Synthesis of (12R,13S)-pyriculariol and (12R,13S)-dihydropyriculariol revealed that the rice blast fungus, Pyricularia oryzae, produces these phytotoxins as racemates.

Synthesis of assumed natural (12R,13S)-enantiomers of pyriculariol (1) and dihydropyriculariol (2), phytotoxins isolated from rice blast disease fungus, Pyricularia oryzae, was achieved using Wittig reaction or microwave-assisted Stille coupling reaction as the key step. The synthesis revealed that the natural 1 and 2 are racemates. Foliar application test on a rice leaf indicated that both the salicylaldehyde core and side chain were necessary for phytotoxic activity.