Pterulinic acid and pterulone, two novel inhibitors of NADH:ubiquinone oxidoreductase (complex I) produced by a Pterula species. II. Physico-chemical properties and structure elucidation

The structures of two novel fungal Antibiotics, isolated from a Pterula species, that interfere with the NADH:ubiquinone oxidoreductase and inhibit the respiration of eucaryotes, were determined by spectroscopic techniques. Both compounds, pterulinic acid (1a) and pterulone (2), contain a 1-benzoxepin ring system and are chlorinated. Pterulinic acid (1a), which was obtained as a 1:5 inseparable mixture of the two isomers (Z)-1a and (E)-1a, in addition contains a furan. Their structures were determined by mass spectrometry and NMR spectroscopy, and 2D heteronuclear correlation experiments permitted the assignment of all NMR signals.