Since module 3 harbors an E domain, we postulate that L-histidine is activated by module 3 and subsequently epimerized to a D-histidine, which leads to an R configuration at the position 3 in Corramycin. The C domain subtypes of modules 6 and 8-12 were determined as L CL subtype and no additional epimerization domains were identified within the respective modules. Consequently, we proposed the S configuration for phenylalanine, both β-hydroxy-valines, both serines and leucine. Since the remaining five stereocenters biosynthetically either arose by hydroxylation through tailoring enzymes or by downstream PKS modifications, we were not able to predict configurations due to a lack of bioinformatics tools. In order to fully elucidate the stereochemistry of Corramycin (1), we performed a total hydrolysis followed by chiral GC/MS analysis of the obtained amino acids. The hydrolysis revealed the absolute configuration of six stereocenters (labelled in blue in Figure ). The relative configuration of the two vic-dihydroxy units was elucidated via acetonide synthesis and ROESY NMR experiments (acetonide 6, Supplementary Figures S and).