Pyrrole groups are found in nature in two primary metabolites (heme and tryptophan) and in a large variety of secondary metabolites (eg pyoluteorin, clorobiocin, congocidine, and prodigiosins). The diversity of these metabolites is mirrored in the multiple biosynthetic pathways leading to pyrrole groups. Six different biosynthetic pathways have been characterized to date,[1, 2] involving various primary metabolite precursors, such as amino ...