Identification of in vitro metabolites of 3‐ethyl‐2,6‐dimethyl‐4H‐pyrido(1,2a)pyrimidin‐4‐one

(2-14C)3-Ethyl-2,6-dimethyl-4H-pyrido(1,2a)pyrimidin-4-one is metabolized in vitro by liver microsomes to at least 12 metabolites. The metabolites were isolated and purified by thin-layer chromatography and high-performance liquid chromatography and identified by mass spectrometry and nuclear magnetic resonance spectrosopy. The mostly mono- and dihydroxylated isomers were distinguished on the bases of their electron ionization mass spectra and the metastable daughter ion spectra of selected ions.