VERSATILE LINKER CHEMISTRY FOR SYNTHESIS OF 3'-MODIFIED DNA

A general method is described for the solid phase supported synthesis of DNA containing 3'-terminal phosphodiesters modified with linkers be aring either amino, thiol, or hydroxyl groups. These products are all made from a common intermediate, obtained by the reaction of trimellit ic anhydride chloride with aminopropyl CPG. The anhydride-derivatized support was then reacted with three appropriate bifunctional spacers, giving DMT-protected hydroxyl solid supports bearing the masked functi onality as an ester, amide, or thioester. DNA synthesis was then perfo rmed, followed by ammonia cleavage and deprotection, giving the hydrox yl-, amino-, or thiol-functionalized DNA S'-phosphate diesters, respec tively. Test mononucleotides synthesized with each of the new supports were identical with control mononucleotides made with 5'-immobilized nucleosides and alkylhydroxyl, alkylamino, and alkylthio phosphoramidi tes. The new supports were then used to prepare several 3'-modified ol igonucleotides, which were characterized by gel electrophoresis, HPLC, and MALDI mass spectroscopy. The amino- and thiol-functionalized DNAs were conjugated with chromophores, and purification of these products was facilitated by use of reversed phase cartridges.