A bio‐inspired cascade reaction has been developed for the construction of the marine natural product ageladine A and a de novo array of its N1‐substitutedderivatives. This cascade features a 2‐aminoimidazole formation that is modeled after an arginine post‐translational modification and an aza‐electrocyclization. It can be effectively carried out in a one‐pot procedure from simple anilines or guanidines