Three-component, one-pot synthesis of benzo[6,7]cyclohepta[1,2-b]pyridine derivatives under catalyst free conditions and evaluation of their anti-inflammatory activity

Bioactivity of selenium-containing pyridinium salts: Prospecting future pharmaceutical constituents to treat liver diseases involving oxidative stress

Redox imbalance leads to oxidative stress that causes irreversible cellular damage. The incorporation of the antioxidant element selenium (Se) in the structure of pyridinium salts has been used as a strategy in chemical synthesis and can be useful in drug development. We investigated the antioxidant activity of Se-containing pyridinium salts (named Compounds 3A, 3B, and 3C) through in vitro tests. We focused our study on liver protein carbonylation, liver lipoperoxidation, free radical scavenging activity (1,1-diphenyl-2-picryl-hydrazil [DPPH]; 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid [ABTS]), and enzyme-mimetic activity assays (glutathione S-transferase [GST]-like; superoxide dismutase [SOD]-like). In addition, 2-(4-chlorophenyl)-2-oxoethyl)-2-((phenylselanyl)methyl)pyridin-1-ium bromide (3C) was selected to evaluate the acute oral toxicity in mice due to the best antioxidant profile. The three compounds were effective in reducing the levels of protein carbonylation and lipoperoxidation in the liver in a µM concentration range. All compounds demonstrated scavenger activity of DPPH and ABTS radicals, and GST-like action. No significant effects were detected in the SOD-like assay. Experimental data also showed that the acute oral treatment of mice with Compound 3C (50 and 300 mg/kg) did not cause mortality or change markers of liver and kidney functions. In summary, our findings reveal the antioxidant potential of Se-containing pyridinium salts in liver tissue, which could be related to their radical scavenging ability and mimetic action on the GST enzyme. They also demonstrate a low toxicity potential for Compound 3C. Together, the promising results open space for future studies on the therapeutic application of these molecules.

Synthesis, anticholinesterase activity, molecular docking, and molecular dynamic simulation studies of 1,3,4-oxadiazole derivatives

Two new series of 1,3,4-oxadiazoles bearing pyridine and thiazole heterocycles (4a-h and 5a-h) were synthesized (2,5-disubstituted-1,3,4-oxadiazoles). The structures of these newly synthesized compounds were confirmed by ¹ H nuclear magnetic resonance (NMR), ¹³ C NMR, high-resolution mass spectrometric and Fourier transform infrared spectroscopic methods. All these compounds were evaluated for their enzyme inhibitory activities against two cholinesterase enzymes, acetylcholinesterase (AChE) and butyrylcholinesterase (BChE). From the studies, we identified compounds 4a, 4h, 5a, 5d, and 5e as selective AChE inhibitors, with IC₅₀ values ranging from 0.023 to 0.037 μM. Furthermore, docking studies of these compounds were performed at the active sites of their target enzymes. The molecular docking study showed that 5e possessed an ideal docking pose with interactions inside AChE.

Electrochemical Selenylative Carbannulation of Biaryl Ynones to Seleno-Dibenzocycloheptenones/Spiro[5.5]Trienones

Electrooxidative-induced synthesis of structurally diverse seleno-dibenzocyclohepten-5-ones and seleno-spiro[5.5]trienones by selenylative carbannulation of biaryl ynones with diaryl diselenide has been developed. The switchable reactivity, intramolecular ortho-annulation or dearomative ipso-annulation, is directed by the substituent present on the ortho-aryl group of aryl-ynone. The prominent features of this method include metal-free, external chemical oxidant-free conditions, and readily accessible substrates.

In-vitro evaluation of antioxidant and anticholinesterase activities of novel pyridine, quinoxaline and s-triazine derivatives

Cholinesterase enzymes such as acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE) cause hydrolysis of acetylcholine (ACh), a neurotransmitter responsible for the cognitive functions of the brain such as acquiring knowledge and comprehension. Therefore, inhibition of these enzymes is an effective process to curb the progressive and fatal neurological Alzheimer's disease (AD). Herein, we explored the potential inhibitory activities of various pyridine, quinoxaline, and triazine derivatives (3a-k, 6a-j and 11a-h) against AChE and BuChE enzymes by following the modified Ellman's method. Further, anti-oxidant property of these libraries was monitored using DPPH (2,2'-diphenyl-1-picryl-hydrazylhydrate) radical scavenging analysis. From the studies, we identified that compounds 6e, 6f, 11b and 11f behaved as selective AChE inhibitors with IC₅₀ values ranging from 7.23 to 10.35 μM. Further studies revealed good anti-oxidant activity by these compounds with IC₅₀ values in the range of 14.80-27.22 μM. The kinetic studies of the active analogues demonstrated mixed-type of inhibition due to their interaction with both the catalytic active sites (CAS) and peripheral anionic sites (PAS) of the AChE. Additionally, molecular simulation in association with fluorescence and circular dichroism (CD) spectroscopic analyses explained strong affinities of inhibitors to bind with AChE enzyme at the physiological pH of 7.2. Binding constant values of 5.4 × 10⁴, 4.3 × 10⁴, 3.2 × 10⁴ and 4.9 × 10⁴ M^-1 corresponding to free energy changes -5.593, -6.799, -6.605 and -8.104 KcalM^-1 were obtained at 25 °C from fluorescence emission spectroscopic studies of 6e, 6f, 11b and 11f, respectively. Besides, CD spectroscopy deliberately explained the secondary structure of AChE partly unfolded upon binding with these dynamic molecules. Excellent in vitro profiles of distinct quinoxaline and triazine compounds highlighted them as the potential leads compared to pyridine derivatives, suggesting a path towards developing preventive or therapeutic targets to treat the Alzheimer's disease.

Synthesis of dibenzocyclohepta[1,2-a]naphthalene derivatives from phenylacetaldehyde and alkynyl benzyl alcohols via sequential electrophilic addition and double Friedel-Crafts reactions

A simple methodology has been developed for the synthesis of substituted 9H-dibenzo[3,4:6,7]-cyclohepta[1,2-a]naphthalenes from phenylacetaldehydes and ortho-alkynyl benzyl alcohols in the presence of a Lewis acid in moderate to good yields within a short reaction time. Interestingly, the reaction proceeds through a highly regioselective electrophilic addition followed by double Friedel-Crafts reaction to form uncommon dibenzo-fused seven-membered carbocycles.

High pressure assisted synthetic approach for novel 6,7-dihydro-5H-benzo[6,7]cyclohepta[1,2-b]pyridine and 5,6-dihydrobenzo[h]quinoline derivatives and their assessment as anticancer agents

A novel, expedient and effective methodology for the synthesis of distinctly substituted 6,7-dihydro-5H-benzo[6,7]cyclohepta[1,2-b]pyridine and 5,6-dihydrobenzo[h]quinoline systems has been developed with a new synthetic platform. This process includes ammonium acetate-mediated cyclocondensation reactions of 3-oxo-2-arylhydrazonopropanals with benzosuberone and tetralone precursors, respectively, using the high-pressure Q-tube reactor, which has been found to be superior to both conventional heating and microwave irradiation. The novel protocol benefits from its high atom efficiency, economy, ease of workup, broad substrate scope and is also applicable to gram-scale synthesis. To identify and confirm the newly synthesized targeted compounds, the X-ray single-crystal as well as all possible spectroscopic methods were utilized. The cytotoxicity of the newly synthesized 6,7-dihydro-5H-benzo[6,7]cyclohepta[1,2-b]pyridine 4a-j and 5,6-dihydrobenzo-[h]quinolines derivatives 6a-e were preliminary examined toward three cell lines of human cancer; lung cancer (A549), breast cancer (MCF-7) and colon cancer (HCT-116), by applying the MTT colorimetric assay. The achieved results reflected the promising profile of the prepared compounds in this study against cancer cells and have shown that members from the synthesized 6,7-dihydro-5H-benzo[6,7]cyclohepta[1,2-b]pyridine 4a-j exhibited promising cytotoxicity's against MCF-7, and A549 cancer cells respectively, while the HCT-116 (colon) cancer cells were inhibited by certain examples of 5,6-dihydrobenzo[h]quinoline derivatives 6c,d. These promising results could serve as a good primary base for further research into the design of anticancer drugs.

Synthesis of benzosuberone-tethered spirooxindoles: 1-3-dipolar cycloaddition of azomethine ylides and arylidene benzosuberones

Expedient synthesis of benzosuberone-tethered spirooxindoles was accomplished by a three-component 1,3-dipolar cycloaddition reaction between azomethine ylide (generated in situ) and arylidene benzosuberone. This protocol offers good yield and wide functional group tolerance under mild reaction condition with high regio- and stereoselectivities.

Design, synthesis, and in vitro antituberculosis activity of benzo[6,7]cyclohepta[1,2-b]pyridine-1,3,4-oxadiazole derivatives

A new antitubercular agents, benzo[6,7]cyclohepta[1,2-b]pyridine-1,3,4- oxadiazole hybrids (6a-o), have been designed and synthesized involving oxidative cyclization of hydrazones by use of di(acetoxy)iodobenzene, characterized by IR,¹ H NMR,¹³ C NMR, and HRMS, and further confirmed by X-ray analysis. All the newly synthesized compounds 4a-o evaluated for their in vitro antimycobacterial activity against Mycobacterium tuberculosis H37Rv (ATCC27294). Among the compounds tested, the compounds 4o (MIC: 1.56 μg/ml) and 4l, 4m (MIC: 3.125 μg/ml) are promising lead analogues and have shown lower cytotoxicity.

Copper-catalyzed cascade annulation between α-bromocarbonyls and biaryl or (Z)-arylvinylacetylenes enabling a direct synthesis of dibenzocycloheptanes and related compounds

Copper-catalyzed cascade annulation of γ,δ-unsaturated α-bromocarbonyls with biaryl or (Z)-arylvinylacetylenes is presented, giving an expeditious access to dibenzocycloheptanes and related compounds in moderate to high yields.