Azide-alkyne Cycloaddition Reaction Research Articles

Expanding the synthesis of a library of potent glucuronic acid glycodendrons for Dengue virus inhibition

Multivalent glycodendrons are valuable tools to mimic many structural and functional features of cell-surface glycoconjugates and its focal position scaffolds represent important components to increase specificity and affinity. Previous work in our group described the preparation of a tetravalent glucuronic acid dendron that binds with good affinity to Dengue virus envelope protein (KD = 22 μM). Herein, the chemical synthesis and binding analysis of a new library of potent glucuronic acid dendrons bearing different functional group at the focal position and different level of multivalency are described. Their chemical synthesis was performed sequentially in three stages and with good yields. Namely a) the chemical synthesis of the oligo and polyalkynyl scaffolds, b) assembling with fully protected glucuronic acid-based azide units by using a microwave assisted copper-catalysed azide-alkyne cycloaddition reaction and c) sequential deprotection of hydroxyl and carboxylic acid groups.Surface Plasmon Resonance studies have demonstrated that the valency and the focal position functional group exert influence on the interaction with Dengue virus envelope protein. Molecular modelling studies were carried out in order to understand the binding observed. This work reports an efficient glycodendrons chemical synthesis that provides appropriate focal position functional group and multivalence, that offer an easy and versatile strategy to find new active compounds against Dengue virus.

Fe3O4@Zein nanocomposites decorated with copper(II) as an efficient, durable, and biocompatible reusable catalyst for click synthesis of novel fluorescent 1,4-disubstituted-1,2,3-triazoles in water

In this paper, we have constructed Fe3O4@Zein-Cu(II) NPs as a novel reusable heterogeneous and superparamagnetic catalyst in Cu-catalysed azide-alkyne cycloaddition reactions (CuAAC). This magnetic Cu(II) nanocomposites were characterized by fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), energy dispersive X-ray analysis (EDX), thermogravimetric analysis (TGA), vibration sample magnetometer (VSM) and X-ray photoelectron spectroscopy (XPS). This biocompatible and inexpensive magnetic nanocomposite catalyses smoothly the regioselective click preparation of new fluorescent 1,4-disubstituted-1,2,3-triazoles of 1,8-naphthilimide and 3-nitrophthalimide with quantum yields 0.153 to 0.371 in good to excellent yields under mild conditions in H2O without using any ligands and reducing agents. The catalyst could be easily recovered with the aid of an external magnet and reused up to seven consecutive runs without significant reduction in its activity.

Synthesis and self-assembly properties of the first fluorescein-based hexacatenar mesogens

First series of fluorescein-based hexacatenar mesogens consisting of a central fluorescein unit and two 1,2,3-triazole dendritic wings were designed and synthesized by using the Williamson reaction and Cu-assisted alkyne-azide cycloaddition reaction. Polarized optical microscopy textures, differential scanning calorimetry curves, and X-ray diffraction (XRD) data demonstrated that all the compounds can self-assemble into hexagonal columnar mesophases. Organogel test demonstrated that these compounds could form organogel in some moderate polar solvents with irregularly winkled morphologies. Density functional theory calculation demonstrated that these mesogens adopted distorted conformation which might be the reason why narrow mesogenic temperature ranges and irregularly winkled morphologies in these compounds are observed.

Photoswitchable Azoheteroarene-Based Chelating Ligands: Light Modulation of Properties, Aqueous Solubility and Catalysis.

We report the design and synthesis of eight photoswitchable phenylazopyridine- and phenylazopyrazole-based molecular systems as chelation-type light-controllable ligands. Besides the studies on fundamental photoisomerization behaviour, the ligands were also screened for light-tuneable properties such as photochromism, phase transition, and solubility, especially in the aqueous medium. This investigation demonstrates how the modulation of aqueous solubility can be achieved through photoisomerization and can further be utilized towards controlling the amount of catalytically active Cu(I) species in the aqueous conditions. Through this approach, light control over the catalytic activity was achieved for Cu-catalyzed azide-alkyne cycloaddition (CuAAC) reactions, along with a partial recovery of the catalytically active species.

New Boron Containing Acridines: Synthesis and Preliminary Biological Study.

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

Self-Assembly of an Anionic [Cu5I8]3- Supramolecular Cluster Driven by Ion-Pair Interaction and Catalytic Properties.

The rational design and controlling synthesis of an anionic cuprous iodide supramolecular cluster with high nuclearity through noncovalent interactions remains a significant challenge. Herein, a cationic organic ligand (L1)3+ was driven by anion-cation ion-pair electrostatic interaction to induce free cuprous iodide to aggregate into an anionic supramolecular cluster, [(Cu5I8)3-(L1)3+] (C1). Moreover, five copper(I) atoms bind with eight iodides through multiply bridged Cu-I bonds associated with intramolecular cuprophilic interactions in this butterfly-shaped cluster core. Supramolecular cluster C1 exhibited a solid-state emission at 380 nm and an emission at 405 nm in acetonitrile at room temperature, respectively. Interestingly, this unprecedented cuprous iodide cluster demonstrated a good catalytic performance for azide-alkyne cycloaddition reaction (CuAAC) and the catalytic yield can be up to 80% for eight different substrates at 80 °C. Furthermore, the density functional theory (DFT) calculation revealed that the thermodynamic-dependent cycloaddition reaction underwent a four-step pathway with an overall energy barrier of -43.6 kcal mol-1 on the basis of intermediates monitored by mass spectrum.

Synthesis, X-ray crystallography, antimicrobial, molecular docking, and DFT study of bis-triazoles linked ampyrone

A new class of bis-triazoles linked with ampyrone molecules was synthesized from ampyrone-linked bis-alkyne with different benzyl azides under Cu(I)-catalyzed azide-alkyne cycloaddition (CuAAC) reaction. All compounds were characterized by FTIR, 1H NMR, 13C NMR, and ESI-MS data. However, the structures of solid crystalline compounds 4a and 4h were finally supported by X-ray crystallographic data. In vitro, antimicrobial activity results of synthesized alkyne 2 and bis-1,2,3-triazoles 4a-4k showed that the incorporation of triazole units has augmented the antimicrobial activity of all compounds, except 4a for E. coli. Also, compound 4f was found potent against all bacterial strains (E. coli, S. aureus, and P. aeruginosa, each with MIC: 0.0178 µmol/mL) with superior efficacy to B. subtilis (MIC: 0.0089 µmol/mL) compared to standard antibacterial drug ciprofloxacin (MIC: 0.0094 µmol/m). Almost all synthesized triazoles showed superior potency to both fungal strains except 4a, 4g, and 4k against R. oryaze, C. albicans, and R. oryaze, respectively. Computational molecular docking and DFT results supported experimental antimicrobial results for improvement in the activity of all triazoles except 4a.

Exploring the Chemical Properties and Medicinal Applications of Tetramethylthiocycloheptyne Sulfoximine Used in Strain-Promoted Azide-Alkyne Cycloaddition Reactions.

The recently developed compound, tetramethylthiocycloheptyne sulfoximine (TMTHSI), has shown to be a promising strained alkyne for strain-promoted azide-alkyne cycloaddition (SPAAC), metal-free click chemistry. This research explores the properties of TMTHSI-based compounds via three aspects: (1) large-scale production, (2) unique stability in acidic conditions and its subsequent use in peptide synthesis, and (3) the functionalization of antibodies. Here, it is shown that (1) scale-up is achieved on a scale of up to 100 g. (2) TMTHSI is remarkably stable against TFA allowing for the site-specific functionalization of peptides on resin. Finally, (3) the functionalization of an antibody with a model payload is very efficient, with antibody conjugation demonstrating more beneficial features such as a high yield and limited hydrophobicity as compared to other alkyne reagent conjugates. These results illustrate the high potential of TMTHSI for diverse bioconjugation applications, with production already being GMP-compatible and a highly efficient conversion resulting in attractive costs of goods.

Synthesis of a Series of Trimeric Branched Glycoconjugates and Their Applications for Supramolecular Gels and Catalysis.

Carbohydrate-derived molecular gelators have found many practical applications as soft materials. To better understand the structure and molecular gelation relationship and further explore the applications of sugar-based gelators, we designed and synthesized eight trimeric branched sugar triazole derivatives and studied their self-assembling properties. These included glucose, glucosamine, galactose, and maltose derivatives. Interestingly, the gelation properties of these compounds exhibited correlations with the peripheral sugar structures. The maltose derivative did not form gels in the tested solvents, but all other compounds exhibited gelation properties in at least one of the solvents. Glucose derivatives showed superior performance, followed by glucosamine derivatives. They typically formed gels in toluene and alcohols; some formed gels in ethanol-water mixtures or DMSO water mixtures. The glycoclusters 9 and 10 demonstrated rate acceleration for the copper-catalyzed azide-alkyne cycloaddition (CuAAC) reactions. These were further studied for their metallogels formation properties, and the copper metallogels from compound 9 were successfully utilized to catalyze click reactions. These metallogels were able to form a gel column, which was effective in converting the reactants into the triazole products in multiple cycles. Moreover, the same gel column was used to transform a second click reaction using different reactants. The synthesis and characterization of these compounds and their applications for catalytic reactions were discussed.

Synthesis of 1,2,3-Triazole-Containing Methoxylated Cinnamides and Their Antileishmanial Activity against the Leishmania braziliensis Species.

Leishmaniasis is a group of infectious diseases caused by protozoan parasites that belong to the genus Leishmania. Currently, there is no human vaccine, and the available treatments are associated with toxicity, high cost, and the emergence of resistant strains. These factors highlight the need to identify new antileishmanial candidates. In this study, we synthesized twenty-four methoxylated cinnamides containing 1,2,3-triazole fragments and evaluated their antileishmanial activity against the Leishmania braziliensis species, which is the main etiological agent responsible for American Tegumentary Leishmaniasis (ATL). The cinnamides were synthetically prepared using nucleophilic acyl substitution and copper(I)-catalyzed azide-alkyne cycloaddition (CuAAC) reactions. The compounds were characterized using infrared, nuclear magnetic resonance, and high-resolution mass spectrometry techniques. We performed preliminary studies to evaluate the biological activity of these compounds against L. braziliensis promastigotes and axenic amastigotes. Compound 28, N-((1-(7-(diethylamino)-2-oxo-2H-chromen-3-yl)-1H-1,2,3-triazole-4-yl) methyl)-3,4-dimethoxy cinnamide, demonstrated relevant antileishmanial activity with low toxicity in murine cells. The selectivity index values for this compound were superior compared with data obtained using amphotericin B. Furthermore, this cinnamide derivative reduced the infection percentage and number of recovered amastigotes in L. braziliensis-infected macrophages. It also induced an increase in reactive oxygen species production, depolarization of the mitochondrial potential, and disruption of the parasite membrane. Taken together, these findings suggest that this synthetic compound holds potential as an antileishmanial candidate and should be considered for future studies in the treatment of ATL.

Sonochemical parallel synthesis of novel 1,2,3-triazoles utilizing gold-supported titania catalyst

BackgroundA lower carbon society can be achieved with innovative recycling and parallel organic and pharmaceutical synthesis practices that reduce the chemical industry's environmental footprint; this is crucial to fulfilling the principles of green chemistry and engineering. MethodRegioselective azide-alkyne cycloadditions were investigated using heterogeneous catalysts based on gold supported on titania (Au/TiO2) and ultrasonic irradiation. The catalysts were used in the base-free synthesis of 1,2,3-triazoles via azide-alkyne click reactions. The catalyzed azide-alkyne cycloaddition reaction protocol was completed in a short amount of time (5 min) with high product yields in parallel synthesis design Significant findingThe superior catalytic efficacy of Au/TiO2 catalysts for achieving the highest product yield emphasizes the ultimate sympathetic of the catalyst structure and role. The scanning electron microscope (SEM) was used to distinguish the synergetic effect of Au/TiO2 catalysts, and the ultrasound irradiation tool for fresh and spent catalysts. Furthermore, the Heteronuclear Multiple Bond Correlation (HMBC) 2D NMR technique was used as a valuable tool to unambiguously assign the obtained structures.

Enolate-Azide [3 + 2]-Cycloaddition Reaction Suitable for DNA-Encoded Library Synthesis.

The DNA-encoded chemical library (DEL) is a powerful hit selection technique in either basic science or innovative drug discovery. With the aim to circumvent the issue concerning DNA barcode damage in a conventional on-DNA copper-catalyzed azide-alkyne cycloaddition reaction (CuAAC), we have successfully developed the first DNA-compatible enolate-azide [3 + 2] cycloaddition reaction. The merits of this DEL chemistry include metal-free reaction and high DNA fidelity, high conversions and easy operation, broad substrate scope, and ready access to the highly substituted 1,4,5-trisubstituted triazoles. Thus, it will not only further enrich the DEL chemistry toolbox but also will have great potential in practical DEL synthesis.

Assembly drives regioselective azide-alkyne cycloaddition reaction

Azide-alkyne cycloaddition reaction is a very common organic reaction to synthesize nitrogen-containing heterocycles. Once catalyzed by Cu(I) or Ru(II), it turns out to be a click reaction and thus is widely applied in chemical biology for labeling. However, besides their poor regioselectivity towards this reaction, these metal ions are not biologically friendly. Hence, it is an urgent need to develop a metal-free azide–alkyne cycloaddition reaction for biomedical applications. In this work, we found that, in the absence of metal ions, supramolecular self-assembly in an aqueous solution could realize this reaction with excellent regioselectivity. Nap-Phe-Phe-Lys(azido)-OH firstly self-assembled into nanofibers. Then, Nap-Phe-Phe-Gly(alkynyl)-OH at equivalent concentration approached to react with the assembly to yield the cycloaddition product Nap-Phe-Phe-Lys(triazole)-Gly-Phe-Phe-Nap to form nanoribbons. Due to space confinement effect, the product was obtained with excellent regioselectivity. Employing the excellent properties of supramolecular self-assembly, we are applying this strategy to realize more reactions without metal ion catalysis.

A Click Chemistry-Based Artificial Metallo-Nuclease.

Artificial metallo-nucleases (AMNs) are promising DNA damaging drug candidates. Here, we demonstrate how the 1,2,3-triazole linker produced by the Cu-catalysed azide-alkyne cycloaddition (CuAAC) reaction can be directed to build Cu-binding AMN scaffolds. We selected biologically inert reaction partners tris(azidomethyl)mesitylene and ethynyl-thiophene to develop TC-Thio, a bioactive C3 -symmetric ligand in which three thiophene-triazole moieties are positioned around a central mesitylene core. The ligand was characterised by X-ray crystallography and forms multinuclear CuII and CuI complexes identified by mass spectrometry and rationalised by density functional theory (DFT). Upon Cu coordination, CuII -TC-Thio becomes a potent DNA binding and cleaving agent. Mechanistic studies reveal DNA recognition occurs exclusively at the minor groove with subsequent oxidative damage promoted through a superoxide- and peroxide-dependent pathway. Single molecule imaging of DNA isolated from peripheral blood mononuclear cells shows that the complex has comparable activity to the clinical drug temozolomide, causing DNA damage that is recognised by a combination of base excision repair (BER) enzymes.

A Polyoxometalate-Based Pathologically Activated Assay for Efficient Bioorthogonal Catalytic Selective Therapy.

Since polyoxometalates (POMs) can undergo reversible multi-electron redox transformations, they have been used to modulate the electronic environment of metal nanoparticles for catalysis. Besides, POMs possess unique electronic structures and acid-responsive self-assembly ability. These properties inspire us to tackle the drawbacks of the well-known copper-catalyzed azide-alkyne cycloaddition (CuAAC) reaction when applied in biomedical applications, such as low catalytic efficiency and unsatisfactory disease selectivity in living systems. Herein, we construct the molybdenum (Mo)-based POM nanoclusters doped with Cu (Cu-POM NCs) as a highly efficient bioorthogonal catalyst, which is responsive to pathologically acid and H2S for selective antibiofilm therapy. Leveraging the merits of POM, the Cu-POM NCs exhibit biofilm-responsive self-assemble behavior, efficient CuAAC reactions-mediated in situ synthesis of antibacterial molecules, and NIR-II photothermal effect selectively triggered by H2S in pathogens. It should be noted that the consumption of bacterial H2S at the pathological site by Cu-POM NCs extremely decreases the number of persister bacteria, which is conducive to the inhibition of bacterial tolerance and elimination of biofilms. Unlocked at pathological sites and endowed with NIR-II photothermal property, the constructed POM-based bioorthogonal catalytic platform provides new insights into the design of efficient and selective bioorthogonal catalysts for disease therapy.

Synthesis and characterization a new polyoxomolybdate C34H114Fe2Mo12N18Na2O66 and study of its catalytic activity in the production of 1,2,3-triazoles

A new polyoxomolybdate, [(C6H12N4-CH3)2Na2(H2O)8](C6H12N4-CH3)2[(H0.5)N(CH2O)3FeMo6O18.5(OH)2.5]2·10H2O (1), was synthesized. The structure of the synthesized polyoxomolybdate was investigated by single-crystal X-ray diffraction analysis and several other identification techniques such as FTIR and EDX analysis. Each unit cell of 1 contains one cation [(C6H12N4-CH3)2Na2(H2O)8]4+ and two hexamethylenetetramine cations (C6H12N4-CH3)+, and two polyanions [(H0.5)N(CH2O)3FeMo6O18.5(OH)2.5]3– with ten water molecules in the crystal lattice. In the polyanion, molybdenum ions are bonded to two terminal oxygen atoms and two μ2- (Mo-Mo) and μ3- (Mo-Fe-Mo) bridging oxygen atoms. Iron in the center of the polyanion 1 is also surrounded by three deprotonated oxygens of trimethanolamine ligand and three μ3- (Mo-Fe-Mo) bridging oxygen atoms. This new polyoxomolybdate was used as an efficient catalyst in the azide–alkyne cycloaddition reaction to produce various 1,2,3-triazoles with high yields. Additional investigations reveal this catalytic system can be refreshed and utilized for up to six successive applications.

Synthesis and biological evaluation of carbohydrate-Coumarin/vanillic acid hybrid as a promising antiparasitic agent

Leishmaniasis is caused by infection with the protozoan parasites Leishmania. It is classified as one of the most significant neglected tropical diseases. It remains a significant global public health concern. Current treatments include the use of pentavalent antimonial, amphotericin B, pentamidine, miltefosine, and paromomycin. However, several limitations such as toxicity, side effect, and resistance to these drugs of certain species are of concern. To combat this disease, effective chemotherapy is urgently required for its treatment and management. In this study, we synthesized a series of carbohydrate-coumarin/vanillic acid hybrids linked through triazole moiety via CuACC (Copper-catalysed azide-alkyne cycloaddition) reaction. These compounds were evaluated for their in vitro antiparasitic activity using MTT assay against Leishmania donovani whereas, all compounds show IC50 value in the range of 65–74 μM.

Two-Step Validation Approach for Tools To Study the DNA Repair Enzyme SNM1A.

We report a two-step validation approach to evaluate the suitability of metal-binding groups for targeting DNA damage-repair metalloenzymes using model enzyme SNM1A. A fragment-based screening approach was first used to identify metal-binding fragments suitable for targeting the enzyme. Effective fragments were then incorporated into oligonucleotides using the copper-catalysed azide-alkyne cycloaddition reaction. These modified oligonucleotides were recognised by SNM1A at >1000-fold lower concentrations than their fragment counterparts. The exonuclease SNM1A is a key enzyme involved in the repair of interstrand crosslinks, a highly cytotoxic form of DNA damage. However, SNM1A and other enzymes of this class are poorly understood, as there is a lack of tools available to facilitate their study. Our novel approach of incorporating functional fragments into oligonucleotides is broadly applicable to generating modified oligonucleotide structures with high affinity for DNA damage-repair enzymes.

Click and bioorthogonal hyaluronic acid hydrogels as an ultra-tunable platform for the investigation of cell-material interactions.

The cellular microenvironment plays a major role in the biological functions of cells. Thus, biomaterials, especially hydrogels, which can be design to mimic the cellular microenvironment, are being increasingly used for cell encapsulation, delivery, and 3D culture, with the hope of controlling cell functions. Yet, much remains to be understood about the effects of cell-material interactions, and advanced synthetic strategies need to be developed to independently control the mechanical and biochemical properties of hydrogels. To address this challenge, we designed a new hyaluronic acid (HA)-based hydrogel platform using a click and bioorthogonal strain-promoted azide-alkyne cycloaddition (SPAAC) reaction. This approach facilitates the synthesis of hydrogels that are easy to synthesize and sterilize, have minimal swelling, are stable long term, and are cytocompatible. It provides bioorthogonal HA gels over an uncommonly large range of stiffness (0.5-45kPa), all forming within 1-15min. More importantly, our approach offers a versatile one-pot procedure to independently tune the hydrogel composition (e.g., polymer and adhesive peptides). Using this platform, we investigate the independent effects of polymer type, stiffness, and adhesion on the secretory properties of human adipose-derived stromal cells (hASCs) and demonstrate that HA can enhance the secretion of immunomodulatory factors by hASCs.

Bioorthogonal Metabolic Labeling Experiments to Introduce Undergraduate Students to Interdisciplinarity at the Interface of Chemistry and Biology

Chemists have always designed and deployed cross-disciplinary approaches that interface chemistry with other disciplines to proffer solutions to many human problems. We designed a laboratory experiment that implements chemistry concepts in a biological model to prime undergraduate students to appreciate interdisciplinarity as an approach to solving complex problems in contemporary society. The experiments can also be implemented with graduate students transitioning to chemical biology research. The experiment introduces students to classical and emerging chemistry and molecular biology techniques─mammalian cell culture, bioorthogonal metabolic labeling, azide–alkyne cycloaddition reaction (“click” chemistry), microplate photometry, gel electrophoresis, and far-western blot analysis─that are routinely used in research at the interface of chemistry and biology. The students cultured a Chinese hamster ovary cell line (CHO-K1) and metabolically labeled the cellular sialoglycans with azide groups. Next, they used a click chemistry reaction to bioconjugate a fluorogenic molecule to the labeled sialoglycans, enabling the detection of the glycans using microplate photometry or far-western blot analysis. The experiment created a context for a first-hand demonstration of bioorthogonal chemical reaction, a concept novel to most undergraduates with traditional chemistry (organic, inorganic, physical chemistry, and analytical) background. The experience allows the students to apply and connect organic chemistry, bioanalytical chemistry, and molecular biology concepts while learning techniques such as microplate reading, SDS PAGE, and western blot imaging that are indispensable to the growing fields of drug discovery, chemical toxicology, chemical biology, and molecular biology. This experiment is ideal for preparing and motivating students to pursue future research opportunities at the interface of chemistry and biology.