1H -1,2,3-triazole-tethered uracil-ferrocene and uracil-ferrocenylchalcone conjugates: Synthesis and antitubercular evaluation

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.

Synthesis and Biological Evaluation of Novel Uracil Derivatives as Thymidylate Synthase Inhibitors

Cell division is driven by nucleic acid metabolism, and thymidylate synthase (TYMS) catalyzes a rate-limiting step in nucleotide synthesis. As a result, thymidylate synthase has emerged as a critical target in chemotherapy. 5-Fluorouracil (5-FU) is currently being used to treat a wide range of cancers, including breast, pancreatic, head and neck, colorectal, ovarian, and gastric cancers The objective of this study was to establish a new methodology for the low-cost, one-pot synthesis of uracil derivatives (UD-1 to UD-5) and to evaluate their therapeutic potential in BC cells. One-pot organic synthesis processes using a single solvent were used for the synthesis of drug analogues of Uracil. Integrated bioinformatics using GEPIA2, UALCAN, and KM plotter were utilized to study the expression pattern and prognostic significance of TYMS, the key target gene of 5-fluorouracil in breast cancer patients. Cell viability, cell proliferation, and colony formation assays were used as in vitro methods to validate the in silico lead obtained. BC patients showed high levels of thymidylate synthase, and high expression of thymidylate synthase was found associated with poor prognosis. In silico studies indicated that synthesized uracil derivatives have a high affinity for thymidylate synthase. Notably, the uracil derivatives dramatically inhibited the proliferation and colonization potential of BC cells in vitro. In conclusion, our study identified novel uracil derivatives as promising therapeutic options for breast cancer patients expressing the augmented levels of thymidylate synthase.

Ferrocene-triazole conjugates: do we know why they are biologically active?

The bioorganometallic chemistry of ferrocene has been gaining significance in recent years. This review presents ferrocene-triazole conjugates displaying significant biological properties. The conjugates have been synthesized via azide-alkyne cycloaddition reactions. The data are summarized according to the type of activity (anticancer, antibacterial and/or antifungal, antiprotozoal, and other effects). The results of studies concerning the understanding of the role of the ferrocene core in their biological activity are highlighted. While generally the mode of action of these organometallic species remains unclear, the importance of redox properties of ferrocene has been postulated in several cases.

New Nucleic Base-Tethered Trithiolato-Bridged Dinuclear Ruthenium(II)-Arene Compounds: Synthesis and Antiparasitic Activity

Aiming toward compounds with improved anti-Toxoplasma activity by exploiting the parasite auxotrophies, a library of nucleobase-tethered trithiolato-bridged dinuclear ruthenium(II)-arene conjugates was synthesized and evaluated. Structural features such as the type of nucleobase and linking unit were progressively modified. For comparison, diruthenium hybrids with other type of molecules were also synthesized and assessed. A total of 37 compounds (diruthenium conjugates and intermediates) were evaluated in a primary screening for in vitro activity against transgenic Toxoplasma gondii tachyzoites constitutively expressing β-galactosidase (T. gondii β-gal) at 0.1 and 1 µM. In parallel, the cytotoxicity in non-infected host cells (human foreskin fibroblasts, HFF) was determined by alamarBlue assay. Twenty compounds strongly impairing parasite proliferation with little effect on HFF viability were subjected to T. gondii β-gal half maximal inhibitory concentration determination (IC₅₀) and their toxicity for HFF was assessed at 2.5 µM. Two promising compounds were identified: 14, ester conjugate with 9-(2-oxyethyl)adenine, and 36, a click conjugate bearing a 2-(4-(hydroxymethyl)-1H-1,2,3-triazol-1-yl)methyl substituent, with IC₅₀ values of 0.059 and 0.111 µM respectively, significantly lower compared to pyrimethamine standard (IC₅₀ = 0.326 µM). Both 14 and 36 exhibited low toxicity against HFF when applied at 2.5 µM and are candidates for potential treatment options in a suitable in vivo model.

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.

Palladium-catalyzed C–H olefination of uridine, deoxyuridine, uridine monophosphate and uridine analogues

The palladium-catalyzed oxidative C–H olefinations of uridine, deoxyuridine, uridine monophosphate and uridine analogues are reported herein. This protocol provides an efficient, atom-economic and environmentally friendly approach to the synthesis of biologically important C5-alkene modified uracil/uridine-containing derivatives and pharmaceutical candidates.

The palladium-catalyzed oxidative C–H olefinations of uridine, deoxyuridine, uridine monophosphate and uridine analogues are reported herein.

Hybridization Approach to Drug Discovery Inhibiting Mycobacterium tuberculosis-An Overview

Tuberculosis is one of the top 10 causes of death worldwide and the leading cause of death from a single infectious agent, mainly due to Mycobacterium tuberculosis (MTB). Recently, clinical prognoses have worsened due to the emergence of multi-drug resistant (MDR) and extensive-drug resistant (XDR) tuberculosis, which lead to the need for new, efficient and safe drugs. Among the several strategies, polypharmacology could be considered one of the best solutions, in particular, the multitarget directed ligands strategy (MTDLs), based on the synthesis of hybrid ligands acting against two targets of the pathogen. The framework strategy comprises linking, fusing and merging approaches to develop new chemical entities. With these premises, this review aims to provide an overview of the recent hybridization approach, in medicinal chemistry, of the most recent and promising multitargeting antimycobacterial candidates.

Synthesis, in vitro and computational studies of novel glycosyl-1, 2, 3-1H-triazolyl methyl benzamide derivatives as potential α-glucosidase inhibitory activity

A series of novel glycosyl-1,2,3-1H-triazolyl methyl benzamide analogues were synthesized by the unambiguous strategy and evaluated for α-glucosidase inhibitory activity. Glycosyl benzamide exhibited a dose-dependent inhibition of α-glucosidase activity. The In-vitro α-glucosidase inhibition activity results indicated that all the synthesized triazolyl methyl benzamide compounds (IC₅₀ values ranging from 25.3 ± 0.8 to 118.5 ± 5.3 μM) exhibited more inhibitory activity in comparison with the standard drug acarbose (IC₅₀ = 750.0 ± 12.5 μM). Among all, the 3 deacetylated glycosyl methyl benzamide derivatives (4c, 4d and 4f) showed promising α-glucosidase enzyme inhibitory activities with IC₅₀ value 25.3 ± 0.8, 26.1 ± 1.5 and 30.6 ± 2.1 respectively. Furthermore, these compounds were subjected to molecular docking and molecular dynamics simulation studies. The molecular docking studies were performed between (PDB ID: 3A4A) target protein and these synthesized molecules. The compounds displayed good docking energies in the range of -7.5 to -7.8 Kcal/mol. This work could be used as an initial approach in identifying potential novel molecules with the promising activity of type-2 diabetes mellitus.

Triazole-containing hybrids with anti-Mycobacterium tuberculosis potential - Part I: 1,2,3-Triazole

Tuberculosis regimens currently applied in clinical practice require months of multidrug therapy, which imposes a major challenge of patient compliance and drug resistance development. Moreover, because of the increasing emergence of hard-to-treat tuberculosis, this disease continues to be a significant threat to the human population. 1,2,3-triazole as a privileged structure has been widely used as an effective template for drug discovery, and 1,2,3-triazole-containing hybrids that can simultaneously act on dual or multiple targets in Mycobacterium tuberculosis have the potential to circumvent drug resistance, enhance efficacy, reduce side effects and improve pharmacokinetic as well as pharmacodynamic profiles. Thus, 1,2,3-triazole-containing hybrids are useful scaffolds for the development of antitubercular agents. This review aims to highlight recent advances of 1,2,3-triazole-containing hybrids with potential activity against various forms of M. tuberculosis, covering articles published between 2015 and 2020. The structure-activity relationship and the mechanism of action are also discussed to facilitate further rational design of more effective drug candidates.

An Updated Review on the Synthesis and Antibacterial Activity of Molecular Hybrids and Conjugates Bearing Imidazole Moiety

The rapid growth of serious infections caused by antibiotic resistant bacteria, especially the nosocomial ESKAPE pathogens, has been acknowledged by Governments and scientists and is one of the world's major health problems. Various strategies have been and are currently investigated and developed to reduce and/or delay the bacterial resistance. One of these strategies regards the design and development of antimicrobial hybrids and conjugates. This unprecedented critical review, in which our continuing interest in the synthesis and evaluation of the bioactivity of imidazole derivatives is testified, aims to summarise and comment on the results obtained from the end of the 1900s until February 2020 in studies conducted by numerous international research groups on the synthesis and evaluation of the antibacterial properties of imidazole-based molecular hybrids and conjugates in which the pharmacophoric constituents of these compounds are directly covalently linked or connected through a linker or spacer. In this review, significant attention was paid to summarise the strategies used to overcome the antibiotic resistance of pathogens whose infections are difficult to treat with conventional antibiotics. However, it does not include literature data on the synthesis and evaluation of the bioactivity of hybrids and conjugates in which an imidazole moiety is fused with a carbo- or heterocyclic subunit.

Therapeutic potential of uracil and its derivatives in countering pathogenic and physiological disorders

Uracil is one of the most notable pharmacophores in medicinal chemistry as the pyrimidine nucleobase forms an integral part of many commercial drugs. Though the name uracil is usually associated with cancer drugs, there are many uracil-based compounds which can treat different diseases when they are employed. So far, there has been no in-depth review concerning uracil drugs in the market, or in the different stages of clinical trials, including those approved or discontinued. The current work focuses on the importance of uracil and its derivatives in treating different diseases. The use of uracil compounds in treating viral infections, cancer, diabetic, thyroid and autosomal recessive disorders are discussed in the review. The mechanism of action of each uracil drug with emphasis on their structure and properties are discussed in detail. The targeted action of these drugs on sites or on the different stages of a disorder/pathogenic life cycle are also discussed. This review encompasses uracil drugs approved as well as those in development from the 1950's onwards. The utility of uracil in drug discovery and its association with a wide range of diseases is brought forth within this review to demonstrate its potential to a wider audience.

Enhancing the Activity of Drugs by Conjugation to Organometallic Fragments

Resistance to chemotherapy is a current clinical problem, especially in the treatment of microbial infections and cancer. One strategy to overcome this is to make new derivatives of existing drugs by conjugation to organometallic fragments, either by an appropriate linker, or by direct coordination of the drug to a metal. We illustrate this with examples of conjugated organometallic metallocene sandwich and half-sandwich complexes, RuII and OsII arene, and RhIII and IrIII cyclopentadienyl half-sandwich complexes. Ferrocene conjugates are particularly promising. The ferrocene-chloroquine conjugate ferroquine is in clinical trials for malaria treatment, and a ferrocene-tamoxifen derivative (a ferrocifen) seems likely to enter anticancer trails soon. Several other examples illustrate that organometallic conjugation can restore the activity of drugs to which resistance has developed.

Phenoxazine-based scaffold for designing G4-interacting agents

A phenoxazine-based scaffold with one or two positively charged arms for selectively G4 stabilizing was synthesized and probed.

Ferrocene-appended pharmacophores: an exciting approach for modulating the biological potential of organic scaffolds

The present review article describes the recent developments (2014–18) on the synthesis of ferrocene-based pharmacophores with the specific benefits of introducing/replacing organic pharmacophores with the ferrocene core for desired bioactivities.

Synthesis, anti-mycobacterial and cytotoxic evaluation of substituted isoindoline-1,3-dione-4-aminoquinolines coupled via alkyl/amide linkers

A series of secondary amine-substituted isoindoline-1,3-dione-4-aminoquinolines were prepared via microwave heating and assayed for their anti-mycobacterial activities. The compound with a butyl chain as a spacer between the two pharmacophores and piperidine as the secondary amine component on the isoindoline ring was the most potent and non-cytotoxic among the synthesized compounds, exhibiting a minimum inhibitory concentration (MIC₉₉) of 6.25 μg mL⁻¹ against Mycobacterium tuberculosis.

A series of secondary amine-substituted isoindoline-1,3-dione-4-aminoquinolines were prepared via microwave heating and assayed for their anti-mycobacterial activities.

A strategic approach to the synthesis of ferrocene appended chalcone linked triazole allied organosilatranes: Antibacterial, antifungal, antiparasitic and antioxidant studies

A series of ferrocene appended chalcone allied triazole coupled organosilatranes (FCTSa 7-FCTSa 12) were synthesised with the aim of amalgamating the pharmacological action of the constituting moieties into a single molecular scaffold. All the synthesised silatranes were well characterized by various spectroscopic techniques like IR, ¹H NMR, ¹³C NMR and elemental analysis. Organosilatranes were then evaluated for their biological alacrity against bacterial and fungal strains compared with the standard drugs Rifampicin and Amphotericin B respectively. The ferrocene conjugates were found to be only moderately effective against the tested microbes. However, the organosilatranes conceded excellent efficacy against parasite G. lamblia with FCTSa 11 arraying the leading results. On the other hand against another parasite T. vaginalis, FCTSa 8 has emerged as an outstanding composite. Further, Total Antioxidant Assay (TAA) with 2,2'-azino-bis-3-(ethylbenzothiazoline-6-sulphonic acid) revealed FCTSa 10 to be the best claimant for radical scavenging activity. Along these lines, introducing some different substituents in the synthesised hybrids may act as a useful strategy for increasing the biological profile of the drugs.

Organometallic Conjugates of the Drug Sulfadoxine for Combatting Antimicrobial Resistance

Fourteen novel arene Ru^II , and cyclopentadienyl (Cp^x ) Rh^III and Ir^III complexes containing an N,N'-chelated pyridylimino- or quinolylimino ligand functionalized with the antimalarial drug sulfadoxine have been synthesized and characterized, including three by X-ray crystallography. The rhodium and iridium complexes exhibited potent antiplasmodial activity with IC₅₀ values of 0.10-2.0 μm in either all, or one of the three Plasmodium falciparum assays (3D7 chloroquine sensitive, Dd2 chloroquine resistant and NF54 sexual late stage gametocytes) but were only moderately active towards Trichomonas vaginalis. They were active in both the asexual blood stage and the sexual late stage gametocyte assays, whereas the clinical parent drug, sulfadoxine, was inactive. Five complexes were moderately active against Mycobacterium tuberculosis (IC₅₀ <6.3 μm), while sulfadoxine showed no antitubercular activity. An increase in the size of both the Cp^x ligand and the aromatic imino substituent increased hydrophobicity, which resulted in an increase in antiplasmodial activity.

Conjugates of Classical DNA/RNA Binder with Nucleobase: Chemical, Biochemical and Biomedical Applications

Among the most intensively studied classes of small molecules (molecular weight < 650) in biomedical research are small molecules that non-covalently bind to DNA/RNA, and another intensively studied class is nucleobase derivatives. Both classes have been intensively elaborated in many books and reviews. However, conjugates consisting of DNA/RNA binder covalently linked to nucleobase are much less studied and have not been reviewed in the last two decades. Therefore, this review summarized reports on the design of classical DNA/RNA binder - nucleobase conjugates, as well as data about their interactions with various DNA or RNA targets, and even in some cases protein targets are involved. According to these data, the most important structural aspects of selective or even specific recognition between small molecule and target are proposed, and where possible related biochemical and biomedical aspects were discussed. The general conclusion is that this, rather new class of molecules showed an amazing set of recognition tools for numerous DNA or RNA targets in the last two decades, as well as few intriguing in vitro and in vivo selectivities. Several lead research lines show promising advancements toward either novel, highly selective markers or bioactive, potentially druggable molecules.

Azide-alkyne cycloaddition en route to 4-aminoquinoline-ferrocenylchalcone conjugates: synthesis and anti-TB evaluation

AIM

Tuberculosis is responsible for 9.6 million infections and 1.5 million deaths in 2015. The development of multidrug-resistant and extensively drug-resistant strains has impeded the development of effective antitubercular therapy. Results/methodology: The present manuscript describes the synthesis of a series of 4-aminoquinoline-ferrocenylchalcone conjugates via Cu-promoted Huisgen's azide-alkyne cycloaddition reaction and evaluation of their antitubercular activities against mc²6230 strain of Mycobacterium tuberculosis. The conjugate 11j proved to be the most potent of the synthesized conjugates with a minimum inhibitory concentration (MIC₉₉) value of 30 μM and proved to be noncytotoxic against HeLa cells.

CONCLUSION

The synthesized conjugates can act as starting point for the development of new antitubercular agents. Synthesis and antitubercular evaluation of 1H-1,2,3-triazole-tethered 4-aminoquinoline-ferrocenylchalcone conjugates. [Formula: see text].