Synthesis and structure-activity relationships of a series of benzazepine derivatives as 5-HT2C receptor agonists

Article abstract of DOI:10.1016/j.bmc.2007.12.009

To identify potent and selective 5-HT_2C receptor agonists, a series of novel benzazepine derivatives were synthesized, and their structure-activity relationships examined. The compounds were evaluated for their 5-HT_2C, 5-HT_2A

Full text of DOI:10.1016/j.bmc.2007.12.009

Available online at www.sciencedirect.com
Bioorganic & Medicinal Chemistry 16 (2008) 3309–3320
Synthesis and structure–activity relationships of a series
of benzazepine derivatives as 5-HT2C receptor agonists
Itsuro Shimada,a,* Kyoichi Maeno,a Yutaka Kondoh,a Hidetaka Kaku,a Keizo Sugasawa,a
Yasuharu Kimura,a Ken-ichi Hatanaka,b Yuki Naitou,a Fumikazu Wanibuchi,a
Shuichi Sakamotoc and Shin-ichi Tsukamotoa
aDrug Discovery Research, Astellas Pharma Inc., 21 Miyukigaoka, Tsukuba, Ibaraki 305-8585, Japan
bSales & Marketing, Astellas Pharma Inc., 2-3-11 Nihonbashi-honcho, Chuo-ku, Tokyo 103-8411, Japan
cTechnology, Astellas Pharma Inc., 3-17-1 Hasune, Itabashi-Ku, Tokyo 174-8612, Japan
Received 8 November 2007; revised 4 December 2007; accepted 4 December 2007
Available online 8 December 2007
Abstract—To identify potent and selective 5-HT2C receptor agonists, a series of novel benzazepine derivatives were synthesized, and
their structure–activity relationships examined. The compounds were evaluated for their 5-HT2C, 5-HT2A, and 5-HT2B receptor
binding affinity and intrinsic activity for the 5-HT2C and 5-HT2A receptors. Among these compounds, 6,7-dichloro-2,3,4,5-tetrahy-
dro-1H-3-benzazepine (6) was effective in a rat penile erection model when administered po, which is a symptom of the serotonin
syndrome reflecting 5-HT2C receptor activation. Moreover, compound 6 was characterized as a partial agonist of 5-HT2A receptors;
therefore, it had little effect on the cardiovascular system.
ꢀ 2007 Elsevier Ltd. All rights reserved.
1. Introduction
(Ki = 0.89 nM) for cloned human 5-HT2C receptors.11
YM348 also exerted antiobesity effects, as it not only de-
creased food intake, but also increased energy expendi-
ture. One negative effect of this compound was that it
increased mean arterial blood pressure (MABP) dose-
dependently. However, this was completely inhibited
by MDL100907,12 a selective 5-HT2A antagonist. This
result suggests that 5-HT2A receptor agonism is associ-
ated with the increases in MABP. High-throughput
screening (HTS) of in-house compound libraries was
conducted in the hope of discovering a novel class of
5-HT2C receptor agonists that had no cardiovascular ef-
fects. This led to the identification of benzazepine deriv-
ative 2 as a 5-HT2C receptor agonist. Compound 2 binds
moderately to the 5-HT2C receptor (Ki = 66 nM) and
was characterized as a partial 5-HT2A receptor agonist
(Emax = 7%).
The 5-HT2C receptor, one of the 14 identified subtypes
of the 5-HT receptor, is of interest because of its poten-
tial as a therapy for obesity, obsessive compulsive disor-
der, and sexual dysfunction.1–3 Many researchers have
focused their attention on the therapeutic potential of
5-HT2C receptor agonists as antiobesity drugs since this
has became a worldwide health issue. Indeed, the most
commonly used 5-HT2C agonist, m-chlorophenylpiper-
azine (mCPP), is known to decrease food intake in hu-
mans4 and rodents.5 It is also known that mCPP’s
hypophagic effect in rats is attenuated by the selective-
5-HT2C antagonist, SB-242084.6 Moreover, some other
5-HT2C receptor agonists such as RO60-0175,7 WAY-
161503,8 YM348,9 and VER-538410 also have been re-
ported to have anorectic effects in rodents.
Of these, YM348 is
5-HT2C receptor agonist that showed high affinity
a
novel and orally active
In this paper, the synthesis and structure–activity rela-
tionships (SAR) of a series of 3-benzazepine derivatives
(2–11) are described. In addition to their binding affini-
ties for 5-HT2 receptors and efficacies for 5-HT2C and 5-
HT2A receptors, a further characterization of a 5-HT2C
receptor-mediated response, penile erection, of com-
pound 6 is shown. In addition, compound 6 has been
characterized as a partial 5-HT2A receptor agonist, that
Keywords: 5-HT2C receptor agonist; Binding affinity; Benzazepine;
YM348.
*
Corresponding author. Tel.: +81 29 852 6684; fax: +81 29 852
5387; e-mail: itsuro.shimada@jp.astellas.com
0968-0896/$ - see front matter ꢀ 2007 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmc.2007.12.009

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I. Shimada et al. / Bioorg. Med. Chem. 16 (2008) 3309–3320
has little effect on blood pressure, which is a matter of
concern with YM348 (1) (Fig. 1).
tro derivatives. The mixture was separated by column
chromatography, and the desired 5-nitro derivative 2
was isolated in the pure form in 47% yield. The methyl
group on both 2 and 19 was removed using a-chloroeth-
yl chloroformate (ACE-Cl) to afford 4-chloro-5-nitro-
benzazepine (3) and 4,5-dichlorobenzazepine (6),
respectively. Boc protection of benzazepine 3 followed
by the reduction of the nitro group yielded 5-amino ana-
logue 20. Acetylation of the amino group of 20, followed
by treatment of the resultant 21 with MeI, afforded the
alkylated compound 22. Deprotection of 22 with aque-
ous HCl produced the 5-methylamino analogue 9.
2. Chemistry
Synthetic routes for the substituted benzazepines 2–11
are shown in Schemes 1–4. Compounds 2, 3, 6, and 9
were synthesized as depicted in Scheme 1. Commercially
available 2-chlorophenylacetic acid (12) or 2,3-dichlor-
ophenylacetic acid (13) was used as starting material.
The condensation of each acid with 2-(methylamino)eth-
anol resulted in amide compounds 14 and 15, which
were reduced by BH3 to give phenethyl amine deriva-
tives 16 and 17. Conversion of alcohols 16 and 17 into
their corresponding chlorides with PCl5, followed by
AlCl3-catalyzed cyclization, resulted in moderate yield
of the seven-membered ring products 18 and 19. Treat-
ment of 4-chlorobenzazepine 18 with fuming nitric acid
in sulfuric acid resulted in a mixture of regio-isomeric ni-
As shown in Scheme 2, reduction of the nitro group on 2
with iron produced a good yield of the 5-amino ana-
logue 23. Diazotization of 23, followed by treatment
with CuCN, resulted in the 5-cyano analogue 24 in
73% yield. The diazonium salt was also treated with
HF-pyridine or CuBr to yield the 5-fluoro and 5-bromo
analogues 25, 26 in 82% and 67% yield, respectively.
Demethylation of the N-methyl compounds 24–26 using
ACE-Cl afforded the compounds 4, 5, and 7.
Cl
Cl
N
O2N
R
N
O
The 4-chloro-5-methoxy derivative 8 was prepared from
the commercially available compound 27 using the
method in Scheme 3. Thus, after hydrogenation of 27
using 10% palladium on carbon in EtOH, the corre-
sponding aniline 28 was converted to the chloro ana-
logue 29 with a good yield. Bromination of 29 using
NBS provided 30, to which a cyano group was then
introduced, followed by reduction using LiAlH4 and
AlCl3 to yield the phenethylamine derivative 32. A reac-
tion between compound 32 and bromoacetaldehyde
N
NH
NH2
YM348 (1)
2
3 : R = NO2
4 : R = CN
5 : R = F
6 : R = Cl
O
O
NH
NH
7 : R = Br
8 : R = OMe
9 : R = NHMe
10
11
Figure 1. Structures of YM348 and benzazepines 2–11.
Cl
Cl
Cl
Cl
O
R
R
R
R
a
c
b
CO2H
N Me
N Me
N Me
HO
HO
16 : R = H
17 : R = Cl
18 : R = H
2 : R = NO2
19 : R = Cl
d
12 : R = H
13 : R = Cl
14 : R = H
15 : R = Cl
Cl
Cl
Cl
R
f, g
R
i, j
R
e
NH
NBoc
NH
3 : R = NO2
6 : R = Cl
20 : R = NH2
22 : R = NMeAc
9 : R = NHMe
h
k
21 : R = NHAc
Scheme 1. Synthetic route to compounds 2, 3, 6, and 9. Reagents: (a) SOCl2, then 2-(methylamino)ethanol, Et3N, CHCl3 or 2-(methylamino)ethanol,
EDCI, HOBt, DMF; (b) BH3ÆTHF, THF; (c) PCl5, 1,2,4-trichlorobenzene; then AlCl3; (d) f-HNO3, H2SO4; (e) CH3CH(Cl)OCOCl; DCE, then
MeOH; (f) Boc2O, Et3N, AcOEt; (g) Fe, NH4Cl, EtOH, H2O; (h) AcCl, Et3N, THF; (i) MeI, NaH, DMF; (j) HCl, AcOEt; (k) cHCl.
Cl
Cl
Cl
H2N
R
R
b, c or d
a
e
2
N Me
N Me
NH
23
24 : R = CN
25 : R = F
26 : R = Br
4 : R = CN
5 : R = F
7 : R = Br
Scheme 2. Synthetic route to compounds 4, 5, and 7. Reagents: (a) Fe, AcOH; (b) NaNO2, cHCl, then CuCN; (c) NaNO2, 70% HF-pyridine; (d)
NaNO2, 47% HBr–H2O; then CuBr; (e) CH3CH(Cl)OCOCl, DCE, then MeOH.

I. Shimada et al. / Bioorg. Med. Chem. 16 (2008) 3309–3320
3311
NO2
NH2
Cl
Cl
MeO
Me
MeO
Me
MeO
Me
MeO
Cl
b
c
a
Br
27
28
29
30
Cl
Cl
MeO
MeO
MeO
d
g
e
f
CN
NH2
NH
OEt
31
32
33
EtO
Cl
Cl
MeO
MeO
h
NH
NH
34
8
Scheme 3. Synthetic route to compound 8. Reagents: (a) Pd–C, H2, EtOH; (b) NaNO2, cHCl; acetone, H2O, then CuCl; (c) NBS, AIBN, CCl4; (d)
KCN, n-BuHSO4, EtOH, H2O; (e) LiAlH4, AlCl3, THF; (f) BrCH2CH(OEt)2; (g) H2SO4; (h) NaBH3(CN), 0.5 M NaH2PO4aq, THF.
EtO
OH
O
O
O
Me
Me
EtO
Me
Me
Me
Me
b
c, d
a
CN
CN
35
36
37
38
O
O
O
NH
O
e, f
g
NH
39
10
OEt
EtO
O
HO
Me
Me
O
Me
Me
Me
Me
Me
Me
O
b
a
+
40
41
42
43
O
O
O
O
c- h
i
+
+
NBoc
NBoc
NH
NH
44
45
11
46
Scheme 4. Synthetic route to compounds 10 and 11. Reagents and conditions: (a) BrCH2CH(OEt)2, NaH, DMF; (b) PPA, benzene; (c) NBS, AIBN,
CCl4; (d) NaCN, DMSO; (e) HBr, AcOH; (f) NaOAc, H2O; (g) BH3ÆMe2S, THF; (h) Boc2O, THF; (i) HCl, AcOEt.
diethyl acetal afforded 2,2-diethoxyethyl derivative 33 in
45% yield, which was treated with H2SO4 to give the
cyclized product 34 in 8% yield. Finally, reduction of
34 using sodium cyanoborohydride provided the desired
compound 8.
phenol (40) via the same reaction sequence. Cyclization
of the phenoxyacetal 41 afforded an inseparable mixture
of the two dimethylbenzofurans 42 and 43 with a total
yield of 59% in a 1:2 ratio, respectively. The mixture
of 42 and 43 was converted into an inseparable mixture
of benzazepines 11 and 46 via a procedure similar to that
described for 10. The resulting compounds, 11 and 46,
were separated as their N-Boc derivatives 44 and 45 by
silica gel column chromatography (20% and 46% yields,
respectively). The Boc groups were removed from 44
and 45 to afford the benzazepine analogues 11 and 46.
Scheme 4 shows the syntheses of the furan-fused com-
pounds 10 and 11. A reaction of 2,3-dimethylphenol
(35) and bromoacetaldehyde diethyl acetal delivered 1-
(2,2-diethoxyethoxy)-2,3-dimethylbenzene (36). Cycliza-
tion of the phenoxyacetal 36 using PPA provided a good
yield of 6,7-dimethylbenzofuran (37). Bromination of 37
using NBS and AIBN in CCl4 produced the bis(bromo-
methyl) compound, which was converted to the dinitrile
38 in 43% yield. Treatment of 38 with HBr in acetic acid
resulted in the cyclized product 39 in 26% yield. Finally,
the borane reduction of 39 produced 7,8,9,10-tetrahy-
dro-6H-furo[2,3-g][3]benzazepine (10) in 56% yield.
The regio-isomer 11 was obtained from 3,4-dimethyl-
3. Results and discussion
3.1. In vitro assays
The synthesized compounds were evaluated for their 5-
HT2C, 5-HT2A, and 5-HT2B receptor binding affinity.

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I. Shimada et al. / Bioorg. Med. Chem. 16 (2008) 3309–3320
5-HT2C, 5-HT2A, and 5-HT2B receptor binding affinities
were determined using the displacement of agonist
([3H]5-HT) radioligand binding to human 5-HT2C and
5-HT2A receptor sites in Chinese hamster ovary (CHO)
cell membranes or 5-HT2B receptor sites in Human
Embryonic Kidney 293-Epstein–Barr virus nuclear anti-
gen (HEK293-EBNA) cell membranes. The intrinsic
activity of the compounds for the human 5-HT2C and
5-HT2A receptors was determined by measurement of
myo-[3H] inositol turnover in CHO cells. The struc-
ture–activity relationships of the novel benzazepine
derivatives obtained are summarized in Tables 1–3.
and optimization of the substituents on this ring was the
next step.
Table 2 shows the results of substitution at the 7-posi-
tion of benzazepine 3 while retaining the 6-chloro group.
Replacing the 7-nitro group on compound 3 with other
electron-withdrawing groups such as the cyano (4) and
halogen (5–7) analogues resulted in some increase in 5-
HT2C affinities except for the fluoro derivative 5
(Ki = 5.1, 43, 8.8, and 2.4 nM, respectively). These ana-
logues have electron-withdrawing groups that allowed
them to retain their profiles as partial agonists
(Emax = 23%, 26%, 27%, and 32%, respectively), which
affects their intrinsic 5-HT2A efficacy. Meanwhile the
introduction of electron-donating groups, such as the
methoxy (8) or methylamino group (9), to the 7-position
led to some loss of 5-HT2C binding affinity (Ki = 20 and
46 nM, respectively). To make matters worse, their
intrinsic 5-HT2A efficacy increased significantly
(Emax = 56% and 90%) compared to those of com-
pounds with electron-withdrawing groups (3–7)
(Emax = 23–38%). Among the compounds evaluated,
the 6,7-dichloro derivative, 6, showed the highest selec-
tivity over 5-HT2A receptors (11-fold).
As shown in Table 1, compound 2 was the first to be iso-
lated via HTS. Although it had a lower 5-HT2C affinity
(Ki = 66 nM) than YM348 (1), compound 2 had an
interesting characteristic: the intrinsic 5-HT2A efficacy
was very low (Emax = 7%). In order to improve the 5-
HT2C affinity, the first step taken was to eliminate the
methyl group on 2. Although the resulting NH deriva-
tive 3 showed some increase in intrinsic 5-HT2A efficacy
(Emax = 38%), the 5-HT2C binding affinity improved 5-
fold over that of 2 (Ki = 14 vs 66 nM). In addition, the
5-HT2B receptor has been implicated in the valvular
hypertrophy.13 YM348 had only 2.8-fold selectivity over
5-HT2B receptors, but compound 3 showed high selec-
tivity over 5-HT2B receptors (21-fold). For this reason,
NH derivative 3 was selected as the preferred template,
Table 3 shows the results of the furan-fused benzaze-
pines 10 and 11. The transformation of the dichloro ben-
zene ring system in compound 6 to the benzofuran ring
Table 1. 5-HT binding affinities and intrinsic activities of compounds 1–3
Cl
O2N
N R
b
Compound
R
Kia (nM)
Selectivity
2A/2C
Emax
5-HT2C
5-HT2A
5-HT2B
2B/2C
5-HT2C
5-HT2A
YM348 (1)
0.89
66
13
2.5
15
6
2.8
15
76
85
86
97
7
2
3
Me
H
400
51
1000
300
14
4
21
38
a Ki for [3H]5-HT binding; human 5-HT2C or 5-HT2A receptors expressed in CHO cells and 5-HT2B receptors expressed in HEK293-EBNA cells.
b Emax indicates intrinsic activity and is expressed as the percentage of maximal stimulation produced by 10 lM 5-HT.
Table 2. 5-HT binding affinities and intrinsic activities of compounds 4–9
Cl
R
NH
a
Compound
R
Kia (nM)
Selectivity
Emax
5-HT2C
5-HT2A
5-HT2B
2A/2C
2B/2C
5-HT2C
5-HT2A
4
5
6
7
8
9
CN
F
5.1
43
30
130
93
65
410
100
25
6
3
13
10
11
10
4
81
80
87
71
88
81
23
26
27
32
56
90
Cl
Br
8.8
2.4
20
11
4
10
62
OMe
NHMe
84
210
3
46
90
2
5
a Refer to Table 1.

I. Shimada et al. / Bioorg. Med. Chem. 16 (2008) 3309–3320
Table 3. 5-HT binding affinities and intrinsic activities of compounds 10 and 11
3313
O
O
NH
NH
10
11
a
Compound
Kia (nM)
Selectivity
Emax
5-HT2C
5-HT2A
5-HT2B
2A/2C
2B/2C
5-HT2C
5-HT2A
10
11
23
20
99
46
34
90
4
2
1
5
57
82
40
47
a Refer to Table 1.
system was based on previous work.14 It was anticipated
that this modification would improve 5-HT2C receptor
affinity, but the furan-fused analogues 10 and 11 led to
a loss of 5-HT2C receptor binding affinity (Ki = 23 and
20 nM, respectively) and selectivity over 5-HT2A recep-
tors (2A/2C = 4- and 2-fold, respectively).
tions. Although the EC50 value of compound 6 for 5-
HT2C receptors was lower than that of YM348
(EC50 = 1.0 vs 38 nM), compound 6 was equipotent to
YM348 in a rat penile erection model when adminis-
tered po, which is a reflection of 5-HT2C receptor activa-
tion in vivo.
The results of SAR studies performed on benzazepine
derivatives indicated that, out of those examined, com-
pound 6 showed the most promising affinity for 5-
HT2C receptors and selectivity over 5-HT2A and 5-
HT2B receptors. Therefore, compound 6 was selected
for further evaluation.
3.3. Cardiovascular effect
Elevated blood pressure is a serious problem for obese
patients. As shown in Figure 2, oral administration of
YM348 (1) at 10 and 30 mg/kg resulted in dose-depen-
dent increases in mean arterial blood pressure (MABP).
These effects were completely inhibited by a selective 5-
HT2A antagonist, MDL100907. These results suggest
that 5-HT2A receptor agonism is associated with the in-
creases in MABP. Therefore, the cardiovascular effect of
compound 6, which has low intrinsic 5-HT2A receptor
activity (Emax = 27%), was examined. As expected, and
unlike YM348 (1), oral administration of compound 6
at 3, 10, and 30 mg/kg had little effect on blood pressure.
3.2. In vivo activity
The 6,7-dichloro derivative 6, which showed high 5-
HT2C binding affinity and the highest selectivity for 5-
HT2A receptors, was assessed for induction of penile
erection in rats, which is a symptom of the serotonin
syndrome reflecting 5-HT2C receptor activation in ro-
dents.15 The results are presented with MED values
[minimum effective dose; that is, the lowest dose that sig-
nificantly (p < 0.05 as compared with vehicle) affected
penile erections] in Table 4.
4. Conclusion
As part of the search for novel 5-HT2C receptor ago-
nists, a series of benzazepine derivatives were synthe-
sized, and their 5-HT2C agonist activity was
investigated. Among these compounds, 6,7-dichloro-
2,3,4,5-tetrahydro-1H-3-benzazepine (6) had good affin-
ity and selectivity for 5-HT2C receptors over 5-HT2A and
5-HT2B receptors. This compound was also found to be
equipotent to YM348 (1) in a rat penile erection model
when administered po, which is a reflection of 5-HT2C
receptor activation in vivo. Moreover, compound 6
has been characterized as a partial 5-HT2A receptor ago-
nist, that has little effect on blood pressure, which is a
matter of concern with YM348 (1).
As previously reported, oral administration of YM348
(1) induced penile erections at
a
low dose
(MED = 0.3 mg/kg). Compound (6) also showed induc-
tion of penile erections starting at a dose of 0.3 mg/kg
po. As in the case of YM348 (1), this effect was com-
pletely inhibited by the selective 5-HT2C receptor antag-
onist, SB242084, which indicates that 5-HT2C activation
was the mechanism that caused 6 to induce penile erec-
Table 4. Functional activities for 5-HT2C and 5-HT2A receptors, and
effect of compounds 1 and 6 on penile erections in rats after po
administration
Compound
EC50 (nM)
MEDa po
(mg/kg)
5. Experimental
5.1. Chemistry
5-HT2C
1.0
38
5-HT2A
YM348 (1)
6
93
260
0.3
0.3
a The lowest dose that significantly (p < 0.05 as compared with vehicle)
affected penile erections was considered to be the minimum effective
dose (MED).
Melting points were determined with a Yanaco MP-
500D or a Buchi B-545 melting point apparatus and
¨
are uncorrected. H NMR spectra were recorded on a
1

3314
I. Shimada et al. / Bioorg. Med. Chem. 16 (2008) 3309–3320
Figure 2. Effect of YM348 and compound 6 on mean arterial blood pressure (MABP) in rats. All points represent means SEM, n = 5 per group.
JEOL JNM-LA300 or a JNM-EX400 spectrometer and
the chemical shifts are expressed in d (ppm) values with
tetramethylsilane as an internal standard (in NMR
description: s, singlet; br s, broad singlet; d, doublet; t,
triplet; q, quartet; dd, doublet of doublets; m, multiplet).
Mass spectra were recorded on a Hitachi M-80 or a
JEOL JMS-LX2000 spectrometer. Elemental analyses
were performed with a Yanaco MT-5 microanalyzer
(C, H, N) and a Yokogawa IC-7000S ion chromato-
graphic analyzer (halogens), and the results were within
0.4% of theoretical values.
5.1.3. 6-Chloro-2,3,4,5-tetrahydro-1H-3-benzazepine-7-
carbonitrile (4). Compound 4 was prepared from 24 using
a procedure similar to that described for 3 (86%). This
compound was subsequently converted to its hydrochlo-
ride. White solid, mp 233–236 ꢁC; 1H NMR (DMSO-d6)
d 3.16–3.36 (6H, m), 3.39–3.46 (2H, m), 7.43 (1H, d,
J = 8.0 Hz), 7.82 (1H, d, J = 8.0 Hz), 9.69 (2H, br s);
FAB-MS m/z 207 [(M+H)+]. Anal. Calcd for
C11H11N2ClÆHCl: C, 54.34; H, 4.97; N, 11.52; Cl, 29.16.
Found: C, 54.28; H, 4.89; N, 11.56; Cl, 29.22.
5.1.4. 6-Chloro-7-fluoro-2,3,4,5-tetrahydro-1H-3-benzaze-
pine (5). Compound 5 was prepared from 25 using a proce-
dure similar to that described for 3 (52%). This compound
was subsequently convertedtoits hydrochloride. White so-
lid; 1H NMR (DMSO-d6) d 3.08–3.28 (6H, m), 3.32–3.46
(2H, m), 7.20–7.30 (2H, m), 9.61 (2H, br s); FAB-MS m/z
200 [(M+H)+]. Anal. Calcd for C10H11NFClÆHCl: C,
50.87; H, 5.12; N, 5.93; F, 8.05; Cl, 30.03. Found: C,
50.75; H, 5.01; N, 5.91; F, 8.01; Cl, 30.22.
5.1.1. 6-Chloro-3-methyl-7-nitro-2,3,4,5-tetrahydro-1H-
3-benzazepine (2). To a solution of 18 (3.65 g, 18.7 mmol)
in H2SO4 (10 mL) was added dropwise concd HNO3
(1.30 mL, 20.6 mmol), while maintaining the temperature
below 0 ꢁC. After stirring for 1 h below 0 ꢁC, the mixture
was poured into ice-water and basified by the addition of
NaOH. The aqueous phase was extracted in CHCl3, and
then the combined extracts were dried over Na2SO4 and
evaporated. The residue was purified by column chroma-
tography on silica gel (CHCl3/MeOH/satd NH3
aq = 50:1:0.1) to yield 2 (2.09 g, 47%) as a yellow solid.
1H NMR (CDCl3) d 2.36 (3H, s), 2.53–2.63 (4H, m),
3.00–3.07 (2H, m), 3.25–3.32 (2H, m), 7.12 (1H, d,
J = 8.0 Hz), 7.52 (1H, d, J = 8.0 Hz); FAB-MS m/z 241
[(M+H)+].
5.1.5. 6,7-Dichloro-2,3,4,5-tetrahydro-1H-3-benzazepine
(6). Compound 6 was prepared from 19 using a procedure
similar to that described for 3 (27%). This compound was
subsequently converted to its hydrochloride. White solid,
1
mp 203–204 ꢁC; H NMR (DMSO-d6) d 3.12–3.27 (6H,
m), 3.38–3.46 (2H, m), 7.24 (1H, d, J = 8.4 Hz), 7.48
(1H, d, J = 8.4 Hz), 9.51 (2H, br s); FAB-MS m/z 216
[(M+H)+]. Anal. Calcd for C10H11NCl2ÆHCl: C, 47.55;
H, 4.79; N, 5.55; Cl, 42.11. Found: C, 47.41; H, 4.69; N,
5.56; Cl, 42.12.
5.1.2. 6-Chloro-7-nitro-2,3,4,5-tetrahydro-1H-3-benzaze-
pine (3). To a solution of 2 (0.36 g, 1.5 mmol) in dichloro-
ethane (6 mL) was added a-chloroethyl chloroformate
(ACE-Cl, 0.18 mL, 1.6 mmol) at room temperature, and
it was heated at reflux for 5 h. The solvent was removed
under reduced pressure and the residue dissolved in
MeOH (6 mL). The resulting solution was heated at reflux
for 2 h and evaporated. To the mixture was added H2O
(30 mL) and saturated aqueous NaHCO3 (10 mL), and
it was extracted with CHCl3. The combined organic
phases were dried over Na2SO4 and evaporated. The res-
idue was purified by column chromatography on silica gel
(CHCl3/MeOH = 100:1–30:1) to yield 3 (0.18 g; 53%).
This compound was subsequently converted to its hydro-
chloride. White solid, mp 235–240 ꢁC; 1H NMR(DMSO-
d6) d 3.16–3.38 (6H, m), 3.42–3.50 (2H, m), 7.46 (1H, d,
J = 8.3 Hz), 7.85 (1H, d, J = 8.3 Hz), 9.70 (2H, br s);
FAB-MS m/z 227 [(M+H)+]. Anal. Calcd for
C10H11N2O2ClÆHCl: C, 45.65; H, 4.60; N, 10.65; Cl,
26.95. Found: C, 45.51; H, 4.39; N, 10.62; Cl, 26.75.
5.1.6. 7-Bromo-6-chloro-2,3,4,5-tetrahydro-1H-3-benzaze-
pine (7). Compound 7 was prepared from 26 using a proce-
dure similar to that described for 3 (28%). This compound
was subsequently convertedtoits hydrochloride. White so-
lid, mp263–266 ꢁC;1H NMR(DMSO-d6)d3.10–3.25(6H,
m), 3.42–3.48(2H,m), 7.16(1H,d, J = 8.0 Hz),7.60(1H,d,
J = 8.0 Hz), 9.63 (2H, br s); FAB-MS m/z 260, 262
[(M+H)+]. Anal. Calcd for C10H11NBrClÆHCl: C, 40.44;
H, 4.07; N, 4.72; Br, 26.90; Cl, 23.87. Found: C, 40.20;
H, 3.91; N, 4.69; Br, 26.92; Cl, 24.06.
5.1.7. 6-Chloro-7-methoxy-2,3,4,5-tetrahydro-1H-3-ben-
zazepine (8). To a solution of 34 (85 mg, 0.40 mmol) in
THF (20 mL) were added 0.5 M aqueous NaH2PO4
(2 mL, 1.0 mmol) and NaBH3CN (254 mg, 4.04 mmol)
at 0 ꢁC. The reaction mixture was stirred at room temper-

I. Shimada et al. / Bioorg. Med. Chem. 16 (2008) 3309–3320
3315
ature for 1 h. To the mixture were added saturated
aqueous NaHCO3, and it was extracted with CHCl3.
The organic phases were dried over MgSO4 and evapo-
rated in vacuo. The residue was purified by column
chromatography on silica gel (CHCl3/MeOH = 10:1) to
yield 8 (53 mg, 63%) as a pale yellow oil. This compound
was subsequently converted to its hydrochloride. White
C12H13NOÆHCl: C, 64.43; H, 6.31; N, 6.26; Cl, 15.85.
Found: C, 64.39; H, 6.29; N, 6.25; Cl, 16.11.
5.1.11. 2-(2-Chlorophenyl)-N-(2-hydroxyethyl)-N-methyl-
acetamide (14). To a solution of (2-chlorophenyl)acetic
acid 12 (25.0 g, 146 mmol) in DMF (250 mL) were added
HOBt (23.7 g, 176 mmol), 1-ethyl-3-(3-dimethylamino-
propyl)-carbodiimide hydrochloride (33.7 g, 176 mmol),
and 2-(methylamino)ethanol (13.2 g, 176 mmol) at room
temperature, and it was stirred at room temperature for
2 h. The reaction mixture was diluted with AcOEt,
washed with 1 M aqueous HCl, H2O, 1 M aqueous
NaOH, and brine, after which it was dried over MgSO4
and concentrated in vacuo to yield 14 (16.4 g, 49%) as a
white solid. 1H NMR (DMSO-d6) d 2.85 (1.68H, s), 3.09
(1.32H, s), 3.33–3.39 (1H, m), 3.42–3.50 (2H, m), 3.56–
3.63 (1H, m), 3.77 (0.88H, s), 3.85 (1.12H, s), 4.65
(0.44H, t, J = 5.3 Hz), 4.89 (0.56H, t, J = 5.3 Hz), 7.23–
7.31 (3H, m), 7.37–7.44 (1H, m); FAB-MS m/z 228
[(M+H)+].
1
solid; H NMR (DMSO-d6) d 3.01–3.50 (8H, m), 3.83
(3H, s), 6.97 (1H, d, J = 8.4 Hz), 7.16 (1H, d,
J = 8.4 Hz), 9.13 (2H, br s); FAB-MS m/z 212
[(M+H)+]. Anal. Calcd for C11H14NOClÆHClÆ0. 3H2O:
C, 52.11; H, 6.20; N, 5.52; Cl, 27.96. Found: C, 52.26;
H, 5.93; N, 5.46; Cl, 27.96.
5.1.8. 6-Chloro-N-methyl-2,3,4,5-tetrahydro-1H-3-ben-
zazepin-7-amine (9). A mixture of 22 (100 mg, 0.35 mmol)
and concd HCl (2 mL) was stirred at 100 ꢁC for 2 h. After
removal of the solvent, the resulting crystals were washed
with MeCN. To the crystals was added saturated aqueous
NaHCO3, and it was extracted with AcOEt. The com-
bined organic phases were washed with brine and dried
over Na2SO4. After removal of the solvent, the residue
was purified by column chromatography on silica gel
(CHCl3/MeOH/satd NH3 aq = 15:1:0.1) to yield 9
(34 mg, 46%). This compound was subsequently con-
verted to its dihydrochloride. White solid, mp 242–
5.1.12. 2-(2,3-Dichlorophenyl)-N-(2-hydroxyethyl)-N-methyl-
acetamide (15). Compound 15 was prepared from (2,3-
dichlorophenyl)acetic acid 13 using a procedure similar
to that described for 14 as a white solid (52%). 1H NMR
(DMSO-d6) d 2.85 (1.68H, s), 3.11 (1.32H, s), 3.32–3.39
(1H, m), 3.43–3.53 (2H, m), 3.56–3.64 (1H, m), 3.86
(0.88H, s), 3.94 (1.12H, s), 4.66 (0.44H, t, J = 5.3 Hz),
4.91 (0.56H, t, J = 5.3 Hz), 7.22–7.35 (3H, m), 7.48–7.56
(1H, m); FAB-MS m/z 262 [(M+H)+].
1
247 ꢁC; H NMR (DMSO-d6) d 2.76 (3H, s), 3.00–3.28
(6H, m), 3.35–3.46 (2H, m), 6.58 (1H, d, J = 8.3 Hz),
7.04 (1H, d, J = 8.3 Hz), 9.57 (2H, br s); FAB-MS m/z
211 [(M+H)+].
5.1.9. 7,8,9,10-Tetrahydro-6H-furo[2,3-g][3]benzazepine
(10). To a solution of 39 (1.00 g, 4.65 mmol) in THF
(20 mL) was added BH3ÆMe2S (1.86 mL, 10 M in Me2S)
at ꢀ20 ꢁC, and it was stirred at room temperature for
3 h. The reaction mixture was cooled to 0 ꢁC, then excess
reagent was treated with MeOH. After stirring at this tem-
perature for 0.5 h, concd HCl (5 mL) was added, and the
mixture was stirred at room temperature for 0.5 h and
basified with 1 M aqueous NaOH. The mixture was then
extracted with CHCl3, dried over Na2SO4, and evapo-
rated. The residue was purified by column chromatogra-
phy on silica gel (CHCl3/MeOH/satd NH3
aq = 30:1:0.1–10:1:0.1) to yield 10 (488 g, 56%) as a pale
yellow solid. This compound was subsequently converted
to its hydrochloride. White solid; 1H NMR (DMSO-d6) d
3.18–3.36 (6H, m), 3.36–3.50 (2H, m), 6.94 (1H, d,
J = 2.0 Hz), 7.12 (1H, d, J = 7.8 Hz), 7.44 (1H, d,
J = 7.8 Hz), 7.98 (1H, d, J = 2.0 Hz), 9.32 (2H, br s);
FAB-MS m/z 188 [(M+H)+].
5.1.13. 2-[[2-(2-Chlorophenyl)ethyl](methyl)amino]etha-
nol (16). To a solution of 14 (18.2 g, 80.0 mmol) in
THF (100 mL) was added BH3ÆTHF (240 mL, 1 M in
THF) at 0 ꢁC, and it was stirred at room temperature
for 0.5 h. To the reaction mixture was added MeOH
(20 mL) at 0 ꢁC. After stirring at this temperature for
0.5 h, 6 M aqueous HCl (100 mL) was added, and the
mixture was stirred at room temperature for 0.5 h and
then concentrated in vacuo. After addition of H2O
(100 mL) and NaOH (40 g) while cooling in an ice bath,
the mixture was extracted with CHCl3, dried over
Na2SO4, and evaporated. The residue was purified by
column chromatography on silica gel (CHCl3/MeOH/
satd NH3 aq = 50:1:0.1) to yield 16 (14.2 g, 83%) as pale
1
yellow oil. H NMR (DMSO-d6) d 2.26 (3H, s), 2.44–
2.60 (4H, m), 2.79–2.87 (2H, m), 3.44–3.50 (2H, m),
4.32 (1H, t, J = 5.5 Hz), 7.17–7.30 (2H, m), 7.23–7.44
(2H, m); FAB-MS m/z 214 [(M+H)+].
5.1.14. 2-[[2-(2,3-Dichlorophenyl)ethyl](methyl)amino]etha-
nol (17). Compound 17 was prepared from 15 using a pro-
cedure similar to that described for 16 as a white solid
5.1.10. 7,8,9,10-Tetrahydro-6H-furo[3,2-g][3]benzazepine
(11). To a solution of 44 (110 mg, 0.38 mmol) in AcOEt
(5 mL) was added HCl–AcOEt (4 M, 10 mL) at 0 ꢁC,
and it was stirred at room temperature for 3 h. After
cooling to 0 ꢁC, to the reaction mixture was added diiso-
propylether (10 mL), and the resulting precipitate was
collected by filtration to yield 11 (74 mg, 87%) as its
1
(81%). H NMR (DMSO-d6) d 2.26 (3H, s), 2.43–2.52
(2H, m), 2.54–2.62 (2H, m), 2.85–2.93 (2H, m), 3.41–3.44
(2H, m), 4.32 (1H, t, J = 5.5 Hz), 7.25–7.32 (1H, m), 7.36
(1H, dd, J = 1.7, 7.7 Hz), 7.48 (1H, dd, J = 1.7, 7.7 Hz);
FAB-MS m/z 248 [(M+H)+].
1
hydrochloride. White solid, mp 227–229 ꢁC; H NMR
(DMSO-d6) d 3.12–3.26 (6H, m), 3.27–3.42 (2H, m),
7.08 (1H, d, J = 2.0 Hz), 7.16 (1H, d, J = 8.4 Hz), 7.39
(1H, d, J = 8.4 Hz), 7.97 (1H, d, J = 2.0 Hz), 9.52 (2H,
br s); FAB-MS m/z 188 [(M+H)+]. Anal. Calcd for
5.1.15. 6-Chloro-3-methyl-2,3,4,5-tetrahydro-1H-3-ben-
zazepine (18). To a solution of 16 (14.0 g, 65.5 mmol) in
1,2,4-trichlorobenzene (85 mL) was added PCl5 (5.21 g,
25.0 mmol), and it was stirred at 110 ꢁC for 0.5 h. To

3316
I. Shimada et al. / Bioorg. Med. Chem. 16 (2008) 3309–3320
the reaction mixture was added portionwise AlCl3 (17.5 g,
131 mmol), and it was stirred at 200 ꢁC for 5 h. After cool-
ing to 50 ꢁC, to the mixture were added H2O (300 mL) and
concd HCl (13 mL). After stirring at room temperature
for 0.5 h, the mixture was extracted with H2O. The aque-
ous layer was basified with 50% aqueous NaOH and ex-
tracted with toluene. The combined organic phases were
washed with H2O and evaporated. The residue was puri-
fied by column chromatography on silica gel (CHCl3/
MeOH/satd NH3 aq = 50:1:0.1) to yield 18 (5.74 g, 45%)
as brown oil. 1H NMR (DMSO-d6) d 2.23 (3H, s), 2.42–
2.52 (4H, m), 2.87–2.95 (2H, m), 3.12–3.19 (2H, m), 7.14
(1H, d, J = 8.1 Hz), 7.37 (1H, d, J = 8.1 Hz); EI-MS m/z
195 [M+].
5.1.19. N-(6-Chloro-2,3,4,5-tetrahydro-1H-3-benzazepin-
7-yl)-N-methylacetamide (22). To a solution of 21 (0.23 g,
0.68 mmol) in DMF (3 mL) were added 60% NaH (30 mg,
0.75 mmol) and MeI (50 lL, 0.80 mmol) at 0 ꢁC, and it
was stirred at room temperature for 5 h. To the mixture
was added H2O, and it was extracted with AcOEt. The
combined organic phases were washed with brine and
dried over Na2SO4. After removal of the solvent, the res-
idue was purified by column chromatography on silica gel
(AcOEt/hexane = 1:3–1:1) to yield N-methyl derivative
(0.21 g) as a white amorphous solid that was used directly
for the next step without further purification.
The N-methyl derivative was dissolved with CHCl3
(5 mL), and then added 4 M HCl–AcOEt (1.5 mL).
After stirring at room temperature for 5 h, the solvent
was removed. The resulting crystal was washed with
AcOEt to yield 22 (0.16 g, 93%) as the hydrochloride
5.1.16.6,7-Dichloro-3-methyl-2,3,4,5-tetrahydro-1H-3-ben-
zazepine (19). Compound 19 was prepared from 17 using a
procedure similar to that described for 18 to yield a yellow
oil (37%). 1H NMR (CDCl3) d 2.37 (3H, s), 2.50–2.65 (4H,
m), 2.90–3.00 (2H, m), 3.15–3.25 (2H, m), 6.96–7.06 (2H,
m), 7.19–7.27 (1H, m); EI-MS m/z 229 [M+].
1
salt. White solid; H NMR (DMSO-d6) d 1.67 (3H, s),
3.04 (3H, s), 3.05–3.35 (6H, m), 3.40–3.50 (2H, m),
7.31 (1H, d, J = 8.1 Hz), 7.36 (1H, d, J = 8.1 Hz), 9.58
(2H, br s); FAB-MS m/z 253 [(M+H)+].
5.1.17. tert-Butyl 7-amino-6-chloro-1,2,4,5-tetrahydro-
3H-3-benzazepine-3-carboxylate (20). To a solution of a
hydrochloride salt of 3 (0.95 g, 3.6 mmol) in AcOEt
(15 mL) were added Boc2O (0.82 g, 3.8 mmol) and Et3N
(0.53 mL, 3.8 mmol) at 0 ꢁC, and it was stirred at room
temperature for 5 h. To the mixture was added H2O
(50 mL), and it was extracted with AcOEt. The combined
organic phases were washed with 5% aqueous NaHSO4,
H2O, and brine, and dried over Na2SO4. After removal
of the solvent, the residue was washed with hexane to yield
the N-Boc derivative (1.07 g, 91%) as a pale yellow solid
which was used directly for the next step without further
purification.
5.1.20. 6-Chloro-3-methyl-2,3,4,5-tetrahydro-1H-3-ben-
zazepin-7-amine (23). Compound 2 (2.09 g, 8.63 mmol)
was dissolved with AcOH (20 mL), and then Fe
(2.42 g, 43.2 mmol) was added. After stirring at 70 ꢁC
for 2 h, the reaction mixture was filtered through Celite
and the solvent was removed in vacuo. The resulting res-
idue was diluted with CHCl3, washed with saturated
aqueous NaHCO3, and dried over MgSO4. After re-
moval of the solvent, the residue was purified by column
chromatography on silica gel (CHCl3/MeOH/satd NH3
aq = 20:1:0.1) to yield 23 (1.62 g, 89%) as a pale brown
1
solid. H NMR (DMSO-d6) d 2.21 (3H, s), 2.35–2.44
(4H, m), 2.69–2.76 (2H, m), 2.97–3.05 (2H, m), 5.02
(2H, s), 6.53 (1H, d, J = 8.1 Hz), 6.77 (1H, d,
J = 8.1 Hz); EI-MS m/z 240 [M+].
The N-Boc derivative was dissolved with EtOH (8 mL),
and then added H2O (3 mL), Fe (0.78 g, 14 mmol), and
NH4Cl (75 mg, 1.4 mmol). After stirring at room temper-
ature for 15 h, the reaction mixture was filtered through
Celite and the solvent was removed in vacuo. The result-
ing residue was purified by column chromatography on
silica gel (AcOEt/hexane = 1:10–1:7) to yield 20 (0.30 g,
5.1.21. 6-Chloro-3-methyl-2,3,4,5-tetrahydro-1H-3-ben-
zazepine-7-carbonitrile (24). H2O (30 mL) and then concd
H2SO4 (1.52 mL, 28.5 mmol) were added to compound 23
(3.00 g, 14.2 mmol). A solution of NaNO2 (1.18 g,
17.1 mmol) in H2O (10 mL) was added to the mixture at
0–5 ꢁC. After stirring at 0 ꢁC for 0.5 h, to the mixture were
added toluene (20 mL), NaHCO3 (4.8 g, 57.1 mmol), and
H2O (10 mL). The reaction mixture was added to a solu-
tion of CuCN (3.19 g, 35.6 mmol), KCN (6.32 g,
97 mmol), H2O (40 mL), and AcOEt (50 mL). After stir-
ring at 70 ꢁC for 2 h, the reaction mixture was diluted with
AcOEt, washed with brine, and dried over MgSO4. After
removal of the solvent, the residue was purified by column
chromatography on silica gel (CHCl3/MeOH/satd NH3
aq = 20:1:0.1) to yield 24 (2.30 g, 73%) as a pale green so-
lid. 1H NMR (DMSO-d6) d 2.24 (3H, s), 2.41–2.49 (4H,
m), 2.87–3.02 (2H, m), 3.10–3.20 (2H, m), 7.34 (1H, d,
J = 8.0 Hz), 7.30 (1H, d, J = 8.0 Hz); FAB-MS m/z 221
[(M+H)+].
1
36%) as a pale yellow solid. H NMR (CDCl3) d 1.46
(9H, s), 2.77–2.86 (2H, m), 3.08–3.16 (2H, m), 3.47–3.60
(4H, m), 6.56 (1H, d, J = 8.1 Hz), 6.82 (1H, d,
J = 8.1 Hz); FAB-MS m/z 296 [M+].
5.1.18. tert-Butyl 7-(acetylamino)-6-chloro-1,2,4,5-tetra-
hydro-3H-3-benzazepine-3-carboxylate (21). To a solu-
tion of 20 (0.35 g, 1.18 mmol) in THF (4 mL) were
added Et3N (0.17 mL, 1.22 mmol) and AcCl (90 lL,
1.27 mmol) at 0 ꢁC, and it was stirred at room tempera-
ture for 5 h. To the mixture was added H2O, and it was
then extracted with AcOEt. The combined organic phases
were washed with brine and dried over Na2SO4. After re-
moval of the solvent, the residue was purified by column
chromatography on silica gel (AcOEt/hexane = 1:5–1:3)
1
to yield 21 (0.33 g, 83%) as white amorphous solid. H
NMR (CDCl3) d 1.46 (9H, s), 2.85–2.95 (2H, m), 3.11–
3.19 (2H, m), 3.49–3.61 (4H, m), 7.03 (1H, d,
J = 8.2 Hz), 8.10 (1H, d, J = 8.2 Hz); FAB-MS m/z 339
[(M+H)+].
5.1.22. 6-Chloro-7-fluoro-3-methyl-2,3,4,5-tetrahydro-1H-
3-benzazepine (25). Compound 23 (0.58 g, 2.75 mmol) was
added to 48% aqueous HBF4 (1.26 mL, 9.63 mmol) at
0 ꢁC. To the mixture was added portionwise NaNO2

I. Shimada et al. / Bioorg. Med. Chem. 16 (2008) 3309–3320
3317
(0.19 g, 2.75 mmol), and it was stirred at 0 ꢁC for 1 h. After
removalofthesolvent,themixturewasstirredat160 ꢁCfor
3 h. After cooling, to the reaction mixture was added satu-
rated aqueous NH3, which was then extracted with CHCl3,
dried over MgSO4, and evaporated in vacuo. The residue
was purified by column chromatography on silica gel
(CHCl3/MeOH/satd NH3 aq = 97:3:0.3) to yield 25
(0.48 g, 82%) as a pale brown oil. 1H NMR (DMSO-d6) d
2.24 (3H, s), 2.40–2.50 (4H, m), 2.86–2.94 (2H, m), 3.06–
3.13 (2H, m), 7.11–7.17 (2H, m); EI-MS m/z 213 [M+].
MgSO4. After removal of the solvent, the residue was puri-
fied by column chromatography on silica gel (AcOEt/hex-
ane = 1:10) to yield 30 (5.94 g, quant.) as a colorless oil. 1H
NMR (DMSO-d6) d 3.86(3H, s), 4.73 (2H, s), 7.14(1H, dd,
J = 1.5, 8.3 Hz), 7.18 (1H, dd, J = 1.5, 8.3 Hz), 7.31 (1H, t,
J = 8.3 Hz).
5.1.27. 2-(2-Chloro-3-methoxyphenyl)ethanamine (32).
To a solution of 30 (5.90 g, 25.1 mmol) in EtOH
(30 mL) and H2O (30 mL) were added KCN (1.79 g,
27.5 mmol) and n-Bu4HSO4 (40 mg) at 0 ꢁC. The reac-
tion mixture was stirred at 50 ꢁC for 4 h. After cooling,
the mixture was poured into water and extracted with
AcOEt. The organic extracts were washed with H2O
and brine, and then dried over MgSO4. After removal
of the solvent, the residue was purified by column chro-
matography on silica gel (AcOEt/hexane = 1:3) to yield
(2-chloro-3-methoxyphenyl)acetonitrile 31 (3.12 g, 68%)
as a white solid.
5.1.23. 7-Bromo-6-chloro-3-methyl-2,3,4,5-tetrahydro-1H-
3-benzazepine (26). A mixture of 23 (0.80 g, 3.80 mmol)
and 47% aqueous HBr (3.3 mL) was refluxed for 0.5 h.
After cooling to 0 ꢁC, to the mixture was added portion-
wise NaNO2 (0.26 g, 3.80 mmol) at 0–10 ꢁC. After stirring
for 0.5 h at 0 ꢁC, the reaction mixture was added dropwise
toa solution of CuBr(0.65 g, 4.56 mmol)and 47% aqueous
HBr (1.3 mL) at 0 ꢁC. After stirring at 0 ꢁC for 2 h, the
reaction mixture was poured into ice-water and basified
with saturated aqueous NH3. The solution was extracted
with CHCl3 and dried over MgSO4. After removal of the
solvent, the residue was purified by column chromatogra-
phy on silica gel (CHCl3/MeOH/satd NH3 aq = 97:3:0.3)
To a stirred suspension of LiAlH4 (0.75 mg, 19 mmol) in
THF (50 mL) was added portionwise AlCl3 at ꢀ20 ꢁC.
After stirring at 0 ꢁC for 0.5 h, to the mixture was added
a solution of 31 (3.00 g, 16.5 mmol) in THF (10 mL) drop-
wise at 0 ꢁC, and it was stirred at room temperature for
3 h. The excess reagent was quenched by the addition of
MeOH, followed by the addition of 15% aqueous NaOH
(0.75 mL) and water (2.5 mL). After stirring for 0.5 h, the
mixture was filtered with Celite and concentrated in vacuo
to yield the crude product, which was purified by column
chromatography on silica gel (CHCl3/MeOH = 10:1) to
1
to yield 26 (0.70 g, 67%) as a colorless oil. H NMR
(DMSO-d6) d 2.23 (3H, s), 2.41–2.49 (4H, m), 2.86–2.93
(2H, m), 3.14–3.21 (2H, m), 7.07 (1H, d, J = 7.9 Hz), 7.51
(1H, d, J = 7.9 Hz); FAB-MS m/z 274, 276 [(M+H)+].
5.1.24. 2-Methoxy-6-methylaniline (28). To a solution of
1-methoxy-3-methyl-2-nitrobenzene 27 (10.0 g, 59.8
mmol) in EtOH (300 mL) was added 10% Pd on carbon
(1.88 g). The mixture was stirred at room temperature
for 2 h under H2. The catalyst was removed by filtration
through Celite and the solvent was removed in vacuo.
The resulting residue was purified by column chromatog-
raphy on silica gel (AcOEt/hexane = 1:9) to yield 28
(8.20 g, quant.) as a colorless oil. 1H NMR (CDCl3)
d 2.18 (3H, s), 3.85 (3H, s), 3.74 (2H, br s), 6.64–6.74
(3H, m).
1
yield 32 (2.19 g; 71%). H NMR (CDCl3) d 3.00–3.14
(4H, m), 3.89 (3H, s), 4.26 (2H, br s), 6.83 (1H, dd,
J = 1.3, 8.0 Hz), 6.90 (1H, dd, J = 1.3, 8.0 Hz), 7.17 (1H,
t, J = 8.0 Hz).
5.1.28. N-[2-(2-Chloro-3-methoxyphenyl)ethyl]-2,2-dieth-
oxyethanamine (33). To a solution of 32 (2.10 g,
11.3 mmol) in DMF (40 mL) were added K2CO3
(7.80 g, 56.4 mmol) and bromoacetaldehyde diethyl ace-
tal (2.29 g, 11.6 mmol). The reaction mixture was stirred
at 50 ꢁC for 6 h. After cooling to room temperature, the
mixture was poured into cold water and extracted with
AcOEt. The organic extracts were washed with H2O,
brine and dried over MgSO4. After removal of the solvent,
the residue was purified by column chromatography on
silica gel (CHCl3/MeOH = 100:1) to yield 33 (1.53 g,
45%) as a pale yellow oil. 1H NMR (CDCl3) d 1.20 (6H,
t, J = 7.0 Hz), 2.77 (2H, d, J = 5.6 Hz), 2.86–2.98 (4H,
m), 3.50–3.58 (2H, m), 3.64–3.74 (2H, m), 3.89 (3H, s),
4.60 (1H, t, J = 5.6 Hz), 6.81 (1H, dd, J = 1.3, 8.2 Hz),
6.87 (1H, dd, J = 1.3, 8.2 Hz), 7.15 (1H, t, J = 8.2 Hz).
5.1.25. 2-Chloro-1-methoxy-3-methylbenzene (29). To a
solution of 28 (8.20 g, 59.8 mmol) in acetone (160 mL)
and H2O (25 mL) was added concd HCl (20 mL). A
solution of NaNO2 (4.54 g, 65.8 mmol) in H2O
(13 mL) was added dropwise to the mixture at 0–5 ꢁC.
After stirring for 0.5 h at 0 ꢁC, to the mixture was added
CuCl (6.51 g, 65.8 mmol). After stirring at room temper-
ature for 1 h, the reaction mixture was diluted with
AcOEt, washed with H2O and brine, and then dried
over MgSO4. After removal of the solvent, the residue
was purified by column chromatography on silica gel
(AcOEt/hexane = 1:10) to yield 29 (8.15 g, 87%) as a col-
orless oil. 1H NMR (DMSO-d6) d 2.32 (3H, s), 3.83 (3H,
s), 6.93 (1H, d, J = 7.9 Hz), 6.97 (1H, d, J = 7.9 Hz),
7.19 (1H, t, J = 7.9 Hz).
5.1.29. 9-Chloro-8-methoxy-2,3-dihydro-1H-3-benzaze-
pine (34). Compound 33 (1.50 g, 4.97 mmol) was added
to concd H2SO4 (10 mL) at 0 ꢁC. The reaction mixture
was stirred at room temperature for 1 h. After cooling,
the mixture was poured into cold water and basified
with 2 M aqueous NaOH. The aqueous phase was ex-
tracted with AcOEt. The combined organic phases were
washed with H2O and brine, and then dried over
MgSO4. After removal of the solvent, the residue was
purified by column chromatography on silica gel
5.1.26. 1-(Bromomethyl)-2-chloro-3-methoxybenzene (30).
To a solution of 29 (4.00 g, 25.5 mmol) in CCl4 (50 mL)
were added NBS (4.32 g, 24.3 mmol) and AIBN (40 mg).
The reaction mixture was heated at reflux for 2 h. After
cooling, tothe mixture was addedsaturated aqueous NaH-
CO3, and it was extracted with CHCl3 and dried over

3318
I. Shimada et al. / Bioorg. Med. Chem. 16 (2008) 3309–3320
(CHCl3/MeOH = 100:1–10:1) to yield 34 (85 mg, 8%) as
a pale yellow oil. 1H NMR (CDCl3) d 3.27–3.35 (2H, m),
3.41–3.50 (2H, m), 3.86 (3H, s), 3.98 (1H, br s), 5.04
(1H, d, J = 9.9 Hz), 6.10–6.18 (1H, m), 6.72 (1H, d,
J = 8.4 Hz), 6.93 (1H, d, d = 8.4 Hz).
J = 8.0 Hz), 8.14 (1H, d, J = 2.4 Hz); FAB-MS m/z 196
[(M+H)+].
5.1.33. 6H-Furo[2,3-g][3]benzazepine-7,9(8H,10H)-dione
(39). Compound 38 (3.50 g, 17.8 mmol) was dissolved in
AcOH (15 mL), and then HBr (33% in AcOH, 30 g) was
added. After stirring at room temperature for 5 h, the
reaction mixture was poured into ice-water, and the
resulting precipitate was collected by filtration and dried
in vacuo to yield a yellow solid (2.54 g) that was used di-
rectly for the next step without further purification.
5.1.30. 1-(2,2-Diethoxyethoxy)-2,3-dimethylbenzene (36).
To a suspension of 60% NaH (4.72 g, 118 mmol) in
DMF (100 mL) was slowly added 2,3-dimethylphenol
35 (10.0 g, 81.9 mmol) at 0 ꢁC. After stirring at this tem-
perature for 0.5 h, to the reaction mixture was added
bromoacetaldehyde diethylacetal (19.37 g, 98.3 mmol),
and it was then heated at 170 ꢁC for 3 h. After cooling
to room temperature, the reaction mixture was poured
into ice-water and extracted with AcOEt. The combined
extracts were washed with 1 M aqueous NaOH, H2O,
and brine, and then dried over MgSO4. After removal
of the solvent, the residue was purified by column chro-
matography on silica gel (AcOEt/hexane = 1:9) to yield
H2O (50 mL) and NaOAc (2.22 g, 27.1 mmol) were
added to the yellow solid, and the reaction mixture
was heated at reflux for 1 h. After cooling to room tem-
perature, the resulting precipitate was collected by filtra-
tion and dried in vacuo. The resulting crude product was
purified by column chromatography on silica gel
(CHCl3/MeOH = 30:1) to yield 39 (1.01 g, 26%) as a yel-
low solid. 1H NMR (DMSO-d6) d 4.20 (3H, s), 4.35 (3H,
s), 6.99 (1H, d, J = 2.2 Hz), 7.24 (1H, d, J = 7.9 Hz),
7.55 (1H, d, J = 7.9 Hz), 8.03 (1H, d, J = 2.2 Hz),
10.49 (1H, br s).
1
36 (15.8 g, 81%) as a colorless oil. H NMR (DMSO-
d6) d 1.15 (3H, t, J = 7.1 Hz), 2.08 (3H, s), 2.20 (3H,
s), 3.52–3.75 (4H, m), 3.90 (1H, d, J = 5.3 Hz), 4.81
(1H, t, J = 5.3 Hz), 6.76 (1H, d, J = 7.9 Hz), 6.78 (1H,
d, J = 7.9 Hz), 7.01 (1H, t, J = 7.9 Hz).
5.1.34. 4-(2,2-Diethoxyethoxy)-1,2-dimethylbenzene (41).
Compound 41 was prepared from 3,4-dimethylphenol
40 using a procedure similar to that described for 36
(73%). 1H NMR (CDCl3) d 1.24 (3H, t, J = 7.0 Hz),
2.18 (3H, s), 2.22 (3H, s), 3.57–3.82 (4H, m), 3.97 (1H,
d, J = 5.2 Hz), 4.82 (1H, t, J = 5.2 Hz), 6.66 (1H, dd,
J = 2.6, 8.0 Hz), 6.74 (1H, d, J = 2.6 Hz), 7.01 (1H, d,
J = 8.0 Hz); FAB-MS m/z 238 [M+].
5.1.31. 6,7-Dimethyl-1-benzofuran (37). To a solution of
36 (15.0 g, 62.9 mmol) in benzene (200 mL) was added
PPA (15.0 g) at room temperature, and the reaction mix-
ture was heated at reflux for 2 h. After cooling to room
temperature, the benzene layer was decanted from the
PPA, diluted with ether, washed with saturated aqueous
NaHCO3, H2O, and brine, and then dried over MgSO4.
After removal of the solvent, the residue was purified by
column chromatography on silica gel (AcOEt/hex-
ane = 1:100) to yield 37 (7.34 g, 80%) as a colorless oil.
1H NMR (CDCl3) d 2.38 (3H, s), 2.44 (3H, s), 6.70
(1H, d, J = 2.2 Hz), 7.04 (1H, d, J = 7.7 Hz), 7.30 (1H,
d, J = 7.7 Hz), 7.56 (1H, d, J = 2.2 Hz).
5.1.35. tert-Butyl 6,7,9,10-tetrahydro-8H-furo[3,2-g]-
[3]benzazepine-8-carboxylate (44) and tert-butyl 5,6,8,9-
tetrahydro-7H-furo[2,3-h][3]benzazepine-7-carboxylate (45).
A mixture of 11 and 46 was prepared from 41 using a pro-
cedure similar to that described for 37, 38, 39, and 10, in
59%, 21%, 61%, and 50% yield. The mixture of 11 and 46
(11/46 = 1:2, 400 mg, 2.14 mmol) was dissolved with THF
(20 mL), and added Boc2O (930 mg, 4.28 mmol). After stir-
ring at room temperature for 1 h, the solvent was evapo-
rated and the resulting residue was purified by column
chromatography on silica gel (AcOEt/hexane = 20:1) to
yield 44 (120 mg, 20%) as a colorless oil and 45 (284 mg,
46%) as a colorless oil.
5.1.32. 2,20-(1-Benzofuran-6,7-diyl)diacetonitrile (38). To
a solution of 37 (7.20 g, 49.3 mmol) in CCl4 (100 mL)
were added NBS (17.5 g, 98.5 mmol) and AIBN
(100 mg). The reaction mixture was heated at reflux
for 3 h. After cooling to room temperature, the reaction
mixture was filtered through Celite, and the filtrate was
evaporated in vacuo. The residue was diluted with ether,
washed with saturated aqueous NaHCO3, H2O, and
brine, dried over MgSO4, and evaporated in vacuo to af-
ford crude 6,7-bis(bromomethyl)-1-benzofuran as a yel-
low solid with was used directly for the next step without
further purification.
1
Compound 44: H NMR (CDCl3) d 1.48 (9H, s), 2.94–
3.03 (2H, m), 3.07–3.14 (2H, m), 3.53–3.68 (4H, m),
6.76 (1H, d, J = 2.1 Hz), 7.06 (1H, d, J = 8.3 Hz), 7.26
(1H, d, J = 8.3 Hz), 7.59 (1H, d, J = 2.1 Hz); FAB-MS
m/z 288 [(M+H)+].
To the obtained yellow solid, DMSO (70 mL) and
NaCN (7.25 g, 150 mmol) were added, and the reaction
mixture was stirred at room temperature for 3 h. The
mixture was poured into ice-water and extracted with
AcOEt. The combined extracts were washed with H2O
and brine, and then dried over MgSO4. After removal
of the solvent, the residue was purified by column chro-
matography on silica gel (AcOEt/hexane = 1:3) to yield
1
Compound 45: H NMR (CDCl3) d 1.48 (9H, s), 2.92–
3.03 (4H, m), 3.52–3.63 (4H, m), 6.68 (1H, dd, J = 0.8,
2.1 Hz), 7.27 (1H, s), 7.33 (1H, s), 7.56 (1H, d,
J = 2.1 Hz); FAB-MS m/z 288 [(M+H)+].
5.1.36. 6,7,8,9-Tetrahydro-5H-furo[2,3-h][3]benzazepine
(46). The hydrochloride salt of 46 was prepared from
45 using a procedure similar to that described for 11
(52%). White solid; H NMR (DMSO-d6) d 3.10–3.28
(8H, m), 6.89 (1H, d, J = 2.0 Hz), 7.47 (1H, s), 7.48
1
38 (4.17 g, 43%) as a yellow solid. H NMR (DMSO-
d6) d 4.23 (3H, s), 4.31 (3H, s), 7.05 (1H, d,
J = 2.4 Hz), 7.37 (1H, d, J = 8.0 Hz), 7.71 (1H, d,
1

I. Shimada et al. / Bioorg. Med. Chem. 16 (2008) 3309–3320
3319
(1H, s), 7.95 (1H, d, J = 2.0 Hz), 9.54 (2H, br s); FAB-
MS m/z 188 [(M+H)+]. Anal. Calcd for C12H13NOÆHCl:
C, 64.43; H, 6.31; N, 6.26; Cl, 15.85. Found: C, 64.17; H,
6.43; N, 6.19; Cl, 16.07.
elute was added to a liquid scintillator (Aquasol-2)
and measured with the liquid scintillation counter.
EC50 values and Emax (%) were calculated by non-linear
analysis using SAS (ver. 6.11) together with an applica-
tion software developed by our company. Emax (%) indi-
cated intrinsic activity and the response produced by
10 lM 5-HT was defined as 100%.
5.2. Biological procedures
5.2.1. Receptor binding assay. The membrane prepara-
tion was washed once with 50 mM Tris–HCl buffer
(pH 7.4) containing 4 mM CaCl2 just before it was used
for the binding assays. The 5-HT2C, 5-HT2A, and 5-
HT2B receptor binding assays with [3H]5-HT were car-
ried out using the methods of Pazos et al.16 with a slight
modification; reaction medium [50 mM Tris–HCl buffer
(pH 7.4) containing 4 mM CaCl2, 10 lM pargyline, and
0.1 mg/mL l-(+)-ascorbic acid] containing [3H]5-HT,
membrane preparation, and test compounds was incu-
bated at 37 ꢁC for 30 min. Non-specific binding was
determined in the presence of 10 lM 5-HT, and specific
binding was calculated as total binding minus non-spe-
cific binding. After incubation, 4 mL of 50 mM Tris–
HCl buffer (pH 7.4) containing 4 mM CaCl2 was added,
and the medium was filtered under vacuum through
Whatman GF/B glass filter pre-treated with 0.1% poly-
ethyleneimine. The filter was washed with the same buf-
fer solution (3· 4 mL). The GF/B glass filter was
immersed in 6 mL of liquid scintillator (Packard, Aqua-
sol-2), and radioactivities were measured with a liquid
scintillation counter (Packard, Tri-Carb-2500TR). The
amounts of protein were measured according to the
method established by Lowry et al.17 Dissociation con-
stants (Kd value) were obtained by Scatchard analysis
using SAS (ver. 6.11) together with an application soft-
ware developed by our company (5-HT2C; 1.6 nM, 5-
HT2A; 9.8 nM, and 5-HT2B; 14 nM). Concentrations
of compounds showing 50% inhibition of receptor bind-
ing, IC50 values, were obtained by non-linear analysis
using SAS (ver. 6.11) together with an application soft-
ware developed by our company. Ki values indicating
affinity for receptors were calculated by using a formula
developed by Cheng and Prussoff.18
5.2.3. Behavioral studies. All experiments were carried out
during 13:00–19:00. Rats were placed individually in
transparent acrylic plastic cages to count the number of
penile erections. A penile erection was defined as previ-
ously described20: repeated pelvic thrusts immediately fol-
lowed by assuming an upright position (on hind limbs), an
emerging, engorged penis, and licking it. The number of
penile erections was observed for 30 min immediately
after test compounds’ po administration.
5.2.4. Cardiovascular effect. The rats were anesthetized
with pentobarbital sodium (60 mg/kg ip), and a catheter
was inserted into the carotid artery to measure the sys-
temic arterial pressure. The rats were used in the study
after a postoperative recovery period of two or more
days. After conscious animals were housed in cages for
blood pressure measurement and stabilized for at least
30 min, YM348 (10–30 mg/kg) or compound 6 (3–
30 mg/kg) was administered orally.
Acknowledgments
The authors are grateful to the staff of the Division of
Analytical Science Laboratories for the elemental analy-
sis and spectral measurements.
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