Biosynthesis of the benz[α]anthraquinone antibiotic PD 116198

The labeling pattern obtained from incorporation of a mixture of sodium 1-¹³C]- and s-¹³C]acetates has confirmed the irregular derivation of the benzα]anthraquinone skeleton of the angucycline antibiotic PD 116198. Subsequent incorporation of sodium 1-¹³C, ¹⁸O₂]-, and 1-¹³C, 2-²H₃]acetates and of ¹⁸O₂ have revealed the origins of the hydrogen and oxygen atoms of the antibiotic. The possibility of a “two-chain” biosynthesis was tested by feeding ²H-labeled orsellinates; however, no incorporation was detected. PD 116198 seems most plausibly derived by rearrangement of an initially-formed linear tetracyclic intermediate.