Oligomerization reactions of ribonucleotides - The reaction of the 5'-phosphorimidazolide of adenosine with diadenosine pyrophosphate on montmorillonite and other minerals

The overall regiospecificity of the 3',5'-phosphodiester bond formation is shown to be increased from 64 to 83 percent when a 9:1 ratio of ImpA to A5'ppA instead of ImpA alone is reacted in the presence of Na(+)-montmorillonite. The major factor in the regiospecificity increase is the formation of 3',5'-linked A5'ppA3'pA and A5'pp-A3'pA3'pA. The results obtained show that ImpA reacts more readily with A5'ppA than it does with another ImpA molecule and that A5'ppA plays a central role in directing the formation of 3',5'-phosphodiester bonds.