FIGURE 4.

Structures of identified products and precursors found in culture broths of wt and deletion mutant strains and their biosynthetic relations. Letters in square brackets indicate methods used for corresponding structure identification: a – elemental composition from isotopic pattern and accurate mass (Supplementary Figures S1A,B); b – comparison of retention times with authentic standards (Supplementary Figure S1C); c – in-source CID MS fragmentation (Supplementary Figure S1D); d – NMR analysis (Supplementary Table S1); e – retro-(bio)synthetic approach (indicated by retrosynthetic arrows starting from completely identified products 13a, 13b, and 14a). ^∗Tentative structure (absolute or relative configuration is proposed based on the knowledge of the major isomer structure).