SYNTHESIS OF NOVEL PHOSPHORAMIDITE REAGENTS FOR THE ATTACHMENT OF ANTISENSE OLIGONUCLEOTIDES TO VARIOUS REGIONS OF THE BENZOPHENANTHRIDINE RING-SYSTEM

Four benzophenanthridine phosphoramidite reagents have been prepared in which the linker chain between the benzophenanthridine and the phosphoramidite moiety is attached to C-2, C-6, C-9, and C-12 of the benzophenanthridine ring system. These benzophenanthridine phosphoramidites should prove to be useful in the syntheses of antisense oligonucleotide-intercalator conjugates in which the linker chain is attached to various regions of the benzophenanthridine intercalator. One of the new benzophenanthridine phosphoramidite reagents was used to prepare an antisense oligonucleotide-intercalator conjugate in which the oligonucleotide TCAGTGGTp was connected at its 5'-hydroxyl group through a linker chain to the C-2 hydroxyl group of a benzophenanthridine.