This research project aims at the preparation and stereoselective transformation of (chiral) β-lactams bearing halogenated side chains and/or β-lactams bearing aa chloro atom into biologically relevant mono-, bi- and tricyclic nitrogen compounds such as new tricyclic β-lactams and bis-aziridines. Furthermore, the development of novel entries into piperidin-3-ones and azetidin-3-ones from 4-(2-bromo-1,1-dimethoxy)-β-lactams will be studied.