Post-synthetic conversion of 5-pivaloyloxymethyluridine present in a support-bound RNA oligomer into biologically relevant derivatives of 5-methyluridine.

A post-synthetic reaction of 5-pivaloyloxymethyluridine (present in a support-bound RNA oligomer) with various nucleophilic reagents furnished efficiently the corresponding products bearing one of the tRNA wobble 5-methyluridines (mnm5U, cmnm5U, τm5U, nm5U, inm5U or cnm5U). The syntheses of oligoribonucleotides modified with inm5U and cnm5U are reported for the first time.