The fragmentation of the antiviral drug adefovir dipivoxil and its two active metabolites, adefovir and monopivoxil adefovir, was investigated using both ion trap and triple-quadrupole mass spectrometers. Fragment ions due to loss of 30 Da were observed and attributed to an unanticipated rearrangement process by loss of formaldehyde. The proposed mechanism is supported with the aid of three newly synthesized adefovir derivatives and with accurate mass measurement. Other fragmentations by loss of a pivaloyl group, loss of water, C-P bond cleavage and C-O bond cleavage were also observed for adefovir derivatives. It was concluded that the compounds containing a >POO-CHR-OCO- group generally displayed a rearrangement reaction by loss of RCHO in collision-induced dissociation, and the process generally required an activation energy lower than for a direct bond cleavage.
Copyright 2004 John Wiley & Sons, Ltd.