Concise synthesis of Didebromohamacanthin A and Demethylaplysinopsine: Addition of Ethylenediamine and Guanidine Derivatives to the Pyrrole-Amino Acid Diketopiperazines in Oxidative Conditions

Oxidative nucleophilic addition of ethylenediamine and guanidine derivatives to pyrrole-amino acid diketopiperazines was shown to provide substituted 5,6-dihydro-2(1H)-piperazinones, quinoxalinones, and 2-aminoimidazolones. On the basis of this methodology, a concise approach to natural products didebromohamacanthin A and demethylaplysinopsine has been demonstrated.