Total synthesis of merrilactone A

Merrilactone A (1) has been shown to possess neurotrophic activity and thus is expected to hold therapeutic potential in the treatment of neurodegeneration diseases. In this paper, we report the total synthesis of (+/-)-1, employing, as key steps, a novel desymmetrization protocol of meso-diketone to construct the core cis-bicyclo[3.3.0]octyl system of 1 (3 --> 2) and a radical cyclization to install the highly congested C9-quaternary carbon (16 --> 17).     

Multicolor photochromism of two- and three-component diarylethene crystals

Novel photochromic single crystals composed of three different kinds of diarylethenes, 1,2-bis(3,5-dimethyl-2-thienyl)perfluorocyclopentene (1a), 1,2-bis(2,5-dimethyl-3-thienyl)perfluorocyclopentene (2a), and 1,2-bis(2-methyl-5-p-methoxyphenyl-3-thienyl)perfluorocyclopentene (3a), have been prepared. The three-component crystals turned yellow, orange, red, purple, blue, green, or black upon irradiation with light of appropriate wavelengths. The colors of the crystals were thermally stable in the dark and completely bleached by irradiation with visible light. Such multicolored photochromic crystals have potential for the application to optoelectronic devices, such as multifrequency three-dimensional optical memory media or full-color displays.     

Synthesis of monodispersed silica nanoparticles with high concentration by the Stöber process

Silica nanoparticles with high concentration were prepared by the sol–gel process based on the Stöber method using tetraethoxysilane as a starting material. It was found that silica sol with about 4 wt% in concentration and with a diameter of about 10 nm was obtained by controlling the reaction conditions in the Stöber process. By removing the solvent under a reduced pressure, the particle concentration was increased up to 15 wt% without aggregation.     

Investigation of radon and thoron concentrations in a landmark skyscraper in Tokyo

The temporal variation of the radon concentration, and the radon and thoron concentrations every 3 months for a year were measured using two types of devices in a landmark skyscraper, the Tokyo Metropolitan Government Daiichi Building. In the measurement of temporal variation of the radon concentration using a pulse type ionization chamber, the average radon concentration was 21 ± 13 Bq m^?3 (2–68 Bq m^?3). The measured indoor radon concentration had a strong relationship with the operation of the mechanical ventilation system and the activities of the office workers. The radon concentration also increased together with temperature. Other environmental parameters, such as air pressure and relative humidity, were not related to the radon concentration. In the long-term measurements using a passive radon and thoron discriminative monitor, no seasonal variation was observed. The annual average concentrations of radon and thoron were 16 ± 8 and 16 ± 7 Bq m^?3, respectively. There was also no relationship between the two concentrations. The annual average effective dose for office workers in this skyscraper was estimated to be 0.08 mSv y^?1 for 2000 working hours per year. When considering the indoor radon exposure received from their residential dwellings using the annual mean radon concentration indoors in Japan (15.5 Bq m^?3), the annual average effective dose was estimated to be 0.37 mSv y^?1. This value was 31 % of the worldwide average annual effective dose.     

Design of chiral bis-phosphoric acid catalyst derived from (R)-3,3'-di(2-hydroxy-3-arylphenyl)binaphthol: catalytic enantioselective Diels-Alder reaction of α,β-unsaturated aldehydes with amidodienes

Chiral bis-phosphoric acid 1 was designed to identify a new class of structural features in chiral Br?nsted acid catalysts. X-ray diffraction analysis revealed the single atropisomer 1, bearing S axial chirality at 3,3'-biaryl substituents on (R)-binaphthyl and intramolecular hydrogen bonding between the two phosphoric acid moieties. The newly designed bis-phosphoric acid 1 was evaluated in the Diels-Alder reaction of α,β-unsaturated aldehydes 4 with 1-N-acylamino-1,3-butadienes 3. After systematic variation of the catalyst substituents, as well as the N-acyl substituents of 1,3-butadiene, the use of an N-Cbz amidodiene 3a in the presence of bis-phosphoric acid 1e with a 2,4,6-tri-isopropylphenyl group was found to be optimal to yield the 1S,6R enantiomeric product 5aa in a Diels-Alder reaction of acrolein (4a). Application of this method to substituted substrates was found to be an efficient approach to the enantioselective synthesis of 3- and 3,6-substituted cyclic formylcarbamates 5. The specific character as well as the utility of 1e was further established by comparing its enantioselectivity, absolute stereochemistry, and catalytic efficiency with those of mono-phosphoric acid 2.     

Identification of Shiga toxins in Shiga toxin-producing Escherichia coli using immunoprecipitation and high-performance liquid chromatography-electrospray ionization mass spectrometry

We developed a rapid and reliable identification method for Shiga toxins in Shiga toxin-producing Escherichia coli (STEC) using immunoprecipitation and high-performance liquid chromatography-electrospray ionization mass spectrometry (HPLC-ESI-MS). Polyclonal antisera specific for Shiga toxin 1 (Stx1) and Shiga toxin 2 (Stx2) were raised in rabbits so as to be used for the immunoprecipitation. The immunoprecipitaion was carried out by mixing sample solutions with 50 microl each of the antisera to Stx1 and Stx2 followed by allowing the mixed solutions to stand for 30 min. The quantity required to obtain the immunoprecipitate was more than 0.5 microg of Shiga toxins. HPLC-ESI-MS analysis of the resulting immunoprecipitates provided accurate molecular weight information on Shiga toxins, leading to direct evidence for the presence of these toxins. It requires at most two days to perform our procedure from toxin extraction to measurement of HPLC-ESI-MS whereas the previous method using isolation procedures required about two weeks to complete. The usefulness of the present method has been demonstrated by identifying Stx1, Stx2 and a variant of Stx2 (Stx2e) in the immunoprecipitates prepared from STEC strains.     

Adsorbed water for the electro-oxidation of methanol at Pt-Ru alloy

Adsorbed water molecules which promote the methanol oxidation reaction (MOR) at Pt-Ru alloy electrode are clearly detected by in-situ FTIR spectroscopy with the attenuated total reflection configuration, which directly supports the "bi-functional mechanism" for the MOR.     

Highly proton conductive polyimide electrolytes containing fluorenyl groups

Novel sulfonated polyimides containing fluorenyl groups show good thermal and oxidative stability as well as a high proton conductivity of 1.67 S cm(-1) at 120 degrees C and 100% RH.