One-Pot Synthesis of α,γ-Dinucleoside 5′-Triphosphates, G5′pppG and A5′pppA, Using S,S′-Bis(4-chlorophenyl) phosphorodithioate

S,S′-Bis(4-chlorophenyl) phosphorodithioate was useful for the synthesis of α,γ-dinucleoside 5′-triphosphates, G5′pppG and A5′pppA starting from the corresponding unprotected nucleoside 5′-phosphates under neutral conditions. G5′pppG was used for the synthesis of m7G5′pppG by means of the N7-methylation of one of two guanine moieties of G5′pppG.