Aqueous-phase Sonogashira alkynylation to synthesize 5-substituted pyrimidine and 8-substituted purine nucleosides.

In this unit, an efficient method for the synthesis of alkyne-modified nucleosides in an aqueous solvent system is described. The method allows direct palladium-catalyzed alkynylation of readily available unprotected 8-bromo-2'-deoxyguanosine (8-BrdG), 8-bromo-2'-deoxyadenosene (8-BrdA), 8-bromoadenosine (8-BrA), and 5-iodo-2'-deoxyuridine (5-IdU) precursors. The optimal catalyst is derived from palladium acetate, tri-(2,4-dimethyl-5-sulfonatophenyl)phosphane (TXPTS), and CuI.