CuAAC-ensembled 1,2,3-triazole-linked isosteres as pharmacophores in drug discovery: review

Synthesis, Biological Evaluation, and Computational Studies of Schiff's Base Derivatives of 4-(4-Amino-5-Mercapto-4H-1,2,4-Triazol-3-Yl)Benzenesulfonamide as Cathepsin B Inhibitors

A library of benzenesulfonamide incorporated Schiff's base derivatives of 4-amino-5-mercapto-1,2,4-triazoles 1a-f, 2a-e, and 3a-e has been synthesized and evaluated in-vitro for their inhibition potential against cathepsin B enzyme. All the tested compounds possessed good to excellent anti-cathepsin B activity (40.62%-74.36%) at 10-7 m concentrations in comparison with the curcumin (51.20%) taken as reference. Among all, compound 3c has shown the highest activity exhibiting 74.36% inhibition followed by 3e and 3b (69.99% and 68.36% inhibition, respectively). Molecular docking was performed for the most active compound 3c and the reference compound, curcumin, to know their interactions in the active site of the target enzyme and the results obtained were in agreement with the experimental values. Additionally, DFT calculations were also performed to determine the values of electronic parameters including energies of highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO), HOMO-LUMO energy gap, chemical hardness, chemical softness, chemical potential, electronegativity, and electrophilicity index.

Synthesis, anti-proliferation, apoptosis induction in breast cancer cells, and aromatase inhibition of coumarin-triazole hybrids: In vitro and in silico studies

Breast cancer is one of the most common cancers found in women worldwide. Besides the availability of clinical drugs, drug resistance and considerable side effects are concerning issues driven the needs for the discovery of novel anticancer agents. Aromatase inhibition is one of the effective strategies for management of hormone-dependent breast cancer. Triazole, coumarin, and isatin are heterocyclic scaffolds holding great attention in the field of drug design. Molecular hybridization is a well-known strategy to achieve new molecules with improved potency and properties. Herein, a set of 27 triazole-based hybrids (i.e., coumarin-triazoles series 5-6 and isatin-triazoles series 7) were synthesized and investigated for their anti-proliferation, apoptosis induction, and aromatase inhibitory potentials. Anti-proliferative study against the hormone-dependent breast cancer (T47D) cell line indicated that coumarin-triazoles 5h (R=NO2) and 6i (R=SO2NH2) were the two most potent antiproliferative agents. Particularly, compound 5h showed comparable potency and superior selectivity index than that of the reference drug, doxorubicin. Moreover, the coumarin-triazole 5h induced cellular apoptosis of the estrogen-dependent breast cancer (MCF-7) cells. Additionally, findings from the aromatase inhibitory assay suggested four compounds as potential aromatase inhibitors (i.e., 5i, 6f, 6g and 6i, IC50 = 1.4-2.4 μM). Two QSAR models with preferable predictive performances were constructed to reveal key properties influencing antiproliferative and aromatase inhibitory effects. Molecular docking was conducted to elucidate the possible binding modalities against the target aromatase enzyme. Key structural features essential for the binding were highlighted. Moreover, the drug-like properties of top-ranking compounds were assessed to ensure their possibilities for successful development.

In vitro and in silico exploration of newly synthesized triazolyl- isonicotinohydrazides as potent antitubercular agents

In the present study, we have reported the synthesis of novel isoniazid-triazole derivatives (4a-r), via the click chemistry approach. The synthesized isoniazid-triazole derivatives have potent in vitro antitubercular activity against the Mycobacterium tuberculosis (MTB) H37Rv strain. Among these compounds, 4b, 4f, 4g, 4j, 4k, 4m, 4o, 4p, and 4r were found to be the most active ones with a MIC value of 0.78 μg/mL. This activity is better than ciprofloxacin (MIC value = 1.56 μg/mL) and ethambutol (MIC value = 3.12 μg/mL). The compounds, 4a, 4c, 4d, 4e, 4h, 4i, 4l, and 4n have displayed activity equal to ciprofloxacin (MIC value = 1.56 μg/mL). The cytotoxicity of the active isoniazid-triazole derivatives was studied against RAW 264.7 cell line by MTT assay at 25 μg/mL concentration and no toxicity was observed. Moreover, in-vitro results were supported by in-silico studies with the known antitubercular target (PanK). The drug-likeness, density functional study, molecular docking, and molecular dynamics simulation studies of isoniazid-triazole derivatives validated the ability to form a stable complex with Pantothenate kinase (PanK), which will result in inhibiting the Pantothenate kinase (PanK). Therefore, the results obtained indicate that this class of compounds may offer candidates for future development, and positively provide drug alternatives for tuberculosis treatment.Communicated by Ramaswamy H. Sarma.

An updated review on 1,2,3-/1,2,4-triazoles: synthesis and diverse range of biological potential

The synthesis of triazoles has attracted a lot of interest in the field of organic chemistry because of its versatile chemical characteristics and possible biological uses. This review offers an extensive overview of the different pathways used in the production of triazoles. A detailed analysis of recent research indicates that triazole compounds have a potential range of pharmacological activities, including the ability to inhibit enzymes, and have antibacterial, anticancer, and antifungal activities. The integration of computational and experimental methods provides a thorough understanding of the structure-activity connection, promoting sensible drug design and optimization. By including triazoles as essential components in drug discovery, researchers can further explore and innovate in the synthesis, biological assessment, and computational studies of triazoles as drugs, exploring the potential therapeutic significance of triazoles.

Design, Synthesis and Application of 1,4-disubstituted 1,2,3-triazole Based Chemosensors: A Promising Avenue

The 1,2,3-triazole-based chemosensors, synthesized through Cu(I)-catalyzed azide-alkyne cycloaddition via 'click chemistry', offer a straightforward yet highly effective method for detecting metal cations and anions with remarkable accuracy, selectivity and sensitivity, making them invaluable across various fields such as chemistry, pharmacology, environmental science and biology. The selective recognition of these ions is crucial due to their significant roles in biological and physiological processes, where even slight concentration variations can have major consequences. The article reviews literature from 2017 to 2024, highlighting advancements in the synthesis of 1,2,3-triazole-based ligands and their application (along with sensing mechanism) for detection of various ions causing health and environmental hazards. The detection aspects have been discussed sequentially for the transition-, inner transition-, and the metals from the s or p block of the periodic table.

Germanyl triazoles as a platform for CuAAC diversification and chemoselective orthogonal cross-coupling

We report the synthesis of germanyl triazoles formed via a copper-catalysed azide-alkyne cycloaddition (CuAAC) of germanyl alkynes. The reaction is often high yielding, functional group tolerant, and compatible with complex molecules. The installation of the Ge moiety enables further diversification of the triazole products, including chemoselective transition metal-catalysed cross-coupling reactions using bifunctional boryl/germyl species.

Synthesis and modification of noscapine derivatives as promising future anticancer agents

Noscapine, a tetrahydroisoquinoline alkaloid, was first isolated from Papaver somniferum and identified by Rabiquet in 1817. It has been used as an anti-tussive agent since the mid-1950 s. After the discovery of its anti-mitotic potential, it was into the limelight once again. Due to its low toxicity, high bioactivity and oral administration, It was regarded as a formidable framework for subsequent modification and advancement in the pursuit of innovative chemotherapeutic agents. Up to now, the rational derivatives of the noscapine have been designed and the biological activities of these analogues have been extensively investigated. This review provides a comprehensive examination of the chemical characteristics of noscapine and its semi-synthetic derivatives up to the present, encompassing a concise investigation into the biological properties of these compounds and additionally a discussion about biosynthesis and total synthesis of noscapine is also provided. In summary, our aim is to contribute to a more thorough comprehension of this structure. It can be asserted that a promising future lies ahead for noscapine and its engineered derivatives as noteworthy candidates for pharmaceutical drugs.

Exploring Novel Coumarin-Tethered Bis-Triazoles: Apoptosis Induction in Human Pancreatic Cancer Cells, Antimicrobial Effects, and Molecular Modelling Investigations

In the present study, we identified that two representative compounds (7 c and 9 f) of our newly synthesized coumarin-tagged bis-triazoles induced apoptosis in human pancreatic cells (PANC-1) by caspase 3/7mediated pathway. Both 7 c and 9 f (IC50=7.15±1.19 and 6.09±0.79 μM, respectively) were found to be ~100 times superior against PANC-1 as compared to the standard drug Gemcitabine (IC50=>500 μM), without showing any toxicity to the normal pancreatic epithelial cells (H6C7). Molecular docking studies further endorsed them as potential pancreatic cancer therapeutics due to their strong hydrogen bonding interactions with the epidermal growth factor receptor (EGFR) enzyme, which is overexpressed in cancerous cells including pancreatic cancer. Additionally, these compounds also showed moderate inhibitory activity against a panel of microbial strains. Overall, our findings reveal that the coumarin hybrids 7 c and 9 f are viable chemotypes to be adopted as templates for the development of new anticancer drugs, particularly against pancreatic cancer.

Discovery of A Synthetic Hub for Regio- and Stereoselective Construction of Triazolyl Vinyl Sulfonyl Fluorides

A new sulfonyl fluoride reagent 1-bromobut-3-ene-1,3-disulfonyl difluoride (BEDF) was developed. This unique reagent possesses two clickable functionalities to be used for both azide-alkyne cycloaddition click and SuFEx click reactions. This new reagent was applied for the regioselective construction of a class of novel triazolyl vinyl sulfonyl fluorides in which the C-4 position 1H-1,2,3-triazoles were functionalized with vinyl sulfonyl fluorides of exclusively E-configuration.

Green synthesis of benzimidazole derivatives using copper(II)-supported on alginate hydrogel beads

The study addresses the challenge of developing sustainable and efficient catalytic systems for the synthesis of benzimidazole derivatives, which are of significant importance in the field of medicinal chemistry due to their diverse biological activities. The objective is to develop a recyclable and environmentally friendly catalyst utilizing copper(II)-loaded alginate hydrogel beads, which can facilitate the synthesis of these compounds while minimizing environmental impact. The preparation process entails crosslinking sodium alginate with copper(II) ions to form hydrogel beads, which are then washed and characterized through techniques such as scanning electron microscopy (SEM), Energy dispersive X-ray spectroscopy (EDX), Fourier Transform Infrared Spectroscopy (FTIR), X-ray diffraction (XRD), Inductively coupled plasma (ICP), and Zeta potential to analyses the morphology, composition and porosity of the beads. The catalytic performance is evaluated through recycling tests, which demonstrate the catalyst's ability to maintain selectivity and activity over multiple reaction cycles. The Cu(II)-Alg hydrogel beads were used for synthesizing substituted benzimidazole derivatives in a water-ethanol solvent at room temperature. This method offers significant advantages, including extremely mild reaction conditions, short reaction times (<1 h), high yields (70-94 %), and ease of processing. The most significant results indicate that the Cu(II)-alginate catalyst exhibits a high loading capacity and retains its catalytic efficiency for at least 3 cycles, thereby highlighting its potential for sustainable applications in organic synthesis.

Green and recyclable catalyst based on chitosan/CuFe2O4 nanocomposite hydrogel for one-step synthesis of 1,2,3-triazoles

The scope of the heterogeneous catalysts has been greatly expanded in last few decades by the development of various catalysts. In this work a new chitosan-based nanocomposite hydrogel (CS/CuFe2O4 NCH) was synthesized as a high-performance heterogeneous catalyst and then, it was utilized for the green synthesis of substituted 1,2,3-triazoles by a multi-component (azide-alkyne-epoxide) cycloaddition reaction. The synthesized nanocomposite hydrogel was investigated by using various instrumental analyses, including FT-IR, XRD, SEM, EDS, HRTEM, DLS, and TGA. The structure of one of the substituted 1,2,3-triazoles was studied by using single-crystal X-ray diffraction analysis. The nanocomposite hydrogel can be easily regenerate after the catalytic reaction. It can be reused frequently without considerable loss of activity. The high catalytic activity, straightforward reaction, easy recyclability, short reaction time, use of a green solvent, and the simple separation of catalyst are the main advantage of the current method, which offers both financial and environmental benefits.

A 'click' based fluorescent probe mimicking the IMPLICATION logic gate for Cu(II) and Pb(II) sensing: DFT and molecular docking studies

'Click' derived 1,2,3-triazole appended scaffolds are intriguing candidates for selective metal ion recognition because of their stereospecificity and efficiency. The presented report uses the 'click' approach to introduce a glyoxal bis-(2-hydroxyanil)-based chemosensor probe (GT) via the CuAAC pathway, which can selectively detect Cu(II) and Pb(II) ions, both of which are among the most hazardous and perturbing environmental pollutants. NMR spectroscopy, IR spectroscopy, and mass spectrometry (LCMS) were used to successfully characterize the synthesized probe. The discerning recognition behaviour of the probe for Cu(II) and Pb(II) ions was established through a chemosensing investigation using fluorescence and UV-vis spectroscopy, wherein the fluorescence spectral analysis demonstrated the probe to mimic the IMPLICATION logic gate. Furthermore, the metal-ligand interaction was also validated by 1H NMR and IR spectroscopy of the synthesized GT-metal complex, and UV-vis spectroscopy was also employed to analyze the effect of time and temperature on the capacity of the probe to bind with Cu(II) and Pb(II) ions. Furthermore, the sensor's atherosclerosis-inhibition potential was investigated in silico utilizing docking analysis with tribbles-1 protein, and a density functional theory (DFT) study enhanced the understanding of its structure using the B3LYP functional and the 6311G++(d,p) basis set.

Novel isatin-triazole based thiosemicarbazones as potential anticancer agents: synthesis, DFT and molecular docking studies

Thiosemicarbazones of isatin have been found to exhibit versatile bioactivities. In this study, two distinct types of isatin-triazole hybrids 3a and 3b were accessed via copper-catalyzed azide-alkyne cycloaddition reaction (CuAAC), together with their mono and bis-thiosemicarbazone derivatives 4a-h and 5a-h. In addition to the characterization by physical, spectral and analytical data, a DFT study was carried out to obtain the optimized geometries of all thiosemicarbazones. The global reactivity values showed that among the synthesized derivatives, 4c, 4g and 5c having nitro substituents are the most soft compounds, with compound 5c having the highest electronegativity and electrophilicity index values among the synthesized series, thus possessing strong binding ability with biomolecules. Molecular docking studies were performed to explore the inhibitory ability of the selected compounds against the active sites of the anticancer protein of phosphoinositide 3-kinase (PI3K). Among the synthesized derivatives, 4-nitro substituted bisthiosemicarbazone 5c showed the highest binding energy of -10.3 kcal mol-1. These findings demonstrated that compound 5c could be used as a favored anticancer scaffold via the mechanism of inhibition against the PI3K signaling pathways.

Design, synthesis and in silico molecular docking evaluation of novel 1,2,3-triazole derivatives as potent antimicrobial agents

Chalcone and triazole scaffolds have demonstrated a crucial role in the advancement of science and technology. Due to their significance, research has proceeded on the design and development of novel benzooxepine connected to 1,2,3-triazolyl chalcone structures. The new chalcone derivatives produced by benzooxepine triazole methyl ketone 2 and different aromatic carbonyl compounds 3 are discussed in this paper. All prepared compounds have well-established structures to a variety of spectral approaches, including mass analysis, 1H NMR, 13C NMR, and IR. Among the tested compounds, hybrids 4c, 4d, 4i, and 4k exhibited exceptional antibacterial susceptibilities with MIC range of 3.59-10.30 μM against the tested S. aureus strain. Compounds 4c, 4d displayed superior antifungal activity against F. oxysporum with MIC 3.25, 4.89 μM, when compared to fluconazole (MIC = 3.83 μM) respectively. On the other hand, analogues 4d, 4f, and 4k demonstrated equivalent antitubercular action against H37Rv strain with MIC range of 2.16-4.90 μM. The capacity of ligand 4f to form a stable compound on the active site of CYP51 from M. tuberculosis (1EA1) was confirmed by docking studies using amino acids Leu321(A), Pro77(A), Phe83(A), Lys74(A), Tyr76(A), Ala73(A), Arg96(A), Thr80(A), Met79(A), His259(A), and Gln72(A). Additionally, the chalcone‒1,2,3‒triazole hybrids ADME (absorption, distribution, metabolism, and excretion), characteristics of molecules, estimations of toxicity, and bioactivity parameters were assessed.

Each Interruption is an Opportunity: Novel Synthetic Strategies Explored Through Interrupted Click Reactions

The particular and unique mechanism of the copper-catalyzed reaction between azides and alkynes (CuAAC) has not only allowed for the efficient synthesis of 1,2,3-trisubstituted 1,4-triazoles in excellent yields and under mild conditions, becoming the quintessential click reaction, but it has also enabled the straightforward formation of a metallocycle intermediate, the copper triazolyl. This, under suitable reaction conditions able to suppress its protonolysis, can be used either for the creation of new bicyclic triazolyl structures or for the generation of novel three or four-component reactions. The aim of this review is to rationalize and unify all these transformations, which are collectively referred to as "interrupted click reactions".

1,2,3-triazole and chiral Schiff base hybrids as potential anticancer agents: DFT, molecular docking and ADME studies

A series of novel 1,2,3-triazole and chiral Schiff base hybrids 2-6 were synthesized by Schiff base condensation reaction from pre-prepared parent component of the hybrids (1,2,3-triazole 1) and series of primary chiral amines and their chemical structure were confirmed using NMR and FTIR spectroscopies, and CHN elemental analysis. Compounds 1-6 were evaluated for their anticancer activity against two cancer PC3 (prostate) and A375 (skin) and MRC-5 (healthy) cell lines by Almar Blue assay method. The compounds exhibited significant cytotoxicity against the tested cancer cell lines. Among the tested compounds 3 and 6 showed very good activity for the inhibition of the cancer cell lines and low toxicity for the healthy cell lines. All the compounds exhibited high binding affinity for Androgen receptor modulators (PDB ID: 5t8e) and Human MIA (PDB ID: 1i1j) inhibitors compared to the reference anticancer drug (cisplatin). Structure activity relationships (SARs) of the tested compounds is in good agreement with DFT and molecular docking studies. The compounds exhibited desirable physicochemical properties for drug likeness.

Design, synthesis, and molecular modeling studies of novel 2-quinolone-1,2,3-triazole-α-aminophosphonates hybrids as dual antiviral and antibacterial agents

With the aim to identify new antiviral agents with antibacterial properties, a series of 2-quinolone-1,2,3-triazole derivatives bearing α-aminophosphonates was synthesized and characterized by 1H NMR, 13C NMR, 31P NMR, single crystal XRD and HRMS analyses. These compounds were examined against five RNA viruses (YFV, ZIKV, CHIKV, EV71 and HRV) from three distinct families (Picornaviridae, Togaviridae and Flaviviridae) and four bacterial strains (S. aureus, E. feacalis, E. coli and P. aeruginosa). The α-aminophosphonates 4f, 4i, 4j, 4k, 4p and 4q recorded low IC50 values of 6.8-10.91 μM, along with elevated selectivity indices ranging from 2 to more than 3, particularly against YFV, CHIKV and HRV-B14. Besides, the synthesized compounds were generally more sensitive toward Gram-positive bacteria, with the majority of them displaying significant potency against E. feacalis. Specifically, an excellent anti-enterococcus activity was obtained by compound 4q with MIC and MBC values of 0.03 μmol/mL, which were 8.7 and 10 times greater than those of the reference drugs ampicillin and rifampicin, respectively. Also, compounds 4f, 4p and 4q showed potent anti-staphylococcal activity with MIC values varying between 0.11 and 0.13 μmol/mL, compared to 0.27 μmol/mL for ampicillin. The results from DFT and molecular docking simulations were in agreement with the biological assays, proving the binding capability of hybrids 4f, 4i, 4j, 4k, 4p and 4q with viral and bacterial target enzymes through hydrogen bonds and other non-covalent interactions. The in silico ADME/Tox prediction revealed that these molecules possess moderate to good drug-likeness and pharmacokinetic properties, with a minimal chance of causing liver toxicity or carcinogenic effects.

Clicking in harmony: exploring the bio-orthogonal overlap in click chemistry

In the quest to scrutinize and modify biological systems, the global research community has continued to explore bio-orthogonal click reactions, a set of reactions exclusively targeting non-native molecules within biological systems. These methodologies have brought about a paradigm shift, demonstrating the feasibility of artificial chemical reactions occurring on cellular surfaces, in the cell cytosol, or within the body - an accomplishment challenging to achieve with the majority of conventional chemical reactions. This review delves into the principles of bio-orthogonal click chemistry, contrasting metal-catalyzed and metal-free reactions of bio-orthogonal nature. It comprehensively explores mechanistic details and applications, highlighting the versatility and potential of this methodology in diverse scientific contexts, from cell labelling to biosensing and polymer synthesis. Researchers globally continue to advance this powerful tool for precise and selective manipulation of biomolecules in complex biological systems.

Dehydroacetic acid a privileged medicinal scaffold: A concise review

From the last decade, research on dehydroacetic acid (DHA) and its derivatives has increased immensely due to its significant role in various fields, including medicine, cosmetics, food industry, and so on. In the medicinal area, DHA plays an essential role in developing novel action-based drugs, which are helpful for treating various diseases. Besides its plethora of biological applications, its chelating ability offers the easiest synthetic route for synthesizing more active metal complexes. DHA derivatives along with their metal complexes show a number of biological activities and also exhibit various interactions with multiple biological targets. This article summarizes recent medicinal applications (2000-onwards) of DHA-based compounds and their analogs, along with their structure-activity relationship (SAR) analysis. Their interactions with different target enzymes are also discussed. This information derived from SAR analysis would be helpful for medicinal chemists working on the development of drugs based on heterocyclic frameworks, particularly those based on the DHA scaffold.

Click chemistry-aided drug discovery: A retrospective and prospective outlook

Click chemistry has emerged as a valuable tool for rapid compound synthesis, presenting notable advantages and convenience in the exploration of potential drug candidates. In particular, in situ click chemistry capitalizes on enzymes as reaction templates, leveraging their favorable conformation to selectively link individual building blocks and generate novel hits. This review comprehensively outlines and introduces the extensive use of click chemistry in compound library construction, and hit and lead discovery, supported by specific research examples. Additionally, it discusses the limitations and precautions associated with the application of click chemistry in drug discovery. Our intention for this review is to contribute to the development of a modular synthetic approach for the rapid identification of drug candidates.

Ampyrone appended 1,2,3-triazole as selective fluorescent Cu(II) ion sensor: DFT and docking findings

The present report describes the application of the 'Click Chemistry' pathway to synthesize a fluorescent probe (APT) based on ampyrone (4-aminoantipyrine), entailing two benzyl groups as the fluorophores coupled to the antipyrine structure through 1,2,3-triazole moieties. Infrared spectroscopy (IR), nuclear magnetic resonance (1H and 13C), and mass spectrometry were the standard spectroscopic methods used to characterize APT. The ion recognition potential of the probe was analyzed through absorption and emission spectroscopy employing a 4:1 combination of CH3CN and H2O, which demonstrated APT to be an efficient sensing agent for Cu(II) ions, wherein the absorption spectrum of the probe displayed a hypsochromic shift with a hyperchromic shift on gradually adding the metal ion solution of Cu(II), whereas quenching of the probe's fluorescence emission on Cu(II) addition was attributed to the chelation-enhanced fluorescence quenching (CHEQ), induced by the d9 electronic configuration of Cu(II). The stoichiometry of the complexation of APT with Cu(II) is indicative of a 1:1 ratio, while the detection limit (LOD) and quantification limit (LOQ) as estimated from the fluorescence titration results were 3.11 µM and 10.35 µM respectively. Furthermore, DFT analysis was also undertaken to yield the energy-optimized structures and HOMO-LUMO density plots of APT and its corresponding Cu(II) complex via the B3LYP/631G+(d,p) level of theory for APT, and LANL2DZ basis set for the APT-Cu(II) complex. Docking analysis of the probe with the synaptic vesicle protein (SV2A) gave glimpses about its anticonvulsant properties.

Recent progress in the synthesis of natural product inspired bioactive glycohybrids

Carbohydrates are a basic structural component that are indispensable to all cellular processes. In addition to being employed as chiral starting materials in the synthesis of a variety of natural products, carbohydrates are recognized as naturally occurring molecules having an enormous variety of functional, stereochemical, and structural properties. The understanding and biological roles of carbohydrate derived molecules can be greatly improved by selectively synthesizing functional carbohydrates through incorporating them with privileged scaffolds. For a deeper understanding of their roles and the development of functional materials based on sugar, it is crucial to develop new techniques for efficiently synthesizing, functionalizing, and modifying carbohydrates. Glycohybrids have a wide range of structural and functional characteristics along with protein-carbohydrate interactions that are crucial to mammalian biology and a number of disease states. This review, consisting the literature from January 2017 to July 2023 and provide an overview of recent developments in the chemical synthesis of glycohybrids based on natural product scaffolds of coumarin, quinolone, naphthalene diimide, indole, isatin, naphthoquinone, imidazole and pyrimidine. The biological activity of active glycohybrids are discussed in this review.

"Click Chemistry": An Emerging Tool for Developing a New Class of Structural Motifs against Various Neurodegenerative Disorders

Click chemistry is a set of easy, atom-economical reactions that are often utilized to combine two desired chemical entities. Click chemistry accelerates lead identification and optimization, reduces the complexity of chemical synthesis, and delivers extremely high yields without undesirable byproducts. The most well-known click chemistry reaction is the 1,3-dipolar cycloaddition of azides and alkynes to form 1,2,3-triazoles. The resulting 1,2,3-triazoles can serve as both bioisosteres and linkers, leading to an increase in their use in the field of drug discovery. The current Review focuses on the use of click chemistry to identify new molecules for treating neurodegenerative diseases and in other areas such as peptide targeting and the quantification of biomolecules.

Targeting NOX2 with Bivalent Small-Molecule p47phox-p22phox Inhibitors

Nicotinamide adenine dinucleotide phosphate oxidase isoform 2 (NOX2) is an enzymatic complex whose function is the regulated generation of reactive oxygen species (ROS). NOX2 activity is central to redox signaling events and antibacterial response, but excessive ROS production by NOX2 leads to oxidative stress and inflammation in a range of diseases. The protein-protein interaction between the NOX2 subunits p47phox and p22phox is essential for NOX2 activation, thus p47phox is a potential drug target. Previously, we identified 2-aminoquinoline as a fragment hit toward p47phoxSH3A-B and converted it to a bivalent small-molecule p47phox-p22phox inhibitor (Ki = 20 μM). Here, we systematically optimized the bivalent compounds by exploring linker types and positioning as well as substituents on the 2-aminoquinoline part and characterized the bivalent binding mode with biophysical methods. We identified several compounds with submicromolar binding affinities and cellular activity and thereby demonstrated that p47phox can be targeted by potent small molecules.

1,2,3-Triazoles in Biomolecular Crystallography: A Geometrical Data-Mining Approach

The 1,2,3-triazole scaffold has become very attractive to identify new chemical entities in drug discovery projects. Despite the widespread use of click chemistry to synthesize numerous 123Ts, there are few drugs on the market that incorporate this scaffold as a substructure. To investigate the true potential of 123Ts in protein-ligand interactions, we examined the noncovalent interactions between the 1,2,3-triazole ring and amino acids in protein-ligand cocrystals using a geometrical approach. For this purpose, we constructed a nonredundant database of 220 PDB IDs from available 123T-protein cocrystal structures. Subsequently, using the Protein Ligand Interaction Profiler web platform (PLIP), we determined whether 1,2,3-triazoles primarily act as linkers or if they can be considered interactive scaffolds. We then manually analyzed the geometrical descriptors from 333 interactions between 1,4-disubstituted 123T rings and amino acid residues in proteins. This study demonstrates that 1,2,3-triazoles exhibit diverse preferred interactions with amino acids, which contribute to protein-ligand binding.

Click Reactions in Medicinal Chemistry

Two decades after K [...].

Azide-Assisted Growth of Copper Nanostructures and Their Application as a Carbon Supported Catalyst in Two-Step Three-Component Azide-Alkyne Cycloadditions

Copper nanostructures were obtained from the reduction of Cu(I) under mild conditions in ethanol/water using sodium-l-ascorbate and sodium azide while performing an amination reaction. When the halobenzene substrate was reacted in the presence of a bulk carbon black (CB) support, clustered copper sub-micrometer particles (SMPs) and microparticles (MPs) form. The growth conditions of the MPs were optimized, and the supported nanostructures were isolated and characterized by scanning electron microscopy, energy dispersive X-ray spectroscopy, thermogravimetry, and inductively-coupled plasma mass spectrometry. The particles are mobile and supported within the CB matrix and proved to be active catalysts in the azide-alkyne cycloaddition (CuAAC). The catalytic competency of the particles was assessed in a two-step three-component azide-alkyne cycloaddition of benzyl bromide, sodium azide, and phenylacetylene as a model reaction. The reaction conditions were optimized, and the optimized conditions were applied for the synthesis of triazole compounds with varying levels of functionalization. The recyclability of the catalysts was investigated, depletion modes were discussed, and the conditions were fine-tuned to reach good recyclability. This demonstrates the broader applicability of the SMPs/MPs as CuAAC-catalyst and its limitations.

New Boron Containing Acridines: Synthesis and Preliminary Biological Study

The synthesis of the first conjugates of acridine with cobalt bis(dicarbollide) are reported. A novel 9-azido derivative of acridine was prepared through the reaction of 9-methoxyacridine with N3CH2CH2NH2, and its solid-state molecular structure was determined via single-crystal X-ray diffraction. The azidoacridine was used in a copper (I)-catalyzed azide-alkyne cycloaddition reaction with cobalt bis(dicarbollide)-based terminal alkynes to give the target 1,2,3-triazoles. DNA interaction studies via absorbance spectroscopy showed the weak binding of the obtained conjugates with DNA. The antiproliferative activity (IC50) of the boronated conjugates against a series of human cell lines was evaluated through an MTT assay. The results suggested that acridine derivatives of cobalt bis(dicarbollide) might serve as a novel scaffold for the future development of new agents for boron neutron capture therapy (BNCT).

Synthesis, α-Glucosidase inhibitory activity and docking studies of Novel Ethyl 1,2,3-triazol-4-ylmethylthio-5,6-diphenylpyridazine-4-carboxylate derivatives

In this work, a novel series of pyridazine-triazole hybrid molecules were prepared and evaluated as inhibitors of rat intestinal α-glucosidase enzyme. Amongst all newly synthesized compounds, 10k showed good inhibition in the series with IC₅₀ value of 1.7 µM which is 100 folds stronger than positive control, acarbose. The cytotoxicity revealed that this compound is not toxic against normal cell line, HDF. The docking studies showed that triazole ring plays an important role in the binding interactions with the active site. The insertion of compound 10k into the active pocket of α-glucosidase and formation of hydrogen bonds with Leu677 was observed from docking studies. The kinetic studies revealed that this compound has uncompetitive mode of inhibition against α-glucosidase enzyme.

Regioselective Synthesis of New Family of 2-Substituted 1,2,3-Triazoles and Study of Their Fluorescent Properties

Modification of 5-aryl-4-trifluoroacetyltriazoles at the NH-moiety was investigated. Screening of the alkylation conditions revealed that using Na₂CO₃ as a base and DMF as a solvent of 2-substituted triazoles can be preferentially prepared in up to 86% yield. In the best cases, the amount of minor 1-alkyl isomer was less than 6%. S_NAr reaction of the 5-aryl-4-trifluoroacetyltriazoles with aryl halides having electron-withdrawing groups led to regiospecific formation of 2-aryltriazoles isolated in good-to-high yields. Chan-Lam reaction of the 5-aryl-4-trifluoroacetyltriazoles with boronic acids afforded 2-aryltriazoles as single isomers in up to 89% yield. The subsequent reaction of the prepared 2-aryltriazoles with primary and secondary amines gave a set of amides of 4-(2,5-diaryltriazolyl)carboxylic acid. The fluorescent properties of the prepared 2-substituted derivatives of triazoles were investigated to demonstrate their utility as new efficient luminophores having more than 60% quantum yields.

Copper(i)-catalyzed click chemistry in deep eutectic solvent for the syntheses of β-d-glucopyranosyltriazoles

In the last two decades, click chemistry has progressed as a powerful tool in joining two different molecular units to generate fascinating structures with a widespread application in various branch of sciences. copper(i)-catalyzed azide-alkyne cycloaddition (CuAAC) reaction, also known as click chemistry, has been extensively utilized as a versatile strategy for the rapid and selective formation of 1,4-disubstituted 1,2,3-triazoles. The successful use of CuAAC reaction for the preparation of biologically active triazole-attached carbohydrate-containing molecular architectures is an emerging area of glycoscience. In this regard, a well-defined copper(i)-iodide complex (1) with a tridentate NNO ligand (L1) was synthesized and effectively utilized as an active catalyst. Instead of using potentially hazardous reaction media such as DCM or toluene, the use of deep eutectic solvent (DES), an emerging class of green solvent, is advantageous for the syntheses of triazole-glycohybrids. The present work shows, for the first time, the successful use of DES as a reaction medium to click various glycosides and terminal alkynes in the presence of sodium azide. Various 1,4-disubstituted 1,2,3-glucopyranosyltriazoles were synthesized and the pure products were isolated by using a very simple work-up process (filtration). The reaction media was recovered and recycled in five consecutive runs. The presented catalytic protocol generated very minimum waste as reflected by a low E-factor (2.21-3.12). Finally, the optimized reaction conditions were evaluated with the CHEM21 green metrics toolkit.

Novel Erlotinib-Chalcone Hybrids Diminish Resistance in Head and Neck Cancer by Inducing Multiple Cell Death Mechanisms

In a search for novel therapeutic options for head and neck squamous cell carcinomas (HNSCCs) generally treated with limited therapeutic success, we synthesized a series of novel erlotinib-chalcone molecular hybrids with 1,2,3-triazole and alkyne linkers and evaluated them for their anticancer activity on Fadu, Detroit 562 and SCC-25 HNSCC cell lines. Time- and dose-dependent cell viability measurements disclosed a significantly increased efficiency of the hybrids compared to the 1:1 combination of erlotinib and a reference chalcone. The clonogenic assay demonstrated that hybrids eradicate HNSCC cells in low micromolar concentrations. Experiments focusing on potential molecular targets indicate that the hybrids trigger the anticancer effect by a complementary mechanism of action that is independent of the canonical targets of their molecular fragments. Confocal microscopic imaging and real-time apoptosis/necrosis detection assay pointed to slightly different cell death mechanisms induced by the most prominent triazole- and alkyne-tethered hybrids (6a and 13, respectively). While 6a featured the lowest IC₅₀ values on each of the three HNSCC cell lines, in Detroit 562 cells, this hybrid induced necrosis more markedly compared to 13. The therapeutic potential indicated by the observed anticancer efficacy of our selected hybrid molecules validates the concept of development and justifies further investigation to reveal the underlying mechanism of action.

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.

Base-mediated ketenimine formation from N-sulfonylthioimidates for the synthesis of 5-amino-1-vinyl/aryl-1,2,3-triazoles

N-Sulfonylthioimidate was converted to ketenimine under basic conditions. The reaction with vinyl/aryl azides was induced to cause dipolar cycloaddition to form 5-amino-1-vinyl/aryl-1,2,3-triazoles. The advantages of this method are high efficiency, structural diversity of products favorable yields and applicability to gram-scale operations.

Expanding the scope of novel 1,2,3-triazole derivatives as new antiparasitic drug candidates

We have previously shown that prenyl and aliphatic triazoles are interesting motifs to prepare new chemical entities for antiparasitic and antituberculosis drug development. In this opportunity a new series of prenyl-1,2,3-triazoles were prepared from isoprenyl azides and different alkynes looking for new antimalarial drug candidates. The compounds were prepared by copper(i) catalyzed dipolar cycloaddition of the isoprenyl azide equilibrium mixture providing exclusively 1,4-disubstituted 1,2,3-triazoles in a regiospecific fashion. The complete collection of 64 compounds was tested on chloroquine-sensitive (CQ sensitive), Sierra Leone (D6), and the chloroquine-resistant, Indochina (W2), strains of Plasmodium falciparum and those compounds which were not previously reported were also tested against Leishmania donovani, the causative agent for visceral leishmaniasis. Thirteen analogs displayed antimalarial activity with IC50 below 10 μM, while the antileishmanial activity of the newly reported analogs could not improve upon those previously reported. Compounds 1o and 1r were identified as the most promising antimalarial drug leads with IC50 below 3.0 μM for both CQ-sensitive and resistant P. falciparum strains with high selectivity index. Finally, a chemoinformatic in silico analysis was performed to evaluate physicochemical parameters, cytotoxicity risk and drug score. The validation of a bifunctional farnesyl/geranylgeranyl diphosphate synthase PfFPPS/GGPPS as the potential target of the antimalarial activity of selected analogs should be further investigated.

CuAAC ensembled 1,2,3-triazole linked nanogels for targeted drug delivery: a review

Copper(i) catalyzed alkyne azide cycloaddition (CuAAC), the quintessential example of 'click chemistry', provides an adaptable and adequate platform for the synthesis of nanogels for sustained drug release at targeted sites because of their better biocompatibility. The coupling of drugs, carried out via various synthetic routes including CuAAC, into long-chain polymeric forms like nanogels has exhibited considerable assurance in therapeutic advancements and intracellular drug delivery due to the progression of water solubility, evacuation of precocious drug release, and improved upthrust of the pharmacokinetics of the nanogels, thereby rendering them as better and efficient drug carriers. The inefficiency of drug transmission to the target areas due to the resistance of complex biological barriers in vivo is a major hurdle that impedes the therapeutic translation of nanogels. This review compiles the data of nanogels synthesized specifically via CuAAC 'click' methodology, as scaffolds for targeted drug delivery and their assimilation into nanomedicine. In addition, it elaborates the ability of CuAAC to graft specific moieties and conjugating biomolecules like proteins and growth factors, onto orthogonally functionalized polymer chains with various chemical groups resulting in nanogels that are not only more appealing but also more effective at delivering drugs, thereby enhancing their site-specific target approach and initiating selective therapies.

Synthesis and Pharmacological Evaluation of Novel Triazole-Pyrimidine Hybrids as Potential Neuroprotective and Anti-neuroinflammatory Agents

OBJECTIVE

Neuroprotection is a precise target for the treatment of neurodegenerative diseases, ischemic stroke, and traumatic brain injury. Pyrimidine and its derivatives have been proven to use antiviral, anticancer, antioxidant, and antimicrobial activity prompting us to study the neuroprotection and anti-inflammatory activity of the triazole-pyrimidine hybrid on human microglia and neuronal cell model.

METHODS

A series of novel triazole-pyrimidine-based compounds were designed, synthesized and characterized by mass spectra, 1HNMR, 13CNMR, and a single X-Ray diffraction analysis. Further, the neuroprotective, anti-neuroinflammatory activity was evaluated by cell viability assay (MTT), Elisa, qRT-PCR, western blotting, and molecular docking.

RESULTS

The molecular results revealed that triazole-pyrimidine hybrid compounds have promising neuroprotective and anti-inflammatory properties. Among the 14 synthesized compounds, ZA3-ZA5, ZB2-ZB6, and intermediate S5 showed significant anti-neuroinflammatory properties through inhibition of nitric oxide (NO) and tumor necrosis factor-α (TNF-α) production in LPS-stimulated human microglia cells. From 14 compounds, six (ZA2 to ZA6 and intermediate S5) exhibited promising neuroprotective activity by reduced expression of the endoplasmic reticulum (ER) chaperone, BIP, and apoptosis marker cleaved caspase-3 in human neuronal cells. Also, a molecular docking study showed that lead compounds have favorable interaction with active residues of ATF4 and NF-kB proteins.

CONCLUSION

The possible mechanism of action was observed through the inhibition of ER stress, apoptosis, and the NF-kB inflammatory pathway. Thus, our study strongly indicates that the novel scaffolds of triazole-pyrimidine-based compounds can potentially be developed as neuroprotective and anti-neuroinflammatory agents.

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

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

3-(1,2,3-Triazol-4-yl)-β-Carbolines and 3-(1H-Tetrazol-5-yl)-β-Carbolines: Synthesis and Evaluation as Anticancer Agents

Herein, the synthesis and anticancer activity evaluation of a series of novel β-carbolines is reported. The reactivity of nitrosoalkenes towards indole was explored for the synthesis of novel tryptophan analogs where the carboxylic acid was replaced by a triazole moiety. This tryptamine was used in the synthesis of 3-(1,2,3-triazol-4-yl)-β-carbolines via Pictet-Spengler condensation followed by an oxidative step. A library of compounds, including the novel 3-(1,2,3-triazol-4-yl)-β-carbolines as well as methyl β-carboline-3-carboxylate and 3-tetrazolyl-β-carboline derivatives, was evaluated for their antiproliferative activity against colorectal cancer cell lines. The 3-(1H-tetrazol-5-yl)-β-carbolines stood out as the most active compounds, with values of half-maximal inhibitory concentration (IC₅₀) ranging from 3.3 µM to 9.6 µM against colorectal adenocarcinoma HCT116 and HT29 cell lines. The results also revealed a mechanism of action independent of the p53 pathway. Further studies with the 3-tetrazolyl-β-carboline derivative, which showed high selectivity for cancer cells, revealed IC₅₀ values below 8 μM against pancreatic adenocarcinoma PANC-1, melanoma A375, hepatocarcinoma HEPG2, and breast adenocarcinoma MCF-7 cell lines. Collectively, this work discloses the 3-tetrazolyl-β-carboline derivative as a promising anticancer agent worthy of being further explored in future works.

Acid-Switchable Synthesis of Trifluoromethylated Triazoles and Isoxazoles via Reaction of CF3-Ynones with NaN3: DFT Study of the Reaction Mechanism

A detailed study of the reaction of CF₃-ynones with NaN₃ was performed. It was found that the reaction permits the selective synthesis of either 4-trifluoroacetyltriazoles or 5-CF₃-isoxazoles. The chemoselectivity of the reaction was switchable via acid catalysis. The reaction of CF₃-ynones with NaN₃ in EtOH produced high yields of 4-trifluoroacetyltriazoles. In contrast, the formation of 5-CF₃-isoxazoles was observed under catalysis by acids. This acid-switchable procedure can be performed at sub-gram scale. The possible reaction mechanism was supported by DFT calculations. The synthetic utility of the prepared 4-trifluoroacetyltriazoles was demonstrated.

Synthesis of Novel Ferrocene-Benzofuran Hybrids via Palladium- and Copper-Catalyzed Reactions

The combination of the ferrocene skeleton with pharmacophores often leads to molecules with interesting biological properties. Five ferrocene-benzofuran hybrids of different structures were synthesized by transition metal catalyzed reactions. The efficiency of both homogeneous and heterogeneous catalytic methods was tested. The products were characterized using 1H, 13C NMR and FTIR spectroscopy, HRMS and cyclic voltammetry. The structure of one of the new compounds was also proved with X-ray crystallography. The new hybrids showed moderate cytotoxicity on MCF-7 and MDA-MB-231 cell lines. It is remarkable that the less curable MDA-MB-231 cell line was more sensitive to treatment with three ferrocene derivatives.

CuAAC-Derived Selective Fluorescent Probe as a Recognition Agent for Pb(II) and Hg(II): DFT and Docking Studies

Copper(I)-catalyzed alkyne-azide cycloaddition (CuAAC) is a resourceful and stereospecific methodology that has considerably yielded promising 1,2,3-triazole-appended "click" scaffolds with the potential for selective metal ion recognition. Based on "click" methodology, this report presents a chemosensor probe (TCT) based on 4-tert-butylcatechol architecture, via the CuAAC pathway, as a selective and efficient sensor for Pb(II) and Hg(II) ions, categorized as the most toxic and alarming environmental contaminants among the heavy metal ions. The synthesized probe was successfully characterized by spectroscopy [IR and NMR (¹H and ¹³C)] and mass spectrometry. The chemosensing study performed in acetonitrile/water (4:1) solvent media, via UV-vis and fluorescence spectroscopy, established its selective sensitivity for Pb(II) and Hg(II) species among the list of explored metal ions with the limits of detection being 8.6 and 11 μM, respectively. Additionally, the ¹H NMR and IR spectra of the synthesized TCT-metal complex also confirmed the metal-ligand binding. Besides, the effect of time and temperature on the binding ability of TCT with Pb(II) and Hg(II) was also studied via UV-vis spectroscopy. Furthermore, density functional theory studies put forward the structural comprehension of the sensor by availing the hybrid density functional (B3LYP)/6311G++(d,p) basis set of theory which was subsequently utilized for investigating its anti-inflammatory potential by performing docking analysis with human leukotriene b4 protein.