Second generation 4-(4-methyl-1H-indol-5-ylamino)-2-phenylthieno[2,3-b]pyridine-5-carbonit rile PKCθ inhibitors

Article abstract of DOI:10.1016/j.bmcl.2008.12.021

Thieno[2,3-b]pyridine-5-carbonitrile 16 with a 4-methyl-5-indolylamine at C-4 and a 5-methoxy-2-(dimethylamino)-methylphenyl group at C-2 had an IC₅₀ value of 16 nM for the inhibition of PKCθ. While moderate inhibition of PKCδ was also observed

Full text of DOI:10.1016/j.bmcl.2008.12.021

Bioorganic & Medicinal Chemistry Letters 19 (2009) 766–769
Contents lists available at ScienceDirect
Bioorganic & Medicinal Chemistry Letters
journal homepage: www.elsevier.com/locate/bmcl
Second generation 4-(4-methyl-1H-indol-5-ylamino)-
2-phenylthieno[2,3-b]pyridine-5-carbonitrile PKCh inhibitors
b
b
b
Biqi Wu a, Diane H. Boschelli a, , Julie Lee , Xiaoke Yang , Divya Chaudhary
*
a Wyeth Research, Chemical and Screening Sciences, 401 N. Middletown Road, Pearl River, NY 10965, USA
Wyeth Research, Inflammation, 200 Cambridge Park Drive, Cambridge, MA 02140, USA
b
a r t i c l e i n f o
a b s t r a c t
Article history:
Thieno[2,3-b]pyridine-5-carbonitrile 16 with a 4-methyl-5-indolylamine at C-4 and a 5-methoxy-2-
(dimethylamino)-methylphenyl group at C-2 had an IC50 value of 16 nM for the inhibition of PKCh. While
moderate inhibition of PKCd was also observed (IC50 = 130 nM), 16 had IC50 values of greater than 5 lM
Received 3 November 2008
Revised 4 December 2008
Accepted 4 December 2008
Available online 10 December 2008
against Lyn and other members of the Src kinase family.
Ó 2008 Elsevier Ltd. All rights reserved.
Keywords:
PKCh
Thieno[2,3-b]pyridine-5-carbonitrile
The members of the protein kinase C (PKC) family of serine
threonine kinases have high sequence and structural homology
but vary in both their tissue expression and activation require-
respectively. Inhibition of either PKCd20,21 or Lyn22,23 is undesir-
able due to the role of these kinases in B-cell
hyperresponsiveness.
ments.1 PKCh, d,
e
, and
forms, whose biochemical regulation requires calcium. The
classic isoforms, , b, and , require both calcium and diacyl-
g make up the subclass of novel iso-
a
c
NH
NH
glycerol, while the atypical isoforms, f and k, do not require
either. PKCh is important in the activation and survival of T
cells2,3 and inhibition of this kinase could be of therapeutic ben-
efit in a variety of disease states including multiple sclerosis,4,5
arthritis,6 asthma,7,8 inflammatory bowel disease,9 and preven-
tion of allograft rejection.10 While three inhibitors of the classi-
cal PKCs, midostaurin,11 enzastaurin,12 and ruboxistaurin,13 along
N
HN
N
HN
N
CN
CN
S
S
1
2
with sotrastaurin, a PKCh inhibitor that also inhibits the
a and b
isoforms,14,15 are currently in clinical trials, no selective inhibitor
of PKCh has advanced to the clinic.
In efforts to retain the potent activity against PKCh and also reduce
the off-target activity, we focused on varying the substituent at the
C-2 position of 2. The para and ortho isomers of 2, namely 4 and 5,
were prepared by Suzuki reaction of 3 with the corresponding com-
mercially available boronic acid or pinacol ester (Scheme 1). The C-2
thiophene analog 6 was obtained by first coupling 3 with 5-formyl-
3-thiopheneboronic acid, followed by reductive amination with
dimethylamine. A similar route was used to prepare the C-2 pyri-
dine analog 7. As shown in Table 1, 4, the para isomer of 2, lost
activity against PKCh and PKCd, but had increased activity against
Lyn. The ortho isomer 5 had greatly decreased activity against all
three kinases, especially Lyn. The C-2 thiophene analog 6 had a sim-
ilar kinase activity profile to that of 2, while the C-2 pyridine analog
7 had a 10-fold decrease in PKCh activity and also lost activity
against PKCd and Lyn.
Small molecule inhibitors of PKCh include 2,4-diaminopyrim-
idines,16 3-pyridinecarbonitriles,17 and thieno[2,3-b]pyridine-5-
carbonitriles18,19 exemplified by 1. We previously reported that
structural modification of 1 by addition of a methyl group to
C-4 of the indole ring and of a meta (dimethylamino)methyl
group to the C-2 phenyl ring dramatically increased the PKCh
activity with 2 having an IC50 value of 7.5 nM, compared to
an IC50 value of 460 nM for the parent compound.18 Unfortu-
nately, 2 was less than 4-fold selective for PKCh over PKCd,
and also inhibited members of the Src family of kinases having
IC50 values of 520 and 28 nM for the inhibition of Lyn and Lck,
* Corresponding author. Tel.: +1 845 602 3567; fax: +1 845 602 5561.
E-mail address: bosched@wyeth.com (D.H. Boschelli).
0960-894X/$ - see front matter Ó 2008 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmcl.2008.12.021

B. Wu et al. / Bioorg. Med. Chem. Lett. 19 (2009) 766–769
767
NH
NH
N
HN
N
HN
CN
CN
a
I
S
S
N
4: para isomer
5: ortho isomer
3
c
b
NH
NH
HN
HN
N
CN
CN
N
S
S
N
N
S
N
6
7
Scheme 1. Reagents: (a) for 4: 4-(N,N-dimethylaminomethyl)phenyl-boronic acid pinacol ester hydrochloride, (Ph3P)4Pd, DME, aq NaHCO3, for 5: 2-(N,N-dimethylamino-
methyl)phenylboronic acid, (dppf)2PdCl2-CH2Cl2, DME, aq NaHCO3; (b) i—5-formyl-3-thiopheneboronic acid, (Ph3P)4Pd, DME, aq NaHCO3, ii—2 M Me2NH in THF, Na(OAc)3BH,
CH2Cl2, DMF, HOAc; (c) i—5-formylpyridine-3-boronic acid pinacol ester (Ph3P)4Pd, DME, aq NaHCO3, ii—2 M Me2NH in THF, Na(OAc)3BH, CH2Cl2, DMF, HOAc.
The C-2 phenyl group was retained for further SAR studies. Sev-
eral mono substituted phenyl derivatives were prepared including
NH
NH
a
the 2-methoxy analog 8 (Scheme 2) which was 10-fold selective for
PKCh over both PKCd and Lyn. Combination of the C-2 phenyl sub-
stituents of 2 and 8 led to the C-2 2-methoxy, 5-(dimethyl-
amino)methylphenyl analog 9. Both 9 and 2 had similar activities
against PKCh and PKCd, but 9 was a more potent inhibitor of both
Lyn, and Lck having IC50 values of 23 and 6.0 nM, respectively.
To determine if the kinase profile of 9 could be enhanced by
replacing the 2-methoxy group with other substituents, the corre-
sponding 2-ethoxy and methyl analogs were prepared as shown in
Scheme 3. Alkylation of 3-bromo-4-hydroxybenzaldehyde with
ethyl iodine, followed by reductive amination with dimethylamine
provided 10. Bromide 10 was converted in situ to the boronic acid
with triisopropoxyborane and n-butyl lithium, and then coupled
with 3 under standard Suzuki conditions to provide 11. Treatment
of 3-iodo-4-methylbenzyl alcohol with p-toluenesulfonyl chloride
followed by addition of dimethylamine provided 12. Using the con-
ditions employed for the preparation of 11 from aryl bromide 10,
the aryl iodine 12 was used to obtain 13. As shown in Table 1,
while 11, the 2-ethoxy analog of 9, retained activity against PKCh,
it exhibited a 3-fold decrease in activity against PKCd and Lyn. De-
HN
N
HN
CN
CN
I
S
S
N
O
8
3
NH
b
HN
N
CN
S
N
O
9
Scheme 2. Reagents: (a) 2-methoxyphenylboronic acid, (Ph3P)4Pd, DME, aq
NaHCO3, (b) i—5-formyl-2-methoxyphenylboronic acid, (Ph3P)4Pd, DME, aq
NaHCO3, ii—2 M Me2NH in THF, Na(OAc)3BH, CH2Cl2, DMF, HOAc.
;
NH
OHC
N
N
HN
N
CN
Br
OH
Br
b
a
S
N
O
10
O
11
NH
HN
HO
N
CN
c
d
I
I
S
N
12
13
Scheme 3. Reagents: (a) i—K2CO3, EtI, acetone, ii—2 M Me2NH in THF, Na(OAc)3BH, CH2Cl2, HOAc; (b) i—(iPrO)3B, n-BuLi, THF, ii—3, (Ph3P)4Pd, DME, aq NaHCO3; (c) i—TsCl,
Et3N, THF, ii—2 M Me2NH in THF; (d) i—(iPrO)3B, n-BuLi, THF, ii—3, (Ph3P)4Pd, DME, aq NaHCO3.

768
B. Wu et al. / Bioorg. Med. Chem. Lett. 19 (2009) 766–769
Table 1
PKCh, PKCd and Lyn inhibitory activity24
NH
HN
R
CN
Ar
S
N
Ar
R
PKCh IC50 (nM)
PKCd IC50 (nM)
Lyn IC50 (nM)
118
218
4
5
6
7
8
9
11
13
14
16
Phenyl
Phenyl
Phenyl
Phenyl
3-Thiophene
3-Pyridine
Phenyl
Phenyl
Phenyl
H
52
7.5
14
93
16
84
23
8.7
9.2
100
12
16
370
26
88
380
51
170
250
24
3400
520
100
37,000
410
2200
310
23
74
230
1700
13,000
3-CH2-NMe2
4-CH2-NMe2
2-CH2-NMe2
5-CH2-NMe2
5-CH2-NMe2
2-OMe
2-OMe, 5-CH2-NMe2
2-OEt, 5-CH2-NMe2
2-Me, 5-CH2-NMe2
2-OMe, 3-CH2-NMe2
5-OMe, 2-CH2-NMe2
82
410
27
Phenyl
Phenyl
Phenyl
130
When 16 was tested against other PKC family members while
only weak inhibition of PKCb, a classic isoform (IC50 = 22 M)
was observed, more potent inhibition of PKC and PKC was seen,
NH
NH
l
g
e
with 16 having IC50 values against these two novel PKCs of 360 and
HN
HN
95 nM, respectively. Kinase profiling of 16 provided an IC50 value of
CN
CN
a
38 lM for Lck, and IC50s of greater than 5 lM against other mem-
I
S
bers of the Src kinase family, including Src, Hck and Fyn, and also
VEGFR, PDGFR, MK2, and p38. While 16 had good permeability
(1.04 Â 10À6 cm/s as measured in a PAMPA assay) and acceptable
S
N
N
b
N
O
14
3
NH
solubility at pH 7.4 (12 lg/mL), this compound had very poor sta-
NH
c
bility in mouse, rat, and human liver microsomes (½ lives of less
than 10 min). Therefore, while we were able to eliminate the Lyn
liability of this series, further structural modification is currently
underway to reduce the PKCd activity and increase the metabolic
stability of these compounds.
HN
N
HN
O
O
CN
CN
S
S
N
CHO
N
16
15
Acknowledgments
Scheme 4. Reagents: (a) i—3-formyl-ii-methoxyphenylboronic acid, (Ph3P)4Pd,
DME, aq NaHCO3, ii—2 M Me2NH in THF, Na(OAc)3BH, CH2Cl2, DMF, HOAc; (b) 2-
formyl-5-methoxyphenylboronic acid, (Ph3P)4Pd, DME, aq NaHCO3; (c) 2 M Me2NH
in THF, Na(OAc)3BH, CH2Cl2, DMF, HOAc.
We thank the Wyeth Chemical Technologies Department for
compound characterization and the pharmaceutical profiling re-
sults, the Wyeth Screening Sciences group for the kinase selectivity
panel results, and Drs. Janis Upeslacis and Tarek Mansour for their
support.
creased activity, at least 10-fold against all three kinases, was seen
with the 2-methyl analog 13.
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