LI Juan-Juan HUA Xue-Wen, FAN Zhi-Jin, ②

JI Xiao-Tianb, c ZONG Guang-Ningb, c LI Feng-Yunb, c

HUANG Yuna② SONG Hai-Binb LIU Chao-Lunb, c

Yury Yu. Morzherind Nataliya P. Belskayad Vasiliy A. Bakulevd

a (Department of Plant Pathology, Sichuan Agricultural University, Chengdu 611130, China)

b (State Key Laboratory of Elemento-organic Chemistry, Nankai University, Tianjin 300071, China)

c (Collaborative Innovation Center of Chemical Science and Engineering(Tianjin), Tianjin 300071, China)

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

1 INTRODUCTION

1,4-Dihydropyridine (1,4-DHP)derivatives play an important role in synthetic, medicinal and bioorganic chemistry[1]. Derivatives of 1,4-dihydropyridines are well-known calcium channel modulators for the treatment of cardiovascular disorders[2-6]. It is worth underlining that the 1,4-DHP moiety is a privileged structure or scaffold for structure derivation at diverse receptors and ion channels[7-8]. 1,4-DHP derivatives possess a broad range of biological activities including antioxidant[9], anti-inflammatory[10], radioprotective[11], anticancer[12-13], antidiabetic[14], immunomodulatory[15], neuroprotective[16],antibacterial[17], antiviral, and reversal of multidrug resistance[18]. 1,4-Dihydropyridine (DHP)[19]scaffold represents the heterocyclic unit of remarkable pharmacological efficiency[20]. The reduced nicotinamide adenine dinucleotide (NADH)as a 1,4-DHP derivative acts as the electron source for the reduction of O2to H2O in the respiratory chain[21-24].Hantzsch esters (2,6-dialkyl-3,5-dialkoxycarbonyl-1,4-dihydropyridines)have been widely used to model the biological hydride transfer mechanism of coenzyme NADH[25].

Scheme 1. Schematic structure and synthesis of the target compound

1,2,3-Thiadiazoles as an important active substructure of heterocyclic compounds have various biological activities. Some 1,2,3-thiadazoles are commercialized as plant activators[26]. Many 1,2,3-thiadizole derivatives have been reported with antiviral[27-28], antitumor[29], antibacterial[30], fungicidal[31-33], and insecticidal activities[34]. Moreover,1,2,3-thiadiazole ring possesses the property of easy breakdown into low molecular weight compounds through the release of N2. It favors the characteristics of environmentally friendly pesticide candidates with low toxicity[35]. Our previous studies discovered some new 1,2,3-thiadizoles with fungicidal activity, antiviral activity and systemic acquired resistance[31,36-37].

In this paper, another type of dihydropyridine containing 1,2,3-thiadiazole and two ester groups in dihydropyridine ring was designed and synthesized.The target compound diethyl 1,4-dihydro-2,6-dimethyl-4-(4-methyl-1,2,3-thiadiazol-5-yl)pyridine-3,5-dicarboxylate was synthesized according to the routine described in Scheme 1. Its crystal structure and biological activity were also detected.

2 EXPERIMENTAL

All reagents and solvents for synthesis and analyses were of analytical grade and used without further purification. Column chromatography purification was carried out by using silica gel (200～300)with ethyl acetate and petroleum ether 1:5 (v/v)as eluent.The melting point was measured on an X-4 binocular microscope (Gongyi Tech. Instrument Co.,Henan, China), and the temperature was not corrected. Infrared (IR)spectra were recorded on a Bruker Vector 22 Fourier transform infrared (FTIR)spectrometer using KBr pellets. Hydrogen Nuclear Magnetic Resonance (1H NMR)spectra were measured at 400 MHz using a Bruker AV-400 spectrometer with deutero-chloroform (CDCl3)as the solvent and tetramethylsilane (TMS)as the internal standard. Elemental analyses (EA)data were obtained on a vario EL CUBE instrument made by German. The single-crystal structure was determined on a Rigaku Saturn 724 CCD diffractometer. The equipment was operated using Mo-Kα radiation (λ =0.71073 ?).

2. 1 Synthesis

In a 50 mL round-bottomed flask, 4-methyl-1,2,3-thiadiazole-5-formaldehyde (0.50 g, 3.90 mmol),ethyl acetoacetate (1.02 g, 7.80 mmol)and ammonium acetate (0.30 g, 3.90 mmol)were stirred in the presence of AlCl3in alcohol under refluxing for 3 h. The progress of the reaction was monitored by TLC. After completion, the reaction mixture was concentrated on rotary evaporator to remove the solvent ethanol. The residue was dissolved with 50 mL ethyl acetate and 50 mL water. The water layer was extracted with 3×50 mL ethyl acetate. The combined organic layer was washed with saturated sodium bicarbonate solution (20 mL)and brine (20 mL), dried over anhydrous sodium sulfate, filtered,and concentrated. The crude product was purified by chromatograph on silica gel (200～300 mesh)by ethyl acetate and petroleum ether (v/v = 1:5, 60～90 ℃)as eluent to afford pure target compound with the yield of 64.96%. m.p.: 163～165 ℃. The title product was recrystallized in ethyl acetate and dichloromethane (v/v = 1:1)for X-ray single-crystal determination. IR (KBr pellet press, ν, cm-1): 3306(NH), 3092 (CH), 2980 (CH3), 1709 (C=O), 1645,1497, 1380, 1273, 1207, 1105, 1045.1H NMR(CDCl3, 400MHz): δ 6.13 (1H, s), 5.50 (1H, s), 4.13(4H, q), 2.77 (3H, s), 2.35 (6H, s), 1.26 (6H, t). EA clacd. (%)for C16H21N3O4S: C, 54.68; H, 6.02; N,11.96%. Found (%): C, 54.51; H, 6.21; N, 11.85.

2. 2 Crystal data and structure determination

The crystal of the target compound was cultivated from ethyl acetate and dichloromethane. The colorless crystal of the title compound with dimensions of 0.20mm × 0.18mm × 0.10mm was selected and mounted on a glass fiber for X-ray diffraction analysis. All measurements were made on a Rigaku Saturn 724 CCD diffractometer MoKα radiation (λ =0.71073 ?). The data were collected at 293(3)K and the crystal is of monoclinic system, space group P21/n, with a = 11.300(2), b = 12.771(3), c =12.826(3)?, β = 96.55(3)o, V = 1839.0(6)?3, Z = 4,density (calculated)= 1.296 g/cm3, and linear absorption coefficient 0.200 mm-1. In the range of 2.26≤θ≤25.02°, 15,007 integrated reflections were collected, reducing to a data set of 3,248 unique with Rint= 0.0681, and completeness of data (to theta =25.02°)of 99.9%. Data were collected and processed using Crystal Clear (Rigaku). An empirical absorption correction was applied using Crystal Clear(Rigaku). The structure was solved by direct methods with SHELXS-97 program[38]. Refinements were done by the full-matrix least-squares on F2with SHELXL-97. All of the non-H atoms were refined anisotropically by full-matrix least-squares to give the final R = 0.0608 and wR = 0.1707 (w =1/[σ2(Fo2)+ (0.1119P)2+ 0.0000P], where P = (Fo2+2Fc2)/3)with (Δ/σ)max= 0.999 and S = 1.019 by using the SHELXL program. The hydrogen atoms were located from a difference Fourier map and refined isotropically. The corrections for absorption were multi-scan, Tmin= 0.9612 and Tmax= 0.9803.The bond lengths were set to 1.54(0.01)? for C(15)–C(16), C(15?)–C(16?), and 1.45(0.01)? for O(4)–C(15), O(4)–C(15?). The atomic displacement parameters were set to SIMU (0.01 C(15)C(16)C(15?)C(16?)). The disordered atom shares were 0.649(9)for C(15), C(16), and 0.351(9)for C(15′),C(16′).

2. 3 Biological screening

2. 3. 1 Fungicide screening

Preliminary screening was conducted by fungi growth inhibition method according to the reference using potato dextrose agar (PDA)as cultivation medium[31]. A stock solution of the target compound was prepared at 500 μg/mL using sterilized water containing 2 drops of N,N-dimethylformamide(DMF)as a solvent, then 1 mL of the stock solution was transferred into a 10 cm diameter of Petri dish, 9 mL of PDA was then added to prepare the plate containing 50 μg/mL of the test compound. Before the plate solidification, the PDA was thoroughly mixed by turning around the Petri dish in the sterilized operation desk 5 times to scatter the compound in PDA evenly. Then, 4 mm of diameter of fungi cake was inoculated on the plate and cultured in the culture tank at 24～26 ℃. The diameter of fungi spread was measured 2 days later.Growth inhibition was then calculated using the corresponding control. Fungi used in this study included Alternaria solani (AS), Botrytis cinerea(BC), Cercospora arachidicola (CA), Gibberella zeae (GZ), Phytophthora infestans (Mont)de Bary(PI), Physalospora piricola (PP), Pellicularia sasakii (PS), Sclerotinia sclerotiorum (SS), and Rhizoctonia cerealis (RC).

2. 3. 2 Insecticide activity of the target compound against Mythimna separata

The activity of the target compounds against M.separata was tested using the leaf-disk method[39-40].Fresh corn leaves were dipped into the 200 μg/mL test water solution for 10 s which was prepared with 5% of acetone to help the compound dissolve. After air-drying for evaporating off the acetone and water,the treated leaves were cut into small pieces and placed in Petri dishes with a 10 cm diameter. Thirty individuals of M. separata were transferred into each Petri dish. The Petri dishes were finally fastened with rubber bands and placed in a standard cultivation room for 72 h at 25 ℃ with 80%humidity. The percentage of mortality was evaluated according to the corresponding CK with water treatment only. The insects without reaction by touching with a brush pen were regarded as a death.

2. 3. 3 Systemic acquired resistance screening

Systemic acquired resistance of the target compound was detected using tobacco against the tobacco mosaic virus (TMV)system as described in ref. 36. The induction activity was evaluated using the antivirus inhibition ratio, which was calculated by the average number of viral inflammations on the inoculated leaves with the corresponding control accordingly. Tiadinil, Virazol and Ningnanmycin were used as positive controls, respectively, and the target compound was tested at the concentration of 100 μg/mL.

2. 3. 4 Protective effect of the target compound against TMV in vivo Healthy fresh tobacco plants at six-leaf stage were selected for the tests. The target compound solution(100 μg/mL)was smeared on the whole leaves, and then the leaves were dried in the greenhouse. After 12 h, TMV at a concentration of 5.88 × 10-2μg/mL was inoculated on the upper three leaves using the conventional juice robbing method, and the solvent was smeared on the lower three leaves as a control.The local lesion numbers were then recorded 2～3 days after inoculation. Three replicates were performed for the target compound, respectively.

2. 3. 5 Inactivation effect of the target compounds against TMV in vivo

Healthy fresh tobacco plants at six-leaf stage were selected for the tests. The TMV virus at a concentration of 5.88 × 10-2μg/mL was inhibited by mixing with the target compound solution (100 μg/mL)at the same volume for 30 min. Then the mixture was inoculated on the upper three leaves using the conventional juice robbing method, and the solvent was smeared on the lower three leaves as a control. The local lesion numbers were then recorded 2～3 days after inoculation. Three replicates were performed for the target compound,respectively.

2. 3. 6 Curative effect of the target compounds on TMV in vivo

Healthy fresh tobacco plants at six-leaf stage were selected for the tests. TMV at a concentration of 5.88 × 10-2μg/mL was inoculated on the whole leaves using the conventional juice robbing method.After the leaves were dried in the greenhouse, the compound solution (100 μg/mL)was smeared on the upper three leaves, and the solvent was smeared on the lower three leaves as control. The local lesion numbers were then recorded 2～3 days after inoculation. Three replicates were performed for the target compound, respectively.

The activities of protection, inactivation, and curative effects against TMV were calculated by the average number of viral inflammations on the inoculated leaves with the corresponding control according to Eq. 1.

where Y is the antivirus inhibition ratio (protection,inactivation, and curative effects in vivo)(%), CK is the average number of viral inflammations on the control leaves in vivo, and A is the average number of viral inflammations on the target compound treated leaves in vivo.

3 RESULTS AND DISCUSSION

The molecular structure and perspective view of the crystal packing in a unit cell of the title compound are shown in Figs. 1 and 2, respectively.The selected bond lengths, bond angles and torsion angles are listed in Table 1.

Table 1. Selected Bond Lengths (?), Bond Angles (°)and Torsion Angles (°)for the Title Compound

Fig. 1. Molecular structure of the title compound shown as thermal probability (hydrogen atoms were omitted)

Fig. 2. Crystal packing of the title compound

As shown in Table 1, bond lengths and bond angles within the thiadiazole ring agree well with the values reported[41]. The sum of N(1)–C(2)–C(1),C(3)–C(2)–N(1) and C(3)–C(2)–C(1) angles is 360°,indicating the sp2hybridization state of C(2) atom.The bond angles of C(5)–C(4)–C(8), C(3)–C(4)–C(8)and C(3)–C(4)–C(5) are 110.7(2)°, 110.3(2)° and 110.8(2)° in turn, which shows the sp3hybridization state of C(4) atom. Due to the non-conjugation of dihydropyridine ring with thiadiazole ring and double ester groups, the bond lengths of C(2)=C(3)(1.358(4) ?), C(5)=C(6)(1.348(4)?)and C(7)=C(8)(1.346(4)?)are slightly the same as that of typical C=C bond (1.34 ?)[42], respectively, the bond length of N(1)=N(2)(1.288(5)?)is somewhat close to that of the N=N bond (1.24 ?), and the bonds of C(4)–C(5)(1.520(4)?)and C(4)–C(8)(1.521(4)?)slightly have the same length as the typical C–C bond (1.54 ?)[43]. Owing to the p-π conjugate effect,the bond lengths of N(3)–C(6)and N(3)–C(7)are 1.376(4)and 1.377(4)?, respectively, which are much shorter than the normal C–N (1.47 ?)[44]but close to C=N (1.33 ?)[44-45]. The torsion angles of N(1)–C(2)–C(3)–C(4)and C(2)–C(3)–C(4)–C(8)are 178.9(3)° and –130.3(3)°, respectively, indicating that the dihydropyridine and thiadiazole rings are non-planar. The torsion angles of C(4)–C(5)–C(6)–N(3)and C(7)–N(3)–C(6)–C(5)are 9.2(4)° and 16.7(5)°, suggesting that the dihydropyridine ring is non-planar. The torsion angles of C(2)– N(1)–N(2)–S(1)and N(2)–S(1)–C(3)–C(2)are res- pectively–1.1(5)° and 0.5(3)°, so the thiadiazole ring is similarly planar. The C(6)–C(5)–C(14)–O(3)and C(7)–C(8)–C(11)–O(2)torsion angles to be –3.1(6)° and–15.9(5)° mean that the ester groups and dihydropyridine ring are non-planar. There are two intermolecular hydrogen bonds in the structure, N(3)–H(3)··N(1)and N(3)–H(3)··N(2), which link the adjacent molecules to form a one-dimensional chain structure (Fig. 2). The parameters of intermolecular hydrogen bonds are given in Table 2. These chains are intersected into a two-dimensional framework by the intermolecular weak interactions at O(2)··H(12A)and O(2)··H(12B). Additionally, weak π-π interactions occur between the thiadiazole rings of the adjacent molecules, which strengthen the integration of the 2-D networks (Fig. 2).

Table 2. Intermolecular Hydrogen Bonds of the Title Compound

4 BIOLOGICAL ACTIVITY

The insecticidal, fungicidal and antiviral activities of the target compound were measured and the results are listed in Tables 3 and 4. The larvicidal activity of the target compound against M. separata was tested by leaf disk method[39-40], and the insect mortality was 25% under the concentration of 200μg/mL. This result demonstrated that the compound had certain extent of insecticidal activity, and our former studies also gave good example of insecticidal activity of 1,2,3-thiadiazole derivatives[46]. The fungicidal activity against the typical fungi commonly occurring in the Chinese agro-ecosystem was detected at 50 μg/mL in vitro according to the fungi growth inhibition method reported[36]. The preliminary screening results indicated that the title compound had a broad spectrum of fungicide against AS,CA, PP, BC, RC and PS with growth inhibition of 45.00%, 43.75%, 50.00%, 51.35%, 51.28% and 63.38% respectively. The induction of systemic acquired resistance of tobacco against tobacco mosaic virus (TMV)determination was also detected under the concentration of 100 μg/mL according to the reported reference[36]. The result indicated that the title compound had a certain antiviral activity as compared with the positive controls tiadinil, virazol and ningnanmycin (Table 4).

All the results indicated that 1,2,3-thiadiazole was a very good active substructure for novel pesticide development. Changing 1,2,3-thiadiazole into dihydropyridine kept the fungicidal activity of dihydropyridine compounds.

Table 3. Fungicidal and Insecticidal Activity of the Title Compound (%)

Table 4. Antiviral Activity of the Title Compound against Tobacco Mosaic Virus (%, 100 μg/mL)

(1)Lavilla, R. Recent developments in the chemistry of dihydropyridines. J. Chem. Soc. Perkin. Trans. 1 2002, 1141?1156.

(2)Bossert, F.; Vater, W. 1,4-Dihydropyridines-a basis for developing new drugs. Med. Res. Rev. 1989, 9, 291?324.

(3)Triggle, D. J. Calcium channel antagonists: clinical uses-past, present and future. Biochem. Pharmacol. 2007, 74, 1?9.

(4)Peri, R.; Padmanabhan, S.; Rutledge, A.; Singh, S.; Triggle, D. J. Permanently charged chiral 1,4-dihydropyridines: molecular probes of L-type calcium channels. Synthesis and pharmacological characterization of methyl (ω-trimethylalkylammonium)1,4-dihydro-2,6-dimethyl-4-(3-nitrophenyl)-3,5-pyridinedicarboxylate iodide, calcium channel antagonists. J. Med. Chem. 2000, 43, 2906?2914.

(5)Karimi, A. R.; Bagherian, F.; Sourinia, M. Synthesis and characterization of 1,4-dihydropyridine-substituted metallophthalocyanines. Mendeleev.Commun. 2013, 23, 224?225.

(6)Jasinski, J. P.; Guild, C.J.; Pek, A. E.; Samshuddin, S.; Narayana, B.; Yathirajan, H. S.; Butcher, R. J. Synthesis and crystal structures of four new dihydropyridine derivatives. J. Chem. Crystallogr. 2013, 43, 429?442.

(7)Triggle, D. J. 1,4-Dihydropyridines as calcium channel ligands and privileged structures. Cell. Mol. Neurobiol. 2003, 23, 293?303.

(8)Moru?ciag, L.; Dr?ghici, C.; Ni?ulescu, G. M. Synthesis of new unsymmetrical 1,4-dihydropyridine derivatives as potential anticancer agents.Farmacia (Bucharest, Romania)2013, 61, 617?624.

(9)Kourimska, L.; Pokorny, J.; Tirzitis, G. The antioxidant activity of 2,6-dimethyl-3,5-diethoxycarbonyl-1,4-dihydropyridine in edible oils. Nahrung.1993, 37, 91?93.

(10)Vaitkuviene, A.; Ulinskaite, A.; Meskys, R.; Duburs, G.; Klusa, V.; Liutkevicius, E. Study of the interaction of 1,4-dihydropyridine derivatives with glucocorticoid hormone receptors from the rat liver. Pharmacol. Rep. 2006, 58, 551?558.

(11)Ivanov, E. V.; Ponomareva, T. V.; Merkushev, G. N.; Duburs, G.; Bisenieks, E.; Dauvorte, A.; Pilshchik, E. M.; Diethone. A new skin radioprotector.Radiobiologia, Radiotherapia 1990, 31, 69?78.

(12)Manpadi, M.; Uglinskii, P. Y.; Rastogi, S. K.; Cotter, K. M.; Wong, Y. S.; Anderson, L. A.; Ortega, A. J.; Van Slambrouck, S.; Steelant, W. F.;Rogelj, S.; Tongwa, P.; Antipin, M. Y.; Magedov I. V.; Kornienko, A. Three-component synthesis and anticancer evaluation of polycyclic indenopyridines lead to the discovery of a novel indenoheterocycle with potent apoptosis inducing properties. Org. Biomol. Chem. 2007, 5,3865?3872.

(13)Idhayadhulla, A.; Kumar, R. S.; Abdul Nasser, A. J.; Manilal, A. Synthesis of some new pyrrole and pyridine derivatives and their antimicrobial,anticancer activities. J. Biol. Chem. 2013, 7, 15?26.

(14)Briede, J.; Stivrina, M.; Stoldere, D.; Vigante, B.; Duburs, G. Effect of cerebrocrast on body and organ weights, food and water intake, and urine output of normal rats. Cell. Biochem. Funct. 2008, 26, 908?915.

(15)Andrzejczak, D.; Gorska, D.; Czarnecka, E. Influence of amlodipine and atenolol on lipopolysaccharide (LPS)-induced serum concentrations of TNF-α, IL-1, IL-6 in spontaneously hypertensive rats (SHR). Pharmacol. Rep. 2006, 58, 711-719.

(16)Klimaviciusa, L.; Klusa, V.; Duburs, G.; Kaasik, A.; Kalda, A.; Zharkovsky, A. Distinct effects of atypical 1,4-dihydropyridines on 1-methyl-4-phenylpyridinium-induced toxicity. Cell. Biochem. Funct. 2007, 25, 15?21.

(17)Gorlitzer, K.; Kramer, C.; Boyle, C. Synthesis and transformations of ethyl 1,4-dihydro-4-oxo-[1]benzofuro[3,2-b]pyridine-3-carboxylate. New antibacterial agents. Pharmazie 2000, 55, 651?658.

(18)Tasaka, S.; Ohmori, H.; Gomi, N.; Iino, M.; Machida, T.; Kiue, A.; Naito, S.; Kuwano, M. Synthesis and structure-activity analysis of novel dihydropyridine derivatives to overcome multidrug resistance. Bioorg. Med. Chem. Lett. 2001, 11, 275?277.

(19)Stout, D. M.; Meyers, A. I. Recent advances in the chemistry of dihydropyridines. Chem. Rev. 1982, 82, 223?243.

(20)Sharma, S. D.; Hazarika, P.; Konwar, D. A simple, green and one-pot four-component synthesis of 1,4-dihydropyridines and their aromatization.Catal. Commun. 2008, 9, 709?714.

(21)Mitchell, P. Keilin's respiratory chain concept and its chemiosmotic consequences. Science 1979, 206, 1148?1159.

(22)Michel, H.; Behr, J.; Harrenga, A.; Kannt, A. Cytochrome c oxidase: structure and spectroscopy. Annu. Rev. Bioph. Biom. 1998, 27, 329?356.

(23)Babcock, G. T.; Wikstrom, M. Oxygen activation and the conservation of energy in cell respiration. Nature 1992, 356, 301?309.

(24)Babcock, G. T. How oxygen is activated and reduced in respiration. P. Natl. Acad. Sci. USA 1999, 96, 12971?12973.

(25)Fukuzumi, S.; Koumitsu, S.; Hironaka, K.; Tanaka, T. Energetic comparison between photoinduced electron-transfer reactions from NADH model compounds to organic and inorganic oxidants and hydride-transfer reactions from NADH model compounds to p-benzoquinone derivatives. J. Am.Chem. Soc. 1987, 109, 305?316.

(26)Fan, Z. J.; Ai, Y. W.; Chen, J. Y.; Wang, H. Y.; Liu, F. L.; Bao, L. L.; Shi, Z. G. Preparation of BTH standard and HPLC analysis of Bion 50%WG. J.Sichuan. Normal. Univ. (Nat. Sci.)2005, 28, 608?610.

(27)Zhan, P.; Liu, X. Y.; Fang, Z. J.; Li, Z. Y.; Pannecouque, C.; De Clercq, E. D. Synthesis and anti-HIV activity evaluation of 2-(4-(naphthalen-2-yl)-1,2,3-thiadiazol-5-ylthio)-N-acetamides as novel non-nucleoside HIV-1 reverse transcriptase inhibitors. Eur. J. Med. Chem.2009, 44, 4648?4653.

(28)Zhan, P.; Liu, X. Y.; Li, Z. Y.; Fang, Z. J.; Li, Z.; Wang, D. F.; Pannecouque, C.; De Clercq, E. D. Novel 1,2,3-thiadiazole derivatives as HIV-1 NNRTIs with improved potency: synthesis and preliminary SAR studies. Bioorg. Med. Chem. 2009, 17, 5920?5927.

(29)Wu, M. J.; Sun, Q. M.; Yang, C. H.; Chen, D. D.; Ding, J.; Chen, Y.; Lin, L. P.; Xie, Y. Y. Synthesis and activity of combretastatin A-4 analogues:1,2,3-thiadiazoles as potent antitumor agents. Bioorg. Med. Chem. Lett. 2007, 17, 869?873.

(30)Gopalakrishnan, M.; Thanusu, J.; Kanagarajan, V. Heterogeneous NaHSO4·SiO2catalyzed one-pot synthesis and in vitro antibacterial and antifungal activities of pyridino-1,2,3-thiadiazoles. J. Sulfur. Chem. 2008, 29, 179?185.

(31)Fan, Z. J.; Yang, Z. K.; Zhang, H. K.; Mi, N.; Wang, H.; Cai, F.; Zuo, X.; Zheng, Q. X.; Song, H. B. Synthesis, crystal structure, and biological activity of 4-methyl-1,2,3-thiadiazole-containing 1,2,4-triazolo[3,4-b][1,3,4]thiadiazoles. J. Agric. Food. Chem. 2010, 58, 2630?2636.

(32)Zuo, X.; Mi, N.; Fan, Z. J.; Zheng, Q. X.; Zhang, H. K.; Wang, H.; Yang, Z. K. Synthesis of 4-methyl-1,2,3-thiadiazole derivatives via Ugi reaction and their biological activities. J. Agric. Food. Chem. 2010, 58, 2755?2762.

(33)Wang, Z. H.; Guo, Y. Z.; Zhang, J.; Ma, L.; Song, H. B.; Fan, Z. J. Synthesis and biological activity of organotin 4-methyl-1,2,3-thiadiazole-5-carboxylates and benzo[1,2,3]thiadiazole-7-carboxylates. J. Agric. Food. Chem. 2010, 58, 2715?2719.

(34)Nombela, G.; Pascual, S.; Aviles, M. A.; Guillard, E.; Muniz, M. Benzothiadiazole induces local resistance to Bemisia tabaci (Hemiptera:Aleyrodidae)in tomato plants. J. Econ. Entomol. 2005, 98, 2266?2271.

(35)Bakulev, V. A.; Mokrushin, V. S. Structure, synthesis, and properties of 1,2,3-thiadiazoles. Khim. Geterotsikl. Soedin. 1986, 1011?1028.

(36)Fan, Z. J.; Shi, Z. G.; Zhang, H. K.; Liu, X. F.; Bao, L. L.; Ma, L.; Zuo, X.; Zheng, Q. X.; Mi, N. Synthesis and biological activity evaluation of 1,2,3-thiadiazole derivatives as potential elicitors with highly systemic acquired resistance. J. Agric. Food. Chem. 2009, 57, 4279?4286.

(37)Zheng, Q. X.; Mi, N.; Fan, Z. J.; Zuo, X.; Zhang, H. K.; Wang, H.; Yang, Z. K. 5-Methyl-1,2,3-thiadiazoles synthesized via Ugi reaction and their fungicidal and antiviral activities. J. Agric. Food. Chem. 2010, 58, 7846?7855.

(38)Sheldrick, G. M. SHELXS-97. Program for Solution of Crystal Structures. University of Gottingen, Germany 1997.

(39)Xu, H.; Zhang, J. L. Natural products-based insecticidal agents. Synthesis and insecticidal activity of novel 4a-arylsulfonyl oxybenzyloxy-2b-chloropodophyllotoxin derivatives against Mythimna separata Walker in vivo. Bioorg. Med. Chem. Lett. 2011, 21, 5177?5180.

(40)Cui, J.; Li, M. L.; Yuan, M. S. Antifeedant activities of tutin and 7-hydroxycoumarin acylation derivatives against Mythimna separate. J. Pestic. Sci.2012, 37, 95?98.

(41)Yang, Z. K.; Fan, Z. J.; Zuo, X.; Zheng, Q. X.; Song, H. B.; You, J. M.; Natalia, P. B.; Vasiliy, A. B. Synthesis and crystal structure of 3,6-bis(4-methyl-1,2,3-thiadiazol-5-yl)-1,2,4-triazolo[3,4-b][1,3,4]thiadiazole. Chin. J. Struct. Chem. 2010, 29, 13?16.

(42)Bartell, L. S.; Roth, E. A.; Hollowell, C. D.; Kuchitsu, K. Electron-diffraction study of the structures of C2H4and C2D4. J. Chem. Phys. 1965, 42,2683?2686.

(43)Gong, X. W.; Li, X.; Li, W. L.; Gao, X.; Xu, W. F.; Zhai, H. M. Synthesis and crystal structure of(E)-4-(benzyloxy)-2-(cinnamoyloxy)-N,N,N-trimethyl-4-oxobutan-1-aminium chloride as a double-prodrug. Chin. J. Struct. Chem. 2008, 27,177?182.

(44)Jian, F. F.; Xiao, H. L.; Zhao, P. S. Hydrothermal synthesis and X-ray characterization of silver(I)complex: diacetylthiocarbamide silver(I)nitrate,[Ag(CH3CONHC(S)NH2)2](NO3). Chin. J. Struct. Chem. 2004, 23, 486?489.

(45)Ye, Z. J.; Shi, L. N.; Shao, X. S.; Xu, X. Y.; Xu, Z. P.; Li, Z. Pyrrole- and dihydropyrrole-fused neonicotinoids: design, synthesis, and insecticidal evaluation. J. Agric. Food Chem. 2013, 61, 312?319.

(46)Wang, H.; Yang, Z. K.; Fan, Z. J.; Wu, Q. J.; Zhang, Y. J.; Mi, N.; Wang, S. X.; Zhang, Z. C.; Song, H. B.; Liu, F. Synthesis and insecticidal activity of N-tert-butyl-N,N?-diacylhydrazines containing 1,2,3-thiadiazoles. J. Agric. Food Chem. 2011, 59: 628?634.