Post‐source decay matrix‐assisted laser desorption/ionization mass spectrometric study of tetracyclic 2,3‐dihydro‐1,5‐benzothiazepines

The fragmentation behavior of six tetracyclic 2,3‐dihydro‐1,5‐benzothiazepine derivatives cationized with protons and silver ions under post‐source decay (PSD) matrix‐assisted laser desorption/ionization (MALDI) conditions is reported. The protonated adduct ions decompose into several structurally important fragment ions, including substituted cyclopropane and benzohydrothiazole cations. Elimination of Ag and H and/or AgH from the silver‐cationized adduct ions of these ([M+Ag] + ) compounds was observed. It was also found that [M+Ag] + produced silver‐depleted fragment ions exclusively. Based on the PSD results a fragmentation pathway is proposed for the [M+H] + and [M+Ag] + precursor ions. Copyright © 2004 John Wiley & Sons, Ltd.