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 i n which the linker chain between the benzophenanthridine and the phosp horamidite moiety is attached to C-2, C-6, C-9, and C-12 of the benzop henanthridine ring system. These benzophenanthridine phosphoramidites should prove to be useful in the syntheses of antisense oligonucleotid e-intercalator conjugates in which the linker chain is attached to var ious regions of the benzophenanthridine intercalator. One of the new b enzophenanthridine phosphoramidite reagents was used to prepare an ant isense oligonucleotide-intercalator conjugate in which the oligonucleo tide TCAGTGGTp was connected at its 5'-hydroxyl group through a linker chain to the C-2 hydroxyl group of a benzophenanthridine.