Synthesis of optically active 2-arylalkanoic acids by the use of 1,2-rearrangement of the aryl group

A new route to the synthesis of optically active 2-arylalkanoic acids was accomplished by using stereospecific 1,2-rearrangement of the aryl group in chiral 1-aryl-2-sulfonyloxyl-l-alkanone acetals.     

Time-resolved measurement of dye-sensitized photocurrent at the ZnO Electrode with a nanosecond pulsed dye laser

A time-resolved dye-sensitized photocurrent of rose bengal on a ZnO electrode consisted of two components, fast (ns) and slow (μs). From the temperature dependence of the rate, the latter was found to be due to the intermediacy of shallow surface traps.     

Electric conductivities of 1:1 electrolytes in liquid methanol along the liquid-vapor coexistence curve up to the critical temperature. II. KBr and KI solutions

The molar conductivities Lambda of KBr and KI in dilute methanol solutions were measured along the liquid-vapor coexistence curve up to the critical temperature (240 degrees C). The concentration dependence of Lambda in each condition was analyzed by the Fuoss-Chen-Justice equation to obtain the limiting molar conductivities and the molar association constants. Using the present data together with the literature ones, the validity of the Hubbard-Onsager (HO) dielectric friction theory based on the sphere-in-continuum model was examined for the translational friction coefficients zeta of the halide ions (the Cl(-), Br(-), and I(-) ions) in methanol in the density range of 2.989rho(c)> or =rho> or =1.506rho(c), where rho(c)=0.2756 g cm(-3) is the critical density of methanol. For all the halide ions studied, the friction coefficient decreased with decreasing density at rho>2.0rho(c), while the nonviscous contribution Deltazeta/zeta increased; Deltazeta was defined as the difference between zeta and the friction coefficient estimated by the Stokes law. The density dependence of zeta and Deltazeta/zeta were well reproduced by the HO theory at rho>2.0rho(c). The HO theory also explained the ion-size dependence of Deltazeta/zeta which decreased with ion-size at rho>2.0rho(c). At rho<2.0rho(c), on the other hand, the HO theory could not explain the density and the ion-size dependences of zeta and Deltazeta/zeta. These results indicated that the application limit of the HO theory lied about rho=2.0rho(c) which is the same as the application limit observed for the alkali metal ions. The present results were also compared with the results in subcritical aqueous solutions.     

Thermo-Optic Switch using Fluorinated Silicon Oxide and Organic Spin-on-Glass Films

A thermo-optic switch in a thin-film optical waveguide was investigated. Fluorinated silicon oxide (SiOF) and organic spin-on-glass (SOG) films were used as core-layer and clad-layer, respectively, in the waveguide structure. The SiOF films were formed at 23#x00B0;C by a liquid-phase deposition (LPD) technique using a supersaturated hydrofluosilicic acid (H₂SiF₆) aqueous solution. Thermal coefficients of the refractive indices for LPD-SiOF and organic SOG films formed on silicon (Si) substrates were #x2212;4.0 #x00D7; 10^#x2212;6/#x00B0;C, #x2212;60 #x00D7; 10^#x2212;6/#x00B0;C at the wavelength of 632.8 nm, respectively. A high extinction ratio of 15 dB was obtained for this switch at the applied voltage of 12.8 V.     

Synthetic Studies on Sialoglycoconjugates 49: Novel Disaccharides and Lactams Composed of Sialic Acid and 1-Deoxynojirimycin-Potential for Biomedical Application

Abstract

Sialic acid-containing glycoconjugates participate in a variety of biological functions on cell surfaces, not only serving as receptors for hormones, viruses and bacteria but also as mediators in cell growth, differentiation, adhesion, oncogenesis and so on. For example, influenza virus^1,2 and tripanosoma cruzi ^3,4 recognize sialic acid in the time of infection to animal cells. Recently, the sialyl-Le^x (sLe^x) and sialyl-Le^a (sLe^a) carbohydrate epitopes have been highlighted as the ligands for selectins, a family of cell adhesion molecules involved in leukocyte traffic^5,6 and tumor metastasis.⁷ 1-Deoxynojirimycin (DNJ) and related compounds are well known⁸ as the potent inhibitors of a-glycosidases and glycoprotein-processing enzymes. Some of the Nsubstituted DNJ derivatives have been noted as antidiabetic and anti-HIV agents.