Complex polyketides, exemplified by the molecules shown in Fig. 1, are produced mainly from a group of mycelia-forming bacteria belonging to the actinomycete family and have applications in medicine or agriculture. Worldwide sales of polyketides exceed $15 B annually. Up to now, all marketed polyketide drugs are either the natural product or a chemically modified version thereof. The need for novel antibiotics, anticancers, and antifungals has underscored great interest in these compounds and the search for new ways to generate chemical diversity around these natural products.