Electrospray tandem mass spectrometry of poly(amino)ester dendrimers: Dissociation rules and structural characterization of defective molecules

Abstract: A poly(amino)ester dendrimer, bearing tert-butyl ester terminations and used as the precursor of an acid-terminating poly(amino)ester dendrimer, was studied by electrospray ionization tandem mass spectrometry to establish its fragmentation rules upon collision-induced dissociation. Mechanisms for dissociation reactions experienced by protonated molecules were proposed and supported by accurate mass measurements. The release of 2-methylprop-1-ene was observed as many times as tert-butyl groups were available. Each of these steps was followed by elimination of carbon dioxide and ethylene within the so-deprotected branches. Detachment of an entire arm, released as a neutral or as a protonated molecule, was found to be a useful complementary process but it mainly proceeded from the singly charged precursor. Three targeted dendritic impurities were structurally characterized by monitoring the occurrence of these reactions together with any deviation from the reference behavior. Detection of these compounds in the precursor sample could account for the presence of defective molecules previously characterized in the acid-terminating poly(amino)ester dendrimer sample. [Copyright &y& Elsevier]