Synthesis of oligonucleoside phosphorodithioates by the H-phosphonothioate method

The phosphorodithioate octamer [(TpS2)7T] was efficiently synthesized using bis(2,6-dimethylphenyl) phosphorochloridate as a coupling agent by application of the H-phosphonothioate method, where oxidation was facilitated using elemental sulfur following completion of oligonucleoside H-phosphonothioates assembly, as with the standard H-phosphonate method.