EFFECT OF PHOSPHATE ACTIVATING GROUP ON OLIGONUCLEOTIDE FORMATION ON MONTMORILLONITE - THE REGIOSELECTIVE FORMATION OF 3',5'-LINKED OLIGOADENYLATES

The effects of amine structure on the montmorillonite-catalyzed oligom erization of the 5'-phosphoramidates of adenosine are investigated. 4- Aminopyridine derivatives yielded oligoadenylates as long as dodecamer s with a regioselectivity for 3',5'-phosphodiester bond formation aver aging 88%. Linear and cyclic oligomers are obtained and no A(5')ppA-co ntaining products are detected. Oligomers as long as the hexanucleotid e are obtained using 2-aminobenzimidazole as the activating group. A p redominance of pA(2')pA is detected in the dimer fraction along with c yclic 3',5'-trimer; no A(5')ppA-containing oligomers were detected. Li ttle or no oligomer formation was observed when morpholine, piperidine , pyrazole, 1,2,4-triazole, and 2-pyridone are used as phosphate-activ ating groups. The effects of the structure of the phosphate activating group on the oligomer structure and chain lengths are discussed.