4-Anilino-7-pyridyl-3-quinolinecarbonitriles as Src kinase inhibitors

Article abstract of DOI:10.1016/j.bmcl.2009.07.043

A series of 4-anilino-7-pyridyl-3-quinolinecarbonitriles was prepared as Src kinase inhibitors. A systematic SAR study of substitutions on both the pyridine ring and the 3-quinolinecarbonitrile core established the requirements for optimal activity. The l

Full text of DOI:10.1016/j.bmcl.2009.07.043

Bioorganic & Medicinal Chemistry Letters 19 (2009) 5071–5074
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Bioorganic & Medicinal Chemistry Letters
journal homepage: www.elsevier.com/locate/bmcl
4-Anilino-7-pyridyl-3-quinolinecarbonitriles as Src kinase inhibitors
a
a
b
b
Nan Zhang a, , Biqi Wu , Diane H. Boschelli , Jennifer M. Golas , Frank Boschelli
*
a Chemical Sciences, Wyeth Research, Pearl River, NY 10965, USA
b Discovery Oncology, Wyeth Research, Pearl River, NY 10965, USA
a r t i c l e i n f o
a b s t r a c t
Article history:
A series of 4-anilino-7-pyridyl-3-quinolinecarbonitriles was prepared as Src kinase inhibitors. A system-
atic SAR study of substitutions on both the pyridine ring and the 3-quinolinecarbonitrile core established
the requirements for optimal activity. The lead compound, 17, showed potent activity in both the Src
enzyme assay and cell assays, and demonstrated in vivo anti-tumor activity in a xenograft model.
Ó 2009 Elsevier Ltd. All rights reserved.
Received 2 June 2009
Revised 6 July 2009
Accepted 7 July 2009
Available online 10 July 2009
Keywords:
4-Anilino-7-pyridyl-3-
quinolinecarbonitriles
Src kinase inhibitors
Cl
Cl
O
Protein kinases are important targets in cancer therapeutics due
to the important roles they play in signal transduction pathways
that regulate cell proliferation and survival in response to external
stimuli.1 Depending on their protein substrate specificity, kinases
are categorized as serine/threonine kinases or tyrosine kinases.
Src kinase is a member of the Src family of non-receptor protein
tyrosine kinases. It plays an essential role in signal transduction
pathways controlling proliferation, migration and angiogenesis.2
Extensive research has demonstrated that small molecule Src
inhibitors may be useful for the treatment of a variety of disease
states, including cancer and osteoporosis.3 A 2-amino-1,3-thia-
zole-5-carboxamide multi-kinase (including Src kinase) inhibitor
dasatinib (SPRYCELÒ) was approved for treatment of Philadelphia
chromosome-positive leukemias.4 Other structural classes of Src
kinase inhibitors including pyrrolo[2,3-d]pyrimidines,5a pyr-
ido[2,3-d]pyrimidines,5b oxindoles,5c purines,5d and quinazolines5e
have been reported in the literature.
Cl
Cl
O
HN
HN
O
O
CN
X
CN
N
N
RO
N
N
2: SKI-606
1: X = H, OMe
Cl
Cl
O
Cl
Cl
O
HN
HN
N
CN
CN
N
X
N
Y
N
X
3: X = O, NMe; Y = S
4: X = O, NMe; Y = O
5: X = O, NMe
A general synthetic approach to 4-anilino-7-pyridyl-3-quino-
linecarbonitriles 11–14 and 17–21, in which the quinoline core is
linked to the C-2 position on the pyridine ring, via an intermediate
8, is shown in Scheme 1. Compound 8 was prepared by bromina-
tion of bromo-methylpyridines 6, followed by SN2 replacement
of the benzylic bromide with amines. From compound 8, bromo-
lithium exchange followed by quenching with tributyltin chloride
provided tributylpyridylstannanes 9, which then underwent Stille
coupling with 7-bromo-3-quinolinecarbonitrile 10a7 or 7-iodo-3-
quinolinecarbonitrile 10b7 to furnish the desired products 11–14
and 17–21 (Tables 1 and 2). This approach is generally applicable
to synthesis of the final compounds described in this Letter.
However, it is not efficient in the generation of a large number of
analogues with different amino groups since the amine was intro-
duced at an early stage.
We previously reported that 7-alkoxy-4-anilino-3-quinoline-
carbonitriles 1 are potent inhibitors of Src kinase activity.6 Among
these, analog 2 (SKI-606) is currently in clinical trials. We then pre-
pared analogs of 1 with a substituted thiophene 3,7 a substituted
furan 4,8 or a substituted phenyl group 59 at C-7 as Src inhibitors.
In our continuing search for an optimal Src kinase inhibitor, we fur-
ther extended our SAR studies and prepared analogs with a pyri-
dine ring at C-7.
* Corresponding author. Tel.: +1 845 602 3425; fax: +1 845 602 5561.
E-mail address: zhangn@wyeth.com (N. Zhang).
0960-894X/$ - see front matter Ó 2009 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmcl.2009.07.043

5072
N. Zhang et al. / Bioorg. Med. Chem. Lett. 19 (2009) 5071–5074
NHAr
N
a
b
CHO
CH3
CH2Br
CN
CH2NR2
a
Br
N
6
Br
N
7
+
Br
N
8
Br
N
22
Br
10a
NHAr
CN
NHAr
N
NHAr
N
d
CN
CN
c
b
CH2NR2
N
Bu3Sn
N
9
R2NCH2
R2N
N
N
N
11-14, 17-21
OHC
23
NHAr
N
Scheme 2. Reagents: (a) 1 equiv Me6Sn2, Pd(PPh3)4; (b) HNR2, NaCNBH3.
CN
X
O
10a X = Br
10b X = I
Br
CO2H
a
Br
c
b
N
O
N
N
Scheme 1. Reagents: (a) 1 equiv NBS; (b) HNR2; (c) n-BuLi, nBu3SnCl; (d) 10a or
10b, PdCl2(PPh3)2.
N
25
24
Br
(i-PrO)2B
N
N
Table 1
O
O
Src inhibitory activity of compounds 11–16
N
26
27
Cl
Cl
O
NHAr
CN
HN
CN
N
N
d
3
O
N
4
5
N
15
2
N
N
Scheme 3. Reagents: (a) CDI, morpholine; (b) BH3ÁMe2S; (c) n-BuLi, (i-PrO)3B; (d)
Pd(PPh3)4, 10a.
6
O
Compd
Pyridyl isomer
Src enzyme IC50 (nM)6e
Src cell IC50 (nM)6a
product 23 selectively, due to the different reactivity of the two
aryl bromides 22 and 10a. Reductive amination of aldehyde 23
gave the final products. This approach has the advantage that the
amino groups are introduced at the last step of the synthesis,
allowing for the parallel synthesis of analogues with different ami-
no groups.
11
12
13
14
15
16
2,3
2,4
2,5
2,6
3,5
3.6
950
26
2.9
24
36
7.0
>10,000
310
170
860
2800
330
The synthesis of 3,5-pyridyl isomer 15 (Scheme 3) started from
5-bromonicotinic acid 24. Amidation followed by reduction gave
morpholinomethyl pyridine 26. Bromo-lithium exchange followed
by boronic acid formation and Suzuki coupling led to compound 15
(Table 1).
The synthesis of 3,6-isomer 16 is shown in Scheme 4. Starting
from 5-hydroxy-2-methylpyridine 28, tosylation and N-oxide for-
mation, followed by treatment with acetic anhydride gave com-
pound 30. Deacetylation of the latter and oxidation afforded the
desired aldehyde 31. Reductive amination, removal of the tosyl
group followed by triflation gave 33, which was coupled with 10a.
The desired compound 16 was isolated from the reaction mixture.
Compounds 34 and 35 (Table 3) were prepared in the same
manner as compound 17, starting from 7-bromo-4-(3,4,5-trimeth-
oxyanilino)-3-quinolinecarbonitrile11a and 7-bromo-4-(2,4-dichlo-
roanilino)-3-quinolinecarbonitrile,11b respectively.
Compounds 11–21, 34, and 35 were evaluated in a Src kinase
assay12 and a Src cellular assay.6a The cell based assay for Src inhi-
bition is a 3 day proliferation assay measuring the anchorage inde-
pendent growth of rat fibroblasts expressing activated human Src.
Antiproliferative activity in this assay correlates with the inhibition
of Src dependent phosphorylation of cellular substrates. Table 1
shows Src inhibitory activity of compounds 11–16, with the quin-
olinecarbonitrile core attached at the C-2 or C-3 position on the
pyridyl ring, and a (4-morpholinyl)methyl group attached at the
C-3, C-4, C-5, or C-6 position on the pyridyl ring. Compound 13,
bearing a quinolinecarbonitrile core at the C-2 position and the
Table 2
Src inhibitory activity of compounds 13, 17–21
Cl
Cl
O
HN
N
CN
R2N
N
Compd NR2
Src enzyme IC50 (nM)6e Src cell IC50 (nM)6a
13
17
18
19
20
4-Morpholinyl
4-Methyl-1-piperazinyl
4-Thiomorpholinyl
1-Oxido-4-thiomorpholinyl
1,1-Dioxido-4-
thiomorpholinyl
2.9
4.0
5.1
1.9
1.8
170
61
230
96
130
21
Dimethylamino
3.9
130
A more efficient route to analogues of 13 (the most potent iso-
mer in Table 1) with various amino groups is shown in Scheme 2.
Starting from 6-bromonicotinaldehyde 22, palladium-catalyzed
selective cross-coupling10 between 22 and 10a gave the desired

N. Zhang et al. / Bioorg. Med. Chem. Lett. 19 (2009) 5071–5074
5073
OTs
Compared with a 2,4-dichloro-5-methoxyanilino group (17), both
3,4,5-trimethoxyanilino (34) and 2,4-dichloroanilino (35) groups
gave lower potency in both the Src kinase assay and the Src cellular
assay.
We further moved the 5-(4-methyl-1-piperazinylmethyl)-2-
pyridyl group from the 7-position on the 3-quinolinecarbonitrile
core (compound 17) to the 6-position (compound 36, prepared
from 6-bromo-4-(2,4-dichloro-5-methoxyanilino)-3-quinolinecar-
bonitrile7). In agreement with what we reported earlier,6b,7 the
6-analogue proved to be much less potent in both the Src kinase
assay and the Src cellular assay (Table 4).
Compound 17, the lead compound in the 4-anilino-7-pyridyl-3-
quinolinecarbonitrile series, showed comparable activity with
SKI-606 and the lead compound in the 7-furanyl-3-quinolinecar-
bonitrile series8 in both the Src kinase assay and the Src cellular
assay. It was further evaluated in an HT-29 colon tumor model,6b
and showed oral efficacy comparable to that of SKI-606.
In summary, we prepared a series of 4-anilino-7-pyridyl-3-
quinolinecarbonitriles as Src kinase inhibitors. A systematic SAR
study illustrated requirements for optimal activity. The best
potency was obtained when the quinolinecarbonitrile core was
attached at the 2-position on the pyridyl ring, and a dialkylami-
nomethyl group was attached at the 5-position on the pyridyl ring.
The SAR on the quinolinecarbonitrile core substitution resembled
that observed in the 7-alkoxy-4-anilino-3-quinolinecarbonitrile
series. The lead compound in the series, compound 17, showed
comparable activity with SKI-606 in both the Src kinase assay
and the Src cellular assay, and demonstrated in vivo anti-tumor
activity in a xenograft model.
OTs
OH
b
a
+
N
O-
29
AcO
CH3
N
CH3
N
30
28
OTs
OTs
O
d
c
e
N
N
OHC
N
32
31
NHAr
N
CN
OTf
f
O
N
O
N
N
33
16
N
Scheme 4. Reagents: (a) TsCl, then mCPBA; (b) Ac2O; (c) CH3OH, then MnO2; (d)
morpholine, NaCNBH3; (e) NaOH, then Tf2O; (f) 10a, Me6Sn2, PdCl2(PPh3)2.
Table 3
Src inhibitory activity of compounds 17, 34, and 35
R
HN
CN
N
N
N
N
Compd
R
Src enzyme IC50 (nM)6e Src cell IC50 (nM)6a
Acknowledgments
17
34
35
2,4-Dichloro-5-methoxy
3,4,5-Trimethoxy
2,4-Dichloro
4.0
18
12
61
360
460
The authors gratefully thank Judy Lucas and other members of
the in vivo study group at Discovery Oncology for the xenograft
study, Chemical Technology Department for compound character-
ization, and Drs. Tarek Mansour and Dennis Powell for manage-
ment and support of this work.
Table 4
Src inhibitory activity of compounds 17, 36, and SKI-606
Cl
Cl
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N
N
N
Compd
Isomer
Src enzyme IC50 (nM)6e
Src cell IC50 (nM)6a
17
36
SKI-606
7
6
4.0
130
3.8
61
2900
100
(4-morpholinyl)methyl group attached at the C-5 position on the
pyridyl ring, was the most potent analogue in both the Src kinase
assay and the Src cellular assay. Analogues with other substitution
patterns proved to be less potent in both assays.
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tion on the pyridyl ring, we then studied the effects of various ami-
no groups at C-5 of the pyridine ring on Src inhibitory activity. As
shown in Table 2, all the analogues (17–21) showed good potency
in the Src kinase assay, with IC50 values ranging from 1.9 nM to
5.1 nM. In the Src cellular assay, compound 17, with a 4-methyl-
1-piperazinylmethyl group at the 5-position on the pyridyl ring,
showed the highest potency.
The SAR of the anilino head-piece at the 4-position on the
quinolinecarbonitrile core (Table 3) mimicked what we reported
earlier on the 7-alkoxy-4-anilino-3-quinolinecarbonitrile series.6a,b

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