Photocatalytic degradation of hexachlorocyclohexane (HCH) by TiO2-pillared fluorine mica

A significant effect of clay host was observed on the photocatalytic activity of TiO2; TiO2-pillared fluorine mica exhibited two orders of magnitude higher activity than TiO2 and TiO2-pillared montmorillonite for the photocatalytic degradation of gamma-HCH.     

Interaction of amphipathic model lipopeptides with phospholipid bilayers.

In order to investigate the conformation and localization of lipopeptides in lipid bilayers, a basic model peptide with a long alkyl chain, Ac-Ser-Val-Lys-Amy-Ser-Trp-Lys-Val-NHCH3 Amy-1; Amy = alpha-aminomyristic acid) was synthesized. Its interaction with neutral and acidic phospholipid bilayers was studied by circular dichroism (CD) spectroscopy, dye leakage and fluorescence measurements. Another peptide, Ac-Leu-Ala-Arg-Leu-Trp-Amy-Arg-Leu-Leu-Ala-Arg-Leu-NHCH3 (Amy-2), which was prepared previously, was used for comparison. The CD data indicated that Amy-1 took a beta-turn and/or a beta-structure in the absence and presence of liposomes. Amy-2 formed a beta-structure in aqueous solution and an alpha-helical structure in liposomes. The dye leakage ability of Amy-1 was much weaker than that of Amy-2. Fluorescence spectroscopic data suggest that the peptides are immersed in lipid bilayers. Based on these results, discussion is made in terms of localization of the peptides in lipid bilayers.     

A synthesis of heteroaromatic analogues of 1-methyl-1,2,3,4-tetrahydroisoquinoline using the Pummerer-type cyclization reaction: observation of tandem cyclization reaction

The sulfoxides 7b and 7d carrying thiophene or benzothiophene as heteroaromatic nucleophiles, when treated with trifluoroacetic anhydride at room temperature (Pummerer reaction), underwent an intramolecular alkylation in an exclusive manner to yield 4,5,6,7-tetrahydro-7-methyl-4-phenylsulfanylthieno[2,3-c]pyridine-6-carbaldehyde (10) and the corresponding benzothiophene derivative (12b) in high yields, respectively. Thus, this route provides biologically interesting nitrogen heterocycles (1b) and (2b). On the other hand, the sulfoxide (7c) carrying benzofuran as a nucleophile on reaction with TFAA yielded not only the Pummerer-type cyclization product (12a), but also the diastereoisomeric tandem cyclization products (13) and (14) having a noble 11-aza-2-oxa-7-thiatricyclo[4.3.3.0(1,5)]dodecane ring system (B). The formation of these products can be readily rationalized by the intervention of the oxonium ion intermediate (21).     

Synthesis and cationic ring‐opening polymerization of oxetane monomer containing five‐membered cyclic carbonate moiety via highly chemoselective addition of CO2

The bicyclic amidinium iodide effectively catalyzed the reaction of carbon dioxide and the epoxy‐containing oxetane under ordinary pressure and mild conditions with high chemoselectivity to give the corresponding oxetane monomer containing five‐membered cyclic carbonate quantitatively. The cationic ring‐opening polymerization of the obtained monomer by boron trifluoride diethyl ether proceeded to give linear polyoxetane bearing five‐membered cyclic carbonate pendant group in high yield. The molecular weight of the polyoxetane was higher than that of polyepoxide obtained by the cationic ring‐opening polymerization of epoxide monomer containing five‐membered cyclic carbonate. The cyclic carbonate functional crosslinked polyoxetanes were also synthesized by the cationic ring‐opening copolymerization of cyclic carbonate having oxetane and commercially available bisoxetane monomers. Analyses of the resulting polyoxetanes were performed by proton nuclear magnetic resonance, size exclusion chromatography, thermogravimetric analysis, and differential scanning calorimetry. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019 , 57, 2606–2615     

Convenient synthesis of cyclic carbonates from CO2 and epoxides by simple secondary and primary ammonium iodides as metal‐free catalysts under mild conditions and its application to synthesis of polymer bearing cyclic carbonate moiety

Hydroiodides of secondary and primary amines effectively catalyzed the reaction of carbon dioxide and epoxides under mild conditions such as ordinary pressure and ambient temperature, to obtain the corresponding five‐membered cyclic carbonates in moderate to high yields. Detailed investigation showed that the catalytic activity was highly affected by the counter anions of the ammonium salts; the iodides catalyzed efficiently the carbonate‐forming reactions, whereas the bromide and chloride counterparts exhibited almost no catalysis. We also revealed that two important factors on the amine moieties that affected the catalytic reactions. First, the catalytic activity increased with increasing bulkiness of the substituents on the ammonium nitrogen atoms. Second, the catalysis became more efficient as the parent amines become more basic. Dicyclohexylammonium iodide was the best catalyst among the ammonium salts investigated in this study. As an application of this reaction system, we synthesized homo‐ and copolymers bearing epoxide pendant groups as substrates, which were converted with high efficiency into the corresponding homo‐ and copolymers bearing cyclic carbonate pendant groups under 1 atm at 45 °C. All polymers were easily purified simply by precipitation in water, and were isolated in high yields (>95%). © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013     

Application of Pesticide Quantification in Unpolished Rice by LC-Dopant-Assisted Atmospheric Pressure Photoionization-MS

We applied liquid chromatography-dopant-assisted atmospheric pressure photoionization-mass spectrometry to quantify four distinct pesticides (isoprothiolane, fenitrothion, fthalide, and ethophenprox) in unpolished rice flour. Although the effect of acetone as a dopant on enhancement of ionization differed among the pesticides, the analytical results by LC-DA-APPI-MS with a dopant flow rate of 50 μL min^?1 were not only repeatable (relative SD < 9%, n = 3) but also comparable to those by gas chromatography–mass spectrometry.     

A validated HPLC‐fluorescence method with a semi‐micro column for routine determination of homocysteine,cysteine and cysteamine,and the relation between the thiol derivatives in normal human plasma

A semi‐micro column HPLC‐fluorescence method for routine determination of thiol derivatives such as homocysteine (Hcy), cysteine (Cys) and cysteamine (CA) is described. The thiol derivatives labeled with ammonium‐7‐fluorobenzo‐2‐oxa‐1,3‐diazole‐4‐sulfonate (SBD‐F) were isocratically separated within 12 min on a semi‐micro ODS column (Daisopak‐SP‐120‐5‐ODS‐BP) with a mixture of 25 mm acetate buffer (pH 2.00) and CH₃CN as a mobile phase. The purity and similarity of SBD‐thiols by a multi‐wavelength fluorescence detector were more than 92.3 and 96.7%. The detection limits of Hcy, Cys and CA at a signal‐to‐noise ratio of 3 were 0.16, 0.47 and 0.03 µm , respectively. Furthermore validation parameters such as accuracy, precision and robustness of the proposed method showed satisfactory results. Almost 850 plasma sample injections (range 572–1076, n = 3) for a column could be performed without differences in retention time and peak heights of labels. As an application of the proposed method, the determination of thiol derivatives in normal human plasma (n = 103) was demonstrated. The correlation coefficients between Hcy vs Cys and Hcy vs CA were 0.38 and −0.35, respectively. Copyright © 2009 John Wiley & Sons, Ltd.