Synthesis and structure-activity studies of side chain analogues of the anti-tubercular agent, Q203

Article abstract of DOI:10.1016/j.ejmech.2016.09.082

The anti-tubercular activity of 6-chloro-2-ethyl-N-(4-(4-(4-(trifluoromethoxy)phenyl)piperidin-1-yl)benzyl)imidazo [1,2-a]pyridine-3-carboxamide (Q203) is modified by varying its side chain. In this study, we synthesized Q203 analogues with different side

Full text of DOI:10.1016/j.ejmech.2016.09.082

Accepted Manuscript
Synthesis and structure-activity studies of side chain analogues of the anti-tubercular
agent, Q203
Sunhee Kang, Young Mi Kim, Ryang Yeo Kim, Min Jung Seo, Zaesung No, Kiyean
Nam, Sanghee Kim, Jaeseung Kim
PII:
S0223-5234(16)30814-5
10.1016/j.ejmech.2016.09.082
EJMECH 8948
DOI:
Reference:
To appear in: European Journal of Medicinal Chemistry
Received Date: 15 July 2016
Revised Date: 23 September 2016
Accepted Date: 24 September 2016
Please cite this article as: S. Kang, Y.M. Kim, R.Y. Kim, M.J. Seo, Z. No, K. Nam, S. Kim, J. Kim,
Synthesis and structure-activity studies of side chain analogues of the anti-tubercular agent, Q203,
European Journal of Medicinal Chemistry (2016), doi: 10.1016/j.ejmech.2016.09.082.
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ACCEPTED MANUSCRIPT

ACCEPTED MANUSCRIPT
Synthesis and structure-activity studies of side chain analogues of the anti-tubercular agent, Q203
Sunhee Kang1, 4, Young Mi Kim1, Ryang Yeo Kim2, Min Jung Seo1, Zaesung No1, Kiyean Nam3, Sanghee
Kim4, *, Jaeseung Kim1, *
2
1Chemistry Platform and Tuberculosis Research Laboratory, Institut Pasteur Korea, 16 Daewangpangyo-ro,
3
712 Beon-gil, Bundang-gu, Seongnam-si, Gyeonggi-do, 463-400, Korea; Qurient Co. Ltd., 242 Pangyo-ro,
Bundang-gu, Seongnam-si, Gyeonggi-do, 463-400, Korea; 4College of Pharmacy, Seoul National University,
1 Gwanak-ro, Gwanak-gu, Seoul, 151-742, Korea
RECEIVED DATE (to be automatically inserted after your manuscript is accepted if required
according to the journal that you are submitting your paper to)
ABSTRACT
The anti-tubercular activity of 6-chloro-2-ethyl-N-(4-(4-(4-(trifluoromethoxy)phenyl)piperidin-1-
yl)benzyl)imidazo[1,2-a]pyridine-3-carboxamide (Q203) is modified by varying its side chain. In this study,
we synthesized Q203 analogues with different side chains and studied their effects on anti-tubercular activity.
Many analogues showed good potency against M. tuberculosis replicating in liquid broth culture medium
(extracellular activity) regardless of chain length and conformational changes. However, a polar character in

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the side chain region was unfavorable for anti-tubercular activity. The analogues, 25, 28, 35, and 36,
displayed excellent activity against M. tuberculosis replicating inside macrophages (intracellular activity) and
promising pharmacokinetic (PK) properties with high drug exposure level and long half-life.
Graphical abstract
Keywords
Tuberculosis, imidazo[1,2-a]pyridine-3-carboxamide (IPA), pharmacokinetics, structure-activity
relationship (SAR), Q203
1. Introduction

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Tuberculosis (TB) is an infectious disease caused by Mycobacterium tuberculosis. In 2014, the number of
new TB cases was 9.6 million, and multidrug-resistant (MDR) and extensively drug-resistant TB occurred in
over 100 countries1. In addition, 1.1 million TB deaths were reported, and 12% of these were caused by co-
infection with human immunodeficiency virus1. Despite many efforts to develop diagnosis and treatment
methods, the mortality rate of TB is unacceptably high. Fortunately, two drugs that have novel modes of
action were recently approved for the treatment of MDR patients worldwide since effective drug regimen
was first developed in the 1940s1. An ATP synthase inhibitor, bedaquiline, was approved by the United
States Food and Drug Administration in 20122-3, and a mycolic acid synthesis inhibitor, delamanid, was
approved by European Medicines Agency in 20134-5. However, because of the continuing emergence of
drug-resistant TB, the dearth of novel chemical entities in clinical trials is still a major threat to TB patients.
Therefore, new drugs with novel targets should be prioritized in the drug development pipeline to respond to
pandemic TB.
Q203 (Figure 1), which has an imidazo[1,2-a]pyridine-3-carboxamide (IPA) scaffold, was developed by our
group as a novel TB drug and is currently in clinical trials6,8-9. Its novel mode of action is through blocking
ATP production by targeting the b subunit of cytochrome bc1 complex, which is involved in the energy
metabolism of M. tuberculosis6-7. Our previous studies revealed that the analogues possess a linear lipophilic
side chain display superior anti-tubercular activity; thus, we suggested that linearity and lipophilicity of side
chain on the right side of the molecule are important in drug potency8. In this study, we designed and
synthesized new analogues of IPA with various chain lengths and flexibility to understand how linearity and

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lipophilicity of the side chain region affects anti-tubercular activity. The study suggests a small set of
analogues which could be alternative drug candidates based on the comparable in vitro potency as well as
promising pharmacokinetic values with Q203.
Figure 1. Structure of Q203.
2. Result and discussion
The synthetic route for the preparation of IPA derivatives is outlined in Schemes 1-4. First, ethyl 2-bromo-
3-oxopentanoate (2) was prepared from commercially available ethyl-3-oxopentanoate (1) by bromination8,10
Compound 2 was condensed with adequate aminopyridines, 3a-e11, to give key intermediate esters, 4a-e,
which were saponified using lithium hydroxide to give acids 5a-e.
.
The coupling counterpart benzylamines were prepared in various ways, as described in Schemes 2-3. The
benzylamines, 7a-b, 9, 11a-b, and 13, that possess a linker between two aryl moieties were synthesized as
shown in Scheme 2. The benzyloxy analogues, 6a and 6b, were prepared from 4-hydroxybenzonitrile and

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adequate benzyl bromide by SN2 reaction. Reductive amination of 4-aminobenzonitrile and 4-
trifluoromethoxybenzaldehyde using sodium triacetoxyborohydride was carried out to yield the aminomethyl
compound 8. Compounds 10a and 10b, which have an oxygen or a nitrogen atom between two aryl rings,
were conveniently synthesized from 4-fluorobenzonitrile and appropriated aniline or phenol by heating in the
presence of potassium carbonate. Methylation of 10b was accomplished using NaH to yield 12. The resulting
benzonitrile intermediates, 6a-b, 8, 10a-b, and 12, were easily reduced to benzylamines, 7a-b, 9, 11a-b, and
13, using lithium aluminum hydride (LAH) in tetrahydrofuran12.
The synthetic route to obtain benzylamines that possess a saturated ring with a linker between two aryl
moieties is shown in Scheme 3. A mixture of 4-fluorobenzonitrile, adequate cyclic amine, and potassium
carbonate in dimethylsulfoxide was heated to 120°C to obtain 14a-f. Compounds 16a-f, which have an
oxygen linker, were synthesized from 14a, 14c, and 14d via Mitsunobu reaction. For the preparation of 18,
the Mitsunobu reaction was also applied to 14e and 4-trifluoromethoxyphenol. Compound 21, which has a
piperazine ring, was synthesized from 14f through deprotection of a t-Boc group and reductive amination
with 4-trifluoromethoxybenzaldehyde in the presence of sodium triacetoxyborohydride. Most of the
benzonitrile intermediates were subsequently converted to benzylamines, 15, 17a-f, 19, and 22, by
employing the same methodology as that used for converting 6 to 7, whereas compound 23 was synthesized
using Raney-Ni at H2 atmosphere.
The synthetic route for the preparation of target IPA derivatives is shown in Scheme 4. General EDC
coupling was accomplished with precursor acids and corresponding amines in the final step of synthesis to

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obtain 24-43. On the other hand, in the case of carbonyl analogues, 45 and 46, acid 5c was first coupled with
amine 23, the tert-butyloxy carbonyl group was removed in acidic conditions, and then the reaction with the
corresponding acyl chloride followed.
Scheme 1. General synthetic scheme of 2-ethylimidazo[1,2-a]pyridine-3-carboxylic acidsa
O
O
O
O
(i)
OEt
OEt
Br
1
2
O
N
O
OEt
OH
5
8
(ii)
N
(iii)
4
3
R1
6
N
N
NH2
R1
R17
2
N
9
1
3a, pyridin-2-amine
4a
, R1 = H
5a, R1 = H
5b
3b
, 5-fluoropyridin-2-amine
4b, R1 = 6-F
4c, R1 = 6-Cl
4d, R1 = 6-Br
4e, R1 = 7-Cl
, R1 = 6-F
5c, R1 = 6-Cl
5d
3c, 5-chloropyridin-2-amine
3d, 5-bromopyridin-2-amine
3e, 4-chloropyridin-2-amine
, R1 = 6-Br
5e, R1 = 7-Cl
aReagents and conditions: (i) NBS, NH4OAc (over 2.0 eq.), Et2O, 6h; (ii) 2, EtOH, reflux, overnight; (iii)
LiOH, EtOH/H2O (3:1, v/v), overnight
Scheme 2. Synthesis of benzylamine counterparts for IPA derivatives as form Ia.

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aReagents and conditions: (i) NaH, DMF, 0°C - room temperature, 4 h; (ii) LAH, THF, 0°C – reflux, 2 h; (iii)
NaBH(OAc)3, MC, overnight; (iv) 4-trifluoromethoxy phenol (for 10a) or 4-trifluoromethoxy aniline (for
10b), K2CO3, DMF or DMSO, 120–150°C, 6 h; (v) NaH, iodomethane, 0°C - room temperature, 2h
Scheme 3. Synthesis of benzylamine analogues for IPA derivatives as form IIa.

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aReagents and conditions: (i) K2CO3, DMSO, 120°C, 4–6 h; (ii) LAH, THF, 0°C - reflux, 2 h; (iii)
corresponding phenol, DIAD, PPh3, MC, overnight; (iv) TFA, MC, 4 h; (v) 4-trifluoromethoxybenzaldedyde,
NaBH(OAc)3, MC, overnight; (vi) Raney-Ni, H2, MeOH, 2 h
Scheme 4. Synthesis of IPA derivatives (24-43, 45, and 46)a

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aReagents and conditions: (i) corresponding amine, EDC, HOBt, TEA, DMF, 80°C, 2–4 h; (ii) TFA, MC, 6
h; (iii) corresponding acyl chloride, TEA, MC, 1.5 h
2.2.
Structure-activity relationship (SAR) study
Structure-activity relationship (SAR) was explored in two types of compounds designated as form I and
form II. Form I compounds have a short linking unit between a cyclic amine and the last phenyl ring,
whereas form II compounds possess an additional cyclic amine moiety. All synthesized compounds were
evaluated for their anti-tubercular activity against H37Rv-GFP in liquid broth culture medium (extracellular
MIC80), and results are summarized in Table 1. Our initial SAR study focused on the molecules that have
flexible linkers, such as ether, methyl ether, amine, and methyl amine between two aryl moieties (24-33,
described as form I). Compounds 24-29 have a methyl ether linker (X = OCH2); thus, they are
conformationally more flexible than Q203. First, a halogen atom was introduced at position 6 or 7 as R1
because our previous experiment showed that a substitution on position 5 or 8 was less potent (data not

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shown). The assay results revealed that the small and highly electronegative fluorine group (25) showed a
3-fold decrease in activity and that the sterically more hindered bromo group (26) led to a 16-fold decrease in
activity (extracellular MIC80 = 84 nM and 432 nM, respectively) compared to compound 24. However, the
chlorine atom, whether it was placed at position 6 or 7, showed increased potency over a hydrogen atom (27
and 28, extracellular MIC80 = 15 nM for both). For R1 substituents, all compounds showed good potency
except for the 6-bromo compound. It suggested that the steric factor seems to be more important than the
electronic factor. Furthermore, changing the R2 group from a trifluoromethoxy group to a fluorine group had
no influence on activity (29, extracellular MIC80 = 20 nM). On the other hand, compound 30, which has an
alkyl amine linker (X = NCH2), showed an approximately 16-fold decrease in MIC values compared to
compound 28, although both have similar linker lengths. In addition, even with a shorter oxygen linker (X =
O), compound 31 showed a 4-fold reduction in potency (extracellular MIC80 = 64 nM) compared to
compound 28. Also, the presence of a hydrogen bond donor (such as X = NH) led to significant activity loss
(32, extracellular MIC80 = 839 nM). Interestingly, for compound 33, in which a hydrogen atom on the
nitrogen of compound 32 was replaced with a methyl group, the activity strikingly recovered to 40 nM in
contrast to 839 nM for compound 32. We explored additional SAR for a set of compounds which have more
extended linker length by the cyclic amine moiety described as form II. For this study, flexible and rotatable
linkers were placed between the second cyclic amine and the last phenyl ring. The cyclic amine was varied to
piperidine, pyrrolidine, and piperazine (34-43, 45, and 46). As shown in Table 1, analogues that have an
ether linker (Z = O) next to the piperidine ring displayed excellent potency, with MIC80 range of 3 to 26 nM,
regardless of the R2 substituent at the end (34-38). 7-Chloro on R1 did not show a big difference in potency

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(38, extracellular MIC80 = 21 nM) compared with the 6-chloro analogue (37). Potency was retained by
analogue 39, which possesses an alkyl linker (Z = CH2) instead of an ether bridge (extracellular MIC80 = 22
nM). The even smaller cyclic amine (pyrrolidine) showed comparable anti-tubercular activity, regardless of
the stereochemistry at its 3-position (40 and 41, extracellular MIC80 = 6 and 14nM, respectively). A flexibly
extended linker (Z = CH2O) showed tolerable potency as well (42, extracellular MIC80 = 37nM), despite its
difference in side chain conformational change compared to compound 37. A series of analogues containing
a piperazine as the cyclic amine in the middle of the side chain to give more polarity was synthesized and
evaluated for anti-tubercular activity (43, 45, and 46). Compound 43, which has a benzyl group next to the
piperazine ring, showed good potency, with a MIC80 value of 15 nM. On the other hand, the carbonyl-
containing analogues, 45 and 46, displayed over a 10-fold decrease in activity compared to compounds 42
and 43, despite having similar chain lengths. These results suggest that a rigid linker would restrict side chain
reorientation for target binding, and that, more importantly, the decreased lipophilicity in the linker region
may adversely affect anti-tubercular activity.
Table 1. Extracellular activity of IPA analogues against M. tuberculosis H37Rva,b

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aExtracellular activity
MIC80
Compound
Form
R1
X
Y
Z
R2
(H37Rv-GFP, nM)
I
I
H
OCH2
‒
OCF3
OCF3
OCF3
OCF3
OCF3
F
27
84
432
15
15
20
250
64
839
40
10
3
24
25
6-F
OCH2
‒
I
6-Br
6-Cl
7-Cl
7-Cl
7-Cl
7-Cl
7-Cl
7-Cl
6-Cl
6-Cl
6-Cl
6-Cl
7-Cl
7-Cl
6-Cl
6-Cl
6-Cl
6-Cl
6-Cl
6-Cl
OCH2
‒
26
I
OCH2
‒
‒
27
I
OCH2
28
I
OCH2
‒
29
I
NCH2
‒
OCF3
OCF3
OCF3
OCF3
F
30
I
O
‒
31
I
NH
‒
32
I
NMe
‒
33
II
II
II
II
II
II
II
II
II
II
II
II
‒
‒
‒
‒
‒
‒
‒
‒
‒
‒
‒
‒
4-piperidyl
4-piperidyl
4-piperidyl
4-piperidyl
4-piperidyl
4-piperidyl
(R)-3-pyrrolidyl
(S)-3-pyrrolidyl
4-piperidyl
4-piperazinyl
4-piperazinyl
4-piperazinyl
O
O
34
Cl
35
O
CF3
OCF3
OCF3
H
26
7
36
O
37
O
21
22
6
38
CH2
O
39
Cl
40
O
Cl
14
37
15
373
534
490
4
41
CH2O
CH2
C(O)CH2
C(O)
OCF3
OCF3
F
42
43
45
F
46
INH
bQ203
aExtracellular MIC80 = inhibitory activity against M. tuberculosis H37Rv replicating in liquid broth culture
medium. MIC80 is the minimum concentration required to inhibit growth by 80% and indicates an average
value of two independent measurements. bAnti-tubercular activity of Q203 were adapted from ref 8.

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2.3. Anti-tubercular activity against M. tuberculosis inside macrophages (Intracellular activity)
The in vitro activity against M. tuberculosis replicating inside macrophages (intracellular MIC80)13 was also
investigated for a small set of compounds (25, 28, 31, 33, 35, 36, and 43) that displayed good extracellular
potency. As shown in Table 2, most of the compounds showed also good potency against M. tuberculosis
replicating inside and in the liquid broth culture medium as well. Compounds 28, 35, and 36, in particular,
showed excellent intracellular potency with a single-digit nanomolar range (intracellular MIC80 = less than 1
nM–9 nM). However, compound 43 exhibited quite decreased intracellular potency despite having the same
extracellular activity as compound 28. It seems that decreased lipophilicity due to the presence of a
piperazine group might have influenced cell permeability in our macrophage infection assay system. Overall,
all analogues, except for compound 43, showed better potency against M. tuberculosis replicating inside
macrophages than against M. tuberculosis in liquid broth culture medium and showed good correlation
between extracellular and intracellular activity, with R2 value of 0.93.
Table 2. Anti-tubercular activity against M. tuberculosis H37Rv-GFP replicating inside macrophages
(Intracellular activity)a,b,c

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aExtracellular
MIC80 (nM)
bIntracellular
Compd
MIC80 (nM)
25
28
31
33
84
15
64
40
28
<1
27
23
3
<1
9
35
26
36
43
15
490
4
82
200
1.43
INH
cQ203
aExtracellular MIC80 = inhibitory activity against M. tuberculosis H37Rv replicating in culture broth medium.
bIntracellular MIC80 = inhibitory activity against M. tuberculosis H37Rv replicating inside macrophages.
MIC80 is the minimum concentration required to inhibit growth by 80% and indicates an average value of
two independent measurements. cAnti-tubercular activity of Q203 were adapted from ref 8.
2.4. Pharmacokinetic evaluation
The in vivo pharmacokinetic properties of compounds 25, 28, 35, and 36 were evaluated in mice after
intravenous (i.v.) and oral (p.o.) administration of 2 and 10 mg/kg, respectively. As shown in Table 3, all
compounds reached maximum concentration in plasma within 2 h after oral dosing. In addition, they showed
not only high drug exposure level in plasma, from 11500 ng∙h/mL to 48900 ng∙h/mL with long half-life (11–
20 h), but also low systemic clearance (2.23–5.77 mL/min/kg). Further they had good oral bioavailability
(51.4 %–80.5 %). These pharmacokinetic values indicate that they are potential anti-tubercular candidates
that can show in vivo efficacy comparable to Q2036,8.

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Table 3. In vivo pharmacokinetic values in mice of compound 25, 28, 35, and 36a
aPK values of Q203 were adapted from ref 6 and 8 for the sake of comparison.
3. Conclusion
In summary, we have synthesized and evaluated analogues of Q203 to understand the role of the right hand
side chain moiety in anti-tubercular activity. Most of the analogues retained activity regardless of chain
length and showed comparable potency. However, the analogues with an amine linker reduced activity.
Based on these results, we postulate that lipophilicity is more important than linearity of side chain in
retaining activity and that the decreased lipophilic character of the linker region negatively affects anti-
tubercular activity.
In addition, we found that a set of analogues, 25, 28, 35, and 36, exhibited better potency against M.
tuberculosis inside macrophages than against M. tuberculosis replicating in liquid broth culture medium.
Based on their promising pharmacokinetic properties with potent intracellular activities, these newly

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synthesized analogues are promising anti-tubercular candidates, which could show efficacy comparable with
Q203. Studies on the in vivo efficacy of these analogues will be reported in due course.
4. Experimental
4.1.Chemistry
All reactions were carried out under an argon atmosphere in oven-dried glassware with magnetic stirring
and the reaction solvents were purified by passage through a bed of activated alumina. Purification of
reaction products was carried out by flash chromatography using silica gel 60 (Merck, 230-400 mesh).
Analytical thin layer chromatography was performed on 0.25 mm silica gel 60-F254 plates (Merck).
Visualization was accomplished with 254nm of UV light and PMA or potassium permanganate stain
followed by heating. Melting points (mp) were measured on an electro thermal melting point apparatus, M-
1
13
565 (BÜCHI). H-NMR (at 400 MHz) and C NMR (at 100 MHz) spectra were recorded on a Varian 400
MHz spectrometer and are reported in ppm using solvent as an internal standard (CDCl3 at 7.26 ppm,
DMSO-d6 at 2.50 for 1H NMR and CDCl3 at 77.2 ppm for 13C NMR). Data are reported as (ap = apparent, s
= singlet, d= doublet, t = triplet, q = quartet, m = multiplet, br = broad; coupling constant(s) in Hz;
integration). LC/MS data were obtained using a Waters 2695 LC and Micromass ZQ spectrometer. Yields
refer to purified products and are not optimized and the 13C NMR data of representative compounds 25, 28,
35 and 36 were reported. The purity of all biologically tested compounds was >95% and minimum inhibitory

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concentration determination (extracellular & intracellular), in vivo pharmacokinetics were performed as
previously described6, 13, 14
.
4.1.1. General Procedure for Preparation of acid counterpart 5a-5e.
The synthetic procedure for preparation of imidazopyridine[1,2-a] carboxylic acids was previously
reported8 and 1H NMR data of carboxylic acid 4d and intermediate ester 4a-4c and 4e are as below.
Ethyl 2-ethylimidazo[1,2-a]pyridine-3-carboxylate (4a). 1H NMR (400 MHz, CDCl3) δ 1.36 (t, J = 7.6 Hz,
3H), 1.43 (t, J = 7.2 Hz, 3H), 3.12 (q, J = 7.6 Hz, 2H), 4.43 (q, J = 7.2 Hz, 2H), 6.95 – 6.98 (m, 1H), 7.35 –
7.39 (m, 1H), 7.63 – 7.65 (m, 1H), 9.31 – 9.33 (m, 1H).
1
Ethyl 2-ethyl-6-fluoroimidazo[1,2-a]pyridine-3-carboxylate (4b). H NMR (400 MHz, CDCl3) δ 1.35 (t, J
= 7.6 Hz, 3H), 1.44 (t, J = 7.6 Hz, 3H), 3.12 (q, J = 7.6 Hz, 2H), 4.44 (q, J = 7.2 Hz, 2H), 7.28 -7.31 (m, 1H),
7.58 -7.62 (m, 1H), 9.31 – 9.33 (m, 1H).
1
Ethyl 6-chloro-2-ethylimidazo[1,2-a]pyridine-3-carboxylate (4c). H NMR (400 MHz, CDCl3) δ 1.35 (t, J
= 7.6 Hz, 3H), 1.44 (t, J = 7.2 Hz, 3H), 3.11 (q, J = 7.6 Hz, 2H), 4.44 (q, J = 7.2 Hz, 2H), 7.35 (dd, J = 9.6,
2.0 Hz, 1H), 7.58 (d, J = 9.6 Hz, 1H), 9.42 (d, J = 2.0 Hz, 1H).
Ethyl 7-chloro-2-ethylimidazo[1,2-a]pyridine-3-carboxylate (4e). 1H NMR (400 MHz, CDCl3) δ 1.34 (t, J
= 7.6 Hz, 3H), 1.43 (t, J = 7.2 Hz, 3H), 3.09 (q, J = 7.6 Hz, 2H), 4.43 (q, J = 7.2 Hz, 2H), 6.95 (dd, J = 7.6,
2.0 Hz, 1H), 7.62 (d, J = 2.0 Hz, 1H), 9.26 (d, J = 7.6 Hz, 1H).
1
Ethyl 6-bromo-2-ethylimidazo[1,2-a]pyridine-3-carboxylic acid (5d). H NMR (400 MHz, DMSO-

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d6) δ 1.24 (t, J = 7.6 Hz, 3H), 3.02 (q, J= 7.6 Hz, 2H), 7.63-7.69 (m, 2H), 9.41 (s, 1H), 13.3 (brs, 1H).
4.1.2. General Procedure for Preparation of 6a-6b.
To a stirred solution of 4-hydroxybenzonitrile (1.68 mmol) in DMF (5 mL) was added NaH (60%
dispersion in paraffin, 2.01 mmol) under ice-bath. After 10min, 4-fluorobenzyl bromide (2.01 mmol) was
added then the resulting solution was further stirred for 4 hours at room temperature. The mixture was
quenched with water (10 mL) and extracted with EtOAc (10 mL × 2). The organic phase was washed with
brine (10 mL), dried over MgSO4 and concentrated in vacuo to give 6a as a white solid. In a similar
manner, 6b was synthesized according to procedure above.
4.1.3. General procedure for preparation of 8 and 21.
To a stirred solution of 4-aminobenzonitrile (4.23 mmol) and 4-(trifluoromehtoxy)benzaldehyde (4.65
mmol) in methylene chloride (10 mL) was added sodium triacetoxyborohydride (6.34 mmol) and the
resulting mixture was stirred for overnight. The mixture was diluted with methylene chloride (10 mL),
washed with saturated Na2CO3 (aq. 10 mL) and brine (10 mL), dried over MgSO4 and concentrated in
vacuo. The crude residue was purified by flash column chromatography (n-hexane:EtOAc = 7:1) to give
8 as a pale yellow solid (85%). In a similar manner, compound 21 was synthesized from 20 according to
this procedure.
4.1.4. General procedure for preparation of 10a-10b and 14a-14f.

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A mixture of 4-fluorobenzonitrile (2.48 mmol), 4-(trifluoromethoxy)phenol (2.73 mmol) and K2CO3
(7.44 mmol) in DMF or DMSO (3 mL) was heated to 150℃ for 6 hours. After the cooling, the mixture
was poured to the water. The resulting solid was filtered, washed with water and dried to give 10a.
In a similar manner, 10b and 14a-14f were synthesized according to this procedure.
4.1.5. General procedure for preparation of compound 12.
To a stirred solution of 10b (1.27 mmol) in anhydrous DMF (5 mL) was added NaH (60% dispersion
in paraffin, 1.91 mmol) under ice-bath. After 20 min, iodomethane (1.91 mmol) was added and the
reaction mixture was allowed to ambient temperature. After 2 hours of stirring, the mixture was quenched
with water (5 mL) and concentrated. The resulting residue was diluted with EtOAc (20 mL) and washed
with water (15 mL) and brine (15 mL). The organic phase was dried over MgSO4 and concentrated in
vacuo. The crude residue was purified by flash column chromatography (n-hexane:EtOAc = 2:1) to give
12.
4.1.6. General procedure for preparation of compound 7a-7b, 9, 11a-11b, 13, 15, 17a-17f, 19 and 22.
To a solution of 6a (1.71 mmol) in THF (10 mL) was added lithium aluminum hydride (5.12 mmol)
under ice-bath and then the resulting mixture was refluxed for 2 hours. The reaction mixture was cooled
to room temperature and quenched with water (5 mL). The insoluble solid was filtered off using cellite
and the filtrate was diluted with sat. Na2CO3 (aq. 15 mL) and extracted with EtOAc (20 mL × 2). The
organic phase was washed with brine (20 mL), dried over MgSO4 and concentrated in vacuo to give 7a.

ACCEPTED MANUSCRIPT
The crude residue was used for next reaction without further purification. In a similar manner,
compound 7b, 9, 11a-11b, 13, 15, 17a-17f, 19 and 22were synthesized according to this procedure.
4.1.7. General procedure for preparation of 16a-16f and18.
To a stirred solution of 14a (1.38 mmol), triphenylphosphine (1.94 mmol) and 4-chlorophenol (1.38
mmol) in methylene chloride (10 mL) was added diisopropyl azodicarboxylate (1.66 mmol) slowly and
the resulting mixture was stirred for overnight. The reaction mixture was diluted with methylene chloride
(10 mL) and washed with water (10 mL) and brine (10 mL). The resulting organic phase was dried over
MgSO4 and concentrated in vacuo. The crude residue was purified by flash column chromatography (n-
hexane:EtOAc = 7:1) to give 16b as a white solid. In a similar manner, compound 16a, 16c-16f and 18
were synthesized according to this procedure.
4.1.8. Synthesis of compound 45 and 46.
To a stirred solution of 44 (14.6 mmol) in methylene chloride (30 mL) was added trifluoroacetic acid
(10 mL) and the resulting mixture was stirred at room temperature for 4h. The reaction mixture was
diluted with water (40 mL) and basified with aqueous 1N NaOH. Then the mixture was extracted with
EtOAc (100 mL × 3) and the combined extract was washed with water (100 mL) and brine (100 mL).
The resulting organic phase was dried over anhydrous Na2SO4 and concentrated to give intermediate
amine with 98% yield. The intermediate amine (2.48 mmol) was dissolved with tetrahydrofuran (5 mL)
and triethylamine (7.4 mmol) was added. The reaction mixture was cooled under ice-bath and benzoyl
chloride (2.98 mmol) was added slowly. The resulting solution was allowed to room temperature and

ACCEPTED MANUSCRIPT
further stirred for 30min. The mixture was diluted with water (100 mL) and extracted with EtOAc (50
mL × 3). The resulting organic phase was washed with brine (20 mL), dried over Na2SO4 and
concentrated. The crude residue was purified by flash column chromatography (PE:EA = 4:1 to 1:2) to
give 45. In a similar manner, compound 46 was synthesized according to this procedure.
4.1.9. General procedure for preparation of 23.
To a stirred solution of 14f (1.55 mmol) in methanol (10 mL) was added a portion of Raney-Ni and the
mixture was stirred for 4h under H2 atmosphere. The reaction mixture was filtered by cellite and the
filtrate was concentrated. The crude residue was purified by flash column chromatography (methylene
chloride:MeOH = 20:1) to give 23.
1
4-((4-(Trifluoromethoxy)benzyl)oxy)benzonitrile (6b). White solid; H NMR (400 MHz, CDCl3) δ 5.10
(s, 2H), 7.01 (d, J = 8.8 Hz, 2H), 7.25 (d, J = 8.4 Hz, 2H), 7.45 (d, J = 8.4 Hz, 2H), 7.59 (d, J = 8.8 Hz,
2H).
1
4-(4-(4-Chlorophenoxy)piperidin-1-yl)benzonitrile (16b). White solid; H NMR (400 MHz, DMSO-
d6) δ 1.60 − 1.68 (m, 2H), 1.98 – 2.02 (m, 2H), 3.24 – 3.40 (m, 2H), 3.68 – 3.74 (m, 2H), 4.61
– 4.66 (m, 1H), 7.01 – 7.06 (m, 4H), 7.31 – 7.34 (m, 2H), 7.57 (d, J = 8.8 Hz, 2H).
1
4-(4-(4-(Trifluoromethyl)phenoxy)piperidin-1-yl)benzonitrile (16c). White solid; H NMR (400 MHz,
CDCl3) δ 1.92 – 1.98 (m, 2H), 2.04 – 2.12 (m, 2H), 3.32 – 3.38 (m, 2H), 3.58 – 3.64 (m, 2H),
4.61 – 4.64 (m, 1H), 6.87 – 6.90 (m, 2H), 6.98 (d, J = 8.8 Hz, 2H), 7.48 – 7.51 (m, 2H), 7.55
(d, J = 8.8 Hz, 2H).
4.1.10.General procedure for amide coupling.

ACCEPTED MANUSCRIPT
The target imidazopyridine[1,2-a]-3-carboxamide derivatives were synthesized using EDC and HOBt
and synthetic procedure was previously reported8.
2-Ethyl-N-(4-((4-(trifluoromethoxy)benzyl)oxy)benzyl)imidazo[1,2-a]pyridine-3-carboxamide (24). White so
1
lid; mp = 138.7 ℃; H NMR (400 MHz, CDCl3) δ 1.36 (t, J = 7.6 Hz, 3H), 2.95 (q, J = 7.6 Hz,
2H), 4.61 (d, J = 5.2 Hz, 2H), 5.03 (s, 2H), 6.15 (brt, J = 5.6 Hz, 1H), 6.86 (ddd, J = 1.2, 7.2, 7.
2 Hz, 1H), 6.93 (d, J = 8.4 Hz, 2H), 7.21 (d, J = 8.0 Hz, 2H), 7.26 – 7.30 (m, 3H), 7.43 (d, J =
8.8 Hz, 2H), 7.56 (d, J = 9.2 Hz, 1H), 9.34 (d, J = 7.2 Hz, 1H); LCMS (ESI) m/z 470 [M + H]+.
2-Ethyl-6-fluoro-N-(4-((4-(trifluoromethoxy)benzyl)oxy)benzyl)imidazo[1,2-a]pyridine-3-carboxamide (25).
White solid; mp = 157.4 ℃; 1H NMR (400 MHz, CDCl3) δ 1.39 (t, J = 7.2 Hz, 3H), 2.96 (q, J = 7
.2 Hz, 2H), 4.63 (d, J = 5.6 Hz, 2H), 5.06 (s, 2H), 6.08 (brt, J = 5.2 Hz, 1H), 6.96 (d, J = 8.8 H
z, 2H), 7.22 – 7.26 (m, 3H), 7.31 (d, J = 8.4 Hz, 2H), 7.46 (d, J = 8.8 Hz, 2H), 7.56 (dd, J = 5.2
, 9.6 Hz, 1H), 9.43 – 9.45 (m, 1H); 13C NMR (100 MHz, CDCl3) δ 13.3, 23.8, 43.2, 69.3, 115.3, 1
15.8, 115.9, 1163.9, 117.0, 118.6, 118.8, 119.3, 121.3, 121.9, 124.4, 129.0, 129.3, 130.8, 135.7, 143.8
, 149.0, 151.8, 152.4, 154.8, 158.2, 161.3; LCMS (ESI) m/z 488 [M + H]+.
6-Bomo-2-ethyl-N-(4-((4-(trifluoromethoxy)benzyl)oxy)benzyl)imidazo[1,2-a]pyridine-3-carboxamide (26).
1
Pale yellow solid; mp = 189.7 ℃; H NMR (400 MHz, CDCl3) δ 1.38 (t, J = 7.6 Hz, 3H), 2.95 (q,
J = 7.6 Hz, 2H), 4.63 (d, J = 5.6 Hz, 2H), 5.05 (s, 2H), 6.08 (brt, J = 5.2 Hz, 1H), 6.96 (d, J =
8.4 Hz, 2H), 7.22 (d, J = 8.4 Hz, 2H), 7.31 (d, J = 8.8 Hz, 2H), 7.38 (dd, J = 1.6, 9.2 Hz, 1H),
7.44 – 7.49 (m, 3H), 9.61 (d, J = 1.6 Hz, 1H); LCMS (ESI) m/z 548 [M + H]+.
6-Chloro-2-ethyl-N-(4-((4-(trifluoromethoxy)benzyl)oxy)benzyl)imidazo[1,2-a]pyridine-3-carboxamide (27).
White solid; mp = 168.5 ℃; 1H NMR (400 MHz, CDCl3) δ 1.39 (t, J = 7.6 Hz, 3H), 2.96 (q, J = 7.6 Hz, 2H),
4.64 (d, J = 5.6 Hz, 2H), 5.06 (s, 2H), 6.05 (brs, 1H), 6.97 (d, J = 8.4 Hz, 2H), 7.20 - 7.33 (m, 5H), 7.46 (d, J =
8.8 Hz, 2H), 7.54 (d, J = 9.2 Hz, 1H), 9.53 (d, J = 1.2 Hz, 1H); LCMS (ESI) m/z 504 [M + H]+.

ACCEPTED MANUSCRIPT
7-Chloro-2-ethyl-N-(4-((4-(trifluoromethoxy)benzyl)oxy)benzyl)imidazo[1,2-a]pyridine-3-carboxamide
1
(28). H NMR (400 MHz, CDCl3) δ 1.39 (t, J = 7.6 Hz, 3H), 2.95 (q, J = 7.6 Hz, 2H), 4.63 (d, J = 5.6 Hz,
2H), 5.06 (s, 2H), 6.03 (brs, 1H), 6.90 (dd, J = 7.6, 2.0 Hz, 1H), 6.97 (d, J = 8.8 Hz, 2H), 7.23 (d, J = 8.0 Hz,
2H), 7.31 (d, J = 8.8 Hz, 2H), 7.46 (d, J = 8.8 Hz, 2H), 7.59 (d, J = 2.0 Hz, 1H), 9.36 (d, J = 7.6 Hz, 1H); 13C
NMR (100 MHz, DMSO-d6) δ 13.5, 22.2, 42.3, 68.6, 114.2, 115.0, 115.5, 116.0, 121.4, 128.4, 129.1, 129.8,
131.8, 132.2, 137.1, 145.1, 148.2, 151.4, 157.5, 160.9; LCMS (ESI) m/z 504 [M + H]+.
7-Chloro-2-ethyl-N-(4-((4-fluorobenzyl)oxy)benzyl)imidazo[1,2-a]pyridine-3-carboxamide (29). Pale
1
yellow solid; mp = 181.0 ℃; H NMR (400 MHz, CDCl3) δ 1.38 (t, J = 7.6 Hz, 3H), 2.95 (q, J = 7.6 Hz,
2H), 4.62 (d, J = 5.6 Hz, 2H), 5.02 (s, 2H), 6.02 (brs, 1H), 6.90 (dd, J = 7.6, 2.4 Hz, 1H), 6.96 (d, J = 8.8 Hz,
2H), 7.07 (dd, J = 8.8, 8.8 Hz, 2H), 7.30 (d, J = 8.8 Hz, 2H), 7.40 (dd, J = 5.6, 8.8 Hz, 2H), 7.58 (d, J = 1.6
Hz, 1H), 9.36 (d, J = 7.6 Hz, 1H); LCMS (ESI) m/z 438 [M + H]+.
7-Chloro-2-ethyl-N-(4-((4-(trifluoromethoxy)benzyl)amino)benzyl)imidazo[1,2-a]pyridine-3-carboxamide
(30). White solid; mp = 169.6 ℃; 1H NMR (400 MHz, CDCl3) δ 1.36 (t, J = 7.6 Hz, 3H), 2.93 (q, J = 7.6 Hz,
2H), 4.18 (brs, 1H), 4.34 (s, 2H), 4.55 (d, J = 5.2 Hz, 2H), 6.00 (brs, 1H), 6.60 (d, J = 8.4 Hz, 2H), 6.87 (d, J
= 7.6 Hz, 1H), 7.17 (d, J = 8.0 Hz, 4H), 7.38 (d, J = 8.0 Hz, 2H), 7.56 (s, 1H), 9.33 (d, J = 7.2 Hz, 1H);
LCMS (ESI) m/z 503 [M + H]+.
7-Chloro-2-ethyl-N-(4-(4-(trifluoromethoxy)phenoxy)benzyl)imidazo[1,2-a]pyridine-3-carboxamide (31).
White solid; mp = 141 - 142 ℃; 1H NMR (400 MHz, CDCl3) δ 1.41 (t, J = 7.6 Hz, 3H), 2.98 (q, J = 7.6 Hz,
2H), 4.68 (d, J = 5.6 Hz, 2H), 6.10 (brs, 1H), 6.91 (dd, J = 2.0, 7.6 Hz, 1H), 6.98 – 7.02 (m, 4H), 7.18 (d, J =

ACCEPTED MANUSCRIPT
8.8 Hz, 2H), 7.37 (d, J = 8.4 Hz, 2H), 7.59 (d, J = 2.0 Hz, 1H), 9.37 (d, J = 7.2 Hz, 1H) ); LCMS (ESI) m/z
490 [M + H]+.
7-Chloro-2-ethyl-N-(4-((4-(trifluoromethoxy)phenyl)amino)benzyl)imidazo[1,2-a]pyridine-3-carboxamide
(32). Pale yellow solid; mp = 200 ℃; 1H NMR (400 MHz, CDCl3) δ 1.40 (t, J = 7.6 Hz, 3H), 2.98 (q, J = 7.6
Hz, 2H), 4.63 (d, J = 5.6 Hz, 2H), 5.73 (s, 1H), 6.05 (brs, 1H), 6.91 (dd, J = 2.0, 7.6 Hz, 1H), 7.03 - 7.07 (m,
4H), 7.12 (d, J = 9.2 Hz, 2H), 7.29 (d, J = 8.8 Hz, 2H), 7.59 (d, J = 1.6 Hz, 1H), 9.36 (d, J = 7.6 Hz, 1H);
LCMS (ESI) m/z 489 [M + H]+.
7-Chloro-2-ethyl-N-(4-(methyl(4-(trifluoromethoxy)phenyl)amino)benzyl)imidazo[1,2-a]pyridine-3-
1
carboxamide (33). White solid; mp = 134 ℃; H NMR (400 MHz, DMSO-d6) δ 1.26 (t, J = 7.6 Hz, 3H),
2.98 (q, J = 7.6 Hz, 2H), 3.24 (s, 3H), 4.50 (d, J = 6.0 Hz, 2H), 6.92 (d, J = 8.8 Hz, 2H), 7.08 - 7.10 (m, 3H),
7.19 (d, J = 8.8 Hz, 2H), 7.35 (d, J = 8.8 Hz, 2H), 7.78 (s, 1H), 8.44 (brs, 1H), 8.97 (d, J = 7.2 Hz, 1H);
LCMS (ESI) m/z 503 [M + H]+.
6-Chloro-2-ethyl-N-(4-(4-(4-fluorophenoxy)piperidin-1-yl)benzyl)imidazo[1,2-a]pyridine-3-carboxamide
(34). Pale yellow solid; mp = 148.4 ℃; 1H NMR (400 MHz, CDCl3) δ 1.39 (t, J = 7.6 Hz, 3H), 1.91 - 1.94
(m, 2H), 2.06 - 2.11 (m, 2H), 2.96 (q, J = 7.6 Hz, 2H), 3.08 - 3.14 (m, 2H), 3.47 - 3.54 (m, 2H), 4.37 - 4.39
(m, 1H), 4.61 (d, J = 5.6 Hz, 2H), 6.01 (brs, 1H), 6.86 - 6.89 (m, 2H), 6.95 - 7.00 (m, 4H), 7.26 - 7.30 (m,
3H), 7.53 (d, J = 8.8 Hz, 1H), 9.53 (d, J = 1.6 Hz, 1H); LCMS (ESI) m/z 507 [M + H]+.
6-Chloro-N-(4-(4-(4-chlorophenoxy)piperidin-1-yl)benzyl)-2-ethylimidazo[1,2-a]pyridine-3-carboxamide
(35). Pale yellow solid; mp = 165.3 ℃; 1H NMR (400MHz, DMSO-d6) δ 0.81 (t, J = 7.6 Hz, 3H), 1.19 –
1.28 (m, 2H), 1.54 – 1.57 (m, 2H), 2.53 (q, J = 7.6 Hz, 2H), 2.55 – 2.59 (m, 2H), 3.00 – 3.06 (m, 2H), 3.98 (d,

ACCEPTED MANUSCRIPT
J = 6.0 Hz, 2H), 4.05 – 4.11 (m, 1H), 6.48 (d, J = 8.8 Hz, 2H), 6.53 – 6.56 (m, 2H), 6.78 (d, J = 8.4 Hz, 2H),
6.83 – 6.87 (m, 2H), 6.98 (dd, J = 9.6, 2.4 Hz, 1H), 7.20 (d, J = 9.6 Hz, 1H), 7.93 (brt, J = 6.0 Hz, 1H), 8.62
(d, J = 2.4 Hz, 1H); 13C NMR (100 MHz, DMSO-d6) δ 13.5, 22.3, 30.3, 42.3, 46.4, 72.9, 116.1, 116.3, 117.6,
118.0, 120.0, 124.6, 125.2, 127.4, 128.7, 129.7, 129.8, 143.7, 150.2, 151.4, 156.3, 160.8; LCMS (ESI) m/z
523 [M + H]+.
6-Chloro-2-ethyl-N-(4-(4-(4-(trifluoromethyl)phenoxy)piperidin-1-yl)benzyl)imidazo[1,2-a]pyridine-3-
carboxamide (36). White solid; 1H NMR (400 MHz, CDCl3) δ 1.39 (t, J = 7.6 Hz, 3H), 1.94 - 1.99 (m, 2H),
2.10 - 2.15 (m, 2H), 2.96 (q, J = 7.6 Hz, 2H), 3.12 - 3.18 (m, 2H), 3.47 - 3.53 (m, 2H), 4.53 - 4.57 (m, 1H),
4.61 (d, J = 5.2 Hz, 2H), 6.02 (brs, 1H), 6.96 (d, J = 8.4 Hz, 2H), 6.98 (d, J = 8.4 Hz, 2H), 7.27 - 7.31 (m,
3H), 7.51 - 7.55 (m, 3H), 9.53 (d, J = 2.0 Hz, 1H); 13C NMR (100 MHz, DMSO-d6) δ 13.5, 22.3, 30.2, 42.3,
46.4, 72.8, 116.2, 116.3, 116.4, 117.5, 120.0, 120.9, 121.2, 121.5, 121.9, 123.6, 125.2, 126.3, 127.3, 127.4,
127.5, 128.7, 129.8, 143.7, 150.1, 151.4, 160.4, 160.9; LCMS (electrospray) m/z 557 [M + H]+.
6-Chloro-2-ethyl-N-(4-(4-(4-(trifluoromethoxy)phenoxy)piperidin-1-yl)benzyl)imidazo[1,2-a]pyridine-3-
1
carboxamide (37). H NMR (400 MHz, CDCl3) δ 1.38 (t, J = 7.6 Hz, 3H), 1.89 - 1.97 (m, 2H), 2.07 - 2.12
(m, 2H), 2.95 (q, J = 7.6 Hz, 2H), 3.09 - 3.15 (m, 2H), 3.48 - 3.53 (m, 2H), 4.42 - 4.47 (m, 1H), 4.60 (d, J =
5.6 Hz, 2H), 6.00 (brs, 1H), 6.88 – 6.93 (m, 3H), 6.96 (d, J = 8.4 Hz, 2H), 7.14 (d, J = 8.8 Hz, 1H), 7.26 -
7.31 (m, 2H), 7.58 (d, J = 2.0 Hz, 1H), 9.36 (d, J = 7.6 Hz, 1H); LCMS (electrospray) m/z 573 [M + H]+.
7-Chloro-2-ethyl-N-(4-(4-(4-(trifluoromethoxy)phenoxy)piperidin-1-yl)benzyl)imidazo[1,2-a]pyridine-3-
carboxamide (38). Pale yellow solid; mp = 141.3 ℃; 1H NMR (400 MHz, CDCl3) δ 1.39 (t, J = 7.6 Hz, 3H),
1.89 -1.97 (m, 2H), 2.07 - 2.12 (m, 2H), 2.96 (q, J = 7.6 Hz, 2H), 3.09 - 3.16 (m, 2H), 3.47 - 3.53 (m, 2H),

ACCEPTED MANUSCRIPT
4.42 - 4.47 (m, 1H), 4.61 (d, J = 5.6 Hz, 2H), 6.01 (brs, 1H), 6.91 (dd, J = 2.0, 6.8 Hz, 2H), 6.96 (d, J = 8.8
Hz, 2H), 7.14 (d, J = 8.8Hz, 2H), 7.26 - 7.30 (m, 3H), 7.53 (d, J = 9.6 Hz, 1H), 9.53 (s, 1H); LCMS (ESI)
m/z 573 [M + H]+.
N-(4-(4-benzylpiperidin-1-yl)benzyl)-7-chloro-2-ethylimidazo[1,2-a]pyridine-3-carboxamide (39). White
1
solid; mp = 103.4 ℃; H NMR (400 MHz, CDCl3) δ 1.35 (t, J = 7.6 Hz, 3H), 1.37 - 1.44 (m, 2H), 1.63 -
1.70 (m, 1H), 1.72 - 1.76 (m, 2H), 2.57 (d, J = 6.8 Hz, 2H), 2.61 - 2.67 (m, 2H), 2.92 (q, J = 7.6 Hz, 2H),
3.63 - 3.66 (m, 2H), 4.57 (d, J = 5.2 Hz, 2H), 6.08 (brs, 1H), 6.84 - 6.87 (m, 1H), 6.90 (d, J = 8.0 Hz, 2H),
7.15 (d, J = 7.2 Hz, 2H), 7.19 - 7.30 (m, 5H), 7.55 (d, J = 1.6 Hz, 1H), 9.29 - 9.32 (m, 1H); LCMS (ESI) m/z
487 [M + H]+.
(S)-6-Chloro-N-(4-(3-(4-chlorophenoxy)pyrrolidin-1-yl)benzyl)-2-ethylimidazo[1,2-a]pyridine-3-
carboxamide (40). Pale yellow solid; mp = 211.8 ℃; 1H NMR (400 MHz, CDCl3 + CD3OD) δ 1.26 (t, J =
7.6 Hz, 3H), 2.20 - 2.25 (m, 2H), 2.85 (q, J = 7.6 Hz, 2H), 3.33 - 3.45 (m, 3H), 3.58 - 3.62 (m, 1H), 4.47 (d,
J = 5.2 Hz, 2H), 4.93 - 4.94 (m, 1H), 6.34 (brs, 1H), 6.49 (d, J = 8.8 Hz, 2H), 6.74 (d, J = 8.8 Hz, 2H), 7.13
- 7.17 (m, 4H), 7.23 -7.26 (m, 1H), 7.43 (d, J = 9.2 Hz, 1H), 9.30 (d, J = 2.0 Hz, 1H); LCMS (ESI) m/z 509
[M + H]+.
(R)-6-Chloro-N-(4-(3-(4-chlorophenoxy)pyrrolidin-1-yl)benzyl)-2-ethylimidazo[1,2-a]pyridine-3-
carboxamide (41). Pale yellow solid; mp = 218.8 ℃; 1H NMR (400 MHz, CDCl3 + CD3OD) δ 1.30 (t, J =
7.6 Hz, 3H), 2.23 - 2.28 (m, 2H), 2.88 (q, J = 7.6 Hz, 2H), 3.40 - 3.49 (m, 3H), 3.61 - 3.65 (m, 1H), 4.51 (d,
J = 5.2 Hz, 2H), 4.96 - 4.97 (m, 1H), 6.22 (brs, 1H), 6.53 (d, J = 8.8 Hz, 2H), 6.77 (d, J = 9.2 Hz, 2H), 7.17

ACCEPTED MANUSCRIPT
- 7.20 (m, 4H), 7.28 (d, J = 2.0 Hz, 1H), 7.47 (d, J = 9.6 Hz, 1H), 9.37 (d, J = 2.0 Hz, 1H); LCMS (ESI) m/z
509 [M + H]+.
6-Chloro-2-ethyl-N-(4-(4-((4-(trifluoromethoxy)phenoxy)methyl)piperidin-1-yl)benzyl)imidazo[1,2-
1
a]pyridine-3-carboxamide (42). Pale yellow solid; mp = 183.6 ℃; H NMR (400 MHz, CDCl3) δ 1.37 (t, J
= 7.6 Hz, 3H), 1.50 - 1.54 (m, 2H), 1.93 - 1.95 (m, 3H), 2.72 - 2.78 (m, 2H), 2.94 (q, J = 7.6 Hz, 2H), 3.71 -
3.74 (m, 2H), 3.82 (d, J = 6.0 Hz, 2H), 4.59 (d, J = 5.6 Hz, 2H), 6.06 (brt, J = 5.6 Hz, 1H), 6.86 (d, J = 9.2
Hz, 2H), 6.94 (d, J = 8.8 Hz, 2H), 7.12 (d, J = 8.8 Hz, 2H), 7.24 - 7.28 (m, 3H), 7.51 (d, J = 9.6 Hz, 1H),
9.50 (d, J = 1.2 Hz, 1H); LCMS (ESI) m/z 587 [M + H]+.
6-Chloro-2-ethyl-N-(4-(4-(4-(trifluoromethoxy)benzyl)piperazin-1-yl)benzyl)imidazo[1,2-a]pyridine-3-
1
carboxamide (43). White solid; mp = 138.1 - 138.7 ℃; H NMR (400 MHz, CDCl3) δ 1.38 (t, J = 7.6 Hz,
3H), 2.58 - 2.61 (m, 4H), 2.95 (q, J = 7.6 Hz, 2H), 3.19 - 2.61 (m, 4H), 3.55 (s, 2H), 4.60 (d, J = 5.6 Hz, 2H),
6.00 (brs, 1H), 6.92 (d, J = 8.8 Hz, 2H), 7.17 (d, J = 8.0 Hz, 2H), 7.26 - 7.30 (m, 3H), 7.38 (d, J = 8.4 Hz,
2H), 7.53 (d, J = 9.2 Hz, 1H), 9.52 (d, J = 2.0 Hz, 1H); LCMS (ESI) m/z 572 [M + H]+.
6-Chloro-2-ethyl-N-(4-(4-(2-(4-fluorophenyl)acetyl)piperazin-1-yl)benzyl)imidazo[1,2-a]pyridine-3-
1
carboxamide (45). White solid; H NMR (300MHz, DMSO-d6) δ 1.24 (t, J = 7.5 Hz, 3H), 2.91 - 3.12 (m,
6H), 3.51 - 3.65 (m, 4H), 3.74 (s, 2H), 4.42 - 4.44 (m, 2H), 6.92 (d, J = 8.7 Hz, 2H), 7.10 (t, J = 8.8 Hz, 2H),
7.19 - 7.31 (m, 4H), 7.69 (dd, J = 9.6, 1.8 Hz, 1H), 7.78 (d, J = 9.6 Hz, 1H), 8.66 (t, J = 5.7 Hz, 1H), 9.10 (s,
1H); LCMS (ESI) m/z 534 [M + H]+.
6-chloro-2-ethyl-N-(4-(4-(4-fluorobenzoyl)piperazin-1-yl)benzyl)imidazo[1,2-a]pyridine-3-carboxamide
(46). White solid; 1H NMR (300 MHz, DMSO-d6) δ 1.25 (t, J = 7.5 Hz, 3H), 3.00 (q, J = 7.5 Hz, 2H), 3.08 -

ACCEPTED MANUSCRIPT
3.28 (m, 4H), 3.31 - 3.91 (m, 4H), 4.43 (d, J = 5.7 Hz, 2H), 6.95 (d, J = 8.7 Hz, 2H), 7.20 - 7.33 (m, 4H),
7.49 (dd, J = 8.4, 5.4 Hz, 2H), 7.70 (dd, J = 9.2, 1.8 Hz, 1H), 7.80 (d, J = 9.2 Hz, 1H), 8.70 (t, J = 5.7 Hz,
1H), 9.10 (s, 1H); LCMS (ESI) m/z 520 [M + H]+.
ASSOCIATED CONTENT
Appendix A. Supplementary data
Supplementary data related to this article can be found at http://
AUTHOR INFORMATION
Corresponding Author
*Jaeseung Kim (Jaeseung K.); Phone: +82-31-8060-1603, Fax.: +82-31-8060-1649, E-mail:
silanediol@gmail.com;
*Sanghee Kim (Sanghee K.); Phone: +82-31-880-2487, E-mail: pennkim@snu.ac.kr
Author Contributions
R.Y.K. performed growth inhibition experiments, S.K., Y.M.K., M.J.S., Z.N., K.N. Sanghee K. and Jaeseung
K. designed and synthesized the compounds, Y.M.K. analyzed purity of the compounds, K.N. designed and