Synthesis and cytotoxicity studies of quinoline-3-carbonitrile derivatives

Article abstract of DOI:10.1016/j.cclet.2010.03.016

A series of quinoline-3-carbonitrile derivatives were designed and synthesized. Their cytotoxicity in vitro against four cancer cell lines (A549, HT-29, MDA-MB-231 and SMMC-7721) were evaluated by standard MTT assay. The pharmacological results showed that most of the prepared compounds displayed excellent selective cytotoxicity toward SMMC-7721 cell line. Among them, compounds 7c, 7e, 11b, 11f and 11g were more active than Gefitinb against SMMC-7721 cell line.

Full text of DOI:10.1016/j.cclet.2010.03.016

Available online at www.sciencedirect.com
Chinese Chemical Letters 21 (2010) 939–942
www.elsevier.com/locate/cclet
Synthesis and cytotoxicity studies of quinoline-3-carbonitrile
derivatives
*
Shu Lan Zhang, Xin Zhai, Shi Jiao Zhang, Hong Hao Yu, Ping Gong
Key Laboratary of Original New Drugs Design and Discovery of Ministry of Education, School of Pharmaceutical Engineering,
Shenyang Pharmaceutical University, Shenyang 110016, China
Received 25 December 2009
Abstract
A series of quinoline-3-carbonitrile derivatives were designed and synthesized. Their cytotoxicity in vitro against four cancer
cell lines (A549, HT-29, MDA-MB-231 and SMMC-7721) were evaluated by standard MTT assay. The pharmacological results
showed that most of the prepared compounds displayed excellent selective cytotoxicity toward SMMC-7721 cell line. Among them,
compounds 7c, 7e, 11b, 11f and 11g were more active than Gefitinb against SMMC-7721 cell line.
# 2010 Ping Gong. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.
Keywords: Quinoline-3-carbonitrile; Synthesis; Cytotoxicity
Targeted therapies [1,2], in cancer treatment, represent a new generation of drugs that interfere with specific
molecular targets (typically proteins) having critical roles to play in tumor growth or progression. Epidermal growth
factor receptor (EGFR), found in high concentration in several solid tumors, is one of the most important targets in
targeted therapies. Gefitinib, the first selective EGFR tyrosine kinase inhibitors, was approved by the FDA in May
2003 for the treatment of advanced non-small-cell lung cancer (NSCLC) [3]. Given the electron withdrawing
properties of a cyano group, the charge distribution within the quinoline-3-carbonitrile ring system was similar to that
of the quinazoline ring system of Gefitinib. The preliminary structural activity relationships (SAR) study demonstrated
activities of quinoline-3-carbonitriles compared to that of Gefitinib were similar in both the enzyme and cell assays [4–
6]. Based on these reported literatures, we replaced quinazoline scaffold with quinoline-3-carbonitrile scaffold. It
should be noted that there are hardly any studies about methylation NH group at position-4 of quinoline-3-carbonitrile
scaffold so far. Thus, in an attempt to develop potent and selective anti-tumor agents, a series of quinoline-3-
carbonitrile derivatives 7a–7g and 11a–11g were synthesized (Fig. 1).
The target compounds were synthesized by a convenient five-step procedure as outlined in Scheme 1. The
commercial available ethyl cyanoacetate was reacted with CH(OEt)3 in the reflux Ac2O using ZnCl2 as catalyst to give
1 as a white solid, and then 4-fluoroaniline was alkylated by Michael addition-elimination with 1 to give the Z/E-
isomerism 2. Next, treatment of 2 with Dowtherm A at reflux afforded 3, which was then treated with an excess of
SOCl2 to give 4 [7]. The side chains 6a–6i was synthesized via a series of substituted anilines with 1H-
* Corresponding author.
E-mail address: gongpinggp@126.com (P. Gong).
1001-8417/$ – see front matter # 2010 Ping Gong. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.
doi:10.1016/j.cclet.2010.03.016

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S.L. Zhang et al. / Chinese Chemical Letters 21 (2010) 939–942
Fig. 1. The structure of Gefitinib and the target compounds.
benzo[d][1,2,3]triazole in the presence of 37% HCHO solution in EtOH at room temperature to give the key important
intermediate 5a–5i, which was then reacted with NaBH4 in dry THF at room temperature to afford 6a–6i. Another
important intermediate 10 was obtained according to the same method as described for 4 when 4-fluoroaniline was
replaced with 4-(trifluoromethoxy)aniline. Finally, the target compounds 7a–7g and 11a–11g could be successfully
obtained via the reaction of 4 and 10 with 6a–6i at 120 8C in DMF, respectively.
With general procedures above, compound 7a–7g and 11a–11g were prepared, and their structures and spectral
1
data of H NMR and MS were outlined in Table 1.
1. Anti-tumor activities
The cytotoxicity of compounds 7a–7g and 11a–11 g was evaluated with four human cancer cell lines (A549: human
lung carcinoma cell line, HT-29: human colon cancer cell line, MDA-MB-231: human breast cancer cell line, SMMC-
7721: human liver cancer cell) by the standard MTT assay [8] in vitro, with Gefitinib as the positive control, and the
results expressed as IC50 were summarized in Table 2.
The pharmacological results indicated that most of the tested compounds displayed excellent selective cytotoxic
activity against SMMC-7721 cell line with IC50 values in the micro-molar level. Four compounds (7c, 7e, 11b and 11f)
were more active than Gefitinb against SMMC-7721 cell line. In the best case, the anti-tumor potency against SMMC-
7721 cell line was almost improved 3.6-times over the reference drug (7e vs. Gefitinib).
Scheme 1. Reagents and conditions: (a) HC(OEt)3, Ac2O, ZnCl2, r.f., 4 h; (b) DMF, 120 8C, 3 h; (c) Dowtherm A, 260 8C, 3 h; (d) SOCl2, DMF, r.f.,
1 h; (e) 37% HCHO, EtOH, r.t., 3 h; (f) NaBH4, THF, r.t. 12 h; (g) DMF, 120 8C, 8 h.

S.L. Zhang et al. / Chinese Chemical Letters 21 (2010) 939–942
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Table 1
The substituents, melting points, 1H NMR and MS data of compounds 7a–7g and 11a–11g.
Compd.
R1
F
R2
mp (8C)
1H NMR (300 MHz, DMSO-d6) d
MS m/z
7a
3-fluoro
145–147
9.18 (s, 1H), 8.27 (dd, 1H, J = 9.2, 5.4 Hz), 7.89 (m, 1H),
7.55 (dd, 1H, J = 9.6, 2.7 Hz), 7.21 (dd, 1H, J = 15.9, 8.2 Hz),
6.77–6.61 (m, 2H), 6.47 (d, 1H, J = 8.3 Hz), 3.51 (s, 3H).
8.34 (s, 1H), 8.11 (d, 1H, J = 9.1 Hz), 7.77–7.61 (m, 2H),
7.47 (t, 1H, J = 7.8 Hz), 7.33 (d, 1H, J = 7.8 Hz),
296.1
7b
F
3-trifluoromethyl
227–228
346.2
7.10 (d, 2H, J = 7.2 Hz), 3.77 (s, 3H).
7c
F
F
3, 5-difluoro
3-methoxy
254–255
137–138
8.38 (s, 1H), 8.05 (d, 1H, J = 10.3 Hz), 7.80–7.60 (m, 2H),
6.80 (t, 1H, J = 9.7 Hz), 6.53 (d, 2H, J = 7.5 Hz), 3.78 (s, 3H).
9.14 (s, 1H), 8.24 (dd, 1H, J = 9.2, 5.4 Hz), 7.85 (m, 1H),
7.47 (dd, 1H, J = 9.8, 2.8 Hz), 7.11 (t, 1H, J = 8.2 Hz),
6.51 (dd, 1H, J = 8.1, 1.9 Hz), 6.39 (s, 1H),
314.1
308.0
7d
6.25 (dd, 1H, J = 8.1, 2.0 Hz), 3.69 (s, 3H), 3.54 (s, 3H).
8.82 (s, 1H), 8.06 (dd, 1H, J = 9.2, 5.8 Hz), 7.72 (m, 1H),
7.43 (dd, 1H, J = 11.1, 2.7 Hz), 7.27 (s, 1H),
7e
F
2,5-dimethyl
154–155
305.9
314.0
7.14 (d, 1H, J = 7.7 Hz), 7.02 (d, 1H, J = 7.8 Hz),
3.71 (s, 3H), 2.29 (s, 3H), 1.88 (s, 3H).
7f
F
F
3,4-difluoro
161–162
166–167
9.14 (s, 1H), 8.26 (dd, 1H, J = 9.2, 5.4 Hz), 7.88 (m, 1H),
7.58 (dd, 1H, J = 9.6, 2.7 Hz), 7.26 (dd, 1H, J = 19.5, 9.3 Hz),
6.99 (m, 1H), 6.58–6.47 (d, 1H, J = 9.0), 3.51 (s, 3H).
9.14 (s, 1H), 8.26 (dd, 1H, J = 9.2, 5.4 Hz), 7.88 (m, 1H),
7.60 (dd, 1H, J = 9.7, 2.8 Hz), 7.24 (t, 1H, J = 9.0 Hz),
7.09 (dd, 1H, J = 6.1, 3.0 Hz,), 6.69 (m, 1H), 3.52 (s, 3H).
9.29 (s, 1H), 8.34 (d, 1H, J = 9.2 Hz), 7.96 (d, 1H, J = 9.3 Hz),
7.76 (s, 2H), 7.50 (s, 1H), 7.37 (s, 2H), 3.65 (s, 3H).
8.38 (s, 1H), 8.29 (s, 1H), 7.77 (s, 2H), 7.47 (t, 1H, J = 8.2 Hz),
7.34 (d, 1H, J = 7.7 Hz), 7.11 (s, 2H), 3.77 (s, 3H).
8.43 (s, 1H), 8.24 (s, 1H), 7.78 (s, 2H), 6.82 (t, 1H, J = 9.6 Hz),
6.56 (d, 2H, J = 7.0 Hz), 3.78 (s, 3H).
7g
3-chloro-4-fluoro
330.0
331.9
11a
11b
11c
11d
OCF3
OCF3
OCF3
OCF3
3-fluoro
140–141
188–190
197–199
88–89
362.0
412.0
380.0
374.1
3-trifluoromethyl
3, 5-difluoro
3-methoxy
9.18 (s, 1H), 8.26 (d, 1H, J = 9.2 Hz), 7.89 (dd, 1H, J = 9.1, 2.0 Hz),
7.61 (s, 1H), 7.13 (t, 1H, J = 8.2 Hz), 6.54 (dd, 1H, J = 8.1, 1.9 Hz),
6.46 (s, 1H), 6.34 (dd, 1H, J = 8.1, 2.0 Hz), 3.68 (s, 3H), 3.59 (s, 3H).
8.93 (s, 1H), 8.08 (d, 1H, J = 9.1 Hz), 7.76 (dd, 1H, J = 9.1, 2.4 Hz),
7.52 (s, 1H), 7.26 (s, 1H), 7.18 (d, 1H, J = 7.8 Hz),
7.07 (d, 1H, J = 7.8 Hz), 3.77 (s, 3H), 2.26 (s, 3H), 1.97 (s, 3H).
8.87 (s, 1H), 8.06 (d, 1H, J = 9.1 Hz), 7.76–7.68 (dd, 1H, J = 9.0, 2.1 Hz),
7.48 (s, 1H), 7.27 (d, 1H, J = 8.6 Hz), 7.10 (s, 2H), 3.73 (s, 3H),
2.27 (s, 3H), 1.98 (s, 3H).
11e
11f
11g
OCF3
OCF3
OCF3
2,5-dimethyl
2,4-dimethyl
3-bromo
134–135
112–113
205–207
372.1
372.2
8.36 (s, 1H), 8.25 (s, 1H), 7.75 (s, 2H), 7.26–7.16 (m, 2H),
7.01 (s, 1H), 6.83 (d, 1H, J = 6.4 Hz), 3.76 (s, 3H).
421.9
423.9
Table 2
The cytotoxicity of compounds 7a–7g and 11a–11g against A549, HT-29, MDA-MB-231 and SMMC-7721 cell lines.
Compd.
IC50 (mmol/L)
Compd.
IC50 (mmol/L)
A549
HT-29
MDA-MB-231
SMMC-7721
A549
HT-29
MDA-MB-231
SMMC-7721
7a
7b
>200
>200
>200
228
>200
NTa
>200
75.30
84.74
>200
NTa
36.24
65.74
27.41
31.24
7.86
11a
11b
11c
11d
11e
11f
106
>200
95
>200
29.18
63.28
75.02
137.1
101.02
26.05
NTa
127
15.32
31.11
64.38
>200
9.96
7c
7d
>200
>200
NTa
>200
81
>200
73.04
>200
110.04
NTa
7e
55
>200
>200
14.68
7f
7g
>200
>200
18.06
>200
>200
5.82
>200
>200
27.08
34.15
38.82
28.07
11g
12.55
Gefitinib
a
Not test.

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S.L. Zhang et al. / Chinese Chemical Letters 21 (2010) 939–942
Among all of those tested compounds, compound 11g displayed the most potent cytotoxicity with IC50 values of
14.68 mmol/L, 26.05 mmol/L and 12.55 mmol/L against A549, MDA-MB-231 and SMMC-7721, respectively.
The conclusions above were made just preliminarily, the further studies on their anti-tumor activities and structure
activity relationship (SAR) are in progressing.
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