The debromokeramadine (2a), which was isolated from the Pacific sponge Agelas cf. mauritiana, is described in this manuscript. We also report the synthesis of the debromokeramadine (2a) and its known brominated analog, keramadine (1), based on the regioselective oxidative addition of a guanidine derivative on N-acylpyrrole dihydropyridines. This flexible approach was applied to the preparation of three debromo-analogs 2b–d by varying the substitution of the guanidine bis-nucleophile. The reaction is a great progress for the regio- and stereoselective synthesis of debromokeramadine (2a) analogs and interesting library of pyrrole-2-aminoimidazole allowing biological activity studies.