Ribose Conformations of 8-Azapurine Nucleosides in Solution

Abstract

The ribose conformations of 8-azaadenosine, 8-azaguanosine, and 8-azainosine have been studied using proton magnetic resonance in ND₃ solutions, in D₂O solutions, and in pyridine solutions. The temperature was varied between - 60 and + 40 ° C in ND₃ and between + 10 and + 60 °C in D₂O solutions. The analysis is based on the two state S ⇌ N model of the ribose moiety proposed by Altona and Sundaralingam. In D₂O, the 8-aza substitution destabilizes the gg rotamer and simultaneously diminishes the population of the S state of the ribose. It is deduced that the anti population of the base is greater in the 8-azapurine (β) ribosides than in the common purine (β) -ribosides.