Synthesis and binding assays of novel 3,3-dimethylpiperidine derivatives with various lipophilicities as σ1 receptor ligands

Article abstract of DOI:10.1016/j.bmc.2011.10.023

Starting from two carbocyclic analogs, a series of 3,3-dimethylpiperidine derivatives was prepared and tested in radioligand binding assays at σ₁ and σ₂ receptors, and at Δ₈-Δ₇ sterol isomerase (SI) site. The novel compounds mostly bear heterocyclic rings or bicyclic nucleus of differing lipophilicities. Compounds 18a and 19a,b demonstrated the highest σ₁ affinity (K_i = 0.14-0.38 nM) with a good selectivity versus σ₂ binding. Among them, 18a had the lowest C log D value (3.01) and only 19b was selective versus SI too. Generally, it was observed that more planar and hydrophilic heteronuclei conferred a decrease in affinity for both σ receptor subtypes.

Full text of DOI:10.1016/j.bmc.2011.10.023

Bioorganic & Medicinal Chemistry 19 (2011) 7612–7622
Contents lists available at SciVerse ScienceDirect
Bioorganic & Medicinal Chemistry
journal homepage: www.elsevier.com/locate/bmc
Synthesis and binding assays of novel 3,3-dimethylpiperidine derivatives
with various lipophilicities as r1 receptor ligands
Savina Ferorelli, Carmen Abate, Maria P. Pedone, Nicola A. Colabufo, Marialessandra Contino,
⇑
Roberto Perrone, Francesco Berardi
Dipartimento Farmacochimico, Università degli Studi di Bari, Via Orabona 4, I-70125 Bari, Italy
a r t i c l e i n f o
a b s t r a c t
Article history:
Starting from two carbocyclic analogs, a series of 3,3-dimethylpiperidine derivatives was prepared and
Received 28 July 2011
Revised 4 October 2011
Accepted 7 October 2011
Available online 17 October 2011
tested in radioligand binding assays at r1 and r2 receptors, and at D8–D7 sterol isomerase (SI) site.
The novel compounds mostly bear heterocyclic rings or bicyclic nucleus of differing lipophilicities. Com-
pounds 18a and 19a,b demonstrated the highest r1 affinity (Ki = 0.14–0.38 nM) with a good selectivity
versus
SI too. Generally, it was observed that more planar and hydrophilic heteronuclei conferred a decrease in
affinity for both receptor subtypes.
r2 binding. Among them, 18a had the lowest ClogD value (3.01) and only 19b was selective versus
Keywords:
r1 Ligands
3,3-Dimethylpiperidines
r
Ó 2011 Elsevier Ltd. All rights reserved.
Structure–activity relationship
D8
r
–
D7 Sterol isomerase binding
Binding
1. Introduction
voltage-gated potassium channels, intracellular Ca2+ release,18 and
intracellular displacement of galactosylceramide-enriched mem-
brane microdomains.19 The modulation of ion channels in the
plasma membrane can regulate the membrane excitability,18 and
modulate the effects of cocaine.18 A recent study identified the r1
receptor as a novel ER chaperone.20 In the CNS the r1 receptors
are involved in various neurotransmitter systems, such as glutama-
tergic, dopaminergic, serotonergic, adrenergic, and cholinergic
systems,21 so that this receptor plays an important role in neuropsy-
The recent high interest in sigma receptors descends from the
discovery that both 1 and
2 subtypes1 are overexpressed in many
human and nonhuman tumors.2–4 For this reason, the pharmacolog-
ical study on -receptor ligands plays an important role in the
r
r
r
cancer research for potential clinical treatment and imaging diagno-
sis applications by means of positron emission tomography (PET),
and single photon emission computed tomography (SPECT)
techniques.5,6
chiatric and neurodegenerative diseases.
r1 Receptor ligands have
The
teins and shares 30% identity with the yeast D8
(SI), so that the belonging of receptors to the family of sterol
isomerases was proposed.7 The
1 receptor is a 29-kDa single pro-
r
1 receptor shows no homology with other mammalian pro-
been proposed and tried clinically for anxiety, depression, schizo-
phrenia, learning and memory improvement, cocaine addiction,
and drug abuse.18
–D7 sterol isomerase
r
r
Several unrelated structures are known to bind selectively the
tor, and the (+)-pentazocine represents a typical selective agonist used also
as a tritiated radioligand (Fig. 1). Other selective 1ligands have been devel-
oped and are routinely used for studying receptors. Examples are 1-[2-
r1 recep-
tein and its gene was cloned from guinea pig liver,8 mouse kidney,
JAR human choriocarcinoma cell line, and from rat and mouse
brain.9 The r2 receptor subtype was not reproduced by clonation,
r
r
and its structure has not been fully identified yet.10,11 The
r
1 recep-
(3,4-dimethoxyphenyl)ethyl]-4-(3-phenylpropyl)piperazine (SA 4503),
N,N-dipropyl-2-[4-methoxy-3-(2-phenylethoxy)phenylethylamine (NE
100), and N-[(2Z)-3-(3-chloro-4-cyclohexylphenyl)-2-propen-1-yl]-N-eth-
ylcyclohexanamine hydrochloride (SR 31747A) (Fig. 1). Currently, the
number of r1 ligands is increasing with the development of new
compounds such as 10-benzyl-3-methoxy-3,4-dihydrospiro[[2]-benzopy-
ran-1, 40-piperidine]22 (A) and ( )-2-(1-benzylpiperidin-4-yl)-2,3-dihydro-
tiocromen-4-one,23 (B) which display high r1 receptor affinity and
selectivity.
tors are distributed in many peripheral tissues of the endocrine and
immune systems (e.g., adrenal gland, testis, ovary, spleen, and blood
leukocytes)12 but they are also concentrated in the central nervous
system (CNS), particularly in brainstem motor regions.13,14 They
are located on the cell and endoplasmic reticulum (ER) mem-
branes15,16 and are formed by two transmembrane domains with
one extracellularloop.17 The
r1 receptor has been proven to regulate
In our previous works, about
type selectivity in the class of 3,3-dimethyl-N-[
and indan-1-yl)alkyl]piperidine.24,25 High
1-receptor affinity and
r
ligands, we investigated
r sub-
⇑
x
-(tetralin-1-yl
Corresponding author. Tel.: +39 080 5442751; fax: +39 080 5442231.
E-mail address: berardi@farmchim.uniba.it (F. Berardi).
r
0968-0896/$ - see front matter Ó 2011 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmc.2011.10.023

S. Ferorelli et al. / Bioorg. Med. Chem. 19 (2011) 7612–7622
7613
N
N
N
HO
CH3
OMe
OMe
CH3
(+)–Pentazocine
SA 4503
Cl
N
O
N
.HCl
OMe
NE 100
SR 31747A
OMe
O
O
S
N
N
A
B
Figure 1. Structures of representative r1 ligands.
a certain r1
/
r
2 selectivity were obtained with an intermediate alkyl
were prepared from ketones 4–7 via Grignard reaction as already re-
ported.30 The compound 8a was prepared after derivatization of the
6,7-dihydro-1H-indol-4(5H)-one (3) to its N-tosyl derivative 4,31
whereas 6,7-dihydro-1-benzofuran-4(5H)-one (5), 6,7-dihydro-1-
benzothiophen-4(5H)-one (6), and 6,7,8,9-tetrahydrobenzo[7]ann-
ulen-5-one (7) were from a commercial source. The intermediate
10a has been previously obtained and reported.32 The intermediate
compound 12 was prepared by alkylation of 3,3-dimethylpiperidine
with bromopropyl derivative 8a. The final compound 13 was pre-
pared by deprotection of the corresponding tosyl derivative 12 in
the presence of K2CO3.33 Bromopropylderivatives 9a and 10a were
aromatizated with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone
(DDQ) to afford the corresponding bromopropylnaphthalenes 14
and 15.34 The final compounds16, 17, 18c, and 19a,b were obtained
from the intermediates 14, 15, 10c, and 11a,b, respectively, and
3,3-dimethylpiperidine,25 as for compound 12. Compound 18a has
already been reported as its oxalate salt.32
The preparation of the (benzofuranyl)methyl compound 22 is
depicted in Scheme 2. 2-Hydroxymethyl-1-benzofuran35 (20) trea-
ted with thionyl chloride provided chloromethyl compound 21,
which was derivatized with 3,3-dimethylpiperidine to give the
final amine compound 22.
The preparation of final compounds 28–31 is depicted in Scheme
3. The esters 24a,b36 were obtained by reaction of indole 23a and
benzotriazole 23b, respectively, with ethyl acrylate, and were re-
duced by LiAlH4 to the alcohols 26a,b. Similarly, the alcohol 26c
was obtained from commercially available ester 25. By treating each
of these alcohols and the commercial product 4-cyclohexylbutan-1-
ol (26d) with mesyl chloride, the corresponding mesyl derivatives
27a–d were prepared.24 These derivatives were reacted with 3,3-
dimethylpiperidine to give the final amine compounds 28–31.25
The preparation of final thiazole-containing derivatives 34 and
36–38 is depicted in Scheme 4. 2-Amino-5,6-dihydro-1,3-ben-
chain of four methylenes with a 6-methoxytetralin (1) or indane (2)
nucleus (Table 1). The tetralin and the indane derivatives have been
designed to interact with the primary hydrophobic site of the r1
receptor model proposed by Glennon,26–28 and the basic nitrogen
atom of 3,3-dimethylpiperidine may interact with a receptor pro-
ton–donor site. Moreover, among various methylpiperidine deriva-
tives, the ligands bearing the 3,3-dimethylpiperidine moiety
selectively bind to r1 relative to r2 receptor, although they pos-
sessed high lipophilicity values.29 In an extension of these works,
we synthesized other analogs in order to obtain compounds with
better selectivity for r1 receptor subtype, with suitable lipophilicity
values for optimal pharmacokinetics. Therefore we prepared and
tested a series of 3,3-dimethylpiperidine derivatives presenting dif-
ferent levels of lipophilicity, where the carbocyclic moieties were
mostly replaced by various heteronuclei. Starting from 1 and 2 as
lead compounds, more lipophilic upper homologs benzosuberanes
were prepared. Less lipophilic compounds were obtained by
replacement of indane and tetralin rings with heterocyclic rings.
Tetrahydroindole, tetrahydrobenzothiophene, and benzosuberane
derivatives were synthesized and investigated as racemates. Other
heterocyclic nuclei were chosen to avoid inconvenient stereogenic
centers, also because the stereoselectivity in these series of com-
pounds plays a marginal role. Furthermore, the length of the inter-
mediate chain, and consequently its flexibility, were varied in
some cases. Giventhe pharmacological similaritybetween r1 recep-
tor and SI, we conducted SI binding assays for a number of
compounds.7,25
2. Chemistry
The synthesis of final compounds 13, 16, 17, 18a,c, and 19a,b, is
depicted in Scheme 1. The key intermediates8a, 9a, 10a,c, and 11a,b

7614
S. Ferorelli et al. / Bioorg. Med. Chem. 19 (2011) 7612–7622
Table 1
ClogD values, binding affinities and selectivities for target compounds
N
(CH2)n
R
Compound
R
n
ClogDa
Ki SEM (nM)
Ki ratio
r2/r1
r1
r2
SI
1b
5-Methoxytetralin-1-yl
Indan-1-yl
4,5,6,7-Tetrahydroindol-4-yl
Benzofuran-4-yl
Benzothiophen-4-yl
4,5,6,7-Tetrahydrobenzothiophen-4-yl
4,5,6,7-Tetrahydrobenzothiophen-4-yl
Benzosuberan-1-ylf
Benzosuberan-1-ylf
Benzofuran-2-yl
Indol-1-yl
Benzotriazol-1-yl
Indol-3-yl
Cyclohexyl
4,5,6,7-Tetrahydrobenzothiazol-7-one-2-aminocarbonyl
4,5,6,7-Tetrahydrobenzothiazol-7-one-2-amino
Benzothiazol-2-amino
Thiazol-2-amino
3,3-Dimethylpiperidin-1-yl
4
4
3
3
3
3
5
3
4
1
3
3
3
4
1
2
2
2
4
4.51
4.03
1.82
2.97
4.67
3.01
4.79
3.88
5.15
2.98
2.74
1.71
2.31
4.06
3.19
2.74
2.96
1.28
1.32
2.12 0.30
1.75 0.12
27.1 2.7
63.5 7.0
52.0 12.0
0.21 0.01d
78%e
0.38 0.18
0.14 0.04
3690 890
50.9 11.1
339 16
247 52
242 59
119 41
42.3 9.8
63.6 12.6
38
0.67 0.19
1.54 0.01
NTc
1.1
0.9
3.07 1.43
2.11 1.00
0.2
7.3
NT
117
138
4.4
0.7
1.2
ꢀ180
2b
13
16
17
18a
18c
19a
19b
22
28
29
30
31
34
36
37
38
28.1 2.1
37.5 0.1
65.9 12.0
1810 100
194 26
1990 490
110 17
19.6 1.9
>104
101
471
0.4
3.8
5.6
2.6
19
NT
NT
NT
41.6 7.2
1.02 0.22
>104
3.8
>104
>104
>104
742 80
3330 1030
414 148
>104
566 160
459 27
14.1 2.6
3.16 0.34
115
1400 470
213
1.3
7.2
29
41
(+)-Pentazocine
DTG
34.3 1.6
( )-Ifenprodil
15.0 2.5
a
b
c
d
e
f
Referred to the corresponding free bases at pH 7.4.
From Ref. 25.
Not tested.
Previous result for oxalate salt in rat brain membranes, Ki > 3960 (Ref. 32).
Pecentage of binding inhibition at 10ꢁ10 M compound.
I. e. 6,7,8,9-tetrahydrobenzo[7]annulen-5-yl.
zothiazol-7(4H)-one37 (32a) and the commercially available 2-ami-
no-1,3-benzothiazole (32b) and 2-amino-thiazole (32c) were sub-
jected to acetylation with chloroacethyl chloride to achieve
chloroacetamides 33a–c. Compounds 33a was derivatized with
3,3-dimethylpiperidine to give the final compounds 34. Compounds
33a–c were then reduced with LiAlH4 to the corresponding chlo-
roderivatives 35a–c. Finally, all the haloalkyl compounds 35a–c
were derivatized with 3,3-dimethylpiperidine to give the final
amine compounds 36–38.25
The preparation of final bis-3,3-dimethylpiperidine derivative
41 is depicted in Scheme 5. Bisimide intermediate 40 was obtained
by derivatization of 2,2-dimethylglutaric acid (39) to the 2,2-dim-
ethylglutaryl chloride and subsequent cyclization with butane-1,4-
diamine. Reduction of this latter compound with LiAlH4 led to the
final diamine compound 41.
((+)-[2S-(2a,6a,11R)]-1,2,3,4,5,6-hexahydro-6,11-dimethyl-3-(3-
methyl-2-butenyl)-2,6-methano-3-benzazocine-8-ol), guinea-pig
brain membranes without cerebellum; (b) r2 receptor, [3H]-DTG
in the presence of 1 lM (+)-pentazocine to mask r1 receptors, rat
liver membranes; and (c) SI site, ( )-[3H]-emopamil, guinea-pig liver
membranes. The following compounds were used to define the spe-
cific binding reported in parentheses: (a) (+)-pentazocine (72–88%),
(b) compound DTG (87–96%), and (c) ( )-ifenprodil (70–85%). Con-
centrations required to inhibit 50% of radioligand specific binding
(IC50) were determined by using 6–9 different concentrations of
the drug studied in two or three experiments with samples in dupli-
cate. Scatchard parameters (Kd and Bmax) and apparent inhibition
constants (Ki) values were determined by nonlinear curve fitting,
using the Prism, version 3.0, GraphPad software.39
The final amine compounds 16, 17, 18a,c, 19a,b, 22, 29, 31,
34–38, and 41 were converted to the corresponding hydrochloride
salts with gaseous HCl in anhydrous Et2O, and then the salts were
recrystallized from MeOH/Et2O. These salts were used for receptor
binding experiments, whereas the compounds 13, 28, and 30 were
used as free bases. The binding results are listed in Table 1, along
with the calculated values of the logarithm of the distribution
coefficient (ClogD) at pH 7.4 for the corresponding free bases.38
4. Results and discussion
4.1. Radioligand binding
The binding data for the new compounds synthesized and the
lead compounds 1 and 2 are reported in Table 1 and are expressed
as Ki values. For all the compounds the ClogD values are reported
and they are included in the 1.28–5.15 range. Among all the
3,3-dimethylpiperidine derivatives only compounds 18a, 19a,b,
and 31 displayed high affinity towards r1 receptor (Ki = 0.14–
1.02 nM). Compounds 19a,b showed subnanomolar r1 receptor
affinity (Ki = 0.38 and 0.14 nM, respectively) and high selectivities
for r1 relative to r2 receptor (101- and 471-fold, respectively).
Moreover, the apparent Hill slope values for 19a,b were ꢀ1. Com-
pounds 13, 16,17, 28, 30, and 41 showed moderate affinities toward
3. Biology
3.1. Receptor binding studies
All the compounds listed in Table 1 were evaluated by radiore-
ceptor binding assays for in vitro affinity at r1 and r2 receptors
and almost all of them were evaluated, at least once, at mammalian
r
1 receptor (Ki = 14.1–63.5 nM), but their
ity was less than five-fold, except for 41 (29-fold). All the other com-
pounds demonstrated either poor or no affinity for both receptor
r1 relative to r2 selectiv-
D8
sources were respectively: (a) r1 receptor, (+)-[3H]-pentazocine
–D7 sterol isomerase (SI) site. The specific radioligands and tissue
r

S. Ferorelli et al. / Bioorg. Med. Chem. 19 (2011) 7612–7622
7615
O
O
A
N
X
m
H
3
4: X = N-Ts, m = 1
5: X = O, m = 1
B or C
6: X = S, m = 1
7: X = HC=CH, m = 2
D
Hal
N
N
n
3,4
E
E
X
N
m
Ts
19a,b
12
13
8a, 9a, 10a,c, 11a,b
F
a: n = 3, Hal = Br
b: n = 4, Hal = Cl
c: n = 5, Hal = Cl
8: X = N-Ts, m = 1
9: X = O, m = 1
10: X = S, m = 1
11: X = HC=CH, m = 2
E
G
N
N
Br
3,5
E
S
X
X
14: X = O
15: X = S
18a,c
16: X = O
17: X = S
Scheme 1. Synthesis of 3,3-dimethylpiperidine derivatives 13, 16, 17, 18a,c, and 19a,b. Reagents: (A) tosyl chloride; (B) cyclopropyl bromide, Mg and then HBr;
(C) Cl–(CH2)4,5–Br, Mg; (D) H2, 5% Pd/C; (E) 3,3-dimetylpiperidine; (F) MeOH/H2O, K2CO3; (G) DDQ.
O
O
O
A
B
CH2OH
CH2Cl
N
20
Scheme 2. Synthesis of 3,3-dimethylpiperidine (benzofuranyl)methyl derivative 22. Reagents: (A) SOCl2; (B) 3,3-dimethylpiperidine.
21
22
subtypes (compounds 22, 29, 34, and 36–38). However, compound
18c did not show concentration-dependent behavior, probably be-
structural requirements are in accordance withthose for 19b. Taking
into consideration the highest-affinity 1 ligand 18a (Ki = 0.21 nM),
a convenient reduced ClogD value and a good selectivity relative to
2 binding were recorded. Elongation of the intermediate chain to
five methylenes (compound 18c) led to a more flexible and highly
lipophilic compound, which bound in a nonspecific manner at r1
receptors. Also interesting are the data of compound 31, since it
demonstrated good r1 receptor affinity (Ki = 1.02 nM) in the same
magnitude order as lead compounds. Nevertheless, it revealed an
r
cause of its highly lipophilic structure. Affinity toward
was only moderate (Ki = 19.6–65.9 nM) for compounds 16, 17,
18a,c, 19a,b, and 31, so that no r1 r2 selectivity was recorded for
r2 receptor
r
/
compounds 16 and 17. For some compounds the SI affinity was also
tested and compound 19a showed one of the highest affinities
known towards SI (Ki = 0.2 nM). Among these 3,3-dimethylpiperi-
dine derivatives only the highest-affinity
r1 ligand 19b can be con-
sidered selective relative to SI site too (ꢀ50-fold). Furthermore, it
about 10-fold higher r2 receptor affinity, and so a worse selectivity.
possesses also the highest ClogD values (5.15). Compared to the lead
In this compound again a lipophilic nucleus as the cyclohexyl ring
and a four-membered intermediate chain are present. The reduced
affinity of compounds 13 compared to compound 18a, might be
due to the presence of the @NH function in the latter compound.
The benzofuran 16 and benzothiophene 17 displayed comparable
lower r1 affinity and selectivity versus r2 receptor. From
comparison of tetrahydrobenzothiophene 18a to benzothiophene
17 it emerges that a rather planar bicyclic structure appeared to be
compounds 1 and 2, the
r1 affinity seems to be strongly influenced
by the replacement of the tetralin and the indane moieties with
other nuclei. Indeed, only compounds 19a,b with a more lipophilic
benzosuberane nucleus and three- or four-methylene intermediate
chain, displayed very high affinities toward
r1 receptor. Therefore,
the compound 19b demonstrated better affinity and selectivity
(471-fold) for r1 receptor than compounds 1 and 2, whose

7616
S. Ferorelli et al. / Bioorg. Med. Chem. 19 (2011) 7612–7622
5. Conclusions
OC2H5
X
With the aim of targeting
r1 receptors whose density is high in
O
X
the CNS and in tumors, we synthesized a series of 3,3-dimethylpi-
peridine derivatives with a wide range of lipophilicity in order to
reach a compromise between pharmacodynamic and pharmacoki-
netics requirements. Lipophilicity of drugs is a determining factor
with a logD <3.0 (pH 7.4) considered suitable for their entrance
in both the CNS40 and peripheral tumors.41 The only compound
of the series potentially reaching this compromise was 18a which
presented a nanomalor r1 affinity, appreciable r1/r2 selectivity
and an optimal lipophilicity (ClogD = 3.01). Compounds with low-
er ClogD values were in general characterized by decreased r1
N
H
N
H
25
23a: X = CH
23b: X = N
B
A
X
B
R
OH
X
O
affinity or r1
higher ClogD values were in general accompanied by noteworthy
1 affinities. In fact, compound 19b presented the highest 1 affin-
ity and r1 r2 selectivity of the series, but its ClogD (5.15) value
was too high to be considered optimal. Apparently, a correlation
between subtype binding and ClogD values exists although
/r2 selectivity. On the other hand, compounds with
N
OC2H5
26a-d
r
r
/
24a,b
C
r
not strictly consistent. Furthermore rather planar bicyclic structure
appeared detrimental for r1 binding, in accordance with a recent
work, in which nonplanar tricyclic compounds derived from Ste-
mona alkaloids displayed nanomolar
new insights for the r1 receptors binding were given and the
promising r1 receptor ligand 18a was developed.
R
OSO2CH3
R =
27a-d
r
1 receptor affinity.42 Overall,
a
N
N
D
N
b
6. Experimental section
6.1. Chemistry
N
R
N
c
Both column chromatography and flash column chromatogra-
phy were performed with 60 Å pore size silica gel as the stationary
N
H
28: R = a
29: R = b
30: R = c
31: R = d
phase (1:30 w/w, 63–200
lm particle size, from ICN and 1:15 w/w,
d
15–40 m particle size, from Merck, respectively). Melting points
l
were determined in open capillaries on a Gallenkamp electrother-
mal apparatus. Purity of tested compounds was established by
combustion analysis, confirming a purity >95%. Elemental analyses
(C, H, N) were performed on an Eurovector Euro EA 3000 analyzer;
the analytical results were within 0.4% of the theoretical values,
unless otherwise indicated. 1H NMR spectra were recorded on a
Mercury Varian 300 MHz using CDCl3 as solvent, unless otherwise
reported. The following data were reported: chemical shift (d) in
ppm, multiplicity (s, singlet; d, doublet; t, triplet; q, quadruplet;
m, multiplet), integration and coupling constants in hertz. Record-
ing of mass spectra was done on an Agilent 6890-5973 MSD gas
chromatograph/mass spectrometer and on an Agilent 1100 series
LC–MSD trap system VL mass spectrometer; only significant m/z
peaks, with their percentage of Infrared spectra were recorded on
a Perkin–Elmer FTIR Spectrum one. Relative absorbance intensity
is reported in parentheses. Chemicals were from Aldrich and
Across and were used without any further purification.
Scheme 3. Synthesis of 3,3-dimethylpiperidine derivatives 28–31. Reagents:
(A) CH@CH–COOEt; (B) LiAlH4; (C) CH3SO2Cl; (D) 3,3-dimethylpiperidine.
detrimental for r1 binding. This is confirmed by all bicyclic com-
pounds with an extensive electronic conjugation, compared to par-
tially cycloaliphatic ones. When an @NH function was present in the
moiety vicariant tetralin or indane, lipophilicity mostly decreases,
but also a hydrogen-bonding donor function was provided. For com-
pound 29, a considerable decrease in the r1 and r2 affinity (Ki = 339
and 1990 nM, respectively) was observed probably because of high-
er hydrophilicity of benzotriazole nucleus compared to indole 13,
28, and 30. The compounds 22, 34, and 36–38 displayed a dramatic
decrease in
r1 receptor affinity: eventually, more hydrophilic het-
eronuclei decreased r1 receptor and sometimes also r2 receptor
binding. In addition their shorter chain (one- or two-methylene)
6.1.1. N-Tosyl-6,7-dihydro-1H-indol-4-(5H)-one (4)
might prevent the interaction with the
phobic site.
Although an accurate correlation between
and ClogD was not pointed out, in general the compounds with
the lowest ClogD values displayed poor affinities toward
receptors.
As for binding at SI site, the compound 19a provided an affinity
comparable to that at r1 receptor and its Ki value was the highest
(0.2 nM) in this class. Also compounds 16 and 17 displayed good SI
affinities (Ki = 1.1 and 0.93 nM, respectively) which, together with
r1 receptor primary hydro-
To a solution of 6,7-dihydro-1H-indol-4-(5H)-one (3) (2.50 g,
18.5 mmol) in toluene (37 mL) was added tetrabutylammonium
hydrogensulfate (0.46 g, 1.35 mmol) and a 50% aqueous solution
of KOH (23 mL). The mixture was stirred, at room temperature
for 10 min, under a stream of N2. Then, a solution of p-toluenesul-
fonyl chloride (3.70 g, 19.5 mmol) in toluene (37 mL) was added
and the reaction mixture was stirred for 4 h, at room temperature.
The separated organic mixture was washed with H2O (3 ꢂ 10 mL),
dried (Na2SO4) and evaporated under reduced pressure to afford
the crude white solid (4.0 g), which was recrystallized by ethanol.
Title compound (4.01 g) was obtained in 75% yield. 1H NMR d 2.04–
2.12 (m, 2H, COCH2CH2CH2), 2.36–2.46 (m + s, 5H, COCH2CH2CH2,
CH3), 2.96 (t, 2H, J = 6.0 Hz, COCH2CH2CH2), 6.61 (d, 1H,
r subtype binding
r
a moderate
r binding, led these compounds to be selective relative
to receptors. However these SI binding data have only an indic-
r
ative value because they were mostly obtained from a unique
experiment.

S. Ferorelli et al. / Bioorg. Med. Chem. 19 (2011) 7612–7622
7617
O
S
N
Ar
NH2
Ar =
no ring
c
a
b
32a-c
A
O
S
N
S
Cl
C
Cl
Ar
N
H
Ar
N
H
N
33a-c
35a-c
B
B
O
S
N
N
O
Ar
N
H
S
N
N
H
N
36: R = a
37: R = b
38: R = c
34
Scheme 4. Synthesis of 3,3-dimethylpiperidine thiazole-containing derivatives 34 and 36–38. Reagents: (A) ClCH2COCl, ethylenglycol dimethylether, Et3N;
(B) 3,3-dimethylpiperidine; (C) BF3O(C2H5)2, (CH3)2SꢃBH3.
O
O
O
O
N
B
A
N
2
HO
OH
O
O
39
40
C
N
N
41
Scheme 5. Synthesis of bis-3,3-dimethylpiperidine derivative 41. Reagents: (A) SOCl2; (B) H2N–(CH2)4–NH2; (C) LiAlH4.
J = 3.5 Hz, CHCHN), 7.23 (d, 1H, J = 3.5 Hz, CHCHN), 7.34–7.74 (m,
CH), 3.48 (t, 2H, J = 6 Hz, CH2Br), 6.24–7.27 (m, 2H, aromatic);
GC–MS m/z 244 (M++2, 22), 243 (M++1, 3), 242 (M+, 22), 121 (100).
4H, aromatic); GC–MS m/z 290 (M++1, 19), 289 (M+, 100), 155
(50), 134 (73), 106 (66), 91 (96), 107 (100).
6.1.1.3. 4-(5-Chloropentyl)-4,5,6,7-tetrahydro-1-benzothiophe
ne (10c). The crude residue was chromatographed on a silica
gel column with petroleum ether/CH2Cl2 (9/1) as eluent. Title com-
pound (0.43 g) was obtained in 25% yield. 1H NMR d 1.26–1.76 (m,
8H, CH2(CH2)2CH2Cl and endo CH2CH2), 1.55–1.62 (m, 4H,
CHCH2(CH2)2CH2CH2Cl), 2.52–2.84 (m, 3H, benzylic CH2 and CH),
3.45 (t, 2H, J = 7 Hz, CH2Cl), 6.60–7.08 (m, 2H, aromatic); GC–MS
m/z 244 (M++1, 7), 243 (M+, 3), 137 (100).
6.1.1.1. 4-(3-Bromopropyl)-1-tosyl-1H-4,5,6,7-tetrahydroindole
(8a). The crude residue was chromatographed on a silica gel col-
umn with petroleum ether/CH2Cl2 (8/2) as eluent. (0.70 g), 41%
yield. 1H NMR d 1.78–3.00 (m + s, 14H, (CH2)3CH(CH2)2CH2Br and
CH3), 3.34–3.50 (m, 2H, CH2Br), 6.35–6.39 (m, 1H, NCHCH), 7.18–
7.20 (m, 1H, NCHCH), 7.29–7.68 (m, 4H, aromatic); GC–MS m/z
397 (M++2, 8), 396 (M++1, 2), 395 (M+, 8), 274 (100).
6.1.1.2. 4-(3-Bromopropyl)-4,5,6,7-tetrahydrobenzofuran(9a).
The crude residue was chromatographed on a silica gel column
with petroleum ether/CH2Cl2 (95/0.5) as eluent. Title compound
(0.30 g) was obtained in 15% yield. 1H NMR d 1.15–2.05 (m, 8H,
CH2(CH2)2CH(CH2)2CH2Br), 2.48–2.65 (m, 3H, benzylic CH2 and
6.1.1.4. 5-(3-Bromopropyl)-6,7,8,9-tetrahydrobenzo[7]annulene
(11a). H NMR d 1.40–1.91(m, 10H, (CH2)3CH(CH2)2CH2Br), 2.70–
2.90 (m, 3H, benzylic CH2 and CH), 3.31–3.71(m, 2H, CH2Br),
7.02–7.18 (m, 4H, aromatic); GC–MS m/z 268 (M++2, 7), 267
(M++1, 4), 266 (M+, 5), 145 (100).
1

7618
S. Ferorelli et al. / Bioorg. Med. Chem. 19 (2011) 7612–7622
6.1.1.5. 5-(4-Chlorobutyl)-6,7,8,9-tetrahydrobenzo[7]annulene
(11b). 1H NMR
1.18–1.91(m, 12H, (CH2)3CH(CH2)3CH2Br),
2.72–2.88 (m, 3H, benzylic CH2 and CH), 3.60 (t, 2H, J = 7 Hz,
CH2Cl), 7.02–7.11 (m, 4H, aromatic); GC–MS m/z 238 (M++2, 9),
237 (M++1, 5), 236 (M+, 24), 145 (100).
yellow oil (1.3 g) in 98% yield. The crude residue was not further
purified. 1H NMR d 4.78 (s, 2H, CH2Cl), 6.78 (s, 1H, OCCH), 7.18–
7.60 (m, 4H aromatic); GC–MS m/z 169 (M++3, 0.9), 168 (M++2,
9), 167 (M++1, 3), 166 (M+, 28), 131 (100).
d
6.1.2. General procedure to obtain final amine compounds 16,
17, 18a,c, 19a,b, and 22
6.1.1.6. 4-[3-(3,3-Dimethylpiperidin-1-yl)-propyl]-1-tosyl-1H-
4,5,6,7-tetrahydroindole
(12). 4-(3-Bromopropyl)-1-tosyl-1H-
In a typical reaction, a representative intermediate (1.0 mmol)
4,5,6,7-tetrahydroindole (8a) (0.38 g, 0.95 mmol) was stirred and re-
fluxed overnight in CH3CN with 3,3-dimethylpiperidine (0.14 g,
1.3 mmol) and Na2CO3. The work up was carried out as previously de-
scribed.24 The crude residue was purified by column chromatography
using CH2Cl2/MeOH (9:1) as eluent to give the target compound as a
yellow oil in 92% yield; 1H NMR d 0.9 (s, 6H, C(CH3)2), 1.21–1.38 (m,
4H, CCH2CH2), 1.58–1.77 (m, 8H, CH(CH2CH2)2), 1.98–2.38 (m, 6H,
CH2N(CH2)2), 2.41 (s, 3H, CH3), 2.58–2,85 (m, 3H, benzylic), 6.13–
7.79 (m, 6H, aromatic); GC–MS m/z 429 (M++1, 4), 428 (M+, 9), 126
(100).
among 1-(x-haloalkyl) derivatives 14, 15, 10a,c, 11a,b, and 21
respectively, was stirred and refluxed overnight with 3,3-dimeth-
ylpiperidine (1.2 mmol) and Na2CO3 (1.2 mmol) in CH3CN. The
mixture was worked up as reported for compound 12. Purification
by column chromatography (CH2Cl2/MeOH 9:1 as eluent, unless
otherwise indicated) afforded final compounds as colorless or pale
yellow oils.
6.1.2.1. 1-[3-(1-Benzofuran-4-yl)propyl]-3,3-dimethylpiperidine
(16). 1H NMR d 0.94 (s, 6H, C(CH3)2), 1.17–1.30 (m, 2H, piperidine
CCH2), 1.55–1.69 (m, 2H, piperidine CCH2CH2), 1.85 (quintet, 2H,
J = 7.7 Hz, ArCH2CH2), 2.01 (s, 2H, CCH2N), 2.21–2.38 (m, 4H,
N(CH2)2), 2.87 (t, 2H, J = 7.7 Hz, benzylic), 6.80–6.83 (m, 1H,
OCHCH), 7.05–7.39 (m, 3H, aromatic), 7.59 (d, 1H, J = 2.5 Hz,
OCH); GC–MS m/z 272 (M++1, 8), 271 (M+, 35), 126 (100). The cor-
responding hydrochloride salt was recrystallized from MeOH/Et2O:
mp 205–207 °C. Anal. (C18H25NOꢃHClꢃ0.25 H2O) C, H, N.
6.1.1.7. 3,3-Dimethyl-1-[3-(1H-4,5,6,7-tetrahydroindol-4-yl)pro-
pyl]piperidine (13). Tosyl derivative 12 (0.080 g, 0.187 mmol) was
stirred and refluxed in MeOH and H2OwithK2CO3 (0.100 g, 0.73 mmol)
for 44 h under N2. Then the mixture was cooled, and the solvent was
removed in vacuo to give a brown oil. This oil was dissolved in H2O
and slowly acidified to pH 2–4 with 20% HCl while maintaining effi-
cient cooling and stirring. The aqueous solution was saturated with so-
lid NaCl and extracted with CH2Cl2 (3 ꢂ 10 mL). The combined extracts
were washed with H2O (3 ꢂ 10 mL) and brine (3 ꢂ 10 mL), dried
(Na2SO4) and concentrated in vacuo to afford a brown oil. The crude
residue was purified by column chromatography using CH2Cl2/MeOH
(9:1) as eluent to give the target compound as a yellow oil in 65% yield;
1H NMR d 1.10 (s, 6H, C(CH3)2), 1.41–1.48 (m, 4H, CCH2CH2), 1.50–1.65
(m, 8H, CH(CH2CH2)2), 2.16–2.38 (m, 6H, CH2N(CH2)2), 2.58–2,78 (m,
3H, benzylic), 5.15 (s, 1H, NH), 5.69–6.20 (m, 2H, aromatic); GC–MS
m/z 275 (M++1, 2), 274 (M+, 21), 273 (100), 160 (32), 126 (45).
6.1.2.2. 1-[3-(1-Benzothiophen-4-yl)propyl]-3,3-dimethylpiper-
idine (17). 1H NMR d 0.96 (s, 6H, C(CH3)2), 1.15–1.28 (m, 2H,
piperidine CCH2), 1.55–1.68 (m, 2H, piperidine CCH2CH2), 1.88
(quintet, 2H, J = 7.6 Hz, ArCH2CH2), 2.01 (s, 2H, CCH2N), 2.22–2.38
(m, 4H, N(CH2)2), 2.99 (t, 2H, J = 7.7, benzylic), 7.14–7.76 (m, 5H,
aromatic); GC–MS m/z 289(M++2, 3), 288 (M++1, 10), 287 (M+,
41), 126 (100). The corresponding hydrochloride salt was recrystal-
lized from MeOH/Et2O: mp 210–212 °C. Anal. (C18H25NSꢃHCl) C, H,
N.
6.1.1.8. 4-(3-Bromopropyl)-1-benzofuran (14). The haloalkyl
compound 9a (1.9 g, 8.0 mmol) was refluxed with 2,2-dichloro-
5,6-dicyano-1,4-benzoquinone (DDQ) (4.3 g, 20 mmol) in toluene
(100 mL) under stirring. This reaction was carried out as previously
described.32 Crude product was purified by column chromatogra-
phy using petroleum ether/CH2Cl2 (8:2) as eluent to give the target
compound as a yellow oil (0.23 g, 12% yield); 1H NMR d 2.25 (m,
2H, J = 6.3 Hz, CH2CH2Br), 2.98–3.10 (m, 2H, benzylic), 3.42 (t, 2H,
J = 6.3 Hz, CH2Br), 6.84 (d, 1H, J = 2.3 Hz, OCHCH), 7.05–7.39 (m,
3H, aromatic), 7.62 (d, 1H, J = 2.2 Hz, OCH); GC–MS m/z 240
(M++2, 49), 239 (M++1, 7), 238 (M+, 47), 131 (100).
6.1.2.3.
3,3-Dimethyl-1-[3-(4,5,6,7-tetrahydro-1-benzothio-
phen-4-yl)propyl]piperidine (18a). This compound, already re-
ported as oxalate salt, was converted to the hydrochloride salt
and then recrystallized from MeOH/Et2O: mp 195–197 °C. Anal.
(C18H29NSꢃHClꢃ0.25H2O) C, H, N.
6.1.2.4.
3,3-Dimethyl-1-[5-(4,5,6,7-tetrahydro-1-benzothio-
1.05 (s, 6H,
phen-4-yl)pentyl]piperidine (18c). 1H NMR
d
C(CH3)2), 1.15–1.57 (m, 8H, piperidine CCH2CH2, CHCH2(CH2)3CH2N),
1.58–1.98 (m, 8H, CCH2N, CHCH2(CH2)4N, and endo CH(CH2)2), 2.18–
2.58 (m, 4H, piperidine NCH2CH2), 2.61–2.92 (m, 5H, (CH2)4CH2N and
benzylic), 6.80–7.08 (m, 2H, aromatic); GC–MS m/z 321 (M++2, 1),
320 (M++1, 5), 319 (M+, 19), 126 (100). The corresponding hydrochlo-
ride salt was recrystallized from MeOH/Et2O: mp 166–169 °C. Anal.
(C20H33NSꢃHClꢃ0.25H2O) C, H, N.
6.1.1.9. 4-(3-Bromopropyl)-1-benzothiophene (15). This com-
pound was prepared as for compound 14. Crude product was puri-
fied by column chromatography using petroleum ether/ethyl
acetate (8:2) as eluent to give the target compound as a yellow
oil (0.51 g, 26% yield); 1H NMR d 2.27 (m, 2H, J = 6.3 Hz, CH2CH2Br),
3.13 (t, 2H, J = 7.1 Hz, benzylic), 3.44 (t, 2H, J = 6.6 Hz, CH2Br), 7.18–
7.77 (m, 5H, aromatic); GC–MS m/z 256 (M++2, 53), 255 (M++1, 8),
254 (M+, 50), 147 (100).
6.1.2.5. 3,3-Dimethyl-1-[3-(6,7,8,9-tetrahydro-5H-benzo[7]ann-
ulen-5-yl)propyl]piperidine (19a). 1H NMR
d 0.90 (s, 6H,
C(CH3)2), 1.10–1.28 (m, 2H, piperidine CCH2CH2], 1.35–1.88 (m,
12H, endo CH(CH2)3, CH(CH2)2CH2N, and piperidine CCH2CH2),
1.90–2.05 (m, 2H, CH(CH2)2CH2N), 2.20–2.32 (m, 4H, piperidine
CH2NCH2), 2.69–2.91 (m, 3H, benzilic), 6.96–7.59 (m, 4H, aro-
matic); GC–MS m/z 301 (M++2, 1), 300 (M++1, 10), 299 (M+ 37),
126 (100). The corresponding hydrochloride salt was recrystallized
from MeOH/Et2O: mp 172–174 °C. Anal. (C21H33NꢃHClꢃ0.25H2O) C,
H, N.
6.1.1.10. 2-Chloromethyl-1-benzofuran (21). Thionyl chloride
(11.2 mmol, 0.8 mL) was added in a dropwise manner to a solution
of (1-benzofuran-2-yl)methanol (20) (1.19 g, 8.0 mmol) in THF
(5.92 mL) and DMF (1.66 mL) at 60 °C. Subsequently, the solution
was stirred at room temperature for 1 h. Then the solvent was
evaporated under reduced pressure and the crude residue was dis-
solved in H2O and extracted with ethyl acetate (3 ꢂ 20 mL). The
collected organic extracts were washed with brine, dried (Na2SO4)
and evaporated under reduced pressure to afford a residue as
6.1.2.6. 3,3-Dimethyl-1-[4-(6,7,8,9-tetrahydro-5H-benzo[7]ann-
ulen-5-yl)butyl]piperidine (19b). 1H NMR d 0.90 (s, 6H, C(CH3)2),
1.10–1.38 (m, 6H, CHCH2(CH2)2CH2N, endo CHCH2CH2), 1.40–1.92

S. Ferorelli et al. / Bioorg. Med. Chem. 19 (2011) 7612–7622
7619
(m, 10H, NCH2CCH2, CHCH2(CH2)3N and endo CHCH2CH2CH2),
1.93–2.05 (m, 2H, piperidine CCH2CH2), 2.15–2.38 (m, 4H,
CH2NCH2), 2.72–2.92 (m, 3H, benzilic), 7.02–7.18 (m, 4H, aro-
matic); GC–MS m/z 315 (M++2, 0.6), 313 (M+ 21), 126 (100). The
corresponding hydrochloride salt was recrystallized from MeOH/
Et2O: mp 189–191 °C. Anal. (C22H35NꢃHClꢃ0.8H2O) C, H, N.
-chromatography, using ethyl acetate/CH2Cl2 (8:2) as eluent, to
give the target compound as an orange-colored oil in 86% yield;
1H NMR d 1.87 (broad s, 1H, OH, D2O exchanged), 2.20–2.38 (m,
2H, CH2CH2CH2OH), 3.65 (t, 2H, J = 6.6 Hz, CH2OH), 4.81 (t, 2H,
J = 5.5 Hz, NCH2), 7.35–8.07 (m, 4H, aromatic); GC–MS m/z 179
(M++2, 0.5), 178 (M++1, 6), 177 (M+, 48), 91 (100). FT-IR: 3386,
2951, 2881, 1733 cmꢁ1
.
6.1.2.7. 3,3-Dimethyl-1-[(1-benzofuran-2-yl)methyl]piperidine
(22). 1H NMR d 0.94 (s, 6H, C(CH3)2), 1.17–1.29 (m, 2H, CCH2CH2),
1.58–1.70 (m, 2H, CCH2CH2), 2.08–2.18 (m, 2H, piperidine NCH2C),
2.38–2.48 (m, 2H, piperidine NCH2CH2), 3.62 (s, 2H, OCCH2N), 6.58
(s, 1H, OCCH), 7.15–7.68 (m, 4H, aromatic); GC–MS m/z 245 (M++2,
0.6), 244 (M++1, 6), 243 (M+, 35), 131 (100). The corresponding
hydrochloride salt was recrystallized from MeOH/Et2O: mp 188–
190 °C. Anal. (C16H21NOꢃHCl) C, H, N.
6.1.3.3. 3-(1H-Indol-3-yl)propan-1-ol (26c). The crude residue
as a yellow oil was purified by column chromatography, using
CH2Cl2/ethyl acetate (7:3) as eluent to give the target compound
as an orange oil in 31% yield; 1H NMR d 1.53 (broad s, 1H, OH,
D2O exchanged), 1.95–2.05 (m, 2H, CH2CH2CH2OH), 2.89 (t, 2H,
J = 6.0 Hz, CCH2), 3.73 (t, 2H, J = 6.1 Hz, CH2OH), 6.99–7.63 (m,
5H, aromatic), 7.98 (s, 1H, NH); GC–MS m/z 177 (M++2, 0.3), 176
(M++1, 5), 175 (M+, 34), 130 (100). FT-IR: 3413, 2937 cmꢁ1
.
6.1.2.8. 3-(Indol-1-yl)propionic acid, ethyl ester (24a). Ethyl
acrylate (4.5 mL, 42 mmol) and K2CO3 (5.9 g, 43 mmol) were added
to a stirred mixture of indole (23a) (4.41 g, 42 mmol) in DMF
(30 mL). The reaction mixture was stirred at room temperature
for 7 h and then concentrated under reduced pressure. The residue
was taken up with CH2Cl2 (30 mL) and washed with H2O
(2 ꢂ 10 mL) The organic phase was dried (Na2SO4) and evaporated
under reduced pressure to give an orange-colored oil (8.57 g, 94%
yield); 1H NMR d 1.21 (t, 3H, J = 7.1 Hz, OCH2CH3), 2.82 (t, 2H,
J = 6.8 Hz CH2CH2CO), 4.12 (q, 2H, J = 7.1 Hz, OCH2CH3), 4.46 (t,
2H, J = 6.8 Hz, NCH2), 6.49 (dd, 1H, J = 3.85 Hz, J0 = 0.69 Hz, aro-
matic NCHCH) 7.09–7.67 (m, 5H, aromatic); GC–MS m/z 219
(M++2, 1), 218 (M++1, 14), 217 (M+, 72), 130 (100). FT-IR: 2982,
6.1.4. General procedure to obtain methanesulfonates 27a–d
Mesyl chloride (0.54 mmol) in CH2Cl2 was added to a solution of
an appropriate alcohol among compounds 26a–c and 4-cyclo-
hexylbutan-1-ol (26d) (1 mmol) and Et3N (1 mmol) in CH2Cl2
(30 mL) at 0 °C. The reaction was worked up as previously
described.23
6.1.4.1. 3-(1H-Indol-1-yl)propylmethanesulfonate(27a)
. The
crude residue was obtained as an orange-colored oil in 52% yield
and was not purified; 1H NMR d 1.92–2.04 (m, 2H, CH2CH2CH2O),
3.00 (s, 3H, CH3), 3.55 (t, 2H, J = 5.6 Hz, CH2O), 4.05 (t, 2H,
J = 6.5 Hz, NCH2), 6.47–7.65 (m, 6H aromatic); GC–MS m/z 255
(M++2, 3), 254 (M++1, 7), 253 (M+, 43), 130 (100).
1731 cmꢁ1
.
6.1.2.9. 3-(1H-1,2,3-Benzotriazol-1-yl)propionic acid, ethyl ester
(24b). This compound was prepared as for 24a starting from
1,2,3-benzotriazole (23b) (5.00 g, 42 mmol) in DMF (30 mL). The
crude yellow oil was purified by flash column chromatography
using petroleum ether/EtOAc (7:3) as eluent to give the target
compound as a white solid (6.44 g, 70% yield); 1H NMR d 1.17 (t,
3H, J = 7.1 Hz, OCH2CH3), 3.09 (t, 2H, J = 6.7 Hz CH2CH2CO), 4.10
(q, 2H, J = 7.1 Hz, OCH2CH3), 4.91 (t, 2H, J = 6.7 Hz, NCH2), 7.33–
8.06 (m, 4H aromatic); GC–MS m/z 221 (M++2, 1), 220 (M++1,
6.1.4.2. 3-(1H-1,2,3-Benzotriazol-1-yl)propyl methanesulfonate
(27b). The crude residue as a brown oil was purified by column
chromatography, using ethyl acetate/CH2Cl2 (8:2) as eluent, to give
the target compound as a white solid in 60% yield; 1H NMR d 2.49
(m, 2H, CH2CH2CH2O), 3.0 (s, 3H, CH3), 4.24 (t, 2H, J = 5.7 Hz, CH2O),
4.81 (t, 2H, J = 6.6 Hz, NCH2), 7.37–8.09 (m, 4H, aromatic); GC–MS
m/z 257 (M++2, 2), 256 (M++1, 4), 255 (M+, 35), 120 (100).
6.1.4.3. 3-(1H-Indol-3-yl)propyl methanesulfonate (27c). The
crude residue obtained as an orange-colored oil in 83% yield was
not purified; 1H NMR d 2.18 (m, 2H, CH2CH2CH2O), 2.95 (s, 3H,
CH3), 4.11–4.30 (m, 2H, CCH2); 4.26 (t, 2H, J = 6.0 Hz, CH2O),
7.01–8.02 (m, 5H aromatic), 7.98 (s, 1H, NH); GC–MS m/z 255
(M++2, 1), 254 (M++1, 3), 253 (M+, 24), 130 (100).
11), 219 (M+, 55), 104 (100). FT-IR: 2983, 1735, 1451 cmꢁ1
.
6.1.3. General procedure to obtain alcohols 26a–c
A solution of one of the esters 24a,b and ethyl 3-(1H-indol-3-
yl)propanoate (25) (0.75 mmol) was added in a dropwise manner
to a suspension of LiAlH4 (1 mmol) in dry THF (20 mL) kept at
0 °C under a stream of N2. The mixture was stirred under reflux
for 6 h (12 h for compound 26c). After cooling to 0 °C, the reaction
mixture was added with H2O, until the hydride was destroyed, and
it was filtered through CeliteÒ. The filtrate was evaporated under
reduced pressure and the crude residue was dissolved in H2O
and extracted with CH2Cl2 (3 ꢂ 20 mL). The collected organic ex-
tracts were dried (Na2SO4) and evaporated under reduced pressure
to afford a residue.
6.1.4.4. 4-Cyclohexylbutyl methanesulfonate (27d). The crude
residue obtained as yellow oil in 81% yield was not purified. 1H
NMR (90 MHz) d 0.90–1.90 (m, 17H, C6H11(CH2)3), 2.91–3.10 (m,
5H, CH2O and CH3); GC–MS m/z 152 (1), 109 (37), 96 (100).
6.1.5. General procedure to obtain final amine compounds 28–
31
Starting from an intermediate (1.0 mmol) among mesylalkyl
derivatives 27a–d the title compounds were obtained as general
procedure described for compounds 16–19 and 22.
6.1.3.1. 3-(1H-Indol-1-yl)propan-1-ol (26a). The crude residue
as a yellow oil was purified by column chromatography, using
petroleum ether/CHCl3 (1:1) as eluent, to give the target compound
as a white oil in 41% yield; 1H NMR d 1.50 (broad s, 1H, OH, D2O
exchanged), 2.04–2.11 (m, 2H, CH2CH2CH2OH), 3.60 (t, 2H,
J = 6.7 Hz, CH2OH), 4.29 (t, 2H, J = 5.9 Hz, NCH2), 6.49–7.65 (m,
6H, aromatic); GC–MS m/z 177 (M++2, 0.5), 176 (M++1, 8), 175
6.1.5.1.
3,3-Dimethyl-1-[3-(1H-indol-1-yl)propyl]piperidine
(28). 1H NMR d 1.02 (s, 6H, C(CH3)2), 1.20–1.38 (m, 4H, CCH2CH2),
1.60–1.78 (m, 2H, ArCH2CH2), 1.95–2.48 (m, 6H, CH2N(CH2)2), 4.24
(t, 2H, J = 6.6, ArCH2), 6.45–7.65 (m, 6H, aromatic); GC–MS m/z 271
(M++1, 8), 270 (M+, 40), 126 (100).
(M+, 56), 130 (100). FT-IR: 3385, 2924, 1662 cmꢁ1
.
6.1.5.2. 3,3-Dimethyl-1-[3-(1H-1,2,3-benzotriazol-1-yl)propyl]
piperidine (29). 1H NMR d 1.02 (s, 6H, C(CH3)2), 1.18–1.26 (m,
2H, CCH2CH2), 1.50–1.78 (m, 2H, CCH2CH2), 1.98–2.50 (m, 8H,
6.1.3.2. 3-(1H-1,2,3-Benzotriazol-1-yl)propan-1-ol (26b). The
crude residue as brown solid was purified by column
a

7620
S. Ferorelli et al. / Bioorg. Med. Chem. 19 (2011) 7612–7622
CH2CH2N(CH2)2), 4.73 (t, 2H, J = 6.6, ArCH2), 7.24–8.09 (m, 4H, aro-
matic); GC–MS m/z 273 (M++1, 0.8), 272 (M+, 4), 126 (100). The cor-
responding hydrochloride salt was recrystallized from MeOH/Et2O:
mp 198–200 °C. Anal. (C16H24N4ꢃHClꢃ0.5H2O) C, H, N.
mixture of reaction was cooled at 0 °C, a solution of 6 N HCl
(0.16 mL, 1 mmol) was added dropwise. The reaction was contin-
ued stirring under reflux for 1 h. Then the reaction mixture was
cooled at 0 °C and alkalized dropwise with a solution of 6 N NaOH.
The aqueous solution was extracted with CH2Cl2 (3 ꢂ 20 mL), the
collected organic phases were dried (Na2SO4) and the solvent
was evaporated under reduced pressure.
6.1.5.3. 3,3-Dimethyl-1-[3-(1H-indol-3-yl)propyl]piperidine (30)
.
1H NMR d 1.02 (s, 6H, C(CH3)2), 1.20–1.38 (m, 4H, piperidine
CCH2CH2), 1.65–1.85 (m, 2H, ArCH2CH2), 1.95–2.14 (m, 2H,
NCH2C), 2.60–2.78 (m, 4H, CH2NCH2), 2.79 (t, 2H, J = 7.3 Hz, ArCH2),
6.96–7.59 (m, 5H, aromatic), 8.06–8.18 (broad s, 1H, NH, D2O ex-
changed); GC–MS m/z 271 (M++1, 2), 270 (M+ 12), 126 (100).
6.1.7.1. 2-(2-Chloroethylamino)-5,6-dihydro-1,3-benzothiazol-
7(4H)-one (35a). The crude residue was an orange-colored oil
and was purified by column chromatography using CHCl3/CH3OH
(9:1) as eluent to give the target compound as a yellow oil in
6.1.5.4.
3,3-Dimethyl-1-[(4-cyclohexyl)butyl]piperidine
30% yield; 1H NMR (DMSO-d6)
d
2.18–2.30 (quintet, 2H,
(31). 1H NMR d 0.9 (m, 8H, CHCH2 and C(CH3)2), 1.04–1.36 (m,
11H, cyclohexyl), 1.38–1.50 (m, 2H, CHCH2CH2), 1.52–1.78 (m,
6H, piperidine CCH2CH2 and CH2CH2N), 1.99 (s, 2H, NCH2C),
2.16–2.36 (m, 4H, CH2NCH2); GC–MS m/z 252 (M++1, 0.6), 251
(M+, 3.5), 126 (100). The corresponding hydrochloride salt was
recrystallized from MeOH/Et2O: mp 225–226 °C. Anal.
(C17H33NꢃHClꢃ0.1H2O) C, H, N.
J = 6.2 Hz, COCH2CH2), 2.61 (t, 2H, J = 6.4 Hz, COCH2CH2CH2),
2.88–2.98 (m, 2H, COCH2CH2), 3.70–3.85 (m, 4H, NHCH2CH2Cl),
7.90 (broad s, 1H, NH, D2O exchanged); GC–MS m/z 232 (M++2,
19), 231 (M++1, 6), 230 (M+, 49), 154 (100).
6.1.7.2. N-(2-Chloroetyl)-1,3-benzothiazol-2-amine (35b) . The
crude residue was purified by column chromatography using
petroleum ether/ethyl acetate (8:2) as eluent to give the target
compound as a yellow oil in 37% yield. 1H NMR (DMSO-d6) d
3.61–3.78 (m, 2H, NHCH2), 3.78–3.82 (m, 2H, CH2Cl), 6.98–7.67
(m, 4H, aromatic), 8.29 (s, 1H, NH, D2O exchanged); GC–MS m/z
214 (M++2, 14), 213 (M++1, 4), 212 (M+, 37),150 (100).
6.1.6. General procedure to obtain chloroacetamides 33a–c
To a solution of the appropriate amine among 2-amino-5,6-
dihydro-1,3-benzothiazol-7-(4H)-one (32a), 2-amino-1,3-benzo-
thiazole (32b), and 2-amino-thiazole (32c) (1 mmol) in ethylengly-
col dimethylether (10 mL), kept at 0 °C, some drops of Et3N were
added and then, a solution of chloroacethyl chloride (1.2 mmol)
in the same solvent (2 mL) was added dropwise. The mixture
was stirred under reflux for 6 h and the solvent was evaporated un-
der reduced pressure. The residue was partitioned between CH2Cl2
and 20% aqueous Na2CO3. The separated organic layers were dried
(Na2SO4) and concentrated under reduced pressure to yield one of
compounds 33a–c as a crude residue. The alkaline aqueous solu-
tion was acidified to pH 2–4 with 3 N HCl and extracted with ethyl
acetate (3 ꢂ 20 mL). The collected organic extracts were dried
(Na2SO4) and evaporated under reduced pressure to afford more
target compound.
6.1.7.3. N-(2-Chloroethyl)-1,3-thiazol-2-amine (35c). The crude
residue was purified by column chromatography using ethyl ace-
tate/CH2Cl2 (6:4) as eluent to give the target compound as a yellow
oil in 63% yield; 1H NMR (DMSO-d6) d 3.49–3.60 (m, 2H, NHCH2),
3.78 (t, 2H, J = 6.0 Hz, CH2Cl), 6.61 (d, 1H, J = 3.6 Hz, NCH), 6.99
(d, 1H, J = 3.6 Hz, SCH), 7.80 (broad s, 1H, NH, D2O exchanged);
GC–MS m/z 164 (M++2, 13), 163 (M++1, 3), 162 (M+, 34), 113
(100), 100 (63).
6.1.8. General procedure to obtain final amine compounds 34,
and 36–38
Starting from an intermediate (1.0 mmol) among 1-(x-haloal-
6.1.6.1. 2-Chloro-N-[7(4H)-oxo-5,6-dihydro-1,3-benzothiazol-2-
yl]acetamide (33a). The crude residue as a brown oil was purified
by column chromatography, using CH2Cl2/CH3OH (8:2) as eluent to
give the target compound as a white semisolid in 75% yield; 1H
NMR d 2.18–2.30 (quintet, 2H, J = 6.0 Hz, COCH2CH2), 2.61 (t, 2H,
J = 6.5 Hz, COCH2CH2CH2), 2.88–2.98 (m, 2H, COCH2CH2), 3.89 (s,
2H, CH2Cl), 6.20 (broad s, 1H, NH, D2O exchanged); GC–MS m/z
246 (M++2, 13), 245 (M++1, 4), 244 (M+, 34), 168 (100).
kyl) derivatives 33a, and 35a–c, respectively, the title compounds
were obtained as for compounds 16–19 and 22.
6.1.8.1. 2-(3,3-Dimethylpiperidin-1yl)-N-[7(4H)-oxo-5,6-dihy-
dro-1,3-benzothiazol-2-yl]acetamide (34). 1H NMR d 1.06 [s,
6H, C(CH3)2], 1.25–1.39 (m, 2H, piperidine CCH2CH2), 1.65–1.86
(m, 2H, piperidine CCH2CH2), 2.18 (quintet, 2H, J = 6.4 Hz,
COCH2CH2), 2.20–2.45 (m, 2H, NCH2C), 2.48–2.70 (m, 4H,
COCH2CH2 and piperidine NCH2), 2.91 (t, 2H, J = 6.2 Hz,
COCH2CH2CH2), 3.20–3.45 (s, 2H, COCH2N), 8.10 (s, 1H, NH, D2O
slowly exchanged); GC–MS m/z 323 (M++2, 1), 322 (M++1, 4), 321
(M+, 21), 126 (100). The corresponding hydrochloride salt was
recrystallized from MeOH/Et2O: mp 250 °C (dec). Anal.
(C16H23N3O2SꢃHClꢃ0.5H2O) C, H, N.
6.1.6.2. N-(1,3-Benzothiazol-2-yl)-2-chloroacetamide (33b) The
crude residue was obtained as a brown oil in 80% yield and was not
purified; 1H NMR d 4.15 (s, 2H, CH2Cl), 8.05 (broad s, 1H, NH, D2O
exchanged), 7.25–8.10 (m, 4H, aromatic); GC–MS m/z 228 (M++2,
12), 227 (M++1, 4), 226 (M+, 32), 150 (100).
6.1.6.3.
2-Chloro-N-(1,3-thiazol-2-yl)acetamide
(33c). The
6.1.8.2. 2-(3,3-Dimethylpiperidin-1yl)-N-[7(4H)-oxo-5,6-dihy-
dro-1,3-benzothiazol-2yl]aminoethane (36). 1H NMR d 1.11 (s,
6H, C(CH3)2), 1.38–1.48 (m, 2H, piperidine CCH2CH2), 1.69–1.98
(m, 6H, piperidine CCH2CH2, NCH2C and COCH2CH2), 2.48–2.80
(m, 6H, piperidine NCH2CH2 and COCH2CH2CH2), 2.82–3.10 (m,
2H, HNCH2CH2N), 3.50–3.91 (m, 3H, HNCH2CH2N and NH, D2O ex-
changed); GC–MS m/z 309 (M++2, 2), 307 (M+, 22), 126 (100). The
corresponding hydrochloride salt was recrystallized from MeOH/
Et2O: mp 265 °C (dec). Anal. (C16H25N3OSꢃHClꢃ0.5H2O) C, H, N.
crude residue was obtained as a brown semisolid in 20% yield
and was not purified; 1H NMR d 4.30 (s, 2H, CH2Cl), 6.20 (broad
s, 1H, NH, D2O exchanged), 7.06 (d, 1H, J = 3.6 Hz, NCH), 7.52 (d,
1H, J = 3.7 Hz, SCH); GC–MS m/z 178 (M++2, 9), 177 (M++1, 2),
176 (M+, 25), 100 (100).
6.1.7. General procedure to obtain compounds 35a–c
To a solution of one of the acetamides 33a–c (1 mmol) in dry
THF (5 mL) was added BF3ꢃO(C2H5)2 (0.13 mL, 1 mmol). While the
mixture was stirred under reflux,
a
solution of (CH3)2SꢃBH3
6.1.8.3. 2-(3,3-Dimethylpiperidin-1-yl)-N-(1,3-benzothiazol-2-
yl)aminoethane (37). 1H NMR d 0.98 (s, 6H, C(CH3)2), 1.27 (m,
2H, CCH2CH2), 1.58–1.78 (m, 2H, CCH2CH2), 2.06–2.29 (m, 2H,
(0.08 mL, 0.09 mmol) in the same solvent (2 mL) was added drop-
wise. Still the reaction was stirred under reflux for 6 h. After the

S. Ferorelli et al. / Bioorg. Med. Chem. 19 (2011) 7612–7622
7621
NCH2C), 2.30–2.56 (m, 2H, piperidine NCH2), 2.58–2.80 (m, 2H,
HNCH2CH2N), 3.42–3.64 (m, 2H, HNCH2CH2N), 6.01–6.42 (broad
s, 1H, NH, D2O exchanged), 7.02–7.61 (m, 4H, aromatic); GC–MS
m/z 290 (M++1, 0.4), 289 (M+, 1.3), 139 (60), 126 (100). The corre-
sponding hydrochloride salt was recrystallized from MeOH/Et2O:
mp 197 °C (dec). Anal. (C16H23N3SꢃHClꢃ0.5H2O) C, H, N.
Life Sciences (Zavantem, Belgium). [3H]-( )-Emopamil (83 Ci/
mmol) was purchased from American Radiolabeled Chemicals
Inc. (St. Louis, MO). (+)-Pentazocine was obtained from Sigma–Al-
drich-RBI s.r.l. (Milan, Italy). DTG and ( )-ifenprodil were pur-
chased from Tocris Cookson Ltd., UK. Male Dunkin guinea-pigs
and Wistar Hannover rats (250–300 g) were from Harlan, Italy.
Supplementary data
6.1.8.4. 2-(3,3-Dimethylpiperidin-1-yl)-N-(1,3-thiazol-2-yl)ami-
noethane (38). 1H NMR d 0.95 (s, 6H, C(CH3)2), 1.19–1.32 (m, 2H,
CCH2CH2), 1.58–1.70 (m, 2H, CCH2CH2); 2.08–2.19 (m, 2H, NCH2C);
2.36–2.57 (m, 2H, piperidine NCH2), 2.62 (t, 2H, J = 5.5 Hz,
HNCH2CH2N), 3.37 (t, 2H, J = 5.5 Hz, HNCH2CH2N); 5.80–6.10
(broad s, 1H, NH, D2O exchanged), 6.47 (d, 1H, J = 3.6 Hz, SCH),
7.10 (d, 1H, J = 3.8 Hz, NCH); GC–MS m/z 240 (M++1, 0.1), 239
(M+, 0.9), 139 (33), 126 (100). The corresponding hydrochloride
salt was recrystallized from MeOH/Et2O: mp 206 °C (dec). Anal.
(C12H21N3Sꢃ2HClꢃ0.5H2O) C, H, N. H: Calculated 7.53, Found 6.88.
Supplementary data (Elemental analyses of the end products.)
associated with this article can be found, in the online version, at
doi:10.1016/j.bmc.2011.10.023.
References and notes
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3,3-Dimethyl-1-[4-(3,3-dimethylpiperidin-1-yl)butyl]
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All the procedures followed to perform the binding assays were
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out according to Matsumoto et al.43 and D8
–D7 SI according to
Moebius et al.44 The radioligands [3H]-DTG (30 Ci/mmol) and (+)-
[3H]-pentazocine (34 Ci/mmol) were purchased from PerkinElmer

7622
S. Ferorelli et al. / Bioorg. Med. Chem. 19 (2011) 7612–7622
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