Palladium-catalysed cascade ring expansion reaction of cyclobutanols that have a propargylic moiety with nucleophiles

Cascade ring rearrangement of four-membered ring systems containing various propargylic components by a palladium catalyst is described. The reactions of cyclobutanols that have a propargylic carbonate moiety with phenols as nucleophiles produce phenoxy-induced cyclopentanones in high yields. The reactions proceed in a regio- and diastereoselective manner to afford the substituted cyclopentanones with high selectivities. Imides also act as nucleophiles to produce the imidyl-induced products. Propargylic bromide successfully reacts with sodium alkoxides to produce the corresponding products in good yields.     

Enantioselective crystal growth of leucine on a self-assembled monolayer with covalently attached leucine molecules

Enantioselective crystal growth of leucine occurs on a solid surface modified with a self-assembled monolayer depending on the chirality of the enantiomer attached, as evidenced by the X-ray diffraction method.     

Evaluation of scopadulciol-related molecules for their stimulatory effect on the cytotoxicity of acyclovir and ganciclovir against Herpes simplex virus type 1 thymidine kinase gene-transfected HeLa cells

Herpes simplex virus type 1 thymidine kinase (HSV TK) is involved in both antiherpetic therapy and cancer gene therapy with acyclovir (ACV) and ganciclovir (GCV). Enhanced sensitivity to these drugs is advantageous in their clinical use. In the present study, scopadulciol (SDC) and its related compounds were evaluated for their stimulatory effect on the cytotoxicity of ACV and GCV by determination of selective toxicities against HSV TK-expressing HeLa cells. Although SDC remarkably potenciated the cytotoxicity of ACV and GCV, the other tested compounds showed only weak selectivity, except for compound 34.     

Dielectric study of the alpha and beta processes in supercooled ethylene glycol oligomer-water mixtures

Broadband dielectric measurements for 65 wt % ethylene glycol oligomer (EGO)-water mixtures with one to six repeat units of EGO molecules were performed in the frequency range of 10 microHz-10 GHz and the temperature range of 128-298 K. In the case of the water-EGO mixtures with one and two repeat units of the EGO molecule (small EGO), the shape of the dielectric loss peak of the primary process is asymmetrical about the logarithm of the frequency of maximum loss above the crossover temperature, T(C). The asymmetric process continues to the alpha process at a low frequency, and an additional beta process appears in the frequency range higher than that of the alpha process below T(C). In contrast, the water-EGO mixtures with three or more repeat units of the EGO molecule (large EGO) show a broad and symmetrical loss peak of the primary process above T(C). The symmetric process continues to the beta process, and an additional alpha process appears in the frequency range lower than that of the beta process below T(C). These different scenarios of the alpha-beta separation related to the shape of the loss peak above T(C) are a result of the difference in the cooperative motion of water and solute molecules. The solute and water molecules move cooperatively in the small EGO-water mixtures above T(C), and this cooperative motion leads to the asymmetric loss peak above T(C) and the alpha process below T(C). For the large EGO-water mixtures, the spatially restricted motion of water confined by solute molecules leads to the symmetric loss peak above T(C) and the beta process below T(C).     

Rapid simultaneous determination of o-phenylphenol, diphenyl, thiabendazole, imazalil and its major metabolite in citrus fruits by liquid chromatography-mass spectrometry using atmospheric pressure photoionization

A simple and rapid simultaneous analytical method of four post-harvest fungicides, o-phenylphenol (OPP), diphenyl (DP), thiabendazole (TBZ), imazalil (IMZ) and its major metabolite R14821 (IMZ-M) in citrus fruits was developed. These compounds were extracted under basic conditions with diethyl ether. The organic layer was washed with water and evaporated at moderate pressure adding methanol. These compounds were determined by liquid chromatography-mass spectrometry (LC-MS) using atmospheric pressure photoionization (APPI). The recoveries of the five compounds added to citrus fruits at 1 microg/g ranged from 67 to 100%, with relative standard deviations (R.S.D.) ranging from 2 to 8%. The detection limits (S/N = 3) were 0.01 microg/g and 0.05 microg/g (DP).     

Abstract quasilinear equations of second order with Wentzell boundary conditions

We introduce a general framework to treat abstract quasilinear equations of second order with Wentzell boundary conditions. As an example we study a wave equation for a second order quasilinear differential operator on with Wentzell boundary conditions.     

Phase-transition phenomena of 0.8 microm superfluid 3He slab

We have investigated the transition phenomena of superfluid 3He in thin 0.8 microm slabs with a cw-NMR method. We found that, just below the phase-transition temperature, only the A phase appeared at any pressure. At lower temperatures, the phase transition to the B phase occurred between 0.3 and 2.74 MPa. We obtained a universal critical thickness delta as a function of pressure. When the reduced slab thickness, d/xi(T), is smaller than delta, only the A phase becomes stable.     

Quantum feedback control of atomic motion in an optical cavity

We study quantum feedback cooling of atomic motion in an optical cavity. We design a feedback algorithm that can cool the atom to the ground state of the optical potential with high efficiency despite the nonlinear nature of this problem. An important ingredient is a simplified state-estimation algorithm, necessary for a real-time implementation of the feedback loop. We also describe the critical role of parity dynamics in the cooling process and present a simple theory that predicts the achievable steady-state atomic energies.     

pH-dependent color change of colloidal dispersions of gold nanoclusters: Effect of stabilizer

Gold nanoclusters protected by 3-mercaptopropionic acid (MPA-Au nanoclusters) were prepared by citrate-reduction of hydrogen tetrachloroaurate(III) in the presence of sodium 3-mercaptopropionate. Color of the dispersions of MPA-Au nanoclusters changed from red to purple by addition of hydrochloric acid and returned from purple to red by addition of an aqueous sodium hydroxide solution. This reversible response can be attributed to synchronized changes between dispersion and ordering of MPA-Au nanoclusters, determined by transmission electron microscopy. Gold nanoclusters protected by poly(acrylic acid) (PAA-Au nanoclusters) were prepared by UV irradiation of an aqueous solution of hydrogen tetrachloroaurate(III) in the presence of poly(sodium acrylate). The pH-dependent spectral change observed for MPA-Au was not observed for PAA-Au. UV-Vis absorption spectra of colloidal dispersions of PAA-Au nanoclusters after addition of hydrochloric acid and an aqueous sodium hydroxide solution were in good agreement with each other, suggesting the stability of PAA-Au nanoclusters to pH change. Received 18 October 2000 and Received in final form 10 April 2002