Does nitrarine form spontaneously in non-enzymic conditions?

Nitrarine, a polycyclic indolic alkaloid isolated from several species of Nitraria (Nitrariaceae), may biosynthetically arise from an usual l-lysine metabolism implying reactive C₅ units such as glutaraldehyde (1) and tetrahydropyridine (2). We have investigated the self-condensation of these units with tryptamine (3) in biomimetic non-enzymic conditions. The resulting reaction medium is complex and contains numerous closely related compounds. Isolation of target compounds from the prepared mixture has been performed using multi-dimensional chromatography including pH-Zone refining centrifugal partition chromatography.