Synthesis and evaluation as potential anticancer agents of novel tetracyclic indenoquinoline derivatives

Synthesis and antitumoral evaluation of natural product-like compounds based on tropolone and benzotropolone derivatives

We present the preparation of a series of novel natural product-like homobarrelenones, norcaranes, and dihydrofluorenones through a diversity-oriented synthetic (DOS) strategy that combines Diels-Alder reactions and phototransformations, as well as their biological evaluation against MCF-7, HT-29, and NCI-H460 human tumor cells. Six of these demonstrated activities in the micromolar range against the three cell lines, and none were predicted as cytotoxic against human nontumor cells according to in silico studies. In addition, within the set of active derivatives, three exhibited low unspecific cytotoxicity in a sperm motility assay. The rich functionality of the new compounds makes them ideal candidates for exhaustive structure-activity relationship studies.

Synthesis of Indenoquinolinones and 2-Substituted Quinolines via [4 + 2] Cycloaddition Reaction

We have reported a metal-free protocol for the synthesis of indenoquinolinones and 2-substituted quinolines via [4 + 2] cycloaddition reaction using readily available 2-aminobenzaldehydes and ketones as starting materials. Different quinoline derivatives can be selectively synthesized by changing the type of ketones. O₂ and dimethyl sulfoxide (DMSO) as co-oxidants play an important role in the synthesis of indenoquinolinones. This condensation/oxidation strategy involves the formation of C-N, C-C, and C-O bonds, with the advantages of high yields and a broad substrate range.

Study and application of graphene oxide in the synthesis of 2,3-disubstituted quinolines via a Povarov multicomponent reaction and subsequent oxidation

The carbocatalyzed synthesis of 2,3-disubstituted quinolines is disclosed. This process involved a three-component Povarov reaction of anilines, aldehydes and electron-enriched enol ethers, which gave the substrate for the subsequent oxidation. Graphene oxide (GO) was exploited as a heterogeneous, metal-free and sustainable catalyst for both transformations. The multicomponent reaction proceeded under simple and mild reaction conditions, exhibited good functional group tolerance, and could be easily scaled up to the gram level. A selection of tetrahydroquinolines obtained was subsequently aromatized to quinolines. The multistep synthesis could also be performed as a one-pot procedure. Investigation of the real active sites of GO was carried out by performing control experiments and a by full characterization of the carbon material by X-ray photoelectron spectroscopy (XPS) and solid-state nuclear magnetic resonance (ssNMR).

Rh(iii)-Catalyzed [3 + 2]/[4 + 2] annulation of acetophenone oxime ethers with 3-acetoxy-1,4-enynes involving C–H activation

A novel, synthetically simple, selective rhodium(iii)-catalyzed [3 + 2]/[4 + 2] annulation cascade reaction to construct complex azafluorenone frameworks has been developed.

Construction of Dispiro-Indenone Scaffolds via Domino Cycloaddition Reactions of α,β-Unsaturated Aldimines with 2-Arylidene-1,3-indenediones and 2,2'-(Arylmethylene)bis(1,3-indenediones)

The catalyst-free domino reaction of α,β-unsaturated N-alkyl or N-arylaldimines with two molecules of 2-arylidene-1,3-indanediones in dry acetonitrile resulted in polysubstituted spiro[indene-2,3'-indeno[2',1':5,6]pyrano[2,3-b]pyridines] in moderate to good yields and with high diastereoselectivity. The reaction mechanism included sequential aza/oxa-Diels-Alder reactions via both endo-transition states. On the other hand, the catalyst-free domino reaction of α,β-unsaturated N-arylaldimines with 2,2'-(arylmethylene)bis(1,3-indenediones) afforded the mixed diastereoisomeric dispiro[indene-2,1'-cyclohexane-3',2″-indene] derivatives in satisfactory yields. The reaction mechanism of this formal [3 + 3] cycloaddition was believed to proceed with sequential nucleophilic 1,4-/1,2-additions.

Gold-catalyzed (4 + 2)-annulations between α-alkyl alkenylgold carbenes and benzisoxazoles with reactive alkyl groups

This work reports new (4 + 2)-annulations of α-alkyl vinylgold carbenes with benzisoxazoles to afford 3,4-dihydroquinoline derivatives with high anti-stereoselectivity.

This work reports new (4 + 2)-annulations of α-alkyl vinylgold carbenes with benzisoxazoles to afford 3,4-dihydroquinoline derivatives with high anti-stereoselectivity. The annulations are operable with carbenes in both acyclic and cyclic forms. This reaction sequence involves an initial formation of imines from α-alkylgold carbenes and benzisoxazoles, followed by a novel carbonyl-enamine reaction to yield 3,4-dihydroquinoline derivatives. This system presents the first alkyl C–H reactivity of α-alkyl gold carbenes with an external substrate.

Regioselective and diastereoselective synthesis of two functionalized 1,5-methanoindeno[1,2-d]azocines via a three-component reaction

The morpholine promoted three-component reaction of N-alkylpiperidinone, indane-1,3-dione and 2-arylideneindane-1,3-dione in ethanol at room temperature resulted in the (1H-1,5-methanoindeno[1,2-d]azocin-12-ylidene)-1H-indene-1,3(2H)-dione derivatives in good yields and with exo-configuration.

The relevance of folkloric usage of plant galls as medicines: Finding the scientific rationale

Galls, the abnormal growths in plants, induced by virus, bacteria, fungi, nematodes, arthropods, or even other plants, are akin to cancers in fauna. The galls which occur in a myriad of forms are phytochemically-distinct from the normal plant tissues, for these are the sites of tug-of-war, just like the granuloma in animals. To counter the stressors, in the form of the effector proteins of the invaders, the host plants elaborate a large repertoire of metabolites, which they normally will not produce. Perturbation of the jasmonic acid pathway, and the overexpression of auxin, and cytokinin, promote the tissue proliferation and the resultant galls. Though the plant family characteristics and the attackers determine the gall biochemistry, most of the galls are rich in bioactive phytochemicals such as phenolic acids, anthocyanins, purpurogallin, flavonoids, tannins, steroids, triterpenes, alkaloids, lipophilic components (tanshinone) etc. Throughout the long trajectory of evolution, humans have learned to use the galls as therapeutics, much like other plant parts. In diverse cultures, the evidence of folkloric usage of galls abound. Among others, galls from the plant genus like Rhus, Pistacia, Quercus, Terminalia etc. are popular as ethnomedicine. This review mines the literature on galling agents, and the medicinal relevance of galls.

Polycyclization Enabled by Relay Catalysis: One-Pot Manganese-Catalyzed C-H Allylation and Silver-Catalyzed Povarov Reaction

In this study, a Mn^I /Ag^I -based relay catalysis process is described for the one-pot synthesis of polycyclic products by a formal [3+2] and [4+2] cycloaddition reaction cascade. A manganese(I) complex catalyzed the first example of directed C-H allylation with allenes, setting the stage for an in situ Povarov cyclization catalyzed by silver(I). The reaction proceeds with high bond-forming efficiency (three C-C bonds), broad substrate scope, high regio- and stereoselectivity, and 100 % atom economy.

Bioorganopromoted green Friedländer synthesis: a versatile new malic acid promoted solvent free approach to multisubstituted quinolines

An efficient new strategy for the green synthesis of a variety of polysubstituted quinolines, using the Friedländer approach is reported, employing malic acid as a catalyst in organic synthesis for the first time.

Synthesis and Antiproliferative Activity of Some Quinoline and Oxadiazole Derivatives

In continuance of our search for newer antiproliferative agents we report herein the synthesis and antiproliferative studies of two series (5a–j and 10a–c) of heterocyclic compounds. All the new compounds were characterized by IR, NMR, and mass spectral data. The antiproliferative activity of 10 compounds (5a–j) was carried out on HeLa (cervix cancer cell line) and MDA-MB-435 (melanoma) and LC50, TGI, and GI50 were calculated, while the antiproliferative activity of 3 compounds (10a–c) was carried out against nine different panels of nearly 60 cell lines (NCI-60) according to the National Cancer Institute (NCI US) Protocol at 10 μM. 1-(7-Hydroxy-4-methyl-2-oxoquinolin-1(2H)-yl)-3-(4-methoxylphenyl)urea (5j) was found to have antiproliferative activity with GI50 of 35.1 μM against HeLa (cervix cancer cell line) and 60.4 μM against MDA-MB-435 (melanoma), respectively. The compounds 10a, 10b, and 10c showed antiproliferative activity with comparatively higher selectivity towards HOP-92 (Non-Small Cell Lung Cancer) with percent growth inhibitions (GIs) of 34.14, 35.29, and 31.59, respectively.

Metal free TBHP-promoted intramolecular carbonylation of arenes via radical cross-dehydrogenative coupling: synthesis of indenoquinolinones, 4-azafluorenones and fluorenones

Analogues of indenoquinolinones, 4-azafluorenones and fluorenones were accessed in good to excellent yields. One of the synthesized derivative is known for antibacterial activity.

Formation of zwitterionic salts via three-component reaction of benzimidazolium bromides, aromatic aldehydes and 1,3-indanedione

The three-component reaction in ethanol in the presence of triethylamine as base catalyst resulted in the unusual charge-separated zwitterionic salts in good yields.

Pd catalyzed facile synthesis of cyclopenta[b]quinolin-1-one via sequential Sonogashira coupling and annulation. An unusual mode of ring closure, using sulphur as a soft nucleophile

Pd mediated one pot sequential Sonogashira coupling followed by annulation using o-alkynyl aldehyde is reported.

Novel synthesis of a series of spiro 1,3-indanedione-fused dihydropyridines through the condensation of a tetrone with N-aryl/alkylenamines in presence of solid support silica sulfuric acid

A convenient protocol for the library synthesis of biologically important 1-aryl-2',6-spiro(1',3'-indanedione)-1H-indeno[1,2-b]quinoline-5,7-diones has been developed. In this one-pot reaction protocol a tetrone is condensed with various N-aryl/alkylenamines of 1,3-cyclohexadiones on the surface of a solid-supported acid catalyst silica sulfuric acid under solvent-free condition. The significant advantages of this methodology are the use of solvent-free reaction conditions, operational simplicity of the reaction, good yield of the products with high atom economy, and employment of a recyclable catalyst. All these favorable factors make the present method convenient, economic, and 'benign by design'.

A review on anticancer potential of bioactive heterocycle quinoline

The advent of Camptothecin added a new dimension in the field anticancer drug development containing quinoline motif. Quinoline scaffold plays an important role in anticancer drug development as their derivatives have shown excellent results through different mechanism of action such as growth inhibitors by cell cycle arrest, apoptosis, inhibition of angiogenesis, disruption of cell migration, and modulation of nuclear receptor responsiveness. The anti-cancer potential of several of these derivatives have been demonstrated on various cancer cell lines. In this review we have compiled and discussed specifically the anticancer potential of quinoline derivatives, which could provide a low-height flying bird's eye view of the quinoline derived compounds to a medicinal chemist for a comprehensive and target oriented information for development of clinically viable anticancer drugs.