Synthesis and antiviral bioactivity of novel chalcone derivatives containing purine moiety

Article abstract of DOI:10.1016/j.cclet.2017.07.006

A series of novel chalcone derivatives containing purine moiety was designed and synthesized, and their antiviral activities against cucumber mosaic virus (CMV) and tobacco mosaic virus (TMV) were evaluated in vivo. Bioactivity assays indicated that some compounds showed good antiviral activities against CMV and TMV. It is worth mentioning that compounds 3o, 3s, 3w, and 3x exhibited excellent curative activity against CMV, with EC₅₀ values of 301.1 μg/mL, 315.7 μg/mL, 282.3 μg/mL, 230.5 μg/mL, respectively, which were better than that of Dufulin (373.7 μg/mL) and Ribavirin (726.3 μg/mL). In addition, the fluorescence spectroscopy experiment results showed that compound 3o showed strong combining capacity to tobacco mosaic virus coat protein.

Full text of DOI:10.1016/j.cclet.2017.07.006

Accepted Manuscript
Title: Synthesis and antiviral bioactivity of novel chalcone
derivatives containing purine moiety
Authors: Yan-Jiao Wang, Da-Gui Zhou, Fang-Cheng He,
Ji-Xiang Chen, Yong-Zhong Chen, Xiu-Hai Gan, De-Yu Hu,
Bao-An Song
PII:
S1001-8417(17)30242-5
DOI:
Reference:
http://dx.doi.org/doi:10.1016/j.cclet.2017.07.006
CCLET 4124
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Chinese Chemical Letters
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17-5-2017
5-7-2017
Pleasecitethisarticleas:Yan-JiaoWang, Da-GuiZhou, Fang-ChengHe, Ji-XiangChen,
Yong-Zhong Chen, Xiu-Hai Gan, De-Yu Hu, Bao-An Song, Synthesis and antiviral
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Lettershttp://dx.doi.org/10.1016/j.cclet.2017.07.006
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Communication
Synthesis and antiviral bioactivity of novel chalcone derivatives
containing purine moiety
Yan-Jiao Wang, Da-Gui Zhou, Fang-Cheng He, Ji-Xiang Chen, Yong-Zhong
Chen, Xiu-Hai Gan, De-Yu Hu, Bao-An Song
State Key Laboratory Breeding Base of Green Pesticide and Agricultural Bioengineering, Key Laboratory of Green Pesticide
and Agricultural Bioengineering, Ministry of Education, Research and Development Center for Fine Chemicals, Guizhou
University, Guiyang 550025, China
 Corresponding authors.
E-mail addresses: basong@gzu.edu.cn (B.-A. Song), dyhu@gzu.eud.cn (D.-Y. Hu).
Graphical abstract
A series of novel chalcone derivatives containing purine group was synthesized and evaluated for their antiviral activities
against cucumber mosaic virus and tobacco mosaic virus. Compound 3o exhibited remarkable antiviral activities and strong
combining capacity to tobacco mosaic virus coat protein.
ABSTRACT
A series of novel chalcone derivatives containing purine moiety was designed and synthesized, and their antiviral activities
against cucumber mosaic virus (CMV) and tobacco mosaic virus (TMV) were evaluated in vivo. Bioactivity assays indicated
that some compounds showed good antiviral activities against CMV and TMV. It is worth mentioning that compounds 3o, 3s,
3w, and 3x exhibited excellent curative activity against CMV, with EC50 values of 301.1 μg/mL, 315.7 μg/mL, 282.3 μg/mL,
230.5 μg/mL, respectively, which were better than that of Dufulin (373.7 μg/mL) and Ribavirin (726.3 μg/mL). In addition, the
fluorescence spectroscopy experiment results showed that compound 3o showed strong combining capacity to tobacco mosaic
virus coat protein.
Keywords: Chalcone derivatives
6-Chloro-purine
Antiviral activity
Cucumber mosaic virus
Tobacco mosaic virus
Interaction mechanisms
ARTICLE INFO
Article history:
Received
Received in revised form
Accepted
Available online
Cucumber mosaic virus (CMV) and tobacco mosaic virus (TMV) are two important plant viruses, which can
cause serious plant disease in plants and can cause considerable damage to agriculture with those parasitic [1,2]. Up
to now, only a few antiviral agents can be widely used to prevent and control CMV and TMV, such as Dufulin and
Ribavirin. However, their inhibitory activities were from 40% to 50% at 500 μg/mL [3,4] and it is difficult to
effectively control the spread of the virus in the field. Therefore, it is imperative to vigorously develop the new,
———

high-efficiency and low toxicity antiviral agents. As positive-sense single-stranded RNA virus, TMV can infect a
wide range of plants, especially tobacco, vegetable and other members of the Solanaceae family. This virus is
globally ubiquitous and unmanageable, which can cause great crop loss [1] and was named “plant cancer”.
Ningnanmycin was found to be more effective in the treatment of TMV. However, it was not used in field trials
because of unstable and expensive [2,3]. Therefore, the development of stable, natural product-based, and
economical antiviral agents is a challenge in pesticide science [4].
Chalcone, as a natural flavonoids, widely exist in medicinal plants [5] with broad-spectrum bioactivity, such as
antifungal [6], anticancer [7,8], antibacterial [9], insecticidal [10,11], and antiviral [12] activities. Some reports
indicated that these bioactivity is due to their molecular flexibility and their ability to bind to different receptors
[13,14]. In our previous study, a number of chalcone derivatives containing malonate (Fig. 1A and B) and
quinazoline (Fig. 1C) groups have been designed and synthesized, and these compounds exhibited potent antiviral
activities against CMV and TMV [15–17].
Meanwhile, purine is an important heterocyclic compounds, which has been widely used as antiviral agent in
medicine [18], such as ganciclovir [19], abacavir [20], famciclovir [21] and so on. Additionally, purine and its
derivatives possess well others pharmacological properties, including anticancer [22], anticonvulsant [23],
antimicrobial [24], herbicidal activity [25], and growth regulating effects [26]. However, the application of purine
and its derivatives in pesticide field was extremely rare, especially in controlling plant virus disease aspect. Our
group found that a series of purine derivatives containing 1,4-pentadien-3-one moiety (Fig. 1D) exhibited potential
antiviral activities against CMV [27].
To extend our study, 1,4-pentadien-3-one moiety was replaced with chalcone structure, and a series of novel
chalcone derivatives containing purine group (Scheme 1) were designed and their antiviral activities against CMV
and TMV were evaluated in vivo. Moreover, the interaction between the target compounds and the tobacco mosaic
virus coat protein (TMV-CP) was tested by means of the fluorescence titration.
The synthetic route of the target compounds was depicted in Scheme 1. Based on reported method [28,29],
intermediates 1 and 2 were prepared. Then, a mixture of intermediates 1 (1.1 mmol) and potassium carbonate (1.8
mmol) in acetonitrile was stirred for 1 h, and 9-substituted-6-chloro-9H-purine (1 mmol) was added and refluxed for
8 h. The solvent was evaporated in vacuo, and the residue was isolated by column chromatography on silica gel
using petroleum ether/ethyl acetate (2:1, v/v) to obtain the title compounds (3a–3z). Their antiviral activities against
CMV and TMV in vivo were evaluated by literature methods [27,30], with Dufulin and Ribavirin as controls.
Meanwhile, the interaction between the target compound and TMV-CP was test by fluorescence spectroscopy
t
i
t
r
a
t
i
o
n
[
1
6
]
During the synthesis of the target compounds, it is worth mentioning that the corresponding target compounds
were not obtained in most reaction conditions when the 9-position of 6-chloropurine was hydrogen including
different solvent, catalyst, and temperature (Table 1). However, it is exciting that the target product was obtained
successfully when the 9-position was substituted with alkyl, in order to obtain the target compounds with high
yields, the reaction conditions of compound 3a were optimized. The results showed that the maximum yield of 3a up
to 67.3% was achieved when solvent, catalyst and temperature was CH3CN, K2CO3 and 75 °C, respectively (Table
1). Under these conditions, other target compounds were synthesized with corresponding chaclone and 6-chloro-9-
substitued-9H-purine. The structures of target compounds were identified by 1H NMR, 13C NMR and HRMS. These
data were collected in the Supporting information. Take compound 3e as an example, the two single peaks at δ 8.53,
1
8.07 in the H NMR spectra indicated the presence of Purine-H. The doublets at δ 7.82 (d, 1H, J = 15.7 Hz) and δ
7.51 (d, 1H, J = 15.7 Hz) indicated the presence of C=CH. The doublets at δ 8.13, 7.55, 7.42, and 7.22 were assigned
to the Ar-H protons. Besides, the spectra shown the presence of -N-CH2- in the form of a quartet at δ 4.36, the triplet
13
at δ 1.59 and the single at δ 2.39 indicated the presence of -N-CH2CH3 and -CH3, respectively. In addition, the C
NMR spectra showed the presences of -C=O, -N-CH2-, Ar-CH3, and -NCH2CH3 at δ 189.4, 39.5, 21.7, and 16.5,
respectively.
The antiviral activity of the title compounds in vivo was tested and shown in Table 2. The results revealed some
compounds exhibited obvious inhibitory activities against CMV and TMV at 500 μg/mL. Notably, compounds 3k,
3o, 3p, 3s, 3w, and 3x demonstrated good curative activities against CMV with the values of 52.3%, 58.3%, 51.3%,
52.5%, 53.3%, and 58.7%, respectively, which were better than that of Dufulin (50.6%) and Ribavirin (40.8%).
Besides, the protective effects of compounds 3e, 3k, 3n, 3o and 3t was 51.9%, 49.0%, 50.5%, 52.4%, and 48.5%,
respectively, which were similar to that of Dufulin (51.5%) and Ribavirin (50.5%). Meanwhile, compounds 3d, 3f,
3p, 3u, 3x, and 3y exhibited good curative activities against TMV with the inhibition ratios of 50.8%, 50.3%, 52.0%,
48.5%, 49.3%, and 49.4%, respectively, which were equivalent to that of Dufulin (49.3%) and superior to Ribavirin
(38.3%). The protective effects of compounds 3e, 3t, and 3w against TMV was 49.2%, 53.7%, and 55.8%,

respectively, which were similar to that of Dufulin (48.1%) and Ribavirin (50.2%). Compounds 3i (80.9%), 3o
(89.1%), 3p (88.2%) and 3u (82.0%) could effectively inactivate TMV, better than Dufulin and Ribavirin.
The EC50 values of curative activities against CMV of all the compounds indicated that compounds 3o, 3s, 3w,
and 3x displayed excellent curative effects against CMV with EC50 values of 301.1, 315.7, 282.3, and 230.5 μg/mL,
respectively, which were better than that of Dufulin (EC50 = 373.7 μg/mL) and Ribavirin (EC50 = 726.3 μg/mL). The
preliminary structure-activity relationships indicated that different substituents had great influences on antiviral
activity. Compounds 3w and 3x in which R2 was 2-chlorpyridin, R1 was substituted with 2-fluoro and 4-chloro
groups, showed better curative activity against CMV. In addition, the title compounds displayed notable inactivation
activities against TMV when R2 was phenyl and R1 was 4-chloro or 4-nitro group, but the curative and protection
activity did not showed the evident trend with electron-donating or electron-withdrawing substituents. When R2 was
2-chlorpyridin and R1 was substituted with 2-methoxyl, 4-chloro or 4-nitro group, the target compounds showed
good curative activities. As for the protection activity, when R2 was 2-chlorpyridin and R1 was substituted with 4-
methyl or 2-fluorine groups, the corresponding compounds displayed better antiviral activities than other compounds.
The results of fluorescence spectroscopy titration (Fig. S1 in Supporting information) revealed that compound 3o
exhibited strong combining capacity to TMV-CP, with the binding constant (Ka) value of 1.95 × 105 L/mol, which
was superior to that of Dufulin (2.40 × 104 L/mol) and Ribavirin (3.31 × 103 L/mol). However, compound 3s (6.46 ×
103 L/mol) and 3h (1.50 × 102 L/mol) showed moderate and weak combining capacity to TMV-CP.
In conclusion, a series of novel chalcone derivatives with purine ring were designed, synthesized according to the
substructure link principle. Compounds 3o, 3s, 3w and 3x exhibited satisfactory curative activities against CMV and
TMV. In addition, compound 3o exhibited strong combining capacity to TMV-CP. This finding indicated that
chalcone derivatives containing purine moiety could be considered as novel lead structures to further research on
new antiviral agents.
Acknowledgment
This research was supported by National Natural Science Foundation of China (Nos. 21562013 and 21362004),
Subsidy Project for Outstanding Key Laboratory of Guizhou Province in China (No. 20154004), the Provincial
University Cooperation Plan of Guizhou Province in China (No. 20147001) and Collaborative Innovation Center for
Natural Products and Biological Drugs of Yunnan.
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Fig. 1. Chemical structures of known antiviral molecules.
Scheme 1. Synthesis route of compounds 3a to 3z.

Table 1
Effect of different conditions for synthesis of title compounds. a
Catalys
t
K2CO3
KOH
T
(oC)
65
Yield
Entry
R
Solvent
b
1
2
H
H
DMF
DMF
0
0
80
Aceton KOH/K
3
H
50
0
e
I
4
5
H
H
H
CH3
CH3
CH3
CH3
CH3OH
CH3CN
DMSO
DMF
DMSO K2CO3
CH3CN K2CO3
CH3CN K2CO3
KOH
DBUc
KOH
K2CO3
65
80
180
25
25
25
0
0
0
20.8
45.7
48.3
67.3
6d
7
8
9
10
75
a Reactions were performed with the molar ratio of 6-chloro-9H-purine: chalcone: catalyst was 1:1.1:1.8.
b Yield of isolated product.
c 1, 8-Diazabicyclo[5.4.0]undec-7-ene.
d Microwave synthesis method.

Table 2
Antiviral activity of the title compounds against CMV and TMV in vivo.a
Compd.
CMV
TMV
Curative
activity b
(%)
Protection
Curative
activity b
(%)
Protection
Inactivation
EC50 values of
curative activity
(μg/mL)
activity b (%)
activity b (%)
activity b
(%)
42.8 ± 2.3
47.2 ± 1.9
43.9 ± 3.3
46.4 ± 2.1
49.4 ± 2.6
48.1 ± 3.1
46.8 ± 2.2
49.3 ± 1.6
43.3 ± 3.4
42.6 ± 3.7
52.3 ± 2.5
43.3 ± 1.4
44.2 ± 1.1
45.2 ± 1.9
58.3 ± 1.3
51.3 ± 2.1
48.5 ± 2.0
47.4 ± 1.7
52.5 ± 2.7
49.4 ± 1.4
49.2 ± 1.9
41.3 ± 3.1
53.3 ± 1.9
58.7 ± 1.3
50.5 ± 3.1
48.9 ± 3.9
50.6 ± 2.4
44.9 ± 2.4
44.5 ± 1.7
44.7 ± 2.0
42.1 ± 2.8
51.9 ± 3.5
40.2 ± 1.2
38.3 ± 1.1.
39.3 ± 2.3
40.5 ± 1.9
43.8 ± 1.8
49.0 ± 2.0
47.3 ± 1.4
45.9 ± 1.2
50.5 ± 1.0
52.4 ± 1.6
40.3 ± 2.9
43.9 ± 2.4
47.5 ± 1.1
45.8 ± 1.9
48.5 ± 1.7
44.0 ± 2.1
44.5 ± 2.4
45.2 ± 3.1
41.5 ± 2.7
43.2 ± 2.9
38.4 ± 3.1
51.5 ± 1.6
50.5 ± 3.0
43.0 ± 2.8
32.9 ± 2.0
44.5 ± 1.8
50.8 ± 1.4
41.2 ± 2.1
50.3 ± 3.2
47.6 ± 2.4
41.2 ± 2.3
39.4 ± 3.1
38.1 ± 2.7
44.2 ± 1.1
41.9 ± 1.0
43.7 ± 1.3
46.2 ± 1.7
42.1 ± 3.2
52.0 ± 1.1
43.3 ± 2.1
44.7 ± 1.4
41.9 ± 2.1
43.0 ± 1.8
48.5 ± 2.5
36.4 ± 2.1
46.4 ± 1.5
49.3 ± 1.3
49.4 ± 1.8
34.8 ± 3.8
49.3 ± 2.1
38.3 ± 1.9
42.3 ± 3.1
33.8 ± 2.1
36.8 ± 3.1
44.8 ± 1.7
49.2 ± 2.3
47.4 ± 1.8
36.8 ± 2.9
44.8 ± 3.1
40.3 ± 2.1
43.5 ± 1.8
40.5 ± 1.1
39.6 ± 1.4
37.7 ± 2.8
43.4 ± 1.0
46.3 ± 2.1
43.2 ± 2.8
40.2 ± 2.7
42.6 ± 1.3
39.7 ± 2.3
53.7 ± 1.0
31.3 ± 3.1
31.7 ± 2.2
55.8 ± 1.2
42.1 ± 2.1
43.6 ± 2.3
37.3 ± 2.9
48.1 ± 1.5
50.2 ± 2.1
69.7 ± 2.7
58.9 ± 3.3
56.6 ± 2.1
68.9 ± 3.2
60.2 ± 3.7
60.5 ± 3.1
51.3 ± 1.9
48.1 ± 2.0
80.9 ± 1.1
65.7 ± 1.4
56.7 ± 2.1
64.4 ± 1.6
67.8 ± 2.5
56.0 ± 2.7
89.1 ± 2.1
88.2 ± 1.8
50.9 ± 2.5
54.4 ± 2.7
75.2 ± 1.7
68.3 ± 1.3
82.0 ± 1.9
70.0 ± 2.1
64.4 ± 1.7
58.8 ± 2.5
76.9 ± 1.3
65.8 ± 2.7
80.5 ± 2.1
71.9 ± 2.5
1026.2 ± 4.9
752.3 ± 5.9
838.2 ± 3.9
823.9 ± 6.5
613.5 ± 9.2
518.2 ± 8.9
490.9 ± 10.3
407.9 ± 6.8
720.5 ± 11.9
712.9 ± 5.9
588.5 ± 7.2
1022.5 ± 11.1
802.9 ± 10.0
744.4 ± 5.7
301.1 ± 4.7
398.0 ± 3.8
395.0 ± 4.8
536.4 ± 7.0
315.7 ± 3.1
561.7 ± 7.7
725.2 ± 4.8
1111.1 ± 8.6
282.3 ± 4.6
230.5 ± 3.0
430.9 ± 6.6
372.5 ± 4.8
373.7 ± 4.9
726.3 ± 3.5
3a
3b
3c
3d
3e
3f
3g
3h
3i
3j
3k
3l
3m
3n
3o
3p
3q
3r
3s
3t
3u
3v
3w
3x
3y
3z
Dufulin
Ribavirin 40.8 ± 1.3
a Average of three replicates; b The concentration of compound is 500 μg/mL.