The synthesis of substituted bipiperidine amide compounds as CCR3 antagonists

Article abstract of DOI:10.1016/j.bmcl.2005.01.016

Bipiperidine amide 1 has been identified as a CC chemokine receptor 3 (CCR3) antagonist. Optimization of its structure-activity relationship has resulted in the identification of cis (R,R)-4-[(3,4-dichlorophenyl)methyl]-3- hydroxymethyl-1′(6-quinolinylcar

Full text of DOI:10.1016/j.bmcl.2005.01.016

Bioorganic & Medicinal Chemistry Letters 15 (2005) 1375–1378
The synthesis of substituted bipiperidine amide compounds as
CCR3 antagonists
Pauline C. Ting,* Joe F. Lee, Jie Wu, Shelby P. Umland, Robert Aslanian, Jianhua Cao,
Youhao Dong, Charles G. Garlisi, Eric J. Gilbert, Ying Huang, James Jakway,
Joseph Kelly, Zhidan Liu, Stuart McCombie, Himanshu Shah, Fang Tian,
Yuntao Wan and Neng-Yang Shih
Schering Plough Research Institute, 2015 Galloping Hill Road, Kenilworth, NJ 07033, USA
Received 2 December 2004; revised 3 January 2005; accepted 6 January 2005
Abstract—Bipiperidine amide 1 has been identified as a CC chemokine receptor 3 (CCR3) antagonist. Optimization of its structure–
activity relationship has resulted in the identification of cis (R,R)-4-[(3,4-dichlorophenyl)methyl]-3-hydroxymethyl-10(6-quinolinyl-
carbonyl)-1,40-bipiperidine 14n, which exhibits potent receptor affinity and inhibition of both calcium flux and eosinophil
chemotaxis.
Ó 2005 Elsevier Ltd. All rights reserved.
Despite advances in the treatment of asthma, including
long acting b-agonists and inhaled corticosteroids, the
incidence of morbidity and mortality due to this disease
has increased. Therefore, additional therapeutic ap-
proaches are needed. A significant characteristic of
airway diseases such as asthma, is the migration of
eosinophils into the lung tissue. The CC chemokine
receptor 3 (CCR3) is a member of the seven transmem-
brane G-protein coupled receptor family, and is the pre-
dominant receptor on eosinophils responsible for
eosinophil chemotaxis.1 It is activated by several chemo-
kines including eotaxins, RANTES, and macrophage
chemoattractant protein-4.2 An antibody to eotaxin
has been shown to decrease eosinophil migration to
the lung and airway hyperreactivity after allergen chal-
lenge in mice.1 The importance of CCR3 antagonists
in allergic inflammation is still being determined.
High-throughput screening of our internal corporate
compound database using a CCR3 membrane binding
assay has led to the identification of several lead struc-
tures as CCR3 antagonists. In particular, compound 1
exhibits reasonable affinity for the CCR3 receptor and
is amenable to a structure–activity relationship study.
The synthesis of compound 1 is depicted in Scheme 1.
Since the amide moiety was introduced at the last
step, a library of various amides and sulfonamides
was rapidly surveyed, and we discovered that the
a,b,c
NH
NH
Br
2
3
d,e
f
N
Br
N
N
Br
Br
N
N
R
NH
1
5
4
O
OMe
Ki = 403 nM
O
Scheme 1. Reagents and conditions: (a) TFAA, CH2Cl2, 88%; (b)
CH3SO3H, 1,3-dibromo-5,5-dimethylhydantoin, CH2Cl2, 45%; (c)
K2CO3, MeOH, H2O, 99%; (d) N-tBOC-4-piperidone, NaB(OAc)3H,
AcOH, ClCH2CH2Cl, 58%; (e) 4 N HCl in dioxane, MeOH, CH2Cl2,
D, 100%; (f) acyl chlorides or sulfonyl chlorides, TEA, CH2Cl2;
carboxylic acids, DEC, HOBT, CH2Cl2, DMF.
*
Corresponding author. Tel.: +1 908 740 3534; fax: +1 908 740
7152; e-mail: pauline.ting@spcorp.com
0960-894X/$ - see front matter Ó 2005 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmcl.2005.01.016

1376
P. C. Ting et al. / Bioorg. Med. Chem. Lett. 15 (2005) 1375–1378
Table 1. In vitro CCR3 membrane binding activity of bipiperidines 5a
and 8a–n
With the 3,4-dichlorobenzyl moiety in hand, we re-
turned to optimization of the amide moiety. As summa-
rized in Table 2, the 2-tolylacetamide could be replaced
with the cinnolinylamide 9d or the quinolinylamides
9e–g and retain CCR3 affinity. However, the isomeric
quinolinylamides 9h–i, the indolinylamides 9j–k, and
the anilines 9a–c (9c could be considered the acyclic
open analogue of 9e) showed reduced CCR3 affinity.
R
N
Me
N
O
Compd
R
Ki (nM)a
66
142 37
111
5a
8a
8b
8c
8d
8e
8f
4-Br–Ph
4-Cl–Ph
4-F–Ph
5
An incremental improvement in the biological activity
was observed with modification of the bipiperidine core.
In particular, substitution was well tolerated at the 3-
position of the second piperidine ring. Synthesis of this
subset of analogues is illustrated in Scheme 3. Wittig
5
4-MeO–Ph
3-Cl–Ph
2-Cl–Ph
792 95
128 53
20%b
3,5-diF–Ph
3,5-diCl–Ph
3,4-diCl–Ph
2,3-diCl–Ph
2,4-diCl–Ph
2,5-diCl–Ph
2-F–4-Cl–Ph
3-F–4-Cl–Ph
3-F–5-Cl–Ph
2255 135
938 195
8g
8h
8i
40
4
103 22
56 21
Table 2. In vitro CCR3 membrane binding activity of bipiperidines 8h
and 9a–k
8j
8k
8l
251 33
145 26
191 48
504 84
Cl
N
8m
8n
Cl
N
R
O
a The assay protocol is described in Refs. 4 and 5.
b % Inhibition @ 1 lM (n = 2).
Compd
R
Ki (nM)
40
Me
Me
4
8h
2-toluoylacetyl-1,4-bipiperidine 5a showed improved
CCR3 affinity (see Table 1).
H
N
9a
9b
9c
9d
9e
9f
100 11
122 10
136 16
We next decided to optimize the substitution pattern on
the phenyl ring, and these analogues were synthesized
according to the route outlined in Scheme 2. The key
step involved a hydroboration and subsequent palla-
dium coupling reaction (Suzuki protocol) to incorporate
the appropriate phenyl ring.3
NH2
NH2
Membrane binding data for selected phenyl analogues
are shown in Table 1. Replacement of the 4-bromo sub-
stituent in 5a with the electron withdrawing chloro 8a or
fluoro 8b resulted in a smaller decrease in CCR3 potency
when contrasted with the electron donating methoxy
group in 8c. Comparison of the ortho (8e), meta (8d),
and para (8a) chloro analogues indicated that substitu-
tion was better tolerated at the meta and para positions.
A number of disubstituted analogues 8f–n were exam-
ined, and only the 3,4-dichlorophenyl-bipiperidine 8h
exhibited a slight improvement in CCR3 affinity.
46
30
38
68
5
2
6
8
N
N
N
N
N
9g
9h
9i
O
d
a,b,c
NH
140 21
X
N
tBOC
N
N
7
6
458
4
N
Me
X
N
NH
8
O
9j
111 10
119 13
Scheme 2. Reagents and conditions: (a) Ph3PMeBr, nBuLi, PhMe,
ꢀ78 °C to rt, 79%; (b) 9-BBN, X-PhBr, Pd(dppf)Cl2, K2CO3, THF,
DMF, D 21–77%; (c) 4 N HCl in dioxane, CH2Cl2, 100%; (d) N-20-
toluoylacetamido-4-piperidone, NaB(OAc)3H, AcOH, ClCH2CH2Cl,
19–57%.
H
N
9k

P. C. Ting et al. / Bioorg. Med. Chem. Lett. 15 (2005) 1375–1378
1377
O
N
O
O
OSi(tBu)Me2
COOMe
a,b,c
OSi(tBu)Me2
a,b,c,d
N
N
H
15
N
tBOC
16
HCl
tBOC
10
tBOC
6
d,e
e,f,g
Cl
Cl
Cl
Cl
Cl
Cl
Cl
Cl
OH
+
OH
Cl
Cl
CN
N
OMe
OH
N
tBOC
11b
tBOC
d,r,s,t,i
h,i
N
H
18
N
N
H
22
11a
tBOC
h,i,j,k,g
17
f,g
d,e,q,i
Cl
Cl
j,k,l,m,i
Cl
Cl
n,o,p
Cl
Cl
Cl
Cl
Cl
Cl
OR1
NHR2
N
Et
N
H
13
NHR
H
F
12
l
l
N
H
N
H
N
H
21
19
20
R
Cl
Cl
Scheme 4. Reagents and conditions: (a) t(BOC)2O, Et3N, MeOH,
CH2Cl2, 100%; (b) NaBH4, THF, MeOH, 92%; (c) Me2(tBu)SiCl,
Et3N, DMAP, CH2Cl2, 83%; (d) oxalyl chloride, DMSO, Et3N,
CH2Cl2, 97%; (e) Ph3PMeBr, nBuLi, PhMe, ꢀ78 °C to rt, 79%;
(f) 9-BBN, 1,2-dichloro-4-iodobenzene, Pd(dppf)Cl2, K2CO3, THF,
DMF, D 69%; (g) nBu4NF, THF, 63%; (h) NaH, MeI, DMF, 100%; (i)
4 N HCl in dioxane, CH2Cl2, 100%; (j) MsCl, Et3N, CH2Cl2, 100%; (k)
NaN3, DMF, D; (l) Ph3P, THF, H2O, D; (m) AcCl or MsCl, Et3N,
CH2Cl2; (n) trichloroethyl chloroformate, Et3N, CH2Cl2, 68%; (o)
bis-(2-methoxyethyl)amino-sulfur trifluoride, CH2Cl2, 50%; (p) Zn,
AcOH, D 81%; (q) H2, (Ph3P)3RhCl, EtOH, 55%; (r) KMnO4, acetone,
H2O, 88%; (s) DEC, HOBT, NH3, CH2Cl2; (t) Burgess reagent,
CH2Cl2.
N
N
N
O
14
Scheme 3. Reagents and conditions: (a) Ph3PMeBr, nBuLi, PhMe,
ꢀ78 °C to rt, 79%; (b) SeO2, tBuOOH, CH2Cl2, 49%; (c) Me2(tBu)-
SiCl, Et3N, DMAP, CH2Cl2, 92%; (d) 9-BBN, 1,2-dichloro-4-iodo-
benzene, Pd(dppf)Cl2, K2CO3, THF, DMF, D 36% of 11a and 38% of
11b; (e) nBu4NF, THF, 95%; (f) KN(TMS)2, MeI or EtI, DMF; (g)
4 N HCl in dioxane, CH2Cl2, 100%; (h) MsCl, Et3N, CH2Cl2, 100%; (i)
NaN3, DMF, D 56%; (j) Ph3P, THF, H2O, D 73%; (k) AcCl or MsCl,
Et3N, CH2Cl2; (l) N-6-quinolinylcarbonyl-4-piperidone, NaB(OAc)3H,
AcOH, ClCH2CH2Cl.
Table 3. In vitro CCR3 membrane binding activity of 3-substituted
bipiperidines 9f and 14a–r
reaction of ketone 6, allylic oxidation, and alcohol pro-
tection provided intermediate 10.3 Hydroboration, pal-
ladium coupling, and removal of the silyl protecting
group produced the cis/trans mixture of 11a/11b, which
were separable by flash chromatography. The hydroxy
group was elaborated or converted into an amino group
through the corresponding azide intermediate. Reduc-
tive amination with N-6-quinolinylcarbonyl-4-piper-
idone gave the target compounds 14.
R
Cl
N
N
Cl
N
O
Compd
R
Ki (nM)
9e
H
Me
30
14
29
23
46
2
14a
14b
14c
14d
14e
14f
14g
14h
14i
2
7
1
2
Additional 3-substituted bipiperidines 14 were con-
structed by the synthetic route pictured in Scheme 4.
Methyl 4-oxo-3-piperidinecarboxylate 15 was protected
as the BOC derivative, reduced to the diol with sodium
borohydride,6 silylated to protect the primary hydroxyl
group, and subjected to Swern oxidation7 to yield
ketone 16. In this case, Wittig reaction, hydroboration,
and palladium coupling, and removal of the silyl pro-
tecting group produced only the cis isomer of alcohol
17. The hydroxyl group in 17 was further functionalized
into a variety of different groups including ether 18,
amine 19, fluoride 20, alkane 21 or nitrile 22.
Et
CH@CH2
CH2F
CN
15%a
29%a
CONH2
OMe (enant A)
OMe (enant B)
OEt (enant A)
OEt (enant B)
NHSO2Me
326 33
2
7.7
32%a
14j
33
1
1002 162
164 28
50 14
14k
14l
NHCOMe
14m
14n
14o
14p
14q
14r
CH2OH (enant A)
CH2OH (enant B)
CH2OMe (enant A)
CH2OMe (enant B)
CH2NHSO2Me
3.5
394 99
41
1
2
The biological activity of the 3-substituted bipiperidines
14 is tabulated in Table 3. The cis isomer displayed sig-
nificantly more activity than the trans isomer (e.g., the
trans isomer of compound 14a has Ki = 263 26 nM).
331 90
205 30
CH2NHCOMe
a % Inhibition @ 1 lM (n = 2).

1378
P. C. Ting et al. / Bioorg. Med. Chem. Lett. 15 (2005) 1375–1378
Table 4. In vitro CCR3 membrane binding and calcium flux activity of
bipiperidines 15a–i.
represented in Table 4. Unexpectedly, the cinnolinyl-
amide 15a did not display the potent CCR3 affinity of
the 3-unsubstituted bipiperidine 9d. However, the quin-
olinylamides 15b–e all showed good CCR3 affinity and
activity in the calcium flux assay. Heterocyclic amides
with two nitrogen atoms such as 15f–i also exhibited rea-
sonable biological profiles.
OMe
Cl
N
Cl
N
R
O
Compd
R
Ki (nM)
Calcium flux IC50 (nM)a
In conclusion, compound 14n was identified as a very
potent CCR3 antagonist9 and exhibited minimal activity
at the CCR4 (11% at 1 lM) or CCR8 receptor (8% at
1 lM). It was active in the calcium flux assay with
IC50 = 9.2 3.2 nM and in the human eosinophil che-
motaxis assay with IC50 = 160 129 nM. For our intact
cell binding assays (n = 2), compound 14n also possessed
good affinity for the human (Ki = 3.3 nM) and monkey
(Ki = 7.2 nM) CCR3 receptors, but lower affinity for
the rat (Ki = 2981 nM) and mouse (Ki = 606 nM)
CCR3 receptors. Although bipiperidine 14n displayed
a reasonable AUC of 1341 ng h/mL at 10 mpk po in a
rat pharmacokinetic study, the lower affinity for the
rat receptor resulted in significant challenges with in
vivo rat profiling. In addition, 14n produced an unde-
sired 85% inhibition at 1 lM in the hERG voltage clamp
assay.10 Therefore, due to the liabilities with this series
of compounds, further advancement was precluded.
15a
86 41
95b
N
N
N
15b
15c
11
26
2
7
25 11
80 13
N
N
15d
18
5
34 16
15e
15f
20 10
48 10
32
2
N
N
N
169 34
References and notes
N
N
15g
15h
15i
34
35
15
8
1
3
82
7
1. Barnes, P. Eur. Respir. J. Suppl. 2001, 34, 67s.
2. Umland, S. P.; Wan, Y.; Shortall, J.; Shah, H.; Jakway,
J.; Garlisi, C. G.; Tian, F.; Egan, R. W.; Billah, M. M.
J. Leukocyte Biol. 2000, 67, 441.
3. Vice, S.; Bara, T.; Bauer, A.; Evans, C. A.; Ford, J.;
Josien, H.; McCombie, S.; Miller, M.; Nazareno, D.;
Palani, A.; Tagat, J. J. Org. Chem. 2001, 66, 2487.
4. Ting, P. C.; Cao, J.; Dong, Y.; Gilbert, E.; Huang, Y.;
Kelly, J.; McCombie, S.; Shih, N. Y. U.S. Provisional
Patent filed February 2004.
N
66 27
N
24
5
N
N
a The assay protocol is described in Refs. 4 and 11.
b n = 1.
5. Dairaghi, D. J.; Oldham, E. R.; Bacon, K. B.; Schall, T. J.
J. Biol. Chem. 1997, 272, 28206.
6. Soai, K.; Oyamada, H. Synthesis 1984, 7, 605.
7. Mancuso, A. J.; Huang, S. L.; Swern, D. J. Org. Chem.
1978, 43, 2480.
8. Chiralcel HPLC columns obtained from Chiral Technol-
ogies, 730 Springdale Dr., Exton, PA 19341.
9. For compound 14n, Ki = 3.1 0.1 nM when MCP-4 is the
substrate in the membrane binding assay.
10. The hERG voltage clamp assay was conducted at Chan-
Test Inc., 14656 Neo Parkway, Cleveland, OH 44128.
11. Calcium flux assay protocol: This assay used CREM3 cells
at 37 °C, in which the human CCR3 receptor was
expressed in the rat Y3 cell line. Compounds were
dissolved in DMSO and diluted with buffer (pH 7.4 HBSS
containing HEPES, BSA, and probenecid). Intracellular
calcium levels were measured with a fluorometric imaging
plate reader (FLIPR from Molecular Devices, Sunnyvale,
CA) at 1 s intervals for 60 s then at 2 s intervals for
60 s.
Enantiomers of highly potent compounds were sepa-
rated by HPLC on a Chiralcel AD column (eluant was
10–30% IPA in hexane with 0.5% diethylamine).8 The
preferred absolute stereochemistry of R,R was deter-
mined by a chiral synthesis.4 Based on these results,
the CCR3 receptor is quite sensitive to the conformation
of the bipiperidine core. A sterically small substituent is
preferred at the 3-position, and the methyl 14a, methoxy
14h, and hydroxymethyl 14n compounds exhibited the
most potent CCR3 affinity (Ki = 3–14 nM). The ethyl
14b, vinyl 14c, fluoromethyl 14d, ethoxy 14j, and meth-
oxymethyl 14p showed slightly lower affinity (Ki = 23–
46 nM). In contrast, the more electron withdrawing
nitrile 14e, carboxamide 14f, sulfonamide 14k and 14q,
and acetamide 14l and 14r were less active. Final combi-
nation of the 4-[(3,4-dichlorophenyl)methyl]-3-methoxy-
1,40-bipiperidine core with various quinolinyl amides are