Efficient and improved synthesis of triazole-linked DNA (TLDNA) oligomers

Triazole-linked Nucleic Acids: Synthesis, Therapeutics and Synthetic Biology Applications

This article covers the triazole-linked nucleic acids where the triazole linkage (TL) replaces the natural phosphate backbone. The replacement is done at either a few selected linkages or all the phosphate linkages. Two triazole linkages, the four-atom TL1 and the six-atom TL2, have been discussed in detail. These triazole-modified oligonucleotides have found a wide range of applications, from therapeutics to synthetic biology. For example, the triazole-linked oligonucleotides have been used in the antisense oligonucleotide (ASO), small interfering RNA (siRNA) and clustered regularly interspaced short palindromic repeats (CRISPR)-Cas9 technology as therapeutic agents. Due to the ease of the synthesis and a wide range of biocompatibility, the triazole linkage TL2 has been used to assemble a functional 300-mer DNA from alkyne- and azide-functionalized 100-mer oligonucleotides as well as an epigenetically modified variant of a 335 base-pair gene from ten short oligonucleotides. These outcomes highlight the potential of triazole-linked nucleic acids and open the doors for other TL designs and artificial backbones to fully exploit the vast potential of artificial nucleic acids in therapeutics, synthetic biology and biotechnology.

Azide-modified Nucleosides as Versatile Tools for Bioorthogonal Labeling and Functionalization

Azide-modified nucleosides are important building blocks for RNA and DNA functionalization by click chemistry based on azide-alkyne cycloaddition. This has put demand on synthetic chemistry to develop approaches for the preparation of azide-modified nucleoside derivatives. We review here the available methods for the synthesis of various nucleosides decorated with azido groups at the sugar residue or nucleobase, their incorporation into oligonucleotides and cellular RNAs, and their application in azide-alkyne cycloadditions for labelling and functionalization.

A Hitchhiker's Guide to Click-Chemistry with Nucleic Acids

Click chemistry is an immensely powerful technique for the fast and efficient covalent conjugation of molecular entities. 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. 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. 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. In this review, we provide a guide to inexperienced and knowledgeable researchers approaching the field of click chemistry with nucleic acids. 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.

1,2,3-Triazole-based sequence-defined oligomers and polymers

This review offers a summary on the advances in the construction of 1,2,3-triazole-based sequence-defined oligomers and polymers through MAAC-based ISG or IEG strategies.

Duplex-forming Oligonucleotide of Triazole-linked RNA

An oligonucleotide of triazole-linked RNA (^TL RNA) was synthesized by performing consecutive copper-catalyzed azide-alkyne cycloaddition reactions for elongation. The reaction conditions that had been optimized for the synthesis of 3-mer ^TL RNA were found to be inappropriate for longer oligonucleotides, and the conditions were reoptimized for the solid-phase synthesis of an 11-mer ^TL RNA oligonucleotide. Duplex formation of the 11-mer ^TL RNA oligonucleotide was examined with the complementary oligonucleotide of natural RNA to reveal the effects of the 2'-OH groups on the duplex stability.

Chimeric RNA Oligonucleotides with Triazole and Phosphate Linkages: Synthesis and RNA Interference

Chimeric RNA oligonucleotides with an artificial triazole linker were synthesized using solution-phase click chemistry and solid-phase automated synthesis. Scalable synthesis methods for jointing units for the chimeric structure have been developed, and after click-coupling of the jointing units with triazole linkers, a series of chimeric oligonucleotides was prepared by utilizing the well-established phosphoramidite method for the elongation. The series of chimeric 21-mer oligonucleotides that possessed the triazole linker at different strands and positions allowed for a screening study of the RNA interference to clarify the preference of the triazole modifications in small-interfering RNA molecules.

Triazole-linked analogues of DNA and RNA ((TL)DNA and (TL)RNA): synthesis and functions

Click chemistry has provided us with access to DNA and RNA analogues with non-natural triazole internucleoside linkages. The bond periodicity of the oligonucleotides was designed to enforce duplex formation with natural congeners, and the non-cleavable linkages protect the oligomers against nuclease digestion. This account reviews the progress of the triazole-linked analogues over the past five years. Reinforced by their synthetic robustness, these analogues may find various utilities as tools for exploratory research.