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Absolute configuration of four chiral isomers of pyrisoxazole and their bioactivity
Ziliang Li1,2, Yunbo Cong1, Xiaohua Ma1,3
1School of Material Science and Engineering, Shenyang University of Technology, Shenyang, P. R. China.
Background:
Pyrisoxazole is a fungicide that has two chiral carbon atoms and four isomers: (3S,5R)-, (3R,5S)-, (3S,5S)-, and (3R,5R)-pyrisoxazole.
Results:
Pure crystals of four pyrisoxazole isomers were prepared by chiral separation and single-crystal cultivation. Their absolute configurations were established by X-ray single crystal diffraction analysis. Bioassays indicated that compound (3S,5R)-pyrisoxazole showed excellent fungicidal activity with a median effective concentration (EC50 ) value of 0.14 μg mL-1 and protective activity with an EC50 value of 13.29 μg mL-1 . These values are superior to the commercial fungicides boscalid and racemic pyrisoxazole.
Conclusions:
The biological activity of racemic pyrisoxazole is due almost exclusively to the isomer (3S,5R)-pyrisoxazole; the other three isomers had very low activity. © 2020 Society of Chemical Industry.
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