Probing biotransformation relationships among pyridoacridines by focusing on oxygenated analogues.

The presence of the MeO-5 in the structure 5-methoxyamphimidine (5) is unusual in the light of a recent analysis of the relationships among sponge- and tunicate-derived pyridoacridines. We explore a possible biochemical pathway, from neoamphimidine (2) to 5-methoxyamphimidine (5). The results of semiempirical and ab initio calculations are presented to help understand the relationships that favor the formation of 5 versus the formation of undiscovered bis-oxygenated pyridoacridines.