Synthesis,X-ray diffraction structures,spectroscopic properties,and in vitro antitumor activity of isomeric (1H-1,2,4-triazole)Ru(III) complexes

Three ruthenium(III) complexes containing 1H-1,2,4-triazole (Htrz), viz., (H(2)trz)[cis-RuCl(4)(Htrz)(2)], 1, (H(2)trz)[trans-RuCl(4)(Htrz)(2)], 2, and (Ph(3)PCH(2)Ph)[trans-RuCl(4)(Htrz)(2)], 3, have been synthesized by reaction between RuCl(3) and excess of the triazole in 2.38 M HCl (1 and 2), while 3 was obtained by metathesis of 2 and [Ph(3)PCH(2)Ph]Cl in water. The products were characterized by IR, UV-vis, electrospray mass spectrometry, cyclic voltammetry, and X-ray crystallography (1 and 3). X-ray diffraction study revealed cis and trans arrangements of the triazole ligands in 1 and 3, correspondingly, and unprecedented monodentate coordination of the triazole through N2 and stabilization of its 4H tautomeric form, which is the disfavored one for the free triazole. The cytotoxicity of 1 and 2 has been assayed in three human carcinoma cell lines SW480, HT29 (colon carcinoma), and SK-BR-3 (mammary carcinoma). Both compounds exhibit antiproliferative activity in vitro. Time-dependent response of all three lines to 1 and 2 and a structure-activity relationship, i.e., higher activity of the trans-isomer 2 than that of cis-species 1, have been observed.     

A simple total synthesis of (±)-ascofuranone

A simple, efficient total synthesis of (±)-ascofuranone is described.     

Excitation cross-section of the protons colliding with hydrogen atoms

The transition amplitude relative to excitation of the hydrogen atoms by protons impact is determinated. The modified correlation approximation is utilized.     

A Diselenide Turn-On Fluorescent Probe for the Detection of Thioredoxin Reductase

We report the first diselenide-based probe for the selective detection of thioredoxin reductase (TrxR), an enzyme commonly overexpressed in melanomas. The probe design involves conjugation of a seminaphthorhodafluor dye with a diselenide moiety. TrxR reduces the diselenide bond, triggering a fluorescence turn-on response of the probe. Kinetic studies reveal favorable binding of the probe with TrxR with a Michaelis–Menten constant (K_m) of 15.89 μm . Computational docking simulations predict a greater binding affinity to the TrxR active site in comparison to its disulfide analogue. In vitro imaging studies further confirmed the diselenide probe exhibited improved signaling of TrxR activity compared to the disulfide analogue.     

Synthesis, structure and redox properties of bis(cyclopentadienyl)dithiolene complexes of molybdenum and tungsten

The compounds [Cp(2)M(S(2)C(2)(H)R)] (M = Mo or W; R = phenyl, pyridin-2-yl, pyridin-3-yl, pyridin-4-yl or quinoxalin-2-yl) and [Cp(2)Mo(S(2)C(2)(Me)(pyridin-2-yl)] have been prepared by a facile and general route for the synthesis of dithiolene complexes, viz. the reaction of [Cp(2)MCl(2)] (M = Mo or W) with the dithiolene pro-ligand generated by reacting the corresponding 4-(R)-1,3-dithiol-2-one with CsOH. These Mo compounds were reported previously (Hsu et al., Inorg. Chem. 1996, 35, 4743); however, the preparative method employed herein is more versatile and generates the compounds in good yield and all of the W compounds are new. Electrochemical investigations have shown that each compound undergoes a diffusion controlled one-electron oxidation (OX(I)) and a one-electron reduction (RED(I)) process; each redox change occurs at a more positive potential for a Mo compound than for its W counterpart. The mono-cations generated by chemical or electrochemical oxidation are stable and the structures of both components of the [Cp(2)Mo(S(2)C(2)(H)R)](+)/[Cp(2)Mo(S(2)C(2)(H)R)] (R = Ph or pyridin-3-yl) redox couples have been determined by X-ray crystallography. For each redox related pair, the changes in the Mo-S, S-C and C-C bond lengths of the {MoSCCS} moiety are generally consistent with OX(I) involving the loss of an electron from a π-orbital that is Mo-S and C-S antibonding and C-C bonding in character. These results have been interpreted successfully within the framework provided by DFT calculations accomplished for [Cp(2)M(S(2)C(2)(H)Ph)](n) (M = Mo or W; n = +1, 0 or -1). The HOMO of the neutral compounds is derived mainly from the dithiolene π(3) orbital (65%); therefore, OX(I) is essentially a dithiolene-based process. The similarity of the potentials for OX(I) (ca. 30 mV) for analogous Mo and W compounds is consistent with this interpretation and the EPR spectra of each of the Mo cations show that the unpaired electron is coupled to the dithiolene proton but relatively weakly to (95,97)Mo. The DFT calculations indicate that the unpaired electron is more localised on the metal in the mono-anions than in the mono-cations. In agreement with this, the EPR spectrum of each of the Mo-containing mono-anions manifests a larger (95,97)Mo coupling (A(iso)) than observed for the corresponding mono-cation and RED(I) for a W compound is significantly (ca. 300 mV) more negative than that of its Mo counterpart. [Cp(2)W(S(2)C(2)(H)(quinoxalin-2-yl))] is anomalous; RED(I) occurs at a potential ca. 230 mV more positive than expected from that of its Mo counterpart and the EPR spectrum of the mono-anion is typical of an organic radical. DFT calculations indicate that these properties arise because the electron is added to a quinoxalin-2-yl π-orbital.     

Synthesis of 3S-Pyrrolidinol from L-Glutamic Acid

A practical synthesis of 3S-pyrrolidinol and derivatives from L-glutamic acid is described.     

Synthesis of (2R, 3S, 4R)-2-Hydroxymethyl-3,4-Dihydroxypyrrolidine Hydrochloride from D-Glucose

(2R, 3S, 4R)-2-Hydroxymethyl-3,4-dihydroxypyrrolidine hydrochlo-ride was synthesized from diacetone-D-glucose.     

Synthesis and ring-opening metathesis of tetraalkoxy-substituted [2.2]paracyclophane-1,9-dienes

Tetraalkoxy-substituted [2.2]paracyclophane-1,9-dienes can be prepared in three steps from dithia[3.3]paracyclophanes. A mixture of pseudo-geminal and pseudo-ortho diastereomers is produced and the pure compounds can be separated by fractional crystallization. The solid state structures of these diastereomers reveal strongly distorted aromatic rings consistent with high levels of ring strain. Reaction of these diastereomers with the second generation Grubbs catalyst shows that only the pseudo-geminal isomer can be ring opened to give cis,trans-distrylbenzenes. The origin of this selectivity is discussed and the photoisomerization of the as-formed cis,trans-product to the all trans isomer is demonstrated.