Design, synthesis and antitumor activity of 6,7-disubstituted-4-(heteroarylamino)quinoline-3-carbonitrile derivatives

Article abstract of DOI:10.1016/j.cclet.2010.01.016

A series of new 6,7-disubstituted-4-(benzothiazol-6-ylamino)quinoline-3-carbonitrile derivatives (12a-l) were synthesized. The cytotoxicity of 12 new compounds was evaluated in AGS, HepG2 and HT-29 cell lines. The results showed that compounds 12g, 12h, 12i, 12k and 12l displayed more potent cytotoxic activities than Bosutinib, compound 12l exhibited the most potent antitumor activity among the tested compounds.

Full text of DOI:10.1016/j.cclet.2010.01.016

Available online at www.sciencedirect.com
Chinese Chemical Letters 21 (2010) 554–557
www.elsevier.com/locate/cclet
Design, synthesis and antitumor activity of 6,7-disubstituted-4-
(heteroarylamino)quinoline-3-carbonitrile derivatives
*
Bao Liu, Qi Dong You , Zhi Yu Li
Department of Medicinal Chemistry, China Pharmaceutical University, Nanjing 210009, China
Received 15 September 2009
Abstract
A series of new 6,7-disubstituted-4-(benzothiazol-6-ylamino)quinoline-3-carbonitrile derivatives (12a–l) were synthesized. The
cytotoxicity of 12 new compounds was evaluated in AGS, HepG2 and HT-29 cell lines. The results showed that compounds 12g,
12h, 12i, 12k and 12l displayed more potent cytotoxic activities than Bosutinib, compound 12l exhibited the most potent antitumor
activity among the tested compounds.
# 2010 Qi Dong You. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.
Keywords: 3-Quinolinecarbonitrile derivatives; Synthesis; Antitumor
Protein tyrosine kinases regulate multiple cellular processes that contribute to tumor development and progression,
including cell growth, differentiation, migration, and apoptosis. Clinical studies conducted over the past decade have
established that tyrosine kinase inhibitors are safe and therapeutically active in selected populations of cancer patients,
and several of these drugs namely, Imatinib, Erlotinib and Gefitinib are now part of the standard treatment regimen for
specific tumor types [1,2]. The rationale for targeting protein tyrosine kinases in human cancer is compelling. Among
small organic molecules, 4-anilino-3-quinolinecarbonitrile was identified as one of more successful chemical class as
HKI-272 and EKB-569 belong to it [3].
The structure–activity relationship studies of 3-quinolinecarbonitrile derivatives have demonstrated that changing
the substituents on the 4-anilino and 7-substituted group affected the kinase selectivity [4]. Using benzothiazole-6-
amine as replacement of the 4-anilino group, as benzothiazoles are therapeutic compounds with a wide range of
biological activities, while 2-substituted benzothiazoles exhibited potent antitumoral activity [5]. In addition, using
amide as replacement of 7-alkoxy part of EKB-569. We designed a series of N-(3-cyano-4-(benzothiazol-6-ylamino)-
6-methylquinoline-7-yl) amides compounds, and the synthetic route of the target compounds is outlined in Scheme 1.
Reaction of benzothiazole-2-amine with fume nitric acid gave compound 1, which was conveniently converted to
compound 2 via Sandmeyer reaction with H3PO4, NaNO2 and HCl giving a diazonium salt followed by reacting with
HCl and CuCl at rt. Reaction of 2 with corresponding amine gave compound 3a–b. Reduction of 3a–b and 1 using Fe
and HOAc in CH3OH gave benzothiazole-6-amine 4a–c, respectively.
* Corresponding author.
E-mail address: youqidong@gmail.com (Q.D. You).
1001-8417/$ – see front matter # 2010 Qi Dong You. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.
doi:10.1016/j.cclet.2010.01.016

B. Liu et al. / Chinese Chemical Letters 21 (2010) 554–557
555
Scheme 1. (a) 90% HNO3, ꢀ5 to 0 8C, 1 h; 87%; (b) (i) H3PO4, NaNO2, HCl, ꢀ10 to 0 8C; (ii) HCl, CuCl, rt, 3 h; 65% (two steps); (c) R1H, rt, 4 h;
87%; (d) Fe, HOAc, 65 8C, 4 h; 65–68%; (e) guanidinium nitrate, H2SO4; 1 h; 71%; (f) ethyl(ethoxymethylene)cyanoacetate, 130 8C, N2, 8 h; 92%;
(g) Ph2O, reflux N2, 8 h; 30%; (h) POCl3, reflux 12 h; 85%; (i) i-PrOH, reflux N2, 8 h; 90–95%; (j) Fe, HOAc, DMF, 65 8C 6 h; yield 62–67%; (k) 3-
chloropropanoyl chloride, DMAP, THF, 0 8C, N2, 1 h; 64–73%; (l) HN(R)2, KI, DMF, 85 8C, N2, 8 h; 65–77%.
Treatment of 4-methylaniline with guanidinium nitrate in H2SO4 at 0 8C gave compound 5 selectively [6], which
was converted to compound 7 by Gould–Jacobs reaction with ethyl (ethoxymethylene)cyanoacetate, followed by
thermal cyclization in biphenyl ether under reflux. Subsequent chlorination of 7 with reflux POCl3 afforded the key
intermediate 8. Reaction of 8 with corresponding benzothiazole-6-amine in i-PrOH at reflux gave 9a–c respectively.
Reduction of 9a–c using Fe and HOAc in DMF gave compound 10a–c. Treatment of 10a–c with 3-chloropropanoyl
chloride in anhydrous THF in the presence of DMAP provided 11a–c. Finally, 11a–c were treated with HNR2 in DMF
in the presence of KI to give target compounds 12a–l. The structures of the target compounds were shown in Table 1
1
and characterized by MS, H NMR spectra and elemental analysis (EA) [7].
The cytotoxicity of 12 new compounds was evaluated in AGS, HepG2, HT-29 cell lines in vitro by the standard
MTT assay[8] with Bosutinib as a positive control and the results are reported in Table 1. The results showed that
compounds containing 2-amino benzothiazole 12a–e were all much less active, but the corresponding dialkyl
amino benzothiazole 12f–l showed more potent than Bosutinib. It be concluded that compounds containing
hydrophobic group at position 2 of benzothiazole are preferred. Compound 12h, 12i, 12l exhibited the most potent
antitumor activity against AGS, HepG2, HT-29 respectively. Compound 12l exhibited the most potent antitumor
activity among the 12 compounds. Therefore, it merits further investigation as the lead compound in continuing
studies.

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B. Liu et al. / Chinese Chemical Letters 21 (2010) 554–557
Table 1
The structures and cytotoxic activity of the target compounds 12a–l against AGS, HepG2, HT-29cells (IC50 at mmol/L).
No.
R0
N(R)2
AGS
HepG2
HT-29
20.76
12a
NH2
40.92
>50
12b
NH2
>50
>50
>50
>50
12c
12d
NH2
NH2
NH2
N(CH2CH3)2
>50
>50
>50
45.01
39.79
12e
12f
>50
>50
>50
N(CH3)2
N(CH3)2
N(CH3)2
21.63
14.64
12.33
12g
12h
9.58
1.56
23.69
4.65
4.20
5.59
12i
N(CH3)2
5.63
3.74
3.61
12j
12k
N(CH3)2
N(CH2CH3)2
N(CH2CH3)2
34.13
11.34
20.54
18.70
11.80
3.69
N(CH2CH3)2
12l
Bosutinib
N(CH2CH3)2
3.55
7.2
10.20
47.7
0.33
4.99
Acknowledgment
The work was supported by National Natural Science Foundation of China (No. 30371676).
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[7] The data of selected compounds: 12a: mp: 183–186 8C. IR (KBr): 3371, 3191, 2948, 2839, 2203, 1626, 1463, 745 cmꢀ1, 1H NMR (300 MHz,
DMSO-d6): d 2.24(s, 3H, CH3N), 2.48(s, 3H, CH3), 2.46–2.51 (m, 6H, CH2), 2.78(m, 4H, CH2), 7.55(s, 2H, NH2), 7.17(dd, 1H, H-50, J1 = 1.8,
J2 = 8.4), 7.36(d, 1H, H-40, J = 8.4), 7.66(d, 1H, H-70, J = 1.8), 7.89(s, 1H, H-5), 8.37(s, 1H, H-8), 8.82(s, 1H, H-2), 9.57(s, 1H, NH), 10.67(s,
1H, CONH); 13C NMR(DMSO-d6): d 19.5, 48.3, 52.7, 55.4, 57.2, 87.5, 112.9, 116.2, 120.2, 120.8, 121.3, 123.9, 124.4, 125.0, 126.8, 128.7,
131.8, 133.4, 135.3, 150.5,150.8, 154.7, 169.8; MS (EI, m/z): 500.2 (M+). Anal. Calcd. for C25H26N8OS.HCl: C 57.41, H 5.20, N 21.42; Found:
C 57.57, H 5.36, N 21.70. 12h: mp: 168–170 8C. IR (KBr): 3421, 3047, 2792, 2204, 1608, 1522, 1290, 883, 540, 1H NMR (300 MHz, DMSO-
d6): d 1.78(s, 4H, CH2), 2.41(s, 3H, CH3), 2.64–2.62(m, 4H), 2.81(s, 2H, CH2CO), 3.16(s, 6H, N(CH3)2), 7.21(d, 1H, H-50, J = 8.4), 7.45(d, 1H,
H-40, J = 8.4), 7.75(s, 1H, H-70), 8.34(s, 1H, H-5), 8.40(s, 1H, H-8), 8.60(s, 1H, H-2), 9.68(s, 1H, NH), 10.69(s, 1H, CONH). 13C NMR(DMSO-

B. Liu et al. / Chinese Chemical Letters 21 (2010) 554–557
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d6): d 18.2, 23.4, 35.1, 51.5, 53.2, 85.1, 114.5, 117.2, 118.1, 118.8, 118.9, 123.3, 124.4, 127.9, 131.1, 132.2, 140.6, 148.3, 150.7, 151.5, 152.8,
168.5, 171.1; MS (EI, m/z): 499.2 (M+). Anal. Calcd. for C26H27N7OS.HCl: C, 59.82; H, 5.41; N, 18.78; Found: C, 60.10; H, 5.78; N, 18.51; 12l:
mp: 143–145 8C. IR (KBr): 3421, 3047, 2204, 1589, 1522, 1407, 1290, 1024, 883, 540 cmꢀ1; 1H NMR (300 MHz, DMSO-d6): d 1.23(t, 6H, 2ꢁ
CH3), 1.44(s, 2H, CH2), 1.58(s, 4H, CH2), 2.48(s, 3H, CH3), 2.50–2.65(m, 2H), 3.18(s, 2H, CH2), 3.55(q, 4H, CH3CH2NCH2CH3), 7.19(dd, 1H,
H-50, J1 = 1.8, J2 = 8.4), 7.43(d, 1H, H-40, J = 8.4), 7.54(s, 2H, NH2), 7.73(d, 1H, H-70, J = 1.8), 8.36(s, 1H, H-5), 8.41(s, 1H, H-8), 8.47(s, 1H,
H-2), 9.70(s, 1H, NH), 10.11(s, 1H, CONH); 13C NMR(DMSO-d6): d 18.8, 23.1, 24.3, 53.5, 56.8, 59.2, 86.2, 113.4, 116.0, 117.2, 118.5, 120.5,
123.7, 140.0, 147.8, 149.8, 1150.5, 151.2, 168.1, 169.8; MS (EI, m/z): 529.2 (M+). Anal. Calcd. for C28H33N7OS.HCl: C, 60.91; H, 6.21, N,
17.76; Found: C, 60.84; H, 6.53, N, 17.41.
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