1 Biosynthesis of the Marine Antibiotic Pentabromopseudilin . 2 . The Pyrrole Ring

Nature has devised many different biosynthetic pathways towards pyrrole rings. Next to the well-studied aminolaevulinic acid based biosynthesis of the porphyrins, it was shown that in the prodigiosins (3) each of the pyrrole rings is build in a different way, starting from proline, serine, glycine and acetate. Proline is also the pyrrole precursor in streptopyrrole, however, the carbonyl group undergoes an unusual rearrangement, similar to the one observed in the biosynthesis of pyralomicin 1a. Verrucarin E is build up entirely from acetate while in the case of glycerinopyrin the heterocycle is formed from leucine. In the biosynthesis of pyrrolnitrin a chemically daunting rearrangement of tryptophan is performed. Pentabromopseudilin (1), a powerful pyrrole based marine antibiotic, was isolated from Pseudomonas