Recent progress in the development of coumarin derivatives as potent anti-HIV agents

Enantioselective synthesis of 4-aryl-3,4-dihydrocoumarins via N-heterocyclic carbene catalyzed β-arylation/cyclization of α-bromoenals

4-Aryl-3,4-dihydrocoumarins are one of the most important structural motifs. Herein, we disclose an enantioselective N-heterocyclic carbene catalyzed β-arylation/cyclization of α-bromoenals with 3-aminophenols under mild conditions. The protocol allows for the rapid preparation of 4-aryl-3,4-dihydrocoumarins in acceptable yields with good enantioselectivities. The products of this reaction could be converted into chiral diarylpropanoic acid derivatives without erosion of the enantioselectivity.

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.

Design, synthesis and bioactivity evaluation of 4-hydroxycoumarin derivatives as potential anti-inflammatory agents against acute lung injury and colitis

Acute lung injury (ALI) and inflammatory bowel disease (IBD) are common inflammatory illnesses that seriously affect people's health. Herein, a series of 4-hydroxylcoumarin (4-HC) derivatives were designed and synthesized. The inhibitory effects of these compounds on LPS-induced interleukin-6 (IL-6) release from J774A.1 cells were then screened via ELISA assay, compound B8 showed 3 times more active than the lead compound 4-HC. The most active compound B8 had the IC50 values of 4.57 μM and 6.51 μM for IL-6 release on mouse cells J774A.1 and human cells THP-1, respectively. Furthermore, we also found that B8 could act on the MAPK pathway. Based on the target prediction results of computer virtual docking, kinase inhibitory assay was carried out, and it revealed that targeting IRAK1 was a key mechanism for B8 to exert anti-inflammatory activity. Moreover, B8 exerted a good therapeutic effect on the dextran sulfate sodium (DSS)-induced colitis model and liposaccharide (LPS)-induced ALI mouse models. The acute toxicity experiments indicated that high-dose B8 caused no adverse reactions in mice, confirming its safety in vivo. Additionally, the preliminary pharmacokinetic (PK) parameters of B8 in SD rats were also examined, revealing a bioavailability (F) of 28.72 %. In conclusion, B8 is a potential candidate of drug for the treatment of ALI and colitis.

PIDA-promoted metal-free [3 + 2] heteroannulation of β-ketothioamides with 4-hydroxy coumarins: chemo-/regioselective access to furo[3,2-c]chromen-4-ones at room temperature

Herein, we report a viable protocol to access furo[3,2-c]chromen-4-ones by engaging easily accessible 4-hydroxy coumarins as a three-atom CCO unit and thioamides as a C2 coupling partner, mediated by phenyliodine(III) diacetate (PIDA) at room temperature in a highly efficient and pot-/step-economical manner. This strategy not only avoids potential toxicity and tiresome workup conditions, but also features operational simplicity, a broad substrate scope, good functional group tolerance, high yields, easy scalability and exclusive selectivity. A mechanistic study has shown that this metal-free reaction is triggered by PIDA via activation of the β-carbon of 4-hydroxy coumarin, followed by a nucleophilic addition/intramolecular cyclization/dethiohydration cascade. High-resolution mass spectra (HRMS) study confirms the key intermediates involved during the course of the reaction, elucidating the reaction pathways, and demonstrates the excellent regio- and chemoselectivity of this approach.

Synthesis of indole derivatives as Alzheimer inhibitors and their molecular docking study

Acetylcholinesterase prevails in the healthy brain, with butyrylcholinesterase reflected to play a minor role in regulating brain acetylcholine (ACh) levels. However, BuChE activity gradually increases in patients with (AD), while AChE activity remains unaffected or decays. Both enzymes therefore represent legitimate therapeutic targets for ameliorating the cholinergic deficit considered to be responsible for the declines in cognitive, behavioural, and global functioning characteristic of AD. Current study described the synthesis of indole-based sulfonamide derivatives (1-23) and their biological activity. Synthesis of these scaffolds were achieved by mixing chloro-substituted indole bearing amine group with various substituted benzene sulfonyl chloride in pyridine, under refluxed condition to obtained desired products. All products were then evaluated for AchE and BuchE inhibitory potential compare with positive Donepezil as standard drug for both AchE and BchE having IC50 = 0.016 ± 0.12 and 0.30 ± 0.010 μM respectively. In this regard analog 9 was found potent having IC50 value 0.15 ± 0.050 μM and 0.20 ± 0.10 for both AchE and BuChE respectively. All other derivatives also found with better potential. All compounds were characterized by various techniques such as 1H, 13C-NMR and HREI-MS. In addition, biological activity was maintained to explore the bioactive nature of scaffolds and their protein-ligand interaction (PLI) was checked through molecular docking study.Communicated by Ramaswamy H. Sarma.

Recent Progress in Synthesis, POM Analyses and SAR of Coumarin-Hybrids as Potential Anti-HIV Agents-A Mini Review

The human immunodeficiency virus (HIV) is the primary cause of acquired immune deficiency syndrome (AIDS), one of the deadliest pandemic diseases. Various mechanisms and procedures have been pursued to synthesise several anti-HIV agents, but due to the severe side effects and multidrug resistance spawning from the treatment of HIV/AIDS using highly active retroviral therapy (HAART), it has become imperative to design and synthesise novel anti-HIV agents. Literature has shown that natural sources, particularly the plant kingdom, can release important metabolites that have several biological, mechanistic and structural representations similar to chemically synthesised compounds. Certainly, compounds from natural and ethnomedicinal sources have proven to be effective in the management of HIV/AIDS with low toxicity, fewer side effects and affordability. From plants, fungi and bacteria, coumarin can be obtained, which is a secondary metabolite and is well known for its actions in different stages of the HIV replication cycle: protease, integrase and reverse transcriptase (RT) inhibition, cell membrane fusion and viral host attachment. These, among other reasons, are why coumarin moieties will be the basis of a good building block for the development of potent anti-HIV agents. This review aims to outline the synthetic pathways, structure-activity relationship (SAR) and POM analyses of coumarin hybrids with anti-HIV activity, detailing articles published between 2000 and 2023.

Pd@GO catalyzed stereo- and regio-selective addition of arenes to alkynes and synthesis of coumarins via C-H functionalization

A stereo- and regio-selective addition of arenes to alkynes via C-H bond functionalization has been developed using palladium nanoparticles supported on graphite oxide (Pd@GO) as the reusable catalyst. The prepared catalyst was characterized by various spectroscopic techniques such as FT-IR, TEM, SEM, EDX, P-XRD, and XPS analysis. The thermal stability of the catalyst was established by TGA. The C-H functionalized products were obtained in good to excellent yields (69-92%) at room temperature. The methodology further extended to the synthesis of biologically and pharmaceutically important coumarin molecules from phenols and alkynes. Good to excellent yields of the coumarins (74-92%) were obtained. After the reaction, the catalyst was separated by centrifugation followed by filtration. The recovered catalyst was washed and reused up to five cycles. The advantages of this method are the simple procedure of the catalyst preparation, high catalytic efficiency, high selectivity, good functional group tolerance, low catalyst loading, and gram-scale synthesis.

Asymmetric synthesis of chiral (thio)chromanes and exploration on their structure-activity relationship in macrophages

A CuCl/(R,R)-Ph-BPE-catalyzed enantioselective hydroallylation of 2H-chromenes and 2H-thiochromenes with allylic phosphate electrophiles is developed, which enables highly efficient and atom-economical asymmetric access to a series of 4-allyl chromanes and thiochromanes in high yields (up to 91%) with excellent enantioselectivities (up to 99% ee). These valuable chiral chromane and thiochromane products can serve as crucial intermediates for accessing bioactive compounds containing oxygen and sulfur atoms. In addition, the antioxidant and anti-inflammatory effects of various chromanes and thiochromanes were investigated in RAW 264.7 macrophages. The chromanes and thiochromanes exhibited significant inhibitory effects on the production of reactive oxygen species (ROS) and the secretion of pro-inflammatory cytokines, including interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α). These findings indicate that the newly synthesized chromanes and thiochromanes hold promise as potential lead compounds for the development of antioxidant and anti-inflammatory drugs.

Antibacterial activities of coumarin-3-carboxylic acid against Acidovorax citrulli

Coumarin-3-carboxylic acid (3-CCA), previously screened from natural coumarins, was found to possess strong antibacterial activity against Acidovorax citrulli (Ac). In order to further evaluate the activity of this compound against plant bacterial pathogens and explore its potential value as a bactericidal lead compound, the activity of 3-CCA against 14 plant pathogenic bacteria in vitro and in vivo was tested. Results showed that 3-CCA exhibited strong in vitro activities against Ac, Ralstonia solanacearum, Xanthomonas axonopodis pv. manihotis, X. oryzae pv. oryzae, and Dickeya zeae with EC50 values ranging from 26.64 μg/mL to 40.73 μg/mL. Pot experiment results showed that 3-CCA had powerful protective and curative effects against Ac. In addition, the protective efficiency of 3-CCA was almost equivalent to that of thiodiazole copper at the same concentration. The results of SEM and TEM observation and conductivity tests showed that 3-CCA disrupted the integrity of the cell membrane and inhibited polar flagella growth. Furthermore, 3-CCA resulted in reductions in motility and extracellular exopolysaccharide (EPS) production of Ac while inhibiting the biofilm formation of Ac. These findings indicate that 3-CCA could be a promising natural lead compound against plant bacterial pathogens to explore novel antibacterial agents.

Synthesis of water-soluble novel bioactive pyridine-based azo coumarin derivative and competitive cytotoxicity, DNA binding, BSA binding study, and in silico analysis with coumarin

The diazo coupliling reaction of 3- amino pyridine with coumarin in water medium produces water soluble 6-[3-pyridyl]azocoumarin. The synthesised compound has been fully charecterised by IR, NMR, and Mass spectroscopy. The frontier molecular orbital calculations reveal that 6-[3-pyridyl]azocoumarin is more biologically and chemically active in comparison to coumarin. The cytotoxicity evaluation confirms that 6-[3-pyridyl]azocoumarin is more active than coumarin against human brain glioblastoma cell lines, LN-229 with IC50 value 9.09 μM (IC50 value for coumarin is 9.9 μM). The compound (I) has been synthesized by coupling of diazotized solution of 3-aminopyridine with coumarin in an aqueous medium at ∼ pH 10. The structure of the compound (I) has been characterized using UV-vis, IR, NMR, and Mass spectral studies. Frontier molecular orbital calculations reveal that 6-[3-pyridyl]azocoumarin (I) is more active chemically and biologically in comparison to coumarin. IC50 value 9.09 and 9.9 μM of 6-[3-pyridyl]azocoumarin and coumarin respectively obtained in cytotoxicity evaluation confirms the enhanced activity of the synthesized compound against human brain glioblastoma cell lines, LN-229. The synthesized compound also shows strong binding interactions with DNA and BSA in comparison with coumarin. The DNA binding study shows groove binding interaction of the synthesized compound with CT-DNA. The nature of interaction, binding parameters and structural variations of BSA in the presence of the synthesized compound and coumarin have been evaluated using several usefull spectroscopy approaches such as UV -Vis, time resolved and stady state flurescence. The molecular docking interaction has been carried out to justify the experimental binding interaction with DNA and BSA.

A comprehensive overview on the role of phytocompounds in human immunodeficiency virus treatment

Acquired immune deficiency syndrome (AIDS) is a worldwide epidemic caused by human immunodeficiency virus (HIV) infection. Newer medicines for eliminating the viral reservoir and eradicating the virus are urgently needed. Attempts to locate relatively safe and non-toxic medications from natural resources are ongoing now. Natural-product-based antiviral candidates have been exploited to a limited extent. However, antiviral research is inadequate to counteract for the resistant patterns. Plant-derived bioactive compounds hold promise as powerful pharmacophore scaffolds, which have shown anti-HIV potential. This review focuses on a consideration of the virus, various possible HIV-controlling methods and the recent progress in alternative natural compounds with anti-HIV activity, with a particular emphasis on recent results from natural sources of anti-HIV agents. Please cite this article as: Mandhata CP, Sahoo CR, Padhy RN. A comprehensive overview on the role of phytocompounds in human immunodeficiency virus treatment. J Integr Med. 2023; Epub ahead of print.

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).

Advances in natural product anti-coronavirus research (2002-2022)

COVID-19 is a severe acute respiratory syndrome caused by coronavirus that has triggered acute respiratory infections in countries around the world. In the last 20 years, there have been several outbreaks of coronaviruses, which have had a tremendous impact on productive life and globalization. Since coronaviruses are mutagenic and highly susceptible to mutation, there are no specific drugs against coronaviruses. Medicines made from natural products gains worldwide attention, and the mechanism and effectiveness of natural products for the treatment of coronavirus-related diseases have received much attention after the global pandemic of COVID-19 in 2020. The vitro research results and clinical data from various countries have shown protective effects of good effects against coronaviruses. This review summarizes representative natural products for the treatment of coronavirus-related diseases in the past 20 years, and demonstrates the promising prospects of natural products against coronavirus-related diseases by listing herbal formulas, Chinese patent medicines and natural small molecule compounds and their therapeutic mechanisms, providing references for subsequent related studies.

Plant Coumarins with Anti-HIV Activity: Isolation and Mechanisms of Action

This review summarizes and systematizes the literature on the anti-HIV activity of plant coumarins with emphasis on isolation and the mechanism of their antiviral action. This review summarizes the information on the anti-HIV properties of simple coumarins as well as annulated furano- and pyranocoumarins and shows that coumarins of plant origin can act by several mechanisms: inhibition of HIV reverse transcriptase and integrase, inhibition of cellular factors that regulate HIV-1 replication, and transmission of viral particles from infected macrophages to healthy ones. It is important to note that some pyranocoumarins are able to act through several mechanisms or bind to several sites, which ensures the resistance of these compounds to HIV mutations. Here we review the last two decades of research on the anti-HIV activity of naturally occurring coumarins.

Molecular recognition of two bioactive coumarin derivatives 7-hydroxycoumarin and 4-methyl-7-hydroxycoumarin by hen egg white lysozyme: Exploring the binding mechanism, thermodynamic parameters and structural changes using multispectroscopic and computational approaches

Multispectroscopic and computational methods of exploring the interaction between a carrier protein and therapeutic compounds provide a preliminary investigation into establishing the efficacy of such compounds. Here, two coumarin derivatives, 7-hydroxycoumarin (7-HC) and 4-methyl-7-hydroxycoumarin (4-Me-7-HC), were selected to carry out numerous biophysical interaction studies with a model carrier protein, hen egg white lysozyme (HEWL). Fluorescence spectroscopy studies conducted between HEWL and 7-HC/4-Me-7-HC revealed the binding constants (K_b) were in the range of 10⁴ M^-1, indicating a moderate nature of binding. The quenching mechanism observed during complexation process was an unusual static quenching due to the effect of temperature on the rate constant. Thermodynamic parameters revealed a positive ΔH and ΔS for HEWL-7-HC/4-Me-7-HC, indicating hydrophobic forces played a dominant role in the interaction process. FRET studies suggested a possible non-radiative energy transfer from the donor (HEWL) to the acceptor (coumarins). Molecular docking studies revealed the interaction of 7-HC/4-Me-7-HC with intrinsic fluorophores, Trp63 and Trp108, Trp108 being an essential residue for binding as proven by molecular dynamic (MD) simulation. MD simulation studies also indicated conformational stability gained by HEWL upon interaction with 7-HC and 4-Me-7-HC. The microenvironment surrounding the Trp residues showed a significant Stoke's shift on carrying out 3-D fluorescence. CD studies revealed a decrease in the alpha helical content of HEWL upon interacting with the ligands. Enzymatic assay conducted for HEWL in the presence of 7-HC/4-Me-7-HC saw an increase in the activity of HEWL, suggesting a change in structural conformation and stability of the protein, altering its activity.Communicated by Ramaswamy H. Sarma.

Facile Synthesis of Some Coumarin Derivatives and Their Cytotoxicity through VEGFR2 and Topoisomerase II Inhibition

Novel semisynthetic coumarin derivatives were synthesized to be developed as chemotherapeutic anticancer agents through topoisomerase II, VEGFR2 inhibition that leads to apoptotic cancer cell death. The coumarin amino acids and dipeptides derivatives were prepared by the reaction of coumarin-3-carboxylic acid with amino acid methyl esters following the N,N-dicyclohexylcarbodiimide (DCC) method and 1-hydroxy-benzotriazole (HOBt), as coupling reagents. The synthesized compounds were screened towards VEGFR2, and topoisomerase IIα proteins to highlight their binding affinities and virtual mechanism of binding. Interestingly, compounds 4k (Tyr) and 6c (β-Ala-L-Met) shared the activity towards the three proteins by forming the same interactions with the key amino acids, such as the co-crystallized ligands. Both compounds 4k and 6c exhibited potent cytotoxic activities against MCF-7 cells with IC₅₀ values of 4.98 and 5.85 µM, respectively causing cell death by 97.82 and 97.35%, respectively. Validating the molecular docking studies, both compounds demonstrated promising VEGFR-2 inhibition with IC₅₀ values of 23.6 and 34.2 µM, compared to Sorafenib (30 µM) and topoisomerase-II inhibition with IC₅₀ values of 4.1 and 8.6 µM compared to Doxorubicin (9.65 µM). Hence, these two promising compounds could be further tested as effective and selective target-oriented active agents against cancer.

Synthesis, In Vitro Biological Evaluation and In Silico Molecular Docking Studies of Indole Based Thiadiazole Derivatives as Dual Inhibitor of Acetylcholinesterase and Butyrylchloinesterase

The current study was conducted to obtain hybrid analogues of indole-based thiadiazole derivatives (1-16) in which a number of reaction steps were involved. To examine their biological activity in the presence of the reference drug Donepezil (0.21 ± 0.12 and 0.30 ± 0.32 M, respectively), the inhibitory potentials of AChE and BuChE were determined for these compounds. Different substituted derivatives showing a varied range of inhibitory profiles, when compared to the reference drug, analogue 8 was shown to have potent activity, with IC50 values for AchE 0.15 ± 0.050 M and BuChE 0.20 ± 0.10, respectively, while other substituted compounds displayed good to moderate potentials. Varied spectroscopic techniques including 1H, 13CNMR and HREI-MS were used to identify the basic skeleton of these compounds. Furthermore, all analogues have a known structure-activity relationship (SAR), and molecular docking investigations have verified the binding interactions of molecule to the active site of enzymes.

Chemistries and applications of DNA-natural product conjugate

Natural products and their derivatives have made great contributions to chemotherapy, especially for the treatment of tumors and infections. Despite the achievements, natural product-based small molecule drugs usually suffer from side effects, short circulation time, and solubility issue. To overcome these drawbacks, a common approach is to integrate another bio-functional motif into a natural product compound, enabling targeted or synergistic therapy. One of the most promising strategies is to form a DNA-natural product conjugate to improve therapeutic purposes. The incorporated DNA molecules can serve as an aptamer, a nucleic-acid-based congener of antibody, to specifically bind to the disease target of interest, or function as a gene therapy agent, such as immuno-adjuvant or antisense, to enable synergistic chemo-gene therapy. DNA-natural product conjugate can also be incorporated into other DNA nanostructures to improve the administration and delivery of drugs. This minireview aims to provide the chemistry community with a brief overview on this emerging topic of DNA-natural product conjugates for advanced therapeutics. The basic concepts to use the conjugation, the commonly used robust conjugation chemistries, as well as applications in targeted therapy and synergistic therapy of using DNA-natural product conjugates, are highlighted in this minireview. Future perspectives and challenges of this field are also discussed in the discussion and perspective section.

Comprehensive Review on Medicinal Applications of Coumarin-Derived Imine–Metal Complexes

Coumarins are fused six-membered oxygen-containing benzoheterocycles that join two synthetically useful rings: α-pyrone and benzene. A survey of the literature shows that coumarins and their metal complexes have received great interest from synthetic chemists, medicinal scientists, and pharmacists due to their wide spectrum of biological applications. For instance, coumarin and its derivatives have been used as precursors to prepare a large variety of medicinal agents. Likewise, coumarin-derived imine–metal complexes have been found to display a variety of therapeutic applications, such as antibacterial, antifungal, anticancer, antioxidant, anthelmintic, pesticidal, and nematocidal activities. This review highlights the current synthetic methodologies and known bioactivities of coumarin-derived imine–metal complexes that make this molecule a more attractive scaffold for the discovery of newer drugs.

Synergistic Effect of Cerium in Dual Photoinduced Ligand-to-Metal Charge Transfer and Lewis Acid Catalysis: Diastereoselective Alkylation of Coumarins

We report the dual role of cerium to promote the photoinduced ligand-to-metal charge transfer (LMCT) process for the generation of the alkyl radical and subsequent Lewis acid catalysis to construct stereodefined C-C bonds. This paradigm utilized ubiquitous carboxylic acids as alkyl radical surrogates and offers excellent diastereoselectivity for the formation of C-4 alkylated coumarins in good to excellent yield. UV-vis spectroscopy studies in combination with in situ Fourier transform infrared spectroscopy are consistent with the proposed mechanism, supporting the participation of the Ce^IV-carboxylate complex in photoinduced LMCT and its subsequent homolysis to generate the alkyl radial through the exclusion of CO₂. Finally, the oxophilicity of cerium enables a two-point complexation with the in situ generated enolate intermediate and facilitates the diastereoselective protonation to form the desired product. Furthermore, this mild and atom-economical catalytic manifolds allow the late-stage modification of pharmaceuticals.

Synthesis of Functionalized N-(4-Bromophenyl)furan-2-carboxamides via Suzuki-Miyaura Cross-Coupling: Anti-Bacterial Activities against Clinically Isolated Drug Resistant A. baumannii, K. pneumoniae, E. cloacae and MRSA and Its Validation via a Computational Approach

N-(4-bromophenyl)furan-2-carboxamide (3) was synthesized by the reaction furan-2-carbonyl chloride (1) and 4-bromoaniline (2) in the presence of Et₃N in excellent yields of 94%. The carboxamide (3) was arylated by employing triphenylphosphine palladium as a catalyst and K₃PO₄ as a base to afford N-(4-bromophenyl)furan-2-carboxamide analogues (5a-i) in moderate to good yields (43–83%). Furthermore, we investigated the in vitro anti-bacterial activities of the respective compounds against clinically isolated drug-resistant bacteria A. baumannii, K. pneumoniae, E. cloacae and S. aureus. The molecule (3) was found to be the most effective activity against these bacteria, particularly NDM-positive bacteria A. baumannii as compared to various commercially available drugs. Docking studies and MD simulations further validated it, expressing the active site and molecular interaction stability.

Antibacterial and antioxidant assay of novel heteroaryl-substituted methane derivatives synthesized via ceric ammonium nitrate (CAN) catalyzed one-pot green approach

Individually, hydroxycoumarin and amino pyrimidine derivatives are of significant biological interest owing to their importance in drugs and pharmaceuticals. To access their combined biological impact into one molecule, we designed a novel, one-pot green approach for synthesizing trisubstituted methanes. A series of new heteroaryl-substituted methanes have been synthesized and subjected to in vitro antibacterial and antioxidant evaluation. Tests against clinical isolates of Escherichia coli (gram-negative) and Staphylococcus aureus showed potent activity of the derivatives 4a, 4b, 4d, 4e, 4f, 4l, and 5 against the former, and 4a, 4e, 4j, and 4l against the later one. Further, antioxidant assay for these TRSMs was also studied where 4a, 4b, 4f, 4j, and 4l exhibited the most promising results. These preliminary bioassay evaluations strongly suggest the promise and scope of these molecules in medical science. A one pot methodology for the synthesis of coumarin and uracil tethered trisubstituted methanes has been reported. The synthesized derivatives were further analyzed for their antibacterial and antioxidant properties to explore their medicinal applications. The salient features of this methodology are operational simplicity, short reaction time, good to moderate yields of the products, easy purification method. Biochemical assay of the synthesized TRSMs a reveals their utility in medicinal & pharma industry.

Recent Advances in Organic Synthesis of 3-Amino- or 4-Aminocoumarins

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Coumarin is a privileged scaffold that contains the unique 2H-chromen-2-one motif, and its derivatives are widely distributed in nature, especially in plants. In recent years, due to their diverse pharmacological activities and remarkable photochemical properties, they have attracted significant attention from scientists, which has also prompted the research on the synthesis approaches and the availability of substrates for these compounds. This article is a brief description of the methods for the synthesis of various coumarin derivatives via two- or multi-component reactions involving 3-amino or 4-aminocoumarin reported during 2015-2021. This review may help expand the development of various analogues with coumarin as the basic unit.

Crystal structure of 3-(3-bromophenyl)-1′,3′-dimethyl-2′H,3H,4H-spiro[furo[3, 2-c]chromene-2,5′-pyrimidine]-2′,4,4′,6′(1′H,3′H) tetraone, C22H15BrN2O6

C22H15BrN2O6, monoclinic, P21/c (No. 14), a = 5.1760 (5) Å, b = 17.5652(19) Å, c = 21.734(2) Å, β = 94.690(3) °, Z = 4, V = 1969.3(3) Å3, R gt (F) = 0.0569, wR ref (F 2) = 0.1206, T = 170 K.

Synthesis and Biological Properties of Coumarin Analogue: A Brief Review

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One of the most prominent aromatic organic chemical compound is Coumarin having formula C9H6O2 which is widely known for its benefits in drug industry. Colourless crystalline solid having sweet scent is coumarin’s physical identity. It serves various purposes such as in synthesis of medicines, laser dyes, perfumes and many more. Having enormous usages it becomes important to synthesize such compound so various reactions were performed in order to obtain coumarins. This review explicates the preparation of coumarin by Pechmann Condensation and its biological characteristics.

Transfer-catalyst-free biomimetic asymmetric reduction of 3-sulfonyl coumarins with a regenerable NAD(P)H model

A novel transfer-catalyst-free biomimetic reduction of the tetrasubstituted olefins 3-sulfonyl coumarins with the chiral and regenerable [2.2]paracyclophane-based NAD(P)H model CYNAM has been developed, affording chiral 3-sulfonyl dihydrocoumarins with excellent enantioselectivities.

Coumarins Synthesis and Transformation via C–H Bond Activation—A Review

For several decades, coumarins have attracted considerable attention due to the fact of their application in diverse fields such as medical science and biomedical research as well as several industrial branches. Recently, many compounds containing the coumarin moiety have been intensively studied, mainly due to the fact of their biological activities such as antitumor, antioxidative, anti-HIV, vasorelaxant, antimicrobial, and anticancer. They are also widely used as fluorescent dyes and probes because of their great structural flexibility and large fluorescent quantum yields. For this reason, numerous attempts have been made to develop new and more practical methods for the synthesis of these compounds. This review aims at providing a comprehensive overview of coumarin synthesis methods by direct C–H bond activation in order to demonstrate the current state-of-the-art methods as well as the current limitations.

Palladium Catalyzed Enantioselective Hayashi-Miyaura Reaction for Pharmaceutically Important 4-Aryl-3,4-dihydrocoumarins

The first palladium-catalyzed asymmetric addition of arylboronic acids to coumarins was successfully established, providing a straightforward asymmetric approach to achieving pharmaceutically important 4-aryl-3,4-dihydrocoumarins. This methodology features easily accessible and bench-stable ligands, a wide substrate scope, mild conditions, and accommodation of electron-withdrawing arylboronic acids.

Visible light photocatalysis in the synthesis of pharmaceutically relevant heterocyclic scaffolds

Visible light and photoredox catalysis have emerged as a powerful and long-lasting tool for organic synthesis, demonstrating the importance of a variety of chemical bond formation methods.

Copper-catalyzed cascade radical cyclization of alkynoates: construction of aryldifluoromethylated coumarins

A mild and simple method is reported for the construction of 3-difluoroarylmethylated coumarins using α,α-difluoroarylacetic acids as an easily handled difluoromethyl source in reaction with ester 3-arylpropiolates under the promotion of copper. The reaction involves a proposed radical-triggered domino decarboxylative aryldifluoromethylation/5-exo cyclization/ester migration process that directly forms Csp²-CF₂Ar and C-C bonds with good functional group tolerance.

Therapeutic Journey and Recent Advances in the Synthesis of Coumarin Derivatives

BACKGROUND

Coumarin is an oxygen-containing compound in medicinal chemistry. Coumarin plays an important role in both natural systems like plants and also in synthetic medicinal applications as drug molecules. Many structurally different coumarin compounds were found to show a big range of similarity with the vital molecular targets for their pharmacological action and small modifications in their structures resulted insignificant changes in their biological activities.

OBJECTIVE

This review gives detailed information about the studies of the recent advances in various pharmacological aspects of coumarins.

METHOD

Various oxygen-containing heterocyclic compounds represented remarkable biological significances. The fused aromatic oxygen-heterocyclic nucleus is able to change its electron density; thus changing the chemical, physical and biological properties respectively due to its multiple binding modes with the receptors, which play crucial role in pharmacological screening of drugs. A number of heterocyclic compounds have been synthesized which have their nucleus derived from various plants and animals. In coumarins, benzene ring is fused with pyrone nucleus which provides stability to the nucleus. Coumarins have shown a wide range of pharmacological activities such as anti-tumour, anti-coagulant, anti-inflammatory, anti-oxidant, antiviral, anti-malarial, anti-HIV and antimicrobial activity etc. Results: Reactive oxygen species like superoxide anion, hydroxyl radical and hydrogen peroxide are a type of unstable molecule that contains oxygen, which reacts with other molecules in the cell during the metabolism process but it may produce cytotoxicity when reactive oxygen species increase in number, by the damage of biological macromolecules. Hydroxyl radical (˙OH), is a strong oxidizing agent and it is responsible for the cytotoxicity by oxygen in different plants, animals and other microbes. coumarin is the oldest and effective compound having antimicrobial activity, anti-inflammatory, antioxidant, antidepressant activity, analgesic, anticonvulsant activity, etc. Naturally existing coumarin compounds act against SARS-CoV-2 by preventing viral replication through the targeting on active site against the Mpro target protein.

CONCLUSION

This review highlights the different biological activities of coumarin derivatives. In this review we provide an updated summary of the researches which are related to recent advances in biological activities of coumarins analogue and their most recent activities against COVID -19. Natural compounds act as a rich resource for novel drug development against various SARS-CoV-2 viral strains including viruses like herpes simplex virus, influenza virus, human immunodeficiency virus, hepatitis B and C viruses, middle east respiratory syndrome and severe acute respiratory syndrome.

Stereoselective Synthesis of Dihydrocoumarins via [1,2]-Phospha-Brook Rearrangement in Three-Component Coupling Reaction of α-Ketoesters, o-Quinone Methides, and Dialkyl Phosphites

A highly regio- and diastereoselective approach for the synthesis of phosphate substituted dihydrocoumarins via Brønsted base catalyzed [1,2]-phospha-Brook rearrangement is reported. The two-step, one-pot Michael addition of α-phosphonyloxy enolates proceeds by coupling of dialkyl phosphite and α-ketoesters to o-quinone methides, followed by an intramolecular cyclization, providing 3,4-dihydrocoumarin frameworks.

Rhodium-Catalyzed Asymmetric Hydrogenation of 3-Benzoylaminocoumarins for the Synthesis of Chiral 3-Amino Dihydrocoumarins

An asymmetric hydrogenation of 3-benzoylaminocoumarins was achieved for the first time using our BridgePhos-Rh catalytic system, providing chiral 3-amino dihydrocoumarins in high yields (up to 98 %) and with excellent enantioselectivities (up to 99.7 % ee). The relationship between the enantioselectivities of the hydrogenations and the dihedral angles and the resulting π-π stacking effects of the BridgePhos-Rh complexes, which were determined by X-ray diffraction analysis, are discussed. The corresponding hydrogenated products allow for many transformations, providing several chiral skeletons with important physiological and pharmacological activities.

Exploring indole-based-thiadiazole derivatives as potent acetylcholinesterase and butyrylcholinesterase enzyme inhibitors

Indole based thiadiazole derivatives (1-18) were synthesized and evaluated for their acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) inhibition. The IC₅₀ values of the synthesized analogues ranging between 0.17 ± 0.05 to 33.10 ± 0.6 μM against (AChE) and 0.30 ± 0.1 to 37.60 ± 0.6 μM against (BChE) enzymes. Among the series compounds 8 (IC₅₀ = 0.17 ± 0.05 μM) (IC₅₀ = 0.30 ± 0.1 μM), 9 (IC₅₀ = 0.30 ± 0.05 μM) (IC₅₀ = 0.60 ± 0.05 μM) and 10 (IC₅₀ = 1.30 ± 0.1 μM) (IC₅₀ = 2.60 ± 0.1) were found to be the most potent analogues bearing para, ortho, and meta-fluoro substitutions on phenyl ring attached to thiadiazole. In addition, all the synthesized scaffolds were characterized by using ¹H NMR, ¹³C NMR spectroscopy, and high-resolution Mass Spectrometry (HR-MS). To apprehend the binding mode of interaction of the most potent synthesized derivatives, a molecular docking study was performed.

Virtual screening of plant-derived compounds against SARS-CoV-2 viral proteins using computational tools

The new SARS-CoV-2, responsible for the COVID-19 pandemic, has been threatening public health worldwide for more than a year. The aim of this work was to evaluate compounds of natural origin, mainly from medicinal plants, as potential SARS-CoV-2 inhibitors through docking studies. The viral spike (S) glycoprotein and the main protease M^pro, involved in the recognition of virus by host cells and in viral replication, respectively, were the main molecular targets in this study. Molecular docking was performed using AutoDock, which allowed us to select the plant actives with the highest affinity towards the viral targets and to identify the interaction molecular sites with the SARS-CoV2 proteins. The best energy binding values for S protein were, in kcal/mol: -19.22 for glycyrrhizin, -17.84 for gitoxin, -12.05 for dicumarol, -10.75 for diosgenin, and -8.12 for delphinidin. For M^pro were, in kcal/mol: -9.36 for spirostan, -8.75 for N-(3-acetylglycyrrhetinoyl)-2-amino-propanol, -8.41 for α-amyrin, -8.35 for oleanane, -8.11 for taraxasterol, and -8.03 for glycyrrhetinic acid. In addition, the synthetic drugs umifenovir, chloroquine, and hydroxychloroquine were used as controls for S protein, while atazanavir and nelfinavir were used for M^pro. Key hydrogen bonds and hydrophobic interactions between natural compounds and the respective viral proteins were identified, allowing us to explain the great affinity obtained in those compounds with the lowest binding energies. These results suggest that these natural compounds could potentially be useful as drugs to be experimentally evaluated against COVID-19.

A phosphine-catalysed one-pot domino sequence to access cyclopentene-fused coumarins

A novel phosphine-catalysed, one-pot domino approach for the annulation of 2-formylphenyl alkynoates with activated methylene compounds to construct various cyclopentene-fused dihydrocoumarins is reported. This developed strategy provides a facile and efficient approach for the synthesis of structurally complex coumarins from inexpensive and readily available alkynoates.

Computational Prospecting for the Pharmacological Mechanism of Activity: HIV-1 Inhibition by Ixoratannin A-2

BACKGROUND

Ixora coccinea is a tropical ornamental shrub employed in ethnomedicine for the treatment of a number of diseases none of which include the Human Immunodeficiency Virus (HIV) infection. Ixoratannin A-2, one of the constituents, was previously identified via virtual-screening and experimentally confirmed to possess significant anti-HIV-1 activity in an in vitro CD4+ replication assay. This activity was observed to be significantly reduced in degree in viruses lacking the protein Vpu. This suggests the involvement of Vpu as well as other extra-Vpu macromolecules in its antiviral activity.

METHODS

In the present computational search for the identity of the other macromolecules that could possibly explain the observed activity, a panel of fourteen established HIV-1 macromolecular targets was assembled against which ixoratannin A-2 and other major phytoconstituents of I. coccinea were virtually screened.

RESULTS

Structural analyses of the computed ligand-bound complexes, as well as the careful investigation of the thermodynamic attributes of the predicted binding, revealed subtle selectivity patterns at the atomistic level that suggest the likely involvement of multiple macromolecular processes. Some of the binding interactions were found to be thermodynamically favourable, including the multidrug-resistant HIV protease enzyme, CXCR4 and the human elongin C protein all of which formed reasonably strong interactions with ixoratannin A-2 and other constituents of I. coccinea.

CONCLUSION

Ixoratannin A-2's ability to favourably interact with multiple HIV-1 and human targets could explain its observed extra-Vpu antiviral activity. This, however, does not imply uncontrolled binding with all available targets; on the other hand, molecular size of ixoratannin A-2 and combination of functional groups confer on it a decent level of selectivity against many of the investigated HIV/AIDS targets.

Synthesis and anticancer evaluation of some coumarin and azacoumarin derivatives

Coumarin and its nitrogen analogue 1-aza coumarin are a class of lactones and lactams, respectively, which are indispensable heterocyclic units to both chemists and biochemists. 1-Aza coumarin derivatives, which ultimately metabolize as the corresponding 8-hydroxy coumarins in the biological system are therefore found to be very good anti-inflammatory, anti-cancer, and analgesic agents. A series of hybrid substituted coumarin and azacoumarin-3-carboxylic acid derivatives (8-methoxycoumarin-3-carboxylic acid (4a), 8-methoxyazacoumarin-3-carboxylic acid (4b), 5-bromo-8-methoxycoumarin-3-carboxylic acid (5a), 5-bromo-8-methoxyazacoumarin-3-carboxylic acid (5b), 2-acetoxy-5-bromo-8-methoxyquinoline-3-carboxylic acid (6), and 5,7-di(phenylazo)-8-methoxycoumarin-3-carboxylic acid (7) were synthesized and structurally proved using spectral and elemental analysis data. Substituted coumarin-3-carboxylic acid (4a and 5a) and Substituted azacoumarin-3-carboxylic acid (4b, 5b and 6) were tested for their in vitro cytotoxic activity against MCF-7 and HepG-2 cell lines.