Cycloadditions as a Method for Oligonucleotide Conjugation

There is a large requirement in modern molecular biology for the production of specifically conjugated oligonucleotides. For instance, oligonucleotides may be conjugated to fluorescent labels to allow sequence specific detection following a biological assay. A number of methods exist for the conjugation of oligonucleotides and mainly rely on the use of a nucleophile attached to the oligonucleotide reacting with reactive species to form the desired product. A new approach to achieve oligonucleotide conjugations is to use cycloadditions. This review covers the growing use of cycloadditions for labelling of oligonucleotides at various positions within the sequence and the advantages over existing techniques. A number of different dienes have been reported and each is reviewed. Finally, the use of these conjugated oligonucleotides is reported with a view, to demonstrate the advantages of using cycloaddition for the conjugations.