Which 3-ribofuranosyl-substituted purine 5'-phosphates undergo template-directed oligomerization?

We have studied the oligomerization reactions of the 2-methylimidazolide derivatives of 3-isoisoguanosine 5'-phosphate (2) and 3-isoxanthosine 5'-phosphate (5) in the presence of a variety of homopolynucleotide templates. In no case did we observe a substantial template-facilitated production of long oligomers. Polyuridylic acid directed the synthesis of low molecular-weight products from both monomers. Polycytidylic acid, polyadenylic acid, polyinosinic acid, and polyguanylic acid were ineffective as templates in the systems that we investigated.