STRUCTURES OF 2 NOVEL PYRICULOL-RELATED COMPOUNDS AND IDENTIFICATION OF NATURALLY PRODUCED EPIPYRICULOL FROM PYRICULARIA-ORYZAE

Two novel pyriculol-related compounds, which contain the benzopyran or benzodioxocin skeleton, and epipyriculol were isolated from a solid agar culture of Pyricularia oryzae, the causal fungus of rice blast disease. They showed phytotoxic activity as well as inhibitory activity toward the spore germination of the fungus itself. Chemical and spectrometric studies showed them to be pyriculol-related compounds, i.e., compound A (I) was 3-(1',3'-pentadienyl)-3,4-dihydro-1H-2-benzopyran-4,8-diol, compound B (II) was 4-(1'-hydroxy-2'-butenyl)-1,4-dihydro-2,3-benzodioxocin-10-ol, and IIIa was epipyriculol, the (10S)-isomer of pyriculol. Nonactive epidihydropyriculol (IIIc), the (10S)-isomer of dihydropyriculol, was also identified.