Design, synthesis, and antiviral activities of 1,5-benzothiazepine derivatives containing pyridine moiety

Article abstract of DOI:10.1016/j.ejmech.2016.09.069

In our previous work, a series of novel benzothiazepine derivatives containing pyridine moiety were successfully synthesized through chalcone 1,3-dipolar cycloaddition and determined their antiviral activity against tobacco mosaic virus (TMV). Bioassay results indicated that most of these target compounds exhibited improved curative, protection, and inactivation activity in?vivo than the commercial agent ningnanmycin. Particularly, compound 3m exhibited marked curative activity against TMV, with an EC₅₀value of 352.2?μM, which was even better than that of ningnanmycin. The compound was identified as the most promising candidate for inhibiting plant virus and an excellent compound with antiviral activities against TMV. Structure–activity relationship experiment indicated that the 1,5-benzothiazepine moiety is crucial for potent anti-TMV activity.

Full text of DOI:10.1016/j.ejmech.2016.09.069

Accepted Manuscript
Design, synthesis, and antiviral activities of 1,5-benzothiazepine derivatives
containing pyridine moiety
Tianxian Li, Jian Zhang, Jianke Pan, Zengxue Wu, Deyu Hu, Baoan Song
PII:
S0223-5234(16)30805-4
10.1016/j.ejmech.2016.09.069
EJMECH 8935
DOI:
Reference:
To appear in: European Journal of Medicinal Chemistry
Received Date: 19 July 2016
Revised Date: 13 September 2016
Accepted Date: 21 September 2016
Please cite this article as: T. Li, J. Zhang, J. Pan, Z. Wu, D. Hu, B. Song, Design, synthesis, and antiviral
activities of 1,5-benzothiazepine derivatives containing pyridine moiety, European Journal of Medicinal
Chemistry (2016), doi: 10.1016/j.ejmech.2016.09.069.
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Graphical Abstract
A series of novel benzothiazepine derivatives containing pyridine moiety were
synthesized and screened for their antiviral activity against TMV in vivo.

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Design, Synthesis, and Antiviral Activities of 1,5-Benzothiazepine Derivatives Containing
Pyridine Moiety
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Tianxian Li, Jian Zhang, Jianke Pan, Zengxue Wu, Deyu Hu, Baoan Song*
State Key Laboratory Breeding Base of Green Pesticide and Agricultural Bioengineering, Key
Laboratory of Green Pesticide and Agricultural Bioengineering, Ministry of Education, Guizhou
University, Huaxi District, Guiyang 550025, P. R. China
*Corresponding author
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Tel.: 86-851-83620521; Fax: 86-851-83622211.
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E-mail: songbaoan22@yahoo.com
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AbstractꢀIn our previous work, a series of novel benzothiazepine derivatives containing pyridine
moiety were successfully synthesized through chalcone 1,3-dipolar cycloaddition and determined
their antiviral activity against tobacco mosaic virus (TMV). Bioassay results indicated that most of
these target compounds exhibited improved curative, protection, and inactivation activity in vivo
than the commercial agent ningnanmycin. Particularly, compound 3m exhibited marked curative
activity against TMV, with an EC50 value of 352.2 µM, which was even better than that of
ningnanmycin. The compound was identified as the most promising candidate for inhibiting plant
virus and an excellent compound with antiviral activities against TMV. Structure–activity
relationship experiment indicated that the 1,5-benzothiazepine moiety is crucial for potent
anti-TMV activity.
Keywords: benzothiazepine derivatives, pyridine, 1,3-dipolar cycloaddition, antiviral activity.
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1. Introduction
Tobacco mosaic virus (TMV) is a widespread plant pathogen and can infect several crops,
including tobacco, tomato, cucumber, pepper, and ornamental plants, resulting in heavy economic
losses [1]. To prevent TMV diseases, researchers have focused on developing novel antiviral
agents, such as ningnanmycin [2], seco-pregnane steroids [3], botanical antiviral agents [4],
quinazolinones derivatives [5], pyridazines derivatives [6], β-carboline derivatives [7], and
Gossypol derivatives [8]. However, these compounds present certain limitations to use, such as
extremely complex synthesis, easily decomposed active ingredients, relatively low
pharmacodynamics [9,10], pesticide-related toxicity, severe pesticide resistance and pesticide
interactions [11]. Therefore, a natural, novel, highly efficient and environmentally friendly
precursors must be developed for anti-plant virus agents .
Chalcones, as natural products with various pharmacological, have been used for development
of biologically functional molecules as activities scaffold. In our previous work, we synthesized
and evaluated three series of chalcone derivatives, including nitromethane, malonate ester
containing pyridine or quinazolinone moiety [12–14]. The bioassay results revealed that these
novel chalcone derivatives showed good antiviral activity against against cucumber mosaic virus
(CMV) and TMV. Preliminarily structure–activity relationship (SAR) studies revealed the new
skeletons and addition patterns at the α,β-positions of the chalcone molecule considerably
influence the antiviral activity of the compounds.
Benzothiazepines, constitute an important class of benzo-fused and seven-membered
heterocyclic compounds containing one nitrogen and one sulfur atom, and thier derivatives have
drawn considerable research attention because of their wide range of pharmacological activities,
such as antiviral [15–17], antimicrobial [18,19], anticancer [20,21], Ca2+ channel antagonist and
vasodilator [22,23], CNS depressant [24], antiplatelet aggregation [25], angiotensin converting
enzyme (ACE) inhibitor [26], AChE inhibition [27], and anticonvulsant agent [28]. However,
biologically active derivatives had been rarely investigated in agricultural field.
To develop 1,3-dipolar cycloaddition chalcone derivatives,
a
series of novel
1,5-benzothiazepines derivatives containing pyridine moiety were designed as potential anti-TMV
agents and synthesized using chalcone at the α,β-position through 1,3-dipolar cycloaddition (Fig.
1). Anti-TMV activities were evaluated via half-leaf method. Bioassay results indicated that most
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of these target compounds exhibited improved curative, protection, and inactivation activity in
vivo compared with the commercial agent ningnanmycin. Especially, compound 3m exhibited
significant curative activity against TMV, with the EC50 value of 352.2 µM, better than that of
ningnanmysin. To the best of our knowledge, it’s the first report on the anti-TMV activity of
1,5-benzothiazepines derivatives containing pyridine moiety.
Fig. 1
2. Results and discussion
2.1. Chemistry
The synthetic route, designed for the title compounds 3a−3z, was summarized in Fig. 2. Using
NaOH solution as catalyst and ethanol as solvent, various substituted aromatic aldehydes were
allowed to react with hydroxyacetophenone for 2–3 d at room temperature to obtain intermediates
1a–1z. Then, using concentrated HCl and anhydrous sodium sulfate as catalysts, intermediates
1a–1z in ethanol and o-aminothiophenol were stirred for 6 h at the reflux temperature to obtain the
key intermediates 2a–2z. Finally, using K2CO3/KI as catalysts, intermediates 2a–2z and
compound 2-chloro-5-chloromethyl-pyridine were stirred at 75 °C for 5 h and then recrystallized
from ethanol to gain the purified target compounds 3a–3z with the yields of 49%–61%. Their
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structures were confirmed by IR, H NMR, 13C NMR, and elemental analysis, and the physical
and analytical data of the target compounds were provided in Table 1.
Fig. 2
Table 1
2.2. Analytical spectral data of the target compounds 3a–3z
The IR spectra of the title products 3a–3z exhibited characteristic absorption bands at 1602
cm−1 to 1449 cm−1 indicating the presence of amidic benzene, Py–rings and C=N. The
characteristic absorptions at 1326 cm−1 to 1021 cm−1 could be attributed to the presence of C–O–C
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group, and 779 cm−1 to 749 cm−1 could be attributed to the presence of C–S–C group. H NMR
analysis indicated that all aromatic ring protons showed multiplets at 8.50 ppm to 6.16 ppm. The
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main characteristic of the H NMR spectra for the target compounds was the presence of the
singlet δH at 5.16 ppm to 5.13 ppm for O–CH2– proton. 3.71–2.84 (t, J = 22.50–25.50 Hz, 1H,
C-2-Hx), 3.36–3.14 (dd, J1 = 12.5–13.5 Hz, J2 = 2.5–4.5 Hz, 1H, C-3-Ha), 6.17–4.93 (dd, J1 =
12.5–13.5 Hz, J2 = 4.50–5.00 Hz, 1H, C-3-Hb), in the abx pattern were characterized for two
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methylene protons at C-3 and one methine proton at C-2. In the 13C NMR spectrum of those title
products 3a–3z, the chemical shifts 168.37 ppm to 166.67 ppm and 68.91 ppm to 32.18 ppm in
13C NMR also confirmed the presence of C=N and O–CH2–, –CH–S, C–CH2–C groups.
2.3. In vivo antiviral activity of the title compounds against TMV
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Antiviral tests of 3a–3z against TMV were conducted and the bioassay results are summarized
in Table 2. As shown in Table 2, most of the title compounds exhibited good antiviral activity
against TMV in vivo and some of the compounds showed even higher bioactivity than the control
ningnanmycin. The results, shown in Table 2, revealed that compounds 3a, 3e, 3g, 3i, 3k, 3m, 3q,
3s, 3t, 3v, 3w, 3x, 3y, and 3z exhibited better curative activity against TMV at 500 µg/mL, with
values of 55%, 52%, 51%, 54%, 54%, 58%, 55%, 53%, 53%, 60%, 53%, 55%, 51% and 53%,
respectively, which were superior to or equally to that of ningnanmycin (54%). Meanwhile,
compounds 3a and 3q exhibited significant protection activity against TMV at 500 µg/mL, with
bioassay values of 70% and 71%, respectively, compared with that of ningnanmycin (66%). In
addition, compound 3s showed higher inactivate efficacy values of 93%, which are slightly higher
than that of ningnanmycin (92%) against TMV at 500 µg/mL. In addition, compounds 3e, 3r, 3u,
3w, 3x, and 3y revealed better inactivation activity against TMV at 500 µg/mL, with inhibition
rates of 92%, 91%, 91%, 92%, 91%, and 90%, respectively, which were similar to that of
ningnanmycin (92%).
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Table 2
Based on previous bioassays, the EC50 values for curative activity against TMV of the target
compounds 3a–3z were also measured and listed in Table 3. Evidently, as shown in Table 3,
compounds 3a, 3g, 3i, 3k, 3m, 3q, 3s, 3t, 3v, 3w, 3x and 3z exhibited remarkable curative activity
against TMV, with EC50 values of 405.4, 454.8, 410.9, 384.8, 352.2, 421.1, 391.9, 477.3, 389.3,
425.9, 419.8, and 508.6 µM, respectively, which were even better than that of ningnanmycin
(560.4 µM). In particularly, compound 3m displayed the best curative activity against TMV in
vivo, with an EC50 value of 352.2 µM, which was superior to the other target compounds. This
research indicated that these target compounds may function as potential lead structures for the
discovery of new antiviral agents.
Table 3
2.4. SAR analysis
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As an extension of this approach, the SAR analysis was deduced on the basis of the values of the
anti-TMV activity shown in Tables 2 and 3. For curative activity, when R substituent group was
3-Br-Ph and 3,4-di-Cl-Ph groups, the corresponding target compounds exhibited excellent curative
activity against TMV compared to that of ningnanmycin. Unfortunately, poor activity was
observed when R was 4-OCH3-Ph, 2-Br-Ph, 3-OCH3-Ph, or 2,4-di-Cl-Ph group, the corresponding
target compounds were demonstrated to have poor curative activity against TMV. Meanwhile, for
protection activity, when R substituent group was Ph or 4-CF3-Ph group, the corresponding
compounds presented relatively better protection activity against TMV compared to ningnanmycin
and the other target compounds. Meanwhile, when R substituent group was 4-OCH3-Ph,
3,4-di-OCH3-Ph, 2-OCH3-Ph, or 3-NO2-Ph group, the corresponding compounds was
demonstrated to have poor anti-TMV activity. In addition, for inactivation activity, when R
substituent group was 4-NO2-Ph, 2-CF3-Ph, 4-Cl-Ph, 2,4-di-Cl-Ph, 2-Cl-6-F-Ph, or 3-NO2-Ph
group, the corresponding compounds showed better anti-TMV activity which was similar to that
of ningnanmycin. In conclusion, SAR analysis showed that the target compounds with
electron-withdrawing groups at the phenyl ring displayed high antiviral activity against TMV.
3. Conclusion
In summary, a series of novel benzothiazepine derivatives containing pyridine moiety were
prepared in moderate yield and first evaluated for their anti-TMV activity. Bioassay results
demonstrated that the target compounds 3a–3z exhibited good curative, protection, and
inactivation activity against TMV. Among the target compounds, compound 3m displayed the best
curative activity against TMV in vivo, with an EC50 value of 352.2 µM, which was superior to that
of ningnanmycin. To the best of our knowledge, this is the first report on the antiviral activity of
this series of benzothiazepine derivatives containing pyridine moiety and the present work
demonstrated that this series of benzothiazepine derivatives containing pyridine moiety can be
used to develop potential agrochemicals. Furthermore, according to the requirements of pesticide
registration in China, further field studies on the biological efficacies, crop safety, and toxicities of
compound 3m as antiviral candidates will be performed in our next work.
4. Experimental
4.1. General methods
The melting points of the products were determined using a WRX-4 monocular microscope
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(Shanghai Yice Apparatus and Equipment Co., Ltd. China) and left untouched. IR spectra were
recorded on a Bruker VECTOR 22 spectrometer in a KBr disk. NMR spectra were acquired using
a JEOL-ECX 500 MHz (125 MHz for 13C) instrument at room temperature. Chemical shifts were
determined relative to the residual solvent peaks of CDCl3 (1H, δ = 7.26 ppm; 13C, δ = 77.0 ppm),
with tetramethylsilane as internal standard. Elemental analysis was performed on an Elementar
Vario-III CHN analyzer. Analytical thin-layer chromatography (TLC) was conducted on silica gel
GF254 (400 mesh). Column chromatographic purification was performed using silica gel. All
reagents and reactants were purchased from commercial suppliers and were of analytical reagent
grade or chemically pure.
4.2. General procedure for the preparation of the key intermediates 2a–2z
As shown in Fig. 2, intermediates 1a–1z and 2a–2z prepared according to previously reported
methods [14,29]. The reactions for the preparation of intermediates 2a–2z were carried out in
ethanol at reflux temperature in the presence of o-aminothiophenol (5 mmol, 535 µL), HCl (5
mmol, 417 µL), C2H5OH (20 mL), Na2SO4 (5 mmol, 0.710 g) and intermediates 1a-1z (5 mmol)
within 2–3 d. Then, the mixture was diluted with distilled water (50 mL) and the residue was then
filtered, washed with ethanol and distilled water, dried under vacuum, and recrystallized from
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ethanol to afford the key intermediates 2a–2z. The physical characteristics, H NMR, 13C NMR,
MS, and elemental analysis data for the key intermediates 2a–2z are reported in the
Supplementary data
4.3. General procedure for the preparation of the target compounds 3a−3z
To a 50 mL three-necked round-bottomed flask equipped with a magnetic stirrer, the key
intermediates 2a–2z (2.00 mmol), acetonitrile (15 mL), K2CO3 (4.00 mmol), and KI (2.00 mmol)
were added. The reactions were reacted for 1–2 h at room temperature. Then, compound
2-chloro-5-chloro methyl pyridine (2.40 mmol) was added to to the resulting mixture and refluxed
for approximately 5 h until TLC indicated that the reaction ended. Then, the mixture was added to
water and stirred for 5 min until the solid precipitated and the residue was filtered, dried under
vacuum, and purified by column chromatography to give the pure target compounds 3a–3z with
the yields of from 49% to 61%. The structures of the target compounds 3a–3z were characterized
using 1H NMR, 13C NMR, MS, and elemental analysis. The physical characteristics, 1H NMR, 13C
NMR, MS, and elemental analysis data for all the target compounds 3a–3z are reported in the
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Supplementary data, and the representative data for 3a are shown below.
4-(4-((6-Chloropyridin-3-yl)methoxy)phenyl)-2-phenyl-2,3-dihydrobenzo[b][1,4]-thiazepine
(3a). Pale yellow solid; m.p. 135 °C–137 °C; yield, 58%; IR (KBr, cm−1) ν: 1597.1–1451.5 (C=N,
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benzene and Py-ring), 1257.6 (C–O), 751.3 (Ar–S–C); H NMR (500 MHz, CDCl3, ppm) δ: 8.49
(d, J = 2.00 Hz, 1H, Py-2-H), 8.04 (d, J = 9.50 Hz, 2H, Ar-2,6-H), 7.79 (dd, J1 = 3.00 Hz, J2 =
9.00 Hz, 1H, Py-4-H), 7.61 (d, 1H, J = 6.50 Hz, 1H, Ar-2-H ), 7.47 (t, J = 15.00 Hz, 1H, Ar-3-H),
7.39 (d, J = 8.00 Hz, 1H, Py-5-H ), 7.31–7.26 (m, 6H, Ar-H), 7.15 (dt, J1 = 2.00 Hz, J2 = 15.00 Hz,
1H, Ar-4-H), 7.05 (d, J = 8.50 Hz, 2H, Ar-3,5-H), 5.14 (s, 2H, CO–CH2), 4.97 (dd, 1H, J1 = 5.00
Hz, J2 = 12.50 Hz, C-3-Ha), 3.28 (dd, J1 = 4.50 Hz, J2 = 13.50 Hz,1H, C-3-Hb), 3.08 (t, J = 22.50
Hz, 1H, C-2-Hx); 13C NMR (125 MHz, CDCl3, ppm) δ: 168.06, 160.57, 152.67, 151.47, 148.86,
144.21, 138.20, 135.17, 131.25, 131.19, 129.86, 129.40, 128.89, 127.95, 126.14, 125.42, 125.21,
124.46, 122.89, 114.95, 66.89, 60.51, 37.51; Anal. Calcd for C27H21ClN2OS (456.01): C, 70.96; H,
4.63; N, 6.13. Found: C, 70.98; H, 5.04; N, 6.17; MS (ESI) m/z: 456.7 ([M+H]ꢁ).
4.4. Antiviral activity against TMV
4.4.1. Extraction of TMV
The upper leaves of Nicotiana tabacum cv. (N. tabacum cv.) K326 inoculated with TMV were
selected and mashed under nitrogen, ground in phosphate buffer, and then filtered through
Gooding method [30]. The filtrate was centrifuged at 10,000 g. The TMV virus was obtained from
the supernatant. Absorbance values were estimated at 260 nm by using an ultraviolet
spectrophotometer.
0.1%, 260 nm
1cm
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virus concentration = (A260 × diluton ratio)/E
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4.4.2. Curative activity of the target compounds against TMV in vivo
Growing Nicotiana tabacum L. (N. tabacum L.) of the four-to-five-leaf stage was selected.
Silicon carbide was evenly spread on the leaves, and 6 × 10−3 mg/mL TMV was dipped and
inoculated using a brush into the whole leaves. Silicon carbide was washed with water after
inoculation for 0.5 h. After the leaves dried naturally, the compound solution was smeared on the
right side of the leaf and the solvent was painted on the left side as control. The number of local
lesions was counted and recorded 3–4 d after the inoculation [31]. Three replicates were
reproduced for each compound.
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4.4.3. Protection activity of the target compounds against TMV in vivo
Growing Nicotiana tabacum L. (N. tabacum L.) of the four-to-five-leaf stage was selected. The
compound solution was smeared on the right side, and solvents were smeared on the left side as
control. Silicon carbide was evenly spread on leaves after 12 h, and the virus was dipped in a
brush and inoculated into the whole leaves. Silicon carbide was washed using water after
inoculation for 0.5 h. N. tabacum L. was placed in a greenhouse at 25–30 °C for 3–4 days, and the
number of local lesions was counted and recorded [32]. Three replicates of each compound were
prepared.
4.4.4. Inactivation activity of the target compounds against TMV in vivo
Growing N. tabacum L. of the four-to-five-leaf stage was selected. The virus was mixed with
the same volume of compound solution for 30 min. The mixture was inoculated into the right side
leaves, and the solvent and the virus mixture were smeared on the left side of the leaves as control.
All leaves were previously scattered with silicon carbide. The number of local lesions was
recorded 3–4 d after the inoculation [32]. Three replicates of each compound were prepared.
4.5. Data analysis
The inhibition rate of the target compound was calculated according to the following formula
(“av” means average).
Inhibition rate (%) = [(av local lesion number of control (not treated with compound) − av local
lesion number smeared with compound) / av local lesion number of control (not treated with
compound)] × 100%
On the base of the previous bioassays, the results of inhibition rate (expressed by EC50) of the
target compounds against TMV were also evaluated at five double-declining concentrations (e.g.,
200, 100, 50, 25, and 12.5 mg/mL) and calculated with SPSS 17.0 software to obtain their
corresponding EC50 values. The experiments were repeated three times for each compound.
Acknowledgments
The authors gratefully acknowledge the National Natural Science Foundation of China (No.
21362004
Abbreviations used
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EC50, half-maximal effective concentration; NMR, nuclear magnetic resonance; TMV, tobacco
mosaic virus; CMV, cucumber mosaic virus; TLC, thin layer chromatography; SAR,
structure–activity relationship; N. tabacum L., Nicotiana tabacum L.
Supplementary data
Supplementary
data
related
to
this
article
can
be
found
at
http://www.sciencedirect.com/science/journal/ejmc.
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Table 1. Physical and analytical data of synthesized compounds 3a–3z.
Elemental analysis (%): Calcd/Found
Compd.
Molecular Formula/M.W.
Yield (%) MP (°C)
C
H
N
C27H21ClN2OS (456.11)
C28H23ClN2OS (470.12)
C25H19ClN2OS2 (462.06)
C28H23ClN2O2S (486.12)
C27H20ClN3O3S (501.09)
C28H20ClF3N2O2S (540.09)
C27H20BrClN2OS (534.02)
C25H19ClN2O2S (446.09)
C27H20ClFN2OS (474.10)
C29H25ClN2O3S (516.13)
C27H20Cl2NOS (490.07)
C27H20BrClN2OS (534.02)
C27H20BrClN2OS (534.02)
C28H23ClN2O2S (486.12)
C27H20ClFN2OS (474.10)
C28H23ClN2O2S (486.12)
C28H20ClF3N2OS (524.09)
C28H20ClF3N2OS (524.09)
C27H20Cl2NOS (490.07)
C27H20ClFN2OS (474.10)
C27H19Cl3N2OS (524.03)
C27H19Cl3N2OS (524.03)
C27H19Cl3N2OS (524.03)
C27H19Cl2FN2OS (508.06)
C27H20ClN3O3S (501.09)
C31H23ClN2OS (506.12)
58%
52%
58%
56%
51%
59%
54%
61%
54%
55%
56%
50%
52%
56%
56%
54%
57%
53%
57%
52%
51%
55%
54%
49%
53%
51%
135–137
95–97
70.96/70.98
71.40/71.32
64.85/64.53
69.06/69.14
64.60/64.72
62.17/61.95
60.52/60.61
67.18/67.03
68.28/68.09
67.37/67.45
65.99/66.02
60.52/60.63
60.52/60.59
69.06/69.21
68.28/67.93
69.06/69.13
64.06/64.25
64.06/63.31
65.99/63.87
68.28/68.21
61.67/61.46
61.67/61.69
61.67/61.57
63.66/63.79
64.60/64.36
73.43/73.49
4.63/5.04
4.92/5.02
4.14/3.86
4.76/4.70
4.02/3.93
3.73/3.80
3.76/3.82
4.29/4.60
4.24/4.47
4.87/5.02
4.10/4.09
3.76/4.01
3.76/3.97
4.76/4.89
4.24/4.25
4.76/4.79
3.84/3.96
3.84/4.11
4.10/4.18
4.24/4.45
3.64/3.78
3.64/3.86
3.64/3.76
3.76/4.01
4.02/4.19
4.57/4.81
6.13/6.17
5.95/6.09
6.05/6.21
5.75/5.80
8.37/8.54
5.18/5.39
5.23/5.53
6.27/6.70
5.90/6.18
5.42/5.68
5.70/5.60
5.23/5.35
5.23/5.35
5.75/5.83
5.90/6.30
5.75/6.02
5.34/5.54
5.34/5.12
5.70/5.65
5.90/6.09
5.33/5.10
5.33/5.58
5.33/5.01
5.50/5.72
8.37/8.29
5.52/5.69
3a
3b
3c
3d
3e
3f
143–145
108–109
112–114
134–136
121–123
135–137
147–148
101–102
149–151
172–173
141–143
162–164
146–147
110–112
98–100
3g
3h
3i
3j
3k
3l
3m
3n
3o
3p
3q
3r
3s
155–157
110–112
113–114
174–176
85–86
3t
3u
3v
3w
3x
3y
3z
147–149
162–163
154–156
129–131

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Table 2 Antiviral activity of the test compounds (500 µg/mL) against TMV in vivo.
Compd.
Curative activity (%)a Protection activity (%)a Inactivation activity (%)a
3a
55 ± 1.4
45 ± 2.1
46 ± 3.1
44 ± 2.6
52 ± 1.8
47 ± 2.2
51 ± 3.4
47 ± 1.6
54 ± 2.6
49 ± 3.9
54 ± 2.2
41 ± 4.4
58 ± 1.8
48 ± 2.6
49 ± 3.2
41 ± 2.9
55 ± 1.4
49 ± 3.4
53 ± 3.2
53 ± 4.0
39 ± 4.9
60 ± 2.2
53 ± 3.4
55 ± 3.8
51 ± 3.6
53 ± 2.3
54 ± 1.0
b
70 ± 1.6
62 ± 2.5
62 ± 2.7
50 ± 1.7
56 ± 2.4
55 ± 2.9
66 ± 2.2
63 ± 2.7
66 ± 2.2
51 ± 3.2
56 ± 3.1
56 ± 3.3
66 ± 1.9
52 ± 3.1
65 ± 2.5
62 ± 3.3
71 ± 2.0
55 ± 3.0
62 ± 2.6
58 ± 3.6
60 ± 3.8
53 ± 2.6
58 ± 2.9
65 ± 3.5
43 ± 2.9
64 ± 1.9
66 ± 0.9
89 ± 2.1
90 ± 1.9
85 ± 1.6
89 ± 1.7
92 ± 2.1
81 ± 1.8
84 ± 1.9
86 ± 2.0
82 ± 1.4
88 ± 2.4
80 ± 3.0
66 ± 2.4
51 ± 4.6
88 ± 2.7
90 ± 3.5
90 ± 2.7
82 ± 3.2
91 ± 2.8
93 ± 3.1
89 ± 2.4
91 ± 2.5
90 ± 2.6
92 ± 3.4
91 ± 2.4
90 ± 3.2
85 ± 3.2
92 ± 1.2
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
ningnanmycinb
aAverage of three replicates. The commercial, agricultural, and antiviral product ningnanmycin
was used for comparison of activity.

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Table 3 The EC50 values for curative activity of the target compounds against TMV in vivo.
Compd.
EC50 (µM) a Toxic regression equation
R
3a
3b
3c
3d
3e
3f
405.4 ± 2.1
799.0 ± 2.6
824.3 ± 1.5
1067.1 ± 2.5
1096.9 ± 1.6
688.3 ± 2.1
454.8 ± 1.8
793.5 ± 3.5
410.9 ± 2.2
778.6 ± 2.6
384.8 ± 1.8
1249.4 ± 1.9
352.2 ± 2.5
584.9 ± 2.6
872.8 ± 2.1
1058.8 ± 2.7
421.1 ± 2.4
542.1 ± 2.3
391.9 ± 2.0
477.3 ± 2.8
1127.8 ± 2.4
389.3 ± 1.6
425.9 ± 1.9
419.8 ± 2.3
786.6 ± 3.0
508.6 ± 2.1
y = 0.5985x + 3.6432
y = 0.3050x + 4.2557
y = 0.4438x + 3.9001
y = 0.4164x + 3.8695
y = 0.1682x + 4.4539
y = 0.2783x + 4.2847
y = 0.3887x + 4.0728
y = 0.4554x + 3.8392
y = 0.4593x + 3.9942
y = 0.2801x + 4.2706
y = 0.6141x + 3.6026
y = 0.3258x + 4.0134
y = 0.4987x + 3.8776
y = 0.2697x + 4.3382
y = 0.4157x + 3.9122
y = 0.355x + 4.0707
y = 0.3802x + 4.1089
y = 0.3214x + 4.2114
y = 0.4464x + 4.0136
y = 0.5642x + 3.6715
y = 0.513x + 3.6702
y = 0.5116x + 3.8184
y = 0.5255x + 3.8264
y = 0.4393x + 3.9769
y =0.4222x + 3.9041
y = 0.4228x + 3.9808
y = 0.7276x + 3.2568
0.9609
0.9908
0.9968
0.9117
0.9748
0.9830
0.9919
0.9817
0.9204
0.9244
0.9592
0.9815
0.9897
0.9208
0.9118
0.8047
0.9348
0.9697
0.9368
0.9650
0.9943
0.9717
0.9787
0.9949
0.9700
0.9756
0.9960
3g
3h
3i
3j
3k
3l
3m
3n
3o
3p
3q
3r
3s
3t
3u
3v
3w
3x
3y
3z
ningnanmycinb 560.4 ± 1.2
b
aAverage of three replicates. The commercial, agricultural, and antiviral product ningnanmycin
was used for comparison of activity.

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Highlights
1. Benzothiazepine were synthesized through 1,3-dipolar cycloaddition.
2. Compound 3m exhibited marked curative activity against TMV.
3. Electron-withdrawing groups are in favors of antiviral activity.