The prooligonucleotide approach: II. Synthesis and stability studies of chimeric oligonucleotide models

Alkylation of a central gap of three phosphorothioate linkages into a dodecathymidine methylphosphonate with different iodoalkyl acylates yielded the corresponding neutral oligonucleotides. Upon incubation of these prooligonucleotides in cell extracts, the bioreversible alkyl acylate masking groups were selectively removed by carboxyesterases present in the milieu.