Synthesis of 1,2,3-Thiadiazole and Thiazole-Based Strobilurins as

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Synthesis of 1,2,3-Thiadizole and Thiazole Based Strobilurins as Potent Fungicide Candidates Lai Chen, Yu-Jie Zhu, Zhijin Fan, Xiao-Feng Guo, Zhi-Ming Zhang, Jing-Hua Xu, YingQi Song, Yury Yurievich Morzherin, Nataliya P. Belskaya, and Vasiliy A. Bakulev J. Agric. Food Chem., Just Accepted Manuscript • DOI: 10.1021/acs.jafc.6b05128 • Publication Date (Web): 05 Jan 2017 Downloaded from http://pubs.acs.org on January 8, 2017

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Journal of Agricultural and Food Chemistry

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Synthesis of 1,2,3-Thiadiazole and Thiazole Based

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Strobilurins as Potent Fungicide Candidates

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Lai Chen, † Yu-Jie Zhu, † Zhi-Jin Fan,*, †, ‡ Xiao-Feng Guo, † Zhi-Ming Zhang, †

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Jing-Hua Xu, † Ying-Qi Song, † Morzherin Y. Yurievich, § Nataliya P. Belskaya, §

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Vasiliy A. Bakulev*, §

7 8 9 10

†

P. R. China

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‡

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Collaborative Innovation Center of Chemical Science and Engineering (Tianjin), Nankai University, Tianjin 300071, P. R. China.

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State Key Laboratory of Elemento-Organic Chemistry, Nankai University, Tianjin 300071,

§

The Ural Federal University Named after the First President of Russia B. N. Yeltsin, Yeltsin UrFU 620002, Ekaterinburg, Russia

16 17

* Address correspondence to this author at State Key Laboratory of Elemento-Organic

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Chemistry, Nankai University, No. 94, Weijin Road, Nankai District, Tianjin 300071,

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P. R. China (telephone +86-13920714666; Fax:+86 22-23503620; e-mail:

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[email protected], or [email protected])

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ACS Paragon Plus Environment


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Abstract Strobilurin fungicides play a crucial role in protecting plants against different

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pathogens and securing food supplies.

A series of 1,2,3-thiadiazole and thiazole

25

based strobilurins were rationally designed, synthesized, characterized and tested

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against various fungi.

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fungicidal activity of the target molecules.

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a relative broad-spectrum of fungicidal activity.

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activities against Gibberella zeae, Sclerotinia sclerotiorum and Rhizoctonia cerealis

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with the median effective concentration (EC50) of 2.68, 0.44 and 0.01 µg/mL

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respectively; it was much more active than positive controls enestroburin,

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kresoxim-methyl and azoxystrobin with EC50 between 0.06 and 15.12 µg/mL.

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Comparable or better fungicidal efficacy of compound 8a than azoxystrobin and

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trifloxystrobin against Sphaerotheca fuliginea and Pseudoperonspera cubensis was

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validated in the cucumber fields at the same application dosages. Therefore,

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compound 8a was a promising fungicidal candidate worthy of further development.

Introduction of 1,2,3-thiadiazole greatly improved the Compounds 8a, 8c, 8d and 10i exhibited Compound 8a showed excellent

37 38

Keyword: Fungicide, strobilurin, 1,2,3-thiadiazole, thiazole, antifungal activity.

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Introduction Plant pathogens can not only cause dramatic crop yield losses, but also greatly

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affect the food security.1

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loss for American corn growers was over one billion US dollars directly from

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southern corn leaf blight which is caused by Cochliobolus heterostrophus, anamorph

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Bipolaris maydis.2

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mycotoxins called polyketides which contaminate grain based foods, causing a serious

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food safety and economic problem in the United States.3

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measures for managing plant pathogens are in great demand.

One extreme example is that estimated annually economic

Some plant pathogens such as the scab fungus could produce

Therefore, effective

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Fungicides are an effective tool for plant disease management,4, 5 especially, new

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fungicides are always welcome for farmers to phytopathogen managements. As the

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second biggest classes of fungicides,6 being developed based on the lead compound

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first isolated from fermentations of Stroblurus tenacellus in 1977 by block electron

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transfer between cytochrome b and cytochrome c1,7 strobilurin fungicides have been

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widely used against major plant pathogens.8

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possesses a similar scaffold called β-methoxyacrylate.

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fungicides have been launched and more are possible in the future.9-18

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Majority of strobilurin fungicides Over a dozen strobilurin

Heterocyclic rings as a substructure is one of the important measures for novel

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pesticide discovery including fungicides development.

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pharmaceuticals and agrochemicals contain at least one heterocyclic ring.19

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Heterocyclic rings functionalities differ from each other in biologically active

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compounds,20 and work as scaffolds in active ingredients, prodrugs, tools for


Approximately 70% of


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fine-tuning physicochemical properties and isosteric replacements of functional

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groups, alicyclic rings or other heterocyclic rings.21

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derivatives possess properties that include environmental compatibility and broad

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spectrum of bioactivities such as antifungal,22 antimicrobial,23 systemic acquired

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resistance24 and antitumor activities.25

Thiadiazole and thiazole

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This study was aimed at developing novel strobilurin fungicides by employing

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the active scaffold of strobilurin fungicides and active 1,2,3-thiadiazole, thiazole or

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thiazole’s derivatives as a substructures to the target molecules (Figure 1).

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of novel 1,2,3-thiadiazole and thiazole based strobilurins were rationally designed,

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synthesized and characterized.

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candidate against Sphaerotheca fuliginea and Pseudoperonspora cubensis in the

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cucumber fields.

A series

The active compound was evaluated as fungicide

74 75 76

Materials and Methods Equipment and materials: Melting points of synthesized compounds were 1

H and

13

77

taken on an X-4 melting point apparatus and were uncorrected.

C NMR

78

spectra were obtained on a Bruker Avance 400 MHZ spectrometer at 400 MHz and

79

100MHz in deutero-chloroform (CDCl3) and tetramethylsilane (TMS) as an internal

80

standard.

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FTICR-MS instrument.

82

elemental analysis instrument.

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1000CCD diffraction meter.

High resolution mass spectra (HRMS) were determined on a 7.0T Elemental analyses were performed on a Vario EL III Crystal structure was recorded by a Bruker SMART

All solvents were of analytical grade.


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General Synthetic Procedure for Compounds 3a-c (Figure 2).

84

Compounds

85

1a and 1b were commercially available.

86

the published procedures.26 Compound 2 was prepared from the corresponding acid

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1.27

88

mL, 18.66 mmol) was added dropwise to a solution of 2 (12.44 mmol) in anhydrous

89

tetrahydrofuran (THF) (45 mL) at -30 °C under N2. The mixture was then stirred at

90

-30 °C for 1 h and at room temperature for another 1 h.

91

complete as monitored with thin layer chromatography (TLC), it was quenched with

92

the sat. aq ammonium chloride (NH4Cl) solution (50 mL).

93

and THF under vacuo, the aqueous phase was extracted with ethyl acetate (3×50 mL).

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The combined organic layers were washed with water (50 mL), saturated brine (50

95

mL), and dried over anhydrous sodium sulfate.

96

evaporated.

97

mm)eluted with a mixture of ethyl acetate and petroleum ether (60-90 °C fraction) at a

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ratio of 1:5 (v/v) to obtain compounds 3a-c in a 90-93% yield (Figure 2).

99

Compound 1c was synthesized according to

A solution of methyl magnesium bromide in ethyl ether (Et2O) (3 mol/L, 6.22

When the reaction was

After removal of Et2O

After filtration, the solvent was

The residue was then purified on a silica gel column (203 mm x 26

General Synthetic Procedure for Compounds 6a-c (Figure 2). Compound 4a

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and 4b were commercially available.

Compound 4c was synthesized as reference

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description.26

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Dess-Martin periodinane (12.00 mmol) was added to a solution of compound 5 (10.87

103

mmol) in dichloromethane in an ice bath.

104

temperature overnight.

105

was then purified on a silica gel column eluted with a mixture of ethyl acetate and

Compound 5 was synthesized by reduction of compound 4.28

The reaction mixture was stirred at room

After filtration, the solvent was evaporated.


The residue


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petroleum ether (60-90 °C fraction) at a ratio of 1:4(v/v) to obtain compounds 6a-c in

107

a 50-80% yield.

108

General Synthetic Procedure for Compounds 8a-f (Figure 3). Compound 7 was

109

prepared according to Strazzolini and Pavsler.29

110

mmol) in 15 mL ethanol was added to the compound 3 or 6 (1.02 mmol) in ethanol

111

(15 mL), followed by addition of a catalytic amount of hydrochloric acid (2 mol/L,

112

0.1 mL.

113

removal of ethanol under vacuum, the residue was purified by recrystallization in

114

ethanol or silica gel column chromatography eluted with a mixture of ethyl acetate

115

and petroleum ether (60-90 °C fraction) at a ratio of 1:9-1:4 (v/v) to obtain the

116

corresponding compound 8 (Figure 3).

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elemental analyses of the target compounds 8a-f were as follows:

118 119 120 121 122 123 124 125 126 127

A solution of compound 7 (1.12

The reaction mixture was stirred at room temperature overnight.

After

The yields, physical properties and HRMS or

Data for 8a: yellow solid; yield, 48%; m.p.: 70-72 oC; Anal. calcd for C16H18N4O4S: C, 53.03; H, 5.01, N, 15.46. Found C, 53.29; H, 4.86, N, 15.40. Data for 8b: yellow solid; yield, 67%; m.p.: 98-100 oC; HRMS (m/z) calcd for C15H16N4O4S: (M+H)+: 349.0892, found: 349.0969. Data for 8c: colorless crystal; yield, 53%; m.p.: 82-83 oC; Anal. calcd for C16H18N4O4S: C, 53.03; H,5.01, N, 15.46. Found C, 53.02; H, 4.99; N, 15.60. Data for 8d: white solid; yield, 70%; m.p.: 82-84

o

C; Anal. calcd for

C15H16N4O4S: C, 51.71; H, 4.63; N, 16.08. Found C, 51.83; H, 4.58; N, 16.23. Data for 8e: white solid; yield, 48%; m.p.: 91-93

o

C; Anal. calcd for

C26H34N4O6S: C, 58.85; H, 6.46; N, 10.56. Found C, 58.25; H, 6.26; N, 10.16.


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Data for 8f: yellow oil; yield, 47%; HRMS (m/z) calcd for C25H32N4O6S (M+H)+: 517.2043, found: 517.2114.

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General Synthetic Procedure for Compounds 10a-o. Compound 9 was

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prepared according to the report of Domagala et al.30 Compounds 9 (0.75 mmol),

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1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (EDCI) (0.17 g, 0.90

133

mmol) and 1-hydroxybenzotriazole (HOBt) (0.11 g, 0.77 mmol) were dissolved in

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dichloromethane (25 mL) in an ice bath and was slowly warmed up to room

135

temperature and stirred for another 45 min.

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(25 mL) was then added followed by addition of trimethylamine (Et3N) (0.09 g, 0.90

137

mmol), the reaction mixture was stirred at room temperature overnight, the organic

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layer was successively washed with water (2×30 mL), saturated brine (40 mL), and

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dried over magnesium sulfate and concentrated in vacuo.

140

residue were then purified on a silica gel eluted with a mixture of ethyl acetate and

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petroleum ether (60-90 °C fraction) at a ratio of 1:1-1:6(v/v) (Figure 4). The yields,

142

physical properties and HRMS, elemental analyses of the target compounds 10a-o

143

were as follows:

144 145 146 147 148 149

A solution of amine in dichloromethane

Compound 10a-o in the

Data for 10a: yellow solid; yield, 83%; m.p.: 70-72 oC; HRMS (m/z) calcd for C17H19F2N5O3S (M+H)+: 412.1177, found: 412.1255. Data for 10b: yellow powder; yield, 89%; m.p.: 110-112 oC; HRMS (m/z) calcd for C18H19N5O3S (M+H)+: 386.1209, found: 386.1285. Data for 10c: yellow powder; yield, 69%; m.p.: 83-85 oC; Anal. calcd for C18H21N5O3S: C, 55.80; H, 5.46, N, 18.08. Found C, 55.83; H, 5.53; N, 18.23.



150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171

Data for 10d: colorless crystal; yield, 68%; m.p.: 71-73 oC; HRMS (m/z) calcd for C16H19N5O3S (M+H)+: 362.1209, found: 362.1289. Data for 10e: yellow oil; yield, 68%; HRMS (m/z) calcd for C20H27N5O3S2 (M+H)+: 450.1555, found: 350.1635. Data for 10f: white solid; yield, 57%; m.p.: 98-101 oC; HRMS (m/z) calcd for C17H19F2N5O3S (M+H)+: 412.1177, found: 412.1257. Data for 10g: colorless crystal; yield, 85%; m.p.: 131-133 oC; HRMS (m/z) calcd for C18H19N5O3S (M+H)+: 386.1209, found: 386.1287. Data for 10h: yellow crystal; yield, 90%; m.p.: 125-127 oC; Anal. calcd for C18H21N5O3S: C, 55.80; H,5.46, N, 18.08. Found C, 55.39; H, 5.53; N, 18.09. Data for 10i: white powder; yield, 82%; m.p.: 123-124 oC; Anal. calcd for C16H19N5O3S: C, 53.17; H, 5.30, N, 19.38. Found C, 52.47; H, 5.43; N, 19.67. Data for 10j: yellow oil; yield, 78%; HRMS (m/z) calcd for C20H27N5O3S2 (M+H)+: 450.1555, found: 450.1632. Data for 10k: yellow oil; yield, 87%; HRMS (m/z) calcd for C27H35F2N 5O5S (M+H)+: 580.2327, found: 580.2393. Data for 10l: yellow oil; yield, 91%; Anal. calcd for C28H35N5O5S: C, 60.74; H, 6.37; N, 12.65. Found C, 60.12; H, 6.18; N, 12.10. Data for 10m: yellow oil; yield, 91%; HRMS (m/z) calcd for C28H37N 5O5S (M+H)+: 556.2515, found: 556.2594. Data for 10n: yellow solid; yield, 64%; m.p.: 101-103 oC; HRMS (m/z) calcd for C26H35N5O5S (M+H)+: 530.2359, found: 530.2442.


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Data for 10o: yellow oil; yield, 96%; HRMS (m/z) calcd for C30H43N5O5S2

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(M+H)+: 618.2706, found: 618.2791.

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Crystal Structure Determination for Compound 8b

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The crystal of compound 8b was obtained from a mixture of dichloromethane

176

and petroleum ether for structure validation (Figure 5).

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compound 8b were recorded on a Bruker SMART 1000CCD diffraction meter

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equipped with graphite-monochromatic Mo Kα radiation (λ = 0.71073 Ǻ).

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9395 measured reflections; 3936 unique (Rint = 0.0308) in the range of 1.96°≤ θ ≤

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27.96°(h, -10 to 10; k, -13 to 13; l, -15 to 15), of which 2775 had |Fo| > 2|Fo|.

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methods were used for the structure solving by the SHELXS-97 program.

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structure were refined anisotropically by full-matrix least-squares for all non-H atoms

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to give the final R=0.0359 and wR=0.1010 (w=1/[σ2((Fo2)+(0.0651P)2+0.0000P],

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where P=(Fo2+2Fc2)/3), (∆/σ)max=0.982 and S=1.029. The hydrogen atoms were

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located according to theoretical models.

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Fungicidal Activity

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X-ray intensity data of

A total of

Direct The

The fungicidal activities against Alternaria solani (A. s), Botrytis cinerea (B. c),

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Cercospora arachidicola (C. a), Gibberella zeae (G. z), Phytophthora infestans (Mont)

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de Bary (P. i), Physalospora piricola (P. p), Pellicularia sasakii (P. s), Sclerotinia

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sclerotiorum (S. s) and Rhizoctonia cerealis (R. c) were detected in vitro at 50µg/mL

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according to a reported method by using azoxystrobin as a positive control.31

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any active compound with growth inhibition over 90% at 50 µg/mL, their median

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effective concentration (EC50) were determined according to the reference by using


For


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enestroburin, kresoxim-methyl and azoxystrobin as positive controls.32

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The preventive activities of the target compounds against Pseudoperonospora

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cubensis, Erysiphe graminis, Puccinia sorghi Schw, Colletotrichum lagenarium were

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conducted at 400 µg/mL by fungal spores inoculation.9

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by mother solution with distilled water (containing 0.1% Tween 80), the mother

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solution was prepared by dissolving each target compound (0.0111 g) in 0.5mL DMF.

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Control plants were sprayed with water solution containing the same concentration of

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DMF and Tween 80 in the test solutions.

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compared with the control plants by checking complete disease control as 100 and no

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disease control as 0.

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Evaluation of Fungicidal Activity of Compound 8a in the Field

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The test solution was diluted

The percentage of disease control was

Azoxystrobin was used as a positive control.

Due to high potency in laboratory and greenhouse, the fungicidal activity of

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compound 8a was further evaluated in the field.

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formulation was prepared.

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cucumbers was conducted in Wuqing County, Tianjin, China.

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suspension concentrate), trifloxystrobin (50% water dispersible granule) and

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pyraclostrobin (350 g/L, emulsifiable concentrate) were used as positive controls.

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An application rates of compound 8a and positive standards were 37.5 and 75 g ai/ha

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for S. fuliginea and P. cubensis, respectively.

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the evaluated as Eqn. 1:

214 215

An emulsifiable concentrate (8.88%)

Its field efficacy against S. fuliginea and P. cubensis on Azoxystrobin (250g/L,

Disease index (DI) was determined by

DI=Σ(A×B)×100/(C×9)

(Eqn. 1)

Where A: number of disease leaves; B: corresponding grade of A; C: total


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number of investigation leaves.

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Preventative efficacy was evaluated as Eqn. 2

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Efficacy (%)=[1-CK0×PT1/(CK1×PT0)]×100%

(Eqn. 2)

219

Where CK0: DI of control group before water application; PT0: DI of treatment

220

group before compound application; CK1: DI of control group after water application;

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PT1: DI of treatment group after compound application.

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conducted by Duncan's Multiple Range Test (DMRT).

Data analysis was

223 224

Results and Discussion

225

Chemistry

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Compounds 3 and 6 were obtained from the corresponding acid 1 and ester 4,

227

respectively (Figure 2).

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between compound 1 and N,O-dimethylhydroxylamine hydrochloride.27

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intermediate 2 was reacted with methyl magnesium bromide in anhydrous THF to

230

give compound 3 in 90-93% yield. After reduction of compound 4 by sodium

231

borohydride and subsequent Dess-Martin oxidation, compound 6 was obtained in

232

50-80% yield.

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Intermediate 2 was prepared with yield 90-98% by reaction This

The compounds 8 were obtained by the reaction between the intermediate 7 and

234

the compounds 3 or 6 catalyzed by hydrochloric acid (Figure 3 ).29

235

10a-10o were prepared by a condensation reaction between the hydrolytic product 9

236

of compounds 8a, 8c or 8e and amine R3NH2 with a yield ranging from 64-96%

237

(Figure 4).

All structures were confirmed by 1H NMR,


13

The compounds

C NMR, HR-MS or


238

elemental analysis.

239

the active scaffold of strobilurin and 1,2,3-thiadiazoles or thiazoles into one molecule,

240

a series of compounds were successfully designed, synthesized and well

241

characterized.

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Fungicidal activity

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Therefore, to develop new strobilurin fungicides by integrating

The in vitro antifungal activities were assessed at 50 µg/mL and results are listed

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in Table 1.

The E-isomer of compound 8a (E-8a) exhibited slightly better fungicidal

245

activities against A. solani, G. zeae, P. piricola, B. cinerea, S. sclerotiorum and R.

246

cerealis than compound 8a (Z-8a). Because the difference between E-8a and Z-8a

247

was not significant, and the two isomers might be interconverted under biological

248

conditions, we used mixtures in all the bioassays in the same way as commercialized

249

positive controls.

250

good activity against G. zeae, B. cinerea, S. sclerotiorum, R. cerealis and P. infestans.

251

Compound E-8a exhibited a similar inhibition to azoxystrobin with 100% activity

252

against G. zeae and S. sclerotiorum.

253

inhibition against G. zeae, R. cerealis and P. infestans to azoxystrobin, and it showed

254

better efficacy against B. cinerea with 100% of growth inhibition than azoxystrobin

255

(79%).

256

infestans with 100% growth inhibition to azoxystrobin.

257

10c, 10d, 10g and 10i also showed the similar activity against PI with 100% growth

258

inhibition to azoxystrobin, and compound 10i exhibited the same activity against G.

Compounds 8 series with a 1,2,3-thiadiazole ring at R1 showed

Compound 8c exhibited similar 100%

Compound 8d had similar activity against S. sclerotiorum, R. cerealis and P. In addition, compounds 10b,


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zeae, R. cerealis and P. infestans as azoxystrobin, having totally inhibited all fungal

260

growth. Table 2 showed EC50 values of compounds 8 and 10 series.

261

Being much better

262

than the positive controls such as enestroburin, kresoxim-methyl and azoxystrobin,

263

the compound 8a showed excellent activities against G. zeae, S. sclerotiorum and R.

264

cerealis with EC50 values of 2.68, 0.44 and 0.01 µg/mL respectively, and compound

265

8a also had a similar EC90 against G. zeae as azoxystrobin, and much better activity

266

against S. sclerotiorum with EC90 more than 10 times than that of the positive controls

267

such as enestroburin, kresoxim-methyl and azoxystrobin.

268

against B. cinerea greater than 20 times than that of the three positive controls such as

269

enestroburin, kresoxim-methyl and azoxystrobin.

Compound 8c had an EC90

270

The in vivo protective activity of all target compounds against P. cubensis, E.

271

graminis, P. sorghi Schw, and C. lagenarium at 400 µg/mL were evaluated (Table 3).

272

It showed that only 8a and 8c displayed better activity against P. cubensis. than the

273

positive control azoxystrobin.

274

1,2,3-thiadiazole ring and methyl group on the side chain at R1 and R2 respectively

275

could

276

exhibited 100% growth inhibition against C. lagenarium, which were higher than

277

azoxystrobin (80%).

278

of activity against E. graminis as azoxystrobin.

This indicated that the introduction of a

increase activities against P. cubensis.

Compounds 10a, 10f and 10n

Compounds 8a, 8c-e, 10d, 10e and 10i exhibited the same level

279

Subsequently, compounds 8a and 8c with good in vivo fungicidal activity were

280

chosen for further experiments in the greenhouse at the concentration of 50 µg/mL,



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12.5 µg/mL, 3.13 µg/mL, 0.78 µg/mL and 0.20 µg/mL.

Compound 8c exhibited

282

lower activity against P. cubensis, P. sorghi Schw and C. lagenarium, however, it

283

showed the same activity against E. graminis as trifloxystrobin and azoxystrobin.

284

Compound 8a exhibited 100% inhibition activity against E. graminis even at 0.20

285

µg/mL, which was equal to azoxystrobin (100% inhibition) and better than

286

trifloxystrobin (95% inhibition) and enestroburin (30% inhibition).

287

exhibited 60% inhibition against P. cubensis at 50 µg/mL, whereas trifloxystrobin

288

only showed 20% inhibition, and enestroburin had no inhibition under the same

289

conditions.

290

warranted further development.

Compound 8a

Therefore, compound 8a exhibited high in vivo fungicidal activity and

291

These results indicated that the introduction of a 1,2,3-thiadiazole ring and a

292

methyl group on the side chain at R1 and R2 respectively could increase fungicidal

293

activities.

294

Evaluation of Fungicidal Activity of Compound 8a under the Field Condition

295

The compound 8a was chosen for field trials in 2015 against S. fuliginea and P.

296

cubensis on cucumbers (Table 5).

297

against S. fuliginea (p nd > nd > > 24.10 18.08

EC50 (µg/mL) and EC90 (µg/mL) P. i P. s EC50 EC90 EC50 EC90 nd nd nd nd 1.41 4.89 nd nd 8.76 70.17 nd nd 7.38 > nd nd 16.66 > nd nd 1.88 > 6.36 99.30 nd nd 13.92 > 0.41 > nd nd 99.84 > 18.40 > 0.71 12.08 10.71 > 0.40 7.58 3.68 >

R. c EC50 0.01 0.27 17.75 nd nd nd nd 0.07 0.12 4.43 0.06

S. s EC90 EC50 c > 0.44 > nd > 53.84 nd nd nd nd nd nd nd nd 16.82 nd 32.54 2.17 145.97 15.12 > 4.04

B. c: Botrytis cinerea; G. z: Gibberella zeae; P. i: Phytophthora infestans (Mont) de Bary; P.

s: Pellicularia sasakii; R. c: Rhizoctonia cerealis; S. s: Sclerotinia sclerotiorum. bnd: not determined; c >: data more than 200 µg/mL;


EC90 6.89 nd > nd nd nd nd nd > 81.89 >

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Table 3. In Vivo Fungicidal Activity of Compounds 8a-f and 10a-o. Fungicidal activity (%) at 400 µg/mL Compd. P. cubensis E. graminis P. sorghi Schw C. lagenarium 100 100 100 85 8a 0 0 0 0 8b 90 100 85 70 8c 0 100 30 80 8d 80 100 80 75 8e 80 60 70 85 8f 0 0 80 100 10a 30 0 85 80 10b 0 0 60 80 10c 0 100 85 85 10d 0 100 60 80 10e 75 30 0 100 10f 0 0 30 80 10g 0 70 60 80 10h 60 100 0 80 10i 65 0 0 0 10j 75 30 50 0 10k 85 0 0 60 10l 0 0 0 80 10m 60 0 80 100 10n 40 0 0 0 10o 85 100 0 80 Azoxystrobin



Table 4. Greenhouse Fungicidal Activity Validation Studies In Vivo. Fungicidal activity (%) C(µg/mL) P. cubensis E. graminis P. sorghi Schw C. lagenarium 0.2 0 100 0 40 8a 0.78 0 100 20 55 3.13 0 100 55 60 12.5 15 100 100 85 50 60 100 100 98 0.2 0 95 10 0 8c 0.78 0 100 25 0 3.13 0 100 40 0 12.5 0 100 75 0 50 0 100 98 30 0 95 95 65 Trifloxystrobin 0.2 0.78 0 100 98 85 3.13 0 100 100 98 12.5 0 100 100 98 50 20 100 100 100 0.2 0 30 30 65 Enestroburin 0.78 0 65 75 85 3.13 0 95 98 95 12.5 0 98 100 98 50 0 100 100 100 0.2 0 98 100 100 Azoxystrobin 0.78 0 100 100 100 3.13 0 100 100 100 12.5 0 100 100 100 50 0 100 100 100 Compd.


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Table 5. Fungicidal Efficacy of Compound 8a in the Cucumber Field. DD c Field Disease Compd. Efficacy(%) 5% 1% 76.61±3.63 ad ce 37.5 1.83 8.23 8a EC S. Azoxystrobin SC 37.5 1.66 9.59 70.19±2.91 bd de fuliginea Trifloxystrobin WG 37.5 1.64 10.04 68.02±5.58 b d CK ndf 1.07 20.63 nd nd nd 75 3.70 5.78 77.52±2.15 a cde 8a EC Trifloxystrobin WG 75 3.73 7.24 72.02±1.61 b d P. 75 3.57 5.78 77.02±1.77 a cd cubensis Pyraclostrobin EC CK nd 3.58 24.96 nd nd nd a b c Base DI, disease index base. After DI, disease index after compound application. DD, distinct difference. da and b: distinct difference at 95% of confidence limits; ec, d and cd: distinct difference at 99% of confidence limits. fnd, not determined. Rate (g ai/ha)

Base DIa

After DIb



FIGURE CAPTIONS Figure 1. Design of the title compounds Figure 2. General synthetic procedure for compounds 3a-c and 6a-c. Figure 3. General synthetic procedure for compounds 8a-f. Figure 4. General synthetic procedure for compounds 10a-o. Figure 5. Crystal structure for compound 8b by X-ray diffraction determination.


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Figure graphics

CH 3

N N

S

S Hetero aryl

β-methoxyacrylate O

N Boc N

N

β-methoxyacrylate

Ph

O

N

Hetero aryl R1

CH 3 O β-methoxyacrylate: H 3 CO

N

O OCH 3 H3 CO

N

1

Figure 1


1

N H

R3


a

Reagents and conditions: (i) Et3N, CH3NHOCH3 HCl, EDCI, DMAP, dry CH2Cl2,

overnight; (ii) CH3MgBr, dry THF, 0 °C to r.t.; (iii) NaBH4, CH3OH;(iv) Dess-Martin periodinane, CH2Cl2, overnight. Figure 2


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Figure 3



Figure 4


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Figure 5



Graphic for table of contents

Fungcide Cadidate


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Synthesis of 1,2,3-Thiadiazole and Thiazole-Based Strobilurins as

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