Synthesis and anti-TMV activity of dialkyl/dibenzyl 2-((6-Substituted- benzo[d]thiazol-2-ylamino)(benzofuran-2-yl)methyl) malonates

Article abstract of DOI:10.3390/molecules181113623

Starting from benzofuran-2-methanal, 6-substituted benzothiazole-2-amines and malonic esters, sixteen title compounds were designed and synthesized seeking to introduce anti-TMV activity. The structures of the newly synthesized compounds were confirmed by 1H-NMR, 13C-NMR, IR spectra, and MS (HREI) analysis. The bioassays identified some of these new compounds as having moderate to good anti-TMV activity. The compounds 5i and 5m have good antiviral activity against TMV with a curative rate of 52.23% and 54.41%, respectively, at a concentration of 0.5 mg/mL.

Full text of DOI:10.3390/molecules181113623

Molecules 2013, 18, 13623-13635; doi:10.3390/molecules181113623
OPEN ACCESS
molecules
ISSN 1420-3049
www.mdpi.com/journal/molecules
Article
Synthesis and Anti-TMV Activity of
Dialkyl/dibenzyl 2-((6-Substituted-benzo[d]thiazol-2-
ylamino)(benzofuran-2-yl)methyl) Malonates
Han Xiao 1,2,*, Pengcheng Zheng 1, Chenghao Tang 1, Ying Xie 1, Fang Wu 1, Jie Song 1,
Jun Zhao 1, Zhining Li 1 and Meichuan Li 1
1
Key Laboratory of Green Pesticide and Agricultural Bioengineering, Ministry of Education,
Guizhou University, Guiyang 550025, China; E-Mails: zhengpc1986@163.com (P.Z.);
chtang1122@163.com (C.T.); xieying0020@126.com (Y.X.); fangwu90@126.com (F.W.);
songjie277@yeah.net (J.S.); zhaojun0020@126.com (J.Z.); aning072@126.com (Z.L.);
lmcuvhn1987@163.com (M.L.)
2
School of Chemistry and Environmental Science, Guizhou Minzu University,
Guiyang 550025, China
* Author to whom correspondence should be addressed; E-Mail: hanx@gzmu.edu.cn;
Tel./Fax: +86-0851-829-2090.
Received: 13 September 2013; in revised form: 24 October 2013 / Accepted: 29 October 2013 /
Published: 4 November 2013
Abstract: Starting from benzofuran-2-methanal, 6-substituted benzothiazole-2-amines and
malonic esters, sixteen title compounds were designed and synthesized seeking to
introduce anti-TMV activity. The structures of the newly synthesized compounds were
1
confirmed by H-NMR, 13C-NMR, IR spectra, and MS (HREI) analysis. The bioassays
identified some of these new compounds as having moderate to good anti-TMV activity. The
compounds 5i and 5m have good antiviral activity against TMV with a curative rate of
52.23% and 54.41%, respectively, at a concentration of 0.5 mg/mL.
Keywords: benzofuran; benzothiazole; β-amino acid ester; anti-TMV activity
1. Introduction
Benzothiazoles have varied biological activities [1–3]. They are widely found in bioorganic and
medicinal chemistry with applications in drug discovery and are still of great scientific interest

Molecules 2013, 18
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nowadays [4]. Benzothiazole moieties are part of compounds showing numerous biological activities
such as anti-bacterial, anti-microbial, anthelmintic, antitumor, anti-inflammatory properties [5–8].
Compounds containing benzofuran moieties are also widespread in Nature, with a broad
spectrum of physiological bioactivities, used as pesticidal, anti-bacterial, insecticide, anti-tumor,
anti-inflammatory [9–11], and so on.
β-Amino ester derivatives are key intermediate in the synthesis of β-lactam antibiotics, which are
important components of many natural products and therapeutic agents [12–14]. Therefore, the
asymmetric synthesis of β-amino ester derivatives has become a field of increasing interest in organic
synthetic chemistry over the past few years [15–20].
As an extension study of our group’s research [19,21], we have now synthesized a series of novel
β-amino ester derivatives containing benzofuran and benzothiazole units. The structures of these newly
synthesized compounds were confirmed by 1H-NMR, 13C-NMR, IR spectra, and MS (HREI) analysis.
Bioassays identified these new compounds as possessing weak to good antiviral activities.
2. Results and Discussion
2.1. Experimental Condition Optimization
Our strategy is outlined in Scheme 1. Benzofuran-2-methanal (1) reacted with 6-substituted
benzothiazoles 2a–d under reflux conditions in toluene, with some acetic acid as catalyst affording the
imines 3a–d. After recrystallization by ethanol, the final compounds were isolated in good yields. All
products 3a–d were characterized by spectroscopic methods.
Scheme 1. Synthesis of imines.
According to the Scheme 2, we tested the influence of the reaction temperature, solvent, and
reaction times. The reaction temperature had a pronounced effect on the yield, solvents such as THF,
acetone, and toluene showed lower yields compared to DCM (Table 1). According to an optimized
procedure, the best result was achieved at 35 °C in DCM.
Scheme 2. Screening of the reaction conditions.
H3C
O
O
O
H
N
O
DCM
O
O
C
S
N
HN C* H O CH3
+
H3C
CH3
O
O
S
O
N

Molecules 2013, 18
13625
Table 1. The optimization of reaction conditions.
Entry
Solvent
THF
THF
PhMe
PhMe
DCM
DCM
Temp. (°C)
Time (h)
Yield (%)
1
2
3
4
5
6
r.t.
r.f.
r.t.
r.f.
r.t.
35
24
12
24
12
24
10
34
38
46
72
62
78
Having established the ideal reaction conditions, the synthetic scope of the reaction was evaluated
with different imines and malonic esters (Scheme 3). The results of our studies are summarized in
Table 2. It can be seen that the reactions afforded good yields.
Scheme 3. Synthesis of compounds 5a−p.
R
N
N
O
O
S
DCM
N
H
HN
C
O
+
+
R1
R1
S
C
R
O
O
O
O
H
O
O R1
R1
O
5
4
R: H, Cl, OCH3, CH3
R1: CH3, C2H5, C3H7, CH2C6H5
Table 2. The yields of the Mannich reactions of imines and malonic esters.
Entry
1
5
5a
5b
5c
5d
5e
5f
5g
5h
5i
5j
5k
5l
5m
5n
5o
5p
R
6-H
6-H
6-H
6-H
6-Cl
6-Cl
6-Cl
R1
-CH3
-C2H5
-C3H7
-CH2C6H5
-CH3
-C2H5
-C3H7
-CH2C6H5
-CH3
-C2H5
-C3H7
-CH2C6H5
-CH3
-C2H5
Time(h)
12
Yield(% a)
82
80
78
62
85
86
82
67
81
80
79
60
81
76
76
64
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
12
12
24
12
12
12
24
12
12
12
24
12
12
12
24
6-Cl
6-OCH3
6-OCH3
6-OCH3
6-OCH3
6-CH3
6-CH3
6-CH3
6-CH3
-C3H7
-CH2C6H5
a Isolated yield after chromatographic purification.

Molecules 2013, 18
13626
2.2. Anti-TMV Activity
The antiviral activity of compound 5 against TMV was assayed by the reported method [9]. As it
can be seen from the results presented in Table 3, some compounds possess good anti-TMV activity,
such as the curative rates against TMV of compounds 5i and 5m which were 52.23% and 54.41%.
These values are close to that of the the commercial control ningnanmycin (curative rate 55.27%).
Table 3. The in vivo antiviral activity towards TMV of the new compounds at 0.5 (mg/mL).
Entry
1
Compound
ꢀProtection Effect % Curative Effect % Inhibition Effect %
5a
57.95
63.08
62.11
48.58
58.67
68.32
56.76
49.77
59.79
58.76
40.20
52.34
68.75
66.04
58.97
46.36
82.03
48.27
47.18
43.83
49.17
46.28
48.34
48.27
44.20
52.23
48.03
46.73
35.53
54.41
48.09
47.93
38.46
55.27
39.72
43.42
33.29
28.45
33.50
43.98
46.77
44.21
40.98
39.27
41.04
29.08
46.88
39.70
42.33
45.96
52.16
2
5b
3
5c
4
5d
5
5e
6
5f
7
5g
8
5h
9
5i
10
11
12
13
14
15
16
17
5j
5k
5l
5m
5n
5o
5p
Ningnanmycin
3. Experimental
3.1. Instruments and Chemicals
Melting points were determined on a XT-4 binocular microscope (Beijing Tech Instrument Co.,
Beijing, China) and were not corrected. IR spectra were recorded on a Bruker VECTOR 22
1
spectrometer in KBr disks. H- and 13C-NMR spectral analyses (solvent CDCl3 or DMSO-d6) were
performed on a JEOL-ECX 500 NMR spectrometer at room temperature using TMS as an internal
standard. Elemental analyses were performed on an Elementar Vario-III CHN analyzer. MS spectra
were recorded with a VG Autospec-3000 spectrometer. Analytical TLC was performed on silica gel
GF254. Column chromatographic purification was carried out using silica gel GF254. Commercial
reagents were used as received, unless otherwise indicated. Reactions were performed under a positive
pressure of dry argon in oven-dried or flame-dried glassware equipped with a magnetic stir bar.
Standard inert atmosphere techniques were used in handling all air and moisture sensitive reagents. All
reagents were of analytical reagent grade or chemically pure. All solvents were dried, deoxygenated
and redistilled before use.

Molecules 2013, 18
13627
3.2. Synthesis
3.2.1. General Synthetic Methods for 3a–d
To a magnetically stirred solution of 6-substituted benzothiazole (6.80 mmol) in toluene (5 mL)
benzofuran-2-methanal (6.80 mmol) dissolved in toluene (5 mL) was added dropwise at room
temperature. After attaching a Dean Stark trap, the reaction was allowed to reflux after adding acetic
acid (0.5 mL). Complete consumption of starting materials was observed after 24 h. After
recrystallization from ethanol the final compounds 3a–d were isolated in good yields.
3.2.2. Characterization of 3a–d
N-(Benzofuran-2-ylmethylene)benzo[d]thiazol-2-amine (3a): yellow solid; mp:173–174 °C; yield: 77%;
1H-NMR (CDCl3) δ (ppm): 8.11 (d, 1H, J = 5 Hz, 11-CH), 7.98 (d, 1H, J = 5 Hz, 9-CH), 7.89 (d, 1H,
J = 5 Hz, 6-CH), 7.77 (d, 1H, J = 10 Hz, 17-CH), 7.61–7.54 (m, 2H, 7-CH, 8-CH), 7.52 (s, 1H, 20-CH),
13
7.47–7.46 (m, 2H, 18-CH, 19-CH), 7.43-7.39 (m, 1H, 14-CH); C-NMR (DMSO-d6) δ (ppm): 171.5
(2-C), 156.4 (16-C), 154.8 (4-C), 151.8 (11-C), 135.1 (12-C), 129.8 (5-C), 129.4 (15-C), 128.0 (8-C),
127.4 (7-C), 125.9 (19-C), 124.7 (18-C), 123.9 (6-C), 123.3 (9-C), 120.2 (17-C), 113.0 (20-C), 112.6
(14-C); IR (KBr, cm−1) ν: 3049, 608, 1556, 1546, 1417, 1309, 1116, 954, 813, 750, 729; MS (ESI):
m/z = 279 ([M+H]+), 301 ([M+Na]+).
N-(Benzofuran-2-ylmethylene)-6-chlorobenzo[d]thiazol-2-amine (3b): yellow solid; mp: 209–212 °C;
yield: 76%; 1H-NMR (CDCl3) δ (ppm): 9.17 (s, 1H, 6-CH), 8.23 (s, 1H, 11-CH), 7.96 (s, 1H, 17-CH),
7.91 (d, 1H, J = 5 Hz, 9-CH), 7.84 (d, 1H, J = 5 Hz, 8-CH), 7.72 (s, 1H, 20-CH), 7.54–7.54 (m, 2H,
13
18-CH, 19-CH), 7.36 (s, 1H, 14-CH); C-NMR (DMSO-d6) δ (ppm): 172.5 (2-C), 156.5 (16-C), 155.3
(4-C), 152.2 (11-C), 150.6 (6-C), 136.5 (12-C), 130.2 (5-C), 129.5 (15-C), 129.2 (8-C), 127.8 (7-C), 124.7
(19-C), 124.4 (18-C), 123.9 (9-C), 122.7 (17-C), 120.6 (20-C), 112.7 (14-C); IR (KBr, cm−1) ν: 3086,
1598, 1539, 1425, 1330, 1294, 1166, 1122, 950, 812, 802, 738, 704, 605; MS (ESI): m/z = 313
([M+H]+), 335 ([M+Na]+).
N-(Benzofuran-2-ylmethylene)-6-methoxybenzo[d]thiazol-2-amine (3c): yellow solid; mp: 147–150 °C;
yield: 64%; 1H-NMR (CDCl3) δ (ppm): 9.09–9.07 (m, 1H, 11-CH), 7.88 (d, 1H, J = 5 Hz, 17-CH ), 7.81
(t, 2H, J = 15 Hz, 6-CH, 8-CH), 7.70 (t, 1H, J = 15 Hz, 9-CH), 7.62 (d, 1H, J = 5 Hz, 20-CH), 7.51 (d,
1H, J = 5 Hz, 19-CH), 7.34 (s, 1H, 14-CH), 7.09-7.07 (m, 1H, 18-CH), 3.81 (s, 3H, 22-C OCH3);
13C-NMR (DMSO-d6) δ (ppm): 168.9 (2-C), 157.9 (16-C), 156.3 (4-C), 153.5 (11-C), 152.4 (6-C),
146.1 (12-C), 136.5 (5-C), 129.1 (15-C), 128.0 (8-C), 124.6 (7-C), 124.0 (19-C), 123.7 (18-C), 119.4
(9-C), 116.6 (17-C), 112.5 (20-C), 105.6 (14-C), 56.2 (22-C); IR (KBr, cm−1) ν: 3093, 1598, 1556,
1541, 1485, 1452, 1429, 1263, 1226, 1120, 1056, 1024, 954, 908, 833, 817, 756, 609; MS (ESI): m/z = 309
([M+H]+), 331 ([M+Na]+).
N-(Benzofuran-2-ylmethylene)-6-methylbenzo[d]thiazol-2-amine (3d): yellow solid; mp: 185–190 °C;
1
yelid: 78%; H-NMR (CDCl3) δ (ppm): 8.37-8.36 (m, 2H, 11-CH, 6-CH), 8.05–8.00 (m, 2H, 9-CH,
17-CH), 7.92–7.90 (m, 2H, 18-CH, 19-CH), 7.51–7.47 (m, 2H, 14-CH, 20-CH), 7.46-7.40 (m, 1H, 8-CH),
13
2.43 (s, 3H, 21-CH3); C-NMR (DMSO-d6) δ (ppm): 181.4 (2-C), 170.5 (16-C), 166.2 (4-C), 154.3

Molecules 2013, 18
13628
(11-C), 129.8 (6-C), 129.3 (12-C), 128.8 (5-C), 126.9 (15-C), 124.7 (8-C), 123.8 (7-C), 122.9 (19-C),
122.5 (18-C), 121.3 (9-C), 120.0 (17-C), 117.9 (20-C), 112.9 (14-C), 21.7 (22-C); IR (KBr, cm−1) ν:
3028, 1602, 1579, 1562, 1473, 1433, 1361, 1305, 1213, 1186, 1120, 956, 916, 858, 825, 750, 740, 686,
609; MS (ESI): m/z = 293 ([M+H]+), 315 ([M+Na]+).
3.2.3. General Synthetic Methods for 5a–p
To a magnetically stirred solution of imines (0.50 mmol) in DCM (5 mL) malonic ester (0.7 mmol)
was added dropwise at room temperature. The reaction was allowed to reach 35 °C, and complete
consumption of starting materials was observed after 12–24 h. After removing the solvent by reduced
pressure distillation, the mixture was subjected to column chromatography on silica gel (EA/PE = 1:7)
to afford compounds 5a–p.
Dimethyl 2-((Benzo[d]thiazol-2-ylamino)(benzofuran-2-yl)methyl) malonate (5a): white solid; mp:
1
70–72 °C; yield 82%; H-NMR (CDCl3) δ (ppm): 7.61–7.58 (m, 2H, 24-CH, 27-CH), 7.52–7.47 (m,
1H, 14-CH), 7.45–7.41 (m, 1H, 17-CH), 7.33–7.26 (m, 2H, 25-CH, 26-CH), 7.24–7.18 (m, 1H, 16-CH),
7.15-7.09 (m, 1H, 15-CH), 6.71 (s, 1H, NH), 6.75 (d, 1H, J = 15 Hz, 11-CH), 6.07 (d, 1H, J = 10 Hz,
13
8-CH), 4.37–4.33 (m, 1H, 2-CH), 3.76 (s, 6H, 28-CH3, 29-CH3); C-NMR (CDCl3) δ (ppm): 168.4
(20-C), 167.1 (1-C), 165.8 (3-C), 155.0 (10-C), 154.1 (13-C), 152.1 (22-C), 131.0 (23-C), 128.1 (12-C),
126.1 (15-C), 124.5 (16-C), 123.1 (25-C), 122.3 (26-C), 121.3 (24-C), 121.0 (27-C), 119.7 (14-C),
111.3 (17-C), 104.7 (11-C), 53.9 (8-C), 53.8 (2-C), 53.1 (28-C), 52.8 (29-C); MS (ESI): m/z = 411
([M+H]+), 433 ([M+Na]+); MS (HREI): C21H18N2O5S Na for +, calculated 410.0940, found 410.0940;
IR (KBr, cm−1) ν 3385, 2951, 1745, 1732, 1595, 1539, 1452, 1435, 1355, 1259, 1207, 1172, 1014, 966,
750, 725.
Diethyl 2-((Benzo[d]thiazol-2-ylamino)(benzofuran-2-yl)methyl) malonate (5b): white solid; mp:
1
110–112 °C; yield 80%; H-NMR (CDCl3) δ (ppm): 7.59 (d, 2H, J = 5 Hz, 24-CH, 27-CH), 7.50 (s,
1H, 14-CH), 7.43 (s, 1H, 17-CH), 7.31–7.26 (m, 3H, 25-CH, 26-CH, 16-CH), 7.20 (s, 1H, 15-CH),
7.12 (s, 1H, NH), 6.75 (s, 1H, 11-CH), 6.08 (s, 1H, 8-CH), 4.33 (d, 1H, J = 5 Hz, 2-CH), 4.25–4.17
13
(m, 4H, 28-CH2, 30-CH2 ), 1.21 (s, 6H, 29-CH3, 31-CH3); C-NMR (CDCl3) δ (ppm): 168.1 (20-C),
166.7 (1-C), 165.9 (3-C), 155.0 (10-C), 154.3 (13-C), 152.1 (22-C), 131.0 (23-C), 128.1 (12-C), 126.0
(15-C), 124.5 (16-C), 123.1 (25-C), 122.2 (26-C), 121.3 (24-C), 120.9 (27-C), 119.6 (14-C), 111.2 (17-C),
104.7 (11-C), 62.5 (28-C), 62.1 (30-C), 54.1 (8-C), 52.8 (2-C), 14.1 (29-C), 14.0 (31-C); MS (ESI):
m/z = 439 ([M+H]+), 461 ([M+Na]+); MS (HREI): C23H22N2O5S Na for +, calculated 438.1249, found
438.1253; IR (KBr, cm−1) ν 3369, 1739, 1718, 1537, 1485, 1454, 1286, 1242, 1201, 1184, 1176, 1018,
947, 802, 758.
Dipropyl 2-((Benzo[d]thiazol-2-ylamino)(benzofuran-2-yl)methyl) malonate (5c): white solid; mp:
1
127–129 °C; yield 78%; H-NMR (CDCl3) δ (ppm): 7.59–7.55 (m, 2H, 24-CH, 27-CH), 7.48 (d, 1H,
J = 5 Hz, 14-CH), 7.42 (d, 1H, J = 5 Hz, 17-CH), 7.30–7.23 (m, 2H, 25-CH, 26-CH), 7.19 (t, 1H, J = 5 Hz,
16-CH), 7.09 (t, 1H, J = 5 Hz, 15-CH), 6.73 (d, 1H, J = 5 Hz, 11-CH), 6.07 (s, 1H, NH), 4.35–4.32 (m,
1H, 8-CH), 4.13-4.09 (m, 4H, 28-CH2, 29- CH2), 3.40 (d, 1H, J = 5 Hz, 2-CH), 1.61–1.56 (m, 4H, 30-CH2,
31-CH2), 0.87-0.82 (m, 6H, 32-CH3, 33-CH3); 13C-NMR (CDCl3) δ (ppm): 168.3 (20-C), 166.8 (1-C),

Molecules 2013, 18
13629
165.7 (3-C), 155.0 (10-C), 154.4 (13-C), 152.2 (22-C), 131.0 (23-C), 128.1 (12-C), 126.0, (15-C)
124.4 (16-C), 123.1 (25-C), 122.2 (26-C), 121.3 (24-C), 120.9 (27-C), 119.7 (14-C), 111.2 (17-C),
104.6 (11-C), 68.0 (28-C), 67.7 (29-C), 54.0 (8-C), 52.8 (2-C), 21.9 (30-C), 21.8 (31-C), 10.3 (32-C),
10.2 (33-C); MS (ESI): m/z = 467 ([M+H]+), 489 ([M+Na]+); MS (HREI): C25H26N2O5S Na for +,
calculated 438.1249, found 466.1550; IR (KBr, cm−1) ν 3356, 2962, 1751, 1724, 1600, 1564, 1548,
1454, 1442, 1386, 1313, 1271, 1176, 1136, 1053, 925, 815, 759, 754.
Dibenzyl 2-((Benzo[d]thiazol-2-ylamino)(benzofuran-2-yl)methyl) malonate (5d): white solid; mp:
1
110–112 °C; yield 62%; H-NMR (CDCl3) δ (ppm): 7.57 (d, 1H, J = 10 Hz, 24-CH), 7.54 (d, 1H,
J = 10 Hz, 27-CH), 7.44 (d, 1H, J = 10 Hz, 14-CH), 7.34–7.32 (m, 10H, 31-CH, 32-CH, 33-CH, 34-CH,
35-CH, 37-CH, 38-CH, 39-CH, 40-CH, 41-CH), 7.25 (s, 1H, NH), 7.19–7.18 (m, 1H, 17-CH), 7.16–7.15
(m, 2H, 25-CH, 26-CH), 7.13–7.11 (m, 2H, 15-CH, 16-CH), 6.65 (s, 1H, 11-CH), 5.17 (s, 4H, 28-CH2,
29-CH2), 4.44 (d, 1H, J = 5 Hz, 8-CH), 3.48 (s, 1H, 2-CH); 13C-NMR (CDCl3) δ (ppm): 167.9 (20-C),
166.4 (1-C), 166.3 (3-C), 165.5 (10-C), 155.0 (13-C), 154.1 (22-C), 152.1 (30-C), 135.3 (36-C), 134.8
(23-C), 134.7 (32-C), 131.1 (34-C), 128.7 (38-C), 128.6 (40-C), 128.5 (12-C), 128.5 (31-C), 128.4 (35-C),
128.3 (37-C), 128.2 (41-C), 128.1 (39-C), 126.0 (33-C), 124.5 (15-C), 123.1 (26-C), 122.2 (25-C),
121.3 (16-C), 120.9 (24-C), 119.7 (17-C), 111.3 (27-C), 104.7 (14-C), 67.4 (11-C), 54.1 (28-C), 54.0
(29-C), 52.6 (8-C), 41.7 (2-C); MS (ESI): m/z = 563 ([M+H]+), 585 ([M+Na]+); MS (HREI):
C33H26N2O5S Na for +, calculated 562.1562, found 562.1569; IR (KBr, cm−1) ν 3352, 2922, 1747,
1716, 1537, 1454, 1444, 1348, 1249, 1172, 954, 750, 727.
Dimethyl 2-(Benzofuran-2-yl((6-chlorobenzo[d]thiazol-2-yl)amino)methyl) malonate (5e): white solid;
1
mp: 115–117 °C; yield 85%; H-NMR (CDCl3) δ (ppm): 7.53 (s, 1H, 24-CH), 7.49 (d, 1H, J = 5 Hz,
27-CH), 7.46 (d, 1H, J = 5 Hz, 14-CH), 7.42 (d, 1H, J = 5 Hz, 17-CH), 7.26 (d, 1H, J = 5 Hz, 25-CH),
7.22–7.17 (m, 2H, 26-CH, 15-CH), 6.73 (d, 1H, J = 5 Hz, 11-CH), 6.03 (s, 1H, NH), 5.29 (d, 1H, J = 5 Hz,
13
8-CH), 4.32-4.31 (m, 1H, 2-CH), 3.73 (s, 6H, 29-CH3, 30-CH3); C-NMR (CDCl3) δ (ppm): 168.4
(20-C), 167.0 (1-C), 165.9 (3-C), 155.0 (10-C), 153.8 (13-C), 150.8 (22-C), 132.2 (23-C), 128.0 (12-C),
127.4 (15-C), 126.5 (16-C), 124.6 (25-C), 123.2 (26-C), 121.4 (24-C), 120.6 (27-C), 120.3 (14-C),
111.3 (17-C), 104.7 (11-C), 53.7 (8-C), 53.4 (2-C), 53.1 (29-C), 52.7 (30-C); MS (ESI): m/z = 445
([M+H]+), 467 ([M+Na]+); MS (HREI): C21H17ClN2O5S Na for +, calculated 444.0547, found
444.0547; IR (KBr, cm−1) ν 3340, 2954, 1745, 1593, 1537, 1483, 1436, 1359, 1226, 1161, 1138, 1037,
974, 954, 875, 812, 759.
Diethyl 2-(Benzofuran-2-yl((6-chlorobenzo[d]thiazol-2-yl)amino)methyl) malonate (5f): white solid;
mp: 92–94 °C; yield 86%; 1H-NMR (CDCl3) δ (ppm): 7.53 (s, 1H, 24-CH), 7.49 (d, 1H, J = 5 Hz, 27-CH),
7.45 (d, 1H, J = 5 Hz, 14-CH), 7.42 (d, 1H, J = 5 Hz, 17-CH), 7.26 (d, 1H, J = 5 Hz, 26-CH), 7.22–7.17
(m, 2H, 15-CH, 16-CH), 6.94 (s, 1H, 11-CH), 6.72 (s, 1H, 8-CH), 6.05 (s, 1H, NH), 4.28 (d, 1H, J = 5 Hz,
13
2-CH), 4.24–4.13 (m, 4H, 28-CH2, 30-CH2), 1.21–1.16 (m, 6H, 29-CH3, 31-CH3); C-NMR (CDCl3)
δ (ppm): 168.1 (20-C), 166.6 (1-C), 165.9 (3-C), 155.0 (10-C), 154.1 (13-C), 150.8 (22-C), 132.2 (23-C),
128.0 (12-C), 127.3 (15-C), 126.5 (16-C), 124.5 (25-C), 123.1 (26-C), 121.3 (24-C), 120.6 (27-C),
120.3 (14-C), 111.3 (17-C), 104.7 (11-C), 62.5 (28-C), 62.2 (30-C), 54.0 (8-C), 52.7 (2-C), 14.1 (29-C),
14.0 (31-C); MS (ESI): m/z = 473 ([M+H]+), 495 ([M+Na]+); MS (HREI): C23H21ClN2O5S Na for +,

Molecules 2013, 18
13630
calculated 472.0860, found 472.0850; IR (KBr, cm−1) ν 3346, 2974, 1741, 1718, 1537, 1483, 1396,
1367, 1301, 1242, 1172, 1029, 974, 812, 763.
Dipropyl 2-(Benzofuran-2-yl((6-chlorobenzo[d]thiazol-2-yl)amino)methyl) malonate (5g): white solid;
1
mp: 88–90 °C; yield 82%; H-NMR (CDCl3) δ (ppm): 7.54 (s, 1H, 24-CH), 7.49 (d, 1H, J = 5 Hz,
27-CH), 7.45 (d, 1H, J = 5 Hz, 14-CH), 7.42 (d, 1H, J = 5 Hz, 17-CH), 7.27–7.22 (m, 2H, 25-CH,
26-CH), 7.20-7.17 (m, 1H, 15-CH), 6.93 (s, 1H, 11-CH), 6.72 (s, 1H, 8-CH), 6.05 (s, 1H, NH), 4.31 (d,
1H, J = 5 Hz, 2-CH), 4.14-4.06 (m, 4H, 29-CH2, 30-CH2), 1.61–1.57 (m, 4H, 31-CH2, 32-CH2), 0.87–0.83
13
(m, 6H, 33-CH3, 34-CH3); C-NMR (CDCl3) δ (ppm): 168.3 (20-C), 166.7 (1-C), 165.8 (3-C), 155.0
(10-C), 154.1 (13-C), 150.8 (22-C), 132.2 (23-C), 128.1 (12-C), 127.3 (15-C), 126.5 (16-C), 124.5 (25-C),
123.1 (26-C), 121.3 (24-C), 120.6 (27-C), 120.3 (14-C), 111.3 (17-C), 104.7 (11-C), 68.0 (29-C), 67.7
(30-C), 54.0 (8-C), 52.7 (2-C), 21.9 (31-C), 21.8 (32-C), 10.4 (33-C), 10.3 (34-C); MS (ESI): m/z = 501
([M+H]+), 523 ([M+Na]+); MS (HREI): C25H25ClN2O5S Na for +, calculated 500.1173, found
500.1171; IR (KBr, cm−1) ν 3357, 2966, 1747, 1720, 1593, 1533, 1483, 1446, 1392, 1354, 1290, 1238,
1197, 1172, 1053, 945, 812, 759.
Dibenzyl 2-(Benzofuran-2-yl((6-chlorobenzo[d]thiazol-2-yl)amino)methyl) malonate (5h): white solid;
mp: 116–118 °C; yield 67%; 1H-NMR (CDCl3) δ (ppm): 7.53 (s, 1H, 24-CH), 7.45 (d, 1H, J = 10 Hz,
27-CH), 7.42 (d, 1H, J = 5 Hz, 14-CH), 7.36–7.66 (m, 7H, 31-CH, 32-CH, 33-CH, 34-CH, 35-CH, 37-CH,
38-CH), 7.26–7.24 (m, 2H, 39-CH, 40-CH), 7.19–7.18 (m, 2H, 17-CH, 41-CH), 7.17–7.15 (m, 2H, 15-CH,
26-CH), 7.13–7.11 (m, 2H, 11-CH, 26-CH), 6.81 (s, 1H, NH), 6.11 (s, 1H, 8-CH), 5.17–5.14 (m, 4H,
13
28-CH2, 29-CH2), 3.47 (s, 1H, 2-CH); C-NMR (CDCl3) δ (ppm): 168.0 (20-C), 166.4 (1-C), 165.6
(3-C), 155.0 (10-C), 153.8 (13-C), 150.8 (22-C), 135.3 (30-C), 134.7 (36-C), 134.6 (23-C), 132.3 (32-C),
128.7 (34-C), 128.6 (38-C), 128.6 (40-C), 128.5 (12-C), 128.5 (31-C), 128.5 (35-C), 128.4 (37-C), 128.4
(41-C), 128.2 (39-C), 128.0 (33-C), 127.4 (15-C), 126.5 (26-C), 124.6 (25-C), 123.2 (16-C), 121.4 (24-C),
120.5 (17-C), 120.4 (27-C), 111.3 (14-C), 104.7 (11-C), 68.2 (28-C), 67.8 (29-C), 54.0 (8-C), 41.9 (2-C);
MS (ESI): m/z = 597 ([M+H]+), 619 ([M+Na]+); MS (HREI): C33H25ClN2O5S Na for +, calculated
596.1173, found 596.1189; IR (KBr, cm−1) ν 3388, 2966, 1745, 1730, 1599, 1543, 1529, 1487, 1454,
1381, 1259, 1220, 1147, 1004, 817, 748, 694.
Dimethyl 2-(Benzofuran-2-yl((6-methoxybenzo[d]thiazol-2-yl)amino)methyl) malonate (5i): white
1
solid; mp: 85–87 °C; yield 81%; H-NMR (CDCl3) δ (ppm): 7.49–7.45 (m, 2H, 24-CH, 27-CH), 7.42
(d, 1H, J = 5 Hz, 14-CH), 7.27–7.23 (m, 1H, 17-CH), 7.20–7.17 (m, 1H, 25-CH), 7.11 (s, 1H, 26-CH),
6.89 (d, 1H, J = 5 Hz, 15-CH), 6.73 (d, 1H, J = 5 Hz, 11-CH ), 6.64 (s, 1H, NH), 6.01 (s, 1H, 8-CH),
4.34–4.32 (m, 1H, 2-CH), 3.80 (s, 3H, 29-C-OCH3), 3.73 (s, 6H, 30-CH3, 31-CH3); 13C-NMR (CDCl3) δ
(ppm): 168.4 (20-C), 167.1 (1-C), 164.1 (3-C), 155.6 (10-C), 154.9 (13-C), 154.2 (22-C), 146.3
(23-C), 132.0 (12-C), 128.1 (15-C), 124.5 (16-C), 123.1 (25-C), 121.3 (26-C), 120.0 (24-C), 113.7 (27-C),
111.3 (14-C), 105.3 (17-C), 104.7 (11-C), 56.1 (8-C), 53.9 (2-C), 53.3 (29-C), 53.1 (30-C), 52.8 (31-C);
MS (ESI): m/z = 441 ([M+H]+), 463 ([M+Na]+); MS (HREI): C22H20N2O6S Na for +, calculated
440.1042, found 440.1047; IR (KBr, cm−1) ν 3377, 2953, 1745, 1724, 1604, 1544, 1483, 1471, 1454,
1436, 1359, 1247, 1170, 1058, 1029, 968, 815, 759.

Molecules 2013, 18
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Diethyl 2-(benzofuran-2-yl((6-methoxybenzo[d]thiazol-2-yl)amino)methyl) malonate (5j): white solid;
mp: 85–88 °C; yield 80%; 1H-NMR (CDCl3): δ (ppm) 7.50–7.45 (m, 2H, 24-CH, 27-CH), 7.42 (d, 1H,
J = 5 Hz, 14-CH), 7.26–7.23 (m, 1H, 17-CH), 7.20–7.17 (m, 1H, 26-CH), 7.11 (s, 1H, 15-CH), 6.90–6.87
(m, 1H, 16-CH), 6.72 (s, 1H, 11-CH), 6.70 (s, 1H, NH), 6.02 (s, 1H, 8-CH), 4.29 (d, 1H,
J = 5 Hz, 2-CH), 4.24–4.14 (m, 4H, 28-CH2, 30-CH2), 3.80 (s, 3H, 25-C-OCH3), 1.21–1.17 (m, 6H,
13
29-CH3, 31-CH3); C-NMR (CDCl3) δ (ppm): 168.1 (20-C), 166.7 (1-C), 164.1 (3-C), 155.5 (10-C),
154.9 (13-C), 154.5 (22-C), 146.3 (23-C), 131.9 (12-C), 128.1 (15-C), 124.4 (16-C), 123.1 (25-C),
121.3 (26-C), 120.0 (24-C), 113.7 (27-C), 111.2 (14-C), 105.3 (17-C), 104.6 (11-C), 62.4 (28-C), 62.1
(30-C), 55.9 (8-C), 54.1 (25-C), 52.7 (2-C), 14.1 (29-C), 14.0 (31-C); MS (ESI): m/z = 469 ([M+H]+), 491
([M+Na]+); MS (HREI): C24H24N2O6S Na for +, calculated 468.1355, found 468.1336; IR (KBr, cm−1)
ν 3377, 2974, 1745, 1712, 1602, 1543, 1490, 1469, 1436, 1280, 1188, 1033, 981, 855, 825, 756.
Dipropyl 2-(Benzofuran-2-yl((6-methoxybenzo[d]thiazol-2-yl)amino)methyl) malonate (5k): white
solid; mp: 67–70 °C; yield 79%; 1H-NMR (CDCl3) δ (ppm): 7.49–7.45 (m, 3H, 24-CH, 27-CH, 14-CH),
7.25–7.06 (m, 3H, 17-CH, 25-CH, 26-CH), 6.89-6.81 (m, 1H, 15-CH), 6.72 (s, 1H, 11-CH), 6.62 (s,
1H, NH), 5.98 (s, 1H, 8-CH), 4.31–4.26 (m, 1H, 2-CH), 4.08–4.01 (m, 4H, 29-CH2, 30-CH2), 3.80 (s,
3H, 28-C-OCH3), 1.60-1.52 (m, 4H, 31-CH2, 32-CH2), 0.87–0.77 (m, 6H, 33-CH3, 34-CH3); 13C-NMR
(CDCl3) δ (ppm): 168.2 (20-C), 166.8 (1-C), 164.0 (3-C), 155.5 (10-C), 155.0 (13-C), 154.5 (22-C),
146.3 (23-C), 132.0 (12-C), 128.2 (15-C), 124.4 (16-C), 123.0 (25-C), 121.2 (26-C), 120.0 (24-C), 113.6
(27-C), 111.2 (14-C), 105.3 (17-C), 104.6 (11-C), 67.9 (29-C), 67.6 (30-C), 56.0 (8-C), 54.1 (2-C),
52.7 (28-C), 21.8 (31-C), 21.7 (32-C), 10.3 (33-C), 10.2 (34-C); MS (ESI): m/z = 497 ([M+H]+), 519
([M+Na]+); MS (HREI): C26H28N2O6S Na for +, calculated 496.1668, found 496.1669; IR (KBr, cm−1)
ν 3348, 2951, 1741, 1716, 1604, 1543, 1483, 1357, 1288, 1172, 1064, 947, 850, 806, 759.
Dibenzyl 2-(Benzofuran-2-yl((6-methoxybenzo[d]thiazol-2-yl)amino)methyl) malonate (5l): white
solid; mp: 110–112 °C; yield 60%; 1H-NMR (CDCl3): δ (ppm) 7.42 (d, 2H, J = 5 Hz, 27-CH, 24-CH),
7.35 (d, 1H, J = 5 Hz, 14-CH), 7.27–7.23 (m, 14H, 31-CH, 32-CH, 33-CH, 34-CH, 35-CH, 37-CH, 38-CH,
39-CH, 40-CH, 17-CH, 41-CH, 15-CH, 26-CH, 11-CH), 6.90–6.88 (m, 1H, 26-CH), 6.64 (s, 1H, NH),
6.01 (s, 1H, 8-CH), 5.19-5.06 (m, 4H, 28-CH2, 29-CH2), 4.43 (d, 1H, J = 5 Hz, 2-CH), 3.80 (s, 3H,
25-C-OCH3); 13C-NMR (CDCl3) δ (ppm): 167.9 (20-C), 166.5 (1-C), 163.8 (3-C), 155.6 (10-C), 155.0
(13-C), 154.2 (22-C), 146.3 (30-C), 134.8 (36-C), 134.7 (23-C), 132.1 (32-C), 128.7 (34-C), 128.6 (38-C),
128.5 (40-C), 128.5 (12-C), 128.5 (31-C), 128.4 (35-C), 128.4 (37-C), 128.3 (41-C), 128.2 (39-C),
128.1 (33-C), 124.4 (15-C), 123.1 (26-C), 121.3 (25-C), 120.1 (16-C), 113.7 (24-C), 111.3 (17-C),
105.3 (27-C), 104.7 (14-C), 68.1 (11-C), 67.8, 67.8 (28-C, 29-C), 56.0 (25-C), 54.2 (8-C), 52.6 (2-C);
MS (ESI): m/z = 593 ([M+H]+), 615 ([M+Na]+); MS (HREI): C34H28N2O6S Na for +, calculated
592.1668, found 592.1687; IR (KBr, cm−1) ν 3350, 2954, 1747, 1716, 1602, 1543, 1469, 1454, 1348,
1222, 1172, 1028, 954, 823, 750, 696.
Dimethyl 2-(Benzofuran-2-yl((6-methylbenzo[d]thiazol-2-yl)amino)methyl) malonate (5m): white
solid; mp: 108–109 °C; yield 81%; 1H-NMR (CDCl3) δ (ppm): 7.48 (d, 1H, J = 5 Hz, 24-CH), 7.45 (d,
1H, J = 5 Hz, 27-CH), 7.42 (d, 1H, J = 5 Hz, 14-CH), 7.38 (s, 1H, 17-CH), 7.25 (t, 1H, J = 15 Hz, 25-CH),
7.29 (t, 1H, J = 15 Hz, 26-CH), 7.10 (d, 1H, J = 5 Hz, 15-CH), 6.72 (s, 1H, 11-CH), 6.71 (s, 1H, NH ),

Molecules 2013, 18
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6.01 (s, 1H, 8-CH), 4.43 (d, 1H, J = 5 Hz, 2-CH), 3.73 (s, 6H, 29-CH3, 30-CH3), 2.38 (s, 3H, 28-CH3);
13C-NMR (CDCl3) δ (ppm): 168.4 (20-C), 167.0 (1-C), 165.1 (3-C), 155.0 (10-C), 154.2 (13-C), 150.0
(22-C), 132.1 (23-C), 131.0 (12-C), 128.1 (15-C), 127.2 (16-C), 124.5 (25-C), 123.1 (26-C), 121.3 (24-C),
121.0 (27-C), 119.3 (14-C), 111.3 (17-C), 104.7 (11-C), 53.8 (8-C), 53.3 (2-C), 53.0 (29-C), 52.8 (30-C),
21.3 (28-C); MS (ESI): m/z = 425 ([M+H]+), 447 ([M+Na]+); MS (HREI): C22H20N2O5S Na for +,
calculated 424.1093, found 424.1097; IR (KBr, cm−1) ν 3361, 2954, 1743, 1724, 1539, 1487, 1454,
1435, 1357, 1224, 1172, 1147, 1033, 972, 817, 759.
Diethyl 2-(Benzofuran-2-yl((6-methylbenzo[d]thiazol-2-yl)amino)methyl) malonate (5n): white solid;
mp: 105–107 °C; yield 76%; 1H-NMR (CDCl3) δ (ppm): 7.48-7.47 (d, 1H, J = 5 Hz, 24-CH), 7.45 (d,
1H, J = 5 Hz, 27-CH), 7.42 (d, 1H, J = 5 Hz, 14-CH), 7.38 (s, 1H, 17-CH), 7.25 (t, 1H, J = 15 Hz, 26-CH),
7.20–7.17 (m, 1H, 15-CH), 7.10 (d, 1H, J = 5 Hz, 16-CH), 6.74 (s, 1H, NH), 6.72 (s, 1H, 11-CH), 6.03
(s, 1H, 8-CH), 4.29 (m, 1H, 2-CH), 4.24–4.14 (m, 4H, 28-CH2, 30-CH2), 2.38 (s, 3H, 25-CH3), 1.21–1.16
13
(m, 6H, 29-CH3, 31-CH3); C-NMR (CDCl3) δ (ppm): 168.1 (20-C), 165.1 (1-C), 155.0 (3-C), 154.5
(10-C), 150.0 (13-C), 133.7 (22-C), 132.0 (23-C), 131.0 (12-C), 128.1 (15-C), 127.2 (16-C), 124.4 (25-C),
123.0 (26-C), 121.3 (24-C), 121.0 (27-C), 119.2 (14-C), 111.2 (17-C), 104.6 (11-C), 62.4 (28-C), 62.1
(30-C), 54.1 (8-C), 52.8 (2-C), 21.3 (25-C), 14.1 (29-C), 14.0 (31-C); MS (ESI): m/z = 453 ([M+H]+),
475 ([M+Na]+); MS (HREI): C24H24N2O5S Na for +, calculated 452.1406, found 452.1407; IR (KBr, cm−1)
ν 3352, 2976, 1743, 1720, 1600, 1560, 1541, 1487, 1456, 1336, 1301, 1238, 1172, 1029, 939, 858,
810, 763.
Dipropyl 2-(Benzofuran-2-yl((6-methylbenzo[d]thiazol-2-yl)amino)methyl) malonate (5o): white solid;
mp: 76–78 °C; yield 73%; 1H-NMR (CDCl3) δ (ppm): 7.48–7.43 (m, 3H, 24-CH, 27-CH, 14-CH), 7.41
(d, 1H, J = 10 Hz, 17-CH), 7.38 (s, 1H, 25-CH), 7.25–7.23 (m, 1H, 26-CH), 7.10–7.08 (m, 1H, 15-CH),
6.80 (s, 1H, 11-CH), 6.71 (s, 1H, NH), 6.04 (s, 1H, 8-CH), 4.33-4.32 (m, 1H, 2-CH), 4.13–4.06 (m, 4H,
29-CH2, 30-CH2), 2.38 (s, 3H, 28-CH3), 1.61-1.56 (m, 4H, 31-CH2, 32-CH2), 0.87–0.82 (m, 6H, 33-CH3,
34-CH3); 13C-NMR (CDCl3) δ (ppm): 168.2 (20-C), 166.8 (1-C), 165.1 (3-C), 155.0 (10-C), 154.5 (13-C),
150.0 (22-C), 132.0 (23-C), 131.0 (12-C), 128.1 (15-C), 127.2 (16-C), 124.4 (25-C), 123.0 (26-C),
121.3 (24-C), 121.0 (27-C), 119.2 (14-C), 111.2 (17-C), 104.6 (11-C), 68.0 (29-C), 67.6 (30-C), 54.1
(8-C), 52.8 (2-C), 21.9 (28-C), 21.8 (31-C), 21.3 (32-C), 10.3 (33-C), 10.2 (34-C); MS (ESI):
m/z = 481([M+H]+), 503 ([M+Na]+); MS (HREI): C26H28N2O5S Na for +, calculated 480.1719, found
480.1711; IR (KBr, cm−1) ν 3365, 2966, 1747, 1722, 1535, 1483, 1456, 1354, 1290, 1172, 1055, 954,
808, 761.
Dibenzyl 2-(Benzofuran-2-yl((6-methylbenzo[d]thiazol-2-yl)amino)methyl) malonate (5p): white solid;
mp: 126–128 °C; yield 64%; 1H-NMR (CDCl3) δ (ppm): 7.43–7.41 (m, 2H, 27-CH, 24-CH), 7.35–7.31 (m,
3H, 14-CH, 31-CH, 32-CH), 7.23–7.14 (m, 10H, 33-CH, 34-CH, 35-CH, 37-CH, 38-CH, 39-CH,
40-CH, 17-CH, , 41-CH, 15-CH), 7.12–7.08 (m, 3H, 26-CH, 11-CH, 26-CH), 6.64–6.62 (m, 1H, NH),
6.10 (s, 1H, 8-CH), 5.17–5.04 (m, 4H, 28-CH2, 29-CH2), 4.43-4.41 (m, 1H, 2-CH), 2.39–2.37 (s, 3H,
25-CH3); 13C-NMR (CDCl3) δ (ppm): 167.9 (20-C), 166.5 (1-C), 165.0 (3-C), 155.0 (10-C), 154.2 (13-C),
150.0 (22-C), 134.8 (30-C), 134.7 (36-C), 132.0 (23-C), 131.1 (32-C), 128.7 (34-C), 128.7 (38-C), 128.6
(40-C), 128.6 (12-C), 128.5 (31-C), 128.5 (35-C), 128.2 (37-C), 128.2 (41-C), 128.1 (39-C), 128.1 (33-C),

Molecules 2013, 18
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127.2 (15-C), 127.2 (26-C), 124.7 (25-C), 123.1 (16-C), 121.4 (24-C), 121.0 (17-C), 119.3 (27-C),
111.3 (14-C), 104.7 (11-C), 68.1 (28-C), 67.8 (29-C), 54.1 (8-C), 52.7 (2-C), 21.4 (25-C); MS (ESI):
m/z = 577 ([M+H]+), 599 ([M+Na]+); MS (HREI): C34H28N2O5S Na for +, calculated 576.1719, found
576.1702; IR (KBr, cm−1) ν 3348, 2954, 1743, 1724, 1537, 1487, 1452, 1382, 1238, 1170, 1012, 910,
808, 731, 702.
3.3. Anti-TMV Activity Section
3.3.1. Purification of Tobacco Mosaic Virus
Using Gooding’s method [21], the upper leaves of Nicotiana tabacum inoculated with TMV were
selected and ground in phosphate buffer and then filtered through double-layer pledget. The filtrate
was centrifuged at 10,000 g, treated with PEG twice, and centrifuged again. The whole experiment was
processed at 4 °C. Absorbance value was estimated at 260 nm by ultraviolet spectrophotometer:
0.1%,260
virus concn = (A260 × dilution ratio)/ E
(1)
1cm
3.3.2. Inhibition Effect of Compound on TMV in Vivo [22]
The virus was inhibited by mingling with the compound solution at the same volume for 30 min.
The mixture was then inoculated on the left side of the leaves of N. tabacum L., whereas the right side of
the leaves was inoculated with the mixture of solvent and the virus for control. The local lesion numbers
were recorded 3–4 days after inoculation [10]. Three repetitions were conducted for each compound.
3.3.3. Curative Effect of Compounds on TMV in Vivo [22]
The leaves of N. tabacum L. growing at the same ages were selected. TMV at a concentration of
6 × 10−3 mg/mL was dipped and inoculated on the whole leaves. Then the leaves were washed with
water and dried. The compound solution was smeared on the left side, and the solvent was smeared on
the right side for control. The local lesion numbers were then recorded 3–4 days after inoculation. For
each compound, three repetitions were conducted to ensure the reliability of the results.
3.3.4. Protective Effect of Compounds on TMV in Vivo [22]
The leaves of N. tabacum L. growing at the same ages were selected. The compound solution was
smeared on the left side for 12 h and the solvent was smeared on the right side for control. The TMV at
a concentration of 6 × 10−3 mg/mL was inoculated on the whole leaves. The local lesion numbers were
then recorded 3–4 days after inoculation. For each compound, three repetitions were conducted to
ensure the reliability of the results:
av local lesion numbers of control (not treated with compound) − av local lesion numbers without drugs
inhibition rate(%) =
av local lesion numbers without drugs

Molecules 2013, 18
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4. Conclusions
Sixteen novel β-amino ester derivatives containing benzofuran and benzothiazole units were
designed and synthesized seeking anti-TMV activity. The bioassays identified these new compounds
as possessing weak to good antiviral activities. The bioassay test results showed that compounds 5i and
5m have good antiviral activity against TMV, with curative rates of 52.23% and 54.41% at a
concentration of 0.5 mg/mL.
Supplementary Materials
Supplementary materials can be accessed at: http://www.mdpi.com/1420-3049/18/11/13623/s1.
Acknowledgments
We are grateful for the Key project of the National Natural Science Foundation of China (No.2132003)
and the National Natural Science Foundation of China (No.20872021) for the financial support.
Conflicts of Interest
The authors declare no conflict of interest.
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Sample Availability: Samples of the compounds 5a–5p are available from the authors.
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