Click Strategy Research Articles

Decarboxylative click cycloaddition: an emerging strategy towards substituted 1,2,3-triazole derivatives.

1,2,3-triazole is a vital structural motif of various drugs and therapeutic leads, as well as a linker for bioconjugation and molecular recognition. Cu-catalysed click cycloaddition of azides with terminal alkynes (CuAAc) is an important reaction to construct the triazole core. In recent years, various decarboxylative click strategies utilizing alkynoic acids as stable surrogates for low boiling or gaseous alkynes have been developed. For instance, propiolic acid, which is easy to transport, is a safe alternative for flammable gaseous acetylene. In this review article, we have covered the recent development in the decarboxylative click cycloaddition of alkynoic acids with azides leading to the synthesis of diversely substituted triazoles, including monosubstituted, 1,4-disubstituted and fully substituted 1,2,3-triazoles. Various aspects such as mechanistic insights and optimization conditions/role of catalyst are highlighted.

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.

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

AbstractHigh‐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.

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.

Disulfide Click Reaction for Stapling of S-terminal Peptides.

A disulfide click strategy is disclosed for stapling to enhance the metabolic stability and cellular permeability of therapeutic peptides. A 17-membered library of stapling reagents with adjustable lengths and angles was established for rapid double/triple click reactions, bridging S-terminal peptides from 3 to 18 amino acid residues to provide 18- to 48-membered macrocyclic peptides under biocompatible conditions. The constrained peptides exhibited enhanced anti-HCT-116 activity with a locked α-helical conformation (IC50 =6.81 μM vs. biological incompetence for acyclic linear peptides), which could be unstapled for rehabilitation of the native peptides under the assistance of tris(2-carboxyethyl)phosphine (TCEP). This protocol assembles linear peptides into cyclic peptides controllably to retain the diverse three-dimensional conformations, enabling their cellular uptake followed by release of the disulfides for peptide delivery.

Disulfide Click Reaction for Stapling of S‐terminal Peptides

AbstractA disulfide click strategy is disclosed for stapling to enhance the metabolic stability and cellular permeability of therapeutic peptides. A 17‐membered library of stapling reagents with adjustable lengths and angles was established for rapid double/triple click reactions, bridging S‐terminal peptides from 3 to 18 amino acid residues to provide 18‐ to 48‐membered macrocyclic peptides under biocompatible conditions. The constrained peptides exhibited enhanced anti‐HCT‐116 activity with a locked α‐helical conformation (IC50=6.81 μM vs. biological incompetence for acyclic linear peptides), which could be unstapled for rehabilitation of the native peptides under the assistance of tris(2‐carboxyethyl)phosphine (TCEP). This protocol assembles linear peptides into cyclic peptides controllably to retain the diverse three‐dimensional conformations, enabling their cellular uptake followed by release of the disulfides for peptide delivery.

Simultaneous detection of heterocyclic aromatic amines and acrylamide in thermally processed foods by magnetic solid-phase extraction combined with HPLC-MS/MS based on cysteine-functionalized covalent organic frameworks.

Acrylamide (AA) and heterocyclic aromatic amines (HAAs), as classic hazards produced during food thermal processing, have been widely concerned, but because of their polarity difference, it is very difficult to detect these contaminants simultaneously. Herein, novel cysteine (Cys)-functionalized magnetic covalent organic frameworks (Fe3O4@COF@Cys) were synthesized via a thiol-ene click strategy and then used as adsorbents for magnetic solid-phase extraction (MSPE). Benefiting from the hydrophobic properties of COFs and the modification of hydrophilic Cys, AA and HAAs could be enriched simultaneously. Then, a rapid and reliable method based on MSPE coupled with HPLC-MS/MS was developed for the simultaneous detection of AA and 5 HAAs in thermally processed foods. The proposed method showed good linearity (R2≥0.9987) with satisfactory limits of detection (0.012-0.210μgkg-1) and recoveries (90.4-102.8%). Actual sample analysis showed that the levels of AA and HAAs in French fries were affected by frying time and temperature, water activity of samples, content and type of reaction precursors, and reuse of oils.

Synthesis of New Polyheterocyclic Pyrrolo[3,4-b]pyridin-5-ones via an Ugi-Zhu/Cascade/Click Strategy.

A diversity-oriented synthesis (DOS) of two new polyheterocyclic compounds was performed via an Ugi-Zhu/cascade (N-acylation/aza Diels-Alder cycloaddition/decarboxylation/dehydration)/click strategy, both step-by-step to optimize all involved experimental stages, and in one pot manner to evaluate the scope and sustainability of this polyheterocyclic-focused synthetic strategy. In both ways, the yields were excellent, considering the high number of bonds formed with release of only one carbon dioxide and two molecules of water. The Ugi-Zhu reaction was carried out using the 4-formylbenzonitrile as orthogonal reagent, where the formyl group was first transformed into the pyrrolo[3,4-b]pyridin-5-one core, and then the remaining nitrile group was further converted into two different nitrogen-containing polyheterocycles, both via click-type cycloadditions. The first one used sodium azide to obtain the corresponding 5-substituted-1H-tetrazolyl-pyrrolo[3,4-b]pyridin-5-one, and the second one with dicyandiamide to synthesize the 2,4-diamino-1,3,5-triazine-pyrrolo[3,4-b]pyridin-5-one. Both synthesized compounds may be used for further in vitro and in silico studies because they contain more than two heterocyclic moieties of high interest in medicinal chemistry, as well as in optics due to their high π-conjugation.

Separation and purification of target flavonoids using covalently connected MOFs@boronic acid-functionalized-COFs magnetic hybrids: Precise identification and enhanced stability

The magnetic boronate based sorbents have been widely used to separation of cis-diol containing flavonoids. However, It's still challenging due to its chemical structural fragility and low grafting efficiency. The major obstacles are low concentration, the hydrophobicity of flavoniods, and complexity of crude extract solutions. For solving these problems, a new kind of covalently connect MOF@boronic acid-functionalized-COFs core–shell hybrid composites based on magnetic colloidal nanocrystal clusters (MCNCs), MCNCs@NH2-UiO-66@BTCA-BA-COFs, with high surface area, abundant binding sites and excellent chemical and structurally stability were synthesized for enhancing the structure stability and selective recognition efficiency. The alkynylation COFs were not only to be facilely grated on the surface of magnetic microsphere@NH2-UiO-66 via Schiff-based reaction but also beneficial to the further modification of azide phenylboronic acid group via click reaction. Such mentioned advantages and covalently connect click strategy could generate highly structure stable and strong binding sites for the template flavonoids (Naringin, NRG). Adsorption equilibrium experiments were reached rapidly within 120 min, and the maximum equilibrium binding capacities of MCNCs@PDA@NH2-UiO-66@BTCA-BA-COFs were 31.20 µmol g−1 for NRG. Moreover, MCNCs@PDA@NH2-UiO-66@BTCA-BA-COFs exhibited a stronger selectivity towards NRG than other competitive targets (i.e rutin, catechol, hesperetin, o-nitrophenol). The MCNCs@PDA@NH2-UiO-66@BTCA-BA-COFs have shown outstanding reusability of 91.99 % loss in enrichment performance towards NRG after seven times repeatedly. The obtained MCNCs@PDA@NH2-UiO-66@BTCA-BA-COFs-based mass spectrum (MS) methods were applied to analyze the purity of NRG products. As excepted, a commercially available NRG with purity (approximately 60 %) could be effectively extracted and concentrated to 93.15 % purity. More interestingly, the separation performance of the sorbents was influenced by hydrophilic and hydrophobic performance. This approach provided an idea for constructing a new kind of hybrid sorbents with both enhanced functionality, suitable hydrophobic performance and fast magnetic-response behavior, which is of great significance to the field of separation and purification of hydrophobic flavonoids.

Design, Synthesis, Anticancer Activity and Molecular Docking of New 1,2,3-Triazole-Based Glycosides Bearing 1,3,4-Thiadiazolyl, Indolyl and Arylacetamide Scaffolds.

New 1,3,4-thiadiazole thioglycosides linked to a substituted arylidine system were synthesized via heterocyclization via click 1,3-dipolar cycloaddition. The click strategy was used for the synthesis of new 1,3,4-thiadiazole and 1,2,3-triazole hybrid glycoside-based indolyl systems as novel hybrid molecules by reacting azide derivatives with the corresponding acetylated glycosyl terminal acetylenes. The cytotoxic activities of the compounds were studied against HCT-116 (human colorectal carcinoma) and MCF-7 (human breast adenocarcinoma) cell lines using the MTT assay. The results showed that the key thiadiazolethione compounds, the triazole glycosides linked to p-methoxyarylidine derivatives and the free hydroxyl glycoside had potent activity comparable to the reference drug, doxorubicin, against MCF-7 human cancer cells. Docking simulation studies were performed to check the binding patterns of the synthesized compounds. Enzyme inhibition assay studies were also conducted for the epidermal growth factor receptor (EGFR), and the results explained the activity of a number of derivatives.

Design, synthesis, and activity of 2-aminochromone core N,N-bis-1,2,3-triazole derivatives using click chemistry.

A new series of 2-aminochromone-based N,N-di-1,2,3-triazole hybrid heterocycles were synthesized in one pot from N,N-terminal dialkyne 2-aminochromone with various organo azides by following the click strategy using classical Cu(I)-catalyzed azide-alkyne [3 + 2] annulation reaction. The synthesized compounds were well characterized by using various spectral analyses such as IR, 1H NMR, 13C NMR, and HRMS data for their structural elucidation. All newly synthesized compounds have been investigated for anti-microbial activity against Gram-positive, Gram-negative bacteria, and fungal strains and exhibited high activity against microbial growth when compared with standard anti-bacterial agents. These derivatives were tested for anti-cancer activity against HeLa cell lines and found that all compounds exhibit good activity with IC50 values ranging from 0.11 to 1.04 µM than standard curcumin (IC50 4.83 ± 0.44 µM). The molecular docking studies of the synthesized compounds with the affinity of ligands toward the target protein dual-specificity tyrosine-regulated kinase 2, DYRK2 (PDB id: 5ZTN) molecular docking were shown a better Moldock score performed compared to standard.Graphic abstract Supplementary InformationThe online version contains supplementary material available at 10.1007/s11696-022-02449-w.

Probing Crowdedness of Artificial Organelles by Clustering Polymersomes for Spatially Controlled and pH-Triggered Enzymatic Reactions.

Most sophisticated biological functions and features of cells are based on self-organization, and the coordination and connection between their cell organelles determines their key functions. Therefore, spatially ordered and controllable self-assembly of polymersomes to construct clusters to simulate complex intracellular biological functions has attracted widespread attention. Here, we present a simple one-step copper-free click strategy to cross-link nanoscale pH-responsive and photo-cross-linked polymersomes (less than 100 nm) to micron-level clusters (more than 90% in 0.5-2 μm range). Various influencing factors in the clustering process and subsequent purification methods were studied to obtain optimal clustered polymeric vesicles. Even when polymeric vesicles separately loaded with different enzymes (glucose oxidase and myoglobin) are coclustered, the overall permeability of the clusters can still be regulated through tuning the pH values on demand. Compared with simple blending of those enzyme-loaded polymersomes, the rate of enzymatic cascade reaction increased significantly due to the interconnected complex microstructure established. The connection of catalytic nanocompartments into clusters confining different enzymes of a cascade reaction provides an excellent platform for the development of artificial systems mimicking natural organelles or cells.

N-Acetylenethio phthalimides: Sequential linkage for compositional click reaction

Click chemistry has become a useful tool for diverse molecular linkage and modification, and the development of new click strategy that enable reversibility and multifunctionality is of high demand for the multifunction and drug release. Herein, compositionally clicking combined regioselective iridium-catalyzed azide-alkynthio cycloaddition (Ir-AAC) and disulfuration has been developed for the sequential linkage from N -acetylenethio phthalimides, naturally occurring thiols and readily available azides. This method has been successfully applied to the construction of drug hybrids, peptide modification and glycosylation. Furthermore, by the design of diacetylenethio phthalimide as a platform molecule, trifunctional conjugants were sequentially linked through independent Ir-AAC, disulfuration and Cu-AAC reaction for hydrophobic tagging ternary PROTACs. An iridium-catalyzed azide-alkynthio phthalimides cycloaddition has been developed for the regioselective construction of diverse N -triazolylthio phthalimides, and the developed compositional cycloaddition and disulfuration click was applied for the reversibly sequential linkage of drug hybrids, peptide modification and glycosylation.

Dynamics of the alkyne → copper(I) interaction and its use in a heteroleptic four-component catalytic rotor.

The HETPYNE (HETeroleptic Phenanthroline and alkYNE metal) and DABCO·(zinc porphyrin)2 interactions were used to assemble the four-component nanorotor ROT-1 that exhibited a highly dynamic alkyne → copper(I) dissociation (k298 = 240 kHz) at 298 K. Quantitative click reaction transformed ROT-1 into the new rotor ROT-2 (k298 = 77 kHz) with a triazole → copper(I) linkage thus opening perspectives for bioorthogonal click strategies to biohybrid machinery.

A fascinating click strategy to novel 1,2,3-triazolium based organic-inorganic hybrids for highly accelerated preparation of tetrazolopyrimidines

Herein, click reaction is used for the preparation of novel organic-inorganic Brønsted acidic ionic solids (BAISs) as new catalysts for the efficient synthesis of tetrazolopyrimidines. A series of mono and disubstituted-1,2,3-triazoles were synthesized under click reaction condition. The prepared 1,2,3-triazoles underwent reaction with 1,4-butanesultone to provide novel solid 1,2,3-triazolium N- butyl sulfonate zwitterions. Then, the reaction of phosphotungstic acid with the obtained zwitterions led to the novel 1,2,3-triazolium-N-butyl sulfonic acid phosphotungstate as acidic ionic solids. The synthesized BAIS catalysts were fully characterized using FTIR, 1H and 13C NMR, XRD, elemental analysis (CHNS), TG and DSC techniques. The introduced novel hybrids were used as efficient catalysts for the synthesis of targeted methyl-7-aryl-4,7-dihydrotetrazolo[1,5-a]pyrimidine-6-carboxylate and 6,6-dimethyl-9-aryl-5,6,7,9-tetrahydrotetrazolo[5,1-b]quinazolin-8(4H)-one derivatives via multicomponent reaction of aromatic aldehydes, active methylene compounds and 5-aminotetrazole. Low amount of the prepared 1,2,3-triazolium-N-butyl sulfonic acids phosphotungstate catalysts (5–10 mmol%) gave desired products in short times (20–45 min) with excellent yields (87–93%). Novelty of the introduced catalysts, ease of recovery and reusability up to four repeated runs with no significant decrease in the yields are highlighted superiorities of the introduced organic-inorganic hybrid catalysts.

Thiol-ene click synthesis of β-cyclodextrin-functionalized covalent organic framework-based magnetic nanocomposites (Fe3O4@COF@β-CD) for solid-phase extraction and determination of estrogens and estrogen mimics

Estrogens and estrogen mimics have been proved to be possible carcinogenic risks to human health and have drawn extensive attention in the fields of food safety. In this work, a thiol-ene click strategy was proposed for synthesis of a novel β-cyclodextrin-functionalized covalent organic framework-based magnetic nanocomposites (Fe3O4@COF@β-CD) and then employed as adsorbents for magnetic solid-phase extraction (MSPE) of estrogens and estrogen mimics. The Fe3O4@COF@β-CD possess the merits of superparamagnetism, large surface area, and excellent adsorption performance to estrogens and estrogen mimics. By combining with high-performance liquid chromatography-fluorescence detector (HPLC-FLD), the developed method gave a good linearity (R2 ≥ 0.9989) and low limits of detection (0.9–3.4 μg kg−1) under the optimized conditions. The applicability of the presented MSPE-HPLC-FLD method was demonstrated by real milk and meat samples analysis, with the satisfactory recoveries ranging from 89.0 to 105.4% and the relative standard deviations (RSDs) ≤ 5.7%.

Designing of chalcone functionalized 1,2,3-triazole allied bis-organosilanes as potent antioxidants and optical sensor for recognition of Sn2+ and Hg2+ ions

This article presents the design, synthesis and characterization of a series of new acetylenic bis-chalcones (5a-5c) and chalcone functionalized 1,2,3-triazole allied bis-organosilanes (6a-6c) using aldol condensation followed by the Cu(I) catalyzed click strategy. The absorption studies of the designed compounds 5a and 6a were examined towards various metal ions that exhibit their high selectivity and sensitivity towards the recognition of Sn2+ and Hg2+ ions. The sensors show reversible nature upon the addition of disodium salt of ethylenediaminetetraacetic acid. Furthermore, the obtained detection limit with sensors 5a and 6a by plotting calibration curve was 0.34 µM and 0.64 µM for Sn2+ ion and 0.31 µM and 0.15 µM for Hg2+ ion respectively. The association constant value calculated for chemosensors 5a and 6a using the Benesi and Hildebrand plot method was 0.69 × 105 M−1 and 0.18 × 105 M−1 towards Sn2+ ion and 0.67 × 106 M−1 and 0.54 × 106 M−1 towards Hg2+ ion respectively. Moreover, the synthesized compounds 5a and 6a were investigated for their biological application by evaluating their cytotoxicity and antioxidant activity.

Functionalized High Mannose‐Specific Lectins for the Discovery of Type I Mannosidase Inhibitors

AbstractAn engineered cyanovirin‐N homologue that exhibits specificity for high mannose N‐glycans has been constructed to aid type I α 1,2‐mannosidase inhibitor discovery and development. Engineering the lectins C‐terminus permitted facile functionalization with fluorophores via a sortase and click strategy. The resulting lectin constructs exhibit specificity for cells presenting high mannose N‐glycans. Importantly, these lectin constructs can also be applied to specifically assess changes in cell surface glycosylation induced by type I mannosidase inhibitors. Testing the utility of these lectin constructs led to the discovery of type I mannosidase inhibitors with nanomolar potency. Cumulatively, these findings reveal the specificity and utility of the functionalized cyanovirin‐N homologue constructs, and highlight their potential in analytical contexts that require high mannose‐specific lectins.

Functionalized High Mannose-Specific Lectins for the Discovery of Type I Mannosidase Inhibitors.

An engineered cyanovirin-N homologue that exhibits specificity for high mannose N-glycans has been constructed to aid type I α 1,2-mannosidase inhibitor discovery and development. Engineering the lectins C-terminus permitted facile functionalization with fluorophores via a sortase and click strategy. The resulting lectin constructs exhibit specificity for cells presenting high mannose N-glycans. Importantly, these lectin constructs can also be applied to specifically assess changes in cell surface glycosylation induced by type I mannosidase inhibitors. Testing the utility of these lectin constructs led to the discovery of type I mannosidase inhibitors with nanomolar potency. Cumulatively, these findings reveal the specificity and utility of the functionalized cyanovirin-N homologue constructs, and highlight their potential in analytical contexts that require high mannose-specific lectins.

Survival of e-commerce entrepreneurs: The importance of brick-and-click and internationalization strategies

• Organizational ecology theory can explain ecommerce entrepreneurs’ survival. • The internationalization is a strategic factor explaining ecommerce entrepreneurs’ survival. • The risk of bankruptcy is low for companies following a brick and click strategy. • The empirical study supports the ‘survival of the fitter’ principle. • It is worth analysing the firms’ accounting information in their first years. E-commerce is a fast-growing industry that attracts many entrepreneurs; however, the survival rate is lower than that of other industries. Entrepreneurs take many strategic decisions that have a significant bearing on the success of their e-commerce ventures. Two are particularly salient for our research: Is it better to start as a pure-click or open a physical store? To what extent should e-commerce ventures internationalize? We also wonder if it is worth reviewing the first annual accounts available. Grounding on organizational ecology theory, we develop a model hypothesizing that (1) the brick-and-click strategy favours survival; (2) internationalization favours survival; (3) firm size and financial health matter; (4) earnings management mediates the relationship between financial health and survival; and (5) the brick-and-click and internationalization strategies mediate the relationship between size and survival. The empirical study is performed by analysing seven years of data on 632 new e-commerce ventures using non-parametric means tests, a Cox regression, and a generalized structural equation model. The study tests the strategies followed by e-commerce entrepreneurs and firm characteristics that influence survival. We find that the risk of bankruptcy is 1.437 times greater for pure-click than for brick-and-click retailers, 2.778 times greater for local players than for internationalized firms, and 1.787 times greater for unprofitable firms than for profitable firms. Hence, it is worth analysing the financial statements provided by entrepreneurs; however, signs of earnings management should be checked. All these factors affect the probability of early bankruptcy as well as explain survival several years later.