Mass spectral fragmentation reactions of angiotensin-converting enzyme (ACE) inhibitors.

A variety of mass spectrometric techniques have been employed in the study of a series of structurally similar compounds used in the treatment of hypertension. The compounds, known collectively as angiotensin-converting enzyme (ACE) inhibitors, all share the amino acid residue proline or some variant thereof, as a common structural element. The gas phase fragmentation behavior of these compounds has been explored systematically using various instruments and techniques. An interesting dissociation process (rearrangement) unique to one of the compounds, lisinopril, has been investigated using isotopic labeling experiments and exact mass measurements. The general nature of the process has been probed through both the positive and negative ion analyses of fourteen related compounds exhibiting structural homology.