Novel Spiroheterocycles by Aziridination of α-Methylene-γ- and δ-Lactams

New potentially bioactive α-spiroaziridino-γ- and δ-lactams have been prepared by treatment of α-methylene- γ- and δ-lactams with ethyl N-{[(4-nitrobenzene)sulphonyl]oxy}carbamate (NsONHCO2Et), in the presence of CaO. These compounds, through reductive aziridine ring opening, can be intermediates for the synthesis of α- or β-amino lactams, useful as conformational constraints in peptides. The above procedure has been successfully extended to one α-methylene-oxindole to obtain a new spirooxindole derivative, potential precursor of natural alkaloids