Template-directed synthesis on short oligoribocytidylates.

The oligonucleotides C(pC)n, n = 4, 5, 6, 7, are efficient templates for the oligomerization of guanosine-5'-phospho-2-methylimidazole (2-MeImpG). They yield oligomeric products that are substantially less regiospecific than those obtained on polycytidylate [poly(C)]. The overall distributions of products obtained on oligo(C)s are generally similar to those of products obtained on oligodeoxycytidylates [oligo(dC)s], but there are substantial differences in the ratios of isomers. The 3'-5'-linked dinucleoside monophosphate GpG efficiently initiates oligomer formation with 2-MeImpG on oligo(C) templates. The pattern of products obtained by chain extension parallels closely that of products obtained directly from 2-MeImpG, except that the former products lack the 5'-terminal phosphate group.