2-alkoxy and 2,2-dialkoxy nitriles from acetals and orthoesters — exchange of alkoxy into cyano group by means of cyanotrimethylsilane

Title transformation is accomplished by the catalytic action of SnCl₂ or BF₃·OEt₂ Lithio derivative of 2,2-dimethoxyacetonitrile is used as synthetic equivalent of methyl lithioformate.     

Importance of single electron-transfer in singlet oxygen reaction in aqueous solution : Oxidation of electron-rich thioanisoles

Oxidation of substituted thioanisoles by chemically generated singlet oxygen was investigated in polar aqueous media. The formation of the superoxide ion was observed during sulphoxidation of 4-hydroxythioanisole (4) in phosphate buffer at pH 7.5. Control experiments indicated that the superoxide ion was formed by a direct reaction between singlet oxygen and 4. The kinetics of the trapping reaction by diphenylsulphoxide indicated the involvement of a single intermediate. The overall rate constants of the reaction of thioanisoles with singlet oxygen in methanol-water (1:1) are one order of magnitude larger than those in benzene. On the basis of these results, a mechanism involving a charge-transfer complex has been proposed for the reaction of electron-rich thioanisoles with singlet oxygen, whereby the charge-transfer complex would produce persulphoxide directly or dissociate to the cation radical and superoxide ion in polar aqueous media.     

Studies on antiulcer drugs. VI. 4-Furyl-2-guanidinothiazoles and related compounds as potent histamine H2-receptor antagonists.

A series of 4-furyl-2-guanidinothiazole derivatives and related compounds were synthesized and evaluated for histamine H2-receptor antagonist and gastric acid antisecretory activities. Among them, compounds I-17, I-48 and I-49 showed high activities in these tests. In addition, compound I-17 possessed potent inhibitory activities on each of the gastric ulcers induced by stress, ethanol and HCl-aspirin. On the other hand, compound I-48 demonstrated antimicrobial activity against Helicobacter Pylori and the potency was far stronger than that of clinically used H2-antagonists. Some structure-activity relationships are discussed.     

Effects of Shosaikoto (kampo medicine) on lipid metabolism in macrophages.

We investigated effects of Shosaikoto treatment on cholesterol metabolism in macrophages. Although macrophages, harvested from mice treated with Shosaikoto, took up a small amount of control low density lipoprotein (LDL) (thiobarbituric acid-reactive substance (TBA-RS) value was 0.27 pmol/mg of protein) as control macrophages, they took up more LDL modified with CuSO4 (TBA-RS value was 6.12 pmol/mg of protein) than control macrophages. Degradation of both control LDL and oxidized LDL was enhanced in Shosaikoto treated macrophages. In the presence of control LDL or in the absence of LDL, incorporation of [3H]oleic acid into chlesteryl oleate was significantly reduced in Shosaikoto treated macrophages. This suggests that acyl-coenzyme A:cholesterol acyltransferase (ACAT) activity in macrophages was partly inhibited by Shosaikoto treatment. On the other hand, in the present of oxidized LDL, cholesteryl ester accumulated in Shosaikoto treated macrophages as much as in controls. However, cholesteryl oleate efflux from macrophages in the presence of high density lipoprotein (HDL) was enhanced in Shosaikoto treated macrophages. These result indicate that Shosaikoto facilitates oxidized LDL catabolism in macrophages, resulting in the augmentation of oxidized LDL uptake and the elimination of cholesterol from macrophages by HDL. These Shosaikoto effects may prevent foam cell formation and the progression of atherosclerotic lesions.     

Alternating copolymers consisting of arylalkyl methacrylates. I. Fluorescence properties of poly(arylalkyl methacrylate-alt-styrene) in organic solution

Alternating and random copolymers of 9-phenanthrylmethyl methacrylate or 2-(9-carbazolyl)ethyl methacrylate with styrene were synthesized and their fluorescence properties were examined. There was no noticeable difference in the spectral features of the alternating and random copolymers in tetrahydrofuran (THF), demonstrating that this type of polymers have no quenching sites in the polymer chains. The fluorescence quenching studies indicated that the alternating copolymers permitted singlet-state energy migration as efficiently as the corresponding random copolymers but less efficiently than the random copolymers with higher chromophore contents. These results strongly suggest that to be chromophores close to each other is most important for facilitation of an intramolecular energy migration. © 1995 John Wiley & Sons, Inc.     

Synthesis and application of chiral bisphosphines through lithiation-conjugate addition tandem cyclization of chiral alpha,beta,psi,omega-unsaturated bisphosphine oxide

Upon treatment with lithium diisopropylamide achiral and chiral alpha,beta,psi,omega-unsaturated bisphosphine oxides underwent lithiation-conjugate addition tandem cyclization to afford the corresponding endo-alpha,beta-unsaturated cyclic bisphosphine oxides; sequential stereoselective reduction of the cyclized bisphosphine oxide gave the corresponding trans- and cis-bisphosphines that were successfully applicable in a catalytic asymmetric hydrogenation as chiral bisphosphine ligands.     

First artificial receptors and chemosensors toward phosphorylated peptide in aqueous solution

The first fluorescent chemosensors toward a native phosphorylated peptide are successfully synthesized. Dinuclear zinc(II)-dipicolylamine-based anthracene (1, 2) can selectively recognize and sense phosphorylated species with an increase in the fluorescence intensity. We also demonstrated that these artificial receptors fluorometrically detect a phosphorylated peptide with high affinity (>107 M-1) in aqueous solution.