Palladium-catalyzed coupling reactions of tetrafluoroethylene with arylzinc compounds

Organofluorine compounds are widely used in all aspects of the chemical industry. Although tetrafluoroethylene (TFE) is an example of an economical bulk organofluorine feedstock, the use of TFE is mostly limited to the production of poly(tetrafluoroethylene) and copolymers with other alkenes. Furthermore, no catalytic transformation of TFE that involves carbon-fluorine bond activation has been reported to date. We herein report the first example of a palladium-catalyzed coupling reaction of TFE with arylzinc reagents in the presence of lithium iodide, giving α,β,β-trifluorostyrene derivatives in excellent yields.     

A Simple Method for Producing Micrometer-Sized Monodisperse Polystyrene Particles in Aqueous Media

A method was developed for producing micrometer-sized, highly monodisperse polystyrene particles in single stage polymerization in aqueous media. The method employs an amphoteric surfactant, dimethyldodecylbetaine, that is added to the reaction system of styrene/K(2)S(2)O(8)/water in early stage of reaction. Polymerizations were carried out over a range of initiator concentrations (4-8 mmol/dm(3) H(2)O). The polymerization procedure could produce particles with an average diameter of 3.4 μm with a coefficient of variation of particle size distribution of 4.0%. Copyright 2000 Academic Press.     

Synthesis and evaluation of beta-carbolinium cations as new antimalarial agents based on pi-delocalized lipophilic cation (DLC) hypothesis

Several beta-carbolines including naturally occurring substances and their corresponding cationic derivatives were synthesized and evaluated for antimalarial (antiplasmodial) activity in vitro and in vivo. A tetracyclic carbolinium salt was elucidated for antileishmanial and antitrypanosomal activities in vitro as well as antiplasmodial activity. Quarternary carbolinium cations showed much higher potencies in vitro than electronically neutral beta-carbolines and a good correlation was observed between pi-delocalized lipophilic cationic (DLC) structure and antimalarial efficacy. beta-Carbolinium compounds exhibit medium suppressive activity in vivo against rodent malaria.     

The (p,n) reaction on cadmium isotopes leading to the ground- and excited-state analogs

The (p, n) reactions to ground- and excited-state analogs on ^110,114,116Cd have been studied at a bombarding energy of 25 MeV. Angular distributions of emitted neutrons leading to ground-state analogs, and 2⁺, 3^? and 4⁺ excited-state analogs were obtained for each target. Angular distributions of differential cross sections to the ground-state analog agree with the predictions obtained from macroscopic DWBA calculations in which a Lane potential is employed. Coupled-channel calculations indicate the importance of two-step processes in the (p, n) transition to an excited-state analog. Further, the calculation using a larger value for the deformation parameter of the isovector part than of the isoscalar one fairly well describes the 2⁺ excited-state analog.     

Production of triterpene acids by cell suspension cultures of Olea europaea

Olive (Olea europaea) contains large quantity of triterpene acids including oleanolic acid (6) as a major one. Varieties of biological activities exhibited by triterpene acids attracted our attentions, especially from pharmaceutical viewpoints. Cell culture of olive plant was induced and its triterpene constituents were studied. From the cell suspension cultures, six ursane type triterpene acids; ursolic acid (9), pomolic acid (10), rotundic acid (11), tormentic acid (12), 2alpha-hydroxyursolic acid (13) and 19alpha-hydroxyasiatic acid (14), and two oleanane type acids; oleanolic acid and maslinic acid (7), have been isolated. Quantity of ursane type triterpene acids produced by cell cultures was larger than that of oleanane type. Further, a multifunctional oxidosqualene cyclase (OSC) named OEA was cloned by homology based PCRs from the same cultured cells. Major product of OEA is alpha-amyrin (ursane skeleton), showing good accordance to higher content of ursane-type triterpene acids in the cultured cells, and strongly suggesting OEA to be a major contributor OSC for their production.     

Antimicrobial sesquiterpenoids from Laurus nobilis L

Activity-guided fractionations of leaf extracts from Laurus nobilis L. led to the isolation of a known sesquiterpene lactone, deacetyl laurenobiolide (1). Compound 1 showed antimicrobial activity against periopathic pathogens (Actinomyces viscosus, Porphyromonas gingivalis, Prevotella intermedia and Actinobacillus actinomycetemcomitans), opportunistic Gram-positive bacteria (Staphylococcus aureus and Streptococcus pyogenes) and fungi (Candida albicans, Cryptococcus neoformans and Aspergillus fumigatus). Furthermore, acetylation and cyclisation of deacetyl laurenobiolide (1) yielded laurenobiolide (2) and a new compound, (5S,6R,7S,8S,10R)-6,8-dihydroxyeudesma-4(15),11(13)-dien-12-oic acid 12,8-lactone (3), respectively. Compounds 2 and 3 also showed antimicrobial activities. All compounds 1-3 demonstrated growth inhibitory effects with minimum inhibitory concentrations ranging from 31 to 1000?μg?mL(-1). This is the first report of compounds 1-3 showing antimicrobial activities.     

Subterranean electrical structure of Kozu-shima volcanic island, Japan

Following the electric current injection experiment carried out in 2009, a VLF-MT (Very Low Frequency Magnetotelluric) survey has been conducted in Kozu-shima Island to obtain further information on the subterranean electrical structure that might help understanding the results of our monitoring of geoelectric potentials. A number of VAN-type pre-seismic geoelectric potential anomalies were observed in 1997-2000, even showing a remarkable "Selectivity". However, similar pre-seismic anomalies were not observed during the Izu-Island volcano-seismic swarm 2000. All these observations would require extremely high degree of heterogeneity in the subterranean electrical structure of the volcanic island and its possible time changes. Several correlations between the results of this survey and the volcanic geology of the island and ground water distribution were found. Further investigation is needed for a complete explanation of the observed phenomena.     

Remote Electronic Tuning of Chiral N-Heterocyclic Carbenes

Our recent efforts to develop novel N-Heterocyclic carbene (NHC)-catalyzed asymmetric reactions are described. During our investigation for development of the acylation reactions via acylazoliums generated by the reactions of NHCs and α-oxidized aldehydes, we have observed significant effects of substitution at a remote site of the carbene carbon of NHCs. In addition, we also observed a significant enhancement of the enantioselectivity by the addition of carboxylate anions. From this observation, we proposed a novel working hypothesis involving a formation of a complex of the substrate and additive to reinforce the recognition of the catalyst for enhancement of the catalytic performance of the asymmetric N-heterocyclic carbene system. By applying this concept, we achieved the kinetic resolutions of both cyclic and acyclic alcohols in excellent enantioselectivities. The effects of the remote substitution were also observed in intramolecular Stetter reaction and intermolecular benzoin reaction. In these reactions, the comparison of the catalytic performance of the NHCs bearing variable remote substitutions provided insights into the reaction mechanism because the remote substitution tuned the electronic nature of NHCs without affecting the steric and electrostatic factors around the reaction site. We also developed an intramolecular benzoin condensation involving two aldehydes, which is challenging to realize. Using the substrates bearing proper protecting groups, we succeeded in the stereo divergent synthesis of a variety of inososes, which are important intermediates for the synthesis of biologically active cyclitols.