Search Results (11)

Cysteine plays a crucial role in the development of an efficient copper-catalyst system, where its thiol group serves as a strong anchoring site for metal coordination. By immobilizing copper onto cysteine-modified, polydopamine-coated magnetite particles, this advanced catalytic platform exhibits exceptional stability and catalytic activity. Chemical modification of the polydopamine (PDA) surface with cysteine enhances copper salt immobilization, leading to the formation of the Fe₃O₄@PDA-Cys@Cu platform. This system was evaluated in palladium-free, copper-catalyzed Sonogashira coupling reactions, effectively catalyzing the coupling of terminal acetylenes with aryl halides. Additionally, the Fe₃O₄@PDA-Cys@Cu platform was employed in click reactions, confirming the enhanced catalytic efficiency due to increased copper content. The reusability of the platform was further investigated, demonstrating improved performance, especially in recyclability tests in click reaction, making it a promising candidate for sustainable heterogeneous catalysis. Full article

Radiolabeled peptides are valuable tools for diagnosis or therapies; they are often radiofluorinated using an indirect approach based on an F-18 prosthetic group. Herein, we are reporting our results on the F-18 radiolabeling of three peptides using two different methods based on click reactions. The first one used the well-known CuAAC reaction, and the second one is based on our recently reported hetero-Diels–Alder (HDA) using a dithioesters (thia-Diels–Alder) reaction. Both methods have been automated, and the ¹⁸F-peptides were obtained in similar yields and synthesis time (37–39% decay corrected yields by both methods in 120–140 min). However, to obtain similar yields, the CuAAC needs a large amount of copper along with many additives, while the HDA is a catalyst and metal-free reaction necessitating only an appropriate ratio of water/ethanol. The HDA can therefore be considered as a minimalist method offering easy access to fluorine-18 labeled peptides and making it a valuable additional tool for the indirect and site-specific labeling of peptides or biomolecules. Full article

ZIF-8 and ZIF-67 containing various percentages of copper were successfully synthesized through a green in-situ thermal (IST) approach based on 2-methylimidazole (2-MIM) as the organic linker. The IST method has several advantages over previously reported studies, including solvent and additive-free reaction conditions, a mild reaction temperature, a single-step procedure, no activation requirements, and the use of the smallest precursor ratio (M/L). The high catalytic performance of Cu/ZIF-8 and Cu/ZIF-67 in click chemistry is attributed to their high specific surface area, excellent porosity, and structural stability. To achieve these features, a range of parameters—such as time, temperature, gas atmosphere, and precursor ratio—were optimized. Several characterization methods were used to confirm the features of the produced catalysts. Overall, the synthesis strategy for achieving the targeted ZIFs with unique features is “green” and does not require further activation or treatment to eliminate side products. This method has great potential for manufacturing metal-organic frameworks on a large scale. Moreover, water was used as a solvent during the click reaction, resulting in high yields and making this an attractive, green, and eco-friendly procedure. Full article

The 1,2,3-triazoles are an important class of organic compounds that are found in a variety of biologically active compounds. The most usual and efficient methodology to synthetize these compounds is the Copper-catalyzed Azide–Alkyne Cycloaddition (CuAAC), preferably by use of click chemistry principles. Therefore, the development of simple, robust, easily accessible and efficient materials as catalysts for this kind of reaction is highly desirable. In this sense, layered hydroxide salts (LHS) emerge as an interesting alternative for the click reaction. Thus, we describe herein the preparation and characterization of copper (II) layered hydroxide salts and their application as catalysts for the CuAAC reaction under solvent-free conditions. This synthetic methodology of CuAAC reaction is attractive as it follows several concepts of green chemistry, such as being easy to perform, allowing purification without chromatographic column, the process forming no sub-products, affording the desired 1,2,3-traizoles in the specific 1,4-disubstituted position in high yield, and having a short reaction time. Moreover, the photocatalysis for the degradation of methyl orange was also highly efficient using the same catalyst. Full article

CuAAC (Cu catalyzed azide-alkyne cycloaddition) click-reaction is a simple and powerful method for the post-synthetic modification of organometallic complexes of transition metals. This approach allows the selective introduction of additional donor sites or functional groups to the periphery of the ligand environment. This is especially important if a metalloligand with free donor sites, which are of the same nature as the primary site for the coordination of the primary metal, has to be created. The concept of post-synthetic modification of organometallic complexes by click-reaction is relatively recent and the currently available experimental material does not yet allow us to identify trends and formulate recommendations to address specific problems. In the present study, we have applied the CuAAC reaction for the post-synthetic modification of diimine mononuclear complexes Re(I), Pt(II) and Ir(III) with C≡C bonds at the periphery of the ligand environment and demonstrated that click-chemistry is a powerful tool for the tunable chemical post-synthetic modification of coordination compounds. Full article

Nanoparticles have emerged as versatile carriers for various therapeutics and can potentially treat a wide range of diseases in an accurate and disease-specific manner. Polymeric biomaterials have gained tremendous attention over the past decades, owing to their tunable structure and properties. Aliphatic polyesters have appealing attributes, including biodegradability, non-toxicity, and the ability to incorporate functional groups within the polymer backbone. Such distinctive properties have rendered them as a class of highly promising biomaterials for various biomedical applications. In this article, well-defined alkyne-functionalized poly(ethylene glycol)-b-poly(ε-caprolactone) (PEG-b-PCL) diblock copolymer was synthesized and studied for pH-responsive delivery of doxorubicin (DOX). The alkyne-functionalized PEG-b-PCL diblock copolymer was prepared by the synthesis of an alkyne-functionalized ε-caprolactone (CL), followed by ring-opening polymerization (ROP) using PEG as the macroinitiator. The alkyne functionalities of PEG-b-PCL were modified through copper(I)-catalyzed alkyne-azide cycloaddition (CuAAC) click reaction to graft aldehyde (ALD) groups and obtain PEG-b-PCL-g-ALD. Subsequently, DOX was conjugated on PEG-b-PCL-g-ALD through the Schiff base reaction. The resulting PEG-b-PCL-g-DOX polymer-drug conjugate (PDC) self-assembled into a nano-sized micellar structure with facilitated DOX release in acidic pH due to the pH-responsive linkage. The nanostructures of PDC micelles were characterized using transmission electron microscopy (TEM) and dynamic light scattering (DLS). In vitro studies of the PDC micelles, revealed their improved anticancer efficiency towards MCF-7 cells as compared to free DOX. Full article

We report a versatile divergent methodology to construct dendrimers from a tetrafunctional core, utilizing the robust copper(I) catalyzed alkyne-azide cycloaddition (CuAAC, “click”) reaction for both dendrimer synthesis and post-synthesis functionalization. Dendrimers of generations 1–3 with 8–32 protected or free OH and acetylene surface groups, were synthesized using building blocks that included acetylene- or azide-terminated molecules with carboxylic acid or diol end groups, respectively. The acetylene surface groups were subsequently used to covalently link cationic amino groups. A preliminary evaluation indicated that the generation one dendrimer with terminal NH₃⁺ groups was the most effective bactericide, and it was more potent than several previously studied dendrimers. Our results suggest that size, functional end groups and hydrophilicity are important parameters to consider in designing efficient antimicrobial dendrimers. Full article

Based on a common structural core of 4,5,6,7-tetrahydro[1,2,3]triazolo[1,5-a]pyridine, a number of bicyclic triazolium ionic liquids 1–3 were designed and successfully prepared. In our hands, this optimized synthesis of ionic liquids 1 and 2 requires no chromatographic separation. Also in this work, ionic liquids 1, 2 were shown to be efficient ionic solvents for fast synthesis of tryptanthrin natural product. Furthermore, a new affinity ionic liquid 3 was tailor-synthesized and displayed its effectiveness in chemoselective extraction of both Cu(II) ions and, for the first time, histidine-containing peptides. Full article

The ball-mill-based mechanochemical activation of metallic copper powder facilitates solvent-free alkyne-azide click reactions (CuAAC). All parameters that affect reaction rate (i.e., milling time, revolutions/min, size and milling ball number) have been optimized. This new, efficient, facile and eco-friendly procedure has been tested on a number of different substrates and in all cases afforded the corresponding 1,4-disubstituted 1,2,3-triazole derivatives in high yields and purities. The final compounds were isolated in almost quantitative overall yields after simple filtration, making this procedure facile and rapid. The optimized CuAAC protocol was efficiently applied even with bulky functionalized β-cyclodextrins (β-CD) and scaled-up to 10 g of isolated product. Full article

The increasing application of positron emission tomography (PET) in nuclear medicine has stimulated the extensive development of a multitude of novel and versatile bioorthogonal conjugation techniques especially for the radiolabeling of biologically active high molecular weight compounds like peptides, proteins or antibodies. Taking into consideration that the introduction of fluorine-18 (t_1/2 = 109.8 min) proceeds under harsh conditions, radiolabeling of these biologically active molecules represents an outstanding challenge and is of enormous interest. Special attention has to be paid to the method of ¹⁸F-introduction. It should proceed in a regioselective manner under mild physiological conditions, in an acceptable time span, with high yields and high specific activities. For these reasons and due to the high number of functional groups found in these compounds, a specific labeling procedure has to be developed for every bioactive macromolecule. Bioorthogonal strategies including the Cu-assisted Huisgen cycloaddition and its copper-free click variant, both Staudinger Ligations or the tetrazine-click reaction have been successfully applied and represent valuable alternatives for the selective introduction of fluorine-18 to overcome the afore mentioned obstacles. This comprehensive review deals with the progress and illustrates the latest developments in the field of bioorthogonal labeling with the focus on the preparation of radiofluorinated building blocks and tracers for molecular imaging. Full article