Synthesis and antiviral activity of novel chiral cyanoacrylate derivatives

Article abstract of DOI:10.1021/jf051050w

2-Cyanoacrylate is an important kind of herbicide targeted in photosystem II. Starting from cyano ethyl acetate, the chiral title compounds were synthesized under microwave irradiation, which has the advantages of shorter reaction time, higher yield, and

Full text of DOI:10.1021/jf051050w

7886 J. Agric. Food Chem. 2005, 53, 7886−7891
Synthesis and Antiviral Activity of Novel Chiral Cyanoacrylate
Derivatives
BAOAN SONG,* HUIPING ZHANG, HUA WANG, SONG YANG, LINHONG JIN,
DEYU HU, LILI PANG, AND WEI XUE
Center for Research and Development of Fine Chemicals, Key Laboratory of Green Pesticide and
Agriculture Bioengineering, Ministry of Education, Guizhou University,
Guiyang 550025, People’s Republic of China
2-Cyanoacrylate is an important kind of herbicide targeted in photosystem II. Starting from cyano
ethyl acetate, the chiral title compounds were synthesized under microwave irradiation, which has
the advantages of shorter reaction time, higher yield, and simpler procedure. A half-leaf method was
used to determine the inhibition and curative efficacies of the eight chiral products against tobacco
mosaic virus in vivo. It was found that chiral compound IIc-R possesses moderate inhibition and
curative effect in vivo with rates of 89.1 and 43.1%, respectively. In the MTT test, these new chiral
compounds were found to possess weak antiproliferation activities to PC3 and A431 cells.
KEYWORDS: 2-Cyanoacrylates; TMV inhibitory agent; antiproliferation bioactivity; microwave; chirality
1. INTRODUCTION
developed including prolonged heating of amine with 2-cyano-
3-(methylthio)-3-aminoacrylate. However, these methods have
many problems such as long reaction times and many side
reactions (12). Recently, organic reactions irradiated by micro-
waves have been developed as safe and convenient methods
for the synthesis of phosphonyl/S-methyl ketene thioacetals (13).
The application of microwave energy to accelerate the organic
reaction is of increasing interest and offers several advantages
over conventional techniques (14). Those synthetic reactions
normally requiring lengthy periods can be achieved conveniently
and rapidly in a microwave oven. Hence, we report herein a
new method for the preparation of chiral cyanoacrylate from
(R)- or (S)-1-phenylethanamine in refluxing n-propanol under
microwave irradiation producing chiral cyanoacrylate with
moderate or high yields (Scheme 1; Table 1). Several ethyl
3-[(R or S)-1-phenylethylamino]-3-(4-substitutedphenylamino)-
2-cyanoacrylates were synthesized, and the bioassay tests
showed that some of these title compounds exhibit good antiviral
activity in vivo and anticancer activity in vitro. The crystal
structure of IIa-R was determined by X-ray single-crystal
structure analysis from which an (E) configuration of the title
compounds was confirmed (Figure 1, Figure 2). To the best
of our knowledge, this is the first report on the synthesis, anti-
TMV bioactivity, and antitumor bioactivity of chiral cyanoacry-
late derivatives.
2-Cyanoacrylates are of considerable importance because of
their versatile biological activity and the possibility for applica-
tion in agrochemistry, for example, herbicides that disrupt
photosynthetic electron transportation at a common binding
domain on the 32 kDa polypeptide of the photosystem II (PSII)
reaction center (1, 2). Among these cyanoacrylates, (Z)-
ethoxyethyl 2-cyano-3-(4-chlorophenyl) methylamino-3-isopro-
pyl-acrylate (CPNPE) exhibits the highest Hill inhibitory activity
yet reported (3-8). To the best of our knowledge, there are no
studies of the antiviral activity of cyanoacrylate in the literature
(9). In our previous work, we designed and synthesized
cyanoacrylates containing a 4-(trifluoromethyl)phenylamino
moiety, which exhibited moderate antiviral bioactivity against
tobacco mosaic virus (TMV) (10). In view of these facts and in
continuation of our interest in the chemistry of cyanoacrylate,
we contemplated undertaking the synthesis of, as yet, unreported
novel chiral compounds containing cyanoacrylate moieties in
order to obtain chiral compounds possessing better biological
activity. To explore the bioactivity of the chiral analogues of
such compounds, also considering that chiral compounds are
the focus of much interest in modern agricultural chemistry
because the chiral isomers are always biologically more active
than their racemic mixtures and are more environmentally
friendly due to their lower usage (11), we decided to design
and synthesize some chiral cyanoacrylates with antiviral activity
through replacement of the methylthio moiety by the (R)- or
(S)-1-phenylethanamine in some 2-cyano-3-(methylthio)-3-
substituted-phenylaminoacrylates. At the same time, many
effective methods for the preparation of cyanoacrylate have been
2. MATERIALS AND METHODS
2.1. Synthetic Procedures. The melting points of the products were
determined on an XT-4 binocular microscope (Beijing Tech Instrument
Co., Beijing, China) and were not corrected. The IR spectra were
1
recorded on a Bruker VECTOR22 spectrometer with KBr disks. H
NMR and 13C NMR spectra were recorded on a Varian-INOVA 400
MHz spectrometer in CDCl3 at room temperature using tetramethyl-
* Author to whom correspondence should be addressed (telephone +86
851 362 0521; fax +86 851 362 2211; e-mail songbaoan22@yahoo.com).
10.1021/jf051050w CCC: $30.25
© 2005 American Chemical Society
Published on Web 09/07/2005

Antiviral Activity of Chiral Cyanoacrylate Derivatives
J. Agric. Food Chem., Vol. 53, No. 20, 2005 7887
Scheme 1
2.2.1. (E)-Ethyl 3-[4-(trifluoromethyl)phenylamino]-2-cyano-3-(me-
thylthio)acrylate (Ia): white crystal; mp, 80-82 °C; yield, 62.1%; IR
(KBr) νmax 3216, 2980, 2208, 1655, 1591, 1563, 1396, 1381, 1324,
1298, 1265, 1167, 1150, 1124, 1113, 1065, 1022, 779 cm-1; δH (400
MHz, CDCl3) 1.27 (t, J ) 6.4 Hz, 3H, CH3-C), 2.05 (s, 3H, S-CH3),
4.54 (q, 2H, O-CH2), 7.82-7.69 (m, 4H, Ar-H), 11.40 (s, 1H, NH);
m/z (EI-MS) 318 (M+). Anal. Calcd for C14H13F3N2O2S: C, 50.91; H,
3.97; N, 8.48. Found: C, 50.94; H, 3.96; N, 8.34.
2.2.2. (E)-Ethyl 3-(4-bromophenylamino)-2-cyano-3-(methylthio)-
acrylate (Ib): white crystal; mp, 130-132 °C; yield, 68.1%; IR (KBr)
νmax 3150, 2993, 2205, 1659, 1556, 1487, 1412, 1377, 1254, 1165,
1028, 843, 779, 660, 588, 519, 411 cm-1; δH (400 MHz, CDCl3) 1.26
(t, J ) 6.8 Hz, 3H, CH3-C), 2.85 (s, 3H, S-CH3), 4.32 (d, J ) 8.8
Hz, 2H, O-CH2), 7.63-7.65 (m, 4H, Ar-H), 11.22 (s, 1H, NH-Ar);
m/z (EI-MS) 328 (M+). Anal. Calcd for C13H13BrN2O2S: C, 45.76; H,
3.84; N, 8.21. Found: C, 45.80; H, 3.78; N, 8.18
Table 1. Results at Different Reaction Conditions for Synthesis of
IIa-R
entry
solvent
time (min)
temp (
°
C)
yielda (%)
1b
n-propanol
n-propanol
n-propanol
n-propanol
n-propanol
n-propanol
n-propanol
n-propanol
n-propanol
n-propanol
n-propanol
n-propanol
n-propanol
n-propanol
n-propanol
n-propanol
n-propanol
ethanol
5
10
20
30
15
30
20
20
20
20
20
60
120
180
240
360
600
45
97
97
97
97
40
40
50
60
70
80
97
97
97
97
97
97
97
78
65
105
24.1
30.3
53.1
54.1
no product
9.8
21.5
33.1
41.2
2b
3b
4b
5b
6b
7b
8b
9b
10b
11c
12c
13c
14c
15c
16c
17c
18b
19b
20b
44.2
no product
no product
no product
no product
no product
22.1
37.8
47.6
31.1
46.9
2.2.3. (E)-Ethyl 3-(4-nitrophenylamino)-2-cyano-3-(methylthio)acry-
late (Ic): white crystal; mp, 118-120 °C; yield, 60.1%; IR (KBr) νmax
3305, 2208, 1653, 1547, 1537, 1269, 1173, 1124, 1119, 1024 cm-1
;
δH (400 MHz, CDCl3) 1.25 (t, 3H, J ) 7.2 Hz, CH3-C), 2.31 (s, 3H,
S-CH3), 4.26 (q, 2H, J ) 7.2 Hz, O-CH2), 7.70 (d, 2H, J ) 8.4 Hz,
Ar-H), 7.81 (d, 2H, J ) 8.4 Hz, Ar-H), 11.49 (s, 1H, NH); m/z (EI-
MS) 307 (M+). Anal. Calcd for C13H13N3O4S: C, 50.81; H, 4.23; N,
13.68. Found: C, 50.94; H, 4.19; N,13.44.
methanol
isopropanol
45
45
a Isolated yields. b Reactions were carried out in 20 mL of solvent under
microwave irradiation, power 600 W. c Reactions were carried out in 20 mL of
solvent under stirring without microwave irradiation.
2.2.4. (E)-Ethyl 3-(3,4,5-trimethoxybenzoamido)-2-cyano-3-(meth-
ylthio)acrylate (Id): white crystal; mp, 162-163 °C; yield, 92.1%; IR
(KBr) νmax 3449, 3333, 2194, 1689, 1610, 1580, 1533, 1504, 1356,
1344, 1327, 1315, 1281, 1232, 1130, 997, 743 cm-1; δH (400 MHz,
CDCl3) 1.38 (t, J ) 6.4 Hz, 3H, C-CH3), 2.65 (s, 3H, S-CH3), 3.82-
3.85 (m, 10H, 3 × OCH3 + ArCONH), 4.32 (q, 2H, O-CH2), 7.24-
7.60 (m, 2H, Ar-H), 12.51 (s, 1H, ArCONNH); m/z (EI-MS) 395 (M+).
Anal. Calcd for C17H21N3O6S: C, 51.64; H, 5.35; N, 10.63. Found: C,
51.63; H, 5.41; N, 10.65.
2.3. General Procedure for the Preparation of Title Compounds
II. A solution of intermediate I (0.4 mmol) in n-PrOH (20 mL) was
stirred, followed by the addition of (R)-1-phenylethanamine or (S)-1-
phenylethanamine (0.4 mmol). The mixture was irradiated in the
microwave oven at 97 °C at 600 W for 20 min. The solvent was
removed under reduced pressure. The crude product was purified by
column chromatography on a silica gel (eluent, ethyl acetate/petroleum
ether, 2:8, v/v) to give the title compounds.
2.3.1. (E)-Ethyl 3-[(R)-1-phenylethylamino]-3-(4-(trifluoromethyl)-
phenylamino)-2-cyanoacrylate (IIa-R) (Figure 1): white crystal; mp,
145-147 °C; yield, 53.1%; [R]25D -210.2 (c 0.4828, acetone); IR (KBr)
νmax 3258, 3125, 2980, 2195, 1666, 1620, 1595, 1327, 1284, 1115,
1067, 702 cm-1; δH (400 MHz, CDCl3) 1.26 (t, J ) 6.4 Hz, 3H, CH3-
C), 1.45 (d, J ) 6.4 Hz, 3H, C-CH3), 4.18-4.28 (br, 3H, OCH2 +
NCH), 7.15-7.31 (m, 9H, Ar-H), 9.61 (d, J ) 6.4 Hz, 1H, C-NH),
silane (TMS) as internal reference. D2O exchange was applied to
confirm the assignment of the signals of NH protons. The mass spectra
were taken on an HP5988A spectrometer operated at 70 eV. Elemental
analysis was performed on an Elementar Vario-III CHN analyzer.
Microwave irradiations were carried out in an XH-100A CNC
microwave-catalysis apparatus at 600 W (Beijing Xianghu Technical
Development Co., Beijing, China). The instrument was equipped with
a refluxing apparatus, together with an internal magnetic stirring motor.
The reagents were all analytically or chemically pure. 2-Cyano-3,3-
(dimethylthio)acrylate was prepared according to a literature method
(15).
2.2. General Procedure for the Preparation of Intermediates Ia-
d. To an oven-dried three-neck 50 mL round-bottom flask fitted with
a magnetic stirring bar was added 2-cyano-3,3-(dimethylthio)acrylate
(2.17 g, 0.01 mol), substituted aniline (0.01 mol), 60% NaH (0.80 g,
0.02 mol), DMF (6 mL), and toluene (6 mL). The resulting mixture
was irradiated in the microwave oven at 80 °C and 600 W for 15 min.
The mixture was then poured into ice water (40 mL) and separated.
The aqueous phase was acidified with 10% HCl to pH 6-7 and filtered.
The residue was dried and recrystallized from ethanol-water to give
the title compounds.

7888 J. Agric. Food Chem., Vol. 53, No. 20, 2005
Song et al.
for C20H20BrN3O2: C, 58.00; H, 4.87; N, 10.13. Found: C, 58.07; H,
4.64; N, 10.07.
2.3.5. (E)-Ethyl 3-[(R)-1-phenylethylamino]-3-(4-nitrophenylamino)-
2-cyanoacrylate (IIc-R): white crystal; mp, 201-203 °C; yield, 65.6%;
D
[R]25 -297.4 (c 0.7616, acetone); IR (KBr) νmax 3233, 2980, 2193,
1670, 1601, 1518, 1340, 1302, 1283, 1258, 1090, 853, 764, 700, 554
cm-1; δH (400 MHz, CDCl3) 1.20 (t, J ) 6.8 Hz, 3H, CH3-C), 1.49
(d, J ) 6.4 Hz, 3H, C-CH3), 4.09-4.22 (m, 2H, O-CH2), 4.87 (t, J
) 7.2 Hz, 1H, N-CH), 7.20-8.14 (m, 9H, Ar-H), 9.44 (d, J ) 6.8
Hz,1H, C-NH), 9.75 (s, 1H, Ar-NH); m/z (EI-MS) 380 (M+). Anal.
Calcd for C20H20N4O4: C, 63.15; H, 5.30; N, 14.73. Found: C, 63.05;
H, 5.25; N, 14.66.
2.3.6. (E)-Ethyl 3-[(S)-1-phenylethylamino]-3-(4-nitrophenylamino)-
2-cyanoacrylate (IIc-S): white crystal; mp, 203-205 °C; yield, 71.2%;
D
[R]25 +283.3 (c 1.0140, acetone); IR (KBr) νmax 3235, 3219, 2980,
2194, 1670, 1601, 1551, 1518, 1497, 1443, 1387, 1340, 1302, 1281,
1257, 1113, 1090, 853, 764, 748, 700, 553 cm-1; δH (400 MHz, CDCl3)
1.20 (t, J ) 6.8 Hz, 3H, CH3-C), 1.49-1.50 (d, J ) 6.8 Hz, 3H,
C-CH3), 4.09-4.22 (m, 2H, O-CH2), 4.89 (t, J ) 7.2 Hz, 1H, N-CH),
7.20-8.14 (m, 9H, Ar-H), 9.44 (d, J ) 6.8 Hz, 1H, C-NH), 9.75 (s,
1H, Ar-NH); m/z (EI-MS) 380 (M+). Anal. Calcd for C20H20N4O4:
C, 63.15; H, 5.30; N, 14.73. Found: C, 63.15; H, 5.00; N, 14.70.
2.3.7. (E)-Ethyl 3-[(R)-1-phenylethylamino]-3-(3,4,5-trimethoxyben-
zoamido)-2-cyanoacrylate (IId-R): white crystal; mp, 168-169 °C;
Figure 1. Molecular structure of compound IIa-R.
D
yield, 98.1%; [R]25 -53.5 (c 0.5468, acetone); IR (KBr) νmax 3302,
2974, 1628, 1582, 1531, 1504, 1412, 1352, 1236, 1128, 997, 839, 698
cm-1; δH (400 MHz, CDCl3) 1.56-1.62 (m, 6H, 2C-CH3), 3.83-
3.88 (m, 12H, OCH2 + CONH + 3 × OCH3), 5.30 (s, 1H, N-CH),
7.00-7.38 (m, 7H, Ar-H), 9.44 (d, J ) 6.4 Hz, 1H, C-NH), 9.75 (s,
1H, ArCON-NH); m/z (EI-MS) 468 (M+). Anal. Calcd for
C24H28N4O6: C, 61.53; H, 6.02; N, 11.96. Found: C, 61.35; H, 6.00;
N, 11.70.
2.3.8. (E)-Ethyl 3-[(S)-1-phenylethylamino]-3-(3,4,5-trimethoxyben-
zoamido)-2-cyanoacrylate (IId-S): white crystal; mp, 158-160 °C;
D
yield, 97.8%; [R]25 +57.3 (c 0.4844, acetone); IR (KBr) νmax 3302,
2974, 1628, 1582, 1531, 1504, 1412, 1352, 1236, 1128, 997, 698; δH
(400 MHz, CDCl3) 1.55 (d, J ) 6.8 Hz, 6H, 2CH3-C), 3.82-3.85 (m,
12H, OCH2 + ArCONH + 3 × OCH3), 5.27-5.31 (m, 1H, N-CH),
6.70-7.38 (m, 7H, Ar-H), 9.44 (d, J ) 6.4 Hz, 1H, C-NH), 9.75 (s,
1H, ArCON-NH); m/z (EI-MS) 468 (M+). Anal. Calcd for
C24H28N4O6: C, 61.53; H, 6.02; N, 11.96. Found: C, 61.45; H, 5.80;
N, 11.80.
Figure 2. Packing diagram of the unit cell of compound IIa-R.
10.54 (s, 1H, Ar-NH); m/z (EI-MS) 389 (M+); Anal. Calcd for
C21H20F3N3O2: C, 62.52; H, 5.00; N, 10.42. Found: C, 62.70; H, 4.96;
N, 10.36.
2.4. Crystal Structure Determination. In the determination of the
structure of the single crystal, X-ray intensity data were recorded on a
Rigaku Raxis-IV diffraction meter using graphite monochromated Mo
KR radiation (λ ) 0.71073 Å). In the range of 2.06° e θ e 25.01°,
3741 independent reflections were obtained. Intensities were corrected
for Lorentz and polarization effects and empirical absorption, and all
data were corrected using the SADABS (16) program. The structure
was solved by direct methods SHELXS-97 program (17). All of the
non-hydrogen atoms were refined on F2 anisotropically by a full-matrix
least-squares method. The hydrogen atoms were located from the
difference Fourier map, but their positions were not refined. The
contributions of these hydrogen atoms were included in structure-
factor calculations. The final least-squares cycle gave wR ) 0.1786, R
) 0.0707, for the 11111 reflection with I > 2σ(I); the weighting scheme
2.3.2. (E)-Ethyl 3-[(S)-1-phenylethylamino]-3-(4-(trifluoromethyl)-
phenylamino)-2-cyanoacrylate (IIa-S): white crystal; mp, 135-137 °C;
yield, 54.1%; [R]25D +253.2 (c 0.7972, acetone); IR (KBr) νmax 3258,
3125, 2980, 2195, 1666, 1620, 1595, 1448, 1327, 1284, 1256, 1115,
1067, 845, 702, 550 cm-1; δH (400 MHz, CDCl3) 1.32 (t, J ) 6.4 Hz,
3H, CH3-C), 1.44 (d, J ) 6.4 Hz, 3H, C-CH3), 4.24-4.35 (br, 3H,
OCH2 + NCH), 7.15-7.27 (m, 9H, Ar-H), 9.60 (d, J ) 6.0 Hz, 1H,
C-NH), 10.53 (s, 1H, Ar-NH); m/z (EI-MS) 403 (M+). Anal. Calcd
for C21H20F3N3O2: C, 62.52; H, 5.00; N, 10.42. Found: C, 62.27; H,
4.99; N, 10.36.
2.3.3. (E)-Ethyl 3-[(R)-1-phenylethylamino]-3-(4-bromophenylamino)-
2-cyanoacrylate (IIb-R): white crystal; mp, 152-153 °C; yield, 50.9%;
D
[R]25 -207.8 (c 0.4620, acetone); IR (KBr) νmax 3258, 3125, 2980,
was w ) 1/[σ2(Fo ) + (0.1046P)2 + 0.000P], where P ) [(Fo ) + 2Fc2]/
3. The maximum and minimum difference peaks and holes are 0.338
and -0.179 e‚A-3, respsctively. s ) 1.203, and (∆/σ)max ) 0.026(4).
Atomic scattering factors and anomalous dispersion corrections were
taken from the International Table for X-ray Crystallography (18).
Crystallographic data (excluding structure factors) for the structure have
been deposited with the Cambridge Crystallographic Data Center as
supplementary publication CCDC-271061 (available free of charge at
http://www.ccdc.cam.ac.uk/conts/retrieving/html or from the CCDC,
12 Union Road, Cambridge CB2 1EZ, U.K.).
2
2
2195, 1666, 1620, 1595, 1448, 1327, 1284, 1256, 1115, 1067, 845,
702, 550 cm-1; δH (400 MHz, CDCl3) 1.23 (t, J ) 7.2 Hz, 3H, CH3-
C), 1.47 (d, J ) 6.8 Hz, 3H, C-CH3), 4.14-4.4.20 (m, J ) 3.6 Hz,
2H, O-CH2), 4.65-4.4.69 (m, 1H, N-CH), 6.99-7.46 (m, 9H, Ar-
H), 9.51 (d, J ) 6.2 Hz, 1H, C-NH), 10.45 (s, 1H, Ar-NH); m/z
(EI-MS) 414 (M+). Anal. Calcd for C20H20BrN3O2: C, 58.00; H, 4.87;
N, 10.13. Found: C, 57.98; H, 4.87; N, 10.14.
2.3.4. (E)-Ethyl 3-[(S)-1-phenylethylamino]-3-(4-bromophenylamino)-
2-cyanoacrylate (IIb-S): white crystal; mp, 153-155 °C; yield, 51.1%;
D
[R]25 +221.7 (c 0.4556, acetone); IR (KBr) νmax 3273, 3115, 2984,
2.5. Antiviral Biological Assay.
2193, 1663, 1607, 1582, 1541, 1487, 1445, 1292, 1271, 1092, 812,
768, 700, 512 cm-1; δH (400 MHz, CDCl3) 1.19 (s, 3H, CH3-C), 1.40
(d, J ) 6.8 Hz, 3H, C-CH3), 4.15-4.4.21 (m, 2H, OCH2), 4.49-4.69
(m, 1H, N-CH), 7.21-6.81 (m, 9H, Ar-H), 9.51 (d, J ) 6.0 Hz, 1H,
C-NH), 10.45 (s, 1H, Ar-NH); m/z (EI-MS) 414 (M+). Anal. Calcd
2.5.1. Purification of Tobacco Mosaic Virus. Using Gooding’s
method (19), the upper leaves of Nicotiana tabacum L. inoculated with
TMV were selected and ground in phosphate buffer and then filtered
through double-layer pledget. The filtrate was centrifuged at 10000g,

Antiviral Activity of Chiral Cyanoacrylate Derivatives
J. Agric. Food Chem., Vol. 53, No. 20, 2005 7889
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.
Table 2. Comparison of Yields between the Microwave-Assisted and
Classical Synthesis of II
yielda (%)
0.1%,260nm
virus concn ) (A260 × dilution ratio)/E
1cm
microwave
assistedb
classical
methodc
entry
compound
solvent
2.5.2. Inhibition Effect of Compound on TMV in ViVo. 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
(20). Three repetitions were conducted for each compound.
2.5.3. Cure Effect of Compound on TMV in ViVo. 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 (20). For each compound,
three repetitions were conducted to ensure the reliability of the results.
1
2
3
4
5
6
7
8
IIa-R
IIa-S
IIb-R
IIb-S
IIc-R
IIc-S
IId-R
IId-S
n-propanol
n-propanol
n-propanol
n-propanol
n-propanol
n-propanol
n-propanol
n-propanol
53.1
54.1
50.9
51.1
65.6
71.2
98.1
97.8
38.9
38.9
31.1
33.3
48.9
56.4
88.1
88.8
a Yields of isolated products. b Reaction conditions: reaction under microwave
irradiation in n-propanol, power 600 W, at 97
C for 20 min. c Reaction conditions:
C under stirring without microwave irradiation
°
using n-propanol as solvent, at 97
for 10 h.
°
of microwave irradiation on the reaction were investigated, and
the results are shown in Table 1. The results indicated that
microwave irradiation can accelerate the reaction (entries 1-10).
When there is no microwave irradiation, the reaction was
relatively slow and no product was detected within 4 h (entries
11-15). When the reaction time was prolonged to 6-10 h
without microwave irradiation, IIa-R could be obtained in 22.1
and 37.8% yield, respectively (entries 16 and 17). While under
microwave irradiation, the yield of IIa-R increased from 24.1
to 53.1% when the reaction time was prolonged from 5 to 20
min in refluxing n-propanol at 97 °C (entries 1-3). When the
reaction time was prolonged further to 30 min under microwave
irradiation, a tiny improvement of yield (54.1%, entry 4) was
obtained compared to that at 20 min (53.1%, entry 3). As for
the reaction temperature, it could be seen that the yield was
relatively low when the reaction was carried out at low
temperature (entries 5-10, 18, and 19) compared with that at
97 °C (entry 3). No substantial improvement was observed when
the reaction system was heated to 105 °C (entry 20). Hence, it
is better for the reaction to be performed at 97 °C than in lower
or higher temperature.
inhibition rate (%) )
av local lesion numbers of control (not treated with compound) -
av local lesion numbers smeared with drugs
av local lesion numbers without drugs
2.6. Herbicidal Activity Bioassay. Several plants including Brassica
campestris, Amaranthus retroflexus L., and Echinochloa crus-galli were
used to test the herbicidal activity of compounds. All of the seeds were
bought from the Institute of Crop, Tianjin Agriculture Science Academy,
People’s Republic of China. The seeds were planted in 6-cm-diameter
plastic boxes containing artificial mixed soil. Before plant emergence,
the boxes were covered with plastic film to retain moisture. Plants were
grown in the greenhouse. The dosage (activity ingredient) was 1500
g/ha. Purified compounds were dissolved in 100 µL of dimethylfor-
mamide (DMF), with the addition of a little Tween 20, and then were
sprayed using a laboratory belt sprayer delivering a spray volume of
750 L ha-1. The same amount of water was sprayed as control.
Compounds were sprayed to treat the soil immediately after seed
planting and were sprayed to the stem and leaves after seed germination.
The fresh weight of aerial tissues was measured 10 days after treatment.
The inhibition percent of aerial tissue fresh weight is used to describe
the control efficiency of compounds.
The present new method for the synthesis of chiral cyano-
acrylate II under microwave irradiation offers several advantages
including faster reaction rates, fewer byproducts, and higher
yields, as compared with the drawbacks of the classical method,
which involves a long tedious process (∼10 h) and gives low
yields. In Table 2 it is easy to observe that the average yields
of products obtained with the microwave method are ∼10%
higher than those obtained with the classical method. The short
reaction time of the microwave method is the advantage of this
method in relation to the other method; the average time ratio
between the two methods is 1:30.
3.2. Antiviral Activity. The antiviral activity of compound
II against TMV is assayed by the reported method (18). It could
be seen from Tables 3 and 4 that these newly synthesized chiral
compounds exhibit promising antiviral activities against TMV
in vivo. Apparently and interestingly, the antiviral data indicate
that the (R) or (S) configuration substantially affects bioactivity
and that the (R) configuration is vital. For example, the
bioactivity to TMV of the (R) isomers of IIa, IIb, IIc, and IId
are all better than those of the (S) isomers. It could be also
seen that the nature of the substituent on the phenyl group affects
the antiviral activity substantially. The electron-withdrawing
property of the substituent is favorable to their antiviral
bioactivity, as shown by the (R) isomer of IIc having a more
potent antiviral activity than the other (R) or (S) isomers and
2.7. MTT Assay against Cell Viability and Proliferation (21).
All compounds tested were dissolved in dimethyl sulfoxide (DMSO)
(1-100 µM solution) and subsequently diluted in the culture medium
before treatment of the cultured cells. Tested cells were plated in 96-
well plates at a density of 3 × 103 cells/well in 100 µL of the proper
culture medium and treated with the compounds at concentrations of
1-100 µM for 72 h. In parallel, the cells were treated with 0.1% DMSO
as control. A 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bro-
mide (MTT) assay (Roche Molecular Biochemicals, 1 465 007) was
performed 30 h later according to the instructions provided by Roche.
This assay is based on the cellular cleavage of the tetrazolium salt,
MTT, into a formazan that is soluble in cell culture medium and is
measured at 550 nm directly in 96-well assay plates. Absorbance is
directly proportional to the number of living cells in culture. Two types
of cells were used in these studies, PC3 (prostate cancer) and A431
(uterus cancer) cell lines (provided by the Cell Bank of the Committee
on Type Culture Collection of the Chinese Academy of Science) were
cultivated in F-12 (for PC3) or RPMI 1640 (for A431) supplemented
with 10% fetal bovine serum (provided by TBD & HyBio. Co.) and 2
mM L-glutamine. Tissue culture reagents were obtained from Gibco
BRL. Also, three repetitions were conducted for each compound.
3. RESULTS AND DISCUSSION
3.1. Synthesis. To optimize the reaction conditions, the
synthesis of IIa-R was carried out under several conditions. The
effects of different solvents, reaction time, and the use or not

7890 J. Agric. Food Chem., Vol. 53, No. 20, 2005
Song et al.
Table 3. Inhibition Effect of the New Chiral Compounds to TMV in Vivo
agent
ningnanmycin
virus A
antofine
IIa-R
IIa-S
IIb-R
IIb-S
IIc-R
IIc-S
IId-R
IId-S
concn (mg/L)
inhibition rate (%)
500
88.9
500
78.4
50
14.0
500
28.9
500
6.1
500
53.4
500
0
500
89.1
500
5.3
500
46.4
500
7.5
Table 4. Curative Effect of the New Chiral Compounds against TMV in Vivo
agent
ningnanmycin
virus A
antofine
IIa-R
IIa-S
IIb-R
IIb-S
IIc-R
IIc-S
IId-R
IId-S
concn (mg/L)
inhibition rate (%)
500
28.9
500
14.6
50
29.2
500
39.1
500
15.2
500
12.3
500
3.4
500
43.1
500
13.1
500
26.7
500
12.1
3.5. Crystal Structure Analysis. It could be seen from the
X-ray single-crystal analysis that chiral compound IIa-R
maintains a planar structure. The configuration of target
compound IIa-R was determined to be (E) by X-ray diffraction.
The bond length of C(9)sC(10) (1.406 Å) is longer than a
normal CdC (1.34 Å), C(12)sO(1) (1.327 Å) is shorter than a
normal single CsO (1.44 Å), C(10)sC(12) (1.454 Å) and
C(10)sC(11) (1.400 Å) are shorter than a normal CsC (1.54
Å), and C(9)sN(1) (1.315 Å) and C(9)sN(2) (1.365 Å) bonds
are shorter than the normal CsN single bond (1.49 Å), which
suggest the existence of an electron density localization among
N(2)sC(9)sC(10)sC(12)sO(2), C(11), and N(1).
Table 5. Herbicidal Activities of Chiral Compounds at a Dose of 1.5
kg of Active Ingredient per Hectare
B. campestris
A. retroflexus L.
E. crus-galli
soil stem
soil
stem
soil
stem
compd
treat
treat
treat
control
control
control
IIa-R
IIa-S
IIb-R
IIb-S
IIc-R
IIc-S
IId-R
IId-S
16.07
21.43
5.38
1.29
21.43
25.00
0
0
0
0
0
0
0
0
0
0
0
11.43
10.00
4.29
10.00
18.57
14.29
5.71
2.86
5.71
0
34.29
0
13.33
7.62
0
30.47
10.94
35.26
17.19
32.13
3.13
10.53
0
0
0
0
26.32
10.53
0
18.75
7.14
3.6. Conclusion. In summary, we described a practical and
efficient procedure for the preparation of chiral cyanoacrylate
compounds through the reaction of intermediate I with (R)-1-
phenylethanamine or (S)-1-phenylethanamine under microwave
irradiation in n-PrOH for 20 min at 97 °C. The reactions were,
in general, very fast and efficient and gave moderate yields. In
the half-leaf method test, the chiral compound IIc-R was found
to possess high antiviral activity against TMV in vivo.
Table 6. Inhibition Ratea (x¯
±
s) of Compounds II to PC3 and A431
Cells at 5
µ
M (P < 0.01)
compd
PC3 cells
A431 cells
IIa-R
IIa-S
IIb-R
IIb-S
IIc-R
IIc-S
IId-R
IId-S
59.4
49.1
1.5
24.7
2.9
0.7
32.1
3.2
±
±
±
±
±
±
±
±
±
4.7
6.0
0.1
11.3
0.3
0.1
14.2
0.2
8.2
43.1
39.9
16.1
19.3
23.6
18.1
25.1
29.4
30.7
±
±
±
±
±
±
±
±
±
9.6
8.1
8.5
9.1
11.2
4.5
7.8
9.2
7.4
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