Design, synthesis and anti-bacterial evaluation of novel 1,3,4-thiadiazole derivatives bearing a semicarbazone moiety

Article abstract of DOI:10.1080/10426507.2018.1436546

Novel 1,3,4-thiadiazole derivatives bearing a semicarbazone moiety were prepared and evaluated for their anti-bacterial activities against Xanthomonas oryzae pv. oryzae (Xoo) and Xanthomonas axonopodis pv. citri (Xac) by performing a turbidimetre test. The products were structurally characterised by IR, ¹H NMR, ¹³C NMR, ¹⁹F NMR and HRMS. Anti-bacterial testing showed that most of the evaluated compounds (6a-6s) exhibited excellent activity (≥74.19%) against Xoo at a concentration of 200?μg/mL, with 50% effective concentration (EC₅₀) values ranging from 12.21 to 67.20?μg/mL, which were superior to the commercial antibacterial agent bismerthiazol (92.23?μg/mL). Among them, compound 2-((2-chloro-1H-indol-3-yl)methylene)-N-(5-((2-chlorobenzyl)thio)-1,3,4-thiadiazol-2-yl)hydrazine-1-carboxamide (6b) demonstrated good inhibitory activity against Xac (89.46% at 200?μg/mL) and Xoo (EC₅₀ = 18.28?μg/mL); compound 2-((2-chloro-1H-indol-3-yl)methylene)-N-(5-((4-methoxybenzyl)thio)-1,3,4-thiadiazol-2-yl)hydrazine-1-carboxamide (6g) displayed excellent activity against Xoo with EC₅₀ value of 12.21?μg/mL.

Full text of DOI:10.1080/10426507.2018.1436546

Phosphorus, Sulfur, and Silicon and the Related Elements
ISSN: 1042-6507 (Print) 1563-5325 (Online) Journal homepage: http://www.tandfonline.com/loi/gpss20
Design, Synthesis and Anti-bacterial Evaluation
of Novel 1,3,4-Thiadiazole Derivatives Bearing a
Semicarbazone Moiety
Jinlin Wan, Yiyuan Gan, Weinan Hu, Jiao Meng, Kun Tian, Xiaoqin Li, Shouqun
Wu, Yang Xu, Guiping Ouyang & Zhenchao Wang
To cite this article: Jinlin Wan, Yiyuan Gan, Weinan Hu, Jiao Meng, Kun Tian, Xiaoqin Li,
Shouqun Wu, Yang Xu, Guiping Ouyang & Zhenchao Wang (2018): Design, Synthesis and Anti-
bacterial Evaluation of Novel 1,3,4-Thiadiazole Derivatives Bearing a Semicarbazone Moiety,
Phosphorus, Sulfur, and Silicon and the Related Elements, DOI: 10.1080/10426507.2018.1436546
To link to this article: https://doi.org/10.1080/10426507.2018.1436546
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Publisher: Taylor & Francis
Journal: Phosphorus, Sulfur, and Silicon and the Related Elements
DOI: https://doi.org/10.1080/10426507.2018.1436546
Design, Synthesis and Anti-bacterial Evaluation of Novel 1,3,4-Thiadiazole
Derivatives Bearing a Semicarbazone Moiety
Jinlin Wana†, Yiyuan Ganb†, Weinan Hub, Jiao Mengb, Kun Tiana, Xiaoqin Lia,
Shouqun Wua, Yang Xua, Guiping Ouyanga,b*, Zhenchao Wangb*
a State Key Laboratory Breeding Base of Green Pesticide and Agricultural
Bioengineering, Key Laboratory of Green Pesticide and Agricultural Bioengineering,
Ministry of Education, Center for Research and Development of Fine Chemicals,
Guizhou University, Guiyang 550025, P. R. China
b College of Pharmacy, Drug Synthetic Engineering Laboratory of Guizhou Province,
Guizhou University, Guiyang 550025, P. R. China
*Corresponding Author: E-Mail addresses: oygp710@163.com; Tel.:
+86-851-8829-7892; Fax: +86-851-8829-7892
*Corresponding Author: E-Mail addresses: wzc.4884@163.com; Tel.:
+86-851-8829-7892; Fax: +86-851-8829-7892
†These authors contributed equally to this work.

Abstract
Novel 1,3,4-thiadiazole derivatives bearing a semicarbazone moiety were
prepared and evaluated for their anti-bacterial activities against Xanthomonas oryzae
pv. oryzae (Xoo) and Xanthomonas axonopodis pv. citri (Xac) by performing a
turbidimetre test. The products were structurally characterised by IR, 1H NMR, 13C
NMR, 19F NMR and HRMS. Anti-bacterial testing showed that most of the evaluated
compounds (6a-6s) exhibited excellent activity (>74.19%) against Xoo at a
concentration of 200 µg/mL, with 50% effective concentration (EC50) values ranging
from 12.21 to 67.20 µg/mL, which were superior to the commercial antibacterial agent
bismerthiazol (92.23 µg/mL). Among them, compound
2-((2-chloro-1H-indol-3-yl)methylene)-N-(5-((2-chlorobenzyl)thio)-1,3,4-thiadiazol-2
-yl)hydrazine-1-carboxamide (6b) demonstrated good inhibitory activity against Xac
(89.46% at 200 µg/mL) and Xoo (EC50 = 18.28 µg/mL); compound
2-((2-chloro-1H-indol-3-yl)methylene)-N-(5-((4-methoxybenzyl)thio)-1,3,4-thiadiazo
l-2-yl)hydrazine-1-carboxamide (6g) displayed excellent activity against Xoo with
EC50 value of 12.21 µg/mL.
Graphical abstract
2

Keywords
1,3,4-thiadiazole; indole; semicarbazone; antibacterial activities
Introduction
Bacterial diseases, such as rice bacterial leaf blight caused by Xanthomonas
oryzae pv. oryzae (Xoo) and citrus canker by Xanthomonas axonopodis pv. citri (Xac),
has led to serious losses each year.[1,2] In recent decades, chemical control has become a
useful tool in regulating the growth of Xanthomonas oryzae pv. oryzae (Xoo) and
Xanthomonas axonopodis pv. citri (Xac), plant pathogens are responsible for high
incidence rates of plant mortality worldwide.[3-5] However, the application of numerous
currently available anti-bacterial agents is limited by their low efficiency, phytotoxic
3

effect and high accumulation in soil.[6,7] For example, bismerthiazol, a major
bactericide for the control of rice bacterial leaf blight, shows low control efficiency at a
high dosage.[8] Furthermore, the emergence of bactericide resistance[9,10] has rendered
the search for new anti-bacterial agents an urgent task in pesticide science.[11]
1,3,4-Thiadiazole derivatives are associated with diverse biological activities
probably due to the presence of =N-C-S group,[12] such as anti-microbial,[12,13]
anti-bacterial,[3] anticancer,[14] anti-inflammatory,[15,16] carbonic anhydrase
inhibitory,[17] anti-depressant,[18] and antioxidant properties.[19] Thus, 1,3,4-thiadiazoles
and related compounds have garnered increasing attention in medicinal chemistry and
technological fields in recently years. Moreover, certain indole intermediates can be
widely used as important synthons for further transformation to various indole
alkaloids. Numerous heterocyclic compounds containing the nitrogen atom and derived
from indole have been designed as potential anti-bacterial, anti-cancer and anti-viral
agents and protein kinase inhibitors.[20–23] The semicarbazone moiety serves as a
building block in numerous drug designs owing to the presence of two NH groups as
both several hydrogen acceptors and donors, in addition to its flexible skeleton.[24-27]
Considering the above mentioned studies, we designed and synthesized a series of
novel thiadiazole derivatives bearing the semicarbazone moiety. The synthetic route is
depicted in Scheme 1. The structures of the target compounds and all first reported
intermediates were confirmed by 1H NMR, 13C NMR, 19F NMR and HRMS.
Preliminary bioassays indicated that most of evaluated compounds 6a-6s exhibited
4

excellent activity (>74.19% of 200 µg/mL and >59.48% of 100 µg/mL) against Xoo,
and relative poor potency (<58.36% of 200 µg/mL and <38.35% of 100 µg/mL) toward
Xac.
[Insert Scheme 1]
Results and Discussion
Chemistry
The synthetic routes to the target compounds are illustrated in Scheme 1.
5-Amino-1,3,4-thiadiazole-2-thiol 1 reacted with the corresponding benzyl
chlorides (R-phCH2-Cl) or bromine halogenated hydrocarbon (R1-Br) in the presence
of NaOH in EtOH at room temperature to afford 2a-2s with 68%–90% yields.[28-30] The
products were treated with phenyl chloroformate in the presence of pyridine in
tetrahydrofuran at 0 °C to yield 3a-3s.[31] Furthermore, a mixture of compounds 3a-3s,
85% hydrazinehydrate and dimethoxyethane was stirred at reflux to yield 4a-4s.[32]
Then, 2-oxindole was treated with Vilsmeier’s reagent to yield
2-chloro-3-formylindole 5,[33] which reacted with 4a-4s to yield the target compounds
6a-6s.
The structures of all target compounds 6a-6s and the unreported intermediates
3a-3s (except for 3o-3r), and 4a-4s were confirmed by 1H NMR, 13C NMR, 19F NMR
and HRMS. The 1H NMR spectrum of intermediates 3a-3s showed characteristic peaks
near δ 12.84 to 12.94 ppm for the NH proton, near δ 4.43 to 4.62 ppm for S-CH2 proton
5

and near δ 6.89 to 7.85 ppm for the phenyl proton. The 13C NMR spectra of
intermediates 3a-3s showed characteristic peaks near δ 158.0 ppm for C=O carbon. In
HRMS, compounds 3a-3s showed molecular ion peaks for [M+H]+, which were in
accordance with their molecular weight within the margin of error.
The 1H NMR spectra of intermediates 4a-4s showed characteristic peaks near δ
8.50 ppm for the NH proton and near δ 4.30 to 4.50 ppm for the S-CH2 proton, but
another NH and NH2 active hydrogen showed no peak. The 13C NMR spectra of
intermediates 4a-4s showed characteristic peaks near δ 161.0 ppm for C=O carbon. The
HRMS spectra of compounds 4a-4s showed molecular ion peaks for [M+H]+ or
[M+Na]+, which were in accordance with their molecular weight.
The 1H NMR spectrum of target compounds 6a-6s showed characteristic peaks
near δ 12.40 ppm for the indole-NH proton, near δ 11.00 ppm for two NH protons and
near δ 8.28 ppm for CH=N. The 13C NMR spectra of target compounds 6a-6s showed
characteristic peaks at approximately δ 143.0 ppm for C=N carbon. The HRMS spectra
(ESI) of compounds 6a-6s showed molecular ion peaks for [M+H]+ or [M+Na]+, which
were in accordance with their molecular weight. In the IR spectra, characteristic
absorption bands for compounds 6a-6s were displayed in the ranges of 3300−3400,
1670−1710 and 1620−1649 cm-1, which corresponded to the N-H, C=O and C=N
groups of all target compounds, respectively. In addition, the 1H NMR, 13C NMR, 19F
NMR and HRMS spectral data of intermediates 3a-3s (except for 3o-3r) and 4a-4s
were provided in support materials.
6

Antibacterial activity
All target compounds were evaluated for their anti-bacterial activity against Xoo
and Xac in vitro by performing a turbidimeter test. Two commercial anti-bacterials,
bismerthiazol and thiodiazole-copper, were selected as the positive controls for
evaluating the bactericidal potency of the synthesized compounds. As illustrated in
Table S 1 (Supplemental Materials), compared with positive controls, most of the
target compounds (6a-6s) displayed markedly lower inhibition rate against Xac,
whereas compounds 6b, 6h, 6j presented relative excellent inhibitory activities against
Xac, with inhibition rates of 89.46%, 71.38%, and 85.59% respectively; these values
were superior to those of thiodiazole-copper (67.36%) and bismerthiazol (65.37%) at
200 µg/mL. In total, the novel synthesized compounds 6a-6s presented lower or
equivalent anti-bacterial activities against Xac compared with positive controls
(thiodiazole-copper and bismerthiazol).
However, most of the title compounds exhibited moderate activity against Xoo.
Among them, compounds 6b, 6e, 6g, 6p, 6q, and 6r appeared highly active for Xoo,
with inhibition rates of 96.31% and 91.22%, 92.32% and 76.74%, 95.27% and 93.41%,
93.32% and 71.82%, 96.64% and 64.33%, 97.29% and 91.55% at 200 and 100 µg/mL
respectively; these values were notably superior to the values of thiodiazole-copper
(68.39% and 35.44% ) and bismerthiazol (72.54% and 54.78%). Novel compounds
6a-6s appear to be promising bactericides against Xoo.
7

The EC50 values of partial target compounds 6a-6s were further investigated due
to their stronger effect against Xoo as compared with the positive controls. As shown in
Table S 2 (Supplemental Materials), compounds 6b, 6c, 6e, 6f, 6g, 6m, 6p, 6q, and 6r
inhibited Xoo in vitro, with EC50 values of 18.28, 67.2, 47.86, 63.09, 12.21, 70.79,
34.30, 36.88, and 20.25 µg/mL, respectively, which were superior to those of
bismerthiazol (92.23 µg/mL). Moreover, among the title compounds, 6b and 6g
presented excellent inhibitory effects against Xoo, markedly exceeding the values of
bismerthiazol.
The inhibitory rates of compounds 6a-6s against Xoo in vitro were measured to
establish structure-activity relationships. When the substituent R was a chlorine atom
as the electron-withdrawing group, compound 6b (R = 2-Cl) exhibited excellent
inhibitory activity against Xoo at the concentrations of 200 and 100 µg/mL. This
compound was superior to compound 6c (R = 3-Cl) and 6d (R = 4-Cl). In addition,
compound 6c (R = 3-Cl) exhibited stronger inhibitory activity compared with
compound 6d (R = 4-Cl). The introduction of the fluorine atom (R = 2-F, 4-F)
exerted minimal influence on enhancing inhibitory activity against Xoo.
With an electron-donating methoxy group as the substituent R, compound 6g (R
= 4-OCH3) appeared highly active, preceding compounds 6e (R = 2-OCH3) and 6f (R
= 3-OCH3). Furthermore, compared with compound 6f (R = 3-OCH3), compound 6e
(R = 2-OCH3) showed stronger inhibitory activity against Xoo. However, when
substituent R was replaced with a methyl group, relatively poor inhibitory activity of
8

the corresponding compounds 6h (R = 2-CH3), 6i (R = 3-CH3) and 6j (R = 4-CH3)
against Xoo were resulted. Finally, when the substituent R1 was an unbranched alkyl
group, compounds 6p (R1 = C2H5), 6q (R1 = C3H7) and 6r (R1 = C4H9) showed
excellent inhibitory activity against Xoo. Among the compounds, 6r showed the best
inhibition activity. Compounds 6o (R1 = CH3) and 6s (R1 = C5H11) exhibited
relatively low activity against Xoo, but their performance was similar to that of
bismerthiazol. In total, substituent R replaced with an electron-donating group
displayed stronger inhibitory activity against Xoo than that replaced with an
electron-withdrawing group.
Experimental
General methods
All reagents were analytical grade or were chemically pure and used without
further treatment unless otherwise noted. The melting point was determined using an
XT-4 binocular microscope (Beijing Tech Instrument, China) and was not corrected.
1H NMR and 13C NMR (solvent DMSO-d6) spectral analyses were performed on a
Bruker 400 NMR spectrometer operated at 400 MHz for 1H NMR, 101MHz for 13C
NMR at room temperature and with TMS as the internal standard.
Mass spectral studies were performed on a quadrupole/electro-stati field orbitrap
mass spectrometer. IR spectra were recorded using KBr discs on a Bruker VECTOR
22 spectrometer. Thin-layer chromatography (TLC) on silica gel GF 254 was used to
9

monitor reaction progress. The supplemental materials section contained the sample
1H NMR, 13C NMR, 19F NMR, HRMS spectra for 3a-3s (except for 3o-3r), 4a-4s,
6a-6s (Figures S 1–S 165, Supplemental Materials).
General Procedure for the preparation of 2a-2s[28-30]
5-Amino-1,3,4-thiadiazole-2-thiol 1 was dissolved in a mixture of NaOH in
absolute EtOH. After 10 min, the corresponding benzyl chlorides (R-PhCH2-Cl) or
bromine halogenated hydrocarbon (R-Br) was added dropwise with vigorous stirring at
room temperature. The reaction was monitored by TLC and completed within 10 h. The
mixture was poured into water, and the precipitate was washed with water to yield
2a-2s.
General Procedure for the preparation of 3a-3s[31]
Phenylchloroformate (1 mmol) was added dropwise to a stirred mixture of
5-(benzylthio)-1,3,4-thiadiazol-2-amine (2a) (1 mmol), tetrahydrofuran and pyridine
(1.1 mmol) at 0 °C . The mixture were stirred for 3−6 h at room temperature, washed
with water (3 x 50 mL), dried over anhydrous Na2SO4 and then filtrated. The solvent
was evaporated under reduced pressure, and the deposited solid was collected and
recrystallized from EtOAc to give 3a as white solid. The synthetic procedure for
compounds 3b-3s was similar to the synthesis of compound 3a.
General Procedure for the preparation of 4a-4s[32]
10

A mixture of compound 3a (1 mmol), 85% hydrazine hydrate (10 mmol) and
dimethoxyethane was stirred at reflux. After completion, the mixture was poured into
water, and the precipitate was washed with EtOAc to produce 4a as white solid. The
product can be used directly in the next step without further purification. The synthetic
procedure for compounds 4b-4s was similar to that for compound 4a.
General Procedure for the preparation of 6a-6s
2-Chloro-3-formylindole 5 (1 mmol) was added to a solution of compound 4a (1
mmol) in EtOH, and the resulting mixture were heated for 2 h at 80 °C. Water (100 mL)
was added, the mixture was filtered and the residue was dried and recrystallized from
MeOH to yield 6a as primrose yellow solid. The synthetic procedure for compounds
6b-6s was similar to that for compound 6a.
Characterization of Compounds 6a-6s
N-(5-(benzylthio)-1,3,4-thiadiazol-2-yl)-2-((2-chloro-1H-indol-3-yl)methylene)hyd
razine-1-carboxamide (6a)
1
Primrose yellow solid; Yield: 84%; m.p. 222−224 °C; H NMR (400 MHz,
DMSO-d6) δ 12.47 (s, 1H, indole-NH), 11.05 (d, J = 75.1 Hz, 2H, NH, NH), 8.37 (d, J
= 6.6 Hz, 1H, ArH), 8.30 (s, 1H, CH=N-), 7.51 (td, J = 7.3, 1.7 Hz, 2H, ArH),
7.41−7.38 (t, J = 7.3, 1.7 Hz 1H, ArH), 7.33 (ddd, J = 8.0, 7.0, 1.8 Hz, 2H, ArH),
7.30−7.22 (t, 12.0Hz, 2H, ArH), 4.55 (s, 2H, CH2); 13C NMR (101 MHz, DMSO-d6) δ
161.1 (s), 157.8 (s), 152.3 (s), 139.6 (s), 137.3 (s), 135.4 (s), 129.5 (s), 129.0 (s), 128.0
11

(s), 127.6(s), 124.3 (s), 123.7 (s), 122.1 (s), 121.6 (s), 111.6 (s), 107.3 (s), 38.2 (s); IR:
3436 (N-H), 1703 (C=O), 1620 (C=N); HRMS (ESI): calcd. for C19H16ON6ClS2
([M+H]+): 443.05100, found: 443.05099.
2-((2-chloro-1H-indol-3-yl)methylene)-N-(5-((2-chlorobenzyl)thio)-1,3,4-thiadiaz
ol-2-yl)hydrazine-1-carboxamide (6b)
1
Primrose yellow solid; Yield: 83%; m.p. 211−213 °C; H NMR (400 MHz,
DMSO-d6) δ 12.47 (s, 1H, indole-NH), 11.05 (d, J = 75.1 Hz, 2H, NH, NH), 8.37 (d, J
= 6.6 Hz, 1H, ArH), 8.30 (s, 1H, CH=N-), 7.51 (td, J = 7.3, 1.7 Hz, 2H, ArH),
7.42−7.37 (m, 1H, ArH), 7.33 (ddd, J = 8.0, 7.0, 1.8 Hz, 2H, ArH), 7.30−7.21 (m, 2H,
ArH), 4.55 (s, 2H, CH2); 13C NMR (101 MHz, DMSO-d6) δ 161.4 (s), 157.0 (s), 152.3
(s), 139.7 (s), 135.4 (s), 134.8 (s), 133.8 (s), 131.9 (s), 130.1(d, J = 4.8 Hz), 127.8 (s),
124.3 (s), 123.7 (s), 122.1 (s), 121.6 (s), 111.6 (s), 107.3 (s), 36.4 (s); IR: 3436 (N-H),
1697 (C=O), 1629 (C=N); HRMS (ESI): calcd. for C19H15ON6Cl2S2 ([M+H]+):
477.01203, found: 477.01199.
2-((2-chloro-1H-indol-3-yl)methylene)-N-(5-((3-chlorobenzyl)thio)-1,3,4-thiadiaz
ol-2-yl)hydrazine-1-carboxamide (6c)
1
White solid; Yield: 85%; m.p. 213−215 °C; H NMR (500 MHz, DMSO-d6 )
δ12.42 (s, 1H, indole-NH), 10.98 (d, J = 119.7 Hz, 2H, NH, NH), 8.31 (d, J = 5.7 Hz,
1H, ArH), 8.23 (s, 1H, CH=N-), 7.46 (s, 1H, ArH), 7.40−7.27 (m, 4H, ArHg),
7.26−7.11 (m, 2H, ArH), 4.44 (s, 2H, CH2); 13C NMR (101 MHz, DMSO-d6) δ 161.2
(s), 157.3 (s), 152.3 (s), 140.2 (s), 139.9 (s), 135.4 (s), 133.5 (s), 130.8 (s), 129.3 (s),
12

128.2 (s), 127.8 (s), 124.3 (s), 123.7 (s), 122.1 (s), 121.6 (s), 111.8 (s), 107.3 (s), 37.3
(s); IR: 3438 (N-H), 1693 (C=O), 1635 (C=N); HRMS (ESI): calcd. for
C19H14ON6Cl2NaS2 ([M+Na]+): 498.99398, found: 498.99316.
2-((2-chloro-1H-indol-3-yl)methylene)-N-(5-((4-chlorobenzyl)thio)-1,3,4-thiadiaz
ol-2-yl)hydrazine-1-carboxamide (6d)
Primrose yellow solid; Yield: 85%; m.p. 224−226 °C; 1H NMR (400 MHz,
DMSO-d6) δ 12.45 (s, 1H, indole-NH), 11.01 (d, J = 67.9 Hz, 2H, NH, NH), 8.34 (d, J
= 6.2 Hz, 1H, ArH), 8.26 (s, 1H, CH=N-), 7.50 (s, 1H, ArH), 7.37 (d, J = 6.1 Hz, 4H,
ArH), 7.24 (dt, J = 13.7 Hz, 2H, ArH), 4.48 (s, 2H, CH2); 13C NMR (101 MHz,
DMSO-d6) δ 161.2 (s), 157.4 (s), 152.3 (s), 140.2 (s), 139.9 (d, J = 53.9 Hz), 135.4 (s),
133.5 (s), 130.8 (s), 129.3 (s), 128.2 (s), 128.0 (s), 127.8 (s), 124.3 (s), 123.7 (s), 122.1
(s), 121.6 (s), 111.6 (s), 107.3 (s), 37.3 (s); IR: 3435 (N-H), 1689 (C=O), 1635 (C=N);
HRMS (ESI): calcd. for C19H15ON6Cl2S2 ([M+H]+): 477.01203, found: 477.01190.
2-((2-chloro-1H-indol-3-yl)methylene)-N-(5-((2-methoxybenzyl)thio)-1,3,4-thiadi
azol-2-yl)hydrazine-1-carboxamide (6e)
Yellow solid; Yield: 91%; m.p. 224−225 °C; 1H NMR (400 MHz, DMSO-d6) δ
12.46 (s, 1H, indole-NH), 11.00 (d, J = 84.5 Hz, 2H, NH, NH), 8.36 (d, J = 6.5 Hz, 1H,
ArH), 8.28 (s, 1H, CH=N-), 7.38 (d, J = 7.0 Hz, 1H, ArH), 7.33 (d, J = 7.5 Hz, 1H,
ArH), 7.30−7.20 (m, 3H, ArH), 7.03 (d, J = 8.1 Hz, 1H, ArH), 6.90 (t, J = 7.4 Hz, 1H,
ArH), 4.41 (s, 2H, CH2), 3.82 (s, 3H, CH3O); 13C NMR (101 MHz, DMSO-d6) δ 161.1
(s), 158.2 (s), 157.6 (s), 152.3 (s), 139.6 (s), 135.4 (s), 130.8 (s), 129.8 (s), 127.6 (s),
13

124.9 (s), 124.3 (s), 123.7 (s), 122.1 (s), 121.6 (s), 120.8 (s), 111.6 (s), 107.3 (s), 55.6
(s), 33.6 (s); IR: 3396 (N-H), 1679 (C=O), 1638 (C=N); HRMS (ESI): calcd. for
C20H18O2N6ClS2 ([M+H]+): 473.06157, found: 473.06082.
2-((2-chloro-1H-indol-3-yl)methylene)-N-(5-((3-methoxybenzyl)thio)-1,3,4-thiadi
azol-2-yl)hydrazine-1-carboxamide (6f)
Primrose yellow solid; Yield: 88%; m.p. 187−189 °C; 1H NMR (400 MHz,
DMSO-d6) δ 12.41 (s, 1H, indole-NH), 10.96 (d, J = 77.2 Hz, 2H, NH, NH), 8.30 (s,
1H, ArH), 8.23 (s, 1H, CH=N- ), 7.33 (d, J = 5.7Hz, 1H, ArH), 7.21 (d, J = 6.0 Hz, 3H,
ArH), 6.96 (s, 2H, ArH), 6.82 (d, J = 5.7 Hz, 1H, ArH), 4.41 (s, 2H, CH2), 3.71 (s, 3H,
CH3); 13C NMR (101 MHz, DMSO-d6) δ 161.0 (s), 159.7 (s), 157.8 (s), 152.3 (s), 139.6
(s), 138.8 (s), 135.4 (s), 130.1 (s), 127.6 (s), 124.3 (s), 123.7 (s), 122.1 (s), 121.6 (s),
115.1 (s), 113.5 (s), 111.6 (s), 107.3 (s), 55.5 (s), 38.2 (s); IR: 3428 (N-H), 1686 (C=O),
1637 (C=N); HRMS (ESI): calcd. for C20H18O2N6ClS2 ([M+H]+): 473.06157, found:
473.06155.
2-((2-chloro-1H-indol-3-yl)methylene)-N-(5-((4-methoxybenzyl)thio)-1,3,4-thiadi
azol-2-yl)hydrazine-1-carboxamide (6g)
Pink solid; Yield: 89%; m.p. 190−191 °C; 1H NMR (400 MHz, DMSO-d6) δ 12.41
(s, 1H, indoe-NH), 10.90 (dd, J = 48.0, 43.6 Hz, 2H, NH, NH), 8.30 (d, J = 5.4 Hz, 1H,
ArH), 8.23 (s, 1H, CH=N-), 7.35−7.26 (m, 4H, ArH), 6.85 (t, J = 6.1 Hz, 3H, ArH),
4.39 (s, 2H, CH2), 3.70 (s, 3H, CH3); 13C NMR (101 MHz, DMSO-d6) δ 161.1 (s),
14

159.2 (s), 156.1 (s), 152.4 (s), 139.6 (s), 135.4 (s), 130.7 (d, J = 3.8 Hz), 129.0 (s), 127.6
(s), 124.3 (s), 123.7 (s), 122.1 (s), 121.6 (s), 114.4 (d, J = 2.0 Hz), 111.6 (s), 107.3 (s),
55.5 (s), 37.8 (s); IR: 3424 (N-H), 1695 (C=O), 1619 (C=N); HRMS (ESI): calcd. for
C20H18O2N6ClS2 ([M+H]+): 473.06157, found: 473.06097.
2-((2-chloro-1H-indol-3-yl)methylene)-N-(5-((2-methylbenzyl)thio)-1,3,4-thiadiaz
ol-2-yl)hydrazine-1-carboxamide (6h)
1
Yellow solid; Yield: 92%; m.p. 200−222 °C; H NMR (400 MHz, DMSO-d6) δ
12.46 (s, 1H, indole-NH), 11.03 (d, J = 70.4 Hz, 2H, NH, NH), 8.36 (d, J = 6.9 Hz, 1H,
ArH), 8.28 (s, 1H, CH=N-), 7.38 (dd, J = 6.7, 1.7 Hz, 1H, ArH), 7.32 (d, J = 7.2 Hz, 1H,
ArH), 7.29−7.17 (m, 4H, ArH), 7.17−7.12 (m, 1H, ArH), 4.49 (s, 2H, CH2), 2.39 (s, 3H,
CH3); 13C NMR (101 MHz, DMSO-d6) δ 161.2 (s), 157.7 (s), 152.3 (s), 139.6 (s), 137.2
(s), 135.4 (s), 134.7 (s), 130.9 (s), 130.4 (s), 128.4 (s), 127.6 (s), 126.5 (s), 124.3 (s),
123.7 (s), 122.1 (s), 121.6 (s), 111.6 (s), 107.3 (s), 36.8 (s), 19.2 (s); IR: 3393(N-H),
1677 (C=O), 1638 (C=N); HRMS (ESI): calcd. for C20H18ON6ClS2 ([M+H]+):
457.06665, found: 457.06659.
2-((2-chloro-1H-indol-3-yl)methylene)-N-(5-((3-methylbenzyl)thio)-1,3,4-thiadiaz
ol-2-yl)hydrazine-1-carboxamide (6i)
1
Yellow solid; Yield: 87%; m.p. 196−198 °C; H NMR (400 MHz, DMSO-d6) δ
12.46 (s, 1H, indole-NH), 11.03 (d, J = 89.9 Hz, 2H, NH, NH), 8.36 (d, J = 6.9 Hz, 1H,
ArH), 8.29 (s, 1H, CH=N-), 7.46−7.35 (m, 1H, ArH), 7.30−7.17 (m, 5H, ArH), 7.10 (d,
J = 6.4 Hz, 1H, ArH), 4.44 (s, 2H, CH2), 2.29 (s, 3H, CH3); 13C NMR (101 MHz,
15

DMSO-d6) δ 161.1 (s), 157.8 (s), 152.4 (s), 139.6 (s), 138.2 (s), 137.1 (s), 135.4 (s),
130.1 (s), 128.9 (s), 128.7 (s), 127.5 (s), 126.6 (s), 124.3 (s), 123.7 (s), 122.1 (s), 121.6
(s), 111.6 (s), 107.3 (s), 38.2 (s), 21.4 (s); IR: 3431 (N-H), 1691 (C=O), 1638 (C=N);
HRMS (ESI): calcd. for C20H18ON6ClS2 ([M+H]+): 457.06665, found: 457.06641.
2-((2-chloro-1H-indol-3-yl)methylene)-N-(5-((4-methylbenzyl)thio)-1,3,4-thiadiaz
ol-2-yl)hydrazine-1-carboxamide (6j)
1
Primrose yellow solid; Yield: 86%; m.p. 219−221 °C; H NMR (400 MHz,
DMSO-d6) δ 12.46 (s, 1H, indole-NH), 11.01 (d, J = 84.2 Hz, 2H, NH, NH), 8.35 (d, J
= 6.9 Hz, 1H, ArH), 8.28 (s, 1H, CH=N-), 7.38 (d, J = 7.0 Hz, 1H, ArH), 7.30 (d, J = 8.0
Hz, 2H, ArH), 7.27−7.20 (m, 2H, ArH), 7.14 (d, J = 7.8 Hz, 2H, ArH), 4.43 (s, 2H,
CH2), 2.28 (s, 3H, CH3); 13C NMR (101 MHz, DMSO-d6) δ 161.0 (s), 157.9 (s), 152.3
(s), 139.6 (s), 137.3 (s), 135.4 (s), 134.1 (s), 129.4 (s), 129.6 (s),127.6 (s), 124.3 (s),
123.7 (s), 122.1 (s), 121.6 (s), 111.6 (s), 107.3 (s), 38.0 (s), 21.2 (s); IR: 3421 (N-H),
1687 (C=O), 1636 (C=N); HRMS (ESI): calcd. for C20H18ON6ClS2 ([M+H]+):
457.06665, found: 457.06628.
2-((2-chloro-1H-indol-3-yl)methylene)-N-(5-((2-fluorobenzyl)thio)-1,3,4-thiadiazo
l-2-yl)hydrazine-1-carboxamide (6k)
Pink solid; Yield: 89%; m.p. 218−220 °C;1H NMR (400 MHz, DMSO-d6) δ 12.47
(s, 1H, indole-NH), 11.04 (d, J = 65.6 Hz, 2H, NH, NH), 8.36 (d, J = 6.2 Hz, 1H, ArH),
8.28 (s, 1H, CH=N-), 7.47 (t, J = 7.0 Hz, 1H, ArH), 7.36 (dd, J = 15.0, 6.6 Hz, 2H,
ArH), 7.32−7.13 (m, 4H, ArH), 4.49 (s, 2H, CH2); 13C NMR (101 MHz, DMSO-d6) δ
16

161.4 (s), 160.9 (d, J = 247.4 Hz), 157.1 (s), 152.3 (s), 139.6 (s), 135.4 (s), 131.9 (d, J =
4.0 Hz), 130.4 (d, J = 8.1 Hz), 127.6 (s), 125.0 (d, J = 4.0 Hz), 124.6−124.1 (m), 123.7
(s), 122.1 (s), 121.6 (s), 116.1 (s), 115.9 (s), 111.6 (s), 107.3 (s), 32.0 (d, J = 2.3 Hz); 19F
NMR (376 MHz, DMSO-d6) δ −117.1 (s); IR: 3433 (N-H), 1683 (C=O), 1635 (C=N);
HRMS (ESI): calcd. for C19H15ON6ClFS2 ([M+H]+): 461.04158, found: 461.04144.
2-((2-chloro-1H-indol-3-yl)methylene)-N-(5-((4-fluorobenzyl)thio)-1,3,4-thiadiazo
l-2-yl)hydrazine-1-carboxamide (6l)
1
Primrose yellow solid; Yield:91%; m.p. 216−218 °C; H NMR (400 MHz,
DMSO-d6) δ 12.48 (s, 1H, indole-NH), 11.04 (d, J = 97.1 Hz, 2H, NH, NH), 8.38 (d, J
= 7.0 Hz, 1H, ArH), 8.32 (s, 1H, CH=N-), 7.47 (dd, J = 8.6, 5.6 Hz, 2H, ArH), 7.41 (dd,
J = 6.6, 1.8 Hz, 1H, ArH), 7.32−7.22 (m, 2H, ArH), 7.17 (t, J = 8.8 Hz, 2H, ArH), 4.49
13
(s, 2H, CH2); C NMR (101 MHz, DMSO-d6) δ 162.0 (d, J = 245.4 Hz), 161.2 (s),
157.6 (s), 152.3 (s), 139.6 (s), 135.5 (s), 133.6 (d, J = 3.0 Hz), 131.5 (d, J = 8.1 Hz),
127.6 (s), 124.3 (s), 123.7 (s), 122.1 (s), 121.63(s), 115.9 (s), 115.7 (s), 111.6 (s), 107.3
(s), 37.4 (s). 19F NMR (376 MHz, DMSO-d6) δ −114.7 (s); IR: 3448 (N-H), 1693
(C=O), 1621 (C=N); HRMS (ESI): calcd. for C19H15ON6ClFS2 ([M+H]+): 461.04158,
found: 461.04074.
2-((2-chloro-1H-indol-3-yl)methyliene)-N-(5-((2-cyanobenzyl)thio)-1,3,4-thiadiaz
ol-2-yl)hydrazine-1-carboxamide (6m)
1
Primrose yellow solid; Yield: 84%; m.p. 209−212 °C; H NMR (400 MHz,
DMSO-d6) δ 12.45 (s, 1H, indole-NH), 11.03 (d, J = 54.0 Hz, 2H, NH, NH), 8.34 (d, J
17

= 5.0 Hz, 1H, ArH), 8.27 (s, 1H, CH=N-), 7.86 (d, J = 7.5 Hz, 1H, ArH), 7.73−7.59 (m,
2H, ArH), 7.50 (t, J = 7.1 Hz, 1H, ArH), 7.37 (d, J = 7.3 Hz, 1H, ArH), 7.30−7.15 (m,
13
2H, ArH), 4.61 (s, 2H, CH2); C NMR (101 MHz, DMSO-d6) δ 161.7 (s), 156.2 (s),
152.2 (s), 141.0 (s), 139.7 (s), 135.4 (s), 133.8 (d, J = 12.0 Hz), 131.0 (s), 129.0 (s),
127.6 (s), 124.3 (s), 123.7 (s), 122.1 (s), 121.6 (s), 117.7 (s), 112.4 (s), 111.6 (s), 107.3
(s), 36.8 (s); IR: 3430 (N-H), 2228 (CN), 1707 (C=O), 1635 (C=N); HRMS (ESI):
calcd. for C20H15ON7ClS2 ([M+H]+): 468.04625, found: 468.04630.
2-((2-chloro-1H-indol-3-yl)methylene)-N-(5-((2,4-dichlorobenzyl)thiio)-1,3,4-thia
diazol-2-yl)hydrazine-1-carboxamide (6n)
1
Primrose yellow solid; Yield: 87%; m.p. 237−239 °C; H NMR (400 MHz,
DMSO-d6) δ 12.45 (s, 1H, indole-NH), 11.03 (d, J = 64.0 Hz, 2H, NH, NH), 8.35 (d, J
= 6.9 Hz, 1H, ArH), 8.27 (s, 1H, CH=N-), 7.66 (d, J = 2.0 Hz, 1H, ArH), 7.52 (d, J = 8.3
Hz, 1H, ArH), 7.45−7.36 (m, 2H, ArH), 7.30−7.20 (m, 2H, ArH), 4.52 (s, 2H, CH2);
13C NMR (101 MHz, DMSO-d6) δ 161.6 (s), 156.6 (s), 152.3 (s), 139.7 (s), 135.4 (s),
134.8 (s), 134.1 (s), 133.7 (s), 133.1 (s), 129.5 (s), 128.0 (s), 127.6 (s), 124.3 (s), 123.7
(s), 122.1 (s), 121.6 (s), 111.6 (s), 107.3 (s), 35.8 (s); IR: 3439 (N-H), 1709 (C=O),
1635 (C=N); HRMS (ESI): calcd. for C19H13ON6Cl3NaS2 ([M+Na]+): 532.95500,
found: 532.95496.
2-((2-chloro-1H-indol-3-yl)methylene)-N-(5-(methylthio)-1,3,4-thiadiazol-2-yl)hy
drazine-1-carboxamide (6o)
18

Yellow solid; Yield: 88%; m.p. 193−195 °C; 1H NMR (400 MHz, DMSO-d6) δ
12.47 (s, 1H, indole-NH), 11.01 (d, J = 92.4 Hz, 2H, NH, NH), 8.36 (d, J = 6.9 Hz, 1H),
8.29 (s, 1H, ArH), 7.38 (d, J = 7.1 Hz, 1H, ArH), 7.30−7.19 (m, 2H, ArH), 2.73 (s, 3H,
CH3); 13C NMR (101 MHz, DMSO-d6) δ 160.3 (s), 152.4 (s), 139.5 (s), 135.4 (s), 127.5
(s), 124.3 (s), 123.7 (s), 122.1 (s), 121.6 (s), 111.6 (s), 107.3 (s), 16.5 (s); IR: 3426
(N-H), 1686 (C=O), 1639 (C=N); HRMS (ESI): calcd. for C13H12ON6ClS2 ([M+H]+):
367.01970, found: 367.01965.
2-((2-chloro-1H-indol-3-yl)methylene)-N-(5-(ethylthio)-1,3,4-thiadiazol-2-yl)hydr
azine-1-carboxamide (6p)
Yellow solid; Yield: 91%; m.p. 240−242 °C; 1H NMR (400 MHz, DMSO-d6) δ
12.45 (s, 1H, indole-NH), 11.01 (d, J = 78.6 Hz, 2H, NH, NH), 8.35 (d, J = 7.2 Hz, 1H,
ArH), 8.28 (s, 1H, CH=N-), 7.38 (dd, J = 6.8, 1.5 Hz, 1H, ArH), 7.29−7.20 (m, 2H,
ArH), 3.22 (q, J = 7.3 Hz, 2H, CH2), 1.36 (t, J = 7.3 Hz, 3H, CH3); 13C NMR (101 MHz,
DMSO-d6) δ 160.7 (s), 158.4 (s), 152.3 (s), 139.6 (s), 135.4 (s), 127.5 (s), 124.3 (s),
123.7 (s), 122.1 (s), 121.6 (s), 111.6 (s), 107.3 (s), 28.6 (s), 15.3 (s); IR: 3429 (N-H),
1688 (C=O), 1621 (C=N); HRMS (ESI): calcd. for C14H14ON6ClS2 ([M+H]+):
381.03535, found: 381.03528.
2-((2-chloro-1H-indol-3-yl)meithylene)-N-(5-(propylthio)-1,3,4-thiadiazol-2-yl)hy
drazine-1-carboxamide (6q)
Yellow solid; Yield: 86%; m.p. 204−206 °C; 1H NMR (400 MHz, DMSO-d6) δ
12.46 (s, 1H, indole-NH), 11.02 (d, J = 83.0 Hz, 2H, NH, NH), 8.35 (d, J = 7.1 Hz, 1H,
19

ArH), 8.28 (s, 1H, CH=N-), 7.42−7.35 (m, 1H, ArH), 7.30−7.18 (m, 2H, ArH), 3.19 (t,
J = 7.1 Hz, 2H, CH2), 1.79−1.65 (m, 2H, CH2), 1.00 (t, J = 7.3 Hz, 3H, CH3); 13C NMR
(101 MHz, DMSO-d6) δ 160.7 (s), 158.6 (s), 152.4 (s), 139.6 (s), 135.4 (s), 124.3 (s),
123.7 (s), 122.1 (s), 121.6 (s), 111.6 (s), 107.3 (s), 36.1 (s), 22.9 (s), 13.4 (s); IR: 3424
(N-H), 1687 (C=O), 1637 (C=N); HRMS (ESI): calcd. for C15H16ON6ClS2 ([M+H]+):
395.05100, found: 395.05112.
N-(5-(butylthio)-1,3,4-thiadiazol-2-yl)-2-((2-chloro-1H-indol-3-yl)methylene)hydr
azine-1-carboxamide (6r)
Yellow solid; Yield: 89%; m.p. 219−221 °C; 1H NMR (400 MHz, DMSO-d6) δ
12.46 (s, 1H, indole-NH), 11.02 (d, J = 93.1 Hz, 2H, NH, NH), 8.35 (d, J = 7.0 Hz, 1H,
ArH), 8.29 (s, 1H, CH=N-), 7.44−7.34 (m, 1H, ArH), 7.32−7.17 (m, 2H, ArH), 3.21 (t,
J = 7.2 Hz, 2H, CH2), 1.78−1.59 (m, 2H, CH2), 1.53−1.32 (m, 2H, CH2), 0.90 (t, J = 7.4
Hz, 3H, CH3); 13C NMR (101 MHz, DMSO-d6) δ 160.1 (s), 158.6 (s), 152.4 (s), 139.5
(s), 135.4 (s), 127.5 (s), 124.3 (s), 123.6 (s), 122.1 (s), 121.6 (s), 111.6 (s), 107.3 (s),
33.9 (s), 31.6 (s), 21.6 (s), 13.9 (s); IR: 3422 (N-H), 1697 (C=O), 1639 (C=N); HRMS
(ESI): calcd. for C16H18ON6ClS2 ([M+H]+): 409.06665, found: 409.06586.
2-((2-chloro-1H-indol-3-yl)methylene)-N-(5-(pentylthio)-1,3,4-thiadiazol-2-yl)hyd
razine-1-carboxamide (6s)
Redish solid; Yield: 79%; m.p. 216−219 °C; 1H NMR (400 MHz, DMSO-d6) δ
12.45 (s, 1H, indole, NH), 11.00 (d, J = 94.7 Hz, 2H, NH, NH), 8.34 (d, J = 7.1 Hz, 1H,
ArH), 8.28 (s, 1H, CH=N-), 7.37 (d, J = 7.1 Hz, 1H, ArH), 7.31−7.17 (m, 2H, ArH),
20

3.18 (t, J = 7.2 Hz, 2H, CH2), 1.75−1.60 (m, 2H, CH2), 1.43−1.23 (m, 4H, CH2, CH2),
0.86 (t, J = 7.1 Hz, 3H, CH3); 13C NMR (101 MHz, DMSO-d6) δ 160.6 (s), 158.6 (s),
152.4 (s), 139.5 (s), 135.4 (s), 127.5 (s), 124.3 (s), 123.6 (s), 122.1 (s), 121.6 (s), 111.6
(s), 107.3 (s), 34.1 (s), 30.6 (s), 29.2 (s), 22.1 (s), 14.3 (s); IR: 3427 (N-H), 1686 (C=O),
1639 (C=N); HRMS (ESI): calcd. for C17H20ON6ClS2 ([M+H]+): 423.08230, found:
423.08127.
Conclusion
Novel 1,3,4-thiadiazole derivatives bearing semicarbazone were synthesized via
embedding the substituted benzyl group or unbranched alkyl group into the thiol of
1,3,4-thiadiazole. The structures of the synthesized compounds, including unreported
intermediates, were identified using 1H NMR, 13C NMR, 19F NMR, IR and HRMS
spectral data.
The anti-bacterial activities of the compounds 6a-6s against Xoo and Xac were also
studied by performing a turbidimetre test. Compounds 6b, 6h and 6j presented good
inhibitory activities against Xac of 89.46%, 71.38%, 85.59%, respectively, which were
superior to those of thiodiazole-copper (67.36%) and bismerthiazol (65.37%). In total,
most of title compounds (6a-6s) displayed markedly lower inhibitory rates against Xac
compared with positive controls. Interestingly, 1,3,4-thiadiazole derivatives displayed
moderate-to-excellent anti-bactrrial activities against Xoo. The preliminary conclusion
of the structure-activity relationship was as follow: for compounds 6a-6n, the
2-substituted mono halogenated derivatives (R = 2-Cl, 2-F) exhibited significant
21

anti-bacterial activity against Xoo which appears to enhance with increase in the size of
the halogen substituent. In addition, introduction of electron-withdrawing group (F, Cl)
in the 3-position or 4-position of benzene ring could not assist in enhancing
anti-bacterial activity against Xoo. In other words, the compound 6b (R = 2-Cl)
presented better anti-bacterial activity against Xoo. With an electron-donating methoxy
group as the substituent R, compound 6g (R = 4-OCH3), 6e (R = 2-OCH3) and 6f (R =
3-OCH3) all appeared good anti-bacterial active against Xoo. Specifically, compound
6g (R = 4-OCH3) shown best activity. However, when substituent R was replaced with
a less bulky methyl group, the corresponding compounds 6h (R = 2-CH3), 6i (R =
3-CH3) and 6j (R = 4-CH3) showed relatively poor inhibitory activity against Xoo.
For compounds 6o-6s with an electron-donating unbranched alkyl group as the
substituent R1, the trend of anti-bacterial activity of compounds 6o-6r against Xoo was
noted with increase in size of the alkyl group: 6o (R1 = CH3) < 6p (R1 = C2H5) < 6q (R1
= C3H7) < 6r (R1 = C4H9). In addition, compound 6r (R1 = C4H9) was also superior to 6s
(R1 = C5H11) in anti-bacterial activity against Xoo. In conclusion, the synthesized title
compounds are more promising bactericides against Xoo relative to Xac.
Funding
This research was financially supported by the Project Enterprises and Business
(H 110029), Guizhou Science Technology Program (No. 20161055), the Young
Talents Scientific Research Foundation of Guizhou Education Department
(KY2017115), the Student Innovation and Entrepreneurship Project of Guizhou
22

University (201610657052), and the Laboratory Opening Project of Guizhou
University (SYSKF-2017-2-078).
References
[1] He, K.; Yang, S. Y.; Li, H.; Wang, H.; Li, Z. L. Eur. J. Plant Pathol. 2014, 140,
665-675.
[2] Perumalsamy, S.; Bharani, M.; Sudha, M.; Nagarajan, P.; Arul, L.; Saraswathi, R.;
Balasubramanian, P.; Ramalingam, J. Plant Breeding. 2010, 129, 400-406.
[3] Li, P.; Shi, L.; Gao, M. N.; Hu, D. Y.; Song, B. A. Bioorg. Med. Chem. Lett. 2015,
25, 481-484.
[4] Xu, W. M.; Han, F. F.; He, M.; Hu, D. Y.; He, J.; Yang, S.; Song, B. A. J. Agric.
Food Chem. 2012, 60, 1036-1041.
[5] Li, P.; Yin, J.; Xu, W. M.; Wu, J.; He, M.; Hu, D. Y.; Yang, S.; Song, B. A. Chem.
Biol. Drug Des. 2013, 82, 546-556.
[6] Imazaki, I.; Nakaho, K. J. Gen. Plant Pathol. 2010, 76, 52-61.
[7] Lo, C. P.; Shanmugaiah, V.; Iacbellis, N. S. J. Agric. Food Chem. 2009, 57,
9454-9461.
[8] Wang, P. Y.; Zhou, L.; Zhou, J.; Wu, Z. B.; Xue, W.; Song, B. A.; Yang, S. Bioorg.
Med. Chem. Lett. 2016, 26, 1214-1217.
23

[9] Zhu, X. F.; Xu, Y.; Peng, D.; Zhang, Y.; Huang, T. T.; Wang, J. X. Crop Prot. 2013,
47, 24-29.
[10] Zhou, X. J.; Wang, J.; Yang, Y. W.; Zhao, T.C.; Gao, B. D. Microbiol. China.
2012, 39, 1479-1486.
[11] Hayward, A. C. Annu. Rev. Phytopathol. 1991, 29, 65-87.
[12] Demirbas, N; Karaoglu, S. A.; Sancak, K. Eur. J. Med. Chem. 2004, 39, 793-804.
[13] Desai, K.; Daxi, A. Indian J. Pharm. Sci. 1992, 54, 183-188.
[14] Azam, M.; Kumar, B.; Shalinis, S.; Surech, B.; Reddy, K.; Reddy, D. Indian J.
Pharm. Sci. 2008, 70, 672-677.
[15] Foroumadi, A.; Emani, S.; Hassan Z. A.; Rajee, M.; Sokhanvar, K.; Moshafi, H.
Bioorg. Med. Chem. Lett. 2005, 15, 4488-4492.
[16] Chou, Y.; Lais, Y.; Pan, L.; Jow, M.; Chern, W.; Guh, H. Biochem. Pharmacol.
2003, 66, 115-124.
[17] Nadeem, S.; Priya, A.; Waquar, A.; Pandeya, S.; Shamsher, M. J. Chem. Pharm.
Res. 2009, 1, 19-30.
[18] Cleici, F.; Pocar, D.; Guido, M.; Loch, A.; Perlini, V.; Brufani, M. J. Med. Chem.
2001, 44, 931-936.
24

[19] Martinez, A.; Alonso, D.; Castro, A.; Aran, J.; Cardelus, I. and Banos, E. Arch.
Pharm. 1999, 332, 191-194.
[20] Rao, V. K.; Chhikara, B. S.; Shirazi, A. N.; Tiwari, R.; Parang, K.; Kumar, A.
Bioorg. Med. Chem. Lett. 2011, 21, 3511-3514.
[21] Chiou, C.; Chen, G. S.; Chen, M.; Li, H.; Shi, L.; Huang, X.; Dai, W.; Chern, J.
ChemMedChem. 2010, 5, 1489-1497.
[22] Rao, V. K.; Rao, M. S.; Jain, N.; Panwar, J.; Kumar, A. Org. Med. Chem. Lett.
2011, 1, 1-7.
[23] Granchi, C.; Roy, S.; Simone, A. D.; Salvetti, I.; Tuccinardi, T.; Martinelli,
A.;Macchia, M.; Lanza, M.; Betti, L.; Giannaccini, G.; Lucacchini, A.; Giovannetti,
E.; Sciarrillo, R.; Peters, G. J.; Minutolo, F. Eur. J. Med. Chem. 2011, 46,
5398-5407.
[24] Qin, M. Z.; Zhai, X.; Xie, H.; Ma, J. J.; Lu, K.; Wang, Y.; Wang, L.; Gu, Y. C.;
Gong, P. Eur. J. Med. Chem. 2014, 81, 47-58.
[25] Liu, Z. J.; Wu, S. S.; Wang , Y.; Li, R.; Wang, J.; Wang, L.; Zhao, Y. F.; Gong, P.
Eur. J. Med. Chem. 2014, 87, 782-793.
[26] Qi, B. H.; Mi, B.; Zhai, X.; Xu, Z.; Zhang, X., Tian, Z. R.; Gong, P. Biorg. Med.
Chem. 2013, 21, 5246-5260.
[27] Zhai, X.; He, Y.; Yang, Z.; Gong, P. Chem. Res. Chin. Univ. 2013, 29, 62-66.
25

[28] Shen, L. H.; Li, H. Y.; Shang, H. X.; Tian, S. T.; Lai, Y. S.; Liu, L. J. Chin. Chem.
Lett. 2013, 24, 299-302.
[29] Zhao, J.; Xuan, L. N.; Zhao, H. C.; Cheng, J.; Fu, X. Y.; Li, S.; Jing, F.; Liu, Y. M.;
Chen, B. C. Chem. Res. Chin. Univ. 2014, 30, 764-769.
[30] Zhao, J.; Chen, B. Q.; Shi, Y. P.; Shi, Y. P.; Liu, Y. M.; Zhao, H. C.; Cheng, J.
Chin. Chem. Lett. 2012, 23, 817-819.
[31] Sheng, C. Q.; Che, X. Y.; Wang, W. Y.; Cao, Y. B.; Miao, Z. Y.; Yao, J. Z.; Zhang,
W. N. Eur. J. Med. Chem. 2011, 46, 5276-5282.
[32] Ma, J.; Bao, G.; Wang, L.; Li, W.; Xu, B.; Du, B.; Gong, P. Eur. J. Med. Chem.
2015, 96, 173-186.
[33] Mortimer, D.; Whiting, M.; Harrity, J. P. A.; Jones, S.; Coldham, I. Tetrahedron
Lett. 2014, 55, 1255-1257.
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Scheme 1
Scheme 1：The synthetic route to the target compounds 6a-6s. (i): NaOH, H2O,
C2H5OH, r.t., 10 h, yield: 73–88%; (ii): phenyl chloroformate, pyridine,
tetrahydrofuran, 0 °C–r.t., 3–6 h, 63%–90%; (iii): 85% hydrazine hydrate, glycol
dimethyl ether, 80 ℃, 2–4 h, 52%–83%; (iv): POCl3, DMF, CH2Cl2, 0 °C–r.t.; (v)
C2H5OH, 80 °C.
27