N-(4-(2-chloro-4-(trifluoromethyl)phenoxy)phenyl)picolinamide as a new inhibitor of mitochondrial complex III: Synthesis, biological evaluation and computational simulations

Article abstract of DOI:10.1016/j.bmcl.2020.127302

Mitochondrial complex III is one of the most promising targets for a number of pharmaceuticals and fungicides. Due to the wide-spread use of complex III-inhibiting fungicides, a considerable increase of resistance has occurred worldwide. Therefore, inhibitors with novel scaffolds and potent activity against complex III are still in great demand. In this article, a new series of amide compounds bearing the diaryl ether scaffold were designed and prepared, followed by the biological evaluation. Gratifyingly, several compounds demonstrated potent activity against succinate-cytochrome c reductase (SCR, a mixture of mitochondrial complex II and complex III), with compound 3w possessing the best inhibitory activity (IC₅₀ = 0.91 ± 0.09 μmol/L). Additional studies verified that 3w was a new inhibitor of complex III. Moreover, computational simulations elucidated that 3w should bind to the Q_o site of complex III. We believe this work will be valuable for the preparation and discovery of more complex III inhibitors.

Full text of DOI:10.1016/j.bmcl.2020.127302

Bioorganic&MedicinalChemistryLetters30(2020)127302
Contents lists available at ScienceDirect
Bioorganic & Medicinal Chemistry Letters
journal homepage: www.elsevier.com/locate/bmcl
N-(4-(2-chloro-4-(trifluoromethyl)phenoxy)phenyl)picolinamide as a new
inhibitor of mitochondrial complex III: Synthesis, biological evaluation and
computational simulations
⁎
⁎
Hua Chenga,1, Lu Yanga,1, Hong-Fu Liua, Rui Zhanga, , Cheng Chenb, , Yuan Wuc, Wen Jiangc
a Department of Chemical Engineering and Food Science, Hubei University of Arts and Science, Xiangyang 441053, PR China
b State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology, Wuhan 430070, PR China
c Key Laboratory of Pesticide & Chemical Biology, Ministry of Education, College of Chemistry, Central China Normal University, Wuhan 430079, PR China
A R T I C L E I N F O
A B S T R A C T
Keywords:
Mitochondrial complex III is one of the most promising targets for a number of pharmaceuticals and fungicides.
Due to the wide-spread use of complex III-inhibiting fungicides, a considerable increase of resistance has oc-
curred worldwide. Therefore, inhibitors with novel scaffolds and potent activity against complex III are still in
great demand. In this article, a new series of amide compounds bearing the diaryl ether scaffold were designed
and prepared, followed by the biological evaluation. Gratifyingly, several compounds demonstrated potent
activity against succinate-cytochrome c reductase (SCR, a mixture of mitochondrial complex II and complex III),
Mitochondrial complex III
Inhibitor
Diaryl ether
Amide
Biological evaluation
Computational simulation
with compound 3w possessing the best inhibitory activity (IC50 = 0.91
0.09 μmol/L). Additional studies
verified that 3w was a new inhibitor of complex III. Moreover, computational simulations elucidated that 3w
should bind to the Qo site of complex III. We believe this work will be valuable for the preparation and discovery
of more complex III inhibitors.
The mitochondrial electron transport chain (ETC), which is com-
posed of oxidative phosphorylation and Krebs cycle, creates an elec-
trochemical proton gradient across the membrane via several redox
reactions. It has been well documented that the electron transfer is from
NADH to O2, with the production of ATP simultaneously.1 In particular,
oxidative phosphorylation contains five different transmembrane pro-
teins/complexes (namely complexes I-V) and two mobile electron car-
riers (ubiquinone and cytochrome c). Among them, complex III (cyto-
chrome bc1 complex) is of vital significance in the life cycle of
eukaryotes. In general, complex III is responsible for the electron
transfer from ubiquinol to cytochrome c. It is also associated with hy-
droquinone oxidation and cytochrome c reduction.2–5 If its activity is
inhibited, the synthesis of ATP in the mitochondria will be blocked,
which is lethal to eukaryotes.2,3,6,7. Most complex III-inhibiting fungi-
cides could inhibit the activity of complex III in eukaryotes at the en-
zyme level, while these fungicides mainly inhibit the activity of com-
plex III during the germination of fungal spores at the physiological
level. Among eukaryotes, spore germination occurs in fungi (not in
plants), so these inhibitors largely prohibited the growth of fungi. With
the above considerations, numerous complex III-inhibiting fungicides
have been discovered and commercialized, which have ranked first for
disease control in worldwide plant protection during the past several
decades.8–10 Meanwhile, significant advances have also been achieved
for complex III inhibitors with different modes of action.8,11–35 How-
ever, most of the existing fungicides suffer from serious resistance
problems.9,36,37 Therefore, more complex III inhibitors with new che-
mical structures and high potency are still in high demand.
In our previous work, a series of 4-aryloxy-N-arylanilines (Series A)
were designed and synthesized via Cu-promoted Chan-Lam-Evans re-
actions.38–41 Afterward, their activity against succinate-cytochrome c
reductase (SCR) was evaluated.42 The results implied that several
compounds showed excellent activity against SCR with their IC50 values
in the nanomolar level. In practice, SCR has been reported as a mixture
of complex II and complex III.43 However, further experiments revealed
that these molecules were neither complex II nor complex III inhibitors
(as depicted in Fig. 1, left column). Considering the potential usefulness
of these molecules and our continuous interest in the development of
potent inhibitors with novel scaffolds, we carried out further structural
modifications from Series A. Due to the significant role of the amide
bond in numerous bioactive molecules,44–46 we attempted to replace
⁎ Corresponding authors.
E-mail addresses: rzhangccnu@163.com (R. Zhang), chengchen@whut.edu.cn (C. Chen).
1 These authors contributed equally to this work.
https://doi.org/10.1016/j.bmcl.2020.127302
Received 3 February 2020; Received in revised form 15 May 2020; Accepted 31 May 2020
Availableonline03June2020
0960-894X/©2020ElsevierLtd.Allrightsreserved.

H. Cheng, et al.
Bioorganic&MedicinalChemistryLetters30(2020)127302
introduced as R3, but only low to moderate inhibition potency was
obtained (entries 10–15). Among all the tested groups, the H atom
demonstrated the best activity and thus was identified as the optimal
group for R3 (entries 2–15 vs. entry 1). If other diphenyl ether structures
were employed, comparable or reduced activity was attained (entries
16–20 vs. entry 2). Interestingly, a pyridine (Y = N) instead of a phenyl
group (Y = CH) led to improved activity (IC50 = 1.21
0.10 μmol/L
0.11 μmol/L for entry 1). However,
for entry 21 vs. IC50 = 1.52
employment of both Ring A and Ring C with pyridine-derived groups
(X = Y = N) resulted in an inhibition ratio of only 14% (entry 22).
From the above results, X and Y were optimized as CH and N, respec-
tively. Furthermore, replacement of the 2,4-Cl2 group with 2-Cl-4-CF3
at the R1 position gave rise to slightly higher activity (entry 23 vs. entry
21). Unfortunately, poor levels of inhibition were produced when
substituents other than H were introduced into both Ring A and Ring B
(entries 24–28). Moreover, a pyrazine-containing target compound
(3c’) was also synthesized, but it merely exhibited moderate inhibitory
Fig. 1. The design strategy.
the amino group of Series A with an amide functionality (as shown in
Fig. 1, right column). The resulting target molecules, namely N-(4-
phenoxyphenyl) benzamides, could give rise to potent activity against
SCR as well as complex II and/or complex III. To our delight, N-(4-(2-
chloro-4-(trifluoromethyl)phenoxy)phenyl)picolinamide (3w), one of
these target compounds, displayed good activity against both SCR and
complex III, leading to an active inhibitor of complex III which has
never been reported before. Furthermore, computational simulations
provided more information about its possible binding mode.
activity against SCR (entry 29, IC50 = 8.72
0.16 μmol/L). Replacing
the electron-withdrawing group (CF3) of compound 3w with an elec-
tron-donating group (CH3) resulted in compound 3d’, which showed
slightly reduced potency than 3w (entry 30 vs. entry 23). Besides,
changing the Cl group with a bulkier Br group gave rise to compound
3e’, which also exhibited marginally lower activity than 3w (entry 31
vs. entry 23). It appeared that both electronic and steric properties af-
fected the inhibitory activity of the resulting target compounds against
SCR, with the Cl and CF3 groups as the optimal groups on the diphenyl
ether skeleton. Finally, compound 3w was identified as the most active
SCR inhibitor, which manifested comparable potency with the two
commercial fungicides (entry 23 vs. entries 32–33).
First of all, the designed target compounds were synthesized using
the traditional amide synthesis from activated carboxylic acids and
amines. In detail, the amide bond was constructed from aromatic car-
boxylic acids and diphenyl ether-containing anilines using 1-ethyl-3-(3-
dimethylaminopropyl) carbodiimide hydrochloride (EDCI) combined
with 1-hydroxybenzotriazole (HOBt) as the activating reagents (as de-
picted in Scheme 1). Using this procedure, total 31 target compounds
were prepared and characterized by NMR and HRMS. To better present
our experimental results, the three phenyl rings were assigned as Ring
A, Ring B and Ring C, respectively (Scheme 1).
Aiming to confirm the inhibiting target of 3w (complex II, complex
III or dual–target), we further tested its activity against SCR, complex II
and complex III (as listed in Table 2). As expected, penthiopyrad se-
lectively inhibited the activity of complex II, while azoxystrobin de-
monstrated outstanding inhibitory activity exclusively against complex
III (entries 2–3). Similar with azoxystrobin, 3w showed an inhibition
rate of only 31% against complex II at the concentration of 10 μmol/L,
but considerably higher activity against complex III (entry 1). There-
fore, compound 3w was identified as a potent inhibitor of complex III.
With the discovery of 3w as an active complex III inhibitor, its
possible binding mode was then elucidated using computational simu-
lations (shown in Fig. 2). Complex III is composed of two binding sites
(Qo site and Qi site), so it’s of great significance to dock 3w into both
sites. It was worth noting that the calculation of the binding free en-
ergies was based on the docking scores in AutoDock 4.2. The docking of
3w into the Qo site imparted the calculated binding energy of
−7.7 kcal/mol for the best binding conformation, while the binding
energy was calculated as −6.7 kcal/mol when it was docked into the Qi
site. These results indicated that 3w would presumably bind to the Qo
site, which inspired us to investigate the binding mode of 3w into the
Qo site of complex III (shown in Fig. 2A). It appeared that crucial non-
polar interactions were formed between this inhibitor and the target
enzyme (PDB ID: 1SQB). The pyridine ring of 3w could enter the hy-
drophobic pocket surrounded by residues P270, F274, Y131 and F128.
Additionally, it could also form π-π stacking interactions with residues
Y131 and F274. Meanwhile, hydrophobic interactions were observed
between the diaryl ether scaffold and residues L294, I298, L121, I146,
M124, F274. Notably, the Cl and CF3 groups on the diphenyl ether
skeleton favored the enhancement of the hydrophobic interactions. As
we know, amide-π stacking interaction is one of the most frequently
observed interactions between proteins and ligands, which can largely
affect the biological activity.47 The amide bond in 3w showed good
amide-π stacking interactions with residues F274 and Y278. In terms of
The inhibitory activity of our target compounds against porcine SCR
was then assayed at a concentration of 10 μmol/L, and those with the
inhibitory rates of above 50% were further selected to determine their
IC50 values (as listed in Table 1). Two commercial SCR-inhibiting fun-
gicides (penthiopyrad and azoxystrobin) were chosen as positive con-
trols. Initially, various aromatic groups were attempted while retaining
the optimized diphenyl ether fragment (2,4-Cl2 as R1, X = CH, R2 = H)
from our previous work (entries 1–15).33 If an unsubstituted phenyl
ring (R3 = H) was introduced as Ring C, a high inhibition rate and an
IC50 value of 1.52
0.11 μmol/L were obtained (entry 1). It seemed
that the substituent positions on Ring C had a significant impact on the
inhibitory activity (entries 2–7). A methyl group employed at different
positions triggered varied inhibition potency, with 3-Me as R3 ex-
hibiting higher performance than the 2-Me and 4-Me counterparts
(entry 3 vs. entries 2 and 4). If 2-Cl, 3-Cl or 4-Cl was introduced as R3, a
similar trend was observed (entries 5–7). Polysubstituted groups were
also employed as R3, but only moderate inhibition rates of 31–46%
were obtained (entries 8–9). Other 3-substituted groups were
Scheme 1. The synthesis of target compounds 3a–3e′.
2

H. Cheng, et al.
Bioorganic&MedicinalChemistryLetters30(2020)127302
Table 1
Inhibitory activity of the synthesized compounds against porcine SCR.
Entry
Compound
X
Y
Z
R1
R2
R3
Yield (%)a
I (%)b IC50 (μmol/L)c
1
3a
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
C
CH
CH
CH
CH
CH
CH
CH
C
CH
CH
C
2,4-Cl2
H
H
33
68
83
49
70
65
53
13
76
74
64
73
73
64
50
90
23
32
54
46
70
22
39
51
55
62
55
54
42
63
38
75b, 1.52
0.11c
0.15c
2
3b
2,4-Cl2
H
2-Me
46b
3
3c
2,4-Cl2
H
3-Me
65b, 1.65
34b
4
3d
CH
CH
C
2,4-Cl2
H
4-Me
5
3e
2,4-Cl2
H
2-Cl
41b
6
3f
2,4-Cl2
H
3-Cl
57b, 2.86
0.27c
7
3g
CH
CH
CH
C
2,4-Cl2
H
4-Cl
11b
8
3h
2,4-Cl2
H
2,4,6-Cl3
31b
9
3i
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
N
2,4-Cl2
H
2-Cl-4-CF3
46b
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
3j
2,4-Cl2
H
3-OMe
49b
3k
C
2,4-Cl2
H
3-tBu
3-F
3-Br
3-OCF3
3-CF3
H
20b
3l
C
2,4-Cl2
H
45b
3m
C
2,4-Cl2
H
49b
3n
C
2,4-Cl2
H
41b
3o
C
2,4-Cl2
H
48b
3p
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
N
H
H
22b
3q
2,4-Cl2
3,5-Cl2
3-Cl
3,5-Cl2
3,5-Cl2
H
H
63b, 1.59
0.12c
3r
2,4,6-Cl3
2,4,6-Cl3
2,4,6-Me3
2,4-Cl2
H
42b
3s
C
H
36b
3t
C
H
27b
3u
CH
N
H
71b, 1.21
0.10c
0.09c
3v
N
2,4-Cl2
H
H
14b
3w
CH
CH
CH
C
N
2-Cl-4-CF3
2-Cl-4-CF3
2,4-Cl2
H
H
75b, 0.91
34b
3x
N
3-Cl
3,5-Cl2
3,5-Cl2
3-Cl
3,5-Cl2
H
H
3y
N
H
26b
3z
N
2,4,6-Cl3
2-naphthyld
2-naphthyld
2-Cl-4-CF3
2-Cl-4-Me
2-Br-4-CF3
H
21b
3a′
CH
CH
CH
CH
CH
N
H
25b
3b′
N
H
21b
3c′
N
H
52b, 8.72
67b, 2.36
65b, 2.57
70b, 2.01
96b, 0.31
0.16c
0.19c
0.23c
0.12c
0.03c
3d′
N
CH
CH
H
H
3e′
N
H
H
penthiopyrad
azoxystrobin
a
b
c
Isolated yields.
Inhibition rates against SCR at a concentration of 10 μmol/L.
IC50 values against SCR.
d
The whole ring A was substituted with a 2-naphthyl group.
Table 2
azoxystrobin, its docking result suggested an analogous binding mode
with 3w (as shown in Fig. 2B). From the above results, it was concluded
that compound 3w could bind well into the Qo pocket of complex III.
Notably, the amide linkage is pivotal for the potent inhibition of 3w
against complex III.
The inhibition effect of the select inhibitors against SCR, complex II and com-
plex III.
In summary, a new series of amides comprising the diaryl ether
scaffold were designed and synthesized based on our previously re-
ported 4-aryloxy-N-arylanilines. With these molecules in hand, their
inhibitory activity was examined against SCR, with several compounds
exhibiting potent activity against SCR. Additional experiments were
carried out to determine the target of representative inhibitor 3w and
its possible binding mode in the target enzyme. The results indicated
that 3w was a potent inhibitor of complex III. Computational simula-
tions showed that 3w could bind into the Qo pocket well and form
strong interactions with the target enzyme. Notably, the evolvement of
an amide bond in 3w induced good amide-π stacking interactions with
residues F274 and Y278. This work can be beneficial for the further
development of other complex III inhibitors.
Entry
Compound
IC50 (μmol/L)
SCR
complex II
complex III
1
2
3
3w
0.91
2.01
0.31
0.09
0.12
0.03
> 10 (31%a)
6.03
0.20
penthiopyrad
azoxystrobin
0.95
0.07
> 10 (11%a)
> 10 (23%a)
0.85
0.05
a
Inhibition rates against SCR at a concentration of 10 μmol/L.
3

H. Cheng, et al.
Bioorganic&MedicinalChemistryLetters30(2020)127302
Fig. 2. (A) The binding mode of 3w in the Qo site of complex III (PDB ID: 1SQB); (B) the binding mode of azoxystrobin in the Qo site of complex III (PDB ID: 1SQB).
Declaration of Competing Interest
of action of the novel selective fungicide cyazofamid: Specifc inhibition of mi-
tochondrial complex III in Phythium spinosum. Pestic Biochem Physio.
2001;71:107–115.
The authors declare that they have no known competing financial
interests or personal relationships that could have appeared to influ-
ence the work reported in this paper.
15. Ohshima T, Komyoji T, Mitani S, Matsuo N, Nakajima T. Development of a novel
fungicide, cyazofamid. J Pestic Sci. 2004;29:136–138.
16. Bolgunas S, Clark DA, Hanna WS, Mauvais PA, Pember SO. Potent inhibitors of the Q
(i) site of the mitochondrial respiration complex III. J Med Chem.
2006;49:4762–4766.
17. Kruglov AG, Andersson MA, Mikkola R, et al. Novel mycotoxin from acremonium
exuviarum is a powerful inhibitor of the mitochondrial respiratory chain complex III.
Chem Res Toxicol. 2009;22:565–573.
Acknowledgments
This research was supported by the National Natural Science
Foundation of China (No. 21502062), Scientific Research Program
Guiding Project of Hubei Provincial Department of Education
(B2019135), the Teachers’ Scientific Research Ability Cultivation Fund,
Hubei University of Arts and Science (Natural Science, Grant No.
2018kypy001) and the Open Foundation of Discipline of Hubei
University of Arts and Science (Grant Nos. XK2019038, XK2019039).
18. Berry EA, Huang LS, Lee DW, Daldal F, Nagai K, Minagawa N. Ascochlorin is a novel,
specifc inhibitor of the mitochondrial cytochrome bc(1) complex. Biochim Biophys
Acta Bioenerg. 2010;1797:360–370.
19. Zhao PL, Wang L, Zhu XL, et al. Subnanomolar inhibitor of cytochrome bc(1) com-
plex designed via optimizing interaction with conformationally flexible residues. J
Am Chem Soc. 2010;132:185–194.
20. Wang F, Li H, Wang L, Yang WC, Wu JW, Yang GF. Design, syntheses, and kinetic
evaluation of 3-(phenylamino)oxazolidine-2,4-diones as potent cytochrome bc(1)
complex inhibitors. Bioorg Med Chem. 2011;19:4608–4615.
21. Vallieres C, Fisher N, Antoine T, et al. HDQ, a potent inhibitor of plasmodium fal-
ciparum proliferation, binds to the quinone reduction site of the cytochrome bc(1)
complex. Antimicrob Agents Chemother. 2012;56:3739–3747.
Appendix A. Supplementary data
22. Hao GF, Wang F, Li H, et al. Computational discovery of picomolar Q(o) site in-
hibitors of cytochrome bc(1) complex. J Am Chem Soc. 2012;134:11168–11176.
23. Yang WC, Li H, Wang F, Zhu XL, Yang GF. Rieske iron-sulfur protein of the cyto-
chrome bc(1) complex: A potential target for fungicide discovery. ChemBioChem.
2012;13:1542–1551.
Supplementary data to this article can be found online at https://
doi.org/10.1016/j.bmcl.2020.127302.
References
24. Zhu XL, Wang F, Li H, Yang WC, Chen Q, Yang GF. Design, synthesis, and bioeva-
luation of novel strobilurin derivatives. Chin J Chem. 2012;30:1999–2008.
25. Capper MJ, O'Neill PM, Fisher N, et al. Antimalarial 4(1H)-pyridones bind to the Q(i)
site of cytochrome bc(1). Proc Natl Acad Sci. 2015;112:755–760.
26. Zhu XL, Zhang MM, Liu JJ, Ge JM, Yang GF. Ametoctradin is a potent Q(o) site
inhibitor of the mitochondrial respiration complex III. J Agric Food Chem.
2015;63:3377–3386.
1. Nicholls DG. Bioenergetics. Academic Press; 2013:91–157.
2. Kim H, Xia D, Yu CA, et al. Inhibitor binding changes domain mobility in the ir-
on–sulfur protein of the mitochondrial bc(1) complex from bovine heart. Proc Natl
Acad Sci. 1998;95:8026–8033.
3. Berry EA, Guergova-Kuras M, Huang LS, Crofts AR. Structure and function of cyto-
chrome bc complexes. Annu Rev Biochem. 2000;69:1005–1075.
4. Crofts AR. The cytochrome bc(1) complex: function in the context of structure. Annu
Rev Physiol. 2004;66:689–733.
27. Cheng H, Shen YQ, Pan XY, Hou YP, Wu QY, Yang GF. Discovery of 1,2,4-triazole-
1,3-disulfonamides as dual inhibitors of mitochondrial complex II and complex III.
New J Chem. 2015;39:7281–7292.
28. Fehr M, Wolf A, Stammler G. Binding of the respiratory chain inhibitor ametoctradin
to the mitochondrial bc(1) complex. Pest Manage Sci. 2016;72:591–602.
29. Chen C, Wu QY, Shan LY, Zhang B, Verpoort F, Yang GF. Discovery of cytochrome bc
(1) complex inhibitors inspired by the natural product karrikinolide. RSC Adv.
2016;6:97580–97586.
5. Xia D, Esser L, Yu L, Yu CA. Structural basis for the mechanism of electron bifurcation
at the quinol oxidation site of the cytochrome bc(1) complex. Photosynth Res.
2007;92:17–34.
6. Hägerhäll C. Succinate: quinone oxidoreductases: variations on a conserved theme.
Biochim Biophys Acta, Bioenerg. 1997;1320:107–141.
30. Cheng H, Wang WQ, Huang L, Cui P, Wu QY. Synthesis and biological activities of
novel triazolesulfonamide derivatives containing quinolin-2-one moiety. Chin J Org
Chem. 2016;36:1065–1072.
7. Cecchini G. Function and structure of complex II of the respiratory chain. Annu Rev
Biochem. 2003;72:77–109.
8. Ypema HL, Gold RE. Kresoxim – methyl: modification of a naturally occurring
compound to produce a new fungicide. Plant Dis. 1999;83:4–19.
9. Bartlett DW, Clough JM, Godwin JR, Hall AA, Hamer M, Parr-Dobrzanski B. The
strobilurin fungicides. Pest Manage Sci. 2002;58:649–662.
31. Alday PH, Bruzual I, Nilsen A, et al. Genetic evidence for cytochrome b Q(i) Site
inhibition by 4 (1H)-quinolone-3-diarylethers and antimycin in toxoplasma gondii.
Antimicrob Agents Chemother. 2017;61:e01866–16.
32. Song Z, Iorga BI, Mounkoro P, Fisher N, Meunier B. The antimalarial compound ELQ-
400 is an unusual inhibitor of the bc(1) complex, targeting both Q(o) and Q(i) sites.
FEBS Lett. 2018;592:1346–1356.
10. Hou YP, Chen YL, Qu XP, Wang JX, Zhou MG. Effects of a novel SDHI fungicide
pyraziflumid on the biology of the plant pathogenic fungi Bipolaris maydis. Pestic
Biochem Physiol. 2018;149:20–25.
33. Cheng H, Fu Y, Chang Q, et al. Synthesis, biochemical evaluation and computational
simulations of new cytochrome bc(1) complex inhibitors based on N-(4-arylox-
yphenyl) phthalimides. Chin Chem Lett. 2018;29:1897–1900.
11. Slater EC. The mechanism of action of the respiratory inhibitor, antimycin. Biochim
Biophys Acta Rev Bioenerg. 1973;301:129–154.
12. Clough JM, Godfrey CRA, Godwin JR, Joseph RSI, Spinks C. Azoxystrobin: a novel
broad-spectrum systemic fungicide. Pestic Outlook. 1996;7:16–20.
13. Ueki M, Machida K, Taniguchi M. Antifungal inhibitors of mitochondrial respiration:
Discovery and prospectives for development. Curr Opin Anti-Infect Invest Drugs.
2000;2:387–398.
34. Zhu XL, Zhang R, Wu QY, et al. Natural product neopeltolide as a cytochrome bc(1)
complex inhibitor: Mechanism of action and structural modifcation. J Agric Food
Chem. 2019;67:2774–2781.
35. Cheng H, Liu HF, Yang L, et al. N-(3,5-Dichloro-4-(2,4,6-trichlorophenoxy)phenyl)
benzenesulfonamide: a new dual-target inhibitor of mitochondrial complex II and
complex III via structural simplification. Bioorg Med Chem. 2020;28:115299.
14. Mitani S, Araki S, Takii Y, Ohshima T, Matsuo N, Miyoshi H. The biochemical mode
4

H. Cheng, et al.
Bioorganic&MedicinalChemistryLetters30(2020)127302
36. Fisher N, Meunier B. Molecular basis of resistance to cytochrome bc(1) inhibitors.
FEMS Yeast Res. 2008;8:183–192.
inhibitory activities against succinate-cytochrome c reductase. Bioorg Med Chem Lett.
2018;28:1330–1335.
37. Dufour MC, Fontaine S, Montarry J, Corio-Costet MF. Assessment of fungicide re-
sistance and pathogen diversity in Erysiphe necator using quantitative real-time PCR
assays. Pest Manage Sci. 2011;67:60–69.
43. Wang WQ, Cheng L, Peng HY, et al. Synthesis and biological activities of new 4-
phenylanilines containing the diphenyl ether moiety. Chin J Org Chem.
2019;39:2851–2859.
38. Chan DMT, Monaco KL, Wang RP, Winters MP. New N- and O-arylations with phe-
nylboronic acids and cupric acetate. Tetrahedron Lett. 1998;39:2933–2936.
39. Evans DA, Katz JL, West TR. Synthesis of diaryl ethers through the copper-promoted
arylation of phenols with arylboronic acids. An expedient synthesis of thyroxine.
Tetrahedron Lett. 1998;39:2937–2940.
44. Xiong L, Zhu XL, Shen YQ, Wishwa WKWM, Li K, Yang GF. Discovery of N-ben-
zoxazol-5-yl-pyrazole-4-carboxamides as nanomolar SQR inhibitors. Eur J Med Chem.
2015;95:424–434.
45. Xiong L, Zhu XL, Gao HW, et al. Discovery of potent succinate-ubiquinone oxidor-
eductase inhibitors via pharmacophore-linked fragment virtual screening approach. J
Agric Food Chem. 2016;64:4830–4837.
40. Lam PYS, Clark CG, Saubern S, et al. New aryl/heteroaryl C-N bond cross-coupling
reactions via arylboronic acid/cupric acetate arylation. Tetrahedron Lett.
1998;39:2941–2944.
46. Xiong L, Li H, Jiang LN, et al. Structure-based discovery of potential fungicides as
succinate ubiquinone oxidoreductase inhibitors. J Agric Food Chem.
2017;65:1021–1029.
41. Ley SV, Thomas AW. Modern synthetic methods for copper-mediated C(aryl)-O,
C(aryl)-N, and C(aryl)-S bond formation. Angew Chem Int Ed. 2003;42:5400–5449.
42. Cheng H, Song W, Nie R, et al. Synthesis of new 4-aryloxy-N-arylanilines and their
47. de Freitas RF, Schapira M. A systematic analysis of atomic protein–ligand interac-
tions in the PDB. MedChemComm. 2017;8:1970–1981.
5