Enhancement of molecular-shape selectivity in high-performance liquid chromatography through multi-anchoring of comb-shaped polymer on silica

Poly(octadecylacrylate) having plural trimethoxysilyl groups in the side chain (co-ODA(n)) was newly synthesized and immobilized onto silica through these groups. The liquid chromatographic behavior of silica-supported co-ODA(n) (Sil-co-ODA(n)) was investigated and compared with that of Sil-ODA(n), in which poly(octadecylacrylate) was immobilized through a terminal trimethoxy group at one side of the polymer main chain. Sil-co-ODA(n) showed higher selectivity for molecular shape, especially molecular planarity of PAHs than Sil-ODA(n).     

Spectroelectrochemistry of a photochromic [2.2]paracyclophane-bridged imidazole dimer: clarification of the electrochemical behavior of HABI

The photochromic behavior of the imidazole dimers can be attributable to the photoinduced homolytic cleavage of the C-N bond between the two imidazole rings. On the other hand, although the simultaneous formation of the imidazolyl radical and imidazole anion by the one-electron reduction of an imidazole dimer was reported, no definitive evidence for this electrochemical reaction has been demonstrated. We report the first direct evidence for the electrochemical generation of the imidazolyl radical from the radical anion of the imidazole dimer by conducting the UV-vis-NIR spectroelectrochemical analysis of the [2.2]paracyclophane-bridged imidazole dimer.     

Effect of externally injected radiation on amplified spontaneous emission in CO

The effect of externally injected radiation on the two-photon laser-induced amplified spontaneous emission (TP-LIASE) is reported. The wave generated via the same LIASE process in a seeder cell acts as a seeder field for the inverted medium created in a main cell. A nearly tenfold gain is achieved in the B¹ Σ ⁺ ?A¹ Π (0, 3) transition of the CO molecule. We demonstrate that the single rotational transition in the B¹ Σ ⁺ ?A¹ Π (0, 4) band is selectively amplified by injection of laser radiation. This pump and seed arrangement facilitates detection of molecular spectra by simply tuning the seed-laser frequency. The polarization effect of the input laser radiation is briefly discussed. Received: 9 June 2000 / Revised version: 2 October 2000 / Published online: 21 February 2001     

Improvement of thermochromic property at low temperatures of CuMo0.94W0.06O4 by Zn substitution

Zinc-doped copper molybdenum oxide, Zn-doped CuMo_0.94W_0.06O₄, was synthesized, and the effects of the Zn doping on the thermochromic property of CuMo_0.94W_0.06O₄ were investigated at low temperatures. X-ray diffractometry and diffuse reflectance UV–Vis spectroscopy clarified that Zn doping for CuMo_0.94W_0.06O₄ promoted the structural phase transition of the γ-phase to the α-phase of CuMo_0.94W_0.06O₄ at low temperatures and Zn-doped CuMo_0.94W_0.06O₄ exhibited a drastic color change in the temperature range of 30–70 °C. Differential scanning calorimetry also confirmed that Zn doping changed the phase transition temperature of CuMo_0.94W_0.06O₄. Consequently, Cu_1?xZn_xMo_0.94W_0.06O₄ with x?=?0.01 exhibited a larger thermal change in the diffuse reflectance spectrum in the visible light range, compared with CuMo_0.94W_0.06O₄. An appropriate Zn-doping ratio was effective for enhancing the thermochromic property of the CuMo_0.94W_0.06O₄ pigment in the visible region in the temperature range of 30–70 °C.

     

Total synthesis of murisolins and evaluation of tumor-growth inhibitory activity

Convergent total syntheses of murisolin (1), natural 16,19-cis-murisolin 2, and unnatural 16,19-cis-murisolin 3 were accomplished by asymmetric alkynylation of alpha-tetrahydrofuranic aldehyde with a diyne and Sonogashira coupling with a gamma-lactone segment as the key steps. Stereoisomers of alpha-tetrahydrofuranic aldehyde were synthesized with high optical purity and the asymmetric alkynylation of these with 1,6-heptadiyne proceeded in good yield and with high diastereoselectivity. The cell-growth inhibition profile and COMPARE analysis of the synthetic compounds 1-3 were also investigated.     

Addition reaction of zinc acetylides to thioiminium salts leading to 3-amino-1-sulfenyl-1,4-enynes

The reaction of thioiminium salts with zinc acetylides took place at 60 °C to give 3-amino-1-sulfenyl-1,4-enynes in moderate to good yields. Two molecules of acetylides were incorporated into the products. Nucleophilic attack of zinc acetylides to thioiminium salts may initially occur to form alkynyl S,N-acetals, followed by their [1,3]-rearrangement to give 3-sulfenyl-1-aminoallenes.     

Trajectory of the spectral/structural rearrangements for photo-oxidative reaction of neat ketoprofen and its cyclodextrin complex

Journal of Inclusion Phenomena and Macrocyclic Chemistry - Ketoprofen is a nonsteroidal anti-inflammatory drug used as mohrus tape which causes unwanted photosensitivity due to UV irradiation. In...     

Acyclic selenoiminium salts: isolation,first structural characterization,and reactions

[reaction: see text] A variety of selenoiminium salts were obtained by reacting the corresponding selenoamides with methyl triflate at room temperature for 30 s. All of the salts were stable under air. The structures of the selenoiminium salts were determined by X-ray molecular analysis. An aromatic selenoiminium salt reacted with BuLi (3 equiv) to give two types of ketones. In a reaction with LiAlH(4)/Te, the selenoiminium salts were converted to telluroamides.     

Synthesis, structure and antitumor activity of a water-soluble platinum complex, (1R,3R,4R,5R)-(-)-quinato(1R,2R-cyclohexanediamine)platinum (II).

The reaction of dihydroxo(1R,2R-cyclohexanediamine)platinum(II) with (-)-quinic acid gave a water soluble complex, (-)-quinato(1R,2R-cyclohexanediamine)platinum(II). The crystal structure of the complex was determined by X-ray analysis. The data indicate a chelation of the alpha-hydroxycarboxylic acid part of quinic acid to platinum(II). The complex shows moderate antitumor activity against murine leukemia L1210 at high doses (T/C x 100 = 179% at a dose of 200 mg/kg).     

Sawtooth oscillation in current-carrying plasma in the large helical device

Sawtooth oscillations have been observed in current-carrying helical plasmas by using electron-cyclotron-emission diagnostics in the Large Helical Device. The plasma current, which is driven by neutral beam injection, reduces the beta threshold of the sawtooth oscillation. When the central q value is increased due to the plasma current, the core region crashes, and, when it is decreased, the edge region crashes annularly. Observed rapid mixture of the plasma in the limited region suggests that these sawtooth crashes are reconnection phenomena. Unlike previous experiments, no precursor oscillation has been observed.