The prooligonucleotide approach. III: Synthesis and bioreversibility of a chimeric phosphorodithioate prooligonucleotide

Alkylation of a central gap of three phosphorodithioate linkages into a dodecathymidine methylphosphonate with methylacylthioethyl iodide (Me-SATE-I) yielded the corresponding neutral oligonucleotide. Upon incubation of the resulting non ionic prooligonucleotide in cell extracts, the bioreversible Me-SATE masking groups were selectively removed by carboxyesterases present in the milieu.