium (III) to various electrophiles, such as enolizable ketones, isocyanate and isocyanide, furnishes the C-C bond formation products in good yields. The pendant benzyl group of the product can be readily removed by hydrogenolysis to give the corresponding secondary amine. Therefore, the present reaction provides a useful synthetic process for a variety of nitrogen-containing compounds including β-amino alcohols and α-amino acid derivatives, disclosing a new method for metalation and C-C bond formation.

Intramolecular Bis-silylation Catalyzed by Palladium-Isocyanide

Abstract: Details of a study on the intramolecular bis-silylation of C-C multiple bonds promoted by a new catalyst system, palladium-tert-alkyl isocyanide, are described. With a disilanyl ether derived from a homoallylic alcohol, intramolecular regioselective addition of the Si-Si linkage to the C=C bond took place to furnish an exo-ring closure product, i.e., 1, 2-oxasilolane. The bis-silylation of alkenes having substituents α to the C=C bond gave trans-3, 4-disubstituted oxasilolanes, while substitution β to the C=C bond favored cis-3, 5-disubstituted oxasilolanes. The 1, 2-oxasilolanes thus produced stereoselectively were oxidatively converted to the corresponding 1, 2, 4-triols. The present methodology for the synthesis of 1, 2, 4-triols was successfully extended to the stereoselective synthesis of 1, 2, 4, 5, 7- and 1, 2, 4, 6, 7-pentaols through a sequence of the intramolecular bis-silylation. The bis-silylation was also performed with alkenes linked to disilanyl groups through a 3-carbon chain and through an amide linkage. Alkenes tethered to disilanyl groups through chains of 2 atoms underwent similar intramolecular bis-silylation. The intramolecular bis-silylation of an alkyne tethered to a disilanyl group furnished a bis-silylated exocyclic olefin. Subsequent hydrogenation from the less-hindered side of the ring produced cis-disubstituted oxasilolane, providing an alternative method for the stereoselective synthesis of 1, 2, 4-triols. The intramolecular bis-silylation under high pressure led to the efficient synthesis of a new cyclic tetrakis(organosilyl)ethene, which possessed a non-twisted structure.

Effects of Greening on the Climate of Tama New Town

Abstract: Observations were carried out to investigate effects of greening on the climate of Tama New Town. It was found that greening areas have significantly reduced the intensity of urban heat island in the town. Effects of greening on the urban heat island intensity was strongest at noon and in the early afternoon with the air temperature inside the Tama New Town Central Park was more than 2°C lower than that at the surrounding commercial or parking areas. Soon after sunset, temperature of the vegetated surface in the park became lower than that of the air and the park became a cool island. At the same time, paved asphalt or concrete surface in the town remained hotter than the atmosphere even at night. The upward sensible heat flux from the ground surface to the atmosphere together with anthropogenic heat made the air temperature in the town higher than that in the park.A turbulent closure model had successfully simulated the heating and dynamical processes in the area. The simulation results revealed that evaporation from water and vegetated surface cooled down the surface in the park.