An approach to prebiotic synthesis of alpha-oligoribonucleotides and description of their properties: selective advantage of beta-RNA over alpha-RNA.

Oligomerization of alpha-adenosine 5'-phosphorimidazolide (alpha-ImpA) has been done in an aqueous solution using a uranyl-ion catalyst or a poly(U) template as a model process of prebiotic synthesis of RNA with alpha-glycosidic linkage. alpha-Oligoriboadenylates up to hexamer were formed from alpha-ImpA by the uranyl-ion catalyst. 3'-5' Linkage was mainly formed in the oligomerization. The poly(U) template mediated the oligomerization of alpha-ImpA, but to a very low extent. The yield and chain length of the resulting alpha-oligomers were far lower than those of the corresponding beta-oligomer formation under the same conditions. Physico-chemical properties of alpha-oligoriboadenylates are presented along with those of the corresponding beta-oligoriboadenylates. The results indicate that beta-RNA is more advantageous than alpha-RNA from the points of their synthesis and properties.