Pyrimorph is a carboxylic acid amide
(CAA) fungicide, which shows
excellent activity against oomycetes such as pepper phytophthora
blight, tomato late blight, and downy mildew
of cucumber. It works mainly by inhibiting the biosynthesis of cell
wall of oomycetes. However, pyrimorph also shows weak activity of
inhibiting mitochondrial complex III, which is the first CAA fungicide
found to act on mitochondria. To improve this effect on mitochondria
and develop fungicides that may have a novel mechanism of action,
in this paper, by disassembling pyrimorph and conjugating the fragments
with the mitochondrial-targeted delivery system (triphenylphosphonium),
three series of mitochondrial-targeting analogues of pyrimorph were
designed and synthesized. The results show that the pyridine-containing
1,1-diaryl is the core module of inhibition mitochondrial function
of pyrimorph. Among these conjugates, compound 3b with
a short linker showed the highest and broad-spectrum fungicidal activity,
strong respiratory inhibition activity, and adenosine 5′-triphosphate
synthesis inhibition activity, suggesting its potential as a fungicide
candidate. 3b exhibited greatly improved action on mitochondria, such as by destroying the
mitochondrial function of pathogens, causing mitochondrial swelling,
weakening its influence on cell wall morphology, and so on. More importantly,
this study provides a method to strengthen the drugs or pesticides
with weak mitochondrial action, which is of special significance for
developing mitochondrial bioactive molecules with the novel action
mechanism.