Abstract
The reaction rates in the Dimroth rearrangements of 9-substituted 1-methyladenines (5a-i) were measured in H2O at various pH's and ionic strength 1.0 at 40°C. In all cases, attack of hydroxide ion on the protonated species of 5 at the 2-position was faster than that on the neutral species by a factor of 90-180. Among nine kinds of 9-substituents in these compounds, the β-D-ribofuranosyl group was found to accelerate both modes of hydroxide attack most significantly. It has been concluded that this rate enhancement is attributable solely to the electron-withdrawing effect of the furanose ring oxygen and not to the 5'-hydroxy group, a potential participant in intramolecular catalysis for the hydroxide attack on the adenine ring at the 2-position.
