1,3-Dimethylpyranonaphthoquinone Biosynthesis in the Fungus Dermocybe cardinalis

The pattern of incorporation of sodium [1,2- 13 C 2 ]acetate into cardinalin 2 1 by the fruit bodies of the toadstool Dermocybe cardinalis shows that both halves of the molecule are formed biosynthetically from an octaketide in which the C 3 and C 3′ methyl groups come from the acetate starter unit while the C 1 and C 1′ methyls originate from the terminal methylene group. This folding pattern is opposite to that observed during the biosynthesis of pyranonaphthoquinones in bacteria.