Medicinal flowers. VI. Absolute stereostructures of two new flavanone glycosides and a phenylbutanoid glycoside from the flowers of Chrysanthemum indicum L.: their inhibitory activities for rat lens aldose reductase

Two new flavanone glycosides, (2S)- and (2R)-eriodictyol 7-O-beta-D-glucopyranosiduronic acids, and a new phenylbutanoid glycoside, (2S, 3S)-1-phenyl-2,3-butanediol 3-O-beta-D-glucopyranoside, were isolated from the flowers of Chrysanthemum indicum L. cultivated in China together with eight flavonoids. The absolute stereostructures of the new compounds were determined on the basis of chemical and physicochemical evidence. Both of the new flavanone glycosides were found to show inhibitory activity for rat lens aldose reductase.     

Counterions of BINAP-Pt(II) and -Pd(II) complexes: novel catalysts for highly enantioselective Diels-Alder reaction

[formula: see text] Platinum and palladium chiral bisphosphine complexes and their counterion effects in asymmetric Diels-Alder reactions have been investigated. The reaction of cyclopentadiene and various bidentate dienophiles in the presence of a catalytic amount of Pt(II)- or Pd(II)-BINAP complex proceeds with excellent endo/exo selectivity as well as endo enantioselectivity (up to 99% ee).     

Bioactive constituents of chinese natural medicines. VI. Moutan cortex. (2): structures and radical scavenging effects of suffruticosides A, B, C, D, and E and galloyl-oxypaeoniflorin

Five paeonol glycosides, suffruticosides A, B, C, D, and E, and a monoterpene glucoside, galloyl-oxypaeoniflorin, were isolated from the glycosidic fraction of Chinese Moutan Cortex, the root cortex of Paeonia suffruticosa Andrews, together with paeonolide, apiopaeonoside, galloyl-paeoniflorin, oxypaeoniflorin, and paeoniflorin. The structures of five suffruticosides and galloyl-oxypaeoniflorin were elucidated on the basis of chemical and physicochemical evidence. Suffruticosides A, B, C, and D, galloyl-oxypaeoniflorin, and galloyl-paeoniflorin exhibited more potent radical scavenging effects than alpha-tocopherol.     

Molecular Recognition Study on a Supramolecular System. Part 21. Inclusion Complexation Thermodynamics of Aliphatic Alcohols by Organoselenium Modified β-Cyclodextrins

The spectrophotometric titrations have beenperformed at 25–40 °C in aqueous solution to give the complexstability constants and the thermodynamic parametersfor the stoichiometric 1 : 1 inclusion complexation ofvarious aliphatic alcohols withmono[6-(phenylseleno)-6-deoxy]--cyclodextrin (2),mono[6-(o-, m-,p-tolylseleno)-6-deoxy]--cyclodextrin (3–5),mono[6-(p-chloro-phenyl-seleno)-6-deoxy]--cyclodextrin(6), mono[6-(benzylseleno)-6-deoxy]--cyclodextrin (7) and mono[6-(naphthaleneseleno)-6-deoxy]--cyclodextrin(8). On thebasis of the present and previous results, themolecular binding abilities and selectivities forguest aliphatic alcohols of the host -cyclodextrinderivatives (2–8) are discussed comparatively and globallyfrom the thermodynamic point of view. Thethermodynamic parameters obtained are criticalfunctions of the size/shape of aliphatic alcohols, andthe position and type of the substituent introduced tothe aromatic ring of -cyclodextrin's sidearm,which are elucidatedin terms of the conformational, electrostatic,hydrogen-bonding, and hydrophobic effects.     

Helical pitch of m-phenylene ethynylene foldamers by double spin labeling

To investigate the helical conformation of oligo(m-phenylene ethynylene)s, a pair of TEMPO spin labels were appended to the backbone. The two TEMPO radicals were separated by the four, five, and six repeating units. ESR spectra of the labeled oligomers were measured in chloroform and in ethyl acetate solvents in which the oligomers are disordered and folded, respectively. The measurement and analysis of ESR spectra revealed that six repeating units make one helical turn.     

Synthesis and antifungal activities of a series of (1,2-disubstituted vinyl)imidazoles.

A series of vinylimidazoles containing a hetero atom such as sulfur or oxygen at a beta-position of the vinyl group was prepared and the antifungal activities were tested. It was found that sulfur-substituted derivatives such as (E)-1-[2-(methylthio)-1-[2-(pentyloxy)phenyl]ethenyl]-1H-imidazole (5a-5) and (E)-1-[1-[2-(hexyloxy)phenyl]-2-(methylthio)ethenyl]-1H-imidazole (5a-6) showed excellent antifungal activities against dermatophytes and yeast cells. The stereochemistry of the hydrochloride salt of 5a-5 was determined by X-ray crystallography. The structure-activity relationships were discussed.     

Bound site of Mo atoms and its local structure in a Mo/HY catalyst characterized by extended X-ray absorption fine structure and density functional calculation

The bound site of Mo atoms and its local structure in a Mo/HY catalyst have been determined by detailed analysis of extended X-ray absorption fine structure (EXAFS). Molybdenum was introduced in the supercage of HY zeolite by cycles of saturated adsorption of Mo(CO)6 at room temperature and subsequent thermal decomposition at 573 K. Two Mo atoms per supercage were immobilized in each CVD-thermal treatment cycle. The Mo loading increased linearly with the cycles up to three cycles at saturation, where six Mo atoms were supported. Temperature-programmed decomposition of the adsorbed Mo(CO)6 was also characterized by GC, QMS, and FT-IR, respectively. The EXAFS analysis including multiple scattering based on theoretical calculations revealed that Mo bound with two oxygen atoms connects to Al, where one of the two oxygen atoms had been associated with a proton. The bound site is called the S(III)' site. The zeolite framework was significantly distorted by the introduction of low-valent Mo, resulting in isolation of the [MoO2Al] unit from the surrounding zeolite framework due to a quasi-disruption of Si-O bonds adjacent to the unit. In the mild oxidation of the low-valent Mo/HY sample two Mo=O bonds were newly formed and the position of Mo was displaced by 0.06 nm so that the distortion of zeolite framework around the Al atom was relieved. The structures were also supported by DFT calculations. This study is the first example that the position of metal cation in zeolite was determined unambiguously by the EXAFS analysis.     

Bioactive constituents from Chinese natural medicines. XIV. New glycosides of beta-carboline-type alkaloid, neolignan, and phenylpropanoid from Stellaria dichotoma L. var. lanceolata and their antiallergic activities

A new beta-carboline-type alkaloidal glycoside, glucodichotomine B, four new neolignan glycosides, dichotomosides A, B, C, and D, and a new phenylpropanoid glycoside, dichotomoside E, were isolated from a Chinese natural medicine, the roots of Stellaria dichotoma L. var. lanceolata. The structures of the new glycosides were determined on the basis of chemical and physicochemical evidence. Among them, dichotomoside D inhibited the release of beta-hexosaminidase (IC(50)=64 microM) as well as tumor necrosis factor-alpha and interleukin-4 (IC(50)=16, 34 microM) in RBL-2H3 cells. These findings suggest that dichotomoside D is more effective against the late-phase reactions in type I allergy than in the immediate phase.     

Voltammetry at partially covered electrodes: Part I. Chronopotentiometry and chronoamperometry at model electrodes

Equations for chronopotentiometry and chronoamperometry at partially covered electrodes have been derived using a model of hexagonal array of cylidrical spaces terminated, at the electrode surface, by concentric active and inactive regions. The boundary value problem was shown to be analogous to that for a charge transfer preceded by a chemical reaction. Experiments with the reduction of ferricyanide on gold model electrodes partially covered with photoresist layer showed excellent agreement with the theory. Application of the equations to estimation of coverage and size of active sites distributed on a electrode surface is discussed.     

Two-carbon ring expansion of cyclobutanone skeletons by nickel-catalyzed intermolecular alkyne insertion

The reaction of cyclobutanone with an alkyne in the presence of a nickel(0) catalyst formally achieves intermolecular alkyne insertion between the carbonyl carbon and the α-carbon of a cyclobutanone, providing a six-membered carbocyclic skeleton.