Design, Synthesis and Antibacterial Activity of Novel Pyrimidine-Containing 4H-Chromen-4-One Derivatives**

Article abstract of DOI:10.1002/cbdv.202100186

A series of pyrimidine-containing 4H-chromen-4-one derivatives were designed and synthesized by combining bioactive substructures. Preliminary biological activity results showed that most of the compounds displayed significant inhibitory activities in vit

Full text of DOI:10.1002/cbdv.202100186

DOI: 10.1002/cbdv.202100186
FULL PAPER
Design, Synthesis and Antibacterial Activity of Novel Pyrimidine-
Containing 4H-Chromen-4-One Derivatives**
Shijun Su+,a Mei Chen+,a Xuemei Tang,a Feng Peng,a Tingting Liu,a Qing Zhou,a Wenliang Zhan,a
Ming He,a Chengwei Xie,*a and Wei Xue*a
a
State Key Laboratory Breeding Base of Green Pesticide and Agricultural Bioengineering,
Key Laboratory of Green Pesticide and Agricultural Bioengineering, Ministry of Education, Guizhou University,
Guiyang 550025, P. R. China, e-mail: cwxie@gzu.edu.cn; wxue@gzu.edu.cn
A series of pyrimidine-containing 4H-chromen-4-one derivatives were designed and synthesized by
combining bioactive substructures. Preliminary biological activity results showed that most of the compounds
displayed significant inhibitory activities in vitro against Xanthomonas axonopodis pv. Citri (X. axonopodis),
Xanthomonas oryzae pv. oryzae (X. oryzae) and Ralstonia solanacearum (R. solanacearum). In particular,
compound 2-[(3-{[5,7-dimethoxy-4-oxo-2-(3,4,5-trimethoxyphenyl)-4H-1-benzopyran-3-yl]oxy}propyl)sulfanyl]-4-
(4-methylphenyl)-6-oxo-1,6-dihydropyrimidine-5-carbonitrile (4c) demonstrated a good inhibitory effect against
X. axonopodis and X. oryzae, with the half-maximal effective concentration (EC50) values of 15.5 and 14.9 μg/mL,
respectively, and compound 2-[(3-{[5,7-Dimethoxy-4-oxo-2-(3,4,5-trimethoxyphenyl)-4H-1-benzopyran-3-yl]oxy}
propyl)sulfanyl]-4-(3-fluorophenyl)-6-oxo-1,6-dihydropyrimidine-5-carbonitrile (4h) showed the best antibacterial
activity against R. solanacearum with an EC50 value of 14.7 μg/mL. These results were better than commercial
reagents bismerthiazol (BT, 51.7, 70.1 and 52.7 μg/mL, respectively) and thiodiazole copper (TC, 77.9, 95.8 and
72.1 μg/mL, respectively). In vivo antibacterial activity results indicated that compound 4c displayed better
curative (42.4%) and protective (49.2%) activities for rice bacterial leaf blight than BT (35.2, 39.1%) and TC (30.8,
27.3%). The mechanism of compound 4c against X. oryzae was analyzed through scanning electron microscopy
(SEM). These results indicated that pyrimidine-containing 4H-chromen-4-one derivatives have important value in
the research of new agrochemicals.
Keywords: 4H-chromen-4-one derivatives, pyrimidine, antibacterial activity, scanning electron microscopy.
oryzae, respectively.[1–3] These bacteria are very serious
and hard to manage effectively in agricultural produc-
Introduction
Plant diseases can cause huge losses in the yield of tion. Therefore, these agrochemicals (bismerthiazol,
economic crops every year, which one of the main thiodiazole-copper and azoxy strobin) are often used
reasons is bacterial infection. Such as, the citrus to prevent bacterial infection.[4,5] But prolonged and
canker, tobacco bacterial wilt and rice bacterial leaf abuse of traditional chemical pesticides will enhance
blight are caused by Xanthomonas axonopodis pv. citri, the resistance of the bacterial, and are harmful to the
Ralstonia solanacearum and Xanthomonas oryzae pv. environment and human health.[6–8] Thus, to explore
novel antibacterial agents with highly-efficient, broad-
spectrum, and environmentally is still an arduous task
in pesticide science.
+
These authors contributed equally to this work.
A previous version of this manuscript has been
**
3,5,7-Trihydroxy-2-(3,4,5-trihydroxyphen-yl)-4H-
chromen-4-one (called “myricetin”) belongs to a
class of natural products which are widely found
in fruits, vegetables, and herbs. It has attracted the
attention of more and more researchers, due to
deposited on a preprint server (https://doi.org/10.21203/
rs.3.rs-92183/v1).
Supporting information for this article is available on the
WWW under https://doi.org/10.1002/cbdv.202100186
Chem. Biodiversity 2021, 18, e2100186
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Chem. Biodiversity 2021, 18, e2100186
the unique chemical structure and diverse bio- the pyrimidine moiety into 4H-chromen-4-one, and a
logical activities.[9] Pharmacological research have variety of pyrimidine-containing 4H-chromen-4-one
shown that myricetin and its derivatives present derivatives were synthesized and their antibacterial
antiviral,[10,11]
antibacterial,[12–14] activity were evaluated (Figure 1).
antioxidation,[15,16]
anticancer,[17–19]
anti-
inflammatory[20] and other biological properties,
but most of them are limited to the field of Results and Discussion
medicine and have few applications in agriculture.
In previous work, myricetin was took as the lead
Chemistry
compound and active fragments were introduced, The structures of the title compounds 4a–4x were
a mass of myricetin derivatives with significant characterized by 1H-NMR, 13C-NMR, 19F NMR and
1
biological activity were discovered. In 2017, Zhong HRMS. In H-NMR spectra, multiplet signals at δ 8.00–
described myricetin derivatives containing 1,3,4- 6.50 ppm shown the presence of protons in aromatic
thiadiazole structure, which displayed good inhib- nucleuses, and a singlet at δ 4.00–3.70 ppm revealed
itory effect on phytopathogenic bacteria.[21] Re- the presence of -OCH3 group, the -O-CH2- and -S-CH2-
cently, Jiang reported a series of dithiocarbamate- characteristic groups between the 4H-chromen-4-one
containing 4H-chromen-4-one derivatives, which skeleton and the substituted pyrimidine were ob-
have good in vitro antibacterial activity against X. served at 4.10–3.37 ppm. The chemical shifts of 13C-
axonopodis and X. oryzae, with an EC50 values were NMR spectra were 172.57–160.77 ppm, 109.12–
0.11 and 1.58 μg/mL, respectively, which were far 106.14 ppm, 27.80–32.12 ppm in which confirmed the
better than commercial agents bismerthiazol and existence of C=O, -CN and -CH2- groups, respectively.
thiodiazole copper.[22]
The HRMS spectra of the title compounds shown
Pyrimidine is an important class of heterocyclic absorption signals of [M+H]+ ions that was consistent
compounds, which has a wide range of applications in with their molecular weight.
medicine and pesticides research, due to its remark-
To further confirm the structures of the title
able biological and pharmacological properties, such compounds, compound 4g was successfully cultured a
as antibacterial,[23–25] antiviral,[26,27] insecticide,[28,29] single crystal and studied by single-crystal X-ray
anticancer,[30,31] antimalarial,[32] herbicida[33] and other analysis as a representative example. The tested single
biological activities.[34] In 2019, Zhang reported a series crystal was crystallized from DMSO and acetone
of derivatives containing pyrimidine ethers were mixture solution containing compound 4g. As shown
synthesized, which have a good control effect on in Figure 2B, C00T…O007 and O00A…C01A were two
cucumber downy mildew.[35] Recently, Bai described important intramolecular hydrogen bonds, which
that some pyrimidine derivatives have significantly combine with 4H-chromen-4-one and pyrimidine het-
inhibitory efficiencies against Gram-positive bacteria, erocycle fragments to construct the main molecular
Gram-negative bacteria and the fungus Candida scaffold of target compound 4g. Besides, as presented
albicans.[36] In order to develop novel, highly efficient in Figure 2C, four intermolecular hydrogen bonds
and environment friendly bactericides, we introduced (O008…H01B, C00J…C00L, C00J…C00L, H01B…O008)
Figure 1. Design strategy for target molecules.
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Chem. Biodiversity 2021, 18, e2100186
Figure 2. Crystal structural (A,B) and crystal packing (C) diagram of title compound 4g.
between neighboring molecules were primary forces bioassays results in Table 2 indicated that some
for establishing the three-dimensional structure of compounds with good antibacterial activities against
target compound 4g. crystallographic data listed in X. axonopodis, X. oryzae and R. solanacearum. The
Table 1. The deposition number is CCDC 2022970.
inhibition rates of the compounds 4b, 4c, 4h and 4o
against X. axonopodis at 100 and 50 μg/mL were 80.4
and 51.4%, 91.3 and 69.0%, 85.3 and 51.4%, 83.2 and
50.5%, respectively, which were better than BT (66.4
and 42.3%), TC(56.9 and 38.3%) and myricetin(44.9
Antibacterial Activity of the Title Compounds against X.
axonopodis, X. oryzae and R. solanacearum in Vitro
The in vitro antibacterial activities of the title com- and 27.5%). The inhibition rates of compounds 4c, 4h
pounds 4a–4x against X. axonopodis, X. oryzae and R. and 4p against X. oryzae at 100 μg/mL were 89.7, 81.3
solanacearum were determined using turbidimeter and 80.8%, respectively, which were superior to BT
tests, and the bismerthiazol, thiadiazole copper, and (50.5%), TC (47.5%) and myricetin (44.0%). Note that
myricetin were tested as the controls. Preliminary the inhibition rates of 4c, 4h, 4n, 4o and 4p against X.
oryzae at 50 μg/mL were 72.1, 56.0, 54.7, 49.5 and
56.1%, respectively, which were superior to BT
(31.0%), TC (29.5%) and myricetin (33.3%). Further-
more, 4c, 4d, 4h, 4k, 4l and 4o have fine antibacterial
activities against R. solanacearum at 100 μg/mL with
the inhibition rates of 90.9, 83.9, 92.8, 88.7, 83.2 and
90.4%, respectively, which were better than BT
(70.3%), TC (57.4%) and myricetin (50.7%). Similarly,
the percentage inhibition of 4c, 4h, 4k and 4o against
R. solanacearum at 50 μg/mL were 72.6, 76.3, 66.4 and
72.0%, respectively, which exceeded BT (44.6%), TC
(36.7%) and myricetin (29.6%).
Table 1. Crystal data of title compound 4g.
Crystal Data
C34 H30 BrN3O9 S
Mr=736.57
triclinic/P-1
Colorless/block
1=1.430
Z=2
°
a=12.025(3) [Å]
b=12.509(4) [Å]
c=14.791(4) [Å]
F(000)=832
α =103.276(15) [ ]
β=112.727(15) [ ]
°
°
γ=102.837(17) [ ]
V=1873.79(9) [Å3]
Based on the preliminary bioassays results in
Table 2, the EC50 values of some target compounds
against X. axonopodis, X. oryzae and R. solanacearum
were further evaluated as shown in Table 3. Com-
pounds 4c, 4h and 4o exhibited fine antibacterial
activities against X. axonopodis, with the EC50 values of
15.5, 28.3, and 29.4 μg/mL, respectively, which ex-
ceeded BT (50.3 μg/mL), and TC (83.2 μg/mL). Com-
pounds 4c, 4h, 4n and 4p demonstrated good inhib-
itory effects against X. oryzae with the EC50 values of
14.9, 23.8, 28.6 and 24.8 μg/mL, which were better
than BT (72.0 μg/mL) and TC (99.2 μg/mL). Com-
pounds 4c, 4d, 4h, 4k, 4l and 4o have better
antibacterial activity against R. solanacearum with the
Data Collection
T
min =0.310, Tmax =0.752
Absorption coefficient:
2.537 [mmÀ 1
]
°
°
3580 Independent reflections
18889 Reflections collected
θ
min =3.870 , θmax =64.332
À 13< =h< =13,
À 14< =k< =14,
À 17< =l< =16
Refinement
Goodness-of-fit: 1.090
R indices (all data)
R1=0.1186, wR2=2964
R indices [I>2r(I)]
Δ1max =0.426 eÅÀ 3
,
Δ1min =À 0.750 eÅÀ 3
R1=0.0835, wR2=2591
438 parameter
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Table 2. Antibacterial activities of the title compounds (4a–4x) against X. axonopodis, X. oryzae and R. solanacearum in vitro.[a]
Compd.
X. axonopodis (%)
100 μg/mL
X. oryzae (%)
100 μg/mL
R. solanacearum (%)
100 μg/mL
50 μg/mL
50 μg/mL
50 μg/mL
4a
4b
4c
4d
4e
4f
4g
4h
4i
4j
4k
4 l
4m
4n
4o
4p
4q
4r
37.9�2.8
80.4�0.3
91.3�0.6
76.7�3.5
28.7�4.2
39.6�2.9
25.3�3.3
85.3�0.7
26.4�2.0
73.5�0.8
31.5�2.7
32.2�1.7
47.1�3.2
77.4�1.5
83.2�0.8
27.1�1.9
23.7�2.8
24.5�1.3
21.9�1.5
20.2�2.5
45.5�3.4
27.8�1.5
29.1�0.8
41.8�3.7
44.9�1.4
56.9�0.7
66.4�1.0
25.6�1.8
51.4�0.9
69.0�1.4
40.9�1.6
20.4�2.6
28.9�2.0
16.7�3.1
51.4�2.0
25.6�1.0
41.9�1.6
24.2�1.7
21.96�5.1
26.4�2.2
42.9�3.2
50.5�2.3
20.3�1.4
19.9�2.8
16.8�1.5
14.7�1.4
17.7�1.2
29.2�6.3
19.7�4.8
20.7�1.3
26.2�2.6
27.5�3.01
38.3�0.9
42.3�1.4
26.3�1.6
20.7�2.4
89.7�0.9
75.1�0.8
50.3�3.7
29.8�1.8
31.2�3.9
81.3�0.6
26.6�2.1
45.2�2.1
32.8�1.9
58.9�1.7
47.7�1.1
78.4�0.6
74.9�0.3
80.8�1.7
47.7�1.3
26.7�2.4
45.2�1.5
26.3�4.5
23.8�5.4
32.6�1.9
44.4�0.7
68.6�3.5
44.0�1.2
47.5�0.3
50.5�1.0
13.6�2.0
13.1�4.2
72.1�1.8
41.70�2.4
24.7�3.0
18.1�3.7
22.1�5.4
56.0�2.2
12.5�0.7
21.8�5.6
21.5�1.6
32.5�3.1
28.7�1.9
54.7�2.1
49.6�2.1
56.1�2.2
34.4�1.5
12.8�1.9
21.1�3.9
21.6�2.4
18.5�1.0
27.9�3.6
28.8�3.0
45.6�2.5
33.3�0.9
29.5�1.0
31.0�0.7
50.5�0.6
46.9�1.6
90.9�1.7
83.9�1.4
34.3�4.2
35.2�3.6
67.0�0.9
92.8�0.6
37.4�5.6
51.2�1.1
88.7�1.4
83.2�1.6
51.8�2.7
28.5�3.4
90.4�0.4
25.9�3.5
48.4�1.2
62.6�0.7
22.2�2.5
44.5�3.8
53.4�1.7
57.5�1.3
80.7�1.8
61.9�1.2
50.7�2.3
70.3�2.1
57.4�2.0
39.2�2.2
32.1�2.1
72.6�2.2
51.2�0.3
24.5�1.6
27.9�1.2
40.8�1.2
76.3�1.2
19.7�4.0
30.2�1.3
66.4�0.31
50.9�2.3
25.1�1.3
17.7�1.6
72.0�0.9
14. �5.8
35.4�1.5
39.2�2.9
12.5�3.4
33.0�1.9
39.4�2.2
37.5�2.7
59.1�1.5
33.2�4.4
29.6�1.1
44.6�2.5
36.7�1.8
4s
4t
4u
4v
4w
4x
Myr[b]
BT[c]
TC[c]
[a] Average of three replicates. [b] The lead compound of myricetin. [c] The commercial bactericides bismerthiazol (BT) and
thiediazole copper (TC).
EC50 values of 16.1, 23.1, 14.7, 17.5, 24.8 and 16.0 μg/ (n=3, 3-F-Ph), 4k (n=3, R=furan), 4l (n=3, R=
mL, respectively, which were superior to BT (43.5 μg/ pyridyl) and 4o (n=4, R=4-CH3-Ph) had better
mL) and TC (64.3 μg/mL).
antibacterial activity against R. solanacearum with the
EC50 values of 16.1, 23.1, 14.7, 17.5, 24.8 and 16.0 μg/
mL, respectively, which were superior to that of BT
(43.5 μg/mL) and TC (64.3 μg/mL) and other substitu-
Structure-Activity Relationships of Antibacterial Activities
As indicated in Tables 2 and Table 3, the R groups had ents. From this analysis, when R were substituted by 4-
significant impact on the antibacterial activity, for CH3-Ph, 4-CH3O-Ph, 3-F-Ph, the corresponding com-
example, 4c (n=3, R=4-CH3-Ph), 4h (n=3, R=3-F- pound exhibited remarkable antibacterial activities
Ph), 4o (n=4, R=4-CH3-Ph) demonstrated a fine against X. axonopodis, X. oryzae and R. solanacearum.
inhibitory effect against X. axonopodis with the EC50
values of 15.5, 28.3 and 29.4 μg/mL,. Compounds 4c
In Vivo Bioactivity of 4c Against Rice Bacterial Leaf Blight
(n=3, R=4-CH3-Ph), 4d (n=3, R=4-OCH3-Ph) and 4p
(n=4, R=4-OCH3-Ph) demonstrated good inhibitory The antibacterial test shown that compound 4c has
effects against X. oryzae with the EC50 value of 14.9, significant anti-X. oryzae biological activity in vitro. To
23.8 and 24.8 μg/mL, which were better than other further verify the antibacterial activity of 4c, a pot
substituents. The presence of donor electron groups experiment was carried out in vivo, and the experi-
and heterocycles effectively enhanced the antibacterial ments of 4c against rice bacterial leaf blight were
activities against R. solanacearum, such as compounds determined using a leaf-cutting method. As shown in
4c (n=3, R=4-CH3-Ph), 4d (n=3, R=4-OCH3-Ph), 4h Table 4 and Figure 3, when the concentration of
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Table 3. The EC50 values of the title compounds against X. axonopodis, X. oryzae and R. solanacearum in vitro.[a]
Tested bacterial
Compds.
Toxic regression equation
r2
EC50/(μg/mL)
X. axonopodis
4b
4c
4d
4h
4j
4n
y=1.5705x+2.6602
y=1.9107x+2.7256
y=1.5736x+2.5280
y=1.7100x+2.5176
y=1.4978x+2.6114
y=1.6002x+2.5541
y=1.7781x+2.3894
y=1.3743x+2.6450
y=1.3153x+2.5117
0.9826
0.9912
0.9825
0.9809
0.9873
0.9947
0.9811
0.9854
0.9822
30.9�2.0
15.5�1.7
37.2�2.1
28.3�1.1
39.3�0.9
33.7�2.2
29.4�2.4
50.3�2.0
83.2�1.7
4o
BT[c]
TC[c]
X. oryzae
4c
4d
4h
4n
y=1.4639x+3.2826
y=1.2237x+3.1804
y=1.4072x+3.0639
y=1.2358x+3.1996
y=1.2425x+3.1428
y=1.3657x+3.0943
y=1.3199x+2.5633
y=1.0632x+2.8928
0.9906
0.9693
0.9961
0.9773
0.9892
0.9978
0.9848
0.9796
14.9�0.9
30.7�1.6
23.8�1.8
28.6�2.6
31.2�0.9
24.8�1.1
72.0�1.9
99.2�2.7
4o
4p
BT[c]
TC[c]
R. solanacearum
4c
4d
4h
4k
4l
4o
4w
BT[c]
TC[c]
y=1.6321x+3.0312
y=1.4199x+3.0625
y=1.6908x+3.0236
y=1.4931x+3.1422
y=1.4276x+3.0175
y=1.5422x+3.1423
y=1.4597x+2.8546
y=1.4267x+2.5425
y=1.2906x+2.5962
0.9929
0.9780
0.9969
0.9857
0.9801
0.9926
0.9833
0.9543
0.9821
16.1�2.3
23.1�1.3
14.7�1.2
17.5�2.0
24.8�1.0
16.0�1.3
29.5�2.5
43.5�3.3
64.3�2.1
[a] Average of three replicates. [c] The commercial agricultural antibacterial agents bismerthiazol (BT) and thiodiazole-copper (TC)
were used as control agents.
Table 4. Curative and protection activity of compound 4c against X. oryzae under greenhouse conditions at 200 μg/mL (14 days
after spraying).[a]
Treatment
Curative activity (%)
Disease index
Protection activity (%)
Disease index
Control efficiency
Control efficiency
4c
48.6
54.8
59.0
84.4
42.4
35.2
30.8
–
45.7
51.4
61.9
84.4
49.2
39.1
27.3
–
BT[c]
TC[c]
Negative control
[a] The experiments were repeated three times. [c] The commercial agricultural antibacterial agents bismerthiazol (BT) and
thiodiazole-copper (TC) were used as control agents.
compound 4c was 200 μg/mL, the curative activity Scanning Electron Microscopy (SEM) Study
against rice bacterial blight was 42.4%, the result
better than BT (35.2%) and TC (30.8%). Meanwhile, The mechanism of compound against X. oryzae was
compound 4c demonstrated excellent protection ac- analyzed by SEM. As shown in Figure 4, the surface
tivity against bacterial blight of rice with the percent- morphology of X. oryzae were smooth and remains
age inhibition of 49.2%, which was superior to BT intact without compound to treatment (Figure 4A).
(39.1%) and TC (27.3%). These results suggested that When the bacteria were treated with compound 4c at
compound 4c can effectively prevent the rice bacterial concentration of 50 μg/mL, bacteria cell membrane
blight.
began to appear different degrees wrinkled (Figure 4B).
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Chem. Biodiversity 2021, 18, e2100186
Figure 3. Curative and protective activity of compound 4c on the bacterial leaf blight of rice.
Figure 4. SEM images for X. oryzae after incubated in different concentration of compound 4c. (A) 0 μg/mL, (B) 50 μg/ mL, and
(C) 100 μg/mL. Scale bar for (A,B, and C) are 2 μm.
When the concentration of compound increased to
Conclusions
100 μg/mL, the bacterial cell membrane showed
invagination and rupture (Figure 4C). Therefore, the In summary, aiming to develop novel and high-
compound 4c destroyed the cell membrane structure, efficient agents with better biological activities, a
to achieve the purpose of antibacterial.
series of pyrimidine-containing 4H-chromen-4-one de-
rivatives were designed and synthesized. In vitro
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antibacterial bioassays showed that most of com- recrystallized with absolute ethanol to obtain Inter-
pounds exhibited significant antibacterial activities mediate 1
against X. axonopodis, X. oryzae and R. solanacearum.
In particular, compound 4c exhibited the best anti-
General Procedure for the Synthesis of Intermediate 2
bacterial activities against X. axonopodis, X. Oryzae,
and compound 4h exhibited the better antibacterial Myricetin iodomethane and anhydrous K2CO3 were
activity against R. solanacearum than TC and BT. In stirred in N, N-dimethylformamide (DMF) for 48 h, and
vivo antibacterial bioassays shown that compound 4c then, it was extracted with methylene chloride and
was more effective than BT and TC in reducing concentrated. Then deglycosylation with concentrated
bacterial blight of rice. Furthermore, the Scanning hydrochloric acid under reflux in ethanol to prepare 3-
electron microscopy of 4c against X. oryzae showed hydroxy-3’,4’,5’,5,7-pentamethoxymyricetin (Intermedi-
that compound destroyed the cell membrane struc- ate 2).[22]
ture of the bacteria, and the damage of the cell
membrane was more serious as the concentration
General Procedure for the Synthesis of Intermediate 3
increased. These results indicated that the pyrimidine-
containing 4H-chromen-4-one derivatives have better Intermediate 2 (2 mmol) and K2CO3 (3 mmol) were
antibacterial activity and could be further study as dissolved in certain amount of N, N-dimeth-
potential replacement templates in the search for ylformamide (DMF), stirred at room temperature for
novel antibacterial agents.
0.5–1 h, the different dibromoalkane (2 mmol) was
added and the reaction system was stirred at room
temperature for 10 h. Mixture was dispersed in 50 mL
ice water when the reaction completed(the reaction
was monitored by TLC), a white solid separated out,
the liquid was removed by filtration, and the solid was
Experimental Section
General
All solvents and reagents were purchased from continuously stirred in a mixed solution of 30 mL
Shanghai Titan Scientific Co., Ltd, and were analytical petroleum ether and ethyl acetate for 3–4 h, then,
grade or chemically pure. The melting point of all filtered and dried under reduced pressure to obtain
compounds (4a–4x) were determined by the X-4B Intermediate 3.[38]
melting point apparatus (Beijing Tech Instrument Co,
Beijing. China). H-NMR, 13C-NMR and 19F NMR were
1
General Procedure for the Synthesis of Title Compounds
obtained on Bruker Ascend-400 spectrometer (Bruker
4a–4x
Optics, Germany) Tetramethylsilane (TMS) as internal
standard and DMSO was used as solvent; Mass spectral A solution of intermediates 1 (3 mmol), intermediates
studies were performed on a quadrupole electrostatic 3 (3 mmol) and K2CO3 (4.5 mmol) in 50 mL DMF was
field orbitrap mass spectrograph (Thermo Scientific, stirred under reflux for 4–5 h, after reaction was
USA). The synthetic route of pyrimidine-containing 4H- completed (the reaction was monitored by TLC). The
Chromen-4-one derivatives was shown in Scheme 1.
mixture was cooled to room temperature, then,
poured into 80 mL ice water and extracted with ethyl
acetate (3×30 mL), organic layer was washed with 5%
hydrochloric acid solution, saturated NaHCO3 aqueous
solution, saturated NaCl solution successively and
dried with anhydrous Na2SO4. Solvent removed under
Chemistry
General Procedure for the Synthesis of Intermediate 1
Based on the previous reported method,[26,37] the ethyl vacuum and crude product was separated by column
cyanoacetate (5 mmol), substituted aromatic aldehyde chromatography with petroleum ether/ethyl acetate
(5 mmol), thiourea (5 mmol) and anhydrous K2CO3 (V:V=1:1) to obtain the title compound 4a. Based on
(7.5 mmol) were added in ethanol (50 mL) for refluxed the similar method, the title compounds 4b–4x were
for about 4–6 h. After the reaction was completed prepared. AII the Spectroscopic data and Spectro-
(the reaction was monitored by TLC), mixture was graphic of compound 4a–4x were provided in Sup-
cooled to room temperature and diluted with ice porting Material.
water, a large amount of solids was precipitated as the
pH adjusted with glacial acetic acid to weak acidity,
the residue was filtered and dried with suction,
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Chem. Biodiversity 2021, 18, e2100186
Scheme 1. The synthesis of target compounds.
Antibacterial Bioassays
modifications.[38] Commercial agents BT and TC were
used as positive control. The test method was
provided in Supporting Information.
Bacteriostatic Activity Test in Vitro
The in vitro antibacterial activities of all the target
compounds against X. axonopodis, X. oryzae and R.
solanacearum were determined by turbidimetric
Scanning Electron Microscopy
method.[39] The test method was provided in Support- To explore the mechanism of compounds 4c against
ing Information.
X. oryzae, scanning electron microscopy (SEM) analysis
was taken according to previous method.[40] This
method is provided in Supporting Information.
In Vivo Antibacterial Activity
The protection and curative activities of compound 4c
against bacterial blight of rice were tested through
potted plants using complete randomized block
design according to a previous method with slight
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Chem. Biodiversity 2021, 18, e2100186
[8] M. H. Chen, X. B. Wang, B. C. Tang, X. Zhang, ‘Synthesis and
Acknowledgements
antibacterial evaluation of novel Schiff base derivatives
containing 4(3H)-quinazolinone moiety’, Chem. Pap. 2016,
70, 1521–1528.
We gratefully acknowledge the National Nature Sci-
ence Foundation of China (No. 21867003), the Science
Fund of Guizhou Province (Nos. 20192452, 20191105).
the Science and Technology Project of Guizhou
Province (Nos. 20185781, 20171028).
[9] S. Jiang, N. Dong, J. Zhang, C. Gan, F. Liu, ‘Separation of
myricetin and dihydromyricetin in ampelopsis grosseden-
tata and their inhibition of cadiomyocyte apoptosis’, J.
Harbin Med. Univ. 2008, 42, 4–6.
[10] X. Tang, C. Zhang, M. Chen, Y. N. Xue, T. T. Liu, W. Xue,
‘Synthesis and antiviral activity of novel myricetin deriva-
tives containing ferulic acid amide scaffolds’, New J. Chem.
2020, 44, 2374–2379.
Author Contribution Statement
[11] X. W. Su, D. H. Souza, ‘Naturally occurring flavonoids
against human norovirus surrogates’, Food Environ. Virol.
2013, 5, 97–102.
[12] X. H. Ruan, C. Zhang, S. C. Jiang, T. Guo, R. J. Xia, Y. Chen, X.
Tang, W. Xue, ‘Design, Synthesis, and Biological Activity of
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Schiff base’, RSC Adv. 2019, 9, 23045–23052.
This study is an outcome of constructive discussion
with Wei Xue and Shijun Su, Mei Chen and Shijun Su
carry out their synthesis and characterization experi-
ments and carried out the H-NMR, 13C-NMR, 19F NMR
1
and HRMS spectral analyses, XueMei Tang, Feng Peng
and Tingting Liu performed the antibacterial activity;
Qing Zhou, Wenliang Zhan and Ming He assists in
scanning electron microscope; Shijun Su and Cheng-
wei Xie were involved in the drafting of the manu-
script and revising the manuscript. All authors read
and approved the final manuscript.
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Received March 25, 2021
Accepted June 18, 2021
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