Synthesis of cyclic peptides modelled on the microcystin and nodularin rings

Several precursor cyclic peptides modelled on the ring systems of microcystin-LR and nodularin were synthesized. Synthesis was best achieved using solid-phase cyclization with solution-phase methods being successful in only one instance. These precursor cyclic peptides are suitable for elaboration with Adda-like hydrophobic side chains in order to produce structure-activity information.