Fig. 4.

Structures of catalipyrones A–J (1–10) from D. catalinae. (A) The 1,11-dioxo-2,6,10-trioxa-anthracenes 1–7 were identified from adult beetles, whereas the 4,8-dioxo-1,9,13-trioxaanthracenes 8–10 are present in the pupal defensive secretion. The stereochemistry of the side chains in 2–9 is proposed in analogy to that determined for 1 (see text). (B) Model for the biosynthesis of 1,11-dioxo-2,6,10-trioxa-anthracenes and 4,8-dioxo-1,9,13-trioxaanthracenes 1–10 from two similarly functionalized tripropionate units (red) and one 5-carbon unit (blue).