Cu(I)-Catalyzed Click Chemistry in Glycoscience and Their Diverse Applications

Dual-function advanced magnetic bacterial cellulose materials: From enhanced adsorption phenomena to an unprecedented circular green catalytic strategy

With the growing emphasis on circular catalysis principles and green chemistry, addressing the dual challenge of wastewater treatment and sustainable catalysis has become increasingly critical. Although the adsorption of copper ions using magnetic biomaterials has been widely investigated, its full potential is still not fully understood. In particular, the reutilization of Cu(II)-loaded magnetic bacterial cellulose in circular green catalytic reactions remains underexplored. This study presents a novel magnetic bacterial cellulose-based material, designated as (BC-BPEM)@Fe3O4NPs, engineered through advanced chemical modifications to address these challenges. The adsorption kinetics followed a pseudo-second-order model, indicating chemisorption as the predominant mechanism. A key challenge addressed in this study was the efficient reuse of Cu(II)-loaded magnetic bacterial cellulose-based material. The recovered material was successfully employed as a catalyst in the synthesis of novel 1,4-disubstituted bis-1,2,3-triazoles under green conditions. Notably, the reaction achieved an impressive rate of 0.219 ± 0.006 mmol.gcat-1.min-1 and a 99 % yield within 15 min, using green deep eutectic solvents (ChCl/Gly) and glutathione as a reducing agent. Remarkably, the catalyst retained its high catalytic performance over 20 cycles, maintaining yields consistently between 99 % and 97 %. This study not only emphasizes the seamless integration of adsorption and catalytic recycling but also highlights the sustainability of the approach. Environmental metrics revealed an E-factor of 0.442 kg waste/kg product, a PMI of 1.442 kg materials/kg product, and an RME of 99.83 %, reinforcing the potential of catalyst in both sustainable catalysis and environmental remediation.

Efficient synthesis of coumarin based triazole linked O-glycoconjugates as new bio-active glycohybrids

Glycohybrids are biologically significant molecules with variety of biological functions and are found as structural motifs in numerous natural products. Here, we report the synthesis of various new coumarin-based O-glycoconjugates as glycohybrids that are chirally enriched and bridged by 1,2,3-triazoles ring system. The1,2,3-triazoles bridging was done via CuAAC click-chemistry. Click chemistry offers several advantages, including high chemo- and regioselectivity, mild reaction conditions, easy purification, and compatibility with multiple functional groups. Two series of O-glycoconjugates as new glycohybrids were designed and efficiently synthesized in very good isolated yields, using d-glucose, d-galactose, d-mannose, d-arabinose, 3,4,6-tri-O-acetyl-D-glucal, 3,4,6-tri-O-acetyl-D-galactal and 3,4-di-O-acetyl-D-arabinal derived 1-O-propargylated glycosides, reacting with various 4-azidocoumarins under click-chemistry reaction conditions. The prepared new coumarin-based O-glycoconjugates as glycohybrids were found to possess anticancer activity against MCF-7 breast cancer cell lines at micromolar concentration.

CuO2@SiO2 nanoparticle assisted click reaction-mediated magnetic relaxation biosensor for rapid detection of Salmonella in food

Foodborne pathogens seriously threaten people's life and well-being. In this study, we developed a novel magnetic relaxation time (PCuMRS) biosensor by integrating phage, differential magnetic separation technology, and copper catalyzed click reaction to enable rapid and sensitive detection of viable Salmonella typhimurium (S. typhimurium) in food within 80 min. This assay utilized phage as the recognition element to accurately differentiate between viable and nonviable S. typhimurium. Initially, we prepared a complex of magnetic nanoparticles (MNPs) and phage to efficiently capture viable S. typhimurium. We synthesized CuO2@SiO2-phage nanoparticles loaded with numerous Cu2+ ions to transform the concentration of S. typhimurium into a corresponding concentration of copper ions, which then modulate the click reaction between magnetic nanoparticles of varying sizes, leading to changes in both the number of small magnetic nanoparticles and magnetic signals. Based on this principle, we established a linear relationship (102-107 CFU/mL) between the concentration of S. typhimurium and the changes in magnetic signal, with a limit of quantification of 80 CFU/mL. Furthermore, the standard recovery rate and coefficient of variation of the sensor are 93.68%-100.36% and 0.59%-4.76%, respectively. The PCuMRS biosensor demonstrates outstanding sensitivity and a short detection time, making it a rapid, sensitive, and accurate method for identifying foodborne pathogens such as S. typhimurium, which has potential for applications in various other fields.

Copper-anchored polysulfonamide-modified UiO-66-NH2/sodium alginate nanocatalyst for sustainable synthesis of 1,2,3-triazoles

An effective nanocomposite comprising a metal-organic framework and porous polysulfonamide-sodium alginate (SA-PS) was developed for phenyl triazole production. The Cu(i) ions were uniformly distributed on the as-prepared UiO-66-NH2@SA-PS matrix, coordinated by sulfonamide groups in a bidentate bridging pattern (UiO-66-NH2@SA-PS/CuI). The nanocatalyst UiO-66-NH2@SA-PS/CuI demonstrated exceptional performance in the synthesis of 1,2,3-triazole derivatives, facilitating high product yields in the reaction of various aryl boronic acids, phenylacetylene, and sodium azide under mild conditions.

Organobase-catalyzed efficient synthesis of 4-acyl-5-aryl tri-substituted triazole linked N-glycosides as glycohybrids

Herein, we report a highly efficient organobase-catalyzed method for the synthesis of fully decorated chiral 4-acyl-5-aryl-trisubstituted-1,2,3-triazole-linked N-glycosidic molecular scaffolds as glycohybrids. This process involves a base-catalyzed 1,3 dipolar cycloaddition reaction, where β-ketoesters react with various glycosyl azides in dimethyl sulfoxide at room temperature, furnishing new glycohybrids in good to excellent yields. This intermolecular reaction is metal-free, exceptionally efficient, versatile, and high-yielding, with a broad substrate scope and remarkable regioselectivity.

Not So Bioorthogonal Chemistry

The advent of bioorthogonal chemistry has transformed scientific research, offering a powerful tool for selective and noninvasive labeling of (bio)molecules within complex biological environments. This innovative approach has facilitated the study of intricate cellular processes, protein dynamics, and interactions. Nevertheless, a number of challenges remain to be addressed, including the need for improved reaction kinetics, enhanced biocompatibility, and the development of a more diverse and orthogonal set of reactions. While scientists continue to search for veritable solutions, bioorthogonal chemistry remains a transformative tool with a vast potential for advancing our understanding of biology and medicine. This Perspective offers insights into reactions commonly classified as "bioorthogonal", which, however, may not always demonstrate the desired selectivity regarding the interactions between their components and the additives or catalysts used under the reaction conditions.

Substrate-Dependent Stereoselective Synthesis of Pyrrolo[3,4-b]Pyridin-5-Ones and Pyridyl Isoindoline-1-Ones Using Bis(benzotriazol-1-yl) Ligand

The documented work highlighted the synthesis of bis(benzotriazol-1-yl) methane derivatives using silicomolybdic acid (SMA) and successfully implemented in the stereoselective synthesis of diverse pyrrolo[3,4-b]pyridin-5-one and pyridyl isoindolinones derivatives in one-pot. The pyridinamide precursor with diverse alkynes furnished Z-selectivity of pyrrolo[3,4-b]pyridin-5-one across exocyclic C=C bond while the various benzamides on treating with 2-ethynyl pyridine afforded (E)-pyridylisoindoline-1-ones as a major isomer. The single-crystal X-ray diffraction provides strong evidence in favor of the existence and orientation of developed compounds. The broad substrate scope, easy accessibility of substrates, high stereoselectivity, scale-up synthesis, and crystal evidence demonstrate the merits of the current decorum.

Structure-activity relationships in the development of single atom catalysts for sustainable organic transformations

Single atom catalysts (SACs), which can provide the combined benefits of homogeneous and heterogeneous catalysts, are a revolutionary concept in the field of material research. The highly exposed catalytic surfaces, unsaturated sites, as well as unique structural and electronic properties of SACs have the potential to catalyze numerous reactions with unmatched efficiency and durability when stabilized on a suitable support. In this review, we have provided an intuitive insight into the strategies adopted in the last 5 years for morphology control of SACs to know about its impact on metal-support interaction and various organic transformations with special reference to metal oxides, alloys, metal-organic frameworks (MOFs) and carbon-based supports. This review also includes a brief description of unparalleled potentials of SACs and the recent advances in the catalysis of industrially important organic transformations, with special emphasis on the C-C cross-coupling reaction, biomass conversion, hydrogenation, oxidation and click chemistry. This unprecedented and unique perspective will highlight the interactions occurring within SACs that are responsible for their high catalytic efficiency, which will potentially benefit various organic transformations. We have also suggested plausible synergy of various other concepts such as defect engineering and piezocatalysis with SACs, which can provide a new direction to sustainable chemistry. A good understanding of the different types of metal-support interactions will help researchers develop morphology-controlled SACs with tunable properties and establish mechanisms for their exceptional catalytic behaviour in industrially important organic transformations.

Recent development on stereoselective intramolecular O-glycosylation methodology

Carbohydrates are increasingly recognized for their versatility as scaffolds in biological, pharmaceutical and biotechnological applications, due to their structural diversity, biocompatibility, hydrophilicity, low toxicity, bioavailability, and excellent ADME properties. The important role of carbohydrates in biological systems deepens, the demand for well-defined and anomerically pure carbohydrates in biomedical research has surged. Chemical synthesis remains the most viable method to meet this demand, despite the inherent challenges in glycosylation reactions. Carbohydrate oligomers, in particular, pose significant difficulties due to the need for complex protecting and leaving group modifications, functionalization, labour-intensive purification, and detailed characterization. A precise stereo and regio-control during glycosylation remains one of the major challenges in organic synthesis. To enhance the selectivity in glycosylation products, the concept of 'Intramolecular Glycosylation' was developed, offering a more advanced and efficient alternative route to conventional methods. Various intramolecular glycosylation methods can be classified primarily into three categories: Intramolecular Aglycone Delivery (IAD), Leaving Group-based Intramolecular Glycosylation, and the Molecular Clamp concept. This review article explores the fundamentals of these three methodologies, their significant advancements, and highlights their growing impact on the stereoselective synthesis of numerous bioactive O-glycosides, glycans with diverse functionalities, complex oligosaccharides, and various macrocycles with definite stereoselectivity.

Emergence of Fluorescent Glycodots for Biomedical Applications

Carbohydrate-functionalized quantum dots exhibit excellent physical characteristics and enhance the steric interaction with biological cells and tissues. Glycoconjugation of quantum dots promotes aqueous solubility, stability, and reduced immunogenicity. Carbohydrate-protein interactions are involved in various vital processes and provide insight into cellular recognition, cell-to-cell communication, pathogenicity, antigen-antibody recognition, and enzymatic action. Quantum dots are fluorescent materials with rich quantum mechanical and unique optical properties, making them valuable for biomedical applications. Recent advancements in quantum dot materials as biomedical tools have led to the development of carbohydrate-conjugated glyco-functionalized quantum dots. These innovations promise application as nanocarriers, imaging agents, fluorescent probes, and theranostics. This review provides an overview of glyco nanotechnology, emphasizing carbohydrate-conjugated metal-, silicon-, and carbon-based quantum dots as glyco dots and their potential biomedical uses. We hope that this study will address the gap in this field and provide a more precise understanding of the subject.

Three-step click assembly using trivalent platforms bearing azido, ethynyl, and fluorosulfonyl groups

Divergent synthesis of triazoles was achieved using newly designed platform molecules possessing azide, alkyne, and fluorosulfonyl moieties. Consecutive conjugations by the sulfur(VI) fluoride exchange and following consecutive triazole formations allowed us to prepare a wide variety of bis(triazole)s by virtue of selective transformations. One-pot triple-click assembly of easily accessible modules led to the facile synthesis of middle-molecular-weight triazoles with various functional moieties.

Metabolic labeling and targeted modulation of adipocytes

Adipocytes play a critical role in energy storage and endocrine signaling and are associated with various diseases such as cancer and diabetes. Facile strategies to engineer adipocytes have long been pursued for elucidating adipocyte biology and developing adipocyte-based therapies. Herein, we report metabolic glycan labeling of adipocytes and subsequent targeted modulation of adipocytes via click chemistry. We show that azido tags expressed on the surface of adipocytes can persist for over 4 days. By conjugating dibenzocyclooctyne (DBCO)-cargos onto azido-labeled adipocytes via click chemistry, the cargos can be retained on the adipocyte membrane for over 12 hours. We further show that signaling molecules including adiponectin, calreticulin, mannose-binding lectin 2, and milk fat globule-EGF factor 8 protein can be conjugated to adipocytes to orchestrate their phagocytosis by macrophages. The azido-labeled adipocytes grafted into mice can also mediate targeted conjugation of DBCO-cargos in vivo. This adipocyte labeling and targeting technology will facilitate the development of adipocyte-based therapies and provides a new platform for manipulating the interaction between adipocytes and other types of cells.

Trivalent oleanolic acid-glucose conjugates: Synthesis and efficacy against Influenza A virus

Influenza A virus (IAV) leads to significant morbidity and mortality due to the seasonal epidemics and spread. We have demonstrated that oleanolic acid (OA) C28 glucose conjugates and OA trimers are capable of effectively blocking the recognition and interaction between the influenza virus and host cells. In this study, a series of OA-glucose trimers were designed and synthesized through the CuAAC reaction. All trimers underwent screening for anti-IAV activities in vitro. Among these, compounds 13a and 13b showed inhibitory activity against the influenza virus, with IC50 values of 0.68 μM and 0.47 μM, respectively, demonstrating greater potency than oseltamivir (IC50 = 1.36 μM). Results from the time-of-addition experiment and hemagglutination inhibition assay suggest that these OA-glucose trimers may disrupt the recognition between the HA protein of IAV and sialic acid receptors on host cells, thus blocking viral entry. Furthermore, it was found that compound 13b effectively inhibits IAV infection in BALB/c mice. This study has elucidated the structure-activity relationships of OA trimers against the influenza virus and highlighted the utility of multivalent OA conjugates for enhancing ligand-target interactions in anti-influenza virus drug design, laying a groundwork for future research into the antiviral applications of these natural products.

Click chemistry-based fluorescence polarization sensor for sensitive detection of ampicillin

Ampicillin (AMP) is a β-lactam antibiotic that can inhibit bacterial wall synthesis. The overuse and misuse of AMP makes it micropollutant that commonly found in food and various environmental media. In this work, a fluorescence polarization sensor was designed to sensitive detection of trace ampicillin based on click chemistry, using graphene oxide (GO) as a fluorescence polarization (FP) signal enhancement element. First, when ampicillin binds to its aptamer (apt), the adjacent alkyne and azide groups are separated, hindering the click-linking reaction. When Carboxyfluorescein (FAM) fluorophore-labeled probe (C-FAM) is added, its protruding 3-terminal FAM is recognized and cleaved by exonuclease I (EXO I), releasing fluorophores free that could not be adsorbed on GO, resulting in a lo0wer polarization signal. If there is no AMP in the system, aptamer probe is connected to its complementary chain ends by a click reaction. After C-FAM hybridizes with apt, the apt/P duplex is opened and the prominent single-stranded ends adsorb on the GO, leading a significantly enhanced FP signal. According to the relationship between the difference in FP values and the concentrations of AMP, the limit of detection of proposed method is as low as 80 pg/mL. This assay has a wide linear range plus excellent selectivity, and has been applied to detect AMP in milk and river water samples with satisfactory results, which demonstrates that the FP sensor has great potential for practical applications in food safety and environmental protection fields.

HFIP-Mediated Synthesis of 4-Aryl-NH-1,2,3-Triazoles and 1,5-Disubstituted 1,2,3-Triazolyl Glycoconjugates

We herein report a multicomponent reaction for the synthesis of N-unsubstituted-1,2,3-triazoles and N-substituted-1,2,3 triazoles from the reaction of aldehydes, nitroalkanes, and sodium azides/glycosyl azides in the presence of 1,1,1,3,3,3-hexafluoroisopropanol, a hydrogen bond-donating reaction medium. This three-component reaction provides a metal-free strategy for sequentially forming one C-C and two C-N bonds in a one-pot fashion. One-pot mild reaction condition, operational simplicity, wide substrate scope, good functional group tolerance, easy purification, high reaction yields, and altogether excellent regioselectivity are the notable advantages of this 1,2,3-triazole-forming protocol. Moreover, this protocol provides practical access to the gram-scale synthesis of potent inhibitors of indoleamine 2,3-dioxygenase 1.

Discovery of Balasubramide Derivative with Tissue-Specific Anti-Inflammatory Activity Against Acute Lung Injury by Targeting VDAC1

Macrophage-mediated inflammatory responses including pyroptosis are involved in the pathogenesis of sepsis and acute lung injury (ALI), for which there are currently no effective therapeutic treatments. The natural product (+)-Balasubramide is an eight-membered lactam compound extracted from the leaves of the Sri Lanka plant Clausena Indica and has shown anti-inflammatory activities, but its poor pharmacokinetic properties limit its further application for ALI. In this study, a compound (+)3C-20 is discovered with improved both pharmacokinetic properties and anti-inflammatory activity from a series of (+)-Balasubramide derivatives. The compound (+)3C-20 exhibits a markedly enhanced inhibitory effect against LPS-induced expressions of pro-inflammatory factors in mouse macrophages and human PBMCs from ALI patients and shows a preferable lung tissue distribution in mice. (+)3C-20 remarkably attenuates LPS-induced ALI through lung tissue-specific anti-inflammatory actions. Mechanistically, a chemical proteomics study shows that (+)3C-20 directly binds to mitochondrial VDAC1 and inhibits VDAC1 oligomerization to block mtDNA release, further preventing NLRP3 inflammasome activation. These findings identify (+)3C-20 as a novel VDAC1 inhibitor with promising therapeutic potential for ALI associated with inflammation.

Enantioconvergent and Site-Selective Etherification of Carbohydrate Polyols through Chiral Copper Radical Catalysis

Going beyond currently reported two electron transformations that formed the core backdrop of asymmetric catalytic site-selective carbohydrate polyol functionalizations, we herein report a seminal demonstration of an enantioconvergent copper catalyzed site-selective etherification of minimally protected saccharides through a single-electron radical pathway. Further, this strategy paves a rare strategy, through which a carboxamide scaffold that is present in some glycomimetics of pharmacological relevance, can be selectively introduced. In light of the burgeoning interest in chiral radical catalysis, and the virtual absence of such stereocontrol broadly in carbohydrate synthesis, our strategy showcased the unknown capability of chiral radical copper catalysis as a contemporary tool to address the formidable site-selectivity challenge on a remarkable palette of naturally occurring saccharides. When reducing sugars were employed, a further dynamic kinetic resolution type glycosylation can be activated by the catalytic system to selectively generate the challenging β-O-glycosides.

Target-Navigated CBT-Cys "Stapling" Coupled with CRISPR/Cas12a Amplification for the Photoelectrochemical Nucleic Acid Assay

Generally, rolling circle amplification (RCA) is based on an enzyme-linked padlock extension reaction. Herein, rapid linking that utilizes click chemistry for joining sticky ends of DNA molecules was developed. The ends of nucleic acid were modified with 2-cyano-6-aminobenzothiazole (CBT) and cystine (Cys-Cys), while glutathione was introduced to break the disulfide bond under target navigation and promote the linkage between CBT and Cys at the terminus of the nucleic acid at pH 7.4. Subsequently, RCA was performed using phi29 polymerase. CRISPR/Cas12a cleavage was triggered by the product of RCA amplification. Assisted by alkaline phosphatase, the electron exchange process between the photoelectroactive Sb@Co(OH)F nanorod and p-aminophenol (p-AP) was collected in the form of photoelectrochemical (PEC) signals. Mass spectrometry, gel electrophoresis, and PEC signals were employed to verify the linking process and the RCA coupled with CRISPR/Cas12a cleavage amplification. CBT-Cys connection exhibited a high reaction rate (23.79 M-1·s-1). This enzyme-free linking process was superior to traditional enzyme catalysis in terms of the reaction environment and linking rate. This efficient nonenzymatic joining system holds great potential for constructing nonhomologous end joining, modifying DNA with molecules, and facilitating nucleic acid-protein modification processes.

Novel quinazolin-4-one based derivatives bearing 1,2,3-triazole and glycoside moieties as potential cytotoxic agents through dual EGFR and VEGFR-2 inhibitory activity

The toxicity that was caused by the developed medications for anticancer treatment is, unfortunately, an earnest problem stemming from the various involved targets, and accordingly, intense research for overcoming such a phenomenon remains indispensable. In the current inquiry, an innovative category of substituted quinazoline-based glycosides incorporating a core of 1,2,3-triazole and attached to distinct acetylated likewise deprotected sugar segments are created and produced synthetically. The resulted 1,2,3-triazolyl-glycosides products were investigated for their ability to cause cytotoxicity to several human cancer cell lines. The quinazoline based glycosyl-1,2,3-triazoles 10-13 with free hydroxy sugar moiety revealed excellent potency against (IC50 range = 5.70-8.10 µM, IC50 Doxorubicin = 5.6 ± 0.30 µM, IC50 Erlotinib = 4.3 ± 0.1 µM). against MCF-7 cancer cell line. In addition, the derived glycosides incorporating quinazolinone and triazole core 6-13 with acetylated and deprotected sugar parts showed excellent and superior potency against HCT-116 (IC50 range = 2.90-6.40 µM). The potent products were revealed as safe cytotoxic agents as indicated by their studied safety profiles. Additional research of promising candidates inhibitory analysis performed against EGFR and VEGFR-2. The hydroxylated glycosides incorporating triazole and quinazoline system 11 and 13 with N-methyl substitution of quinazolinone, gave excellent potency against EGFR (IC50 = 0.35 ± 0.11 and 0.31 ± 0.06 µM, correspondingly) since glycoside 13 revealed comparable IC50 (3.20 ± 0.15 µM) to sorafenib against VEGFR-2. For more understanding of its action mode, it was analyzed how the 1,2,3-triazolyl glycoside 13 made an effect on the apoptosis induction and the arrest of the cell cycle. It was revealed that it had the ability to stop HCT-116 cells in their cell cycle's G1 stage. Moreover, the influence of quinazolinone-1,2,3-triazole-glycoside 13 upon p53, Bax, and Bcl-2 levels in HCT-116 units was also studied for future approaches toward its behavior. Additionally, the latter derivative may trigger apoptosis, as indicated by a significant increase in apoptotic cells. Furthermore, molecular docking was simulated to make an obvious validation and comprehension acquirement of the binding's characteristics also attractions among the most forceful compounds side by side with their aimed enzymes.

Assessing the catalytic potential of novel halogen substituted carbene NHC (F, Cl, Br, I) catalysts in [3 + 2] cycloaddition reactions: A computational investigation

This study investigated the catalytic behavior of NHC-X ligands (X = F, Cl, Br, I) in cycloaddition reactions, focusing on both mononuclear and binuclear pathways. Using NCI (noncovalent interaction), RDG (reduced density gradient), ELF (electron localization function), and LOL (localized orbital locus) computational analyses, the electronic interactions and stability of the ligands were examined. The results showed that NHC-Cl exhibited the least steric hindrance and strongest transition state stabilization, making it the most efficient catalyst. NHC-F also demonstrated strong stabilization, particularly in the binuclear pathway. In contrast, NHC-Br showed moderate efficiency, whereas NHC-I was the least effective owing to higher Gibbs free energy values and greater steric hindrance, especially in polar solvents such as water and acetonitrile. This study emphasizes the crucial role of solvent effects and thermodynamic factors in influencing the catalytic efficiency. These findings provide a framework for optimizing NHC-based catalysts for chemical transformations.

Covalently crosslinked coacervates: immobilization and stabilization of proteins with enhanced enzymatic activity

Coacervates represent models for membrane-free protocells and thus provide a simple route to synthetic cellular-like systems that provide selective encapsulation of solutes. Here, we demonstrate a simple and versatile post-coacervation crosslink method using the thiol-ene click reaction in aqueous media to prepare covalently crosslinked coacervates. The crosslinking of the coacervate enables stability at extreme pH where the uncrosslinked coacervate fully disassembles. The crosslinking also enhances the hydrophobicity within the coacervate environment to increase the encapsulation efficiency of bovine serum albumin (BSA), as compared to the uncrosslinked coacervate. Additionally, the crosslinked coacervate increases the stabilization of BSA at low pH. These crosslinked coacervates can act as carriers for enzymes. The enzymatic activity of alkaline phosphatase (ALP) is enhanced within the crosslinked coacervate compared to the ALP in aqueous solution. The post-coacervation crosslink approach allows the utilization of coacervates for encapsulation of biologicals under conditions where the coacervate would generally disassemble. We demonstrate that these crosslinked coacervates enable the protection of encapsulated protein against denaturation at extreme pH and enhance the enzymatic activity with encapsulation. This click approach to stabilization of coacervates should be broadly applicable to other systems for a variety of biologics and environmentally sensitive molecules.

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.

Electrochemical C-H Azidation and Diazidation of Anilines for the Synthesis of Aryl Azides and Diazides

The increasing importance and need in many aspects have driven the rapid development of synthetic studies toward aryl azides. In this paper, electrochemical C-H azidation and diazidation of anilines have been developed using TMSN3 as an azide source. A range of functional groups can be tolerated under the optimized reaction conditions.

A CuSO4/Bicinchoninic acid/Reducing sugar based stable and non-ROS catalyst system for the CuAAC reaction in bioanalysis

The limitations of commonly used sodium ascorbate-based catalyst system for copper-catalyzed azide-alkyne cycloaddition (CuAAC) reaction include excess production of reactive oxygen species and rapid catalyst deactivation. In this study instead of using a highly active reducing agent, such as, sodium ascorbate, we chose reducing sugar as a mild reducing agent to build up the catalyst system for CuAAC reaction. Interestingly, the bicinchoninic acid (BCA) assay system containing reducing sugar satisfies the essential elements of the catalyst system for CuAAC reaction. We found that CuSO4/BCA/Reducing sugar system can catalyze the CuAAC reaction but with low yield. Rational analyses of various parameters in CuSO4/BCA/Glucose catalyst system suggested storage at room temperature might enhance the catalytic activity, which was proven to be the case. Importantly, the system remains stable at room temperature and minimal H2O2 was detected. Notably, our study showed that the coordination between the slow reduction of Cu(I) by reducing sugar and the selective chelation of Cu(I) by BCA is key to developing this system. The CuSO4/BCA/Reducing sugar catalyst system was successfully applied to various CuAAC reaction based bioanalyses, and it is suitable for the CuAAC reaction based bioanalyses that are sensitive to ROS or request long reaction time.

Click-chemistry-inspired synthesis of new series of 1,2,3-triazole fused chromene with glucose triazole conjugates: Antibacterial activity assessment with molecular docking evaluation

A series of new 1,2,3-triazole fused chromene based glucose triazole conjugates were synthesized from chromene fused 1,2,3-triazolyl extended alkyne and 2,3,4,6-tetra-O-acetyl-β-d-glucopyranosyl azide in good to excellent yield by a copper catalyzed azide-alkyne cycloaddition (CuAAC) reaction. The major advantages include mild reaction conditions, high yield, good substrate scope, and shorter reaction time. The antibacterial efficacy of the compounds were assessed in vitro against human pathogenic Gram-negative E. coli and Gram-positive S. aureus bacteria. Compound 24j was found to be the most potent molecule with zone of inhibition (ZI) of 17 mm and minimum inhibitory concentration (MIC) of 25 μg mL-1 in E. coli and ZI of 16 mm and MIC of 25 μg mL-1 in S. aureus. Also, it significantly inhibited E. coli DNA-gyrase in silico with a binding affinity of -9.4 kcal/mol. Among all the synthesized compounds, 24i, 24d, 24e and 24f showed significant antibacterial activity against both strains and inhibited DNA-gyrase in silico with good binding affinities. Hence, these 1,2,3-triazole fused chromene based glucose triazole conjugates may evolve to be powerful antibacterial agents in recent future, according to structure-activity relationships based on strong antibacterial properties and molecular docking studies.

Cycloaddition and Skeleton Rearrangement of Heterocyclic Ketene Aminals (HKAs) with 1-Diazonaphthalen-2(1H)-ones for the Synthesis of Functionalized 1,2,3-Triazoles

We developed a protocol for the synthesis of highly functionalized 5,6-dihydro-imidazo[1,2-c][1,2,3]triazole derivatives 4-5 (DHITs) from 1-diazonaphthalen-2(1H)-one derivatives with heterocyclic ketene aminals (HKAs). This strategy involved cycloaddition and skeletal rearrangement entailing the heating of a mixture of substrates 1 with HKAs 2-3 and THF without any catalyst. As a result, a series of DHITs 4-5 were produced by cleaving one bond (1 C═N bond) and forming three bonds (1 N-N and 2 C-N bonds) in a single step. This protocol achieved the dual functionalization of diazo building blocks involving both the aromatic nitrogen alkylation reaction to form an ArC-N bond without any metal catalyst and the intermolecular cycloaddition of the N═N bond. These strategies can be used to synthesize functionalized DHITs for combinatorial and parallel syntheses via one-pot reactions without any catalyst.

Silicomolybdic Acid Cluster as Biocompatible Catalyst for One-Pot Tandem Synthesis of Orthogonally Protected Glycosides

The present paper describes a new and practical approach for the one-pot preparation of O-isopropylidene derivatives and also orthogonally protected S- and O-glycosides from the corresponding unprotected saccharides by employing 2 mol % of a silicomolybdic acid (SMA) cluster as a versatile and biocompatible catalyst. The present protocol is applicable to two-step one-pot tandem transformations, which include the O-isopropylidation, spiroketal functionalization, 4,6-O-arylidene acetalations, and arylidene acetylation processes under relatively mild reaction conditions. One-pot sequential transformations, low catalyst loading, rapid transformation, high to excellent reaction yields, mild reaction conditions, and a nontoxic biocompatible workup procedure are the notable advantages of devised protocol.

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.

Synthetic approaches of carbohydrate based self-assembling systems

Carbohydrate-based self-assembling systems are essential for the formation of advanced biocompatible materials via a bottom-up approach. The self-assembling of sugar-based small molecules has applications encompassing many research fields and has been studied extensively. In this focused review, we will discuss the synthetic approaches for carbohydrate-based self-assembling (SA) systems, the mechanisms of the assembly, as well as the main properties and applications. This review will mainly cover recent publications in the last four years from January 2020 to December 2023. We will essentially focus on small molecule self-assembly, excluding polymer-based systems, which include various derivatives of monosaccharides, disaccharides, and oligosaccharides. Glycolipids, glycopeptides, and some glycoconjugate-based systems are discussed. Typically, in each category of systems, the system that can function as low molecular weight gelators (LMWGs) will be discussed first, followed by self-assembling systems that produce micelles and aggregates. The last section of the review discusses stimulus-responsive self-assembling systems, especially those forming gels, including dynamic covalent assemblies, chemical-triggered systems, and photoresponsive systems. The review will be organized based on the sugar structures, and in each category, the synthesis of representative molecular systems will be discussed next, followed by the properties of the resulting molecular assemblies.

Site-selective S-gem-difluoroallylation of unprotected peptides with 3,3-difluoroallyl sulfonium salts

Bench-stable 3,3-difluoroallyl sulfonium salts (DFASs), featuring tunable activity and their editable C-β and gem-difluoroallyl group, proved to be versatile fluoroalkylating reagents for site-selective S-gem-difluoroallylation of cysteine residues in unprotected peptides. The reaction proceeds with high efficiency under mild conditions (ambient temperature and aqueous and weak basic conditions). Various protected/unprotected peptides, especially bioactive peptides, are site-selectively S-gem-difluoroallylated. The newly added gem-difluoroallyl group and other functional groups derived from C-β of DFASs are poised for ligation with bio-functional groups through click and radical chemistry. This stepwise "doubly orthogonal" modification of peptides enables the construction of bioconjugates with enhanced complexity and functionality. This proof of principle is successfully applied to construct a peptide-saccharide-biotin chimeric bioconjugate, indicating its great potential application in medicinal chemistry and chemical biology.

Simultaneous Detection of Micro-RNAs by a Disposable Biosensor via the Click Chemistry Connection Strategy

Simultaneous detection of multiple breast cancer-associated miRNAs significantly raises the accuracy and reliability of early diagnosis. In this work, disposable carbon fiber paper serves as the biosensing interface, linking DNA probes via click chemistry to efficiently capture targets and signals efficiently. DNA probes have multiple recognition domains that trigger a cascade reaction through the helper probes and targets, resulting in two signals output. The signals are centrally encapsulated in the pore of the MIL-88(Fe)-NH2. The signal carriers are directed by signal probes to the recognition domains that correspond to the DNA probes. The biosensor is selective and stable, and it can quantify miRNA-21 and miRNA-155 simultaneously with detection limits of 0.64 and 0.54 fmol/L, respectively. Furthermore, it demonstrates satisfactory performance in tests conducted with normal human serum and cell lysate. Overall, this method makes a satisfactory exploration to realize an inexpensive and sensitive biosensor for multiple biomarkers.

Ferrocenyl-triazole complexes and their use in heavy metal cation sensing

Complexes tris((1-ferrocenyl-1H-1,2,3-triazol-4-yl)methyl)amine (3), bis((1-ferrocenyl-1H-1,2,3-triazol-4-yl)methyl)amine (6), bis((1-ferrocenyl-1H-1,2,3-triazol-4-yl)methyl)ether (7), and 1-ferrocenyl-1H-1,2,3-triazol-4-yl)methanamine (9) were synthesized using the copper-catalyzed click reaction. Complexes 3, 6, 7, and 9 were characterized using NMR (1H and 13{1H}) and IR spectroscopy, elemental analysis, and mass spectrometry. Structures of 3, 7, and 9 in the solid state were determined using single-crystal X-ray diffraction. It was found that the triazole rings were planar and slightly twisted with respect to the cyclopentadienyl groups attached to them. Chains and 3D network structures were observed due to the presence of π⋯π and C-H⋯N interactions between the cyclopentadienyl and triazole ligands. A reversible redox behavior of the Fc groups between 239 and 257 mV with multicycle stability was characteristic for all the compounds, revealing that the electrochemically generated species Fc+ remained soluble in dichloromethane. Electrochemical sensor tests demonstrated the applicability of all the complexes to enhance the quantification sensing behavior of the screen-printed carbon electrode (SPCE) toward Cd2+, Pb2+, and Cu2+ ions.

Analysis of carbohydrates and glycoconjugates by matrix-assisted laser desorption/ionization mass spectrometry: An update for 2021-2022

The use of matrix-assisted laser desorption/ionization (MALDI) mass spectrometry for the analysis of carbohydrates and glycoconjugates is a well-established technique and this review is the 12th update of the original article published in 1999 and brings coverage of the literature to the end of 2022. As with previous review, this review also includes a few papers that describe methods appropriate to analysis by MALDI, such as sample preparation, even though the ionization method is not MALDI. The review follows the same format as previous reviews. It is divided into three sections: (1) general aspects such as theory of the MALDI process, matrices, derivatization, MALDI imaging, fragmentation, quantification and the use of computer software for structural identification. (2) Applications to various structural types such as oligo- and polysaccharides, glycoproteins, glycolipids, glycosides and biopharmaceuticals, and (3) other general areas such as medicine, industrial processes, natural products and glycan synthesis where MALDI is extensively used. Much of the material relating to applications is presented in tabular form. MALDI is still an ideal technique for carbohydrate analysis, particularly in its ability to produce single ions from each analyte and advancements in the technique and range of applications show little sign of diminishing.

Stereoselective synthesis of α-glycosyl azides: allyl glycosyl sulfones as radical precursors

Despite their critical importance in drug development and biochemistry, efficiently synthesizing α-glycosyl azides has continued to pose significant challenges. In this report, we introduce a universal and practical radical reaction for the stereoselective synthesis of α-glycosyl azides using bench-stable allyl glycosyl sulfones as the donor. This method is characterized by its mild reaction conditions, high stereoselectivity, and extensive scope of glycosyl units. Moreover, the accessibility of several structurally complex drug-sugar conjugates underscores the practicality of our approach.

Enantioselective copper-catalyzed azidation/click cascade reaction for access to chiral 1,2,3-triazoles

Chiral 1,2,3-triazoles are highly attractive motifs in various fields. However, achieving catalytic asymmetric click reactions of azides and alkynes for chiral triazole synthesis remains a significant challenge, mainly due to the limited catalytic systems and substrate scope. Herein, we report an enantioselective azidation/click cascade reaction of N-propargyl-β-ketoamides with a readily available and potent azido transfer reagent via copper catalysis, which affords a variety of chiral 1,2,3-triazoles with up to 99% yield and 95% ee under mild conditions. Notably, chiral 1,5-disubstituted triazoles that have not been accessed by previous asymmetric click reactions are also prepared with good functional group tolerance.

Hetero Diels-Alder reactions of isolable N-borylenamines

A new strategy for N-borylenamines by reaction of 2-alkynyl benzyl azides with B(C6F5)3 was developed. This novel 1,3-carboboration reaction proceeded via a 5-exo-dig cyclization/formal 1,1-carboboration/B(C6F5)2 shift reaction sequence. Additionally, N-borylenamines can undergo hetero Diels-Alder (HDA) reactions with a variety of dienophiles. Our results are an attractive complement to HDA reactions.

Synthesis, structural, multitargeted molecular docking analysis of anti-cancer, anti-tubercular, DNA interactions of benzotriazole based macrocyclic ligand

Biologically important macromolecule 1, 1', 3, 3' Bis - [2,3,5,6-Tetramethyl-p-phenylenebis(methylene)] dibenzotriazlinium dibromide hydrate (BTD) was synthesized and characterized using FT-IR, NMR and single-crystal XRD (SCXRD). SCXRD revealed that the compound was crystallized as a monoclinic system and associated through weak intermolecular interactions like H-bonding and π- π stacking interactions. These weak intermolecular interactions in BTD were studied using Crystal Explorer and Gaussian. The calculated energies for the Highest Occupied Molecular Orbital (HOMO) and the Lowest Unoccupied Molecular Orbital (LUMO) showed the stability and reactivity of the title compound. Molecular electrostatic potential (MEP) surface analysis was used to investigate the crystal's nucleophilic and electrophilic reactive sites. The molecular shape and intermolecular interactions in the crystal structure were determined using Hirshfeld surface analysis and fingerprint plots. Anticancer, anti-bacterial and DNA binding ability of BTD were investigated by experimental and theoretical techniques. The obtained results suggest that BTD possesses better anti-cancer, anti-bacterial and DNA binding abilities. The mode of action of antibiotic and anticancer approach was discussed. This provides promising therapeutic advantages for further development.

A New Insight Into The Huisgen Reaction: Heterogeneous Copper Catalyzed Azide-Alkyne Cycloaddition for the Synthesis of 1,4-Disubstituted Triazole (From 2018-2023)

The Huisgen cycloaddition, often referred to as 1,3-Dipolar cycloaddition, is a well-established method for synthesizing 1,4-disubstituted triazoles. Originally conducted under thermal conditions [3+2] cycloaddition reactions were limited by temperature, prolonged reaction time, and regioselectivity. The introduction of copper catalyzed azide-alkyne cycloaddition (CuAAC) revitalized interest, giving rise to the concept of "click chemistry". The CuAAC has emerged as a prominent method for producing 1,2,3-triazole with excellent yields and exceptional regioselectivity even in unfavorable conditions. Copper catalysts conventionally facilitate azide-alkyne cycloadditions, but challenges include instability and recycling issues. In recent years, there has been a growing demand for heterogeneous and porous catalysts in various chemical reactions. Chemists have been more interested in heterogenous catalysts as a result of the difficulties in separating homogenous catalysts from reaction products. These catalysts are favored for their abundant active sites, extensive surface area, easy separation from reaction mixtures, and the ability to be reused. Heterogeneous catalysts have garnered significant attention due to their broad industrial utility, characterized by cost-effectiveness, stability, resistance to thermal degradation, and ease of removal compared to their homogeneous counterparts. The present review covers recent advancements from year 2018 to 2023 in the field of click reactions for obtaining 1,2,3-triazoles through Cu catalyzed 1,3-dipolar azide-alkyne cycloaddition and the properties of the catalyst, reaction conditions such as solvent, temperature, reaction time, and the impact of different heterogeneous copper catalysts on product yield.

Unusual triflic acid-promoted oligomerization of arabinofuranosides during glycosylation

We discovered an unusual triflic acid-promoted oligomerization of arabinofuranosides during glycosylation of the primary hydroxy group of α-(1 → 5)-linked tetraarabinofuranoside bearing 4-(2-chloroethoxy)phenyl aglycone with α-(1 → 5), β-(1 → 2)-linked tetraarabinofuranoside containing N-phenyltrifluoroacetimidoyl leaving group, which led to octa-, dodeca- and hexadecaarabinofuranosides. The possible mechanism of triflic acid-promoted oligomerization was proposed. The choice of promoter was found to be a critical factor for the discovered oligomerization of arabinofuranosides. The obtained octa-, dodeca- and hexadecaarabinofuranosides may serve as useful blocks in the synthesis of oligosaccharide fragments of polysaccharides of Mycobacterium tuberculosis.

Iterative click reactions using trivalent platforms for sequential molecular assembly

A facile synthesis of multi(triazole)s by iterative click reactions is disclosed. Good functional group tolerance of sequential click assembly by sulfur-fluoride exchange (SuFEx), copper-catalyzed azide-alkyne cycloaddition (CuAAC), and thia-Michael reaction realizes the iterative click reactions. Diverse multi(triazole)-type mid-molecules can be synthesized easily from readily available modules through good chemoselective reactions without functional group transformation steps.

Chemical Synthesis of Modified RNA

Ribonucleic acids (RNAs) play a vital role in living organisms. Many of their cellular functions depend critically on chemical modification. Methods to modify RNA in a controlled manner-both in vitro and in vivo-are thus essential to evaluate and understand RNA biology at the molecular and mechanistic levels. The diversity of modifications, combined with the size and uniformity of RNA (made up of only 4 nucleotides) makes its site-specific modification a challenging task that needs to be addressed by complementary approaches. One such approach is solid-phase RNA synthesis. We discuss recent developments in this field, starting with new protection concepts in the ongoing effort to overcome current size limitations. We continue with selected modifications that have posed significant challenges for their incorporation into RNA. These include deazapurine bases required for atomic mutagenesis to elucidate mechanistic aspects of catalytic RNAs, and RNA containing xanthosine, N4-acetylcytidine, 5-hydroxymethylcytidine, 3-methylcytidine, 2'-OCF3, and 2'-N3 ribose modifications. We also discuss the all-chemical synthesis of 5'-capped mRNAs and the enzymatic ligation of chemically synthesized oligoribonucleotides to obtain long RNA with multiple distinct modifications, such as those needed for single-molecule FRET studies. Finally, we highlight promising developments in RNA-catalyzed RNA modification using cofactors that transfer bioorthogonal functionalities.

Asymmetric Pd/Organoboron-Catalyzed Site-Selective Carbohydrate Functionalization with Alkoxyallenes Involving Noncovalent Stereocontrol

Herein, we demonstrate the robustness of a synergistic chiral Pd/organoboron system in tackling a challenging suite of site-, regio-, enantio- and diastereoselectivity issues across a considerable palette of biologically relevant carbohydrate polyols, when prochiral alkoxyallenes were employed as electrophiles. In view of the burgeoning role of noncovalent interactions (NCIs) in stereoselective carbohydrate synthesis, our mechanistic experiments and DFT modeling of the reaction path unexpectedly revealed that NCIs such as hydrogen bonding and CH-π interactions between the resting states of the Pd-π-allyl complex and the borinate saccharide are critically involved in the stereoselectivity control. Our strategy thus illuminates the untapped potential of harnessing NCIs in the context of transition metal catalysis to tackle stereoselectivity challenges in carbohydrate functionalization.

Mechanistic Basis of the Cu(OAc)2 Catalyzed Azide-Ynamine (3 + 2) Cycloaddition Reaction

The Cu-catalyzed azide-alkyne cycloaddition (CuAAC) reaction is used as a ligation tool throughout chemical and biological sciences. Despite the pervasiveness of CuAAC, there is a need to develop more efficient methods to form 1,4-triazole ligated products with low loadings of Cu. In this paper, we disclose a mechanistic model for the ynamine-azide (3 + 2) cycloadditions catalyzed by copper(II) acetate. Using multinuclear nuclear magnetic resonance spectroscopy, electron paramagnetic resonance spectroscopy, and high-performance liquid chromatography analyses, a dual catalytic cycle is identified. First, the formation of a diyne species via Glaser-Hay coupling of a terminal ynamine forms a Cu(I) species competent to catalyze an ynamine-azide (3 + 2) cycloaddition. Second, the benzimidazole unit of the ynamine structure has multiple roles: assisting C-H activation, Cu coordination, and the formation of a postreaction resting state Cu complex after completion of the (3 + 2) cycloaddition. Finally, reactivation of the Cu resting state complex is shown by the addition of isotopically labeled ynamine and azide substrates to form a labeled 1,4-triazole product. This work provides a mechanistic basis for the use of mixed valency binuclear catalytic Cu species in conjunction with Cu-coordinating alkynes to afford superior reactivity in CuAAC reactions. Additionally, these data show how the CuAAC reaction kinetics can be modulated by changes to the alkyne substrate, which then has a predictable effect on the reaction mechanism.

Access to Reverse Glycosyl Azides and Rare Sugar-Based Glycosyl Azides via Radical Decarboxylative Azidation: Divergent Synthesis of 4'-C-Azidonucleosides as Potential Antiviral Agents

The radical decarboxylative azidation of structurally diverse uronic acids has been established as an efficient approach to reverse glycosyl azides and rare sugar-derived glycosyl azides under the action of Ag2CO3, 3-pyridinesulfonyl azide, and K2S2O8. The power of this method has been highlighted by the divergent synthesis of 4'-C-azidonucleosides using Vorbrüggen glycosylation of nucleobases with 4-C-azidofuranosyl acetates. The antiviral assessment of the resulting nucleosides revealed one compound as a potential inhibitor of covalently closed circular DNA.

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.

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.

Exploring bi-carbazole-linked triazoles as inhibitors of prolyl endo peptidase via integrated in vitro and in silico study

A serine protease called prolyl endopeptidase (PEP) hydrolyses the peptide bonds on the carboxy side of the proline ring. The excessive PEP expression in brain results in neurodegenerative illnesses like dementia, Alzheimer's disease, and Parkinson's disease. Results of the prior studies on antioxidant activity, and the non-cytotoxic effect of bi-carbazole-linked triazoles, encouraged us to extend our studies towards its anti-diabetic potential. Hence, for this purpose all compounds 1-9 were evaluated to reveal their anti-prolyl endo peptidase activity. Fortunately, seven compounds resulted into significant inhibitory capability ranging from 26 to 63 µM. Among them six compounds 4-9 exhibited more potent inhibitory activity with IC50 values 46.10 ± 1.16, 42.30 ± 1.18, 37.14 ± 1.21, 26.29 ± 0.76, 28.31 ± 0.64 and 31.11 ± 0.84 µM respectively, while compound 3 was the least active compound in the series with IC50 value 63.10 ± 1.58 µM comparing with standard PEP inhibitor bacitracin (IC50 = 125 ± 1.50 µM). Moreover, mechanistic study was performed for the most active compounds 7 and 8 with Ki values 24.10 ± 0.0076 and 23.67 ± 0.0084 µM respectively. Further, the in silico studies suggested that the compounds exhibited potential interactions and significant molecular conformations, thereby elucidating the structural basis for their inhibitory effects.

Enzyme-Mediated Bioorthogonal Cascade Catalytic Reaction for Metabolism Intervention and Enhanced Ferroptosis on Neuroblastoma

It remains a tremendous challenge to explore effective therapeutic modalities against neuroblastoma, a lethal cancer of the sympathetic nervous system with poor prognosis and disappointing treatment outcomes. Considering the limitations of conventional treatment modalities and the intrinsic vulnerability of neuroblastoma, we herein develop a pioneering sequential catalytic therapeutic system that utilizes lactate oxidase (LOx)/horseradish peroxidase (HRP)-loaded amorphous zinc metal-organic framework, named LOx/HRP-aZIF, in combination with a 3-indole-acetic acid (IAA) prodrug. On the basis of abnormal lactate accumulation that occurs in the tumor microenvironment, the cascade reaction of LOx and HRP consumes endogenous glutathione and a reduced form of nicotinamide adenine dinucleotide to achieve the first stage of killing cancer cells via antioxidative incapacitation and electron transport chain interference. Furthermore, the generation of reactive oxygen species induced by HRP and IAA through bioorthogonal catalysis promotes ferritin degradation and lipid peroxidation, ultimately provoking self-enhanced ferroptosis with positive feedback by initiating an endogenous Fenton reaction. This work highlights the superiority of the natural enzyme-dependent cascade and bioorthogonal catalytic reaction, offering a paradigm for synergistically enzyme-based metabolism-ferroptosis anticancer therapy.

Clickable X-ray Nanoprobes for Nanoscopic Bioimaging of Cellular Structures

Synchrotron-based X-ray microscopy (XRM) has garnered widespread attention from researchers due to its high spatial resolution and excellent energy (element) resolution. Existing molecular probes suitable for XRM include immune probes and genetic labeling probes, enabling the precise imaging of various biological targets within cells. However, immune labeling techniques are prone to cross-interference between antigens and antibodies. Genetic labeling technologies have limited systems that allow express markers independently, and moreover, genetically encoded labels based on catalytic polymerization lack a fixed morphology. When applied to cell imaging, this can result in reduced localization accuracy due to the diffusion of labels within the cells. Therefore, both techniques face challenges in simultaneously labeling multiple biotargets within cells and achieving high-precision imaging. In this work, we applied the click reaction and developed a third category of imaging probes suitable for XRM, termed clickable X-ray nanoprobes (Click-XRN). Click-XRN consists of two components: an X-ray-sensitive multicolor imaging module and a particle-size-controllable morphology module. Efficient identification of intra- and extracellular biotargets is achieved through click reactions between the probe and biomolecules. Click-XRN possesses a controllable particle size, and its loading of various metal ions provides distinctive signals for imaging under XRM. Based on this, we optimized the imaging energy of Click-XRN with different particle sizes, enabling single-color and two-color imaging of the cell membrane, cell nucleus, and mitochondria with nanoscale spatial nanometers. Our work provides a potent molecular tool for investigating cellular activities through XRM.

What is the future of click chemistry in drug discovery and development?

INTRODUCTION

The concept of click chemistry was introduced in 2001 as an effective, efficient, and sustainable approach to making functional groups harnessing the thermodynamic properties of a set of known chemical reactions that are based on nature. Some of the most common examples include reactions that produce 1,2,3-triazoles, which have been used with great success in drug discovery and development, and in chemical biology. The reactions unite two molecules quickly and irreversibly, and the reactions can be performed inside living cells, without harming the cell.

AREAS COVERED

The main focus of this perspective is the future of click chemistry in drug discovery and development, exemplified by novel click chemistry approaches and other aspects of the drug development enterprise, like SPAAC and analogous techniques, PROTACs, as well as diversity-oriented click chemistry.

EXPERT OPINION

Drug discovery and development has benefited enormously from the amazing advances that have been made in the field of click chemistry since 2001. The methods most likely to have the most future applications include metal-catalyzed azide-alkyne cycloadditions giving 1,2,3-triazoles, SPAAC for medical diagnostics and vaccine development, other congeners, Sulfur-Fluoride Exchange (SuFEx) and Diversity-Oriented Clicking (DOC), a concept with diverse molecular methodology with the potential for obtaining extensive molecular diversity.