THE SOLID-PHASE SYNTHESIS OF 2'-5'-LINKED OLIGORIBOADENYLATES CONTAINING 8-BROMOADENINE

To increase the accessibility of 8-bromo-2',5'-oligoadenylates, we dev eloped a synthesis of 2'-5'-linked oligoriboadenylates containing vary ing numbers of 8-bromoadenosine residues based on the use of a CPG-LCA solid support and the phosphoramidite approach. Although N-6-benzoyl protection was satisfactory for incorporation of nonmodified adenine r esidues into 2',5'-oligonucleotides, the effective incorporation of 8- bromoadenine into such 2',5'-linked oligomers required use of a non ac yl protecting group. Amidine protection of the purine exocyclic amino function proved compatible with all aspects of the phophoramidite appr oach and with the hydroxyl protection groups employed.