Proposed biosynthetic pathway for the production of lomaiviticin A. (A) Biosynthetic hypothesis for synthesis of ‘ethyl’-kinobscurinone. (B) Biosynthetic hypothesis for tailoring of the core benzo[b]fluorene scaffold. The order of biosynthetic steps has not been confirmed. Abbreviations: PKS = polyketide synthase, CoA = coenzyme A, KS = ketosynthase, CLF = chain length factor, ACP = acyl carrier protein, AT = acyltransferase, KR = ketoreductase, TDP = thymidine diphosphate.