Synthesis of [60]fullerene adducts bearing carbazole moieties by Bingel reaction and their properties

Carbazole-linked [60]fullerene adducts were successfully prepared by the Bingel reactions using carbazole derivatives bearing one or two ethyl malonate moieties. In the latter cases, specific bisadduct regioisomers were obtained, depending on the spacer unit between two ethyl malonate moieties. [reaction: see text]     

Bifurcation and Lorentz-factor scaling of relativistic magnetized plasma expansion

We report the long-term results of 2 1/2-dimensional particle-in-cell simulations of the relativistic expansion of strongly magnetized electron-positron plasmas. When the simulation is carried to >150 light-crossing time of the initial plasma, the plasma pulse exhibits a number of remarkable properties. These include the repeated bifurcation of the pulse profile, development of a power-law momentum distribution with low-energy cutoff, and a simple scaling law for the peak Lorentz factor.     

Mechanistic aspects of thiyl radical-promoted acyl radical cyclization of formylenoate-cyclization versus oxidation

Treatment of formylalkenoates 1 and 7 with 2,2'-azobis(2-methylpropanenitrile) (AIBN) in the presence of dioxygen gave oxygenated carboxylic acids 5, 6, 8, 9 instead of acyl radical cyclization products, through preferential reaction of the corresponding acyl radicals with dioxygen rather than intramolecular attack to an enoate moiety. The reaction of 1 with AIBN in the absence of dioxygen recovered starting 1 in 98% yield.     

Synthesis of novel starburst and dendritic polyhedral oligosilsesquioxanes

The hydrosilylative reaction utilizing octakis(dimethylsiloxy)silsesquioxane and silsesquioxane disilanols bearing alkenylsilyl moieties produces a series of starburst-type giant silsesquioxanes and a second-generation dendritic molecule as well as a boron-containing one.     

Influence of dissolved oxygen content on multibubble sonoluminescence with ambient-pressure reduction

The efficiency of chemical reactions in the presence of ultrasound at reduced pressures has been monitored using the influence of dissolved oxygen (DO) content on a luminol solution undergoing multibubble sonoluminescence. From these measurements under the condition of constant ultrasonic frequency and constant amplitude of sound pressure, it is shown that the intensity of sonoluminescence is higher at subatmospheric ambient pressure than at atmospheric pressure under the same degree of saturation. Also, it is found that there is an appropriate content of DO to produce the highest intensity of the luminescence and its value varies with ambient pressure.     

Improved total synthesis of (±)-Tetragocarbone A

Stereoselective total synthesis of (±)-tetragocarbone A isolated from the propolis of an Australian stingless bee, Tetragonula carbonaria, has been developed by focusing on the latent symmetry of 1. The requisite 1R*, 3R*, 6S* stereogenic centers were selectively installed by hydroxy group directing reactions including the late stage desymmetrization of the 1,3-diketone. The target natural product was successfully prepared in 12 steps from phloroglucinol on 300 mg.     

Relationship between physicochemical characteristics and functional properties of chitosan

In order to select an ideal chitosan (CS) species as a material for implantation vehicle to control drug release in the body, the relationship between physicochemical characteristics (including molecular weight, degree of deacetylation, and viscosity) and functional properties (including ability to form spherical gel, control of drug release from CS gel, and biodegradation of CS) was investigated for various CS. The ease of spherical gel formation in aqueous amino acid solution or aqueous solution containing metal ions was affected mainly by viscosity of the CS solution. Drug diffusion rate from the CS gel was controlled by density of the gel matrix structure, which was governed by viscosity of the CS solution prior to gelation. Biodegradation of CS tended to vary with degree of deacetylation. However, linear relationships for these trends were not observed, and the possibility that characteristics other than CS molecular weight, degree of deacetylation, and viscosity of the CS solution, such as distribution of acetamide groups in the CS molecule affect functional properties of CS, was also indicated. These observations demonstrate that CS functions are affected by various CS characteristics and that investigation of individual CS characteristics is important for the selection of the appropriate CS as a material for drug delivery vehicles.