Discovery and structure-activity relationships of a novel isothiazolone class of bacterial type II topoisomerase inhibitors.

There is an urgent and unmet medical need for new antibacterial drugs that tackle infections caused by multidrug-resistant (MDR) pathogens. During the course of our wider efforts to discover and exploit novel mechanism of action antibacterials, we have identified a novel series of isothiazolone based inhibitors of bacterial type II topoisomerase. Compounds from the class displayed excellent activity against both Gram-positive and Gram-negative bacteria with encouraging activity against a panel of MDR clinical Escherichia coli isolates when compared to ciprofloxacin. Representative compounds also displayed a promising in vitro safety profile.

Quinol derivatives as potential trypanocidal agents.

Quinols have been developed as a class of potential anti-cancer compounds. They are thought to act as double Michael acceptors, forming two covalent bonds to their target protein(s). Quinols have also been shown to have activity against the parasite Trypanosoma brucei, the causative organism of human African trypanosomiasis, but they demonstrated little selectivity over mammalian MRC5 cells in a counter-screen. In this paper, we report screening of further examples of quinols against T. brucei. We were able to derive an SAR, but the compounds demonstrated little selectivity over MRC5 cells. In an approach to increase selectivity, we attached melamine and benzamidine motifs to the quinols, because these moieties are known to be selectively concentrated in the parasite by transporter proteins. In general these transporter motif-containing analogues showed increased selectivity; however they also showed reduced levels of potency against T. brucei.

Synthesis of antitumour (1H-1,2,3-triazol-4-yl)-4-hydroxycyclohexa-2,5-dien-1-ones by copper-catalysed Huisgen cycloadditions.

4-Ethynyl-4-hydroxycyclohexa-2,5-dien-1-one 5 undergoes cycloaddition reactions with a range of substituted azides in the presence of copper salts to form 1,4-disubstituted triazoles 8-11 bearing the 4-hydroxycyclohexa-2,5-dien-1-one (quinol) pharmacophore; one example of an isomeric 1,5-disubstituted triazole 12 was formed from 5 and benzyl azide in the presence of a ruthenium catalyst. Compounds were screened for growth-inhibitory activity against five cancer cell lines of colon, breast and lung origin, but were overall less potent than the benzothiazolyl- and indolyl-substituted quinols 2 and 3.

Antitumor polycyclic acridines. 20. Search for DNA quadruplex binding selectivity in a series of 8,13-dimethylquino[4,3,2-kl]acridinium salts: telomere-targeted agents.

The growth-inhibitory activities of an extensive series of quaternized quino[4,3,2- kl]acridinium salts against tumor cell lines in vitro have been measured and their biological properties interpreted in the light of differential binding to different DNA isoforms. Selectivity for quadruplex DNA binding and stabilization by compounds were explored through an array of methods: UV absorption and fluorescence emission spectroscopy, surface plasmon resonance, and competition dialysis. Quadruplex DNA interaction was further characterized through FRET and DNA polymerase arrest assays. Telomerase inhibition, inferred from the TRAP assay, is attributed to quadruplex stabilization, supported by the strong correlation (R(2) = 0.81) across the series between quadruplex DNA binding affinity and TRAP inhibition potency. Growth inhibition potency in the NCI60 human tumor cell line panel is more marked in compounds with greater DNA duplex binding affinity (R(2) = 0.82). Quantification of relative quadruplex and duplex binding affinity constants puts some of these ligands among the most selective quadruplex DNA interactive agents reported to date.

Quinols as novel therapeutic agents. 7.1 Synthesis of antitumor 4-[1-(arylsulfonyl-1H-indol-2-yl)]-4-hydroxycyclohexa-2,5-dien-1-ones by Sonogashira reactions.

Interaction of 2-iodoaniline or 5-fluoro-2-iodoaniline with a range of arylsulfonyl chlorides affords sulfonamides that undergo Sonogashira couplings under thermal or microwave conditions with the alkyne 4-ethynyl-4-hydroxycyclohexa-2,5-dien-1-one followed by cyclization to 4-[1-(arylsulfonyl-1H-indol-2-yl)]-4-hydroxycyclo-hexa-2,5-dien-1-ones. This method allows for incorporation of a range of substituents into the arylsulfonyl moiety, and compounds showed selective in vitro inhibition of cancer cell lines of colon and renal origin, a feature of compounds bearing the quinol pharmacophore.

Antitumor quinols: role of glutathione in modulating quinol-induced apoptosis and identification of putative cellular protein targets.

Novel heteroaromatic quinols 4-(benzothiazol-2-yl)-4-hydroxycyclohexa-2,5-dienone (1) and 4-(1-benzenesulfonyl-1H-indol-2-yl)-4-hydroxycyclohexa-2,5-dienone (2) are promising novel anticancer agents. They exhibit in vitro antiproliferative activity against colon, renal, and breast carcinoma cell lines as well as in vivo antitumor activity in colon, renal, and breast tumor xenografts. Elucidation of the mechanism of antitumor action of these compounds is of great importance. We show in this study that the compounds induced apoptosis as demonstrated by caspase 3 and PARP cleavage at doses causing G(2)/M cell cycle arrest. Glutathione was found to play an important role in modulating quinol-mediated cytotoxicity. In HCT 116 cells, treatment with 1 and 2 caused a 2- to 3-fold increase in the total glutathione content, suggestive of a glutathione-mediated antioxidant response. Indeed, buthionine sulfoximine (BSO)-induced glutathione depleted cells were 6-10 times more sensitive to 1 and 2, while glutathione monoethyl ester supplementation decreased the antitumor potencies by 2-3 times. In further studies we determined other cellular proteins which bind to an immobilized quinol analog, and identified several proteins including beta-tubulin, heat shock protein 60, and peroxiredoxin 1 as potential molecular targets of quinols that may contribute to their proapoptotic and antiproliferative effects.

Synthesis and properties of bioactive 2- and 3-amino-8-methyl-8H-quino[4,3,2-kl]acridine and 8,13-dimethyl-8H-quino[4,3,2-kl]acridinium salts.

Cyclisation of 9-(benzotriazol-1-yl)acridine to the pentacycle 8H-quino[4,3,2-kl]acridine in a range of low-boiling solvents is mechanistically distinct from previously published photochemical (carbene) and thermolytic (radical) cyclisations. Fragmentation of the triazole ring of to a diazonium intermediate, and its subsequent heterolysis (-N(2)) and cyclisation is facilitated by solvation of intermediate zwitterionic species. Derivatives of 2- and 3-aminoquinoacridines methylated in the 8-position can be converted to 8,13-dimethylquino[4,3,2-kl]acridinium iodide salts with methyl iodide and were required for biological examination as potential telomerase inhibitors. The chloro group in 3-chloro-8-methyl-8H-quino[4,3,2-kl]acridine can be replaced efficiently by benzylamino, 4-morpholinyl and cyano substituents in palladium(0) mediated reactions.

Studies on high-temperature amination reactions of aromatic chlorides using discrete palladium-N-heterocyclic carbene (NHC) complexes and in situ palladium/imidazolium salt protocols.

The palladium catalysed coupling of aryl chlorides and amines can be readily achieved with short reaction times when carried out at high temperatures under thermal or microwave conditions. These coupling protocols are successful using two co-ordinate palladium-N-heterocyclic carbene complexes, or imidazolium salt protocols.

Programming Organic Molecules: Design and Management of Organic Syntheses through Free-Radical Cascade Processes.

Cascade, domino, or tandem processes, that link together two or more transformations in one pot, are increasing in popularity because they lead to improvements in synthetic efficiency and decreases in environmental impact. Not only do these cascades contain choice mechanistic gems but they also deliver compact and elegant syntheses of complex natural products. Longer cascades require more functional groups precisely configured within carefully designed initial molecular architectures. Such "purposeful" molecules can be thought of as chemical algorithms.This article surveys the phenomenal range of unimolecular free-radical cascades. A convenient system for classifying free-radical cascades is described that is useful for evaluating and comparing cascades and aids the design of synthetic routes to polycyclic structures.Double cyclization cascades lead to cyclopentylcyclopentane or bicyclo[3.3.0]octane derivatives. Precursors that contain a ring as a template have been used to control stereochemistry in syntheses of triquinanes and many related compounds. Of the cascades containing ring-cleavage steps, the most useful are the ring expansions which have opened up new synthetic routes to medium ring polycycles.The key design features of three-stage unimolecular free-radical cascades that yielded steroid structures, are linear arrays of radical acceptor units associated with methyl groups distributed every fifth C-atom in the precursor polyenes. Ring cleavage is the reverse of cyclization. In special, symmetrical structures, therefore, this led to sequences that were reversible, thus launching endlessly repeating cascades supported by delightfully fluxional structures. The science of "programming" organic molecules to achieve particular target structures is maturing rapidly. Coordination and classification of the welter of information in this area is intended to facilitate design and hence to extend the range and complexity of attainable structures.