Unusual current‐voltage characteristics of single crystalline and bicrystalline La0.7Ca0.3MnO3 films

The current‐voltage characteristics of single crystalline and bicrystalline La_0.7Ca_0.3MnO₃ films were measured and analyzed. Several epitaxial films, as well as 45° [001]‐tilt grain boundaries, display current‐voltage characteristics which are asymmetric with respect to polarity reversal of the bias current. One epitaxial film has a polarity dependent resistance of ～340kΩ and of ～670kΩ in forward and in reverse direction, respectively.     

Application of dibutyltin oxide method to regioselective acylation and alkylation of tylosin at C-4'

4'-O-Acyl-, 4'-O-alkyl- and 4'-deoxy-tylosin derivatives were synthesized using 2'-O-acetyl-3',4'-O-(dibutyl-stannio)tylosin as a synthetic intermediate. The in vitro biological evaluation showed that the new derivatives were active against macrolide-resistant clinical isolates of bacteria and mycoplasmas, and that they were resistant to hepatic esterase.     

Elimination of the 4-hydroxyl group of the alkaloids related to morphine—I

Sinomenine, an alkaloid of the Japanese plant Sinomenium acutum, was converted to the 4-phenylether by the Ullmann reaction in a good yield. The Clemmensen reduction of sinomenine-phenylether and of its derivatives gave (+)-3-methoxy-4-phenoxy-N-methyl-Δ^x-morphinan.

Hydrogenation and successive sodium-liquid ammonia reduction of (+)-3-methoxy-4-phenoxy-N-methyl-Δ^x-morphinan gave (+)-3-methoxy-N-methylmorphinan.     

Elimination of the 4-hydroxyl group of the alkaloids related to morphine—II

Dihydrothebaine-φ, dihydrothebainone-Δ⁵-enol methylether and dihydrothebainone were converted to the respective 4-phenylethers by Ullmann reaction in good yields. These phenylether derivatives were reduced to 4-desoxy compounds by sodium-liquid ammonia reduction.

Clemmensen reduction of the phenylether and the desoxy derivatives gave (-)-3-methoxy-4-phenoxy-N-methyl-morphinan and (-)-3-methoxy-N-methylmorphinan respectively.     

Isolation of heptadepsin, a novel bacterial cyclic depsipeptide that inhibits lipopolysaccharide activity

Lipopolysaccharide (LPS) is considered to cause various inflammatory reactions. We searched among microbial secondary metabolites for compounds that could inhibit LPS-stimulated adhesion between human umbilical vein endothelial cells (HUVEC) and human myelocytic cell line HL-60 cells. In the course of our screening, we isolated a novel cyclic depsipeptide, which we named heptadepsin, from the whole culture broth of Paenibacillus sp. The addition of heptadepsin prior to LPS stimulation decreased HL-60 cell-HUVEC adhesion without showing any cytotoxicity. It also inhibited the cellular adhesion induced by lipid A, the active component of LPS, but it did not inhibit TNF-alpha or IL-1beta-induced cell adhesion. The result of surface plasmon resonance (SPR) analysis revealed that heptadepsin interacted with lipid A directly. Thus, heptadepsin, a novel naturally occurring cyclic heptadepsipeptide, was shown to inactivate LPS by direct interaction with LPS.     

Reaction of 4-nitro-1,2-phenylenedl4mine with 1-(4-R-phenyl)-3-(4-nitrophenyl)propenones

By the reaction of 4-nitro-1,2 phenylenediamine with 1-(p-R-phenyl)-3-(4-nitrophenyl)propenones, Michael adducts with a 1:2 composition have been obtained. A stagewise scheme is proposed for the formation of these compounds. The structure of one of the products has been established by means of x-ray structure analysis.Deceased     

Preparation of polymethyl methacrylate with well-controlled stereoregularity by anionic polymerization in an ionic liquid solvent

This study investigates the effect of ionic liquids (ILs) on the anionic polymerization of methyl methacrylate (MMA). Polymethyl methacrylate (PMMA), an isotactic polymer, is prepared by anionic polymerization at a high reaction temperature with an IL that acts as both solvent and additive. The most plausible reaction mechanism is determined using ¹H NMR and Fourier-transform infrared spectroscopy. The electrostatic interaction between MMA and the IL increases the apparent steric hindrance in MMA, resulting in the isotactic PMMA.