Synthesis, Crystal Structure, Docking and Antifungal Activity of a New Pyrazole Acylurea Compound①

JIN Tao ZHAI Zhi-Wen HAN Liang WENG Jian-Quan TAN Cheng-Xia LIU Xing-Hai

?

Synthesis, Crystal Structure, Docking and Antifungal Activity of a New Pyrazole Acylurea Compound①

JIN Tao ZHAI Zhi-Wen HAN Liang WENG Jian-Quan TAN Cheng-Xia LIU Xing-Hai②

(310014)

pyrazole acyl urea, synthesis, crystal structure, fungicidal activities, docking;

1 INTRODUCTION

In the past decades, heterocyclic derivatives received important attention because of their diverse biological activities[1-5]. Pyrazole derivatives dis- played various activities, such as anti-inflammatory activity[6], antifungal activity[7], nematicidal active- ty[8-12], antibacterial activity[13], antinociceptive activity[14], antitumor activity[15], and antitubercular activity[16]. Furthermore, many pyrazole carboxa- mide derivatives had been developed as commercial fungicides target succinate dehydrogenase (SDH), including furametpyr, penthiopyrad, isopyrazam, sedaxane, bixafen and fluxapyroxad. On the other hand, urea substrate is always an important key building block in many active compounds. These derivatives exhibited wide activities, such as antiproliferative activity[17], antifungal activity[18]and insecticidal activity[19].

In view of these facts mentioned above, and also as a part of our work on the synthesis of bioactive lead compounds for drug discovery[20-28], the title compound was designed by introducing urea phar- macophore into pyrazole carboxamide scaffold. A new pyrazole carboxamide derivativewas synthe- sized and characterized by1H NMR and H RMS. The single-crystal structure of the title compound was determined by X-ray diffraction. The antifungal activity of the title compound was tested and the docking was carried out to study the mode of action.

2 EXPERIMENTAL

2. 1 Instruments

Melting points were determined using an X-4 apparatus and uncorrected.1H NMR spectra were measured on a Bruker AV-400 instrument using TMS as an internal standard and CDCl3as the solvent. Mass spectra were determined on a Thermo Finnigan LCQ Advantage LC/mass detector instru- ment. Elemental analyses were performed on a Vario EL elemental analyzer. Crystallographic data of the compound were collected on a Rigaku Saturn diffractometer. All the reagents were of analytical grade or freshly prepared before use.

2. 2 General procedure

The intermediates 1, 2, 3, 4, 5 and 6 were synthesized according to the reference[29]. To a solution of 1-methyl-3-(trifluoromethyl)-1H-pyra- zole-4-carbonyl isocyanate (1 mmol) in CH2Cl2(5 mL), the 3,5-dimethylaniline was dropwise added. The mixture was stirred at room temperature for overnight. The title compound was given by filtration.Yield60%, m.p. 209 ℃.1H NMR (CDCl3, 400 MHz),: 2.26(s, 6H, 2CH3), 3.98(s, 3H, CH3), 6.75(s, 1H, Ph), 7.20(s, 2H, Ph), 8.74(s, 1H, CH), 10.53(s, 1H, NH), 10.94(s, 1H, NH). HR-ESI-MS for C15H10N4S2: calcd. 341.1220, found: 341.1218[M+H]+.

2. 4 Structure determination

A colorless crystal suitable for X-ray diffraction study was cultivated in the test tube from EtOH by self-volatilization. A crystal with dimensions of 0.20mm × 0.18mm × 0.12mm was mounted on a Rigaku Saturn diffractometer equipped with a graphite-monochromatic Moradiation (= 0.71073 ?). Intensity data were collected at 113(2) K by using a multi-scan mode in the range of 3.11≤≤7.53° with the following index ranges: –15≤≤13, –15≤≤15 and –17≤≤17. A total of 20584 reflections were collected and 7171 were independent (int= 0.0257), of which 5864 with> 2() were observed. The crystal structure was solved by direct methods with SHELXS-97[30]and refined by full-matrix least-squares refinements based on2with SHELXL-97. All non-hydrogen atoms were refined anisotropically, and all hydrogen atoms were located in the calculated positions and refined with a riding model. The final refinement converged at= 0.0347,= 0.1005 (= 1/[2(F2) + (0.0635)2+ 0.0643P], where= (F2+ 2F2)/3),= 1.078 and (Δ/)max= 0.001.

3 RESULTS AND DISCUSSION

3. 1 Synthesis and spectra analysis

The synthetic route for the preparation of the title pyrazole compound is depicted in Scheme 1. In this paper, ethyl trifluoroacetoacetate and triethyl orthoformate took place smoothly in the presence of acetic anhydride, resulting in the formation of intermediate 1. Then the pyrazole ring was cyclized from intermediate 1 and methylhydrazine. After that, the key intermediate pyrazole isocyanate was given via hydrosis, acylation, ammoniation from inter- mediate 2. Finally, the target compound was obtained by using isocyanate and 3,5-dimethylani- line at room temperature with high yield.

The structure of the pure title product was confirmed by1H NMR and H RMS. From the1H NMR data, the appearance of signals at 2.26 and 3.98 ppm is assigned to two methyl protons of benzene and pyrazole rings, respectively. The two NH protons are found at 10.53 and 10.94 ppm as single peaks. The high resolution mass spectroscopy of the title compound is in agreement with the molecular formula C15H10N4S2.

3. 2 Crystal structure

Generally, the average bond lengths and bond angles of pyrazole and phenyl rings were normal ranges. The N(2)–C(4) (1.3445(14) ?) and N(1)–C(2) (1.3265(15) ?) bonds were longer than the general C=N double bond length of 1.27 ?, which indicated significant electron delocalization in the fused ring system. The torsion angles of C(7)–N(3)–C(6)–C(3) and C(8)–N(4)–C(7)–N(3) are 178.09(10)° and –171.51(10)° respectively, which indicated the two carbonyl groups are opposite. The angle between the pyrazole and benzene rings is 127o.

Scheme 1. Synthetic route of title compound

Fig.1. Molecular structure of the title compound

Table 1. Selected Bond lengths (?) and Bond angles (°) for the Title Compound

The title compound has an extensive network of hydrogen bonding. The parameters of intramole- cular and intermolecular bonds are given in Table 2. They are linked together by four N–H···O hydrogen bonds.

Table 2. Hydrogen-bond Parameters (?) of the Title Compound

3. 3 Fungicidal activity and docking

Antifungal activities were evaluated according to reference[28]. The fungicidal activities of the title compound against(FO),(CM),(BC)and(PS) were evaluatedat 100μg/mL. The primary bioassay showed that the title compound exhibited good inhibitory activity against FO,CM, BCandPS. Its inhibitory rates to FO,CM,BCandPS were 5.19%, 53.50%, 88.55% and 70.62%, respectively. In order to study the action mode of the title compound and the target, the binding modes between SDH (PDB:2FBW) and the active compound 7 were selected as exemplified in the case of representative compound by using the Discovery studio. Compound 7 can tightly occupy the binding site of SDH, and the docking resultis shown in Fig.2. From the docking results,com-pound 7 held two hydrogen bonds. The Oand F atoms of NHCO group in pyrazole ring of 7 can form tightinteraction with Tyr58 and Trp173 in hinge domain of SDH via two hydrogen bonds, respectively. The results indicated that the key active group is trifluoromethyland acyl amide groups.

Fig. 2. Docking mode of the title compound with SDH

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11 December 2017;

20 March 2018 (CCDC 1823250)

① This work was funded by Zhejiang Provincial Science Foundation of China (No.LY16C140007).

. E-mail: xhliu@zjut.edu.cn

10.14102/j.cnki.0254-5861.2011-1919