A Convenient Synthesis of Juglone Via Neutral Salcomine Oxidation

1,5-Dihydroxynaphthalene and its derivatives can be oxidized by molecular oxygen in the presence of catalytic amounts of salcomine under neutral conditions to afford the corresponding 1,4-naphthoquinones as the major products.     

Time Courses and Time‐Resolved Spectra of Firefly Bioluminescence Initiated by Two Methods of ATP Injection and Photolysis of Caged ATP

The time‐dependent characteristics of firefly bioluminescence initiated by manual injection of adenosine triphosphate (ATP) into buffer solution containing luciferin (Ln), luciferase (Luc) and Mg²⁺ were measured with a resolution of 10 ms, and compared with those obtained by photolysis of caged ATP. The time course depends on pH; both rise and decay rates decrease when pH is lowered from 7.8 to 6.8. In contrast, the parameter λ in the kinetic formula related to diffusion of ATP is almost independent of pH. The pH dependence of the time course of bioluminescence can be explained by the same pH tendency as the rate of ATP binding at the active site of Luc. The time‐resolved spectra can be decomposed into two Gaussian components with maxima at 2.2 and 2.0 eV. At pH 7.8, the band at 2.2 eV is more intense than that at 2.0 eV for all three concentration conditions. At lower pH, the band at 2.2 eV becomes weaker than that at 2.0 eV. The intensity ratio of the 2.0 and 2.2 eV bands is constant for duration time of 600 s for both injection and photolysis experiments, and the above conclusions are unaffected by the concentration ratio [Ln]/[Luc].     

Synthesis of Novel Spiro[indol-2,2′-pyrroles] Using Isocyanide-Based Multicomponent Reaction

An efficient and facile method for the synthesis of novel spiro[indole-2,2′-pyrroles] from N-methyl-3-isatin imines, t-butyl isocyanide, and dialkyl acetylenedicarboxylate has been achieved by [3 + 2] cyclo addition reaction. All the products were purified by column chromatography as yellow solids and confirmed with ¹H NMR, ¹³C NMR, fast atom bombardment, mass, and infrared. Compound 11 was further confirmed with x-ray analysis.     

Officinatrione: an unusual (17S)-17,18-seco-lupane skeleton,and four novel lupane-type triterpenoids from the roots of Taraxacum officinale

Novel 5 lupane-type of triterpenois, i.e., 3β-acetoxy-18α,19α-epoxylupan-21β-ol (1), 18α,19α-epoxy-21β-hydroxylupan-3-one (2), lup-18-ene-3,21-dione (3), lupa-18,21-dien-3β-yl acetate (4), and (17S)-17,18-seco-lup-19(21)-ene-3,18,22-trione (5), named officinatrione, as well as 16 known compounds from the roots of Taraxacum officinale collected in Takatsuki city, Osaka, Japan. Of the above compounds, 5 was the first lupane-type triterpene, of which the D-ring was open to form a nine-membered ring. Compounds 2 and 5 exhibited moderate cytotoxic activities against L1210 cell line (IC₅₀ 10.5 and 10.1 μM).     

A convergent total synthesis of antiplasmodial C2 symmetric (+)-ekeberin D4

The first concise total synthesis of C₂ symmetric (+)-ekeberin D₄ (1) that exhibits antiplasmodial activity has been achieved in total nine steps and 27% yield from the known diol 4. The efficient synthetic method features the regio- and diastereoselective epoxidation of 4 and convergent coupling between half fragments 2 and 3 by taking into account the C₂ symmetric property.     

Flavin-catalyzed aerobic oxidation of sulfides in aqueous media

An aerobic, organocatalytic, and aqueous method for the oxidation of sulfides is described. Synthetic flavin, 5-ethyl-3,7,8,10-tetramethylisoalloxazinium perchlorate, acts as an efficient catalyst for the oxidation of sulfides in water under an oxygen atmosphere (1 atm) with the assistance of ascorbic acid as a reductant. This is an inexpensive, convenient, and environmentally benign method for the selective oxidative transformation of sulfides into sulfoxides.     

Additional cytotoxic substances isolated from the sponge-derived Gymnascella dankaliensis

A continuous investigation of secondary metabolites produced by the sponge-derived fungus, Gymnascella dankaliensis, has yielded a new polyketide tyrosine derivative, dankastatin C (3) and the known steroid, demethylincisterol A₃ (4), which was originally found from a Homaxinella marine sponge. The stereostructure of the new compound has been determined based on the analysis of 1D and 2D NMR data. Dankastatin C (3) showed potent cell growth inhibitory activity against the murine P388 cell line.     

DNA aggregation and cleavage in CGE induced by high electric field in aqueous solution accompanying electrokinetic sample injection

The phenomenon of peak area decrease due to high injection voltage (V_inj, e.g. 10–30 kV, 200–600 V/cm in the 50 cm capillary) was found in the analysis of very dilute DNA fragments (<0.2 mg/L) by using high‐sensitive electrokinetic supercharging‐CGE. The possibility of DNA cleavage in aqueous solution was suggested, in addition to the aggregation phenomenon that is already known. The analysis of intentionally voltage‐affected fragments (at 200 V/cm) also showed decreased peak areas depending on the time of the voltage being applied. Computer simulation suggested that a high electric field (a few kV/cm or more) could be generated partly between the electrode and the capillary end during electrokinetic injection (EKI) process. After thorough experimental verification, it was found that the factors affecting the damage during EKI were the magnitude of electric field, the distance between tips of electrode and capillary (D_e/c), sample concentration and traveling time during EKI in sample vials. Furthermore, these factors are correlating with each other. A low conductivity of diluted sample would cause a high electric field (over a few hundred volts per centimeter), while the longer D_e/c results in a longer traveling time during EKI, which may cause a larger degree of damage (aggregation and cleavage) on the DNA fragments. As an important practical implication of this study, when the dilute DNA fragments (sub mg/L) are to be analyzed by CGE using EKI, injection voltage should be kept as low as possible.     

Photoinduced alignment of polymer liquid crystals containing azobenzene moieties in the side group VII. On He-Ne laser beam irradiation

Photoinduced alignment in a polymer liquid crystal prepared from 6-{1-[4-(2-cyano-4-nitrophenylazo)phenyl]piperazino}hexyl acrylate and 4'-[6-(methacryloyloxy)hexyloxy]-4-cyanobiphenyl was investigated for the first time on irradiation with a polarized He-Ne laser beam at 633 nm. The azobenzene moieties as well as the inert cyanobiphenyl mesogenic units were aligned with the molecular long axis perpendicular to the polarization direction of the irradiation light. Alignment induced on short irradiation was reversible, while that induced under prolonged irradiation was irreversible due to the occurrence of crosslinking which might be caused by photoinduced decomposition of the azobenzene moieties during the photoirradiation process.     

Synthesis and properties of polyfluoro(silyl)acetylene nanoparticles by reaction of fluoro(silyl)acetylenes with triethylamine

Fluoro(silyl)acetylenes, which were prepared by reaction of 1,1-difluoroethylene with silyl chlorides, reacted with triethylamine to give dark-brown colored polyfluoro(silyl)acetylene powders in excellent to moderate isolated yields. In contrast, the corresponding nonfluorinated acetylene was unable to react with triethylamine at all to afford poly(silyl)acetylene under similar conditions. Polyfluoro(silyl)acetylenes thus obtained were nanometer size-controlled cubic fine particles with a good dispersibility and stability in a variety of solvents. These polyfluoro(silyl)acetylene nanoparticles exhibited clear absorption and emission spectra related to the conjugated units in polymer main chain. Furthermore, these polyfluoro(silyl)acetylene nanoparticles were applied to the surface modification of poly(methyl methacrylate) [PMMA] film to exhibit a higher oleophobicity imparted by fluorine on their surface, compared to that on the reverse side.