Preparation of Imino and Amino N-15 Enriched 2-Aminopurine Deoxynucleoside

We report the synthesis of N-15 enriched 2-aminopurine-2′-deoxynucleoside (APdR). Both ring and 2-amino nitrogens were labelled via a Dimroth rearrangement of the free base. The corresponding deoxynucleoside was prepared enzymatically. Results of both proton and N-15 NMR studies show that the predominant tautomeric form of APdR is amino and the N1 position is shown to be the site of protonation.