Complexes 3g Research Articles

Pokeweed antiviral protein restores levels of cellular APOBEC3G during HIV-1 infection by depurinating Vif mRNA

Pokeweed antiviral protein (PAP) is an RNA glycosidase that inhibits production of human immunodeficiency virus type 1 (HIV-1) when expressed in human culture cells. Previously, we showed that the expression of PAP reduced the levels of several viral proteins, including virion infectivity factor (Vif). However, the mechanism causing Vif reduction and the consequences of the inhibition were not determined. Here we show that the Vif mRNA is directly depurinated by PAP. Because of depurination at two specific sites within the Vif ORF, Vif levels decrease during infections and the progeny viruses that are generated are ∼10-fold less infectious and compromised for proviral integration. These results are consistent with PAP activity inhibiting translation of Vif, which in turn reduces the effect of Vif to inactivate the host restriction factor APOBEC3G (apolipoprotein B mRNA-editing enzyme, catalytic polypeptide-like editing complex 3G). Our findings identify Vif mRNA as a new substrate for PAP and demonstrate that derepression of innate immunity against HIV-1 contributes to its antiviral activity.

Chiral Calcium Organophosphate-Catalyzed Enantioselective Electrophilic Amination of Enamides

Highly enantioselective direct amination of enamides catalyzed by chiral nonracemic calcium bis(phosphate) complex 3g afforded optically active 1,2-hydrazinoimines 4. Following a subsequent in situ hydrolysis or reduction, 2-hydrazinoketones 5 or syn-1,2-disubstituted 1,2-diamines 6 were obtained in high yields and excellent enantiomeric excess.

Allosteric Tuning of the Intra‐Cavity Binding Properties of a Calix[6]arene through External Binding to a ZnII Center Coordinated to Amino Side Chains

Molecular recognition by calix[6]arene-based receptors bearing three primary alkylamino side chain arms (1) is described. Complexation of Zn(II) ion provides the dinuclear mu-hydroxo complex 2G(OH), XRD characterization of which, together with solution studies, provided evidence of its hosting of neutral polar organic guests G. Treatment of this complex with a carboxylic acid or a sulfonamide (XH) results in the formation of mononuclear species 3G(X), one of which (X = Cl) has been characterized by XRD. A dicationic complex 3G(RNH2) is obtained upon treatment of 2G(OH) with a mixture of an alkylamine and a strong acid. Each of these Zn(II) complexes features a tetrahedral metal ion bound to the three amino arms of ligand 1 and to an exogenous ligand (either HO-, X-, or RNH2) sitting outside of the cavity. As a result, the metal ion structures the calixarene core, constraining it in a cone conformation suitable for guest hosting. The receptor properties of these compounds have been explored in detail and are compared with those of the trisammonium receptor 1G(3H+), based on the same calixarene core, as well as those of the trisimidazole-based dicationic Zn funnel complexes. This study reveals very different host properties, in spite of the common hydrophobic, pi-basic, and hydrogen-bonding acceptor properties of the calixarene cores. A harder external ligand produces a less polarized receptor that is consequently particularly sensitive to the hydrogen-bonding ability of its guest. The less electron-rich the apical ligand, and a fortiori the trisammonium host, the more sensitive the receptor to the dipole moment of the guest. All this stands in contrast with the funnel Zn complexes, in which the coordination link plays a dominant role. It is also shown that the asymmetry of an exo-coordinated enantiopure amino ligand is sensed by the guest. This supramolecular system nicely illustrates how the receptor properties of a hydrophobic cavity can be allosterically tuned by the environment.

Bimetallic Fluorine-Substituted Anilido−Aldimine Zinc Complexes for CO2/(Cyclohexene Oxide) Copolymerization

Regioselective nucleophilic aromatic substitution of an o-fluorine occurs to afford fluorine-substituted o-phenylene-bridged bis(anilido-aldimine) compounds o-C6H4[(C6H2R2)N=CH-C6F4-(H)N(C6H3R'2)]2 when Li(H)N-C6H3R'2 (R' = iPr, Et, Me) is reacted with o-C6H4[(C6H2R2)N=CH-C6F5]2 (R = iPr, Et, Me) in a nonpolar solvent such as diethyl ether or toluene. Successive additions of Me2Zn and SO2 gas to the bis(anilido-aldimine) compounds afford quantitatively dinuclear mu-methylsulfinato zinc complexes o-C6H4[[(C6H2R2)N=CH-C6F4-N(C6H3R'2)-kappa2N,N]Zn(mu-OS(O)Me)]2 (R = iPr, R' = iPr, 3a; R = iPr, R' = Me, 3c; R = Et, R' = (i)Pr, 3d; R = Et, R' = Et, 3e; R = Et, R' = Me, 3f; R = Me, R' = iPr, 3g; R = Me, R' = Et, 3h; R = Me, R' = Me, 3i). The molecular structure of 3c was confirmed by X-ray crystallography. Fluorine-substituted complexes 3a-i show significantly higher TOF (turnover frequencies) than the unfluorinated analogues for CO2/(cyclohexene oxide) copolymerization. The TOF is highly sensitive to the substituents R and R', and the highest TOF (2480 h(-1)) is obtained with 3g (R = Me, R' = iPr). Complex 3g is less sensitive to the residual protic impurities present in the monomers and shows activity at such a low catalyst concentration as [Zn]:[cyclohexene oxide] = 1:50,000, at which the unfluorinated analogue is completely inactive. By realizing the activity at such an extremely low [Zn]:[cyclohexene oxide] ratio, we achieve a high TON (turnover number) up to 10,100. High-molecular-weight polymers (M(n), 100,000-200,000) are obtained with a rather broad molecular-weight distribution (M(w)/M(n), 1.3-2.5). The obtained polymers are not perfectly alternating, and variable carbonate linkages (65-85%) are observed depending on the N-aryl ortho substituents R and R' and the polymerization conditions.

Self-Assembly, Reorganization, and Photophysical Properties of Silver(I)−Schiff-Base Molecular Rectangle and Polymeric Array Species

A self-assembly of AgClO(4) with a Schiff-base ligand N,N'-bis(pyridin-2-ylmethylene)benzene-1,4-diamine (1) gave a 1D zigzag polymeric array [[Ag(2)(C(18)H(14)N(4))(2)](ClO(4))(2)(CH(3)CN)](n) (3), while the self-assembly of AgClO(4) with 3,3'-dimethyl-N,N'-bis(pyridin-2-ylmethylene)biphenyl-4,4'-diamine (2) afforded the molecular rectangle [[Ag(2)(C(26)H(22)N(4))(2)](ClO(4))(2)] (4). The structures of 3 and 4 were characterized by single-crystal X-ray diffraction analysis. Structural data for 3 indicate that the Ag(I) ion is coordinated by two ligands of 1 in a distorted tetrahedral fashion thereby leading to a 1D zigzag polymeric array. The zigzag chains are interdigitated with weak pi-pi stacking interactions. The structure of 4 consists of a discrete molecular rectangle where the silver atom has a distorted square-planar coordination with the pyridyl ligands and azomethine nitrogen atoms of 2. An intramolecular pi-pi interaction between the phenyl rings of adjacent Schiff-base 2 functions to stabilize the rectangular architecture. The Ag(I)-Schiff-base coordination polymer 3 is not stable in solution. The degradation and reorganization of 3 to form a [2 x 2] grid architecture [[Ag(4)(C(26)H(22)N(4))(4)](ClO(4))(4)] (3g) was supported in a FAB-MS study. The rectangular structure of 4 remains intact in solution at ambient temperature. The complexes 3g and 4 exhibit unusual luminescence behavior in solution at room temperature with significantly red-shifted emission in the visible region.

Reactivity of the [η2‐Bis(tert‐butylsulfonyl)acetylene](carbonyl)(η5‐cyclopentadienyl)cobalt Complex Towards Electron‐Rich and ‐Poor Acetylenes

AbstractThe electron‐rich aminoacetylenes Et2NC2R (2a–c, R = SPh, PPh2, and Ph, respectively) react smoothly with [η2‐bis(tert‐butylsulfonyl)acetylene](carbonyl)(η5‐cyclopentadienyl)co‐balt (1) to form the donor–acceptor stabilized (η4‐cyclobutadiene)cobalt complexes 3a–c in good yields. However, treatment of the electron‐poor borylacetylenes 2d–f with the cobalt complex 1 does not lead to the expected (η4‐cyclobutadiene)cobalt complexes. Analogously, the reaction of bis(1‐phenylethynyl)sulfide (2g) with two equivalents of 1 gives rise to the sulfur‐bridged bis[η4‐(cyclobutadiene)cobalt] complex 3g. The new cobalt complexes were characterized by NMR spectroscopy, mass spectrometry, and by X‐ray structure analysis for 3a, which reveals almost equal C–C bond lengths within the cyclobutadiene ring. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)

Synthesis, redox chemistry, molecular and electronic structure of some cyclopentadienylcobalt pentafulvene complexes

The pentafulvene complexes [(C 5R 5)Co(C 6H 4R′R′′)] 3d (R=H, R′=Me, R′′=Ph), 3f (R=H, R′=Ph, R′′=C 6H 4NO 2-4), 3g (R=H, R′=R′′=SMe) and 9 (R=Me, R′=R′′=Ph) were prepared from the respective fulvenes and [(C 5R 5)Co(C 2H 4) 2] 8a, b. Protonation of 3 occurs at the fulvene C-α to give substituted cobaltocenium cations. The crystal and molecular structures of 3g, 9 and of the protonation product [ 3e+H] + (R=R′=Ph) were determined. In the neutral complexes the non-planar fulvene ligands are essentially η 4-coordinated with short uncoordinated exocyclic carbon–carbon double bonds. In contrast, the protonated species exhibit η 5-coordinated planar five-membered rings. Using cyclic voltammetry, the complexes 3e, f and 9 were shown to reversibly undergo one-electron oxidation and reduction reactions to give the cations [ 3e] +, [ 3f] +, [ 9] + and anions [ 3e] −, [ 3f] −, [ 9] −. Complex 3g also forms an anion [ 3g] −, but oxidation is irreversible. The X-band ESR spectra of [ 3e] −, [ 3e] + and of [ 9] −, [ 9] + were recorded. In marked contrast to the cations, the anion radicals exhibit considerable anisotropy of the g and A tensors. d-Electron spin densities ρ d=0.5 for the radical anions were derived from a detailed analysis and simulation of the ESR spectra. Using extended Hückel and Fenske–Hall MO calculations for the model complex [(C 5H 5)Co(C 5H 4CH 2)] 3h, the ESR and electrochemical properties were explained by the different metal participation in the HOMO (=SOMO of the cation radicals) and LUMO (=SOMO of the anion radicals).

Photochemisches verhalten von tricarbonyl-η 5:1-(2-cyclopentadiendiyl)ethyl-molybdän und -wolfram gegenüber cyclischen dienen

Tricarbonyl-η 5:1-(2-cyclopentadiendiyl)ethyl-molybdenum ( 1) and -tungsten ( 2) were reacted photochemically with 1,3-cyclopentadiene ( A), 1,3-cyclohexadiene ( B), 1,3-cycloheptadiene ( C), norbornadiene ( D), 1,5-cyclooctadiene ( E), 2,3-dihydrofurane ( F), 1,3,5-cycloheptatriene ( G) and 1,3,5,7-cyclooctatetraene ( H). 1 reacts with A, B, D, E, and F to give the complexes [Mo(η 5:1-C 5H 4C 2H 4)(CO) 2(η 2-diene)] ( 3A, 3B, 3D, 3E, 3F) and [Mo(η 5:1-C 5H 4C 2H 4)(CO)(η 4-diene)] ( 4A, 4B, 4E). There is only spectroscopic evidence for the formation of the labile 1,3,5-cycloheptatriene complexes 3G and 4G. H inserts into the MoC bond to give [Mo(η 5:3-C 5H 4C 2H 4C 8H 8)(CO) 2] ( 5H). Complex 2 reacts similarly to give [W(η 5:1-C 5H 4C 2H 4)(CO) 2(η 2-diene)] ( 6A, 6B, 6C, 6G, 6G′, 6H), [W(η 5:1-C 5H 4C 2H 4)(CO)(η 4-diene)] ( 7A, 7B, 7C, 7G), and [W(η 5:3-C 5H 4C 2H 4C n H 8)(CO) 2] ( n = 7: 8G, n = 8: 8H). The crystal and molecular structure of 7B was determined by X-ray crystallography.