Discovery of 3H-imidazo[4,5-c]quinolin-4(5H)-ones as potent and selective dipeptidyl peptidase IV (DPP-4) inhibitors

Article abstract of DOI:10.1016/j.bmc.2012.07.046

In recent years, dipeptidyl peptidase IV inhibitors have been noted as valuable agents for treatment of type 2 diabetes. Herein, we report the discovery of a novel potent DPP-4 inhibitor with 3H-imidazo[4,5-c]quinolin-4(5H) -one as skeleton. After efficient optimization of the lead compound 2a at the 7- and 8-positions using a docking study, we found 28 as a novel DPP-4 inhibitor with excellent selectivity against various DPP-4 homologues. Compound 28 showed strong DPP-4 inhibitory activity compared to marketed DPP-4 inhibitors. We also found that a carboxyl group at the 7-position could interact with the residue of Lys554 to form a salt bridge. Additionally, introduction of a carboxyl group to 7-position led to both activity enhancement and reduced risk for hERG channel inhibition and induced phospholipidosis. In our synthesis of compounds with 7-carboxyl group, we achieved efficient regioselective synthesis using bulky ester in the intramolecular palladium coupling reaction.

Full text of DOI:10.1016/j.bmc.2012.07.046

Bioorganic & Medicinal Chemistry 20 (2012) 5864–5883
Contents lists available at SciVerse ScienceDirect
Bioorganic & Medicinal Chemistry
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Discovery of 3H-imidazo[4,5-c]quinolin-4(5H)-ones as potent and selective
dipeptidyl peptidase IV (DPP-4) inhibitors
⇑
Yohei Ikuma , Hitoshi Hochigai, Hidenori Kimura, Noriko Nunami, Tomonori Kobayashi,
Katsuya Uchiyama, Yudai Furuta, Mutsuko Sakai, Masakuni Horiguchi, Yumi Masui,
Kazuhiko Okazaki, Yasuhiro Sato, Hiroyuki Nakahira
Drug Research Division, Dainippon Sumitomo Pharma Co., Ltd, 3-1-98 Kasugade Naka, Konohana-ku, Osaka 554-0022, Japan
a r t i c l e i n f o
a b s t r a c t
Article history:
In recent years, dipeptidyl peptidase IV inhibitors have been noted as valuable agents for treatment of
type 2 diabetes. Herein, we report the discovery of a novel potent DPP-4 inhibitor with 3H-imi-
dazo[4,5-c]quinolin-4(5H)-one as skeleton. After efficient optimization of the lead compound 2a at the
7- and 8-positions using a docking study, we found 28 as a novel DPP-4 inhibitor with excellent selectiv-
ity against various DPP-4 homologues. Compound 28 showed strong DPP-4 inhibitory activity compared
to marketed DPP-4 inhibitors. We also found that a carboxyl group at the 7-position could interact with
the residue of Lys554 to form a salt bridge. Additionally, introduction of a carboxyl group to 7-position
led to both activity enhancement and reduced risk for hERG channel inhibition and induced phospholip-
idosis. In our synthesis of compounds with 7-carboxyl group, we achieved efficient regioselective synthe-
sis using bulky ester in the intramolecular palladium coupling reaction.
Received 18 June 2012
Revised 25 July 2012
Accepted 27 July 2012
Available online 5 August 2012
Keywords:
Dipeptidyl peptidase IV
3H-Imidazo[4,5-c]quinolin-4(5H)-one
Type 2 diabetes
Lys554
Ó 2012 Elsevier Ltd. All rights reserved.
1. Introduction
promising approach for treatment of T2D with low risk of hypogly-
cemia.7,8 Actually, clinical proof of concept has already been estab-
Type 2 diabetes (T2D) is a major metabolic disorder affecting
approximately 194 million people worldwide. This number is esti-
mated to reach 366 million by 2030.1 Currently used antidiabetic
lished with DPP-4 inhibitors, which proved to be more efficient and
safer than conventional antidiabetic agents.8,9 Based on these clin-
ical findings, a number of DPP-4 inhibitors, including Sitagliptin,10
Vildagliptin,11 Saxagliptin,12 Alogliptin13 and Linagliptin14 (Fig. 1)
have already been approved as new valuable agents for treatment
of T2D.
agents, such as PPARc agonists, sulphonylurea derivatives, and
biguanide and -glucosidase inhibitors, produce beneficial effects
a
on T2D by effectively increasing insulin secretion or decreasing
glucose absorption. However, these agents are known to be associ-
ated with a number of side effects, including hypoglycemia, weight
gain, gastrointestinal disorders, and lactic acidosis, all of which are
known to decrease quality of life for T2D patients. Even Pioglitaz-
one, the widely used antidiabetic agent, has recently been reported
to be associated with increased risk of bladder cancer after treat-
ment for two years or more,2,3 although no direct relationship
was found between treatment with this drug and occurrence of
cancer in diabetics. Under these circumstances, intensive efforts
have been made to find better and safer oral drugs for T2D.
Glucagon-like peptide-1 (GLP-1) is secreted from the gut in re-
sponse to glucose absorption following meal ingestion and stimu-
lates insulin secretion from b-cells of the pancreas, thereby
contributing to maintenance of postmeal glycemic control.4 As
GLP-1 in plasma is rapidly degraded by the serine protease dipep-
tidyl peptidase IV (DPP-4),5,6 inhibition of DPP-4 is emerging as a
Considering that T2D requires chronic treatment, highly selec-
tive DPP-4 inhibitors with low affinity for DPP-4 homologues,
including DPP-8,15 DPP-916 and FAP 17 are desirable. The require-
a,
ment for DPP-4 selectivity over DPP-8 and DPP-9 has become a hot
debate over the years. While inhibition of DPP-8 and DPP-9 is re-
ported to be associated with alopecia, thrombocytopenia, reticulo-
cytopenia, enlarged spleen, multiorgan histopathological changes,
and mortality in rats and GI toxicity in dogs,18 there is a report
indicating that an alternative mechanism, not DPP-8/DPP-9 inhibi-
tion, likely causes these toxicities.19 In this way, it seems that the
physiological roles of DPP-8, DPP-9 and FAPa in human have not
yet been completely elucidated. However, we believe that charac-
terizing the selectivity of DPP-4 inhibitors is important, because it
is sensible, when considering T2D patients long term treatment, to
confine inhibition to the target enzyme where we know the effect.
Vildagliptin and Saxagliptin inhibit DPP-8 and DPP-9 with Ki and
IC50 values of 810 and 244, and 95 and 104 nM, respectively.20 Fur-
thermore, it has been shown that Linagliptin inhibits FAP
is known to play a role in embryonic wound healing and tissue
a, which
⇑
Corresponding author. Tel.: +81 6 6466 5193; fax: +81 6 6466 5491.
E-mail address: yohei-ikuma@ds-pharma.co.jp (Y. Ikuma).
0968-0896/$ - see front matter Ó 2012 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.bmc.2012.07.046

Y. Ikuma et al. / Bioorg. Med. Chem. 20 (2012) 5864–5883
5865
Table 1
F
F
F
H2N
DPP-4 inhibitory activity of 2 derivatives with different substituents at the 5-position
O
O
CN
H
N
N
N
N
HO
N
N
Cl
CF3
Sitagliptin
Vildagliptin
5 O
R
N
N
CN
N
Me
O
NC
N
N
N
N
Me
NH2
N
N
O
N
N
N
O
NH2
N
HO
O
N
MeN
O
NH2
Me
NH2
Saxagliptin
Linagliptin
Alogliptin
Figure 1. Marketed DPP-4 inhibitors.
Compounds
R
h-DPP-4 IC50 (nM)
2
H
Me
Et
nPr
Bn
418
103
400
3400
>10000
remodeling,21 with an IC50 value of 89 nM.20 From a safety point of
view, our search for DPP-4 inhibitors as drug candidates started
with the aim of obtaining compounds with a selectivity for DPP-
4 superior to that of Vildagliptin, Saxagliptin or Linagliptin. As
Sitagliptin and Alogliptin already have excellent selectivity for
DPP-4, we aimed at finding compounds with superior DPP-4 inhib-
itory activity and presumably better efficacy. As a result of our ef-
forts,22 3H-imidazo[4,5-c]quinolin-4(5H)-one 28 was found as
potent and highly selective DPP-4 inhibitor. Herein, we report
the discovery and evaluation of novel DPP-4 inhibitors with 3H-
imidazo[4,5-c]quinolin-4(5H)-one scaffold. We also describe an
efficient regioselective synthesis of selected compounds with sub-
stituents at the 7-position using intramolecular palladium cou-
pling reaction.
2a
2b
2c
2d
Glu205
Try631
2.92Å
Lys554
2.78 Å
Glu206
By high-throughput screening of our chemical library, 1 was
identified as a weak DPP-4 inhibitor (Fig. 2, bovine DPP-4 IC50
676 nM). In our optimization of 1, we focused on the piperazine
ring, which is similar to the 3-amino piperidine moiety of reported
DPP-4 inhibitors. Reports describing Alogliptin and other anti-dia-
betic agents14 indicate that the (R)-3-amino piperidine group is
essential for activity, as this group interacts with Glu205/Glu206
of DPP-4 protein. Thus, we decided to substitute the piperazine
ring of 1 by an (R)-3-amino-piperidine ring. Furthermore, results
of a docking study based on published DPP-4 enzyme-inhibitor
crystal structures23 indicated that the hydrophobic residue of
Try547 could be located in a position that overlaps with the 2-
Tyr547
Figure 3. Docking structure of 2a active site with 2RGU of DPP-4.
Next, we carried out a docking study to design a strategy for 2a
optimization (Fig. 3). As expected, a primary amino group at the
piperidine moiety could form a salt bridge to Glu205/Glu206, since
the distance between Glu205 and Glu206, and the amino group of
2a was 2.92 and 2.78 Å, respectively. A chlorobenzyl group at the
3-position was expected to occupy the S1 pocket as previously re-
ported. Similarly, a carbonyl group at the 4-position was antici-
pated to give an effective hydrogen bond to the main chain NH
of Tyr631, while the 3H-imidazo[4,5-c]quinolin-4(5H)-one moiety
was hoped to cover the phenyl moiety of Tyr547, affording the
and 3-positions in 1. The
p stacking interaction between 1 and
DPP-4 protein could be formed by introduction of a fused aromatic
ring at the 2- and 3-positions. Considering the above view, we
decided to convert the Xanthine ring and designed a novel diverse
3H-imidazo[4,5-c]quinolin-4(5H)-one scaffold that has not been
reported previously. Lead generation allowed us to obtain com-
pound 2 with acceptable DPP-4 inhibitory activity (h-DPP-4 IC50
418 nM). To further improve this inhibitory activity, the effect of
a substitution at the 5-position of 2 was investigated (Table 1).
Methylation (2a) improved DPP-4 inhibitory activity by 4-fold,
while introduction of a sterically more bulky substituent, such as
an ethyl (2b), propyl (2c) or benzyl group (2d), was not well toler-
ated. Thus, a methyl group at the 5-position was considered suit-
able, giving 2a as lead compound with moderate DPP-4
inhibitory activity. Compounds DPP-4 inhibitory activity was mea-
sured using human plasma DPP-4.24
p
-stack. Furthermore, we found that Lys55425 residue was posi-
tioned near the benzene ring of the 3H-imidazo[4,5-c]quinolin-
4(5H)-one scaffold and considered that interaction between this
residue and a hydrophilic substituent on the benzene ring would
significantly improve DPP-4 inhibitory activity. By this conforma-
tion, Lys554 would interact with the substituent at the 7-position.
We hypothesized that an acidic substituent, such as a carboxyl
group at the 7-position, would be especially effective in improving
the affinity for DPP-4 due to formation of a salt bridge, especially.
Based on the above information, we performed 2a optimization,
principally by introducing substituents at the 6–9 positions.
Cl
2. Chemistry
O4
O
3
H5N
N
N
N
HN
O
Compounds 2a, 8a, 8b, 8e and 8p–8t were prepared according
to the reported procedure26 shown in Scheme 1. Intermediate 3
was obtained in four steps. Replacement of one phenoxy group
in the commercially available diphenylcyanocarbonimidate with
(R)-3-tert-butoxycarbonylaminopiperidine followed by treatment
with excess amount of glycine ethyl ester in one pot, N-alkylation
with 2-chlorobenzyl bromide, cyclization with sodium hydride and
N
N
NH
3
6
7
N
2 N
NH2
Me
9
8
1
2
bovine DPP-4 IC50 676 nM
bovine DPP-4 IC50 112 nM
human DPP-4 IC50 418 nM
Figure 2. Synthesis of the DPP-4 inhibitor 2 from the HTS hit 1.

5866
Y. Ikuma et al. / Bioorg. Med. Chem. 20 (2012) 5864–5883
Cl
Cl
Cl
m
5
R=H
5a R=o-OMe
R=o-CO2Me
5q R=p-Me
5r R=p-F
o
a, b, c, d
p
e
O
I
PhO OPh
f
EtO2C
I
HO2C
I
N
N
N
N
N
N
R=p-OCHF2
5b
5s
5t
5x
N
NCN
N
N
N
R
H
R=p-CO2Me
R=p-CH2CO2Et
5e R=m-Ph
NHBoc
R=H
NHBoc
Cl
NHBoc 5p R=p-OMe
3
6
4
Cl
Cl
7
R=H
2a R=H
8a R=6 OMe
m
o
6a R=o-OMe
7a R=6-OMe
-
p
O
O
O
h
g
i
R=o-CO2Me
R=6-CO2Me
7b
6b
R=6-CO2Me
8b
N
N
N
N
N
N
N
MeN
6
7
R
MeN
6
6e R= -Ph
7e R=7-Ph
7p R=8-OMe
7q R=8-Me
m
8e R=7-Ph
N
N
R
Me
I
N
6p R=p-OMe
6q R=p-Me
6r R=p-F
8p
R=8-OMe
NHBoc
NHBoc
NH2
HCl
7R
9
8q R=8-Me
9
8
8
7r R=8-F
8r R=8-F
R=p-OCHF2
R=p-CO2Me
R=p-CH2CO2Et
R=8-OCHF2
R=8-CO2Me
R=8-CH2CO2Et
6s
6t
7s
7t
7x
R=8-OCHF2
8s
j
R=8-CO2Me
8t
6x
Cl
Cl
i
O
O
O
R=6-CO2H
R=8-CO2H
R=6-CO2H
R=8-CO2H
7c
7w
8c
N
N
N
N
MeN
MeN
6
8w
N
N
6
9x R=8-CH2CO2H
8x R=8-CH2CO2H
NHBoc
NHBoc
7R
NH2
HCl
9
7R
9
8
8
k
Cl
Cl
O
i
N
N
N
N
MeN
MeN
N
N
NH2 HCl
8COR
8COR
7u R=NH2
7v R=NMe2
8u R=NH2
8v R=NMe2
i
Scheme 1. Reagents and conditions: (a) (R)-3-tert-butoxycarbonylaminopiperidine (1.0 equiv), PrOH, rt then EtO2CCH2NH2 (5.0 equiv), Et3N (5.0 equiv), 80 °C, 92%; (b) 2-
chlorobenzylbromide (1.5 equiv), K2CO3 (3.0 equiv), MeCN, 40 °C, 74%; (c) NaH (1.5 equiv), THF, 15 °C, quant.; (d) isoamylnitrite (5.0 equiv), CH2I2 (10 equiv), toluene, 80 °C,
53%; (e) 1 M NaOH (1.5 equiv), EtOH, 80 °C, quant.; (f) (1) (COCl)2 (1.3 equiv), DMF (cat.), CH2Cl2, rt (2) DIPEA (3.0 equiv), R-substituted aniline (1.3 equiv), toluene, rt, 48–86%;
(g) K2CO3 (4.0 equiv), MeI (4.0 equiv), DMF, rt, 81%-quant.; (h) Pd(OAc)2 (10 mol %), PPh3 (20 mol %), Ag2CO3 (2.0 equiv), DMF, 150 °C, 60–90%; (i) HCl, dioxane, rt, 59%-quant.;
(j) 1 M NaOH/MeOH/THF (1/1/1), 80 °C, 58%-quant.; (k) WSCÁHCl (1.5 equiv), HOBt (1.5 equiv), TEA (1.5–3.0 equiv), NH4OH (1.5 equiv) or NHMe2ÁHCl (2.0 equiv), DMF, rt,
73%-quant.
Sandmeiyer reaction gave the imidazole 3. Alkaline hydrolysis of 3
afforded 4, and amidation with the corresponding anilines, fol-
lowed by N-methylation provided 6, 6a, 6b, 6e, 6p–6t, and 6x. Pal-
ladium coupling reaction of these compounds proceeded well, and
removal of the Boc group afforded 2a, 8a, 8b, 8e and 8p–8t. Alka-
line hydrolysis of 7b, 7t, and 7x, followed by removal of the Boc
group gave 8c, 8w, and 8x. The carboxylic acid 7w was reacted
with ammonia or dimethylamine to afford the amides 7u and 7v.
8u and 8v were obtained by removal of the Boc group.
of 10 possessing a methyl ester gave a mixture of 13a and 13b
(13a/13b = 4/1, entry 1) inseparable by silica-gel column chroma-
tography. It was therefore necessary to establish an efficient regio-
selective synthetic method to obtain 8n. Considering the reaction
mechanism, cyclization could proceed to form the cationic inter-
mediates 16 and 1726 through oxidative addition of aryliodide to
Pd(0) followed by abstraction of the iodide with Ag2CO3. As
7-substituted derivatives were afforded via intermediate 16, it was
necessary to increase the abundance of 16 for higher selectivity.
To solve this problem, we attempted to use a sterically more bulky
ester than the methyl ester to obtain the preferred intermediate 16
In the synthesis of 7-substituted derivatives, especially with a
carboxyl group (Scheme 2), intramolecular palladium cyclization
Cl
Cl
Cl
Cl
CO2R
N
O
O
O
a
O
b
N
N
N
N
N
N
MeN
MeN
MeN
N
N
N
N
N
N
Table
HCl
NH2
Me
7
7
I
NHBoc
NHBoc
NHBoc
RO2C
CO2R
HO2C
9
13a
14a
15a
13b
8n
10: R = Me
11: R = Et
12: R = tBu
14b
15b
Reagents and Conditions: (a) Pd(OAc)2 (10 mol%), PPh
Entry
CO (2.0 equiv), DMF, 150 °C; (b) HCl, dioxane, 80 °C
3 (20 mol%), Ag2
Substrate
R
3
Product ratioa
Yield
(a / b)
1
2
3
10 Me
13 : 4 / 1
14 : 14 / 1
15 : 28 / 1
76% (13a+13b)
none
11 Et
12 tBu
15a : 73%b
a The ratio was determined by HPLC. b Isolated yield.
Scheme 2. Regioselective synthesis of 8n with carboxyl group at the 7-position. Reagents and conditions: (a) Pd(OAc)2 (10 mol %), PPh3 (20 mol %), Ag2CO3 (2.0 equiv), DMF,
150 °C; (b) HCl, dioxane, 80 °C.

Y. Ikuma et al. / Bioorg. Med. Chem. 20 (2012) 5864–5883
5867
Cl
Cl
Cl
CO2R
N
O
O
O
Me
Me
Pd
6
6
N
N
N
N
N
N
RO2C 7
N
N
7
8
N
N
N
Me
I
Pd
Pd
8
NHBoc
NHBoc
NHBoc
NHBoc
NHBoc
9CO2R
9
16
17
Cl
Cl
O
O
N
N
N
N
MeN
MeN
N
N
7
RO2C
9 CO2R
18
19
Figure 4. Proposed mechanism for predominantly producing 7-ester derivatives.
Cl
Cl
Cl
Cl
O
O
O
N
O
d
e
a, b, c
N
N
R2
N
N
4
N
N
MeN
R1
9o
9z
MeN
MeN
MeN
N
N
HCl
NH2
N
N
N
NHBoc
NHBoc
(7o/7z=3.3/1)
NHBoc
EtO2C
CO2Et
R1
9 R2
87o
8z
R1=CH2CO2H R2=H
R1=CH2CO2H R2=H
R1=H R2=CH2CO2H
7o
7z
R1=H R2=CH2CO2H
Scheme 3. Synthesis of 8o and 8z. Reagents and conditions: (a) (1) (COCl)2 (1.3 equiv), DMF (cat.), CH2Cl2, rt (2) DIPEA (3.0 equiv), ethyl 2-(3-aminophenyl)acetate
(1.3 equiv), toluene, rt, 62%; (b) K2CO3 (4.0 equiv), MeI (4.0 equiv), DMF, rt; (c) Pd(OAc)2 (10 mol %), PPh3 (20 mol %), Ag2CO3 (2.0 equiv), DMF, 150 °C, 7o 43% for 2 steps, 7z
13% for 2 steps; (d) 1 M NaOH/MeOH/THF (1/1/1), rt; (e) HCl, dioxane, rt, 8o 88% for 2 steps, 8z 53% for 2 steps.
by steric hindrance between Pd and R group in the intermediate
state (Fig. 4). By use of an ethyl ester (11), selectivity was certainly
improved (14a/14b = 14/1, entry 2). This result encouraged us to
deprotection of the Boc group (Scheme 4). This allowed us to solve
another problem, as regioselective synthesis of 9-substituted com-
pounds could be achieved. Palladium coupling reaction of 6y pos-
t
use Bu ester as a more bulky ester. As expected, intramolecular
sessing a chlorine atom as auxiliary, followed by selective
palladium coupling reaction of 12 possessing tBu ester afforded
15a with excellent selectivity (15a/15b = 28/1, entry 3). Fortu-
nately, the mixture of 15a and 15b was separable by silica-gel col-
umn chromatography to give 15a in good yield. Treatment of 15a
with hydrochloric acid at 80 °C afforded the desired compound
8n after removal of the Boc group and tert-butyl ester.
As shown in Scheme 3, the carboxyl methyl derivatives 8o and
8z were synthesized by the same procedure described in Schemes
1 and 2. A palladium coupling reaction using ethyl ester was
carried out to obtain a mixture of 7o and 7z as it was necessary
to synthesize both 8o and 8z. The product ratio of 7o to 7z was
approximately 3.3:1, and the mixture was separable by silica-gel
column chromatography.
dechlorination gave 7ya. 8y was provided by alkaline hydrolysis
of 7ya followed by removal of the Boc group. Selective dehalogen-
ation reaction could be used to eliminate the high steric hindrance
between the chlorine or bromine atom at the 6-position and the N-
methyl group. Synthesis of derivatives with various substituents at
the 7-position was carried out as depicted in Scheme 5. The amino
group of 8n was protected by Boc group to give 7n. Compound 7n
was treated with ethyl chloroformate followed by reduction with
NaBH4 to afford the hydroxymethyl 7i, which was converted to
the methylether 7h by alkylation of the hydroxyl group. 7i was
deprotected with trifluoroacetic acid to give 8i, and 7n was con-
verted to 7k and 7l by condensation with ammonia or dimethyl-
amine and to 7j by alkylation with iodomethane. Dehydration of
7k with trifluoroacetic acid anhydride gave the nitrile 7m. 7f with
a methyl group at the 7-position was prepared by iodination of 7i,
followed by reduction of the iodine atom with sodium
borohydride. The desired compounds 8f, 8h, 8k, 8l, 8j and 8m were
Compound 8d with a fluorine atom at the 7-position could be
synthesized from the precursor 6d possessing a bromine atom as
auxiliary at the ortho-position by palladium coupling reaction, fol-
lowed by Pd/C-catalyzed debromination under hydrogen, and
Cl
Cl
Cl
R1
Cl
p
O
O
O
a
b
c or d
O
m
N
N
R1
N
N
N
N
R2
N
MeN
R3
R2
MeN
R3
R2
MeN
N
N
N
N
N
oR3
R3
N
Me
I
6
9
HCl
NH2
NHBoc
NHBoc
R1
R1=H, R2=F, R3=H
R1=CO2Me, R2=H, R3=H
R2
R1
R1=H, R2=F, R3=H
R1=CO2H, R2=H, R3=H
NHBoc
7
8
6d R1=H, R2=F, R3=Br
6y
R1=H, R2=F, R3=Br
7da
7ya
8d
8y
7d
7y
R1=CO2Me, R2=H, R3=Cl
R1=CO2Me, R2=H, R3=Cl
Scheme 4. Regioselective synthesis of 8d and 8y. Reagents and conditions: (a) Pd(OAc)2 (10 mol %), PPh3 (20 mol %), Ag2CO3 (2.0 equiv), DMF, 150 °C, 7d 21%, 7y 57%; (b) Pd/
C, H2, MeOH, rt, 7da quant., 7ya 97%; (c) HCl, dioxane, rt, quant.; (d) (1) 1 M NaOH, THF/MeOH (1/1), rt (2) HCl, dioxane, rt, quant.

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Y. Ikuma et al. / Bioorg. Med. Chem. 20 (2012) 5864–5883
Cl
Cl
Cl
Cl
Cl
a
O
O
O
b
c
O
O
O
d
N
N
N
N
MeN
HO2C
MeN
HO2C
N
N
N
N
N
N
MeN
MeN
MeN
MeN
N
N
N
N
N
N
NH2
HCl
NHBoc
NHBoc
NHBoc
NH2
HCl
HO
MeO
MeO
8n
7n
Cl
7i
7h
8h
Cl
O
e or f
d
R=NH2
N
N
8k
7n
N
N
MeN
N
N
R=NMe2
R =OMe
8l
8j
HCl
NHBoc
NH2
R
R
R=NH2
7k
O
O
R=NMe2
R =OMe
7l
7j
g
Cl
Cl
O
O
O
h
N
N
N
N
MeN
NC
MeN
NC
N
N
NHBoc
NH2
7m
8m
Cl
Cl
Cl
O
O
i
j
k
N
N
N
N
7i
N
N
MeN
Me
MeN
Me
MeN
N
N
NHBoc
NH2
NHBoc
I
l
20
7f
8f
Cl
O
N
N
MeN
N
NH2
HO
8i
Scheme 5. Synthesis of 7-substituted derivatives. Reagents and conditions: (a) (Boc)2O (1.3 equiv), sat. NaHCO3/THF (1/1), rt, 60%; (b) ClCO2Et (1.5 equiv), TEA (2.0 equiv),
THF, 0 °C then NaBH4 (3.0 equiv), H2O, rt, 57%; (c) NaH (1.2 equiv), MeI (1.2 equiv), DMF, rt, 86%; (d) HCl, dioxane, rt, 95%-quant.; (e) WSCÁHCl (1.5 equiv), HOBt (1.5 equiv),
TEA (1.5 equiv), NH4OH (1.5 equiv) or NHMe2ÁHCl (2.0 equiv), DMF, rt, 7 k 80%, 7 l quant.; (f) MeI (2.0 equiv), K2CO3 (3.0 equiv), DMF, rt, quant.; (g) TFAA (4.5 equiv), THF,
65 °C then K2CO3 (4.0 equiv), MeOH, rt, 44%; (h) TFA, CHCl3, rt, then sat. NaHCO3, 88%; (i) I2 (2.0 equiv), imidazole (2.5 equiv), PPh3 (1.5 equiv), THF, rt, 25%; (j) NaBH4
(3.0 equiv), DMSO, 50 °C, 91%; (k) HCl, dioxane, rt then sat. NaHCO3, quant.; (l) TFA, CHCl3, rt (2) K2CO3 (3.0 equiv), MeOH, rt, 75%.
Cl
O
O
O
O
O
3N
N
N
N
N
N
N
N
H
N
a
b
c
d
MeN
MeN
MeN
MeN
MeN
N
N
N
N
N
HCl
NH2
N
NHBoc
NHBoc
NHBoc
NHBoc
CO2Me
CO2Me
CO2Me
CO2H
CO2H
7t
21
22a
23a
24a
Scheme 6. Conversion of substituents in 8-carobxyl derivatives. Reagents and conditions: (a) Pd/C, HCO2NH4 (10 equiv), MeOH, reflux, 83%; (b) benzyl bromide (2.0 equiv),
K2CO3 (3.0 equiv), DMF, 60 °C, 99%; (c) 1M NaOH/THF/MeOH (1/1/1), rt, 54%; (d) HCl, dioxane, rt, quant.
Cl
O
O
O
O
R
R
b
a
H
N
c, d
N
N
N
N
MeN
MeO2C
MeN
MeO2C
MeN
MeO2C
MeN
HO2C
N
N
N
N
N
N
N
NHBoc
NHBoc
NHBoc
NH2
HCl
25
7j
28 R=2-chloro-5-fluorobenzyl
26 R=2-chloro-5-fluorobenzyl
27 R=5-fluoro-2-methylbenzyl
29 R=5-fluoro-2-methylbenzyl
Scheme 7. Synthesis of 28 and 29. Reagents and conditions: (a) Pd/C, HCO2NH4 (10 equiv), MeOH, reflux, 54%; (b) 2-chloro-5-fluorobenzyl bromide or 5-fluoro-2-
methylbenzyl bromide (2.0 equiv), K2CO3 (3.0 equiv), DMF, 60 °C, 26 71%, 27 66%; (c) 1 M NaOH/THF/MeOH (1/1/1), rt; (d) HCl, dioxane, rt, 28 90%, 29 84%.
readily obtained by removal of the Boc group of 7f, 7h, 7k, 7l, 7j
and 7m, respectively.
Conversion of the moiety at the 3-position is shown in Schemes
6 and 7. Pd/C catalytic hydrogenation of 7t with HCO2NH4 in MeOH
under reflux afforded 21 in high yield. N-benzylation at the 3-posi-
tion using benzyl bromide, alkaline hydrolysis and removal of the
Boc group gave 24a. Compounds 24b–24n were synthesized from
21 in the same manner described for compound 24a using various
halide. Compound 7j was converted to 28 and 29 by the same pro-
cedure described in Scheme 6 (Scheme 7).

Y. Ikuma et al. / Bioorg. Med. Chem. 20 (2012) 5864–5883
5869
Cl
Cl
O
Cl
O
a
e
b
c or d
EtO2C
R1
N
N
R2
N
N
3
N
N
HN
N
N
N
5
N
HCl
NHBoc
NHBoc
NH2
R1
NO2
30 R1=H
32 R1=H
2
2b
R2=H
31 R1=OMe
33 R1=OMe
R2=Et
2c
2d
R2=Pr
R2=Bn
Cl
Cl
O
N
O
c
N
N
33
MeN
MeO
MeN
MeO 7
N
N
HCl
N
NHBoc
NH2
7g
8g
Scheme 8. Alternative synthetic route to 2, 2b-2d and 8g. Reagents and Conditions: (a) Pd(PPh3)4 (10 mol %), Na2CO3 (2.0 equiv), 2-(2-nitrophenyl)-4,4,5,5-tetramethyl-
1,3,2-dioxaborolane or 2-(4-methoxy-2-nitrophenyl)-4,4,5,5-tetramethyl-1,3,2-dioxaborolane (1.5 equiv), DME–H2O (1/1), reflux, 30 40%, 31 89%, ; (b) Fe (6.0 equiv), AcOH,
80 °C, 32 92%; (c) HCl, dioxane, rt, 2 83%, 8 g 89%; (d) (1) R2-halide (3.0 equiv), K2CO3 (3.0 equiv), DMF, rt (2) HCl, dioxane, rt, 60–80% for 2 steps; (e) K2CO3 (2.0 equiv), MeI
(2.0 equiv), DMF, 74% for 2 steps.
Another synthetic route26 for introduction of various alkyl sub-
stituents at the 5-position or a methoxy group at the 7-position are
shown in Scheme 8. Suzuki-Miyaura cross coupling reaction of 3
with the corresponding pinacol boronate yielded 30 and 31, which
were converted to 3H-imidazo[4,5-c]quinolin-4(5H)-one 32 and 33
by reduction of the nitro group and subsequent intramolecular
amidation. Removal of the Boc group in 32 resulted in compound
2. 32 was alkylated with various alkyl halide, followed by N-Boc
deprotection to afford 2b–2d. After N-methylation of 33, deprotec-
tion of the Boc group of the resulting 7g provided 8g. Using the
above synthetic method, we could achieve efficient regioselective
synthesis with substituent at the 7- or 9-position and produce
3H-imidazo[4,5-c]quinolin-4(5H)-ones with various substituent
at the 3, 5 and 6–9 positions.
3. Results and discussion
In order to validate our hypothesis, 8a–8z with substituents at
the 6–9 positions were evaluated for their DPP-4 inhibitory activ-
ity. The results are shown in Table 2. Generally, a substituent at the
6-position had no beneficial effect on the inhibitory activity,
although a carboxyl group (8c) slightly improved the activity. As
for substitution at the 7-position, a hydrophobic fluoro or phenyl
group (8d, 8e) slightly improved the activity, while a methyl group
(8f) decreased the activity by approximately 3-fold compared to
that of 2a. Hydrophobic substituents had no important contribu-
tion to the inhibitory activity. Meanwhile, 8g with a methoxy
group showed approximately 2-fold more potent inhibitory activ-
ity than 2a, and 8h with a methylene linked to 8g and 8i with a hy-
droxyl methyl group were more than 3-fold active than 8g. A
methyl ester (8j), carbamoyl (8k) or dimethylamide (8l) group re-
sulted in good inhibitory activity with IC50 values of 16, 12 and
10 nM respectively. Additionally, introduction of a cyano group
led to further improvement in DPP-4 inhibitory activity (8m,
Table 2
In vitro activity of the synthesized DPP-4 inhibitors
Cl
O
N
N
MeN
N
6
NH2
7 R
9
8
Compounds
R
h-DPP-4 IC50 (nM)
6.3 nM). Especially,
a carboxyl group produced a dramatic
8a
8b
8c
8d
8e
8f
8g
8h
8i
8j
8k
8l
8m
8n
8o
8p
8q
8r
6-OMe
660
271
72
66
72
340
66
17
22
16
12
10
6.3
1.6
3.8
90
94
56
60
improvement in inhibitory activity (8n, 1.6 nM) with the resulting
8n being 64-fold more active than 2a. A carboxyl methyl group as
alternative to the carboxyl substituent could also result in potent
DPP-4 interaction (8o, 3.8 nM). As for substitution at the 8-posi-
tion, a methoxy or methyl group (8p, 8q) produced no improve-
ment in DPP-4 inhibitory activity. A fluoro or difluoromethoxy
group led to a slight improvement in the activity (8r, 8s), while a
methyl ester group (8t) and an amide group (8u, 8v) led to accept-
able DPP-4 inhibition. Interestingly, a carboxyl group significantly
increased DPP-4 inhibitory activity as was the case with a substitu-
tion at the 7-position (8w). Surprisingly, 8x with a methylene in-
serted into carboxyl group of 8w showed further improvement of
the activity. The effect of a carboxyl group at the 9-position (8y)
was significantly less potent than that of a substituent at the 7-
or 8-position, although the 9-carboxy methyl 8z was good DPP-4
inhibitor. Introduction of hydrophilic substituent at the 7- or 8-po-
sition was found to be effective, especially, a carboxyl group or a
carboxyl methyl group improved the activity dramatically.
6-CO2Me
6-CO2H
7-F
7-Ph
7-Me
7-OMe
7-CH2OMe
7-CH2OH
7-CO2Me
7-CONH2
7-CONMe2
7-CN
7-CO2H
7-CH2CO2H
8-OMe
8-Me
8-F
8s
8t
8-OCHF2
8-CO2Me
8-CONH2
8-CONMe2
8-CO2H
8-CH2CO2H
9-CO2H
9-CH2CO2H
21
14
13
5.8
3.5
54
17
8u
8v
8w
8x
8y
8z
To verify the interaction between the potent DPP-4 inhibitor 8n
with a 7-carboxyl group and DPP-4 protein, a docking study was
attempted, and the results are shown in Fig. 5. Compound 8n
exhibited a binding mode similar to that shown by 2a with a

5870
Y. Ikuma et al. / Bioorg. Med. Chem. 20 (2012) 5864–5883
Table 3
In vitro activity of DPP-4 inhibitors with various moiety at 3-position
Glu205
R
O
N 3
Tyr631
Tyr547
MeN
Glu206
N
N
NH2
7 X
8
Compounds
X
R
h-DPP-4 IC50 (nM)
Lys554
8w
8-CO2H
—
—
—
—
—
—
—
—
—
—
—
—
—
—
2-Chlorobenzyl
Benzyl
2-Methylbenzyl
2-Methoxybenzyl
2-Fluorobenzyl
3-Chlorobenzyl
5.8
64
11
38
160
110
>10000
150
6900
3500
8900
51
90
25
4.8
0.48
0.55
2.78 Å
24a
24b
24c
24d
24e
24f
24g
24h
24i
24j
24k
24l
24m
24n
28
4-Chlorobenzyl
3-Methoxybenzyl
4-Methoxybenzyl
2-Chlorophenethyl
cyclohexylmethyl
methylbut-2-enyl
But-2-ynyl
2,5-Dichlorobenzyl
2-chloro-5-fluorobenzyl
2-Chloro-5-fluorobenzyl
5-Fluoro-2-methylbenzyl
Figure 5. Docking structure of 8n in the active site from 2RGU of DPP-4.
Arg125
Lys554
7-CO2H
—
29
4.71 Å
the carboxyl methyl group of 8x might further interact with the
residue of Arg560 by bridging of a water molecule and afford en-
hanced DPP-4 inhibitory activity. As mentioned above, it was
found that introduction of a carboxyl substituent at the 7- or 8-po-
sition is important for enhanced inhibitory activity in this series of
DPP-4 inhibitors.
Arg560
Asp556
Tyr456
Arg429
Tyr585
Finally, to further improve DPP-4 inhibitory activity, optimiza-
tion of the moiety at the 3-position, which occupies the S1 pocket,
was attempted using 8n and 8w with a 7- or 8-carboxyl group (Ta-
ble 3). First, we examined the effect of a substituent on the benzyl
group. A chlorine atom at the ortho position of 8w increased the
inhibitory activity by 10-fold compared to the non-substituted
24a. Next, an electron-donating or electron-withdrawing group
was introduced to investigate the effect of a substitution at the
ortho position (24bꢀ24d). Although a methyl group (24b) was
acceptable, a methoxy (24c) or a fluoro group (24d) were not
favorable for the inhibitory activity. It was subsequently found that
the size of atom in the S1 pocket is important for DPP-4 inhibitory
activity and that a chlorine atom or a methyl group are favorable.
Additionally, the preferred position of the substituent was ortho
(8w, 24c) > meta (24e, 24g) > para (24f, 24h). However, a substitu-
ent at a site beside the benzyl group, such as at the 2-chlorophen-
ethyl (24i) or cyclohexylmethyl group (24j), resulted in significant
loss of activity. Substituents that were reported with other DPP-4
inhibitors such as those in 24k and 24l also resulted in remarkable
loss of activity. Based on the above, we believed that compounds
inhibitory activity would be further enhanced by introducing a
new substituent into the 2-substituted benzyl group, such as a 2-
chloro or a 2-methyl benzyl group. As our docking study showed
that the S1 pocket is almost completely occupied by 2-substitued
benzyl group, we realized that a substitution at the 5-position of
the benzyl group would be possible due to the remaining slight
space. Although the activity of the 2,5-dichloro substituted 24m
was slightly decreased, we considered that a chlorine atom was a
little larger than the available space and that the smaller fluorine
atom might be suitable. The inhibitory activity of 24n with a 5-flu-
oro-2-chloro benzyl group was slightly improved (24n, 4.8 nM).
Thus the most suitable moiety at the 3-position was found to be
5-fluoro-2-chlorobenzyl group. To further increase the activity,
the 5-fluoro-2-chlorobenzyl group was attached a 7-carboxy com-
pound, such as 8n. This led to 28, which showed the most potent
Figure 6. Docking structure of 8x in the active site from 2RGU of DPP-4.
distance between the 7-carboxyl group and the residue of Lys554
of 2.78 Å. Accordingly, we could confirm that the 7-carboxyl group
makes a salt bridge interaction with Lys554. This interaction serves
to significantly enhance the inhibitory activity, giving the most po-
tent inhibitor. Although 8o with a carboxyl methyl group was also
thought to interact with the residue of Lys554, DPP-4 inhibitory
activity of 8o was weaker than that of 8n as the carboxyl methyl
group was shifted from the most appropriate position for interac-
tion with Lys554 compared to the carboxyl group of 8n. A hydro-
gen bond between the oxygen atom of the methoxy methyl
group (8h) or the hydroxy methyl group (8i) and the residue of
Lys554 afforded acceptable activity. Although hydrophilic substit-
uents were acceptable, the resulting inhibitory activity was weaker
than that of the carboxyl group or the carboxyl methyl group, since
interaction with the residue of Lys554 was weak compared to the
electrovalent bond of the salt bridge. In order to understand the
interaction between a carboxyl substituent at the 8-position and
DPP-4 protein, a docking study using 8x was performed (Fig. 6).
Although no amino acid residue could directly interact with the
carboxyl or carboxyl methyl group in the vicinity of the 8-position,
there was a hydrophilic space surrounded by the residues of
Lys554, Arg560, Asp556, Tyr456, Arg429 and Try585. Therefore, a
hydrophilic substituent was considered to be acceptable. Espe-
cially, significant improvement of activity was achieved by intro-
duction of
a carboxyl methyl or carboxyl group. Although
8-carboxyl methyl group was positioned close to Arg560, the dis-
tance between the two was not appropriate for interaction (4.71
Å). Considering that a carboxyl methyl group led to more potent
DPP-4 inhibitory activity than a carboxyl group, it is believed that

Y. Ikuma et al. / Bioorg. Med. Chem. 20 (2012) 5864–5883
5871
Table 4
DPP-4 inhibitory activity of 28 and other marketed drugs (IC50 nM)
Entry
DPP-4
FAP
a
DPP-2
DPP-8
DPP-9
Fold selectivity
DPP-9
DPP-8
FAP
28
0.48
Ki = 3
3.37
1.0
4
18
30,600
NA
NA
89
>100,000
>100,000
>10,000
>500,000
>30,000
>100,000
>100,000
>100,000
>100,000
Ki = 810
244
>40,000
>100,000
48,000
>100,000
Ki = 95
104
>10,000
>100,000
>10,000
>208,000
270
72
>40,000
>25,000
>2667
>208,000
32
31
>10,000
>25,000
>5550
63,750
NA
NA
89
>25,000
>5550
Vildagliptin
Saxagliptin
Linagliptin
Alogliptin
Sitagliptin
Note: NA, Not available.
DPP-4 inhibitory activity in our series (0.48 nM). Compound 29
with a 5-fluoro-2-methyl benzyl group also showed potent inhibi-
tory activity (0.55 nM). The effect of a fluorine atom in the docking
study suggests interaction with the residue of Arg125 by forming a
hydrogen bond and/or hydrophobic interaction by full occupation
of the S1 pocket.
than 8-fold potent DPP-4 inhibitory activity compared to Aloglip-
tin. Furthermore, 28 showed excellent selectivity against various
DPP-4 homologues superior to that of Vildagliptin, Saxagliptin or
Linagliptin. It is therefore believed that 28 could be more valuable
and safer drug for T2D than marketed DPP-4 inhibitors. Unfortu-
nately, 28 showed poor oral absorption in rat PK test. Therefore,
further studies, including improvement of 28 oral absorption, are
underway and will be reported and discussed in due course.
Compound 28 was evaluated for its inhibition of DPP-4 homo-
logues, including DPP-227, DPP-8, DPP-9 and FAP
a, and the results
were compared to those of marketed DPP-4 inhibitors20 (Table 4).
Vildagliptin and Saxagliptin inhibited both DPP-8 and DPP-9 with a
selectivity ratio for DPP-4 over DPP-9 of only about 30-fold. On the
other hand, 28 showed no inhibition of DPP-8 or DPP-9. While
5. Experimental section
Melting points were determined on an electrothermal appara-
tus without correction. 1H NMR and 13C NMR spectra were
recorded on a JEOL JNM-LA300 spectrometer and a Brucker
AVANCE 400 spectrometer in the stated solvents using tetrameth-
ylsilane as an internal standard. Chemical shift (d) are expressed in
parts per million. IR spectra were recorded on a JEOL JIR-SPX60
spectrometer as ATR. High resolution MS spectra were recorded
on a Thermo Fisher Scientific LTQ orbitrap Discovery MS equip-
ment. Elemental analysis was conducted at Sumitomo Analytical
Center Inc. Reactions were followed by TLC on silica gel 60 F254
using precoated TLC plates (E. Merck). Column chromatography
was carried out on a Yamazen W-prep system using prepacked sil-
ica gel or amino silica gel or performed on silica gel 60 (230–400 or
70–230 mesh, Merck). Unless otherwise noted, all materials were
obtained from commercial suppliers and used without further
purification. All solvents were of the commercially available grade.
Reactions requiring anhydrous conditions were performed under
nitrogen atmosphere.
Linagliptin inhibited FAP
tivity ratio for DPP-4 over FAP
FAP , and the selectivity ratio overwhelmingly surpassed that of
Linagliptin. 28 showed excellent selectivity against all DPP-4
homologues and exhibited more than 8-fold and 37-fold potent
DPP-4 inhibitory activity than Alogliptin and Sitagliptin, respec-
tively. Based on these findings, it was assumed that 28 would have
excellent pharmacological profile. Next, we evaluated compound
28 inhibition of hERG channel to assess its risk for cardiac distur-
bance. Although both 8h and 8m inhibited hERG channel with an
a
with an IC50 value of 89 nM and a selec-
a
of 89-fold, 28 hardly inhibited
a
IC50 values of 1.81 and 1.20
lM, respectively, compound 28 had
no effect on hERG channel (IC50 >10
lM). Drug induced phospho-
lipidosis is another specific toxicity associated with compounds
lipophilicity.28 Accordingly, we evaluated compounds 28, 8h and
8m for their phospholipid index (PI) compared to the reference
standard propranolol (PI = 1.00 at 30
hepatocytes.29 The PIs of 8h and 8m were 0.33 and 0.37 at a con-
centration of 3 M, respectively, whereas the PI of 28 was 0.014
and 0.008 at the concentration of 3 and 30 M, respectively. These
lM) using isolated human
l
Compounds 3, 4, 5, 6, 7, 7a, 7b, 7e, 7p, 7q, 7r, 2a, 8a, 8b, 8e, 8p,
8q, 8r, 30 and 32 were synthesized as previously reported.26
l
findings confirmed that 28 induced no phospholipidosis. Com-
pound 28 also showed no concerns related to introduction of car-
boxyl group and formation of zwitter-ion.30 Furthermore,
compound 28 exhibited no CYP inhibition (IC50 >50 lM; 1A2,
2A6, 2C8, 2C9, 2C19, 2D6, 3A4) and no induced enzyme, making
5.1. Methyl 4-({[2-{(3R)-3-[(tert-butoxycarbonyl)amino]
piperidin-1-yl}-1-(2-chlorobenzyl)-4-iodo-1H-imidazol-5-yl]
carbonyl}amino)benzoate (5t)
it a compound with clean safety profile.
To a solution of 4 (56.08 g, 100 mmol) in CH2Cl2 (1.3 L) were
added (COCl)2 (16.5 g, 130 mmol) and DMF (5 ml) at 0 °C. The reac-
tion mixture was stirred at room temperature for 4 h and concen-
trated under reduced pressure. The residue was azeotroped with
toluene and redissolved in toluene (1.3 L). To this solution was
added DIPEA (38.8 g, 300 mmol) followed by methyl 4-aminoben-
zoate (19.7 g, 130 mmol). The reaction mixture was stirred at room
temperature for 12 h. The reaction mixture was then quenched
with saturated NH4Cl aqueous solution, extracted with EtOAc,
washed with brine, dried over Na2SO4, and concentrated under re-
duced pressure. The residue was purified by silica-gel column
chromatography to give 5t (54.63 g, yield 79%) as a white amor-
phous. 1H NMR (300 MHz, CDCl3) d 8.30 (br s, 1H), 8.01 (d,
J = 8.7 Hz, 2H), 7.62 (d, J = 8.7 Hz, 2H), 7.39–7.36 (m, 1H), 7.22–
7.13 (m, 2H), 6.82–6.78 (m, 1H), 5.58 (d, J = 16.2 Hz, 1H), 5.50 (d,
J = 16.2 Hz, 1H), 4.93–4.90 (m, 1H), 3.90 (s, 3H), 3.77 (br s, 1H),
4. Conclusion
In summary, we optimized the lead comound 2a and obtained a
series of novel DPP-4 inhibitors with 3H-imidazo[4,5-c]quinolin-
4(5H)-one scaffold. In our synthesis of these derivatives, we could
achieve efficient regioselective synthesis of 7- or 9-substituted
compounds. Using tBu ester, compounds, such as 8n with a car-
boxyl group at the 7-position, could be obtained in good yield
and regioselectivity. As a result of our effort, we could efficiently
synthesize 3H-imidazo[4,5-c]quinolin-4(5H)-ones with hydro-
philic substituent at the 7- and 8-positions. We found that a car-
boxyl group at the 7-position enhances DPP-4 inhibitory activity
by interacting with Lys554 residue. Further optimization led to
28 as the most potent DPP-4 inhibitor in our series. 28 has more

5872
Y. Ikuma et al. / Bioorg. Med. Chem. 20 (2012) 5864–5883
3.31 (dd, J = 3.3, 12.0 Hz, 1H), 2.93–2.84 (m, 3H), 1.78–1.54 (m, 4H),
1.49 (s, 9H); HRMS (ESI) [M+H]+ calcd for C29H34O5N5ClI 694.1288,
found 694.1272; IR (ATR): 1714, 1675, 1591, 1513, 1434, 1405,
1311, 1280, 1243, 1222, 1172, 1110, 1060 cmÀ1; Anal. calcd for
amorphous. 1H NMR (400 MHz, DMSO-d6) d 8.69 (d, J = 2.1 Hz,
1H), 8.37 (br s, 3H), 8.09 (dd, J = 2.1, 8.9 Hz, 1H), 7.69 (d,
J = 9.0 Hz, 1H), 7.51 (dd, J = 1.1, 7.9 Hz, 1H), 7.33–7.28 (m, 1H),
7.25–7.21 (m, 1H), 6.71 (d, J = 6.7 Hz, 1H), 5.62 (d, J = 17.2 Hz,
1H), 5.56 (d, J = 17.2 Hz, 1H), 3.73–3.69 (m, 1H), 3.64 (s, 3H),
3.38–3.36 (m, 1H), 3.28–3.23 (m, 1H), 3.11–3.08 (m, 1H), 2.88–
2.83 (m, 1H), 1.99–1.97 (m, 1H), 1.78–1.75 (m, 1H), 1.63–1.49
(m, 2H); 13C NMR (100 MHz, DMSO-d6) d 166.0, 157.8, 154.2,
141.2, 140.4, 135.2, 131.1, 129.5, 129.1, 128.9, 127.8, 127.1,
123.5, 123.3, 119.3, 116.2, 116.1, 52.4, 52.3, 51.0, 46.4, 46.3, 29.2,
27.5, 22.2; HRMS (ESI) [M+H]+ calcd for C25H27O3N5Cl 480.1797,
found 480.1787; IR (ATR): 1710, 1670, 1652, 1646, 1594, 1558,
1521, 1506, 1473, 1288, 1261, 1112, 1004 cmÀ1; Anal. Cacld for
C25H26O3N5ClÁ2.75HCl: C, 51.75; H, 4.99; N, 12.07, found: C,
51.69; H, 5.36; N, 11.69.
C29H33O5N5ClI: C, 50.19; H, 4.79; N, 10.09, found: C, 50.52; H,
4.95; N, 9.92.
5.2. Methyl 4-[{[2-{(3R)-3-[(tert-butoxycarbonyl)amino]
piperidin-1-yl}-1-(2-chlorobenzyl)-4-iodo-1H-imidazol-5-yl]
carbonyl}(methyl)amino]benzoate (6t)
A
mixture of 5t (109 mg, 0.157 mmol), K2CO3 (86.8 mg,
0.628 mmol), and MeI (39.1 l, 0.63 mmol) in DMF (2 ml) was stir-
l
red at room temperature for 12 h. The reaction mixture was
quenched with saturated NH4Cl aqueous solution and extracted
with EtOAc. The organic layer was washed with saturated NH4Cl
aqueous solution twice and brine, dried over Na2SO4, and concen-
trated under reduced pressure. The residue was purified by silica-
gel column chromatography to give 6t (91.6 mg, yield 82%) as a
pale yellow amorphous. 1H NMR (300 MHz, CDCl3) d 7.87 (d,
J = 8.1 Hz, 2H), 7.46–7.43 (m, 1H), 7.34–7.18 (m, 3H), 6.79 (br s,
2H), 5.24 (br s, 2H), 4.99–4.97 (m, 1H), 3.90 (s, 3H), 3.82 (br s,
1H), 3.32 (br s, 1H), 3.23 (s, 3H), 3.00 (br s, 2H), 2.92–2.86 (m,
1H), 1.80–1.79 (m, 2H), 1.64 (m, 2H), 1.42 (s, 9H); 13C NMR
(75 MHz, CDCl3) d 166.2, 161.9, 155.9, 155.0, 147.0, 146.9, 134.2,
133.4, 131.4, 130.1, 130.0, 129.9, 129.9, 127.6, 126.9, 125.1, 79.2,
56.2, 52.2, 51.9, 46.4, 46.1, 38.1, 29.5, 28.3, 22.5; HRMS (ESI)
[M+H]+ calcd for C30H36O5N5ClI 708.1444, found 708.1428; IR
(ATR): 1716, 1704, 1699, 1652, 1646, 1635, 1506, 1488, 1473,
1456, 1436, 1363, 1276, 1241, 1170, 1105, 1049 cmÀ1; Anal. Cacld
for C30H35O5N5ClIÁ1.25H2O: C, 49.32; H, 5.17; N, 9.59, found: C,
49.17; H, 4.87; N, 9.33.
5.5. 2-{(3R)-3-[(tert-Butoxycarbonyl)amino]piperidin-1-yl}-3-
(2-chlorobenzyl)-5-methyl-4-oxo-4,5-dihydro-3H-imidazo[4,5-
c]quinoline-8-carboxylic acid (7w)
A mixture of 7t (3.77 g, 6.49 mmol) and 1 M NaOH (16 ml) aque-
ous solution in THF (16 ml) and MeOH (16 ml) was stirred at room
temperature for 12 h. The mixture was concentrated under reduced
pressure. The residue was acidified with 10% KHSO4 aqueous solu-
tion and extracted with EtOAc. The organic layer was washed with
brine, dried over Na2SO4, and concentrated under reduced pressure
to give 7w (2.13 g, yield 58%). 1H NMR (300 MHz, DMSO-d6) d 8.67
(d, J = 1.8 Hz, 1H), 8.05 (dd, J = 2.1, 8.7 Hz, 1H), 7.65 (d, J = 8.7 Hz,
1H), 7.48 (dd, J = 0.9, 7.8 Hz, 1H), 7.30–7.17 (m, 2H), 6.90 (d,
J = 7.8 Hz, 1H), 6.67 (d, J = 7.2 Hz, 1H), 5.57 (d, J = 18.0 Hz, 1H),
5.51 (d, J = 18.0 Hz, 1H), 3.63 (s, 3H), 3.52–3.25 (m, 3H), 2.86–2.70
(m, 2H), 1.80–1.67 (m, 2H), 1.59–1.51 (m, 1H), 1.39–1.27 (m,
10H); HRMS (ESI) [M+H]+ calcd for C29H33O5N5Cl 566.2165, found
566.2162; IR (ATR): 1700, 1685, 1654, 1508, 1457, 1388, 1309,
1238, 1168, 1116 cmÀ1; Anal. calcd for C29H32ClN5O5: C, 61.53; H,
5.70; N, 12.37, found: C, 61.63; H, 5.73; N, 12.07.
5.3. Methyl 2-{(3R)-3-[(tert-butoxycarbonyl)amino]piperidin-1-
yl}-3-(2-chlorobenzyl)-5-methyl-4-oxo-4,5-dihydro-3H-
imidazo[4,5-c]quinoline-8-carboxylate (7t)
A mixture of 6t (172 mg, 0.243 mmol), Pd(OAc)2 (5.46 mg,
0.0234 mmol), PPh3 (12.7 mg, 0.0484 mmol), and Ag2CO3
(133.9 mg, 0.486 mmol) in DMF (2 ml) was stirred at 150 °C for
1 h. After cooling to room temperature, the reaction mixture was
diluted with EtOAc and filtered through a Celite pad. The filtrate
was washed with saturated NH4Cl aqueous solution twice and
brine. The organic layer was dried over Na2SO4 and concentrated
under reduced pressure. The residue was purified by silica-gel col-
umn chromatography to give 7t (119.8 mg, yield 85%) as a pale yel-
low solids. Mp 186–188 °C; 1H NMR (300 MHz, CDCl3) d 8.95 (d,
J = 1.8 Hz, 1H), 8.18 (dd, J = 2.1, 9.0 Hz, 1H), 7.47 (d, J = 11.6 Hz,
1H), 7.42 (d, J = 7.5 Hz, 1H), 7.27–7.12 (m, 2H), 6.70 (d, J = 6.9 Hz,
1H), 5.78 (d, J = 17.4 Hz, 1H), 5.63 (d, J = 17.4 Hz, 1H), 5.40–5.37
(m, 1H), 3.98 (s, 3H), 3.84 (br s, 1H), 3.76 (s, 3H), 3.48–3.31 (m,
1H), 3.24–3.18 (m, 1H), 3.10 (m, 2H), 1.78 (m, 4H), 1.44 (s, 9H);
HRMS (ESI) [M+H]+ calcd for C30H35O5N5Cl 580.2321, found
580.2314; IR (ATR): 1718, 1689, 1652, 1569, 1500, 1446, 1429,
1388, 1353, 1313, 1274, 1234, 1174, 1124, 1110, 1066,
1039 cmÀ1; Anal. calcd for C30H34ClN5O5: C, 62.12; H, 5.91; N,
12.09, found: C, 62.11; H, 5.88; N, 12.07.
5.6. 2-[(3R)-3-Aminopiperidin-1-yl]-3-(2-chlorobenzyl)-5-
methyl-4-oxo-4,5-dihydro-3H-imidazo[4,5-c]quinoline-8-
carboxylic acid hydrochloride (8w)
To a solution of 7w (39.9 mg, 0.0705 mmol) in 1,4-dioxane
(1 ml) was added 4 N HCl-1,4-dioxane (1 ml). The reaction mixture
was stirred at room temperature for 2 h and concentrated under
reduced pressure to give 8w (40.2 mg, quantitative yield) as a
white amorphous. 1H NMR (300 MHz, CD3OD)
d 8.96 (d,
J = 2.0 Hz, 1H), 8.25 (dd, J = 2.0, 9.0 Hz, 1H), 7.73 (d, J = 9.0 Hz,
1H), 7.49 (dd, J = 1.1, 7.7 Hz, 1H), 7.35–7.23 (m, 2H), 6.98 (d,
J = 8.2 Hz, 1H), 5.71 (s, 2H), 3.93 (brd, J = 11.3 Hz, 1H), 3.74–3.37
(m, 3H), 3.64 (s, 3H), 3.21–3.06 (m, 1H), 2.16 (m, 1H), 1.87–1.72
(m, 3H); 13C NMR (100 MHz, DMSO-d6) d 166.8, 157.6, 154.0,
141.2, 140.0, 135.1, 130.9, 129.3, 128.9, 128.9, 127.7, 126.8,
124.3, 123.5, 119.1, 116.0, 115.9, 52.3, 50.9, 46.4, 46.1, 29.2, 27.5,
22.1; HRMS (ESI) [M+H]+ calcd for C24H25O3N5Cl 466.1640, found
466.1636; IR(ATR): 2886, 1668, 1645, 1216, 1118 cmÀ1; Anal. calcd
for C24H24O3N5ClÁ5HClÁH2O: C, 43.27; H, 4.69; N, 10.51, found: C,
43.33; H, 4.59; N, 10.47.
5.4. Methyl 2-[(3R)-3-aminopiperidin-1-yl]-3-(2-chlorobenzyl)-
5-methyl-4-oxo-4,5-dihydro-3H-imidazo[4,5-c]quinoline-8-
carboxylate hydrochloride (8t)
5.7. tert-Butyl {(3R)-1-[8-carbamoyl-3-(2-chlorobenzyl)-5-
methyl-4-oxo-4,5-dihydro-3H-imidazo[4,5-c]quinolin-2-yl]-
piperidin-3-yl}carbamate (7u)
To a solution of 7t (22.1 mg, 0.0381 mmol) in 1,4-dioxane (1 ml)
was added 4 N HCl-1,4-dioxane (1 ml). The reaction mixture was
stirred at room temperature for 2 h and concentrated under re-
duced pressure to give 8t (21.9 mg, quantitative yield) as a white
A mixture of 7w (233.4 mg, 0.412 mmol), WSCÁHCl (119 mg,
0.62 mmol), HOBt (94.7 mg, 0.62 mmol), TEA (86.2 ll, 0.62 mmol),
and 28% NH4OH (37.6
ll, 0.62 mmol) in DMF (2 ml) was stirred at
room temperature for 3 h. The reaction mixture was quenched

Y. Ikuma et al. / Bioorg. Med. Chem. 20 (2012) 5864–5883
5873
with saturated NH4Cl aqueous solution and extracted with EtOAc.
The organic layer was washed with saturated NH4Cl aqueous solu-
tion twice, saturated NaHCO3 aqueous solution and brine, dried
over Na2SO4, and concentrated under reduced pressure. The resi-
due was purified by silica-gel column chromatography to give 7u
(170.6 mg, yield 73%) as a white amorphous. 1H NMR (400 MHz,
DMSO-d6) d 8.64 (d, J = 2.0 Hz, 1H), 8.18 (br s, 1H), 8.04 (dd,
J = 2.0, 9.0 Hz, 1H), 7.61 (d, J = 9.0 Hz, 1H), 7.48 (dd, J = 1.0, 8.2 Hz,
1H), 7.40 (br s, 1H), 7.29–7.25 (m, 1H), 7.22–7.18 (m, 1H), 6.87
(d, J = 7.7 Hz, 1H), 6.66 (d, J = 7.6 Hz, 1H), 5.59 (d, J = 17.2 Hz, 1H),
5.54 (d, J = 17.2 Hz, 1H), 3.63 (s, 3H), 3.49–3.38 (m, 2H), 3.26–
3.23 (m, 1H), 2.84–2.71 (m, 2H), 1.78–1.68 (m, 2H), 1.57–1.54
(m, 1H), 1.38–1.22 (m, 10H); 13C NMR (100 MHz, DMSO-d6) d
167.5, 158.1, 155.0, 154.3, 141.8, 139.1, 135.4, 131.2, 129.4,
128.9, 128.1, 127.7, 127.4, 126.9, 122.0, 119.1, 116.1, 115.5, 77.9,
55.2, 50.7, 46.7, 46.3, 29.8, 29.1, 28.4, 23.5; HRMS (ESI) [M+H]+
calcd for C29H34O4N6Cl 565.2330, found 565.2328; IR(ATR): 1677,
1662, 1618, 1527, 1508, 1457, 1434, 1388, 1349, 1309, 1238,
steps as a white amorphous. 1H NMR (400 MHz, DMSO-d6) d
8.38 (br s, 3H), 8.29 (d, J = 7.5 Hz, 1H), 7.70 (d, J = 7.2 Hz,
1H), 7.51 (d, J = 7.5 Hz, 1H), 7.42–7.38 (m, 1H), 7.33–7.29
(m, 1H), 7.26–7.22 (m, 1H), 6.74 (d, J = 7.2 Hz, 1H), 5.58 (s,
2H), 3.73–3.56 (m, 1H), 3.48 (s, 3H), 3.38–3.16 (m, 2H), 3.07
(m, 1H), 2.88–2.84 (m, 1H), 1.96 (m, 1H), 1.77 (m, 1H),
1.62–1.50 (m, 2H); 13C NMR (100 MHz, DMSO-d6)
d 170.2,
157.8, 155.1, 141.5, 135.7, 135.2, 131.2, 129.5, 129.4, 129.1,
127.9, 127.2, 124.5, 124.1, 122.1, 118.9, 118.0, 52.3, 51.4,
46.4, 46.3, 34.9, 27.4, 22.1; HRMS (ESI) [M+H]+ calcd for
C
24H25O3N5Cl 466.1640, found 466.1627; IR(ATR): 1704, 1664,
1557, 1490, 1471, 1367, 1220, 1199, 1124, 1095, 1066,
1049, 1018 cmÀ1
.
5.11. {2-[(3R)-3-Aminopiperidin-1-yl]-3-(2-chlorobenzyl)-5-
methyl-4-oxo-4,5-dihydro-3H-imidazo[4,5-c]quinolin-8-
yl}acetic acid hydrochloride (8x)
1170, 1114, 1051 cmÀ1
.
Compound 8x was prepared from 4 in a manner similar to
that described for compound 8w with a yield of 48% for 5
steps as a white amorphous. 1H NMR (400 MHz, DMSO-d6) d
8.33 (br s, 3H), 8.06 (d, J = 2.0 Hz, 1H), 7.55–7.50 (m, 2H),
7.45 (dd, J = 2.0, 8.7 Hz, 1H), 7.32–7.28 (m, 1H), 7.24–7.20 (m,
1H), 6.64 (dd, J = 1.1, 6.6 Hz, 1H), 5.64 (s, 2H), 3.74 (s, 2H),
3.67–3.64 (m, 1H), 3.61 (s, 3H), 3.32 (m, 1H), 3.25–3.20 (m,
1H), 3.11–3.08 (m, 1H), 2.87–2.81 (m, 1H), 1.97–1.95 (m,
1H), 1.78–1.76 (m, 1H), 1.61–1.44 (m, 2H); 13C NMR
5.8. 2-[(3R)-3-Aminopiperidin-1-yl]-3-(2-chlorobenzyl)-5-
methyl-4-oxo-4,5-dihydro-3H-imidazo[4,5-c]quinoline-8-
carboxamide hydrochloride (8u)
To a solution of 7u (98.3 mg, 0.174 mmol) in 1,4-dioxane (2 ml)
was added 4 N HCl-1,4-dioxane (2 ml). The reaction mixture was
stirred at room temperature for 4 h and concentrated under re-
duced pressure to give 8u (72.5 mg, yield 83%) as a white amor-
phous. 1H NMR (400 MHz, DMSO-d6, free form)
d 8.66 (d,
(100 MHz, DMSO-d6)
d 173.0, 157.4, 154.2, 141.0, 136.3,
J = 2.1 Hz, 1H), 8.21 (br s, 1H), 8.05 (dd, J = 2.1, 8.9 Hz, 1H), 7.89–
7.87 (m, 1H), 7.61 (d, J = 8.9 Hz, 1H), 7.50 (dd, J = 1.1, 7.9 Hz, 1H),
7.41 (br s, 1H), 7.31–7.27 (m, 1H), 7.23–7.19 (m, 1H), 6.64 (d,
J = 6.7 Hz, 1H), 5.58 (s, 2H), 3.63 (s, 3H), 3.55–3.52 (m, 1H), 3.17–
3.14 (m, 1H), 3.07–3.03 (m, 1H), 2.95–2.82 (m, 2H), 1.89–1.86 (m,
1H), 1.71–1.67 (m, 1H), 1.51–1.34 (m, 2H); 13C NMR (100 MHz,
DMSO-d6, free form) d 167.5, 158.1, 154.3, 141.8, 139.2, 135.4,
131.1, 129.5, 129.0, 128.0, 127.8, 127.4, 127.0, 122.1, 119.1, 116.1,
115.5, 55.8, 50.9, 46.9, 46.2, 30.7, 29.1, 22.9; HRMS (ESI) [M+H]+
calcd for C24H26O2N6Cl 465.1800, found 465.1795; IR (ATR): 1652,
135.4, 131.1, 130.1, 129.5, 129.4, 129.0, 127.8, 127.0, 122.7,
119.0, 116.1, 115.8, 52.4, 51.2, 46.3, 46.3, 28.9, 27.4, 27.4,
22.2; HRMS (ESI) [M+H]+ calcd for C25H27O3N5Cl 480.1797,
found 480.1785; IR(ATR): 2867, 1733, 1670, 1621, 1575,
1508, 1448, 1417, 1378, 1245, 1157, 1047 cmÀ1; Anal. calcd
for C25H26O3N5ClÁ2.50HCl: C, 52.58; H, 5.03; N, 12.26, found:
C, 52.61; H, 5.11; N, 12.09.
1610, 1558, 1506, 1471, 1444, 1388, 1313, 1124 cmÀ1
.
5.12. tert-Butyl {(3R)-1-[3-(2-chlorobenzyl)-8-
(dimethylcarbamoyl)-5-methyl-4-oxo-4,5-dihydro-3H-
imidazo[4,5-c]quinolin-2-yl]piperidin-3-yl}carbamate (7v)
5.9. 2-[(3R)-3-Aminopiperidin-1-yl]-3-(2-chlorobenzyl)-8-
(difluoromethoxy)-5-methyl-3,5-dihydro-4H-imidazo[4,5-c]-
quinolin-4-one hydrochloride (8s)
A mixture of 7w (264.6 mg, 0.467 mmol), WSCÁHCl (134 mg,
0.699 mmol), HOBt (107 mg, 0.699 mmol), TEA (195 ll,
Compound 8s was prepared from 4 in a manner similar to that
described for compound 8t with total yield of 41% for 4 steps as a
white amorphous. 1H NMR (400 MHz, DMSO-d6) d 8.32 (br s, 3H),
7.85 (d, J = 2.8 Hz, 1H), 7.64 (d, J = 9.3 Hz, 1H), 7.53–7.49 (m, 1H),
7.40 (d, J = 2.8 Hz, 1H), 7.34 (t, J (H, F) = 74 Hz, 1H), 7.31–7.27 (m,
1H), 7.23–7.19 (m, 1H), 6.66 (d, J = 6.8 Hz, 1H), 5.63 (s, 2H), 3.63–
3.56 (m, 4H), 3.38–3.31 (m, 1H), 3.25–3.20 (m, 1H), 3.10–3.06 (m,
1H), 2.86–2.82 (m, 1H), 1.96–1.93 (m, 1H), 1.78–1.74 (m, 1H),
1.62–1.48 (m, 2H); 13C NMR (100 MHz, DMSO-d6) d 157.6, 154.0,
145.9, 140.5, 135.3, 134.8, 131.1, 129.5, 129.1, 127.8, 127.0, 120.3,
119.5, 117.8, 117.2, 117.1, 116.7 (t, J (C-F) = 257 Hz), 52.4, 51.1,
46.3, 34.3, 29.1, 27.4, 22.1; HRMS (ESI) [M+H]+ calcd for
C24H25O2N5ClF2 488.1659, found 488.1643; IR(ATR): 1675, 1635,
1.40 mmol), and NHMe2ÁHCl (76.2 mg, 0.934 mmol) in DMF
(2 ml) was stirred at room temperature for 2 h. The reaction
mixture was quenched with saturated NH4Cl aqueous solution
and extracted with EtOAc. The organic layer was washed with
saturated NH4Cl aqueous solution twice, saturated NaHCO3 aque-
ous solution and brine, dried over Na2SO4, and concentrated un-
der reduced pressure. The residue was purified by silica-gel
column chromatography to give 7v (303 mg, quantitative yield)
as a white amorphous. 1H NMR (400 MHz, CDCl3) d 8.37 (br s,
1H), 7.61 (dd, J = 1.5, 8.6 Hz, 1H), 7.45 (d, J = 8.8 Hz, 1H), 7.40
(dd, J = 1.0, 8.8 Hz, 1H), 7.22–7.18 (m, 1H), 7.15–7.11 (m, 1H),
6.68 (d, J = 7.5 Hz, 1H), 5.77 (d, J = 16.8 Hz, 1H), 5.65 (d,
J = 16.8 Hz, 1H), 3.81 (br s, 1H), 3.75 (s, 3H), 3.43 (dd, J = 2.8,
12.5 Hz, 1H), 3.20–3.09 (m, 9H), 1.77–1.55 (m, 4H), 1.43 (s,
9H); 13C NMR (100 MHz, CDCl3) d 170.9, 158.2, 155.1, 155.0,
141.8, 138.0, 135.0, 131.9, 130.1, 129.5, 128.5, 127.3, 127.1,
126.4, 121.6, 119.5, 116.6, 114.8, 79.0, 54.9, 51.4, 46.3, 45.8,
39.7, 35.4, 29.4, 29.0, 28.3, 21.7; HRMS (ESI) [M+H]+ calcd for
1508, 1465, 1444, 1396, 1216, 1108, 1049, 1002 cmÀ1
.
5.10. 2-[(3R)-3-Aminopiperidin-1-yl]-3-(2-chlorobenzyl)-5-
methyl-4-oxo-4,5-dihydro-3H-imidazo[4,5-c]quinoline-6-
carboxylic acid hydrochloride (8c)
C
31H38O4N6Cl 593.2643, found 593.2642; IR(ATR): 1700, 1683,
1652, 1506, 1496, 1473, 1457, 1388, 1363, 1307, 1270, 1243,
1168, 1114, 1089, 1049 cmÀ1
Compound 8c was prepared from 4 in a manner similar to
that described for compound 8w with total yield of 23% for 5
.

5874
Y. Ikuma et al. / Bioorg. Med. Chem. 20 (2012) 5864–5883
5.13. 2-[(3R)-3-Aminopiperidin-1-yl]-3-(2-chlorobenzyl)-N,N,5-
trimethyl-4-oxo-4,5-dihydro-3H-imidazo[4,5-c]quinoline-8-
carboxamide hydrochloride (8v)
29.4, 28.3, 28.1, 22.4; HRMS (ESI) [M+H]+ calcd for C33H42O5N5ClI
750.1914, found 750.1892; IR(ATR): 1700, 1652, 1646, 1635,
1506, 1488, 1363, 1303, 1243, 1160, 1128, 1079, 1049,
1008 cmÀ1; Anal. Cacld for C33H41O5N5ClI ÁÁH2O: C, 51.60; H,
5.64; N, 9.12, found: C, 51.41; H, 5.40; N, 8.93.
Compound 8v was prepared from 7v in a manner similar to that
described for compound 8u with a yield of 92% as a white amor-
phous. 1H NMR (400 MHz, DMSO-d6) d 8.41 (br s, 3H), 8.20 (s,
1H), 7.65–7.60 (m, 2H), 7.51 (dd, J = 1.1, 7.9 Hz, 1H), 7.32–7.28
(m, 1H), 7.24–7.20 (m, 1H), 6.71 (d, J = 7.0 Hz, 1H), 5.64 (d,
J = 17.2 Hz, 1H), 5.59 (d, J = 17.2 Hz, 1H), 3.70–3.66 (m, 1H), 3.63
(s, 3H), 3.37–3.35 (m, 1H), 3.29–3.23 (m, 1H), 3.10–3.08 (m, 1H),
3.01 (s, 6H), 2.90–2.85 (m, 1H), 1.97–1.94 (m, 1H), 1.77–1.74 (m,
1H), 1.63–1.58 (m, 1H), 1.53–1.48 (m, 1H); 13C NMR (100 MHz,
DMSO-d6) d 169.7, 156.6, 153.9, 139.3, 137.9, 135.0, 131.1, 130.4,
129.6, 129.2, 128.0, 127.8, 127.2, 121.5, 118.9, 115.9, 114.8, 59.4,
52.3, 50.9, 46.8, 46.2, 43.8, 29.2, 27.3, 22.1; HRMS (ESI) [M+H]+
calcd for C26H30O2N6Cl 493.2113, found 493.2114; IR(ATR): 1672,
5.17. tert-Butyl 2-{(3R)-3-[(tert-butoxycarbonyl)amino]
piperidin-1-yl}-3-(2-chlorobenzyl)-5-methyl-4-oxo-4,5-
dihydro-3H-imidazo[4,5-c]quinoline-7-carboxylate (15a)
Compound 15a was prepared from 12 in a manner similar to
that described for compound 7t with a yield of 73% as a white
amorphous. 1H NMR (300 MHz, CDCl3) d 8.31 (d, J = 8.4 Hz, 1H),
8.12 (d, J = 1.2 Hz, 1H), 7.91 (dd, J = 1.2, 8.4 Hz, 1H), 7.41 (dd,
J = 1.5, 7.8 Hz, 1H), 7.27–7.11 (m, 2H), 6.70 (d, J = 6.0 Hz, 1H),
6.10–6.08 (m, 1H), 5.79 (d, J = 17.1 Hz, 1H), 5.65 (d, J = 17.1 Hz,
1H), 3.83 (br s, 1H), 3.80 (s, 3H), 3.45 (dd, J = 3.3, 12.6 Hz, 1H),
3.24 (dd, J = 5.4, 12.6 Hz, 1H), 3.10–3.08 (m, 2H), 1.73–1.54 (m,
13H), 1.44 (s, 9H); 13C NMR (75 MHz, CDCl3) d 165.6, 158.4,
155.2, 155.1, 141.3, 137.1, 134.9, 132.0, 131.3, 129.6, 128.6,
127.2, 126.5, 122.9, 122.6, 120.5, 120.2, 116.2, 81.6, 79.1, 54.8,
51.5, 46.4, 45.7, 29.4, 29.1, 28.5, 28.2, 21.5; HRMS (ESI) [M+H]+
calcd for C33H41O5N5Cl 622.2791, found 622.2780; IR (ATR):
1706, 1652, 1506, 1473, 1390, 1365, 1307, 1240, 1224, 1160,
1618, 1506, 1471, 1444, 1394, 1319, 1243, 1118, 1051 cmÀ1
.
5.14. Methyl 3-[{[2-{(3R)-3-[(tert-butoxycarbonyl)amino]
piperidin-1-yl}-1-(2-chlorobenzyl)-4-iodo-1H-imidazol-5-yl]
carbonyl}(methyl)amino]benzoate (10)
Compound 10 was prepared from 4 in a manner similar to that
described for compound 6t with total yield of 57% for 2 steps as a
white amorphous. 1H NMR (300 MHz, CDCl3) d 8.35 (d, J = 8.1 Hz,
1H), 8.16 (d, J = 1.3 Hz, 1H), 7.97 (dd, J = 1.3, 8.1 Hz, 1H), 7.41 (dd,
J = 1.5, 7.9 Hz, 1H), 7.36–7.25 (m, 2H), 7.20–7.18 (m, 1H), 6.93 (br
s, 1H), 5.25–4.95 (m, 3H), 4.10 (s, 3H), 3.80 (br s, 1H), 3.32 (dd,
J = 3.3, 11.9 Hz, 1H), 3.18 (s, 3H), 2.99–2.91 (m, 3H), 1.83–1.53
(m, 4H), 1.42 (s, 9H).
1108, 1039 cmÀ1
.
5.18. 2-[(3R)-3-Aminopiperidin-1-yl]-3-(2-chlorobenzyl)-5-
methyl-4-oxo-4,5-dihydro-3H-imidazo[4,5-c]quinoline-7-
carboxylic acid hydrochloride (8n)
To a solution of 15a (337.5 mg, 0.542 mmol) in 1,4-dioxane
(4 ml) was added 4 N HCl-1,4-dioxane (4 ml). The reaction mixture
was stirred at 80 °C for 4 h and concentrated under reduced pres-
sure to give 8n (283 mg, quantitative yield) as a white amorphous.
1H NMR (400 MHz, DMSO-d6) d 8.33 (s, 3H), 8.22 (d, J = 8.1 Hz, 1H),
8.07 (d, J = 1.5 Hz, 1H), 7.89 (dd, J = 1.5, 8.1 Hz, 1H), 7.50 (dd, J = 1.2,
7.8 Hz, 1H), 7.31–7.27 (m, 1H), 7.24–7.20 (m, 1H), 6.69 (dd, J = 1.4,
7.6 Hz, 1H), 5.65 (d, J = 17.1 Hz, 1H), 5.59 (d, J = 17.1 Hz, 1H), 3.66
(s, 3H), 3.66–3.64 (m, 1H), 3.30 (br s, 1H), 3.26–3.21 (m, 1H),
3.09–3.06 (m, 1H), 2.86–2.82 (m, 1H), 1.96 (m, 1H), 1.77–1.75
(m, 1H), 1.60–1.51 (m, 2H); 13C NMR (100 MHz, DMSO-d6) d
167.0, 157.5, 154.0, 140.3, 136.8, 135.0, 130.9, 130.1, 129.3,
128.9, 127.6, 126.8, 122.8, 122.2, 120.1, 119.5, 116.5, 52.3, 51.1,
46.4, 46.3, 28.9, 27.4, 22.2; HRMS (ESI) [M+H]+ calcd for
5.15. Ethyl 3-[{[2-{(3R)-3-[(tert-butoxycarbonyl)amino]
piperidin-1-yl}-1-(2-chlorobenzyl)-4-iodo-1H-imidazol-5-yl]
carbonyl}(methyl)amino]benzoate (11)
Compound 11 was prepared from 4 in a manner similar to that
described for compound 6t with total yield of 17% for 2 steps as a
white amorphous. 1H NMR (400 MHz, CDCl3) d 7.86 (d, J = 7.8 Hz,
1H), 7.70 (br s, 1H), 7.42 (dd, J = 1.1, 7.9 Hz, 1H), 7.34–7.28 (m,
3H), 7.18 (m, 1H), 6.95 (m, 1H), 5.25 (br s, 1H), 5.08 (br s, 1H),
4.89 (br s, 1H), 4.47 (q, J = 7.2 Hz, 2H), 3.79 (br s, 1H), 3.32–3.29
(m, 1H), 3.16 (s, 3H), 2.98–2.87 (m, 3H), 1.77 (m, 2H), 1.64–1.63
(m, 1H), 1.56–1.49 (m, 1H), 1.42–1.25 (m, 13H); 13C NMR
(100 MHz, CDCl3) d 165.7, 162.0, 155.6, 155.0, 142.7, 134.0,
133.5, 131.4, 131.2, 130.3, 129.9, 129.8, 128.9, 127.8, 127.5,
127.0, 126.8, 83.9, 79.2, 61.2, 56.2, 51.9, 46.6, 46.1, 38.8, 31.6,
28.4, 22.6, 14.3; HRMS (ESI) [M+H]+ calcd. for C31H38O5N5ClI
722.1601, found 722.1591; IR(ATR): 1716, 1635, 1538, 1506,
1488, 1473, 1444, 1417, 1363, 1280, 1236, 1168, 1103, 1049,
C
24H25O3N5Cl 466.1640, found 466.1637; IR(ATR): 2869, 1716,
1679, 1652, 1623, 1508, 1473, 1457, 1444, 1419, 1394, 1326,
1245, 1222, 1178, 1130, 1052, 1041 cmÀ1
Anal. Cacld for
24H24O3N5ClÁ2HClÁ2H2O: C, 50.14; H, 5.26; N, 12.18, found: C,
50.15; H, 5.29; N, 12.06.
.
C
1008 cmÀ1
.
5.19. {2-[(3R)-3-Aminopiperidin-1-yl]-3-(2-chlorobenzyl)-5-
methyl-4-oxo-4,5-dihydro-3H-imidazo[4,5-c]quinolin-7-yl}
acetic acid hydrochloride (8o)
5.16. tert-Butyl 3-[{[2-{(3R)-3-[(tert-butoxycarbonyl)amino]
piperidin-1-yl}-1-(2-chlorobenzyl)-4-iodo-1H-imidazol-5-yl]
carbonyl}(methyl)amino]benzoate (12)
Compound 8o was prepared from 4 in a manner similar to that
described for compound 8t with total yield of 23% for 5 steps as a
white amorphous. 1H NMR (400 MHz, DMSO-d6) d 8.36 (br s, 3H),
8.16 (d, J = 8.0 Hz, 1H), 7.54–7.50 (m, 2H), 7.33–7.27 (m, 2H),
7.24–7.20 (m, 1H), 6.71 (d, J = 7.6 Hz, 1H), 5.63 (s, 2H), 3.77 (s,
2H), 3.70–3.64 (m, 2H), 3.60 (s, 3H), 3.33–3.24 (m, 1H), 3.12–3.09
(m, 1H), 2.89–2.85 (m, 1H), 1.97–1.94 (m, 1H), 1.78–1.75 (m,
1H), 1.62–1.49 (m, 2H); 13C NMR (100 MHz, DMSO-d6) d 172.7,
157.1, 154.2, 140.8, 137.4, 136.1, 135.3, 131.1, 129.5, 129.1,
127.8, 127.1, 124.0, 122.2, 118.6, 116.7, 114.5, 52.4, 51.1, 46.5,
46.3, 41.2, 29.0, 27.3, 22.1; HRMS (ESI) [M+H]+ calcd for
Compound 12 was prepared from 4 in a manner similar to that
described for compound 6t with total yield of 50% for 2 steps as a
white amorphous. 1H NMR (400 MHz, CDCl3) d 7.81 (d, J = 7.8 Hz,
1H), 7.67 (s, 1H), 7.42 (dd, J = 1.3, 7.6 Hz, 1H), 7.34–7.28 (m, 4H),
7.16 (br s, 1H), 5.26 (br s, 1H), 5.05 (br s, 1H), 4.85–4.59 (m, 1H),
3.79 (br s, 1H), 3.29 (d, J = 10.4 Hz, 1H), 3.16 (s, 3H), 2.96 (m,
3H), 1.76 (m, 2H), 1.59 (s, 9H), 1.54–1.50 (m, 2H), 1.41 (s, 9H);
13C NMR (100 MHz, CDCl3) d 164.6, 161.9, 155.5, 154.9, 142.5,
133.7, 133.4, 132.8, 130.8, 129.8, 129.7, 129.7, 128.7, 127.6,
127.5, 126.9, 126.6, 83.9, 81.3, 79.0, 56.2, 51.8, 46.4, 46.0, 38.6,
C25H27O3N5Cl 480.1797, found 480.1786; IR(ATR): 1683, 1670,

Y. Ikuma et al. / Bioorg. Med. Chem. 20 (2012) 5864–5883
5875
1652, 1635, 1589, 1558, 1540, 1506, 1473 cmÀ1; Anal. calcd for
IR(ATR): 2915, 1652, 1575, 1558, 1540, 1508, 1456, 1444, 1419,
1375, 1319, 1245, 1095, 1039 cmÀ1
C25H26O3N5ClÁ2.25HClÁ1.75H2O: C, 50.59; H, 5.39; N, 11.80, found:
.
C, 50.73; H, 45.47; N, 11.67.
5.23. 2-[(3R)-3-Aminopiperidin-1-yl]-3-(2-chlorobenzyl)-7-
fluoro-5-methyl-3,5-dihydro-4H-imidazo[4,5-c]quinolin-4-one
hydrochloride (8d)
5.20. {2-[(3R)-3-Aminopiperidin-1-yl]-3-(2-chlorobenzyl)-5-
methyl-4-oxo-4,5-dihydro-3H-imidazo[4,5-c]quinolin-9-yl}
acetic acid hydrochloride (8z)
Compound 8d was prepared from 4 in a manner similar to that
described for compound 8y with total yield of 14% for 5 steps as a
white amorphous. 1H NMR (400 MHz, DMSO-d6) d 8.19–8.13 (m,
4H), 7.52–7.46 (m, 2H), 7.32–7.20 (m, 3H), 6.65 (d, J = 8.0 Hz,
1H), 5.60 (s, 2H), 3.58 (s, 3H), 3.49–3.46 (m, 1H), 3.37–3.33 (m,
1H), 3.23–3.18 (m, 1H), 3.08–3.05 (m, 1H), 2.86–2.82 (m, 1H),
1.98–1.93 (m, 1H), 1.75 (m, 1H), 1.58–1.49 (m, 2H); 13C NMR
(100 MHz, DMSO-d6) d 159.9, 156.5, 153.2, 138.9 (d, 1J (C, F) =
238 Hz), 137.8, 134.2, 129.9, 128.2 (d, 2J (C, F) = 44 Hz), 128.1 (d,
2J (C, F) = 44 Hz), 126.7 (d, 3J (C, F) = 8.8 Hz), 125.8, 122.9 (d, 3J
(C, F) = 8.8 Hz), 117.1 (d, 4J (C, F) = 4.0 Hz), 112.1, 109.1, 108.9,
51.2, 50.0, 45.2, 42.7, 28.1, 26.3, 20.9; HRMS (ESI) [M+H]+ calcd
Compound 8z was prepared from 4 in a manner similar to that
described for compound 8t with total yield of 4.3% for 5 steps as a
white amorphous. 1H NMR (400 MHz, DMSO-d6) d 8.38 (br s, 3H),
8.16 (d, J = 8.0 Hz, 1H), 7.52–7.50 (m, 2H), 7.32–7.27 (m, 2H),
7.24–7.21 (m, 1H), 6.71 (d, J = 7.5 Hz, 1H), 5.63 (s, 2H), 3.77 (s,
2H), 3.72–3.67 (m, 1H), 3.60 (s, 3H), 3.33–3.25 (m, 2H), 3.12–3.09
(m, 1H), 2.90–2.85 (m, 1H), 1.95 (m, 1H), 1.78–1.76 (m, 1H),
1.62–1.47 (m, 2H); 13C NMR (100 MHz, DMSO-d6) d 172.6, 157.1,
154.2, 140.5, 137.5, 136.1, 135.3, 131.1, 129.5, 129.1, 127.8,
127.1, 124.0, 122.2, 118.6, 116.7, 114.5, 52.4, 51.1, 46.5, 46.2,
40.5, 28.9, 27.3, 22.1; HRMS (ESI) [M+H]+ calcd for C25H27O3N5Cl
480.1797, found 480.1783; IR(ATR): 2867, 1718, 1670, 1625,
for
1673, 1652, 1577, 1523, 1508, 1473, 1415, 1394, 1353, 1309,
1243, 1224, 1149, 1128, 1106, 1051, cmÀ1
C23H24ON5ClF 440.1648, found 440.1638; IR(ATR): 2921,
1604, 1513, 1475, 1444, 1326, 1245, 1162, 1122, 1051, 1000 cmÀ1
.
.
5.21. Methyl 2-{(3R)-3-[(tert-butoxycarbonyl)amino]piperidin-
1-yl}-3-(2-chlorobenzyl)-5-methyl-4-oxo-4,5-dihydro-3H-
imidazo[4,5-c]quinoline-9-carboxylate (7ya)
5.24. 2-{(3R)-3-[(tert-Butoxycarbonyl)amino]piperidin-1-yl}-3-
(2-chlorobenzyl)-5-methyl-4-oxo-4,5-dihydro-3H-imidazo[4,5-
c]quinoline-7-carboxylic acid (7n)
A mixture of compound 7y (16.9 mg, 0.0275 mmol) which was
prepared from 4 in a manner similar to that described for com-
pound 7t with total yield of 11% in 3 steps, and 10% Pd/C (50%
wet, 40.0 mg) in MeOH (5 ml) was stirred at room temperature un-
der H2 atmosphere for 4 h. The reaction mixture was filtered
through a Celite pad, and the filtrate was concentrated under re-
duced pressure. The residue was purified by silica-gel column
chromatography to give 7ya (15.5 mg, yield 97%) as a white amor-
phous. 1H NMR (300 MHz, CDCl3) d 7.56–7.49 (m, 2H), 7.40 (d,
J = 7.5 Hz, 1H), 7.32 (dd, J = 2.4, 5.9 Hz, 1H), 7.23–7.11 (m, 2H),
6.71 (d, J = 7.3 Hz, 1H), 5.80 (d, J = 17.0 Hz, 1H), 5.65 (d,
J = 17.0 Hz, 1H), 4.69 (brd, J = 7.7 Hz, 1H), 4.03 (s, 3H), 3.81–3.79
(m, 1H), 3.76 (s, 3H), 3.39 (dd, J = 3.1, 12.1 Hz, 1H), 3.04–2.96 (m,
3H), 1.74–1.49 (m, 4H), 1.42 (s, 9H); 13C NMR (75 MHz, CDCl3) d
170.5, 157.6, 154.9, 154.8, 140.6, 137.7, 134.9, 131.9, 129.9,
129.5, 128.6, 127.6, 127.2, 126.7, 120.7, 120.2, 116.2, 113.6, 79.4,
60.4, 55.5, 52.8, 51.5, 46.3, 29.3, 28.3, 22.3, 14.2; HRMS (ESI)
[M+H]+ calcd for C30H35O5N5Cl 580.2321, found 580.2305; IR(ATR):
1733, 1716, 1652, 1506, 1496, 1471, 1457, 1311, 1278, 1213,
A
mixture of 8n (1.53 g, 3.05 mmol), (Boc)2O (864 mg,
3.97 mmol) in THF (10 ml) and saturated NaHCO3 aqueous solution
(10 ml) was stirred at room temperature for 3 h. The reaction mix-
ture was quenched with 5% KHSO4 aqueous solution and extracted
with CHCl3. The organic layer was washed with brine, dried over
Na2SO4, and concentrated under reduced pressure. The residual so-
lid was triturated with hexane to afford 7n (1.04 g, yield 60%) as a
white amorphous. 1H NMR (400 MHz, DMSO-d6)
d 8.18 (d,
J = 8.1 Hz, 1H), 8.06 (d, J = 1.1 Hz, 1H), 7.88 (dd, J = 1.1, 8.1 Hz,
1H), 7.48 (dd, J = 1.0, 7.9 Hz, 1H), 7.29–7.25 (m, 1H), 7.22–7.17
(m, 1H), 6.93 (d, J = 7.7 Hz, 1H), 6.66 (m, 1H), 5.57 (d, J = 17.6 Hz,
1H), 5.53 (d, J = 17.6 Hz, 1H), 3.66 (s, 3H), 3.48–3.22 (m, 3H),
2.84–2.71 (m, 2H), 1.78–1.76 (m, 1H), 1.69–1.66 (m, 1H), 1.55–
1.50 (m, 1H), 1.39–1.29 (m, 10H); 13C NMR (100 MHz, DMSO-d6)
d 167.4, 158.1, 155.0, 154.2, 140.8, 136.9, 135.3, 131.2, 130.1,
129.4, 128.9, 127.7, 126.9, 122.8, 122.3, 120.0, 119.8, 116.5, 77.9,
55.1, 50.6, 46.6, 40.3, 29.8, 28.8, 28.4, 23.4; HRMS (ESI) [M+H]+
calcd for C29H33O5N5Cl 566.2165, found 566.2155; IR(ATR): 2935,
1685, 1646, 1621, 1585, 1558, 1508, 1473, 1446, 1409, 1365,
1168 cmÀ1
.
1349, 1307, 1241, 1222, 1168, 1122, 1070, 1049, 1039, 1024 cmÀ1
.
5.22. 2-[(3R)-3-Aminopiperidin-1-yl]-3-(2-chlorobenzyl)-5-
methyl-4-oxo-4,5-dihydro-3H-imidazo[4,5-c]quinoline-9-
carboxylic acid hydrochloride (8y)
5.25. tert-Butyl {(3R)-1-[7-carbamoyl-3-(2-chlorobenzyl)-5-
methyl-4-oxo-4,5-dihydro-3H-imidazo[4,5-c]quinolin-2-yl]
piperidin-3-yl}carbamate (7k)
Compound 8y was prepared from 7ya in a manner similar to
that described for compound 8w with total yield of 99% for 2 steps
as a white amorphous. 1H NMR (400 MHz, DMSO-d6) d 8.27 (br s,
3H), 7.69 (d, J = 8.3 Hz, 1H), 7.61–7.57 (m, 1H), 7.52 (d, J = 7.7 Hz,
1H), 7.39 (d, J = 7.4 Hz, 1H), 7.35–7.28 (m, 1H), 7.24–7.21 (m,
1H), 6.66 (d, J = 7.4 Hz, 1H), 5.64 (s, 2H), 3.65 (s, 3H), 3.49–3.37
(m, 2H), 3.23–3.15 (m, 1H), 3.07–3.04 (m, 1H), 2.92–2.87 (m,
1H), 1.93 (br s, 1H), 1.72–1.62 (m, 2H), 1.48–1.46 (m, 1H); 13C
NMR (100 MHz, DMSO-d6) d169.8, 156.2, 153.7, 139.4, 137.5,
135.1, 130.9, 130.8, 129.3, 128.9, 127.9, 127.6, 126.7, 121.2,
119.3, 116.7, 112.1, 51.9, 50.6, 46.1, 45.6, 29.1, 27.1, 21.3; HRMS
(ESI) [M+H]+ calcd for C24H25O3N5Cl 466.1640, found 466.1630;
Compound 7k was prepared from 7n in a manner similar to that
described for compound 7u with a yield of 80% as a white amor-
phous. 1H NMR (400 MHz, CDCl3) d 8.31 (d, J = 8.1 Hz, 1H), 8.03
(s, 1H), 7.63 (dd, J = 1.0, 8.1 Hz, 1H), 7.40 (dd, J = 0.9, 7.9 Hz, 1H),
7.21–7.18 (m, 1H), 7.15–7.11 (m, 1H), 6.68 (d, J = 7.2 Hz, 1H),
6.02 (br s, 1H), 5.77 (d, J = 16.8 Hz, 1H), 5.64 (d, J = 16.8 Hz, 1H),
3.82 (br s, 1H), 3.77 (s, 3H), 3.44 (dd, J = 3.2, 12.7 Hz, 1H), 3.22
(dd, J = 4.9, 12.6 Hz, 1H), 3.08–3.06 (m, 2H), 1.83–1.65 (m, 4H),
1.46 (s, 9H); 13C NMR (100 MHz, CDCl3) d 168.9, 158.4, 155.2,
155.1, 141.2, 137.5, 134.9, 132.5, 132.0, 129.6, 128.6, 127.2,
126.5, 122.9, 120.4, 120.1, 119.8, 115.0, 79.1, 54.9, 51.5, 46.4,

5876
Y. Ikuma et al. / Bioorg. Med. Chem. 20 (2012) 5864–5883
45.8, 29.2, 28.5, 28.2, 21.6; HRMS (ESI) [M+H]+ calcd for
29H34O4N6Cl 565.2325, found 565.2309; IR(ATR): 1716, 1699,
1683, 1652, 1646, 1635, 1558, 1540, 1521, 1506, 1473, 1457,
1386, 1363, 1319, 1224, 1164, 1039 cmÀ1
5.29. Methyl 2-{(3R)-3-[(tert-butoxycarbonyl)amino]piperidin-
1-yl}-3-(2-chlorobenzyl)-5-methyl-4-oxo-4,5-dihydro-3H-
imidazo[4,5-c]quinoline-7-carboxylate (7j)
C
.
A
mixture of 7n (1.02 g, 1.80 mmol), K2CO3 (746 mg,
5.26. 2-[(3R)-3-Aminopiperidin-1-yl]-3-(2-chlorobenzyl)-5-
methyl-4-oxo-4,5-dihydro-3H-imidazo[4,5-c]quinoline-7-
carboxamide hydrochloride (8k)
5.40 mmol), and MeI (224 l, 3.60 mmol) in DMF (5 ml) was stirred
l
at 45 °C for 4 h. After cooling to room temperature, the reaction
mixture was quenched with saturated NH4Cl solution and ex-
tracted with EtOAc. The organic layer was washed with saturated
NH4Cl aqueous solution twice and brine, dried over Na2SO4, and
concentrated under reduced pressure. The residue was purified
by silica-gel column chromatography to give 7j (1.12 g, quantita-
tive yield) as a pale yellow amorphous. 1H NMR (400 MHz, CDCl3)
d 8.33 (d, J = 8.2 Hz, 1H), 8.15 (d, J = 1.1 Hz, 1H), 7.97 (d, J = 8.2 Hz,
1H), 7.41 (dd, J = 1.0, 7.9 Hz, 1H), 7.22–7.18 (m, 1H), 7.15–7.11 (m,
1H), 6.68 (d, J = 7.6 Hz, 1H), 6.16 (br s, 1H), 5.77 (d, J = 16.8 Hz, 1H),
5.65 (d, J = 16.8 Hz, 1H), 3.99 (s, 3H), 3.81 (br s, 1H), 3.80 (s, 3H),
3.43 (dd, J = 3.3, 12.8 Hz, 1H), 3.24 (dd, J = 4.2, 12.5 Hz, 1H), 3.09–
3.08 (m, 2H), 1.74–1.62 (m, 3H), 1.54–1.52 (m, 1H), 1.46 (s, 9H);
13C NMR (100 MHz, CDCl3) d 167.5, 159.0, 155.9, 155.6, 141.7,
137.8, 135.6, 132.6, 130.2, 129.9, 129.2, 127.8, 127.1, 123.6,
123.4, 121.2, 121.1, 117.0, 79.7, 55.4, 53.0, 52.1, 47.0, 46.4, 30.0,
29.8, 29.1, 22.1; HRMS (ESI) [M+H]+ calcd for C30H35O5N5Cl
580.2321, found 580.2314; IR (ATR): 1716, 1652, 1646, 1508,
Compound 8k was prepared from 7k in a manner similar to that
described for compound 8u with a quantitative yield as a white
amorphous. 1H NMR (400 MHz, DMSO-d6) d 8.37 (br s, 3H), 8.28
(br s, 1H), 8.20 (d, J = 8.1 Hz, 1H), 8.06 (s, 1H), 7.87 (dd, J = 1.0,
8.1 Hz, 1H), 7.58–7.49 (m, 2H), 7.32–7.29 (m, 1H), 7.25–7.16 (m,
1H), 6.71 (d, J = 7.2 Hz, 1H), 5.65 (d, J = 17.2 Hz, 1H), 5.59 (d,
J = 17.2 Hz, 1H), 3.68 (s, 3H), 3.50–3.45 (m, 1H), 3.34 (br s, 1H),
3.28–3.25 (m, 1H), 3.09–3.06 (m, 1H), 2.87–2.82 (m, 1H), 1.95
(m, 1H), 1.78–1.75 (m, 1H), 1.61–1.49 (m, 2H); 13C NMR
(100 MHz, DMSO-d6) d167.6, 157.5, 154.3, 140.5, 137.1, 135.3,
134.0, 131.1, 129.5, 129.1, 127.9, 127.1, 122.0, 121.6, 119.8,
118.3, 115.1, 52.3, 51.1, 46.4, 43.8, 29.1, 27.4, 22.1; HRMS (ESI)
[M+H]+ calcd for C24H26O2N6Cl 465.1800, found 465.1790; IR(ATR):
1672, 1598, 1444, 1122, 1041 cmÀ1
.
5.27. tert-Butyl {(3R)-1-[3-(2-chlorobenzyl)-7-
1307, 1257, 1238, 1220, 1164, 1108, 1049, 1033 cmÀ1
.
(dimethylcarbamoyl)-5-methyl-4-oxo-4,5-dihydro-3H-
imidazo[4,5-c]quinolin-2-yl]piperidin-3-yl}carbamate (7l)
5.30. Methyl 2-[(3R)-3-aminopiperidin-1-yl]-3-(2-
chlorobenzyl)-5-methyl-4-oxo-4,5-dihydro-3H-imidazo[4,5-
Compound 7l was prepared from 7n in a manner similar to that
described for compound 7v with a quantitative yield as a white
amorphous. 1H NMR (400 MHz, CDCl3) d 8.31 (d, J = 8.0 Hz, 1H),
7.53 (d, J = 1.1 Hz, 1H), 7.40 (dd, J = 1.1, 7.9 Hz, 1H), 7.33 (d,
J = 8.0 Hz, 1H), 7.22–7.18 (m, 1H), 7.15–7.11 (m, 1H), 6.68 (d,
J = 7.5 Hz, 1H), 6.25 (br s, 1H), 5.77 (d, J = 16.8 Hz, 1H), 5.65 (d,
J = 16.8 Hz, 1H), 3.82 (br s, 1H), 3.74 (s, 3H), 3.43 (dd, J = 3.2,
12.9 Hz, 1H), 3.25 (dd, J = 4.3, 12.9 Hz, 1H), 3.17 (s, 3H), 3.09–
3.07 (m, 2H), 3.03 (s, 3H), 1.73–1.50 (m, 4H), 1.46 (s, 9H); 13C
NMR (75 MHz, CDCl3) d 171.2, 158.3, 155.2, 155.1, 141.5, 137.5,
136.0, 135.0, 132.0, 129.6, 128.6, 127.2, 126.5, 122.7, 120.7,
119.9, 117.8, 114.0, 79.0, 54.7, 51.5, 46.4, 45.7, 39.7, 35.5, 29.4,
29.1, 28.4, 21.4; HRMS (ESI) [M+H]+ calcd for C31H38O4N6Cl
593.2638, found 593.2621; IR(ATR): 1700, 1635, 1583, 1508,
1467, 1444, 1405, 1388, 1363, 1315, 1241, 1162, 1122, 1087,
c]quinoline-7-carboxylate hydrochloride (8j)
Compound 8j was prepared from 7j in a manner similar to that
described for compound 8t with a quantitative yield as a white
amorphous. 1H NMR (400 MHz, CD3OD, free form) d 8.18 (d,
J = 8.2 Hz, 1H), 8.01 (d, J = 1.2 Hz, 1H), 7.87 (dd, J = 1.2, 8.2 Hz,
1H), 7.46 (dd, J = 1.1, 8.0 Hz, 1H), 7.28–7.24 (m, 1H), 7.19–7.15
(m, 1H), 6.67 (dd, J = 1.1, 7.7 Hz, 1H), 5.62 (d, J = 16.8 Hz, 1H),
5.53 (d, J = 16.8 Hz, 1H), 3.97 (s, 3H), 3.64 (s, 3H), 3.52 (dd,
J = 3.5, 11.6 Hz, 1H), 3.20–3.17 (m, 1H), 2.97–2.80 (m, 3H), 1.98–
1.94 (m, 1H), 1.75–1.61 (m, 2H), 1.43–1.28 (m, 1H); 13C NMR
(100 MHz, DMSO-d6) d 166.2, 158.4, 154.1, 140.8, 136.8, 135.2,
131.0, 129.4, 129.0, 128.6, 127.8, 127.4, 127.0, 122.6, 122.4,
120.1, 116.2, 58.6, 52.6, 50.6, 47.4, 46.2, 33.3, 28.8, 23.5; HRMS
(ESI) [M+H]+ calcd for C25H27O3N5Cl 480.1797, found 480.1792;
IR(ATR): 1718, 1652, 1623, 1525, 1506, 1471, 1436, 1405, 1309,
1068, 1049, 1039 cmÀ1
.
1259, 1240, 1222, 1108, 1049, 1039, 1033, 1000 cmÀ1
.
5.28. 2-[(3R)-3-Aminopiperidin-1-yl]-3-(2-chlorobenzyl)-N,N,5-
trimethyl-4-oxo-4,5-dihydro-3H-imidazo[4,5-c]quinoline-7-
carboxamide hydrochloride (8l)
5.31. tert-Butyl {(3R)-1-[3-(2-chlorobenzyl)-7-cyano-5-methyl-
4-oxo-4,5-dihydro-3H-imidazo[4,5-c]quinolin-2-yl]piperidin-3-
yl}carbamate (7m)
Compound 8l was prepared from 7l in a manner similar to that
described for compound 8v with a yield of 95% as a white amor-
phous. 1H NMR (400 MHz, DMSO-d6) d 8.41 (br s, 3H), 8.22 (d,
J = 8.0 Hz, 1H), 7.58 (s, 1H), 7.51 (dd, J = 0.6, 7.9 Hz, 1H), 7.36 (d,
J = 8.0 Hz, 1H), 7.32–7.29 (m, 1H), 7.24–7.21 (m, 1H), 6.71 (d,
J = 7.4 Hz, 1H), 5.66 (d, J = 17.6 Hz, 1H), 5.61 (d, J = 17.6 Hz, 1H),
3.71–3.66 (m, 1H), 3.63 (s, 3H), 3.38–3.24 (m, 2H), 3.11–3.03 (m,
1H), 3.03 (s, 3H), 2.95 (s, 3H), 2.89–2.84 (m, 1H), 1.95 (m, 1H),
1.78–1.76 (m, 1H), 1.62–1.49 (m, 2H); 13C NMR (100 MHz,
DMSO-d6) d169.9, 157.5, 154.2, 140.5, 137.1, 136.6, 135.2, 131.1,
129.5, 129.1, 127.8, 127.1, 122.2, 121.0, 119.4, 116.7, 114.4, 52.3,
51.1, 46.4, 46.3, 43.8, 35.0, 29.0, 27.4, 22.1; HRMS (ESI) [M+H]+
calcd for C26H30O2N6Cl 493.2113, found 493.2101; IR(ATR): 1677,
1639, 1602, 1498, 1475, 1442, 1409, 1398, 1321, 1245, 1205,
To a solution of 7k (255.8 mg, 0.410 mmol) in THF (3 ml) was
added trifluoroacetic acid anhydride (256 ll, 1.84 mmol) at room
temperature. The reaction mixture was stirred at 65 °C for 3 h.
After cooling to room temperature, the reaction mixture was sup-
plemented with K2CO3 (226 mg, 1.64 mmol) and MeOH (3 ml), and
the whole was stirred at room temperature for 3 h. The reaction
mixture was quenched with saturated NH4Cl aqueous solution, ex-
tracted with EtOAc, washed with brine, dried over Na2SO4, and
concentrated under reduced pressure. The residue was purified
by silica-gel column chromatography to give 7m (99.6 mg, yield
44%) as a white amorphous. 1H NMR (400 MHz, CDCl3) d 8.35 (d,
J = 8.1 Hz, 1H), 7.70 (d, J = 1.0 Hz, 1H), 7.56 (d, J = 8.1 Hz, 1H),
7.42 (dd, J = 1.2, 7.9 Hz, 1H), 7.23–7.19 (m, 1H), 7.16–7.12 (m,
1H), 6.67 (d, J = 7.4 Hz, 1H), 5.99 (br s, 1H), 5.76 (d, J = 16.8 Hz,
1122, 1051, 1039 cmÀ1
.

Y. Ikuma et al. / Bioorg. Med. Chem. 20 (2012) 5864–5883
5877
1H), 5.64 (d, J = 16.8 Hz, 1H), 3.82–3.78 (m, 1H), 3.74 (s, 3H), 3.45
5.34. 2-[(3R)-3-Aminopiperidin-1-yl]-3-(2-chlorobenzyl)-7-
(hydroxymethyl)-5-methyl-3,5-dihydro-4H-imidazo[4,5-c]-
quinolin-4-one (8i)
(dd, J = 3.2, 12.7 Hz, 1H), 3.22 (dd, J = 4.7, 12.9 Hz, 1H), 3.08 (m,
2H), 1.78–1.70 (m, 3H), 1.61–1.51 (m, 1H), 1.46 (s, 9H); 13C NMR
(100 MHz, CDCl3) d 158.6, 155.1, 154.7, 140.8, 137.2, 134.6,
132.0, 129.6, 128.7, 127.2, 126.4, 124.9, 123.6, 120.8, 120.3,
119.0, 118.6, 111.1, 79.1, 54.8, 51.4, 46.5, 45.8, 31.5, 29.1, 28.4,
21.6; HRMS (ESI) [M+H]+ calcd for C29H32O3N6Cl 547.2219, found
547.2206; IR(ATR): 1700, 1652, 1581, 1508, 1471, 1444, 1409,
To a solution of 7i (40.3 mg, 0.073 mmol) in CHCl3 (2 ml) was
added trifluoroacetic acid (112 l, 1.45 mmol) at room tempera-
l
ture. The reaction mixture was stirred at room temperature for
2 h, and concentrated under reduced pressure. The residue was
azeotroped with toluene and dissolved in MeOH (3 ml). To this
solution was added K2CO3 (30.3 mg, 0.219 mmol) and the reaction
mixture was stirred at room temperature for 3 h, and concentrated
under reduced pressure. The residue was purified by silica-gel col-
umn chromatography to give 8i (24.7 mg, yield 75%) as a white
amorphous. 1H NMR (300 MHz, CDCl3) d 8.14 (br s, 1H), 7.36 (m,
2H), 7.24–7.14 (m, 3H), 6.72 (br s, 1H), 5.67 (br s, 2H), 4.78 (br s,
2H), 3.64 (s, 3H), 3.37–3.33 (m, 1H), 3.18 (m, 1H), 2.93 (m, 2H),
2.76–2.73 (m, 1H), 1.87–1.62 (m, 4H); 13C NMR (75 MHz, CDCl3)
d 158.4, 155.2, 142.3, 141.5, 137.5, 135.4, 131.8, 129.4, 128.5,
127.2, 126.7, 122.8, 120.8, 119.2, 116.2, 112.9, 65.0, 58.9, 51.0,
47.4, 46.3, 33.2, 29.0, 23.3; HRMS (ESI) [M+H]+ calcd for
1390, 1365, 1315, 1240, 1162, 1124, 1070, 1049, 1041 cmÀ1
.
5.32. 2-[(3R)-3-Aminopiperidin-1-yl]-3-(2-chlorobenzyl)-5-
methyl-4-oxo-4,5-dihydro-3H-imidazo[4,5-c]quinoline-7-
carbonitrile (8m)
To a solution of 7m (99.6 mg, 0.182 mmol) in CHCl3 (2 ml)
was added trifluoroacetic acid (0.5 ml, 6.49 mmol) at room tem-
perature. The reaction mixture was stirred at room temperature
for 2 h, and concentrated under reduced pressure. To the residue
was added saturated NaHCO3 aqueous solution, and the whole
was extracted with CHCl3, washed with brine, dried over Na2SO4,
and concentrated under reduced pressure to give 8m (72.0 mg,
yield 88%) as a white amorphous. 1H NMR (300 MHz, CDCl3) d
8.33 (d, J = 8.0 Hz, 1H), 7.68 (s, 1H), 7.55 (dd, J = 1.3, 8.1 Hz,
1H), 7.40 (dd, J = 1.3, 7.9 Hz, 1H), 7.23–7.10 (m, 2H), 6.70 (d,
J = 7.5 Hz, 1H), 5.71 (d, J = 17.0 Hz, 1H), 5.64 (d, J = 17.0 Hz, 1H),
3.72 (s, 3H), 3.39–3.36 (m, 1H), 3.27–3.23 (m, 1H), 2.98–2.91
(m, 2H), 2.77–2.70 (m, 1H), 1.92–1.87 (m, 1H), 1.76–1.55 (m,
2H), 1.31–1.20 (m, 1H); 13C NMR (75 MHz, CDCl3) d 159.5,
155.4, 141.9, 137.9, 135.6, 132.5, 130.2, 129.3, 127.9, 127.3,
125.6, 124.3, 121.6, 121.2, 119.7, 119.3, 111.6, 59.5, 51.5, 48.0,
47.3, 33.4, 29.7, 24.0; HRMS (ESI) [M+H]+ calcd for C24H24ON6Cl
447.1695, found 447.1694; IR(ATR): 1646, 1619, 1504, 1463,
1444, 1407, 1392, 1349, 1319, 1243, 1226, 1159, 1122,
C
24H27O2N5Cl 451641, found 452.1848; IR(ATR): 1641, 1581,
1508, 1471, 1444, 1413, 1392, 1353, 1319, 1214, 1159, 1120,
1049, 1039 cmÀ1
.
5.35. tert-butyl {(3R)-1-[3-(2-chlorobenzyl)-7-
(methoxymethyl)-5-methyl-4-oxo-4,5-dihydro-3H-imidazo-
[4,5-c]quinolin-2-yl]piperidin-3-yl}carbamate (7h)
To a solution of 7i (147.4 mg, 0.267 mmol) in THF (2 ml) was
added sodium hydride (60% in oil, 12.8 mg, 0.32 mmol) at 0 °C.
The reaction mixture was stirred at 0 °C for 10 min. To this reaction
mixture was added MeI (19.9 ll, 0.32 mmol) at 0 °C, and the whole
was stirred at room temperature for 3 h. The reaction mixture was
quenched with saturated NH4Cl aqueous solution, extracted with
EtOAc, washed with brine, dried over Na2SO4, and concentrated
under reduced pressure. The residue was purified by silica-gel col-
umn chromatography to give 7h (129.6 mg, yield 86%) as a white
amorphous. 1H NMR (400 MHz, CDCl3) d 8.28 (d, J = 8.0 Hz, 1H),
7.43 (d, J = 1.1 Hz, 1H), 7.40 (dd, J = 1.1, 8.0 Hz, 1H), 7.28
(d, J = 8.1 Hz, 1H), 7.21–7.17 (m, 1H), 7.14–7.10 (m ,1H), 6.67 (d,
J = 7.5 Hz, 1H), 6.26 (br s, 1H), 5.77 (d, J = 16.8 Hz, 1H), 5.65 (d, J =
16.8 Hz, 1H), 4.62 (s, 2H), 3.81 (m, 1H), 3.75 (s, 3H), 3.46 (s, 3H),
3.42 (dd, J = 3.2, 12.9 Hz, 1H), 3.28–3.23 (m, 1H), 3.08–3.07 (m,
2H), 1.73–1.62 (m, 4H), 1.46 (s, 9H); 13C NMR (100 MHz, CDCl3) d
158.7, 155.9, 155.8, 142.5, 139.3, 138.3, 135.8, 132.5, 130.1,
129.1, 127.8, 127.2, 123.5, 122.2, 119.8, 117.0, 114.4, 79.6, 75.3,
58.9, 55.4, 52.2, 46.8, 46.4, 30.0, 29.6, 29.1, 22.0; HRMS (ESI)
[M+H]+ calcd for C30H37O4N5Cl 566.2529, found 566.2525; IR(ATR):
1700, 1652, 1646, 1583, 1508, 1473, 1457, 1444, 1417, 1388, 1363,
1049 cmÀ1
.
5.33. tert-Butyl {(3R)-1-[3-(2-chlorobenzyl)-7-(hydroxymethyl)-
5-methyl-4-oxo-4,5-dihydro-3H-imidazo[4,5-c]quinolin-2-
yl]piperidin-3-yl}carbamate (7i)
To a solution of 7n (471.5 mg, 0.833 mmol) and TEA (232
1.67 mmol) in THF (4 ml) was added ethyl chloroformate (119
l
l
l,
l,
1.25 mmol) at 0 °C. The reaction mixture was stirred at 0 °C for
1.5 h. To this reaction mixture was added sodium borohydride
(94.5 mg, 2.50 mmol) in H2O (1 ml) at 0 °C. The reaction mixture
was stirred at room temperature for 5 h and then quenched with
saturated NH4Cl aqueous solution, extracted with EtOAc, washed
with brine, dried over Na2SO4, and concentrated under reduced
pressure. The residue was purified by silica-gel column chroma-
tography to give 7i (261 mg, yield 57%) as a white amorphous.
1H NMR (400 MHz, CDCl3) d 8.24 (d, J = 7.9 Hz, 1H), 7.44 (br s,
1H), 7.41 (dd, J = 1.0, 7.9 Hz, 1H), 7.28 (d, J = 8.1 Hz, 1H), 7.21–
7.19 (m, 1H), 7.14–7.10 (m, 1H), 6.68 (d, J = 7.6 Hz, 1H), 5.76
(d, J = 17.2 Hz, 1H), 5.64 (d, J = 17.2 Hz, 1H), 4.85 (br s, 2H),
3.82 (br s, 1H), 3.72 (s, 3H), 3.43 (dd, J = 3.1, 12.9 Hz, 1H), 3.25
(dd, J = 4.1, 12.7 Hz, 1H), 3.08–3.07 (m, 2H), 1.73–1.51 (m, 4H),
1.47 (s, 9H); 13C NMR (75 MHz, CDCl3) d 158.1, 155.3, 155.2,
141.9, 141.4, 137.7, 135.1, 131.9, 129.5, 128.5, 127.2, 126.5,
123.0, 120.9, 119.2, 116.3, 113.0, 79.0, 65.3, 54.7, 51.6, 46.3,
45.7, 29.5, 29.0, 28.5, 21.4; HRMS (ESI) [M+H]+ calcd for
1315, 1241, 1159, 1101, 1070, 1049, 1039 cmÀ1
.
5.36. 2-[(3R)-3-aminopiperidin-1-yl]-3-(2-chlorobenzyl)-7-
(methoxymethyl)-5-methyl-3,5-dihydro-4H-imidazo[4,5-c]
quinolin-4-one hydrochloride (8h)
Compound 8h was prepared from 7h in a manner similar to that
described for compound 8t with a quantitative yield as a white
amorphous. 1H NMR (400 MHz, DMSO-d6) d 8.41 (br s, 3H), 8.20
(d, J = 8.0 Hz, 1H), 7.52–7.50 (m, 2H), 7.33–7.28 (m, 2H), 7.24–
7.20 (m, 1H), 6.73 (d, J = 7.2 Hz, 1H), 5.62 (s, 2H), 4.57 (s, 2H),
3.70–3.66 (m, 1H), 3.61 (s, 3H), 3.34 (s, 3H), 3.30–3.25 (m, 2H),
3.11–3.08 (m, 1H), 2.89–2.87 (m, 1H), 1.96–1.94 (m, 1H), 1.76–
1.74 (m, 1H), 1.62–1.51 (m, 2H); 13C NMR (100 MHz, DMSO-d6) d
156.6, 154.1, 139.6, 139.6, 137.5, 135.1, 131.1, 129.5, 129.1,
C
29H35O4N5Cl 552.2372, found 552.2354; IR(ATR): 1685, 1637,
1581, 1508, 1473, 1444, 1413, 1388, 1363, 1317, 1241, 1160,
1122, 1068, 1049, 1039 cmÀ1
.

5878
Y. Ikuma et al. / Bioorg. Med. Chem. 20 (2012) 5864–5883
127.8, 127.2, 122.6, 121.8, 118.5, 114.6, 114.5, 73.8, 57.9, 52.3,
51.0, 46.7, 46.3, 29.0, 27.3, 22.1; HRMS (ESI) [M+H]+ calcd for
(d, J = 16.8 Hz, 1H), 5.65 (d, J = 16.8 Hz, 1H), 3.72 (s, 3H), 3.40–
3.37 (m, 1H), 3.23–3.19 (m, 1H), 2.98–2.92 (m, 2H), 2.79 (dd,
J = 8.4, 11.9 Hz, 1H), 2.53 (s, 3H), 1.72–1.60 (m, 2H), 1.30–1.26
(m, 2H); 13C NMR (75 MHz, CDCl3) d 158.9, 155.9, 143.2, 139.1,
138.3, 136.2, 132.4, 130.0, 129.1, 127.9, 127.4, 124.2, 123.2,
119.4, 115.8, 115.5, 59.3, 51.7, 48.0, 46.9, 33.6, 29.6, 23.9, 22.8;
HRMS (ESI) [M+H]+ calcd for C24H27ON5Cl 436.1899, found
436.1897; IR(ATR): 1645, 1581, 1508, 1471, 1444, 1409, 1390,
C
25H29O2N5Cl 466.2004, found 466.2003; IR(ATR): 1670, 1637,
1602, 1473, 1444, 1417, 1386, 1326, 1249, 1199, 1159, 1108,
1051, 1039, 1033 cmÀ1
.
5.37. tert-Butyl {(3R)-1-[3-(2-chlorobenzyl)-7-(iodomethyl)-5-
methyl-4-oxo-4,5-dihydro-3H-imidazo[4,5-c]quinolin-2-yl]-
piperidin-3-yl}carbamate (20)
1319, 1243, 1226, 1160, 1122, 1068, 1049, 1039 cmÀ1
.
A
mixture of 7i (274.3 mg, 0.497 mmol), I2 (252 mg,
5.40. Methyl 2-{(3R)-3-[(tert-butoxycarbonyl)amino]piperidin-
1-yl}-5-methyl-4-oxo-4,5-dihydro-3H-imidazo[4,5-c]quinoline-
8-carboxylate (21)
0.99 mmol), imidazole (84.6 mg, 1.25 mmol), and PPh3 (196 mg,
0.75 mmol) in THF (2 ml) was stirred at room temperature for
16 h. The reaction mixture was quenched with saturated Na2S2O3
aqueous solution, extracted with EtOAc, washed with saturated
NH4Cl aqueous solution, saturated NaHCO3 aqueous solution and
brine, dried over Na2SO4, and concentrated under reduced pres-
sure. The residue was purified by silica-gel column chromatogra-
phy to give 20 (81.5 mg, yield 25%) as a pale yellow amorphous.
1H NMR (400 MHz, CDCl3) d 8.22 (d, J = 8.0 Hz, 1H), 7.42 (d,
J = 1.1 Hz, 1H), 7.40 (dd, J = 1.1, 7.9 Hz, 1H), 7.33 (d, J = 8.0 Hz,
1H), 7.21–7.17 (m, 1H), 7.13–7.09 (m, 1H), 6.64 (d, J = 7.6 Hz,
1H), 6.23 (br s, 1H), 5.75 (d, J = 17.3 Hz, 1H), 5.64 (d, J = 17.3 Hz,
1H), 4.63 (s, 2H), 3.82 (m, 1H), 3.74 (s, 3H), 3.42 (dd, J = 3.2,
12.9 Hz, 1H), 3.24 (dd, J = 4.4, 12.8 Hz, 1H), 3.08–3.07 (m, 2H),
1.73 (m, 2H), 1.62–1.58 (m, 1H), 1.53–1.47 (m, 1H), 1.47 (s, 9H);
HRMS (ESI) [M+H]+ calcd for C29H34O3N5ClI 662.1389, found
662.1375. IR(ATR): 1700, 1683, 1652, 1583, 1508, 1473, 1446,
A mixture of 7t (1.90 g, 3.28 mmol), 10% Pd/C (50% wet, 0.95 g),
HCO2NH4 (2.07 g, 32.8 mmol) in MeOH (15 ml) was stirred under
reflux for 2 h. After cooling to room temperature, the reaction mix-
ture was filtered through a Celite pad. To the filtrate was added
H2O, and the whole was extracted with CHCl3, washed with brine,
dried over Na2SO4, and concentrated under reduced pressure to
give 21 (1.23 g, yield 83%) as a white amorphous. 1H NMR
(300 MHz, DMSO-d6) d 12.13 (br s, 1H), 8.55 (s, 1H), 7.97 (d,
J = 8.7 Hz, 1H), 7.59 (d, J = 8.7 Hz, 1H), 6.98 (d, J = 7.8 Hz, 1H),
4.12–4.02 (m, 2H), 3.88 (s, 3H), 3.69 (s, 3H), 3.45 (br s, br s, 1H),
2.99–2.91 (m, 1H), 2.87–2.79 (m, 1H), 1.85–1.74 (m, 2H), 1.55–
1.52 (m, 2H), 1.40 (s, 9H); 13C NMR (100 MHz, DMSO-d6) d 165.5,
156.0, 154.4, 152.9, 142.1, 139.6, 127.3, 122.9, 121.9, 117.9,
115.6, 115.1, 78.7, 51.6, 50.4, 45.7, 45.4, 29.7, 28.5, 27.8, 22.6;
HRMS (ESI) [M+H]+ calcd for C23H30O5N5 456.2241, found
456.2229; IR(ATR): 1716, 1683, 1652, 1558, 1515, 1456, 1311,
1253, 1168, 1105, 1052 cmÀ1. Anal. calcd for C23H29O5N5Á0.75H2O:
C, 58.90; H, 6.55; N, 14.93, found: C, 58.93; H, 6.32; N, 14.69.
1417, 1394, 1363, 1319, 1243, 1164, 1049 cmÀ1
.
5.38. tert-Butyl {(3R)-1-[3-(2-chlorobenzyl)-5,7-dimethyl-4-
oxo-4,5-dihydro-3H-imidazo[4,5-c]quinolin-2-yl]piperidin-3-
yl}carbamate (7f)
5.41. Methyl 3-benzyl-2-{(3R)-3-[(tert-
A mixture of 20 (81.5 mg, 0.123 mmol) and NaBH4 (14.0 mg,
0.369 mmol) in DMSO (2 ml) was stirred at 50 °C for 3 h. After
cooling to room temperature, the reaction mixture was quenched
with saturated NH4Cl aqueous solution, extracted with EtOAc,
washed with saturated NH4Cl aqueous solution twice and brine,
dried over Na2SO4, and concentrated under reduced pressure. The
residue was purified by silica-gel column chromatography to give
7f (59.7 mg, yield 91%) as a pale yellow powder. Mp 207–209 °C;
1H NMR (400 MHz, CDCl3) d 8.20 (br s, 1H), 7.40 (dd, J = 0.8,
7.8 Hz, 1H), 7.24 (br s, br s, 1H), 7.21–7.10 (m, 3H), 6.67 (d,
J = 7.3 Hz, 1H), 5.76 (d, J = 16.8 Hz, 1H), 5.65 (d, J = 16.8 Hz, 1H),
3.82–3.78 (m, 1H), 3.73 (s, 3H), 3.44–3.41 (m, 1H), 3.28–3.26 (m,
1H), 3.08 (m, 2H), 2.53 (s, 3H), 1.73–1.51 (m, 4H), 1.47 (s, 9H);
13C NMR (100 MHz, CDCl3) d 158.6, 155.9, 155.9, 142.8, 139.2,
138.3, 135.9, 132.5, 130.1, 129.1, 127.8, 127.2, 124.1, 123.3,
119.3, 115.7, 115.3, 79.6, 55.3, 52.2, 46.8, 46.4, 30.1, 29.5, 29.1,
22.8, 22.0; HRMS (ESI) [M+H]+ calcd for C29H35O3N5Cl 536.2423,
found 536.2420; IR(ATR): 1700, 1646, 1583, 1508, 1473, 1411,
butoxycarbonyl)amino]piperidin-1-yl}-5-methyl-4-oxo-4,5-
dihydro-3H-imidazo[4,5-c]quinoline-8-carboxylate (22a)
A
mixture of 21 (82.4 mg, 0.181 mmol), K2CO3 (75.0 mg,
0.543 mmol), and BnBr (43.1 l, 0.362 mmol) in DMF (2 ml) was
l
stirred at 65 °C for 3 h. After cooling to room temperature, the reac-
tion mixture was quenched with saturated NH4Cl aqueous solu-
tion, and extracted with EtOAc. The organic layer was washed
with saturated NH4Cl aqueous solution twice and brine, dried over
Na2SO4, and concentrated under reduced pressure. The residue was
purified by silica-gel column chromatography to give 22a (97.8 mg,
yield 99%) as a white powder. Mp 205–207 °C; 1H NMR (300 MHz,
CDCl3) d 8.93 (d, J = 2.0 Hz, 1H), 8.16 (dd, J = 2.0, 9.0 Hz, 1H), 7.46
(d, J = 9.0 Hz, 1H), 7.33–7.21 (m, 2H), 7.19–7.17 (m, 2H), 5.77 (d,
J = 15.4 Hz, 1H), 5.55 (d, J = 15.4 Hz, 1H), 5.21–5.19 (m, 1H), 3.99
(s, 3H), 3.87–3.80 (m, 1H), 3.79 (s, 3H), 3.46 (dd, J = 2.9, 12.2 Hz,
1H), 3.16–3.11 (m, 3H), 1.86–1.71 (m, 2H), 1.65–1.58 (m, 2H),
1.41 (s, 9H); 13C NMR (75 MHz, CDCl3) d 166.6, 158.4, 155.2,
155.0, 142.2, 140.3, 137.2, 128.9, 128.7, 127.5, 126.5, 124.7,
123.8, 119.3, 116.7, 114.6, 79.2, 55.5, 52.0, 51.3, 48.3, 46.2, 29.6,
29.2, 28.3, 22.3; HRMS (ESI) [M+H]+ calcd for C30H36O5N5
546.2711, found 546.2699; IR (ATR): 1714, 1652, 1569, 1496,
1465, 1456, 1436, 1427, 1390, 1365, 1309, 1276, 1240, 1166,
1126, 1112, 1064 cmÀ1; Anal. calcd for C30H35O5N5: C, 66.04; H,
6.47; N, 12.84, found: C, 65.84; H, 6.53; N, 12.77.
1390, 1363, 1317, 1243, 1164, 1049 cmÀ1
.
5.39. 2-[(3R)-3-Aminopiperidin-1-yl]-3-(2-chlorobenzyl)-5,7-
dimethyl-3,5-dihydro-4H-imidazo[4,5-c]quinolin-4-one (8f)
To a solution of 7f (54.0 mg, 0.10 mmol) in 1,4-dioxane (2 ml)
was added 4 N HCl-1,4-dioxane (2 ml). The reaction mixture was
stirred at room temperature for 4 h, and concentrated under re-
duced pressure. To the residue was added saturated NaHCO3 aque-
ous solution, and the whole was extracted with CHCl3, washed
with brine, dried over Na2SO4, and concentrated under reduced
pressure to give 8f (50.7 mg, quantitative yield) as a white amor-
phous. 1H NMR (300 MHz, CDCl3) d 8.16 (d, J = 8.0 Hz, 1H), 7.39
(d, J = 7.7 Hz, 1H), 7.23–7.12 (m, 4H), 6.71 (d, J = 7.7 Hz, 1H), 5.72
5.42. 2-{(3R)-3-[(tert-butoxycarbonyl)amino]piperidin-1-yl}-5-
methyl-4-oxo-4,5-dihydro-3H-imidazo[4,5-c]quinoline-8-
carboxylic acid (23a)
A mixture of 22a (85.8 mg, 0.157 mmol) and 1 M NaOH aqueous
solution (1 ml) in THF (1 ml) and MeOH (1 ml) was stirred at room

Y. Ikuma et al. / Bioorg. Med. Chem. 20 (2012) 5864–5883
5879
temperature for 6 h. The mixture was concentrated under reduced
pressure. The residue was supplemented with 10% KHSO4 aqueous
solution until the pH reached at 2ꢀ3. the resulting solids were fil-
tered, washed sequentially with water, Et2O and hexane, and dried
in vacuo to give 23a (44.8 mg, yield 54%) as a white amorphous. 1H
NMR (400 MHz, DMSO-d6) d 8.66 (s, 1H), 8.05 (d, J = 8.7 Hz, 1H),
7.60 (d, J = 8.9 Hz, 1H), 7.31–7.24 (m, 2H), 7.24–7.17 (m, 3H),
6.93 (d, J = 7.5 Hz, 1H), 5.57 (s, 2H), 3.68 (s, 3H), 3.53 (br s, 1H),
3.42–3.39 (m, 1H), 3.30–3.27 (m, 1H), 2.88–2.74 (m, 2H), 1.79–
1.71 (m, 2H), 1.61–1.58 (m, 1H), 1.37 (m, 1H), 1.37 (s, 9H); 13C
NMR (100 MHz, DMSO-d6) d 166.9, 157.6, 154.4, 153.9, 141.2,
138.7, 137.2, 128.4, 128.0, 126.7, 126.1, 122.8, 122.8, 118.2,
115.5, 114.8, 77.3, 54.6, 50.1, 47.3, 46.1, 29.1, 28.4, 27.7, 22.8;
HRMS (ESI) [M+H]+ calcd for C29H34O5N5 532.2554, found
532.2537; IR(ATR): 1700, 1652, 1506, 1496, 1456, 1386, 1307,
(d, J = 8.8 Hz, 1H), 7.25–7.21 (m, 1H), 7.03 (d, J = 8.7 Hz, 1H),
6.82–6.78 (m, 1H), 6.53 (d, J = 7.0 Hz, 1H), 5.52 (s, 2H), 3.85 (s,
3H), 3.74–3.69 (m, 1H), 3.64 (s, 3H), 3.43–3.38 (m, 1H), 3.22–
3.19 (m, 1H), 3.15–3.12 (m, 1H), 2.87–2.82 (m, 1H), 1.98–1.96
(m, 1H), 1.72–1.69 (m, 1H), 1.59–1.45 (m, 2H); 13C NMR
(100 MHz, DMSO-d6) d 167.1, 157.9, 156.1, 154.3, 141.3, 140.2,
129.0, 128.5, 125.9, 125.7, 124.4, 123.7, 120.7, 119.4, 116.1,
116.0, 110.8, 55.7, 52.3, 50.7, 46.2, 43.9, 29.1, 27.6, 22.2; HRMS
(ESI) [M+H]+ calcd for C25H28O4N5 462.2136, found 462.2136; IR
(ATR): 1714, 1652, 1569, 1506, 1463, 1436, 1386, 1309, 1245,
1108, 1051, 1024 cmÀ1
.
5.46. 2-[(3R)-3-aminopiperidin-1-yl]-3-(2-fluorobenzyl)-5-
methyl-4-oxo-4,5-dihydro-3H-imidazo[4,5-c]quinoline-8-
carboxylic acid hydrochloride (24d)
1240, 1166, 1116 cmÀ1
.
Compound 24d was prepared from 21 in a manner similar to
that described for compound 24a with total yield of 55% for 3 steps
as a white amorphous. 1H NMR (400 MHz, DMSO-d6) d 8.69 (d,
J = 2.0 Hz, 1H), 8.43 (br s, 3H), 8.05 (dd, J = 2.0, 9.0 Hz, 1H), 7.65
(d, J = 9.0 Hz, 1H), 7.34–7.29 (m, 1H), 7.25–7.20 (m, 1H), 7.10–
7.07 (m, 1H), 6.89–6.86 (m, 1H), 5.68 (d, J = 16.8 Hz, 1H), 5.62 (d,
J = 16.8 Hz, 1H), 3.73–3.68 (m, 1H), 3.64 (s, 3H), 3.38–3.36 (m,
1H), 3.25–3.15 (m, 2H), 2.94–2.89 (m, 1H), 1.98 (m, 1H), 1.82–
1.79 (m, 1H), 1.66–1.51 (m, 2H); 13C NMR (100 MHz, DMSO-d6) d
167.0, 159.6 (d, 1J (C, F) = 243 Hz), 157.8, 154.3, 141.1, 140.2,
129.5 (d, 3J (C, F) = 7.9 Hz), 129.1, 128.0 (d, 4J (C, F) = 3.9 Hz),
124.8 (d, 2J (C, F) = 25 Hz), 124.8 (d, 3J (C, F) = 8.0 Hz), 124.5,
123.7, 119.1, 116.0, 115.8, 115.4 (d, 2J (C, F) = 21 Hz), 52.4, 51.0,
46.3, 43.8, 29.2, 27.4, 22.1; HRMS (ESI) [M+H]+ calcd for
5.43. 2-{(3R)-3-[(tert-butoxycarbonyl)amino]piperidin-1-yl}-3-
benzyl-5-methyl-4-oxo-4,5-dihydro-3H-imidazo[4,5-
c]quinoline-8-carboxylic acid hydrochloride (24a)
Compound 24a was prepared from 23a in a manner similar to
that described for compound 8t with a quantitative yield as a white
amorphous. 1H NMR (400 MHz, DMSO-d6) d 8.68 (d, J = 2.0 Hz, 1H),
8.43 (br s, 3H), 8.05 (dd, J = 2.0, 8.9 Hz, 1H), 7.66 (d, J = 8.9 Hz, 1H),
7.32–7.28 (m, 2H), 7.25–7.22 (m, 1H), 7.17 (d, J = 7.2 Hz, 2H), 5.68
(d, J = 16.0 Hz, 1H), 5.62 (d, J = 16.0 Hz, 1H), 3.74–3.70 (m, 1H), 3.68
(s, 3H), 3.37–3.35 (m, 1H), 3.22–3.15 (m, 2H), 2.87–2.82 (m, 1H),
1.99–1.97 (m, 1H), 1.82–1.79 (m, 1H), 1.62–1.49 (m, 2H); 13C
NMR (100 MHz, DMSO-d6) d 167.1, 157.7, 154.5, 141.1, 140.2,
137.8, 129.1, 128.8, 127.6, 126.7, 124.5, 123.7, 119.1, 116.0,
115.9, 52.5, 51.1, 48.1, 46.4, 29.3, 27.5, 21.1; HRMS (ESI) [M+H]+
calcd for C24H26O3N5 432.2030, found 432.2015; IR (ATR): 1700,
1670, 1652, 1594, 1506, 1496, 1456, 1375, 1305, 1216, 1114,
C
24H25O3N5F 450.1936, found 450.1925; IR (ATR): 1716, 1673,
1596, 1508, 1456, 1375, 1317, 1218, 1126 cmÀ1
.
5.47. 2-[(3R)-3-aminopiperidin-1-yl]-3-(3-chlorobenzyl)-5-
methyl-4-oxo-4,5-dihydro-3H-imidazo[4,5-c]quinoline-8-
carboxylic acid hydrochloride (24e)
1049 cmÀ1
.
5.44. 2-{(3R)-3-[(tert-butoxycarbonyl)amino]piperidin-1-yl}-5-
methyl-3-(2-methylbenzyl)-4-oxo-4,5-dihydro-3H-imidazo[4,5-
c]quinoline-8-carboxylic acid hydrochloride (24b)
Compound 24e was prepared from 21 in a manner similar to
that described for compound 24a with total yield of 54% for 3
steps as a white amorphous. 1H NMR (400 MHz, DMSO-d6) d
8.68 (d, J = 2.0 Hz, 1H), 8.42 (br s, 3H), 8.06 (dd, J = 2.0, 8.8 Hz,
1H), 7.68 (d, J = 9.0 Hz, 1H), 7.37–7.32 (m, 3H), 7.17–7.10 (m,
1H), 5.69 (d, J = 16.4 Hz, 1H), 5.61 (d, J = 16.4 Hz, 1H), 3.72–
3.66 (m, 4H), 3.38 (m, 1H), 3.24–3.13 (m, 2H), 2.88–2.84 (m,
1H), 1.98 (m, 1H), 1.85–1.82 (m, 1H), 1.64–1.51 (m, 2H); 13C
NMR (100 MHz, DMSO-d6) d 167.0, 157.8, 154.5, 142.2, 140.3,
140.2, 133.4, 130.8, 129.1, 127.6, 126.7, 125.4, 124.5, 123.7,
119.0, 116.1, 116.0, 52.4, 51.2, 47.5, 46.3, 29.3, 27.4, 22.0; HRMS
(ESI) [M+H]+ calcd for C24H25O3N5Cl 466.1640, found 466.1627;
IR (ATR): 1700, 1670, 1594, 1508, 1473, 1457, 1419, 1375,
Compound 24b was prepared from 21 in a manner similar to
that described for compound 24a with total yield of 70% for 3 steps
as a white amorphous. 1H NMR (400 MHz, DMSO-d6) d 8.71 (d,
J = 2.0 Hz, 1H), 8.35 (br s, 3H), 8.06 (dd, J = 2.0, 8.8 Hz, 1H), 7.65
(d, J = 8.8 Hz, 1H), 7.23–7.21 (m, 1H), 7.15–7.11 (m, 1H), 7.06–
7.02 (m, 1H), 6.47 (d, J = 7.6 Hz, 1H), 5.58 (d, J = 17.2 Hz, 1H),
5.51 (d, J = 17.2 Hz, 1H), 3.74–3.66 (m, 1H), 3.66 (s, 3H), 3.40–
3.38 (m, 1H), 3.28–3.23 (m, 1H), 3.13–3.10 (m, 1H), 2.90–2.85
(m, 1H), 2.38 (s, 3H), 1.94 (m, 1H), 1.76–1.75 (m, 1H), 1.61–1.57
(m, 1H), 1.51–1.46 (m, 1H); 13C NMR (100 MHz, DMSO-d6) d
167.1, 157.8, 154.2, 141.1, 140.2, 136.1, 134.6, 130.2, 129.0,
127.0, 126.3, 124.5, 124.4, 123.7, 119.3, 116.0, 116.0, 52.3, 50.9,
46.4, 46.2, 29.1, 27.4, 22.0, 18.9; HRMS (ESI) [M+H]+ calcd for
1313, 1216, 1110 cmÀ1
.
5.48. 2-[(3R)-3-aminopiperidin-1-yl]-3-(4-chlorobenzyl)-5-
methyl-4-oxo-4,5-dihydro-3H-imidazo[4,5-c]quinoline-8-
carboxylic acid hydrochloride (24f)
C
25H28O3N5 446.2187, found 446.2173; IR (ATR): 1700, 1670,
1623, 1596, 1506, 1457, 1386, 1317, 1245, 1220, 1106, 1051 cmÀ1
.
5.45. 2-[(3R)-3-aminopiperidin-1-yl]-3-(2-methoxybenzyl)-5-
methyl-4-oxo-4,5-dihydro-3H-imidazo[4,5-c]quinoline-8-
carboxylic acid hydrochloride (24c)
Compound 24f was prepared from 21 in a manner similar to
that described for compound 24a with total yield of 86% for 3 steps
as a white amorphous. 1H NMR (400 MHz, DMSO-d6) d 8.67 (d,
J = 1.9 Hz, 1H), 8.42 (br s, 3H), 8.04 (dd, J = 1.9, 8.8 Hz, 1H), 7.65
(d, J = 8.8 Hz, 1H), 7.36 (d, J = 8.4 Hz, 2H), 7.21 (d, J = 8.4 Hz, 2H),
5.66 (d, J = 16.0 Hz, 1H), 5.60 (d, J = 16.0 Hz, 1H), 3.71–3.65 (m,
4H), 3.37 (m, 1H), 3.23–3.14 (m, 2H), 2.89–2.84 (m, 1H), 1.97 (m,
1H), 1.85–1.82 (m, 1H), 1.63–1.52 (m, 2H); 13C NMR (100 MHz,
Compound 24c was prepared from 21 in a manner similar to
that described for compound 24a with total yield of 11% for 3 steps
as a white amorphous. 1H NMR (400 MHz, DMSO-d6) d 8.69 (d,
J = 2.0 Hz, 1H), 8.28 (br s, 3H), 8.05 (dd, J = 2.0, 8.8 Hz, 1H), 7.66

5880
Y. Ikuma et al. / Bioorg. Med. Chem. 20 (2012) 5864–5883
DMSO-d6) d 167.0, 157.7, 154.5, 141.1, 140.1, 136.8, 132.1, 129.1,
128.8, 128.7, 124.5, 123.7, 119.0, 116.0, 115.9, 52.4, 51.2, 47.5,
46.3, 29.3, 27.4, 22.0; HRMS (ESI) [M+H]+ calcd for C24H25O3N5Cl
466.1640, found 466.1624; IR (ATR): 1700, 1670, 1596, 1506,
5.52. 2-[(3R)-3-aminopiperidin-1-yl]-3-(cyclohexylmethyl)-5-
methyl-4-oxo-4,5-dihydro-3H-imidazo[4,5-c]quinoline-8-
carboxylic acid hydrochloride (24j)
1490, 1471, 1317, 1218 cmÀ1
.
Compound 24j was prepared from 21 in a manner similar to
that described for compound 24a with total yield of 60% for 3 steps
as a white amorphous. 1H NMR (400 MHz, DMSO-d6) d 8.68 (br s,
1H), 8.44 (br s, 3H), 8.04 (d, J = 7.7 Hz, 1H), 7.67 (d, J = 7.7 Hz,
1H), 4.19 (br s, 2H), 3.71 (s, 3H), 3.48–3.38 (m, 3H), 3.12–3.07
(m, 1H), 2.96 (m, 1H), 2.11 (br s, 1H), 1.88–1.61 (m, 7H), 1.33–
0.84 (m, 7H); 13C NMR (100 MHz, DMSO-d6) d 167.0, 157.8,
154.5, 140.7, 140.2, 129.0, 124.4, 123.8, 118.9, 116.0, 115.7, 52.8,
51.0, 50.9, 46.7, 43.8, 29.8, 29.3, 27.8, 26.0, 25.3, 22.8; HRMS
(ESI) [M+H]+ calcd calcd for C24H32O3N5 438.2500, found
438.2484; IR (ATR): 1699, 1670, 1592, 1521, 1508, 1465, 1457,
5.49. 2-[(3R)-3-aminopiperidin-1-yl]-3-(3-methoxybenzyl)-5-
methyl-4-oxo-4,5-dihydro-3H-imidazo[4,5-c]quinoline-8-
carboxylic acid hydrochloride (24g)
Compound 24g was prepared from 21 in a manner similar to
that described for compound 24a with total yield of 78% for 3 steps
as a white amorphous. 1H NMR (400 MHz, DMSO-d6) d 8.68 (d,
J = 2.0 Hz, 1H), 8.40 (br s, 3H), 8.05 (dd, J = 2.0, 8.9 Hz, 1H), 7.66
(d, J = 8.9 Hz, 1H), 7.23–7.19 (m, 1H), 6.82–6.78 (m, 2H), 6.70 (d,
J = 7.7 Hz, 1H), 5.64 (d, J = 16.4 Hz, 1H), 5.57 (d, J = 16.4 Hz, 1H),
3.74–3.64 (m, 7H), 3.37–3.36 (m, 1H), 3.22–3.17 (m, 2H), 2.88–
2.83 (m, 1H), 2.00–1.97 (m, 1H), 1.83–1.80 (m, 1H), 1.62–1.51
(m, 2H); 13C NMR (100 MHz, DMSO-d6) d 167.0, 159.5, 157.7,
154.5, 141.0, 140.1, 139.4, 130.0, 129.1, 124.5, 123.7, 119.1,
118.7, 116.0, 116.0, 115.9, 112.7, 55.2, 52.4, 51.0, 48.0, 46.4, 29.3,
27.5, 22.2; HRMS (ESI) [M+H]+ calcd calcd for C25H28O4N5
462.2136, found 462.2120; IR (ATR): 1700, 1670, 1652, 1594,
1419, 1375, 1305, 1253, 1230, 1112, 1043 cmÀ1
.
5.53. 2-[(3R)-3-aminopiperidin-1-yl]-5-methyl-3-(3-methylbut-
2-en-1-yl)-4-oxo-4,5-dihydro-3H-imidazo[4,5-c]quinoline-8-
carboxylic acid hydrochloride (24k)
Compound 24k was prepared from 21 in a manner similar to
that described for compound 24a with total yield of 17% for 3 steps
as a white amorphous. 1H NMR (400 MHz, DMSO-d6) d 8.68 (d,
J = 1.3 Hz, 1H), 8.47 (br s, 3H), 8.03 (d, J = 8.8 Hz, 1H), 7.66 (dd,
J = 1.3, 8.8 Hz, 1H), 5.39 (m, 1H), 5.00–4.95 (m, 1H), 4.90–4.83
(m, 1H), 3.75 (m, 1H), 3.70 (s, 3H), 3.48–3.38 (m, 2H), 3.32–3.20
(m, 1H), 3.09–3.02 (m, 1H), 2.08–1.99 (m, 1H), 1.93 (br s, 2H),
1.78–1.66 (m, 1H), 1.19 (s, 3H), 1.18 (s, 3H); 13C NMR (100 MHz,
DMSO-d6) d 167.0, 156.7, 154.2, 140.1, 136.4, 129.0, 124.4, 123.7,
123.7, 120.8, 118.9, 115.9, 115.5, 52.8, 51.0, 46.5, 43.5, 29.4, 29.4,
29.3, 27.6, 22.4; HRMS (ESI) [M+H]+ calcd for C22H28O3N5
410.2187, found 410.2176; IR (ATR): 1716, 1683, 1635, 1508,
1558, 1506, 1456, 1375, 1218, 1049 cmÀ1
.
5.50. 2-[(3R)-3-aminopiperidin-1-yl]-3-(4-methoxybenzyl)-5-
methyl-4-oxo-4,5-dihydro-3H-imidazo[4,5-c]quinoline-8-
carboxylic acid hydrochloride (24h)
Compound 24h was prepared from 21 in a manner similar to
that described for compound 24a with total yield of 54% for 3 steps
as a white amorphous. 1H NMR (400 MHz, DMSO-d6) d 8.67 (d,
J = 1.9 Hz, 1H), 8.47 (br s, 3H), 8.04 (dd, J = 1.9, 8.8 Hz, 1H), 7.65
(d, J = 8.8 Hz, 1H), 7.16 (d, J = 8.6 Hz, 2H), 6.86 (d, J = 8.6 Hz, 2H),
5.60 (d, J = 15.2 Hz, 1H), 5.53 (d, J = 15.2 Hz, 1H), 3.72–3.65 (m,
7H), 3.39–3.38 (m, 1H), 3.23–3.18 (m, 2H), 2.91–2.85 (m, 1H),
2.01 (m, 1H), 1.84–1.83 (m, 1H), 1.64–1.55 (m, 2H); 13C NMR
(100 MHz, DMSO-d6) d 167.0, 158.7, 157.5, 154.5, 140.8, 140.1,
129.6, 129.1, 128.3, 124.4, 123.7, 118.9, 116.0, 115.7, 114.1, 55.2,
52.5, 51.1, 47.6, 46.4, 29.3, 27.5, 22.2; HRMS (ESI) [M+H]+ calcd
for C25H28O4N5 462.2136, found 462.2119; IR (ATR): 1700, 1670,
1596, 1511, 1457, 1378, 1309, 1243, 1176, 1110, 1025 cmÀ1; Anal.
calcd calcd for C25H27O4N5Á3HClÁ2.25H2O: C, 49.11; H, 5.69; N,
11.45, found: C, 49.31; H, 5.63; N, 11.23.
1473, 1456, 1375, 1311, 1216 cmÀ1
.
5.54. 2-[(3R)-3-aminopiperidin-1-yl]-3-(but-2-yn-1-yl)-5-
methyl-4-oxo-4,5-dihydro-3H-imidazo[4,5-c]quinoline-8-
carboxylic acid hydrochloride (24l)
Compound 24l was prepared from 21 in a manner similar to
that described for compound 24a with total yield of 41% for 3 steps
as a white amorphous. 1H NMR (400 MHz, DMSO-d6) d 8.63 (d,
J = 2.0 Hz, 1H), 8.25 (br s, 3H), 8.05 (dd, J = 2.0, 8.8 Hz, 1H), 7.67
(d, J = 8.8 Hz, 1H), 5.18 (d, J = 19.2 Hz, 1H), 5.12 (d, J = 19.2 Hz,
1H), 3.75 (s, 3H), 3.60–3.48 (m, 3H), 3.31–3.19 (m, 2H), 2.04–2.01
(m, 1H), 1.94–1.90 (m, 1H), 1.79 (s, 3H), 1.76–1.67 (m, 2H); 13C
NMR (100 MHz, DMSO-d6) d 167.1, 157.2, 154.3, 141.1, 140.2,
129.0, 124.4, 123.6, 118.6, 116.0, 116.0, 81.0, 74.6, 52.1, 50.8,
46.2, 35.3, 27.5, 25.0, 22.0, 3.3; HRMS (ESI) [M+H]+ calcd for
5.51. 2-[(3R)-3-aminopiperidin-1-yl]-3-[2-(2-chlorophenyl)
ethyl]-5-methyl-4-oxo-4,5-dihydro-3H-imidazo[4,5-c]
quinoline-8-carboxylic acid hydrochloride (24i)
C
21H24O3N5 394.1874, found 394.1874; IR (ATR): 1699, 1652,
Compound 24i was prepared from 21 in a manner similar to
that described for compound 24a with total yield of 25% for 3 steps
as a white amorphous. 1H NMR (400 MHz, DMSO-d6) d 8.62 (d,
J = 1.6 Hz, 1H), 8.31 (br s, 3H), 8.05 (dd, J = 1.6, 8.8 Hz, 1H), 7.69
(d, J = 8.8 Hz, 1H), 7.41 (d, J = 7.8 Hz, 1H), 7.24–7.21 (m, 1H),
7.16–7.12 (m, 1H), 6.99 (d, J = 6.9 Hz, 1H), 4.53 (t, J = 6.0 Hz, 2H),
3.75 (s, 3H), 3.69–3.65 (m, 1H), 3.39–3.36 (m, 1H), 3.21 (t,
J = 6.0 Hz, 2H), 3.10–3.06 (m, 1H), 2.94–2.91 (m, 1H), 2.83–2.78
(m, 1H), 2.06–2.03 (m, 1H), 1.77 (m, 1H), 1.57–1.49 (m, 2H); 13C
NMR (100 MHz, DMSO-d6) d 167.0, 157.7, 154.6, 141.3, 140.2,
135.4, 133.4, 131.4, 129.3, 129.0, 129.0, 128.9, 127.4, 124.4,
123.7, 118.9, 116.0, 52.8, 51.0, 46.6, 44.6, 34.4, 29.4, 27.9, 22.8;
HRMS (ESI) [M+H]+ calcd for C25H27O3N5Cl 480.1797, found
480.1782; IR (ATR): 1699, 1646, 1569, 1498, 1437, 1386, 1303,
1569, 1538, 1506, 1457, 1375, 1309, 1241, 1110 cmÀ1
.
5.55. 2-[(3R)-3-aminopiperidin-1-yl]-3-(2,5-dichlorobenzyl)-5-
methyl-4-oxo-4,5-dihydro-3H-imidazo[4,5-c]quinoline-8-
carboxylic acid hydrochloride (24m)
Compound 24m was prepared from 21 in a manner similar to
that described for compound 24a with total yield of 40% for 3 steps
as a white amorphous. 1H NMR (400 MHz, DMSO-d6) d 8.70 (d,
J = 2.0 Hz, 1H), 8.42 (br s, 3H), 8.06 (dd, J = 2.0, 8.9 Hz, 1H), 7.65
(d, J = 8.9 Hz, 1H), 7.56 (d, J = 8.5 Hz, 1H), 7.40 (dd, J = 2.2, 8.5 Hz,
1H), 6.86 (d, J = 2.2 Hz, 1H), 5.58 (d, J = 17.6 Hz, 1H), 5.52 (d,
J = 17.6 Hz, 1H), 3.72–3.69 (m, 1H), 3.63 (s, 3H), 3.37 (m, 1H),
3.30–3.24 (m, 1H), 3.15–3.10 (m, 1H), 2.93–2.88 (m, 1H),
1255, 1238, 1114, 1049, 1033 cmÀ1
.

Y. Ikuma et al. / Bioorg. Med. Chem. 20 (2012) 5864–5883
5881
1.98–1.97 (m, 1H), 1.78 (m, 1H), 1.64–1.47 (m, 2H); 13C NMR
(100 MHz, DMSO-d6) d 167.0, 157.7, 154.2, 141.1, 140.2, 137.4,
132.4, 131.3, 130.0, 129.2, 129.1, 127.1, 124.5, 123.8, 119.1,
116.1, 115.8, 52.2, 50.9, 46.5, 46.2, 29.2, 27.4, 22.0; HRMS (ESI)
[M+H]+ calcd for C24H24O3N5Cl2 500.1251, found 500.1240; IR
(ATR): 1652, 1646, 1623, 1558, 1506, 1457, 1419, 1386, 1313,
5.59. Methyl 2-{(3R)-3-[(tert-butoxycarbonyl)amino]piperidin-
1-yl}-3-(5-fluoro-2-methylbenzyl)-5-methyl-4-oxo-4,5-
dihydro-3H-imidazo[4,5-c]quinoline-7-carboxylate (27)
Compound 27 was prepared from 25 in a manner similar to that
described for compound 22a with a yield of 66% as a white amor-
phous. 1H NMR (400 MHz, CDCl3) d 8.35 (d, J = 8.2 Hz, 1H), 8.15 (d,
J = 1.0 Hz, 1H), 7.97 (d, J = 8.2 Hz, 1H), 7.16–7.12 (m, 1H), 6.85–6.80
(m, 1H), 6.24 (dd, J = 2.3, 9.8 Hz, 1H), 6.03 (br s, 1H), 5.62 (d,
J = 16.8 Hz, 1H), 5.48 (d, J = 16.8 Hz, 1H), 3.99 (s, 3H), 3.84–3.82
(m, 1H), 3.79 (s, 3H), 3.44 (dd, J = 3.3, 12.8 Hz, 1H), 3.19–3.10 (m,
3H), 1.80–1.67 (m, 3H), 1.56–1.46 (m, 1H), 1.46 (s, 9H); 13C NMR
(100 MHz, CDCl3) d 166.8, 161.5 (d, 1J (C, F) = 242 Hz), 158.0,
155.1, 154.9, 141.0, 137.6 (d, 3J (C, F) = 6.8 Hz), 137.1, 131.6 (d, 3J
(C, F) = 7.8 Hz), 129.9 (d, 4J (C, F) = 2.9 Hz), 129.2, 122.8, 122.7,
120.4, 120.3, 116.3, 113.7 (d, 2J (C, F) = 21 Hz), 111.4 (d, 2J (C, F)
= 23 Hz), 79.0, 55.0, 52.3, 51.2, 46.2, 45.9, 29.5, 29.0, 28.3, 21.7,
18.3; HRMS (ESI) [M+H]+ calcd for C31H37O5N5F 578.2773, found
578.2766; IR(ATR): 1716, 1652, 1506, 1307, 1259, 1220, 1164,
1216, 1101, 1049 cmÀ1
.
5.56. 2-[(3R)-3-aminopiperidin-1-yl]-3-(2-chloro-5-
fluorobenzyl)-5-methyl-4-oxo-4,5-dihydro-3H-imidazo[4,5-
c]quinoline-8-carboxylic acid hydrochloride (24n)
Compound 24n was prepared from 21 in a manner similar to
that described for compound 24a with total yield of 75% for 3 steps
as a white amorphous. 1H NMR (400 MHz, DMSO-d6) d 8.71 (d,
J = 2.0 Hz, 1H), 8.40 (br s, 3H), 8.06 (dd, J = 2.0, 8.8 Hz, 1H), 7.67
(d, J = 8.8 Hz, 1H), 7.59–7.56 (m, 1H), 7.22–7.17 (m, 1H), 6.64 (dd,
J = 2.8, 9.4 Hz, 1H), 5.57 (d, J = 17.6 Hz, 1H), 5.52 (d, J = 17.6 Hz,
1H), 3.72–3.67 (m, 1H), 3.64 (s, 3H), 3.41–3.37 (m, 1H), 3.29–
3.24 (m, 1H), 3.12–3.09 (m, 1H), 2.93–2.88 (m, 1H), 1.97 (m, 1H),
1.80–1.77 (m, 1H), 1.63–1.51 (m, 2H); 13C NMR (100 MHz,
DMSO-d6) d 167.0, 161.3 (d, 1J (C, F) = 243 Hz), 157.5, 154.2,
140.9, 140.2, 137.8 (d, 3J (C, F) = 7.4 Hz), 131.4 (d, 3J (C, F) =
8.4 Hz), 129.2, 126.4 (d, 4J (C, F) = 2.6 Hz), 124.5, 123.8, 119.1,
116.1 (d, 2J (C, F) = 24 Hz), 116.0, 115.7, 114.5 (d, 2J (C, F) =
25 Hz), 52.2, 51.0, 46.7, 46.1, 46.1, 29.2, 27.4, 22.0; HRMS (ESI)
[M+H]+ calcd for C24H24O3N5ClF 484.1546, found 484.1533; IR
1108 cmÀ1
.
5.60. 2-[(3R)-3-aminopiperidin-1-yl]-3-(2-chloro-5-
fluorobenzyl)-5-methyl-4-oxo-4,5-dihydro-3H-imidazo[4,5-c]-
quinoline-7-carboxylic acid hydrochloride (28)
Compound 28 was prepared from 26 in a manner similar to that
described for compound 24a with total yield of 90% for 2 steps as a
white powder. All of the following equipment data is methane sul-
fonic acid salt of 28. Mp 208–211 °C; 1H NMR (400 MHz, DMSO-d6)
d 8.20 (d, J = 8.2 Hz, 1H), 8.07 (d, J = 1.2 Hz, 1H), 7.98 (br s, 3H), 7.90
(dd, J = 1.3, 8.2 Hz, 1H), 7.60–7.57 (m, 1H), 7.22–7.17 (m, 1H), 6.60
(dd, J = 3.0, 9.4 Hz, 1H), 5.57 (s, 2H), 3.67 (s, 3H), 3.62 (dd, J = 2.8,
12.4 Hz, 1H), 3.38 (br s, 1H), 3.23–3.18 (m, 1H), 3.11–3.08 (m,
1H), 2.89–2.88 (m, 1H), 2.34 (s, 3H), 1.95 (m, 1H), 1.78 (m, 1H),
1.57–1.55 (m, 2H); 13C NMR (100 MHz, DMSO-d6) d 167.3, 161.3
(d, 1J (C, F) = 243 Hz), 157.8, 154.3, 140.7, 137.9 (d, 3J (C, F) =
7.5 Hz), 137.1, 131.4 (d, 3J (C, F) = 8.7 Hz), 130.4, 126.4 (d, 4J (C,
F) = 2.7 Hz), 123.0, 122.4, 120.2, 119.7, 116.7, 116.2 (d, 2J (C, F) =
22.7 Hz), 114.4 (d, 2J (C, F) = 24.6 Hz), 52.3, 51.2, 46.6, 46.3, 29.0,
27.5, 22.0; HRMS (ESI) [M+H]+ calcd for C24H24O3N5ClF 484.1546,
found 484.1547; IR(ATR): 1673, 1639, 1467, 1151, 1124,
(ATR): 1714, 1670, 1627, 1594, 1471, 1425, 1251, 1224, 1112 cmÀ1
.
5.57. Methyl 2-{(3R)-3-[(tert-butoxycarbonyl)amino]piperidin-
1-yl}-5-methyl-4-oxo-4,5-dihydro-3H-imidazo[4,5-c]quinoline-
7-carboxylate (25)
Compound 25 was prepared from 7j in a manner similar to that
described for compound 21 with a yield of 54% as a white amor-
phous. 1H NMR (300 MHz, DMSO-d6) d 8.31 (br s, 1H), 8.10 (d,
J = 8.2 Hz, 1H), 8.04 (d, J = 1.1 Hz, 1H), 7.83 (dd, J = 1.1, 8.2 Hz,
1H), 6.98 (d, J = 8.0 Hz, 1H), 4.18–4.14 (m, 1H), 4.05–4.01 (m,
1H), 3.90 (s, 3H), 3.74 (s, 3H), 3.43 (br s, 1H), 2.97–2.90 (m, 1H),
2.83–2.76 (m, 1H), 1.85–1.74 (m, 2H), 1.55–1.51 (m, 1H), 1.40–
1.32 (m, 10H); HRMS (ESI) [M+H]+ calcd for C23H30O5N5
456.2241, found 456.2241; IR(ATR): 1716, 1683, 1646, 1618,
1041 cmÀ1
.
5.61. 2-[(3R)-3-aminopiperidin-1-yl]-3-(5-fluoro-2-
methylbenzyl)-5-methyl-4-oxo-4,5-dihydro-3H-imidazo[4,5-
c]quinoline-7-carboxylic acid hydrochloric acid (29)
1594, 1515, 1307, 1267, 1224, 1168, 1108 cmÀ1
.
5.58. Methyl 2-{(3R)-3-[(tert-butoxycarbonyl)amino]piperidin-
1-yl}-3-(2-chloro-5-fluorobenzyl)-5-methyl-4-oxo-4,5-dihydro-
3H-imidazo[4,5-c]quinoline-7-carboxylate (26)
Compound 29 was prepared from 27 in a manner similar to that
described for compound 24a with total yield of 84% for 2 steps as a
white powder. Mp 231–234 °C; 1H NMR (400 MHz, DMSO-d6, Me-
SO3H salt) d 8.20 (d, J = 8.2 Hz, 1H), 8.07 (d, J = 1.2 Hz, 1H), 7.98 (br
s, 3H), 7.90 (dd, J = 1.2, 8.2 Hz, 1H), 7.28–7.24 (m, 1H), 7.01–6.96
(m, 1H), 6.28 (dd, J = 2.8, 10.0 Hz, 1H), 5.51 (s, 2H), 3.67 (s, 3H),
3.63–3.62 (m, 1H), 3.39–3.38 (br s, 1H), 3.24–3.19 (m, 1H), 3.12–
3.09 (m, 1H), 2.89–2.85 (m, 1H), 2.35 (s, 3H), 2.34 (s, 3H), 1.94–
1.90 (m, 1H), 1.76–1.75 (m, 1H), 1.56–1.50 (m, 2H); 13C NMR
(100 MHz, DMSO-d6, HCl salt) d 167.4, 161.1 (d, 1J (C, F) =
239 Hz), 157.8, 154.2, 140.6, 138.7 (d, 3J (C, F) = 7.9 Hz), 137.1,
132.0 (d, 3J (C, F) = 8.0 Hz), 130.7 (d, 4J (C, F) = 2.9 Hz), 130.3,
123.0, 122.3, 120.3, 119.7, 116.7, 113.7 (d, 2J (C, F) = 23.0 Hz),
111.7 (d, 2J (C, F) = 22.8 Hz), 52.3, 51.7, 46.4, 46.3, 28.9, 27.5,
22.0, 18.2; HRMS (ESI) [M+H]+ calcd for C25H27O3N5F 464.2092,
found 464.2076; IR (ATR): 1716, 1683, 1635, 1506, 1473, 1456,
1230 cmÀ1; Anal. calcd for C25H26O3N5FÁ2.25MeSO3HÁ2.5H2O: C,
45.16; H, 5.56; N, 9.66, found: C, 45.06; H, 5.63; N, 9.76.
Compound 26 was prepared from 25 in a manner similar to that
described for compound 22a with a yield of 71% as a white amor-
phous. 1H NMR (400 MHz, CDCl3) d 8.35 (d, J = 8.1 Hz, 1H), 8.16 (d,
J = 1.0 Hz, 1H), 7.98 (d, J = 8.1 Hz, 1H), 7.40–7.36 (m, 1H), 6.94–6.89
(m, 1H), 6.44–6.41 (m, 1H), 6.09 (br s, 1H), 5.70 (d, J = 16.8 Hz, 1H),
5.61 (d, J = 16.8 Hz, 1H), 3.99 (s, 3H), 3.82 (m, 1H), 3.80 (s, 3H), 3.45
(dd, J = 3.2, 12.8 Hz, 1H), 3.24–3.09 (m, 3H), 1.77–1.46 (m, 4H), 1.46
(s, 9H); 13C NMR (100 MHz, CDCl3) d 166.6, 161.5 (d, 1J (C, F) =
245 Hz), 158.0, 155.1, 154.7, 141.0, 137.2 (d, 3J (C, F) = 7.3 Hz),
137.0, 130.7 (d, 3J (C, F) = 8.2 Hz), 129.2, 126.6 (d, 4J (C, F) =
2.9 Hz), 122.8, 122.6, 120.2, 120.1, 116.3, 115.6 (d, 2J (C, F) =
23 Hz), 113.7 (d, 2J (C, F) = 25 Hz), 78.9, 54.8 52.3, 51.4, 46.1,
45.7, 29.3, 29.0, 28.3, 21.6; HRMS (ESI) [M+H]+ calcd for
C
30H34O5N5ClF 598.2227, found 598.2227; IR(ATR): 1716, 1652,
1506, 1471, 1309, 1240, 1220, 1168, 1110 cmÀ1
.

5882
Y. Ikuma et al. / Bioorg. Med. Chem. 20 (2012) 5864–5883
5.62. 2-[(3R)-3-aminopiperidin-1-yl]-3-(2-chlorobenzyl)-3,5-
dihydro-4H-imidazo[4,5-c]quinolin-4-one (2)
5.65. 2-[(3R)-3-aminopiperidin-1-yl]-5-benzyl-3-(2-
chlorobenzyl)-3,5-dihydro-4H-imidazo[4,5-c]quinolin-4-one
hydrochloride (2d)
Compound 2 was prepared from 32 in a manner similar to that
described for compound 8t with a yield of 83% as a white amor-
phous. 1H NMR (300 MHz, DMSO-d6) d 11.60 (s, 1H), 8.28 (br s,
3H), 7.50–7.26 (m, 7H), 6.69 (m, 1H), 5.63 (s, 2H), 3.65–3.62 (m,
1H), 3.24–3.07 (m, 2H), 2.94 (m, 1H), 2.81 (m, 1H), 1.93 (m, 1H),
1.74 (m, 1H), 1.52 (m, 2H); 13C NMR (100 MHz, DMSO-d6) d
157.1, 154.8, 142.2, 136.6, 135.3, 131.1, 129.5, 129.1, 128.3,
127.8, 127.1, 122.2, 121.7, 119.4, 116.1, 115.5, 52.4, 51.1, 46.4,
46.2, 27.5, 22.2; HRMS (ESI) [M+H]+ calcd for C22H23ON5Cl
408.1586, found 408.1576; IR (ATR): 1652, 1616, 1506, 1473,
Compound 2d was prepared from 32 in a manner similar to that
described for compound 2b with total yield of 69% for 2 steps as a
white amorphous. 1H NMR (400 MHz, DMSO-d6) d 8.40 (br s, 3H),
8.21 (d, J = 7.7 Hz, 1H), 7.50 (d, J = 7.7 Hz, 1H), 7.43 (d, J = 3.6 Hz,
1H), 7.32–7.16 (m, 6H), 7.10 (d, J = 7.3 Hz, 2H), 6.76 (d, J = 7.4 Hz,
1H), 5.67 (s, 2H), 5.52 (br s, 2H), 3.69–3.64 (m, 1H), 3.37–3.25
(m, 2H), 3.16–3.13 (m, 1H), 2.92–2.87 (m, 1H), 1.97 (m, 1H), 1.78
(m, 1H), 1.63–1.52 (m, 2H); 13C NMR (100 MHz, DMSO-d6) d
157.0, 153.8, 140.7, 136.6, 135.9, 134.6, 130.5, 128.8, 128.4,
128.1, 128.0, 127.1, 126.5, 126.4, 125.9, 121.9, 121.8, 118.0,
115.8, 115.6, 51.7, 50.5, 45.9, 45.6, 43.5, 26.7, 21.4; HRMS (ESI)
[M+H]+ calcd for C29H29ON5Cl 498.2055, found 498.2042; IR
(ATR): 1670, 1646, 1637, 1610, 1575, 1540, 1515, 1508, 1442,
1396, 1353, 1326, 1176, 1153 cmÀ1; Anal. calcd for C29H28ON5-
ClÁ2HClÁÁ1.75H2O: C, 57.81; H, 5.60; N, 11.62, found: C, 58.15; H,
5.51; N, 11.28.
1444, 1419, 1386, 1214, 1049 cmÀ1
.
5.63. 2-[(3R)-3-aminopiperidin-1-yl]-3-(2-chlorobenzyl)-5-
ethyl-3,5-dihydro-4H-imidazo[4,5-c]quinolin-4-one
hydrochloride (2b)
To a solution of 32 (61.3 mg, 0.121 mmol) and K2CO3 (50.0 mg,
0.363 mmol) in DMF (2 ml) was added EtI (29.0 ll, 0.363 mmol).
The reaction mixture was stirred at room temperature for 12 h,
quenched with saturated NH4Cl aqueous solution, and extracted
with EtOAc. The organic layer was washed with saturated NH4Cl
aqueous solution twice and brine, dried over Na2SO4, and concen-
trated under reduced pressure. The residue was purified by silica-
gel column chromatography to give tert-Butyl {(3R)-1-[3-(2-chloro-
benzyl)-5-ethyl-4-oxo-4,5-dihydro-3H-imidazo[4,5-c]quinolin-2-
yl]piperidin-3-yl}carbamate (58.9 mg, yield 91%). To a solution of
the tert-Butyl {(3R)-1-[3-(2-chlorobenzyl)-5-ethyl-4-oxo-4,5-dihy-
dro-3H-imidazo[4,5-c]quinolin-2-yl]piperidin-3-yl}carbamate (58.9 mg,
0.11 mmol) in 1,4-dioxane (0.5 ml) was added 4 N HCl-1,4-dioxane
(2 ml). The reaction mixture was stirred at room temperature for
2 h and concentrated under reduced pressure to give 34a
(41.8 mg, yield 80%) as a white powder. Mp 207–210 °C; 1H NMR
(400 MHz, DMSO-d6) d 8.30 (br s, 3H), 8.19 (d, J = 7.4 Hz, 1H),
7.64 (d, J = 8.5 Hz, 1H), 7.59–7.55 (m, 1H), 7.51 (d, J = 7.8 Hz,
1H), 7.36–7.28 (m, 2H), 7.24–7.20 (m, 1H), 6.68 (d, J = 7.4
Hz, 1H), 5.64 (s, 2H), 3.70–3.58 (m, 2H), 3.49–3.45 (m, 1H), 3.31
(br s, 1H), 3.24–3.19 (m, 1H), 3.11–3.08 (m, 1H), 2.87–2.82 (m,
1H), 1.98–1.94 (m, 1H), 1.75 (br s, 1H), 1.59–1.51 (m, 2H), 1.16
(t, J = 6.8 Hz, 3H); 13C NMR (100 MHz, DMSO-d6) d 156.7, 153.2,
140.4, 135.5, 134.7, 130.4, 128.8, 128.4, 128.2, 127.1, 126.3,
121.8, 121.6, 118.1, 115.8, 114.9, 51.7, 50.4, 45.6, 43.1, 35.5, 26.7,
21.4, 12.6; HRMS (ESI) [M+H]+ calcd for C24H27ON5Cl 436.1899,
found 436.1887; IR (ATR): 1670, 1637, 1592, 1477, 1442, 1240,
5.66. {2-[2-{(3R)-3-[(tert-butoxycarbonyl)amino]piperidin-1-
yl}-1-(2-chlorobenzyl)-5-(ethoxycarbonyl)-1H-imidazol-4-yl]-
5-methoxyphenyl}(hydroxy)oxoammonium (31)
A mixture of 3 (353 mg, 0.599 mmol), 2-(4-methoxy-2-nitro-
phenyl)-4,4,5,5-tetramethyl-1,3,2-dioxaborolane (251 mg, 0.90
mmol), Pd(PPh3)4 (69.2 mg, 0.060 mmol) and Na2CO3 (127 mg,
1.20 mmol) was stirred under reflux for 10 h. After cooling to room
temperature, the mixture was diluted with EtOAc and filtered
through a Celite pad. The filtrate was washed with saturated NaH-
CO3 aqueous solution, and the organic layer was dried over Na2SO4
and concentrated under reduced pressure. The residue was puri-
fied by silica-gel column chromatography to give 31 (329.0 mg,
yield 89%) as a pale yellow amorphous. 1H NMR (300 MHz, CDCl3)
d 7.57 (d, J = 2.6 Hz, 1H), 7.51 (d, J = 8.6 Hz, 1H), 7.41–7.38 (m, 1H),
7.25–7.20 (m, 2H), 7.17 (dd, J = 2.6, 8.4 Hz, 1H), 6.68 (d, J =6.8 Hz,
1H), 5.50 (s, 2H), 5.16–5.13 (m, 1H), 3.93 (q, J = 7.0 Hz, 2H), 3.91
(s, 3H), 3.77 (br s, 1H), 3.34 (dd, J = 3.3, 12.1 Hz, 1H), 2.98–2.94
(m, 3H), 1.74 (m, 2H), 1.63–1.55 (m, 2H), 1.42 (s, 9H), 0.89 (t,
J = 7.0 Hz, 3H); 13C NMR (75 MHz, CDCl3) d 159.7, 159.5, 155.6,
155.0, 149.8, 143.3, 135.1, 133.3, 131.7, 129.3, 128.4, 127.4,
126.2, 122.7, 118.7, 116.8, 109.0, 79.2, 60.3, 55.9, 55.7, 51.9, 46.9,
46.0, 29.5, 28.3, 24.8, 22.2; HRMS (ESI) [M+H]+ calcd for
C
30H37O7N5Cl 614.2376, found 614.2360; IR (ATR): 1699, 1527,
1506, 1490, 1456, 1444, 1363, 1353, 1330, 1297, 1276, 1232,
1170, 1072, 1049, 1039 cmÀ1
1199, 1160, 1122, 1085, 1051, 1041, 1027 cmÀ1
.
.
5.64. 2-[(3R)-3-aminopiperidin-1-yl]-3-(2-chlorobenzyl)-5-
propyl-3,5-dihydro-4H-imidazo[4,5-c]quinolin-4-one
hydrochloride (2c)
5.67. 2-[(3R)-3-aminopiperidin-1-yl]-3-(2-chlorobenzyl)-7-
methoxy-5-methyl-3,5-dihydro-4H-imidazo[4,5-c]quinolin-4-
one (7g)
Compound 2c was prepared from 32 in a manner similar to that
described for compound 2b with total yield of 60% for 2 steps as a
white powder. Mp 197–200 °C; 1H NMR (400 MHz, DMSO-d6) d
8.32 (br s, 3H), 8.19 (d, J = 7.6 Hz, 1H), 7.62 (d, J = 8.6 Hz, 1H),
7.58–7.54 (m, 1H), 7.56 (d, J = 7.8 Hz, 1H), 7.36–7.28 (m, 2H),
7.23–7.19 (m, 1H), 6.68 (d, J = 7.6 Hz, 1H), 5.63 (s, 2H), 4.22–4.18
(m, 2H), 3.71–3.64 (m, 1H), 3.26–3.21 (m, 2H), 3.11–3.08 (m,
1H), 2.88–2.83 (m, 1H), 1.97–1.95 (m, 1H), 1.75 (br s, 1H), 1.61–
1.48 (m, 4H), 0.88 (t, J = 7.3 Hz, 3H); 13C NMR (100 MHz, DMSO-
d6) d 156.7, 153.4, 140.3, 135.8, 134.6, 130.4, 128.8, 128.4, 128.2,
127.1, 126.3, 121.8, 121.6, 118.0, 115.7, 115.1, 51.7, 50.4, 45.7,
45.6, 41.8, 26.7, 21.4, 20.3, 10.5; HRMS (ESI) [M+H]+ calcd for
A mixture of Fe (253 mg, 4.53 mmol) in acetic acid (5 ml) was
stirred at 80 °C for 30 min. To this suspension was added 31
(278.3 mg, 0.453 mmol) in acetic acid (3 ml) dropwise, and the
mixture was stirred at 80 °C for 4 h. After cooling to room temper-
ature, the mixture was diluted with EtOAc and filtered through a
Celite pad. The filtrate was washed with water, saturated NaHCO3
aqueous solution twice and brine, dried over Na2SO4, and concen-
trated in vacuo. To a mixture of the residue and K2CO3 (125 mg,
0.906 mmol) in DMF (3 ml) was added MeI (56.4 ll, 0.906 mmol).
The reaction mixture was stirred at 65 °C for 7 h. After cooling to
room temperature, the reaction mixture was quenched with satu-
rated NH4Cl aqueous solution, and extracted with EtOAc. The or-
ganic layer was washed with saturated NH4Cl aqueous solution
twice and brine, dried over Na2SO4, and concentrated under
C
25H29ON5Cl 450.2055, found 450.2044; IR (ATR): 1670, 1637,
1592, 1473, 1442, 1355, 1128, 1051, 1039 cmÀ1
.

Y. Ikuma et al. / Bioorg. Med. Chem. 20 (2012) 5864–5883
5883
10. Kim, D.; Wang, L.; Beconi, M.; Eiermann, G. J.; Fischer, M. H.; Huaibing, H.;
Hickey, G. J.; Kowalchick, J. E.; Leiting, B.; Lyons, K.; Marsilio, F.; McCann, M. E.;
Patel, R. A.; Petrov, A.; Scapin, G.; Patel, S. B.; Sinha Roy, R.; Wu, J. K.; Wyvratt,
M. J.; Zhang, B. B.; Zhu, L.; Thornberry, N. A.; Weber, A. E. J. Med. Chem. 2005, 48,
141.
11. Villhauer, E. B.; Brinkman, J. A.; Naderi, G. B.; Burkey, B. F.; Dunning, B. E.;
Prasad, K.; Mangold, B. L.; Russell, M. E.; Hughes, T. E. J. Med. Chem. 2003, 46,
2774.
12. Augeri, D. J.; Robl, J. A.; Betebenner, D. A.; Magnin, D. R.; Khanna, A.; Robertson,
J. G.; Wang, A.; Simpkins, L. M.; Taunk, P.; Huang, Q.; Han, S.-P.; Abboa-Offei, B.;
Cap, M.; Xin, L.; Tao, L.; Tozzo, E.; Welzel, G. E.; Egan, D. M.; Marcinkeviciene, J.;
Chang, S. Y.; Biller, S. A.; Kirby, M. S.; Parker, R. A.; Hamann, L. G. J. Med. Chem.
2005, 48, 5025.
13. Feng, J.; Zhang, Z.; Wallace, M. B.; Sttaford, J. A.; Kaldor, S. W.; Kassel, D. B.;
Navre, M.; Shi, L.; Skene, R. J.; Asakawa, T.; Takeuchi, K.; Xu, R.; Webb, D. R.;
Gwaltney, S. L. J. Med. Chem. 2007, 50, 2297.
reduced pressure. The residue was purified by silica-gel column
chromatography to give 7g (184.2 mg, yield 74% for 2 steps) as a
pale yellow amorphous. 1H NMR (300 MHz, CDCl3) d 8.20 (d,
J = 8.6 Hz, 1H), 7.39 (d, J = 7.9 Hz, 1H), 7.20–7.09 (m, 2H), 6.93–
6.88 (m, 2H), 6.68 (d, J = 7.1 Hz, 1H), 6.34 (br s, 1H), 5.73 (d,
J = 17.0 Hz, 1H), 5.61 (d, J = 17.0 Hz, 1H), 3.93 (s, 3H), 3.81 (br s,
1H), 3.69 (s, 3H), 3.41 (dd, J = 3.1, 13.0 Hz, 1H), 3.25 (dd, J = 4.6,
12.5 Hz, 1H), 3.06 (br s, 2H), 1.79–1.72 (m, 4H), 1.46 (s, 9H); 13C
NMR (75 MHz, CDCl3) d 160.8, 158.8, 156.1, 143.1, 139.8, 136.0,
132.6, 130.2, 129.1, 127.8, 127.2, 127.2, 124.7, 118.2, 111.6,
110.0, 100.5, 79.6, 56.2, 55.4, 52.3, 46.9, 46.4, 30.2, 29.7, 29.1,
22.0; HRMS (ESI) [M+H]+ calcd for C29H35O4N5Cl 552.2372, found
552.2371; IR (ATR): 1700, 1646, 1577, 1508, 1473, 1417, 1388,
14. Eckhardt, M.; Lanqkopf, E.; Mark, M.; Tadayyon, M.; Thomas, L.; Nar, H.;
Pfrengle, W.; Guth, B.; Lotz, R.; Sieger, P.; Fuchs, H.; Himmelsbach, F. J. Med.
Chem. 2007, 50, 6450.
1363, 1315, 1236, 1164, 1066, 1039 cmÀ1
.
15. Abbott, C. A.; Yu, D. M.; Woollatt, E.; Sutherland, G. R.; McCaughan, G. W.;
Gorrell, M. D. Eur. J. Biochem. 2000, 267, 6140.
5.68. 2-[(3R)-3-aminopiperidin-1-yl]-3-(2-chlorobenzyl)-7-
methoxy-5-methyl-3,5-dihydro-4H-imidazo[4,5-c]quinolin-4-
one (8g)
16. (a) Olsen, C.; Wagtmann, N. Gene 2002, 299, 185; (b) Ajami, K.; Abbott, C. A.;
McCaughan, G. W.; Gorrell, M. D. Biochim. Biophys. Acta 2004, 1679, 18.
17. Scallan, M. J.; Raj, B. K. M.; Calvo, B.; Garin-Chesa, P.; Sanz-Moncasi, M. P.;
Healey, J. H.; Old, L. J.; Rettig, W. Proc. Natl. Acad. Sci. U.S.A. 1994, 91, 5657.
18. Lankas, G. R.; Leiting, B.; Roy, R. S.; Eiermann, G. J.; Beconi, M. G.; Biftu, T.; Chan,
C. C.; Edmondson, S.; Feeney, W. P.; He, H.; Ippolito, D. E.; Kim, D.; Lyons, K. A.;
Ok, H. O.; Patel, R. A.; Petrov, A. N.; Pryor, K. A.; Qian, X.; Reigle, L.; Woods, A.;
Wu, J. K.; Zaller, D.; Zhang, X.; Zhu, L.; Weber, A. E.; Thornberry, N. A. Diabetes
2005, 54, 2988.
19. Burkey, B. F.; Hoffmann, P. K.; Hassiepen, U.; Trappe, J.; Juedes, M.; Foley, J. E.
Diabetes Obes. Metab. 2008, 10, 1057.
20. Rajesh, G.; Sameer, S. W.; Ranjeet, K. T.; Kishore, V. L. P.; Santosh, K. S.; Manojit,
P. Curr. Drug Targets 2009, 10, 71.
Compound 8g was prepared from 7g in a manner similar to that
described for compound 8t with a yield of 89% as a white amor-
phous. 1H NMR (400 MHz, DMSO-d6) d 8.41 (br s, 3H), 8.21 (d,
J = 8.4 Hz, 1H), 7.51 (d, J = 7.8 Hz, 1H), 7.32–7.28 (m, 1H), 7.25–
7.21 (m, 1H), 7.02–7.00 (m, 2H), 6.77 (d, J = 7.4 Hz, 1H), 5.59 (s,
2H), 3.89 (s, 3H), 3.70 (d, J = 10.2 Hz, 1H), 3.58 (s, 3H), 3.37–3.27
(m, 2H), 3.12–3.09 (m, 1H), 2.92–2.87 (m, 1H), 1.97–1.94 (m,
1H), 1.75 (m, 1H), 1.62–1.49 (m, 2H); 13C NMR (100 MHz, DMSO-
d6) d 160.3, 156.4, 154.2, 139.1, 135.2, 131.0, 129.5, 129.1, 128.4,
127.8, 127.1, 123.9, 116.9, 110.2, 109.0, 100.4, 55.8, 52.3, 51.0,
46.6, 46.3, 29.0, 27.2, 22.1; HRMS (ESI) [M+H]+ calcd for
21. (a) Pilar, G.-C.; Lloyd, J. O.; Wolfgang, J. R. Proc. Natl. Acad. Sci. U.S.A. 1990, 87,
7235; (b) Teresa, R.-M.; Nathalie, E. B.; Elena, V. S.; Dorothy, C. B. Oncogene
2004, 23, 5435.
22. Other series of our DPP-4 inhibitors were priviously reported, see; (a) Nishio,
Y.; Kimura, H.; Tosaki, S.; Sugaru, E.; Sakai, M.; Horiguchi, M.; Masui, Y.; Ono,
M.; Nakagawa, T.; Nakahira, H. Bioorg. Med. Chem. Lett. 2010, 20(24), 7246; (b)
Nishio, Y.; Kimura, H.; Sawada, N.; Sugaru, E.; Sakai, M.; Horiguchi, M.; Ono, M.;
Furuta, Y.; Sakai, M.; Masui, Y.; Otani, M.; Hashizuka, T.; Honda, Y.; Deguchi, J.;
Nakagawa, T.; Nakahira, H. Bioorg. Med. Chem. 2011, 19(18), 5490.
23. Published structures of DPP-4 with bound inhibitors include: (a) Kim, D.;
Wang, L.; Beconi, M.; Eiermann, G. J.; Fisher, M. H.; He, H.; Hickey, G. J.;
Kowalchick, J. E.; Leiting, B.; Lyons, K.; Marsilio, F.; McCann, M. E.; Patel, R. A.;
Petrov, A.; Scapin, G.; Patel, S. B.; Roy, R. S.; Wu, J. K.; Wyvratt, M. J.; Zhang, B.
B.; Zhu, L.; Thornberry, N. A.; Weber, A. E. J. Med. Chem. 2005, 48, 141; (b)
Hiramatsu, H.; Yamamoto, A.; Kyono, K.; Higashiyama, Y.; Fukushima, C.;
Shima, H.; Sugiyama, S.; Inaka, K.; Shimizu, R. Biol. Chem. 2004, 385, 561; (c)
Oefner, C.; D’Arcy, A.; MacSweeney, A.; Pierau, S.; Gardiner, R.; Dale, G. E. Acta
Crystallogr. Sect. D: Biol. Crystallogr. 2003, D59, 1206; (d) Rasmussen, H. B.;
Branner, S.; Wiberg, F. C.; Wagtmann, N. Nat. Struct. Mol. Biol. 2003, 10, 19.
24. The standard assay was modified from a previously published method [Ref.10,
27]. Briefly, human plasma and test compounds were incubated with surrogate
substrate (Gly-Pro-AMC) and after adding 5% acetic acid to stop the reaction,
amount of free AMC generated in proportion to DPP-4 activity was measured
fluorometrically. A typical reaction contains 50% human plsama, 50 uM Gly-
Pro-AMC and buffer (100 mM HEPES, pH 7.5, 0.1 mg/mL BSA).
25. Miyamoto, Y.; Banno, Y.; Yamashita, T.; Fujimoto, T.; Oi, S.; Moritoh, Y.;
Asakawa, T.; Kataoka, O.; Yashiro, H.; Takeuchi, K.; Suzuki, N.; Ikedo, K.;
Kosaka, T.; Tsubotani, S.; Tani, A.; Sasaki, M.; Funami, M.; Amano, M.;
Yamamoto, Y.; Aertgeerts, K.; Yano, J.; Maezaki, H. J. Med. Chem. 2011, 54, 831.
26. Ikuma, Y.; Nakahira, H. Tetrahedron 2011, 67(49), 9509.
27. Leiting, B.; Pryor, K. D.; Wu, J. K.; Marsilio, F.; Patel, R. A.; Craik, C. S.; Ellman, J.
A.; Cummings, R. T.; Thornberry, N. A. Biochem. J. 2003, 371, 525.
28. Gum, R. J.; Hickman, D.; Fagerland, J. A.; Heindel, M. A.; Gagne, G. D.; Schmidt, J.
M.; Michaelides, M. R.; Davidsen, S. K.; Ulrich, R. G. Biochem. Pharmacol. 2001,
62, 1661.
C
24H27O2N5Cl 452.1848, found 452.1838; IR (ATR): 1675, 1652,
1635, 1604, 1558, 1508, 1473, 1457, 1436, 1419, 1251, 1047 cmÀ1
.
Acknowledgments
Authors thank M. Honma and M. Tada for recording MS spectra
and K. Bando for performing the elemental analysis and T. Taniga-
wa for recording IR spectra.
References and notes
1. Colberg, S. R. ACSM’S Health Fitness J. 2008, 12, 16. For latest information, please
see the website of World Health Organization at http://www.who.int/diabetes/
facts/world_figures/en/.
2. Lewis, J. D.; Ferrara, A.; Peng, T.; Hedderson, M.; Bilker, W. B.; Quesenberry, C.
P., Jr.; Vaughn, D. J.; Nessel, L.; Selby, J.; Strom, B. L. Diabetes Care 2011, 34(4),
916.
3. Ferrara, A.; Lewis, J. D.; Quesenberry, C. P., Jr.; Peng, T.; Strom, B. L.; Van Den
Eeden, S. K.; Ehrlich, S. F.; Habel, L. A. Diabetes Care 2011, 34(4), 923.
4. (a) Arulmozhi, D. K.; Portha, B. Eur. J. Pharm. Sci. 2006, 28, 96; (b) Knudsen, L. B.
J. Med. Chem. 2004, 47, 4128.
5. (a) Kieffer, T. J.; Mclntosh, C. H. S.; Pederson, R. A. Endocrinology 1995, 136,
3585; (b) Deacon, C. F.; Nauck, M. A.; Toft-Nielson, M.; Pridal, L.; Willms, B.;
Holst, J. J. Diabetes 1995, 44, 1126.
6. For recent reviews see: (a) Havale, S. H.; Pal, M. Bioorg. Med. Chem. 2009, 17,
1783; (b) Mest, H.-J.; Mentlein, R. Diabetlogia 2005, 48, 616; (c) Weber, A. E. J.
Med. Chem. 2004, 47, 4135; (d) Augustyns, K.; Van der Veken, P.; Senten, K.;
Haemers, A. Expert Opin. Ther. Patents 2003, 13, 499.
7. Drucker, D. J.; Nauck, M. A. Lancet 2006, 368, 1696.
8. Ahren, B. Expert Opin. Emerg. Drugs 2008, 13, 593.
29. Mortuza, G. B.; Neville, W. A.; Delaney, J.; Waterfield, C. J.; Camilleri, P. Biochim.
Biophys. Acta 2003, 1631, 136.
30. Craig, J.; Elizabeth, M. M.; Zoran, R.; Grant, W. J. Med. Chem. 2006, 49, 5029.
9. (a) Pei, Z. Curr. Opin. Drug Discov. Devel. 2008, 11, 512; (b) Gwaltney, S. L., II Curr.
Top. Med. Chem. 2008, 8, 1545.