Seven-Coordinate Group 6 Metal Hydrides Obtained by H Activation at B(CF) Adducts of N Complexes: Frustrated Lewis Pair-Type Reactivity of The B-N Linkage.

The adducts 2 of general formula trans-[(L)M{RP(CH)PR}{NB(CF)}] (L=ø or N, M=Mo or W, R=Et or Ph), formed from Lewis acid-base pairing of B(CF) to a dinitrogen ligand of zero-valent group 6 bis(phosphine) complexes trans-[M{RP(CH)PR}(N)] are shown to react with dihydrogen to afford hepta-coordinated bis(hydride) complexes [M(H){RP(CH)PR}{NB(CF)}] 3 which feature the rare ability to activate both dinitrogen and dihydrogen at a single metal center, except in the case where M=Mo and R=Ph for which fast precipitation of insoluble [Mo(H)(dppe)] (dppe=1,2-bis(diphenylphosphino)ethane) occurs. The frustrated Lewis pair (FLP)-related reactivity of the B-N linkage in compounds 3 was explored and led to distal N functionalization without involvement of the hydride ligands. It is shown in one example that the resulting bis(hydride) diazenido compounds may also be obtained through a sequence involving first FLP-type N-functionalization followed by oxidative addition of H.

Antibacterial and antibiofilm properties of two cyclic dipeptides produced by a new desert Streptomyces sp. HG-17 strain against multidrug-resistant pathogenic bacteria.

Introduction: The emergence of multidrug-resistant bacteria and biofilms requires discovering new antimicrobial agents from unexplored environments.

Objectives: This study aims to isolate and characterize a new actinobacterial strain from the Hoggar Mountains in southern Algeria and evaluate its ability to produce bioactive molecules with potential antibacterial and antibiofilm activities.

Methods: A novel halotolerant actinobacterial strain, designated HG-17, was isolated from the Hoggar Mountains, and identified based on phenotypic characterizations, 16S rDNA sequence analysis, and phylogenetic analysis.

From Stilbenes to carbo-Stilbenes: an Encouraging Prospect.

Beyond previously described carbo-naphthalene and carbo-biphenyl, a novel type of bis-carbo-benzenic molecules is envisaged from the stilbene parent. The synthesis, structure, spectroscopic and electrochemical properties of two such carbo-stilbenes are described at complementary experimental and computational DFT levels. In the selected targets, the bare skeletal carbo-mer of carbo-stilbene is decorated by 8 or 10 phenyl groups, 0 or 2 tert-butyl groups, and 2 n-octyl chains, the later substituents being introduced to compensate anticipated solubility issues.

Acetate exchange mechanism on a Zr oxo hydroxo cluster: relevance for reshaping Zr-carboxylate coordination adaptable networks.

The kinetics and mechanism of the acetate ligand exchange with free acetic acid in [ZrO(OH)(OCCH)], used as a molecular model of crosslink migration in [ZrO(OH)(carboxylate)(OH)]-based coordination adaptable networks with vitrimer-like properties, has been thoroughly investigated by dynamic H NMR and DFT calculations. The compound maintains its -symmetric Zr structure in CDCl and CD, while it splits into its Zr subunits in CDOD and DO. In the Zr structure, the topologically different acetates (3 chelating, 6 belt-bridging, 2 intercluster-bridging and 1 inner-face-bridging) of the Zr subunits behave differently in the presence of free CHCOOH: very fast exchange for the chelating (coalesced resonance at room temperature), slower exchange for the belt-bridging (line broadening upon warming), no observable exchange up to 65 °C (by EXSY NMR) for the intercluster- and inner-face-bridging.

Mechanochemical Studies on Coupling of Hydrazines and Hydrazine Amides with Phenolic and Furanyl Aldehydes-Hydrazones with Antileishmanial and Antibacterial Activities.

Hydrazone compounds represent an important area of research that includes, among others, synthetic approaches and biological studies. A series of 17 hydrazones have been synthesized by mechanochemical means. The fragments chosen were phenolic and furanyl aldehydes coupled with 12 heterocyclic hydrazines or hydrazinamides.

An Experimental and Computational Investigation Rules Out Direct Nucleophilic Addition on the N Ligand in Manganese Dinitrogen Complex [Cp(CO) Mn(N )].

We have re-examined the reactivity of the manganese dinitrogen complex [Cp(CO) Mn(N )] (1, Cp=η -cyclopentadienyl, C H ) with phenylithium (PhLi). By combining experiment and density functional theory (DFT), we have found that, unlike previously reported, the direct nucleophilic attack of the carbanion onto coordinated dinitrogen does not occur. Instead, PhLi reacts with one of the CO ligands to provide an anionic acylcarbonyl dinitrogen metallate [Cp(CO)(N )MnCOPh]Li (3) that is stable only below -40 °C.

Synthesis and Coordination of a Bisphosphine-[NHC-borane] Compound: A Ligand Framework for Bimetallic Structure Featuring a Boron-Bridging Moiety.

We report herein the synthesis of a bisphosphine-[NHC-BH] compound and its coordination toward gold. The ligand is shown to support a bimetallic structure bisphosphine-[NHC-BH](AuCl). The abstraction of one chloride from the gold metal center triggers the activation of a BH fragment, leading to the reductive elimination of H and the formation of a dicationic Au complex featuring Au centers at the +0.

Assemblies of poly(-vinyl-2-pyrrolidone)-based double hydrophilic block copolymers triggered by lanthanide ions: characterization and evaluation of their properties as MRI contrast agents.

Because of the formation of specific antibodies to poly(ethylene glycol) (PEG) leading to life-threatening side effects, there is an increasing need to develop alternatives to treatments and diagnostic methods based on PEGylated copolymers. Block copolymers comprising a poly(-vinyl-2-pyrrolidone) (PVP) segment can be used for the design of such vectors without any PEG block. As an example, a poly(acrylic acid)--poly(-vinyl-2-pyrrolidone) (PAA--PVP) copolymer with controlled composition and molar mass is synthesized by reversible addition-fragmentation chain transfer (RAFT) polymerization.

-Heterocyclic Carbene-Iridium Complexes as Photosensitizers for In Vitro Photodynamic Therapy to Trigger Non-Apoptotic Cell Death in Cancer Cells.

A series of seven novel iridium complexes were synthetized and characterized as potential photosensitizers for photodynamic therapy (PDT) applications. Among them, four complexes were evaluated in vitro for their anti-proliferative activity with and without irradiation on a panel of five cancer cell lines, namely PC-3 (prostate cancer), T24 (bladder cancer), MCF7 (breast cancer), A549 (lung cancer) and HeLa (cervix cancer), and two non-cancerous cell models (NIH-3T3 fibroblasts and MC3T3 osteoblasts). After irradiation at 458 nm, all tested complexes showed a strong selectivity against cancer cells, with a selectivity index (SI) ranging from 8 to 34 compared with non-cancerous cells.

Design of Anti-infectious Agents from Lawsone in a Three-Component Reaction with Aldehydes and Isocyanides.

The first effective synthetic approach to naphthofuroquinones via a reaction involving lawsone, various aldehydes, and three isocyanides under microwave irradiation afforded derivatives in moderate to good yields. In addition, for less-reactive aldehydes, two naphtho-enaminodione quinones were obtained for the first time, as result of condensation between lawsone and isocyanides. X-ray structure determination for and 2D-NMR spectra of confirmed the obtained structures.

A New Saharan Strain of Streptomyces sp. GSB-11 Produces Maculosin and N-acetyltyramine Active Against Multidrug-Resistant Pathogenic Bacteria.

Multi-resistant bacterial pathogens are a major public health problem for treating nosocomial infections owing to their high resistance to antibiotics. The objective of this research was to characterize the bioactive molecules secreted by a novel moderately halophilic actinobacterium strain, designated GSB-11, exhibiting a strong antagonistic activity against several multidrug-resistant pathogenic bacteria. This potential strain was identified by phenotypic, genotypic (16S rRNA), and phylogenetic analyses.

Synthesis and Antimalarial Activities of New Hybrid Atokel Molecules.

The currently spreading resistance of the malaria parasite Plasmodium falciparum to artemisinin-based combination therapies makes an urgent need for new efficient drugs. Aiming to kill artemisinin-resistant Plasmodium, a series of novel hybrid drugs named Atokels were synthesized and characterized. Atokels are based on an 8-amino- or 8-hydroxyquinoline entity covalently bound to a 1,4-naphthoquinone through a polyamine linker.

-to- isomerization triggers hydride transfer from Mn(I) complex -[(dppm)Mn(CO)H].

Low-temperature IR and NMR studies combined with DFT calculations revealed the mechanistic complexity of apparently simple reactions between Mn(I) complex -[(dppm)Mn(CO)H] and Lewis acids (LA = PhC, B(CF)) involving the formation of so-far elusive meridional hydride species -[(dppm)Mn(CO)H⋯LA] and unusual dearomatization of the PhC cation upon hydride transfer.

Alkoxyamines Designed as Potential Drugs against and Parasites.

Malaria and schistosomiasis are major infectious causes of morbidity and mortality in the tropical and sub-tropical areas. Due to the widespread drug resistance of the parasites, the availability of new efficient and affordable drugs for these endemic pathologies is now a critical public health issue. In this study, we report the design, the synthesis and the preliminary biological evaluation of a series of alkoxyamine derivatives as potential drugs against and parasites.

An Artemisinin-Derivative-(NHC)Gold(I) Hybrid with Enhanced Cytotoxicity through Inhibition of NRF2 Transcriptional Activity.

A family of hybrid complexes combining two biologically active motifs, an artemisinin derivative and a cationic bis(NHC)-gold(I) unit, has been synthesized. One of these complexes, 2 a, has been analyzed by single-crystal X-ray diffraction. 2 a shows strong anticancer activities on a large panel of human cancer cell models (prostate, breast, lung, liver, bladder, bone, acute and chronic myeloid leukemias) with GI values in the nm range, together with a high selectivity.

Mzabimycins A and B, novel intracellular angucycline antibiotics produced by sp. PAL114 in synthetic medium containing L-tryptophan.

In our previous studies, the production of four bioactive molecules by sp. PAL114 in complex ISP2 broth medium has been described. Three of these molecules belong to the angucycline family.

π-Stacking Interactions of Graphene-Coated Cobalt Magnetic Nanoparticles with Pyrene-Tagged Dendritic Poly(Vinylidene Fluoride).

This study investigates the non-covalent coating of cobalt magnetic nanoparticles (MNPs) involving a graphene surface with pyrene-tagged dendritic poly(vinylidene fluoride) (PVDF). Dendrimers bearing a pyrene moiety were selected to play the role of spacers between the graphene surface of the MNPs and the PVDF chains, the pyrene unit being expected to interact with the surface of the MNPs. The pyrene-tagged dendritic spacer 11 decorated with ten acetylenic units was prepared and fully characterized.

Carboxylic acid-capped ruthenium nanoparticles: experimental and theoretical case study with ethanoic acid.

Given that the properties of metal nanoparticles (NPs) depend on several parameters (namely, morphology, size, surface composition, crystalline structure, etc.), a computational model that brings a better understanding of a structure-property relationship at the nanoscale is a significant plus in order to explain the surface properties of metal NPs and also their catalytic viability, in particular, when envisaging a new stabilizing agent. In this study we combined experimental and theoretical tools to obtain a mapping of the surface of ruthenium NPs stabilized by ethanoic acid as a new capping ligand.

Antimicrobial activities of novel bipyridine compounds produced by a new strain of isolated from Saharan soil.

The actinobacterium strain ABH26 closely related to , isolated from an Algerian Saharan soil sample, exhibited highly antagonist activity against Gram-positive bacteria, yeasts and filamentous fungi. Its ability to produce antimicrobial compounds was investigated using several solid culture media. The highest antimicrobial activity was obtained on Bennett medium.

Ionic Polypeptide Polymers with Unusual β-Sheet Stability.

Incorporating charged amino acid side chains in polypeptide polymer backbones to improve solubility usually leads to reduced secondary structuring. Here we show that highly water soluble (>15 mg.mL) β-sheets can be obtained via nucleotide monophosphate grafting onto simple poly(γ-propargyl- L-glutamate) backbone.

Metalloporphyrin-Catalyzed Oxidation of Sunitinib and Pazopanib, Two Anticancer Tyrosine Kinase Inhibitors: Evidence for New Potentially Toxic Metabolites.

Oxidation of two tyrosine kinase inhibitors (TKIs) sunitinib and pazopanib, using a chemical catalytic system able to mimic the cytochrome P450 type oxidation, allowed us to prepare  putative reactive/toxic metabolites of these anticancer drugs. Among these metabolites, aromatic aldehyde derivatives were unambiguously characterized. Such biomimetic oxidation of TKI-type drugs was essential to facilitate the identification of low amounts of aldehydes generated from these TKIs when incubated with human liver microsomes (HLM), which are classical models of human hepatic metabolism.

ortho-Phenyl dialkylphosphonium sulfonate compounds: two rotamers in equilibrium.

Two known and two new ortho-phenyl phosphonium-sulfonate compounds have been synthesized and analyzed in solution and in the solid state. When the phosphonium moiety bears alkyl substituents, two rotamers are in equilibrium in solution. These two rotamers have been entirely characterized and are shown to differ by the spatial arrangement of the phosphonium proton relative to the sulfonate moiety.

Oligomycins A and E, major bioactive secondary metabolites produced by Streptomyces sp. strain HG29 isolated from a Saharan soil.

An actinobacterial strain, HG29, with potent activity against pathogenic, toxigenic and phytopathogenic fungi was isolated from a Saharan soil sample of Algeria. On the basis of morphological and chemotaxonomic characteristics, the strain was classified in the genus Streptomyces. Analysis of the 16S rRNA gene sequence showed a similarity level of 99.

Coordination-Driven Folding in Multi-Zn -Porphyrin Arrays Constructed on a Pillar[5]arene Scaffold.

Pillar[5]arene derivatives bearing peripheral porphyrin subunits have been efficiently prepared from a deca-azide pillar[5]arene building block (17) and Zn -porphyrin derivatives bearing a terminal alkyne function (9 and 16). For the resulting deca-Zn -porphyrin arrays (18 and 20), variable temperature NMR studies revealed an intramolecular complexation of the peripheral Zn -porphyrin moieties by 1,2,3-triazole subunits. As a result, the molecules adopt a folded conformation.

Streptomyces sp. AT37 isolated from a Saharan soil produces a furanone derivative active against multidrug-resistant Staphylococcus aureus.

A novel actinobacterium strain, named AT37, showed a strong activity against some multidrug-resistant Staphylococcus aureus, including methicillin-resistant S. aureus MRSA ATCC 43300, other clinical isolates of MRSA and vancomycin resistant S. aureus VRSA S1.