Studies on the constituents of the leaves of Baccharis dracunculifolia (Asteraceae) and their cytotoxic activity

A new sesquiterpene, named baccharisketone (1), and a new monoterpene, p-methoxythymol acetate (2), were isolated from the leaves of Baccharis dracunculifolia along with seventeen known compounds (3-19). The structures of the new compounds were determined by spectroscopic means. The growth inhibitory activity of the isolated compounds against leukemia cells (L 1210) was tested and three terpene phenols (4, 6, 17) and five sesquiterpene alcohols (8, 10, 11, 13, 16) were found to exhibit strong cytotoxic activity.     

Construction of tricyclic enone, a common precursor for aphidicolane and stemodane B/C/D-ring system

Synthesis of a tricyclic enone (B/C/D ring system), a common key precursor for the aphidicolane- and stemodane-type diterpene, is described. The key reaction for the construction of the quaternary carbon center is allylation of epoxide at the more substituted carbon with an organotitanium reagent. Asymmetric reduction with DIP-Cl followed by stereoselective cyclization of spirocyclic ketone and the functional group modification gave the desired tricyclic enone in good yield.     

Subcellular topological effect of particle monolayers on cell shapes and functions

We studied topological effects of subcellular roughness displayed by a closely packed particle monolayer on adhesion and growth of endothelial cells. Poly(styrene-co-acrylamide) (SA) particles were prepared by soap-free emulsion copolymerization. Particle monolayers were prepared by Langmuir–Blodgett deposition using particles, which were 527 (SA053) and 1270 nm (SA127) in diameter. After 24-h incubation, cells tightly adhered on a tissue culture polystyrene dish and randomly spread. On the other hand, cells attached on particle monolayers were stretched into a narrow stalk-like shape. Lamellipodia spread from the leading edge of cells attached on SA053 monolayer to the top of the particles and gradually gathered to form clusters. This shows that cell–cell adhesion became stronger than cell–substrate interaction. Cells attached to SA127 monolayer extended to the reverse side of a particle monolayer and engulfed particles. They remained immobile without migration 24 h after incubation. This shows that the inhibition of extensions on SA127 monolayer could inhibit cell migration and cell proliferation. Cell growth on the particle monolayers was suppressed compared with a flat TCPS dish. The number of cells on SA053 gradually increased, whereas that on SA127 decreased with time. When the cell seeding density was increased to 200,000 cells cm⁻², some adherent cells gradually became into contact with adjacent cells. F-actin condensations were formed at the frame of adherent cells and the thin filaments grew from the edges to connect each other with time. For the cell culture on SA053 monolayer, elongated cells showed a little alignment. Cells showed not arrangement of actin stress fibers but F-actin condensation at the contact regions with neighboring cells. Interestingly, the formed cell monolayer could be readily peeled from the particle monolayer. These results indicate that endothelial cells could recognize the surface roughness displayed by particle monolayers and the response was dependent on the pitch of particle monolayers.     

Pressure effect on the electrical conductivity and superconductivity of beta-(BDA-TTP)2I3

The pressure-induced electrical conductivity properties of beta-(BDA-TTP)2I3 have been investigated; the salt exhibits a dramatic change in the conductivity behaviour above ca. 10 kbar and undergoes a superconducting transition with an onset near 10 K.     

Nonlinear optics with phase-controlled pulses in the sub-two-cycle regime.

Nonlinear optical effects due to the phase between carrier and envelope are observed with 5 fs pulses from a Kerr-lens mode-locked Ti:sapphire laser. These sub-two-cycle pulses with octave spanning spectra are the shortest pulses ever generated directly from a laser oscillator. Detection of the carrier-envelope phase slip is made possible by simply focusing the short pulses directly from the oscillator into a BBO crystal. As a further example of nonlinear optics with such short pulses, the interference between second- and third-harmonic components is also demonstrated.     

Novel syntheses of murrayaquinone A and furostifoline through 4-oxygenated carbazoles by allene-mediated electrocyclic reactions starting from 2-chloroindole-3-carbaldehyde.

The formal total synthesis of murrayaquinone A (1) and the total synthesis of furostifoline (5) were completed by the construction of 4-oxygenated 3-methylcarbazoles 7 based on a new type of electrocyclic reaction through 2-alkenyl-3-allenylindole intermediates 8 derived from the 2-alkenyl-3-propargylindoles 9, starting from 2-chloroindole-3-carbaldehyde (11). The N,O-bisbenzyloxymethyl group of 16c and 22 underwent a Birch reduction followed by treatment with Triton B to produce the known 4-hydroxy-3-methylcarbazole (7a) and 4-hydroxy-3-methylfuro[3,2-a]carbazole (7b) as precursors of murrayaquinone A (1) and furostifoline (5), respectively. The trifluoromethanesulfonyloxy-3-methylfuro[3,2-alcarbazole (24), prepared from 7b, was subjected to reductive cleavage to provide furostifoline (5).     

Orientation-dependent interactions in polymer systems: Segmental orientation,miscibility, and self-organization

Three co-operative phenomena that are supposed to originate in the orientation-dependent interactions among polymer segments are discussed and attempted to be interpreted in terms of a common set of polymer models.     

Step bunching behaviour on the {0 0 0 1} surface of hexagonal SiC

Surface topography of the {0 0 0 1} facet plane of as-grown 6H- and 4H-SiC crystals was studied ex situ by Nomarski optical microscopy (NOM) and atomic force microscopy (AFM). The surface polarity and the polytype of grown crystals largely affect the growth surface morphology of SiC{0 0 0 1} via differences in several thermodynamic and kinetic parameters. NOM observations revealed giant steps of a few micrometers in height on the {0 0 0 1} growth facet, and it was found that a morphological transition of the growth facet occurred when the growth conditions were changed. AFM imaging of the stepped structure of SiC{0 0 0 1} detected steps of height equal to the unit c-lattice parameter (c=1.512 nm for 6H-SiC and 1.005 nm for 4H-SiC). They are fairly straight and very regularly arranged, giving rise to equidistant step trains. Upon nitrogen doping, these regular step trains on the 6H-SiC(0 0 0  )C and 4H-SiC(0 0 0  )C surfaces became unstable: the equidistant step trains were transformed into meandering macrosteps of height greater than 10 nm. In this paper, we discuss the mechanism of macrostep formation (step bunching) on the SiC{0 0 0 1} surfaces through the consideration of the interplay between step energetics (repulsive step interaction) and kinetics (asymmetric step kinetics) on the growing crystal surface and elucidate how they affect the growth surface morphology of the SiC{0 0 0 1} facet.     

Synthesis and structure-activity relationship of a new series of potent angiotensin II receptor antagonists: pyrazolo[1,5-a]pyrimidine derivatives.

We have already reported 7-oxo-4,7-dihydropyrazolo[1,5-a]pyrimidine-3-carboxylic acid derivatives, which are potent in vitro angiotensin II (AII) antagonists, but have no oral antihypertensive activity. Removal of the carboxylic acid and replacement of the heteroaromatic system afforded potent in vitro antagonists. Removal of the carbonyl oxygen and changing the position of the biphenyltetrazole substituent were critical to the display of oral activity. To improve the in vitro and oral activities, modifications were made of the substituents at the 3- and 5-positions of the pyrazolo[1,5-a]pyrimidine. Structure-activity studies showed the methyl substituent at the 3-position to be essential for potent in vivo activity. We present the design, syntheses, and biological data of a series of pyrazolo[1,5-a]pyrimidine derivatives, which are orally active AII receptor antagonists.