Synthesis of 14C-radiolabeled oligonucleotides with a novel phosphoramidite reagent

A novel solid-phase synthesis of 5′-radiolabeled oligonucleotides is described. The labeling reaction is carried out by the phosphoramidite method with the aid of [4,6-di-14C]-5′-dimethoxytritylthymidine building block 1. The feasibility of the method is demonstrated by preparation of 3′-phosphorylated dodecathymidylate phosphorothioate containing radiolabeled nucleoside at the 5′-terminus.