Visible-Light-Induced Synthesis of 1,2,3,4-Tetrahydroquinolines through Formal [4+2] Cycloaddition of Acyclic α,β-Unsaturated Amides and Imides with N,N-Dialkylanilines

1,2,3,4-Tetrahydroquinolines should be applicable to the development of new pharmaceutical agents. A facile synthesis of 1,2,3,4-tetrahydroquinolines that is achieved by a photoinduced formal [4+2] cycloaddition reaction of acyclic α,β-unsaturated amides and imides with N,N-dialkylanilines under visible-light irradiation, in which a new Ir^III complex photosensitizer, a thiourea, and an oxidant act cooperatively in promoting the reaction, is reported. The photoreaction enables the synthesis of a wide variety of 1,2,3,4-tetrahydroquinolines, while controlling the trans/cis diastereoselectivity (>99:1) and constructing contiguous stereogenic centers. A chemoselective cleavage of an acyclic imide auxiliary is demonstrated.     

Formation of dinuclear copper(II) complex with N,N,N',N'-tetrakis(2-pyridylmethyl)-1,2-ethanediamine in aqueous solution

The polynuclear complexation of divalent 3d transition metal cations with N,N,N',N'-tetrakis(2-pyridylmethyl)-1,2-ethanediamine (tpen) in aqueous solution was investigated. It was found that copper(II) forms a dinuclear complex with tpen in an aqueous solution containing chloride. The composition of the complex was determined as Cu(2)Cl(2)(tpen)(2+). Furthermore, the stability constant of the complex was determined and its structure was postulated to be (mu-Cl)(2).     

Comparison of the effects of different antiviral treatments on the antioxidant systems of stroma-free hemoglobin

The effect of virus inactivation by 1,9-dimethylmethylene blue (DMMB) phototreatment, methylene blue (MB) phototreatment or heat on the activities of antioxidant systems of stroma-free hemoglobin (SFH) was studied. DMMB photoinactivated human immunodeficiency virus by > 3.69 log10 under conditions that inactivated 3.33 log10 of vesicular stomatitis virus (VSV). Under conditions which inactivated VSV by 6.10 log10 (1.37 J/cm2 irradiation and 2 microM DMMB), there was little change in the methemoglobin (Met-Hb) formation, concentration of reduced glutathione (GSH), or superoxide dismutase (SOD), catalase (CAT) or glutathione peroxidase (GPX) activities. However, the activity of glutathione reductase (GR) was decreased by 77%. Under conditions that inactivated VSV by 5.69 log10 (1.37 J/cm2 irradiation and 24 microM MB) there was little effect of MB phototreatment on SOD, CAT, GPX and GSH activities. However, GR activity was decreased by 74% and Met-Hb content reached 3.98%. Under conditions that inactivated VSV by more than 6.20 log10 (60 degrees C for 2 min), virucidal heat treatment resulted in 27% Met-Hb formation and decreased GPX activity by 43%. No significant decline in SOD, CAT or GR activities or GSH concentration was observed. These results suggest that, compared with heat treatment and MB phototreatment, virucidal DMMB treatment preserves not only the oxidative state of hemoglobin but also the antioxidant systems against superoxide and hydrogen peroxide, although the reduced GR activity may limit the quenching capacity of antioxidants in DMMB-treated SFH.     

A simple and highly repeatable colorimetric toxicity assay method using 2,6-dichlorophenolindophenol as the redox color indicator and whole eukaryote cells

A simple and highly reproducible toxicity assay method was studied by employing 2,6-dichlorophenolindophenol (DCIP) as a redox color indicator, baker’s yeast Saccharomyces cerevisiae, and a thermostable three-consecutive-stir unit. The absorbance of DCIP was decreased by increasing the metabolism activity of S. cerevisiae to intake glucose as an organic substance. By optimizing the measurement conditions, we obtained highly sensitive responses to glucose between 0.75 and 30 mg/L (eight points, n = 3) with an incubation time of the reaction mixture of 10 min at 30 °C. An excellent value of 1.15% was obtained as the average of the repeatability from eight points. Next, for the characterization of this method, we investigated the influence on the colorimetric response of dissolved substances, such as inorganic ions and surfactants, in natural water. Furthermore, the colorimetric responses to several toxicants were examined using Cu²⁺, Mn²⁺, Zn²⁺, Cr³⁺, and Fe³⁺ as heavy-metal ions and simazine as an agricultural chemical. As a result, notable colorimetric responses were obtained for Cu²⁺ and Mn²⁺ at several concentrations, and the results were compared with those obtained using river water as a real sample. In the stability test, responses to 30 mg/L glucose were obtained for 28 days when the yeast cell suspension was stored at 4 °C (response reduction, 43.9%; average of the relative standard deviation for nine testing days, 22.7%; average of repeatability, 1.01%). Figure Graphical image of the colorimetric toxicity assay     

Synthesis and characterization of polyester dendrimers from acetoacetate and acrylate

New aliphatic polyester-type dendrimers were synthesized using a new AB2-type building block 3, prepared from benzyl acetoacetate and 2 equiv of tert-butyl acrylate by acetoacetic acid ester synthesis. The reiterative [deprotection by HCO2H, then EDCI/DMAP coupling] sequence using divergent growth method gave [G1]-4tBu-[G5]-64tBu dendrimers. 13C NMR relaxation time (T1) measurements on the carboxy carbons show that the extended chain conformations are predominant in CDCl3. [structure: see text]     

Inclusion Complexation of a Seleno-Organic Antioxidant, Ebselen, with Cyclodextrins in Aqueous Solution

The interaction of ebselen, 2-phenyl-1,2-benzisoselenazol-3(2H)-one, a novel neuroprotective agent, with cyclodextrins (CyDs) in aqueous solution was studied by the solubility method and spectroscopic methods. The ability of sulfobutyl ether -CyD (SBE7--CyD, average degree of substitution= 6.2) to solubilize ebselen was greater, and its stability constant (> 2000 M^-1) was significantly higher than those (< 1000 M^-1) of other CyD complexes employed. The stability constant of the complexes rose as hydrophobicity of the substituents of CyDs increased, whereas it was negligibly affected by change in ionic strength of the medium, indicating a significant contribution of hydrophobic interaction in the complexation. SBE7--CyD gave positive and negative CD bands at around 320 and 350 nm, respectively, indicating that the guest is embedded in the asymmetric locus of the CyD cavity. ¹H-NMR spectroscopic studies suggested that the mono-substituted benzene ring of ebselen is preferably included in the cavity of SBE7--CyD. The results indicate that SBE7--CyD is useful as a solubilizing agent for ebselen.     

Phosphorylcholine (PC)-bonded protein A affinity chromatographic medium for high-throughput purification with reduced non-specific protein adsorption

A protein A affinity chromatographic medium based on porous silica modified with phosphorylcholine (PC) groups and amino groups (PNSP) was synthesized. The PC groups functioned as suppressors of non-specific protein adsorption. Recombinant protein A was bound to the amino groups on PNSP with a glutaraldehyde used as a spacer (PNSP-PA). The PC groups and amino groups were immobilized on porous-silica particles using two silane coupling reagents, PC-bound silane, and 3-aminopropyltrimethoxysilane. After optimizing various factors in the synthetic process, the resultant protein A medium showed improvements in non-specific protein adsorption, dynamic binding capacity, and chemical stability under basic conditions compared with conventional protein A affinity media.     

Resistance fluctuations in integer quantum-Hall transitions

We have studied the resistance fluctuations (RF) in integer quantum-Hall transitions for high-mobility two-dimensional electron gas systems. The role of coherence in RF is examined by investigating the conductance through two scattering regions, that are spatially separated but interfere quantum-mechanically with each other. The phase coherence does not play a substantial role in determining the pattern of RF, whereas it affects the amplitude of RF.