Phenylglycidyl ether adducts of 2'-deoxycytidine and 2'-deoxyadenosine: Stability in solution and structure analysis by electrospray tandem mass spectrometry.

The adducts of phenylglycidyl ether with 2'-deoxyadenosine (dAdo) and 2'-deoxycytidine (dCyd) exhibit structural modifications. The N-1 adduct of dAdo underwent rearrangement to the N-6 adduct; the N-3 adduct of dCyd was deaminated to the corresponding 2'-deoxyuridine adduct. These structural modifications were studied by using liquid chromatography-electrospray tandem mass spectrometry, and kinetic data for both reactions are presented. The low energy (+) collision-activated dissociation spectra of the dAdo adducts allow the two positional isomers N-1 versus N-6 to be distinguished. The structure of the latter is independently proven by an extended NMR study. For the dCyd and 2'-deoxyuridine adducts, information about the alkylation site is found in the (-) collision-activated dissociation spectra. These spectra show the presence of an unexpected N-4-alkylated dCyd in addition to the two epimeric N-3 adducts.