Structural basis of head to head polyketide fusion by CorB† †Electronic supplementary information (ESI) available: Result of the feeding experiments, synthesis of 1 including 1H NMR and 13C NMR, sequence analysis, X-ray data statistics, topology plot, structure comparison, density representation, primer sequences and strains and plasmids. See DOI: 10.1039/c5sc02488a Click here for additional data file.

a Interfaculty Institute of Biochemistry, University Tübingen, Hoppe-Seyler-Str. 4, 72076 Tübingen, Germany. b Department of Molecular Biology and Genetics, Aarhus University, Gustav Wieds Vej 10C, DK 8000 Aarhus C, Denmark. c Leibniz Institute for Natural Product Research and Infection Biology (HKI), 07745 Jena, Germany. d Max Planck Institute for Plant Breeding Research, Carl-von-Linné-Weg 10, 50829 Köln, Germany. e Institute for Pharmaceutical Biology, University of Bonn, Nussallee 6, 53115 Bonn, Germany. f Chair for Natural Product Chemistry, Friedrich Schiller University, 07737 Jena, Germany. g Center for Plant Molecular Biology, University Tübingen, Auf der Morgenstelle 1, 72076 Tübingen, Germany. h Department of Pediatrics, Vanderbilt University School of Medicine, Nashville, TN 37232, USA.