Synthesis and antimicrobial activities of Schiff bases derived from 5-chloro-salicylaldehyde

Article abstract of DOI:10.1016/j.ejmech.2006.11.010

A series of Schiff bases (compounds 1-26) were synthesized by reacting 5-chloro-salicylaldehyde and primary amines, 15 (compounds 2-4, 6, 7, 10, 12-17, 23, 25 and 26) of which were first reported. The chemical structures of these compounds were confirmed

Full text of DOI:10.1016/j.ejmech.2006.11.010

European Journal of Medicinal Chemistry 42 (2007) 558e564
http://www.elsevier.com/locate/ejmech
Short communication
Synthesis and antimicrobial activities of Schiff bases
derived from 5-chloro-salicylaldehyde
Lei Shi, Hui-Ming Ge, Shu-Hua Tan, Huan-Qiu Li, Yong-Chun Song,
Hai-Liang Zhu*, Ren-Xiang Tan
Institute of Functional Biomolecules, State Key Laboratory of Pharmaceutical Biotechnology, Nanjing University,
Nanjing, Jiangsu 210093, People’s Republic of China
Received 27 September 2006; received in revised form 21 November 2006; accepted 23 November 2006
Available online 29 November 2006
Abstract
A series of Schiff bases (compounds 1e26) were synthesized by reacting 5-chloro-salicylaldehyde and primary amines, 15 (compounds 2e4,
1
, 7, 10, 12e17, 23, 25 and 26) of which were first reported. The chemical structures of these compounds were confirmed by means of H NMR,
C NMR, ESI-MS and elemental analyses. The compounds were assayed for antibacterial (Bacillus subtilis, Escherichia coli, Pseudomonas
6
1
3
fluorescence and Staphylococcus aureus) and antifungal (Aspergillus niger, Candida albicans and Trichophyton rubrum) activities by MTT
3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl trtrazolium bromide) method. Among the compounds tested, (E )-4-chloro-2-((4-fluorobenzylimino)-
(
methyl)phenol (2) showed the most favorable antimicrobial activity with MICs of 45.2, 1.6, 2.8, 3.4, and 47.5 mg/mL against B. subtilis, E. coli,
P. fluorescence, S. aureus and A. niger, respectively.
Ó 2006 Elsevier Masson SAS. All rights reserved.
Keywords: Aldehyde; Primary amine; Schiff base; Antibacterial activity; Antifungal activity; Structureeactivity relationship
1
. Introduction
Schiff bases of 5-chloro-salicylaldehyde and their antimicro-
bial properties were reported. The results of this study may
be useful to researchers attempting to gain more understanding
of the antimicrobial activity of Schiff base compounds.
Compounds with the structure of AC ¼ NB are known as
Schiff bases, which are usually synthesized from the conden-
sation of primary amines and active carbonyl groups. Some
Schiff bases were reported to possess antibacterial [1e6], an-
tifungal [3e6] and antitumor activities [7,8]. Lots of re-
searchers studied the synthesis, characterization and
structureeactivity relationship (SAR) of Schiff bases [9e
2. Chemistry
In the present study, 26 primary amines were subjected to
reaction with 5-chloro-salicylaldehyde to prepare the corre-
sponding Schiff bases (Scheme 1). All the compounds gave
1
2]. It is also reported that Salicylaldehyde derivatives, with
one or more halo-atoms in the aromatic ring, showed variety
of biological activities like antibacterial and antifungal activi-
ties [13]. These investigations led to the conception that Schiff
bases of 5-chloro-salicylaldehyde would possess potential an-
timicrobial properties. In this paper, the synthesis of some
1
13
satisfactory chemical analyses (ꢀ0.4%). H NMR, C NMR
and ESI-MS spectra were consistent with the assigned
structures.
3. Results and discussion
The ways in which different Schiff base compounds react
with bacteria and fungi vary due to the difference in their
*
Corresponding author. Tel.: þ86 25 8359 2085; fax: þ86 25 8359 3201.
E-mail address: zhuhl@nju.edu.cn (H.-L. Zhu).
0223-5234/$ - see front matter Ó 2006 Elsevier Masson SAS. All rights reserved.
doi:10.1016/j.ejmech.2006.11.010

L. Shi et al. / European Journal of Medicinal Chemistry 42 (2007) 558e564
559
Cl
CHO
Cl
R1
R1
NH2
N
OH
OH
1
2
3
4
5
6
7
8
9
1
R1 =
R1 = F
R1 = HO
R1 =
H N
R2
NH2
2
Cl
R2
Cl
N
N
N
R1 = O N
2
OH
HO
N
R1 =
1
2
2
2
2
2
2
2
9 R2=
H
N
R1 =
O
0 R2=
1 R2=
2 R2=
3 R2=
4 R2=
5 R2=
6 R2=
N
R1 =
R1 =
O
Me
O
O
N
Me
N
0 R1 =
Me
Me
Me
Me
HN
Me
11 R1 =
N
12 R1 =
Me
Me
HN
Me
13 R1 =
O
N
1
1
1
1
1
4 R1 =
5 R1 =
6 R1 =
7 R1 =
Et
N
Et
Me
N
Me
8 R1 = HO
Scheme 1. Syntheses of the Schiff bases.
structures. Structural analysis of these compounds may pro-
vide some explanation for the structureeactivity relationships.
Such an analysis might be helpful in the design of better inhib-
itors. The biological activity of a particular substance depends
on a complex sum of individual properties including compound
structure, affinity for the target site, survival in the medium of
application, survival within the biological system, transport
properties, and state of the target organism [14]. In this study,

560
L. Shi et al. / European Journal of Medicinal Chemistry 42 (2007) 558e564
we focused our attention on the structureeactivity
relationships.
Compounds 1e5 and 7 showed higher antibacterial activity
than lots of other compounds. This result disclosed that com-
pounds with aromatic rings were more active than compounds
with aliphatic chains.
All the synthesized compounds were screened for antibac-
terial activity against two Gram (þ) bacterial strains (Bacillus
subtilis and Staphylococcus aureus) and two Gram (ꢁ) bacte-
rial strains (Escherichia coli and Pseudomonas fluorescence)
by MTT method. The MICs (minimum inhibitory concentra-
tions) of the compounds against four bacteria are presented
in Table 1. The activity of reference compounds kanamycin
Compounds 6, 8e14, 25 and 26 had a slight difference in
the structure. All of them contained a subset similar to cyclo-
hexyl, but their antibacterial activity was very different. Com-
pound 8 showed the highest activity, compounds 9, 12 and 13
exhibited moderate activity while compounds 6, 10, 14, 25 and
26 almost had no activity. The order of activity indicated that
the activity of compounds against bacterial strains was de-
creased when the complexity of the cyclohexyl-like subset
was increased. The results also implied that heteroatoms
such as oxygen and nitrogen were helpful in the activity of
the compounds. Compound 5 with a cyclopentyl ring was
more active than the compounds above. This observation
indicated that simpler and smaller the alicyclic ring higher
the activity of the compounds.
(
0
Nanjing Zhuyan Biotechnology Co. Ltd, Amresco
60D0504, Nanjing 210002, China) and penicillin (North
China Pharmaceutical Co. Ltd, D0211107, Hebei 050015,
China) was included. Compounds 5, 10, 14, 16, 17 and 23e
2
6 were found to be inactive against all the bacterial strains.
Compound 21 showed highest activity against B. subtilis
1.8 mg/mL) while compounds 2, 3 and 7 exhibited moderate
(
activity (45.2e49.8 mg/mL). Compounds 1, 2, 7, 8, 15, 21
and 22 showed significant activity against E. coli (1.6e
5
(
.7 mg/mL) while compound 9 exhibited moderate activity
48.6 mg/mL). Compounds 1e3, 7, 8, 15, 19, 21 and 22
showed significant activity against P. fluorescence (2.5e
.2 mg/mL) while compounds 4, 9, 11 and 20 exhibited mild
to moderate activity (12.5e40.5 mg/mL). Compounds 2 and
showed significant activity against S. aureus (1.8e3.4 mg/mL)
while compounds 4, 5, 9, 12, 13 and 18 exhibited mild activity
15.5e25 mg/mL).
The antifungal activity of the compounds was studied with
three fungal strains (Aspergillus niger, Candida albicans and
Trichophyton rubrum) by MTT method. The results are sum-
marized in Table 1. Ketoconazole (Sigma-Aldrich Inc, 3050
Spruce Street, St. Louis) was used as reference for inhibitory
activity against fungi. Almost none of the compounds showed
antifungal activity except compound 18 which showed mild
activity (12.5 mg/mL) against C. albicans and compound 2
5
3
(
Table 1
Antimicrobial activity of the synthesized compounds
Compound
Minimum inhibitory concentrations (mg/mL)
Bacillus
subtilis
Escherichia
coli
Pseudomonas
fluorescence
Staphylococcus
aureus
Aspergillus
niger
Candida
albicans
Trichophyton
rubrum
1
2
3
4
5
6
7
8
9
>50
45.2
48.5
>50
>50
>50
49.8
>50
>50
>50
>50
>50
>50
>50
>50
>50
>50
>50
>50
>50
1.8
3.1
1.6
3.2
2.8
>50
3.4
>50
47.5
>50
>50
>50
>50
>50
>50
>50
>50
>50
>50
>50
>50
>50
>50
>50
>50
>50
>50
>50
>50
>50
>50
>50
>50
7.8
>50
>50
>50
>50
>50
>50
>50
>50
>50
>50
>50
>50
>50
>50
>50
>50
>50
12.5
>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
>50
>50
>50
>50
5.7
3.1
1.8
12.5
>50
>50
5.2
19.5
18.5
>50
>50
>50
25.0
>50
>50
22.5
18.5
>50
>50
>50
>50
15.5
>50
>50
>50
>50
>50
>50
>50
>50
>50
1
3.5
2.5
48.6
>50
>50
>50
>50
>50
4.1
12.5
>50
40.5
>50
>50
>50
3.4
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
>50
>50
>50
>50
>50
4.9
>50
>50
>50
2.8
32.5
3.6
>50
>50
>50
>50
>50
>50
0.39
0.78
5.0
4.5
>50
>50
>50
>50
>50
3.9
>50
>50
>50
>50
>50
3.9
Ketoconazole
Kanamycin
Penicillin
>50
>50
>50
>50
>50
>50
>50
>50
2

L. Shi et al. / European Journal of Medicinal Chemistry 42 (2007) 558e564
561
exhibited moderate activity (47.5 mg/mL) against A. niger.
These results revealed that most of the synthesized compounds
exhibited significant antibacterial activity but showed low an-
tifungal activity.
161.8, 135.9, 133.4, 131.9, 131.2, 123.4, 121.2, 119.8,
þ
þ
116.6, 62.5. ESI-MS: 264.0 (C H ClFNO , [M þ H] ).
1
4 12
Anal. Calcd for C H ClFNO: C, 63.77%; H, 4.20%; N,
4 11
1
5.31%. Found: C, 63.96%; H, 4.22%; N, 5.34%.
The study on structureeactivity relationships of these
Schiff base derivatives indicated that the hydrophilicity and
aromaticity seemed to be important for the antimicrobial
activity. Generally speaking, the activity of compounds was
increased with the increase of hydrophilicity and aromaticity
of the compounds. Heteroatoms were helpful in the activity
of the compounds. Compound 2 was found to be the most po-
tent antimicrobial agent indicated that fluorine atom played an
important role in the antimicrobial activity.
4.1.1.3. (E )-4-Chloro-2-((4-hydroxyphenethylimino)methyl)-
phenol (3). Yellow crystals, yield 90%, mp: 116e118 C, H
ꢂ
1
NMR (500 MHz, DMSO-d , d ppm): 2.83 (t, J ¼ 6.6 Hz,
6
2H); 3.78 (t, J ¼ 6.6 Hz, 2H); 6.66 (d, J ¼ 7.4 Hz, 2H); 6.87
(d, J ¼ 9.0 Hz, 1H); 7.02 (d, J ¼ 7.4 Hz, 2H); 7.33 (dd,
J ¼ 9.0 and 2.5 Hz, 1H); 7.48 (d, J ¼ 2.5 Hz, 1H); 8.44 (s,
1
3
1H); 9.16 (s, 1H); 13.64 (s, 1H). C NMR (DMSO-d ,
6
d ppm): 165.8, 160.9, 156.8, 133.2, 131.8, 131.0, 130.6,
123.0, 120.9, 119.9, 116.3, 61.3, 37.0. ESI-MS: 276.2
þ
þ
4
. Experimental protocols
(C H ClNO , [M þ H] ). Anal. Calcd for C H ClNO :
1
5
15
2
15 14
2
C, 65.34%; H, 5.12%; N, 5.08%. Found: C, 65.49%; H,
5.10%; N, 5.05%.
4
.1. Chemistry
All chemicals (reagent grade) used were commercially
available. 5-chloro-salicylaldehyde (>95%) was purchased
from Zhangjiagang Feihang Industry Co., Ltd, Jiangsu, China
4.1.1.4. (E )-4-Chloro-2-((pyridin-3-ylmethylimino)methyl)phe-
ꢂ
1
nol (4). Yellow crystals, yield 86%, mp: 92e94 C, H NMR
(500 MHz, DMSO-d , d ppm): 4.85 (s, 2H); 6.91 (d,
6
1
and was used without further purification. All the H NMR and
J ¼ 8.8 Hz, 1H); 7.37 (m, 1H); 7.40 (m, 1H); 7.60 (d,
1
3
C NMR spectra were recorded on a Bruker DRX 500 or
DPX 300 model Spectrometer in DMSO-d . Chemical shifts
J ¼ 2.0 Hz, 1H); 7.76 (d, J ¼ 7.5 Hz, 1H); 8.51 (d,
13
J ¼ 4.8 Hz, 1H); 8.59 (s, 1H); 8.72 (s, 1H); 13.10 (s, 1H).
6
1
d) for H NMR spectra were reported in parts per million to
(
C NMR (DMSO-d , d ppm): 166.9, 160.2, 150.4, 149.9,
137.0, 135.4, 133.5, 131.9, 125.1, 123.5, 121.2, 119.8, 60.8.
6
residual solvent protons. ESI-MS spectra were recorded on
a Mariner System 5304 Mass spectrometer. Elemental analy-
ses were performed on a CHN-O-Rapid instrument and were
within ꢀ0.4% of the theoretical values. Melting points were
measured on a Boetius micro melting point apparatus.
þ
þ
ESI-MS: 247.1 (C H ClN O , [M þ H] ). Anal. Calcd for
1
3
12
2
C H ClN O: C, 63.29%; H, 4.49%; N, 11.36%. Found: C,
1
3
11
2
63.41%; H, 4.53%; N, 11.42%.
4
.1.1.5. (E )-4-Chloro-2-((4-nitrophenylimino)methyl)phenol
ꢂ
1
4
.1.1. General method for the synthesis of compounds 1e18
Equimolar quantities (0.6 mmol) of 5-chloro-salicylalde-
(5). Yellow crystals, yield 88%, mp: 190e192 C,
H
NMR (500 MHz, DMSO-d , d ppm): 7.04 (d, J ¼ 8.9 Hz,
6
hyde and the primary amine with one amino group were dis-
solved in methanol (10 mL) and stirred at room temperature
for 10 min to give a clear solution. After standing for approx-
imately 3 d, the precipitates were separated by filtration, re-
crystallized from methanol, washed with methanol for three
times, and dried in a vacuum desiccator containing anhydrous
CaCl2.
1H); 7.50 (dd, J ¼ 8.9 and 2.7 Hz, 1H); 7.58 (d,
J ¼ 8.9 Hz, 2H); 7.82 (d, J ¼ 2.7 Hz, 1H); 8.32 (d,
J ¼ 8.9 Hz, 2H); 8.95 (s, 1H); 12.14 (s, 1H). ESI-MS:
þ
2 3
þ
277.0 (C H ClN O , [M þ H] ). Anal. Calcd for
1
3
10
C H ClN O : C, 56.43%; H, 3.28%; N, 10.13%. Found:
1
3
9
2 3
C, 56.49%; H, 3.31%; N, 10.11%.
4
.1.1.6. (E )-2-((1-Benzylpiperidin-4-ylimino)methyl)-4-chloro-
ꢂ
1
4
low crystals, yield 92%, mp: 83e84 C,
.1.1.1. (E )-2-((Benzylimino)methyl)-4-chlorophenol (1). Yel-
phenol (6). Yellow crystals, yield 83%, mp: 99e101 C, H
NMR (500 MHz, DMSO-d , d ppm): 1.65 (m, 2H); 1.79 (m,
ꢂ
1
H
500 MHz, DMSO-d , d ppm): 4.82 (s, 2H); 6.91 (d,
NMR
6
(
2H); 2.14 (m, 2H); 2.76 (m, 2H); 3.36 (m, 1H); 3.49 (s,
2H); 6.89 (d, J ¼ 8.9 Hz, 1H); 7.25 (m, 1H); 7.31e7.35 (m,
5H); 7.53 (d, J ¼ 2.1 Hz, 1H); 8.59 (s, 1H); 13.30 (s, 1H).
6
J ¼ 8.9 Hz, 1H); 7.30 (t, J ¼ 7.2 Hz, 1H); 7.34 (d,
J ¼ 7.2 Hz, 2H); 7.35 (m, 1H); 7.39 (d, J ¼ 7.2 Hz, 2H);
þ
2
þ
13
7
.60 (d, J ¼ 2.5 Hz, 1H); 8.71 (s, 1H); 13.53 (s, 1H). ESI-
ESI-MS: 329.2 (C H ClN O , [M þ H] ).
C NMR
1
9
22
þ
þ
MS: 246.1 (C H ClNO , [M þ H] ). Anal. Calcd for
(DMSO-d , d ppm): 164.2, 160.7, 139.8, 133.2, 131.8,
6
1
4
13
C H ClNO: C, 68.44%; H, 4.92%; N, 5.70%. Found: C,
1
130.0, 129.4, 128.1, 123.1, 121.0, 119.8, 63.5, 53.4, 52.3,
34.2. Anal. Calcd for C H ClN O: C, 69.40%; H, 6.44%;
N, 8.52%. Found: C, 69.56%; H, 6.47%; N, 8.48%.
4 12
6
8.68%; H, 4.96%; N, 5.68%.
1
9
21
2
4
(
.1.1.2. (E )-4-Chloro-2-((4-fluorobenzylimino)methyl)phenol
ꢂ
1
2). Yellow crystals, yield 92%, mp: 97e99 C, H NMR
4.1.1.7. (E )-4-Chloro-2-((furan-2-ylmethylimino)methyl)phe-
ꢂ
1
(
300 MHz, DMSO-d , d ppm): 4.80 (s, 2H); 6.91 (d,
6
nol (7). Yellow crystals, yield 92%, mp: 77e78 C,
H
NMR (500 MHz, DMSO-d , d ppm): 4.81 (s, 2H); 6.40 (d,
J ¼ 8.8 Hz, 1H); 7.20 (t, J ¼ 8.9 Hz, 2H); 7.36 (m, 1H); 7.40
6
(
1
d, J ¼ 8.9 Hz, 2H); 7.59 (d, J ¼ 2.5 Hz, 1H); 8.69 (s, 1H);
J ¼ 2.9 Hz, 1H); 6.45 (m, 1H); 6.92 (d, J ¼ 8.9 Hz, 1H);
7.37 (dd, J ¼ 8.9 and 2.7 Hz, 1H); 7.61 (d, J ¼ 2.7 Hz, 1H);
1
3
3.42(s, 1H). C NMR (DMSO-d , d ppm): 166.5, 163.7,
6

562
L. Shi et al. / European Journal of Medicinal Chemistry 42 (2007) 558e564
1
3
7
(
.65 (d, J ¼ 1.8 Hz, 1H); 8.66 (s, 1H); 13.21 (s, 1H). C NMR
C H ClN O: C, 58.31%; H, 6.78%; N, 15.69%. Found: C,
13 18 3
58.46%; H, 6.84%; N, 15.76%.
DMSO-d , d ppm): 167.1, 160.0, 152.6, 144.2, 133.5, 131.9,
6
1
23.6, 121.2, 119.8, 112.0, 109.2, 55.8. ESI-MS: 234.2
ꢁ
ꢁ
(C H ClNO , [M ꢁ H] ). Anal. Calcd for C H ClNO :
C, 61.16%; H, 4.28%; N, 5.94%. Found: C, 61.04%; H,
4.1.1.13. (E )-4-Chloro-2-((3-morpholinopropylimino)methyl)-
1
2
9
2
12 10
2
1
phenol (13). Yellow oil, yield 72%, H NMR (300 MHz,
4
.24%; N, 5.93%.
DMSO-d , d ppm): 1.78 (m, 2H); 2.32 (m, 6H); 3.56 (m,
6
4
H); 3.62 (m, 2H); 6.88 (d, J ¼ 8.8 Hz, 1H); 7.33 (dd,
4
.1.1.8. (E )-4-Chloro-2-((2-morpholinoethylimino)methyl)phe-
J ¼ 8.8 and 2.4 Hz, 1H); 7.52 (d, J ¼ 2.4 Hz, 1H); 8.53 (s,
ꢂ
1
13
1H); 13.72 (s, 1H). C NMR (DMSO-d , d ppm): 165.9,
nol (8). Yellow powder, yield 84%, mp: 51e53 C, H NMR
500 MHz, DMSO-d , d ppm): 2.42 (m, 4H); 2.59 (t,
6
(
161.4, 133.2, 131.7, 122.9, 121.0, 120.0, 67.5, 57.6, 57.1,
ꢁ
6
ꢁ
J ¼ 6.4 Hz, 2H); 3.55 (m, 4H); 3.72 (t, J ¼ 6.4 Hz, 2H); 6.88
54.7, 28.4. ESI-MS: 281.1 (C H ClN O , [M ꢁ H] ).
14 19 2 2
1
4
18
2 2
(
d, J ¼ 8.9 Hz, 1H); 7.33 (dd, J ¼ 8.9 and 2.4 Hz, 1H); 7.53
Anal. Calcd for C H ClN O : C, 59.47%; H, 6.77%; N,
9.91%. Found: C, 59.58%; H, 6.72%; N, 9.97%.
(
d, J ¼ 2.4 Hz, 1H); 8.54 (s, 1H); 13.70 (s, 1H). ESI-MS:
ꢁ
2 2
ꢁ
2
C H ClN O : C, 58.10%; H, 6.38%; N, 10.42%. Found: C,
67.2 (C H ClN O , [M ꢁ H] ). Anal. Calcd for
13 17 2 2
1
3
16
4.1.1.14. (E )-4-Chloro-2-((cyclohexylmethylimino)methyl)phe-
ꢂ
1
nol (14). Yellow crystals, yield 82%, mp: 49e51 C, H
5
8.24%; H, 6.36%; N, 10.43%.
NMR (500 MHz, DMSO-d , d ppm): 0.98 (m, 2H); 1.13 (m,
6
4
Yellow crystals, yield 85%, mp: 41e42 C, H NMR
.1.1.9. (E )-4-Chloro-2-((cyclohexylimino)methyl)phenol (9).
1H); 1.20 (m, 2H); 1.59 (m, 2H); 1.68 (m, 4H); 3.45 (d,
J ¼ 6.2 Hz, 2H); 6.88 (d, J ¼ 8.8 Hz, 1H); 7.33 (dd, J ¼ 8.8
and 2.4 Hz, 1H); 7.52 (d, J ¼ 2.4 Hz, 1H); 8.49 (s, 1H);
ꢂ
1
(
500 MHz, DMSO-d , d ppm): 1.38e1.77 (m, 10H); 3.36
6
1
3
(
1
m, 1H); 6.88 (d, J ¼ 8.8 Hz, 1H); 7.34 (dd, J ¼ 8.8 and
13.88 (s, 1H). C NMR (DMSO-d , d ppm): 166.0, 160.5,
6
.8 Hz, 1H); 7.52 (d, J ¼ 1.8 Hz, 1H); 8.57 (s, 1H); 13.93 (s,
133.3, 131.9, 123.0, 120.8, 120.0, 66.1, 39.7, 31.9, 27.4,
þ
þ
þ
þ
1
for C H ClNO: C, 65.68%; H, 6.78%; N, 5.89%. Found: C,
H). ESI-MS: 238.1 (C H ClNO , [M þ H] ). Anal. Calcd
26.8. ESI-MS: 252.2 (C H ClNO , [M þ H] ). Anal. Calcd
14 19
1
3
17
for C H ClNO: C, 66.79%; H, 7.21%; N, 5.56%. Found: C,
14 18
1
3
16
6
5.46%; H, 6.82%; N, 5.92%.
66.83%; H, 7.23%; N, 5.52%.
4
.1.1.10. (E )-Ethyl 4-(5-chloro-2-hydroxybenzylideneamino)-
4.1.1.15.
(E )-4-Chloro-2-((cyclopentylimino)methyl)phenol
ꢂ
1
piperidine-1-carboxylate (10). Yellow powder, yield 82%,
mp: 144e146 C, H NMR (500 MHz, DMSO-d , d ppm):
(15). Yellow crystals, yield 94%, mp: 45e47 C, H NMR
(300 MHz, DMSO-d , d ppm): 1.62 (m, 4H); 1.74 (m, 2H);
ꢂ
1
6
6
1
.19 (t, J ¼ 7.2 Hz, 3H); 1.54 (m, 2H); 1.80 (m, 2H); 3.39
1.91 (m, 2H); 3.86 (m, 1H); 6.88 (d, J ¼ 8.8 Hz, 1H); 7.32
(dd, J ¼ 8.8 and 2.6 Hz, 1H); 7.53 (d, J ¼ 2.6 Hz, 1H); 8.55
(
2
m, 1H); 3.55 (m, 2H); 3.89 (m, 2H); 4.04 (q, J ¼ 7.2 Hz,
1
3
H); 6.90 (d, J ¼ 8.7 Hz, 1H); 7.35 (dd, J ¼ 8.7 and 2.4 Hz,
H); 7.55 (d, J ¼ 2.4 Hz, 1H); 8.61 (s, 1H); 13.85 (s, 1H).
(s, 1H); 13.76 (s, 1H). C NMR (DMSO-d , d ppm): 163.7,
6
1
161.0, 133.0, 131.7, 123.0, 120.9, 119.8, 69.8, 35.4, 25.1.
þ
1
3
C NMR (DMSO-d , d ppm): 164.6, 160.4, 156.0, 133.3,
6
ESI-MS: 224.1 (C H ClNO, [M þ H] ). Anal. Calcd for
12 15
1
31.9, 123.3, 121.2, 119.8, 65.0, 49.0, 42.9, 33.8, 15.9. ESI-
þ
C H ClNO: C, 64.43%; H, 6.31%; N, 6.26%. Found: C,
1
2 14
þ
MS: 311.1 (C H ClN O , [M þ H] ). Anal. Calcd for
64.35%; H, 6.37%; N, 6.31%.
1
5
20
2 3
C H ClN O : C, 57.97%; H, 6.16%; N, 9.01%. Found: C,
1
5
19
2 3
5
8.12%; H, 6.12%; N, 8.98%.
4.1.1.16. (E )-4-Chloro-2-((3-(diethylamino)propylimino)me-
thyl)phenol (16). Yellow crystals, yield 86%, mp: 75e77 C,
ꢂ
1
4
.1.1.11. (E )-4-Chloro-2-((2,2,6,6-tetramethylpiperidin-4-yli-
H NMR (300 MHz, DMSO-d , d ppm): 0.91 (t, J ¼ 7.1 Hz,
6
mino)methyl)phenol (11). Yellow crystals, yield 80%, mp:
6H); 1.72 (m, 2H); 2.40 (m, 6H); 3.59 (t, J ¼ 6.6 Hz, 2H);
6.87 (d, J ¼ 8.9 Hz, 1H); 7.31 (dd, J ¼ 8.9 and 2.5 Hz, 1H);
ꢂ
25e126 C, H NMR (500 MHz, DMSO-d , d ppm): 1.07
6
1
1
1
3
(
1
1
s, 6H); 1.18 (s, 6H); 1.25 (m, 2H); 1.67 (m, 2H); 3.80 (m,
H); 6.88 (d, J ¼ 8.8 Hz, 1H); 7.33 (dd, J ¼ 8.8 and 2.1 Hz,
7.49 (d, J ¼ 2.5 Hz, 1H); 8.51 (s, 1H); 13.78 (s, 1H).
C
NMR (DMSO-d , d ppm): 166.1, 161.0, 133.2, 131.8, 124.9,
6
H); 7.52 (d, J ¼ 2.1 Hz, 1H); 8.65 (s, 1H); 13.92 (s, 1H).
123.7, 121.4, 57.2, 50.5, 47.6, 28.0, 12.0. ESI-MS: 269.2
þ
þ
þ
þ
ESI-MS: 295.2 (C H ClN O , [M þ H] ). Anal. Calcd for
(C H ClN O , [M þ H] ). Anal. Calcd for C H ClN O:
1
6
24
2
14 22
2
14 21
2
C H ClN O: C, 65.18%; H, 7.86%; N, 9.50%. Found: C,
1
C, 62.56%; H, 7.88%; N, 10.42%. Found: C, 62.73%; H,
7.78%; N, 10.48%.
6
23
2
6
5.33%; H, 7.89%; N, 9.43%.
4
.1.1.12. (E )-4-Chloro-2-((2-(piperazin-1-yl)ethylimino)me-
4.1.1.17. (E )-4-Chloro-2-((3-(dimethylamino)propylimino)me-
1
ꢂ
thyl)phenol (12). Yellow oil, yield 74%,
H
300 MHz, DMSO-d , d ppm): 2.36e2.69 (m, 10H); 3.69 (t,
NMR
thyl)phenol (17). Yellow crystals, yield 84%, mp: 76e78 C,
1
(
H NMR (500 MHz, DMSO-d , d ppm): 1.74 (m, 2H); 2.11 (s,
6
6
J ¼ 6.4 Hz, 2H); 6.87 (d, J ¼ 8.9 Hz, 1H); 7.33 (dd, J ¼ 8.9
and 2.6 Hz, 1H); 7.51 (d, J ¼ 2.6 Hz, 1H); 8.51 (s, 1H);
6H); 2.54 (t, J ¼ 7.0 Hz, 2H); 3.59 (t, J ¼ 6.7 Hz, 2H); 6.87 (d,
J ¼ 8.9 Hz, 1H); 7.32 (dd, J ¼ 8.9 and 2.4 Hz, 1H); 7.50 (d,
1
3
13
J ¼ 2.4 Hz, 1H); 8.51 (s, 1H); 13.81 (s, 1H). C NMR
1
3.75 (s, 1H). C NMR (DMSO-d , d ppm): 166.4, 161.7,
6
1
33.4, 131.8, 122.7, 120.8, 120.2, 59.7, 56.3, 54.7, 46.4.
þ
(DMSO-d , d ppm): 166.0, 161.1, 133.3, 131.8, 124.9, 123.0,
6
þ
þ
ESI-MS: 268.2 (C H ClN O , [M þ H] ). Anal. Calcd for
121.3, 57.4, 57.2, 45.8, 28.8. ESI-MS: 241.2 (C H ClN O ,
12 18
1
3
19
3
2

L. Shi et al. / European Journal of Medicinal Chemistry 42 (2007) 558e564
563
þ
[
7
M þ H] ). Anal. Calcd for C H ClN O: C, 59.87%; H,
Anal. Calcd for C H Cl N O : C, 58.13%; H, 4.59%; N,
17 16 2 2 2
7.98%. Found: C, 57.96%; H, 4.52%; N, 7.89%.
1
2
17
2
.12%; N, 11.64%. Found: C, 59.76%; H, 7.09%; N, 11.68%.
0
0
0
4
.1.1.18. (E )-4-Chloro-2-((2-hydroxyethylimino)methyl)phenol
4.1.2.5. 2,2 -(1E,1 E )-(3,3 -(Methylazanediyl)bis(propane-3,1-
diyl)bis(azan-1-yl-1-ylidene))bis(methan-1-yl-1-ylidene)bis(4-
ꢂ
1
(
18). Yellow crystals, yield 83%, mp: 44e46 C, H NMR
1
(
500 MHz, DMSO-d , d ppm): 3.65 (m, 4H); 4.75 (t,
chlorophenol) (23). Yellow oil, yield 74%, H NMR (300 MHz,
6
J ¼ 3.4 Hz, 1H); 6.87 (d, J ¼ 8.8 Hz, 1H); 7.32 (dd, J ¼ 8.8
and 2.4 Hz, 1H); 7.53 (d, J ¼ 2.4 Hz, 1H); 8.49 (s, 1H); 13.76
DMSO-d , d ppm): 1.76 (m, 4H); 2.15 (s, 3H); 2.36 (t,
6
J ¼ 6.7 Hz, 4H); 3.61 (t, J ¼ 6.5 Hz, 4H); 6.88 (d, J ¼ 8.8 Hz,
2H); 7.32 (dd, J ¼ 8.8 and 2.4 Hz, 2H); 7.49 (d, J ¼ 2.4 Hz,
þ
2
þ
(
s, 1H). ESI-MS: 200.1 (C H ClNO , [M þ H] ). Anal. Calcd
9
11
1
3
for C H ClNO : C, 54.15%; H, 5.05%; N, 7.02%. Found: C,
10
2H); 8.51 (s, 2H); 13.75 (s, 2H). C NMR (DMSO-d ,
9
2
6
5
4.02%; H, 5.08%; N, 7.09%.
d ppm): 165.7, 161.5, 133.1, 131.6, 122.8, 120.9, 120.1, 57.4,
þ
þ
5
5.9, 43.0, 29.2. ESI-MS: 422.2 (C H Cl N O , [M þ H] ).
2
1
26
2 3 2
Anal. Calcd for C H Cl N O : C, 59.72%; H, 5.97%; N,
21 25 2 3 2
9.95%. Found: C, 59.91%; H, 5.92%; N, 9.98%.
4
1
.1.2. General method for the synthesis of compounds
9e26
They were prepared by a similar procedure to that de-
0
0
4.1.2.6. 2,2 -(1E,1 E )-(Hexane-1,6-diylbis(azan-1-yl-1-ylidene))
bis(methan-1-yl-1-ylidene)bis(4-chlorophenol) (24). Yellowpow-
der, yield 82%, mp: 117e118 C, H NMR (500 MHz, DMSO-d ,
ꢂ
1
scribed above, with 5-chloro-salicylaldehyde (0.6 mmol) and
the primary amine (0.3 mmol), which have two amino groups.
6
d ppm): 1.38 (m, 4H); 1.64 (m, 4H); 3.59 (t, J ¼ 6.5 Hz, 4H); 6.88
(
d, J ¼ 8.9 Hz, 2H); 7.33 (dd, J ¼ 8.9 and 2.4 Hz, 2H); 7.52
0
0
4
.1.2.1. 2,2 -(1E,1 E )-(Ethane-1,2-diylbis(azan-1-yl-1-ylidene))
(d, J ¼ 2.4 Hz, 2H); 8.53 (s, 2H); 13.59 (s, 2H). ESI-MS: 393.2
þ þ
20 23 2 2 2 20 22 2 2 2
bis(methan-1-yl-1-ylidene)bis(4-chlorophenol) (19). Yellow
(C H Cl N O , [M þ H] ). Anal. Calcd for C H Cl N O :
ꢂ
1
powder, yield 80%, mp: 163e165 C, H NMR (300 MHz,
C, 61.08%; H, 5.64% N, 7.12%. Found: C, 61.24%; H, 5.55%;
N, 7.16%.
DMSO-d , d ppm): 3.93 (s, 4H); 6.89 (d, J ¼ 8.8 Hz, 2H);
6
7
8
.34 (dd, J ¼ 8.8 and 2.6 Hz, 2H); 7.54 (d, J ¼ 2.6 Hz, 2H);
þ
0
0
.58 (s, 2H); 13.42 (s, 2H). ESI-MS: 337.1 (C H Cl N O ,
1
4.1.2.7. 2,2 -(1E,1 E )-(Cyclohexane-1,3-diylbis(methylene))bis
(azan-1-yl-1-ylidene)bis(methan-1-yl-1-ylidene)bis(4-chloro-
6
15
2
2
2
þ
[
4
M þ H] ). Anal. Calcd for C H Cl N O : C, 56.99%; H,
1
6
14
2 2 2
ꢂ
1
.18%; N, 8.31%. Found: C, 57.13%; H, 4.14%; N, 8.38%.
phenol) (25). Yellow powder, yield 84%, mp: 120e122 C, H
NMR (500 MHz, DMSO-d , d ppm): 0.93 (m, 2H); 1.32 (m,
6
0
0
0
4
.1.2.2. 2,2 -(1E,1 E )-(2,2 -Azanediylbis(ethane-2,1-diyl)bis(azan-
-yl-1-ylidene))bis(methan-1-yl-1-ylidene)bis(4-chlorophenol)
2H); 1.67 (m, 2H); 1.74 (m, 4H); 3.47 (d, J ¼ 2.8 Hz, 4H);
13
1
6.88 (d, J ¼ 8.8 Hz, 2H); 7.33 (dd, J ¼ 8.8 and 2.5 Hz, 2H);
ꢂ
1
20). Yellow powder, yield 82%, mp: 54e56 C, H NMR
(
7.52 (d, J ¼ 2.5 Hz, 2H); 8.50 (s, 2H); 13.63 (s, 2H).
C
NMR (DMSO-d , d ppm): 166.0, 160.3, 133.2, 131.8, 122.9,
(
300 MHz, DMSO-d , d ppm): 2.83 (m, 4H); 3.60 (m, 4H);
6
6
6
7
.83 (d, J ¼ 8.8 Hz, 2H); 7.22 (dd, J ¼ 8.8 and 2.5 Hz, 2H);
.43 (d, J ¼ 2.5 Hz, 2H); 8.50 (s, 2H); 13.63 (s, 2H). ESI-
120.8, 120.0, 66.0, 34.6, 31.7, 30.4, 26.2. ESI-MS: 419.2
þ
þ
(C H Cl N O , [M þ H] ). Anal. Calcd for C H Cl N O :
2
2
25
2
2
2
22 24
2 2 2
þ
2 3 2
þ
MS: 380.1 (C H Cl N O , [M þ H] ). Anal. Calcd for
C, 63.01%; H, 5.77%; N, 6.68%. Found: C, 62.85%; H, 5.81%;
N, 6.60%.
1
8
20
C H Cl N O : C, 56.85%; H, 5.04%; N, 11.05%. Found:
1
8
19
2 3 2
C, 56.98%; H, 5.02%; N, 11.09%.
4
.1.2.8. 4-Chloro-2-((E )-(2-(4-((E )-5-chloro-2-hydroxybenzy-
0
0
4
.1.2.3. 2,2 -(1E,1 E )-(Propane-1,2-diylbis(azan-1-yl-1-ylide-
lideneamino)-4-methylcyclohexyl)propan-2-ylimino)methyl)-
phenol (26). Yellow powder, yield 78%, mp: 123e124 C, H
NMR (300 MHz, DMSO-d , d ppm): 1.22e1.28 (m, 11H);
ꢂ
1
ne))bis(methan-1-yl-1-ylidene)bis(4-chlorophenol) (21). Yel-
ꢂ
1
low powder, yield 86%, mp: 126e128 C, H NMR
500 MHz, DMSO-d , d ppm): 1.31 (d, J ¼ 5.6 Hz, 3H);
6
(
3
1.55 (m, 5H); 1.83 (m, 2H); 6.78 (d, J ¼ 8.8 Hz, 1H); 6.83
(d, J ¼ 8.4 Hz, 1H); 7.29 (dd, J ¼ 8.8 and 2.7 Hz, 1H); 7.32
(dd, J ¼ 8.4 and 2.8 Hz, 1H); 7.56 (d, J ¼ 2.7 Hz, 1H); 7.59
6
.78e3.84 (m, 3H); 6.88 (d, J ¼ 8.4 Hz, 1H); 6.90 (d,
J ¼ 8.5 Hz, 1H); 7.33e7.35 (m, 2H); 7.54 (d, J ¼ 2.4 Hz,
2
H); 8.55 (s, 1H); 8.58 (s, 1H); 13.45 (s, 1H); 13.46 (s, 1H).
(d, J ¼ 2.8 Hz, 1H); 8.52 (s, 1H); 8.61 (s, 1H); 13.60 (s, 1H);
þ
13
13.68 (s, 1H). C NMR (DMSO-d , d ppm): 164.1, 163.0,
ESI-MS: 351.0 (C H Cl N O , [M þ H] ). Anal. Calcd for
1
7
17
2
2
2
6
C H Cl N O : C, 58.13%; H, 4.59%; N, 7.98%. Found: C,
1
161.8, 160.9, 133.3, 133.2, 132.1, 131.8, 122.3, 122.0, 120.7,
120.5, 119.7, 118.9, 63.1, 59.2, 48.2, 39.3, 29.4, 25.4, 23.5.
7
16
2 2 2
5
8.18%; H, 4.56%; N, 7.82%.
þ
þ
ESI-MS: 447.2 (C H Cl N O , [M þ H] ). Anal. Calcd for
2
4
29
2 2 2
0
0
4
.1.2.4. 2,2 -(1E,1 E )-(Propane-1,3-diylbis(azan-1-yl-1-ylide-
C H Cl N O : C, 64.43%; H, 6.31%; N, 6.26%. Found: C,
24 28 2 2 2
ne))bis(methan-1-yl-1-ylidene)bis(4-chlorophenol) (22). Yel-
64.56%; H, 6.25%; N, 6.37%.
ꢂ
1
low crystals, yield 88%, mp: 85e86 C,
(
H
NMR
500 MHz, DMSO-d , d ppm): 2.03 (m, 2H); 3.68 (t,
4.2. Antimicrobial activity
6
J ¼ 6.7 Hz, 4H); 6.89 (d, J ¼ 8.8 Hz, 2H); 7.35 (dd, J ¼ 8.8
and 2.6 Hz, 2H); 7.54 (d, J ¼ 2.6 Hz, 2H); 8.57 (s, 2H);
The antibacterial activity of the synthesized compounds was
tested against B. subtilis, E. coli, P. fluorescence and S. aureus
ꢁ
1
3.57 (s, 2H). ESI-MS: 349.3 (C H Cl N O , [MꢁH] ).
1
7
15
2 2 2

564
L. Shi et al. / European Journal of Medicinal Chemistry 42 (2007) 558e564
using MH medium (MuellereHinton medium: casein hydroly-
sate 17.5 g, soluble starch 1.5 g, beef extract 1000 mL), the an-
tifungal activity of the compounds was tested against A. niger,
C. albicans and T. rubrum using RPMI-1640 medium (RPMI-
Acknowledgement
The work was co-financed by grants (Projects 30672516
and 20432030) from National Natural Science Foundation of
China.
1
640 (GIBCO BRL) 10 g, NaHCO 2.0 g, 0.165 mol/L mor-
3
pholinepropanesulfonic acid (MOPS) (Sigma) 34.5 g, triple
distilled water 900 mL, buffered to pH 7.0 with 1 mol/L
ꢂ
NaOH (25 C), metered volume to 1000 mL, filtered steriliza-
ꢂ
References
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were determined by a colorimetric method using the dye
MTT [15]. A stock solution of the synthesized compound
[
[
[
[
[
[
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and applied to microtitration plates with serially diluted com-
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were visually determined on each of the microtitration plates,
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Na HPO $12H O 2.9 g, KH PO 0.2 g, NaCl 8.0 g, KCl 0.2 g,
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5
(
1999) 11e17.
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[8] E.M. Hodnett, J.W. Dunn, J. Med. Chem. 13 (1970) 768e770.
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[
[
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(
2
4
2
2
4
2002) 3821e3823.
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40 (2006) 51e56.
1
00 mL of isopropanol containing 5% 1 mol/L HCl was added
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to extract the dye. After 12 h of incubation at room tempera-
ture, the optical density (OD) was measured with a microplate
reader at 550 nm. The observed MICs are presented in Table 1.