Regiolone and Isosclerone, Two Enantiomeric Phytotoxic Naphthalenone Pentaketides: Computational Assignment of Absolute Configuration and Its Relationship with Phytotoxic Activity

The absolute configurations of regiolone and isosclerone, two enantiomeric bioactive naphthalenone pentaketides produced by fungi and plants, have been unambiguously assigned by ab initio computational prediction of their theoretical optical rotatory powers and electronic circular dichroism spectra. Isosclerone is produced by the plant pathogen Botrytis cinerea, whereas regiolone is produced by B. fabae. The phytotoxic activities of the two compounds were tested for comparison on faba bean (host of both pathogens) and vine plants (host of only B. cinerea); the (R) configuration at C-4 was found to be a fundamental structural feature for bioactivity.