Design, synthesis, and fungicidal evaluation of novel oxysterol binding protein inhibitors for combatting resistance associated with oxathiapiprolin

doi:10.1016/j.pestbp.2020.104673

Pesticide Biochemistry and Physiology

Volume 169, October 2020, 104673

https://doi.org/10.1016/j.pestbp.2020.104673 Get rights and content

Highlights

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The binding model of fungicide oxathiapiprolin with OSBP was defined.
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Novel piperidinyl-thiazole-isoxazoline skeleton was designed.
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The compounds were evaluated for their oomycete control.
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Compound 1e exhibited potent low resistance risk for Phytophthora capsica.

Abstract

Oxathiapiprolin, the first successful oxysterol binding protein (OSBP) inhibitor for oomycete control, is regarded as an important milestone in the history of fungicide discovery. However, its interaction with OSBP remain unclear. Moreover, some plant pathogenic oomycetes have developed medium to high resistance to oxathiapiprolin. In this paper, the three-dimensional (3D) structure of OSBP from Phytophthora capsici (pcOSBP) was built, and its interaction with oxathiapiprolin was systematically investigated by integrating molecular docking, molecular dynamics simulations, and molecular mechanics Poisson-Boltzmann surface area (MM/PBSA) calculations. The computational results showed that oxathiapiprolin bound to pcOSBP forms H-bonds with Leu73, Lys74, Ser69, and water molecules. Then, based on its interaction with pcOSBP, oxathiapiprolin was structurally modified to discover new analogs with high fungicidal activity and a low risk of resistance. Fortunately, compound 1e was successfully designed and synthesized as the most potent candidate, and it showed a much lower resistance risk (RF < 1) against LP3-M and LP3-H in P. capsici. The present work indicated that the piperidinyl-thiazole-isoxazoline moiety is useful for further optimization. Furthermore, compound 1e could be used as a lead compound for the discovery of new OSBP inhibitors.

Graphical abstract

A series of derivatives 1e-1j, 2a-2 h were designed and synthesized based on the PLI of oxathiapiprolin. Compound 1e with high potency was identified as a promising inhibitor for design new OSBP inhibitors.

Introduction

Plant diseases caused by oomycete pathogens are particularly devastating for important crops, including potatoes, grapes and vegetable crops. Controlling plant oomycete pathogenic infections is very important for the production of food and has a significant impact on human health (Thornton and Wills, 2015; Chadfield and Pautasso, 2012; Barchenger et al., 2018). Oxathiapiprolin is an oomycete fungicide developed by DuPont in 2015 (Pasteris et al., 2015, Pasteris et al., 2016, Pasteris et al., 2019). As one of the most effective fungicides, oxathiapiprolin has great potency against many plant oomycete pathogens, including Phytophthora capsici (P. capsici), Phytophthora infestans (P. infestans), Peronophythora litchii, Plasmopara viticola, Peronospora parasitica, Pseudoperonospora cubensis, Pythium ultimum, etc. (Miao et al., 2016a, Miao et al., 2016b; Bittner and Mila, 2016; Qu et al., 2016; Cohen et al., 2018). However, resistance remains an unavoidable problem for oxathiapiprolin. Liu et al. reported that the risk of P. capsici developing resistance to oxathiapiprolin was moderate (resistance factor > 300) (Miao et al., 2016a, Miao et al., 2016b). Therefore, overcoming resistance is an important challenge for designing new fungicides to control oomycete diseases.

The piperidinyl-thiazole-isoxazoline moiety in oxathiapiprolin is the key core structure, as it provides significant fungicidal activity. Due to the novelty of this chemical scaffold, structural optimization based on oxathiapiprolin has become a hotspot in the field of fungicide development. For example, Chen et al designed and synthesized isoxazoline-containing piperidinylthiazole derivatives with good activity against Sclerotinia sclerotiorum (Wu et al., 2019). Wu et al. (2018) obtained 21 novel isothiazole-thiazole derivatives with good activity against P. cubensis. However, all these design protocols were based on the chemical structure of oxathiapiprolin and did not consider the binding interactions with the target.

Biological chemistry and molecular biochemistry experiments have shown that the target of oxathiapiprolin is oxysterol binding protein (OSBP)-related protein (ORP) (Andreassi II et al., 2012). To date, the interaction between oxathiapiprolin and OSBP from oomycete pathogens is not clear, making the development of novel fungicides quite challenging. To discover new lead compounds for controlling oomycete pathogens, the 3D structure of OSBP from P. capsici was built using the homology modeling method, and then the interaction of P. capsici OSBP (pcOSBP) with oxathiapiprolin was studied via molecular docking, molecular dynamics (MD) simulations and molecular mechanics Poisson-Boltzmann surface area calculations (MM/PBSA). Then, oxathiapiprolin was structurally optimized based on its binding mode. Finally, the target compounds were evaluated by fungicidal activity experiments in vivo and in vitro. Fortunately, some compounds displayed good preventive effects against cucumber downy mildew in vivo. In addition, compound 1e showed potent activity against the resistant pathogens of P. capsici.

Section snippets

Materials and instruments

Unless noted, all reagents were obtained from commercial sources and used directly without further treatment. All solvents of analytical reagent grade were dried by standard methods before use. Using the residual tetramethylsilane (TMS) signal as the reference, ¹H NMR and ¹³C NMR spectra were obtained on a Mercury-Plus 400/600 spectrometer in chloroform‑d (CDCl₃) or dimethyl sulfoxide‑d₆ (DMSO‑d₆). High-resolution mass spectrometry (HRMS) data were obtained on a Waters MALDI Synapt G2 HDMS, and

Interaction between pcOSBP with Oxathiapiprolin

An understanding of the protein-ligand interaction (PLI) mechanism is very important for drug design (Lin et al., 2019; Hao et al., 2012). However, until now, it has been hard to elucidate the PLI of oxathiapiprolin towards its target. In our previous studies, we successfully determined the PLI of the commercial fungicide ametoctradin (Zhu et al., 2015), carboxamide fungicides (Zhu et al., 2014), and the natural product neopeltolide (Zhu et al., 2019) by using molecular docking followed by MD

Conclusions

In summary, the PLI of the commercial fungicide oxathiapiprolin with pcOSBP was successfully determined by integrating molecular docking, MD simulations, and MM/PBSA calculations. The results showed that oxathiapiprolin formed a T-cation-π interaction with Arg174 and hydrogen bonds with Ser69, Leu73, Lys74 and water molecules. Based on its binding mode, a series of oxathiapiprolin derivatives were designed and synthesized by replacing the pyrazole ring with liner alkyl chains and/or three- to

Acknowledgements

The research was supported in part by the National Key Research and Development Program of China (2017YFD0200506), the National Natural Science Foundation of China (No.21977035, 21772057), and the Program of Introducing Talents of Discipline to Universities of China (111 program, B17019).

References (43)

R.J. Bittner et al.
Effects of Oxathiapiprolin on Phytophthora Nicotianae, the causal agent of black shank of tobacco
Crop Prot.
(2016)
P.J. Crowley et al.
The role of molecular Modeling in the Design of Analogues of the fungicidal natural products Crocacins A and D
Bioorg. Med. Chem.
(2008)
G.D. Hawkins et al.
Pairwise solute Descreening of solute charges from a dielectric medium
Chem. Phys. Lett.
(1995)
R.J. Pasteris et al.
Discovery of Oxathiapiprolin, a new oomycete fungicide that targets an oxysterol binding protein
Bioorg. Med. Chem.
(2016)
Andreassi II, J.L., Gutteridge, S., Pember, S.O., Sweigard, J.A., 2012. US Patent...
D.W. Barchenger et al.
Challenges and strategies for breeding resistance in Capsicum annuum to the multifarious pathogen
Phytophthora capsici. Front. Plant Sci.
(2018)
A.D. Becke
Density-functional thermochemistry III. The Role of Exact Exchange
J. Chem. Phys.
(1993)
A.D. Becke
A new mixing of Hartree-Fock and local density-functional theories
J. Chem. Phys.
(1993)
S. Bienert et al.
The SWISS-MODEL repository - new features and functionality
Nucleic Acids Res.
(2017)
V. Chadfield et al.
Phytophthora Ramorum in England and Wales: which environmental variables Predict County disease incidence ?
Forest Pathol.
(2012)

F. Chen et al.

Activity of the novel fungicide Syp-Z048 against plant pathogens

Sci. Rep.

(2014)

P.K. Chi et al.

On downy blight of litchi Chinensis (Sonn. I). The pathogen and its infection process

Acta Phytopathol. Sin.

(1984)

Y. Cohen

The novel Oomycide Oxathiapiprolin inhibits all stages in the asexual life cycle of Pseudoperonospora Cubensis - causal agent of cucurbit downy mildew

PLoS One

(2015)

Y. Cohen et al.

Oxathiapiprolin-based Fungicides Provide Enhanced Control of Tomato Late Blight Induced by Mefenoxam-Insensitive Phytophthora infestans

Plos One

(2018)

M.L. Connolly

Analytical molecular surface calculation

J. Appl. Crystallogr.

(1983)

J. Dong et al.

Allosteric enhancement of ORP1-mediated cholesterol transport by PI(4,5)P-2/PI(3,4)P-2

Nat. Commun.

(2019)

W. Fry

Phytophthora Infestans: the plant (and R gene) destroyer

Mol. Plant Pathol.

(2008)

A.Y.L. Guan et al.

Design, synthesis, and structure-activity relationship of new Pyrimidinamine derivatives containing an Aryloxy pyridine moiety

J. Agric. Food Chem.

(2017)

G.F. Hao et al.

Computational discovery of Picomolar Q(o) site inhibitors of cytochrome bc(1) complex

J. Am. Chem. Soc.

(2012)

M.K. Hausbeck et al.

Phytophthora Capsici on vegetable crops: research Progress and management challenges

Plant Dis.

(2004)

G.D. Hawkins et al.

Parametrized models of aqueous free energies of solvation based on pairwise Descreening of solute atomic charges from a dielectric medium

J. Phys. Chem.

(1996)

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