A chiral synthesis of four stereoisomers of 1,3-dimethyl-1,2,3,4-tetrahydroisoquinoline, an inducer of Parkinson-like syndrome

Four stereoisomers of 1,3-dimethyl-1,2,3,4-tetrahydroisoquinoline, an inducer of Parkinson-like syndrome, were synthesized by applying a new method of 1,2,3,4-tetrahydroisoquinoline (TIQ) synthesis utilizing the Pummerer reaction as a key step. The chiral centers at C-1 and C-3 were constructed by two routes starting from alaninol (3) and 1-phenylethylamine (4) as a chiral source. Enantiomerically pure 1,3-dimethyl-TIQs (1R,3S)-(2) [corrected], (1S,3R)-(ent-2) [corrected], (1S,3S)-(1) [corrected], and (1R,3R)-(ent-1) [corrected] were prepared in a stereochemically unambiguous manner from 3 in 11 steps (route I) and from 4 in 6 steps (route II). The conformations of tetrahydroisoquinoline ring in 1-methyl, 3-methyl, and 1,3-dimethyl-TIQs were discussed on the basis of their CD, 1H-NMR spectra, and steric energies.     

Investigation of the Formation and Energy Density of High-Current Pulsed Electron Beams

High-current pulsed electron beams (HCPEB) irradiation is a new potential method to polish hard steels and alloys. After HCPEB machining, the performance of machined surface, such as corrosion resistance and microstructure, has been greatly improved. Because of its good performance, HCPEB irradiation is playing more and more important roles in polishing hard steels and alloys. However, it is not clear about the energy density of HCPEB under different beam conditions. In this study, experiments have been conducted to investigate the formation of HCPEB and its energy density. Then, effects of argon gas pressure and the applied voltage to solenoid coil on the formation of HCPEB are analyzed. Finally, a mathematical model is developed to describe the relationship between five dominant beam parameters with the energy density of HCPEB, which has a good accuracy in comparison to the experimental results.     

Magnetic properties of small nickel oxide clusters enclosed inY-zeolite

The magnetization of small nickel oxide clusters containing less than four nickel atoms (sample A) and about ten atoms (sample B), respectively, formed inside the supercages ofY-zeolite, was studied in the magnetic field below 50 kOe and in the temperature range of 2 to 600 K. The magnetic susceptibility of sample A obeyed a Curie-Weiss' (C-W) law above about 20 K with a C-W temperature of 12 K. A saturation behavior was observed in the magnetization versus field (M-H) curve below about 20 K. A hysteresis in the M-H curve and a remanent magnetization were found below about 7 K. A similar behavior was observed for sample B. The observed positive C-W temperature indicates a ferromagnetic interaction between nickel ions in each cluster, which is semiquantitatively consistent with nearest neighbor ferromagnetic interactions previously reported for antiferromagnetic NiO single crystals. The hysteresis suggests an enhanced magnetic anisotropy energy in the present clusters.     

Spectrofluorimetric assays for rat liver phenol sulphotransferases I/II and III/IV based on a common substrate

A spectrofluorimetric method for the separate assay of two subgroups of rat liver phenol sulphotransferases (PSTs I and II and PSTs III and IV) has been established. The method is based on the enzyme reaction using two different concentrations of p-hydroxybenzaldehyde (10 μM for PSTs III/IV and 3 mM for PSTs I/II) as the substrate and the spectrofluorimetric determination of the product p-formylphenyl sulphate by means of its reaction with 1,4-dimethyl-3-carbamoylpyridinium chloride, a selective reagent for aromatic aldehydes without free phenolic hydroxy groups. The detection limit of the sulphate is 50–70 pmol in the enzyme reaction mixutre. The K_m values for p-hydroxybenzaldehyde with PSTs I/II and III/IV were 1.1 mM and 2.1 μM, respectively. The effects of growth and of dexamethasone treatment of rats on the liver PST activities were also studied.     

Adjacent- versus remote-site electron injection in TiO2 surfaces modified with binuclear ruthenium complexes

Nanocrystalline thin films of TiO2 cast on an optically transparent indium tin oxide glass were sensitized with ruthenium homo- and heterobinuclear complexes, [LL'Ru(BL)RuLL']n+ (n = 2, 3), where L and L' are 4,4'-dicarboxy-2,2'-bipyridine (dcb) and/or 2,2'-bipyridine (bpy) and BL is a rigid and linear heteroaromatic entity (tetrapyrido[3,2-a:2',3'-c:3",2"-h:2'",3'"-j]phenazine (tpphz) or 1,4-bis([1,10]phenanthroline[5,6-d]imidazol-2-yl)benzene (bfimbz)). The photophysical behavior of the RuII-RuII diads in solution indicated the occurrence of intercomponent energy transfer from the upper-lying Ru --> bpy charge-transfer (CT) excited state of the Ru(bpy)(2) moiety to the lower-lying Ru --> dcb CT excited state of the Ru(bpy)(dcb) (or Ru(dcb)(2)) subunit in the heterobinuclear complexes. These sensitizer diads adsorbed on nanostructured TiO2 surfaces in a perpendicular or parallel attachment mode. Adsorption was through the dcb ligands on one or both chromophoric subunits. The behavior of the adsorbed species was studied by nanosecond time-resolved transient absorption and emission spectroscopy, as well as by photocurrent measurements. In the TiO2-adsorbed samples where BL was bfimbz, the electron injection kinetics was very fast and could not be resolved because an electron is promoted from the metal center to the dcb ligand directly linked to the semiconductor. In the TiO2-adsorbed samples where BL was tpphz, for which, in the excited state, a BL localization of the lowest-lying metal-to-ligand charge transfer (MLCT) is observed, slower injection rates (9.5 x 10(7) s(-1) in [(bpy)(2)Ru(tpphz)Ru(bpy)(dcb(-))](3+)/TiO2 and 5.5 x 10(7) s(-1) in [(bpy)(dcb)Ru(tpphz)Ru(bpy)(dcb(-))](3+)/TiO2) were obtained. Among the systems, the heterotriad assembly [(bpy)(2)Ru(bfimbz)Ru(bpy)(dcb(2-))](2+)/TiO2 gave the best photovoltaic performance. In the first case, this was attributed to a fast electron injection initiated from a dcb-localized MLCT; in the second case, this is attributed to improved molecular orientation on the surface, which was due to rigidity and, at the same time, linearity of the heterotriad system, resulting in a slower charge recombination between the injected electron and the hole.     

The Christiansen effect of brightly colored colloidal dispersion with an amphiphilic polymer

A novel coloration phenomenon in a colloidal dispersion with an amphiphilic polymer was found. The dispersion consists of tetrahydrofuran (THF), an aqueous solution of sodium thiosulfate (Na(2)S(2)O(3).5H(2)O), and hydroxypropylcellulose (HPC). The dispersion was emulsified by HPC as an amphiphilic polymer, so that the aqueous phase was confined in droplets in the THF matrix. It typically appeared bluish violet at room temperature and turned into blue with increasing temperature. In this system, the refractive indices of the inside and outside of the droplet coincided at a certain wavelength at which the light passes through without scattering, which is called the Christiansen effect. The color observed was successfully simulated by Mie's scattering theory in combination with the Christiansen effect.     

Characterization of aggregate structures of phospholipid in the process of vesicle solubilization with sodium cholate using laser light scattering method

The aggregate structures formed during vesicle solubilization by sodium cholate, and their properties, were characterized by static laser light scattering (SLS) and electrophoretic light scattering (ELS) methods. The change in dissymmetry value Z₄₅ was observed by examining the regions of vesicles and micelles. The angular light scattering intensity data could be fitted with a modified shell model for the vesicles and a hollow cylinder model for the mixed micelles. In the case of the vesicles, the scattering curves were fitted with a spherical shell model by introducing the interparticle scattering factor S(q) and taking into account the intervesicle positional correlations, which is a function of the fractal dimension (D) and the interparticle correlation length (L). On the basis of the physical meanings of the fractal dimension and interparticle correlation length, the molecular packings of the membrane and the repulsive interaction between the vesicles were analyzed. Furthermore, using electrophoretic light scattering (ELS) the zeta potentials on the mixed vesicles were found to increase with the molar ratio (Re) of sodium cholate to egg yolk phosphatidylcholine (EggPC) in the membrane. It is suggested that the electrostatic properties of the vesicles result in repulsive interaction which is responsible for no fusion of the mixed vesicles. In addition, in the transition from vesicles to micelles, a cylinder-like micelle appeared as an intermediate structure.     

Synthesis of new chiral sulfinyldiacetic acid derivatives and attempt at chemoselective asymmetric Pummerer reaction

(R(S))-1 (85% ee) was prepared by utilizing a porcin pancreatic lipase-promoted hydrolysis of sulfinyldiacetic acid dimethyl ester (8) which was derived from thiodiacetic acid (7). (R(S))-1 (99% ee) and (S(S))-1 (99% ee) were readily obtained by methanolysis of (R(S),S)-12 and (S(S),S)-12 with MeONa in MeOH. (R(S),S)-12 and (S(S),S)-12 were furnished by chromatographic separation of the diastereomeric mixture, obtained by oxidation of thiodiacetic mono-carboxylic acid (11) with 30% H2O2 followed by dehydrative condensation of the resultant sulfinyldiacetic mono-carboxylic acid with 4(S)-isopropyl-1,3-thiazolidine-2-thione. (R(S))-1 (99% ee) was successively treated with (TMS)2NLi, Ac2O, and TMSOTf to give a major chiral-3 product in 75% ee and in a highly chemoselective manner (chiral-3:chiral-2=93:7).