first totalsynthesis of oteromycin was investigated. Our previously reported convergent strategy for the synthesis of α-acyl-γ-hydroxy-γ-lactams was first applied for the totalsynthesis, however, the final deprotection of the methoxyaminal moiety could not be achieved since an unexpected intramolecular Diels–Alder (IMDA) reaction occurred. Therefore, a novel one-pot four-step cascade reaction starting