Alkaloids from marine organisms. Part 7: Synthesis of bisdemethylaaptamine and bisdemethyloxyaaptamine—a biomimetic approach to the aaptamines?

Aaptamines are marine alkaloids with a unique 1H-benzo[d,e][1,6]naphthyridine structure and interesting biological properties. Bisdemethylaaptamine and bisdemethyloxyaaptamine were synthesized in four steps on a Bischler–Napieralski route including an oxidative formation of the crucial C9a–N1-bond. This synthetic approach may serve as a model for an oxidative Pictet–Spengler biosynthesis of the aaptamines.