A multireceptorial binding reinvestigation on an extended class of σ ligands: N-[ω-(indan-1-yl and tetralin-1-yl)alkyl] derivatives of 3,3-dimethylpiperidine reveal high affinities towards σ1 and EBP sites

Article abstract of DOI:10.1016/S0968-0896(01)00011-6

New 1-[ω-(2,3-dihydro-1H-inden-1-yl)- and (2,3-dihydro-5-methoxy-1H-inden-1-yl)alkyl]- and 1-[ω-(1,2,3,4-tetrahydronaphthalen-1-yl)- and (6-methoxy- or 6-fluoro-1,2,3,4-tetrahydronaphthalen-1-yl)alkyl] derivatives of 3,3-dimethylpiperidine were synthesized, as homologous compounds of an existing series of σ ligands, in order to carry out σ receptor subtypes structure-affinity relationships. The new compounds and some of their related analogues, already reported, were tested in new multireceptorial radioligand binding assays. As reference compounds, the known σ₁ ligands SA 4503, BD 1008 and NE 100 were also prepared and tested. All reported compounds showed high σ₁ affinity assayed by (+)-[³H]-pentazocine on guinea-pig brain (apparent K_i=1.75-72.2 nM) and moderate or low σ₂ affinity by [³H]-DTG on rat liver, in contrast with previous results. One tertiary amine function spaced by a five-membered chain from a phenyl group is the structural feature shared by the most active compounds 26 and 43 and some reference σ₁ ligands. The reported σ₁ ligands, including reference compounds, also demonstrated a high affinity towards EBP (Δ₈-Δ₇ sterol isomerase) site (apparent K_i=0.48-14.8 nM) and some of them (37 and 44) were good ligands at L-type Ca⁺⁺ channel. 1-[4-(2,3-Dihydro-1H-inden-1-yl)butyl]-3,3-dimethylpiperidine (26) was the best mixed σ₁ and EBP ligand (apparent K_i=1.75 and 1.54 nM, respectively) with a good selectivity versus σ₂ receptor (138- and 157-fold, respectively).

Full text of DOI:10.1016/S0968-0896(01)00011-6

Bioorganic & Medicinal Chemistry 9 (2001) 1325±1335
A Multireceptorial Binding Reinvestigation on an Extended
Class of ꢀ Ligands: N-[!-(Indan-1-yl and Tetralin-1-yl)alkyl]
Derivatives of 3,3-Dimethylpiperidine Reveal High Anities
Towards ꢀ1 and EBP Sites
Francesco Berardi,* Savina Ferorelli, Nicola Antonio Colabufo, Marcello Leopoldo,
Roberto Perrone and Vincenzo Tortorella
Á
Dipartimento Farmaco-Chimico, Universita di Bari, via Orabona 4, I-70126 Bari, Italy
Received 4October 2000; accepted 5 January 2001
AbstractÐNew 1-[o-(2,3-dihydro-1H-inden-1-yl)- and (2,3-dihydro-5-methoxy-1H-inden-1-yl)alkyl]- and 1-[o-(1,2,3,4-tetra-
hydronaphthalen-1-yl)- and (6-methoxy- or 6-¯uoro-1,2,3,4-tetrahydronaphthalen-1-yl)alkyl] derivatives of 3,3-dimethylpiperidine
were synthesized, as homologous compounds of an existing series of s ligands, in order to carry out s receptor subtypes structure±
anity relationships. The new compounds and some of their related analogues, already reported, were tested in new multi-
receptorial radioligand binding assays. As reference compounds, the known s1 ligands SA 4503, BD 1008 and NE 100 were also
prepared and tested. All reported compounds showed high s1 anity assayed by (+)-[3H]-pentazocine on guinea-pig brain
(apparent Ki=1.75±72.2 nM) and moderate or low s2 anity by [3H]-DTG on rat liver, in contrast with previous results. One
tertiary amine function spaced by a ®ve-membered chain from a phenyl group is the structural feature shared by the most active
compounds 26 and 43 and some reference s1 ligands. The reported s1 ligands, including reference compounds, also demonstrated a
high anity towards EBP (Á8±Á7 sterol isomerase) site (apparent Ki=0.48±14.8 nM) and some of them (37 and 44) were good
ligands at L-type Ca++ channel. 1-[4-(2,3-Dihydro-1H-inden-1-yl)butyl]-3,3-dimethylpiperidine (26) was the best mixed s1 and EBP
ligand (apparent Ki=1.75 and 1.54nM, respectively) with a good selectivity versus s2 receptor (138- and 157-fold, respectively).
# 2001 Elsevier Science Ltd. All rights reserved.
Introduction
proved to be implicated in the cytotoxicity and cell
apoptosis.14 Several compounds, including (+)-benzo-
morphans15 and more simpli®ed structures containing
substituted piperidine or piperazine, have been reported
to bind at s1 receptor with high anity,16 whereas high-
anity and selective s2 receptor ligands are needed to
better investigate s2 receptor nature and functions.
Indeed, the design of really selective s receptor subtype
ligands is complicated by the anity towards other
receptor systems, such as dopamine D2, serotonin
5-HT1A and 5-HT2, opiate, NMDA complex and others.
Moreover, the recent cloning of human s1 receptor17
has evidenced that its structure is di€erent from other
known mammalian proteins. It shares a similarity with the
ERG-2p yeast isomerase but not with emopamil binding
protein (EBP), the human sterol Á8±Á7 isomerase.18
Nevertheless, several s1 ligands and Ca++ channel
modulators have shown anities for EBP site.19 The
relationship between s receptor and EBP site is a novel
intriguing area of challenge in designing new selective
ligands. In a recent work, we began to investigate s-subtype
The design of selective s ligands has become an attractive
®eld in the search of new agents for schizophrenia,1À3
depression,4 memory impairment,5 cocaine-induced
toxicity,6 neuronal damages7 and other CNS-related
pathologies.8 Moreover, several human tumoral cell
lines express s receptors,9 so that positron emission
tomography (PET) cancer diagnosis is another applica-
tive area for s ligands.10 On the basis of molecular
size and pharmacological pro®le, two s receptor
subtypes are universally recognized and functionally
distinguished.11,12 s1 Receptors are involved in several
modulations, such as those of NMDA-stimulated neuro-
transmitter systems,13 synthesis and release of dopamine
and acetylcholine and opiate analgesia. s2 Receptor
regulates intracellular Ca++ storage and has been
*Corresponding author. Tel.: +39-80-544-2751; fax: +39-80-544-2231;
e-mail: berardi@farmchim.uniba.it
0968-0896/01/$ - see front matter # 2001 Elsevier Science Ltd. All rights reserved.
PII: S0968-0896(01)00011-6

1326
F. Berardi et al. / Bioorg. Med. Chem. 9 (2001) 1325±1335
selectivity in a new class of 3,3-dimethyl-N-[o-(tetralin-
1-yl)-alkyl]piperidine and some related compounds.20
Although several compounds reached very high s2 ani-
ties and selectivities, no clear structure±anity relation-
ship emerged. As an extension of that work, more
related structures were synthesized. The e€ects of the
length of the intermediate alkyl chain between 3,3-
dimethylpiperidine moiety and the tetralin or the indane
nucleus appeared particularly interesting to focus upon.
In fact, previously assayed ligands, bringing two- to
®ve-methylene spacer, purportedly appeared to indi€er-
ently bind at s1 and s2 receptors with high anity. In
this paper, we reinvestigate s1/s2 selectivity of such com-
pounds by more updated and reliable binding methods.
In another contemporary work, compounds 23, 37 and
42±44 demonstrated Ca++ antagonist activity, by inhi-
biting electrically-induced stimulations in guinea pig
ileum longitudinal muscle/myenteric plexus prepara-
tions and they gave completely di€erent results, when
reexamined with new s binding protocols. This ®nding
led us to assay them for L-type Ca++ channel anity.
In this work, we extended that binding assay to the
ligands displaying the highest s1 anities to prove their
selectivities. Further suggestions for a reinvestigation
came from preliminary results of another collaborative
work, that revealed the ability of compounds 37 and
(S)-(+)-39 to inhibit a post-squalenic step of cholesterol
biosynthesis and cell proliferation in rat aortic myocytes.21
In order to evidence the pharmacological similarity
between s1 receptor and EBP,22 we assayed a limited
number of reported compounds in the EBP binding. We
also prepared the known s1 ligands SA 4503, claimed to
be an agonist, and BD 1008 and NE 100 reported to be
antagonists (Chart 1) and we tested them as reference
compounds in the above binding assays. They were
chosen because they were also used in the above Ca++
antagonism assays and were easy to synthesize.
Chemistry
The synthesis of these classes of compounds has already
been reported.20 The properties of new ®nal compounds
are described in Table 1. Their spectral data and those
of their new respective intermediate compounds are
reported in the Experimental. No longer commercially
available 3,3-dimethylpiperidine23 was prepared in a new
way, described in Scheme 1. 2,2-Dimethylglutaric
acid (1) was derivatized to the acyl chloride with SOCl2
and then with benzylamine to the monoamide, which
was heated at 200 ꢀC to give the imide 2. Reduction to
3,3-dimethyl-1-benzylpiperidine (3) with LiAlH4 and
subsequent debenzylation by catalytic hydrogenation
a€orded 3,3-dimethylpiperidine (4). For compounds 24
and 41, with an ethylenic intermediate chain, the syn-
thetic pathways are reported in Scheme 2. The esters
6a and 6b were prepared starting from corresponding
1-indanone (5a) and 6-methoxy-1-tetralone (5b) via a,b-
unsaturated esters and were reduced to the alcohols 7a,b
with LiAlH4.24 Derivatization of 7a,b to the methylsul-
fonate derivatives 8a,b with methanesulfonyl chloride
and subsequent reaction with 3,3-dimethylpiperidine
Chart 1.

F. Berardi et al. / Bioorg. Med. Chem. 9 (2001) 1325±1335
Table 1. Physical properties of new compounds
1327
Compounda
Yield (%)
Column chromatography eluent
Formulab
Recryst. solv.
Mp (ꢀC)
24
26
27
28
31
32
33
38
41
45
48
49
84Ð
45
61
44
53
57
50
51
53
65
60
46
C
CHCl3
CH2Cl2/CH3OH, 19:1
CHCl3
CHCl3
CH2Cl2/CH3OH, 19:1
CHCl3/CH3OH, 19:1
CHCl3
CH2Cl2/CH3OH, 19:1
CHCl3
CHCl3
18H27Nꢁ HCl
C20H31Nꢁ HCl
CH3OH/Et2O
CH2Cl2/Et2O
CH2Cl2/Et2O
CH2Cl2/Et2O
CH2Cl2/Et2O
CH2Cl2/Et2O
CH2Cl2/Et2O
CH2Cl2/Et2O
CH3OH/Et2O
CH2Cl2/Et2O
CH3OH/Et2O
CH2Cl2/Et2O
203±205
158±159
160
C21H33Nꢁ HCl
C22H35Nꢁ HCl
160±161
168±169
125±127
186±187
138±139
211±214
123±124
148±150
152±153
C21H33NOꢁ HCl
C22H35NOꢁ HCl
C23H37NOꢁ HClꢁ 1=2H2O
C23H37N.HCl
C20H31NOꢁ HCl
C24H39NOꢁ HCl
C21H32FNꢁ HClꢁ 2=3H2O
C22H34FNꢁ HCl
CHCl3
aWhite to ivory-colored crystalline powders; for their structures see Table 2.
bAnalyses for C, H, N; the results were within Æ0.4% of the theoretical values for the formulas given.
yielded compounds 24 and 41. The remaining new
compounds were prepared according to the yet reported
procedure, starting from corresponding indanones 9a,b
or tetralones 10a±c and the appropriate o-chloro-n-
alkylmagnesium bromide (Scheme 3).25 The compounds
28, 33, 38 and 45, with a six-membered alkyl chain, were
obtained from the respective 1-indanone or 1-tetralone
and 1-bromo-6-chloro-n-hexane. For the synthesis of
¯uorinated compounds 48 and 49, the starting product
6-¯uoro-1-tetralone (10c) was prepared following a
known synthetic pathways.26 The compounds SA 4503
[1-(3,4-dimethoxyphenethyl)-4-(3-phenylpropyl)pipera-
zine],27 BD 1008 [N-[2-(3,4-dichlorophenyl)ethyl]-N-
methyl-2-(1-pyrrolidinyl)ethylamine],28 and NE 100
[N,N-dipropyl-2-[4-methoxy-3-(2-phenylethoxyl)phenyl]-
ethylamine]29 were synthesized according to the respec-
tive literature.
Pharmacology
The reported compounds were evaluated as hydrochloride
salts (compound 30 as hydrogen oxalate) for in vitro
anity by radioreceptor binding assays. The speci®c
Scheme 1. Reagents: (a) SOCl2; (b) benzylamine; (c) LiAlH4, THF;
(d) H2, 10% Pd/C, MeOH.
Scheme 2. Reagents: (a) NaH (60% mineral oil dispersion), triethyl phosphonoacetate; (b) H2, 10% Pd/C; (c) LiAlH4; (d) CH3SO2Cl; (e) 3,3-
dimethylpiperidine.

1328
F. Berardi et al. / Bioorg. Med. Chem. 9 (2001) 1325±1335
Scheme 3. Reagents: (a) 4-chloro-n-butyl-MgBr (n=4), 5-chloro-n-pentyl-MgBr (n=5), 6-chloro-n-hexyl-MgBr (n=6); (b) HCl; (c) H2, 10% Pd/C;
(d) 3,3-dimethylpiperidine.
radioligands and tissue sources were respectively: (a) s1
receptor, (+)-[3H]-pentazocine ((+)-[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) s2 receptor, [3H]-DTG (1,3-
di(2-tolyl)guanidine) in the presence of 1 mM (+)-penta-
zocine to mask s1 receptors, rat liver membranes; (c) L-
type Ca++ channel, (À)-[3H]-D 888 (desmethoxyver-
apamil), rat brain membranes; (d) EBP sites, (Æ)-[3H]-
emopamil, guinea-pig liver membranes; (e) 5-HT1A
receptor, [3H]-8-OH-DPAT, rat hippocampus mem-
branes; (f) MK 801 site, [3H]-MK 801 in the presence of
100 mM d-glutamate and 100 mM l-glycine to mask
corresponding sites in the NMDA receptor, rat brain
cortex. The following compounds were used to de®ne
speci®c binding, reported in parentheses: (a) haloperidol
((4-[4-(4-chlorophenyl)-4-hydroxy- 1 -piperidinyl] - 1 - (4 -
¯uorophenyl) - 1 - butanone) (75±90%), (b) DTG (75±
90%), (c) (Æ)-verapamil (68±82%), (d) (Æ)-ifenprodil
(65%), (e) 8-OH-DPAT (80%) and (f) MK 801 (95%).
They were chosen as presently the most used reference
compounds, according to the methods described in
Experimental.
considered more reliable, because of a higher s1 receptor
density in the guinea-pig brain and higher s1 anity
and selectivity of (+)-[3H]-pentazocine compared to
(+)-[3H]-SKF 10047. For the latter we found
Ki=58.8Æ5.1 nM at the s1 receptor on such tissue. On
the other hand, the s2 anities measured on rat liver
were generally lower than those on guinea-pig brain
reported for the same compounds.20 Indeed, previously
reported s2 anities were actually s total anities, as
measured in the absence of any s1 masking agent. The
present reinvestigation and widening on tetralin and
indane derivatives can now allow a better de®nition of s
receptor subtypes structure±anity relationship for 3,3-
dimethylpiperidine derivatives. These compounds
showed higher anities towards s1 than s2 receptor, or
comparable in few cases (compounds 24, 25, 27 and 34),
consistently with their structural similarity with penta-
zocine. The most active ligand at s1 receptor was com-
pound 26 (Ki=1.75 nM), which also presented the best
selectivity versus s2 receptor (138-fold). In the remain-
ing homologous of the indane series 24±28 the s1 a-
nity does not change with the length of intermediate
alkyl chain. Similarly, the tetralin derivatives of the ser-
ies 34±38 displayed comparable s1 anities and selec-
tivities versus s2 receptor. Taking into consideration the
tetralin substitution, both in the 3-(tetralin-1-yl)propyl
derivatives 35, 39, 42 and 46, and in the 4-(tetralin-1-
yl)butyl derivatives 36, 40, 43 and 47, the highest s1
anities and s1/s2 selectivities were obtained for 6-
methoxy derivatives 42 and 43, respectively (Ki=2.36
and 2.12 nM; 73- and 117-fold, respectively). Therefore,
the e€ect of the length of the intermediate alkyl chain
was examined in the homologous series of 6-methoxyte-
tralin derivatives 41±45. It was evidenced that the pre-
sence of an alkyl chain of three to ®ve methylene units
results in high-anity s1 ligands, four-membered com-
pound 43 resulting as the most selective versus s2 receptor.
In the corresponding 2,3-dihydro-5-methoxy-1H-indene
series 30±33, a ®ve-methylene chain originated the most
active and selective compound 32. The enantiomers (S)-
(+)-39 and (R)-(À)-39 and rac-emic 39 gave comparable
Concentrations required to inhibit 50% of radioligand
speci®c binding (IC50) were determined by using six to
nine di€erent concentrations of the drug studied in three
experiments with samples in duplicate. The apparent
inhibition constants (Ki) were determined from IC50
values by using the Cheng±Pruso€ equation.
Results and Discussion
All tested compounds 23±49 (Table 2) were s1 ligands
with high to moderate anity (apparent Ki=1.75 to
72.5 nM). For several reinvestigated tetralin derivatives,
these results are rather di€erent from those previously
obtained20 on rat brain with (+)-[3H]-SKF 10047. It is
presumable that di€erences among the species occur for
the tissues used. However, the present results can be

F. Berardi et al. / Bioorg. Med. Chem. 9 (2001) 1325±1335
Table 2. s Binding anities and selectivities
1329
Compound
R1
R2
R3
m
n
KiÆSEM (nM)
Ki ratio
s1
s2
ꢀ1=ꢀ2
23a,b
24
25
26
27
28
29
30
31
32
33
34
35
36
37b
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
OCH3
H
H
H
H
H
H
H
H
H
OCH3
OCH3
OCH3
OCH3
H
H
H
H
H
H
H
H
H
1
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
3
2
23.1Æ8.2
23.8Æ6.8
9.68Æ1.7426.1
Æ0.12
350Æ52
28.1Æ8.7
Æ2.0
15
1
3
3
41.75
5
6
41.99
3
48.02
5
6
2
3
436.0
5
6
3
242Æ59
31.7Æ1.1
296Æ93
97.2Æ0.1
56.6Æ4.2
162Æ29
75.4Æ14.6
231Æ37
41.1Æ2.2
203Æ37
242Æ32
318Æ86
369Æ35
206Æ67
219Æ16
174Æ2
138
1.5
13
49
16
20
36
14
0.6
10
7
16
21
10
19
5
21.6Æ10.1
22.1Æ2.7
Æ0.56
H
H
OCH3
OCH3
OCH3
OCH3
H
H
H
H
H
H
H
H
H
OCH3
OCH3
OCH3
OCH3
OCH3
H
3.53Æ0.83
Æ0.89
2.10Æ0.23
16.8Æ6.8
72.5Æ3.9
19.8Æ5.3
Æ4.5
20.0Æ3.2
17.5Æ2.3
20.0Æ5.9
11.6Æ2.1
33.2Æ10.6
Æ0.77
38
(Æ)-39
(S)-(+)-39
(R)-(À)-39
3
3
42.71
2
3
42.12
5
40
41
183Æ62
88.7Æ14.0
172Æ28
247Æ52
409Æ33
289Æ17
173Æ5426
160Æ38
Æ57c
68
12
73
117
93
10
7.64Æ0.85
2.36Æ0.44
Æ0.30
42b
43b
44b
45
4.39Æ1.67
28.2Æ8.8
6.64Æ0.19
Æ6.9
6
3
46
47
48
OCH3
OCH3
H
H
F
F
421.4
424
5
7
18
39
.0
24 Æ8.44
3.97Æ1.37
0.012 ± 0.48e
1.72Æ0.49
1.03Æ0.14212
1.91Æ0.19
49
H
155Æ20
77.5Æ10.9
82.8Æ17.2
Æ24206
SA4503d
BD1008f
NE100g
(+)-Pentazocineb
DTGb
48
25.4Æ2.1
Haloperidol
1.09Æ0.16
a1H-inden-3-yl (Á2,3).
bKi data are simultaneously being published elsewhere.
c(+)-SKF10047 was used to mask s1 receptors.
dLiterature data: s1, IC50=17.4Æ1.9 nM; s2, IC50=1784Æ314nM (ref 30).
eThree experiments' results falling in the reported range. In the other two experiments not dose-dependent curves were obtained, a plateau being
observed in the concentration range of 10À10±10À7 M.
fLiterature data: s1, Ki=2.2Æ0.65 nM; s2, Ki=8.10Æ2.2 nM (ref 31).
gLiterature data: s1, IC50=1.5 nM; s2, IC50=85 nM (ref 32).
Ki values both for s1 and s2 receptor anity, so that no
remarkable stereoselectivity was evidenced. Their abso-
lute con®gurations were derived from a recent determi-
nation.33 Fluorinated tetra-lin 49 demonstrated a good
s1 anity and selectivity; thus it can be proposed as a
PET agent, when derivatized with 18F. The s1 anity of
the most potent derivatives 26 and 43 was comparable to
that of the reference compounds tested. All these com-
pounds, except DTG, share structural features consist-
ing in one basic nitrogen atom spaced by a ®ve-
membered chain from a phenyl ring. In this respect, NE
100 can be considered a cyclovinylogue. The lack of a
second nitrogen or oxygen atom at a distance of two
methylenes seems to enhance s1 versus s2 selectivity for
our compounds, as well as for NE 100.
The restricted series of compounds tested at L-type Ca++
channel, including reference compounds, revealed moder-
ate anity (Table 3). The lowest Ki values, comparable to
that of verapamil, were reached by (tetralin)pentyl deriva-
tives 37 and 44. High-anity s1 ligands 26 and 32 also
resulted as particularly selective versus this type of channel.
As it would be expected, for the tested compounds the
s1 anities joined up with high EBP anities and in
almost all cases surprisingly exceeded them, as it can be

1330
F. Berardi et al. / Bioorg. Med. Chem. 9 (2001) 1325±1335
Table 3. Other binding anities and selectivities
Compound
KiÆSEM (nM)
EBP
Ki ratio
s1/EBP
L-type Ca++ channel
5-HT1A
MK 801a
a
23
26
29
32
35
37
380Æ127b
514Æ85
3.85Æ0.60
1.54Æ0.01
7370
6
1.1
109Æ25.4
1800Æ365
537Æ116
14.7Æ2.2b
229Æ48
1.67Æ0.44
1.68Æ0.26
2.48Æ1.23
0.50Æ0.10
1.12Æ0.18
1.03Æ0.13
Æ0.08
1.3
12
8
40
10
31
6
4
3
7
3520
>917
>917
>917
>917
(Æ)-39
(S)-(+)-39
(R)-(À)-39
40
42
43
44
46
49
SA 4503
BD 1008
NE 100
(Æ)-Verapamil
(Æ)-Ifenprodil
8-OH-DPAT
MK 801
223Æ19
170Æ61
8
90.3Æ17.40.4
65.4Æ8.6b
415Æ42b
20.8Æ6.6b
0.57Æ0.02
0.67Æ0.19
0.59Æ0.12
0.76Æ0.149
Æ3.7
9120
>10,000
>10,000
>917
.8
253Æ3414
156Æ15c
0.3
1.72Æ0.53
3.94Æ0.02
14.6Æ4.1
1810
1090
90.9Æ23.1
87.5Æ12.2
42.0Æ0.4b
0.4
0.07
3.64Æ0.44
1.73Æ0.10
3.49Æ0.27
aData without SEM are taken from one experiment.
bThese Ki data are simultaneously being published elsewhere.
cLiterature datum: 22.3% inhibition at 10 mM (ref 30).
seen from respective apparent Ki ratio (Table 3). There-
fore, no highly selective s1/EBP ligand was found in this
assay. Fluorinated compound 49 demonstrated the
lowest anity for EBP site (Ki=14.8 nM) with a mod-
erate selectivity s1/EBP. In contrast, compounds (Æ)-
39 and (À)-39 showed the highest EBP selectivity versus
s1 receptor (40- and 31-fold, respectively). Therefore,
since most of the tested compounds bound at s1 receptor,
they resulted mixed s1 and EBP ligands. The anity
towards EBP was enhanced by the presence of a meth-
oxyl group in 5- or 6-position on the tetralin nucleus.
Similarly, this situation occurs for SA 4503.
inhibition of cholesterol formation and cell anti-
proliferative activity might be elicited also by s1 ligands
and could be strengthened by mixed s1/EBP ligands.
Experimental
Chemistry
Column chromatography was performed with 1:30 ICN
silica gel 60A (63±200 mm) as the stationary phase.
Melting points were determined in open capillaries on a
Gallenkamp electrothermal apparatus. Elemental ana-
lyses (C,H,N) were performed on a Carlo Erba model
1106 analyser. 1H NMR spectra were recorded either on
a Varian EM-390, where indicated 90 MHz (TMS as
internal standard), or a Bruker AM 300 WB (300 MHz)
instrument, with CDCl3 as solvent; 13C NMR were
obtained on a Varian NMR 300 Mercury-VX (75 MHz)
instrument; all values are reported in ppm (d). Infrared
spectra were recorded on a Perkin-Elmer, Spectrum
one, FTIR. Recording of mass spectra was done on a
HP 5995C gas chromatography/mass spectrometer,
electron impact 70 eV, equipped with a HP59970A
workstation; only signi®cant m/z peaks, with their %
relative intensity in parentheses, are herein reported. All
spectra were in accordance with the assigned structures.
All target compounds were transformed into their hydro-
chloride or hydrogen oxalate salts in the usual manner.
Finally, no considerable anities were noticed at sero-
tonin 5-HT1A receptor and MK 801 site for the few
tested compounds.
Conclusions
These 3,3-dimetilpiperidine derivatives are a new class
of high-anity s1 ligands. Besides, a signi®cant s1 sub-
type selectivity was achieved in this class of compounds.
Good results were obtained with an intermediate alkyl
chain of four or ®ve methylenes and a 6-methoxy-
1,2,3,4-tetrahydronaphthalene nucleus, but the best ligand
was the indane derivative 26. The high ¯exibility of such a
chain permits to ®t in with the distance of the nitrogen
atom and the phenyl ring, as in the pentazocine. A second
intermediate nitrogen atom in the chain seems to be not
essential for s1 anity, but it enhances s2 anity. These
®ndings agree with the conclusions reported in the recent
literature.31 It is presumable that more rigid structures can
separate EBP anity from s1 anity. However, if the
belonging of s1 receptor to the EBP family will be con-
®rmed by analogous functions in the sterol biosynthesis,
1-Benzyl-3,3-dimethylpiperidin-2,5-dione (2). 2,2-Dime-
thylglutaric acid (1) (15.0 g, 94mmol) mixed with SOCl 2
(70 mL) was re¯uxed for 5 h, under stirring. Then the
excess of SOCl2 was removed under reduced pressure.
To a solution of the acyl chloride in 1,2-dimethoxy-
ethane (40 mL), was added dropwise a solution of

F. Berardi et al. / Bioorg. Med. Chem. 9 (2001) 1325±1335
1331
benzylamine (10.2 mL, 93 mmol) in the same solvent (20
mL) and the mixture was re¯uxed for 15 h, under stirring.
Then the solvent was evaporated in vacuo and the crude
residue was warmed for 8 h at 200 ꢀC. The residue was
chromatographed (petroleum ether/ethyl acetate 8:2, as
eluent) to give 2 as a colorless oil in 74% yield. 1H NMR
(90 MHz) 1.25 (s, 6H, 2 CH3), 1.80 (t, 2H, J=6 Hz,
(CH3)2CCH2), 2.72 (t, 2H, J=6 Hz, CH2CO), 4.90 (s,
2H, benzylic), 7.25 (s, 5H, aromatic); IR (neat) 1724,
1679 cmÀ1; GC/MS m/z 233 (M++2, 2), 232 (M++1,
21), 231 (M+, 100), 188 (92), 146 (66).
2H, OCH2CH3), 6.60±7.30 (m, 3H, aromatic); IR
(CHCl3) 1730 cmÀ1; GC/MS m/z 249 (M++1, 5), 248
(M+, 27), 174(15), 161 (100).
2,3-Dihydro-1H-indene-1-ethanol (7a). The title com-
pound was chromatographed using CHCl3/CH3OH 9:1
1
as eluent to give a colorless oil (93% yield). H NMR
(90 MHz) 1.35±1.80 (m, 3H, endo CH2 and OH, D2O
exchanged), 1.91±2.50 (m, 2H, CHCH2), 2.65±2.98 (m,
2H, benzylic CH2), 3.02±3.38 (m, 1H, benzylic CH),
3.77 (t, 2H, J=6 Hz, CH2OH), 7.00±7.38 (m, 4H,
aromatic); IR (CHCl3) 3629, 1056 cmÀ1; GC/MS m/z
163 (M++1, 5), 162 (M+, 44), 144 (37), 129 (52), 117
(100), 115 (56).
1-Benzyl-3,3-dimethylpiperidine (3). A solution of imide
2 (16.0 g, 78 mmol) in anhydrous THF (200 mL) was
added dropwise to a cooled suspension of LiAlH4 (6.00 g,
0.16 mol) in the same solvent (200 mL). The mixture
was re¯uxed for 24h, under stirring. To the cooled sus-
pension were added some drops of water to destroy the
excess of the hydride. The mixture was ®ltered and the
®ltrate concentrated to dryness. The residue was taken up
with CH2Cl2. This solution was washed with water, dried
over Na2SO4 and concentrated under reduced pressure to
give the amine 3 as a colorless oil (12.6 g, 80% yield). 1H
NMR (90 MHz) 0.88 (s, 6H, 2 CH3), 1.05±1.30 (m, 2H,
(CH3)2)CCH2, 1.35±1.70 (m, 2H, piperidine CH2), 1.95
(s, 2H, NCH2C(CH3)2), 2.28 (t, 2H, J=6 Hz, CH2N),
3.40 (s, 2H, benzylic), 7.15±7.45 (m, 5H, aromatic); IR
(neat) 2794, 739, 698 cmÀ1; GC/MS m/z 204(M ++1,
11), 203 (M+, 65), 202 (50), 146 (27), 134 (75), 91
(100).
6-Methoxy-1,2,3,4-tetrahydronaphthalene-1-ethanol (7b).
It was chromatographed using CH2Cl2 as eluent to give
1
a colorless oil (67% yield). H NMR (90 MHz) 1.50±
2.15 (m, 7H, (CH2)2CHCH2 and OH, D2O exchanged),
2.65±3.15 (m, 3H, benzylic), 3.70±4.00 and 3.87 (m+s,
5H, CH2OH and CH3), 6.65±7.35 (m, 3H, aromatic);
GC/MS m/z 190 (83), 161 (17), 134(100).
2,3-Dihydro-1H-indene-1-ethyl, methanesulfonate (8a).
The crude residue was chromatographed (petroleum
ether/ethyl acetate, 8:2, as eluent) to obtain the pure
1
product as a white solide (65% yield). H NMR (90
MHz) 1.55±2.13 (m, 2H, endo CH2), 2.20±2.65 (m, 2H,
CHCH2), 2.85±3.12 (m, 5H, SO2CH3 and benzylic
CH2), 3.15±3.55 (m, 1H, benzylic CH), 4.49 (t, 2H, J=6
Hz, CH2O), 7.19±7.45 (m, 4H, aromatic); GC/MS m/z
241 (M++1, 2), 240 (M+, 16), 145 (18), 144 (93), 143
(21), 129 (100), 117 (85).
3,3-Dimethylpiperidine (4). 1-Benzyl-3,3-dimethylpiperi-
dine (3) (12.6 g, 62 mmol) was dissolved in MeOH and
hydrogenated at normal pressure and room temperature
in the presence of 10% Pd/C (0.50 g) until the uptake
ceased. The catalyst was removed by ®ltration through
Celite1 and the solvent was removed by distillation at
normal pressure. The residue was fractionated by dis-
tillation at normal pressure (bp 105±108 ꢀC; lit.23 136±
6-Methoxy-1,2,3,4-tetrahydronaphthalene-1-ethyl, methane-
sulfonate (8b). It was chromatographed, eluting with
ethyl acetate/petroleum ether 8:2, to give a colorless oil
(78% yield). 1H NMR (90 MHz) 1.60±2.25 (m, 6H,
(CH2)2CHCH2), 2.60±2.90 (m, 2H, benzylic), 2.95±3.05
(m, 4H, SO2CH3 and benzylic CH), 3.81 (s, 3H, OCH3),
4.35 (t, 2H, J=6 Hz, CH2O), 6.60±7.25 (m, 3H,
aromatic); IR (CHCl3) 1380, 1173 cmÆ1; GC/MS m/z
285 (M++1, 7), 284(M +, 40), 162 (27), 161 (100), 160
(25).
138 ꢀC), a€ording a colorless oil (3.8 g, 54% yield). H
1
NMR (90 MHz) 0.91 (s, 6H, 2 CH3), 1.15±1.65 (m, 4H,
(CH3)2CCH2CH2), 1.85 (s, 1H, NH, D2O exchanged),
2.45 (s, 2H, (CH3)2CCH2NH), 2.75 (t, 2H, J=6 Hz,
CH2CH2NH); GC/MS m/z 114(M ++1, 6), 113 (M+,
64), 98 (31), 57 (51), 44 (100).
Compounds 11a,b±16a,b. They were obtained as pure
colorless oils by column chromatography (petroleum
ether/CH2Cl2, 9:1 as eluent).
2,3-Dihydro-1H-indene-1-acetic acid, Ethyl Ester (6a).
This compound was chromatographed (petroleum
ether/ethyl acetate, 99:1 as eluent) to give a colorless oil
1
1
(88% yield). H NMR (90 MHz) 1.25 (t, 3H, J=6 Hz,
3-(4-Chlorobutyl)-1H-indene (11a). 25% yield; H NMR
CH3), 1.18±1.85 (m, 1H, endo CHH), 2.18±3.00 (m, 5H,
endo CHH, benzylic CH2 and CH2CO), 3.35±3.78 (m,
1H, benzylic), 4.15 (q, 2H, J=6 Hz, OCH2), 7.02±7.30
(m, 4H, aromatic); IR (CHCl3) 1725 cmÀ1; GC/MS m/z
204(M +, 48), 130 (48), 117 (100), 116 (74), 115 (45).
1.78±2.04(m, H4 , (C H2)2CH2Cl), 2.57±2.69 (m, 2H,
allylic), 3.32±3.36 (m, 2H, benzylic), 3.59 (t, 2H, J=7
Hz, CH2Cl), 6.23 (br t, 1H, vinylic), 7.21±7.48 (m, 4H,
aromatic); GC/MS m/z 208 (M++2, 6), 207 (M++1,
3), 206 (M+, 18), 130 (91), 129 (100), 128 (61), 115 (41).
6-Methoxy-1,2,3,4-tetrahydronaphthalene-1-acetic acid,
Ethyl Ester (6b). It was chromatographed, eluting with
petroleum ether/ethyl acetate, 9:1, to give a colorless oil
(43% yield). H NMR (90 MHz) 1.30 (t, 3H, J=9 Hz,
CH3CH2O), 1.65±2.10 (m, 4H, endo CH2CH2), 2.60±
3-(4-Chlorobutyl)-6-methoxy-1H-indene (11b). 18% yield;
1H NMR 1.82±1.97 (m, 4H, (CH2)2CH2Cl), 2.52±2.55
(m, 2H, CH2 allylic), 3.28±3.29 (m, 2H, benzylic), 3.57
(t, 2H, J=7 Hz, CH2Cl), 3.82 (s, 3H, CH3), 6.07 (t, 1H,
J=2 Hz, vinylic), 6.83±7.24(m, 3H, aromatic); GC/MS
m/z 238 (M++2, 9), 237 (M++1, 6), 236 (M+, 27), 201
(29), 173 (30), 160 (100), 159 (48), 145 (28).
1
2.91 (m, 4H, benzylic CH2 and CH2CO), 3.10±3.52 (m,
1H, benzylic CH), 3.84(s, 3H, OCH ), 4.05±4.41 (m,
3

1332
F. Berardi et al. / Bioorg. Med. Chem. 9 (2001) 1325±1335
1
3-(5-Chloropentyl)-1H-indene (12a). 21% yield; 1H NMR
1.51±1.89 (m, 6H, (CH2)3CH2Cl), 2.54±2.61 (m, 2H,
allylic), 3.30±3.34(m, 2H, benzylic), 3.55 (t, 2H, J=7
Hz, CH2Cl), 6.19±6.21 (m, 1H, vinylic), 7.16±7.47 (m, 4H,
aromatic); GC/MS m/z 222 (M++2, 3), 221 (M++1, 1),
220 (M+, 9), 130 (100), 129 (69), 128 (52), 115 (32).
1-(4-Chlorobutyl)-2,3-dihydro-1H-indene (17a). H NMR
1.38±2.04(m, 7H, C HHCH(CH2)3), 2.27±2.38 (m, 1H,
CHHCH), 2.78±3.29 (m, 3H, benzylic), 3.60 (t, 2H, J=7
Hz, CH2Cl), 7.11±7.27 (m, 4H, aromatic); GC/MS m/z
210 (M++2, 2), 209 (M++1, 1), 208 (M+, 7), 117
(100), 115 (24).
3-(5-Chloropentyl)-6-methoxy-1H-indene (12b). 29% yield;
1H NMR (90 MHz) 1.32±2.00 (m, 6H, (CH2)3CH2Cl),
2.32±2.68 (m, 2H, allylic), 3.19±3.21 (m, 2H, benzylic),
3.52 (t, 2H, J=7 Hz, CH2Cl), 3.85 (t, 3H, CH3), 6.02 (br
t, 1H, vinylic), 6.70±7.32 (m, 3H, aromatic); GC/MS m/z
252 (M++2, 4), 251 (M++1, 2), 250 (M+, 13), 173
(21), 160 (100), 159 (26), 115 (33).
1-(4-Chlorobutyl)-2,3-dihydro-5-methoxy-1H-indene (17b).
1H NMR 1.32±1.86 (m, 7H, CHHCH(CH2)3), 2.22±
2.33 (m, 1H, CHHCH), 2.73±3.07 (m, 3H, benzylic),
3.55 (t, 2H, J=7 Hz, CH2Cl), 3.77 (s, 3H, CH3), 6.68±
7.08 (m, 3H, aromatic); GC/MS m/z 240 (M++2, 2),
239 (M++1, 1), 238 (M+, 8), 147 (100).
1
1-(5-Chloropentyl)-2,3-dihydro-1H-indene (18a). H NMR
3-(6-Chlorohexyl)-1H-indene (13a). 56% yield; 1H NMR
(90 MHz) 1.28±2.00 (m, 8H, (CH2)4CH2Cl), 2.47±2.75
(m, 2H, allylic), 3.32±3.47 (m, 2H, benzylic), 3.60 (t, 2H,
J=7 Hz, CH2Cl), 6.28±6.33 (m, 1H, vinylic), 7.19±7.61 (m,
4H, aromatic); GC/MS m/z 236 (M++2, 3), 235 (M++1,
2), 234(M +, 10), 130 (100), 129 (48), 128 (39), 115 (24).
1.39±1.91 (m, 9H, CHHCH(CH2)4), 2.24±2.35 (m, 1H,
CHHCH), 2.78±3.16 (m, 3H, benzylic), 3.56 (t, 2H, J=7
Hz, CH2Cl), 7.12±7.25 (m, 4H, aromatic); GC/MS m/z
224(M ++2, 2), 223 (M++1, 1), 222 (M+, 6), 117
(100), 115 (22).
1-(5-Chloropentyl)-2,3-dihydro-5-methoxy-1H-indene (18b).
1H NMR 1.38±1.89 (m, 9H, CHHCH(CH2)4), 2.21±
2.32 (m, 1H, CHHCH), 2.73±3.06 (m, 3H, benzylic),
3.52 (t, 2H, J=7 Hz, CH2Cl), 3.77 (s, 3H, CH3), 6.68±
7.08 (m, 3H, aromatic); GC/MS m/z 254(M ++2, 2),
253 (M++1, 1), 252 (M+, 5), 147 (100).
3-(6-Chlorohexyl)-6-methoxy-1H-indene (13b). 26% yield;
1H NMR (90 MHz) 1.27±2.00 (m, 8H, (CH2)4CH2Cl),
2.55 (br t, 2H, allylic), 3.25±3.38 (m, 2H, benzylic), 3.55
(t, 2H, J=7 Hz, CH2Cl), 3.88 (s, 3H, CH3), 6.03±6.19
(m, 1H, vinylic), 6.80±7.35 (m, 3H, aromatic); GC/MS
m/z 266 (M++2, 4), 265 (M++1, 2), 264(M +, 11), 160
(100), 159 (20), 115 (27).
1
1-(6-Chlorohexyl)-2,3-dihydro-1H-indene (19a). H NMR
(90 MHz) 1.18±1.98 (m, 11H, CHHCH(CH2)5), 2.01±
2.44 (m, 1H, CHHCH), 2.70±3.18 (m, 3H, benzylic),
3.46 (t, 2H, J=7 Hz, CH2Cl), 7.07±7.35 (m, 4H, aro-
matic); GC/MS m/z 238 (M++2, 2), 237 (M++1, 1),
236 (M+, 7), 117 (100), 115 (23).
4-(4-Chlorobutyl)-1,2-dihydro-7-¯uoronaphthalene (14c).
30% yield; 1H NMR (90 MHz) 1.56±1.97 (m, 4H,
(CH2)2CH2Cl), 2.00±2.51 (m, 4H, allylic), 2.70 (br t, 2H,
benzylic), 3.52 (t, 2H, J=7 Hz, CH2Cl), 5.78 (t, 1H,
J=5 Hz, vinylic), 6.62±7.28 (m, 3H, aromatic); GC/MS
m/z 240 (M++2, 5), 239 (M++1, 2), 238 (M+, 16), 162
(73), 159 (22), 147 (100), 146 (53), 133 (24).
1-(6-Chlorohexyl)-2,3-dihydro-5-methoxy-1H-indene (19b).
1H NMR (90 MHz) 1.22±1.98 (m, 11H,
CHHCH(CH2)5), 2.06±2.48 (m, 1H, CHHCH), 2.69±3.18
(m, 3H, benzylic), 3.52 (t, 2H, J=7 Hz, CH2Cl), 3.80 (s,
3H, CH3), 6.62±7.18 (m, 3H, aromatic); GC/MS m/z
268 (M++2, 3), 267 (M++1, 2), 266 (M+, 8), 147
(100).
4-(5-Chloropentyl)-1,2-dihydro-7-¯uoronaphthalene (15c).
17% yield; 1H NMR (90 MHz) 1.20±1.97 (m, 6H,
(CH2)3CH2Cl), 2.04±2.54 (m, 4H, allylic), 2.59±2.91 (m,
2H, benzylic), 3.52 (t, 2H, J=7 Hz, CH2Cl), 5.82 (br t,
1H, vinylic), 6.62±7.31 (m, 3H, aromatic); GC/MS m/z
254(M ++2, 3), 253 (M++1, 2), 252 (M+, 10), 162
(100), 159 (21), 147 (78), 146 (51), 133 (24).
1-(4-Chlorobutyl)-6-¯uoro-1,2,3,4-tetrahydronaphthalene
(20c). 1H NMR (90 MHz) 1.33±2.04(m, 10H, (C H2)2CH-
(CH2)3), 2.61±2.89 (m, 3H, benzylic), 3.58 (t, 2H, J=7
Hz, CH2Cl), 6.70±7.33 (m, 3H, aromatic); GC/MS m/z
242 (M++2, 2), 241 (M++1, 1), 240 (M+, 5), 149
(100), 109 (18).
4-(6-Chlorohexyl)-1,2-dihydronaphthalene (16a). 24% yield;
1H NMR (90 MHz) 1.10±2.01 (m, 8H, (CH2)4CH2Cl),
2.21±2.58 (m, 4H, allylic), 2.61±3.00 (m, 2H, benzylic), 3.56
(br t, 2H, CH2Cl), 5.88 (br t, 1H, vinylic), 7.01±7.48 (m, 4H,
aromatic); GC/MS m/z 250 (M++2, 3), 249 (M++1, 2),
248 (M+, 9), 144 (100), 129 (80), 128 (51), 115 (24).
1-(5-Chloropentyl)-6-¯uoro-1,2,3,4-tetrahydronaphthalene
(21c). 1H NMR (90 MHz) 1.23±2.05 (m, 12H,
(CH2)2CH(CH2)4), 2.52±2.93 (m, 3H, benzylic), 3.57 (t,
2H, J=7 Hz, CH2Cl), 6.70±7.30 (m, 3H, aromatic);
4-(6-Chlorohexyl)-1,2-dihydro-7-methoxynaphthalene (16b).
33% yield; 1H NMR (90 MHz) 1.20±1.83 (m, 8H,
(CH2)4CH2Cl), 2.00±2.51 (m, 4H, allylic), 2.67 (br t, 2H,
benzylic), 3.44 (t, 2H, J=7 Hz, CH2Cl), 3.79 (s, 3H, CH3),
5.68 (br t, 1H, vinylic), 6.62±7.23 (m, 3H, aromatic);
GC/MS m/z 280 (M++2, 4), 279 (M++1, 2), 278 (M+,
12), 174(100), 159 (25).
GC/MS m/z 256 (M++2, 1), 255 (M++1, 1), 254(M +
,
4), 149 (100), 109 (21).
1-(6-Chlorohexyl)-1,2,3,4-tetrahydronaphthalene (22a).
1H NMR (90 MHz) 0.78±1.90 (m, 14H, (CH2)2CH-
(CH2)5), 2.57±2.91 (m, 3H, benzylic), 3.51 (t, 2H, J=7
Hz, CH2Cl), 7.01±7.20 (m, 4H, aromatic); GC/MS m/z
252 (M++2, 2), 251 (M++1, 1), 250 (M+, 5), 131
(100), 91 (20).
Compounds 17a,b±22a,b. These compounds were
obtained as colorless oils in the 90±99% yields.

F. Berardi et al. / Bioorg. Med. Chem. 9 (2001) 1325±1335
1333
1-(6-Chlorohexyl)-6-methoxy-1,2,3,4-tetrahydronaphthalene
(22b). 1H NMR (90 MHz) 1.22±1.98 (m, 14H,
(CH2)2CH(CH2)5), 2.57±2.88 (m, 3H, benzylic), 3.52 (t,
2H, J=7 Hz, CH2Cl), 3.80 (s, 3H, CH3), 6.60±7.20 (m,
3H, aromatic); GC/MS m/z 282 (M++2, 1), 281
(M++1, 1), 280 (M+, 4), 161 (100).
140.19, 145.77, 158.81; GC/MS m/z 330 (M++1, 2),
329 (M+, 7), 147 (16), 126 (100).
1-[6-(2,3-Dihydro-5-methoxy-1H-inden-1-yl)hexyl]-3,3-di-
methylpiperidine (33). 1H NMR 0.97 (s, 6H, 2 CH3),
1.25±1.79 (m, 15H, CH(CH2)5, piperidine CH2CH2 and
endo CHH), 1.85±2.30 (m, 7H, NCH2C(CH3)2,
CH2NCH2 and endo CHH), 2.71±3.35 (m, 3H, benzylic),
3.76 (s, 3H, OCH3), 6.67±7.24(m, 3H, aromatic); GC/
MS m/z 344 (M++1, 5), 343 (M+, 21), 126 (100).
1-[2-(2,3-Dihydro-1H-inden-1-yl)ethyl]-3,3-dimethylpiper-
1
idine (24). H NMR 0.94(s, 6H, 2CH ), 1.15±1.35 (m,
3
2H, CH2C(CH3)2), 1.50±1.78 (m, 4H, piperidine CH2
and endo CH2), 1.95±2.19 (m, 3H, CHCH2 and
NCHHC(CH3)2), 2.20±2.45 (m, 5H, CH2NCH2 and
NCHHC(CH3)2), 2.75±3.02 (m, 2H, benzylic CH2),
3.07±3.20 (m, 1H, benzylic CH), 7.05±7.32 (m, 4H, aro-
matic); GC/MS m/z 258 (M++1, 10), 257 (M+, 43),
127 (25), 126 (100), 115 (20).
3,3-Dimethyl-1-[6-(1,2,3,4-tetrahydronaphthalen-1-yl)-
hexyl]piperidine (38). 1H NMR 0.95 (s, 6H, 2 CH3),
1.17±1.89 (m, 18H, (CH2)2CH(CH2)5 and piperidine
CH2CH2), 1.90±2.49 (m, 6H, CH2NCH2 e NCH2C-
(CH3)2), 2.71±2.74(m, 3H, benzylic), 7.01±7.15 (m, 4H,
aromatic); GC/MS m/z 328 (M++1, 3), 327 (M+, 11),
126 (100).
1-[4-(2,3-Dihydro-1H-inden-1-yl)butyl]-3,3-dimethylpiper-
1
idine (26). H NMR 0.95 (s, 6H, 2 CH3), 1.22 (t, 2H,
J=6 Hz, CH2C(CH3)2), 1.35±1.90 (m, 9H, CH(CH2)3,
piperidine CH2 and endo CHH), 2.03 (br s, 2H,
NCH2C(CH3)2), 2.21±2.32 (m, 5H, CH2NCH2, endo
CHH), 2.76±3.13 (m, 3H, benzylic), 7.10±7.22 (m, 4H,
aromatic); 13C NMR 22.95, 25.88, 27.46, 27.83, 30.99,
31.70, 32.42, 35.23, 37.96, 45.10, 55.41, 59.36, 66.38,
123.82, 124.65, 122.23, 126.42, 144.28, 148.00; GC/MS
m/z 286 (M++1, 1), 285 (M+, 6), 126 (100), 117 (20).
3,3-Dimethyl-1-[2-(6-methoxy-1,2,3,4-tetrahydronaphthalen-
1-yl)ethyl]piperidine (41). 1H NMR 0.94(2 s, 6H, 2 CH 3),
1.15±1.25 (m 2H, CH2C(CH3)2), 1.45±1.74 (m, 6H, endo
CH2CH2 and piperidine CH2), 1.75±1.88 (m, 2H,
CHCH2), 1.89±2.15 (m, 2H, NCH2C(CH3)2), 2.20±2.45
(m, 4H, CH2NCH2), 2.65±2.85 (m, 3H, benzylic), 3.75
(s, 3H, OCH3), 6.65±7.12 (m, 3H, aromatic); GC/MS m/
z 302 (M++1, 8), 301 (M+, 33), 160 (20), 126 (100).
1-[5-(2,3-Dihydro-1H-inden-1-yl)pentyl]-3,3-dimethylpiper-
1
3,3-Dimethyl-1-[4-(6-methoxy-1,2,3,4-tetrahydronaphthalen-
1-yl)butyl]piperidine (43). This compound has been
idine (27). H NMR 0.95 (s, 6H, 2 CH3), 1.22 (t, 2H,
1
J=6 Hz, CH2C(CH3)2), 1.29±1.88 (m, 11H, CH(CH2)4,
piperidine CH2 and endo CHH), 2.04(br s, 2H,
NCH2C(CH3)2), 2.20±2.31 (m, 5H, CH2NCH2 and endo
CHH), 2.21±3.12 (m, 3H, benzylic), 7.10±7.22 (m, 4H,
aromatic); GC/MS m/z 300 (M++1, 1), 299 (M+, 6),
126 (100), 117 (18).
already characterized20 by H NMR and GC/MS; 13C
NMR 20.07, 22.78, 25.44, 27.23, 27.83, 30.36, 30.95,
37.04, 37.12, 37.83, 55.29, 55.39, 59.29, 66.19, 112.05,
113.64, 129.69, 133.99, 138.43, 157.43.
3,3-Dimethyl-1-[6-(6-methoxy-1,2,3,4-tetrahydronaphthalen-
1-yl)hexyl]piperidine (45). 1H NMR 0.97 (s, 6H, 2 CH3),
1.23±1.84(m, 18H, (C H2)2CH(CH2)5 and piperidine
1-[6-(2,3-Dihydro-1H-inden-1-yl)hexyl]-3,3-dimethylpiperi-
1
dine (28). H NMR 0.94(s, 6H, 2 CH ), 1.21±1.84(m,
3
CH2CH2), 1.85±2.64(m, 6H, CH 2NCH2
NCH2C(CH3)2), 2.65±2.71 (m, 3H, benzylic), 3.74(s,
e
15H, CH(CH2)5, piperidine CH2CH2 and endo CHH),
2.01 (br s, 2H, NCH2C(CH3)2), 2.15±2.30 (m, 5H,
CH2NCH2 and endo CHH), 2.74±3.08 (m, 3H,
benzylic), 7.09±7.24(m, 4H, aromatic); GC/MS m/z 314
(M++1, 2), 313 (M+, 7), 126 (100), 117 (18).
3H, OCH3), 6.56±7.24(m, 3H, aromatic); GC/MS m/z
358 (M++1, 4), 357 (M+, 14), 126 (100).
3,3-Dimethyl-1-[4-(6-¯uoro-1,2,3,4-tetrahydronaphthalen-
1
1-yl)butyl]piperidine (48). H NMR 0.92 (s, 6H, 2 CH3),
1-[4-(2,3-Dihydro-5-methoxy-1H-inden-1-yl)butyl]-3,3-di-
methylpiperidine (31). 1H NMR 0.92 (s, 6H, 2 CH3),
1.19 (t, 2H, J=6 Hz, CH2C(CH3)2), 1.34±1.82 (m, 9H,
CH(CH2)3, piperidine CH2 and endo CHH), 2.00 (br s,
2H, NCH2C(CH3)2), 2.20±2.31 (m, 5H, CH2NCH2 and
endo CHH), 2.74±3.03 (m, 3H, benzylic), 3.76 (s, 3H,
OCH3), 6.67±7.07 (m, 3H, aromatic); GC/MS m/z 316
(M++1, 4), 315 (M+, 18), 126 (100).
1.19 (br t, 2H, CH2C(CH3)2), 1.28±1.84(m, 12H,
(CH2)2CH(CH2)3 and piperidine CH2), 1.99 (s, 2H,
NCH2C(CH3)2), 2.22±2.26 (m, 4H, CH2NCH2), 2.70±
2.72 (m, 3H, benzylic), 6.70±7.24(m, 3H, aromatic);
GC/MS m/z 318 (M++1, 1), 317 (M+, 5), 149 (15), 126
(100), 109 (15).
3,3-Dimethyl-1-[5-(6-¯uoro-1,2,3,4-tetrahydronaphthalen-
1-yl)pentyl]piperidine (49). 1H NMR 0.92 (s, 6H, 2 CH3),
1.19 (t, 2H, J=6 Hz, CH2C(CH3)2), 1.25±1.88 (m, 14H,
(CH2)2CH(CH2)4 and piperidine CH2), 2.00 (s, 2H,
NCH2C(CH3)2), 2.15±2.24(m, 4H, CH 2NCH2), 2.68±
2.75 (m, 3H, benzylic), 6.70±7.24(m, 3H, aromatic); 13C
NMR 19.68, 22.89, 27.17, 27.46, 27.56, 27.77, 28.01,
30.08, 30.92, 37.16, 37.22, 37.91, 55.35, 59.40, 66.36,
112.51, 112.78, 115.03, 115.29, 130.05, 130.16, 137.36,
139.18, 139.28, 162.49; GC/MS m/z 332 (M++1, 2),
331 (M+, 9), 149 (15), 126 (100).
1-[5-(2,3-Dihydro-5-methoxy-1H-inden-1-yl)pentyl]-3,3-
1
dimethylpiperidine (32). H NMR 0.92 (s, 6H, 2 CH3),
1.19 (t, 2H, J=6 Hz, CH2C(CH3)2), 1.24±1.81 (m, 11H,
CH(CH2)4, piperidine CH2 and endo CHH), 1.99 (br s,
2H, NCH2C(CH3)2), 2.20±2.31 (m, 5H, CH2NCH2 and
endo CHH), 2.71±3.04(m, 3H, benzylic), 3.76 (s, 3H,
OCH3), 6.67±7.08 (m, 3H, aromatic); 13C NMR 22.88,
27.18, 27.86, 28.08, 30.92, 31.87, 32.84, 35.59, 37.89,
44.23, 55.39, 55.61, 59.46, 66.31, 110.07, 112.01, 124.25,

1334
F. Berardi et al. / Bioorg. Med. Chem. 9 (2001) 1325±1335
.
Radioligand binding assays
of 50 mM Tris HCl, pH 7.6, were suspended hippo-
campus membranes, 1.0 nM [3H]-8-OH-DPAT, the
drug or reference compound (six to nine concentra-
tions). Incubation at 37 ꢀC for 20 min was terminated
by rapid ®ltration on GF/B ®lters which were washed
twice with 3 mL of ice-cold bu€er. The non speci®c
binding was de®ned in the presence of 1.0 mM 8-OH-
DPAT. The Kd value used for 8-OH-DPAT was 8.8
nM.
ꢀ1 Binding. The s1 receptor anities were determined as
described by Matsumoto et al.34 with minor modi®ca-
tions. Brie¯y, in a total volume of 1.0 mL of 50 mM
.
Tris HCl, pH 8.0, were suspended guinea-pig brain
membranes, 1.7 nM (+)-[3H]-pentazocine and the drug
studied or reference compound (six to nine concentra-
tions). Incubation at room temperature for 120 min was
.
terminated with 1 mL of ice-cold 50 mM Tris HCl, pH
8.0 and vacuum ®ltration through GF/B ®lters that
were presoaked in 0.5% PEI for 60 min. The ®lters were
washed twice with ice-cold bu€er. The non speci®c
binding was de®ned in the presence of (+)-pentazocine
1 mM. The Kd (2.89 nM) and Bmax (540 fmol/mg of
protein) were determined in a Scatchard experiment.
MK 801 site binding. The MK 801 receptor anities
were determined as described by Bergeron et al.38 with
minor modi®cations. In a total volume of 1.0 mL of 5 mM
.
Tris HCl, pH 7.7 were suspended rat brain membranes, 2
nM [3H]-MK 801, 100 mM d-glutamic acid, 100 mM
l-glycine, the drug or reference compound (six to nine
concentrations). Incubation at room temperature for 60
min was terminated by rapid ®ltration on GF/B ®lters,
which were washed by threeÂ4.0 mL of ice-cold bu€er.
The non speci®c binding was de®ned in the presence of
1 mM MK 801. The Kd value used for MK 801 was 11 nM.
ꢀ2 Binding. Anities for s2 receptor were determined as
described by Matsumoto et al.34 with minor modi®ca-
tions. Brie¯y, in a total volume of 1.0 mL of 50 mM
.
Tris HCl, pH 8.0, were suspended rat liver membranes,
2.5 nM [3H]-DTG, 1 mM (+)-pentazocine, the drug
studied or reference compound (six to nine concentra-
tions). Incubation at room temperature for 120 min was
Acknowledgements
.
terminated with 1 mL of ice-cold 50 mM Tris HCl, pH
8.0 and vacuum ®ltration through GF/B ®lters that
were presoaked in 0.5% PEI for 60 min. The ®lters were
washed twice with ice-cold bu€er. The non speci®c
binding was de®ned in the presence of 10 mM DTG. The
Kd (10.4nM) and Bmax (1520 fmol/mg of protein) were
determined in a Scatchard experiment.
This study was supported by research grant no.
9903108895-005 from Universita degli Studi di Bari and
MURST (Italy) for the scienti®c program in C07X ®eld-
2000±2002: `Arylpiperazine derivatives: structural mod-
i®cations to modulate their activity toward some C.N.S.
receptors, 5-HT1A, D2, D4, sigma-1 and sigma-2,
involved in pathological events such as depression,
schizophrenia and Alzheimer'.
L-Type Ca++ channel binding. The Ca++ channel ani-
ties were determined as described by Reynolds et al.35
with minor modi®cations. In a total volume of 1.0 mL
of 50 mM Hepes, pH 7.4, were suspended rat brain
membranes, 0.2 nM (À)-[3H]-desmethoxyverapamil, the
drug or reference compound (six to nine concentra-
tions). Incubation at room temperature for 60 min was
terminated by rapid ®ltration on GF/C ®lters which
were washed twice with 1 mL of ice-cold bu€er. The
non speci®c binding was de®ned in the presence of 10
mM (Æ)-verapamil. The Kd value used for (À)-[3H]-des-
methoxyverapamil was 0.55 nM.
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