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The NaBH4 (or TBABH4)-promoted electrochemically reductive cleavage of aryl C-O bonds in diaryl ethers to produce phenols and arenes with high yields and excellent selectivities at room temperature was reported. Air- and water-tolerable, this process also works on the cleavage of aryl alkyl and benzyl ethers. The application to break the β-O-4, α-O-4, and 4-O-5 lignin model compounds is also illustrated, which highlights the advance toward the goal of lignin conversion. [ABSTRACT FROM AUTHOR]

The paper reports a green synthetic route for nanosized hematite colloids with an excellent monodispersity, using green vitriol and ammonia as raw materials. The reaction conditions of the synthetic route were studied and the as-prepared samples were characterized by XRD, TEM, TG-DTA, DLS, and XPS. The results indicated that the key factors for the monodispersity of the colloidal product were preheating reactants and washing repeatedly the intermediate Fe(OH)3. When the initial pH was set as 4 or 5, the transformation product of Fe(OH)3 was the pure α-Fe2O3 with the minim adsorptive sulfate ions. Contrarily, the mixtures of α-Fe2O3 and α-FeOOH were obtained at the pH 6 or 7, which were related to the mechanism of transformation reaction. In addition, the concentration of Fe(OH)3 should be less than or equal to 0.2 mol/L in order to prepare the qualified nanosized hematite colloids. The researches proved that the excellent monodispersity of the colloidal product resulted from a fine dispersion state of the synthetic system during the whole process and that it was a significant way to obtain the nanosized metallic oxide colloids from the corresponding metal hydroxide due to avoidance of hyperspeed centrifugal separation or dialysis operation. [ABSTRACT FROM AUTHOR]

Subendothelial collagen supports platelet adhesion, activation, and thrombus growth at sites of vascular damage. Previous studies have shown that chalcones possess antiplatelet activity, but their mechanism of action is not fully understood. In this study, a recently synthesized chalcone, 2′-ethoxy-5′-methoxy-2-(5-methylthienyl)chalcone (EMMTC), was used to investigate chalcone effects on platelet aggregation and adhesion. We found that EMMTC potently inhibited collagen-induced platelet aggregation with an IC50 of 1.01 μmol/l. In contrast, it did not inhibit thrombin- and ADP-induced platelet aggregation. EMMTC could inhibit arachidonic acid (AA)-induced platelet aggregation and collagen- and AA-induced thromboxane B2 (TXB2) formation, suggesting that cyclooxygenase and/or thromboxane synthase were affected during this process. Moreover, EMMTC suppressed collagen-induced protein tyrosine phosphorylation, including phospholipase C-γ2 (PLC-γ2), phosphatidylinositol-3 kinase (PI-3K), Src, Fyn and LAT. Strikingly, EMMTC also blocked platelet adhesion to immobilized collagen and convulxin (a snake venom-derived protein that activates platelet glycoprotein VI receptor). The attenuation of phosphorylation of focal adhesion kinase (FAK) was observed during adhesion. Taken together, our results presented here demonstrate that the chalcone derivative EMMTC affects collagen-induced protein tyrosine phosphorylation and TXB2 formation and functionally blocks collagen-induced platelet aggregation and adhesion. Copyright © 2009 S. Karger AG, Basel [ABSTRACT FROM AUTHOR]

The PdCl2-catalyzed cyclocarbonylation reaction of propargylic amines with CuCl2 and benzoquinone afforded (E)-α-chloroalkylidene-β-lactams in moderate to good yields. The formation of the corresponding Z-isomers or five-membered products was not observed. The reaction of the readily available optically active prop argylic amines provides a convenient synthesis of the corresponding (E)-α-chloroalkylidene-β-lactams with high ee values. The structure and the stereochemistry of the products were established by the X-ray single-crystal diffraction study of (E)-6d and (E)-6e, which indicates that the stereoselectivity in this reaction is different from what was observed with propargylic alcohols. A rationale for this reaction was proposed. [ABSTRACT FROM AUTHOR]

A good regio- and stereoselectivity was observed for the PdCl2-catalyzed cyclocarbonylation of 2-alkynols with CuCl2 affording (Z)-α-chloroalkylidene-β-lactones. The highly optically active (Z)-α-chloroalkylidene-β-lactones could be easily prepared from the readily available optically active prop argylic alcohols. The Pd(II)-catalyzed cyclocarbonylation of 2-alkynols with CuBr2 was also studied. Although the yields of (Z)-α-bromoalkylidene-β-lactones were low, due to the relatively higher activity of the C-Br bond, the coupling reactions of (Z)-α-bromoalkylidene-β-lactones were quite smooth to afford the corresponding products in high yields. A rationale for this reaction is discussed. [ABSTRACT FROM AUTHOR]

The title complex has prepared by the reaction of TbL 3 , Cu(NO 3 ) 2 and phen in H 2 O/EtOH (where L = α-methylacrylato; phen = 1,10-phenanthroline) and its structure determined by X-ray diffraction methods. The complex crystallizes in the triclinic space group P ī with Z = 1, a = 11.569(2), b = 14.584(3), c = 11.479(2) Å, α = 101.03(2), β = 104.37(2), γ = 74.01(1)°, and the structure was refined to R = 0.041 for 6463 observed reflections. The structure contains a discrete tetranuclear CuTbTbCu molecule. Copper(II) and terbium(III) are bridged by three bidentate carboxyl groups with a Tb ··· Cu separation of 3.9059(9) Å. The Tb ion is eight coordinate and exhibits a distorted square antiprism. The Cu ion is five coordinate and has distorted pyramidal geometry. [ABSTRACT FROM AUTHOR]

The ethyl acetate fractions of aqueous extracts from two submerged macrophytes Potamogeton malaianus and Potamogeton maackianus were analyzed by gas chromatograph-mass spectrometry (GC-MS). The allelopathic activities and joint effects of the main components in ethyl acetate fractions on Microcystis aeruginosa were also determined. The results indicated that primary compositions in the ethyl acetate fractions were fatty acids, phenolic acids and hydroxy fatty acids that possessed antialgal activities. The joint effect assay for palmitic acid, benzoic acid and lactic acid showed that the additional effects were observed in the mixed organic acid, namely, the inhibitory effects of mixture groups were stronger than that of each compound alone on the growth of M. aeruginosa. [ABSTRACT FROM AUTHOR]

The title cluster, [Ru(C7H11B10ClN2O6)(C2H3N)(C18H15P)] or [1,2-{3,5-(NO2)2(C6H3)COO}-1-(PPh3)-1-(CH3CN)-3-Cl-1-RuB10H8], has an iso- closo 11-vertex RuB10 core geometry with the metal occupying the unique six-connected apical position, giving the characteristic 11-vertex iso- closo [ MB10] metalloborane 1:2:4:2:2 stack. The ruthenium centre has three exo-polyhedral ligands: one triphenyl­phosphine, one aceto­nitrile and one 3,5-dinitro­benzoate, which is coordinated through Ru—O and B—O bonds, resulting in an exocyclic five-membered Ru/O/C/O/B ring. [ABSTRACT FROM AUTHOR]

A novel, highly stereoselective synthesis of an azaspirocyclic core, which contains four stereogenic carbons consistent with structures of natural halichlorine and pinnaic acid, is presented. Lipase PS-catalyzed selective acylation, asymmetric methylation on the α-methylene of the bicyclic lactone, and an asymmetric Michael addition of the tertiary nitro cyclopentane were concisely used to conquer the challenging problem of successfully constructing the C9 quarternary carbon center with complete stereocontrol. The spiropiperidine ring was formed by reduction of the δ-nitroketone, intramolecular condensation, and then highly stereoselective reduction of the cyclic nitrone with NaBH4. This spirocyclic core is a key intermediate in Danishefsky's synthesis of pinnaic acid and halichlorine. [ABSTRACT FROM AUTHOR]