Synthesis, chromatographic resolution, and anti-human immunodeficiency virus activity of (+/-)-calanolide A and its enantiomers

Bioinspired Pyrano[2,3-f]chromen-8-ones: Ring C-Opened Analogues of Calanolide A: Synthesis and Anti-HIV-1 Evaluation

We have designed and synthesized a series of bioinspired pyrano[2,3-f]coumarin-based Calanolide A analogs with anti-HIV activity. The design of these new calanolide analogs involved incorporating nitrogen heterocycles or aromatic groups in lieu of ring C, effectively mimicking and preserving their bioactive properties. Three directions for the synthesis were explored: reaction of 5-hydroxy-2,2-dimethyl-10-propyl-2H,8H-pyrano[2,3-f]chromen-8-one with (i) 1,2,4-triazines, (ii) sulfonylation followed by Suzuki cross-coupling with (het)aryl boronic acids, and (iii) aminomethylation by Mannich reaction. Antiviral assay of the synthesized compounds showed that compound 4 has moderate activity against HIV-1 on enzymes and poor activity on the cell model. A molecular docking study demonstrates a good correlation between in silico and in vitro HIV-1 reverse transcriptase (RT) activity of the compounds when docked to the nonnucleoside RT inhibitor binding site, and alternative binding modes of the considered analogs of Calanolide A were established.

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.

New Role for Photoexcited Na2 Eosin Y via the Direct Hydrogen Atom Transfer Process in Photochemical Visible-Light-Induced Synthesis of 2-Amino-4H-Chromene Scaffolds Under Air Atmosphere

The Knoevenagel-Michael cyclocondensation of malononitrile, aryl aldehydes, and resorcinol was used as a multicomponent green tandem strategy for the metal-free synthesis of 2-amino-4H-chromene scaffolds. Through a visible-light-induced process, the photo-excited state functions derived from Na₂ eosin Y were used as direct hydrogen atom transfer catalysts in aqueous ethanol at ambient temperature. The purpose of this study was to examine the further use of an organic dye that does not contain metal and is inexpensive and commercially available. Na₂ eosin Y is synthesized by photochemical means using the least amount of catalyst, which results in excellent yields, energy efficiency, and environmental friendliness, high atom economy, time-saving features, and ease of operation. As a result, some properties of green and sustainable chemistry are met. This kind of cyclization can be performed on a gram scale, indicating the potential utility of this reaction in industry.

West African medicinal plants and their constituent compounds as treatments for viral infections, including SARS-CoV-2/COVID-19

Objectives

The recent emergence of the COVID-19 pandemic (caused by SARS-CoV-2) and the experience of its unprecedented alarming toll on humanity have shone a fresh spotlight on the weakness of global preparedness for pandemics, significant health inequalities, and the fragility of healthcare systems in certain regions of the world. It is imperative to identify effective drug treatments for COVID-19. Therefore, the objective of this review is to present a unique and contextualised collection of antiviral natural plants or remedies from the West African sub-region as existing or potential treatments for viral infections, including COVID-19, with emphasis on their mechanisms of action.

Evidence acquisition

Evidence was synthesised from the literature using appropriate keywords as search terms within scientific databases such as Scopus, PubMed, Web of Science and Google Scholar.

Results

While some vaccines and small-molecule drugs are now available to combat COVID-19, access to these therapeutic entities in many countries is still quite limited. In addition, significant aspects of the symptomatology, pathophysiology and long-term prognosis of the infection yet remain unknown. The existing therapeutic armamentarium, therefore, requires significant expansion. There is evidence that natural products with antiviral effects have been used in successfully managing COVID-19 symptoms and could be developed as anti-COVID-19 agents which act through host- and virus-based molecular targets.

Conclusion

Natural products could be successfully exploited for treating viral infections/diseases, including COVID-19. Strengthening natural products research capacity in developing countries is, therefore, a key strategy for reducing health inequalities, improving global health, and enhancing preparedness for future pandemics.

Graphical abstract

Design, synthesis and structure-activity relationship studies of novel spirochromanone hydrochloride analogs as anticancer agents

Aim: Literature reports suggest spirochromanone derivatives exhibit anticancer activity. Methodology: The authors designed and synthesized 18 spirochromanone derivatives (Csp 1-18). The compounds were characterized and evaluated for anticancer activity against human breast cancer (MCF-7) and murine melanoma (B16F10) cell lines. Results: The anticancer activity ranged from 4.34 to 29.31 μm. The most potent compounds, Csp 12 and Csp 18, were less toxic against the human embryonic kidney (HEK-293) cell line and ∼ two/∼four fold selective toward MCF-7 than B16F10 in comparison to the reference, BG-45. Csp 12 caused 28.6% total apoptosis, leading to significant cytotoxicity, and arrested the G2 phase of the cell cycle in B16F10 cells. A molecular docking study of Csp 12 exhibited effective binding at the active site of the epidermal growth factor receptor kinase domain. Conclusion: This study highlights the importance of spirochromanones as anticancer agents.

Direct Michael addition/decarboxylation reaction catalyzed by a composite of copper ferrite nanoparticles immobilized on microcrystalline cellulose: an eco-friendly approach for constructing 3,4-dihydrocoumarin frameworks

A composite of copper ferrite oxide nanoparticles immobilized on microcrystalline cellulose (CuFe₂O₄@MCC) was synthesized. The synthesized composite was characterized by FESEM with EDS-Mapping, TEM, P-XRD, TEM, and BET analysis and investigated for its catalytic activity toward Tandem Michael addition and decarboxylation of coumarin-3-carboxylic acid with cyclic 1,3-diketones to obtain novel 3,4-dihydrocoumarin derivatives. This protocol was established with wide substrate scope and significant yield. The significant characteristics of this methodology are mild reaction conditions, easy setup procedure, non-toxic, and cost-effectiveness. A gram-scale synthesis with low catalyst loading was also demonstrated.

Composites of copper ferrite oxide nanoparticles immobilized on microcrystalline cellulose were synthesized and studied for their catalytic activity toward the preparation of novel 3,4-dihydrocoumarin derivatives.

4-(Dimethylamino)pyridine as an Efficient Catalyst for One-Pot Synthesis of 1,4-Pyranonaphthoquinone Derivatives viaMicrowave-Assisted Sequential Three Component Reaction in Green Solvent

Novel 1,4-pyranonaphthoquinone derivatives were successfully synthesized via the microwave-assisted three-component reaction of 1,4-naphthoquinone, malononitrile, and various arylaldehydes in ethanol in the presence of 4-(dimethylamino)pyridine (DMAP) as a catalyst, and subsequently evaluated in terms of their antimicrobial and antifungal activities. This synthetic procedure has the notable advantages of environmental friendliness, short reaction time, good yield, and convenient operation.

Synthesis of 3,3-Dihalogenated 2-Aminochromanones via Tandem Dihalogenation and Cyclization of o-Hydroxyarylenaminones with NXS (X = Cl or Br)

An unprecedented method for the synthesis of dichlorinated and dibrominated 2-amino-substituted chromanones is developed by employing enaminones and NCS/NBS as starting materials under microwave irradiation. The reactions proceed quickly to deliver products without using any catalyst or additive, thus providing practical access to 3,3-dihalogenated 2-aminochromanones.

Natural Products with Inhibitory Activity against Human Immunodeficiency Virus Type 1

Infections caused by human immunodeficiency virus (HIV) are considered one of the main public health problems worldwide. Antiretroviral therapy (ART) is the current modality of treatment for HIV-1 infection. It comprises the combined use of several drugs and can decrease the viral load and increase the CD4⁺ T cell count in patients with HIV-1 infection, thereby proving to be an effective modality. This therapy significantly decreases the rate of morbidity and mortality owing to acquired immunodeficiency syndrome (AIDS) and prolongs and improves the quality of life of infected patients. However, nonadherence to ART may increase viral resistance to antiretroviral drugs and transmission of drug-resistant strains of HIV. Therefore, it is necessary to continue research for compounds with anti-HIV-1 activity, exhibiting a potential for the development of an alternative or complementary therapy to ART with low cost and fewer side effects. Natural products and their derivatives represent an excellent option owing to their therapeutic potential against HIV. Currently, the derivatives of natural products available as anti-HIV-1 agents include zidovudine, an arabinonucleoside derivative of the Caribbean marine sponge (Tectitethya crypta), which inhibits the reverse transcriptase of the virus. This was the first antiviral agent approved for treatment of HIV infection. Additionally, bevirimat (isolated from Syzygium claviflorum) and calanolide A (isolated from Calophyllum sp.) are inhibitors of viral maturation and reverse transcription process, respectively. In the present review, we aimed to describe the wide repertoire of natural compounds exhibiting anti-HIV-1 activity that can be considered for designing new therapeutic strategies to curb the HIV pandemic.

In search of therapeutic candidates for HIV/AIDS: rational approaches, design strategies, structure-activity relationship and mechanistic insights

The HIV/AIDS pandemic is a serious threat to the health and development of mankind, which has affected about 37.9 million people worldwide. The increasing negative health, economic and social impacts of this disease have led to the search for new therapeutic candidates for the mitigation of AIDS/HIV. However, to date, there is still no treatment that can cure this disease. Furthermore, the clinically available drugs have numerous severe side effects. Hence, the synthesis of novel agents from natural leads is one of the rational approaches to obtain new drugs in modern medicinal chemistry. This review article is an effort to summarize recent developments with regards to the discovery of novel analogs with promising biological potential against HIV/AIDS. Herein, we also aim to discuss prospective directions on the progress of more credible and specific analogues. Besides presenting design strategies, the present communication also highlights the structure-activity relationship together with the structural features of the most promising molecules, their IC50 values, mechanistic insights and some interesting key findings revealed during their biological evaluation. The interactions with the amino acid residues of the enzymes responsible for HIV-1 inhibition are also discussed. This collection will be of great interest for researchers working in this area.

Targeting Solid Tumors With BTK Inhibitors

The repurposing of FDA-approved Bruton's tyrosine kinase (BTK) inhibitors as therapeutic agents for solid tumors may offer renewed hope for chemotherapy-resistant cancer patients. Here we review the emerging evidence regarding the clinical potential of BTK inhibitors in solid tumor therapy. The use of BTK inhibitors may through lead optimization and translational research lead to the development of new and effective combination regimens for metastatic and/or therapy-refractory solid tumor patients.

Synthesis and anticancer activities of some new coumarin derivatives including the triazole ring and their in silico molecular docking studies

The synthesis, docking study, and investigation of the anticancer activities of some coumarin derivatives containing the triazole ring are reported in this study. The newly synthesized compounds were screened for their in vitro anticancer activity against the cell lines CRL5807 (human bronchioalveolar carcinoma), CRL5826 (human squamous cell carcinoma), MDA-MB231 (human breast cancer cells), HTB177 (human lung cancer), PC-3 (human prostate adenocarcinoma), PANC-1 (human pancreatic cancer cells), used as cancer cells, and CCD34Lu (normal human lung fibroblasts), used as a healthy cell line. Cytotoxicity effects of the samples were determined by the MTT (3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide) assay. In silico studies were also performed to explore the binding interactions of the molecules.

Synthesis and crystal structure of methyl 2-(2-((tert-butoxycarbonyl)amino)phenyl)-2-(4-oxo-4H-chromen-3-yl)acetate, C23H23NO6

C23H23NO6, monoclinic, P21/n (no. 14), a = 7.5845(4) Å, b = 14.7024(5) Å, c = 18.1433(6) Å, β = 98.753(4)°, V = 1999.62(14) Å3, Z = 4, R gt(F) = 0.0389, wR ref(F 2) = 0.0965, T = 293 K.

A catalyst-free approach to synthesis of spiroacenaphthylene-pyranopyrazole derivatives in water media

A simple approach for the synthesis of spiroacenaphthylene-pyranopyrazole derivatives was achieved via the reaction between acenaphthoquinone, pyrazolones, and activated methylene compounds (malononitrile derivatives) in water as a green solvent without using any catalyst in order to avoid the use of transition metal. This method has the advantages of mild reaction condition, short reaction time, easy workup, excellent yields, and avoidance of environmentally hazardous solvents.

Design, Synthesis, and Biological Evaluation of Novel Fused Spiro-4H-Pyran Derivatives as Bacterial Biofilm Disruptor

This study aims to synthesize novel fused spiro-4H-pyran derivatives under green conditions to develop agents having antimicrobial activity. The synthesized compounds were initially screened for in vitro antibacterial activity against two Gram-positive and three Gram-negative bacterial strains, and all the compounds exhibited moderate to potent antibacterial activity. However, compound 4l showed significant inhibition toward all the bacterial strains, particularly against Streptococcus pneumoniae and Escherichia coli with minimum inhibitory concentration values of 125 μg/mL for each. The toxicity studies of selected compounds (4c, 4e, 4l, and 4m) using human red blood cells as well as human embryonic kidney (HEK-293) cells showed nontoxic behavior at desired concentration. Growth kinetic and time-kill curve studies of 4l against S. pneumoniae and E. coli supported its bactericidal nature. Interestingly, compound 4l showed a synergistic effect when used in combination with ciprofloxacin against selected strains. Biofilm formation in the presence of a lead compound, as assessed by XTT assay, showed complete disruption of the bacterial biofilm visualized by scanning electron microscopy. Overall, the findings suggest 4l to be considered as a promising lead for further development as an antibacterial agent.

A catalyst- and solvent-free protocol for the sustainable synthesis of fused 4H-pyran derivatives

An efficient and cost-effective method was developed for the synthesis of two kinds of fused 4H-pyran derivatives, namely, dihydropyrano[2,3-c]pyrazole 4 and pyrano[3,2-c]chromenone 6. The reactions of 3-methyl-1-phenyl-5-pyrazolone/4-hydroxycoumarin with aromatic aldehydes and (E)-N-methyl-1-(methylthio)-2-nitroethenamine (NMSM), involving the Knoevenagel, Michael-addition, O-cyclization and elimination reactions under thermal heating, afforded the desired products. The synthesized compounds were characterized by standard spectroscopic techniques. Further, the structures of pyrazole-fused 4H-pyran 4a and coumarin-fused 4H-pyran 6b were confirmed by single-crystal XRD analysis. The short reaction time, good-to-excellent yields, elimination of the use of expensive, metallic and toxic catalysts or hazardous organic solvents and high atom-economy are some noteworthy features of this protocol.

A practical and greener method for the synthesis of highly functionalized pyrazole and coumarin fused 4H-pyran derivatives by exploring NMSM under neat conditions at 110 °C is described.

Synthesis and evaluation of antimicrobial activity, cytotoxic and pro-apoptotic effects of novel spiro-4H-pyran derivatives

A new library of spiropyrans were synthesized via a one-pot four component reaction of cyanoacetohydrazide, ninhydrin, malononitrile and various cyclic CH-acids in EtOH at reflux conditions. The products were isolated and tested in vitro for antibacterial effects on Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). Furthermore cytotoxic activity of the spiropyrans on non-small-cell lung cancer cells (A549 cells), a breast epithelial cancer cell line (MCF-7), human malignant melanoma cells (A375), prostate cancer cells (PC3 cells, LNCaP cells) and normal cells HDF (human dermal fibroblast) was investigated. Interestingly, it was found that compounds 5a, 5b, 5f, 5g and 5i have the best MIC against S. auerus and compound 5a displayed the most potent activity against A549, A375, and LNCaP tumor cells. Moreover, DAPI staining of the A549 cancer cell lines that were treated with 5a were associated with the death of A549 cells. By using RT-PCR method, it was finally confirmed that apoptosis occurs in A549 cells by up-regulated Bax expression and down-regulated Bcl-2 expression from the mitochondrial pathway of apoptosis.

Green Chemistry Preparation of thiochromeno[4,3-b]pyran and benzo[h]thiazolo[2,3-b]quinazoline Derivatives using HSBM Technique over ZnAl2O4 Nano-Powders

AIM AND OBJECTIVE

The aim of this paper is to introduce HSBM as a green and environmentally friendly technique for the synthesis of thiochromeno[4,3-b]pyran and benzo[h]thiazolo[2,3-b]quinazoline derivatives over ZnAl2O4 nanopowders as an efficient catalyst.

MATERIALS AND METHODS

ZnAl2O4 nanopowders were synthesized via a co-precipitation of Zn(NO3)2 and Al(NO3)3 salts and were characterized by XRD, FE-SEM, TEM and DLS techniques. The as-prepared ZnAl2O4 nano-powders have been used as a catalyst on the synthesis of pyran nucleus using high-speed ball milling (HSBM) technique. The structure of products was confirmed with NMR analysis.

RESULTS

ZnAl2O4 exhibits a cubic crystal structure (Space group: Fd-3m) with the average crystallite size of 41 nm. The average particle size of ZnAl2O4 nano-powders determined by DLS technique is 55 nm. The catalytic activity of nano-powders was examined on the synthesis of 2- amino-4,5-dihydro-4-arylthiochromeno[4,3-b]pyran-3-carbonitriles, (8Z)-2-amino-8-arylidene-4,5, 7,8-tetrahydro-4-arylthiopyrano[4,3-b]pyran-3-carbonitriles, 4-aryl-3,4,5,6-tetrahydrobenzo[h]quinazoline- 2(1H)-thiones and 4-aryl-1,3,4,5-tetrahydro-2H-thiochromeno[4,3-d]pyrimidine-2-thione derivatives. All products were obtained in high yields with short reaction times.

CONCLUSION

ZnAl2O4 nanopowders were prepared via a cost-effective co-precipitation method and showed good potential for the synthesis of 4H-pyran analogous in good yields. The salient advantages of HSBM technique include environmentally friendly with reduced solvents, is a simple technique and has low energy costs.

One-pot synthesis of 2-amino-4H-chromene derivatives by MNPs@Cu as an effective and reusable magnetic nanocatalyst

MNPs@Cu as an effective, recyclable nanocatalyst was prepared and characterized using Fourier transform infrared spectroscopy, thermogravimetric analysis vibrating sample magnetometry, scanning electron microscopy, energy dispersive X-ray spectroscopy and X-ray diffraction.