Scaffold oriented synthesis. Part 4: Design, synthesis and biological evaluation of novel 5-substituted indazoles as potent and selective kinase inhibitors employing heterocycle forming and multicomponent reactions

Article abstract of DOI:10.1016/j.bmcl.2011.01.001

We report the synthesis and biological evaluation of 5-substituted indazoles as kinase inhibitors. The compounds were synthesized in a parallel synthesis fashion from readily available starting materials employing heterocycle forming and multicomponent reactions and were evaluated against a panel of kinase assays. Potent inhibitors were identified for Gsk3β, Rock2, and Egfr.

Full text of DOI:10.1016/j.bmcl.2011.01.001

Bioorganic & Medicinal Chemistry Letters 21 (2011) 1480–1483
Contents lists available at ScienceDirect
Bioorganic & Medicinal Chemistry Letters
journal homepage: www.elsevier.com/locate/bmcl
Scaffold oriented synthesis part 4: Design, synthesis and biological evaluation
of novel 5-substituted indazoles as potent and selective kinase inhibitors
employing heterocycle forming and multicomponent reactions
⇑
Irini Akritopoulou-Zanze , Brian D. Wakefield, Alan Gasiecki, Douglas Kalvin , Eric F. Johnson,
Peter Kovar, Stevan W. Djuric
Global Pharmaceutical Research and Development, Abbott Laboratories, 100 Abbott Park Road, Abbott Park, IL 60044, USA
a r t i c l e i n f o
a b s t r a c t
Article history:
We report the synthesis and biological evaluation of 5-substituted indazoles as kinase inhibitors. The
compounds were synthesized in a parallel synthesis fashion from readily available starting materials
employing heterocycle forming and multicomponent reactions and were evaluated against a panel of
kinase assays. Potent inhibitors were identified for Gsk3b, Rock2, and Egfr.
Received 24 November 2010
Revised 29 December 2010
Accepted 3 January 2011
Available online 11 January 2011
Ó 2011 Elsevier Ltd. All rights reserved.
Keywords:
Kinase scaffolds
Kinase inhibitors
Gsk3b inhibitors
Rock2 inhibitors
Egfr inhibitors
Imidazopyrimidine
Imidazopyridines
Van Leusen reactions
MCR, multicomponent reactions
As part of our efforts to enhance the Abbott compound collec-
tion with kinase inhibitors1 we disclosed previously the implemen-
tation of [2+3] cycloaddition reactions to prepare novel and potent
indazole and aminoindazole kinase inhibitors.2 The rationale be-
hind this approach was the ability to rapidly explore the ATP bind-
ing site of numerous kinases, utilizing readily available starting
materials, without compromising the novelty of the final mole-
cules. In this report we describe our efforts in applying the same
strategy employing heterocycle forming and multicomponent
reactions to suitably substituted indazoles (Fig. 1).
The majority of the reaction sequences utilized shared common
starting materials and intermediates and were highly divergent.
Starting with 5-bromoindazole 1 (Scheme 1), aryl acetyl ketone
intermediate 6 could be obtained via Stille coupling of 3 with
Boc protected indazole 2. Alternatively, substituted ketones of gen-
eric structure 6 could be obtained from the 5-carboxylic acid inda-
zole 4 via Weinreb amide 5. Bromination of ketones 6 provided
intermediates 7 which were poised for heterocycle forming reac-
Heterocycle Formations
Multicomponent reactions
FG
Het
N
N
N
N
H
H
Proposed new
scaffolds
Figure 1. Design of novel molecules based on known kinase hinges.
tions with aminopyrimidines and thioamides to yield imidazopyr-
imidine and thiazole substituted indazoles 8 and 9, respectively.
Amino-substituted fused imidazo-pyridines, -pyrimidines, -pyr-
azines and -thiazoles 11 and 12 (Scheme 2) could be obtained in one
step by applying multicomponent reactions3 to commercially avail-
able aldehyde 10. Aldehyde 10 could also be used as an input in Van
Leusen reactions4 to afford imidazolyl-indazoles 14. It should be
noted that although the above-mentioned procedureswere synthet-
ically facile the resulting final molecules were highly complex and to
our knowledge had never been made before.
Having secured numerous analogs in a highly efficient manner
we proceeded to evaluate them in a panel of kinase assays.2 We
again identified highly potent kinase inhibitors that exhibited a
⇑
Corresponding author. Tel.: +1 847 9375006; fax: +1 847 9350310.
E-mail address: irini.zanze@abbott.com (I. Akritopoulou-Zanze).
Present address: 1201 Lockwood Drive, Buffalo Grove, IL 60089, USA.
0960-894X/$ - see front matter Ó 2011 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmcl.2011.01.001

I. Akritopoulou-Zanze et al. / Bioorg. Med. Chem. Lett. 21 (2011) 1480–1483
1481
N
N
NH2
OEt
N
Br
Br
a
N
N
N
SnBu3
N
N
3
N
N
N
O
O
R1
H
b
N
Boc
e
H
Br
1
4
2
5
f
8
N
O
O
R1
R1
R2
S
d, a
f
N
N
c
H
N
O
HO
Boc
N
N
6
7
S
N
N
N
H
R2
NH2
H
N
R1
N
H
9
Scheme 1. (a) Boc2O, DMAP, CH2Cl2, rt, quant; (b) PdCl2(PPh3)2, toluene, 100 °C, ON, 36%; (c) CH3ONHCH3, CH2Cl2, DMF, Et3N, EDC, rt, 24 h, 44%; (d) R1CH2MgCl, THF, 0 °C to
rt, 58 %; (e) pyÅHBr3, THF, 40 °C, 42%; (f) EtOH, 80 °C, 24 h, 25–71%.
variety of selectivity patterns depending on the heterocycle and its
substituents in the 5-position of the indazole ring.
Y
X
N
N
Imidazopyrimidine ring attachments provided potent inhibitors
for Rock2 and Gsk3b (Table 1) with a phenyl substituted heterocy-
cle being much more potent than the parent (8b vs. 8a). Compound
8b also exhibited some Pim1 activity although it was much more
potent against Rock2 and Gsk3b. Thiazolyl-indazoles 9 were, in
general, more selective for Rock2 over Gsk3b but not as potent as
8b. Benzylamino and phenethylamino substitutions at the 2 posi-
tion of the thiazole ring improved Rock2 potency, however the
compounds were also potent against Aurora2 (compounds 9e
and 9f). Interestingly, anilino substituted compound 9d, while
equipotent for Rock2 and Aurora2 was about threefold more
selective for Gsk3b. The additional substitution of a phenyl ring
in the 5-position of the thiazole ring diminished the Gsk3b activity
(compound 9g vs. 9d).
A reverse trend was observed with amino-substituted imidazo-
fused heterocyclic attachments to the indazole ring (compound 11,
Table 2). In this case the compounds were more selective for Gsk3b
over Rock2. The highest inhibitory activity against Gsk3b was
observed with imidazopyrimidines which were much more potent
than imidazopyridines (11c vs. 11a). Depending on the substitu-
ents on the amino group of the 3 position of the imidazole ring
the Rock2 activity could also be attenuated. A cyclohexyl or a
phenyl substituent (compounds 11c and 11f, respectively)
X
NH2
Y
N
NH
R3
N
H
N
a
11
S
NH2
OHC
S
N
N
N
N
N
H
a
10
N
NH
R3
C-
N+
N
H
12
R5
b
O
R5
S
O
N
N
13
N
R4
N
H
14
Scheme 2. (a) Sc(OTf)3, MeOH, R3N+„CÀ, rt, 10–74%; (b) R4NH2, DMF, 60 °C, 4 h,
then K2CO3, tosmic 13, 60 °C, ON, 4–23%.
Table 1
Kinase inhibitory activity of 2-(indazol-5-yl)-3-substituted imidazopyrimidines 8 and 4-(indazol-5-yl)-2,5-substituted thiazoles 9a
R2
N
N
R1
N
N
S
N
R1
N
N
H
N
H
8
9
Compound
R1
H
R2
Aurora2
Ki ( M)
Egfr
Ki (
Gsk3b
Jak2
Kdr
Ki (
Pak4
Ki ( M)
Pim1
Ki ( M)
Rock2
Ki ( M)
l
l
M)
Ki (lM)
Ki (l
M)
l
M)
l
l
l
8a
8b
>4.900
>1.800
0.141
ND
>8.880
>3.750
1.664
0.226
>4.900
ND
0.010
ND
>8.880
>3.750
0.339
0.006
9a
9b
H
H
4.45
ND
ND
2.861
4.472
ND
ND
>8.880
>8.880
>3.750
>3.750
4.156
2.899
0.513
0.909
2.125
H2N
(continued on next page)

1482
I. Akritopoulou-Zanze et al. / Bioorg. Med. Chem. Lett. 21 (2011) 1480–1483
Table 1 (continued)
Compound
R1
H
R2
Aurora2
Ki ( M)
Egfr
Gsk3b
Ki ( M)
Jak2
Kdr
Ki (
Pak4
Ki ( M)
Pim1
Ki ( M)
Rock2
Ki ( M)
l
Ki (l
M)
l
Ki (l
M)
l
M)
l
l
l
N
H
9c
3.406
0.834
ND
3.925
0.289
ND
>8.880
>8.880
>3.750
>3.750
1.952
2.656
0.888
0.864
9d
H
>1.800
>1.800
ND
ND
N
H
N
H
9e
9f
H
H
0.588
0.810
>5.450
>5.450
>1.450
ND
>8.880
>8.880
>3.750
>3.750
>8.570
>8.570
0.136
0.364
N
H
9g
>4.900
>4.900
ND
ND
>5.450
3.402
ND
ND
>8.880
>8.880
>3.750
>3.750
>8.570
>8.570
1.413
0.822
N
H
N
H
9h
a
Ki values are based on six point curves.
Table 2
Kinase inhibitory activity of 6-(indazol-5-yl)-3-substituted fused imidazoles 11 and 6-(indazol-5-yl)-5-substituted imidazothiazoles 12a
S
Y
X
N
N
N
N
N
N
NH
NH
R3
R3
N
N
H
H
11
12
Compound
Y
X
R3
Aurora2
Ki ( M)
Egfr
Gsk3b
Ki ( M)
Jak2
Kdr
Pak4
Pim1
Rock2
Ki (lM)
l
Ki (l
M)
l
Ki (
l
M)
Ki (l
M)
Ki (lM)
Ki (
lM)
11a
11b
11c
C
N
C
C
C
N
8.666
2.066
5.333
ND
2.611
ND
ND
ND
ND
2.307
1.846
0.307
2.475
ND
ND
ND
ND
ND
ND
ND
ND
>1.800
0.010
0.245
11d
11e
C
C
N
N
4.340
>1.800
ND
0.017
0.019
ND
ND
>8.880
>8.880
>3.750
>3.750
0.242
0.114
0.065
0.116
>4.900
11f
12
C
N
2.805
1800
ND
ND
0.121
0.642
ND
ND
>8.880
5.339
>3.750
ND
>8.570
1.292
1.565
0.622
Cl
a
Ki values are based on six point curves.
imparted the highest selectivity for Gsk3b over Rock2. Small
aliphatic group substitutions maintained similar Gsk3b potencies,
however they also exhibited potent Rock2 inhibition (compounds
11d and 11e). Imidazo thiazole 12 was equipotent for Gsk3b and
Rock2 but much less potent than its imidazo pyrimidine counter-
part 11c.
(Table 3). By preparing a diverse library of analogs 14 single digit
nanomolar Egfr inhibitors were identified.
In conclusion, we have demonstrated that by applying hetero-
cycle ring forming and multicomponent reactions to the suitably
functionalized 5-position of the indazole ring we could obtain
potent kinase inhibitors.
A
completely different activity profile was obtained with
In the past, it has often been debated whether one could achieve
selectivity with kinase inhibitors targeting the ATP binding site.
Subsequently it was shown that kinases can be classified in a
imidazoloindazoles 14. These compounds were potent Egfr
inhibitors but did not inhibit any of the other kinases of our panel

I. Akritopoulou-Zanze et al. / Bioorg. Med. Chem. Lett. 21 (2011) 1480–1483
1483
Table 3
Kinase inhibitory activity of 5-(indazol-5-yl)-1,4-substituted imidazoles 14a
F
N
N
R4
N
N
H
14
Compound
R4
Aurora2
Ki ( M)
Egfr
Ki (
Gsk3b
Ki ( M)
Jak2
Ki (
Kdr
Ki (
Pak4
Ki ( M)
Pim1
Ki ( M)
Rock2
Ki (lM)
l
l
M)
l
l
M)
lM)
l
l
14a
14b
>4.900
>4.900
0.067
0.017
>5.450
>5.450
>1.450
>1.450
>8.880
>8.880
>3.750
>3.750
>8.570
>8.570
>6
N
O
O
>6
>6
N
N
14c
14d
>4.900
>4.900
0.027
0.008
>5.450
>5.450
>1.450
>1.450
>8.880
>8.880
>3.750
>3.750
>8.570
>8.570
>6
N
a
Ki values are based on six point curves.
different manner based on small molecule selectivity data5 rather
than genetic sequencing.6 Furthermore once thought selective
molecules were found to inhibit additional kinases upon further
testing.7 Extensive profiling of numerous kinase chemotypes and
the availability of crystal structures of inhibitor/kinase complexes
resulted in a wealth of information that has been used in a variety
of ways to explain and/or predict kinase selectivity.8
The data presented in the present and previous communica-
tions suggests that although there are general trends governing
the activity of various chemotypes, each compound possessed its
own unique activity print thus allowing for manipulation of selec-
tivity. We have been exploring this concept with extensive analog-
ing and testing against large panels of kinases and the results of
these efforts will be reported in due course.
groups for their support with library synthesis, purification and
analytical services, respectively.
References and notes
1. Akritopoulou-Zanze, I.; Hajduk, P. J. Drug Discovery Today 2009, 14, 291.
2. Akritopoulou-Zanze, I.; Wakefield, B. D.; Gasiecki, A.; Kalvin, D.; Johnson, E. F.;
Kovar, P.; Djuric, S. W. Bioorg. Med. Chem. Lett. 2011, 21, 1476.
3. (a) Blackburn, C.; Guan, B.; Fleming, P.; Shiosaki, K.; Tsai, S. Tetrahedron Lett.
1998, 39, 3635; (b) Groebke, K.; Weber, L.; Mehlin, F. Synlett 1998, 661; (c)
Bienaymé, H.; Bouzid, K. Angew. Chem., Int. Ed. 1998, 37, 2234.
4. Leusen, D. v.; Leusen, A. M. v. Org. React. 2001, 57, 417.
5. Vieth, M.; Higgs, R. E.; Robertson, D. H.; Shapiro, M.; Gragg, E. A.; Hemmerle, H.
Biochim. Biophys. Acta 2004, 1697, 243.
6. Manning, G.; Whyte, D. B.; Martinez, R.; Hunter, T.; Sudarsanam, S. Science 2002,
298, 1912.
7. Fabian, M. A.; Biggs, W. H.; Treiber, D. K.; Atteridge, C. E.; Azimioara, M. D.;
Benedetti, M. G.; Carter, T. A.; Ciceri, P. E.; Philip, T.; Floyd, M.; Ford, J. M.; Galvin,
M.; Gerlach, J. L.; Grotzfeld, R. M.; Herrgard, S.; Insko, D. E.; Insko, M. A.; Lai, A.
G.; Lelias, J.-M.; Mehta, S. A.; Milanov, Z. V.; Velasco, A. M.; Wodicka, L. M.; Pate,
H. K.; Zarrinkar, P. P.; Lockhart, D. J. Nat. Biotechnol. 2005, 23, 329.
8. (a) Ghose, A. K.; Herbertz, T.; Pippin, D. A.; Salvino, J. M.; Mallamo, J. P. J. Med.
Chem. 2008, 51, 5149; (b) Liao, J. J.-L. J. Med. Chem. 2007, 50, 409; (c) Sutherland,
J. J.; Higgs, R. E.; Watson, I.; Vieth, M. J. Med. Chem. 2008, 51, 2689.
Acknowledgments
The authors thank Dr. Vijaya Gracias for helpful suggestions for
the design of imidazoloindazoles and the Abbott High Throughput
Synthesis, High Throughput Purification and Structural Chemistry