Click Chemistry Approach for Bis-Chromenyl Triazole Hybrids and Their Antitubercular Activity

Novel Coumarin-Nucleobase Hybrids with Potential Anticancer Activity: Synthesis, In Vitro Cell-Based Evaluation, and Molecular Docking

A new series of compounds planned by molecular hybridization of the nucleobases uracil and thymine, or the xanthine theobromine, with coumarins, and linked through 1,2,3-triazole heterocycles were evaluated for their in vitro anticancer activity against the human tumor cell lines: colon carcinoma (HCT116), laryngeal tumor cells (Hep-2), and lung carcinoma cells (A549). The hybrid compound 9a exhibited better activity in the series, showing an IC50 of 24.19 ± 1.39 μM against the HCT116 cells, with a selectivity index (SI) of 6, when compared to the cytotoxicity against the non-tumor cell line HaCat. The in silico search for pharmacological targets was achieved through molecular docking studies on all active compounds, which suggested that the synthesized compounds possess a high affinity to the Topoisomerase 1-DNA complex, supporting their antitumor activity. The in silico toxicity prediction studies suggest that the compounds present a low risk of causing theoretical mutagenic and tumorigenic effects. These findings indicate that molecular hybridization from natural derivative molecules is an interesting approach to seek new antitumor candidates.

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.

Design, synthesis and antitubercular assessment of 1, 2, 3-triazole incorporated thiazolylcarboxylate derivatives

A library of 1, 2, 3-triazole incorporated thiazolylcarboxylate derivatives (7a-q) and (8a-j) were synthesized and evaluated for their in-vitro antitubercular activity against Mycobacterium tuberculosis H37Rv. The two compounds 7h and 8h have displayed excellent antitubercular activity with MIC values of 3.12 and 1.56 µg/mL respectively (MIC values of standard drugs; Ciprofloxacin 1.56 μg/mL & Ethambutol 3.12 μg/mL). Whereas, the four compounds 7i, 7n, 7p and 8i displayed noticeable antitubercular activity with a MIC value of 6.25 µg/mL. The active compounds of the series were further studied for their cytotoxicity against RAW264.7 cell line using MTT assay. Furthermore, to study the probable mechanism of antitubercular action, physicochemical property profiling, DFT calculation and molecular docking study were executed on mycobacterial cell wall target Decaprenylphosphoryl-β-d-ribose 2'-epimerase 1 (DprE1). Among all the compounds, 7h (-10 kcal/mol) and 8h (-10.1 kcal/mol) exerted the highest negative binding affinity against the targeted DprE1 (PDB: 4NCR) protein.

Coumarin Triazoles as Potential Antimicrobial Agents

Currently, in hospitals and community health centers, microbial infections are highly common diseases and are a leading cause of death worldwide. Antibiotics are generally used to fight microbial infections; however, because of the abuse of antibiotics, microbes have become increasingly more resistant to most of them. Therefore, medicinal chemists are constantly searching for new or improved alternatives to combat microbial infections. Coumarin triazole derivatives displayed a variety of therapeutic applications, such as antimicrobial, antioxidant, and anticancer activities. This review summarizes the advances of coumarin triazole derivatives as potential antimicrobial agents covering articles published from 2006 to 2022.

Emerging impact of triazoles as anti-tubercular agent

Tuberculosis, a disease of poverty is a communicable infection with a reasonably high mortality rate worldwide. 10 Million new cases of TB were reported with approx 1.4 million deaths in the year 2019. Due to the growing number of drug-sensitive and drug-resistant tuberculosis cases, there is a vital need to develop new and effective candidates useful to combat this deadly disease. Despite tremendous efforts to identify a mechanism-based novel antitubercular agent, only a few have entered into clinical trials in the last six decades. In recent years, triazoles have been well explored as the most valuable scaffolds in drug discovery and development. Triazole framework possesses favorable properties like hydrogen bonding, moderate dipole moment, enhanced water solubility, and also the ability to bind effectively with biomolecular targets of M. tuberculosis and therefore this scaffold displayed excellent potency against TB. This review is an endeavor to summarize an up-to-date innovation of triazole-appended hybrids during the last 10 years having potential in vitro and in vivo antitubercular activity with structure activity relationship analysis. This review may help medicinal chemists to explore the triazole scaffolds for the rational design of potent drug candidates having better efficacy, improved selectivity and minimal toxicity so that these hybrid NCEs can effectively be explored as potential lead to fight against M. tuberculosis.

Design, Synthesis, Spectroscopic Characterisation and In Vitro Cytostatic Evaluation of Novel Bis(coumarin-1,2,3-triazolyl)benzenes and Hybrid Coumarin-1,2,3-triazolyl-aryl Derivatives

In this work, a series of novel 1,2,3-triazolyl-coumarin hybrid systems were designed as potential antitumour agents. The structural modification of the coumarin ring was carried out by Cu(I)-catalysed Huisgen 1,3-dipolar cycloaddition of 7-azido-4-methylcoumarin and terminal aromatic alkynes to obtain 1,4-disubstituted 1,2,3-triazolyl-coumarin conjugates 2a-g, bis(1,2,3-triazolyl-coumarin)benzenes 2h-i and coumarin-1,2,3-triazolyl-benzazole hybrids 4a-b. The newly synthesised hybrid molecules were investigated for in vitro antitumour activity against five human cancer cell lines, colon carcinoma HCT116, breast carcinoma MCF-7, lung carcinoma H 460, human T-lymphocyte cells CEM, cervix carcinoma cells HeLa, as well as human dermal microvascular endothelial cells (HMEC-1). Most of these compounds showed moderate to pronounced cytotoxic activity, especially towards MCF-7 cell lines with IC₅₀ = 0.3-32 μM. In addition, compounds 2a-i and 4a-b were studied by UV-Vis absorption and fluorescence spectroscopy and their basic photophysical parameters were determined.

Coumarin-1,2,3-triazole Hybrid Molecules: An Emerging Scaffold for Combating Drug Resistance

Undoubtedly, antibiotics have saved billions of lives, but lack of novel antibiotics, development of resistance mechanisms in almost all clinical isolates of bacteria, and recurrent infections caused by persistent bacteria hamper the successful treatment of the infections. Due to the widespread emergence of resistance, even the new families of anti-microbial agents have a short life expectancy. Drugs acting on a single target often lead to drug resistance and are associated with various side effects. For overcoming this problem, either multidrug therapy, or a single drug acting on multiple targets may be used. The latter is called 'hybrid molecules,' which are formed by clubbing two biologically active pharmacophores together, with or without an appropriate linker. In this rapidly evolving era, the development of natural product-based hybrid molecules may be a super-alternative to multidrug therapy, for combating drug resistance caused by various bacterial and fungal strains. Coumarins (benzopyran-2-one) are one of the earliest reported plant secondary metabolites having a clinically proven diverse range of pharmacological properties. On the other hand, 1,2,3-triazole is a common pharmacophore in many drugs responsible for polar interactions, improving the solubility and binding affinity to biomolecular targets. In this review, we discuss recent advances in Coumarin-1,2,3-triazole hybrids as potential anti-bacterial agents, aiming to provide a useful platform for the exploration of new leads with a broader spectrum, more effectiveness and less toxicity with multiple modes of action for the development of cost-effective and safer drugs in the future.

Coumarin hybrid derivatives as promising leads to treat tuberculosis: Recent developments and critical aspects of structural design to exhibit anti-tubercular activity

Tuberculosis (TB) is a highly contagious airborne disease with nearly 25% of the world's population infected with it. Challenges such as multi drug resistant TB (MDR-TB), extensive drug resistant TB (XDR-TB) and in rare cases totally drug resistant TB (TDR-TB) emphasizes the critical and urgent need in developing novel TB drugs. Moreover, the prolonged and multi drug treatment regime suffers a major drawback due to high toxicity and vulnerability in TB patients. This calls for intensified research efforts in identifying novel molecular scaffolds which can combat these issues with minimal side effects. In this pursuit, researchers have screened many bio-active molecules among which coumarin have been identified as promising candidates for TB drug discovery and development. Coumarins are naturally occurring compounds known for their low toxicity and varied biological activity. The biological spectrum of coumarin has intrigued medicinal researchers to investigate coumarin scaffolds for their relevance as anti-TB drugs. In this review we focus on the recent developments of coumarin and its critical aspects of structural design required to exhibit anti-tubercular (anti-TB) activity. The information provided will help medicinal chemists to design and identify newer molecular analogs for TB treatment and also broadens the scope of exploring future generation potent yet safer coumarin based anti-TB agents.

Hybrids of Coumarin Derivatives as Potent and Multifunctional Bioactive Agents: A Review

BACKGROUND

Coumarins exhibit a plethora of biological activities, e.g. antiinflammatory and anti-tumor. Molecular hybridization technique has been implemented in the design of novel coumarin hybrids with several bioactive groups in order to obtain molecules with better pharmacological activity and improved pharmacokinetic profile.

OBJECTIVE

Therefore, we tried to gather as many as possible biologically active coumarin hybrids referred in the literature till now, to delineate the structural characteristics in relation to the activities and to have a survey that might help the medicinal chemists to design new coumarin hybrids with drug-likeness and varied bioactivities.

RESULTS

The biological activities of the hybrids in most of the cases were found to be different from the biological activities presented by the parent coumarins. The results showed that the hybrid molecules are more potent compared to the standard drugs used in the evaluation experiments.

CONCLUSION

Conjugation of coumarin with varied pharmacophore groups/druglike molecules responsible for different biological activities led to many novel hybrid molecules, with a multitarget behavior and improved pharmacokinetic properties.

Novel Aminopyrazole Tagged Hydrazones as Anti-Tubercular Agents: Synthesis and Molecular Docking Studies

BACKGROUND

Pyrazole derivatives have been reported to possess numerous pharmacological activities viz., anti-inflammatory, antipsychotic, etc. Our group has disclosed that pyrazole benzamides display potent antibacterial and anti-tubercular activities.

OBJECTIVE

Synthesis of new pyrazole acetamides which possess hydrazone group to be evaluated for antitubercular activity.

METHODS

The key intermediate 5-aminopyrazole was synthesized with the known procedure, which is then converted into chloroacetamide. This compound than resulted in hydrazine derivative and finally converted into aromatic hydrazones. All the compounds were screened for antitubercular activity.

RESULTS

All the synthesized compounds have been characterized by their spectral data obtained and subjected to anti-tubercular activity. Among all the twenty tested compounds, three compounds, 5a5, 5b5 and 5b7 have demonstrated MIC value of 3.12 μg/mL against MTB H37Rv. Docking studies revealed important hydrogen bonding interactions with InhA.

CONCLUSION

Three compounds 5a5, 5b5 and 5b7 were found to be most potent among the series of compounds. Docking studies of compounds explained the presence of hydrogen bonding and π- π stacking interactions with InhA. Further synthesis of more such derivatives with optimized groups would produce compounds with more potent anti-tubercular activity.

Click chemistry based regioselective one-pot synthesis of coumarin-3-yl-methyl-1,2,3-triazolyl-1,2,4-triazol-3(4H)-ones as newer potent antitubercular agents

Coumarin-3-yl-methyl-1,2,3-triazolyl-1,2,4-triazol-3(4H)-ones (8k-z) were synthesized via copper(I)-catalyzed azide-alkyne cycloaddition click chemistry. The synthesized hybrid molecules were characterized by spectral studies. Compounds 8k-z were screened for their in vitro anti-TB activity by using the Microplate Alamar Blue assay and for cytotoxicity using the MTT assay. Some of the compounds were found to be most potent against the tested Mycobacterium tuberculosis H37Rv strain with a MIC of 1.60 µg/ml. Further, docking the compounds into the InhA binding pocket showed strong binding interactions and effective overall docking scores were recorded. The drug-likeness and toxicity studies were computed using Molinspiration and Protox, respectively.

Synthesis and antimycobacterial activity of 1-(β-d-Ribofuranosyl)-4-coumarinyloxymethyl- / -coumarinyl-1,2,3-triazole

A series of β-d-ribofuranosyl coumarinyl-1,2,3-triazoles have been synthesized by Cu-catalyzed cycloaddition reaction between azidosugar and 7-O-/7-alkynylated coumarins in 62-70% overall yields. The in vitro antimycobacterial activity evaluation of the synthesized triazolo-conjugates against Mycobacterium tuberculosis revealed that compounds were bactericidal in nature and some of them were found to be more active than one of the first line antimycobacterial drug ethambutol against sensitive reference strain H37Rv, and 7 to 420 times more active than all four first line antimycobacterial drugs (isoniazid, rifampicin, ethambutol and streptomycin) against multidrug resistant clinical isolate 591. Study of in silico pharmacokinetic profile indicated the drug like characters for the test molecules. Further, transmission electron microscopic experiments revealed that these compounds interfere with the constitution of bacterial cell wall possibly by targeting mycobacterial InhA and DNA gyrase enzymes. Study conducted on the activities of the test compounds on bacterial InhA and DNA gyrase revealed that the most bactericidal test compound, N¹-(β-d-ribofuranosyl)-C⁴-(4-methylcoumarin-7-oxymethyl)-1,2,3-triazole (6b) and its corresponding directly linked conjugate N¹-(β-d-ribofuranosyl)-C⁴-(4-methylcoumarin-7-yl)-1,2,3-triazole (11b) significantly inhibited the activity of both the enzymes. The results were further supported by molecular docking studies of the compound 6b and 11b with bacterial InhA and DNA gyrase B enzymes. Further, the cytotoxicity study of some of the better active compounds on THP-1 macrophage cell line using MTT assay showed that the synthesized compounds were non-cytotoxic.

Synthesis and Biological Evaluation of Novel Hybrid Molecules Containing Purine, Coumarin and Isoxazoline or Isoxazole Moieties

Introduction:

The 1,3-dipolar cycloaddition reactions of nitrile oxides formed in situ (in the presence of NCS and Et₃N) from the oximes of (purin-9-yl)acetaldehyde or (coumarinyloxy)acetaldehyde with allyloxycoumarins or 9-allylpurines, respectively resulted in 3,5-disubstituted isoxazolines. The similar reactions of propargyloxycoumarins or 9-propargylpurines led to 3,5-disubstituted isoxazoles by treatment with PIDA and catalytic amount of TFA.

Methods:

The new compounds were tested in vitro as antioxidant agents and inhibitors of soybean lipoxygenase LO, AChE and MAO-B.

Results:

The majority of the compounds showed significant hydroxyl radical scavenging activity. Compounds 4k and 4n presented LO inhibitory activity.

Conclusion:

Compound 13e presents an antioxidant significant profile combining anti-LO, anti-AChE and anti-MAO-B activities.

Recent advances of pyrazole-containing derivatives as anti-tubercular agents

One-third of the world's population infected tuberculosis (TB), and more than 1 million deaths annually. The co-infection between the mainly pathogen Mycobacterium tuberculosis (MTB) and HIV, and the incidence of drug-resistant TB, multi-drug resistant TB, extensively drug-resistant TB as well as totally drug-resistant TB have further aggravated the mortality and spread of this disease. Thus, there is an urgent need to develop novel anti-TB agents against both drug-susceptible and drug-resistant TB. The wide spectrum of biological activities and successful utilization of pyrazole-containing drugs in clinic have inspired more and more attention towards this kind of heterocycles. Numerous of pyrazole-containing derivatives have been synthesized for searching new anti-TB agents, and some of them showed promising potency and may have novel mechanism of action. This review aims to outline the recent achievements in pyrazole-containing derivatives as anti-TB agents and their structure-activity relationship.

Triazole derivatives and their anti-tubercular activity

Tuberculosis (TB) remains one of the most widespread and leading deadliest diseases, threats one-third of the world's population. Although numerous efforts have been undertaken to develop new anti-TB agents, only a handful of compounds have entered human trials in the past 5 decades. Triazoles including 1,2,3-triazole and 1,2,4-triazole are one of the most important classes of nitrogen containing heterocycles that exhibited various biological activities. Triazole derivatives are regarded as a new class of effective anti-TB candidates owing to their potential anti-TB potency. Thus, molecules containing triazole moiety may show promising in vitro and in vivo anti-TB activities and might be able to prevent the drug resistant to certain extent. This review outlines the advances in the application of triazole-containing hybrids as anti-TB agents, and discusses the structure-activity relationship of these derivatives.

6-tert-Butyl-4-[(4-hydroxymethyl-2H-1,2,3-triazol-2-yl)methyl]-2H-chromen-2-one

In the title compound, C17H19N3O3, the triazole ring and the chromene ring system [maximum deviation = 0.018 (2) Å for the O atom] bridged via a methylene C atom, are inclined to one another by 73.2 (1)°. In the crystal, molecules are linked by O—H...N hydrogen bonds, forming zigzag chains along [001]. The chains are linked by C—H...O hydrogen bonds, forming layers parallel to (010), and these layers are linked by C—H...π and π–π interactions [intercentroid distance = 3.557 (1) Å], forming a three-dimensional newwork. The hydroxymethyl group at the 4-position of the triazole ring is disordered over two sets of sites, with a refined occupancy ratio of 0.418 (11):0.584 (11).

One pot Click chemistry: A three component reaction for the synthesis of 2-mercaptobenzimidazole linked coumarinyl triazoles as anti-tubercular agents

2-Propargylthiobenzimidazole 1, 4-bromomethyl coumarins/1-aza-coumarins 2/3 and sodium azide have been reacted in one pot under Click chemistry conditions to give exclusively 1,4-disubstituted triazoles 5a-n. Anti-tubercular assays against M. tuberculosis (H37Rv) coupled with in silico molecular docking studies indicated that dimethyl substituents 5c and 5d showed promising activity with higher C-score values.

A click chemistry approach for the synthesis of mono and bis aryloxy linked coumarinyl triazoles as anti-tubercular agents

A series of mono and bis-triazole coumarin hybrids 6a-u and 9a-f respectively have been synthesized using 4-(azidomethyl)-2H-chromen-2-ones 5a-i and aryl propargyl ethers 2a-c/8 employing Click chemistry modified protocol for Azide-Alkyne cycloadditions(CuAAC). Anti-tubercular screening showed moderate activity for mono aryloxy compounds 6a-u with MIC 50-100 μg/mL, whereas the bis compounds 9a-f were more effective with MICs between 0.2 and 12.5 μg/mL. Molecular modeling and 3D-QSAR measurements using CoMFA and Topomer CoMFA further supported the observed results. The bis compound 9b showed excellent activity with MIC value as low as 0.2 μg/mL.

Recent progress in the drug development of coumarin derivatives as potent antituberculosis agents

Tuberculosis (TB) is still a challenging worldwide health problem and mycobacterium tuberculosis (MTB) remains one of the most deadly human pathogens. TB is the second leading infectious cause of mortality today behind only HIV/AIDS. The impetus for developing new structural classes of antituberculosis drugs comes from the emergence of multi-drug resistant (MDR) strains. The development of MDR strains to commonly used drugs is due to, longer durations of therapy as results of resistance, and the resurgence of the disease in immune compromised patients. Therefore, there is an urgent need to explore new antitubercular (anti-TB) agents. Ironically, the low number of potentially new chemical entities which can act as anti-TB candidates is of great importance at present situation. Considering the severity of the problem, WHO has prepared a strategic plan in Berlin declaration 2007 to stop TB, globally. Among the oxygen heterocycles, coumarin derivatives are important motifs, which can be widely found in many natural products, and many of them displaying diverse biological activities. This spectacular spectrum of applications has intrigued organic and medicinal chemists for decades to explore the natural coumarins or their synthetic analogs for their applicability as anti-TB drugs. To pave the way for the future research, there is a need to collect the latest information in this promising area. In the present review, we collated published reports on coumarin derivatives to shed light on the insights on different types of methods reported for their preparations, characterizations and anti-TB applications, so that its full therapeutic potential class of compounds can be utilized for the treatment of tuberculosis. Therefore, the objective of this review is to focus on important coumarin analogs with anti-TB activities, and structure-activity relationships (SAR) for designing the better anti-TB agents. It is hoped that, this review will be helpful for new thoughts in the quest for rational designs of more active and less toxic coumarin-based anti-TB drugs.

Crystal structure of 4-azido-methyl-6-isopropyl-2H-chromen-2-one

In the title mol-ecule, C13H13N3O2, the benzo-pyran ring system is essentially planar, with a maximum deviation of 0.017 (1) Å. In the crystal, weak C-H⋯O hydrogen bonds link mol-ecules into ladders along [010]. In addition, π-π inter-actions between inversion-related mol-ecules, with centroid-centroid distances in the range 3.679 (2)-3.876 (2) Å, complete a two-dimensional network parallel to (001).

Triazole: A Promising Antitubercular Agent

Tuberculosis is a contagious disease with comparatively high mortality worldwide. The statistics shows that around three million people throughout the world die annually from tuberculosis and there are around eight million new cases each year, of which developing countries showed major share. Therefore, the discovery and development of effective antituberculosis drugs with novel mechanism of action have become an insistent task for infectious diseases research programs. The literature reveals that, heterocyclic moieties have drawn attention of the chemists, pharmacologists, microbiologists, and other researchers owing to its indomitable biological potential as anti-infective agents. Among heterocyclic compounds, triazole (1,2,3-triazole/1,2,4-triazole) nucleus is one of the most important and well-known heterocycles, which is a common and integral feature of a variety of natural products and medicinal agents. Triazole core is considered as a privileged structure in medicinal chemistry and is widely used as 'parental' compounds to synthesize molecules with medical benefits, especially with infection-related activities. In the present review, we have collated published reports on this versatile core to provide an insight so that its complete therapeutic potential can be utilized for the treatment of tuberculosis. This review also explores triazole as a potential targeted core moiety against tuberculosis and various research ongoing worldwide. It is hoped that this review will be helpful for new thoughts in the quest for rational designs of more active and less toxic triazole-based antituberculosis drugs.