Design, synthesis, and physicochemical and biological characterization of a new iron chelator of the family of hydroxychromenes

A thiochromenone antibiotic derived from the Pseudomonas quinolone signal selectively targets the Gram-negative pathogen Moraxella catarrhalis

The Pseudomonas quinolone signal (PQS) is an important quorum sensing signal of the pathogen Pseudomonas aeruginosa. We discovered an additional activity of PQS as a narrow spectrum antibiotic. Exploiting the privileged structure of PQS by the synthesis of heteroatom-substituted analogues led to a class of 2-alkyl-3-hydroxythiochromen-4-ones with highly potent antibiotic activity against the nasopharyngeal pathogen Moraxella catarrhalis. Synthetic optimization resulted in minimum inhibitory concentrations in the nanomolar range even for clinical isolates of M. catarrhalis. Surprisingly, the growth of other human pathogens and commensals, including closely related Moraxella species, was not inhibited, indicating exceptional species selectivity. Mechanistic studies revealed that the antibiotic was bactericidal and likely inhibits a target in the primary energy metabolism causing rapid depletion of the cellular ATP pool.

Synthetic quinolone signal analogues inhibiting the virulence factor elastase of Pseudomonas aeruginosa

We explore the chemical space of Pseudomonas quinolone signal analogs as privileged structures and report the discovery of a thioquinolone as a potent inhibitor of the important virulence factor elastase of the human pathogen Pseudomonas aeruginosa. We provide evidence that the derivative binds to the active site zinc of elastase and additionally acts as a fluorescent zinc sensor.

Synthesis of 2-alkyl-substituted chromone derivatives using microwave irradiation

A base-promoted condensation between 2-hydroxyacetophenones and aliphatic aldehydes has been studied. The reaction has been optimized to afford 2-alkyl-substituted 4-chromanones in an efficient manner using microwave heating. Performing the reaction using diisopropylamine in EtOH at 170 degrees C for 1 h gave moderate to high yields (43-88%). The 4-chromanones could be further converted into highly functionalized 2,3,6,8-tetrasubstituted chromones in which a 3-substituent (acetate, amine, or bromine) was introduced via straightforward chemical transformations.

3-Hydroxy-2-(5-hydroxypentyl)-4H-chromen-4-one: A Bidentate or Tridentate Iron(III) Ligand?

The pK(a) value and iron affinity constants for 3-hydroxy-2-(5-hydroxypentyl)-4H-chromen-4-one 1 have been determined by spectrophotometry using aqueous methanol solutions. The extrapolated affinity constants beta(1), beta(2), and beta(3)( )()for iron(III) in aqueous solution were 9.95, 18.69, and 26.02, respectively, with a corresponding pFe(3+) value of 14.64. Job plot and MS spectra data demonstrated that the 3:1 species is favored at pH 7.0. These results indicate that 1 acts as a bidentate ligand when coordinated to iron(III).

Gold(III) Dithiocarbamate Derivatives for the Treatment of Cancer: Solution Chemistry, DNA Binding, and Hemolytic Properties

Gold(III) compounds are emerging as a new class of metal complexes with outstanding cytotoxic properties and are presently being evaluated as potential antitumor agents. We report here on the solution and electrochemical properties, and the biological behavior of some gold(III) dithiocarbamate derivatives which have been recently proved to be one to 4 orders of magnitude more cytotoxic in vitro than the reference drug (cisplatin) and to be able to overcome to a large extent both intrinsic and acquired resistance to cisplatin itself. Their solution properties have been monitored in order to study their stability under physiological conditions; remarkably, they have shown to undergo complete hydrolysis within 1 h, the metal center remaining in the +3 oxidation state. Their DNA binding properties and ability in hemolyzing red blood cells have been also evaluated. These gold(III) complexes show high reactivity toward some biologically important isolated macromolecules, resulting in a dramatic inhibition of both DNA and RNA synthesis and inducing DNA lesions with a faster kinetics than cisplatin. Nevertheless, they also induce a strong and fast hemolytic effect (compared to cisplatin), suggesting that intracellular DNA might not represent their primary or exclusive biological target.

Synthesis, Structural Characterization, Solution Chemistry, and Preliminary Biological Studies of the Ruthenium(III) Complexes [TzH][trans-RuCl4(Tz)2] and [TzH][trans-RuCl4(DMSO)(Tz)]·(DMSO), the Thiazole Analogues of Antitumor ICR and NAMI-A

Two ruthenium(III) complexes bearing the thiazole ligand, namely, thiazolium (bisthiazole) tetrachlororuthenate (I, TzICR) and thiazolium (thiazole, DMSO) tetrachlororuthenate (II, TzNAMI) were prepared and characterized. The crystal structures of both complexes were solved by X-ray diffraction methods and found to match closely those of the corresponding imidazole complexes. The behavior in aqueous solution of bothTzICR and TzNAMI was analyzed spectroscopically. The time-dependent spectrophotometric profiles resemble closely those of the related ICR and NAMI-A anticancer compounds, respectively. It is observed that replacement of imidazole with thiazole, a less basic ligand, produces a significant decrease of the ligand exchange rates in the case of the NAMI-like compound. The main electrochemical features of these ruthenium(III) thiazole complexes were determined and compared to those of ICR and NAMI-A. Moreover, some preliminary data were obtained on their biological properties. Notably, both complexes exhibit higher reactivity toward serum albumin than toward calf thymus DNA; cytotoxicity is negligible in line with expectations. A more extensive characterization of the pharmacological properties in vivo is presently in progress.