Tetrahydropyridine derivatives with inhibitory activity on the production of proinflammatory cytokines: Part 2

Article abstract of DOI:10.1016/j.bmcl.2010.03.022

We previously reported a novel pyrrole derivative 1 which possesses a tetrahydropyridine group at the β-position with a proinflammatory cytokine TNFα production inhibitor. Herein, we report the synthesis and biological activity of N- and α-position substituted tetrahydropyridine derivatives. In this series, we found that compound 3o showed good inhibitory activity in vitro (inhibition of lipopolysaccharide (LPS)-induced TNFα production in human whole blood, IC₅₀ = 0.44 μM) and compound 3i demonstrated potent inhibitory activity in vivo (inhibition of LPS-induced TNFα production in mice, ID₅₀ = 1.42 mg/kg). Crown Copyright

Full text of DOI:10.1016/j.bmcl.2010.03.022

Bioorganic & Medicinal Chemistry Letters 20 (2010) 2435–2437
Contents lists available at ScienceDirect
Bioorganic & Medicinal Chemistry Letters
journal homepage: www.elsevier.com/locate/bmcl
Tetrahydropyridine derivatives with inhibitory activity on the production
of proinflammatory cytokines: Part 2
b
c
d
d
Akira Nakao a, , Nobuyuki Ohkawa , Takayoshi Nagasaki , Takashi Kagari , Hiromi Doi ,
*
Takaichi Shimozato d, Shigeru Ushiyama e, Kazumasa Aoki a
a Medicinal Chemistry Research Laboratories II, Daiichi Sankyo Co., Ltd, 1-16-13 Kitakasai, Edogawa-ku, Tokyo134-8630, Japan
b Medicinal Chemistry Research Laboratories I, Daiichi Sankyo Co., Ltd, 1-2-58 Hiromachi, Shinagawa-ku, Tokyo140-8710, Japan
c Research Department II, Daiichi Sankyo RD Associe Co., Ltd, 1-2-58 Hiromachi, Shinagawa-ku, Tokyo 140-8710, Japan
d Biological Research Laboratories III, Daiichi Sankyo Co., Ltd, 1-16-13 Kitakasai, Edogawa-ku, Tokyo 134-8630, Japan
e R&D Planning Department, Daiichi Sankyo Co., Ltd, 1-2-58 Hiromachi, Shinagawa-ku, Tokyo 140-8710, Japan
a r t i c l e i n f o
a b s t r a c t
Article history:
We previously reported a novel pyrrole derivative 1 which possesses a tetrahydropyridine group at the b-
Received 12 January 2010
Revised 27 February 2010
Accepted 4 March 2010
Available online 10 March 2010
position with a proinflammatory cytokine TNF
biological activity of N- and -position substituted tetrahydropyridine derivatives. In this series, we
found that compound 3o showed good inhibitory activity in vitro (inhibition of lipopolysaccharide
(LPS)-induced TNF production in human whole blood, IC50 = 0.44 M) and compound 3i demonstrated
potent inhibitory activity in vivo (inhibition of LPS-induced TNF production in mice, ID50 = 1.42 mg/kg).
a production inhibitor. Herein, we report the synthesis and
a
a
l
a
Keywords:
Analgesic and anti-inflammatory agent
p38 MAP kinase
Crown Copyright Ó 2010 Published by Elsevier Ltd. All rights reserved.
Cytokine
TNFa
IL-1b
Excessive production of proinflammatory cytokines, including
TNF
and IL-1b,1 is implicated in many inflammatory diseases2
reported previously (Scheme 1).5 The introduction of a N- and
a-substituted tetrahydropyridinyl group to the b-position of the
a
and its inhibition is a proven therapeutic strategy in suppressing
inflammation. Anti-cytokine biological agents are proven to be
clinically effective in the treatment of rheumatoid arthritis (RA),
ankylosing spondylitis, Crohn’s disease and psoriasis by the block-
pyrrole ring was carried out by a bromine–lithium exchange of 2
followed by 1,2-addition with piperidin-4-one derivatives. Subse-
quent dehydroxylation of the tertiary alcohol was carried out in
excellent yield by exposure to trifluoroacetic acid (TFA) concur-
rently with deprotection of the triisopropylsilyl (TIPS) group with
tetrabutylammonium fluoride (TBAF) to give the tetrahydropyri-
ade of TNF
a
function.3 Therefore, the discovery and development
of orally active proinflammatory cytokine inhibitors for the treat-
ment of numerous inflammatory diseases have been pursued by
many pharmaceutical research groups.4
dine derivatives 3a–o. All of the a-substituted tetrahydropyridinyl
analogues 3i–o were racemic compounds.
We have previously reported5 the pyridylpyrrole derivative
possessing tetrahydropyridine at the b-position of the pyrrole ring
Regioisomers 3i and 3j were separated6 by silica gel column
chromatography and their structures were determined by NMR
studies. The NOE experiments, with a strong NOE from HA to HB
1 (Fig. 1) as a potent inhibitor of proinflammatory cytokine TNF
a
production. In an attempt to find more potent compounds than
1, we designed and synthesized the alkyl substituent to be intro-
duced to a N- and
a-position on the tetrahydoropyridinyl group.
Herein, we report our results which have led to the identification
of potent pyrrole-based inhibitors of the proinflammatory cytokine
TNFa, 3i and 3o.
Tetrahydropyridine derivatives 3a–o were synthesized in accor-
dance with our established synthetic route which has been
* Corresponding author.
E-mail address: nakao.akira.g5@daiichisankyo.co.jp (A. Nakao).
Figure 1.
0960-894X/$ - see front matter Crown Copyright Ó 2010 Published by Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmcl.2010.03.022

2436
A. Nakao et al. / Bioorg. Med. Chem. Lett. 20 (2010) 2435–2437
Table 1
In vitro, in vivo activities and Clog P values of N-substituted tetrahydropyridine
derivatives
Clog Pc
a
b
Compd
R
IC50
(
lM)
ID50 (mg/kg)
1
H
1.86 (1.45–2.31)
3.96 (2.63–5.97)
1.21 (0.72–2.05)
0.98 (0.75–1.28)
0.52 (0.29–0.95)
1.38 (0.77–2.48)
>10
5.98
2.89
6.67
6.18
6.75
45%d
3.04
3.48
4.01
4.32
4.54
7.19
4.72
5.27
3a
3b
3c
3d
3e
3f
Methyl
Ethyl
i-Propyl
n-Propyl
n-Octyl
t-Butyl
Benzyl
e
—
e
3g
>30
—
a
Inhibition of LPS-induced TNFa production in human whole blood. Results are
given as mean and S.D. of three to four determinations.
b
Inhibition of LPS-induced TNFa production in mice. N = 5.
Clog P values calculated using PALLAS (INFOCOM CORPORATION).
% Inhibition at 20 mg/kg.
Not tested.
c
d
e
In order to search for the relationship between the in vivo efficacy
and molecular property, we calculated Clog P values7 as a polar
parameter of the molecule, and these values were shown in the left
column in Table 1. The Clog P value of 3a, which exhibited the most
effective in vivo potency, was 3.48. In comparison, Clog P values of
3b, 3c, 3d, and 3e showed unexpectedly lower efficacy in vivo than
that of 3a and were 4.01, 4.32, 4.54, and 7.19, respectively. Despite
the slightly lower in vitro potency of 3a compared to those of
3b–e, it is speculated that the good in vivo efficacy of 3a (ID50 ca.
3 mg/kg) demonstrated that compounds having a Clog P value
between ca. 3.5 and 4.0 is preferable to this in vivo system.
Scheme 1. Reagents and conditions: (a) n-BuLi, THF, À78 °C then piperidin-4-one
derivatives, then rt; (b) TFA, CH2Cl2, rt, then TBAF, THF, rt.
Next, we designed and synthesized a-substituted N-methyltet-
rahydropyridine derivatives, which were evaluated in terms of
their inhibitory activities in vitro (Table 2). Tetramethyl analogue
3h showed lower activity than that of 3a, while methyl geometric
isomers 3i and 3j showed potent inhibitory activity, IC50 = 0.63 and
Figure 2.
1.28 lM, respectively. Therefore, regarding the a-substitution of
the 1,2,3,6-tetrahydropyridin-4-yl group, a substitution of the 6-
position was preferable to that of the 2-position in demonstrating
good inhibitory activity. Although, allyl (3k) and benzyl (3l) deriv-
atives, having a rather sterically hindered group at the 6-position,
showed less potency. These results suggest that the introduction of
a methyl group to the 6-position of the 1,2,3,6-tetrahydropyridin-
4-yl group exhibited the most enhanced inhibitory activity in vitro.
We then evaluated the in vivo efficacy of these derivatives. While
3h decreased in in vivo efficacy as with in vitro, 3i showed excellent
inhibitory activity (ID50 = 1.42 mg/kg), which was twofold potent
compared to that of regioisomer 3j (ID50 = 2.73 mg/kg), Clog P values
of 3h and 3i were 5.56 and 3.83, respectively. In this series, the Clog P
values of 3i and 3j, similarly analogue 3a (ID50 = <3 mg/kg), indi-
cated good in vivo efficacy and were less than four.
had no enhancement between HC and HD (Fig. 2). Compounds 3k–
o were synthesized and determined in a similar manner.
First, the designed and synthesized N-substituted tetrahydro-
pyridine derivatives were evaluated in terms of their inhibitory
activities in LPS-induced TNFa
production in human whole blood.5
N-unsubstituted analogue 1 was used as a reference for the com-
parison of the in vitro and in vivo potencies of the new analogues
(Table 1).
Compound 3a, having a methyl group on nitrogen, showed low-
er inhibitory activity than that of 1, while ethyl (3b) and isopropyl
(3c) analogues were more effective. In particular, n-propyl deriva-
tive 3d showed the most potent inhibitory activity (IC50 = 0.98 lM).
Octyl analogue 3e, possessing an alkyl chain elongated substituent,
exhibited good inhibitory activity, but tert-butyl (3f) and benzyl
(3g) derivatives which have a rather sterically hindered group, their
Based on these results, we further examined the effects of sub-
stituent on nitrogen atom of 6-methyl 1,2,3,6-tetrahydropyridin-4-
yl. The biological activities are summarized in Table 3.
potency decreased by less than IC50 = 10
Subsequently, we evaluated the inhibitory activity of these
derivatives in the LPS-induced TNF
production in mice.5 Com-
lM.
Regarding in vitro activities as compared with 3i, unsubstituted
a
analogue 3m kept its potency (IC50 = 0.71
tive 3n decreased in efficacy. Compound 3o, possessing a n-propyl
group, showed the most potent inhibitory activity (IC50 = 0.44 M).
lM), while ethyl deriva-
pound 3a showed the most effective activity (ID50 = 2.89 mg/kg),
which was more than twofold as potent as that of 1. However, ana-
logues 3b, 3c, and 3d demonstrated good in vitro efficacy and
showed lower activity than that of 1. Furthermore, 3e dropped
unexpectedly in in vivo potency.
l
In terms of in vivo activities, contrary to our expectation, 3o
showed lower efficacy than that of 3i and was the same potency
as that of 3m, ID50 = 2.29 and 2.79 mg/kg, respectively.

A. Nakao et al. / Bioorg. Med. Chem. Lett. 20 (2010) 2435–2437
2437
Table 2
4.5–5.0, which are large for the in vivo system. On the other hand,
N-methyl, -methyltetrahydropyridine derivative 3i, showed the
In vitro, in vivo activities and Clog P values of
pyridine derivatives
a
-substituted N-methyltetrahydro-
a
most potent in vivo efficacy (ID50 = 1.42 mg/kg) and had a 3.83
Clog P value. From these results, the in vivo efficacy of this series
would rest on the balance of the in vitro potency and lipophilicity,
therefore, in order to obtain more effective compounds in vivo, it
would be necessary for the Clog P value to be less than four with
higher inhibitory activity in vitro.
In order to develop a new anti-inflammatory agent, we synthe-
a
b
Compd
R
IC50
(l
M)
ID50 (mg/kg)
Clog Pc
sized and evaluated derivatives possessing a N-and
tetrahydropyridinyl group at the b-position of the pyrrole ring as
scaffold 1. Analogue 3o, which has N-n-propyl, an -methyl
tetrahydropyridinyl group, showed potent inhibitory activity in
a-substituted
3a
3.96 (2.63–5.97)
8.44 (5.26–13.54)
2.89
3.48
a
LPS-induced TNF
a
production in human whole blood. Further-
3h
7.27
5.56
more, N-methyl,
a-methyl analogue 3i, exhibited the most potent
inhibitory activity in the LPS-induced TNFa production in mice.
Based on these results, we plan to further investigate pyridylpyr-
3i
3j
0.63 (0.42–0.93)
1.28 (0.96–1.70)
1.42
2.73
3.83
3.83
roles possessing N- and
groups.
a-substituted chiral tetrahydoropyridinyl
Supplementary data
Supplementary data associated with this article can be found, in
the online version, at doi:10.1016/j.bmcl.2010.03.022.
e
3k
3l
48.7%d
30.8%d
—
4.58
5.57
e
References and notes
—
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a
Inhibition of LPS-induced TNF
a production in human whole blood. Results are
given as mean and S.D. of three to four determinations.
b
Inhibition of LPS-induced TNF
a
production in mice. N = 5.
c
d
e
Clog P values calculated using PALLAS (INFOCOM CORPORATION).
Inhibition at 10
Not tested.
lM.
3. (a) Goldsmith, D. R.; Wagstaff, A. J. BioDrugs 2005, 19, 401; (b) Feldman, S. R.;
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H. T.; Peese, K. M.; Sweeney, F. J.; Taylor, T. J.; Trebino, C. E.; Abramov, Y. A.;
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Aoki, K. Bioorg. Med. Chem. Lett. 2009, 16, 4607; (b) IC50 values were calculated
from liner regression curves obtained from the% inhibition and the logarithmic
value of the concentrations of the test compounds by the last-squares method.
The 95% confidence intervals (C.I.) were calculated by Fieller’s theorem. IC50
values and their 95% C.I. values were calculated using the SAS System for
Windows (SAS Institute Inc.).
6. The crude ratio of regioisomers were approximately 1:1 by NMR studies. The
isolated yield indicated in Scheme 1.
7. The program, PALLAS from INFOCOM CORPORATION, was used to calculate the
log P value.
Table 3
In vitro, in vivo activities and Clog P values of N- substituted
pyridine derivatives
a-methyltetrahydro-
Clog Pc
a
b
Compd
R
IC50
(
lM)
ID50 (mg/kg)
3m
3i
3n
3o
H
0.71 (0.15–1.72)
0.63 (0.42–0.93)
1.61 (0.94–2.75)
0.44 (0.32–0.61)
2.29
1.42
5.28
2.79
3.56
3.83
4.53
5.06
Methyl
Ethyl
n-Propyl
a
Inhibition of LPS-induced TNF
a production in human whole blood. Results are
given as mean and S.D. of three to four determinations.
b
Inhibition of LPS-induced TNF
Clog P values calculated using PALLAS (INFOCOM CORPORATION).
Inhibition at 10 lM.
a
production in mice. N = 5.
c
d
The N-n-propyl analogues, both a-unsubstituted and a-methyl
substituted tetrahydropyridine 3d and 3o, demonstrated unex-
pectedly low potency in vivo, despite their potent in vitro activi-
ties. This result could be explained by their Clog P values such as