Synthesis of Succinimide-Containing Chromones, Naphthoquinones, and Xanthones under Rh(III) Catalysis: Evaluation of Anticancer Activity

A rhodium-catalyzed cascade C-H activation/annulation strategy for the expeditious assembly of pyrrolidinedione-fused 1,2-benzothiazines

A cascade annulation strategy triggered by rhodium(III)-catalyzed C-H activation has been reported for the expeditious assembly of pyrrolidinedione-fused 1,2-benzothiazines from free NH-sulfoximines with maleimides under mild conditions. Without the need for inert atmosphere protection, a broad range of sulfoximines with maleimides were well tolerated, producing diverse fused-thiazine derivatives in moderate to good yields. Additionally, the late-stage transformation of the target product demonstrated the potential synthetic value of this protocol.

Unlocking the potential of 1,4-naphthoquinones: A comprehensive review of their anticancer properties

Cancer encompasses a group of pathologies with common characteristics, high incidence, and prevalence in all countries. Although there are treatments available for this disease, they are not always effective or safe, often failing to achieve the desired results. This is why it is necessary to continue the search for new therapies. One of the strategies for obtaining new antitumor drugs is the use of 1,4-naphthoquinone as a scaffold in synthetic or natural products with antitumor activity. This review focuses on compiling studies related to the antitumor activity of 1,4-naphthoquinone and its natural and synthetic derivatives over the last 10 years. The work describes the main natural naphthoquinones with antitumor activity and classifies the synthetic naphthoquinones based on the structural modifications made to the scaffold. Additionally, the formation of metal complexes using naphthoquinones as a ligand is considered. After a thorough review, 197 synthetic compounds with potent biological activity against cancer have been classified according to their chemical structures and their mechanisms of action have been described.

Design, synthesis, and biological evaluation of novel ciprofloxacin derivatives as potential anticancer agents targeting topoisomerase II enzyme

A series of novel ciprofloxacin (CP) derivatives substituted at the N-4 position with biologically active moieties were designed and synthesised. 14 compounds were 1.02- to 8.66-fold more potent than doxorubicin against T-24 cancer cells. Ten compounds were 1.2- to 7.1-fold more potent than doxorubicin against PC-3 cancer cells. The most potent compounds 6, 7a, 7b, 8a, 9a, and 10c showed significant Topo II inhibitory activity (83-90% at 100 μM concentration). Compounds 6, 8a, and 10c were 1.01- to 2.32-fold more potent than doxorubicin. Compounds 6 and 8a induced apoptosis in T-24 (16.8- and 20.1-fold, respectively compared to control). This evidence was supported by an increase in the level of apoptotic caspase-3 (5.23- and 7.6-fold, sequentially). Both compounds arrested the cell cycle in the S phase in T-24 cancer cells while in PC-3 cancer cells the two compounds arrested the cell cycle in the G1 phase. Molecular docking simulations of compounds 6 and 8a into the Topo II active site rationalised their remarkable Topo II inhibitory activity.

Regioselective peri-C-H selenylation of aromatic compounds with weakly coordinating ketone groups

A novel and versatile method for peri-C-H selenylation of aromatic compounds bearing ketone groups, including chromones, xanthones, acridinones, quinolinones and naphthoquinones with diselenides under Ru(II) catalysis is presented. Various chromones and diselenides are applicable for this transformation, affording 5-selenyl chromones in a highly regioselective manner in good to excellent yields. This transformation is easy to scale up and the desired products can be further modified. Most importantly, this transformation allows the late-stage selenylation of bioactive compounds. Mechanistic studies show that radicals may be involved in this novel transformation.

Synthesis of Succinimide-Linked Indazol-3-ols Derived from Maleimides under Rh(III) Catalysis

The structural modification of N-aryl indazolols as tautomers of N-aryl indazolones has been established as a hot topic in pharmaceutics and medicinal chemistry. We herein disclose the rhodium(III)-catalyzed 1,4-addition reaction of maleimides with N-aryl indazol-3-ols, which provides the succinimide-bearing indazol-3-ol scaffolds with complete regioselectivity and a good functional group tolerance. Notably, the versatility of this protocol is demonstrated by the use of drug-molecule-linked and fluorescence-probe-linked maleimides.

New Experimental Conditions for Diels-Alder and Friedel-Crafts Alquilation Reactions with Thiophene: A New Selenocyanate with Potent Activity against Cancer

The reactivity of thiophene in Diels-Alder reactions is investigated with different maleimide derivatives. In this paper, we have synthesized for the first time the Diels-Alder adducts of thiophene at room temperature and atmospheric pressure. Maleimido-thiophene adducts were promoted by AlCl₃. The effects of solvent, time, temperature and the use of different Lewis acids were studied, showing dramatic effects for solvent and Lewis acid. Furthermore, the catalysis with AlCl₃ is highly stereoselective, preferably providing the exo form of the adduct. Additionally, we also discovered the ability of AlCl₃ to catalyze the arylation of maleimides to yield 3-aryl succinimides in a straightforward manner following a Friedel-Crafts-type addition. The inclusion of a selenocyanate group contributes to the cytotoxic activity of the adduct. This derivatization (from compound 7 to compound 15) results in an average GI₅₀ value of 1.98 µM in the DTP (NCI-60) cell panel, resulting in being especially active in renal cancer cells.

Advances in the site-selective C-5, C-3 and C-2 functionalization of chromones via sp2 C-H activation

In this work, site-selective C-H activation at C-5, C-3 and C-2 positions of chromones for the introduction of structural diversity to the chromone scaffold was studied. The keto group of the chromone moiety acts as the directing group for the selective functionalization of chromones at the C-5 position. Furthermore, the C-H functionalization at the electron-rich C-3 position of the chromone can be achieved using electrophilic coupling partners. The C-H functionalization at the C-2 position can be possible using nucleophilic coupling partners. The direct functionalization methods provide a better pathway for the generation of C-5, C-3 and C-2-substituted chromones with good atom economy than that of classical pre-functionalized reaction protocols.

The first N-ligand assisted Pd catalyzed asymmetric synthesis of 3-arylsuccinimides as novel antifungal leads

The first palladium/chiral nitrogenous ligand-catalyzed enantioselective addition of aryl boronic acids to various maleimides was reported.

Switchable regioselective hydroalkylation of 2-arylindoles with maleimides

A condition-based switchable regioselective hydroalkylation of 2-arylindoles with maleimides has been developed. The reaction in the presence of a Ru(ii)-catalyst resulted in hydroalkylation at the ortho-position of the C2-aryl ring via C-H activation whereas the reaction in the absence of the catalyst in TFE resulted in C3-hydroalkylation. Various functional groups both on the indole ring and on the 2-phenyl ring were tolerated and a wide range of hydroalkylated products were obtained in moderate to high (37-88%) yields.

A novel synthetic microtubule inhibitor exerts antiproliferative effects in multidrug resistant cancer cells and cancer stem cells

The success of cancer chemotherapy is limited by multidrug resistance (MDR), which is mainly caused by P-glycoprotein (P-gp) overexpression. In the present study, we describe a novel microtubule inhibitor, 5-(N-methylmaleimid-3-yl)-chromone (SPC-160002), that can be used to overcome MDR. A synthetic chromone derivative, SPC-160002, showed a broad spectrum of anti-proliferative effects on various human cancer cells without affecting P-gp expression and its drug efflux function. Treatment with SPC-160002 arrested the cell cycle at the M phase, as evidenced using fluorescence-activated cell sorting analysis, and increased the levels of mitotic marker proteins, including cyclin B, pS10-H3, and chromosomal passenger complex. This mitotic arrest by SPC-160002 was mediated by promoting and stabilizing microtubule polymerization, similar to the mechanism observed in case of taxane-based drugs. Furthermore, SPC-160002 suppressed the growth and sphere-forming activity of cancer stem cells. Our data herein strongly suggest that SPC-160002, a novel microtubule inhibitor, can be used to overcome MDR and can serve as an attractive candidate for anticancer drugs.

Rh(III)-Catalyzed Regioselective C8-Alkylation of Quinoline N-Oxides with Maleimides and Acrylates

Herein, we disclose the Rh(III)-catalyzed selective C8-alkylation of quinoline N-oxides with maleimides and acrylates. The main features of the reaction include complete C8-selectivity and broad substrate scope with good to excellent yields. The reaction also proceeded well with unprotected maleimide. The applicability of the developed methodology is demonstrated with gram-scale synthesis and post-modification of the alkylated product. Preliminary mechanistic study revealed that the reaction proceeds through a five-membered rhodacycle and involves proto-demetalation step.

2,3-Dichloro-5,6-dicyano-1,4-benzoquinone (DDQ)-Mediated Tandem Oxidative-Coupling/Annulation of o-Hydroxyaryl Enaminones with Cycloheptatriene

A DDQ-mediated tandem reaction of easily available o-hydroxy­aryl enaminones and cycloheptatriene is disclosed. It provides an effective and convenient method for the synthesis of 3-(cycloheptatrienyl)-substituted chromones in moderate to excellent yields with good functional group tolerance; this reaction involves an oxidative coupling and intramolecular annulation pathway.

Cobalt-catalyzed 2-(1-methylhydrazinyl)pyridine-assisted cyclization of thiophene-2-carbohydrazides with maleimides: efficient synthesis of thiophene-fused pyridones

A cobalt-catalyzed direct C-H/N-H functionalization of thiophene-2-carbohydrazides with maleimides by utilizing 2-(1-methylhydrazinyl)pyridine (MHP) as an easily removable bidentate directing group has been developed. This formal [4+2] cycloaddition has been achieved for the first time, and it provides an alternative and versatile approach to construct thiophene-fused pyridones using an inexpensive cobalt catalyst. The C-H/N-H activation cascade protocol showed a high efficiency and a broad substrate scope, and the products were obtained in good to excellent yields.

Synthesis and Biological Evaluation of Pyrazoline and Pyrrolidine-2,5-dione Hybrids as Potential Antitumor Agents

In search of novel and effective antitumor agents, pyrazoline-substituted pyrrolidine-2,5-dione hybrids were designed, synthesized and evaluated in silico, in vitro and in vivo for anticancer efficacy. All the compounds exhibited remarkable cytotoxic effects in MCF7 and HT29 cells. The excellent antiproliferative activity toward MCF7 (IC₅₀ =0.78±0.01 μM), HT29 (IC₅₀ =0.92±0.15 μM) and K562 (IC₅₀ =47.25±1.24 μM) cell lines, prompted us to further investigate the antitumor effects of the best compound S2 (1-(2-(3-(4-fluorophenyl)-5-(p-tolyl)-4,5-dihydro-1H-pyrazol-1-yl)-2-oxoethyl)pyrrolidine-2,5-dione). In cell-cycle analysis, S2 was found to disrupt the growth phases with increased cell population in G₁ /G₀ phase and decreased cell population in G₂ /M phase. The excellent in vitro effects were also supported by inhibition of anti-apoptotic protein Bcl-2. In vivo tumor regression studies of S2 in HT29 xenograft nude mice, exhibited equivalent and promising tumor regression with maximum TGI, 66 % (i. p. route) and 60 % (oral route) at 50 mg kg^-1 dose by both the routes, indicating oral bioavailability and antitumor efficacy. These findings advocate that hybridization of pyrazoline and pyrrolidine-2,5-dioes holds promise for the development of more potent and less toxic anticancer agents.

Ruthenium(II)-Catalyzed C-H Activation of Chromones with Maleimides to Synthesize Succinimide/Maleimide-Containing Chromones

An efficient route for the coupling of maleimides with chromones at the C5-position has been developed under Ru(II) catalysis. It could provide 1,4-addition products and oxidative Heck-type products by switching additives. Benzoic acid led to the formation of 1,4-addition products under solvent-free conditions, and silver acetate was promoted to the generation of oxidative Heck-type products. Various maleimides and chromones were suitable for this transformation, affording the desired products with good to excellent yields in a short reaction time. To understand the mechanism of this reaction, deuteration studies and control experiments have been performed.

Current Strategies in Development of New Chromone Derivatives with Diversified Pharmacological Activities: A Review

Chromone derivatives possess a spectrum of biological activities. Chromone has been recognized as a privileged structure for new drug invention and development. Substitution pattern of chromone scaffold determines different type of biological activities. The type, number and position of substituents connected to the chromone core play a vital role in determining pharmacological activities. In the present review, we have discussed new chromone derivatives as anticancer, anti-diabetic, antimicrobial, anti-inflammatory, antioxidant and as anti-Alzheimer agents. This review deals with the chromone derivatives prepared by combining chromone molecule with various natural and synthetic pharmacophores and pharmacological activities presented by them. The main aim is to highlight the diversified pharmacological activities exhibited by chromone hybrid molecules during the last eight to ten years.

Transition metal-catalyzed coupling of heterocyclic alkenes via C–H functionalization: recent trends and applications

Heterocyclic alkenes and their derivatives are an important class of reactive feedstock and valuable synthons. This review highlights the transition-metal-catalyzed coupling of heterocyclic alkenes via a C–H functionalization strategy.

Toward C2-nitrogenated chromones by copper-catalyzed β-C(sp2)–H N-heteroarylation of enaminones

The synthesis of C2-nitrogenated chromones has been performed via reactions of enaminones and nitrogen nucleophiles based on an unconventional β-C–H bond functionalization and a featured chromone annulation of enaminones.

Functionalization of 9-thioxanthone at the 1-position: From arylamino derivatives to [1]benzo(thio)pyrano[4,3,2-de]benzothieno[2,3-b]quinolines of biological interest

Original 1-amino substituted thioxanthone derivatives were easily prepared from the bare heterocycle by a deprotometalation-iodolysis-copper-catalyzed CN bond formation sequence. This last reaction delivered mono- or/and diarylated products depending on the aniline involved. 1-Amino-9-thioxanthone was also prepared and reacted with 2-iodoheterocycles. Interestingly, while 1-(arylamino)-9-thioxanthones could be isolated, their subsequent cyclization was found to deliver original hexacyclic derivatives of helicoidal nature. Evaluation of their photophysical properties revealed high fluorescence in polar media, indicating potential applications for biological imaging. These compounds being able to inhibit PIM1 kinase, their putative binding mode was examined through molecular modeling experiments. Altogether, these results tend to suggest the discovery of a new family of fluorescent PIM inhibitors and pave the way for their future rational optimization.

Regioselective C–H alkylation and alkenylation at the C5 position of 2-amino-1,4-naphthoquinones with maleimides under Rh(iii) catalysis

Rh(iii)-Catalyzed substituent enabled alkylation and alkenylation of 1,4-naphthoquinones with maleimides under acidic and basic conditions is described.