In order to discover novel potential antifungal agents, a series of 6-substituted 3-butylphthalide derivatives were designed, synthesized and evaluated for their antifungal activities against nine phytopathogenic fungi. Preliminary bioassay tests showed that five 3-butylphthalide derivatives exhibited more potent antifungal activities than hymexazol at the concentration of 50 μg/mL. Especially, 3-butyl-6-nitro-2-benzofuran-1(3H)-one and 3-butyl-6-hydroxy-5-nitro-2-benzofuran-1(3H)-one had significant fungicidal activity against some phytopathogenic fungi. The EC 50 of 3-butyl-6-nitro-2-benzofuran-1(3H)-one against FS, FO and FG were 6.6, 9.6 and 16.0 μg/mL, respectively. The EC 50 of 3-butyl-6-hydroxy-5-nitro-2-benzofuran-1(3H)-one against BC, PO, VM, SS and AS were 6.3, 5.9, 10.0, 4.5 and 8.4 μg/mL, respectively. The preliminary structure-activity relationships (SARs) of all target compounds were also investigated.
Graphic abstract
In order to discover novel antifungal agents, three series of simple 2-aminobenzoxazole derivatives were designed, synthesized and evaluated for their antifungal activities against eight phytopathogenic fungi. The in vitro antifungal results showed that most of the target compounds exhibited excellent and broad-spectrum antifungal activities to all the tested fungi. Particularly, the six compounds
3a
,
3b
,
3c
,
3e
,
3m
and
3v
displayed the most potent antifungal activity, with EC
50
value of 1.48–16.6 µg/mL, which were much superior to the positive control hymexazol. The in vivo study further confirmed that compounds
3a
,
3c
,
3e
and
3m
displayed good preventative effect against
Botrytis cinerea
at the concentration of 100 µg/mL. The structure–activity relationships research provides significant reference for the further structural optimization of 2-aminobenzoxazole as potential fungicides.
Forty-four 2-aminobenzoxazole derivatives were designed and synthesized as agricultural antifungal agents, the in vitro and in vivo antifungal experiments showed that compounds
3a
,
3b
,
3c
,
3e
,
3m
and
3v
exhibited excellent and broad-spectrum antifungal activities compare with the commercial fungicide hymexazol.
Supplementary Information
The online version contains supplementary material available at 10.1007/s11030-021-10213-7.
In order to obtain novel bioactive compounds with significant antifungal activities, two series of 3-substituted phthalide derivatives were designed and synthesized via reduction, bromine substitution, and etherification. In addition, the antifungal activities of all target compounds against nine phytopathogenic fungi in vitro were tested by using the mycelial growth rate method at the concentration of 50 μg mL−1. Preliminary bioassay tests showed that some compounds exhibited more potent antifungal activities as compared with hymexazol. The preliminary structure-activity relationships (SARs) of all target compounds were also investigated.
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