![]() ![]() The facile formation and high chemical stability of triazole linkages make the azide–alkyne cycloaddition a fascinating strategy for labeling and ligation of nucleic acids. (5−8) Researchers have applied azide-alkyne cycloadditions to various biological substrates, (5) developed catalysts of high efficiency and diverse reactivity (9)-some metal complexes favor the production of the 1,5-disubstituted adduct-and investigated “activated” alkyne groups for rapid triazole formation in the absence of metal catalysts. Since its discovery, Cu(I)-catalyzed azide alkyne cycloaddition has been widely used within the fields of biology, biochemistry, and biotechnology. This reaction is known as the copper-catalyzed azide alkyne cycloaddition (CuAAC), and its compatibility with a wide range of biological substrates and synthetic conditions makes CuAAC the flagship among click conjugations. The Cu(I) core has a dual effect in that it activates the slow-reacting alkyne group thus accelerating the azide–alkyne condensation kinetics by ∼10 7–10 8-fold, (1) and it organizes the reacting groups by “templation” so that only a regiospecific 1,4-disubstituted adduct is formed. Research carried out separately and simultaneously by Meldal (3) and Sharpless (4) addressed these limitations by introducing a copper(I) catalyst. Only electron-deficient alkynes-albeit not bioorthogonal-can be substrates for the autonomous noncatalyzed cycloaddition by conjugate addition mechanisms. The slow reaction progress is due to the high chemical stability of canonical alkynes. However, for more than four decades application of this reaction was limited by the requirement for high temperatures, long reaction times, and poor regiospecificity (both the 1,4- and 1,5-isomeric adducts are formed). These groups are chemically unreactive toward most functional moieties of other biological substrates (such as lipids, proteins, and nucleic acids) and can therefore be considered to be bioorthogonal and biocompatible. (2) Azide and alkyne functionalities can be easily introduced in the scaffold of large organic constructs of biological relevance. It consists of the condensation of organic azides with alkyne groups to form 1,2,3-triazole linkages. Diels–Adler reaction, Huisgen’s cycloaddition).įor many years Huisgen’s cycloaddition has been applied in various branches of chemistry. N-hydroxysuccinimide active ester couplings) and ( iv) cycloadditions ( e. ![]() Michael addition, epoxidation, dihydroxylation, aziridination) ( iii) nonaldol like chemistry ( e. Currently, four types of reactions follow these criteria and include ( i) nucleophilic substitutions ( ii) additions to C–C multiple bonds ( e. (1) The name epitomizes chemical transformations that are simple to execute, that involve readily available starting reagents, that are compatible with an aqueous environment or no solvent, and that require simple product separation ( i. Sharpless used the term “click chemistry” to define a set of reactions which are broad in scope, high yielding, stereospecific, and result in few or no byproducts. Synthetic methodologies that use modular approaches to efficiently generate biologically relevant constructs are of paramount importance for the fast and high-throughput production of molecular probes, for screening assays, and for the development of pharmaceuticals. We discuss in detail the chemistry, the available modified-nucleosides, and applications of AAC reactions in nucleic acid chemistry and provide a critical view of the advantages, limitations, and open-questions within the field. In this review, we provide a guide to inexperienced and knowledgeable researchers approaching the field of click chemistry with nucleic acids. Application of AAC chemistry to nucleic acids allows labeling, ligation, and cyclization of oligonucleotides efficiently and cost-effectively relative to previously used chemical and enzymatic techniques. Azide–alkyne cycloadditions (AAC) are still the leading technology among click reactions due to the facile modification and incorporation of azide and alkyne groups within biological scaffolds. ![]() Its broad scope has positively impacted on multiple scientific disciplines, and its implementation within the nucleic acid field has enabled researchers to generate a wide variety of tools with application in biology, biochemistry, and biotechnology. Click chemistry is an immensely powerful technique for the fast and efficient covalent conjugation of molecular entities.
0 Comments
Leave a Reply. |