A biomimetic reaction between beta,beta'-diaminoketones (e.g. kynuramine, kynurenine or o,o'-diaminobenzophenone) and a variety of cyclohexanediones and quinones leading to pyrido[2,3,4-kl)acridines is described. The synthesis of several di- and tetrahydropyrido[2,3,4-kl)acridine derivatives (7, 10, 12 and 15) as well as benzoderivatives of the marine alkaloids eilatin (1) and ascididemin (2), compounds 28 and 30, has been accomplished. Additionally, the new heterocycles isoeilatin (24), and diazapentacene 19 have also been synthesized. Al newly prepared heterocycles have been fully characterized by IR, MS and mainly by NMR spectroscopy. An analogous synthesis has been developed for pyrrolo[2,3,4-kl)acridines, the heterocyclic core of the bioactive marine alkaloids the plakinidines (31 A-C).
