Post-Synthetic Modification of Oligonucleotides via Orthogonal Amidation and Copper Catalyzed Cycloaddition Reactions

An efficient multicomponent orthogonal protocol was developed for post-synthetic oligonucleotide modification using commercially available 2′-O-methyl ester and 2′-O-propargyl nucleoside scaffolds. Amidation of methyl esters with primary amines was achieved in the presence of 2′-propargyl groups which were utilized for subsequent copper catalyzed cycloaddition with GalNAc-azide. The methodology was applied to generate siRNA composed of multiple amide and triazole conjugates. Computational methods were used to illustrate the impact of substitution at the 2′-position. This a powerful post-oligomerization technique for rapidly introducing diversity to oligonucleotide design.