Synthesis and antiviral bioactivities of 2-cyano-3-substitutedamino(phenyl) methylphosphonylacrylates (Acrylamides) containing alkoxyethyl moieties

Article abstract of DOI:10.1021/jf902861m

An efficient reaction under microwave irradiation has been developed for the synthesis of a series of novel 2-cyano-3-substituted-amino(phenyl) methylphosphonylacrylates (acrylamides) II. The products obtained in shorter reaction time with moderate yields are fully characterized by elemental analysis, IR, ¹H, ¹³C, and ³¹P NMR spectral data. The role of introducing various substituents and the effect of incorporating a-aminophosphonates with an alkoxyethyl moiety into the parent cyanoacrylate (acrylamide) structure are investigated. Among the studied compounds, both II-17 and II-24 displayed good in vivo curative, protection, and inactivation effects, which were comparable to those of the commercial reference ningnanmycin (inhibitory rates of 58.8, 60.2, 78.9% and 60.0, 58.9, 85.5%, respectively, at 500 mg/L against TMV). To the best of the authors' knowledge, this is the first report on the synthesis and antiviral activity of the title compounds II.

Full text of DOI:10.1021/jf902861m

2730 J. Agric. Food Chem. 2010, 58, 2730–2735
DOI:10.1021/jf902861m
Synthesis and Antiviral Bioactivities of 2-Cyano-3-substituted-
amino(phenyl) Methylphosphonylacrylates (Acrylamides)
Containing Alkoxyethyl Moieties†
§
,
J
IA-QIANG
Y
ANG
,
§,# BAO
-
AN
S
ONG,*,§ PINAKI S. BHADURY,§ ZHUO
C
HEN
§
§
S
ONG
Y
ANG,§ XUE-JIAN
C
AI,§ D
E
-Y
U
HU
,
AND
W
EI
X
UE
§Center for Research and Development of Fine Chemicals, Key Laboratory of Green Pesticide and
Agricultural Bioengineering, Ministry of Education, Guizhou University, Guiyang 550025, People’s
Republic of China, and #Laboratory of Medicinal Chemistry, Zunyi Medical College, Zunyi 563003,
People’s Republic of China
An efficient reaction under microwave irradiation has been developed for the synthesis of a series of
novel 2-cyano-3-substituted-amino(phenyl) methylphosphonylacrylates (acrylamides) II. The pro-
ducts obtained in shorter reaction time with moderate yields are fully characterized by elemental
analysis, IR, 1H, 13C, and 31P NMR spectral data. The role of introducing various substituents and
the effect of incorporating R-aminophosphonates with an alkoxyethyl moiety into the parent
cyanoacrylate (acrylamide) structure are investigated. Among the studied compounds, both II-17
and II-24 displayed good in vivo curative, protection, and inactivation effects, which were compar-
able to those of the commercial reference ningnanmycin (inhibitory rates of 58.8, 60.2, 78.9% and
60.0, 58.9, 85.5%, respectively, at 500 mg/L against TMV). To the best of the authors’ knowledge,
this is the first report on the synthesis and antiviral activity of the title compounds II.
KEYWORDS: 2-Cyanoacrylate; alkoxyethyl; R-aminophosphonate; microwave irradiation; anti-TMV
activity
INTRODUCTION
certain suitably derivatized phosphonates (18-20), particularly
those bearing two alkoxyethyl moieties instead of simple dialkyl
ones (21), are associated with high antiviral activities. To meet the
ever-increasing demand for the development of effective envir-
onmentally benign antiviral agents for protecting crops from the
deadly TMV, we envisioned that the introduction of phospho-
nates bearing alkoxyethyl moiety into the parent cyanoacrylate
(acrylamide) scaffold might lead to the generation of new potent
agents with desired activity. The rationale behind the synthetic
design of novel structure II containing an alkoxyethyl moiety
tunable by variation of substituents R1, R2, and R3 is shown
in Figure 1. Although cyonoacrylate derivatives containing an
R-aminophosphonate moiety derived from dialkyl phosphites
have previously been prepared (17) (structure A, Figure 1), to
the best of our knowledge to date no attempt has been made to
prepare similar compounds bearing an alkoxyethyl moiety. As
the introduction of fluorine may lead to a marked change in the
bioactivity of phosphonates (22-26), we also studied the role of
fluorine atom (R1) in some of our title compounds and explored
the potential of cyanoacrylate (cyanoacrylamide) derivatives of
R-aminophosphonates II (Figure 1) in protecting crops against
viral attack. The various methods reported for the preparation
of cyanoacrylate derivatives suffer from serious drawbacks
such as long reaction times accompanied by the formation of
side reaction products (5-9, 17). The poor nucleophilicity of
R-aminophosphonates containing alkoxyethyl and fluorinated
groups can further retard the rate of the reaction, making the
design of the synthetic route to the title compounds more difficult.
2-Cyanoacrylates and their derivatives act as potent growth
inhibitors of weeds due to their ability to disrupt photosystem II
(PSII) electron transport at a common binding domain on the 32
kDa polypeptide at the PSII reaction center (1-4). These com-
pounds exhibit a wide range of bioactivities with immense
potential to be employed as herbicides, fungicides, plant viru-
cides, and antitumor agents (5-13). Some of these cyanoacrylate
derivatives obtained by conventional nucleophilic displacement
of methylthio moieties of 2-cyano-3-(methylthio) acrylates by
(R)- or (S)-1-phenylethanamine, phenylamino group, and aryl
(heterocyclic) amine displayed moderate to good effect against
tobacco mosaic virus (TMV) in vivo (14, 15). Unfortunately, the
reactions leading to these acrylates are generally sluggish but
could be accelerated by the application of microwave irradia-
tion (14). Encouraged by our earlier result that cyanoacrylates
bearing phosphonyl moieties possessed high in vivo curative,
protection, and inactivation effects against TMV (16), we recently
prepared similar cyanoacrylate derivatives bearing an R-amino-
phosphonate unit to obtain novel structure A (Figure 1) having
good effect against TMV with inhibitory rate at 500 mg/L (17).
However, these compounds A derived from simple dialkyl
phosphites did not have the desired anti-TMV activity to combat
the severity of the plant disease caused by the virus. Fortunately,
†Part of the ECUST-Qian Pesticide Cluster.
*Corresponding author (fax 0086-851-3622211; e-mail songbaoan22@
yahoo.com).
pubs.acs.org/JAFC
Published on Web 12/10/2009
© 2009 American Chemical Society

Article
J. Agric. Food Chem., Vol. 58, No. 5, 2010 2731
Figure 1. Strategic design of the target cyanoacrylates (acrylamides II) bearing alkoxyethyl moieties.
Scheme 1. Synthetic Route to 2-Cyano-3-substituted-amino(phenyl) Methylphosphonylacrylate (Acrylamide) Analogues II Containing Alkoxyethyl Moieties
Because the reaction rates for the synthesis of cyanoacrylates and
R-aminophosphonates are found to be markedly accelerated
under microwave irradiation (14,21), we undertook the synthesis
of the title compounds under similar conditions for improving
reaction yields and shortening reaction times (Scheme 1). Com-
pounds II were completely characterized by IR, 1H, 13C, 31P
NMR, and elemental analysis data. Some of the synthesized
compounds showed excellent anti-TMV activities. To the best of
our knowledge, this is the first report on the synthesis and the
anti-TMV bioactivity of the title compounds.
was stirred for 2 h at room temperature, extracted with ethyl acetate (3 ꢀ
20 mL), and the solvent was removed under reduced pressure. Pure
products were obtained as oils by silica gel column chromatography using
ethyl acetate/petroleum ether (2:1). The data for Ia-Id can be found in the
Supporting Information.
General Procedure for the Preparation of 2-Cyano-3,3-di-
methylthioacrylate (Acrylamide) Intermediates 7. Esters 6a-6e were
prepared conveniently from cyanoacetic acid and primary alcohols in the
presence of a catalytic amount of anhydrous H2SO4 under reflux condi-
tion. Amides 6f and 6g were synthesized from ethyl cyanoacetate and the
corresponding amine in excellent yields by carrying out the reaction at
room temperature for 1 h. Compound 6 (20 mmol) was added dropwise to
a mixture of potassium hydroxide powder (40 mmol) and anhydrous
acetonitrile (30 mL) at 5 °C. The mixture was stirred for 1.5 h, and then a
solution of carbon disulfide (20 mmol) in anhydrous acetonitrile (5 mL)
was added over a period of 15 min. The reaction mixture was stirred for 4 h
at room temperature. After the solution had been cooled to 0 °C, dimethyl
sulfate (40 mmol) was added, and the resulting mixture was stirred at room
temperature for 6 h. The solvent was removed under reduced pressure, and
then water (30 mL) and ethyl acetate (50 mL) were added to the residue.
The organic layer was separated and dried with anhydrous magnesium
sulfate. Ethyl acetate was evaporated to afford the corresponding 7. The
data for 7a-7g can be found in the Supporting Information.
General Procedure for Conventional Preparation of 2-Cyano-3-
substituted-amino(phenyl) Methylphosphonylacrylates (Acrylamides) II.
A mixture of 2-cyano-3,3-dimethylthioacrylate (acrylamide) (7a-7g) (0.15
mmol) and R-aminophosphonate containing an alkoxyethyl moiety
(Ia-Id) (0.15 mmol) in ethanol (10 mL) was refuxed and stirred for
12 h. The progress of the reaction was monitored by TLC; the solvent was
evaporated under reduced pressure, and the residue was washed with
water, filtered off, and purified by silica gel column chromatography
(petroleum ether/ethyl acetate, 1:2, v/v) to give the title compounds.
General Procedure for Microwave Preparation of 2-Cyano-3-
substituted-amino(phenyl) Methylphosphonylacrylates (Acrylamides) II.
A mixture of 2-cyano-3,3-dimethylthioacrylate (acrylamide) (7a-7g) (0.15
mmol) and R-aminophosphonate containing an alkoxyethyl moiety
(Ia-Id) (0.15 mmol) in ethanol (10 mL) was placed in a microwave tube,
which was then sealed and placed in the Discovery synthesizer and
irradiated at 100 °C and 140 W and 100 psi for 30 min. Upon completion
MATERIALS AND METHODS
Instruments. The melting points of the products were determined on
an XT-4 binocular microscope (Beijing Tech Instrument Co., China) and
were not corrected. The IR spectra were recorded on a Bruker VECTOR
1
22 spectrometer in a KBr disk. H, 13C, and 31P NMR (solvent CDCl3)
spectra were performed on a JEOL-ECX 500 NMR spectrometer at room
temperature using tetramethylsilane as an internal standard. Elemental
analysis was performed on an Elementar Vario-III CHN analyzer.
Microwave irradiations were carried out in a CEM-Auto Focused
Coupling. Analytical thin-layer chromatography was performed on silica
gel GF254. Column chromatographic purification was carried out using
silica gel. All reagents were of analytical reagent grade or chemically pure.
All solvents were dried, deoxygenated, and redistilled before use.
Synthetic Procedures. Compounds 3, intermediates 4, and inter-
mediates 5 were synthesized according to the literature methods (4,27,28),
as described, with minor modifications of reaction temperature and
reaction time.
General Procedure for the Preparation of O,O0-Bis(2-alkoxyethyl)-
1-amino(phenyl) Methylphosphonate Intermediates I. The aldehyde (15
mmol) was added to ammonium hydroxide (30%, 15 mL), and the
solution was stirred for 5 h at reflux. During this time, a white precipitate
formed, which was removed by filtration and then dried. Dialkoxyethyl
phosphite (6 mmol) was added to this solid, and the resulting solution was
stirred for 12 h at 80 °C. p-Toluenesulfonic acid (6 mmol) in 50 mL of THF
was added to the reaction mixture, which was stirred for 4 h at 0 °C. The
precipitate was removed by filtration, washed with THF (20 mL), and then
added to 15 mL of aqueous ammonium hydroxide (10%). The mixture

2732 J. Agric. Food Chem., Vol. 58, No. 5, 2010
Yang et al.
Table 1. Time Optimization of Microwave-Assisted Synthesis of II-1
of the reaction, the solvent was removed under reduced pressure, and the
residue was washed with water, filtered off, and purified by silica gel
column chromatography (petroleum ether/ethyl acetate, 1:2, v/v) to give
the title compounds. The data for II-1 are shown below, whereas data for
II-2-II-28 can be found in the Supporting Information.
entry
time (min)
yielda (%)
1
2
3
4
5
6
7
8
5
10
15
20
25
30
35
40
10.3
16.8
27.6
42.8
43.1
43.4
42.9
41.6
Data for II-1: colorless oil; IR (KBr, cm-1) ν 3127.1, 3096.0, 2857.2,
2834.3, 2206.9, 1670.3, 1593.2, 1554.6, 1516.0, 1492.9, 1396.4, 1348.2,
1284.5, 1207.3, 1055.6, 781.3, 742.5; 1H NMR (500 MHz, CDCl3) δ 2.53 (s,
3H, SCH3), 3.32 (s, 6H, 2OCH3), 3.43-3.54 (m, 4H, 2OCH2), 3.82 (s, 3H,
OCH3), 4.00-4.18 (m, 4H, 2OCH2), 5.73 (q, J = 5.74 Hz, 1H, CH),
7.39-7.42 (m, 5H, ArH), 10.95 (s, 1H, NH); 13C NMR (125 MHz, CDCl3)
δ 172.3, 172.2, 168.3, 129.0, 128.7, 128.6, 128.0, 127.8, 127.7, 117.9, 71.4,
71.3, 66.3, 66.2, 58.9, 58.8, 52.1, 51.9, 18.4; 31P NMR (200 MHz, CDCl3) δ
20.08. Anal. Calcd for C19H27N2O7PS: C, 49.78; H, 5.94; N, 6.11. Found:
C, 49.92; H, 5.82; N, 6.28.
a Yields of isolated products.
Table 2. Temperature Optimization of Microwave-Assisted Synthesis of II-1
yielda (%)
Antiviral Biological Assay. Purification of Tobacco Mosaic
Virus. Using Gooding’s method (29), the upper leaves of Nicotiana
tabacum L. inoculated with TMV were selected, ground in phosphate
buffer, and then filtered through a double-layer pledget. The filtrate was
centrifuged at 10000g, treated twice with poly(ethylene glycol), and
centrifuged again. The whole experiment was carried out at 4 °C.
Absorbance values were estimated at 260 nm using an ultraviolet spectro-
photometer.
entry
temp (°C)
1
2
3
4
5
6
40
60
10.3
16.8
27.6
43.4
40.5
36.5
80
100
120
140
a Yields of isolated products.
,
260nm
virus concn ¼ ðA260 ꢀ dilution ratioÞ=E0:1%
1cm
Table 3. Power Optimization of Microwave-Assisted Synthesis of II-1
Protective Effect of Compounds against TMV in Vivo. The
compound solution was smeared on the left side, whereas the solvent
served as the control on the right side of growing N. tabacum L. leaves
of the same ages. The leaves were then inoculated with the virus after
12 h. A brush was dipped in TMV of 6 ꢀ 10-3 mg/mL to inoculate
the leaves, which were previously scattered with silicon carbide. The
leaves were then washed with water and rubbed softly along the nervature
once or twice. The local lesion numbers appearing 3-4 days after
inoculation were counted. The experiment was repeated three times with
each compound.
entry
power (W)
yielda (%)
1
2
3
4
5
6
7
60
80
26.4
33.7
43.4
45.8
46.6
47.0
47.0
100
120
140
160
200
Inactivation Effect of Compounds against TMV in Vivo. The virus
was inhibited by mixing 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. The experiment was repeated three
times with each compound.
a Yields of isolated products.
conventional synthesis where the temperature could not be raised
beyond the boiling point of ethanol (75-80 °C), the microwave-
assisted syntheses could be successfully executed at higher tem-
perature as the reactions were carried out in a sealed tube under a
pressurized atmosphere. To study the effect of reaction time on
the synthesis of the model compound, at first all of the reactions
were carried at a fixed power of 100 W and temperature of 100 °C.
The isolated yields of compound II-1 varied from 10.3 to 43.4%
when the reaction time was between 5 and 40 min (Table 1). The
optimum reaction time corresponding to maximum yield was
found to be 30 min (entry 6 in Table 1), beyond which a slight
reduction in the yield occurred. The synthesis of the model
compound was further studied at various temperatures, keeping
the power constant at 100 W (Table 2). The highest yield in this
case was recorded at 100 °C, and above this temperature the yield
was lowered (entries 5 and 6 in Table 2), presumably due to the
thermal decomposition of the intermediate R-aminophosphonate
at high temperature. For power optimization, the reaction was
executed under the same set of conditions (Table 3) at different
microwave powers. In the beginning, the yield of compound
II-1 increased appreciably from 26.4 to 46.6% with increasing
power input from 60 to 140 W (entries 1-5 in Table 3). However,
this upward trend in the yield was less noticeable at higher
powers (entries 6-7 in Table 3). Thus, under the optimized
conditions, the best result can be achieved when 1 equiv of
the nucleophilic component O,O0-bis(2-alkoxyethyl)-1-amino-
(phenyl) methylphosphonate reacts with 2-cyano-3,3-dimethyl-
thioacrylate (acrylamide) under microwave conditions in ethanol
at 100 °C and 140 W microwave power for 30 min. A comparison
of the yields from the conventional and microwave-assisted
Curative Effect of Compounds against TMV in Vivo. Growing
leaves of N. tabacum L. of the same ages were selected. The TMV
(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
counted and recorded 3-4 days after inoculation. The experiment was
repeated three times with each compound. The inhibition rate of the
compound was then calculated according to the following formula (av
denotes average, and controls were not treated with compound).
inhibition rate ð%Þ ¼
f½av local lesion no: of control ðnot treated with compdÞ
av local lesion no: smeared with drugsꢁ=
av local lesion no: of controlg ꢀ 100%
-
RESULTS AND DISCUSSION
Synthesis. As can be observed from Scheme 1, the preparation
of title compound II involves a multistep synthesis, and the
overall yield is therefore affected by complexity of individual
steps. The microwave reaction conditions for the final step
leading to the synthesis of title compounds were optimized for
various reaction parameters, for example, reaction time, tem-
perature, and power input, by taking II-1 as the model. Unlike

Article
J. Agric. Food Chem., Vol. 58, No. 5, 2010 2733
Table 4. Comparison of Conventional and Microwave-Assisted Procedures
for the Synthesis of Compounds II
Table 5. Protection Effect, Inactivation Effect, and Curative Effect of the New
Compounds against TMV in Vivo
traditional heating
microwave irradiation
curative
effect
(%)
concn
(mg/L)
protection
effect (%)
inactivation
effect (%)
compd R1 R2
R3
time (h) yielda (%) time (min) yielda (%)
agent
II-1
II-2
H
H
H
H
H
H
H
CH3 OCH3
CH3 OC2H5
12
12
12
12
12
12
12
12
12
12
12
12
12
12
12
12
12
12
12
12
12
12
12
12
12
12
12
12
19.6
20.3
21.2
18.8
18.0
22.9
21.7
20.1
21.2
19.7
19.9
18.5
24.6
23.3
20.0
18.9
19.1
19.5
17.2
22.6
22.8
20.7
21.0
19.2
19.0
17.2
22.9
23.1
30
30
30
30
30
30
30
30
30
30
30
30
30
30
30
30
30
30
30
30
30
30
30
30
30
30
30
30
46.6
43.2
44.1
44.3
49.4
50.1
41.8
41.2
49.3
47.1
45.5
42.1
53.3
50.0
49.1
45.3
42.5
44.6
44.0
42.7
49.6
48.0
45.3
41.8
44.3
40.9
52.2
42.5
II-1
II-2
500
500
500
500
500
500
500
500
500
500
500
500
500
500
500
500
500
500
500
500
500
500
500
500
500
500
500
500
500
0
0
28.8
32.1
43.1
23.7
31.0
43.2
29.6
34.5
21.7
9.9
21.0
40.0
0
28.3
41.9
12.2
21.0
66.7
32.1
41.0
0
II-3
II-4
CH3 OC2H4OCH3
CH3 OC2H4OC2H5
CH3 OC2H4OPh
CH3 NH2
II-3
II-4
II-5
II-6
II-5
II-6
14.4
50.0
39.7
22.0
0
II-7
II-8
CH3 NHCH2Ph
II-7
II-8
2-F CH3 OCH3
2-F CH3 OC2H5
II-9
II-9
II-10
II-11
II-12
II-13
II-14
II-15
II-16
II-17
II-18
II-19
II-20
II-21
II-22
II-23
II-24
II-25
II-26
II-27
II-28
2-F CH3 OC2H4OCH3
2-F CH3 OC2H4OC2H5
2-F CH3 OC2H4OPh
2-F CH3 NH2
II-10
II-11
II-12
II-13
II-14
II-15
II-16
II-17
II-18
II-19
II-20
II-21
II-22
II-23
II-24
II-25
II-26
II-27
II-28
0
0
21.9
29.0
30.0
39.9
0
33.3
44.0
44.8
40.8
0
31.4
41.8
22.0
28.6
4.3
2-F CH3 NHCH2Ph
H
H
H
H
H
H
H
C2H5 OCH3
C2H5 OC2H5
45.9
60.2
40.7
3.8
35.4
78.9
29.5
31.9
80.0
40.1
12.0
33.4
85.5
40.2
23.7
33.9
79.9
96.0
51.1
58.8
46.4
44.1
56.7
47.3
33.0
45.6
60.0
41.9
27.7
30.6
54.3
58.9
C2H5 OC2H4OCH3
C2H5 OC2H4OC2H5
C2H5 OC2H4OPh
C2H5 NH2
54.4
34.5
0
C2H5 NHCH2Ph
2-F C2H5 OCH3
2-F C2H5 OC2H5
12.9
58.9
31.0
30.7
30.0
55.4
57.7
2-F C2H5 OC2H4OCH3
2-F C2H5 OC2H4OC2H5
2-F C2H5 OC2H4OPh
2-F C2H5 NH2
2-F C2H5 NHCH2Ph
a Yields of isolated products.
Ningnanmycin
syntheses was performed, and the results are shown in Table 4.
We can conclude from Table 4 that although the improvement in
the yield was marginal (e.g., for compound II-5 an overall
improvement of 31.4% from conventional to MV mode), the
microwave-assisted synthesis brought about a significant reduc-
tion of reaction time from 12 h to 30 min.
compared against that of Ningnanmycin, a commercially available
nitrogenous virucide usually produced by Strepcomces noursei var.
xichangensisn var. TMV was assayed by the earlier methods
reported in the literature (14, 30). The compounds were evaluated
for their suitability as antiviral agents against TMV. The antiviral
activities were measured at 500 mg/L in vivo, and the data are
presented in Table 5. Among the studied compounds, cyano-
acrylate derivatives II-17 (R1 = H, R2 = Et, R3 = OC2H4OCH3)
and II-24 (R1 = 2-F, R2 = Et, R3 = OC2H4OCH3) displayed
remarkable protection activities (60.2 and 58.9%, respectively)
and curative rates (58.8 and 60.0%, respectively) against TMV,
which were comparable to the protection activity (57.7%) and
curative rate (58.9%) shown by the commercial reference Ning-
nanmycin. It can also be noted from the data presented in Table 5
that cyanoacrylamide derivatives such as II-6, II-7, II-14, II-20,
II-21, and II-28, contrary to II-17 and II-24, showed only
moderate to good protection activities of 50.0, 39.7, 39.9, 54.4,
34.5, and 55.4%, respectively, at 500 mg/L, and nonfluorinated
cyanoacrylates II-1, II-4, and II-15 and fluorinated cyanoacryl-
ates II-9, II-10, and II-22 were found to be completely ineffective
against TMV. The curative activities of the title compounds
depend to a certain extent on the nature of the substituents; com-
pounds II-3, II-6, II-12, II-16, II-18, II-19, II-20, II-21, II-23, II-25,
and II-28 showed curative activities of up to 43.1, 43.2, 41.8, 51.1,
46.4, 44.1, 56.7, 47.3, 45.6, 41.9, and 54.3%, respectively, at 500 mg/
L against TMV. As for inactivation bioactivities, except for
cyanoacrylates II-17 and II-24 and cyanoacrylamides II-6, II-20,
and II-28, which showed moderate to good inactivation bioactiv-
ities (78.9, 85.5, 66.7, 80.0, and 79.9%, respectively), all other
compounds exhibited lower inactivation bioactivities against
TMV at the concentration of 500 mg/L. Comparison of biological
activities among all target compounds leads us to conclude that the
All of the products were unequivocally characterized by IR and
NMR spectral data and elemental analyses. The characteristic IR
absorption bands for NH (3100-3430 s cm-1), CdN (2200-
2210 s cm-1), CdO (1640-1720 s cm-1), CdC (1520-1590
s cm-1), PdO (1240-1280 cm-1), C;OC (1200-1230 cm-1),
and PO;C (1001-1040 cm-1) confirmed the presence of the
functional groups. In 1H NMR spectra, all aromatic protons
revealed the expected multiplet near 6.91-7.50 ppm. The NH
protons of compounds II appeared considerably downfield in the
region of 10.75-12.05 ppm due to the existence of hydrogen
bonding with the acrylate (acrylamide). The chemical shift of
SCH3 appeared near 2.25-2.57 ppm and PCH of ester showed up
at 5.52-6.10 ppm. The H atom at the R-C exhibited a quartet due
to the coupling with the adjacent phosphorus. The chemical shifts
of OCH2 generally appeared in the region of 3.17-4.55 ppm. The
typical phosphorus resonance at 18.78-20.80 ppm in the 31P
NMR spectra of all target compounds confirmed the presence of
a phosphorus center coupled to adjacent CH. All of the none-
quivalent carbon atoms were identified in 13C NMR and the total
number of protons calculated from the integration curve ac-
corded (in 1H NMR) with the assigned structures.
Antiviral Activity and Structure-Activity Relationship. To
study the role of different substituents (R1, R2, and R3) in
imparting antiviral activity and to establish a structure-activity
relationship based on the experimental data, the antiviral
potencies of the title cyanoacylates (acrylamides) II were

2734 J. Agric. Food Chem., Vol. 58, No. 5, 2010
Yang et al.
anti-TMV activities of the products are higher if the cyanoacrylate
ester is derived from R3 = OC2H4OCH3 instead of OCH3 or
OC2H4OPh, and the aminophosphonate component is derived
from R2 = Et instead of Me. The cyanoacrylamide derivatives,
in general, displayed greater anti-TMV activities compared to their
cyanoacrylate analogues. The screening of our experimental
data (Table 5) clearly showed that II-17 and II-24 had excellent
protection effects, appreciable curative activity, and moderate
inactivation activity against TMV, which are different from most
of the 2-cyanoacrylate derivatives reported in our previous
work (14-17). As the two most effective compounds II-17 and
II-24 are structurally similar except for the fluorine substitution at
the ortho position in the aromatic ring, the role of fluorine
incorporation for changing activity of the studied compounds
appears to be insignificant.
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In conclusion, a series of novel cyanoacrylate (cyanoacryl-
amide) derivatives incorporating R-aminophosphonate moieties
derived from dialkoxyethyl phosphites were synthesized via
microwave-assisted procedure. The method offers several advan-
tages such as fast reaction rate, moderate yields, and environ-
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pounds possessing excellent anti-TMV activities have potential to
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analogues. The cyanoacrylates II-17 and II-24 showed excellent
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to those of the standard Ningnanmycin against TMV. The
changes in hydrophobic and electrostatic interactions obtained
by structural variation with different substituents might be
responsible for the observed enhancement in anti-TMV acti-
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was to obtain a potent antiviral agent by preparing different
title compounds containing alkoxyethyl and fluorinated
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pronounced compared to the former. The present work suc-
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cyanoacrylate derivatives could be significantly improved by
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alkoxyethyl moieties. Further studies on structural optimiza-
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Received for review June 2, 2009. Revised manuscript received October
22, 2009. Accepted November 19, 2009. We thank the National Key
Program for Basic Research (No. 2003CB114404) and the National
Natural Science Foundation of China (No. 20672024) for financial
support.
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