THE PROOLIGONUCLEOTIDE APPROACH .4. SYNTHESIS OF CHIMERIC PROOLIGONUCLEOTIDES WITH 6 ENZYMOLABILE MASKING GROUPS AND UNEXPECTED DESULFURIZATION SIDE REACTION

Chimeric dodecanucleotides exhibiting a central gap of 6 phosphorothio ate internucleoside linkages masked with pivaloyloxymethyl groups and uncharged or charged flanks were synthesized by alkylation of the corr esponding phosphorothioate oligos. In total CEM cell extract, they sel ectively yielded the unmasked charged oligos with a half-time of about 30 hours. Furthermore during alkylation of phosphorothioate linkages a partial desulfurization was observed. (C) 1997, Published by Elsevie r Science Ltd.