Synthesis and cytotoxicity of 1,6,7,8-substituted 2-(4'-substituted phenyl)-4-quinolones and related compounds: identification as antimitotic agents interacting with tubulin

Mechanistic studies on regioselective dephosphorylation of phosphate prodrugs during a facile synthesis of antitumor phosphorylated 2-phenyl-6,7-methylenedioxy-1H-quinolin-4-one

Phosphorylation of 2-(3-hydroxy-5-methoxyphenyl)-6,7-methylenedioxy-1H-quinolin-4-one (1) afforded diphosphate 2. We found that, upon treatment with methanol under mild conditions, 2 can undergo facile and highly regioselective dephosphorylation to give the monophosphate 3, with a phosphate group remaining on the phenyl ring. The details of the dephosphorylation process were postulated and then probed by LC-MS and HPLC analyses. Furthermore, as a preliminary study, the water soluble monophosphate prodrug 4 was tested for antitumor activity against a MCF-7 xenograft nude mice model.

Identification of diaryl 5-amino-1,2,4-oxadiazoles as tubulin inhibitors: the special case of 3-(2-fluorophenyl)-5-(4-methoxyphenyl)amino-1,2,4-oxadiazole

The combination of experimental (inhibition of colchicine binding) and computational (COMPARE, docking studies) data unequivocally identified diaryl 5-amino-1,2,4-oxadiazoles as potent tubulin inhibitors. Good correlation was observed between tubulin binding and cytostatic properties for all tested compounds with the notable exception of the lead candidate, 3-(3-methoxyphenyl)-5-(4-methoxyphenyl)amino-1,2,4-oxadiazole (DCP 10500078). This compound was found to be substantially more active in our in vitro experiments than the monofluorinated title compound, 3-(2-fluorophenyl)-5-(4-methoxyphenyl)amino-1,2,4-oxadiazole (DCP 10500067/NSC 757486), which in turn demonstrated slightly better tubulin binding activity. Comparative SAR analysis of 25 diaryl 5-amino-1,2,4-oxadiazoles with other known tubulin inhibitors, such as combretastatin A-4 (CA-4) and colchicine, provides further insight into the specifics of their binding as well as a plausible mechanism of action.

Design and synthesis of 2-(3-alkylaminophenyl)-6-(pyrrolidin-1-yl)quinolin-4-ones as potent antitumor agents

2-(3-Alkylaminophenyl)-6-(pyrrolidin-1-yl)quinolin-4-ones 1-3 were synthesized and screened for anti-proliferative activity against three human cancer cell lines, as well as the normal cell line Detroit 551. All of the synthesized target compounds 1-3 demonstrated potent cytotoxic activity against the cancer cell lines, but weak inhibitory activity toward the normal cell line. 2-(3-Methyl aminophenyl)-6-(pyrrolidin-1-yl)quinolin-4-one (1), one of the potent compounds in vitro, was also tested in an in vivo Hep3B xenograft nude mice model, and its significant anticancer activity was reconfirmed. Therefore, compound 1 merits further investigation as an antitumor clinical trial candidate and potential anticancer agent.

KHC-4 anti-cancer effects on human PC3 prostate cancer cell line

A bicyclic chemical structure, such as that found in flavonoids, was discovered to have anti-cancer activity. Further synthetic structural modification created a series of 2-phenyl-4-quinolone analogs, especially KHC-4, with the same bicyclic chemical structure. This new structure was reported to have stronger anti-cancer activity. In KHC-4 treatments for 72 h on human prostate cancer PC3 cells, cytotoxic effects (IC(50) =0.1 μM) increased dose dependently, causing Cdk1/cyclin B1 complex activity mannered cell cycle and proliferation. KHC-4 treatments suppressed Bcl-2 and Bcl-xL protein levels and upregulated Bax. At the same concentration, pro-caspase 9 protein was cleaved to an activated form, leading to cell apoptosis. Furthermore, the MMP-2 protein levels also decreased through KHC-4 treatment in PC3. In conclusion, KHC-4 presents great prostate cancer therapeutic effects for cell proliferation inhibition, induction of apoptosis and protection against tumor migration.

Cytotoxic petrosiacetylenes from the marine sponge Petrosia sp

A novel petrosiacetylene analog (petrosiacetylene E) has been isolated from the Korean marine sponge Petrosia sp., along with petrosiacetylene A, B and C. Their structures were elucidated on the basis of spectroscopic methods and the stereochemistry of the new compound was determined by using the modified Mosher's method. Petrosiacetylene E showed higher cytotoxicity against five human cancer cell lines than petrosiacetylene A and B, presumably due to the additional hydroxy group located at C-16.

Recent advances in the synthesis of N-containing heteroaromatics via heterogeneously transition metal catalysed cross-coupling reactions

N-containing heteroaromatics are important substructures found in numerous natural or synthetic alkaloids. The diversity of the structures encountered, as well as their biological and pharmaceutical relevance, have motivated research aimed at the development of new economical, efficient and selective synthetic strategies to access these compounds. Over more than 100 years of research, this hot topic has resulted in numerous so-called "classical synthetic methods" that have really contributed to this important area. However, when the selective synthesis of highly functional heteroaromatics like indoles, quinolones, indoxyls, etc. is considered these methods remain limited. Recently transition metal-catalysed (TM-catalysed) procedures for the synthesis of such compounds and further transformations, have been developed providing increased tolerance toward functional groups and leading generally to higher reaction yields. Many of these methods have proven to be the most powerful and are currently applied in target- or diversity-oriented syntheses. This review article aims at reporting the recent developments devoted to this important area, focusing on the use of heterogeneous catalysed procedures that include either the formation of the heterocyclic ring towards the nuclei or their transformations to highly substituted compounds.

Synthesis, characterization of some benzazoles bearing pyridine moiety: search for novel anticancer agents

Thirteen novel benzazole derivatives were synthesized as possible anticancer agents. The first intermediate 1,3-benzothiazol-2-ylacetonitrile (2) was synthesized via cyclodeamination reaction of o-aminothiophenol (1) with malononitrile. Also, the second intermediate 5,6-dimethyl-1H-benzimidazol-2-ylacetonitrile (10) was afforded via cyclocondensation reaction between 4,5-dimethyl-1,2-phenylenediamine (9) and ethylcyanoacetate. Nucleophilic reaction of benzimidazolyl NH of compound (10) with ethylcyanoacetate afforded benzimidazolyl-3-oxopropanenitrile (11). On the other hand, methylenation of CH(2) function of compound (10) with dimethylformamide/dimethylacetal afforded benzimidazolylprop-2-enenitrile 12. The synthesis of benzothiazoylpyridines 5a,b and 8a,b as well as benzimidazolylpyridines, 14a,b and 17a-d was carried out through Michael addition of compounds 2 or 10 with arylidenemalononitriles 3a,b and 4a-d. The combination of pharmacophoric anticancer moieties, pyridine and benzazoles was the base on which target compounds 5a,b, 8a,b, 14a,b and 17a-d were designed. Among the synthesized compounds, four derivatives 10 and 17b-d were selected by National Cancer Institute (NCI), USA to be screened for their anticancer activity at a single high dose (10(-5) M) against a panel of 60 cancer cell lines. Compound 17b 4-[p-chlorophenyl]pyridine and 17d 4-[p- methoxyphenyl] pyridine exhibited a broad and moderate antitumor activity against 41 tumor cell lines belonging to the nine subpanels employed and are selected for further evaluation at five dose level screening.

4-Chloro-benzaldehyde (1-isobutyl-1H-imidazo[4,5-c]quinolin-4-yl)hydrazone monohydrate

In the title compound, C(21)H(20)ClN(5)·H(2)O, the 1H-imidazo[4,5-c]quinoline ring is approximately planar, with a maximum deviation of 0.0795 (7) Å, and it forms a dihedral angle of 7.65 (3)° with the chloro-phenyl ring. In the crystal, the components are linked into chains along the a axis via inter-molecular N-H⋯O, O-H⋯N and C-H⋯O hydrogen bonds. One of the H atoms of the water mol-ecule is disordered over two positions with a site-occupancy ratio of 0.80 (4):0.20 (4).

N-((1-benzyl-1H-1,2,3-triazol-4-yl)methyl)arylamide as a new scaffold that provides rapid access to antimicrotubule agents: synthesis and evaluation of antiproliferative activity against select cancer cell lines

A series of N-((1-benzyl-1H-1,2,3-triazol-4-yl)methyl)arylamides was synthesized by copper-catalyzed azide-alkyne cycloaddition (CuAAC) and afforded inhibitors of cancer cell growth. For example, compound 13e had an IC(50) of 46 nM against MCF-7 human breast tumor cells. Structure-activity relationship (SAR) studies demonstrated that (i) meta-phenoxy substitution of the N-1-benzyl group is important for antiproliferative activity and (ii) a variety of heterocyclic substitutions for the aryl group of the arylamide are tolerated. In silico COMPARE analysis of antiproliferative activity against the NCI-60 human tumor cell line panel revealed a correlation to clinically useful antimicrotubule agents such as paclitaxel and vincristine. This in silico correlation was supported by (i) in vitro inhibition of tubulin polymerization, (ii) G(2)/M-phase arrest in HeLa cells as assessed by flow cytometry, and (iii) perturbation of normal microtubule activity in HeLa cells as observed by confocal microscopy. The results demonstrate that N-((1-benzyl-1H-1,2,3-triazol-4-yl)methyl)arylamide is a readily accessible small molecule scaffold for compounds that inhibit tubulin polymerization and tumor cell growth.

Synthesis and preclinical evaluations of 2-(2-fluorophenyl)-6,7-methylenedioxyquinolin-4-one monosodium phosphate (CHM-1-P-Na) as a potent antitumor agent

CHM-1 [2-(2-fluorophenyl)-6,7-methylenedioxyquinolin-4-one] (1) has a unique antitumor mechanism of action. However, because 1 has relatively low hydrophilicity, it was evaluated only via ip administration, which is not clinically acceptable. In this study, we synthesized the monosodium phosphate salt (CHM-1-P-Na, 4) of 1 as a hydrophilic prodrug. Compound 4 was rapidly converted into 1 following iv and po administration and also possessed excellent antitumor activity in a SKOV-3 xenograft nude mice model. Compound 4 also had clear-cut pharmacological effects on enzymes related with tumor cells. Neither 4 nor 1 significantly affected normal biological function in a safety pharmacology profiling study. Compound 1 caused apoptotic effects in breast carcinoma cells via accumulation of cyclin B1, and importantly, the endogenous levels of the mitotic spindle checkpoint proteins BubR1 directly correlated with cellular response to microtubule disruption. With excellent antitumor activity profiles, 4 is highly promising for development as an anticancer clinical trials candidate.

CHM-1, a new vascular targeting agent, induces apoptosis of human umbilical vein endothelial cells via p53-mediated death receptor 5 up-regulation

CHM-1 (2'-fluoro-6,7-methylenedioxy-2-phenyl-4-quinolone) has been identified as a potent antitumor agent in human hepatocellular carcinoma; however, its role in tumor angiogenesis is unclear. This study investigated the effects of CHM-1 and the mechanisms by which it exerts its antiangiogenic and vascular disrupting properties. Using a xenograft model antitumor assay, we found that CHM-1 significantly inhibits tumor growth and microvessel formation. Flow cytometry, immunofluorescence microscopy, and cell death enzyme-linked immunosorbent assay kit revealed that CHM-1 inhibits growth of human umbilical vein endothelial cells (HUVEC) by induction of apoptotic cell death in a concentration-dependent manner. CHM-1 also suppresses HUVEC migration and capillary-like tube formation. We were able to correlate CHM-1-induced apoptosis in HUVEC with the cleavage of procaspase-3, -7, and -8, as well as with the cleavage of poly(ADP-ribose) polymerase by Western blotting assay. Such sensitization was achieved through up-regulation of death receptor 5 (DR5) but not DR4 or Fas. CHM-1 was also capable of increasing the expression level of p53, and most importantly, the induction of DR5 by CHM-1 was abolished by p53 small interfering RNA. Taken together, the results of this study indicate that CHM-1 exhibits vascular targeting activity associated with the induction of DR5-mediated endothelial cell apoptosis through p53 up-regulation, which suggests its potential as an antivascular and antitumor therapeutic agent.

Cytotoxic Activity and Three-Dimensional Quantitative Structure Activity Relationship of 2-Aryl-1,8-naphthyridin-4-ones

A series of substituted 2-arylnaphthyridin-4-one analogues, which were previously synthesized in our laboratory, were evaluated for their in vitro cytotoxic activity against human lung cancer A549 and human renal cancer Caki-2 cells using MTT assay. Some compounds (11, 12, and 13) showed stronger cytotoxicity than colchicine against both tumor cell lines, and compound 13 exhibited the most potent activity with IC(50) values of 2.3 and 13.4 microM, respectively. Three-dimensional quantitative structure activity relationship (3D-QSAR) studies of comparative molecular field analysis (CoMFA) and comparative molecular similarity indices analysis (CoMSIA) were performed. Predictive 3D-QSAR models were obtained with q(2) values of 0.869 and 0.872 and r(2) (ncv) values of 0.983 and 0.993 for CoMFA and CoMSIA, respectively. These results demonstrate that CoMFA and CoMSIA models could be reliably used in the design of novel cytotoxic agents.

Novel quinolone CHM-1 induces apoptosis and inhibits metastasis in a human osterogenic sarcoma cell line

Novel 2-phenyl-4-quinolone compounds have potent cytotoxic effects on different human cancer cell lines. In this study, we examined anticancer activity and mechanisms of 20-fluoro-6,7-methylenedioxy-2-phenyl-4-quinolone (CHM-1) in human osterogenic sarcoma U-2 OS cells. CHM-1-induced apoptosis was determined by flow cytometric analysis, DAPI staining, Comet assay, and caspase inhibitors. CHM-1-inhibited cell migration and invasion was assessed by a wound healing assay, gelatin zymography, and a Transwell assay. The mechanisms of CHM-1 effects on apoptosis and metastasis signaling pathways were studied using Western blotting and gene expression. CHM-1 induced G2/M arrest and apoptosis at an IC(50) (3 microM) in U-2 OS cells and caspase-3, -8, and -9 were activated. Caspase inhibitors increased cell viability after exposure to CHM-1. CHM-1-induced apoptosis was associated with enhanced ROS generation, DNA damage, decreased DeltaPsi(m) levels, and promotion of mitochondrial cytochrome c release. CHM-1 stimulated mRNA expression of caspase-3, -8, and -9, AIF, and Endo G. In addition, CHM-1 inhibited cell metastasis at a low concentration (<3 microM). CHM-1 inhibited the cell metastasis through the inhibition of MMP-2, -7, and -9. CHM-1 also decreased the levels of MAPK signaling pathways before leading to the inhibition of MMPs. In summary, CHM-1 is a potent inducer of apoptosis, which plays a role in the anticancer activity of CHM-1.

Synthesis of a quinolone library from ynones

A library of 72 quinolones was synthesized from substituted anthranilic acids, using ynone intermediates. These masked β-dicarbonyl synthons allowed cyclization under milder conditions than previously reported quinolone syntheses.

Heterocyclic analogs of thioflavones: synthesis and NMR spectroscopic investigations

The synthesis of several hitherto unknown heterocyclic ring systems derived from thioflavone is described. Coupling of various o-haloheteroarenecarbonyl chlorides with phenylacetylene gives 1-(o-haloheteroaryl)-3-phenylprop-2-yn-1-ones, which were treated with NaSH in refluxing ethanol to yield the corresponding bi- and tricyclic annelated 2-phenylthiopyran-4-ones. Detailed NMR spectroscopic investigations of the ring systems and their precursors are presented.

Design and synthesis of 2-(3-benzo[b]thienyl)-6,7-methylenedioxyquinolin-4-one analogues as potent antitumor agents that inhibit tubulin assembly

As part of our continuing investigation of azo-flavonoid derivatives as potential anticancer drug candidates, a series of 2-aryl-6,7-methylenedioxyquinolin-4-one analogues was designed and synthesized. The design combined structural features of 2-(2-fluorophenyl)-6,7-methylenedioxyquinolin-4-one (CHM-1), a previously discovered compound with potent in vivo antitumor activity, and 2-arylquinolin-4-ones, identified by CoMFA models. The newly synthesized analogues were evaluated for cytotoxicity against seven human cancer cell lines, and structure-activity relationship (SAR) correlations were established. Analogues 1, 37, and 39 showed potent cytotoxicity against different cancer cell lines. Compound 1 demonstrated selective cytotoxicity against Hep 3B (hepatoma) cells. Compound 37 was cytotoxic against HL-60 (leukemia), HCT-116 (colon cancer), Hep 3B (hepatoma), and SK-MEL-5 (melanoma) cells. Compound 39 exhibited broad cytotoxicity against all seven cancer cell lines, with IC50 values between 0.07 and 0.19 microM. Results from mechanism of action studies revealed that these new quinolone derivatives function as antitubulin agents.

Selective targeting of tumorigenic cancer cell lines by microtubule inhibitors

For anticancer drug therapy, it is critical to kill those cells with highest tumorigenic potential, even when they comprise a relatively small fraction of the overall tumor cell population. We have used the established NCI/DTP 60 cell line growth inhibition assay as a platform for exploring the relationship between chemical structure and growth inhibition in both tumorigenic and non-tumorigenic cancer cell lines. Using experimental measurements of “take rate” in ectopic implants as a proxy for tumorigenic potential, we identified eight chemical agents that appear to strongly and selectively inhibit the growth of the most tumorigenic cell lines. Biochemical assay data and structure-activity relationships indicate that these compounds act by inhibiting tubulin polymerization. Yet, their activity against tumorigenic cell lines is more selective than that of the other microtubule inhibitors in clinical use. Biochemical differences in the tubulin subunits that make up microtubules, or differences in the function of microtubules in mitotic spindle assembly or cell division may be associated with the selectivity of these compounds.

Fluoroquinolones from Imidoylketenes and Iminopropadienones, R - N=C=C=C=O

3-Fluoro-, 4-fluoro-, and 2,3,4-trifluorophenyliminopropadienones have been generated by flash vacuum thermolysis (FVT) of 5-[(fluoroarylamino)methoxymethylene]-2,2-dimethyldioxan-4,6-dione (Meldrum’s acid) derivatives. Their reaction with methanol affords interconverting imidoylketenes and oxoketenimines, which are employed in a synthesis of fluoroquinolones. The same quinolones are obtained from methyl 1-fluoroaryl-1,2,3-triazole-4-carboxylates, which on FVT eliminate N2 to generate oxoketenimines. Rearrangement of the oxoketenimines to imidoylketenes and cyclization afford the quinolones.