The prooligonucleotide approach IV : Synthesis of chimeric prooligonucleotides with 6 enzymolabile masking groups and unexpected desulfurization side reaction

Chimeric dodecanucleotides exhibiting a central gap of 6 phosphorothioate internucleoside linkages masked with pivaloyloxymethyl groups and uncharged or charged flanks were synthesized by alkylation of the corresponding phosphorothioate oligos. In total CEM cell extract, they selectively yielded the unmasked charged oligos with a half-time of about 30 hours. Furthermore during alkylation of phosphorothioate linkages a partial desulfurization was observed. Chimeric dodecanucleotides exhibiting a central gap of 6 phosphorothioate internucleoside linkages masked with enzymolabile pivaloyloximethyl groups and uncharged or charged flanks selectively yielded. in total CEM cell extract. the unmasked charged oligos with a half-time of about 30 hours. Furthermore during alkylation reaction of phosphorothioate linkages. partial desulfurization was observed.