Identification of 3,4-dihydro-2H-thiochromene 1,1-dioxide derivatives with a phenoxyethylamine group as highly potent and selective α1D adrenoceptor antagonists

Article abstract of DOI:10.1016/j.ejmech.2017.07.071

A series of phenoxyethylamine derivatives was designed and synthesized to discover potent and selective human α_1D adrenoceptor (α_1D adrenergic receptor; α_1D–AR) antagonists. Compound 7 was taken from our internal compound collection as an attractive starting point and exhibited moderate binding affinity for α_1D–AR and high selectivity against α_1A– and α_1B–ARs. We focused on modifying the 2-methylsulfonylbenzyl group of 7 to discover novel compounds structurally distinct from other reported α₁–AR antagonists containing the phenoxyethylamine motif. Study of structure activity relationship guided by a targeted ligand-lipophilicity efficiency score led to the discovery of a novel scaffold of 3,4-dihydro-2H-thiochromene 1,1-dioxide for selective α_1D–AR antagonists. Further optimization studies resulted in the identification of (4S)-N⁴-[2-(2,5-difluorophenoxy)ethyl]-N⁶-methyl-3,4-dihydro-2H-thiochromene-4,6-diamine 1,1-dioxide, (S)–41, as a novel, highly potent and selective α_1D–AR antagonist. Herein, we provide details of the structure activity relationship of the phenoxyethylamine analog for the potency and selectivity.

Full text of DOI:10.1016/j.ejmech.2017.07.071

Accepted Manuscript
Identification of 3,4-dihydro-2H-thiochromene 1,1-dioxide derivatives with a
phenoxyethylamine group as highly potent and selective α
antagonists
adrenoceptor
1D
Nobuki Sakauchi, Hideki Furukawa, Junya Shirai, Ayumu Sato, Haruhiko Kuno, Reiko
Saikawa, Masato Yoshida
PII:
S0223-5234(17)30593-7
10.1016/j.ejmech.2017.07.071
EJMECH 9634
DOI:
Reference:
To appear in: European Journal of Medicinal Chemistry
Received Date: 10 May 2017
Revised Date: 27 July 2017
Accepted Date: 28 July 2017
Please cite this article as: N. Sakauchi, H. Furukawa, J. Shirai, A. Sato, H. Kuno, R. Saikawa, M.
Yoshida, Identification of 3,4-dihydro-2H-thiochromene 1,1-dioxide derivatives with a phenoxyethylamine
group as highly potent and selective α
Chemistry (2017), doi: 10.1016/j.ejmech.2017.07.071.
adrenoceptor antagonists, European Journal of Medicinal
1D
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ACCEPTED MANUSCRIPT
Graphical abstract
Cl
NH
SAR study
Cl
O
HCl
F
H
H
N
N
F
F
O
SO2
SO2
7
41
(S)-
1D Ki = 0.3 nM
1A Ki = 130 nM, 1B Ki = 150 nM
1D Ki = 17 nM
1A Ki = 1800 nM, 1B Ki = 1100 nM

Identification of 3,4-dihydro-2H-thiochromene 1,1-dioxide derivatives with a
ACCEPTED MANUSCRIPT
phenoxyethylamine group as highly potent and selective α1D adrenoceptor
antagonists
Authors:
Nobuki Sakauchi,* Hideki Furukawa, Junya Shirai, Ayumu Sato, Haruhiko Kuno, Reiko Saikawa
and Masato Yoshida
Author Affiliations:
Pharmaceutical Research Division, Takeda Pharmaceutical Company Limited, 26-1, Muraoka-
Higashi 2-chome, Fujisawa, Kanagawa 251-8555, Japan
*Corresponding author
Nobuki Sakauchi
Axcelead Drug Discovery Partners Limited, 26-1, Muraoka-Higashi 2-chome, Fujisawa, Kanagawa
251-8555, Japan
E-mail address: nobuki.sakauchi@takeda.com (N.Sakauchi)1
1
AR, Adrenoceptor; BH3, borane; Boc2O, di-tert-butyl bicarbonate; t-BuXphos, 2-di-tert-
butylphosphino-2',4',6'-tri-isopropyl-1,1'-biphenyl; BOO, bladder outlet obstruction; BPH, benign
prostatic hyperplasia; (COCl)2, oxalyl chloride; mCPBA, m-chloroperoxybenzoic acid; DME, 1,2-
dimethoxyethane; dppf, 1,1'-bis(diphenylphophino)ferrocene; Et3N, triethylamine; HCl,
hydrochloric acid; HOBt, 1-hydroxybenzotriazole monohydrate; H2SO4, sulfuric acid; K2CO3,
potassium carbonate; MeONH2, methoxyamine; NaOMe, sodium methoxide; NaSMe, sodium
thiomethoxide; NMP, N-methyl-2-pyrrolidone; Pd/C, palladium on carbon; Pd2dba3,
tris(dibenzylideneacetone)dipalladium(0);
Pd(OAc)2,
palladium(II)
acetate;
Pd(PPh3)4,
tetrakis(triphenylphosphine)palladium(0); i-Pr2NEt, N,N-diisopropylethylamine; WSC, 1-(3-
dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride; Xantphos, 4,5-bis(diphenylphosphino)-
9,9-dimethylxanthene;
Zn(CN)2, zinc cyanide.
Xphos,
2-(dicyclohexylphosphino)-2',4',6'-tri-isopropyl-1,1'-biphenyl,

Abstract
ACCEPTED MANUSCRIPT
A series of phenoxyethylamine derivatives was designed and synthesized to discover potent
and selective human α1D adrenoceptor (α1D adrenergic receptor; α1D–AR) antagonists. Compound 7
was taken from our internal compound collection as an attractive starting point and exhibited
moderate binding affinity for α1D–AR and high selectivity against α1A– and α1B–ARs. We focused
on modifying the 2-methylsulfonylbenzyl group of 7 to discover novel compounds structurally
distinct from other reported α1–AR antagonists containing the phenoxyethylamine motif. Study of
structure activity relationship guided by a targeted ligand-lipophilicity efficiency score led to the
discovery of a novel scaffold of 3,4-dihydro-2H-thiochromene 1,1-dioxide for selective α1D–AR
antagonists. Further optimization studies resulted in the identification of (4S)-N4-[2-(2,5-
difluorophenoxy)ethyl]-N6-methyl-3,4-dihydro-2H-thiochromene-4,6-diamine 1,1-dioxide, (S)–41,
as a novel, highly potent and selective α1D–AR antagonist. Herein, we provide details of the
structure activity relationship of the phenoxyethylamine analog for the potency and selectivity.
Keywords: phenoxyethylamine derivatives, selective human α1D adrenoceptor antagonist, 3,4-
dihydro-2H-thiochromene 1,1-dioxide, ligand–lipophilicity efficiency (LLE)

1. Introduction
ACCEPTED MANUSCRIPT
The α1 adrenergic receptors (α1 adrenoceptors, α1–ARs) are a part of the G protein-coupled
receptor (GPCR) superfamily and are classified into three receptor subtypes, α1A, α1B and α1D-ARs
[1−4]. The functions and tissue distribution of each receptor subtype are known to be different. It
has been demonstrated that α1A-ARs mediate smooth muscle contractions in the human prostate and
are predominantly expressed in the bladder neck, prostate, and prostatic urethra [5−8]. Some
literature reports suggest that α1B-ARs regulate vasoconstriction of large human arteries, and are
extensively expressed in the vascular smooth muscle [9,10]. The α1D-ARs are widely found in the
human bladder detrusor muscle and epicardial coronary arteries [11−13].
Several non-subtype-selective α1-AR antagonists, such as doxazosin and alfuzosin, are used
in the treatment of hypertension and lower urinary tract symptoms associated with benign prostatic
hyperplasia (BPH), a urologic disorder prevalent in elderly men [14,15].
Subtype-selective α1-AR ligands help understand the functional role of each receptor subtype
and avoid unfavorable side effects in therapy. Increasing evidence for the involvement of α1A-AR in
bladder outlet obstruction (BOO) in patients with BPH has encouraged the use of α1A-AR selective
antagonists in symptomatic therapy of BPH [5,7]. Presently, a α1A- and α1D-AR dual antagonist 1
(tamsulosin) and a highly selective α1A-AR antagonist 2 (silodosin) are available on the market for
the treatment of BPH [16]. However, the effort to develop α1B–AR or α1D-AR selective ligands has
been less fruitful than the search for α1A- and α1D-AR dual or α1A-AR selective ligands. For example,
cyclazosin and L–765,314 have been reported as selective α1B-AR antagonists [17]. Antagonism of
α1B-AR may cause cardiovascular side effects such as orthostatic hypotension, tachycardia,
arrhythmia, and dizziness [18−20]. Regarding α1D-AR antagonists, we recently reported the
discovery and optimization of iminopyridine derivatives yielding compound 3 (TAK–259), as a

potent, orally available, and selective α1D antagonist with antiurinary frequency effects [21]. In
ACCEPTED MANUSCRIPT
addition, 4 (BMY7378) is well known as an α1D-AR ligand that also binds the serotonergic 5-HT1A
receptor [22]. Furthermore, compound 5 (SNAP 8719) shows improved selectivity against the
serotonergic 5-HT1A receptor compared to 4, and a phenoxyethylamine derivative 6 has been
reported as a selective α1D-AR antagonist [23].
Figure 1. Structures of reported α1-ARs antagonists. Blue lines indicate phenoxyethylamine analog.
Table 1. In vitro data and clog P of 6, TAK-259 and 7.

ACCEPTED MANUSCRIPT
aKi value for α1D was obtained by displacement of 7-methoxy-[3H]-prazosin from cloned human
receptor.
bLLE = −log(Ki)−clog P.
cEffects on the phenylephrine-induced contractions of the bladder strips taken from the rats with
BOO (n = 2−11).
dThe data were taken from the literature [23].
In the course of discovering the selective α1D-AR antagonist 3, we were interested in
expanding the range of α1D-AR antagonists and sought a new series of compounds structurally
different from 3. The phenoxyethylamine derivative 7 was obtained from our internal compound
collection with the phenoxyethylamine scaffold (Table 1). Compound 7, containing a 5-chloro-2-
methylsulfonylbenzyl group, showed higher subtype selectivity for α1A- and α1B-ARs than 6 did [23].
Compound 6 was also reported as a selective α1D–AR antagonist with the phenoxyethylamine motif.
However, a structure activity relationship (SAR) study of 6 using a human α1D-AR binding assay
showed room for improvement in subtype selectivity, while the functional assay of this compound
using rat tissue showed a more than 100-fold α1D-AR antagonistic selectivity over α1A-AR.
Therefore, we considered 7 to be an attractive starting point for further modification. In comparison
with the clinical compound TAK-259, compound 7 exhibited lower binding affinity and effects on
phenylephrine–induced bladder contraction in isolated bladder strips taken from rats with BOO,
which were used for the in vitro evaluation of non-voiding contraction treatment in our previous

report [21]. Hence, we started the SAR study of 7 to increase its potency by introducing various
ACCEPTED MANUSCRIPT
amine functionalities on the phenoxyethylamine analog along with an adjustment of LLE score, as
shown in Figure 2. Herein, we describe the identification of 3,4-dihydro-2H-thiochromene 1,1-
dioxide derivative (S)-41 as a highly potent and selective α1D-AR antagonist.
Figure 2. Design strategy.
2. Chemistry
The synthesis of target compounds is depicted in Scheme 1–3. Scheme 1 outlines the synthesis
of 7, 10–12, 16, 17, 22 and 23. Phenol 8 was treated with 1,2-bromoethane in the presence of
aqueous sodium hydroxide (NaOH) to afford phenoxyethylbromide 9, followed by treatment of
corresponding benzylamines to provide 2-chloro-5-fluorophenyloxyethylamine derivatives 7, 10, 11
and 12, respectively. Condensation of phenoxyethylamine 13 with an appropriate carboxylic acid
yielded phenoxyethylamides 14 and 15, followed by reduction using borane-tetrahydrofuran
complex (BH3·THF) to provide phenoxyethylamines 16 and 17, respectively. Condensation of
phenoxyacetic acids 18 and 19 with appropriate amines afforded phenoxyacetamides 20 and 21,
respectively, followed by reduction using BH3·THF to obtain phenoxyethylamines 22 and 23,
respectively.
Scheme 1. Synthesis of 7, 10–12, 16, 17, 22 and 23a

Cl
Cl
Cl
a
ACCEPTED MANbUSCRIPT
H
N
Br
F
OH
F
O
F
O
R1
MeO2S
8
9
7 : R1=
Cl
Cl
10: R1=
11: R1=
MeO2S
12: R1=
SO2
Cl
O
Cl
Cl
HCl
NH2
c (and d)
e
H
R2
H
N
F
N
R2
F
O
F
O
O
13
14: R2=
15: R2=
16: R2=
17: R2=
MeO2S
MeO2S
MeO2S
MeO2S
HCl
f or g
h
R3
R3
R3
H
H
OH
N
N
O
O
R4
O
R4
O
O
18: R3= 2-Cl-5-F
20a,b: R3= 2-Cl-5-F
22a,b: R3= 2-Cl-5-F
19: R3= 2,5-
21b,c: R3= 2,5-
23b,c: R3= 2,5-
di-F
di-F
di-F
MeO
R4=
SO2
SO2
Me SO2Me
a
b
c
aReagents and conditions: (a) 1,2-dibromoethane, 1 M NaOH, 90 °C; (b) benzylamines, K2CO3,
EtOH, 90 °C; (c) carboxylic acids, WSC, HOBt, Et3N, DMF; (d) mCPBA, AcOEt; (e) BH3·THF,
THF, 0 to 80 °C; (f) amines, WSC, HOBt, Et3N, CH3CN or DMF; (g) (COCl)2, cat. DMF, THF,
then amines, Et3N, THF; (h) BH3·THF, THF, 0 to 80 °C then 4 M HCl in AcOEt.
Phenethylamine 25 and thiochroman-4-amine 32 for the synthesis of 22a and 23c were
prepared as shown in Scheme 2. Acetophenone 24 was converted into 25 via oxime formation and

reduction. Alkylation of benzenethiol 26 with 3-bromopropionic acid followed by cyclization with
ACCEPTED MANUSCRIPT
concentrated sulfuric acid and oxidation of the sulfanyl group with m-chloroperoxybenzoic acid
(mCPBA) yielded thiochromanone derivative 29. Thiochroman-4-amine 31 was obtained by
reduction of the bromo group in 29 and amination of the ketone group. Finally, substitution of the
fluoro group in 31 with sodium methoxide afforded amine 32.
Scheme 2. Synthesis of intermediates 25 and 32a
aReagents and conditions: (a) MeONH2·HCl, pyridine; (b) BH3·THF, THF, 0 to 80 °C then 4 M HCl
in AcOEt; (c) 8 M NaOH, H2O, then 3-bromopropionic acid, K2CO3, H2O; (d) conc. H2SO4; (e)
mCPBA, AcOEt, 0 °C; (f) Pd/C, H2, EtOH; (g) BH3·THF, THF, 0 to 80 °C; (h) NaOMe, MeOH, rt
to 95 °C.
Scheme 3 demonstrates the synthesis of compounds 37–41. Intermediates 35 and 36 were
prepared by using a method similar to that described in Scheme 1. Compound 35 was obtained by
amination of 33a–c, followed by oxidation, and subsequent condensation and reduction with
BH3·THF. Boc-protection of the amine group yielded 36. The phenoxyethylamine derivatives 37a–c,
which contained methoxy groups on the thiochromene ring, were afforded by substitution of the
bromo group with potassium hydroxide followed by methylation of hydroxy group and removal of

the protecting group. Intermediate 34d, which was obtained by amination and oxidation of 33d, was
ACCEPTED MANUSCRIPT
converted to 38 through condensation and reduction with BH3·THF followed by salt formation with
4 M HCl in AcOEt. Intermediate 36a was used as a starting material for the synthesis of 39–41. The
methylsulfonyl derivative 39 was prepared by introduction of a methylsulfanyl group into 36a,
followed by oxidation and removal of the protecting group, and salt formation. The carboxamide
derivative 40 was obtained by methoxycarbonylation of 36a, followed by hydrolysis, amidation, and
removal of the protecting group and salt formation. Finally, the methylamine derivative 41 was
obtained by introduction of a methylamino group into 36a, followed by removal of the protecting
group and salt formation. The optically active compounds (R)-41 and (S)-41 were prepared by chiral
supercritical fluid chromatography (SFC) of 41. The stereochemistry was determined by single X-
ray crystal structure analysis as shown in Figure 3.
Scheme 3. Synthesis of 37–41a

ACCEPTED MANUSCRIPT
aReagents and conditions: (a) MeONH2·HCl, pyridine; (b) BH3·THF, THF, 0 to 80 °C then Boc2O,
AcOEt; (c) mCPBA, AcOEt then 4 M HCl in AcOEt; (d) 19, WSC, HOBt, Et3N, DMF; (e)
BH3·THF, THF, 0 to 80 °C; (f) Boc2O, AcOEt, (g) KOH, Pd2dba3, t-BuXphos, DME, H2O, 100 °C;
(h) Iodomethane, K2CO3, DMF, (i) 4 M HCl in AcOEt; (j) Zn(CN)2, Pd(PPh3)4, DMF, 100 °C; (k)
NaSMe, Pd2dba3, Xantphos, xylene, 140 °C; (l) mCPBA, AcOEt; (m) CO, Pd(OAc)2, dppf, Et3N,
MeOH, THF; (n) 1N NaOH, THF; (o) HOBt·NH3, WSC, i-Pr2NEt, DMF; (p) Methylamine, Pd2dba3,
X-Phos, NaO-t-Bu, toluene, 100 °C; (q) optical resolution by chiral supercritical fluid
chromatography (SFC).

ACCEPTED MANUSCRIPT
Figure 3. ORTEP diagram of (S)-41, thermal ellipsoids are drawn at 50% probability.
3. Results and Discussion
All compounds were evaluated for their affinities toward cloned human α1–ARs in binding
assays, and the results were expressed as Ki values. Clog P values were determined by ACD labs ver.
12.0 [24].
First, we investigated the substituent effect at the amine residue as shown in Figure 2, to
determine the most important substituents of 7 to drive its potency and selectivity (Table 2). The 3-
chlorobenzyl derivative 10 and 2-methylsulfonylbenzyl derivative 11 were synthesized in order to
confirm the essential moiety for α1–AR binding affinity. The removal of chloro group led to an
increase in the binding affinity for α1D-AR. Therefore, 11 was selected for further investigation.
Next, the influence of linker length between the core scaffold amine and the N-terminal phenyl ring
was investigated. Compounds 16 (phenethyl) and 17 (3-phenylpropyl) showed binding affinities
equipotent to that of 11; however, the LLE score decreased with increasing clog P values. As for the
subtype selectivity, a longer linker length worsened the selectivity (11 vs 16 and 17). This indicated
that a methylene linker is essential for selective α1D-AR binding, while linker lengths of more than
two atoms are needed to exhibit binding affinity for both α1A- and α1B-ARs. These observations are
consistent with the known structures and biological activities of tamsulosin, silodosin, and 6, which
had linkers of two or three atoms and showed binding affinity for α1A- and α1B-ARs (Figure 4). We
then decided to determine if the binding affinity would be affected by the introduction of a methyl

group at the benzylic position. Thus, the 2-methylsulfonylphenethyl derivative 22a was synthesized
ACCEPTED MANUSCRIPT
and found to have a significantly reduced α1D-AR binding affinity, presumably due to an unfavorable
conformation of the 2-methylsulfonyl group caused by the introduction of the methyl group. We
therefore postulated that immobilization of the methylsulfonyl moiety into a favorable conformation
around the ortho-position could be used to favor strong binding affinity. Indeed, the thiochromene
derivative 22b exhibited binding affinity equipotent to that of 11, while the dihydrobenzothiophene
derivative 12 showed a decreased binding affinity due to an undesired position of sulfonyl moiety.
This suggested that the orientation of the sulfonyl group must be quite restricted to demonstrate both
strong binding affinity and high subtype selectivity for α1D-AR.
Table 2. Affinity towards cloned human α1A-, α1B- and α1D-ARs and physicochemical properties of
2-chloro-5-fluorophenoxyethylamine derivatives.

Cl
ACCEPTED MANUSCR
H
IPT
R
N
F
O
Ki (nM)a
α 1B
compd
R
LLEb clog P
α1A
α 1D
Cl
7
1800 1100
17
4.3
3.49
SO2Me
Cl
10
11
>270 >120 65
>270 >120 4.3
2.2
5.7
5.00
2.65
SO2Me
16
17
150
50
30
44
8.6
9.1
5.2
4.8
2.84
3.22
MeO2S
MeO2S
22a
12
>270 >120 >94
>270 >120 >94
>270 >120 3.9
—
2.96
2.92
3.17
Me SO2Me
—
SO2
22b
5.2
SO2
aKi value for α1D was obtained by displacement of 7-methoxy-[3H]-prazosin from cloned human
receptor.
bLLE = −log(Ki)−clog P.

ACCEPTED MANUSCRIPT
Figure 4. Linker length at the amine residue of 1, 2, 6, 11 and 22b.
On the basis of the results shown in Table 2, it was determined that linker length was crucial
for subtype selectivity for α1A- and α1B-AR, and immobilization by cyclization was an acceptable
approach to retain the potency for α1D-AR. Thus, we selected the 2-methylsulfonylbenzyl derivative
11 and thiochromene derivative 22b, which showed higher binding activities and LLE scores than
compound 7 did, to evaluate their effects on phenylephrine–induced bladder contractions in isolated
bladder strips taken from rats with BOO (Table 3). Both compounds showed better bladder
contraction-inhibitory potency than 7 did. In particular, 22b showed a 4.6-fold higher potency than
11 did. This indicated that rigidification of the structure was an effective method of inhibiting α1D-
AR-mediated bladder contractions.
Table 3. Evaluation of the selected compounds.

aKi value for α1D was obtained by displacement of 7-methoxy-[3H]-prazosin from cloned human
ACCEPTED MANUSCRIPT
receptor.
bLLE = −log(Ki)−clog P.
cEffects on the phenylephrine-induced contractions of the bladder strips taken from the rats with
BOO (n = 2−11).
dNumbers in brackets represent 95% confidence interval.
Next, we evaluated in vitro pharmacokinetic properties (absorption, distribution, metabolism,
elimination [ADME]) of 22b. This compound exhibited improved human metabolic stability and
less ability to inhibit cytochrome P-450 3A4 inhibition (CYP3A4) as shown in Table 4. Thus, we
investigated the substituent effect at the phenoxy residue on the terminal phenyl ring. In comparison
with 22b, 23b with a 2,5-difluorophenoxy substituent demonstrated better in vitro ADME properties
and similar LLE, but showed a lower Ki value. Accordingly, further optimization was carried out
with the 2,5-difluorophenoxy substituent pattern.
Table 4. Profiles of 22b and 23b.
aKi value for α1D was obtained by displacement of 7-methoxy-[3H]-prazosin from cloned human
receptor.
bLLE = −log(Ki)−clog P.
First, we examined the SAR of the thiochromene ring by introducing methoxy groups onto 4
positions. Stronger binding affinity was observed when methoxy was substituted onto the 5- or 6-

position, although a lower binding affinity was confirmed when methoxy was substituted onto the 7-
ACCEPTED MANUSCRIPT
or 8-position. It is notable that the 6-methoxy derivative 37a demonstrated a more than 10-fold
higher binding affinity than 23b did. This result implied that introduction of the substituent onto the
6-position of the thiochromene ring provides the highest affinity. Next, we explored various
substituents at the 6-position to determine which showed the strongest potency. Compounds 38 (R =
fluoro), 39 (R = methylsulfonyl), and 40 (R = aminocarbonyl) showed weaker potency than 37a did.
Interestingly, compound 41 (R= methylamino) showed 2-fold higher binding affinity to α1D-AR and
a better LLE score than 37a without loss of ADME properties. These results indicated that 6-
methylamino group of 41 is the optimal substituent.
Table 5. Affinity for cloned human α1-AR and physicochemical properties for (2,5-di-
fluorophenoxyethyl)thiochroman-4-amine 1,1-dioxide derivatives.
6
F
7
5
H
R
N
8
F
O
SO2
LLEb
5.1
compd
R
H
α 1D Kia
clog P Clint (human)
CYP3A4
(µL/min/mg) (%inh. at 10 µM)
(nM)
23b
17
2.63
44
26.5
23c
37a
37b
9.5
1.5
38
5-OMe
6-OMe
5.0
5.8
4.4
2.98
2.98
2.98
87
53
71
28.6
22.7
34.3
7-OMe
8-OMe
6-F
37c
38
170 3.8
2.98
2.90
1.62
34
39
11
17.1
23.1
5.2
12
5.0
6-SO2Me
6-CONH2
39
310 4.9
40
41
86
5.4
1.71
2.89
19
45
12.5
26.1
6-NHMe 0.85 6.2
aKi value for α1D was obtained by displacement of 7-methoxy-[3H]-prazosin from cloned human
receptor.
bLLE = −log(Ki)−clog P.

From the results shown in Table 5, we selected 41 for further evaluation. The biochemical
ACCEPTED MANUSCRIPT
data from in vitro studies of 41 are shown in Table 6. This analog exhibited more than 400-fold AR-
subtype selectivity for α1D-AR over α1A- and α1B-ARs, and dose-dependently inhibited bladder
contractions with an IC30 value of 80 nM. We then evaluated the difference between the two
enantiomers of 41. The eutomer, (S)-41, showed better a IC30 value than the racemate, with high
subtype selectivity. The other optically resolved chiral derivatives tended to yield similar results
(data not shown). Additionally, the α1D-AR binding affinity, subtype selectivity over α1A- and α1B-
ARs, and inhibitory activity on the phenylephrine-induced contractions of bladder strips of (S)-41
were equivalent to those for TAK–259.
Table 6. In vitro biochemical activity profile of 41.
Ki (nM)a
Selectivity
phenylephrine-induced Clint (human)
CYP3A4
compd
LLEb
contractionc, IC30 (nM)d
(µL/min/mg) (%inh. at 10 µM)
1A/1D 1B/1D
1D
1A
1B
41
350 430
0.85 6.2
4.3
410
19
510
>20
500
80 [6.7–970]
–
45
59
45
26.1
26.7
20.7
41
41
1200 >1200 62
(R)-
130 150
0.30 6.6
430
5.5 [3.0–10]
(S)-
TAK-259 220 880
1.1 8.7
200
800
12 [5.6–19]
1
-1.9
aKi value for α1D was obtained by displacement of 7-methoxy-[3H]-prazosin from cloned human
receptor.
bLLE = −log(Ki)−clog P.
cEffects on the phenylephrine-induced bladder contractions in rats with BOO (n = 7 − 8).
dNumbers in brackets represent 95% confidence interval.
4. Conclusion
In this report, we describe the discovery of (4S)-N4-[2-(2,5-difluorophenoxy)ethyl]-N6-
methyl-3,4-dihydro-2H-thiochromene-4,6-diamine 1,1-dioxide, (S)-41, as a novel and selective
human α1D-AR antagonist containing a phenoxyethylamine based scaffold. Our modification
activities using LLE score as an evaluation index led to the identification of an important structural

motif contributing to selective α1D-AR antagonist activity. First, retaining subtype selectivity was
ACCEPTED MANUSCRIPT
indispensable to choose the proper linker length between the amine and phenyl ring. Next,
thiochromene analog by conformational constraint approach of the sulfonyl group was found as
more suitable substituent for inhibition of the bladder contractions. Further SAR exploration resulted
in the identification of the highly selective and potent α1D-AR antagonist (S)-41 equivalent to our
clinical compound TAK–259. These results indicated that (S)-41 is worthy of further investigation
for the development of drugs for the treatment of overactive bladder symptoms.
5. Experimental Section
5.1 Chemistry
Reagents and solvents were obtained from commercial sources and used without further
purification. Melting points were determined on a BÜCHI B-545 melting point apparatus and were
uncorrected. Proton nuclear magnetic resonance (1H NMR) spectra and carbon nuclear magnetic
resonance (13C NMR) spectra were recorded on Bruker Ultra Shield-300 (300 MHz), 400 (400
MHz) or Bruker Avance II 600 (600 MHz) instruments. Chemical shifts are given in δ values (ppm)
with tetramethylsilane as an internal standard. Abbreviations are used as follows: s = singlet, d =
doublet, t = triplet, tt = triplet of triplets, m = multiplet, dd = doublet of doublets, ddd = doublet of
doublet of doublets, br = broad, quin = quintet. Coupling constants (J values) are given in hertz (Hz).
Elemental analyses were carried out by Takeda Analytical Laboratories, Ltd., and were within
±0.4% of the theoretical values unless otherwise noted. Low-resolution mass spectra (MS) were
determined on a Shimadzu UFLC/MS (Prominence UFLC high pressure gradient system/LCMS-
2020) with an L-column 2 ODS (3.0 × 50 mm I.D., CERI, Japan), and Waters Liquid
Chromatography–Mass Spectrometer System (MS), using a CAPCELL PAK UG-120 ODS
(Shiseido Co., Ltd.) column (2.0 mm i.d. × 50 mm) with aqueous CH3CN (10–95%) containing
0.05% trifluoroacetic acid (TFA), or an HP-1100 (Agilent Technologies) apparatus for monitoring at
220 nm. All MS experiments were performed using electrospray ionization (ESI) in positive ion
mode. HPLC separation was carried out using a Gilson system employing the following conditions;
Column: Shiseido Capcelpak C18 UG-120, S-5 µM, 20 x 50 mm or YMC CombiPrep Hydrosphere

C18 HS-340-CC, S-5 µM, 20 x 50 mm; Mobile phase: A: 0.1% trifluoroacetic acid in water, B:
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0.1% trifluoroacetic acid in acetonitrile; gradient cycle: 0.00 min (A/B＝95/5), 1.10 min (A/B＝
95/5), 5.00 min (A/B＝0/100), 6.40 min (A/B＝0/100), 6.50 min (A/B＝95/5); flow rate; 20
ml/min; detection UV 200 nm. After purification by preparative HPLC, the solutions were
neutralized by PL-HCO3 MP tube (200 mg cartridge, Polymer Laboratories Ltd.). Reaction progress
was determined by thin layer chromatography (TLC) analysis on Merck Kieselgel 60 F254 plates or
Fuji Silysia NH plates. Chromatographic purification was carried out on silica gel columns (Merck
Kieselgel 60, 70–230 mesh; Merck, 230–400 mesh; or Chromatorex NH-DM 1020, 100–200 mesh)
or on Purif-Pack (SI ɸ 60 µm or NH ɸ 60 µm, Fuji Silysia Chemical, Ltd.). Yields are not optimized.
5.1.1. General procedure for the preparation of compounds 7, 10–12
A mixture of 9 (0.54 g, 2.15 mmol), benzylamine (1.95 mmol) and K2CO3 (4.88 mmol) in
EtOH (20 mL) was stirred for 24 h at 90 °C, poured into water and extracted with AcOEt. The
extract was washed with brine, dried with MgSO4 and concentrated in vacuo. The residue was
purified by column chromatography on NH silica gel (AcOEt/ hexane) to give 7 and 10–12 as free
bases. The free bases of 7 and 10–12 were then dissolved in EtOH (1 mL) and 4 M HCl in AcOEt (1
mL) was added. The resulting precipitate was collected by filtration and recrystallized from EtOH
and Et2O to give 7, 10–12.
5.1.2.
2-(2-Chloro-5-fluorophenoxy)-N-[5-chloro-2-(methylsulfonyl)benzyl]ethanamine
hydrochloride (7)
Yield 8%. 1H NMR (300 MHz, DMSO-d6): δ 3.33 (s, 3H), 3.52 (br. s. 2H), 4.45 (t, 2H, J = 4.7 Hz),
4.67 (br. s., 2H), 6.90 (td, 1H, J = 8.4, 2.8 Hz), 7.22 (dd, 1H, J = 10.6, 2.7 Hz), 7.51 (dd, 1H, J = 8.7,
6.1 Hz), 7.76–7.90 (m, 1H), 7.96–8.11 (m, 2H), 9.45 (br. s., 2H). 13C NMR (75 MHz, DMSO-d6) δ
45.0, 46.6, 47.6, 65.6, 103.0, 109.2, 117.5, 130.5, 131.3, 132., 133.0, 133.9, 138.9, 139.2, 154.6,

160.4. Mp 180–182 °C. Anal. Calcd for C16H17Cl3FNO3S: C, 44.82; H, 4.00; N, 3.27. Found: C,
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44.85; H, 4.16; N, 3.23. LC–MS (ESI) m/z: 393.1 [M+H+−(HCl)].
5.1.3. 2-(2-Bromoethoxy)-1-chloro-4-fluorobenzene (9)
A mixture of 8 (25.0 g, 0.171 mol) and 1,2-dibromoethane (64.1 g, 0.341 mol) in 1 M NaOH
(171 mL) was stirred for 16 h at 90 °C and extracted with AcOEt. The extract was washed with
brine, dried with MgSO4 and concentrated in vacuo. The residue was purified by column
chromatography on silica gel (AcOEt/hexane = 1:10) to give the title compound (16.7 g, 39%) as a
colorless oil. 1H NMR (300 MHz, CDCl3): δ 3.59–3.76 (m, 2H), 4.32 (t, 2H, J = 6.4 Hz), 6.59–6.75
(m, 2H), 7.32 (dd, 1H, J = 5.9 Hz).
5.1.4. N-(3-Chlorobenzyl)-2-(2-chloro-5-fluorophenoxy)ethanamine hydrochloride (10)
Yield 10%. 1H NMR (300 MHz, DMSO-d6): δ 3.38 (t, 2H, J = 5.1 Hz), 4.31 (s, 2H), 4.44 (t, 2H, J =
5.1 Hz), 6.89 (td, 1H, J = 8.5, 3.0 Hz), 7.21 (dd, 1H, J = 10.6, 2.7 Hz), 7.40–7.59 (m, 4H), 7.71 (s,
1H), 9.59 (br. s., 2H). 13C NMR (101 MHz, DMSO-d6) δ 44.9, 49.7, 65.1, 102.5, 108.7, 116.9, 128.9,
130.0, 130.5, 130.8, 133.1, 134.4, 154.1, 160.3, 162.7. Mp 165–166 °C. Anal. Calcd for
C15H15Cl3FNO: C, 51.38; H, 4.31; N, 3.99. Found: C, 51.37; H, 4.28; N, 3.84. LC–MS (ESI) m/z:
314.0 [M+H+−(HCl)].
5.1.5. 2-(2-Chloro-5-fluorophenoxy)-N-[2-(methylsulfonyl)benzyl]ethanamine (11).
Yield 21%. 1H NMR (300 MHz, CDCl3): δ 3.14 (t, 2H, J = 5.1 Hz), 3.29 (s, 3H), 4.06–4.18 (m, 2H),
4.31 (s, 2H), 6.59–6.71 (m, 2H), 7.29 (dd, 1H, J = 8.5, 5.9 Hz), 7.43–7.52 (m, 1H), 7.54–7.66 (m,
2H), 8.09 (d, 1H, J = 7.6 Hz). NH proton was not observed. 13C NMR (76 MHz, DMSO-d6) δ 44.53,

47.30, 49.61, 68.90, 102.08, 107.81, 116.70, 127.80, 129.03, 130.48, 131.40, 133.56, 138.95, 154.90,
ACCEPTED MANUSCRIPT
159.90, 163.12. LC–MS (ESI) m/z: 358.0 [M+H+].
5.1.6.
N-[2-(2-Chloro-5-fluorophenoxy)ethyl]-2,3-dihydro-1-benzothiophen-3-amine
1,1-
dioxide hydrochloride (12)
Yield 4%. 1H NMR (300 MHz, DMSO-d6): δ 3.29–3.45 (m, 1H), 3.46–3.62 (m, 1H), 3.89–4.10 (m,
1H), 4.17–4.34 (m, 1H), 4.47 (br. s., 2H), 5.33–5.62 (m, 1H), 6.89 (dt, 1H, J = 2.6, 8.5 Hz), 7.22 (dd,
1H, J = 10.9, 2.6 Hz), 7.50 (dd, 1H, J = 8.7, 6.0 Hz), 7.69–8.05 (m, 3H), 8.09–8.32 (m, 1H), 9.60–
11.17 (m, 2H). 13C NMR (101 MHz, DMSO-d6) δ 43.7, 52.1, 53.5, 64.9, 102.4, 108.6, 116.7, 121.2,
127.7, 130.7, 131.5, 134.2, 139.6, 154.0, 160.2, 162.6. Mp 219–222 °C. LC–MS (ESI) m/z: 356.1
[M+H+−(HCl)].
5.1.7. N-[2-(2-Chloro-5-fluorophenoxy)ethyl]-2-[2-(methylsulfonyl)phenyl]acetamide (14)
A mixture of 13 (1.24 g, 5.49 mmol), 2-[2-(methylsulfanyl)phenyl]acetic acid (1.00 g, 5.49
mmol), WSC (1.26 g, 6.59 mmol), HOBt (1.01 g, 6.59 mmol) and Et3N (0.83 g, 8.23 mmol) in DMF
(20 mL) was stirred for 14 h at 60 °C, poured into water and extracted with AcOEt. The extract was
washed with 1 M HCl, aq. NaHCO3 and brine, dried with MgSO4 and concentrated in vacuo. To a
solution of the residue in AcOEt (50 mL) was added 70 % mCPBA (2.91 g, 11.8 mmol) at room
temperature. The reaction mixture was stirred for 2 h at room temperature and poured into aq.
sodium thiosulfate. The separated organic layer was washed with aq. NaHCO3 and brine, dried with
1
MgSO4 and concentrated in vacuo to give the title compound (1.28 g, 62%) as a colorless solid. H
NMR (300 MHz, CDCl3) δ 3.12 (s, 3H), 3.67 (q, 2H, J = 5.3 Hz), 4.00–4.07 (m, 4H), 6.58–6.75 (m,
3H), 7.27–7.33 (m, 1H), 7.43–7.63 (m, 3H), 8.05 (d, 1H, J = 7.9 Hz). Mp 165–167 °C. LC–MS
(ESI) m/z: 386.0 [M+H+].

5.1.8. N-[2-(2-Chloro-5-fluorophenoxy)ethyl]-3-[2-(methylsulfonyl)phenyl]propanamide (15)
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A mixture of 13 (0.99 g, 4.38 mmol), 3-[2-(methylsulfanyl)phenyl]propanoic acid (1.00 g, 4.38
mmol), WSC (1.09 g, 5.69 mmol), HOBt (0.87 g, 5.69 mmol), and Et3N (0.89 g, 8.76 mmol) in
DMF (20 mL) was stirred for 3 days at 50 °C, poured into 1 M HCl and extracted with AcOEt. The
extract was washed with aq. NaHCO3 and brine, dried with MgSO4 and concentrated in vacuo to
give the title compound (1.35 g, 77%) as a colorless solid. 1H NMR (300 MHz, CDCl3) δ 2.59–2.68
(m, 2H), 3.10 (s, 3H), 3.26–3.36 (m, 2H), 3.69 (q, 2H, J = 5.3 Hz), 4.03 (t, 2H, J = 5.1 Hz), 6.19 (br.
s., 1H), 6.60–6.70 (m, 2H), 7.27–7.43 (m, 3H), 7.47–7.55 (m, 1H), 8.00 (d, 1H, J = 7.9 Hz). Mp 96–
97 °C. Anal. Calcd for C18H19ClFNO4S: C, 54.07; H, 4.79; N, 3.50. Found C, 54.04; H, 4.73; N,
3.37. LC–MS (ESI) m/z: 400.1 [M+H+].
5.1.9. 2-(2-Chloro-5-fluorophenoxy)-N-{2-[2-(methylsulfonyl)phenyl]ethyl}ethanamine (16)
To a solution of 14 (1.00 g, 2.59 mmol) in THF (50 mL) was added 1 M BH3 in THF (9.0 mL) at
0 °C. After stirring at 80 °C for 4 h, the reaction was quenched with ice. The whole was added to 1
M HCl and stirred at 80 °C for 14 h. The mixture was cooled to room temperature and diluted with
AcOEt. The aqueous layer was basified by 8 M NaOH and extracted with AcOEt and THF. The
extract was washed with brine, dried with MgSO4 and concentrated in vacuo to give the title
compound (80.0 mg, 8%) as a colorless oil. 1H NMR (300 MHz, CDCl3) δ 3.03–3.16 (m, 7H), 3.21–
3.30 (m, 2H), 4.10 (t, 2H, J = 5.1 Hz), 6.58–6.71 (m, 2H), 7.24–7.32 (m, 1H), 7.36–7.47 (m, 2H),
7.53–7.63 (m, 1H), 8.05 (d, 1H, J = 7.9 Hz). 13C NMR (75 MHz, DMSO-d6) δ 33.3, 44.8, 48.0, 51.2,
69.8, 102.7, 108.3, 117.3, 127.3, 129.1, 131.0, 132.5, 134.0, 139.5, 140.5, 155.5, 162.0. LC–MS
(ESI) m/z: 372.1 [M+H+].
5.1.10.
(17)
N-[2-(2-chloro-5-fluorophenoxy)ethyl]-3-[2-(methylsulfonyl)phenyl]propan-1-amine

The title compound was prepared in a manner similar to that described for the synthesis of 16.
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Yield 5%. 1H NMR (300 MHz, CDCl3) δ 1.87–2.02 (m, 2H), 2.82 (t, 2H, J = 6.8 Hz), 3.03–3.16 (m,
7H), 4.11 (t, 2H, J = 5.1 Hz), 6.57–6.73 (m, 2H), 7.27–7.32 (m, 1H), 7.34–7.45 (m, 2H), 7.51–7.60
13
(m, 1H), 7.99–8.08 (m, 1H). C NMR (76 MHz, DMSO-d6) δ 29.8, 31.7, 44.2, 47.7, 48.7, 69.3,
102.2, 107.8, 116.7, 126.6, 128.6, 130.5, 131.7, 133.5, 138.7, 142.0, 155.0, 161.5. LC–MS (ESI)
m/z: 386.1 [M+H+].
5.1.11. General procedure for the preparation of compounds 20 and 21
A mixture of amine (1.30 mmol), 18 or 19 (1.30 mmol), WSC (1.95 mmol), HOBt (1.95 mmol)
and Et3N (2.60 mmol) in CH3CN (5 mL) was stirred for 2 h at room temperature, poured into water
and extracted with AcOEt. The extract was washed with brine, dried with MgSO4 and concentrated
in vacuo. The residue was purified by column chromatography on silica gel (AcOEt/ hexane) to
afford 20 and 21, respectively.
5.1.12. 2-(2-Chloro-5-fluorophenoxy)-N-{1-[2-(methylsulfonyl)phenyl]ethyl}acetamide (20a)
Yield 91%. 1H NMR (300 MHz, CDCl3): δ 1.59 (d, 3H, J = 6.6 Hz), 3.44 (s, 3H), 4.35–4.60 (m, 2H),
5.75–5.88 (m, 1H), 6.65 (dd, 1H, J = 9.6, 2.8 Hz), 6.73–6.82 (m, 1H), 7.37–7.49 (m, 4H), 7.56–7.65
(m, 1H), 8.01–8.08 (m, 1H). LC–MS (ESI) m/z: 386.0 [M+H+].
5.1.12.
2-(2-Chloro-5-fluorophenoxy)-N-(1,1-dioxido-3,4-dihydro-2H-thiochromen-4-
yl)acetamide (20b)
1
Yield 89%. H NMR (300 MHz, CDCl3): δ 2.59–2.87 (m, 2H), 3.39–3.57 (m, 2H), 4.61 (s, 2H),
5.49 (td, 1H, J = 8.4, 5.1 Hz), 6.65–6.80 (m, 2H), 7.18 (d, 1H, J = 8.3 Hz), 7.34 (dd, 1H, J = 8.9, 5.8
Hz), 7.39–7.46 (m, 1H), 7.51–7.62 (m, 2H), 7.90–8.02 (m, 1H). Mp 120–121 °C. Anal. Calcd for

C17H15ClFNO4S: C, 53.20; H, 3.94; N, 3.65. Found: C, 53.31; H, 4.03; N, 3.65. LC–MS (ESI) m/z:
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382.0 [M−H+].
5.1.13.
(21b)
2-(2,5-Difluorophenoxy)-N-(1,1-dioxido-3,4-dihydro-2H-thiochromen-4-yl)acetamide
1
Yield 85%. H NMR (300 MHz, CDCl3): δ 2.57–2.84 (m, 2H), 3.36–3.57 (m, 2H), 4.54–4.68 (m,
2H), 5.50 (td, 1H, J = 8.3, 5.3 Hz), 6.65–6.78 (m, 2H), 7.00–7.14 (m, 2H), 7.34–7.43 (m, 1H), 7.48–
7.64 (m, 2H), 7.91–8.01 (m, 1H). LC–MS (ESI) m/z: 368.0 [M+H+].
5.1.14.
2-(2,5-Difluorophenoxy)-N-(5-methoxy-1,1-dioxido-3,4-dihydro-2H-thiochromen-4-
yl)acetamide (21c)
1
Yield 89%. H NMR (300 MHz, CDCl3) δ 2.70–2.80 (m, 2H), 3.25–3.35 (m, 1H), 3.45–3.60 (m,
1H), 3.83 (s, 3H), 4.50 (d, 1H, J = 14.7 Hz), 4.58 (d, 1H, J = 14.7 Hz), 5.54 (quin, 1H, J = 3.5 Hz),
6.64–6.76 (m, 3H), 6.96–7.10 (m, 2H), 7.49–7.56 (m, 2H). LC–MS (ESI) m/z: 396.0 [M−H+].
5.1.15. General procedure for the preparation of compounds 22 and 23
To a solution of 20 or 21 (1.14 mmol) in THF (5 mL) was added 1 M BH3 in THF (3.4 mL) at
0 °C. After stirring at 70 °C for 2 h, the reaction was quenched with ice. The whole was added to 1
M HCl and stirred at 70 °C for 2 h. The mixture was cooled to room temperature and diluted with
AcOEt. The aqueous layer was basified by 8 M NaOH and extracted with AcOEt. The extract was
washed with brine, dried with MgSO4, and concentrated in vacuo. To the residue was added 4 M
HCl in AcOEt at room temperature. The resulting precipitate was filtered off and washed with
diisopropyl ether to give 22 or 23.

5.1.16.
N-[2-(2-Chloro-5-fluorophenoxy)ethyl]-1-[2-(methylsulfonyl)phenyl]ethanamine
ACCEPTED MANUSCRIPT
hydrochloride (22a)
Yield Quant. 1H NMR (300 MHz, CDCl3) δ 1.97 (d, 3H, J = 6.8 Hz), 3.12–3.20 (m, 3H), 3.25–3.60
(m, 2H), 4.32–4.62 (m, 2H), 5.52–5.70 (m, 1H), 6.58–6.76 (m, 2H), 7.22–7.36 (m, 1H), 7.54–7.67
(m, 1H), 7.75–7.89 (m, 1H), 8.00–8.17 (m, 1H), 8.33–8.47 (m, 1H), 9.67–9.94 (m, 1H), 10.80–11.05
13
(m, 1H). C NMR (76 MHz, DMSO-d6) δ 19.9, 44.7, 53.0, 59.7, 64.9, 102.5, 108.6, 116.9, 128.6,
129.5, 130.7, 134.7, 137.0, 139.0, 154.1, 159.8, 163.0. LC–MS (ESI) m/z: 372.1 [M+H+−(HCl)].
5.1.17.
N-[2-(2-Chloro-5-fluorophenoxy)ethyl]-3,4-dihydro-2H-thiochromen-4-amine
1,1-
dioxide hydrochloride (22b)
Yield 9%. 1H NMR (300 MHz, DMSO-d6): δ 2.84 (br. s., 2H), 3.48–3.96 (m, 4H), 4.43 (br. s., 2H),
4.95 (br. s., 1H), 6.81–6.95 (m, 1H), 7.22 (dd, 1H, J = 10.4, 2.5 Hz), 7.52 (dd, 1H, J = 8.7, 6.1 Hz),
13
7.76 (br. s., 2H), 7.93 (br. s., 2H), 9.60 (br. s., 2H). C NMR (76 MHz, DMSO-d6) δ 22.5, 43.1,
45.2, 52.5, 65.0, 102.4, 108.6, 116.8, 123.5, 130.6, 132.8, 139.5, 154.2, 158.7, 159.1, 159.8, 163.1.
Mp 193–194 °C. Anal. Calcd for C17H18Cl2FNO3S: C, 50.25; H, 4.47; N, 3.45. Found: C, 50.01; H,
4.66; N, 3.45. LC–MS (ESI) m/z: 370.0 [M+H+−(HCl)].
5.1.18. N-[2-(2,5-Difluorophenoxy)ethyl]-3,4-dihydro-2H-thiochromen-4-amine 1,1-dioxide
hydrochloride (23b)
Yield 74%. 1H NMR (300 MHz, DMSO-d6): δ 2.67–2.95 (m, 2H), 3.46–3.58 (m, 2H), 3.59–3.74 (m,
1H), 3.82–4.01 (m, 1H), 4.32–4.51 (m, 2H), 4.83–5.01 (m, 1H), 6.76–6.91 (m, 1H), 7.15–7.38 (m,
13
2H), 7.65–7.82 (m, 2H), 7.84–8.03 (m, 2H), 9.47–9.95 (m, 2H). C NMR (76 MHz, DMSO-d6) δ
22.5, 43.2, 45.2, 52.6, 64.8, 103.2, 107.2, 116.6, 123.4, 130.7, 130.7, 132.7, 139.6, 146.4, 149.7,
156.6, 159.8. Mp 153–156 °C. Anal. Calcd for C17H18ClF2NO3S: C, 52.38; H, 4.65; N, 3.59. Found:
C, 52.30; H, 4.75; N, 3.56. LC–MS (ESI) m/z: 354.1 [M+H+−(HCl)].

ACCEPTED MANUSCRIPT
5.1.19. N-[2-(2,5-Difluorophenoxy)ethyl]-5-methoxy-3,4-dihydro-2H-thiochromen-4-amine 1,1-
dioxide hydrochloride (23c)
Yield 66%. 1H NMR (400 MHz, DMSO-d6) δ 2.60–2.80 (m, 1H), 2.85–3.00 (m, 1H), 3.50–3.70 (m,
3H), 3.86 (s, 3H), 4.18–4.36 (m, 1H), 4.36–4.60 (m, 2H), 4.80–4.95 (m, 1H), 6.80–6.90 (m, 1H),
7.20–7.38 (m, 2H), 7.41 (d, 1H, J = 8.4 Hz), 7.49 (d, 1H, J = 8.4 Hz), 7.72 (t, 1H, J = 8.3 Hz), 8.64
(br. s., 1H), 9.92 (br. s. , 1H). 13C NMR (101 MHz, DMSO-d6) δ 21.8, 44.4, 44.9, 48.5, 56.4, 64.8,
103.2, 107.2, 114.4, 115.1, 116.6, 118.5, 132.4, 140.0, 146.4, 148.1, 156.9, 158.3. Anal. Calcd for
C18H20ClF2NO4S: C, 51.49; H, 4.80; N, 3.34. Found C, 51.60; H, 4.82; N, 3.37. LC–MS (ESI) m/z:
384.1 [M+H+−(HCl)].
5.1.20. 1-[2-(Methylsulfonyl)phenyl]ethanamine hydrochloride (25)
A mixture of 24 (5.11 g, 25.8 mmol) and MeONH2·HCl (2.80 g, 33.5 mmol) in pyridine (30
mL) was stirred overnight at room temperature, poured into water and extracted with AcOEt. The
extract was washed with 1 M HCl and brine, dried with MgSO4 and concentrated in vacuo. To a
solution of the residue in THF (100 mL) was added 1 M BH3 in THF (75 mL) at 0 °C. After stirring
at 80 °C for 4 h, the mixture was cooled to room temperature and 1 M HCl (120 mL) was added.
After stirring at 80 °C for 2 h, the mixture was cooled to room temperature and diluted with AcOEt.
The separated aqueous layer was basified with 8 M NaOH and extracted with AcOEt and THF. The
extract was washed with brine, dried with MgSO4 and concentrated in vacuo. The residue was
dissolved in MeOH and 4 M HCl in AcOEt (20 mL) was added. The resulting precipitate was
filtered off and washed with AcOEt to give the title compound (1.35 g, 22%) as a colorless solid. 1H
NMR (300 MHz, DMSO-d6) δ 1.55 (d, 3H, J = 6.8 Hz), 3.36 (s, 3H), 5.21 (br. s., 1H), 7.63–7.72 (m,
1H), 7.83–7.91 (m, 1H), 7.97–8.06 (m, 2H), 8.68 (br. s., 3H). Mp 238–240 °C. LC–MS (ESI) m/z:
200.0 [M+H+−(HCl)].

ACCEPTED MANUSCRIPT
5.1.21. 3-[(2-Bromo-5-fluorophenyl)sulfanyl]propionic acid (27)
A mixture of 26 (2.38 g, 11.5 mmol) and 8 M NaOH (1.8 mL) in H2O (5.8 mL) was stirred at
room temperature for 10 min. To the mixture was added a solution of 3-bromopropionic acid (1.76 g,
11.5 mmol) and K2CO3 (0.80 g, 5.79 mmol) in H2O (5.3 mL) at room temperature, and the mixture
was stirred at room temperature for 5 days. The reaction mixture was acidified by 1 M HCl, and
extracted with AcOEt. The extract was washed with H2O and brine, dried with MgSO4 and
concentrated to provide the title compound (3.18 g, 11.4 mmol, 99%) as a pale solid, which was
1
collected with hexane. H NMR (300 MHz, CDCl3) δ 2.77 (t, 2H, J = 7.2 Hz), 3.20 (t, 2H, J =
7.2Hz), 6.74–6.81 (m, 1H), 6.98 (dd, 1H, J = 9.0, 2.7 Hz), 7.49 (dd, 1H, J = 8.4, 5.1 Hz), 7.62 (dd,
1H, J = 9.0, 5.4 Hz). Mp 124–126 °C.
5.1.22. 8-Bromo-5-fluoro-2,3-dihydro-4H-thiochromen-4-one (28)
A mixture of 27 (2.0 g, 7.17 mmol) in conc. H2SO4 (20 mL) was stirred at room temperature for
30 min and poured into ice and H2O. The product was extracted with AcOEt and the extract was
washed with H2O and brine , dried with MgSO4 and concentrated in vacuo. The residue was purified
by column chromatography on silica gel (AcOEt/hexane = 19:1–4:1) to provide the title compound
1
(692 mg, 37%) as a brown solid. H NMR (300 MHz, CDCl3) δ 2.95–3.00 (m, 2H), 3.23–3.28 (m,
2H), 6.78 (dd, 1H, J = 10.8, 8.7 Hz), 7.60 (dd, 1H, J = 9.0, 4.8 Hz). Mp 102–104 °C. LC–MS (ESI)
m/z: 258.8 [M−H+].
5.1.23. 8-Bromo-5-fluoro-2,3-dihydro-4H-thiochromen-4-one 1,1-dioxide (29)
To a solution of 28 (0.62 g, 2.38 mmol) in AcOEt (20 mL) was added mCPBA (1.17 g, 4.75
mmol) at 0 °C, and the mixture was stirred at room temperature for 14 h and poured into aq.
NaHCO3. The separated organic layer was washed with aq. NaHCO3 and brine, dried with MgSO4

1
and concentrated to provide the title compound (0.63 g, 91%) as a colorless solid. H NMR (300
ACCEPTED MANUSCRIPT
MHz, CDCl3) δ 3.35–3.39 (m, 2H), 3.74–3.79 (m, 2H), 7.27 (dd, 1H, J = 10.2, 8.7 Hz), 7.94 (dd, 1H,
J = 9.0, 4.5 Hz). Mp 162–165 °C.
5.1.24. 5-Fluoro-2,3-dihydro-4H-thiochromen-4-one 1,1-dioxide (30)
A mixture of 29 (1.00 g, 3.41 mmol) and Pd/C (0.50 g) in EtOH (100 mL) was stirred at room
temperature for 14 h under H2 atmosphere. The mixture was filtrated through Celite and
concentrated in vacuo. The precipitate was collected by diisopropyl ether to provide the title
1
compound (713 mg, 98%) as a colorless solid. H NMR (300 MHz, CDCl3) δ 3.37–3.42 (m, 2H),
3.67–3.71 (m, 2H), 7.44 (ddd, 1H, J = 9.6, 8.1, 1.8 Hz), 7.76–7.87 (m, 2H). Mp 140–141 °C.
5.1.25. 5-Fluoro-3,4-dihydro-2H-thiochromen-4-amine 1,1-dioxide (31)
A mixture of 30 (577 mg, 2.69 mmol) and MeONH2·HCl (292 mg, 3.50 mmol) in pyridine (5
mL) was stirred at room temperature for 14 h. The mixture was poured into 1 M HCl and extracted
with ethyl acetate. The separated organic layer was washed with 1 M HCl and water, dried with
MgSO4 and concentrated in vacuo. The residue was purified by column chromatography on silica
gel (AcOEt/hexane = 1:9–1:2) to provide a white powder. To a solution of the obtained powder in
THF (5 mL) was added 1 M BH3 in THF (13.4 mL) at 0 °C. The resulting mixture was stirred at
80 °C for 1.5 h, and then the reaction mixture was allowed to reach room temperature and 1 M HCl
(27 mL) was added. The mixture was stirred at 80 °C for 1 h, cooled to room temperature, basified
with 8 M NaOH (4 mL) and extracted with AcOEt. The extract was washed with water, dried with
MgSO4 and concentrated in vacuo. The residue was purified by column chromatography on silica
gel (AcOEt/hexane = 1:1–7:3, then MeOH/AcOEt = 1:19) to provide the title compound (420 mg,
1
73%) as a colorless solid. H NMR (400 MHz, CDCl3) δ 2.35–2.42 (m, 1H), 2.74–2.88 (m, 1H),
3.24 (ddd, 1H, J = 8.7, 6.3, 2.4 Hz), 3.80–3.92 (m, 1H), 4.55 (t, 1H, J = 3.9 Hz), 7.23–7.30 (m, 1H),