Predicted exocyclic amino group alkylation of 2 '-deoxyadenosine and 2 '-deoxyguanosine by the isopropyl cation

Diisopropyltriazene in aqueous 10% acetonitrile (pH 7.0 +/- 0.4) yields N-6 -isopropyl-2'-deoxyAdo as the predominant product and N-2-isopropyl-2'-deox yGuo in yields comparable with the O-6 adduct in reactions with 2'-deoxyAdo and 2'-deoxyGuo, respectively. These observations are inconsistent with wh at is expected on the basis of the regnant hypothesis concerning factors th at determine atom site selectivity in diazonium ion-mediated alkylations. A n alternative explanation based on the fleeting existence of the reactive i ntermediates involved is consistent with these observations.