Click Chemistry for Drug Development and Diverse Chemical–Biology Applications

Design, synthesis and biological evaluation of glucose metabolism inhibitors as anticancer agents

Compared to normal cells, tumour cells exhibit an upregulation of glucose transporters and an increased rate of glycolytic activity. In previous research, we successfully identified a promising hit compound BH10 through a rigorous screening process, which demonstrates a potent capacity for inhibiting cancer cell proliferation by targeting glucose metabolism. In the current study, we identify Kelch-like ECH-associated protein 1 (Keap1) as a potential protein target of BH10via avidin pull-down assays with biotinylated-BH10. Subsequently, we present a comprehensive analysis of a series of BH10 analogues characterized by the incorporation of a naphthoimidazole scaffold and the introduction of a triazole ring with diverse terminal functional groups. Notably, compound 4d has emerged as the most potent candidate, exhibiting better anti-cancer activities against HEC1A cancer cells with an IC50 of 2.60 μM, an extended biological half-life, and an improved pharmacokinetic profile (compared to BH10) in mice.

Nanoplasmonic biosensors for environmental sustainability and human health

Monitoring the health conditions of the environment and humans is essential for ensuring human well-being, promoting global health, and achieving sustainability. Innovative biosensors are crucial in accurately monitoring health conditions, uncovering the hidden connections between the environment and human well-being, and understanding how environmental factors trigger autoimmune diseases, neurodegenerative diseases, and infectious diseases. This review evaluates the use of nanoplasmonic biosensors that can monitor environmental health and human diseases according to target analytes of different sizes and scales, providing valuable insights for preventive medicine. We begin by explaining the fundamental principles and mechanisms of nanoplasmonic biosensors. We investigate the potential of nanoplasmonic techniques for detecting various biological molecules, extracellular vesicles (EVs), pathogens, and cells. We also explore the possibility of wearable nanoplasmonic biosensors to monitor the physiological network and healthy connectivity of humans, animals, plants, and organisms. This review will guide the design of next-generation nanoplasmonic biosensors to advance sustainable global healthcare for humans, the environment, and the planet.

Synthesis Principle and Practice with Radioactive Iodines and Astatine: Advances Made So Far

Radioactive iodines and astatine, possessing distinct exploitable nuclear properties, play indispensable roles in the realms of nuclear imaging and therapy. Their analogous chemical characteristics shape the design, preparation, and substrate range for tracers labeled with these radiohalogens through interconnected radiosynthetic chemistry. This perspective systematically explores the labeling methods by types of halogenating reagents─nucleophilic and electrophilic─underpinning the rational design of such compounds. It delves into the rapidly evolving synthetic strategies and reactions in radioiodination and radioastatination over the past decade, comparing their intrinsic relationships and highlighting variations. This comparative analysis illuminates potential radiosynthetic methods for exploration. Moreover, stability concerns related to compounds labeled with radioactive iodines and astatine are addressed, offering valuable insights for radiochemists and physicians alike.

Fluoromethylketone-Fragment Conjugates Designed as Covalent Modifiers of EcDsbA are Atypical Substrates

Disulfide bond protein A (DsbA) is an oxidoreductase enzyme that catalyzes the formation of disulfide bonds in Gram-negative bacteria. In Escherichia coli, DsbA (EcDsbA) is essential for bacterial virulence, thus inhibitors have the potential to act as antivirulence agents. A fragment-based screen was conducted against EcDsbA and herein we describe the development of a series of compounds based on a phenylthiophene hit identified from the screen. A novel thiol reactive and "clickable" ethynylfluoromethylketone was designed for reaction with azide-functionalized fragments to enable rapid and versatile attachment to a range of fragments. The resulting fluoromethylketone conjugates showed selectivity for reaction with the active site thiol of EcDsbA, however unexpectedly, turnover of the covalent adduct was observed. A mechanism for this turnover was investigated and proposed which may have wider ramifications for covalent reactions with dithiol-disulfide oxidoreducatases.

Smart Bioorthogonal Nanozymes: From Rational Design to Appropriate Bioapplications

Bioorthogonal chemistry has provided an elaborate arsenal to manipulate native biological processes in living systems. As the great advancement of nanotechnology in recent years, bioorthogonal nanozymes are innovated to tackle the challenges that emerged in practical biomedical applications. Bioorthogonal nanozymes are uniquely positioned owing to their advantages of high customizability and tunability, as well as good adaptability to biological systems, which bring exciting opportunities for biomedical applications. More intriguingly, the great advancement in nanotechnology offers an exciting opportunity for innovating bioorthogonal catalytic materials. In this comprehensive review, the significant progresses of bioorthogonal nanozymes are discussed with both spatiotemporal controllability and high performance in living systems, and highlight their design principles and recent rapid applications. The remaining challenges and future perspectives are then outlined along this thriving field. It is expected that this review will inspire and promote the design of novel bioorthogonal nanozymes, and facilitate their clinical translation.

Metal-free nitro/azido cyclization of 1-acryloyl-2-cyanoindoles to access NO2/N3-featuring pyrrolo[1,2-a] indolediones

An H2O/heating or [bis(trifluoroacetoxy)iodo]benzene promoted radical cascade nitro/azide cyclization of 1-acryloyl-2-cyanoindoles with tert-butyl nitrite/azidotrimethylsilane was accomplished, which offered a series of nitro/azide-featuring pyrrolo[1,2-a]indolediones in good yields. Meanwhile, some scale-up experiments and substituent transformations were performed to test the synthetic value. In addition, the corresponding radical intermediates were successfully detected by HRMS to support the possible reaction pathway.

Hypervalent Iodine Amino Acid Building Blocks for Bioorthogonal Peptide Macrocyclization

Ethynylbenziodoxol(on)es (EB(X)xs) reagents have emerged as useful reagents for peptide/protein modification due to their versatile reactivity and high selectivity. Herein, we report the successful introduction of ethynylbenziodoxoles (EBxs) on different amino acid building blocks (Lys/Orn/Dap), and show their compatibility with both solid phase peptide synthesis (SPPS) and solution phase peptide synthesis (SPS). The selective incorporation of the EBx core into peptide sequences enable efficient macrocyclizations under mild conditions for the synthesis of topologically unique cyclic and bicyclic peptides.

Ligand-Based Pharmacophoric Design and Anti-inflammatory Evaluation of Triazole Linked Semisynthetic Labdane Conjugates

This study employed a ligand-based pharmacophoric approach to design and synthesize 33 novel semisynthetic labdane-appended triazolyl isatins to discover potential anti-inflammatory agents. The anti-inflammatory efficacy of the derivatives was evaluated by their ability to inhibit the production of NO, TNF-α, and IL-6, in lipopolysaccharide-induced RAW264.7 macrophages. The initial screening revealed that compound 7a ((1-(2-(2,3-dioxoindolin-1-yl)ethyl)-1H-1,2,3-triazol-4-yl)methyl (E)-3-formyl-5-((1S,4aS,8aS)-5,5,8a-trimethyl-2-methylenedecahydronaphthalen-1-yl)pent-3-enoate) exhibited an anti-inflammatory effect (NO inhibition, IC50 = 3.13 μΜ), surpassing both the positive control indomethacin (NO inhibition, IC50 = 7.31 μΜ) and the parent compound labdane dialdehyde. Notably, 7a reduced the levels of pro-inflammatory cytokines TNF-α and IL-6 while increasing the levels of the anti-inflammatory cytokine IL-10. Mechanistic studies revealed that 7a downregulated the expression of COX-2 and iNOS by inhibiting the NF-κB signaling pathway. In silico molecular modeling studies on NF-κB proteins support these findings, suggesting that 7a is a promising candidate for developing into a potent anti-inflammatory clinical agent.

Practice of green chemistry strategies in synthetic organic chemistry: a glimpse of our sincere efforts in green chemistry research

This feature article summarises our recent contributions (2019-2023) in designing and developing a handful of promising organic transformations for accessing several diversely functionalised biologically relevant organic scaffolds, following the green chemistry principles, particularly focusing on the application of low-energy visible light, electrochemistry, ball-milling, ultrasound, and catalyst- and additive-free synthetic strategies.

Halogen-Atom Transfer Enabled Catalytic Enantioselective Coupling to Chiral Trifluoromethylated Alkynes via Dual Nickel and Photocatalysis

With halogen-atom transfer as an effective tool, a novel catalytic enantioselective protocol to generate chiral trifluoromethylated alkynes has been established by a cooperative photoredox and nickel catalysis system, providing a straightforward and modular route to access this type of product in good yields and enantioselectivities. The halogen-atom transfer process is essential for the reaction and this novel strategy offers another promising way to utilize alkyl halides with highly negative reduction potentials. It firstly expands nickel-catalyzed asymmetric reductive cross-couplings of organohalides from the traditional single-electron transfer to halogen-atom transfer.

Fragment-Based Design and Synthesis of Symmetrical bis-Peptidotriazoles Using Alkylidene bis-Amide Formations and Subsequent Triazole Ligation with β-Acetamido Carbonyl Scaffolds

A novel and efficient fragment-based assembly of symmetrical bis-peptidotraizoles has been developed based on double Sharpless azide-alkyne click chemistry. A new Cu(II) catalyzed protocol with a wide substrate scope was developed for accessing the symmetrical alkylidene bis-azidoamide fragment that yields the products in very good yields at room temperature without employing column purifications. The propargylated β-acetamido ketone fragment was accessed using another Cu(II) catalyzed room temperature MCR protocol. A fast double-click reaction (2 h) of symmetrical alkylidene bis-azidoamides with propargylated β-acetamido ketone fragments leads to the formation of unusual symmetrical bis-peptidotriazoles.

Small molecule- and peptide-drug conjugates addressing integrins: A story of targeted cancer treatment

Targeted cancer treatment should avoid side effects and damage to healthy cells commonly encountered during traditional chemotherapy. By combining small molecule or peptidic ligands as homing devices with cytotoxic drugs connected by a cleavable or non-cleavable linker in peptide-drug conjugates (PDCs) or small molecule-drug conjugates (SMDCs), cancer cells and tumours can be selectively targeted. The development of highly affine, selective peptides and small molecules in recent years has allowed PDCs and SMDCs to increasingly compete with antibody-drug conjugates (ADCs). Integrins represent an excellent target for conjugates because they are overexpressed by most cancer cells and because of the broad knowledge about native binding partners as well as the multitude of small-molecule and peptidic ligands that have been developed over the last 30 years. In particular, integrin αVβ3 has been addressed using a variety of different PDCs and SMDCs over the last two decades, following various strategies. This review summarises and describes integrin-addressing PDCs and SMDCs while highlighting points of great interest.

Enabling Modular Click Chemistry Library through Sequential Ligations of Carboxylic Acids and Amines

High-throughput synthesis and screening of chemical libraries play pivotal roles in drug discovery. Click chemistry has emerged as a powerful strategy for constructing highly modular chemical libraries. However, the development of new click reactions and unlocking new clickable building blocks remain exceedingly challenging. Herein, we describe a double-click strategy that enables the sequential ligations of widely available carboxylic acids and amines with fluorosulfuryl isocyanate (FSO2NCO) via a modular amidation/SuFEx (sulfur-fluoride exchange) process. This method provides facile access to chemical libraries of N-fluorosulfonyl amides (RCONHSO2F) and N-acylsulfamides (RCONHSO2NR'R'') in near-quantitative yields under simple and practical conditions. The robustness and efficiency of this double click strategy is showcased by the facile construction of chemical libraries in 96-well microtiter plates from a large number of carboxylic acids and amines. Preliminary biological activity screening reveals that some compounds exhibit high antimicrobial activities against Gram-positive bacterium S. aureus and drug-resistant MRSA (MIC up to 6.25 μg ⋅ mL-1). These results provide compelling evidence for the potential application of modular click chemistry library as an enabling technology in high-throughput medicinal chemistry.

DOTA-Based Plectin-1 Targeted Contrast Agent Enables Detection of Pancreatic Cancer in Human Tissue

Pancreatic ductal adenocarcinoma (PDAC) is a highly aggressive and lethal malignancy with extremely poor patient survival rates. A key reason for the poor prognosis is the lack of effective diagnostic tools to detect the disease at curable, premetastatic stages. Tumor surgical resection is PDAC's first-line treatment, however distinguishing between cancerous and healthy tissue with current imaging tools remains a challenge. In this work, we report a DOTA-based fluorescent probe targeting plectin-1 for imaging PDAC with high specificity. To enable heterogeneous functionalization of the DOTA-core with multiple targeting peptide units and the fluorophore, a novel, fully clickable synthetic route that proceeds in one pot was developed. Extensive validation of the probe set the stage for PDAC detection in mice and human tissue. Altogether, these findings may pave the way for improved clinical understanding and early detection of PDAC progression as well as more accurate resection criteria.

Copper Dispersed Covalent Organic Framework for Azide-Alkyne Cycloaddition and Fast Synthesis of Rufinamide in Water

A crystalline porous bipyridine-based Bpy-COF with a high BET surface area (1864 m2 g-1) and uniform mesopore (4.0 nm) is successfully synthesized from 1,3,5-tris-(4'-formyl-biphenyl-4-yl)triazine and 5,5'-diamino-2,2'-bipyridine via a solvothermal method. After Cu(I)-loading, the resultant Cu(I)-Bpy-COF remained the ordered porous structure with evenly distributed Cu(I) ions at a single-atom level. Using Cu(I)-Bpy-COF as a heterogeneous catalyst, high conversions for cycloaddition reactions are achieved within a short time (40 min) at 25 °C in water medium. Moreover, Cu(I)-Bpy-COF proves to be applicable for aromatic and aliphatic azides and alkynes bearing various substituents such as ester, hydroxyl, amido, pyridyl, thienyl, bulky triphenylamine, fluorine, and trifluoromethyl groups. The high conversions remain almost constant after five cycles. Additionally, the antiepileptic drug (rufinamide) is successfully prepared by a simple one-step reaction using Cu(I)-Bpy-COF, proving its practical feasibility for pharmaceutical synthesis.

Design, Construction, and Validation of a Yeast-Displayed Chemically Expanded Antibody Library

In vitro display technologies, exemplified by phage and yeast display, have emerged as powerful platforms for antibody discovery and engineering. However, the identification of antibodies that disrupt target functions beyond binding remains a challenge. In particular, there are very few strategies that support identification and engineering of either protein-based irreversible binders or inhibitory enzyme binders. Expanding the range of chemistries in antibody libraries has the potential to lead to efficient discovery of function-disrupting antibodies. In this work, we describe a yeast display-based platform for the discovery of chemically diversified antibodies. We constructed a billion-member antibody library that supports the presentation of a range of chemistries within antibody variable domains via noncanonical amino acid (ncAA) incorporation and subsequent bioorthogonal click chemistry conjugations. Use of a polyspecific orthogonal translation system enables introduction of chemical groups with various properties, including photo-reactive, proximity-reactive, and click chemistry-enabled functional groups for library screening. We established conjugation conditions that facilitate modification of the full library, demonstrating the feasibility of sorting the full billion-member library in "protein-small molecule hybrid" format in future work. Here, we conducted initial library screens after introducing O-(2-bromoethyl)tyrosine (OBeY), a weakly electrophilic ncAA capable of undergoing proximity-induced crosslinking to a target. Enrichments against donkey IgG and protein tyrosine phosphatase 1B (PTP1B) each led to the identification of several OBeY-substituted clones that bind to the targets of interest. Flow cytometry analysis on the yeast surface confirmed higher retention of binding for OBeY-substituted clones compared to clones substituted with ncAAs lacking electrophilic side chains after denaturation. However, subsequent crosslinking experiments in solution with ncAA-substituted clones yielded inconclusive results, suggesting that weakly reactive OBeY side chain is not sufficient to drive robust crosslinking in the clones isolated here. Nonetheless, this work establishes a multi-modal, chemically expanded antibody library and demonstrates the feasibility of conducting discovery campaigns in chemically expanded format. This versatile platform offers new opportunities for identifying and characterizing antibodies with properties beyond what is accessible with the canonical amino acids, potentially enabling discovery of new classes of reagents, diagnostics, and even therapeutic leads.

Recent Advances in the Domino Annulation Reaction of Quinone Imines

Quinone imines are important derivatives of quinones with a wide range of applications in organic synthesis and the pharmaceutical industry. The attack of nucleophilic reagents on quinone imines tends to lead to aromatization of the quinone skeleton, resulting in both the high reactivity and the unique reactivity of quinone imines. The extreme value of quinone imines in the construction of nitrogen- or oxygen-containing heterocycles has attracted widespread attention, and remarkable advances have been reported recently. This review provides an overview of the application of quinone imines in the synthesis of cyclic compounds via the domino annulation reaction.

Organic Dye Photocatalyzed Synthesis of Functionalized Lactones and Lactams via a Cyclization-Alkynylation Cascade

An organic dye photocatalyzed lactonization-alkynylation of easily accessible homoallylic cesium oxalates using ethynylbenziodoxolone (EBX) reagents has been developed. The reaction gave access to valuable functionalized lactones and lactams in up to 88% yield via the formation of two new C-C bonds. The transformation was carried out on primary, secondary, and tertiary homoallylic alcohols and primary homoallylic amines and could be applied to the synthesis of spirocyclic compounds as well as fused and bridged bicyclic lactones.

Ring-Opening Coupling of Cyclopropanol with 1,2,3-Triazole for the Synthesis of Fused Triazoles

A radical ring-opening arylation of cyclopropanol with 1,2,3-triazole has been achieved. This synthetic protocol provides straightforward access to a wide range of structurally diverse and chiral 4,5,6,7-tetrahydro[1,2,3]triazolo[1,5-a]pyridines with high efficiency from readily available chiral cyclopropanols.

Halo-1,2,3-triazoles: Valuable Compounds to Access Biologically Relevant Molecules

1,2,3-triazole is an important building block in organic chemistry. It is now well known as a bioisostere for various functions, such as the amide or the ester bond, positioning it as a key pharmacophore in medicinal chemistry and it has found applications in various fields including life sciences. Attention was first focused on the synthesis of 1,4-disubstituted 1,2,3-triazole molecules however 1,4,5-trisubstituted 1,2,3-triazoles have now emerged as valuable molecules due to the possibility to expand the structural modularity. In the last decade, methods mainly derived from the copper(I)-catalyzed azide-alkyne cycloaddition (CuAAC) reaction have been developed to access halo-triazole compounds and have been applied to nucleosides, carbohydrates, peptides and proteins. In addition, late-stage modification of halo-triazole derivatives by metal-mediated cross-coupling or halo-exchange reactions offer the possibility to access highly functionalized molecules that can be used as tools for chemical biology. This review summarizes the synthesis, the functionalization, and the applications of 1,4,5-trisubstituted halo-1,2,3-triazoles in biologically relevant molecules.

Synthesis and Study of Steering of Azido-tetrazole Behavior in Tetrazolo[1,5-c]pyrimidin-5-amine-Based Energetic Materials

Tetrazoles and their derivatives are essential for compound synthesis due to their versatility, effectiveness, stability in air, and cost-efficiency. This has stimulated interest in developing techniques for their production. In this work, four compounds, tetrazolo[1,5-c]pyrimidin-5-amine (1), N-(4-azidopyrimidin-2-yl)nitramide (2), tetrazolo[1,5-c]pyrimidin-5(6H)-one (3), and tetrazolo[1,5-a]pyrimidin-5-amine (4), were obtained from commercially available reagents and straightforward synthetic methodologies. These new compounds were characterized by infrared (IR), 13C, and 1H NMR spectroscopy, differential scanning calorimetry (DSC), and single-crystal X-ray diffraction. The solvent, temperature, and electron-donating group (EDG) factors that were responsible for the steering of azido-tetrazole equilibrium in all compounds were also studied. In addition, the detonation performance of the target compounds was calculated by using heats of formation (HOFs) and crystal densities. Hirshfeld surface analysis was used to examine the intermolecular interactions of the four synthesized compounds. The results show that the excellent properties of 1-4 are triggered by ionic bonds, hydrogen bonds, and π-π stacking interactions, indicating that these compounds have the potential to be used in the development of high-performance energetic materials. Additionally, DFT analysis is in support of experimental results, which proved the effect of different factors that can influence the azido-tetrazole equilibrium in the synthesized pyrimidine derivatives in the solution.

Asymmetric Three-Component Radical Alkene Carboazidation by Direct Activation of Aliphatic C-H Bonds

Azide compounds are widely present in natural products and drug molecules, and their easy-to-transform characteristics make them widely used in the field of organic synthesis. The merging of transition-metal catalysis with radical chemistry offers a versatile platform for radical carboazidation of alkenes, allowing the rapid assembly of highly functionalized organic azides. However, the direct use of readily available hydrocarbon feedstocks as sp3-hybridized carbon radical precursors to participate in catalytic enantioselective carboazidation of alkenes remains a significant challenge that has yet to be addressed. Herein, we describe an iron-catalyzed asymmetric three-component radical carboazidation of electron-deficient alkenes by direct activation of aliphatic C-H bonds. This approach involves intermolecular hydrogen atom transfer between a hydrocarbon and an alkoxy/aryl carboxyl radical, leading to the formation of a carbon-centered radical. The resulting radical then reacts with electron-deficient alkenes to generate a new radical species that undergoes chiral iron-complex-mediated C-N3 bond coupling. An array of valuable chiral azides bearing a quaternary stereocenter were directly accessed from widely available chemical feedstocks, and their synthetic potential is further demonstrated through more facile transformations to give other valuable enantioenriched building blocks.

Arylazopyrazoles for Conjugation by CuAAC Click Chemistry

Molecular photoswitches are increasingly being implemented in bioactive compounds and responsive materials. For this purpose, photoswitches must be coupled to a wide variety of substrates and scaffolds. We present a library of "clickable" arylazopyrazoles (AAPs), which can be conjugated by Cu-catalyzed alkyne azide cycloaddition (CuAAC). All synthesized AAP alkynes show good photostationary states (at least 88%) and long half-life times of the Z-isomer (18 to 108 h). The AAP azides decompose upon exposure to ultraviolet (UV) irradiation, but after CuAAC, all AAPs exhibit good photophysical properties.

Modular preparation of biphenyl triazoles via click chemistry as non-competitive hyaluronidase inhibitors

Hyaluronidase is a promising target in drug discovery, given its overexpression in a range of physiological and pathological processes, including tumor migration, skin aging, sagging, and wrinkling, as well as inflammation and bacterial infections. In this study, to identify novel hyaluronidase inhibitors, we applied click chemistry for the modular synthesis of 370 triazoles in 96-well plates, starting with biphenyl azide. Utilizing an optimized turbidimetric screening assay in microplates, we identified Fmoc-containing triazoles 5 and 6, as well as quinoline-containing triazoles 15 and 16, as highly effective hyaluronidase inhibitors. Subsequent research indicated that these triazoles potentially interact with a novel binding site of hyaluronidase. Notably, these inhibitors displayed minimal cytotoxicity and showed promising anti-inflammatory effects in LPS-stimulated macrophages. Remarkably, compound 6 significantly reduced NO release by 74 % at a concentration of 20 μM.

Exploring the potential of the vitamin B12 derivative azidocobalamin to undergo Huisgen 1,3-dipolar azide-alkyne cycloaddition reactions

There is considerable interest in using the metalloprotein cofactor vitamin B12 as a vehicle to deliver drugs and diagnostic agents into mammalian or bacterial cells by exploiting the B12-specific active uptake pathways. Conjugation of the cargo via the β-axial site or the 5'-OH of the ribose of the nucleotide are the most desirable sites, to maximise intracellular uptake. Herein we show the potential of conjugation at the beta-azido ligand of the vitamin B12 derivative azidocobalamin via a click-type azide-alkyne 1,3-dipolar cycloaddition (Huisgen cycloaddition) reaction. Reacting azidocobalamin with dimethyl acetylenedicarboxylate at 40 °C results in essentially stoichiometric conversion of azidocobalamin to the corresponding triazolato complex. The stability of the complex as a function of pH and in the presence of cyanide were investigated. The complex is stable in pD 7.0 phosphate buffer for 24 h. The rate of beta-axial ligand substitution was found to be one order of magnitude slower for the triazolatocobalamin complex compared with azidocobalamin.

Visualization of Modified Bisarylbutadiyne-Tagged Small Molecules in Live-Cell Nuclei by Stimulated Raman Scattering Microscopy

Visualizing the distribution of small-molecule drugs in living cells is an important strategy for developing specific, effective, and minimally toxic drugs. As an alternative to fluorescence imaging using bulky fluorophores or cell fixation, stimulated Raman scattering (SRS) imaging combined with bisarylbutadiyne (BADY) tagging enables the observation of small molecules closer to their native intracellular state. However, there is evidence that the physicochemical properties of BADY-tagged analogues of small-molecule drugs differ significantly from those of their parent drugs, potentially affecting their intracellular distribution. Herein, we developed a modified BADY to reduce deviations in physicochemical properties (in particular, lipophilicity and membrane permeability) between tagged and parent drugs, while maintaining high Raman activity in live-cell SRS imaging. We highlight the practical application of this approach by revealing the nuclear distribution of a modified BADY-tagged analogue of JQ1, a bromodomain and extra-terminal motif inhibitor with applications in targeted cancer therapy, in living HeLa cells. The modified BADY, methoxypyridazyl pyrimidyl butadiyne (MPDY), revealed intranuclear JQ1, while BADY-tagged JQ1 did not show a clear nuclear signal. We anticipate that the present approach combining MPDY tagging with live-cell SRS imaging provides important insight into the behavior of intracellular drugs and represents a promising avenue for improving drug development.

Poly-pharmacology of existing drugs: How to crack the code?

Drug development in oncology is highly challenging, with less than 5% success rate in clinical trials. This alarming figure points out the need to study in more details the multiple biological effects of drugs in specific contexts. Indeed, the comprehensive assessment of drug poly-pharmacology can provide insights into their therapeutic and adverse effects, to optimize their utilization and maximize the success rate of clinical trials. Recent technological advances have made possible in-depth investigation of drug poly-pharmacology. This review first highlights high-throughput methodologies that have been used to unveil new mechanisms of action of existing drugs. Then, we discuss how emerging chemo-proteomics strategies allow effectively dissecting the poly-pharmacology of drugs in an unsupervised manner.

Protein click chemistry and its potential for medical applications

A revolution in chemical biology occurred with the introduction of click chemistry. Click chemistry plays an important role in protein chemistry modifications, providing specific, sensitive, rapid, and easy-to-handle methods. Under physiological conditions, click chemistry often overlaps with bioorthogonal chemistry, defined as reactions that occur rapidly and selectively without interfering with biological processes. Click chemistry is used for the posttranslational modification of proteins based on covalent bond formations. With the contribution of click reactions, selective modification of proteins would be developed, representing an alternative to other technologies in preparing new proteins or enzymes for studying specific protein functions in different biological processes. Click-modified proteins have potential in diverse applications such as imaging, labeling, sensing, drug design, and enzyme technology. Due to the promising role of proteins in disease diagnosis and therapy, this review aims to highlight the growing applications of click strategies in protein chemistry over the last two decades, with a special emphasis on medicinal applications.

Furan Dearomatization: A Route to Diverse Fluoroalkyl/Aryl Triazoles

The 5-fluoroalkyl-1,2,3-triazoles, serving as a pivotal element in medicinal chemistry, hold substantial research significance. In this work, we developed a furan dearomatization reaction for the synthesis of various 5-fluoroalkyl-1,2,3-triazoles, which contains -CF3, -CF2H, -CF2CF3, -CF2CF2CF3, -CF2CO2Et, and -C6F5. This methodology relies on the intermolecular [3 + 2] cycloaddition/furan ring-opening triggered by α-fluoroalkyl furfuryl cation with azides to stereoselectively synthesize a series of (E)-fluoroalkyl enone triazoles. The reaction proceeds without metal participation, exhibits excellent substrate tolerance, and has excellent synthetic utility.

Expedient Azide-Alkyne Huisgen Cycloaddition Catalyzed by a Combination of VOSO4 with Cu(0) in Aqueous Media

A series of vanadium(III), vanadyl(IV/V) species, inorganic metal oxides, and transition-metal oxides was examined as cocatalysts with Cu(0) powder for copper(I)-catalyzed azide-alkyne cycloaddition. Among them, vanadyl(IV) species bearing acetylacetonate, acetate, and sulfate, vanadyl(V) isopropoxide, and vanadate were suitable for the click reactions of per-acetyl and per-benzyl β-azido glycosides with three different terminal alkynes in CH3CN. Water-soluble vanadyl(IV) sulfate was further selected for efficient click reactions for unprotected β-glycosyl azides and even compatible with a thiol-containing substrate in aqueous media at ambient temperature.

Dipeptide-catalysed Michael reaction under physiological conditions: Examination of potential bioorthogonality

Reactions for drug synthesis under cell-like conditions or even inside living cells can potentially be used e.g., to minimize toxic side effects, to maximize bioactive compound efficacy and/or to address drug delivery problems. Those reactions should be bioorthogonal to enable the generation of drug-like compounds with sufficiently good yields. In the known bioorthogonal Michael reactions, using thiols and phosphines as nucleophiles (e.g., in CS and CP bond formation reactions) is very common. No bioorthogonal Michael addition with a carbon nucleophile is known yet. Therefore, the development of such a reaction might be interesting for future drug discovery research. In this work, the metal-free Michael addition between cyclohexanone and various trans-β-nitrostyrenes (CC bond formation reaction), catalysed by a dipeptide salt H-Pro-Phe-O-Na+, was investigated for the first time in the presence of glutathione (GSH) and in phosphate-buffered saline (PBS). We demonstrated that with electron-withdrawing substituents on the aromatic ring and in β-position of the trans-β-nitrostyrene yields up to 64% can be obtained under physiological conditions, indicating a potential bioorthogonality of the studied Michael reaction. In addition, the selected Michael products demonstrated activity against human ovarian cancer cells A2780. This study opens up a new vista for forming bioactive compounds via CC bond formation Michael reactions under physiological (cell-like) conditions.

Novel molecular hybrids of EGCG and quinoxaline: Potent multi-targeting antidiabetic agents that inhibit α-glucosidase, α-amylase, and oxidative stress

Diabetes mellitus is a multifactorial disease and its effective therapy often demands several drugs with different modes of action. Herein, we report a rational design and synthesis of multi-targeting novel molecular hybrids comprised of EGCG and quinoxaline derivatives that can effectively inhibit α-glucosidase, α-amylase as well as control oxidative stress by scavenging ROS. The hybrids showed superior inhibition of α-glucosidase along with similar α-amylase inhibition as compared to standard drug, acarbose. Most potent compound, 15c showed an IC50 of 0.50 μM (IC50 of acarbose 190 μM) against α-glucosidase. Kinetics studies with 15c revealed a competitive inhibition against α-glucosidase. Binding affinity of 15c (-9.5 kcal/mol) towards α-glucosidase was significantly higher than acarbose (-7.7 kcal/mol). 15c exhibited remarkably high antioxidant activity (IC50 = 18.84 μM), much better than vitamin C (IC50 = 33.04 μM). Of note, acarbose shows no antioxidant activity. Furthermore, α-amylase activity was effectively inhibited by 15c with an IC50 value of 16.35 μM. No cytotoxicity was observed for 15c (up to 40 μM) in MCF-7 cells. Taken together, we report a series of multi-targeting molecular hybrids capable of inhibiting carbohydrate hydrolysing enzymes as well as reducing oxidative stress, thus representing an advancement towards effective and novel therapeutic approaches for diabetes.

Design, synthesis, and docking study of saccharin N-triazolyl glycoconjugates

To achieve better-repurposed motifs, saccharin has been merged with biocompatible sugar molecules via a 1,2,3-triazole linker, and ten novel 1,2,3-triazole-appended saccharin glycoconjugates were developed in good yield by utilizing modular CuAAC click as regioselective triazole forming tool. The docking study indicated that the resulting hybrid molecules have an overall substantial interaction with the CAXII macromolecule. Moreover, the galactose triazolyl saccharin analogue 3h has a binding energy of -8.5 kcal/mol with 5 H-bonds, and xylosyl 1,2,3-triazolyl saccharin analogue 3d has a binding energy of -8.2 kcal/mol with 6 H-bond interactions and have exhibited the highest binding interaction with the macromolecule system.

Identification of clickable HIV-1 capsid-targeting probes for viral replication inhibition

Of the targets for HIV-1 therapeutics, the capsid core is a relatively unexploited but alluring drug target due to its indispensable roles throughout virus replication. Because of this, we aimed to identify "clickable" covalent modifiers of the HIV-1 capsid protein (CA) for future functionalization. We screened a library of fluorosulfate compounds that can undergo sulfur(VI) fluoride exchange (SuFEx) reactions, and five compounds were identified as hits. These molecules were further characterized for antiviral effects. Several compounds impacted in vitro capsid assembly. One compound, BBS-103, covalently bound CA via a SuFEx reaction to Tyr145 and had antiviral activity in cell-based assays by perturbing virus production, but not uncoating. The covalent binding of compounds that target the HIV-1 capsid could aid in the future design of antiretroviral drugs or chemical probes that will help study aspects of HIV-1 replication.

Synthesis of Cu3Fe4V6O24 Nanoparticles to Produce 1,2,3-Triazoles by Azide-Alkyne Cycloaddition Reactions

This paper presents the fabrication of novel Cu3Fe4V6O24 nanoparticles (NPs) via a facile sol-gel method as efficient nanocatalysts (NCs) to produce azide-alkyne 1,3-dipolar cycloaddition compounds. The effect of the calcination time on the formation of NPs was investigated. The as-prepared NPs were characterized using X-ray diffraction (XRD), Fourier transform infrared (FTIR), scanning electron microscopy (SEM), electron-dispersive X-ray spectroscopy (EDX), transmission electron microscopy (TEM), vibrating sample magnetometer (VSM), and Brunauer-Emmett-Teller (BET) analyses. Cu3Fe4V6O24 NCs were applied to azide-alkyne 1,3-dipolar cycloaddition reactions. The effect of the catalyst loading, temperature, and time of reaction was optimized to improve the efficiency of the NC function by the response surface methodology-central composite design (RSM-CCD) method. In optimal conditions, the yield of the reaction was 96%. In addition, the effect of different solvents on the yield of the reaction was investigated. Moreover, Cu3Fe4V6O24 NPs efficiently catalyze different 1,2,3-triazoles in excellent yields.

Synthesis of Self Permeable Antisense PMO Using C5-Guanidino-Functionalized Pyrimidines at the 5'-End Enables Sox2 Downregulation in Triple Negative Breast Cancer Cells

Delivery of macromolecular drugs inside cells has been a huge challenge in the field of oligonucleotide therapeutics for the past few decades. Earliest natural inspirations included the arginine rich stretch of cell permeable HIV-TAT peptide, which led to the design of several molecular transporters with varying numbers of rigid or flexible guanidinium units with different tethering groups. These transporters have been shown to efficiently deliver phosphorodiamidate morpholino oligonucleotides, which have a neutral backbone and cannot form lipoplexes. In this report, PMO based delivery agents having 3 or 4 guanidinium groups at the C5 position of the nucleobases of cytosine and uracil have been explored, which can be assimilated within the desired stretch of the antisense oligonucleotide. Guanidinium units have been connected by varying the flexibility with either a saturated (propyl) or an unsaturated (propargyl) spacer, which showed different serum dependency along with varied cytoplasmic distribution. The effect of cholesterol conjugation in the delivery agent as well as at the 5'-end of full length PMO in cellular delivery has also been studied. Finally, the efficacy of the delivery has been studied by the PMO mediated downregulation of the stemness marker Sox2 in the triple-negative breast cancer cell line MDA-MB 231. These results have validated the use of this class of delivery agents, which permit at a stretch PMO synthesis where the modified bases can also participate in Watson-Crick-Franklin base pairing for enhanced mRNA binding and protein downregulation and could solve the delivery problem of PMO.

Biochemical and computational inhibition of α-glucosidase by novel metronidazole-linked 1H-1,2,3-triazole and carboxylate moieties: kinetics and dynamic investigations

In the current study, metronidazole derivatives containing 1H-1,2,3-triazole and carboxylate moieties were evaluated in vitro and by computational methods for their anti-diabetic potential to insight into their medicinal use for the management of type II diabetes mellitus. Interestingly all 14 compounds displayed high to significant inhibitory capability against the key carbohydrate's digestive enzyme α-glucosidase with IC50 values in range of 9.73-56.39 μM, as compared to marketed drug acarbose (IC50 = 873.34 ± 1.67 μM). Compounds 5i and 7c exhibited the highest inhibition, therefore, these two compounds were further evaluated for their mechanistic studies to explore its type of inhibition. Compounds 5i and 7c both displayed a concentration-dependent (competitive type of inhibition) with Ki values 7.14 ± 0.01, 6.15 ± 0.02 μM, respectively, which conclude their favourable interactions with the active site residues of the α-glucosidase. Interestingly all compounds are non-cytotoxic against BJ cell line. To further validate our findings, in-silico approaches like molecular docking, and molecular dynamic simulations were applied to investigate the mode of bindings of compounds with the enzyme and identifies their inhibition mechanism, which strongly complements our experimental findings.Communicated by Ramaswamy H. Sarma.

Constructing triazole-modified quinazoline derivatives as selective c-MYC G-quadruplex ligands and potent anticancer agents through click chemistry

c-MYC is a hallmark of various cancers, playing a critical role in promoting tumorigenesis. The formation of G-quadruplex (G4) in the c-MYC promoter region significantly suppresses its expression. Therefore, developing small-molecule ligands to stabilize c-MYC G4 formation and subsequentially suppress c-MYC expression is an attractive topic for c-MYC-driven cancer therapy. However, achieving selective ligands for c-MYC G4 poses challenges. In this study, we developed a series of triazole-modified quinazoline (TMQ) derivatives as potential c-MYC G4 ligands and c-MYC transcription inhibitors from 4-anilinoquinazoline lead 7a using click chemistry. Importantly, the c-MYC G4 stabilizing ability and antiproliferation activity were well correlated among these new derivatives, particularly in the c-MYC highly expressed colorectal cancer cell line HCT116. Among them, compound A6 exhibited good selectivity in stabilizing c-MYC G4 and in suppressing c-MYC transcription better than 7a. This compound induced G4 formation, selectively inhibited G4-related c-MYC transcription and suppressed the progression of HCT116 cells. These findings identify a new c-MYC transcription inhibitor and provide new insights for optimizing c-MYC G4-targeting ligands.

Copper-Catalyzed Selective Three-Component 1,2-Phosphonoazidation of 1,3-Dienes

We report a copper-catalyzed selective 1,2-phosphonoazidation of conjugated dienes. This three-component reaction is achieved by using readily available P(O)-H compounds and bench-stable NaN3. Salient features of this strategy include its mild reaction conditions, broad functional group tolerance, and high chemoselectivity and regioselectivity. Moreover, the compatibility with the late-stage functionalization of drug molecules, the potential for scalable production, and the feasibility of further modifications of the products underscore the practical utility of this protocol in synthetic applications.

Oxidative cascade cyclization of N-arylacrylamides with TMSN3

An azido-radical-triggered cyclization of N-(o-cyanobiaryl)acrylamides with TMSN3via a C(sp3)-N/C(sp2)-C(sp3)/C(sp2)-N bond formation cascade is described. This reaction features mild conditions and high bond-forming efficiency, making it an efficient method for the construction of azide-substituted pyridophenanthridines.

Recent drug design strategies and identification of key heterocyclic scaffolds for promising anticancer targets

Cancer, a noncommunicable disease, is the leading cause of mortality worldwide and is anticipated to rise by 75% in the next two decades, reaching approximately 25 million cases. Traditional cancer treatments, such as radiotherapy and surgery, have shown limited success in reducing cancer incidence. As a result, the focus of cancer chemotherapy has switched to the development of novel small molecule antitumor agents as an alternate strategy for combating and managing cancer rates. Heterocyclic compounds are such agents that bind to specific residues in target proteins, inhibiting their function and potentially providing cancer treatment. This review focuses on privileged heterocyclic pharmacophores with potent activity against carbonic anhydrases and kinases, which are important anticancer targets. Evaluation of ongoing pre-clinical and clinical research of heterocyclic compounds with potential therapeutic value against a variety of malignancies as well as the provision of a concise summary of the role of heterocyclic scaffolds in various chemotherapy protocols have also been discussed. The main objective of the article is to highlight key heterocyclic scaffolds involved in recent anticancer drug design that demands further attention from the drug development community to find more effective and safer targeted small-molecule anticancer agents.

MOFs Modulate Copper Trafficking in Tumor Cells for Bioorthogonal Therapy

In situ drug synthesis using the copper-catalyzed azide-alkyne cycloaddition (CuAAC) reaction has attracted considerable attention in tumor therapy because of its satisfactory effectiveness and reduced side-effects. However, the exogenous addition of copper catalysts can cause cytotoxicity and has hampered biomedical applications in vivo. Here, we design and synthesize a metal-organic framework (MOF) to mimic copper chaperone, which can selectively modulate copper trafficking for bioorthogonal synthesis with no need of exogenous addition of copper catalysts. Like copper chaperones, the prepared ZIF-8 copper chaperone mimics specifically bind copper ions through the formation of coordination bonds. Moreover, the copper is unloaded under the acidic environment due to the dissipation of the coordination interactions between metal ions and ligands. In this way, the cancer cell-targeted copper chaperone mimics can selectively transport copper ions into cells. Regulation of intracellular copper trafficking may inspire constructing bioorthogonal catalysis system with reduced metal cytotoxicity in live cells.

PCy3-assisted Ag(I)-catalyzed click reaction for regioselective synthesis of 1,4-disubstituted 1,2,3-triazoles at room temperature

An approach towards Cu-free click chemistry has been developed in this work. Silver-catalyzed PCy3-ligand-assisted synthesis of 1,4-disubstituted 1,2,3-triazoles at room temperature has been developed. Regioselectivity of the reaction was confirmed from the results of single-crystal X-ray diffraction (SC-XRD) of one of the products. SC-XRD of ex situ-generated Ag-PCy3 complex helped us propose a plausible mechanism for the reaction. This reaction was indicated to exhibit a catalytic activity level similar to that for the in situ-generated complex. The methodology was found to work well with benzyl azides, phenyl azides, terminal alkynes and internal alkynes in aqueous medium. The one-pot three-component reaction leading to 1,2,3-triazole synthesis also proceeded well.

CuI/DMAP-Catalyzed Oxidative Alkynylation of 7-Azaindoles: Synthetic Scope and Mechanistic Studies

An efficient and practical method for the N-alkynylation of 7-azaindoles has been established by using CuI/DMAP catalytic system at room temperature and in open air. This simple protocol has been successfully employed in the synthesis of a wide range of N-alkynylated 7-azaindoles with good yields. Also, this approach is well-suited for large-scale N-alkynylation reactions. The designed N-alkynylated 7-azaindoles were further subjected to Cu-/Ir-catalyzed alkyne-azide cycloaddition (CuAAC/IrAAC) or "click" reaction for the rapid synthesis of 1,4-/1,5 disubstituted 1,2,3-triazole decorated 7-azaindoles. A mechanistic study based on density functional theory (DFT) calculations and ultraviolet-visible (UV) spectroscopic studies revealed that the CuI and DMAP combination formed a [CuII (DMAP)2 I2 ] species, which acts as an active catalyst. The DFT method was used to assess the energetic viability of an organometallic in the C-N bond formation pathway originating from the [CuII (DMAP)2 I2 ] complex. We expect that the newly designed Cu/DMAP/alkyne system will offer valuable insights into the field of Cu-catalyzed transformations.

Synthesis of Hypervalent Iodine Diazo Compounds and Their Application in Organic Synthesis

Diazomethyl-substituted iodine(III) compounds with electron-withdrawing groups (EWG) connected to diazo methyl center were a type of donor-acceptor diazo compounds with potential reaction abilities similar to ordinary diazo compounds. Although several diazomethyl-substituted iodine(III) compounds were synthesized and used in the nucleophilic substitution reactions as early as 1994, the synthesis and application of new iodine(III) diazo compounds have only been reported to a certain extent in recent years. In the presence of rhodium catalyst, photocatalyst, or nucleophiles, diazomethyl-substituted iodine(III) compounds can be converted into rhodium-carbenes, diazomethyl radicals, ester radicals or nucleophilic intermediates, which can be used as key intermediates for the formation of chemical bonds. The aim of this review is to give an overview of diazomethyl-substituted iodine(III) compounds in organic synthesis.

Copper phosphorylated cellulose nanofibers mediated azide-alkyne cycloaddition click reaction in water

Heterogenous copper-catalyzed azide-alkyne cycloaddition reaction (CuAAC) was performed by using the phosphorylated carbohydrate-based cellulose nanofibers loaded with copper(II) ions. The copper-containing phosphorylated cellulose nanofibers (here after noted Cu(II)-PCNFs) were prepared in two different morphologies, namely the paper and foam ones and characterized by different techniques, including Scanning Electronic Microscopy (SEM), Energy Dispersive X-ray (EDX), Brauner-Emmett-Teller (BET), FT-IR spectroscopy (FTIR), Thermal Gravimetric Analysis (TGA), X-ray Photoelectron spectroscopy (XPS) and Atomic Force Microscopy (AFM). Cu(II)-PCNFs showed high activity in the CuAAC reaction when applied to the ligation of various organic azides and terminal alkynes without any reducing agent, resulting in the regioselective synthesis of 1,4-disubstituted-1,2,3-triazoles in water at room temperature. These nanofibers were recovered and reused with no significant loss of catalytic activity or selectivity. A carbohydrate-based bio-support cellulose as reliable heterogenous catalyst was efficiently developed in view of taking the click chemistry concept to sustainable chemistry.

Novel mitochondrial and DNA damaging fluorescent Calix[4]arenes bearing isatin groups as aromatase inhibitors: Design, synthesis and anticancer activity

Breast cancer causes a high rate of mortality all over the world. Therefore, the present study focuses on the anticancer activity of new lower rim-functionalized calix[4]arenes integrated with isatin and the p-position of calixarenes with 1,4-dimethylpyridinium iodine against various human cancer cells such as MCF-7 and MDA-MB-231 breast cancer cell lines, as well as the PNT1A healthy epithelial cell line. It was observed that compound 6c had the lowest values in MCF-7 (8.83 µM) and MDA-MB-231 (3.32 µM). Cell imaging and apoptotic activity studies were performed using confocal microscopy and flow cytometry, respectively. The confocal imaging studies with 6c showed that the compound easily entered the cell, and it was observed that 6c accumulated in the mitochondria. The Comet assay test was used to detect DNA damage of compounds in cells. It was found that treated cells had abnormal tail nuclei and damaged DNA structures compared with untreated cells. In vitro human aromatase enzyme inhibition profiles showed that compound 6c had a remarkable inhibitory effect on aromatase. Compound 6c displayed a significant inhibition capacity on aromatase enzyme with the IC50 value of 0.104 ± 0.004 µM. Thus, not only the anticancer activity of the new fluorescent derivatives, which are the subject of this study, but the aromatase inhibitory profiles have also been proven.

Cassia fistula galactomannan stabilized copper nanocatalyst as an efficient, recyclable heterogeneous catalyst for the fast clickable [3+2] Huisgen cycloadditions in water

In this study, we have first time investigated the synthesis of copper nanocatalyst by using biopolymer galactomannan, naturally extracted from Cassia fistula pods. The methodology involved for the preparation of copper nanocatalyst is economical, efficient, environment friendly, and did not involve further processing for stabilization or reduction of copper nanoparticles. The morphology and structural characterization of the nanocatalyst was performed by using different techniques such as FT-IR, 1H NMR, SEM, EDX, HR-TEM, XRD, XPS, ICP-MS, BET, and TGA analysis. The prepared copper nanocatalyst is applied for the click [3+2] Huisgen cycloadditions of various azides and alkynes, employing water as environmentally benign solvent. In comparison to earlier reported methods, our method requires lowest catalyst loading, less reaction time, excellent yields and have wide substrate scope. Additionally, the catalyst was easily recovered by simple filtration and recycled at least ten consecutive times without any appreciable loss of efficiency and selectivity. The effect of mannose and galactose (Man/Gal) ratio of Cassia fistula galactomannan on the catalytic activity were also investigated.

Recent Progress on Synthesis of Functionalized 1,5-Disubstituted Triazoles

Immediately after the invention of 'Click Chemistry' in 2002, the regioselective 1,2,3- triazole scaffolds resulted from respective organic azides and terminal alkynes under Cu(I) catalysis have been well recognized as the functional heterocyclic core at the centre of modern organic chemistry, medicinal chemistry, and material sciences. This CuAAC reaction has several notable features including excellent regioselectivity, high-to-excellent yields, easy to execute, short reaction time, modular in nature, mild condition, readily available starting materials, etc. Moreover, the resulting regioselective triazoles can serve as amide bond isosteres, a privileged functional group in drug discovery and development. More than hundreds of reviews had been devoted to the 'Click Chemistry' in special reference to 1,4-disubstituted triazoles, while only little efforts were made for an opposite regioisomer i.e., 1,5-disubstituted triazole. Herein, we have presented various classical approaches for an expeditious synthesis of a wide range of biologically relevant 1,5- disubstituted 1,2,3-triazole analogues. The syntheses of such a class of diversly functionalized triazoles have emerged as a crucial investigation in the domain of chemistry and biology. This tutorial review covers the literature assessment on the development of various synthetic protocols for the functionalized 1,5-disubstituted triazoles reported during the last 12 years.

Green Approach Toward Triazole Forming Reactions for Developing Anticancer Drugs

Compounds containing triazole have many significant applications in the dye and ink industry, corrosion inhibitors, polymers, and pharmaceutical industries. These compounds possess many antimicrobial, antioxidant, anticancer, antiviral, anti-HIV, antitubercular, and anticancer activities. Several synthetic methods have been reported for reducing time, minimizing synthetic steps, and utilizing less hazardous and toxic solvents and reagents to improve the yield of triazoles and their analogues synthesis. Among the improvement in methods, green approaches towards triazole forming biologically active compounds, especially anticancer compounds, would be very important for pharmaceutical industries as well as global research community. In this article, we have reviewed the last five years of green chemistry approaches on click reaction between alkyl azide and alkynes to install 1,2,3-triazole moiety in natural products and synthetic drug-like molecules, such as in colchicine, flavanone cardanol, bisphosphonates, thiabendazoles, piperazine, prostanoid, flavonoid, quinoxalines, C-azanucleoside, dibenzylamine, and aryl-azotriazole. The cytotoxicity of triazole hybrid analogues was evaluated against a panel of cancer cell lines, including multidrug-resistant cell lines.