“…Currently only the solid-phase synthesis of dithioate DNA is known (21), the only reported RNA-related phosphorodithioate chemistry is the phosphorothioamidite solution-phase synthesis of dimer ribonucleotides containing intemucleotidic phosphorodithioate linkages (22). We used a solid-phase synthetic method for the synthesis of 3 based on the 3'-phosphorothioamidite 2 (Matulic-Adamic, J., Haeberli, P., Karpeisky, A., Beigelman, L., Usman, N. unpublished observations).…”