Enamines as novel antibacterials and their structure-activity relationships

Article abstract of DOI:10.1016/j.ejmech.2007.11.026

Twenty-six enamines were synthesized to screen for the antimicrobial activity. Out of the compounds, 22 were reported for the first time. Their chemical structures including E/Z-configurations were clearly determined by ¹H NMR, ESI mass spectra

Full text of DOI:10.1016/j.ejmech.2007.11.026

Available online at www.sciencedirect.com
European Journal of Medicinal Chemistry 43 (2008) 1828e1836
http://www.elsevier.com/locate/ejmech
Original article
Enamines as novel antibacterials and their
structureeactivity relationships
Zhu-Ping Xiao a,b, Rui-Qin Fang a, Huan-Qiu Li a, Jia-Yu Xue a,
Yi Zheng a, Hai-Liang Zhu a,
*
a Institute of Functional Biomolecules, State Key Laboratory of Pharmaceutical Biotechnology, Nanjing University, Nanjing 210093, PR China
b Department of Chemistry, Shangrao Normal College, Shangrao 334000, PR China
Received 25 April 2007; received in revised form 13 October 2007; accepted 22 November 2007
Available online 8 December 2007
Abstract
Twenty-six enamines were synthesized to screen for the antimicrobial activity. Out of the compounds, 22 were reported for the first time.
Their chemical structures including E/Z-configurations were clearly determined by 1H NMR, ESI mass spectra and elemental analyses, coupled
with three selected single-crystal structures. In general, these synthetic compounds were shown to be more effective to inhibit growth of bacteria
than fungi. The most active compound, (E )-ethyl 3-(4-hydroxyphenylamino)-2-(4-chlorophenyl)acrylate (1b), showed considerable antibacterial
activities against Staphylococcus aureus ATCC 6538 with MIC of 0.5 mg/mL and against Pseudomonas fluorescens ATCC 13525 with MIC of
1.5 mg/mL, which was superior to the positive controls penicillin and kanamycin, respectively. Structureeactivity relationship analysis revealed:
as for A-ring, the compounds substituted at 3,5-positions were more active than 2,4-position-substituted derivatives, and halo-substituted analogs
at 2-position had essentially same activities as the 4-position-substituted derivatives. Increase of steric hindrance around the nitrogen atom led to
an inactive compound.
O
O
OEt
R1
A
R1
R2
OEt
H
N
R2
R3
R3
A
NH
B
B
Cl
R4
R4
Cl
E-isomer
Z-isomer
Ó 2007 Elsevier Masson SAS. All rights reserved.
Keywords: Enamine; Antibacterial; Crystal structure; Structureeactivity relationship
1. Introduction
a Schiff base, shows a high similarity to the corresponding
Schiff base in chemical structure, which leads to the concep-
tion that a stable enamine may possess similar biological
properties as a Schiff base does. Our recent work [8] affirmed
their activities and disclosed early structureeactivity relation-
ships (SARs). Most significantly, an E-isomer exhibited higher
antibacterial activity than the corresponding Z-isomer. Sec-
ondly, electron-donating groups on A-ring helped to enhance
the activities, whereas electron-withdrawing group on B-ring
did the same thing. In light of these observations, we were
Since the first Schiff base metal complex was synthesized
by Schiff in 1869, the study of antibacterial, antifungal and
antitumor activities of Schiff bases and their metal complexes
has been widely discussed [1e7]. An enamine, a tautomer of
* Corresponding author. Tel.: þ86 25 8359 2572; fax: þ86 25 8359 2672.
E-mail address: zhuhl@nju.edu.cn (H.-L. Zhu).
0223-5234/$ - see front matter Ó 2007 Elsevier Masson SAS. All rights reserved.
doi:10.1016/j.ejmech.2007.11.026

Z.-P. Xiao et al. / European Journal of Medicinal Chemistry 43 (2008) 1828e1836
1829
O
OEt
HCO2Et
NaH
O
OEt
R1
A
H
N
R2
R3
B
Cl
Cl
R4
R1
OHC
CO2Et
1a - 12a
R2
R3
NH2
EtOH
+
O
60 - 80 °C
R2
R1
R4
OEt
Cl
R3
NH
A
n
a - l
B
R4
Cl
1b - 12b
1
2
3
4
5
6
7
8
9
R1 = R2 = R4= H, R3 = OH;
a
b
c
d
e
f
R1 = R2 = R4 = H, R3 = OH;
R1 = R3 = H, R2 = R4 = OCH3;
R1 = H, R3 = OBn, R2 = R4 = Br;
R1 = H, R3 = OMe, R2 = R4 = Br;
R1 = H, R3 = OH, R2 = R4 = Br;
R1 = R2 = R4 = H, R3 = F;
R1 = R3 = H, R2 = R4 = OCH3;
R1 = H, R3 = OBn, R2 = R4 = Br;
R1 = H, R3 = OMe, R2 = R4 = Br;
R1 = H, R3 = OH, R2= R4 = Br;
R1 = R2 = R4 = H, R3 = F;
R1 = F, R2 = R3 = R4 = H;
R1 = R3 = Cl, R2 = R4 = H;
R1 = R3 = F, R2 = R4 = H;
R1 = R3 = Br, R2 = R4 = H;
R1 = R3 = H, R2 = R4 = Cl;
R1 = R3 = H, R2 = R4 = F;
R1 = F, R2 = R3 = R4 = H;
g
h
i
R1 = R3 = Cl, R2 = R4 = H;
R1 = R3 = F, R2 = R4 = H;
10 R1 = R3 = Br, R2 = R4 = H;
11 R1 = R3 = H, R2 = R4 = Cl;
12 R1 = R3 = H, R2 = R4 = F;
j
k
l
An "a" is for a Z-isomer and a "b" is for an
E-isomer. For example, 1a is a Z-isomer
and 1b is an E-isomer.
Scheme 1.
encouraged to use the most active enamine ((E )-ethyl 3-(3,5-
dichlorophenylamino)-2-(4-chlorophenyl)acrylate (11b) with
MIC of 1.1 mg/mL against Staphylococcus aureus ATCC
6538 and of 25.7 mg/mL against Pseudomonas fluorescens
ATCC 13525) as a precursor compound for further optimiza-
tion and to undertake more extensive study into the SAR, the
results of which are described below.
a dehydration reaction of aldehydes (neo) with different aryl-
amines (aem). The crude products consisted of the mixture of
Z- and E-isomer (1ae12a and 1be12b). Subsequent purifica-
tion by flash chromatography provided 1ae12a and 1be12b
as pure isomers. It is noted that 13 and 14 were only given
as E-isomers, for which steric hindrance around the nitrogen
atom may be responsible. The total yields of Z- and E-isomer
and uncorrected melting points are summarized in Table 1. An
E-isomer had higher melting points than that of the corre-
sponding Z-isomer, but melting points of 9a and 9b was
reversed, which is difficult to explain. The stereochemistry
2. Results and discussion
2.1. Chemistry
In our recent paper [8], we reported that some enamines
were comparable or superior to penicillin and kanamycin in
vitro antimicrobial activity. For the optimization of antibacte-
rial activity, we subsequently shifted our focus to the modifi-
cation of the A-ring and amino group moiety as a means of
increasing potency (Scheme 1). Twenty-six compounds were
synthesized for this consideration, and 22 of them were re-
ported for the first time. The synthesis of compounds
1ae12a and 1be12b followed the general pathway outlined
in Scheme 1, while that of compounds 13 and 14 is shown
in Scheme 2. The designed enamines were prepared by
O
OHC
CO2Et
OEt
EtOH
NH
+
A
N
60 - 80 °C
B
R5
n - o
R5
m
13 - 14
n
R5 = Cl;
R5 = OCH3;
13 R5 = Cl;
14 R5 = OCH3;
o
Scheme 2.

1830
Z.-P. Xiao et al. / European Journal of Medicinal Chemistry 43 (2008) 1828e1836
Table 1
Percent yields and melting points of enamines
Fig. 1 gives perspective views of compounds 2b, 6a and 14
with the atomic labeling system. The dihedral angles between
two phenyl planes are 20.33(16)ꢀ, 74.60(23)ꢀ and 89.91(08)ꢀ
for compounds 2b, 6a and 14, respectively. Although the ethyl
group of 6a and 14 was disordered, the configurations of the
enamines could be identified obviously. Compound 6a was
a Z-isomer and the compounds 2b and 14 were both E-isomers.
As shown in Table 4, there are intramolecular CeH /O
hydrogen bonds in all three crystal structures, intermolecular
NeH/Cl hydrogen bond in 2b and intramolecular NeH/O
hydrogen bond in 6a. Due to the intramolecular N1eH1/
O1 hydrogen bond (in 6a), the 1H NMR signal of H1
(d ¼ 10.31 ppm) was shifted downfield compared to the corre-
sponding resonance in compound 6b (d ¼ 8.53 ppm). The spe-
cific hydrogen resonance (d at about 10 ppm) helped to assign
compounds 1ae12a as Z-isomers. Similarly, based on the crys-
Compound
Formula
Yield, %
86.3
Mp., ꢀC (uncorrected)
1a
C
C
17H16ClNO3
17H16ClNO3
149e150
152e153
101e103
108e109
119e120
122e124
138e139
154e156
175e176
181e183
68e70
1b
2a
C19H20ClNO4
C19H20ClNO4
68
67
76
92
94
96
97
64
97
78
83
2b
3a
C
C
24H20Br2ClNO3
24H20Br2ClNO3
3b
4a
C18H16Br2ClNO3
C18H16Br2ClNO3
4b
5a
C
C
17H14Br2ClNO3
17H14Br2ClNO3
5b
6a
C17H15ClFNO2
C17H15ClFNO2
6b
7a
118e119
85e86
92e93
101e102
117e118
131e132
54e55
C
C
17H15ClFNO2
17H15ClFNO2
7b
8a
C17H14Cl3NO2
C17H14Cl3NO2
8b
9a
1
tal structure of 2b and data of H NMR, 1be12b were deter-
C
C
17H14ClF2NO2
17H14ClF2NO2
mined as E-configuration. As for compounds 13 and 14, their
configurations were not determined by the aforementioned
method because the specific hydrogen signal (bonded with
nitrogen) did not exist. Fortunately, the configuration of com-
pound 14 was determined by X-ray crystal structure. The sim-
ilarity of the 1H NMR spectra of compounds 13 and 14
suggested that compound 13 was also of the E-configuration.
9b
10a
10b
11a
11b
12a
12b
13
C17H14Br2ClNO2
17H14Br2ClNO2
C17H14Cl3NO2
17H14Cl3NO2
C17H14ClF2NO2
17H14ClF2NO2
92e94
C
108e110
115e116
126e128
106e107
118e120
93e94
C
C
C20H20ClNO2
C21H23NO3
93
94
14
88e89
2.3. Biological activity
of all newly reported enamines (1ae10a, 1be10b, 13 and 14)
In order to determine whether the geometrical isomers are
configurationally stable in aqueous media, specified quantities
of the test compounds (1ae12a and 1be12b) were added to
the RPMI-1640 media and heated at 37 ꢀC for 24 h. TLC mon-
itoring indicated that the geometrical isomers are configura-
tionally stable in the test media. The minimum inhibitory
concentration (MIC) was determined for each compound
along with penicillin and kanamycin as standard controls.
All of the synthetic compounds were evaluated for their anti-
microbial activities against four bacteria (Bacillus subtilis
ATCC 6633, Escherichia coli ATCC 35218, P. fluorescens
ATCC 13525 and S. aureus ATCC 6538) and three fungi (As-
pergillus niger ATCC 16404, Candida albicans ATCC 10231
and Trichophyton rubrum ATCC 10218), and the results are
presented in Table 5. These compounds displayed very poor
activity (MICs > 50 mg/mL) against fungal strains, but they
showed good activity against bacterial strains, especially
against S. aureus ATCC 6538 and P. fluorescens ATCC
13525. The most active agents against the two bacterial strains
were compounds 1b, 2b and 5b (with MICs of 0.5, 0.9 and 1.0
against S. aureus ATCC 6538; 1.5, 1.6 and 3.7 against P. fluo-
rescens ATCC 13525). As expected, their Z-isomers (com-
pounds 1a, 2a and 5a) showed much lower inhibitions under
the same conditions. This indicated that E-isomer was more
active than Z-isomer, which agreed with the published obser-
vations [8]. Modifications of the A-ring moiety resulted in
three compounds (1b, 2b and 5b) which showed a significant
increase in activity against P. fluorescens ATCC 13525 and
a slight increase against S. aureus ATCC 6538 compared to
the lead compound 11b.
1
was determined by their H NMR spectra together with the
crystal structures of the selected compounds.
2.2. Description of the crystal structure and
determination of stereochemistry
Among these compounds, the crystal structures of com-
pounds 2b, 6a and 14 were determined by X-ray diffraction
analysis. The crystallographic data of them are presented in
Table 2, and their selected bond lengths/angles and torsion
angles are given in Table 3. The bond angles related to atoms
C13 and C14 are all in normal values. The bond distances of
˚
C13eC14 (1.343(8)e1.358(3) A) conformed to the value for
a C]C double bond, while the bond lengths of C13eN1
˚
(1.347(7)e1.361(3) A) were shorter than standard CeN sin-
˚
gle bond (1.48 A) but longer than C]N double bond
˚
(1.28 A), which might be induced by the conjugation of the
p orbital of N1 and the p molecular orbital of C13eC14 dou-
ble bond. There was another evidence to prove that C13eC14
were double bonds. The proof is that the torsion angles of
N1eC13eC14eC15 and N1eC13eC14eC7 were close to
0ꢀ or 180ꢀ (Table 3). Namely, N1eC13eC14eC15eC7
was coplanar. In fact, the N1, H13, C13, C14, C15 and C7
were in a least-square plane with the mean deviations of
˚
0.014, 0.015 and 0.0596 A for 2b, 6a and 14, respectively.
Compounds 2b, 6a and 14 were therefore identified as en-
amines. By comparing their 1H NMR spectra (2b, 6a and
14) with others all synthetic compounds were determined as
enamines.

Z.-P. Xiao et al. / European Journal of Medicinal Chemistry 43 (2008) 1828e1836
1831
Table 2
Crystal structure data for 2b, 6a and 14
Compounds
2b
6a
14
Formula
C19H20ClNO4
361.81
C17H15ClFNO2
319.75
C21H23NO3
337.40
Mr
Crystal size/mm3
Crystal system
Space group
0.30 ꢁ 0.20 ꢁ 0.10
Triclinic
P-1
0.30 ꢁ 0.20 ꢁ 0.10
Orthorhombic
P212121
0.30 ꢁ 0.20 ꢁ 0.20
Triclinic
P-1
˚
a/A
9.6010(19)
9.6071(19)
10.368(2)
77.84(3)
8.2330(16)
10.618(2)
17.944(4)
90
8.9720(18)
9.6660(19)
11.696(2)
107.16(3)
100.58(3)
99.09(3)
˚
b/A
˚
c/A
a/ꢀ
b/ꢀ
g/ꢀ
75.42(3)
113.89(3)
904.7(3)
90
90
3
˚
V/A
1568.6(5)
4
1.354
928.1(3)
2
1.207
Z
2
1.328
Dc/(g/cm3)
m/mmꢂ1
F(000)
0.234
380
0.260
664
0.08
360
Max. and min. trans.
q Range/ꢀ
0.9770 and 0.9331
2.07/25.25
0/11, ꢂ11/11, ꢂ12/12
3493/3280
3280/0/234
0.0280
0.9745 and 0.9261
2.23/26.02
0/10, ꢂ13/13, ꢂ22/0
3368/3060
3060/41/203
0.0900
0.9841 and 0.9763
1.88/25.00
0/10, ꢂ11/11, ꢂ13/13
3481/3251
3251/24/231
0.0311
Index range (h, k, l )
Reflections collected/unique
Data/restraints/parameters
Rint
Goodness-of-fit on F2
R1, wR2 [I > 2s(I )]
R1, wR2
1.017
1.051
0.0739/0.1601
0.1587/0.2116
1.062
0.0606/0.1598
0.1053/0.1826
0.0514/0.1096
0.0891/0.1247
0.017(2)
Extinction coefficient
3
(Dr)max, (Dr)min/(e/A )
˚
0.210/ꢂ0.203
0.346/ꢂ0.233
0.237/ꢂ0.239
P
P
R1 ¼ j(jFoj ꢂ jFcj)j/ jFoj.
P
P
wR2 ¼ [ w(jFoj ꢂ jFcj)2/ wjFoj2]1/2, w ¼ [s2(Fo)2 þ (0.1(max(0, Fo2) þ 2F2c)/3)2]ꢂ1
.
Scanning Table 5, we found that there is no clear SAR
against P. fluorescens ATCC 13525, so the SAR analysis is
based on the results of growth inhibition against S. aureus
ATCC 6538. Inspection of the chemical structure of the final
compound (Scheme 1) suggested that it could be divided into
two subunits: A-ring and B-ring. A series of compounds
substituted at nitrogen or on A-ring in different positions
were synthesized to determine how the substituents affected
the antibacterial activities. A comparison of the substitution
pattern on A-ring demonstrated that the 2-position-substituted
analogs were comparable to the activities of the 4-position-
substituted derivatives such as 6a, 7a, 6b and 7b. However,
introduction of groups at 3,5-positions afforded much more
potent compounds (11a, 11b, 12a and 12b) than 2,4-position-
substituted analogs (8a, 8b, 9a and 9b). Most significantly,
and 14) were determined by X-ray diffraction analysis. In gen-
eral, these synthesized compounds were shown to be more ef-
fective to inhibit growth of bacteria than fungi. As a result of
optimization for chemical structure of enamine 11b, com-
pounds 1b, 2b and 5b showed considerable antibacterial
activities against S. aureus ATCC 6538 (MIC ¼ 0.5, 0.9 and
1.0 mg/mL) and P. fluorescens ATCC 13525 (MIC ¼ 1.5, 1.6
and 3.7 mg/mL). As for A-ring, the SAR disclosed that intro-
duction of groups at 3,5-positions gave much more potent
compounds than that at 2,4-positions, and halo-substituted an-
alogs at 2-position had essentially same activities against S.
aureus ATCC 6538 and P. fluorescens ATCC 13525 as those
at 4-position. Increase of steric hindrance around the nitrogen
atom led to an inactive compound.
compounds (1b, 6b, 11b, 2b and 12b) with strong electron-
donating substituents on the A-ring had greater antibacterial ac-
tivity, which was illustrated by the potency order CH3O > Cl > F.
Replacement of a hydroxy group (5b) at 4-position on A-ring
by a methoxy or benzoxy group (3b and 4b) led to a slight de-
crease in antibacterial activity. Inactive compounds 13 and 14
disclose that increase of the steric hindrance around N atom sig-
nificantly decreased the antibacterial activity.
4. Experiments
4.1. Crystallographic studies
X-ray single-crystal diffraction data for compounds 2b, 6a
and 14 were collected on a Bruker SMARTAPEX CCD diffrac-
˚
tometer at 293(2) K using Mo Ka radiation (l ¼ 0.71073 A) by
the u scan mode. The program SAINTwas used for the integra-
tion of the diffraction profiles. All the structures were solved by
direct methods using the SHELXS program of the SHELXTL
package and refined by full-matrix least-squares methods with
SHELXL [9]. All non-hydrogen atoms of compounds 2b, 6a
and 14 were refined with anisotropic thermal parameters except
3. Conclusions
Twenty-six enamines (1ae12a, 1be12b, 13 and 14) were
synthesized and the molecular structures of three (2b, 6a

1832
Z.-P. Xiao et al. / European Journal of Medicinal Chemistry 43 (2008) 1828e1836
Table 3
Selected bond lengths (A) and torsion angles ( ) of compounds 2b, 6a and 14
Incubation was continued at room temperature for 4e5 h.
ꢀ
˚
The content of each well was removed, and 100 mL of isopro-
panol containing 5% 1 mol/L HCl was added to extract the
dye. After 12 h of incubation at room temperature, the optical
density (OD) was measured with a microplate reader at
550 nm. The observed MICs are presented in Table 5.
Compounds 2b 6a 14
˚
Bond lengths (A)
C1eN1
C7eC14
1.418(3)
1.400(7)
1.425(3)
1.485(3)
1.353(3)
1.345(3)
1.467(3)
1.450(3)
1.499(8)
1.347(7)
1.343(8)
1.475(3)
1.361(3)
1.358(3)
1.471(3)
1.447(3)
C13eN1
C13eC14
C14eC15
C16eO2
4.3. Chemistry
1.476(8)
1.4006(11)/
1.4008(11)a
1.4995(12)/
1.4995(11)a
All chemicals (reagent grade) used were purchased from
Aldrich (USA). Separation of the compounds by column chro-
matography was carried out with silica gel 60 (200e300 mesh
ASTM, E. Merck). The quantity of silica gel used was 50e100
times the weight charged on the column. Then, the eluates
were monitored using TLC. Melting points (uncorrected)
were determined on a XT4 MP apparatus (Taike Corp., Bei-
jing, China). ESI mass spectra were obtained on a Mariner
C16eC17
1.503(4)
1.5143(12)/
1.5092(11)a
Bond angles (ꢀ)
C14eC13eN1
126.6(2)
115.3(2)
123.5(2)
121.2(2)
125.1(2)
127.2(6)
119.7(6)
118.2(6)
122.1(5)
125.8(5)
130.1(2)
113.5(2)
126.0(2)
119.8(2)
119.2(2)
C13eC14eC15
C13eC14eC7
C15eC14eC7
C13eN1eC1
Torsion angles (ꢀ)
N1eC13eC14eC15
N1eC13eC14eC7
C8eC7eC14eC13
C12eC7eC14eC13
C13eC14eC15eO1
C13eC14eC15eO2
C14eC13eN1eC1
C6eC1eN1eC13
C2eC1eN1eC13
a
1
System 5304 mass spectrometer, and H NMR spectra were
ꢂ178.1(2)
2.4(4)
3.6(10)
ꢂ179.4(6)
ꢂ117.8(7)
57.4(8)
175.4(2)
ꢂ14.0(4)
134.6(3)
ꢂ48.4(3)
ꢂ10.1(4)
167.9(2)
164.3(2)
147.3(2)
ꢂ34.5(4)
recorded on a Bruker PX500 or DPX300 spectrometer at
25 ꢀC with TMS and solvent signals allotted as internal stan-
dards. Chemical shifts were reported in ppm (d). Elemental
analyses were performed on a CHN-O-Rapid instrument and
were within ꢃ0.4% of the theoretical values.
ꢂ121.1(3)
59.3(3)
ꢂ2.3(4)
2.7(10)
177.6(2)
ꢂ176.2(3)
ꢂ159.1(3)
21.8(4)
ꢂ176.4(6)
ꢂ171.7(6)
11.8(9)
ꢂ169.9(6)
4.3.1. General synthesis method of enamines
The starting materials (aldehyde neo) for the synthesis of
enamines have been previously published [11e13]. Equimolar
quantities (6 mmol) of the appropriate substituted aromatic
amines and the aldehyde (neo) in absolute alcohol (18 mL)
were heated at 70e80 ꢀC for 1e4 h. The excess solvent was
removed under reduced pressure. The residue was purified
by a flash chromatography with EtOAcepetroleum ether to af-
ford two fractions. The first fraction gave a Z-isomer, and the
second fraction gave an E-isomer. But as for compounds 13
and 14, chromatography was unnecessary due to the formation
of only one isomer. They were alternatively purified by crys-
tallization from EtOAcepetroleum.
There are two values for disordered C16(A), C16(B) or C17(A), C17(B).
disordered C16A and C16B in 6a and C17A and C17B in 14. All
hydrogen atoms were generated theoretically onto the parent
atoms and refined isotropically with fixed thermal factors ex-
cept that the hydrogen atom of N1 in 2b was located in a differ-
ence Fourier map.
4.2. Antimicrobial activity
The antibacterial activities of the synthesized compounds
were tested against B. subtilis ATCC 6633, E. coli ATCC
35218, P. fluorescens ATCC 13525 and S. aureus ATCC
6538 using MH medium. The antifungal activities of the com-
pounds were tested against A. niger ATCC 16404, C. albicans
ATCC 10231 and T. rubrum ATCC 10218 using RPMI-1640
medium. The MICs of the test compounds were determined
by a colorimetric method using the dye MTT [10]. A stock so-
lution of the synthesized compound (50 mg/mL) in DMSO was
prepared and graded quantities of the test compounds were in-
corporated in specified quantity of sterilized liquid medium
(MH medium for antibacterial activity and RPMI-1640 me-
dium for antifungal activity). A specified quantity of the me-
dium containing the test compound was poured into
microtitration plates. Suspension of the microorganism was
prepared to contain approximately 105 cfu/mL and applied to
microtitration plates with serially diluted compounds in
DMSO to be tested and incubated at 37 ꢀC for 24 and 48 h
for bacteria and fungi, respectively. After the MICs were visu-
ally determined on each of the microtitration plates, 50 mL of
PBS containing 2 mg of MTT/mL was added to each well.
4.3.2. (Z )-Ethyl 3-(4-hydroxyphenylamino)-
2-(4-chlorophenyl)acrylate (1a)
Light yellow powder, 1H NMR (500 MHz, DMSO-d6): 1.21
(t, J ¼ 7.0 Hz, 3H); 4.17 (q, J ¼ 7.0 Hz, 2H); 6.73 (d, J ¼ 8.8 Hz,
2H); 7.11 (d, J ¼ 8.8 Hz, 2H); 7.32 (d, J ¼ 8.6 Hz, 2H); 7.37
(d, J ¼ 8.6 Hz, 2H); 7.53 (d, J ¼ 13.1 Hz, 1H); 10.19 (d,
J ¼ 13.2 Hz, 1H). MS (ESI): 318.1 (C17H17ClNO3, [M þ H]þ).
Anal. Calcd for C17H16ClNO3: C, 64.26; H, 5.08; N, 4.41;
found: C, 64.37; H, 5.06; N, 4.38.
4.3.3. (E )-Ethyl 3-(4-hydroxphenylamino)-
2-(4-chlorophenyl)acrylate (1b)
Light yellow crystal, 1H NMR (300 MHz, DMSO-d6): 1.18
(t, J ¼ 6.9 Hz, 3H); 4.08 (q, J ¼ 6.9 Hz, 2H); 6.70 (d,
J ¼ 8.8 Hz, 2H); 6.99 (d, J ¼ 8.9 Hz, 2H); 7.26 (d,
J ¼ 8.6 Hz, 2H); 7.42 (d, J ¼ 8.6 Hz, 2H); 7.92 (s, 1H). MS
(ESI): 318.1 (C17H17ClNO3, [M þ H]þ). Anal. Calcd for
C17H16ClNO3: C, 64.26; H, 5.08; N, 4.41; found: C, 64.37;
H, 5.06; N, 4.38.

Z.-P. Xiao et al. / European Journal of Medicinal Chemistry 43 (2008) 1828e1836
1833
Fig. 1. Molecular structures of 2b, 6a and 14. Displacement ellipsoids are drawn at the 30% probability level.
4.3.4. (Z )-Ethyl 3-(3,5-dimethoxyphenylamino)-
(C19H21ClNO4, [M þ H]þ). Anal. Calcd for C19H20ClNO4: C,
2-(4-chlorophenyl)acrylate (2a)
63.07; H, 5.57; N, 3.87; found: C, 63.13; H, 5.55; N, 3.84.
1
White powder, H NMR (500 MHz, DMSO-d6): 1.20 (t,
J ¼ 7.1 Hz, 3H); 3.74 (s, 6H); 4.26 (q, J ¼ 7.1 Hz, 2H); 6.16
(d, J ¼ 1.9 Hz, 1H); 6.48 (d, J ¼ 1.8 Hz, 2H); 7.35 (d,
J ¼ 8.6 Hz, 2H); 7.38 (d, J ¼ 8.8 Hz, 2H); 7.68 (d,
J ¼ 12.7 Hz, 1H); 10.26 (d, J ¼ 12.8 Hz, 1H). MS (ESI): 362.1
4.3.5. (E )-Ethyl 3-(3,5-dimethoxyphenylamino)-
2-(4-chlorophenyl)acrylate (2b)
1
Colorless crystal, H NMR (300 MHz, DMSO-d6): 1.19 (t,
J ¼ 7.1 Hz, 3H); 3.70 (s, 6H); 4.10 (q, J ¼ 7.1 Hz, 2H); 6.12
(d, J ¼ 2.1 Hz, 1H); 6.34 (d, J ¼ 2.2 Hz, 2H); 7.25 (d,
J ¼ 8.6 Hz, 2H); 7.40 (d, J ¼ 8.6 Hz, 2H); 7.99 (s, 1H). MS
(ESI): 362.1 (C19H21ClNO4, [M þ H]þ). Anal. Calcd for
C19H20ClNO4: C, 63.07; H, 5.57; N, 3.87; found: C, 63.15;
H, 5.56; N, 3.87.
Table 4
Hydrogen-bond geometry (A, ꢀ) in compounds 2b, 6a and 14
˚
DeH/A
DeH
H/A
D/A
DeH/A
Compound 2b
C13eH13/O1
N1eH1/Cl1#1
Compound 6a
N1eH1/O1
C16BeH16B/O1
Compound 14
C13eeH13/O1
0.930
0.88(3)
2.390
3.03(3)
2.768(3)
3.848(3)
104.1
156(2)
4.3.6. (Z )-Ethyl 3-(4-benzyloxy-3,5-dibromophenylamino)-
2-(4-chlorophenyl)acrylate (3a)
0.86
0.97
2.10
2.28
2.711(7)
2.630(3)
127.9
100.3
1
White powder, H NMR (300 MHz, DMSO-d6): 1.22 (t,
J ¼ 7.1 Hz, 3H); 4.20 (q, J ¼ 7.0 Hz, 2H); 4.93 (s, 2H); 7.39
(m, 5H); 7.45 (d, J ¼ 8.3 Hz, 2H); 7.60 (d, J ¼ 8.1 Hz, 2H);
7.66 (d, J ¼ 12.6 Hz, 1H); 7.77 (s, 2H); 10.20 (d, J ¼ 12.6 Hz,
0.93
2.36
2.760(3)
105.9
Symmetry code: #1 ꢂx þ 1, ꢂy þ 1, ꢂz þ 2.

1834
Z.-P. Xiao et al. / European Journal of Medicinal Chemistry 43 (2008) 1828e1836
Table 5
MICs of the synthetic compounds
4.3.9. (E )-Ethyl 3-(3,5-dibromo-4-methoxyphenylamino)-2-
(4-chlorophenyl)acrylate (4b)
1
Compound
Minimum inhibitory concentrations (mg/mL)
Colorless crystal, H NMR (300 MHz, DMSO-d6): 1.19 (t,
J ¼ 7.1 Hz, 3H); 3.74 (s, 3H); 4.11 (q, J ¼ 7.0 Hz, 2H); 7.25
(d, J ¼ 8.3 Hz, 2H); 7.45 (d, J ¼ 8.2 Hz, 2H); 7.48 (s, 2H);
7.91 (d, J ¼ 13.0 Hz, 1H); 8.65 (d, J ¼ 13.0 Hz, 1H). MS
(ESI): 487.8 (C18H17Br2ClNO3, [M þ H]þ). Anal. Calcd for
C18H16Br2ClNO3: C, 44.16; H, 3.29; N, 2.86; found: C,
44.35; H, 3.27; N, 2.84.
A
B
C
D
E
F
G
1a
1b
>50
>50
>50
>50
>50
>50
43.3
>50
>50
>50
49.8
>50
46.6
>50
>50
>50
>50
>50
>50
>50
>50
>50
>50
48.2
>50
>50
e
38.9
>50
>50
>50
>50
>50
48.6
>50
>50
>50
43.4
>50
>50
>50
>50
>50
47.3
48
13.1
1.5
44.9
0.5
>50
>50
>50
>50
>50
>50
>50
>50
>50
>50
>50
>50
>50
>50
>50
>50
>50
>50
>50
>50
>50
>50
>50
>50
>50
>50
7.8
>50
>50
>50
>50
>50
>50
>50
>50
>50
>50
>50
>50
>50
>50
>50
>50
>50
>50
>50
>50
>50
>50
>50
>50
>50
>50
3.9
>50
>50
>50
>50
>50
>50
>50
>50
>50
>50
>50
>50
>50
>50
>50
>50
>50
>50
>50
>50
>50
>50
>50
>50
>50
>50
3.9
2a
2b
36.3
1.6
>50
0.9
3a
3b
>50
8.5
>50
3.4
4a
4b
48.1
6.1
47.7
2.2
4.3.10. (Z )-Ethyl 3-(3,5-dibromo-4-hydroxyphenylamino)-
2-(4-chlorophenyl)acrylate (5a)
5a
5b
>50
3.7
33.5
1.0
Light yellow powder, 1H NMR (300 MHz, DMSO-d6): 1.22
(t, J ¼ 7.1 Hz, 3H); 4.19 (q, J ¼ 7.0 Hz, 2H); 7.35 (d,
J ¼ 8.8 Hz, 2H); 7.40 (d, J ¼ 8.8 Hz, 2H); 7.59 (d,
J ¼ 12.5 Hz, 1H); 7.87 (s, 2H); 10.16 (d, J ¼ 12.4 Hz, 1H).
MS (ESI): 473.9 (C17H15Br2ClNO3, [M þ H]þ). Anal. Calcd
for C17H14Br2ClNO3: C, 42.94; H, 2.97; N, 2.95; found: C,
42.83; H, 2.96; N, 2.94.
6a
6b
>50
>50
46
>50
35.6
>50
41.2
>50
12.3
>50
40.9
32.1
8.2
7a
7b
>50
>50
7.1
8a
8b
9a
9b
>50
>50
23.8
4.5
10a
10b
>50
>50
>50
>50
>50
13.5
>50
>50
e
4.3.11. (E )-Ethyl 3-(3,5-dibromo-4-hydroxyphenylamino)-
2-(4-chlorophenyl)acrylate (5b)
11a
11b
>50
25.7
>50
31.5
38.5
41.5
e
>50
1.1
Light yellow powder, 1H NMR (300 MHz, DMSO-d6): 1.18
(t, J ¼ 7.1 Hz, 3H); 4.10 (q, J ¼ 7.0 Hz, 2H); 6.78 (s, 1H); 7.24
(d, J ¼ 8.2 Hz, 2H); 7.40 (s, 2H); 7.43 (d, J ¼ 8.4 Hz, 2H);
7.87 (d, J ¼ 12.3 Hz, 1H); 8.65 (d, J ¼ 12.4 Hz, 1H). MS
(ESI): 473.9 (C17H15Br2ClNO3, [M þ H]þ). Anal. Calcd for
C17H14Br2ClNO3: C, 42.94; H, 2.97; N, 2.95; found: C,
42.50; H, 2.99; N, 2.96.
12a
12b
>50
1.9
13
14
>50
>50
e
Ketoconazole
Kanamycin
Penicillin
0.39
0.78
3.9
e
3.9
e
1
e
e
e
2
e
e
e
Note: A, Bacillus subtilis ATCC 6633; B, Escherichia coli ATCC 35218; C,
Pseudomonas fluorescens ATCC 13525; D, Staphylococcus aureus ATCC
6538; E, Aspergillus niger ATCC 16404; F, Candida albicans ATCC 10231;
G, Trichophyton rubrum ATCC 10218.
4.3.12. (Z )-Ethyl 3-(4-fluorophenylamino)-2-
(4-chlorophenyl)acrylate (6a)
1
White powder, H NMR (300 MHz, DMSO-d6): 1.22 (t,
J ¼ 7.1 Hz, 3H); 4.19 (q, J ¼ 7.1 Hz, 2H); 7.16 (t, J ¼ 8.4 and
9.1 Hz, 2H); 7.34 (m, 4H); 7.34 (d, J ¼ 8.9 Hz, 2H); 7.99 (d,
J ¼ 12.5 Hz, 1H); 10.31 (d, J ¼ 12.6 Hz, 1H). MS (ESI): 320.1
(C17H16ClFNO2, [M þ H]þ). Anal. Calcd for C17H15ClFNO2:
C, 63.86; H, 4.73; N, 4.38; found: C, 63.94; H, 4.70; N, 4.34.
1H). MS (ESI): 564.0 (C24H21Br2ClNO3, [M þ H]þ). Anal.
Calcd for C24H20Br2ClNO3: C, 50.96; H, 3.56; N, 2.48; found:
C, 50.75; H, 3.55; N, 2.47.
4.3.7. (E )-Ethyl 3-(4-benzyloxy-3,5-dibromophenylamino)-
2-(4-chlorophenyl)acrylate (3b)
4.3.13. (E )-Ethyl 3-(4-fluorophenylamino)-2-
1
White powder, H NMR (300 MHz, DMSO-d6): 1.20 (t,
(4-chlorophenyl)acrylate (6b)
1
J ¼ 7.1 Hz, 3H); 4.12 (q, J ¼ 7.0 Hz, 2H); 4.92 (s, 2H); 7.26
(d, J ¼ 8.4 Hz, 2H); 7.44 (m, 5H); 7.53 (s, 2H); 7.56 (d,
J ¼ 8.0 Hz, 2H); 7.93 (d, J ¼ 13.2 Hz, 1H); 8.68 (d,
J ¼ 13.0 Hz, 1H). MS (ESI): 564.1 (C24H21Br2ClNO3,
[M þ H]þ). Anal. Calcd for C24H20Br2ClNO3: C, 50.96; H,
3.56; N, 2.48; found: C, 50.82; H, 3.56; N, 2.47.
Colorless crystal, H NMR (300 MHz, DMSO-d6): 1.19 (t,
J ¼ 6.9 Hz, 3H); 4.10 (q, J ¼ 7.0 Hz, 2H); 7.14 (m, 4H); 7.27
(d, J ¼ 8.2 Hz, 2H); 7.44 (d, J ¼ 8.4 Hz, 2H); 7.97 (d,
J ¼ 12.9 Hz, 1H); 8.53 (d, J ¼ 12.2 Hz, 1H). MS (ESI): 320.1
(C17H16ClFNO2, [M þ H]þ). Anal. Calcd for C17H15ClFNO2:
C, 63.86; H, 4.73; N, 4.38; found: C, 63.94; H, 4.70; N, 4.34.
4.3.8. (Z )-Ethyl 3-(3,5-dibromo-4-methoxyphenylamino)-2-
4.3.14. (Z )-Ethyl 3-(2-fluorophenylamino)-2-
(4-chlorophenyl)acrylate (4a)
(4-chlorophenyl)acrylate (7a)
1
1
White powder, H NMR (500 MHz, DMSO-d6): 1.21 (t,
White powder, H NMR (500 MHz, DMSO-d6): 1.22 (t,
J ¼ 7.1 Hz, 3H); 3.75 (s, 3H); 4.19 (q, J ¼ 7.1 Hz, 2H); 7.35
(d, J ¼ 8.6 Hz, 2H); 7.39 (d, J ¼ 8.6 Hz, 2H); 7.64 (d,
J ¼ 12.5 Hz, 1H); 7.72 (s, 2H); 10.17 (d, J ¼ 12.5 Hz, 1H).
MS (ESI): 487.9 (C18H17Br2ClNO3, [M þ H]þ). Anal. Calcd
for C18H16Br2ClNO3: C, 44.16; H, 3.29; N, 2.86; found: C,
44.34; H, 3.26; N, 2.88.
J ¼ 7.1 Hz, 3H); 4.21 (q, J ¼ 7.0 Hz, 2H); 7.02 (m, 1H); 7.17
(t, J ¼ 7.6 Hz, 1H); 7.29 (m, 1H); 7.37 (d, J ¼ 8.6 Hz, 2H);
7.41 (d, J ¼ 8.8 Hz, 2H); 7.64 (t, J ¼ 8.6 Hz, 1H); 7.77 (d,
J ¼ 12.5 Hz, 1H); 10.50 (d, J ¼ 12.6 Hz, 1H). MS (ESI): 320.1
(C17H16ClFNO2, [M þ H]þ). Anal. Calcd for C17H15ClFNO2:
C, 63.86; H, 4.73; N, 4.38; found: C, 63.66; H, 4.76; N, 4.40.

Z.-P. Xiao et al. / European Journal of Medicinal Chemistry 43 (2008) 1828e1836
1835
4.3.15. (E )-Ethyl 3-(2-fluorophenylamino)-2-
J ¼ 8.8 Hz, 1H); 7.76 (d, J ¼ 12.2 Hz, 1H); 7.88 (s, 1H); 10.75
(d, J ¼ 12.5 Hz, 1H). MS (ESI): 457.9 (C17H15Br2ClNO2,
[M þ H]þ). Anal. Calcd for C17H14Br2ClNO2: C, 44.43; H,
3.07; N, 3.05; found: C, 44.53; H, 3.04; N, 3.02.
(4-chlorophenyl)acrylate (7b)
1
Colorless crystal, H NMR (500 MHz, DMSO-d6): 1.18 (t,
J ¼ 7.1 Hz, 3H); 4.10 (q, J ¼ 7.0 Hz, 2H); 7.05 (t, J ¼ 5.5 and
7.0 Hz, 1H); 7.15 (t, J ¼ 7.7 Hz, 1H); 7.22 (t, J ¼ 8.4 Hz,
1H); 7.29 (d, J ¼ 8.3 Hz, 2H); 7.33 (d, J ¼ 8.3 Hz, 1H); 7.45
(d, J ¼ 8.3 Hz, 2H); 7.98 (d, J ¼ 12.0 Hz, 1H); 8.83 (d,
J ¼ 12.1 Hz, 1H). MS (ESI): 320.1 (C17H16ClFNO2,
[M þ H]þ). Anal. Calcd for C17H15ClFNO2: C, 63.86; H,
4.73; N, 4.38; found: C, 63.66; H, 4.70; N, 4.39.
4.3.21. (E )-Ethyl 3-(2,4-dibromophenylamino)-2-
(4-chlorophenyl)acrylate (10b)
1
Colorless crystal, H NMR (500 MHz, DMSO-d6): 1.20 (t,
J ¼ 7.3 Hz, 3H); 4.13 (q, J ¼ 7.4 Hz, 2H); 7.36 (d, J ¼ 8.2 Hz,
2H); 7.40 (d, J ¼ 8.8 Hz, 2H); 7.52 (m, 2H); 7.55 (d, J ¼ 2.2 Hz,
1H); 7.81 (d, J ¼ 12.8 Hz, 1H); 8.01 (d, J ¼ 13.1 Hz, 1H). MS
(ESI): 457.9 (C17H15Br2ClNO2, [M þ H]þ). Anal. Calcd for
C17H14Br2ClNO2: C, 44.43; H, 3.07; N, 3.05; found: C, 44.54;
H, 3.06; N, 3.01.
4.3.16. (Z )-Ethyl 3-(2,4-dichlorophenylamino)-2-
(4-chlorophenyl)acrylate (8a)
1
White powder, H NMR (500 MHz, DMSO-d6): 1.22 (t,
J ¼ 7.4 Hz, 3H); 4.22 (q, J ¼ 7.0 Hz, 2H); 7.38 (d, J ¼ 8.9 Hz,
3H); 7.42 (d, J ¼ 8.9 Hz, 2H); 7.66 (d, J ¼ 2.5 Hz, 1H); 7.70
(d, J ¼ 9.2 Hz, 1H); 7.80 (d, J ¼ 12.2 Hz, 1H); 10.78 (d,
J ¼ 12.2 Hz, 1H). MS (ESI): 370.0 (C17H15Cl3NO2,
[M þ H]þ). Anal. Calcd for C17H14Cl3NO2: C, 55.09; H, 3.81;
N, 3.78; found: C, 55.29; H, 3.78; N, 3.74.
4.3.22. (Z )-Ethyl 3-(3,5-dichlorophenylamino)-2-
(4-chlorophenyl)acrylate (11a)
White powder, 1H NMR (500 MHz, DMSO-d6): 1.22
(t, J ¼ 7.1 Hz, 3H); 4.20 (q, J ¼ 7.1 Hz, 2H); 7.15 (s, 1H); 7.37 (d,
J ¼ 8.4 Hz, 2H); 7.41 (d, J ¼ 8.4 Hz, 2H); 7.52 (s, 2H); 7.71 (d,
J ¼ 12.6 Hz, 1H); 10.28 (d, J ¼ 12.5 Hz, 1H). MS (ESI): 370.0
(C17H15Cl3NO2, [M þ H]þ). Anal. Calcd for C17H14Cl3NO2: C,
55.09; H, 3.81; N, 3.78; found: C, 55.13; H, 3.80; N, 3.75.
4.3.17. (E )-Ethyl 3-(2,4-dichlorophenylamino)-2-
(4-chlorophenyl)acrylate (8b)
1
White powder, H NMR (500 MHz, DMSO-d6): 1.16 (t,
J ¼ 7.0 Hz, 3H); 4.09 (q, J ¼ 7.0 Hz, 2H); 7.31 (d, J ¼ 8.2 Hz,
2H); 7.34 (d ꢁ d, J ¼ 8.9, 2.5 Hz, 1H); 7.42 (d, J ¼ 13.4 Hz,
1H); 7.43 (d, J ¼ 8.9 Hz, 1H); 7.46 (d, J ¼ 8.6 Hz, 2H); 7.53
(d, J ¼ 2.5 Hz, 1H); 7.96 (d, J ¼ 13.1 Hz, 1H). MS (ESI):
369.0 (C17H15Cl3NO2, [M þ H]þ). Anal. Calcd for
C17H14Cl3NO2: C, 55.09; H, 3.81; N, 3.78; found: C, 55.24;
H, 3.77; N, 3.76.
4.3.23. (E )-Ethyl 3-(3,5-dichlorophenylamino)-2-
(4-chlorophenyl)acrylate (11b)
Colorless crystal, 1H NMR (500 MHz, DMSO-d6): 1.19
(t, J ¼ 6.9 Hz, 3H); 4.12 (q, J ¼ 7.0 Hz, 2H); 7.11 (s, 1H); 7.26 (d,
J ¼ 7.9 Hz, 2H); 7.27 (s, 2H); 7.46 (d, J ¼ 8.2 Hz, 2H); 7.97 (d,
J ¼ 12.9 Hz, 1H); 8.81 (d, J ¼ 12.9 Hz, 1H). MS (ESI): 370.1
(C17H15Cl3NO2, [M þ H]þ). Anal. Calcd for C17H14Cl3NO2: C,
55.09; H, 3.81; N, 3.78; found: C, 55.12; H, 3.82; N, 3.80.
4.3.18. (Z )-Ethyl 3-(2,4-difluorophenylamino)-2-
(4-chlorophenyl)acrylate (9a)
4.3.24. (Z )-Ethyl 3-(3,5-difluorophenylamino)-2-
1
White powder, H NMR (300 MHz, DMSO-d6): 1.22 (t,
(4-chlorophenyl)acrylate (12a)
1
J ¼ 7.0 Hz, 3H); 4.20 (q, J ¼ 7.3 Hz, 2H); 7.08 (t, J ¼ 7.8 Hz,
1H); 7.36 (d, J ¼ 8.6 Hz, 3H); 7.40 (d, J ¼ 8.8 Hz, 2H); 7.68
(m, 1H); 7.73 (d, J ¼ 12.5 Hz, 1H); 10.43 (d, J ¼ 12.2 Hz,
1H). MS (ESI): 338.1 (C17H15ClF2NO2, [M þ H]þ). Anal.
Calcd for C17H14ClF2NO2: C, 60.45; H, 4.18; N, 4.15; found:
C, 60.26; H, 4.17; N, 4.18.
Colorless crystal, H NMR (300 MHz, DMSO-d6): 1.19 (t,
J ¼ 7.1 Hz, 3H); 4.18 (q, J ¼ 7.1 Hz, 2H); 6.77 (d, J ¼ 9.3 Hz,
1H); 7.17 (d, J ¼ 8.1 Hz, 2H); 7.34 (d, J ¼ 8.9 Hz, 2H); 7.38
(d, J ¼ 8.4 Hz, 2H); 7.65 (d, J ¼ 12.5 Hz, 1H); 10.30 (d,
J ¼ 12.8 Hz, 1H). MS (ESI): 338.1 (C17H15ClF2NO2,
[M þ H]þ). Anal. Calcd for C17H14ClF2NO2: C, 60.45; H,
4.18; N, 4.15; found: C, 60.48; H, 4.19; N, 4.16.
4.3.19. (E )-Ethyl 3-(2,4-difluorophenylamino)-2-
(4-chlorophenyl)acrylate (9b)
4.3.25. (E )-Ethyl 3-(3,5-difluorophenylamino)-2-
1
Colorless crystal, H NMR (500 MHz, DMSO-d6): 1.22 (t,
(4-chlorophenyl)acrylate (12b)
1
J ¼ 7.3 Hz, 3H); 4.20 (q, J ¼ 7.4 Hz, 2H); 7.07 (t, J ¼ 8.8 Hz,
1H); 7.28 (d, J ¼ 8.3 Hz, 1H); 7.36 (d, J ¼ 8.5 Hz, 2H); 7.42
(d, J ¼ 8.3 Hz, 2H); 7.68 (m, 1H); 7.72 (d, J ¼ 12.0 Hz, 1H);
7.86 (d, J ¼ 12.2 Hz, 1H). MS (ESI): 338.1 (C17H15ClF2NO2,
[M þ H]þ). Anal. Calcd for C17H14ClF2NO2: C, 60.45; H,
4.18; N, 4.15; found: C, 60.25; H, 4.20; N, 4.19.
Colorless crystal, H NMR (500 MHz, DMSO-d6): 1.19 (t,
J ¼ 7.2 Hz, 3H); 4.11 (q, J ¼ 7.2 Hz, 2H); 6.75 (d, J ¼ 9.1 Hz,
1H); 6.94 (d, J ¼ 9.1 Hz, 2H); 7.26 (d, J ¼ 8.3 Hz, 2H); 7.46
(d, J ¼ 8.3 Hz, 2H); 7.97 (d, J ¼ 12.9 Hz, 1H); 8.87 (d,
J ¼ 13.0 Hz, 1H). MS (ESI): 338.0 (C17H15ClF2NO2,
[M þ H]þ). Anal. Calcd for C17H14ClF2NO2: C, 60.45; H,
4.18; N, 4.15; found: C, 60.42; H, 4.18; N, 4.17.
4.3.20. (Z )-Ethyl 3-(2,4-dibromophenylamino)-2-
(4-chlorophenyl)acrylate (10a)
White powder, 1H NMR (500 MHz, DMSO-d6): 1.22 (t,
J ¼ 7.1 Hz, 3H); 4.22 (q, J ¼ 7.1 Hz, 2H); 7.37 (d, J ¼ 8.6 Hz,
2H); 7.42 (d, J ¼ 8.6 Hz, 2H); 7.53 (d, J ¼ 8.8 Hz, 1H); 7.60 (d,
4.3.26. (E )-Ethyl 3-(1,2,3,4-tetrahydroquinolin-1-yl)-2-(4-
chlorophenyl)acrylate (13)
1
Light yellow crystal, H NMR (500 MHz, CDCl3): 1.26 (t,
J ¼ 7.0 Hz, 3H); 1.76 (m, 2H); 2.73 (t, J ¼ 6.4 Hz, 2H); 3.01

1836
Z.-P. Xiao et al. / European Journal of Medicinal Chemistry 43 (2008) 1828e1836
(t, J ¼ 5.8 Hz, 2H); 4.21 (q, J ¼ 7.0 Hz, 2H); 6.98 (t, J ¼ 7.4 Hz,
1H); 7.01 (d, J ¼ 8.0 Hz, 1H); 7.06 (d, J ¼ 7.7 Hz, 1H); 7.19 (d,
J ¼ 8.6 Hz, 2H); 7.20 (t, J ¼ 7.2 Hz, 1H); 7.28 (d, J ¼ 8.6 Hz,
2H); 8.00 (s, 1H). MS (ESI): 342.1 (C20H21ClNO2,
[M þ H]þ). Anal. Calcd for C20H20ClNO2: C, 70.27; H, 5.90;
N, 4.10; found: C, 70.34; H, 5.89; N, 4.12.
References
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Light yellow crystal, 1H NMR (300 MHz, DMSO-d6): 1.17
(t, J ¼ 7.0 Hz, 3H); 1.65 (m, 2H); 2.66 (t, J ¼ 6.2 Hz, 2H);
2.95 (t, J ¼ 5.6 Hz, 2H); 3.74 (s, 3H); 4.09 (q, J ¼ 7.0 Hz,
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Acknowledgements
The work was financed by grants (Project 30772627 and
30672516) from National Natural Science Foundation of
China.
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