Apparent anomalous behavior of polar substituents on the benzene ring in the regioselectivity of di-π-methane rearrangement of 5,6-benzo-2-azabicyclo[2.2.2]octadienones

Polar substituent effects on the aromatic ring emerge in the regioselectivity of the di-π-methane rearrangement of the title compounds when they possess the structural feature of including the bridgehead carbon in a saturated ring; the importance of the environment at the bridgehead carbon is pointed out.     

Circular dichroism of hydrolysable tannins-II dehydroellagitannins

The CD spectra of dehydroellagitannins and related compounds have empirically shown that the absolute configuration at C-1′ of the dehydrohexahydroxydiphenoyl group can be determined by the Cotton effect around 200 nm.     

Ultra-low intensity electron beams of a linear accelerator for irradiation

Ultra-low intensity electron pulsed beams for irradiation have been developed by the use of the electron linear accelerator at Radiation Research Center of Osaka Prefecture University. The energy and the pulse width of the beams are about 4–12 MeV and 0.5–4 μs, respectively. The minimum beam charge has been estimated to be about several aC/pulse. These electrons are basically mono energetic, controllable, collimated and synchronized with the master oscillator of the accelerator, which are favorable features for various uses compared with β-ray sources. Especially, the system is suitable for evaluation of response of radiation detectors. In this study, the response of the TLD for high energetic electron irradiation was also evaluated by the use of these electrons.     

Aluminium alkyl complexes supported by [OSSO] type bisphenolato ligands: synthesis, characterization and living polymerization of rac-lactide

Aluminium alkyl complexes [(OSSO)AlR](1-3: R = Me, Et) were isolated in good yields from the protonolysis reaction of AlR3 with the corresponding tetradentate 1,omega-dithiaalkanediyl-bridged bisphenols (1,4-dithiabutanediyl-bis(6-tert-butyl-4-methylphenol), etbmpH2; ortho-xylylenedithio-bis(6-tert-butyl-4-methylphenol), xytbmpH2). The monomeric structures of all three complexes were confirmed by X-ray diffraction studies. Complexes 1 and 2 have an isotypic packing arrangement. The aluminium center is coordinated by the etbmp ligand and one alkyl group with distorted trigonal bipyramidal geometry. Complex 3 shows Cs symmetry with square pyramidal geometry around the metal center. Substitution reaction of complex 1 with trityl alcohol gave the monomeric alkoxide complex [(etbmp)Al(OCPh3)] 4, which has a similar trigonal bipyramidal geometry around the aluminium atom as complex 1. In the presence of isopropanol, complexes 1-3 initiated the living ring-opening polymerization of rac-lactide (PDI = 1.03-1.06, Mw/Mn). The ligand structure influenced the tacticity of the obtained polymer, with complex 3 giving heterotactic-enriched polylactides.     

Determination of atropine in biological specimens by high-performance liquid chromatography

A sensitive and selective method for the determination of atropine in biological specimens has been developed. Samples alkalinized with sodium hydroxide were extracted with dichloromethane, and the organic phase was evaporated in a water-bath at 50 degrees C for ca. 10 min. The residue was dissolved in the mobile phase and injected into a reversed-phase column (TSK gel ODS-120A). The retention time for atropine could be varied by changing either the acetonitrile-water ratio in the mobile phase or the pH of the mobile phase. Acetonitrile-water (2:8, v/v) containing 6 mM phosphoric acid was used as mobile phase. Samples of 200 microliters or less were injected into the chromatography and measured at 215 nm. The recoveries of atropine added to drug-free specimens were satisfactory with coefficients of variation of 4% or less. Ninety-two compounds tested did not interfere with the assay of atropine. The method has been applied for monitoring atropine concentrations in cases of organophosphate and drug poisoning.     

Cationic rare-earth metal trimethylsilylmethyl complexes supported by THF and 12-crown-4 ligands: synthesis and structural characterization

To expand the limited range of rare-earth metal cationic alkyl complexes known, a series of mono- and dicationic trimethylsilylmethyl complexes supported by THF and 12-crown-4 ligands with [BPh4]-, [BPh3(CH2SiMe3)]-, [B(C6F5)4]-, [B(C6F5)3(CH2SiMe3)]-, and [Al(CH2SiMe3)4]- anions were prepared from corresponding neutral precursors [Ln(CH2SiMe3)3Ln] (Ln = Sc, Y, Lu; L = THF, n = 2 or 3; L = 12-crown-4, n = 1) as solvent-separated ion pairs. The syntheses of the monocationic derivatives [Ln(CH2SiMe3)2(12-crown-4)n(THF)m]+[A]- are all high yielding and proceed rapidly in THF solution at room temperature. A "one pot" procedure using the neutral species directly for the syntheses of a number of lutetium and yttrium dicationic derivatives [Ln(CH2SiMe3)(12-crown-4)n(THF)m]2+[A]-2 with a variety of different anions, a class of compounds previously limited to just a few examples, is presented. When BPh3 is used to generate the ion triple, the presence of 12-crown-4 is required for complete conversion. Addition of a second equiv of 12-crown-4 and a third equiv of [NMe2PhH]+[B(C6F5)4]- abstracts a third alkyl group from [Ln(CH2SiMe3)(12-crown-4)2(THF)x]2+[B(C6F5)4]-2 (Ln = Y, Lu). X-ray crystallography and variable-temperature (VT) NMR spectroscopy reveal a structural diversity within the known series of neutral 12-crown-4 supported tris(trimethylsilylmethyl) complexes [Ln(CH2SiMe3)3(12-crown-4)] (Ln = Sc, Y, Sm, Gd-Lu) in the solid and solution states. The X-ray structure of [Sc(CH2SiMe3)3(12-crown-4)] exhibits incomplete 12-crown-4 coordination. VT NMR spectroscopy indicates fluxional 12-crown-4 coordination on the NMR time scale. X-ray crystallography of only the second structurally characterized dicationic rare-earth metal alkyl complex [Y(CH2SiMe3)(12-crown-4)(THF)3]2+[BPh4]-2 shows exocyclic 12-crown-4 coordination at the 8-coordinate metal center with well separated counteranions. 11B and 19F NMR spectroscopy of all mono- and dicationic rare-earth metal complexes reported demonstrate that the anions are symmetrical and noncoordinating on the NMR time scale. A series of trends within the 1H and 13C{1H} NMR resonances arising from the Ln-CH2 groups and, in the case of yttrium, the 1JYC coupling constants at the Y-CH2 group and the 89Y chemical shift values are discussed.     

Synthesis and characterization of manganese and rhenium tricarbonyl complexes with (O,O,O)-donor ligands

Complexes of the type [(C₅H₅)Co{P(O)R₂}₃]^?, R = OCH₃, OC₂H₅, react as tridentate oxygen ligands L^? with [MBr(CO)₅], M = Mn, Re, in hexane or tetrahydrofuran to give the tricarbonyl derivatives [LM(CO)₃]. The slightly volatile yellow crystalline compounds have been characterized by elemental analysis, ¹H NMR, IR and mass spectra. The low CO stretching frequencies indicate that the ligands L^? are good π-donor ligands.     

Time-dependent complex formation of dendritic poly(L-lysine) with plasmid DNA and correlation with in vitro transfection efficiencies

Dendritic poly(L-lysine) of the 6th generation shows high transfection efficiency into several cultivated cells with low cytotoxicity. In order to understand the mechanism of complex formation with plasmid DNA, the complex was observed using atomic force microscopy. After mixing for 15 min, 1-2 microns assemblies of complexes composed of several small particles (50-200 nm) were observed. At the same time, individual small complexes of 50 to 500 nm were observed on a mica surface. After incubation for 2 h, only the large complexes were found on the mica surface. As a result of further dynamic light scattering analysis and measurement of the transfection efficiency at different time points, the transfection efficiency of KG6 was found to increase with increasing size of the DNA-complexes. This result indicates that large complexes of more than 1 micron are major species that contribute to transfection in vitro.     

Quantitative measurements of oxidative stress in mouse skin induced by X-ray irradiation

To find efficient methods to evaluate oxidative stress in mouse skin caused by X-ray irradiation, several markers and methodologies were examined. Hairless mice were irradiated with 50 Gy X-rays and skin homogenates or skin strips were prepared. Lipid peroxidation was measured using the skin homogenate as the level of thiobarbituric acid reactive substances. The level of lipid peroxidation increased with time after irradiation and was twice that of the control at 78 h. ESR spectra of skin strips showed a clear signal for the ascorbyl radical, which increased with time after irradiation in a manner similar to that of lipid peroxidation. To measure levels of glutathione (GSH) and its oxidized forms (GSSG) simultaneously, two HPLC methods, sample derivatization with 1-fluoro-2,4-dinitrobenzene and detection with a UV detector (method A) and no derivatization and detection with an electrochemical detector (method B), were compared and the latter was found to be better. No significant change was observed within 24 h after irradiation in the levels of GSH and GSSG measured by method B. The GSH/GSSG ratio may be a less sensitive parameter for the evaluation of acute oxidative stress caused by X-ray irradiation in the skin. Monitoring the ascorbyl radical seems to be a good way to evaluate oxidative stress in skin in vivo.     

A spectroscopic study on defluorination of poly(tetrafluoroethylene) by alkyllithium/electron-donating solvents

Defluorination of PTFE by alkyllithium/electron-donating solvents such as N,N,N',N'-tetramethylethylenediamine (TMEDA), hexamethylphosphoramide (HMPA) was studied by means of spectroscopy such as ESR, 7Li- and 13C-NMR, XPS, UV-Vis and IR. Based on the experimental results, it was concluded that an electron from radical species, which was generated in the alkyllithium/electron-donating solvent, was transferred onto PTFE molecule so as to eliminate fluorine atoms from the PTFE and to form carbon-centered radicals on the PTFE; concomitantly, the alkyl group of the alkyllithium was transferred onto the PTFE. Combined with the experimental results of the phenyllithium/HMPA system, mechanism of the fluorine atom elimination reactions from PTFE by the radical species is discussed.