8-Hydroxyquinolin-2(1H)-one analogues as potential β2-agonists: Design, synthesis and activity study

Article abstract of DOI:10.1016/j.ejmech.2021.113697

β₂-Agonists that bind to plasmalemmal β₂-adrenoceptors causing cAMP accumulation are widely used as bronchodilators in chronic respiratory diseases. Here, we designed and synthesized a group of 8-hydroxyquinolin-2(1H)-one analogues and studied their β₂-agonistic activities with a cellular cAMP assay. Compounds B05 and C08 were identified as potent (EC₅₀ < 20 pM) and selective β₂-agonists among the compounds tested. They behaved as partial β₂-agonists in non-overexpressed HEK293 cells, and possessed rapid smooth muscle relaxant actions and long duration of action in isolated guinea pig tracheal strip preparations. In summary, B05 and C08 are β₂-agonists with potential applicability in chronic respiratory diseases.

Full text of DOI:10.1016/j.ejmech.2021.113697

European Journal of Medicinal Chemistry 224 (2021) 113697
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European Journal of Medicinal Chemistry
journal homepage: http://www.elsevier.com/locate/ejmech
8-Hydroxyquinolin-2(1H)-one analogues as potential b2-agonists:
Design, synthesis and activity study
,
,
,
Gang Xing a b, Zhengxing Zhi a b, Ce Yi a b, Jitian Zou c, Xuefeng Jing d,
Anthony Yiu-Ho Woo c, Bin Lin a b, Li Pan a **, Yuyang Zhang c ***, Maosheng Cheng a
,
,
b,
,
, b, *
a Department of Medicinal Chemistry, School of Pharmaceutical Engineering, Shenyang Pharmaceutical University, Shenyang, 110016, China
b Key Laboratory of Structure-Based Drug Design and Discovery of Ministry of Education, Shenyang Pharmaceutical University, Shenyang, 110016, China
c Department of Pharmacology, School of Life Sciences and Biopharmaceutics, Shenyang Pharmaceutical University, Shenyang, 110016, China
d General Hospital of Fuxin Mining Industry Group of Liaoning Health Industry Group, Fuxin, 12300, China
a r t i c l e i n f o
a b s t r a c t
Article history:
b2-Agonists that bind to plasmalemmal b2-adrenoceptors causing cAMP accumulation are widely used as
bronchodilators in chronic respiratory diseases. Here, we designed and synthesized a group of 8-
hydroxyquinolin-2(1H)-one analogues and studied their b2-agonistic activities with a cellular cAMP
assay. Compounds B05 and C08 were identified as potent (EC50 < 20 pM) and selective b2-agonists
among the compounds tested. They behaved as partial b2-agonists in non-overexpressed HEK293 cells,
and possessed rapid smooth muscle relaxant actions and long duration of action in isolated guinea pig
tracheal strip preparations. In summary, B05 and C08 are b2-agonists with potential applicability in
chronic respiratory diseases.
Received 6 April 2021
Received in revised form
19 June 2021
Accepted 7 July 2021
Available online 10 July 2021
Keywords:
Asthma
COPD
© 2021 Elsevier Masson SAS. All rights reserved.
b2-adrenoceptor agonist
Indacaterol
Olodaterol
Formoterol
1. Introduction
tightness and cough. COPD is characterized by persistent respira-
tory symptoms and airflow limitation that is due to airway and/or
Asthma and chronic obstructive pulmonary disease (COPD) are
common chronic diseases of the pulmonary system [1,2]. According
to the Global Burden of Disease Study 2017, 544.9 million people
worldwide had a chronic respiratory disease in 2017 [3], which
account for 495,000 deaths due to asthma and 3.2 million deaths
due to COPD [4]. The Global Initiative for Asthma (GINA) defined
asthma as a heterogeneous disease of the airway characterized by
typical symptoms such as wheeze, shortness of breath, chest
alveolar abnormalities usually caused by significant exposure to
noxious particles or gases. Both genetic and environmental factors
contribute to the development of asthma and COPD [5e7]. Smok-
ing, second-hand smokes, household air pollution, ambient par-
ticulate matters, ozone, and occupational particulates are
considered as the six external causes for COPD. Smoking and
occupational exposures are also environmental risk factors for
asthma [8].
b2-Agonists, mAChR antagonists, PDE4 inhibitors and ICS
(inhaled corticosteroids) constitute the major drug classes for
pharmaceutical management of asthma and COPD [9,10]. b2-Ago-
nists are still the cornerstone for the treatment of chronic respi-
ratory diseases [11]. Inhaled long-acting b2-agonists have achieved
a vast development in the past two decades, resulting in the mar-
keting of drugs such as salmeterol [12,13], formoterol [14], inda-
caterol [15] and olodaterol [16,17], the latter two also known as the
ultra-long-acting b2-agonists. In addition, a number of small mol-
ecules are under clinical development, such as abediterol [18],
bedoradrine [19], and PF-610355 [20](Fig. 1).
* Corresponding author. Department of Medicinal Chemistry, School of Phar-
maceutical Engineering, Shenyang Pharmaceutical University, Shenyang, 110016,
China.
** Corresponding author. Department of Medicinal Chemistry, School of Phar-
maceutical Engineering, Shenyang Pharmaceutical University, Shenyang, 110016,
China
*** Corresponding author. Department of Medicinal Chemistry, School of Phar-
maceutical Engineering, Shenyang Pharmaceutical University, Shenyang, 110016,
China.
E-mail addresses: panli65@aliyun.com (L. Pan), 13614053862@163.com
(Y. Zhang), mscheng@syphu.edu.cn (M. Cheng).
https://doi.org/10.1016/j.ejmech.2021.113697
0223-5234/© 2021 Elsevier Masson SAS. All rights reserved.

G. Xing, Z. Zhi, C. Yi et al.
European Journal of Medicinal Chemistry 224 (2021) 113697
Fig. 1. The structure of salmeterol, formoterol, indacaterol, olodaterol, abediterol, bedoradrine, PF-610355, XY-1 (9g), XY-2 ((R)-18c), and XY-3 ((R)-18c).
We have previous synthesized compounds based on indacaterol
and olodaterol, and studied their biological activities as b2-agonists
[21,22]. Representative compounds XY-1, XY-2, and XY-3 (Fig. 1),
referring respectively to compounds 9g [21], (R)-18c [21] and (R)-
18c [22] in the original articles, had EC50 values ranging from 21e36
2. Results and discussion
2.1. Chemistry
The synthetic pathways for the primary amines starting through
commercially available different substituted benzaldehydes are
provided in Scheme 1, Scheme 2, and Scheme 3. Compounds 4e01
to 4e08 were obtained by Wittig reaction and reduction reaction
from benzaldehyde. Derivatives 8e01 to 8e14 were achieved
through aldol condensation, reduction, and Leuckart reaction. Un-
der the same condition to prepare compound 11 through Ritter
reaction and deacetylation, intermediate 11 was finally converted
into compounds 13e01 to 13e11 by treatment with MeMgBr.
The key intermediate 14 was prepared as described in our
previous study [21]. The synthetic pathway of the target com-
pounds was depicted in Scheme 4. Different amines reacted with
intermediate 14 in the presence of DMSO, MeOH and NaBH4 and
the subsequent Bn was removed under the condition of H2/Pd/C,
yielding compounds A01 to A08, B01 to B14, and C01 to C13.
Compounds (R,R)-B04, (R)-C07, and (R)-C08 were synthesized as
pM. Their b2
1.77 to 5.68 with compound XY-2 being the most selective. A high
b2 b1-selectivity is an important attribute for b2-agonists used as
/b1-selectivity (b2 pEC50 - b1 pEC50) varied widely from
/
bronchodilators for reduced cardiac side effects [23]. Here, we
report our renewed efforts in the discovery of highly potent and
selective b2-agonists. In the present study, the 5-(2-amino-1-
hydroxyethyl)-8-hydroxyquinolin-2(1H)-one scaffold of indaca-
terol was combined with the tail group of formoterol or olodaterol
to produce compounds of series A, B and C with a varied number of
methyl groups on the a-carbon of the amino group and different
substituents on the tail benzene moiety (Fig. 2). The biological ac-
tivities of these target compounds were studied. Structure-activity
relationship analyses were then performed on these compounds to
see how methyl substitution on the
activity.
a-carbon affect b2-agonistic
2

G. Xing, Z. Zhi, C. Yi et al.
European Journal of Medicinal Chemistry 224 (2021) 113697
Fig. 2. Structure-aided and design strategy for the target compounds.
Scheme 1. Reagents and conditions: (a) 2-diethoxyphosphorylacetonitrile, NaH, dry oxolane, 30 min, 90e95%; (b) 10% Pd/C, H2, MeOH, 1 h, 95e98%; (c) BH3, dry oxolane, 80 ꢀC, 2 h,
85e95%.
Scheme 2. Reagents and conditions: (a) 10% NaOH, acetone, 70e80%; (b) 10% Pd/C, H2, EtOH, 1 h, 95e98%; (c) 10% Pd/C, HCOONH4, MeOH, 70 ꢀC, 53e62%.
Scheme 3. Reagents and conditions: (a) 10% NaOH, acetone, 70e80%; (b) 10% Pd/C, H2, EtOH, 1 h, 95e98%; (c) MeMgBr, dry oxolane, 0 ꢀC, 40 min, 80e90%; (d) (i) CH3CN,
concentrated H2SO4, 0 ꢀC, 5 h, 70e80%; (ii) KOH, ethylene glycol, 180 ꢀC, 20 h, 80e95%.
described in Scheme 5. The key intermediate 15 was prepared from
asymmetric induction with the use of a chiral catalyst (R)-2-
methyl-CBS-oxazaborolidine ((R)-CBS) [24]. We obtained (R,R)-
B04 by semipreparative HPLC with a stereochemical purity value of
99.3%. The ee values of (R)-C07 and (R)-C08 were determined by
HPLC and found to be 99.32% and 99.15%, respectively. (refer to the
HPLC spectra in Supporting Information).
broadly classified into the a and the b subtypes. b-ARs can be
further classified into the b1-, b2-and b3-AR [25]. In airway smooth
muscles, b2-ARs are abundantly expressed, whereas b1-ARs are the
predominant subtype expressed in the heart [26]. Activation of the
b2-AR by an agonist results in the accumulation of cAMP which
leads to smooth muscle relaxation in airways [27]. We evaluated
the biological activities of the titled compounds in human embry-
onic kidney 293 (HEK-293) cells overexpressing the human b1-AR
or b2-AR. The intrinsic activities of a subset of compounds were also
studied in non-overexpressed HEK293 cells with endogenous hu-
man b2-ARs.
2.2. b2-Agonistic activity and structure-activity relationship
analysis
Adrenoceptors (adrenergic receptors, ARs) belong to the su-
perfamily of the G protein-coupled receptors (GPCRs). ARs are
Compounds A01-A08 in Table 1 have no side groups on the
aminopropylbenzene backbone of the tail group. Compounds A01-
3

G. Xing, Z. Zhi, C. Yi et al.
European Journal of Medicinal Chemistry 224 (2021) 113697
Scheme 4. Reagents and conditions: (a) (i) sodium borohydride, MeOH, DMSO, 1 h, 40e55%; (ii) 5% Pd/C, MeOH, H2, 1 h, 85e99%; (iii) ethyl acetate-HCl, 2 h.
i
Scheme 5. Preparation of (R,R)-B04, (R)-C07, and (R)-C08. (a) (i) RNH2, PrOH, 85 ꢀC, 12 h, 45%; (ii) 10% Pd/C, H2, MeOH, 1 h, 90e95%.
A03 contain a terminal methyl-substituted benzene ring at various
positions. The meta-substituted compound A02 exhibited a higher
activity as compared with compounds A01 and A03, with similar
the same levels of b2-agonistic activity and selectivity compared
with compound XY-1. The 3,4,5-trimethoxy-substituted compound
A08 had an activity comparable to that of olodaterol and a selec-
tivity about 50-fold higher than those of salmeterol and olodaterol.
It was only slightly less potent compared with compound XY-1 but
its selectivity was much higher, approaching that of XY-2.
subtype selectivity. Compound A02 showed the same level of b2
-
agonistic activity and lower selectivity compared with its analogue,
compound XY-1. Fluorine is a potential bioisoster for substituent
groups such as hydrogen, carbonyl, sulfonyl and cyanide on a drug
molecule. We attempted to introduce fluorine-containing groups
into the terminal benzene ring of the 5-(2-amino-1-hydroxyethyl)-
8-hydroxyquinolin-2(1H)-one derivatives. Compounds A04-A07
had comparable levels of b2-agonistic activity, with A07 having the
highest potency. Compound A04 and A06 were roughly equipotent
A previous study has suggested that an 8-hydroxyquinolin-
2(1H)-one analogue with an a-methyl aminoindane tail had higher
binding affinity towards the b2-AR compared with the parent
compound indacaterol [28]. Conversely, a demethylated derivative
of (R,R)-fenoterol had a lower affinity towards the b2-AR compared
with (R,R)-fenoterol [29]. We investigated whether introduction of
a methyl group on the carbon atom next to the amino group as in
formoterol [30] and fenoterol would increase activity. Compounds
in Table 2 were synthesized and assayed. All single substituted
analogues exhibited higher activities as compared with the
to compound XY-2 and displayed a reduced b2/b1-selectivity
compared with compounds XY-1 and XY-2. Compound A07 had a
potency exceeding those of the reference compounds isoprenaline,
salmeterol and olodaterol, and an excellent selectivity. It showed
4

G. Xing, Z. Zhi, C. Yi et al.
European Journal of Medicinal Chemistry 224 (2021) 113697
Table 3
Table 1
Chemical Structures of Compounds C01 to C11 and Their Activities in Stimulating
cAMP Accumulation in HEK293 Cells Expressing b2-or b1-Adrenoceptors.
Chemical Structures of Compounds A01 to A08 and Their Activities in Stimulating
cAMP Accumulation in HEK293 Cells Expressing b2-or b1-Adrenoceptors.
a
a
b
Compound
R3
b1 pEC50
b2 pEC50
b2 - b1
a
a
b
Compound
R1
b1 pEC50
b2 pEC50
b2 - b1
C01
C02
C03
C04
C05
C06
C07
C08
C09
C10
C11
(R)-C07
(R)-C08
XY-2
p-OCH3
m-OCH3
o-OCH3
p-CH3
m-CH3
o-CH3
p-Cl
m-Cl
o-Cl
p-OH
m-OH
p-Cl
8.11 0.35
8.12 0.24
8.69 0.11
7.61 0.13
8.58 0.05
8.67 0.18
8.51 0.07
7.98 0.04
8.76 0.08
7.65 0.21
8.62 0.06
9.07
10.51 0.35
10.58 0.02
10.65 0.17
10.78 0.22
10.71 0.08
10.75 0.24
10.90 0.04
11.20 0.17
10.74 0.24
10.44 0.31
10.74 0.12
10.75
2.40
2.46
1.96
3.17
2.13
2.08
2.39
3.22
1.98
2.79
2.12
1.68
1.43
A01
A02
A03
A04
A05
A06
A07
A08
XY-1
XY-2
Isoprenaline
Salmeterol
Olodaterol
o-CH3
m-CH3
p-CH3
m-F
7.77
7.84
7.52
8.35
7.79
8.37
7.11
5.00
10.24 0.09
10.42
10.02 0.20
10.61 0.08
10.33 0.09
10.67
2.46
2.57
2.49
2.25
2.53
2.30
3.44
5.08
p-F
3,5-diF
m-CF3
3,4,5-triOCH3
10.55
10.08
6.66 0.10c
5.00 0.00c
8.90
10.44 0.02c
10.68 0.28c
9.67
3.66c
5.68c
0.77
3.44
3.15
6.43
6.91
9.87
10.06
m-Cl
9.22
10.65
5.00 0.00c
8.85 0.45d
8.90
10.68 0.28c
10.62 0.04d
9.67
5.68c
1.77d
0.77
3.44
3.15
a
XY-3
Data represent mean
SEM obtained from at least four independent
pEC50 at the b1-
Isoprenaline
Salmeterol
Olodaterol
experiments.
b
6.43
6.91
9.87
10.06
Selectivity is defined as pEC50 at the b2-adrenoceptor
-
adrenoceptor.
c
Adopted from Ref. 21.
a
Data represent mean
SEM obtained from at least four independent
experiments.
b
Selectivity is defined as pEC50 at the b2-adrenoceptor - pEC50 at the b1
-
Table 2
adrenoceptor.
c
Chemical Structures of Compounds B01 to B14 and Their Activities in Stimulating
cAMP Accumulation in HEK293 Cells Expressing b2-or b1-Adrenoceptors.
Adopted from Ref. 21.
d
Adopted from Ref. 22.
compounds B01eB03. Compounds B01eB03 displayed similar
potency and selectivity. Remarkable potency and selectivity were
also observed in compounds bearing the methoxy motif, as illus-
trated in compounds B04 and B05, and especially B06. The b2/b1-
selectivity of B06 was highest in this series which was similar to
that of salmeterol or olodateol. It seems that the position of the
methoxy group on the terminal benzene ring had little influence on
activity. Addition of a fluorine group in the m- or p-positions yiel-
ded compounds B07 and B08, with similar activities (b2 pEC50
values equal to 10.63 and 10.55, respectively). The methyl-
substituted compounds B09, B10 and B11 displayed higher activ-
ities compared with the references. However, they possessed a
lower selectivity compared with salmeterol and olodateol. The p-
and m-hydroxyl-substituted compounds B12 and B13 was sub-
stantially equipotent and were among the most potent compounds
in this series. The 3,4,5-trimethoxy-substituted compound B14
offered a moderate b2-agonistic activity comparable to compounds
B04eB06.
a
a
b
Compound
R2
b1 pEC50
b2 pEC50
b2 - b1
B01
B02
B03
B04
B05
B06
B07
B08
B09
B10
B11
B12
B13
B14
(R,R)-B04
Isoprenaline
Salmeterol
Olodaterol
o-Cl
m-Cl
p-Cl
o-OCH3
m-OCH3
p-OCH3
m-F
8.34 0.03
8.35 0.16
8.20 0.15
8.81 0.07
8.59 0.27
7.35 0.11
8.51 0.06
7.98 0.01
8.17 0.19
7.98 0.12
8.39 0.03
8.35 0.02
8.63 0.39
7.45 0.07
8.73
10.47 0.12
10.14 0.25
10.48 0.05
10.83 0.15
10.67 0.14
10.74 0.22
10.63 0.26
10.55 0.19
10.76 0.39
10.42 0.37
10.89 0.05
10.97 0.03
10.87 0.01
10.35 0.10
10.54
2.13
1.79
2.28
2.02
2.08
3.39
2.12
2.57
2.59
2.44
2.50
2.62
2.24
2.90
1.81
0.77
3.44
3.15
p-F
o-CH3
p-CH3
m-CH3
p-OH
m-OH
3,4,5-triOCH3
o-OCH3
It has been documented that olodaterol analogues with two
geminal methyl groups on the
[16,17,31]. Next, we investigated a series of compounds with
dimethyl substitution on the carbon of the aminopropylbenzene
a carbon could be potent b2-agonists
8.90
6.43
6.91
9.67
9.87
10.06
a
scaffold thus completing structure-activity relationship analysis of
substitution at this position with different number of the methyl
group. The high b2 pEC50 values of the compounds in Table 3 sug-
gest that a wide range of substitutions on the terminal benzene ring
could be tolerated, including methoxy substitution (C01eC03),
methyl substitution (C04eC06), chlorine substitution (C07eC09)
and hydroxyl substitution (C10, C11). In particular, compounds C04
and C08 exhibited selectivity on par with salmeterol and olodaterol,
a
Data represent mean
SEM obtained from at least four independent
pEC50 at the b1-
experiments.
b
Selectivity is defined as pEC50 at the b2-adrenoceptor
-
adrenoceptor.
reference compounds isoprenaline, salmeterol and olodaterol. We
incorporated a chlorine group into the benzene ring obtaining
5

G. Xing, Z. Zhi, C. Yi et al.
European Journal of Medicinal Chemistry 224 (2021) 113697
Table 4
similar activity and selectivity (compare Tables 2 and 3). To inves-
tigate the role of stereochemistry on the compounds’ activity, we
synthesized the (R) enantiomers of the highly potent compounds
Intrinsic activities of selected compounds on HEK293 cells endogenously expressing
human b2-adrenoceptors.
Compound
IA
Compound
IA
Compound
IA
B04, C07 and C08 with respect to the chiral center with the
b-hy-
droxyl group. The (R) enantiomers were found to have similar b2
-
A01
A02
A03
A04
A05
A06
A07
A08
63.60
70.20
75.63
75.41
66.98
71.18
70.85
53.78
64.67
69.93
48.36
B06
B07
B08
B09
B10
B11
B12
B13
85.48
62.38
78.11
83.14
82.73
72.31
72.65
85.32
78.85
74.24
50.62
C02
C03
C04
C05
C06
C07
C08
C09
74.49
84.63
81.30
65.48
70.02
76.95
72.87
78.84
67.62
73.39
100
agonistic activities compared with the racemates (Tables 2 and 3).
Despite of the fact that (R,R)-B04, (R)-C07 and (R)-C08 had higher
b2-agonistic activities compared with salmeterol and olodaterol,
they also had higher b1-agonistic activities rendering their selec-
tivity one order of magnitude lower than that of salmeterol or
olodaterol.
B04
B05
salmeterol
B14
C01
olodaterol
C10
C11
isoprenaline
2.3. Intrinsic activity study
A subset of the test compounds were then tested for their
abilities to stimulate cAMP accumulation in HEK293 cells endoge-
nously expressing human b2-ARs, and intrinsic activities (IAs) of the
compounds were determined where the IA of isoprenaline was
defined as 100%. These compounds exhibited IAs ranging from 50%
to 86% where the IAs of the long-acting b2-agonists salmeterol and
olodaterol were found to be 48.36% and 50.62%, respectively
(Table 4). It was concluded that all the new compounds tested were
partial b2-agonists in this system.
with potency exceeding the latter. Their selectivity was between
that of the 5-hydroxy-4H-benzo [1,4]oxazin-3-one analogue XY-3
[22] and the 8-hydroxyquinolin-2(1H)-one analogue XY-2 [21],
and their potency was similar to or higher than that of XY-2 and XY-
3. The data further indicate that methyl substitution was superior to
methoxy substitution in terms of potency. Chlorine substitution
was also favorable as suggested by the b2 pEC50 values of C07, C08
and C09 (10.90, 11.20 and 10.74, respectively). The hydroxyl ana-
logues C10 and C11 also had high potency comparing with the
references but their selectivity, similar to the methoxy analogues
C01eC03, was lower than that of salmeterol and olodaterol. There
was no obviously improvement in potency and selectivity in (R)-
C07 and (R)-C08 compared with C07 and C08.
2.4. The smooth muscle relaxant activities on isolated tracheal
strips
Our strategy was to maintain the 5-(2-amino-1-hydroxyethyl)-
8-hydroxyquinolin-2(1H)-one moiety which maximally preserve
affinity and selectivity of the compounds to the b2-AR, and then
The smooth muscle relaxant effect is an important indicator of
the biological activity of b2-agonists in vivo. The test compounds
were profiled through a smooth muscle relaxation assay on isolated
guinea pig tracheal strips (Table 5). Isoprenaline, salmeterol and
olodaterol were used as reference compounds. In order to compare
the effects of different compounds assaying on different tissue
preparations, relaxant responses of the compounds were expressed
as percentages of the maximal contractile effects induced by his-
tamine. Concentration - relaxation curves were constructed using
GraphPad Prism, version 8.0. Emax (maximal relaxant effect) rep-
resents the maximal relaxant effect obtained with the maximal
concentrations of the compounds. The potency (pD2) value
varied the number of the methyl group on the
a carbon relative to
the central amino accompanied with different substitutions on the
tail benzene ring. It was demonstrated that dimethyl or methyl
substitution on the
a carbon as in B09eB10 and C04eC06 pro-
moted activity as compared with compounds A01-A03 without
substitution (compare Table 2 to Table 1, and Table 3 to Table 1). A
similar feature was also found among the fluorinated compounds
B07eB08 and A04-A05 (compare Tables 2 and 1). In general, B and
C series compounds with one or two methyl substitution had
Table 5
Summary of the values of pD2 and Emax of compounds and the reference
b
2-agonists on isolated guinea pig trachea.
Compound
Compound
pD2
Emax
pD2
Emax
A01
A02
A03
A04
A05
A06
A07
A08
B01
B02
B03
B04
B05
B06
B07
B08
B09
B10
B11
B12
7.72 0.14
7.66 0.15
8.21 0.30
7.50 0.14a
7.39 0.17*a
125.03 6.35* #a
144.08 12.24* #a
138.26 10.64* #a
153.51 10.48*
153.33 7.28* #a
76.71 7.25* #a
95.51 3.91* #a
111.22 7.67* #a
95.26 6.12* #a
104.57 9.51* #a
86.61 6.42* #a
129.54 15.45* #a
196.39 9.69
B13
B14
(R,R)-B04
C01
C02
C03
C04
C05
C06
C07
C08
C09
C10
7.61 0.17
163.50 6.39
141.24 11.15*
94.33 5.01*
160.72 9.63
112.14 13.71*
141.17 8.33*
92.66 7.22*
151.90 16.19
122.43 5.65*
111.58 4.01*
213.75 49.28
#a
#a
7.22 0.15* #a
7.35 0.13* #a
7.86 0.21
#a
7.45 0.09*a
6.86 0.41* #a
7.35 0.09* #a
7.37 0.34a
5.87 0.05* #a
7.69 0.26
#a
#a
8.83 0.38*
6.93 0.07*
7.74 0.23
7.87 0.16
7.16 0.10*
8.31 0.24#
7.62 0.14a
7.33 0.13*
7.48 0.13a
6.61 0.56*
6.57 0.05*
7.39 0.25a
7.58 0.10a
7.08 0.52a
7.97 0.24
#a
#a
#a
#a
#a
#a
5.29 0.41* ba
7.58 0.16a
6.90 0.05* #a
6.37 0.03* #a
7.56 0.20a
5.97 0.21* #a
7.71 0.14
#a
123.83 11.62*
82.74 2.71a #a
#a
103.92 11.34* #a
163.31 11.12
C11
102.89 5.56*
#a
#a
#a
(R)-C07
(R)-C08
salmeterol
olodaterol
isoprenaline
95.33 4.37*
134.31 9.76*
172.45 9.61
169.76 6.01
180.57 9.20
100.32 12.63* #a
92.13 2.60* #a
95.87 10.65* #a
119.02 10.11* #a
71.26 16.90* #a
#a
8.15 0.27
7.84 0.19
The pharmacodynamic parameters were determined in isolated guinea-pig tracheal slices pre-contracted with histamine (5 ꢁ 10ꢂ5 M). Data are expressed as means S.D.
(n ¼ 4).
*p < 0.05, compared with that of Iso.
#p < 0.05, compared with that of Sal.
ap < 0.05, compared with that of Olo.
6

G. Xing, Z. Zhi, C. Yi et al.
European Journal of Medicinal Chemistry 224 (2021) 113697
represents the negative logarithm of the concentration of the drug,
at which a relaxation is equal to 50% of the drug's own maximal
effect (EC50). EC50 was determined by non-linear regression anal-
ysis using GraphPad Prism, version 8.0. The probability of differ-
ences between the mean data of two groups was calculated by
paired Student's t-test with a statistical software SPSS 26.0 and
p < 0.05 was considered significant.
prominent smooth muscle relaxant effects. Their Emax values were
fair (>160%) as compared with references (170e180%). The pD2
values of B13, C01, A04 and A05 were similar to those of isoprenaline
and salmeterol. The Emax values of compounds A04 and A05 were
lower than those of the references. The rest of the test compounds
had much lower Emax values relative to the references.
As shown in Fig. 3 and Table 5, the Emax values of compounds B05
and C08 were higher than those of the other test compounds and
were comparable to those of isoprenaline, salmeterol and oloda-
terol. Compounds B05 and C08 had lower pD2 values relative to the
references. Compounds B07, B13 and C01 were found to produce
2.5. The measurement of onset time and duration of action on
tracheal muscles
On the basis of the activity data from the cAMP assay and the
smooth muscle relaxation assay, the single methyl-substituted
Fig. 3. Summary of concentration e relaxation curves of selected compounds on contracted guinea pig trachea. Isoprenaline, salmeterol and olodaterol were served as references.
Data were expressed as relaxation percentages of the maximum contraction induced by histamine (5 ꢁ 10ꢂ5 M) and as means S.D. (n ¼ 4). (A) Concentration e relaxation curves
of compounds B05, B07, B13, and C08 on contracted guinea pig trachea. (B) Concentration e relaxation curves of compounds A04, A05, C01, and C05 on contracted guinea pig
trachea. (C) Concentration e relaxation curves of compounds A02, A03, B14 and (R)-C08 on contracted guinea pig trachea. (D) Concentration e relaxation curves of compounds B04,
B11, C02, C06, and C09 on contracted guinea pig trachea. (E) Concentration e relaxation curves of compounds A08, B02, B06, B08, C07 and C11 on contracted guinea pig trachea. (F)
Concentration e relaxation curves of compounds A07, B01, B10, C04 and (R,R)-C04 on contracted guinea pig trachea. (G) Concentration e relaxation curves of compounds A06, B03,
B09, B12 and C10 on contracted guinea pig trachea.
7

G. Xing, Z. Zhi, C. Yi et al.
European Journal of Medicinal Chemistry 224 (2021) 113697
analogue B05 and the double methyl-substituted analogue C08,
with high potency and selectivity for the b2-AR and high tracheal
relaxant efficacy, were then evaluated for onset time and duration
of action on isolated tracheal muscles. As shown in Table 6, rapid
onset of action and long duration of action were observed for
compounds B05 and C08. Compound B05 exhibited a slightly
longer onset time compared with isoprenaline, salmeterol and
olodaterol. The onset time of C08 was similar to that of isoprena-
line. In addition to their potential fast action onset, compounds B05
and C08 were also found to produce long-lasting smooth muscle
relaxant effects for over 12 h. These data suggest that compounds
B05 and C08 might behave as long-acting b2-agonists in vivo.
hydrogen bond interactions with any amino acid residues in the
binding pocket. The emphasis of hydrophobic interactions in the
tail region could be the reason for the small differences in the
experimental b2 pEC50 values for the 5-(2-amino-1-hydroxyethyl)-
8-hydroxyquinolin-2(1H)-one derivatives with different sub-
stitutions on the terminal benzene ring (Tables 1e3).
3. Conclusion
We have designed and synthesized a new cohort of 5-(2-amino-
1-hydroxyethyl)-8-hydroxyquinolin-2(1H)-one derivatives as b2
AR agonists and studied their b2-agonistic activities. Activity data
suggest that -dimethyl or -methyl substitution on the amino tail
-
a
a
2.6. Molecular docking analysis of compounds B05 and C08
group mildly improved activity. Compounds B05 and C08 were
found to be potent (EC50 < 20 pM) and selective b2-agonists. They
behaved as partial b2-agonists in non-overexpressed HEK293 cells
and possessed rapid smooth muscle relaxant actions and long
duration of action in isolated guinea pig tracheal strip preparations.
Experimental data and molecular docking once again verify the
high b2-agonistic activity of the 5-(2-amino-1-hydroxyethyl)-8-
hydroxyquinolin-2(1H)-one analogues. Collectively, the present
data support that B05 and C08 could be better b2-agonists for the
treatment of chronic respiratory diseases.
To gain a deeper insight into the superior biological activities of
compounds B05 and C08, the binding poses of the compounds on
the human b2-AR (PDB: 4LDL) were obtained by molecular docking
€
using the Schrodinger Maestro software package. The 8-
hydroxyquinolin-2(1H)-one moiety of B05 and C08 exhibited
multiple interactions with the b2-AR (Fig. 4). The phenolic hydroxyl
group formed hydrogen bond interactions with Ser207. Ser203
formed two hydrogen bonds with the oxygen atom and the nitro-
gen atom on the lactam. In addition, we also observed
p
ꢂ
s in-
teractions and interactions between the 8-hydroxyquinolin-
p p
ꢂ
4. Experimental section
2(1H)-one moiety and residues Val114 and Phe290. The amino
group of the 2-amino-1-phenylethanol core was charged at pH 7.4
leading to a salt bridge with Asp113. Residues Asp113 and Asn312
4.1. Chemistry
also interacted with the oxygen atom of the b-OH group via two
NMR spectroscopic measurement was performed for com-
pounds dissolved in DMSO‑d6 on a 400 MHz or 600 MHz Bruker
spectrometer. The high-resolution mass spectra (HRMS) of the
target compounds were produced by an Agilent 6530 accurate-
mass Q-TOF LC-MS system. All the final compounds were purified
by column chromatography through silica gel (300e400 mesh).
Thin layer chromatography (TLC) on silica gel plates was used to
monitor the progress of the reaction. All starting materials were
purchased from commercial suppliers.
hydrogen bonds. Consequently, these key interactions might
contribute to the stable binding of the 5-(2-amino-1-
hydroxyethyl)-8-hydroxyquinolin-2(1H)-one scaffold to the b2-AR
and the remarkable biological activities of the 5-(2-amino-1-
hydroxyethyl)-8-hydroxyquinolin-2(1H)-one analogues. The pro-
pylbenzene moiety fitted well into the hydrophobic pocket making
hydrophobic interactions with Ile309 and other hydrophobic resi-
dues. Interestingly, the oxygen atom on the terminal methoxy
group in B05 and the chlorine atom in C08 did not engage in
4.1.1. General procedures for the preparation of compounds 4e01 to
4e08
Table 6
Onset time (Ot50) and duration of action (DoA) of B05, C08, isoprenaline, salmeterol
and olodaterol.
To a solution of NaH (2.39 g, 99.0 mmol) in anhydrous THF
(100 mL) chilled on ice, diethyl (cyanomethyl)phosphonate (14.0 g,
79.3 mmol) in anhydrous THF (50 mL) was added. The reaction was
stirred at room temperature for 50 min. Then, a solution of
substituted benzaldehyde (66.2 mmol) was added dropwise to the
reaction mixture. The reaction was stirred at room temperature for
1 h. Removal of the solvent gave a residue. The residue was washed
with H2O (300 mL) and filtered dried to give compound 2. To a
Compound
Ot50 (min)
DoA (h)
B05
C08
isoprenaline
salmeterol
olodaterol
4.97 0.11
3.43 0.31
3.10 0.42
4.23 0.34
2.31 0.49
>12
>12
e
>12
>12
Fig. 4. Binding modes of compounds B05 (A) and C08 (B) at the b2-adrenoceptor active site.
8

G. Xing, Z. Zhi, C. Yi et al.
European Journal of Medicinal Chemistry 224 (2021) 113697
solution of 2 in MeOH, 10% Pd/C (0.1 equiv.) was added and the
mixture was stirred at room temperature for 1 h under 2 atm of
hydrogen. The Pd/C was filtered and the solvent was evaporated to
yield compound 3. To a solution of 3 in anhydrous THF, BH3∙THF
was added under nitrogen atmosphere. The solution was stirred at
60 ꢀC for 40 min. The reaction was quenched with MeOH and
evaporated in vacuum to produce compounds 4e01 to 4e08.
4.1.7. 8-Hydroxy-5-(1-hydroxy-2-((3-(p-tolyl)propyl)amino)ethyl)
quinolin-2(1H)-one hydrochloride (A03)
White solid; yield 93%; 1H NMR (600 MHz, DMSO‑d6)
d 10.53 (s,
2H), 9.48 (s, 1H), 8.76 (s, 1H), 8.31 (d, J ¼ 9.9 Hz, 1H), 7.32e7.07 (m,
2H), 7.02 (dd, J ¼ 10.3, 5.0 Hz, 3H), 6.55 (d, J ¼ 9.8 Hz, 1H), 5.48 (dd,
J ¼ 10.0, 2.2 Hz, 1H), 3.18e2.78 (m, 4H), 2.61 (td, J ¼ 7.5, 3.2 Hz, 2H),
2.40e2.11 (m, 3H), 2.07e1.81 (m, 2H). 13C NMR (151 MHz, DMSO‑d6)
d
160.10, 142.82, 140.06, 136.79, 135.89, 128.32, 128.02, 127.85,
127.68, 126.06, 124.70, 121.40, 119.09, 116.06, 113.46, 64.60, 52.86,
46.12, 31.40, 26.31, 20.41. Calcd. for C21H24N2O3 [MþH]þ 353.1787;
found 351.1884.
4.1.2. General procedures for the preparation of compounds 8e01
to 8e14
To a solution of substituted benzaldehyde (80.6 mmol) in
anhydrous acetone (100 mL), 1 M NaOH (80.6 mmol) in water was
added. The reaction was stirred at room temperature for 2 h.
Removal of the solvent gave a residue. H2O (300 mL) was added to
the residue. The mixture was extracted with EtOAc (3 ꢁ 50 mL),
washed with brine, and dried over Na2SO4. The solvent was
removed under reduced pressure to obtain compound 6. To a so-
lution of 3 in EtOAc, 10% Pd/C (0.1 equiv.) was added. The mixture
was stirred at room temperature for 1 h under 2 atm of hydrogen.
The Pd/C was filtered and the solvent was removed to yield com-
pound 7. HCOONH4 was added to a solution of 7 and 10% Pd/C (0.1
equiv.) in MeOH (100 mL). The reaction mixture was heated to 75 ꢀC
for 5 h. The mixture was cool to room temperature and the solvent
was evaporated to yield a residue. H2O (100 mL) was added to the
residue. The mixture was extracted with EtOAc (3 ꢁ 50 mL), washed
with brine, and dried over Na2SO4. The solvent was removed under
reduced pressure to obtain compounds 8e01 to 8e14.
4.1.8. 5-(2-((3-(3-fluorophenyl)propyl)amino)-1-hydroxyethyl)-8-
hydroxyquinolin-2(1H)-one hydrochloride (A04)
White solid; yield 94%; 1H NMR (600 MHz, DMSO‑d6)
d 10.52 (s,
2H), 9.50 (s, 1H), 8.76 (s, 1H), 8.31 (d, J ¼ 9.9 Hz, 1H), 7.34 (dd,
J ¼ 14.4, 7.8 Hz, 1H), 7.15 (d, J ¼ 8.1 Hz, 1H), 7.10e6.96 (m, 4H), 6.55
(d, J ¼ 9.8 Hz, 1H), 5.48 (d, J ¼ 8.3 Hz, 1H), 3.26e2.82 (m, 4H),
2.78e2.60 (m, 2H), 2.00 (dd, J ¼ 15.2, 8.2 Hz, 2H). 13C NMR
(101 MHz, DMSO‑d6) d 163.94, 161.53, 161.16, 144.27, 144.20, 143.86,
136.86, 130.77, 130.69, 129.07, 128.98, 124.94, 124.92, 122.59, 120.16,
117.12, 115.57, 115.36, 114.50, 113.41, 113.20, 65.71, 53.86, 47.00,
32.09, 27.04. Calcd. for C20H21FN2O3 [MþH]þ 357.1536; found
357.1538.
4.1.9. 5-(2-((3-(4-fluorophenyl)propyl)amino)-1-hydroxyethyl)-8-
hydroxyquinolin-2(1H)-one hydrochloride (A05)
White solid; yield 91%; 1H NMR (600 MHz, DMSO‑d6)
d 10.52 (s,
2H), 9.38 (s,1H), 8.74 (s,1H), 8.29 (d, J ¼ 9.9 Hz,1H), 7.27 (dd, J ¼ 8.5,
5.6 Hz, 2H), 7.20e7.08 (m, 3H), 7.01 (d, J ¼ 8.1 Hz, 1H), 6.55 (d,
J ¼ 9.9 Hz, 1H), 5.46 (d, J ¼ 9.9 Hz, 1H), 3.13e2.85 (m, 4H), 2.69e2.57
4.1.3. General procedures for the preparation of compounds 13e01
to 13e11
Compounds 13e01 to 13e11 were synthesized from different
substituted benzaldehydes as previously reported [21].
(m, 2H), 2.01e1.87 (m, 2H). 13C NMR (151 MHz, DMSO‑d6)
d 168.00,
160.93, 160.08, 159.33, 142.78, 136.29, 136.27, 135.73, 129.46, 129.41,
127.97, 127.89, 121.53, 119.08, 116.03, 114.53, 114.39, 113.39, 64.62,
59.15, 52.75, 45.96, 30.54, 26.41, 20.16,13.48. Calcd. for C20H21FN2O3
[M ꢂ H]- 355.1536; found 355.1510.
4.1.4. General procedures for the preparation of compounds A01-
A08, B01eB14, and C01eC11
Compounds A01-A08, B01eB14, and C01eC11 were obtained by
combining intermediate 14 with different primary amines (4e01 to
4e08, 8e01 to 8e14 and 13e01 to 13e11) in a 2-step reaction as
previously reported [21].
4.1.10. 5-(2-((3-(3,5-difluorophenyl)propyl)amino)-1-
hydroxyethyl)-8-hydroxyquinolin-2(1H)-one hydrochloride (A06)
White solid; yield 93%; 1H NMR (600 MHz, DMSO‑d6)
d 10.53 (s,
2H), 9.56 (s, 1H), 8.76 (s, 1H), 8.32 (d, J ¼ 9.9 Hz, 1H), 7.16 (d,
J ¼ 8.2 Hz, 1H), 7.11e6.91 (m, 4H), 6.55 (d, J ¼ 9.8 Hz, 1H), 5.49 (d,
J ¼ 9.8 Hz, 1H), 3.06 (t, J ¼ 10.5 Hz, 1H), 3.02e2.87 (m, 3H),
2.79e2.63 (m, 2H), 2.10e1.94 (m, 2H). 13C NMR (151 MHz,
4.1.5. 8-Hydroxy-5-(1-hydroxy-2-((3-(o-tolyl)propyl)amino)ethyl)
quinolin-2(1H)-one hydrochloride (A01)
White solid; yield 97%; 1H NMR (600 MHz, DMSO‑d6)
d 10.53 (s,
DMSO‑d6)
d 163.70, 163.61, 162.07, 161.98, 161.18, 145.97, 143.88,
2H), 9.48 (s, 1H), 8.76 (s, 1H), 8.31 (d, J ¼ 9.9 Hz, 1H), 7.32e7.07 (m,
2H), 7.02 (dd, J ¼ 10.3, 5.0 Hz, 3H), 6.55 (d, J ¼ 9.8 Hz, 1H), 5.48 (dd,
J ¼ 10.0, 2.2 Hz, 1H), 3.18e2.78 (m, 4H), 2.61 (td, J ¼ 7.5, 3.2 Hz, 2H),
2.40e2.11 (m, 3H), 2.07e1.81 (m, 2H). 13C NMR (151 MHz, DMSO‑d6)
136.92, 129.09, 128.95, 122.53, 120.17, 117.14, 114.51, 112.05, 112.02,
111.92, 111.89, 102.19, 102.02, 101.85, 65.69, 53.86, 46.79, 31.97,
26.67. Calcd. for C20H20F2N2O3 [MþH]þ 375.1442; found 375.1539.
d
160.10, 142.82, 140.06, 136.79, 135.89, 128.32, 128.02, 127.85,
4.1.11. 8-Hydroxy-5-(1-hydroxy-2-((3-(3-(trifluoromethyl)phenyl)
propyl)amino)ethyl)quinolin-2(1H)-one hydrochloride (A07)
127.68, 126.06, 124.70, 121.40, 119.09, 116.06, 113.46, 64.60, 52.86,
46.12, 31.40, 26.31, 20.41. Calcd. for C21H24N2O3 [MþH]þ 353.1787;
found 351.1961.
White solid; yield 93%; 1H NMR (600 MHz, DMSO‑d6)
d 10.50 (d,
J ¼ 7.5 Hz, 2H), 9.29 (s, 1H), 8.71 (s, 1H), 8.27 (d, J ¼ 9.9 Hz, 1H), 7.60
(s, 1H), 7.56 (t, J ¼ 7.1 Hz, 2H), 7.15 (d, J ¼ 8.1 Hz, 1H), 7.00 (d,
J ¼ 8.2 Hz, 1H), 6.55 (d, J ¼ 9.8 Hz, 1H), 6.15 (d, J ¼ 3.6 Hz, 1H), 5.44
(d, J ¼ 10.0 Hz, 1H), 3.07 (s, 1H), 2.99 (d, J ¼ 24.7 Hz, 3H), 2.81e2.70
(m, 2H), 2.01 (qd, J ¼ 13.6, 7.2 Hz, 2H). 13C NMR (151 MHz, DMSO‑d6)
4.1.6. 8-Hydroxy-5-(1-hydroxy-2-((3-(m-tolyl)propyl)amino)ethyl)
quinolin-2(1H)-one hydrochloride (A02)
White solid; yield 96%; 1H NMR (600 MHz, DMSO‑d6)
d 10.53 (s,
2H), 9.48 (s, 1H), 8.76 (s, 1H), 8.31 (d, J ¼ 9.9 Hz, 1H), 7.32e7.07 (m,
2H), 7.02 (dd, J ¼ 10.3, 5.0 Hz, 3H), 6.55 (d, J ¼ 9.8 Hz, 1H), 5.48 (dd,
J ¼ 10.0, 2.2 Hz, 1H), 3.18e2.78 (m, 4H), 2.61 (td, J ¼ 7.5, 3.2 Hz, 2H),
2.40e2.11 (m, 3H), 2.07e1.81 (m, 2H). 13C NMR (151 MHz, DMSO‑d6)
d 161.17, 143.86, 142.80, 136.76, 133.04, 129.92, 129.71, 129.50,
129.02, 125.68, 125.30, 125.28, 123.88, 123.35, 122.66, 120.18, 117.11,
114.45, 65.74, 53.76, 46.99, 32.09, 27.23. Calcd. for C21H21F3N2O3
[MþH]þ 407.1504; found 407.1629.
d
160.10, 142.82, 140.06, 136.79, 135.89, 128.32, 128.02, 127.85,
127.68, 126.06, 124.70, 121.40, 119.09, 116.06, 113.46, 64.60, 52.86,
46.12, 31.40, 26.31, 20.41. Calcd. for C21H24N2O3 [MþH]þ 353.1787;
found 353.1886.
4.1.12. 8-Hydroxy-5-(1-hydroxy-2-((3-(3,4,5-trimethoxyphenyl)
propyl)amino)ethyl)quinolin-2(1H)-one hydrochloride (A08)
White solid; yield 97%; 1H NMR (600 MHz, DMSO‑d6)
d 10.49 (d,
9

G. Xing, Z. Zhi, C. Yi et al.
European Journal of Medicinal Chemistry 224 (2021) 113697
J ¼ 8.4 Hz, 2H), 9.31 (s, 1H), 8.70 (s, 1H), 8.28 (d, J ¼ 9.9 Hz, 1H), 7.15
(d, J ¼ 8.2 Hz, 1H), 7.00 (d, J ¼ 8.2 Hz, 1H), 6.55 (d, J ¼ 9.9 Hz, 1H),
6.53 (s, 1H), 6.15 (d, J ¼ 3.6 Hz, 1H), 5.45 (d, J ¼ 10.0 Hz, 1H), 3.76 (s,
6H), 3.62 (s, 3H), 3.06 (d, J ¼ 8.2 Hz, 1H), 3.04e2.98 (m, 1H),
2.97e2.90 (m, 2H), 2.60 (dd, J ¼ 15.0, 7.5 Hz, 2H), 2.06e1.88 (m, 2H).
1.86e1.64 (m, 1H), 1.31 (dd, J ¼ 14.0, 6.5 Hz, 3H). 13C NMR (151 MHz,
DMSO‑d6)
d 160.09, 156.34, 156.32, 142.80, 135.77, 128.94, 128.91,
128.10, 128.08, 128.06, 128.03, 127.86, 126.89, 121.51, 119.75, 119.73,
119.11, 116.06,113.42,110.11,110.09, 64.71, 64.57, 54.63, 52.89, 52.81,
50.03, 49.89, 32.03, 31.18, 25.05, 24.86, 15.21, 14.54. Calcd. for
13C NMR (151 MHz, DMSO‑d6)
d
161.16, 153.25, 143.86, 136.87,
C
22H26N2O4 [MþH]þ 383.1893; found 383.1981.
136.78, 136.16, 129.05, 128.99, 122.66, 120.16, 117.10, 114.46, 105.98,
65.74, 60.42, 56.26, 53.84, 47.09, 32.79, 27.35. Calcd. for C23H28N2O6
[MþH]þ 429.1947; found 429.2046.
4.1.17. 8-Hydroxy-5-(1-hydroxy-2-((4-(3-methoxyphenyl)butan-2-
yl)amino)ethyl)quinolin-2(1H)-one hydrochloride (B05)
White solid; yield 94%; 1H NMR (400 MHz, DMSO‑d6)
d 10.45 (s,
4.1.13. 5-(2-((4-(2-chlorophenyl)butan-2-yl)amino)-1-
2H), 9.28 (s, 1H), 8.56 (s, 1H), 8.27 (d, J ¼ 9.8 Hz, 1H), 7.29e7.10 (m,
2H), 7.06e6.96 (m, 1H), 6.90e6.66 (m, 3H), 6.55 (d, J ¼ 9.8 Hz, 1H),
5.47 (d, J ¼ 9.5 Hz, 1H), 3.72 (d, J ¼ 4.6 Hz, 3H), 3.21 (s, 1H), 3.02 (d,
J ¼ 5.7 Hz, 2H), 2.75e2.63 (m, 1H), 2.57 (dd, J ¼ 12.0, 7.9 Hz, 1H),
2.09 (d, J ¼ 9.6 Hz, 1H), 1.83e1.67 (m, 1H), 1.29 (dd, J ¼ 14.8, 6.5 Hz,
hydroxyethyl)-8-hydroxyquinolin-2(1H)-one hydrochloride (B01)
White solid; yield 91%; 1H NMR (400 MHz, DMSO‑d6)
d 10.47 (s,
2H), 9.63e9.24 (m, 1H), 8.59 (s, 1H), 8.30 (dd, J ¼ 9.9, 3.5 Hz, 1H),
7.37e7.26 (m, 2H), 7.22 (dd, J ¼ 10.0, 4.2 Hz, 2H), 7.18 (dd, J ¼ 8.4,
3.7 Hz, 1H), 7.01 (dd, J ¼ 8.2, 1.2 Hz, 1H), 6.55 (d, J ¼ 9.9 Hz, 1H),
5.56e5.29 (m, 1H), 3.22 (d, J ¼ 3.8 Hz, 1H), 3.11e2.91 (m, 2H), 2.71
(tt, J ¼ 22.0, 11.3 Hz, 1H), 2.63e2.52 (m, 1H), 2.21e2.03 (m, 1H),
1.90e1.65 (m, 1H), 1.31 (dd, J ¼ 15.1, 6.5 Hz, 3H). 13C NMR (101 MHz,
3H). 13C NMR (151 MHz, DMSO‑d6)
d 160.08, 158.74, 158.72, 142.78,
141.85, 141.83, 135.64, 128.83, 128.80, 128.03, 128.01, 127.89, 121.64,
119.92, 119.89, 119.14, 119.11, 116.05, 113.44, 113.39, 110.78, 110.75,
64.79, 64.62, 54.81, 54.80, 54.32, 52.81, 52.74, 50.08, 49.86, 33.43,
32.43, 30.45, 30.30, 30.20, 28.40, 15.24, 15.13, 14.56, 14.45. Calcd. for
DMSO‑d6)
d 161.14, 143.85, 141.38, 141.35, 136.80, 129.14, 128.98,
128.89, 128.86, 128.75, 128.72, 126.49, 122.65, 120.23, 117.15, 114.50,
65.87, 65.69, 53.94, 53.89, 51.21, 51.04, 49.06, 34.64, 33.71, 31.54,
31.38, 16.20, 15.58. Calcd. for C21H23ClN2O3 [MþH]þ 387.1397;
found 387.1890.
C
22H26N2O4 [MþH]þ 383.1893; found 383.1999.
4.1.18. 8-Hydroxy-5-(1-hydroxy-2-((4-(4-methoxyphenyl)butan-2-
yl)amino)ethyl)quinolin-2(1H)-one hydrochloride (B06)
White solid; yield 98%; 1H NMR (400 MHz, DMSO‑d6)
d 10.46 (s,
4.1.14. 5-(2-((4-(3-chlorophenyl)butan-2-yl)amino)-1-
2H), 9.42 (s, 1H), 8.58 (s, 1H), 8.30 (dd, J ¼ 9.9, 3.2 Hz, 1H), 7.28e7.08
(m, 3H), 7.02 (d, J ¼ 8.2 Hz, 1H), 6.93e6.78 (m, 2H), 6.56 (d,
J ¼ 9.9 Hz, 1H), 6.14 (s, 1H), 5.57e5.39 (m, 1H), 3.72 (d, J ¼ 3.0 Hz,
3H), 3.19 (d, J ¼ 8.4 Hz, 1H), 3.02 (s, 2H), 2.65 (ddd, J ¼ 14.3, 9.6,
4.8 Hz,1H), 2.60e2.53 (m,1H), 2.21e1.97 (m,1H),1.92e1.59 (m,1H),
hydroxyethyl)-8-hydroxyquinolin-2(1H)-one hydrochloride (B02)
White solid; yield 92%; 1H NMR (400 MHz, DMSO‑d6)
d 10.47 (s,
2H), 9.53 (s, 1H), 8.61 (s, 1H), 8.32 (d, J ¼ 10.0 Hz, 1H), 7.31 (ddd,
J ¼ 12.1, 7.6, 3.2 Hz, 2H), 7.23 (d, J ¼ 6.8 Hz, 2H), 7.18 (dd, J ¼ 8.0,
3.8 Hz, 1H), 7.02 (d, J ¼ 8.2 Hz, 1H), 6.55 (d, J ¼ 9.8 Hz, 1H), 5.52 (d,
J ¼ 9.5 Hz,1H), 3.23 (d, J ¼ 6.8 Hz,1H), 3.09e2.93 (m, 2H), 2.71 (ddd,
J ¼ 14.7, 10.0, 4.8 Hz, 1H), 2.65e2.53 (m, 1H), 2.19e2.05 (m, 1H), 1.79
1.30 (dd, J ¼ 15.0, 6.5 Hz, 3H). 13C NMR (151 MHz, DMSO‑d6)
d 161.17,
158.04, 143.86, 136.77, 133.15, 133.11, 129.70, 129.67, 129.14, 128.97,
122.69, 120.20, 120.17, 117.12, 114.46, 114.29, 114.26, 65.85, 65.67,
55.45, 53.87, 53.80, 51.22, 51.02, 34.88, 33.90, 30.63, 30.46, 16.20,
15.54. Calcd. for C22H26N2O4 [MþH]þ 383.1893; found 383.1988.
(ddd, J ¼ 18.1, 13.0, 4.6 Hz, 1H), 1.31 (dd, J ¼ 15.5, 6.5 Hz, 3H). 13
C
NMR (151 MHz, DMSO‑d6)
d 160.08, 158.74, 158.72, 142.78, 141.85,
141.83, 135.64, 128.83, 128.80, 128.03, 128.01, 127.89, 121.64, 119.92,
119.89, 119.14, 119.11, 116.05, 115.63, 115.59, 113.44, 113.39, 112.84,
110.78, 110.75, 64.79, 64.62, 54.81, 54.80, 54.32, 52.81, 52.74, 50.08,
49.86, 33.43, 32.43, 30.45, 30.30, 15.13, 14.45. Calcd. for
4.1.19. 5-(2-((4-(3-fluorophenyl)butan-2-yl)amino)-1-
hydroxyethyl)-8-hydroxyquinolin-2(1H)-one hydrochloride (B07)
White solid; yield 97%; 1H NMR (400 MHz, DMSO‑d6)
d 10.47 (s,
C
21H23ClN2O3 [MþH]þ 387.1397; found 387.1471.
2H), 9.51 (s,1H), 8.60 (s, 1H), 8.31 (dd, J ¼ 10.0, 2.4 Hz,1H), 7.33 (dtd,
J ¼ 8.1, 6.4, 4.7 Hz, 1H), 7.18 (dd, J ¼ 8.2, 2.5 Hz, 1H), 7.13e7.06 (m,
2H), 7.05e6.98 (m, 2H), 6.55 (d, J ¼ 9.9 Hz, 1H), 5.51 (td, J ¼ 9.1,
4.5 Hz, 1H), 3.22 (s, 1H), 3.01 (t, J ¼ 10.5 Hz, 2H), 2.75 (dt, J ¼ 16.4,
5.8 Hz, 1H), 2.68e2.56 (m, 1H), 2.21e2.08 (m, 1H), 1.87e1.70 (m,
1H), 1.30 (dd, J ¼ 15.1, 6.5 Hz, 3H). 13C NMR (151 MHz, DMSO‑d6)
4.1.15. 5-(2-((4-(4-chlorophenyl)butan-2-yl)amino)-1-
hydroxyethyl)-8-hydroxyquinolin-2(1H)-one hydrochloride (B03)
White solid; yield 93%; 1H NMR (400 MHz, DMSO‑d6)
d 10.48 (s,
2H), 9.60 (s, 1H), 8.62 (d, J ¼ 6.1 Hz,1H), 8.34 (dd, J ¼ 9.9, 3.2 Hz,1H),
7.34 (d, J ¼ 4.3 Hz, 1H), 7.30e7.27 (m, 1H), 7.23 (dd, J ¼ 15.3, 8.5 Hz,
2H), 7.18 (dd, J ¼ 5.4, 2.8 Hz, 1H), 7.07e6.97 (m, 1H), 6.55 (d,
J ¼ 9.9 Hz, 1H), 5.59e5.45 (m, 1H), 3.22 (d, J ¼ 3.6 Hz, 1H), 3.02 (d,
J ¼ 5.8 Hz, 2H), 2.72 (ddd, J ¼ 18.6, 9.9, 4.6 Hz, 1H), 2.59 (ddd,
J ¼ 14.0, 11.0, 7.0 Hz, 1H), 2.13 (tdd, J ¼ 10.6, 7.1, 3.8 Hz, 1H),
d
169.74, 162.45, 160.84, 160.09, 143.32, 143.29, 143.27, 142.79,
135.74, 129.69, 129.67, 129.65, 129.59, 128.07, 127.87, 123.87, 123.86,
123.84, 123.82, 123.80, 123.78, 121.56, 119.13, 119.11, 116.07, 116.06,
114.50, 114.47, 114.42, 114.36, 114.33, 114.28, 113.39, 112.27, 112.13,
64.74, 64.58, 59.15, 52.68, 50.12, 49.97, 45.68, 34.93, 33.13, 32.21,
30.04, 29.90, 29.81, 20.16, 17.43, 15.10, 14.48, 13.48. Calcd. for
1.88e1.68 (m, 3H). 13C NMR (101 MHz, DMSO‑d6)
d 161.16, 143.87,
141.40, 141.37, 140.43, 136.91, 131.08, 130.67, 130.64, 129.17, 128.95,
128.88, 128.85, 128.79, 128.75, 128.72, 126.48, 122.58, 120.22, 117.16,
114.53, 65.84, 65.66, 53.94, 53.89, 53.79, 51.29, 51.12, 49.05, 34.61,
34.37, 33.72, 33.52, 31.55, 31.38, 30.77, 30.62, 16.17, 15.58. Calcd. for
C
21H23FN2O3 [MþH]þ 371.1693; found 371.1792.
4.1.20. 5-(2-((4-(4-fluorophenyl)butan-2-yl)amino)-1-
hydroxyethyl)-8-hydroxyquinolin-2(1H)-one hydrochloride (B08)
C
21H23ClN2O3 [MþH]þ 387.1397; found 387.1489.
White solid; yield 96%; 1H NMR (400 MHz, DMSO‑d6)
d 10.46 (s,
2H), 9.45 (s,1H), 8.59 (s,1H), 8.30 (d, J ¼ 9.9 Hz,1H), 7.27 (dd, J ¼ 8.4,
5.6 Hz, 2H), 7.18 (dd, J ¼ 8.2, 3.3 Hz,1H), 7.11 (ddd, J ¼ 8.8, 7.7, 4.7 Hz,
2H), 7.01 (d, J ¼ 8.2 Hz, 1H), 6.55 (d, J ¼ 9.8 Hz, 1H), 5.51 (d,
J ¼ 9.1 Hz, 1H), 3.23 (d, J ¼ 6.8 Hz, 1H), 3.10e2.92 (m, 2H), 2.70 (ddd,
J ¼ 10.6, 7.8, 3.5 Hz, 1H), 2.65e2.54 (m, 1H), 2.17e2.03 (m, 1H),
1.85e1.69 (m, 1H), 1.30 (dd, J ¼ 15.2, 6.5 Hz, 3H). 13C NMR (151 MHz,
4.1.16. 8-Hydroxy-5-(1-hydroxy-2-((4-(2-methoxyphenyl)butan-2-
yl)amino)ethyl)quinolin-2(1H)-one hydrochloride (B04)
White solid; yield 96%; 1H NMR (400 MHz, DMSO‑d6)
d 10.49 (s,
2H), 9.47 (d, J ¼ 55.1 Hz, 1H), 8.57 (s, 1H), 8.32 (dd, J ¼ 10.0, 1.2 Hz,
1H), 7.28e7.10 (m, 3H), 7.07e6.99 (m, 1H), 6.95 (dd, J ¼ 7.8, 3.5 Hz,
1H), 6.87 (td, J ¼ 7.4, 3.5 Hz, 1H), 6.55 (dd, J ¼ 9.9, 2.2 Hz, 1H),
5.60e5.41 (m, 1H), 3.75 (d, J ¼ 2.6 Hz, 3H), 3.23 (s, 1H), 3.09e2.90
(m, 2H), 2.72e2.60 (m, 1H), 2.60e2.52 (m, 1H), 2.14e1.92 (m, 1H),
DMSO‑d6)
d 160.90, 160.08, 159.30, 142.78, 136.43, 136.41, 136.39,
135.71, 129.47, 129.44, 129.42, 129.39, 128.06, 127.88, 121.58, 119.12,
119.10, 116.05, 114.55, 114.51, 114.43, 114.42, 114.41, 114.37, 113.38,
10

G. Xing, Z. Zhi, C. Yi et al.
European Journal of Medicinal Chemistry 224 (2021) 113697
64.76, 64.58, 55.49, 52.73, 52.71, 50.13, 49.96, 47.97, 45.70, 33.61,
32.66, 29.56, 29.40, 15.11, 14.48. Calcd. for C21H23FN2O3 [MþH]þ
371.1693; found 371.1785.
1H), 1.66 (s, 1H), 1.24 (dd, J ¼ 16.3, 5.2 Hz, 3H). 13C NMR (151 MHz,
DMSO‑d6)
d 161.15, 156.01, 143.78, 136.80, 131.35, 129.56, 129.53,
128.99, 122.62, 120.24, 117.18, 115.64, 115.61, 114.48, 55.39, 53.68,
30.72, 30.58. Calcd. for C21H24N2O4 [MþH]þ 369.1736; found
369.1820.
4.1.21. 8-Hydroxy-5-(1-hydroxy-2-((4-(o-tolyl)butan-2-yl)amino)
ethyl)quinolin-2(1H)-one hydrochloride (B09)
White solid; yield 94%; 1H NMR (400 MHz, DMSO‑d6)
d
10.46 (s,
4.1.26. 8-Hydroxy-5-(1-hydroxy-2-((4-(3,4,5-trimethoxyphenyl)
2H), 9.45 (s,1H), 8.59 (s,1H), 8.30 (d, J ¼ 9.9 Hz,1H), 7.27 (dd, J ¼ 8.4,
5.6 Hz, 2H), 7.18 (dd, J ¼ 8.2, 3.3 Hz,1H), 7.11 (ddd, J ¼ 8.8, 7.7, 4.7 Hz,
2H), 7.01 (d, J ¼ 8.2 Hz, 1H), 6.55 (d, J ¼ 9.8 Hz, 1H), 5.51 (d,
J ¼ 9.1 Hz, 1H), 3.23 (d, J ¼ 6.8 Hz, 1H), 3.10e2.92 (m, 2H), 2.70 (ddd,
J ¼ 10.6, 7.8, 3.5 Hz, 1H), 2.65e2.54 (m, 1H), 2.17e2.03 (m, 1H),
1.85e1.69 (m, 1H), 1.30 (dd, J ¼ 15.2, 6.5 Hz, 3H). 13C NMR (151 MHz,
butan-2-yl)amino)ethyl)quinolin-2(1H)-one hydrochloride (B14)
White solid; yield 95%; 1H NMR (400 MHz, DMSO‑d6)
d 10.45 (s,
2H), 9.49 (s, 1H), 8.59 (s, 1H), 8.32 (dd, J ¼ 10.0, 3.8 Hz, 1H), 7.18 (dd,
J ¼ 8.2, 2.3 Hz, 1H), 7.01 (d, J ¼ 8.2 Hz, 1H), 6.54 (t, J ¼ 4.9 Hz, 2H),
6.13 (s, 1H), 5.50 (dd, J ¼ 15.0, 8.2 Hz, 1H), 3.75 (d, J ¼ 5.3 Hz, 6H),
3.61 (d, J ¼ 3.6 Hz, 3H), 3.19 (d, J ¼ 12.8 Hz, 1H), 3.01 (t, J ¼ 6.5 Hz,
2H), 2.74e2.59 (m, 1H), 2.57 (s, 1H), 2.25e2.04 (m, 1H), 1.86e1.65
(m, 1H), 1.30 (dd, J ¼ 15.1, 6.5 Hz, 3H). 13C NMR (151 MHz, DMSO‑d6)
DMSO‑d6)
d 160.90, 160.08, 159.30, 142.78, 136.43, 136.41, 136.39,
135.71, 129.47, 129.44, 129.42, 129.39, 128.06, 127.88, 121.58, 119.12,
119.10, 116.05, 114.55, 114.51, 114.43, 114.42, 114.41, 114.37, 113.38,
64.76, 64.58, 55.49, 52.73, 52.71, 50.13, 49.96, 47.97, 45.70, 33.61,
32.66, 29.56, 29.40, 15.11, 14.48. Calcd. for C22H26N2O3 [MþH]þ
367.1943; found 367.2031.
d
160.09, 152.17, 152.16,142.76,135.97,135.96, 135.72,135.06, 128.11,
127.88, 121.59, 119.10, 119.07, 116.04, 113.38, 104.92, 104.88, 64.83,
64.64, 59.33, 55.19, 52.73, 52.70, 50.25, 49.98, 33.49, 32.63, 30.73,
30.65, 15.20, 14.54. Calcd. for C24H30N2O6 [MþH]þ 443.2104; found
443.2210.
4.1.22. 8-Hydroxy-5-(1-hydroxy-2-((4-(m-tolyl)butan-2-yl)amino)
ethyl)quinolin-2(1H)-one hydrochloride (B10)
4.1.27. 8-Hydroxy-5-(1-hydroxy-2-((4-(4-methoxyphenyl)-2-
methylbutan-2-yl)amino)ethyl)quinolin-2(1H)-one hydrochloride
(C01)
White solid; yield 95%; 1H NMR (400 MHz, DMSO‑d6)
d 10.46 (s,
2H), 9.50 (s, 1H), 8.59 (s, 1H), 8.31 (d, J ¼ 9.9 Hz, 1H), 7.17 (td, J ¼ 7.9,
4.1 Hz, 2H), 7.01 (dd, J ¼ 14.4, 6.5 Hz, 4H), 6.55 (d, J ¼ 9.8 Hz, 1H),
5.52 (d, J ¼ 8.8 Hz, 1H), 3.22 (s, 1H), 3.01 (d, J ¼ 5.4 Hz, 2H), 2.67 (qd,
J ¼ 10.1, 4.7 Hz, 1H), 2.56 (dd, J ¼ 11.2, 6.4 Hz, 1H), 2.27 (d, J ¼ 4.2 Hz,
3H), 2.10 (dd, J ¼ 13.3, 10.0 Hz, 1H), 1.77 (dqd, J ¼ 14.9, 10.1, 5.2 Hz,
1H), 1.30 (dd, J ¼ 15.2, 6.5 Hz, 3H). 13C NMR (151 MHz, DMSO‑d6)
White solid; yield 96%; 1H NMR (400 MHz, DMSO‑d6)
d
8.48e8.20 (m, 1H), 7.12 (dt, J ¼ 16.7, 8.2 Hz, 4H), 6.83 (d, J ¼ 8.6 Hz,
2H), 6.50 (d, J ¼ 9.9 Hz, 1H), 5.34 (s, 1H), 3.71 (s, 3H), 3.39 (d,
J ¼ 1.7 Hz, 2H), 2.86 (d, J ¼ 5.7 Hz, 2H), 1.87e1.60 (m, 2H), 1.29e1.21
(m, 6H). 13C NMR (151 MHz, DMSO‑d6)
d 172.67, 161.32, 157.88,
d
160.08, 142.78, 140.20, 140.17, 136.81, 136.78, 135.73, 128.35,
143.81, 137.36, 134.15, 129.60, 128.84, 122.23, 120.17, 117.24, 114.57,
114.22, 114.15, 103.49, 71.15, 70.78, 55.45, 49.32, 29.03, 21.84, 19.65,
18.71. Calcd. for C23H28N2O4 [MþH]þ 397.2049; found 397.2147.
128.32, 128.06, 127.87, 127.70, 127.67, 126.04, 124.72, 124.69, 121.57,
119.11, 119.09, 116.05, 113.39, 64.75, 64.58, 52.84, 52.78, 50.13,
49.95, 33.57, 32.63, 30.40, 30.24, 20.41, 20.40, 15.12, 14.48. Calcd. for
C
22H26N2O3 [MþH]þ 367.1943; found 367.2064.
4.1.28. 8-Hydroxy-5-(1-hydroxy-2-((4-(3-methoxyphenyl)-2-
methylbutan-2-yl)amino)ethyl)quinolin-2(1H)-one hydrochloride
(C02)
4.1.23. 8-Hydroxy-5-(1-hydroxy-2-((4-(p-tolyl)butan-2-yl)amino)
ethyl)quinolin-2(1H)-one hydrochloride (B11)
White solid; yield 97%; 1H NMR (400 MHz, DMSO‑d6)
d 10.44 (s,
White solid; yield 93%; 1H NMR (400 MHz, DMSO‑d6)
d
10.40 (s,
2H), 9.39 (s, 1H), 8.41 (d, J ¼ 10.0 Hz, 1H), 8.25 (d, J ¼ 10.0 Hz, 1H),
7.18 (t, J ¼ 8.1 Hz, 2H), 6.98 (d, J ¼ 8.2 Hz, 1H), 6.83e6.67 (m, 3H),
6.54 (d, J ¼ 9.9 Hz, 1H), 5.43 (d, J ¼ 8.7 Hz, 1H), 3.71 (d, J ¼ 4.3 Hz,
3H), 2.98 (t, J ¼ 13.2 Hz, 2H), 2.68e2.52 (m, 2H), 1.96e1.82 (m, 2H),
1H), 9.11 (s, 2H), 8.30 (dd, J ¼ 9.9, 3.2 Hz,1H), 7.16 (dd, J ¼ 8.2, 3.8 Hz,
1H), 7.12e7.05 (m, 4H), 7.01 (dd, J ¼ 8.1, 2.0 Hz, 1H), 6.53 (t,
J ¼ 7.9 Hz, 1H), 5.42 (s, 1H), 3.12 (s, 1H), 2.97 (s, 2H), 2.70e2.58 (m,
1H), 2.55 (dd, J ¼ 9.9, 6.7 Hz, 3H), 2.03 (s, 1H), 1.79e1.61 (m, 1H),
1.26 (dd, J ¼ 12.4, 6.5 Hz, 3H). 13C NMR (101 MHz, DMSO‑d6)
1.44e1.24 (m, 6H). 13C NMR (151 MHz, DMSO‑d6)
d 160.07, 158.72,
142.80, 142.32, 135.63, 128.84, 128.80, 128.04, 127.89, 121.67, 119.88,
119.79, 119.13, 116.06, 113.41, 113.36, 113.30, 110.72, 64.74, 58.45,
54.32, 47.38, 28.76, 24.37, 22.01, 21.94. Calcd. for C23H28N2O4
[MþH]þ 397.2049; found 397.2180.
d
161.16, 143.76, 138.35, 136.83, 135.32, 129.43, 129.40, 128.96,
128.62, 128.59, 122.60, 120.21, 117.18, 114.45, 53.62, 31.13, 31.00,
21.07. Calcd. for C22H26N2O3 [MþH]þ 367.1943; found 367.2031.
4.1.24. 8-Hydroxy-5-(1-hydroxy-2-((4-(3-hydroxyphenyl)butan-2-
4.1.29. 8-Hydroxy-5-(1-hydroxy-2-((4-(2-methoxyphenyl)-2-
methylbutan-2-yl)amino)ethyl)quinolin-2(1H)-one hydrochloride
(C03)
yl)amino)ethyl)quinolin-2(1H)-one hydrochloride (B12)
White solid; yield 94%; 1H NMR (400 MHz, DMSO‑d6)
d 9.29 (s,
1H), 8.27 (dd, J ¼ 9.9, 3.4 Hz, 1H), 7.16 (dd, J ¼ 8.1, 4.1 Hz, 1H), 7.03
(dtd, J ¼ 9.4, 8.0, 1.5 Hz, 2H), 6.69e6.57 (m, 3H), 6.54 (d, J ¼ 9.8 Hz,
1H), 5.37 (s, 1H), 3.08 (s, 1H), 2.95 (s, 2H), 2.57 (dd, J ¼ 10.0, 4.8 Hz,
1H), 2.45 (d, J ¼ 14.5 Hz, 1H), 1.99 (s, 1H), 1.69 (s, 1H), 1.27e1.20 (m,
White solid; yield 93%; 1H NMR (400 MHz, DMSO‑d6)
d 10.47 (s,
2H), 9.53 (s, 1H), 8.48 (t, J ¼ 9.9 Hz, 1H), 8.32 (d, J ¼ 9.9 Hz, 1H),
7.29e7.09 (m, 3H), 7.03 (d, J ¼ 8.2 Hz, 1H), 6.93 (d, J ¼ 8.0 Hz, 1H),
6.86 (t, J ¼ 7.3 Hz,1H), 6.55 (d, J ¼ 9.9 Hz,1H), 5.50 (d, J ¼ 9.1 Hz,1H),
3.65 (s, 3H), 3.11e2.86 (m, 2H), 2.59 (dd, J ¼ 10.5, 5.0 Hz, 2H),
1.89e1.72 (m, 2H), 1.38 (s, 6H). 13C NMR (151 MHz, DMSO‑d6)
3H). 13C NMR (151 MHz, DMSO‑d6)
d 161.15, 157.87, 143.68, 136.93,
129.71, 128.96, 122.51, 120.23, 119.31, 119.28, 117.24, 115.64, 115.62,
114.49, 113.38, 60.21, 53.53, 31.64, 31.51, 21.23, 14.56. Calcd. for
d
160.08, 156.26, 142.80, 135.61, 128.97, 128.34, 128.10, 127.89,
C
21H24N2O4 [MþH]þ 369.1736; found 369.1817.
126.88, 121.67, 119.75, 119.12, 116.06, 113.39, 110.07, 64.73, 58.40,
54.48, 47.40, 36.72, 23.59, 22.18, 22.15. Calcd. for C23H28N2O4
[MþH]þ 397.2049; found 397.2137.
4.1.25. 8-Hydroxy-5-(1-hydroxy-2-((4-(4-hydroxyphenyl)butan-2-
yl)amino)ethyl)quinolin-2(1H)-one hydrochloride (B13)
White solid; yield 91%; 1H NMR (600 MHz, DMSO‑d6)
d
10.45 (s,
4.1.30. 8-Hydroxy-5-(1-hydroxy-2-((2-methyl-4-(p-tolyl)butan-2-
1H), 9.19 (s,1H), 8.25 (dd, J ¼ 9.3, 5.3 Hz,1H), 7.25e7.10 (m,1H), 6.99
(d, J ¼ 6.9 Hz, 3H), 6.68 (s, 2H), 6.55 (d, J ¼ 9.7 Hz, 1H), 5.38 (s, 1H),
3.10 (s, 1H), 2.97 (s, 2H), 2.57 (s, 1H), 2.45 (d, J ¼ 6.6 Hz, 1H), 1.99 (s,
yl)amino)ethyl)quinolin-2(1H)-one hydrochloride (C04)
White solid; yield 92%; 1H NMR (400 MHz, DMSO‑d6)
d
10.41 (s,
2H), 9.59 (s, 1H), 8.45 (d, J ¼ 9.1 Hz, 1H), 8.32 (d, J ¼ 9.9 Hz, 1H), 7.21
11

G. Xing, Z. Zhi, C. Yi et al.
European Journal of Medicinal Chemistry 224 (2021) 113697
(d, J ¼ 8.2 Hz, 1H), 7.09 (s, 4H), 7.01 (d, J ¼ 8.2 Hz, 1H), 6.55 (d,
J ¼ 9.9 Hz, 1H), 5.49 (d, J ¼ 9.1 Hz, 1H), 3.18e2.86 (m, 2H), 2.59 (dd,
J ¼ 9.9, 5.0 Hz, 2H), 2.25 (s, 3H), 1.96e1.79 (m, 2H), 1.37 (d,
NMR (101 MHz, DMSO‑d6) d 161.13, 143.86, 139.13, 136.77, 133.20,
131.30, 129.78, 129.13, 128.86, 128.73, 127.94, 122.70, 120.25, 117.17,
114.49, 65.87, 59.57, 59.44, 48.50, 37.86, 27.91, 23.00, 14.56. Calcd.
for C22H25ClN2O3 [MþH]þ 401.1554; found 401.1645.
J ¼ 6.0 Hz, 1H). 13C NMR (101 MHz, DMSO‑d6)
d 161.12, 143.85,
138.65, 136.76, 135.33, 129.41, 129.13, 129.00, 128.59, 122.70, 120.24,
117.18, 114.51, 65.86, 59.58, 48.53, 29.37, 23.11, 23.04, 21.06. Calcd.
for C23H28N2O3 [M ꢂ H]- 379.2100; found 379.2387.
4.1.36. 8-Hydroxy-5-(1-hydroxy-2-((4-(4-hydroxyphenyl)-2-
methylbutan-2-yl)amino)ethyl)quinolin-2(1H)-one hydrochloride
(C10)
4.1.31. 8-Hydroxy-5-(1-hydroxy-2-((2-methyl-4-(m-tolyl)butan-2-
White solid; yield 96%; 1H NMR (400 MHz, DMSO‑d6)
d 10.47 (d,
yl)amino)ethyl)quinolin-2(1H)-one hydrochloride (C05)
J ¼ 6.5 Hz, 2H), 9.27 (d, J ¼ 60.3 Hz, 2H), 8.42 (d, J ¼ 9.5 Hz, 1H), 8.26
(d, J ¼ 9.9 Hz, 1H), 7.21 (d, J ¼ 8.2 Hz, 1H), 7.00 (dd, J ¼ 8.3, 3.0 Hz,
3H), 6.67 (dd, J ¼ 8.8, 2.3 Hz, 2H), 6.56 (d, J ¼ 9.9 Hz,1H), 6.16 (s,1H),
5.44 (d, J ¼ 9.3 Hz, 1H), 3.12e2.90 (m, 2H), 2.50 (dt, J ¼ 3.5, 1.7 Hz,
2H), 1.92e1.78 (m, 2H), 1.35 (d, J ¼ 5.9 Hz, 6H). 13C NMR (151 MHz,
White solid; yield 90%; 1H NMR (400 MHz, DMSO‑d6)
d 10.47 (s,
2H), 9.64 (s, 1H), 8.46 (d, J ¼ 9.8 Hz, 1H), 8.33 (d, J ¼ 10.0 Hz, 1H),
7.28e7.08 (m, 2H), 7.09e6.94 (m, 4H), 6.55 (d, J ¼ 9.9 Hz, 1H),
5.57e5.43 (m, 1H), 3.12e2.89 (m, 2H), 2.68e2.54 (m, 2H), 2.26 (s,
3H), 2.01e1.80 (m, 2H), 1.37 (d, J ¼ 5.2 Hz, 6H). 13C NMR (101 MHz,
DMSO‑d6)
d 169.74, 160.07, 154.90, 142.80, 135.50, 130.59, 128.45,
DMSO‑d6)
d
161.13, 143.87, 141.70, 137.88, 136.79, 129.39, 129.14,
127.99, 127.91, 121.73, 119.17, 116.06, 114.52, 113.33, 64.82, 58.46,
47.24, 27.82, 22.01, 21.94. Calcd. for C22H26N2O4 [MþH]þ 383.1893;
found 383.2017.
128.98, 128.76, 127.06, 125.79, 122.68, 120.24, 117.17, 114.49, 65.83,
59.55, 48.54, 29.74, 23.10, 23.03, 21.45. Calcd. for C23H28N2O3
[MþH]þ 381.2100; found 381.2206.
4.1.37. 8-Hydroxy-5-(1-hydroxy-2-((4-(3-hydroxyphenyl)-2-
methylbutan-2-yl)amino)ethyl)quinolin-2(1H)-one hydrochloride
(C11)
4.1.32. 8-Hydroxy-5-(1-hydroxy-2-((2-methyl-4-(o-tolyl)butan-2-
yl)amino)ethyl)quinolin-2(1H)-one hydrochloride (C06)
White solid; yield 97%; 1H NMR (400 MHz, DMSO‑d6)
d
10.44 (s,
White solid; yield 91%; 1H NMR (400 MHz, DMSO‑d6)
d 10.45 (s,
2H), 9.68 (d, J ¼ 8.5 Hz, 1H), 8.45 (t, J ¼ 9.8 Hz, 1H), 8.34 (d,
J ¼ 9.9 Hz, 1H), 7.21 (d, J ¼ 8.2 Hz, 1H), 7.17e7.07 (m, 4H), 7.01 (d,
J ¼ 8.2 Hz, 1H), 6.54 (d, J ¼ 9.9 Hz, 1H), 5.50 (d, J ¼ 9.2 Hz, 1H),
3.11e2.89 (m, 2H), 2.61 (dd, J ¼ 9.3, 6.6 Hz, 2H), 2.28 (s, 3H), 1.84
(dd, J ¼ 11.1, 6.4 Hz, 2H), 1.41 (d, J ¼ 9.4 Hz, 6H). 13C NMR (101 MHz,
2H), 9.51 (s, 1H), 9.30 (s, 1H), 8.43 (s, 1H), 8.29 (d, J ¼ 10.0 Hz, 1H),
7.21 (d, J ¼ 8.2 Hz,1H), 7.12e6.93 (m, 2H), 6.74e6.48 (m, 4H), 6.16 (s,
1H), 5.47 (d, J ¼ 8.9 Hz, 1H), 3.00 (s, 2H), 2.55 (dd, J ¼ 8.2, 4.3 Hz,
2H), 2.01e1.77 (m, 2H), 1.36 (d, J ¼ 7.4 Hz, 6H). 13C NMR (151 MHz,
DMSO‑d6)
d 161.15, 157.89, 143.86, 143.14, 136.66, 129.75, 129.10,
DMSO‑d6)
d
161.12, 143.85, 139.91, 136.81, 135.96, 130.56, 129.20,
128.99, 122.78, 120.23, 119.28, 117.16, 115.63, 114.44, 113.40, 65.87,
65.38, 59.54, 48.41, 29.79, 23.04, 22.99, 15.64. Calcd. for C22H26N2O4
[MþH]þ 383.1893; found 383.1967.
129.15, 128.98, 126.57, 126.48, 122.66, 120.23, 117.17, 114.50, 65.84,
65.37, 59.58, 48.52, 38.30, 27.41, 22.89, 19.27, 15.63. Calcd. for
C
23H28N2O3 [MþH]þ 381.2100; found 381.2192.
4.1.38. 8-Hydroxy-5-((1R)-1-hydroxy-2-((4-(2-methoxyphenyl)
butan-2-yl)amino)ethyl)quinolin-2(1H)-one hydrochloride ((R,R)-
B04)
4.1.33. 5-(2-((4-(4-chlorophenyl)-2-methylbutan-2-yl)amino)-1-
hydroxyethyl)-8-hydroxyquinolin-2(1H)-one hydrochloride (C07)
White solid; yield 96%; 1H NMR (400 MHz, DMSO‑d6)
d
10.47 (s,
(R,R)-B04 was obtained by semipreparative HPLC.
2H), 9.67 (d, J ¼ 8.9 Hz, 1H), 8.46 (d, J ¼ 9.0 Hz, 1H), 8.33 (d,
J ¼ 9.9 Hz, 1H), 7.44e7.12 (m, 5H), 7.02 (d, J ¼ 8.2 Hz, 1H), 6.55 (d,
J ¼ 9.9 Hz, 1H), 5.50 (d, J ¼ 9.1 Hz, 1H), 3.00 (t, J ¼ 12.6 Hz, 2H), 2.64
(dd, J ¼ 9.4, 4.1 Hz, 2H), 1.93 (dd, J ¼ 15.6, 7.0 Hz, 2H), 1.37 (dd,
White solid; yield 95%; ee > 99%; 1H NMR (600 MHz, DMSO‑d6)
d
10.50 (s, 2H), 9.55e9.33 (m, 1H), 8.65e8.52 (m, 1H), 8.31 (dd,
J ¼ 10.0, 2.2 Hz, 1H), 7.20e7.15 (m, 3H), 7.02 (dd, J ¼ 8.1, 2.0 Hz, 1H),
6.97e6.93 (m, 1H), 6.90e6.85 (m, 1H), 6.55 (dd, J ¼ 9.9, 3.5 Hz, 1H),
5.54e5.46 (m, 1H), 3.75 (d, J ¼ 4.5 Hz, 3H), 3.27e3.19 (m, 1H),
3.07e2.95 (m, 2H), 2.69e2.61 (m, 1H), 2.59e2.52 (m, 1H),
2.07e2.00 (m, 1H), 1.80e1.68 (m, 1H), 1.31 (dd, J ¼ 21.5, 6.5 Hz, 3H).
Calcd. for C22H26N2O4 [M ꢂ H]- 381.1893; found 381.1989.
J ¼ 6.7, 4.1 Hz, 6H). 13C NMR (101 MHz, DMSO‑d6)
d 161.14, 143.87,
140.86, 136.80, 131.03, 130.64, 129.13, 128.98, 128.77, 122.68, 120.25,
117.19, 114.50, 65.82, 59.57, 59.51, 48.53, 29.10, 23.09, 23.01. Calcd.
for C22H25ClN2O3 [MþH]þ 401.1554; found 401.1687.
4.1.34. 5-(2-((4-(3-chlorophenyl)-2-methylbutan-2-yl)amino)-1-
4.1.39. General process for preparation of compounds (R)-C07, and
hydroxyethyl)-8-hydroxyquinolin-2(1H)-one hydrochloride (C08)
(R)-C08
White solid; yield 97%; 1H NMR (400 MHz, DMSO‑d6)
d
10.46 (s,
Compounds (R)-C07, and (R)-C08 were obtained as previously
2H), 9.59 (s,1H), 8.44 (s,1H), 8.31 (dd, J ¼ 10.0,1.7 Hz,1H), 7.34e7.16
(m, 5H), 7.01 (d, J ¼ 8.2 Hz, 1H), 6.55 (d, J ¼ 9.8 Hz, 1H), 5.49 (d,
J ¼ 8.9 Hz, 1H), 3.01 (t, J ¼ 17.8 Hz, 2H), 2.66 (dt, J ¼ 13.6, 6.4 Hz, 2H),
1.98e1.85 (m, 2H), 1.37 (dd, J ¼ 6.4, 3.0 Hz, 6H). 13C NMR (101 MHz,
reported [21,22].
4.1.40. (R)-5-(2-((4-(4-chlorophenyl)-2-methylbutan-2-yl)amino)-
1-hydroxyethyl)-8-hydroxyquinolin-2(1H)-one hydrochloride ((R)-
C07)
DMSO‑d6)
d 161.13, 144.49, 143.87, 136.79, 133.46, 130.70, 128.86,
128.73, 128.64, 127.56, 126.44, 122.69, 120.25, 117.18, 114.50, 65.84,
59.51, 48.54, 29.40, 23.14, 23.03, 14.56. Calcd. for C22H25ClN2O3
[MþH]þ 401.1554; found 401.1652.
White solid; yield 93%; ee > 99%; 1H NMR (600 MHz, DMSO‑d6)
d
10.49 (s, 2H), 9.62 (s, 1H), 8.45 (t, J ¼ 10.9 Hz, 1H), 8.32 (d,
J ¼ 9.9 Hz, 1H), 7.29 (t, J ¼ 7.5 Hz, 2H), 7.22 (d, J ¼ 6.5 Hz, 3H),
7.03e7.00 (m, 1H), 6.55 (d, J ¼ 9.8 Hz, 1H), 5.49 (d, J ¼ 9.6 Hz, 1H),
3.04e2.95 (m, 2H), 2.66e2.62 (m, 2H), 1.93 (t, J ¼ 8.4 Hz, 2H), 1.38
(d, J ¼ 10.2 Hz, 6H). Calcd. for C22H25ClN2O3 [MþH]þ 401.1554;
found 401.1576.
4.1.35. 5-(2-((4-(2-chlorophenyl)-2-methylbutan-2-yl)amino)-1-
hydroxyethyl)-8-hydroxyquinolin-2(1H)-one hydrochloride (C09)
White solid; yield 94%; 1H NMR (400 MHz, DMSO‑d6)
d 10.46 (s,
2H), 9.61 (d, J ¼ 9.5 Hz, 1H), 8.49 (dd, J ¼ 15.5, 10.4 Hz, 1H), 8.32 (d,
J ¼ 10.0 Hz, 1H), 7.39 (ddd, J ¼ 15.5, 7.5, 1.7 Hz, 1H), 7.32e7.17 (m,
4H), 7.01 (d, J ¼ 8.2 Hz, 1H), 6.55 (d, J ¼ 9.9 Hz, 1H), 5.49 (d,
J ¼ 9.2 Hz, 1H), 3.01 (dd, J ¼ 19.4, 9.8 Hz, 2H), 2.80e2.58 (m, 2H),
4.1.41. (R)-5-(2-((4-(3-chlorophenyl)-2-methylbutan-2-yl)amino)-
1-hydroxyethyl)-8-hydroxyquinolin-2(1H)-one hydrochloride ((R)-
C08)
1.89 (ddd, J ¼ 13.6,12.5, 7.1 Hz, 2H),1.39 (dd, J ¼ 12.8, 5.9 Hz, 6H). 13
C
White solid; yield 90%; ee > 99%; 1H NMR (600 MHz, DMSO‑d6)
12

G. Xing, Z. Zhi, C. Yi et al.
European Journal of Medicinal Chemistry 224 (2021) 113697
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d
10.49 (s, 2H), 9.64 (s, 1H), 8.44 (d, J ¼ 10.6 Hz,1H), 8.32 (dd, J ¼ 9.9,
2.3 Hz, 1H), 7.35e7.27 (m, 2H), 7.23e7.19 (m, 3H), 7.02 (d, J ¼ 8.1 Hz,
1H), 6.55 (d, J ¼ 9.8 Hz, 1H), 5.49 (d, J ¼ 9.7 Hz, 1H), 3.06e2.93 (m,
2H), 2.70e2.60 (m, 2H), 1.93 (t, J ¼ 8.6 Hz, 2H), 1.38 (d, J ¼ 10.3 Hz,
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Declaration of competing interest
The authors have no relevant affiliations or financial involve-
ment with any organization or entity with a financial interest in or
financial conflict with the subject matter or materials discussed in
the manuscript. This includes employment, consultancies, hono-
raria, stock ownership or options, expert testimony, grants or pat-
ents received or pending, or royalties.
[17] T. Bouyssou, C. Hoenke, K. Rudolf, P. Lustenberger, S. Pestel, P. Sieger, R. Lotz,
C. Heine, F.H. Büttner, A. Schnapp, I. Konetzki, Discovery of olodaterol, a novel
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~
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Acknowledgments
[19] K. Matsuda, M. Makhay, K. Johnson, Y. Iwaki, Evaluation of bedoradrine sulfate
(MN-221), a novel, highly selective beta2-adrenergic receptor agonist for the
treatment of asthma via intravenous infusion, J. Asthma 49 (2012)
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R. Webster, R.M. Jones, J.L. Burrows, N. Feeder, S.C. Taylor, F.J. Spence, Inha-
This work was supported by the National Natural Science
Foundation of China (grant number 81872752 to M.S.C.) and The
Ministry of Science and Technology of the People's Republic of
China “13th Five-Year” major new drug initiative (grant number
2019ZX09739-004 to M.S.C.).
lation by design: novel ultra-long-acting
b(2)-adrenoreceptor agonists for
inhaled once-daily treatment of asthma and chronic obstructive pulmonary
disease that utilize a sulfonamide agonist headgroup, J. Med. Chem. 53 (2010)
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Appendix A. Supplementary data
[21] G. Xing, L. Pan, C. Yi, X. Li, X. Ge, Y. Zhao, Y. Liu, J. Li, A. Woo, B. Lin, Y. Zhang,
M. Cheng, Design, synthesis and biological evaluation of 5-(2-amino-1-
Supplementary data to this article can be found online at
https://doi.org/10.1016/j.ejmech.2021.113697.
hydroxyethyl)-8-hydroxyquinolin-2(1H)-one derivatives as potent
b2-
adrenoceptor agonists, Bioorg. Med. Chem. 27 (2019) 2306e2314.
[22] C. Yi, G. Xing, S. Wang, X. Li, Y. Liu, J. Li, B. Lin, A.Y. Woo, Y. Zhang, L. Pan,
M. Cheng, Design, synthesis and biological evaluation of 8-(2-amino-1-
hydroxyethyl)-6-hydroxy-1,4-benzoxazine-3(4H)-one derivatives as potent
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