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We have recently shown that quinoxaline 1,4-dioxide (QdNO) derivatives, namely 2-benzoyl-3-phenyl-6,7-dichloroquinoxaline 1,4-dioxide (DCQ), 2-benzoyl-3-phenyl-quinoxaline 1,4-dioxide (BPQ) and 2-acetyl-3-methyl-quinoxaline 1,4-dioxide (AMQ), suppress the growth of T-84 human colon cancer cells. Here we show that the growth-suppressive effects of QdNOs are due to their ability to induce cell cycle arrest and/or apoptosis. While AMQ blocked more than 60% of cells at the G2/M phase without inducing apoptosis, DCQ caused a significant increase in apoptotic cells with no noticeable effects on the cycling of cells. Treatment with BPQ resulted in G2/M cell cycle arrest and induction of apoptosis. With regard to the effects of QdNOs on molecules that regulate apoptosis and the G2 to M transition, both BPQ and AMQ inhibited the expression of cyclin B, while DCQ significantly decreased the levels of Bcl-2 and increased Bax expression. Next, we investigated whether transforming growth factor-beta1 (TGF-beta1) and/or extracellular signal-regulated kinase (ERK) mediate the antiproliferative and apoptotic effects of QdNOs in colon cancer cells. Interestingly, the above QdNOs increased differentially total TGF beta1 mRNA expression and decreased TGF alpha mRNA and ERK phosphorylation. None of these QdNOs induced changes in TGF beta-2 mRNA expression. The addition of a specific inhibitor of MEK greatly enhanced apoptosis in cells treated with DCQ, suggesting that the inhibition of ERK phosphorylation may explain, to an extent, the apoptogenic effects of this compound. Taken together, these findings provide insights into possible molecular mechanisms of growth inhibition by QdNOs that could aid in their evaluation for anticancer therapy. [ABSTRACT FROM AUTHOR] more...

Focuses on the claims of researchers that 2,1-benzisoxazole derivatives are indazalones. Method for the preparation of 3-oxy-substituted 2H-indazole; Structure of 2-N-benzylindazalone; Result of the experimental, physical and spectral data of the isolated intermediates and products. more...

Reaction options, alkoxide vs hydroxide vs amine addition to the key intermediate (o-nitrosoimine) generated in the Davis-Beirut reaction of an o-nitrobenzylamine substrate, are reported to explain the nucleophilic addition selectivity of this one-pot indazole-forming process. The hydroxide addition/deprotection pathway as well as the fate of the resulting o-nitrosobenzaldehyde were both uncovered with several o-nitrobenzylamine substrates, and design elements required for an efficient double Davis-Beirut reaction, inspired by new mechanistic insights, were defined. [ABSTRACT FROM AUTHOR] more...

The discovery of a new variation on the Davis-Beirut reaction is described in which an atypical heterocyclic framework (the anthranil or benzo[c]isoxazole framework) is formed as the result of diversion of a key reactive intermediate away from its expected reactivity--a potentially general approach to reaction design and development. Experimental and computational support for the proposed mechanism and origins of altered reactivity are described. [ABSTRACT FROM AUTHOR] more...

Two operationally simple one-pot protocols have been developed for the synthesis of amino-functionalized benzo[4,5]imidazo[2,1-a]isoquinolines and isoquinolino[3,4-b]quinoxalines. Optimization data and substrate scope for these atom-economical transformations, which engage commercially available o-phenylenediamines and o-cyanobenzaldehydes, are discussed. [ABSTRACT FROM AUTHOR] more...

A heterocycle-to-heterocycle strategy is presented for the preparation of highly fluorescent and solvatochromic dibenzonaphthyridinones (DBNs) via methodology that leads to the formation of a tertiary, spiro-fused carbon center. A linear correlation between the results of photophysical experiments and time dependent density functional theory calculations was observed for the λmax of excitation for DBNs with varying electronic character. [ABSTRACT FROM AUTHOR] more...

A variety of quinoline-4-amines were synthesized from substituted 3-(2-nitrophenyl)isoxazoles utilizing Zn0 or Fe0 dust and HOAc using a reductive heterocyclization process. The starting isoxazoles were synthesized from readily available starting materials. A brief survey of functional groups tolerated in this reductive heterocyclization was performed and several 10-amino-3,4-dihydrobenzo[ b][1,6]naphthyridin-1(2 H)-one and 9-amino-3,4-dihydroacridin-1(2 H)-one examples were synthesized. [ABSTRACT FROM AUTHOR] more...

Myeloperoxidase (MPO) produces hypohalous acids as a key component of the innate immune response; however, release of these acids extracellularly results in inflammatory cell and tissue damage. The two-step, one-pot Davis–Beirut reaction was used to synthesize a library of 2 H -indazoles and 1 H -indazolones as putative inhibitors of MPO. A structure–activity relationship study was undertaken wherein compounds were evaluated utilizing taurine-chloramine and MPO-mediated H 2 O 2 consumption assays. Docking studies as well as toxicophore and Lipinski analyses were performed. Fourteen compounds were found to be potent inhibitors with IC 50 values <1 μM, suggesting these compounds could be considered as potential modulators of pro-oxidative tissue injury pertubated by the inflammatory MPO/H 2 O 2 /HOCl/HOBr system. [ABSTRACT FROM AUTHOR] more...

Background Although tumor hypoxia poses challenges against conventional cancer treatments, it provides a therapeutic target for hypoxia-activated drugs. Here, we studied the effect of the hypoxiaactivated synthetic quinoxaline di-N-oxide DCQ against breast cancer metastasis and identified the underlying mechanisms. Methods The human breast cancer cell lines MCF-7 (p53 wildtype) and MDA-MB-231 (p53 mutant) were treated with DCQ under normoxia or hypoxia. Drug toxicity on non-cancerous MCF- 10A breast cells was also determined. In vitro cellular responses were investigated by flow cytometry, transfection, western blotting, ELISA and migration assays. The anti-metastatic effect of DCQ was validated in the MDA-MB-231 xenograft mouse model. Results DCQ selectively induced apoptosis in both human breast cancer cells preferentially under hypoxia without affecting the viability of non-cancerous MCF-10A. Cancer cell death was associated with an increase in reactive oxygen species (ROS) independently of p53 and was inhibited by antioxidants. DCQ-induced ROS was associated with DNA damage, the downregulation of hypoxia inducible factor-1 alpha (HIF-1α), and inhibition of vascular endothelial growth factor (VEGF) secretion. In MCF-7, HIF-1α inhibition was partially via p53-activation and was accompanied by a decrease in p-mTOR protein, suggesting interference with HIF-1α translation. In MDA-MB-231, DCQ reduced HIF-1α through proteasomal-dependent degradation mechanisms. HIF-1α inhibition by DCQ blocked VEGF secretion and invasion in MCF-7 and led to the inhibition of TWIST in MDA-MB-231. Consistently, DCQ exhibited robust antitumor activity in MDA-MB-231 breast cancer mouse xenografts, enhanced animal survival, and reduced metastatic dissemination to lungs and liver. Conclusion DCQ is the first hypoxia-activated drug showing anti-metastatic effects against breast cancer, suggesting its potential use for breast cancer therapy. [ABSTRACT FROM AUTHOR] more...

Abstract: The Davis–Beirut reaction, which provides an efficient synthesis of 2H-indazoles and, subsequently, indazolones, is shown to proceed rapidly from o-nitrosobenzaldehyde and primary amines under both acid and base catalysis. Experimental and theoretical evidence in support of a reaction mechanism is provided in which o-nitrosobenzylidine imine is a pivotal intermediate in this N,N-bond forming heterocyclization reaction. The Davis–Beirut reaction is also shown to effectively synthesize a number of novel 3-amino-2H-indazole derivatives. [Copyright &y& Elsevier] more...

The parent 5H-indazolo[3,2-b]benzo[d]-1,3-oxazine heterocycle as well as a series of novel analogues have been synthesized utilizing two subsequent intramolecular heterocyclizations in one pot. A variety of diversity groups were added to explore the scope of this reaction and to provide a number of new compounds for biological screening. [ABSTRACT FROM AUTHOR] more...

1,2,4,5-Tetrazines (prepared from aryl nitriles) condense with isoxazolylcyclobutanones (prepared from 3-benzenesulfonyl-3-vinylcyclobutanol) in methanolic KOH to give conformationally restricted 6-isoxazol-5-yl-6,7-dihydro-5H-[1,2]diazocin-4-ones. The solution IH NMR spectra of dihydrodiazocinone la with phenyl moieties at C3 and C8 reveal two conformations of the eight-membered heterocycle that are non-interconverting on the NMR time scale at ambient temperature. The kinetics of the conversion process, followed by ¹H NMR between 21 and 70 °C in DMSO solution, yield an activation energy of ∼21 kcal/mol relative to the kinetic conformer and show anequilibrated ratio of ∼5:1 of the thermodynamic to the kinetic conformers. The electronic structure calculations on a model dihydrodiazocinone predict geometries for the two conformations. One of these geometries agrees with the X-ray crystallographic analysis of the thermodynamic conformation of 1a. [ABSTRACT FROM AUTHOR] more...

A novel one-step synthesis route to fully substituted pyrazol-4-ols is reported. This simple yet nonobvious method for the construction of pyrazol-4-ols by the condensation fragmentation-cyclization-extrusion reactions of thietanones with 1,2,4,5-tetrazines is reported. All of the elements of the thietanone except its sulfur are incorporated in these novel products. [ABSTRACT FROM AUTHOR] more...

[Display omitted] • Davis–Beirut reaction inspired nitroso Diels–Alder protocol. • Nitrophenyl starting material has the para position substituted with a 2°-amine or 2°-alcohol. • Concomitant benzylic oxidation and nitro reduction delivers a nitrosophenyl intermediate. • One-pot procedure delivers aryldihydro-1,2-oxazines in moderate yields. A Davis–Beirut reaction inspired nitroso Diels–Alder protocol is reported. The starting material for the procedure is a nitrophenyl moiety with the para position appropriately substituted with a 2°-amine (see 5) or 2°-alcohol (see 6). Deprotonation at the benzylic position followed by concomitant oxidation of the benzylic position and reduction of the nitro moiety delivers a nitrosophenyl intermediate, which subsequently undergoes a nitroso Diels–Alder reaction. This one-pot procedure delivers aryldihydro-1,2-oxazines in moderate yields. [ABSTRACT FROM AUTHOR] more...