Gold(I) complexes bearing phosphole ligands: Synthesis and antimalarial activity

A series of gold(I)-monophosphole complexes have been synthesized and characterized. The introduction of a nitrogen moiety in the complex structure was envisioned either by choosing the bis(trifluoromethanesulfonyl)imidate ligand as the X-ligand or by preparing a new pyrrolidinophosphole ligand as the L-ligand. All the complexes have been evaluated in vitro for their antimalarial activity. These gold–phosphole complexes showed moderate activities with IC₅₀ values ranging from 9.7 to 24 μM against Plasmodium falciparum chloroquine-resistant strains.     

Highly Anti-Selective One-Pot Multicomponent Synthesis of Mannich-Type N-Acylated β-Amino Acid Derivatives by Copper or Sodium Salt Catalysis

A stereo-defined process has been developed for the synthesis of Mannich-type products using readily available copper sulfate or sodium chloride as catalyst. Good to excellent diastereoselectivity has been achieved for a broad array of substrates. The observed diastereoselectivity is explained on the basis of the steric interaction between the acyloxy group of the aldehyde carbon and the more hindered α-substituted enolate anion. This steric interaction helps the addition to take place through the less-hindered face to produce the anti-isomers predominantly.

Supplemental materials are available for this article. Go to the publisher's online edition of Synthetic Communications® to view the free supplemental file.     

Supramolecular Assemblies of Phosphorylated Cavitands

The recent results in the chemistry of cavitands have proved that they are very efficient molecular receptors and potential precursors of molecular devices. In this context, we have investigated the synthesis and binding properties of phosphorylated cavitands. The stereoselective synthesis and the structural studies of the new compounds showed that these bowl-shaped molecules possess a well defined aromatic cavity surrounded by four phosphoryl groups (P=O or P=S). They are very efficient ligands for metal and organic cations. They are able to encapsulate cationic species by cooperative effect of the preorganized aromatic cavity and the four phosphorylated groups. Moreover, the upper and lower rim functionalitics can lead to the formation of molecular capsules and supramolecular assemblies whose properties and structures have been investigated by X-ray diffraction and NMR studies in solution.     

Phenanthroline–dipyrromethene conjugates: synthesis,characterization, and spectroscopic investigations

Mono- and tri-topic ligands, based on dipyrromethenes and the 1,10-phenanthroline nucleus, as well as BF₂ complexes derived thereof are described. While BODIPY 12 has been X-ray crystallographically characterized, the structural features of the free ligands 9 and 10 may render them useful as precursors for the elaboration of novel supramolecular architectures.     

Synthesis,characterization and biological activity of Hg(II), Fe(III) complexes with 1,3,4-oxadiazole, 1,2,4-triazole derivatives from L-methionine

Four novel heterocyclic1,3,4-oxadiazole, 1,2,4-triazole derivatives, namely: 5-[1-amino-3-(methylsulfanyl)propyl]-1,3,4-oxadiazole-2(3H)-thione (4), 4-amino-5-[1-amino-3-(methylsulfanyl)propyl]-4H-1,2,4-triazole-3-thiol (5), 1-amino-3-[1-amino-3-(methylsulfanyl)propyl]-1H-1,2,4-triazole-5-thiol (7), and 5-[1-amino-3-(methylsulfanyl)propyl]-1H-1,2,4-triazole-3-thiol (9) have been synthesized from l-methionine and characterized by different spectroscopic techniques (FT-IR, UV–Vis, ¹H NMR, ¹³C NMR and MS). Complex formation with Hg⁺⁺ and Fe⁺⁺⁺ ions were formed from the four heterocyclic 4, 5, 7 and 9. The antimicrobial activities for synthetic intermediates and final four products were assisted using paper disk diffusion method against Gram-negative bacteria: Escherichia coli, Pseudomonas aeroginosae and Gram-positive bacteria: Staphylococus aureus 25923, Staphylococus aureus 43300 and showed variant activity against some of the microorganisms tested.     

Synthesis of a novel carboxy functionalized PyOX-ligand

A short and convenient synthesis of a carboxy functionalized PyOX-core is presented. The carboxy functionality offers a wide variety of possibilities for further modification. In this paper, the core is functionalized with a mercapto tail.     

Sorption of Lead(II) on Two Chelating Resins: From the Exchange Coefficient to the Intrinsic Complexation Constant

The sorption of inorganic lead(II) on two cationic resins containing different complexing groups, the iminodiacetic Chelex 100 and the carboxylic Amberlite CG-50, was investigated. The Gibbs-Donnan model was used to describe and predict the sorption through the determination of the intrinsic complexation constants. These quantities, even though non-thermodynamic, characterize the sorption as being independent of experimental conditions. The sorption mechanism for metals on complexing resins was also studied by adding a competitive soluble ligand that shifts the sorption curves to higher pH. The ligand competes with the resin for complexation with the metal ion. Lead(II) is strongly sorbed on Chelex 100 through the formation of two complexes in the resin phase: MHL with log ₁₀ β _111i =−0.3 and ML with log ₁₀ β _111i =−3.7. The presence of the competitive ligand in solution allows for the determination of a third complex. Furthermore, on Amberlite CG-50 the sorption is rather strong and involves the formation of the complex ML, in more acidic solution, with log ₁₀ β _110i =−2.0. In the presence of the ligand PyDA, the ML(OH) complex was characterized by log ₁₀ β _11−1i =−5.6. In all the experiments the hydrolysis reactions in the aqueous phase are considered quantitatively.     

Competition Between Thiol and Phosphine Ligands During the Synthesis of Au Nanoclusters

Reduction of a mixture of Ph₃PAuCl and CH₃(CH₂)₅SH with NaBH₄ yields predominately phosphine encapsulated nanoclusters with Au cores <1 nm, similar to the product isolated when the alkane thiol is not present in the reaction. When Et₃N is added to a solution of Ph₃PAuCl and CH₃(CH₂)₅SH, a Au–S bond is formed, and the subsequent reduction of this thiolate results in the formation of >2 nm core thiol encapsulated Au nanoclusters as the majority product. This latter reduction has been examined in more detail through in situ ³¹P NMR experiments, and a solution exchange reaction is observed wherein the PPh₃ generated by the reduction displaces thiol from the surface of the nanocluster product. This thiol displacement occurs with loss of a Au atom from the nanocluster core, as observed by NMR. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.

Synthesis and reactivity of neodymium(III) amido-tethered N-heterocyclic carbene complexes

The reaction of the heteroleptic Nd(III) iodide, [Nd(L′)(N″)(μ-I)] with the potassium salts of primary aryl amides [KN(H)Ar′] or [KN(H)Ar^*] affords heteroleptic, structurally characterised, low-coordinate neodymium amides [Nd(L′)(N″)(N(H)Ar′)] and [Nd(L′)(N″)(N(H)Ar^*)] cleanly (L′ = t-BuNCH₂CH₂[C{NC(SiMe₃)CHNt-Bu}], N″ = N(SiMe₃)₂, Ar′ = 2,6-Dipp₂C₆H₃, Dipp = 2,6-Prⁱ₂C₆H₃, Ar^* = 2,6-(2,4,6-Prⁱ₃C₆H₂)₂C₆H₃). The potassium terphenyl primary amide [KN(H)Ar^*] is readily prepared and isolated, and structurally characterised. Treatment of these primary amide-containing compounds with alkali metal alkyl salts results in ligand exchange to give alkali metal primary amides and intractable heteroleptic Nd(III) alkyl compounds of the form [Nd(L′)(N″)(R)] (R = CH₂SiMe₃, Me). Attempted deprotonation of the Nd-bound primary amide in [Nd(L′)(N″)(N(H)Ar^*)] with the less nucleophilic phosphazene superbase Bu^tNP{NP(NMe₂)₃}₃ resulted in indiscriminate deprotonations of peripheral ligand CH groups.     

Substrate binding to cytochromes P450

P450s have attracted tremendous attention owing to not only their involvement in the metabolism of drug molecules and endogenous substrates but also the unusual nature of the reaction they catalyze, namely, the oxidation of unactivated C–H bonds. The binding of substrates to P450s, which is usually viewed as the first step in the catalytic cycle, has been studied extensively via a variety of biochemical and biophysical approaches. These studies were directed towards answering different questions related to P450s, including mechanism of oxidation, substrate properties, unusual substrate oxidation kinetics, function, and active-site features. Some of the substrate binding studies extending over a period of more than 40 years of dedicated work have been summarized in this review and categorized by the techniques employed in the binding studies.