A review: Biologically active 3,4-heterocycle-fused coumarins

Entry to 4,5-fused coumarin frameworks via radical-promoted alkylative intramolecular C5-annulation

An unprecedented radical-promoted strategy involving a domino alkylation/intramolecular C5-annulation of N-acryloyl-4-amino coumarin has been devised for the assembly of 4,5-fused coumarin scaffolds. This protocol employs silver-catalyzed oxidative decarboxylation for the generation of alkyl radicals from carboxylic acids, which were used as radical precursors. This method has also been extended to a diverse range of carbon-centered radicals generated from 2-oxo acids, a 1,3-dicarbonyl compound, isopropanol and acetone.

Copper(I)-Catalyzed Formal [4 + 2] Cyclocondensation of ortho-Hydroxybenzyl Alcohol, Aromatic Terminal Alkynes, and Sulfonyl Azides: An Alternative Approach to 2-Sulfonyliminocoumarins

In this paper, an alternative and efficient copper(I)-catalyzed synthesis of 2-sulfonyliminocoumarins is developed through a three-component reaction of ortho-hydroxybenzyl alcohol, alkynes, and p-toluenesulfonyl azide. The proposed route for access to the 2-iminocoumarin ring involves a [4 + 2] hetero-Diels-Alder reaction between ortho-quinone methide and ketenimine intermediates generated in situ.

Novel Coumarins Derivatives for A. baumannii Lung Infection Developed by High-Throughput Screening and Reinforcement Learning

With the increasing resistance of Acinetobacter baumannii (A. baumannii) to antibiotics, researchers have turned their attention to the development of new antimicrobial agents. Among them, coumarin-based heterocycles have attracted much attention due to their unique biological activities, especially in the field of antibacterial infection. In this study, a series of coumarin derivatives were synthesized and screened for their bactericidal activities (Ren et al. 2018; Salehian et al. 2021). The inhibitory activities of these compounds on bacterial strains were evaluated, and the related mechanism of the new compounds was explored. Firstly, the MIC values and bacterial growth curves were measured after compound treatment to evaluate the antibacterial activity in vitro. Then, the in vivo antibacterial activities of the new compounds were assessed on A. baumannii-infected mice by determining the mice survival rates, counting bacterial CFU numbers, measuring inflammatory cytokine levels, and histopathology analysis. In addition, the ROS levels in the bacterial cells were measured with DCFH-DA detection kit. Furthermore, the potential target and detailed mechanism of the new compounds during infection disease therapy were predicted and evidenced with molecular docking. After that, ADMET characteristic prediction was completed, and novel, synthesizable, drug-effective molecules were optimized with reinforcement learning study based on the probed compound as a training template. The interaction between the selected structures and target proteins was further evidenced with molecular docking. This series of innovative studies provides important theoretical and experimental data for the development of new anti-A. baumannii infection drugs.

An In-Depth Exploration of Six Decades of the Kröhnke Pyridine Synthesis

The Kröhnke Pyridine Synthesis has been discovered about six decades ago (1961), by Fritz Kröhnke and Wilfried Zecher at the University of Giessen. The original method involved the reaction of α-pyridinium methyl ketone salts with α,β-unsaturated carbonyl compounds in the presence of a nitrogen source, frequently ammonium acetate. Since its discovery, the Kröhnke methodology has been demonstrated to be suitable for the preparation of mono-, di-, tri- and tetra-pyridines, with important applications in several research fields. Over the years, a number of modifications to the original approach have been developed and reported, enabling for the broad applicability of these methods even in modern days, also for the synthesis of non-pyridine compounds. In this critical and tutorial review, we will thoroughly explore and discuss the potential of the original method, the refinements that have been made over the years, as well as some applications arising from each type of pyridine and/or non-pyridine compounds produced by Kröhnke's approach.

An Overview of the Synthesis of 3,4-Fused Pyrrolocoumarins of Biological Interest

3,4-Fused pyrrolocoumarins, synthetically prepared or naturally occurring, possess interesting biological properties. In this review, the synthetic strategies for the synthesis of the title compounds are presented along with their biological activities. Two routes are followed for that synthesis. In one, the pyrrole ring is formed from coumarin derivatives, such as aminocoumarins or other coumarins. In the other approach, the pyranone moiety is built from an existing pyrrole derivative or through the simultaneous formation of coumarin and pyrrole frameworks. The above syntheses are achieved via 1,3-dipolar cycloaddition reactions, Michael reaction, aza-Claisen rearrangement reactions, multi-component reactions (MCR), as well as metal-catalyzed reactions. Pyrrolocoumarins present cytotoxic, antifungal, antibacterial, α-glucosidase inhibition, antioxidant, lipoxygenase (LOX) inhibition, and fluorescent activities, as well as benzodiazepine receptor ability.

Click chemistry beyond metal-catalyzed cycloaddition as a remarkable tool for green chemical synthesis of antifungal medications

Click chemistry is widely used for the efficient synthesis of 1,4-disubstituted-1,2,3-triazole, a well-known scaffold with widespread biological activity in the pharmaceutical sciences. In recent years, this magic ring has attracted the attention of scientists for its potential in designing and synthesizing new antifungal agents. Despite scientific and medical advances, fungal infections still account for more than 1.5 million deaths globally per year, especially in people with compromised immune function. This increasing trend is definitely related to a raise in the incidence of fungal infections and prevalence of antifungal drug resistance. In this condition, an urgent need for new alternative antifungals is undeniable. By focusing on the main aspects of reaction conditions in click chemistry, this review was conducted to classify antifungal 1,4-disubstituted-1,2,3-triazole hybrids based on their chemical structures and introduce the most effective triazole antifungal derivatives. It was notable that in all reactions studied, Cu(I) catalysts generated in situ by the reduction in Cu(II) salts or used copper(I) salts directly, as well as mixed solvents of t-BuOH/H2O and DMF/H2O had most application in the synthesis of triazole ring. The most effective antifungal activity was also observed in fluconazole analogs containing 1,2,3-triazole moiety and benzo-fused five/six-membered heterocyclic conjugates with a 1,2,3-triazole ring, even with better activity than fluconazole. The findings of structure-activity relationship and molecular docking of antifungal derivatives synthesized with copper-catalyzed azide-alkyne cycloaddition (CuAAC) could offer medicinal chemistry scientists valuable data on designing and synthesizing novel triazole antifungals with more potent biological activities in their future research.

Coumarin-furo[2,3-d]pyrimidone hybrid molecules targeting human liver cancer cells: synthesis, anticancer effect, EGFR inhibition and molecular docking studies

The design, synthesis and investigation of antitumor activities of some coumarin-furo[2,3-d]pyrimidone hybrid molecules are reported. In vitro, HepG2 cells were used to investigate the cytotoxicity of 6a-n and 10a-n. The results demonstrated that coupling a furopyrimidone scaffold with coumarin through a hydrazide linker can effectively improve their synergistic anticancer activity. The coumarin-furo[2,3-d]pyrimidone combination 10a exhibited significant inhibitory activity against HepG2 cells with IC50 = 7.72 ± 1.56 μM, which is better than those of gefitinib and sorafenib. It is worth mentioning that the coumarin-furo[2,3-d]pyrimidone combination 10a showed excellent inhibition of the EGFR enzymatic activity with IC50 = 1.53 μM and 90% inhibition at 10 μM concentration. In silico investigation predicts the possibility of direct binding between the new coumarin-furo[2,3-d]pyrimidone hybrid molecules and the EGFR. The results suggest that coumarin-furo[2,3-d]pyrimidone hybrid molecules are potential antitumor agents targeting human liver cancer cells.

Synthesis and antiproliferative evaluation of novel 3,5,8-trisubstituted coumarins against breast cancer

Aim: This study focused on designing and synthesizing novel derivatives of 3,5,8-trisubstituted coumarin. Results: The synthesized compounds, particularly compound 5, exhibited significant cytotoxic effects on MCF-7 cells, surpassing staurosporine, and reduced toxicity toward MCF-10A cells, highlighting potential pharmacological advantages. Further, compound 5 altered the cell cycle and significantly increased apoptosis in MCF-7 cells, involving both early (41.7-fold) and late stages (33-fold), while moderately affecting necrotic signaling. The antitumor activity was linked to a notable reduction (4.78-fold) in topoisomerase IIβ expression. Molecular modeling indicated compound 5's strong affinity for EGFR, human EGF2 and topoisomerase II proteins. Conclusion: These findings highlight compound 5 as a multifaceted antitumor agent for breast cancer.

Iodine-Catalyzed Diversity-Oriented Synthesis of 3,4-Heterocycle-Fused Coumarins from 4-Aminocoumarins and Aurones in Different Solvent

An unprecedented protocol has been developed for the synthesis of 3,4-heterocycle-fused coumarins from 4-aminocoumarins and aurones through iodine-catalyzed cascade reactions. Dihydropyridine-fused coumarin, pyridine-fused coumarin, and pyrrole-fused coumarin derivatives were achieved in good yields with high selectivity when CH3CN, AcOH, and DMSO were used as the solvent, respectively. This protocol provides several advantages, such as easily available starting materials, high atom economy, friendly environment, and simple procedure.

Iodomethane in C1 chemistry: application in palladium-catalyzed [2 + 2 + 1] annulation

An efficient palladium-catalyzed [2 + 2 + 1] annulation of 3-iodochromones, bridged olefins, and iodomethane is described, affording a range of chromone-containing polycyclic compounds. Additionally, the corresponding deuterated products were smoothly obtained with iodomethane-d3 instead of iodomethane. Moreover, the synthetic utility of this method is further substantiated by gram scale preparation and application to late-stage modification of estrone.

Iodine-Catalyzed Cascade Annulation of 4-Hydroxycoumarins with Aurones: Access to Spirocyclic Benzofuran-Furocoumarins

An attractive approach for the preparation of spirocyclic benzofuran-furocoumarins has been developed through iodine-catalyzed cascade annulation of 4-hydroxycoumarins with aurones. The reaction involves Michael addition, iodination, and intramolecular nucleophilic substitution in a one-step process, and offers an efficient method for easy access to a series of valuable spirocyclic benzofuran-furocoumarins in good yields (up to 99%) with excellent stereoselectivity. Moreover, this unprecedented protocol provides several advantages, including readily available materials, an environmentally benign catalyst, a broad substrate scope, and a simple procedure.

Combined experimental and computational investigations of the fluorosolvatochromism of chromeno[4,3-b]pyridine derivatives: Effect of the methoxy substitution

Extensive research has been conducted on the spectral properties of chromeno[4,3-b]pyridine derivatives, owing to their potential applications in sensing, optoelectronic devices, and drug discovery. This study presents a comprehensive investigation into the fluorosolvatochromism of selected chromeno[4,3-b]pyridine derivatives, with a particular emphasis on the impact of methoxy substitution. Three derivatives were synthesized and subjected to spectral analysis: chromeno[4,3-b]pyridine-3-carboxylate (I) as the parent compound, and its 7-methoxy (II) and 8-methoxy (III) substituted derivatives.The UV-Vis absorption spectra of all derivatives exhibited a broad band with a maximum absorption wavelength that remained unaffected by the surrounding medium. However, distinct fluorescence properties were observed among them. Specifically, derivative II displayed notable fluorescence, while derivatives I and III exhibited no fluorescence properties. Furthermore, derivative II exhibited a fluorescence spectrum that is significantly influenced by the polarity of the medium. To investigate the fluorosolvatochromic behavior in depth, we conducted a comprehensive analysis using various neat solvents with different polarities and hydrogen bonding capabilities. The results obtained revealed a significant positive fluorosolvatochromism, with a bathochromic shift in the fluorescence spectrum as the solvent polarity increased. To understand how specific and non-specific interactions between the solute and the solvent affected the fluorosolvatochromism of II, we employed the four empirical scales model of Catalán. The obtained results demonstrated that intramolecular charge transfer played a crucial role in the fluorescence behavior of II. To provide a molecular-level explanation for the experimental spectral properties, we utilized the DFT and TD-DFT/B3LYP/6-31 + G(d) computational methods with the IEFPCM implicit solvation approach. The spectral differences between II and III were rationalized in terms of the frontier molecular orbitals (FMOs: the HOMO and LUMO), where distinct natures were observed among the examined derivatives. This study offers valuable insights into the impact of methoxy substitution on the physical and chemical properties of chromeno[4,3-b]pyridine derivatives, specifically concerning their spectral properties as elucidated by their fluorosolvatochromic behavior.

An Efficient One-Pot Synthesis of Pyrido[2,3-c]coumarins via Serial Catalysis and Its Application in Concise Formal Synthesis of Santiagonamine

Versatile and high-yielding one-pot synthesis of polysubstituted pyrido[2,3-c]coumarins from N-Boc-N-coumarinyl propargylamine derivatives was achieved via serial catalysis using AgSbF6. Using this approach, the concise formal synthesis of santiagonamine was successfully accomplished. This simple and versatile method could be used to increase the potential of the pyrido[2,3-c]coumarin scaffold for diverse synthetic and biological applications.

Lysosome-Specific Coumarin-Based Fluorescent Bioprobes for in Vivo Polarity Sensing and Cancer Treatment

About 90% of cancer deaths worldwide are caused by the spread of cancer cells from the primary tumor to distant organs (metastasis). Therefore, there is an urgent need for an early diagnosis and treatment before cancer metastasis occurs. Lysosomes have emerged as attractive targets for cancer diagnosis and treatment because polar defects in lysosomes can induce apoptosis and cell death. Coumarin is a known polar-sensitive dye with good biocompatibility; because of this, we constructed two fluorescent probes of coumarin derivatives with the "D-π-A" structure, CouN-1 and CouN-2, through three simple reactions. In molecular design, due to morpholine's prominent lysosomal targeting characteristics, it was used as both lysosomal targeting motifs and an electron donor (D), while coumarin was used as an electron acceptor (A). The experimental results strongly proved that CouN-1 and CouN-2 have a good linear relationship with the polarity change of Δf = 0.209-0.308. In addition, both in vitro and in vivo imaging results have shown that CouN-1 and CouN-2 can specifically identify and monitor tumor sites. In the cell uptake and apoptosis experiments, the two probes also showed a strong antiproliferation effect on cancer cells. All of these characteristics demonstrated the potential of these two polarity-sensitive biological probes, CouN-1 and CouN-2, in the diagnosis and treatment of cancer.

BiCl3-catalyzed green synthesis of 4-hydroxy-2-quinolone analogues under microwave irradiation

Traditional chemical synthesis, which involves the use of dangerous protocols, hazardous solvents, and toxic products and catalysts, is considered environmentally inappropriate and harmful to human health. Bearing in mind its numerous drawbacks, it has become crucial to substitute conventional chemistry with green chemistry which is safer, more ecofriendly and more effective in terms of time and selectivity. Elaborating synthetic protocols producing interesting new compounds using both microwave heating and heterogeneous non-toxic catalysts is acknowledged as a green approach that avoids many classical chemistry-related problems. In the current study, β-enaminones were used as precursors to the synthesis of modified 4-hydroxy-2-quinolone analogues. The synthesis was monitored in a benign way under microwave irradiation and was catalyzed by bismuth chloride III in an amount of 20 mol%. This method is privileged by using a non-corrosive, non-toxic, low-cost and available bismuth Lewis acid catalyst that has made it more respectful to the demands of green chemistry. The synthesized compounds were obtained in moderate to good yields (51-71%) and were characterized by 1H, 13C NMR, and IR spectroscopy as well as elemental analysis. Compound 5i was subjected to a complete structural elucidation using the X-ray diffraction method, and the results show the obtention of the enolic tautomeric form.

Unveiling the antitumor potential of novel N-(substituted-phenyl)-8-methoxycoumarin-3-carboxamides as dual inhibitors of VEGFR2 kinase and cytochrome P450 for targeted treatment of hepatocellular carcinoma

Being the sixth most diagnosed cancer and the fourth leading cause of cancer-related deaths worldwide, liver cancer is considered as a serious disease with a high prevalence and poor prognosis. Current anticancer drugs for liver cancer have drawbacks, such as limited efficacy in later stages of the disease, toxicity to healthy cells, and the potential for drug resistance. There is ample evidence that coumarin-based compounds are potent anticancer agents, with numerous analogues currently being investigated in preclinical and clinical studies. The current study aimed to explore the antitumor potency of a new class of 8-methoxycoumarin-3-carboxamides against liver cancer. Toward this aim, we have designed, synthesized, and characterized a new set of N-(substituted-phenyl)-8-methoxycoumarin-3-carboxamide analogues. The assessment of antitumor activity revealed that the synthesized class of compounds possesses substantial cytotoxicity toward Hep-G2 cells when compared to staurosporine, without significant impact on normal cells. Out of the synthesized compounds, compound 7 demonstrated the most potent cytotoxic effect against Hep-G2 cells with an IC50 of 0.75 µM, which was more potent than the drug staurosporine (IC50 = 8.37 µM). The investigation into the mechanism behind the antiproliferative activity of compound 7 revealed that it interferes with DNA replication and induces DNA damage, leading to cell cycle arrest as demonstrated by a significant decrease in the percentage of cells in the G1 and G2/M phases, along with an increase in the percentage of cells in the S phase. Flow cytometric analysis further revealed that compound 7 has the ability to trigger programmed cell death by inducing necrosis and apoptosis in HepG-2 cells. Further explorations into the mechanism of action demonstrated that compound 7 displays a potent dual-inhibitory activity toward cytochrome P450 and vascular endothelial growth factor receptor-2 (VEGFR-2) proteins, as compared to sorafenib drug. Further, detailed computational studies revealed that compound 7 displays a considerable binding affinity toward the binding cavity of VEGFR2 and CYP450 proteins. Taken together, our findings indicate that the newly synthesized class of compounds, particularly compound 7, could serve as a promising scaffold for the development of highly effective anticancer agents against liver cancer.

Synthesis, Antioxidant and Antiproliferative Evaluation, Molecular Docking and DFT Studies of Some Novel Coumarin and Fused Coumarin Derivatives

N'-[(4-Chloro-2-oxo-2H-chromen-3-yl)methylene]-2-cyanoacetohydrazide (3) was synthesized in excellent yield from the condensation of 4-Chloro-2-oxo-2H-chromene-3-carbaldehyde with cyanoacetohydrazide. Compound 3 was utilized as a building block to synthesize novel coumarin and heterocycle-fused coumarin derivatives. The chemical structures of all the new coumarin compounds were identified by spectral analyses. Some of the new coumarins compounds were screened in human cancer cell lines (HEPG-2, MCF-7, HCT-116 and PC-3) to learn about their cytotoxic effects in addition to the study of their DNA damage and antioxidant activity. Three of these compounds exhibited remarkable antioxidant and anti-proliferative activities. Moreover, they have the capability to protect DNA from damage induced by bleomycin. Molecular docking, DFT and molecular electrostatic potential studies were performed on the compounds in vitro.

2,9-Dimethyl-4H-oxazolo[5’,4’:4,5]pyrano[3,2-f]quinolin-4-one

The new 2,9-dimethyl-4H-oxazolo[5’,4’:4,5]pyrano[3,2-f]quinolin-4-one was successfully prepared through the three-component iodine-catalyzed reaction of n-butyl vinyl ether with the new 8-amino-2-methyl-4H-chromeno[3,4-d]oxazol-4-one. The latter was prepared by the reduction of 2-methyl-8-nitro-4H-chromeno[3,4-d]oxazol-4-one with Pd/C in a hydrogen atmosphere. The above nitro compound was synthesized by the condensation of N-(4-hydroxy-6-nitro-2-oxo-2H-chromen-3-yl)acetamide with P2O5 under microwave irradiation. The above acetamide derivative was prepared during the nitration of 2-methyl-4H-chromeno[3,4-d]oxazol-4-one with H2SO4 and KNO3. The structure of the newly synthesized compounds was confirmed by FT-IR, LC-MS, 1H-NMR, and 13C-NMR analyses. Preliminary biological tests show significant anti-lipid peroxidation activity for the title compound and the other synthesized new intermediates, as well as interesting soybean lipoxygenase inhibition for acetamide 2 (IC50 55 μM) and nitro-compound 3 (IC50 27 μM).

Recent Progress in Cyclic Aryliodonium Chemistry: Syntheses and Applications

Hypervalent aryliodoumiums are intensively investigated as arylating agents. They are excellent surrogates to aryl halides, and moreover they exhibit better reactivity, which allows the corresponding arylation reactions to be performed under mild conditions. In the past decades, acyclic aryliodoniums are widely explored as arylation agents. However, the unmet need for acyclic aryliodoniums is the improvement of their notoriously low reaction economy because the coproduced aryl iodides during the arylation are often wasted. Cyclic aryliodoniums have their intrinsic advantage in terms of reaction economy, and they have started to receive considerable attention due to their valuable synthetic applications to initiate cascade reactions, which can enable the construction of complex structures, including polycycles with potential pharmaceutical and functional properties. Here, we are summarizing the recent advances made in the research field of cyclic aryliodoniums, including the nascent design of aryliodonium species and their synthetic applications. First, the general preparation of typical diphenyl iodoniums is described, followed by the construction of heterocyclic iodoniums and monoaryl iodoniums. Then, the initiated arylations coupled with subsequent domino reactions are summarized to construct polycycles. Meanwhile, the advances in cyclic aryliodoniums for building biaryls including axial atropisomers are discussed in a systematic manner. Finally, a very recent advance of cyclic aryliodoniums employed as halogen-bonding organocatalysts is described.

2H-Pyrano[3,2-c]chromene-2,5(6H)-diones: Synthesis, Characterization, Photophysical and Redox Studies for Potential Optoelectronic Applications

Herein, we report the preparation of 2H-pyrano[3,2-c]chromene-2,5(6H)-diones 3a-x by reacting 4-hydroxycoumarins 1a-b with Baylis-Hillman adducts 2a-w having electron releasing or electron withdrawing groups on benzyl ring of the pyranochromene moiety and study of their photophysical properties. The study of optical and electrochemical properties of the prepared compounds reveals that the electron releasing and electron withdrawing groups has not much impact on ground and excited state electronic behavior on pyranochromene moiety. The density functional theory suggests the highest occupied molecular orbital and lowest unoccupied molecular orbitals spread on coumarin moiety of pyranochromene unit. Further, these compounds are thermally stable (up to 200 °C) and lead to blue or green emission that should facilitate the development of organic light emitting diodes (OLEDs).

1,2,4‐Triazole and benzimidazole fused dihydropyrimidine derivatives: Design, green synthesis, antibacterial, antitubercular, and antimalarial activities

This study reports the design and synthesis of novel 1,2,4-triazolo/benzimidazolo-pyrimidine linked 1-benzyl-4-[(p-tolyloxy)methyl]-1,2,3-triazole derivatives as potent antimicrobial agents according to their in vitro antibacterial, antifungal, antitubercular as well as antimalarial activities. An efficient, ecologically benign, and facile multicomponent synthesis was employed to synthesize these derivatives. The synthesis is accelerated with the mild and eco-friendly organocatalyst tetrabutylammonium bromide, providing a yield of 82%-96% within the short reaction time of 0.5-1.5 h. Compared with the MIC values of ciprofloxacin and ampicillin on the respective strains, compound d2 showed better activity against Escherichia coli and Streptococcus pyogenes and compound d8 showed better MIC against Staphylococcus aureus. Additionally, compounds d3, d4, and d5 showed potent MIC values against Pseudomonas aeruginosa. All triazolo-pyrimidine derivatives d1-d8 showed potent inhibitory action against Gram-positive strains. Compound e3 showed good potency against Mycobacterium tuberculosis H37Rv. The IC₅₀ values of d3 and e2 indicated better activity against Plasmodium falciparum. Collectively, these derivatives depict potent multifaceted activity and provide promising access for further antimicrobial and antimalarial investigations.

Design, synthesis, theoretical study, antioxidant, and anticholinesterase activities of new pyrazolo-fused phenanthrolines

Pyrazole-fused phenanthroline compounds were obtained through several synthetic routes. NMR, HRMS, and IR techniques were used to characterize and confirm the chemical structures. Crystal structures were obtained from compounds 3a, 5b, 5j, 5k, and 5n and analyzed using X-ray diffraction. Compounds were evaluated as acetyl (AChE) and butyrylcholinesterase (BChE) inhibitors, and the results showed a moderate activity. Compound 5c presented the best activity against AChE (IC50 = 53.29 μM) and compound 5l against BChE enzyme (IC50 = 119.3 μM). Furthermore, the ability of the synthetic compounds to scavenge cationic radicals DPPH and ABTS was evaluated. Compound 5e (EC50 = 26.71 μg mL-1) presented the best results in the DPPH assay, and compounds 5e, 5f and 5g (EC50 = 11.51, 3.10 and <3 μg mL-1, respectively) showed better ABTS cationic radical scavenging results. Finally, in silico analyses indicated that 71% of the compounds show good oral availability and are within the ranges established by the Lipinski criteria.

[CMMIM][BF4 -] Ionic Liquid-Catalyzed Facile, One-Pot Synthesis of Chromeno[4,3-d]pyrido[1,2-a]pyrimidin-6-ones: Evaluation of Their Photophysical Properties and Theoretical Calculations

Herein, we have developed a novel synthetic route for the synthesis of chromeno[4,3-d]pyrido[1,2-a]pyrimidin-6-one derivatives 8a-q using an acid ionic liquid [CMMIM][BF₄ ^-] 4 via one-pot, three-component synthesis in aqueous ethanol at room temperature. A series of 17 derivatives have been successfully prepared with up to 93% yield. All the synthesized derivatives were well characterized using ¹H-NMR, ¹³C-NMR, and FT-IR spectral techniques. Additionally, the photophysical properties of 12 selected derivatives including molar extinction coefficient (ε), Stokes shift (Δυ̅), and quantum yield (Φ) varying from 0.52095 × 10⁴ to 0.93248 × 10⁴, 4216 to 4668 cm^-1, and 0.0088 to 0.0459, respectively, have been determined. Furthermore, the experimental data are supported by density functional theory (DFT) and time-dependent DFT calculations. Theoretical investigations showed a trend similar to experimental results.

In-silico molecular modelling, MM/GBSA binding free energy and molecular dynamics simulation study of novel pyrido fused imidazo[4,5-c]quinolines as potential anti-tumor agents

With an alarming increase in the number of cancer patients and a variety of tumors, it is high time for intensive investigation on more efficient and potent anti-tumor agents. Though numerous agents have enriched the literature, still there exist challenges, with the availability of different targets and possible cross-reactivity. Herein we have chosen the phosphoinositide 3-kinase (PI3K) as the target of interest and investigated the potential of pyrido fused imidazo[4,5-c]quinoline derivatives to bind strongly to the active site, thereby inhibiting the progression of various types of tumors. The AutoDock, Glide and the Prime-MM/GBSA analysis are used to execute the molecular docking investigation and validation for the designed compounds. The anti-tumor property evaluations were carried out by using PASS algorithm. Based on the GLIDE score, the binding affinity of the designed molecules towards the target PI3K was evaluated. The energetics associated with static interactions revealed 1j as the most potential candidate and the dynamic investigations including RMSD, RMSF, Rg, SASA and hydrogen bonding also supported the same through relative stabilization induced through ligand interactions. Subsequently, the binding free energy of the Wortmannin and 1j complex calculated using MM-PBSA analysis. Further evaluations with PASS prediction algorithm also supported the above results. The studies reveal that there is evidence for considering appropriate pyrido fused imidazo[4,5-c]quinoline compounds as potential anti-tumor agents.

The Synthesis and Biological Evaluation of Aloe-Emodin-Coumarin Hybrids as Potential Antitumor Agents

A series of novel aloe-emodin–coumarin hybrids were designed and synthesized. The antitumor activity of these derivatives was evaluated against five human tumor cell lines (A549, SGC-7901, HepG2, MCF-7 and HCT-8). Some of the synthesized compounds exhibited moderate to good activity against one or more cell lines. Particularly, compound 5d exhibited more potent antiproliferative activity than the reference drug etoposide against all tested tumor cell lines, indicating that it had a broad spectrum of antitumor activity and that it may provide a promising lead compound for further development as an antitumor agent by structural modification. Furthermore, the structure–activity relationship study of the synthesized compounds was also performed.

A Two-Step Approach to a Hexacyclic Lamellarin Core via 1,3-Dipolar Cycloaddition of Isoquinolinium Ylides to Nitrostilbenes

The 1,3-dipolar cycloaddition reaction of isoquinolinium ylides to nitrostilbenes provides an approach to 1,2-diarylpyrrolo[2,1-a]isoquinolinium-3-carboxylates and then to a complete hexacyclic lamellarin core.

Research progress of coumarins and their derivatives in the treatment of diabetes

Diabetes is a group of metabolic diseases characterised by chronic hyperglycaemia caused by multiple causes, which is caused by insulin secretion and/or utilisation defects. It is characterised by increased fasting and postprandial blood glucose levels due to insulin deficiency or insulin resistance. It is reported that the harm of diabetes mainly comes from its complications, and the cardiovascular disease caused by diabetes is the primary cause of its harm. China has the largest number of diabetic patients in the world, and the prevention and control of diabetes are facing great challenges. In recent years, many kinds of literature have been published abroad, which have proved that coumarin and its derivatives are effective in the treatment of diabetic complications such as nephropathy and cardiovascular disease. In this paper, the types of antidiabetic drugs and the anti-diabetic mechanism of coumarins were reviewed.

Synthesis of Novel Thiazole Derivatives Bearing β-Amino Acid and Aromatic Moieties as Promising Scaffolds for the Development of New Antibacterial and Antifungal Candidates Targeting Multidrug-Resistant Pathogens

Rapidly growing antimicrobial resistance among clinically important bacterial and fungal pathogens accounts for high morbidity and mortality worldwide. Therefore, it is critical to look for new small molecules targeting multidrug-resistant pathogens. Herein, in this paper we report a synthesis, ADME properties, and in vitro antimicrobial activity characterization of novel thiazole derivatives bearing β-amino acid, azole, and aromatic moieties. The in silico ADME characterization revealed that compounds 1-9 meet at least 2 Lipinski drug-like properties while cytotoxicity studies demonstrated low cytotoxicity to Vero cells. Further in vitro antimicrobial activity characterization showed the selective and potent bactericidal activity of 2a-c against Gram-positive pathogens (MIC 1-64 µg/mL) with profound activity against S. aureus (MIC 1-2 µg/mL) harboring genetically defined resistance mechanisms. Furthermore, the compounds 2a-c exhibited antifungal activity against azole resistant A. fumigatus, while only 2b and 5a showed antifungal activity against multidrug resistant yeasts including Candida auris. Collectively, these results demonstrate that thiazole derivatives 2a-c and 5a could be further explored as a promising scaffold for future development of antifungal and antibacterial agents targeting highly resistant pathogenic microorganisms.

3-(Bromoacetyl)coumarins: unraveling their synthesis, chemistry, and applications

This review emphasizes recent developments in synthetic routes of 3-(bromoacetyl)coumarin derivatives. Also, chemical reactions of 3-(bromoacetyl)coumarins as versatile building blocks in the preparation of critical polyfunctionalized heterocyclic systems and other industrially significant scaffolds are described. Recent advances of 3-(bromoacetyl)coumarins as attractive starting points towards a wide scale of five and six-membered heterocyclic systems such as thiophenes, imidazoles, pyrazoles, thiazoles, triazoles, pyrans, pyridines, thiadiazins as well as fused heterocyclic systems have been reported. Additionally, this review covers a wide range of analytical chemistry, fluorescent sensors, and biological applications of these moieties, covering the literature till May 2021.

Crowned Macrocycles Containing Two Pyrrolo[1,2-a] Indoles Created By Intramolecular Fusion

Heterocyclic fused-ring systems are of utmost importance because of their presence in many natural products with biological activity. Pyrroloindoles are tricyclic heterocycles that are present in various bioactive and medicinally valuable compounds. Herein, we report the synthesis of phenylene-bridged bis-pyrrolo[1,2-a]indole crowned macrocycles 1-3 in which the pyrrolo[1,2-a]indole moieties were formed via intramolecular fusion. The macrocycles were thoroughly characterized by 1D and 2D NMR, HRMS and X-ray crystallographic studies. The X-ray structure revealed that the two pyrrolo[1,2-a]indole moieties were parallel to each other, and one pyrrolo[1,2-a]indole unit was deviated by an angle of 9.54° while the other pyrrolo[1,2-a]indole unit was deviated by an angle of 12.0° from the mean plane defined by 28 core atoms. The macrocycles 1-3 absorb in the visible region and readily undergo oxidations because of their electron rich nature. The macrocycles 1-3 upon treatment with trifluoroacetic acid (TFA) generates the corresponding cation radicals 1-3^.+ which were stable in the open air for a week. The cation radicals 1-3^.+ absorb strongly in the NIR region and the experimental observations on crowned macrocycles 1-3 were corroborated by DFT and TD-DFT studies.

Copper(II)-Catalyzed Tandem Reaction: Synthesis of Furo[3,2-c]coumarin Derivatives and Evaluation for Photophysical Properties

An efficient protocol for synthesizing furo[3,2-c]coumarin derivatives is described. The novel reaction could afford the desired furocoumarins with good to excellent yields in a mild and rapid manner. Large substrate scope screening and scale-up preparation have also been accomplished, and selected compounds were evaluated for their photophysical properties.

4-Amino-2-(p-tolyl)-7H-chromeno[5,6-d]oxazol-7-one

The new 4-amino-2-(p-tolyl)-7H-chromeno[5,6-d]oxazol-7-one was successfully prepared through the Au/TiO2-catalyzed NaBH4 activation and chemoselective reduction of the new 4-nitro-2-(p-tolyl)-7H-chromeno[5,6-d]oxazol-7-one. The latter was synthesized by the one-pot tandem reactions of 6-hydroxy-5,7-dinitrocoumarin with p-tolylmethanol under Au/TiO2 catalysis. The dinitrocoumarin was obtained by the nitration of 6-hydroxycoumarin with cerium ammonium nitrate (CAN). The structure of the synthesized compounds was confirmed by FT-IR, HR-MS, 1H-NMR and 13C-NMR analysis. Preliminary biological tests show low anti-lipid peroxidation activity for the title compound.

Synthetic Routes to Coumarin(Benzopyrone)-Fused Five-Membered Aromatic Heterocycles Built on the α-Pyrone Moiety. Part II: Five-Membered Aromatic Rings with Multi Heteroatoms

Coumarins are natural heterocycles that widely contribute to the design of various biologically active compounds. Fusing different aromatic heterocycles with coumarin at its 3,4-position is one of the interesting approaches to generating novel molecules with various biological activities. During our continuing interest in assembling information about fused five-membered aromatic heterocycles, and after having presented mono-hetero-atomic five-membered aromatic heterocycles in Part I. The current review Part II is intended to present an overview of the different synthetic routes to coumarin (benzopyrone)-fused five-membered aromatic heterocycles with multi-heteroatoms built on the pyrone ring, covering the literature from 1945 to 2021.

Diverse synthesis of pyrrolo/indolo[3,2-c]coumarins as isolamellarin-A scaffolds: a brief update

This review presents a different synthetic approach of pyrrolo/indolo[3,2-c]coumarins via classical reactions including metal-catalyzed and green reaction protocols.

4-Chloro-3-formylcoumarin as a multifaceted building block for the development of various bio-active substituted and fused coumarin heterocycles: a brief review

This review presents the diverse synthesis of 3,4-substituted coumarins and 5-, 6- and 7-membered ring fused coumarins using 4-chloro-3-formylcoumarin as the precursor via classical reactions including metal-catalyzed and green reaction protocols.