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A total synthesis of dehydroantofine was achieved by employing a novel, regioselective azahetero Diels-Alder reaction of the easily accessible 3,5-dichloro-2 H -1,4-oxazin-2-one with 4-ethynyl-1,2-dimethoxybenzene as a key step. Further, we demonstrated that dehydroantofine is a promising candidate as a new antimalarial agent in a biological assay with chloroquine-resistant Plasmodium falciparum .

Streptococcus mutans is the main pathogen of dental caries and adheres to the tooth surface via soluble and insoluble glucans produced by the bacterial glucosyltransferase enzyme. Thus, the S. mutans glucosyltransferase is an important virulence factor for this cariogenic bacterium. Sulfated vizantin effectively inhibits biofilm formation by S. mutans without affecting its growth. In this study, less S. mutans biofilm formation occurred on hydroxyapatite discs coated with sulfated vizantin than on noncoated discs. Sulfated vizantin showed no cytotoxicity against the human gingival cell line Ca9-22. Sulfated vizantin dose-dependently inhibited the extracellular release of cell-free glucosyltransferase from S. mutans and enhanced the accumulation of cell-associated glucosyltransferase, compared with that observed with untreated bacteria. Sulfated vizantin disrupted the localization balance between cell-associated glucosyltransferase and cell-free glucosyltransferase, resulting in inhibited biofilm maturation. These results indicate that sulfated vizantin can potentially serve as a novel agent for preventing dental caries.

Phosphonic acid (phosphonate) that possesses a carbon-phosphours bond is a chemically stable form of organic phosphorus. Various phosphonic acids are widely distributed in oceanic waters; in particular, methylphosphonic acid (namely methylphosphonate) is believed to be responsible for global methane production. To discuss the microbial degradation of phosphonic acids, we investigated the utilization of phosphonic acid compounds by cultures of marine bacteria, Phaeobacter sp., Ruegeria sp. (Rhodobacterales), and Thalassospira sp. (Rhodospirillales). These bacterial cultures were able to grow on methylphosphonic acid as well as on the tested alkyl-, carboxy-, aminoalkyl-, and hydroxyalkyl-phosphonic acid compounds. Cell yields and growth rates of Ruegeria and Thalassospira cultures grown on methyl-, ethyl-, propyl-, and butyl-phosphonic acid compounds tended to decrease with increasing alkyl chain length. In contrast, Phaeobacter sp. grew well on such alkyl-phosphonic acids. Our results suggest that these marine bacteria, which exhibit varied utilization, are involved in microbial degradation of various phosphonic acid compounds.

Thallusin is the only known natural product that induces cell differentiation followed by formation of a thallus during the growth of green macroalgae such as Monostroma and Ulva . Herein, various thallusin analogues based on the terpen skeleton were synthesized to study the structure−activity relationships of thallusin. The potency of the synthetic analogues was investigated in an experimental assay, which demonstrated that the 19-methyl group in thallusin is essential for potent morphogenesis-inducing activity.

A m -C 2 B 10 H 11 HgCl/AgOTf-catalyzed reaction of allyl silyl ethers with N -Boc- N ′-tosylhydrazine has been developed. Under mild conditions, the resulting allyl hydrazine products were transformed into naked alkenes in good yield. Furthermore, the used m -C 2 B 10 H 11 HgCl could be recovered quantitatively.

Hg(OTf)2-catalyzed aryl-allene cyclization accompanied by formation of a quaternary carbon center has been realized. Deuterium-labeling experiments and computational modeling were used to propose a novel catalytic pathway involving direct H-transfer from the aromatic ring to the vinyl mercury moiety followed by mercury 1,2-migration.

An asymmetric synthesis of (−)- and (+)-ketorolac was achieved with 89% ee using a novel Friedel–Crafts (FC) type C–C bond forming cyclization of an allyl alcohol containing a pyrrole ring core in the presence of a bimetallic gold(I) salt complex prepared from a 2:2:1 combination of AuCl·SMe2, AgOTf and chiral Quinaphos.

Lipopolysaccharide (LPS) antagonists have attracted considerable interest as promising candidates for the treatment of severe sepsis triggered by Gram-negative bacteria. In this article, we describe the development of a novel LPS antagonist based on chemical hybridization of vizantin and the hydrophobic molecular unit of LPS (lipid A). Vizantin, 6,6'-bis-O-(3-nonyldodecanoyl)-α,α'-trehalose, was designed as an immunostimulator from a structure-activity relationship (SAR) study with trehalose 6,6'-dicorynomycolate (TDCM). Our recent study indicated that vizantin displays adjuvant activity by specifically binding to the Toll-like receptor 4 (TLR4)/MD2 protein complex. Because lipid A unit (or LPS) is also known to trigger an inflammatory response via the same TLR4/MD2 complex as vizantin, we designed a hybrid compound of vizantin and lipid A with the aim of developing a novel biofunctional glycolipid. Focusing on the antagonism to Escherichia coli LPS in an in vitro model with human macrophages (THP-1 cells), we identified a potent LPS antagonist among the synthesized hybrid compounds. The novel LPS antagonist effectively inhibited LPS-induced release of tumor necrosis factor-alpha (TNF-α) in a dose-dependent manner with an IC50 value of 3.8 nM, making it a candidate for the treatment drug of Gram-negative sepsis and/or septic shock.

Development of reusable heterogeneous catalysts has attracted a great deal of attention for both environmental and atom-economic reasons. In particular, a considerable amount of work has focused on reusable heavy- and rare-metal catalysts in order to limit the use and/or minimize the generation of problematic metal waste upon disposal. Herein is reported the development of a new polysiloxane-linked m-carbaboranylmercury (SiCB–Hg) catalyst, which can be used for various mercury salt-induced reactions such as the regioselective cyclization of 1,3-dienes and allyl alcohols, the intermolecular amination of allyl alcohols with sulfamates, and the cycloisomerization of alkynes. The catalyst can be completely recovered by simple filtration, with residual mercury in the filtrate

Hg(OTf)2-catalyzed aryl–allene cyclization accompanied by formation of a quaternary carbon center has been realized. Deuterium-labeling experiments and computational modeling were used to propose a novel catalytic pathway involving direct H-transfer from the aromatic ring to the vinyl mercury moiety followed by mercury 1,2-migration.

An efficient method for carbon–nitrogen bond formation between ally silyl ethers and N,N-acyltosylhydrazine was developed under very mild conditions using 2 mol% of mercuric triflate [Hg(OTf)2] as a catalyst. This method does not require the use of any ligand system or supplementary additives and is applicable to the preparation of various N-allylhydrazides with good to excellent yields.

The title salt efficiently promotes the formation of pyrrolidine, piperidine, indole, quinoline, isoquinoline, and tetrahydronaphthalene derivatives.

The combination of carbaboranylmercuric chloride (new type of bulky Lewis acid) and silver triflate efficiently catalyzes cycloisomerization of 1,3-dienes at room temperature. The catalytic system gives allyl-substituted azacycles and cycloalkanes in excellent yields with high to complete regioselectivity.

Speaker authentication has received much attention recently in biometrics authentication technology since it needs only microphones and telephone networks which are standard equipments for voice communication and widely used. However, there are problems where speaker authentication systems are sensitive to noise. Thus, Iijima et al. [7] attempted to utilize bone-conducted speech that is robust against noise, instead of airconducted speech. Additionally, a speech transformation method was suggested for improving the authentication accuracy in highly noisy environments. In this paper, we analyze the problem of Iijima's speech transformation method and propose two new speech transformation methods. Experiments verify that the proposed speech transformation methods are effective in highly noisy environments.

Workshop on research and development of JIEDI (JAXA Ion Engine Development Initiatives) tool for numerical evaluation of ion engine grid lifetime, The plasma parameters, electron number density and electron energy distribution function, in a miniature microwave discharge ion thruster were successfully measured by means of laser Thomson scattering without perturbations. A photon counting method and a double monochromator were used against small Thomson scattering signal and strong stray laser light. The result shows an electron energy distribution function is Maxwellian, since the scattered spectrum can be fitted by Gaussian at the temperature of 1.5 eV. An electron density is 2.3 x 10(sup 18) m(exp -3). The measured electron number density and electron temperature values were found to be reasonable compared with estimation deduced form extracted ion beam current., 資料番号: AA0064642006, レポート番号: JAXA-RR-09-004

In order to improve the thrust performance of a miniature microwave discharge ion thruster, the relationship between electron number density/temperature and operational conditions, mass flow rate, incident microwave power and magnetic field strength were measured by means of laser Thomson scattering. A photon counting method and a triple grating spectrometer were used against a small Thomson scattering signal and a strong stray laser light. Electron number density increased with incident microwave power and was saturated at critical incident microwave power; it was about 1.2 × 1018 m−3 at incident microwave power >8 W. In addition, electron number density increased with mass flow rate and became saturated; it was about 1.7 × 1018 m−3 at mass flow rate > 0.04 mg s−1. The electron number density gradually increased with an increase in the number of magnets, i.e. magnetic field strength. There was a sudden jump at thirteen magnets, although the thruster failed to ignite at fourteen magnets. This is because there is an optimum distance between the antenna and the electron cyclotron resonance layer. These results suggest that future improvement in thrust efficiency in miniature microwave discharge ion thrusters may come from the fine adjustment of the magnetic field configuration inside the discharge chamber.