(Phys.org)—Type II polyketides are a class of compounds found in nature as secondary metabolites derived from microorganisms. Their complex structures are characterized by fused polycyclic aromatic rings decorated with a profusion of ketones and hydroxyl groups. Many common antibiotics, anti-fungal, and anti-cancer drugs are type II polyketides or are derivatives of these naturally-occurring compounds. However the “laboratory synthesis” of type II polyketides is often challenging; as in living systems, it is a highly selective multi-step enzymatic process.