Origin of the C3-unit in placidenes: further insights into taxa divergence of polypropionate biosynthesis in marine molluscs and fungi

Structural diversity of polypropionates arises from the amazing combination of acetate and propionate units. Feeding experiments with single and doubly 13C-labelled precursors prove that the Mediterranean slug Placida dendritica utilizes intact C3-units for the biosynthesis of placidenes (e.g., 1-5), prototypes of a family of pyrone-containing polypropionates largely represented in fungi and marine invertebrates. These results show that fungi and molluscs have elaborated two distinct polyketide pathways for the synthesis of similar or even identical compounds.