N-Acetylcysteine Displaces Glutathionyl-Moieties from Hg2+ and MeHg+ to Form More Hydrophobic Complexes at Near-Physiological Conditions.

The anthropogenic release of Hg is associated with an increased human exposure risk. Since Hg2+ and MeHg+ have a high affinity for thiols, their interaction with L-glutathione (GSH) within mammalian cells is fundamentally involved in their toxicological chemistry and excretion. To gain insight into the interaction of these mercurials with multiple small molecular weight thiols, we have investigated their competitive interactions with GSH and N-acetylcysteine (NAC) at near-physiological conditions, using a liquid chromatographic approach. This approach involved the injection of each mercurial onto a reversed-phase (RP)-HPLC column (37 °C) using a PBS buffer mobile phase containing 5.0 mM GSH to simulate cytosolic conditions with Hg being detected in the column effluent by an inductively coupled plasma atomic emission spectrometer (ICP-AES). When the 5.0 mM GSH mobile phase was amended with up to 10 mM NAC, gradually increasing retention times of both mercurials were observed. To explain this behavior, the experiment with 5.0 mM NAC and 5.0 mM GSH was replicated using 50 mM Tris buffer (pH 7.4), and the Hg-containing fractions were analyzed by electrospray ionization mass spectrometry. The results revealed the presence of Hg(GS)(NAC) and Hg(NAC)2 for Hg2+ and MeHg(GS) and MeHg(NAC) for MeHg+, which suggests that the coordination/displacement of GS-moieties from each mercurial by the more hydrophobic NAC can explain their retention behavior. Since the biotransformations of both mercurials were observed at near-physiological conditions, they are of toxicological relevance as they provide a biomolecular explanation for some results that were obtained when animals were administered with each mercurial and NAC.

A beneficial kinetic effect of an η(5)-C5Me4H ligand.

C-H activation of benzene at 26 °C by (η(5)-C(5)Me(5))W(NO)(CH(2)CMe(3))(η(3)-CH(2)CHCHMe) results after 4 h in the production of five new organometallic complexes, only two of which are isomers of the desired (η(5)-C(5)Me(5))W(NO)(C(6)H(5))(η(3)-CH(2)CHCHMe) compound. In contrast, the identical reaction involving the η(5)-C(5)Me(4)H analogue affords only the phenyl complexes during the first 24 h, thereby facilitating their isolation in good yields. This striking difference in reactivity can be attributed to the lesser steric demands of the η(5)-C(5)Me(4)H ligand that result in its complexes reacting at a significantly slower rate.

Acid-, water- and high-temperature-stable ruthenium complexes for the total catalytic deoxygenation of glycerol to propane.

The ruthenium aqua complexes [Ru(H(2)O)(2)(bipy)(2)](OTf)(2), [cis-Ru(6,6'-Cl(2)-bipy)(2)(OH(2))(2)](OTf)(2), [Ru(H(2)O)(2)(phen)(2)](OTf)(2), [Ru(H(2)O)(3)(2,2':6',2''-terpy)](OTf)(2) and [Ru(H(2)O)(3)(Phterpy)](OTf)(2) (bipy = 2,2'-bipyridine; OTf(-) = triflate; phen = phenanthroline; terpy = terpyridine; Phterpy = 4'-phenyl-2,2':6',2''-terpyridine) are water- and acid-stable catalysts for the hydrogenation of aldehydes and ketones in sulfolane solution. In the presence of HOS(O)(2)CF(3) (triflic acid) as a dehydration co-catalyst they directly convert 1,2-hexanediol to n-hexanol and hexane. The terpyridine complexes are stable and active as catalysts at temperatures > or = 250 degrees C and in either aqueous sulfolane solution or pure water convert glycerol into n-propanol and ultimately propane as the final reaction product in up to quantitative yield. For the terpy complexes the active catalyst is postulated to be a carbonyl species [(4'-R-2,2':6',2''-terpy)Ru(CO)(H(2)O)(2)](OTf)(2) (R = H, Ph) formed by the decarbonylation of aldehydes (hexanal for 1,2-hexanediol and 3-hydroxypropanal for glycerol) generated in the reaction mixture through acid-catalyzed dehydration. The structure of the dimeric complex [{(4'-phenyl-2,2':6',2''-terpy)Ru(CO)}(2)(mu-OCH(3))(2)](OTf)(2) has been determined by single crystal X-ray crystallography (Space group P1 (a = 8.2532(17); b = 12.858(3); c = 14.363(3) A; alpha = 64.38(3); beta = 77.26(3); gamma = 87.12(3) degrees, R = 4.36 %).

X-ray structures of cyclophanes derived from naphtho[1,2-c:5,6-c]difuran and the synthesis, structure, and reaction kinetics of its 1,3,6,8-tetrasilylated derivative.

A silylated derivative of naphtho[1,2-c:5,6-c]difuran, 1,3,6,8-tetrakis(tert-butyldimethylsilyl)naphtho[1,2-c:5,6-c]difuran, has been isolated and its X-ray crystal structure determined. Bond localization confirms the polyene character of this isobenzofuran ring system. This molecule undergoes two successive Diels-Alder reactions with second-order rate constants differing by over 2 orders of magnitude, consistent with predictions based on their structure-count ratios and with the reactivity of the novel 1,3-bis(tert-butyldimethylsilyl)isobenzofuran. Crystal structures of two cyclophanes derived from the reaction of naphtho[1,2-c:5,6-c]difuran and bis(imide) or bis(ester) dienophiles show marked differences in the conformation of the aliphatic chain found in the solid state.

(2R,3aR,4S,7R,7aS,9R,10aR,11S,14R,14aS)-rel-3a,4,7,7a,10a,11,14,14a-Octa-hydro-4,14:7,11-diep-oxy-2,9-propanona-phtho[1,2-f:5,6-f']diisoindole-1,3,8,10-tetrone (9CI): a cyclo-phane derived from naphtho[1,2-c:5,6-c]difuran.

The title compound, C(25)H(18)N(2)O(6), is a naphthalenophane styled in the manner of Warrener's alicyclic cyclo-phanes or mol-ecular racks wherein a trimethyl-ene tether is perfectly staggered between the two N atoms such that the central methyl-ene H atoms point toward the naphthalene π-system. The dihedral angle between the mean planes of the two benzene rings is 7.61 (7)°.

Naphtho[1,2-c:5,6-c]difuran: a reactive linker and cyclophane precursor.

Naphtho[1,2-c:5,6-c]difuran has been isolated in a 9-step synthesis from 2,6-dimethylnaphthalene. It is a highly reactive diene similar in nature to the related isobenzofuran. In Diels-Alder reactions, its intermediate monoadducts are actually less reactive that the parent difuran making possible sequential Diels-Alder reactions with different dienophiles. Reaction with a tethered bis(dienophile) leads to the production of a naphthalenic cyclophane.