The biosynthesis of the pseudopterosins continues with an aromatization to erogorgiaene (3), two oxidations to a dihyroxyerogorgiaene (4, then 5), and another oxidation to an ortho-hydroxyquinone (6).
As an advanced method delivering tetraanthraporphyrins, the dihydroisoindole method based on an oxidative aromatization of the closest partially hydrogenated porphyrin precursor was applied.
