Synthesis of RNA 5'-Azides from 2'-O-Pivaloyloxymethyl-Protected RNAs and Their Reactivity in Azide-Alkyne Cycloaddition Reactions.

Commercially available 2'-O-pivaloyloxymethyl (PivOM) phosphoramidites were employed in an SPS protocol for RNA 5' azides. The utility of the N3-RNAs in CuAAC and SPAAC was demonstrated by RNA 5' labeling, chemical ligation including fragment joining and cyclization, and bioconjugation. As a result, several new RNA conjugates that may be valuable tools for studies on biological events such as innate immune response (cyclic dinucleotides), post-transcriptional gene regulation (circular RNAs), or mRNA turnover (m7G capped RNAs) were obtained.