Effect of phosphate activating group on oligonucleotide formation on montmorillonite: The regioselective formation of 3′,5′-linked oligoadenylates

Article abstract of DOI:10.1021/ja00103a006

The effects of amine structure on the montmorillonite-catalyzed oligomerization of the 5′-phosphoramidates of adenosine are investigated. 4-Aminopyridine derivatives yielded oligoadenylates as long as dodecamers with a regioselectivity for 3′,5′-phosphodiester bond formation averaging 88%. Linear and cyclic oligomers are obtained and no A⁵′ppA-containing products are detected. Oligomers as long as the hexanucleotide are obtained using 2-aminobenzimidazole as the activating group. A predominance of pA²′pA is detected in the dimer fraction along with cyclic 3′,5′-trimer; no A⁵′ppA-containing oligomers were detected. Little or no oligomer formation was observed when morpholine, piperidine, pyrazole, 1,2,4-triazole, and 2-pyridone are used as phosphate-activating groups. The effects of the structure of the phosphate activating group on the oligomer structure and chain lengths are discussed.