1-Aryl-4-[(1-tetralinyl)alkyl]piperazines: Alkylamido and alkylamino derivatives. Synthesis, 5-HT(1A) receptor affinity, and selectivity

Article abstract of DOI:10.1021/jm960087s

The synthesis and binding profile on 5-HT(1A), 5-HT₂, D-1, D-2, α₁, and α₂receptors of the N-4 long-chain arylpiperazines 22-40 are reported, where an amino or amido function is inserted into the intermediate chain linked

Full text of DOI:10.1021/jm960087s

J . Med. Chem. 1996, 39, 3195-3202
3195
1-Ar yl-4-[(1-tetr a lin yl)a lk yl]p ip er a zin es: Alk yla m id o a n d Alk yla m in o
Der iva tives. Syn th esis, 5-HT1A Recep tor Affin ity, a n d Selectivity. 31
Roberto Perrone,* Francesco Berardi, Marcello Leopoldo, and Vincenzo Tortorella
Dipartimento Farmaco-chimico, Universita` di Bari, via Orabona, 4, 70126 Bari, Italy
Maria Gioia Fornaretto, Carla Caccia, and Robert A. McArthur
Pharmacia S.p.A., via Giovanni XXIII, 23, 20014 Nerviano (MI), Italy
Received J anuary 29, 1996X
The synthesis and binding profile on 5-HT1A, 5-HT2, D-1, D-2, R1, and R2 receptors of the N-4
long-chain arylpiperazines 22-40 are reported, where an amino or amido function is inserted
into the intermediate chain linked to the R position of the tetralin nucleus. Unlike the buspirone
analogues, for the amido derivatives studied in this paper, the terminal amide function of long-
chain piperazines is not important for 5-HT1A receptor affinity binding, and its removal yields
high-affinity 5-HT1A receptor agents.
Serotonin (5-hydroxytryptamine, 5-HT) is involved in
many physiological and pathophysiological processes in
the brain which are mediated by the specific interaction
of 5-HT with several different receptors. The classifica-
tion of these receptor subtypes, their role, and their
respective ligands are reported in several recent
reviews.2-8 The 5-HT1A receptors are to date the best-
characterized subtypes, and it is generally accepted that
they are involved in psychiatric disorders such as
depression and anxiety.
an amine or amide function into the methylene spacer
between the basic nitrogen atom and the tetralin
nucleus.
Several compounds from different chemical classes
possess high affinity for 5-HT1A receptors.8 Among
these, some long-chain arylpiperazine compounds with
a terminal amide fragment, such as buspirone (1) and
ipsapirone (2) are effective antianxiety and antidepres-
sant drugs.
On the other hand, Misztal et al.14 assumed that the
terminal amide fragment in buspirone-like ligands
stabilized the 5-HT1A receptor-ligand complex by either
π-electron or local dipole-dipole interaction. However,
although a hydrocarbon chain with a terminal amide
fragment significantly influences the ability to bind to
other receptors, its role is not yet clear.
In the present paper, we therefore report the synthe-
sis and the binding profile on 5-HT1A, 5-HT2, D-1, D-2,
R1, and R2 receptors of the N-4 long-chain arylpipera-
zines 22-40 (Table 1) where the -CONHR or -CH2-
NR or -NRCH2 or -NHCO function is linked to the R
position of the tetralin nucleus, in place of two meth-
ylene groups which were present in the previously
reported arylpiperazines.1 The arylpiperazine and te-
tralin moieties used for the compounds in the present
work are those present in agents with the highest
affinity for the 5-HT1A receptor;13 they are 1-(2-meth-
oxyphenyl)-, 1-phenyl-, and 1-(2-pyridyl)piperazine and
5-methoxy-1,2,3,4-tetrahydronaphthalene. Some com-
pounds present a methyl group on the nitrogen atom of
the amide function (28-30), or of the amine function
(36), to prevent a possible intramolecular hydrogen
bond.
However, even if the long-chain arylpiperazines rep-
resent the class most throughly studied to date, their
selectivity versus dopaminergic D-2 and adrenergic R
receptors is not yet clear, with the result that several
papers have been published by different researchers.9-12
In order to contribute toward solving this problem, in
two recent papers1,13 we have described a new model of
long-chain arylpiperazines, with a dihydronaphthalene
or tetralin nucleus on the terminal part of the side
chain. Since for these compounds the affinity and
selectivity values on the 5-HT1A receptor were very
encouraging, and since we noted that the incorporation
of an amine function into the spacer, in place of a
methylene group, as in compound 3, causes an increase
in selectivity versus D-2, R1, and R2 receptors compared
to the corresponding compounds 4, we decided to insert
Ch em istr y
Synthesis of the final compounds is illustrated in
Scheme 1. Compounds derived from 5-methoxy-1,2,3,4-
tetrahydronaphthalene-1-carboxylic acid (9) were pre-
pared by reacting 5-methoxy-1-tetralone (8) with tri-
methylsilyl cyanide, giving the trimethylsilyl cyanohy-
drin derivative, according to the literature.15 This was
hydrolyzed, dehydrated, and then reduced in a single
* To whom correspondence should be addressed.
X Abstract published in Advance ACS Abstracts, J uly 1, 1996.
S0022-2623(96)00087-8 CCC: $12.00 © 1996 American Chemical Society

3196 J ournal of Medicinal Chemistry, 1996, Vol. 39, No. 16
Ta ble 1. Physical Properties
Perrone et al.
compd
X
Y
Ar
formulaa
mp, °C
recryst solv
3b
4b
NH
CH2
CH2
CH2
CH2
2-CH3O-Ph
2-CH3O-Ph
Ph
2-Py
2-CH3O-Ph
Ph
2-CH3O-Ph
2-Py
Ph
2-CH3O-Ph
2-Py
Ph
2-CH3O-Ph
Ph
Ph
Ph
2-Py
CH2
CH2
CH2
CH2
CO
CO
CO
CO
CO
CO
CO
CO
CO
CH2
NH
NH
NH
NH
N(CH3)
NH
NH
NH
NH
5b
6b
7b
CH2CH2
NHCH2
NHCH2
NHCH2
NHCH2CH2
NHCH2CH2
NHCH2CH2
N(CH3)CH2
N(CH3)CH2
N(CH3)CH2CH2
NHCH2
CH2
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
C24H31N3O2‚HCl
235-239 dec
150 dec
210 dec
MeOH
C25H33N3O3‚2HCl
CH2Cl2/Et2O
MeOH/Et2O
MeOH/Et2O
CH2Cl2/Et2O
MeOH/Et2O
MeOH/Et2O
CH2Cl2/petroleum ether
MeOH/Et2O
MeOH/Et2O
CH2Cl2/Et2O
CH2Cl2/Et2O
MeOH/Et2O
CH2Cl2/Et2O
MeOH/Et2O
MeOH/Et2O
MeOH/Et2O
MeOH/Et2O
MeOH/Et2O
C23H30N4O2‚3HCl
C25H33N3O2‚2HCl
180-185 dec
C26H35N3O3‚2HCl
194-196
C24H32N4O2‚2HCl‚3/2H2O
C25H33N3O2‚HCl‚H2O
C26H35N3O3‚2HCl
213 dec
257-259
175-178 dec
C26H35N3O2‚2HCl
199 dec
C24H33N3O‚3HCl
242 dec
247 dec
C23H31N3O‚2HCl‚2/3H2O
C22H30N4O‚3HCl‚1/2H2O
C24H33N3O‚2HCl
CH2
156-159 dec
261-263 dec
144-147 dec
141-144 dec
244 dec
CH2CH2
CH2CH2
CH2
CO
COCH2
Ph
2-CH3O-Ph
2-CH3O-Ph
Ph
C25H35N3O2‚2HCl‚2/3H2O
C25H35N3O2‚2HCl‚5/3H2O
C23H29N3O2‚HCl
Ph
C24H31N3O2‚2HCl
200-203 dec
COCH2
COCH2
2-CH3O-Ph
2-Py
C25H33N3O3‚2HCl
211-213
C23H30N4O2‚2HCl‚1/2H2O
251-253 dec
a
b
Analyses for C,H,N; results were within (0.4% of the theoretical values for the formulas given. Formerly published compounds.1,13
Sch em e 1a
a
Reagents: (A) (CH3)3SiCN, ZnI2; (B) concentrated HCl, CH3COOH, SnCl2‚H2O; (C) DCC; (D) LiAlH4; (E) p-toluenesulfonic acid; (F)
NaBH4; (G) CH3OCOCl; (H) NH2OH‚HCl, CH3COONa; (I) H2, Pd/C (10%); (J ) BrCH2COCl or ClCH2CH2COCl; (K) N-arylpiperazines. b P,
4-phenylpiperazin-1-yl; M, 4-(2-methoxyphenyl)piperazin-1-yl; PY, 4-(2-pyridyl)piperazin-1-yl.
step to obtain compound 9. Then amides 22-30 were
obtained by reacting compound 9 with the corresponding
amines 11-19, synthesized as already described,16,17 in
the presence of 1,3-dicyclohexylcarbodiimide (DCC).
Amine 31 was prepared from amide 22 by reduction
with LiAlH4. Amines 11-19 were also used to obtain
amines 3 and 32-35 according to a recently reported
synthetic pathway.1 The N-methylated derivative 36
was obtained by treating 3 with methyl chloroformate18
to yield its carbamate, which was then reduced with
LiAlH4. In order to prepare the naphthalenamine
amidic derivatives, 5-methoxy-1,2,3,4-tetrahydro-1-
naphthalenamine (10) was synthesized by catalytic
hydrogenation of the oxime of 5-methoxy-1-tetralone (8),
as reported.19 Then amine 10 was acylated with bro-
moacetyl chloride or 3-chloropropionyl chloride to give

1-Aryl-4-[(1-tetralinyl)alkyl]piperazines
J ournal of Medicinal Chemistry, 1996, Vol. 39, No. 16 3197
Ta ble 2. Binding Affinitiesa and Selectivities
IC50, nM
selectivity vs 5-HT1A
receptor, IC50 ratio
5-HT1A
5-HT2
D-2
R1
R2
compd
[3H]-8-OH-DPAT [3H]ketanserin
[3H]spiroperidol
[3H]prazosin
[3H]yohimbine 5-HT2
D-2
R1
R2
3
4
5
6
7.7 ( 0.8
2580 ( 150
330 ( 30
230 ( 30
250 ( 20
NTc
380 ( 40
18 ( 2
220 ( 20
6.5 ( 0.6
43 ( 5
280 ( 40
17 ( 2
335
429
460
463
49
23
220
259
9b
10
13
14
12
7
9
3
1
4
10
13
38
41
106
8
29
8
86
122
45b
1
5
5
0.3
5
3
5
1
1
10
8
15
12
88
102
1
36
22
520
89
0.77 ( 0.09
0.50 ( 0.05
0.54 ( 0.06
1.73 ( 0.22b
110 ( 20
140 ( 10
15.4 ( 0.8b
4040 ( 440
448 ( 51
2440 ( 230
783 ( 82
116 ( 13
819 ( 26
882 ( 71
332 ( 45
594 ( 55
1100 ( 170
1200 ( 150
1850 ( 200
2160 ( 190
1060 ( 90
73 ( 8
260 ( 30
48 ( 5
66 ( 7
7
78.3 ( 5.5b
427 ( 46
166 ( 16
838 ( 61
19 ( 2
NTc
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
416 ( 37
1560 ( 160
1710 ( 160
1270 ( 130
349 ( 40
2040 ( 160
428 ( 31
848 ( 75
1070 ( 100
134 ( 12
1900 ( 130
2720 ( 350
9140 ( 820
2690 ( 80
3300 ( 300
1740 ( 250
>10 000
1850 ( 290
1380 ( 140
7220 ( 70
186 ( 20
564 ( 48
746 ( 80
250 ( 37
183 ( 21
144 ( 16
1420 ( 180
310 ( 47
95 ( 11
788 ( 98
458 ( 57
112 ( 10
>10 000
2680 ( 450
1250 ( 140
1330 ( 270
>10 000
810 ( 80
4
49
7
6
128
5
3
4
1
16
30
187
51
330
200
4
40
42
3
35
8
1
1
1
12
3
35 ( 3
173 ( 20
63 ( 7
16 ( 2
95 ( 9
84 ( 9
327 ( 48
510 ( 22
297 ( 29
159 ( 10
1150 ( 120
790 ( 76
725 ( 55
626 ( 65
881 ( 103
887 ( 62
5980 ( 390
313 ( 8
271 ( 20
307 ( 30
134 ( 13
116 ( 13
92 ( 6
49 ( 5
2
53 ( 5
15
46
13
10 ( 2
8.7 ( 1.9
5310 ( 580
311 ( 32
38 ( 6
>10 000
1200 ( 70
841 ( 83
726 ( 83
>10 000
2970 ( 390
761 ( 62
1900 ( 200
280 ( 30
5.2 ( 0.6
4
22
5
10
20
14
1
4
4
9
33
10
153 ( 7
135 ( 19
30 ( 3
2.1 ( 0.2
534 ( 57
>10 000
>10 000
buspirone
8-OH-DPAT
ketanserin
haloperidol
prazosin
>10 000
3.4 ( 0.3
4.8 ( 0.5
1.4 ( 0.6
yohimbine
30 ( 3
a
b
Compounds 22-40 showed very high affinity binding values on D-1 receptor (IC50 > 1000 nM). Previously published data,1 here
c
reported for comparison. Not tested.
the intermediates 20 and 21, respectively. The amina-
tion of these halo derivatives with the appropriate
N-arylpiperazine provided the final amides 37-40.
methylene-spaced arylpiperazine derivatives 4-6 (see
Table 1), which had been previously studied1 and were
reinvestigated in the Pharmacia laboratories (IC50
)
0.77, 0.50, and 0.54 nM, respectively, for the 5-HT1A
receptor), it should be noted (see Figure 1) that replacing
the R-methylene group in the spacer with a secondary
amine group, as for the corresponding compounds 3, 32,
and 33, respectively, led to a decrease in affinity for the
P h a r m a cology
Final compounds (Table 2) were evaluated for in vitro
affinity on dopamine D-1 and D-2, serotonin 5-HT1A and
5-HT2, and adrenergic R1 and R2 receptors by radioli-
gand binding assays. All the compounds were used in
the form of hydrochloride salts and were water-soluble.
The following specific radioligands and tissue sources
were used (a) dopamine D-1 receptorss[3H]SCH-23390,
rat striatal membranes; (b) dopamine D-2 receptorss
[3H]spiroperidol, rat striatal membranes; (c) serotonin
5-HT1A receptorss[3H]-8-OH-DPAT, rat hippocampus
membranes; (d) serotonin 5-HT2 receptorss[3H]-
ketanserin, rat brain prefrontal cortex membranes; (e)
R1-adrenergic receptorss[3H]prazosin, rat brain cortex
membranes; (e) R2-adrenergic receptorss[3H]yohimbine,
rat brain cortex membranes.
Concentrations required to inhibit 50% of radioligand
specific binding (IC50) were determined by using eight
to nine different concentrations of the drug studied.
Specific binding was defined as described in the Experi-
mental Section under Pharmacological Methods; in all
binding assays, it represents more than 80% of total
binding, except for R2 (>60%). The results were ana-
lyzed by using the LIGAND program to determine IC50
values.
5-HT1A receptor, less so for the first compound (IC50
)
7.7 nM) than for the other two (IC50 ) 92 and 49 nM,
respectively). Compound 36, an N-methyl derivative of
3, showed a similar affinity value to 3 (IC50 ) 8.7 nM).
On the other hand, it should be noted that the insertion
of an amine function into the 1-(2-methoxyphenyl)-
piperazine derivative 3 led to an increase in selectivity
versus D-2 and R receptors, compared to the corre-
sponding reference compound 4, whereas for the phenyl
and 2-pyridyl derivatives 32 and 33 we observed a
decrease in selectivity compared to 5 and 6, respectively.
Finally, the three-membered amidic derivative 37 proved
to have negligible affinity for 5-HT1A receptor (IC50
5310 nM) compared to the corresponding amino deriva-
)
tive 32 and the reference compound 5.
We can therefore deduce that, for those derivatives
with three atoms in the spacer, a basic moiety at the
end of the alkyl chain is required for better affinity than
an amide function. Among the amino derivatives, the
1-(2-methoxyphenyl)piperazine derivative 3 proved to
have the highest affinity and selectivity for 5-HT1A
receptor.
Resu lts a n d Discu ssion
The values of affinity and selectivity for the arylpip-
erazine derivatives with four atoms in the spacer
showed the same behavior. In this case the previously
The results of the binding assays are illustrated in
Table 2. Considering as a term of comparison the three

3198 J ournal of Medicinal Chemistry, 1996, Vol. 39, No. 16
Perrone et al.
F igu r e 1.
studied1 arylpiperazine derivative 7 (see Table 1), with
an alkyl spacer of four methylene units (IC50 ) 1.73 nM),
was used as a term of comparison. It should be noted
that the corresponding amino compound 1-(2-meth-
oxyphenyl)piperazine derivative 35 showed a slight
decrease in affinity (IC50 ) 10 nM) whereas the amino
compound of the 1-phenylpiperazine derivative 34 showed
a more remarkable decrease (IC50 ) 53 nM). Regarding
the selectivity versus D-2 and R1 receptors, we observed
the same behavior as above; in fact, the amino deriva-
tive of 1-(2-methoxyphenyl)piperazine showed a higher
selectivity than the corresponding reference compound
7, whereas for derivative 34 the selectivity was lower.
For the amido derivatives with four atoms in the
spacer, both those derived from 1-aminotetralin, 38-
40, and those derived from 1-tetrahydronaphthoic acid,
22-24, showed lower affinity for 5-HT1A receptor than
the corresponding amino compounds 34 and 35. How-
ever, among these amido compounds, the 1-(2-meth-
oxyphenyl)piperazine derivatives showed moderate af-
finities (IC50 ) 35-38 nM), whereas the others proved
to have low affinity, and the relative selectivity values
were very poor. The insertion of the methyl group on
the amide function, as in 28 and 29, led to no advantage
for affinity. The displacement of the amino group in
the intermediate chain from the R position, as in 34, to
the â position, as in 31, led to a decrease in affinity.
The lengthening of the intermediate chain from four to
five atoms in amido derivatives 25-27 and 30 led to a
significant improvement in the affinity for 5-HT1A
receptor, and in this group also, the 1-(2-methoxyphe-
nyl)piperazine derivative 26 showed the highest affinity
(IC50 ) 16 nM). As for the affinity for D-1 and 5-HT2
receptors, the IC50 values were very high, making it
impossible to carry out a structure-activity relationship
(SAR).
In conclusion, in comparison with the arylpiperazine
derivatives 4-7,1 bearing a methylene spacer, of which

1-Aryl-4-[(1-tetralinyl)alkyl]piperazines
J ournal of Medicinal Chemistry, 1996, Vol. 39, No. 16 3199
N-[2-(4-P h en ylp ip er a zin -1-yl)eth yl]-5-m eth oxy-1,2,3,4-
tetr a h yd r on a p h th a len e-1-ca r boxa m id e (22). This com-
pound was prepared in a 73% yield from 4-(2-aminoethyl)-1-
phenylpiperazine (11) (0.68 g, 3.3 mmol) according to the
general procedure: 1H NMR (CDCl3) 1.57-1.87 and 2.28-2.37
(mm, 4H, endo CH2CH2), 2.41-2.58 and 2.65-2.81 [mm, 8H,
benzyl CH2, CH2N(CH2)2], 2.98 [br t, 4H, (CH2)2NAr], 3.24-
3.37 (m, 2H, NHCH2), 3.62-3.66 (s + t, 4H, CHCO, CH3), 6.10
(br s, 1H, NH), 6.62-7.32 (mm, 8H, aromatic); GC/MS m/ z
394 (M+ + 1, 1), 393 (M+, 5), 188 (13), 175 (100), 132 (27).
N-[2-[4-(2-Meth oxyph en yl)piper azin -1-yl]eth yl]-5-m eth -
oxy-1,2,3,4-tetr a h yd r on a p h th a len e-1-ca r boxa m id e (23).
This compound was prepared according to the general proce-
dure (59% yield) by starting from 4-(2-aminoethyl)-1-(2-meth-
oxyphenyl)piperazine (12) (0.75 g, 3.2 mmol): 1H NMR (CDCl3)
1.63-1.89 and 2.29-2.36 (mm, 4H, endo CH2CH2), 2.41-2.58
and 2.73-2.80 [mm, 8H, benzyl CH2, CH2N(CH2)2], 2.86 [br s,
4H, (CH2)2NAr], 3.26-3.32 (m, 2H, NHCH2), 3.65 (br t, 1H,
CHCO), 3.73 and 3.83 (2 s, 6H, 2 CH3), 6.09 (br s, 1H, NH),
6.68-7.14 (mm, 7H, aromatic); GC/MS m/ z 424 (M+ + 1, 5),
423 (M+, 19), 206 (13), 205 (100), 190 (17).
the 1-(2-methoxyphenyl)piperazine compound 4 was the
least selective, the insertion of an amine function into
the corresponding compound led to a slight decrease in
affinity and an increase in selectivity only in the
2-methoxyphenyl derivatives 3 and 35. By contrast, a
worsening of affinity and selectivity derives from the
insertion of an amide function, even though the length-
ening of the intermediate chain led to a lesser decrease
in affinity, as in the case of derivatives with five atoms
in the spacer, 25-27, and in particular for the 1-(2-
methoxyphenyl)piperazine compound 26. It can there-
fore be stated that, unlike the buspirone analogues and
in agreement with Al-Bermawy,10 for the amido deriva-
tives in this paper, the terminal amide function of long-
chain piperazines is not important for binding, and its
removal yields high-affinity 5-HT1A receptor agents.
Exp er im en ta l Section
N -[2-[4-(2-P yr id yl)p ip e r a zin -1-yl]e t h yl]-5-m e t h oxy-
1,2,3,4-tetr a h yd r on a p h th a len e-1-ca r boxa m id e (24). This
compound was synthesized from 4-(2-aminoethyl)-1-(2-py-
ridyl)piperazine (13) (0.62 g, 3.0 mmol) according to the general
procedure (73% yield): 1H NMR (CDCl3) 1.58-1.93 and 2.28-
2.36 (mm, 4H, endo CH2CH2), 2.38-2.82 [mm, 8H, benzyl CH2,
CH2N(CH2)2], 3.24-3.44 [mm, 6H, (CH2)2NAr, NHCH2], 3.63-
3.68 (s + t, 4H, CHCO, CH3), 6.04 (br s, 1H, NH), 6.58-7.48
(mm, 6H, aromatic), 8.16-8.18 (m, 1H, aromatic NdCH); GC/
MS m/ z 395 (M+ + 1, 9), 394 (M+, 32), 232 (22), 176 (100),
147 (38), 127 (29), 121 (60).
N-[3-(4-P h en ylp ip er a zin -1-yl)-n -p r op yl]-5-m et h oxy-
1,2,3,4-tetr a h yd r on a p h th a len e-1-ca r boxa m id e (25). Us-
ing the general procedure described above, from 4-(3-amino-
n-propyl)-1-phenylpiperazine (14) (1.05 g, 4.8 mmol), this
compound was obtained in a 68% yield: 1H NMR (CDCl3)
1.63-1.95 and 2.12-2.22 (mm, 6H, endo CH2CH2, CH2CH2-
CH2), 2.50-2.75 [mm, 8H, benzyl CH2, CH2N(CH2)2], 3.16 [br
t, 4H, (CH2)2NAr], 3.22-3.40 (m, 2H, NHCH2), 3.64 (t, 1H, J
) 5.5 Hz, CHCO), 3.68 (s, 3H, CH3), 6.34 (br t, 1H, NH), 6.63-
7.30 (mm, 8H, aromatic); GC/MS m/ z 408 (M+ + 1, 10), 407
(M+, 37), 392 (67), 289 (21), 275 (100), 246 (45), 175 (41), 161
(39).
N-[3-[4-(2-Meth oxyp h en yl)p ip er a zin -1-yl]-n -p r op yl]-5-
m e t h oxy-1,2,3,4-t e t r a h yd r on a p h t h a le n e -1-ca r b oxa m -
id e (26). This compound was prepared from 4-(3-amino-n-
propyl)-1-(2-methoxyphenyl)piperazine (15) (0.90 g, 3.6 mmol)
according to the general procedure (72% yield): 1H NMR
(CDCl3) 1.69-1.96 and 2.13-2.22 (mm, 6H, endo CH2CH2,
CH2CH2CH2), 2.45-2.77 [mm, 8H, benzyl CH2, CH2N(CH2)2],
2.96 [br s, 4H, (CH2)2NAr], 3.28-3.35 (m, 2H, NHCH2), 3.65
(t, 1H, J ) 5.4 Hz, CHCO), 3.72 and 3.83 (2 s, 6H, 2 CH3),
6.26 (br t, 1H, NH), 6.66-7.14 (mm, 7H, aromatic); GC/MS
m/ z 438 (M+ + 1, 15), 437 (M+, 53), 423 (27), 422 (100), 288
(32), 276 (26), 275 (87), 246 (44), 205 (73), 190 (32), 161 (35).
N-[3-[4-(2-P yr idyl)piper azin -1-yl]-n -pr opyl]-5-m eth oxy-
1,2,3,4-tetr a h yd r on a p h th a len e-1-ca r boxa m id e (27). This
compound was synthesized as above from 4-(3-amino-n-pro-
pyl)-1-(2-pyridyl)piperazine (16) (1.06 g, 4.8 mmol) (64%
yield): 1H NMR (CDCl3) 1.57-1.94 and 2.15-2.27 (mm, 6H,
endo CH2CH2, CH2CH2CH2), 2.30-2.74 [mm, 8H, benzyl CH2,
CH2N(CH2)2], 3.21-3.48 [mm, 6H, (CH2)2NAr, NHCH2], 3.57-
3.77 (s + t, 4H, CHCO, CH3), 6.23 (br s, 1H, NH), 6.56-7.48
(mm, 6H, aromatic), 8.14-8.17 (m, 1H, aromatic NdCH); GC/
MS m/ z 409 (M+ + 1, 14), 408 (M+, 51), 406 (40), 314 (43),
289 (39), 246 (68), 161 (51), 107 (100).
Ch em istr y. Column chromatographies were performed
with 1:30 ICN silica gel 60A (63-200 µm) as the stationary
phase. Melting points were determined in open capillaries on
a Gallenkamp electrothermal apparatus. Elemental analyses
were performed by the Microanalytical Section of our depart-
ment on solid samples only; the analytical results (C,H,N) were
within (0.4% of the theoretical values. 1H NMR spectra were
recorded on a Bruker AM 300 WB instrument. Chemical shifts
are reported in parts per million (ppm, δ). Recording of mass
spectra was done on a HP 5995C gas chromatograph/mass
spectrometer, electron impact 70 eV, equipped with HP59970A
workstation; only significant m/ z peaks, with their percent
relative intensity in parentheses, are herein reported. All
compounds had NMR and mass spectra that were fully
consistent with their structure.
5-Met h oxy-1,2,3,4-t et r a h yd r on a p h t h a len e-1-ca r b ox-
ylic Acid (9). A mixture of 5-methoxy-1-tetralone (8) (12.5
g, 71 mmol), zinc iodide (0.50 g), and trimethylsilyl cyanide
(25.0 g, 252 mmol) was stirred for 48 h at room temperature
under nitrogen. The reaction mixture was diluted with CHCl3
and washed with an aqueous NaHCO3 saturated solution. The
separated organic layer was dried over Na2SO4 and concen-
trated under reduced pressure to give the crude trimethylsilyl
cyanohydrin that was chromatographed (petroleum ether/ethyl
acetate, 9:1, as eluent). The trimethylsilyl cyanohydrin of 8
(18.4 g, 66.8 mmol) was heated at 140 °C for 65 h in the
presence of tin(II) chloride dihydrate (65.0 g, 288 mmol), glacial
acetic acid (60 mL), and concentrated hydrochloric acid (60
mL). The reaction mixture was cooled and diluted with 250
mL of CHCl3; then the layers were separated, and the aqueous
layer was back-extracted with ether. The basic aqueous layer
was cooled, acidified, and extracted three times with CHCl3.
The combined organic layers were dried (Na2SO4) and con-
centrated in vacuo to give a crude product that was chromato-
graphed (CH2Cl2/MeOH, 19:1, as eluent) to afford pure 9 as a
pale yellow solid (6.06 g, 44% yield): mp 105-106 °C (from
petroleum ether); 1H NMR (CDCl3) 1.72-2.51 (mm, 4H, endo
CH2CH2), 2.53-2.79 (mm, 2H, benzyl CH2), 3.76-3.87 (s +
m, 4H, CHCO, CH3), 6.71-7.15 (mm, 3H, aromatic), 10.80 (br
s, 1H, OH, D2O exchanged); GC/MS m/ z 207 (M+ + 1, 6), 206
(M+, 50), 161 (100), 160 (30), 115 (23), 91 (27).
Gen er a l P r oced u r e for th e P r ep a r a tion of Am id es 22-
30. To a stirred solution of 5-methoxy-1,2,3,4-tetrahydronaph-
thalene-1-carboxylic acid (9) (0.52 g, 2.5 mmol) and DCC (0.68
g, 3.3 mmol) in CH2Cl2 was added dropwise a solution of the
appropriate amine 11-19 (3.0 mmol), in the same solvent. The
reaction mixture was stirred overnight at room temperature;
then a few milliliters of glacial acetic acid was added to
decompose the excess reagent. The insoluble urea was re-
moved by filtration, the filtrate was washed with 2 N NaOH,
and the organic layer was separated and dried over Na2SO4.
Evaporation of the solvent in vacuo provided the crude amide
which was chromatographed (CH2Cl2/MeOH, 19:1, as eluent)
to give the expected pure amides 22-30 as almost white to
pale yellow semisolids.
N-Meth yl-N-[2-(4-p h en ylp ip er a zin -1-yl)eth yl]-5-m eth -
oxy-1,2,3,4-tetr a h yd r on a p h th a len e-1-ca r boxa m id e (28).
This compound was obtained in a 68% yield according to the
general procedure starting from 4-[2-(methylamino)ethyl]-1-
phenylpiperazine (17) (1.45 g, 6.6 mmol): 1H NMR (DMSO-
d6)20 1.56-1.91 (mm, 4H, endo CH2CH2), 2.53-2.67 [mm, 8H,
benzyl CH2, CH2N(CH2)2], 2.90 and 3.13 (2 s, 3H, NCH3), 3.11
[br t, 4H, (CH2)2NAr], 3.32-3.41 and 3.56-3.69 [2 m, 2H,
N(CH3)CH2], 3.74 (s, 3H, OCH3), 4.11 (br s, 1H, CHCO), 6.50-

3200 J ournal of Medicinal Chemistry, 1996, Vol. 39, No. 16
Perrone et al.
7.22 (mm, 8H, aromatic); GC/MS m/ z 408 (M+ + 1, 3), 407
(M+, 13), 188 (31), 175 (100), 132 (21).
1-(2-Meth oxyp h en yl)-4-[N-(5-m eth oxy-1,2,3,4-tetr a h y-
d r on a p h th a len -1-yl)-3-a m in o-n -p r op yl]p ip er a zin e (35):
1H NMR (CDCl3) 1.68-1.97 (mm, 7H, endo CH2CH2, CH2CH2-
CH2, NH, 1H, D2O exchanged), 2.44-2.84 [mm, 10H, NHCH2,
CH2N(CH2)2, benzyl CH2], 3.06 [br s, 4H, (CH2)2NAr], 3.73 (br
t, 1H, CHNH), 3.78 and 3.84 (2 s, 6H, 2 CH3), 6.67-7.14 (mm,
7H, aromatic); GC/MS m/ z 410 (M+ + 1, 1), 409 (M+, 3), 261
(29), 247 (59), 245 (31), 219 (35), 205 (100), 190 (46), 161 (87).
1-(2-Meth oxyph en yl)-4-[2-[N-(5-m eth oxy-1,2,3,4-tetr ah y-
d r on a p h th a len -1-yl)m eth yla m in o]eth yl]p ip er a zin e (36).
To a solution of 1-(2-methoxyphenyl)-4-[N-(5-methoxy-1,2,3,4-
tetrahydronaphthalen-1-yl)-2-aminoethyl]piperazine (3) (2.01
g, 5.1 mmol) in 50 mL of CHCl3 was added 50 mL of 2.4%
aqueous NaOH. Then methyl chloroformate (0.79 mL, 10.2
mmol) in CHCl3 was added dropwise to the ice-cooled mixture,
under vigorous stirring. The cold mixture was stirred for 1 h
and then acidified with 6 N HCl and stirred at 25 °C for 0.5 h.
The layers were separated, and the aqueous portion was
extracted with CHCl3. The organic portions were combined,
washed first with aqueous NaHCO3 and then with water, dried
over Na2SO4, and concentrated under reduced pressure to yield
the oily carbamate derivative. To a stirred suspension of
LiAlH4 (0.39 g, 10.3 mmol) in anhydrous THF was added a
solution of the carbamate derivative in the same solvent. The
mixture was refluxed for 24 h and then cooled, and the excess
reagent was decomposed with a few drops of water. The
mixture was filtered and the filtrate concentrated under
reduced pressure. The residue was diluted with CHCl3 and
washed with water. The separated organic layer was dried
over Na2SO4 and evaporated in vacuo to afford the N-
methylated derivative 36 (1.76 g, 84% yield): 1H NMR (CDCl3)
1.53-1.62 and 1.93-2.05 (mm, 4H, endo CH2CH2), 2.27 (s, 3H,
NCH3), 2.38-2.81 [mm, 10H, NHCH2, CH2N(CH2)2, benzyl
CH2], 3.08 [br s, 4H, (CH2)2NAr], 3.79 and 3.90 (m + 2 s, 7H,
2 CH3, CHNH), 6.65-7.35 (mm, 7H, aromatic); GC/MS m/ z
410 (M+ + 1, 1), 409 (M+, 4), 205 (31), 204 (25), 161 (100).
N-(5-Meth oxy-1,2,3,4-tetr a h yd r on a p h th a len -1-yl)br o-
m oa ceta m id e (20). A cooled solution of 5-methoxy-1,2,3,4-
tetrahydro-1-naphthalenamine (10) (2.50 g, 14.1 mmol) in
CH2Cl2, was stirred vigorously with 2% aqueous NaOH (18.3
mmol) while bromoacetyl chloride (1.59 mL, 18.3 mmol) in CH2-
Cl2 was added dropwise. The same NaOH solution was then
used in drops to maintain pH at 9, and at costant pH the layers
were separated. The organic phase was washed with 3 N HCl
and water and then dried over Na2SO4 and evaporated under
reduced pressure. The crude residue was eluted with CHCl3
to give compound 20 as a white solid (3.23 g, 77% yield): mp
N-[2-[4-(2-Meth oxyph en yl)piper azin -1-yl]eth yl]-N-m eth -
yl-5-m eth oxy-1,2,3,4-tetr a h yd r on a p h th a len e-1-ca r boxa -
m id e (29). This compound was prepared from 1-(2-meth-
oxyphenyl)-4-[2-(methylamino)ethyl]piperazine (18) (0.72 g, 3.3
mmol) as above (78% yield): 1H NMR (DMSO-d6)20 1.59-1.92
(mm, 4H, endo CH2CH2), 2.52-2.64 [mm, 8H, benzyl CH2,
CH2N(CH2)2], 2.90 and 3.14 (2 s, 3H, NCH3), 2.94 [br s, 4H,
(CH2)2NAr], 3.34-3.39 and 3.55-3.68 [2 m, 2H, N(CH3)CH2],
3.74 and 3.76 (2 s, 6H, 2 OCH3), 4.11 (br t, 1H, CHCO), 6.51-
7.06 (mm, 7H, aromatic); GC/MS m/ z 438 (M+ + 1, 2), 437
(M+, 6), 218 (20), 205 (100), 190 (20).
N-Met h yl-N-[3-(4-p h en ylp ip er a zin -1-yl)-n -p r op yl]-5-
m e t h oxy-1,2,3,4-t e t r a h yd r on a p h t h a le n e -1-ca r b oxa m -
id e (30). This compound was prepared according to the
general procedure (60% yield) from 4-[3-(methylamino)-n-
propyl]-1-phenylpiperazine (19) (1.35 g, 5.8 mmol): 1H NMR
(DMSO-d6)20 1.57-1.89 (mm, 6H, endo CH2CH2, CH2CH2CH2),
2.27-2.64 [mm, 8H, benzyl CH2, CH2N(CH2)2], 2.87 and 3.12
(2 s, 3H, NCH3), 3.04-3.11 [mm, 4H, (CH2)2NAr], 3.35 and
3.49 [2 br t, 2H, N(CH3)CH2], 3.74 and 3.75 (2 s, 3H, OCH3),
4.11 and 4.18 (2 br t, 1H, CHCO), 6.43-7.21 (mm, 8H,
aromatic); GC/MS m/ z 422 (M+ + 1, 7), 421 (M+, 25), 419 (30),
406 (47), 303 (29), 289 (100), 260 (73), 258 (27), 175 (38), 161
(61).
4-[N-[(5-Met h oxy-1,2,3,4-t et r a h yd r on a p h t h a len -1-yl)-
m eth yl]-2-a m in oeth yl]-1-p h en ylp ip er a zin e (31). To a
stirred suspension of LiAlH4 (0.10 g, 2.6 mmol) in anhydrous
THF (20 mL) was added amide 22 (1.02 g, 2.6 mmol), in the
same solvent. The reaction mixture was refluxed for 2 h.
After cooling, a few drops of water was added, the suspension
was filtered, and the filtrate was concentrated under reduced
pressure. The residue was diluted with water and extracted
twice with CH2Cl2. The separated organic layers were dried
over Na2SO4 and concentrated under reduced pressure to give
a crude residue which was chromatographed (CH2Cl2/MeOH,
19:1, as eluent). Pure 31 was a pale yellow oil (0.45 g, 46%
yield): 1H NMR (CDCl3) 1.74-1.87 (mm, 4H, endo CH2CH2),
2.49-2.75 [mm, 9H, benzyl CH2, CH2N(CH2)2, NH, 1H, D2O
exchanged], 2.87 (br t, 2H, NHCH2CH2), 2.93 (d, 2H, J ) 3.4
Hz, CHCH2NH), 3.08-3.10 (mm, 5H, (CH2)2NAr, CHCH2NH),
3.75 (s, 3H, CH3), 6.62-7.31 (mm, 8H, aromatic); GC/MS m/ z
380 (M+ + 1, 1), 379 (M+, 3), 261 (22), 247 (21), 218 (60), 176
(37), 175 (100).
Gen er a l P r oced u r e for th e P r ep a r a tion of Am in es 32-
35. The following compounds were prepared and purified
according to the method described for compound 3,1 starting
from 5-methoxy-1-tetralone (8) and 4-(2-aminoethyl)-1-phe-
nylpiperazine (11), 4-(2-aminoethyl)-1-(2-pyridyl)piperazine
(13), 4-(3-amino-n-propyl)-1-phenylpiperazine (14), and 4-(3-
amino-n-propyl)-1-(2-methoxyphenyl)piperazine (15), respec-
tively.
1
166-167 °C (from CHCl3/n-hexane); H NMR (CDCl3) 1.73-
1.93 and 1.95-2.05 (mm, 4H, endo CH2CH2), 2.55-2.75 (m,
2H, benzyl CH2), 3.81 (s, 3H, CH3), 3.88 (s, 2H, CH2Br), 5.08-
5.14 (m, 1H, CHNH), 6.67-7.18 (mm, 4H, aromatic, NH); GC/
MS m/ z 299 (M+ + 2, 3), 297 (M+, 3), 176 (14), 160 (100), 159
(26).
4-[N-(5-Meth oxy-1,2,3,4-tetr a h yd r on a p h th a len -1-yl)-2-
a m in oeth yl]-1-p h en ylp ip er a zin e (32): 1H NMR (CDCl3)
1.68-1.98 (mm, 5H, endo CH2CH2, NH, 1H, D2O exchanged),
2.48-2.88 [mm, 10H, CH2CH2N(CH2)2, benzyl CH2], 3.18 [br
t, 4H, (CH2)2NAr], 3.75-3.79 (s + t, 4H, CH3, CHNH), 6.68-
7.29 (mm, 8H, aromatic); GC/MS m/ z 366 (M+ + 1, 1), 365
(M+, 3), 176 (56), 175 (78), 162 (20), 161 (100), 132 (37).
4-[N-(5-Meth oxy-1,2,3,4-tetr a h yd r on a p h th a len -1-yl)-2-
a m in oeth yl]-1-(2-p yr id yl)p ip er a zin e (33): 1H NMR (CDCl3)
1.68-2.01 (mm, 5H, endo CH2CH2, NH, 1H, D2O exchanged),
2.48-2.88 [mm, 10H, CH2CH2N(CH2)2, benzyl CH2], 3.51 [br
t, 4H, (CH2)2NAr], 3.55-3.79 (s + t, 4H, CH3, CHNH), 6.58-
7.48 (mm, 6H, aromatic), 8.16-8.18 (m, 1H, aromatic NdCH);
GC/MS m/ z 367 (M+ + 1, 2), 366 (M+, 9), 177 (23), 176 (100),
161 (72), 147 (44), 121 (76).
4-[N-(5-Meth oxy-1,2,3,4-tetr a h yd r on a p h th a len -1-yl)-3-
am in o-n -pr opyl]-1-ph en ylpiper azin e (34): 1H NMR (CDCl3)
1.69-1.98 (mm, 7H, endo CH2CH2, CH2CH2CH2, NH, 1H, D2O
exchanged), 2.41-2.85 [mm, 10H, NHCH2, CH2N(CH2)2, benzyl
CH2], 3.16 [br t, 4H, (CH2)2NAr], 3.70-3.81 (s + t, 4H, CH3,
CHNH), 6.66-7.28 (mm, 8H, aromatic); GC/MS m/ z 380 (M+
+ 1, 1), 379 (M+, 6), 247 (72), 245 (33), 189 (33), 176 (47), 175
(92), 161 (100), 160 (30).
N-(5-Meth oxy-1,2,3,4-tetr ah ydr on aph th alen -1-yl)-3-ch lo-
r op r op a n a m id e (21). This compound was prepared from
compound 10 (5.12 g, 28.9 mmol), 2% aqueous NaOH (37.7
mmol), and 3-chloropropionyl chloride (3.60 mL, 37.7 mmol)
as for compound 20. The crude residue was chromatographed
(CHCl3/ethyl acetate, 9:1, as eluent) to give compound 21 as a
white solid (5.52 g, 71% yield): mp 167-168 °C (from Et2O);
1H NMR (CDCl3) 1.73-2.01 (mm, 4H, endo CH2CH2), 2.52-
2.73 (m + t, 4H, benzyl CH2, COCH2), 3.73-3.86 (m + s, 5H,
CH3, CH2Cl), 5.12-5.18 (m, 1H, CHNH), 5.95 (br d, 1H, NH),
6.69-7.15 (mm, 3H, aromatic); GC/MS m/ z 269 (M+ + 2, 2),
268 (M+ + 1, 1), 267 (M+, 5), 160 (100), 159 (25).
N-(5-Meth oxy-1,2,3,4-tetr ah ydr on aph th alen -1-yl)-4-ph e-
n ylp ip er a zin oa ceta m id e (37). The derivative 20 (2.03 g,
6.8 mmol) was refluxed overnight with 1-phenylpiperazine
(2.21 g, 13.6 mmol) and a slight excess of NaHCO3 in
acetonitrile. After cooling, the mixture was concentrated
under reduced pressure, and the residue was taken up with
water and extracted with CHCl3. The chloroform phase was
dried over Na2SO4, the solvent was evaporated, and the crude
residue was chromatographed (CH2Cl2/MeOH, 19:1, as eluent)
to give 37 as a pale yellow semisolid (2.47 g, 96% yield): 1H
NMR (CDCl3) 1.72-1.86 and 1.97-2.04 (mm, 4H, endo CH2-

1-Aryl-4-[(1-tetralinyl)alkyl]piperazines
J ournal of Medicinal Chemistry, 1996, Vol. 39, No. 16 3201
CH2), 2.56-2.73 [mm, 6H, benzyl CH2, CH2N(CH2)2], 3.11 [br
s, 6H, (CH2)2NAr, CH2N(CH2)2], 3.80 (s, 3H, CH3), 5.15-5.28
(m, 1H, CHNH), 6.70-7.26 (mm, 8H, aromatic), 7.37 (br d,
1H, NH); GC/MS m/ z 380 (M+ + 1, 6), 379 (M+, 25), 175 (100),
161 (26), 132 (26).
N-(5-Meth oxy-1,2,3,4-tetr ah ydr on aph th alen -1-yl)-4-ph e-
n ylp ip er a zin op r op a n a m id e (38). This compound was ob-
tained as described for compound 37 (0.92 g, 59% yield)
starting from derivative 21 (1.44 g, 3.9 mmol) and 1-phe-
nylpiperazine (1.27 g, 7.8 mmol): 1H NMR (CDCl3) 1.72-1.96
(mm, 4H, endo CH2CH2), 2.42 [t, 2H, J ) 6.0 Hz, CH2N(CH2)2],
2.46-2.60 [mm, 6H, benzyl CH2, CH2N(CH2)2], 2.66 (t, 2H, J
) 5.9, COCH2), 2.80-2.95 [mm, 4H, (CH2)2NAr], 3.69 (s, 3H,
CH3), 5.05-5.11 (m, 1H, CHNH), 6.61-7.26 (mm, 8H, aro-
matic), 8.70 (br d, 1H, NH); GC/MS m/ z 394 (M+ + 1, 8), 393
(M+, 29), 378 (60), 275 (24), 161 (100), 160 (27).
N-(5-Meth oxy-1,2,3,4-tetr a h yd r on a p h th a len -1-yl)-4-(2-
m eth oxyp h en yl)p ip er a zin op r op a n a m id e (39). This com-
pound was prepared according to the method described for
compound 38 (1.40 g, 52% yield) starting from 21 (1.67 g, 6.2
mmol) and 1-(2-methoxyphenyl)piperazine (2.38 g, 12.4
mmol): 1H NMR (CDCl3) 1.72-1.94 (mm, 4H, endo CH2CH2),
2.41 [t, 2H, J ) 6.0 Hz, CH2N(CH2)2], 2.47-2.80 [mm, 12H,
benzyl CH2, CH2N(CH2)2, (CH2)2NAr, COCH2], 3.74 and 3.81
(2 s, 6H, 2 CH3), 5.05-5.11 (m, 1H, CHNH), 6.65-7.12 (mm,
7H, aromatic), 8.96 (br d, 1H, NH); GC/MS m/ z 424 (M+ + 1,
11), 423 (M+, 41), 409 (27), 408 (100), 205 (27), 191 (21), 161
(66), 160 (31).
N-(5-Meth oxy-1,2,3,4-tetr a h yd r on a p h th a len -1-yl)-4-(2-
p yr id yl)p ip er a zin op r op a n a m id e (40). Compound 40 was
synthesized (1.34 g, 61% yield) starting from 21 (1.50 g, 5.6
mmol) and 1-(2-pyridyl)piperazine (1.83 g, 11.2 mmol): 1H
NMR (CDCl3) 1.73-2.01 (mm, 4H, endo CH2CH2), 2.44 [t, 2H,
J ) 6.0 Hz, CH2N(CH2)2], 2.48-2.58 [mm, 6H, benzyl CH2,
CH2N(CH2)2], 2.66 (t, 2H, J ) 5.8 Hz, COCH2), 3.22-3.32 [mm,
4H, (CH2)2NAr], 3.71 (s, 3H, CH3), 5.07-5.28 (m, 1H, CHNH),
6.53-7.48 (mm, 6H, aromatic), 8.13-8.17 (m, 1H, aromatic
NdCH), 8.56 (br s, 1H, NH); GC/MS m/ z 395 (M+ + 1, 8), 394
(M+, 31), 392 (22), 300 (61), 275 (55), 176 (29), 161 (97), 160
(87), 127 (46), 121 (31), 119 (22), 107 (100).
Hyd r och lor id e Sa lts: Gen er a l P r oced u r e. The hydro-
chloride salts were prepared by adding an HCl ethereal
solution to a methanolic solution of amine. Recrystallization
solvents, crystallization formulas, and melting points are listed
in Table 1. They were obtained as white to sandy yellow
crystals or crystalline powders.
P h a r m a cologica l Meth od s. All binding studies were
performed in rat brain areas. Male Wistar rats, weighing
175-200 g, were killed by decapitation under light anesthesia
and the various brain regions dissected out very quickly on
an ice-cold plate. Depending on the receptor to be studied,
the different areas were used following the methods described
in the next paragraphs.
D-1 Dop a m in er gic Bin d in g Assa y. The binding assay
for D-1 dopaminergic receptors was essentially that described
by Billard et al.21 Corpora striata were homogenized in 30
vol (w/v) of ice-cold 50 mM Tris‚HCl buffer (pH 7.7 at 25 °C)
using a Polytron PT10 homogenizer (setting 5 for 20 s).
Homogenates were centrifuged twice for 10 min at 50000g with
resuspension of the pellet in fresh buffer. The final pellet was
resuspended in ice-cold Tris‚HCl (50 mM) containing 120 mM
NaCl, 5 mM KCl, 2 mM CaCl2, 1 mM MgCl2, 0.1% ascorbic
acid, and 10 µM pargyline (pH 7.1 at 37 °C). Each assay tube
contained 50 µL of drug solution, 50 µL of [3H]SCH-23390 to
achieve a final concentration of 0.4 nM, and 900 µL of
resuspended membranes (3 mg of fresh tissue). The tubes
were incubated for 15 min at 37 °C, and the incubation was
terminated by rapid filtration under vacuum through What-
man GF/B glass fiber filters. The filters were washed three
times with 5 mL of ice-cold 50 mM Tris‚HCl buffer (pH 7.7 at
25 °C). The radioactivity bound to the filters was measured
by a liquid scintillation counter. Specific [3H]SCH-23390
binding was defined as the difference between binding in the
absence or presence of 0.1 µM piflutixol.
Creese et al.22 Corpora striata were homogenized in 30 vol
(w/v) of ice-cold 50 mM Tris‚HCl buffer (pH 7.7 at 25 °C) using
a Polytron PT10 homogenizer (setting 5 for 20 s). Homoge-
nates were centrifuged twice for 10 min at 50000g with
resuspension of the pellet in fresh buffer. The final pellet was
resuspended in ice-cold Tris‚HCl (50 mM) containing 120 mM
NaCl, 5 mM KCl, 2 mM CaCl2, 1 mM MgCl2, 0.1% ascorbic
acid, and 10 µM pargyline (pH 7.1 at 37 °C). Each assay tube
contained 50 µL of drug solution, 50 µL of [3H]spiroperidol to
achieve a final concentration of 0.4 nM, and 900 µL of
resuspended membranes (3 mg of fresh tissue). The tubes
were incubated for 15 min at 37 °C, and the incubation was
terminated by rapid filtration under vacuum through What-
man GF/B glass fiber filters. The filters were washed three
times with 5 mL of ice-cold 50 mM Tris‚HCl buffer (pH 7.7 at
25 °C). The radioactivity bound to the filters was measured
by a liquid scintillation counter. Specific [3H]spiroperidol
binding was defined as the difference between binding in the
absence or presence of 1 µM (+)-butaclamol.
5-HT1A Ser oton er gic Bin d in g Assa y. The procedure used
in radioligand binding assay has been published in detail by
Hall et al.23 Hippocampus was homogenized in 30 vol (w/v) of
ice-cold 50 mM Tris‚HCl buffer (pH 7.2 at 25 °C) using a
Polytron PT10 homogenizer (setting 5 for 20 s). Homogenates
were centrifuged twice for 10 min at 50000g with resuspension
of the pellet in fresh buffer. After the second centrifugation,
the pellet was resuspended in homogenization buffer and the
suspension incubated 10 min at 37 °C. After it had been
centrifuged and washed twice more, the final pellet was
resuspended in ice-cold Tris‚HCl (50 mM) containing 4 mM
CaCl2, 0.1% ascorbic acid, and 10 µM pargyline (pH 7.4 at 25
°C). Each assay tube contained 50 µL of drug solution, 50 µL
of [3H]-8-OH-DPAT to achieve a final concentration of 0.8 nM,
and 900 µL of resuspended membranes (10 mg of fresh tissue).
The tubes were incubated for 30 min at 25 °C, and the
incubation was terminated by rapid filtration under vacuum
through Whatman GF/B glass fiber filters. The filters were
washed three times with 5 mL of ice-cold 50 mM Tris‚HCl
buffer (pH 7.2 at 25 °C). The radioactivity bound to the filters
was measured by a liquid scintillation counter. Specific [3H]-
8-OH-DPAT binding was defined as the difference between
binding in the absence or presence of 10 µM 5-HT.
5-HT2 Ser oton er gic Bin d in g Assa y. The procedure used
in radioligand binding assay has been published in detail by
Leysen et al.24 Prefrontal cortex was homogenized in 30 vol
(w/v) of ice-cold 50 mM Tris‚HCl buffer (pH 7.2 at 25 °C) using
a Polytron PT10 homogenizer (setting 5 for 20 s). Homoge-
nates were centrifuged three times for 10 min at 50000g with
resuspension of the pellet in fresh buffer. The final pellet was
resuspended in ice-cold 50 mM Tris‚HCl (pH 7.4 at 37 °C).
Each assay tube contained 50 µL of drug solution, 50 µL of
[3H]ketanserin to achieve a final concentration of 0.8 nM, and
900 µL of resuspended membranes (5 mg of fresh tissue). The
tubes were incubated for 15 min at 37 °C, and the incubation
was terminated by rapid filtration under vacuum through
Whatman GF/B glass fiber filters. The filters were washed
three times with 5 mL of ice-cold 50 mM Tris‚HCl buffer (pH
7.2 at 25 °C). The radioactivity bound to the filters was
measured by a liquid scintillation counter. Specific [3H]-
ketanserin binding was defined as the difference between
binding in the absence or presence of 1 µM methysergide.
r1-Ad r en er gic Bin d in g Assa y. The procedure used in
radioligand binding assay has been published in detail by
Greengrass and Bremner.25 Brain cortex was homogenized
in 30 vol (w/v) of ice-cold 50 mM Tris‚HCl buffer (pH 7.2 at 25
°C) using a Polytron PT10 homogenizer (setting 5 for 20 s).
Homogenates were centrifuged twice for 10 min at 50000g with
resuspension of the pellet in fresh buffer. The final pellet was
resuspended in ice-cold 50 mM Tris‚HCl (pH 7.4 at 25 C°).
Each assay tube contained 50 µL of drug solution, 50 µL of
[3H]prazosin to achieve a final concentration of 0.4 nM, and
900 µL of resuspended membranes (10 mg of fresh tissue). The
tubes were incubated for 30 min at 25 °C, and the incubation
was terminated by rapid filtration under vacuum through
Whatman GF/B glass fiber filters. The filters were washed
D-2 Dop a m in er gic Bin d in g Assa y. The procedure used
in radioligand binding assay has been published in detail by

3202 J ournal of Medicinal Chemistry, 1996, Vol. 39, No. 16
Perrone et al.
(13) Perrone, R.; Berardi, F.; Colabufo, N. A.; Tortorella, V.; Fioren-
tini, F.; Olgiati, V.; Vanotti, E.; Govoni, S. Mixed 5-HT1A/D-2
activity of a new model of arylpiperazine: 1-aryl-4-[3-(1,2-
dihydronaphthalen-4-yl)-n-propyl]piperazines. 1. Synthesis and
structure-activity relationships. J . Med. Chem. 1994, 37, 99-
104.
three times with 5 mL of ice-cold 50 mM Tris‚HCl buffer (pH
7.2 at 25 °C). The radioactivity bound to the filters was
measured by a liquid scintillation counter. Specific [3H]-
prazosin binding was defined as the difference between binding
in the absence or presence of 1 µM phentolamine.
(14) Misztal, S.; Bojarski, A.; Mackowiak, M.; Boksa, J .; Bielecka,
Z.; Mokrosz, J . L. Structure-activity relationship studies of CNS
agents. 6. Effect of terminal amide fragment on 5-HT1A and
5-HT2 receptor affinity for N-[3-(4-aryl-1-piperazinyl)propyl]
derivatives of 3,4-dihydroquinolin-2-(1H)-one and its isomeric
isoquinolinones. Med. Chem. Res. 1992, 2, 82-87.
r2-Ad r en er gic Bin d in g Assa y. The procedure used in
radioligand binding assay has been published in detail by
Perry and U’Prichard.26 Brain cortex was homogenized in 30
vol (w/v) of ice-cold 5 mM Tris‚HCl, 5 mM EDTA buffer (pH
7.3 at 25 °C) using a Polytron PT10 homogenizer (setting 5
for 20 s). Homogenates were centrifuged three times for 10
min at 50000g with resuspension of the pellet in fresh buffer.
The final pellet was resuspended in ice-cold 50 mM Tris‚HCl,
0.5 mM EDTA (pH 7.5 at 25 °C). Each assay tube contained
50 µL of drug solution, 50 µL of [3H]yohimbine to achieve a
final concentration of 1 nM, and 900 µL of resuspended
membranes (10 mg of fresh tissue). The tubes were incubated
for 30 min at 25 °C, and the incubation was terminated by
rapid filtration under vacuum through Whatman GF/B glass
fiber filters. The filters were washed three times with 5 mL
of ice-cold 50 mM Tris‚HCl, 0.5 mM EDTA buffer (pH 7.5 at
25 °C). The radioactivity bound to the filters was measured
by a liquid scintillation counter. Specific [3H]yohimbine bind-
ing was defined as the difference between binding in the
absence or presence of 10 µM phentolamine.
(15) Belletire, J . L.; Howard, H.; Donahue, K. A facile synthesis of
phenylacetic acids from aryl ketones. Synth. Commun. 1982, 12,
763-770.
(16) Perrone, R.; Berardi, F.; Leopoldo, M.; Tortorella, V.; Lograno,
M. D.; Daniele, E.; Govoni, S. 5-HT and DA receptor affinity of
arylpiperazine derivatives with terminal benzamide fragment.
Farmaco 1994, 49, 567-572.
(17) Perrone, R.; Berardi, F.; Leopoldo, M.; Tortorella, V.; Lograno,
M. D.; Daniele, E.; Govoni, S. 5-HT1A and D-2 receptor affinity
of o-methoxyphenylpiperazine derivatives with terminal benza-
mide fragment on N-4 alkyl chain. 2. Farmaco 1995, 50, 505-
510.
(18) Horner, J . K.; Skinner, W. A. A general method for selective
N-methylation of substituted tryptamines. Can. J . Chem. 1966,
44, 315-319.
(19) Sarges, R.; Tretter, J . R.; Tenen, S. S.; Weissman, A. 5,8-
Disubstituted 1-aminotetralins. A class of compounds with a
novel profile of central nervous system activity. J . Med. Chem.
1973, 16, 1003-1011.
(20) The reported NMR data were obtained at 20 °C. The appearance
of spectra recorded at higher temperatures changed as detailed
below. Compound 28: The two sharp peaks observed at δ ) 2.90
and 3.13 begin to broaden on raising the temperature; the two
peaks merged at 80 °C; the multiplet at δ ) 3.32-3.41 became
a broad peak at 70 °C that merged with signals at δ ) 3.56-
3.69 at 80 °C. Compound 29: The two sharp peaks observed at
δ ) 2.90 and 3.14 begin to broaden on raising the temperature;
the two peaks merged at 80 °C; the multiplet at δ ) 3.34-3.39
became a broad singlet at 70 °C that merged with signals at δ
) 3.55-3.68 at 80 °C. Compound 30: The two sharp peaks
observed at δ ) 2.87 and 3.12 begin to broaden on raising the
temperature; the two peaks merged at 80 °C; the two broad
triplets at δ ) 3.35 and 3.49 merged at 60 °C and coalesced at
80 °C; the two singlets at δ ) 3.74 and 3.75 coalesced at 50 °C;
the two broad triplets at δ ) 4.11 and 4.18 merged at 40 °C and
coalesced in a broad singlet at 60 °C. Therefore there is evidence
that the compounds 28-30 present two stable conformational
isomers at room temperature.
Ack n ow led gm en t. The financial support from CNR
is gratefully acknowledged.
Refer en ces
(1) For part 2, see: Perrone, R.; Berardi, F.; Colabufo, N. A.;
Leopoldo, M.; Tortorella, V.; Fiorentini, F.; Olgiati, V.; Ghiglieri,
A.; Govoni, S. High affinity and selectivity on 5-HT1A receptor
of 1-aryl-4-[(1-tetralin)alkyl]piperazines. 2. J . Med. Chem. 1995,
38, 942-949.
(2) Peroutka, S. J . The molecular pharmacology of 5-hydroxy-
tryptamine receptor subtypes. In Serotonin receptor subtypes:
basic and clinical aspect; Peroutka, S. J ., Ed.; J ohn Wiley & Sons
Ltd.: New York, 1991; pp 65-80.
(3) Audia, J . E.; Cohen, M. L. Serotonin modulators and cardiovas-
cular/gastrointestinal diseases. Annu. Rep. Med. Chem. 1991,
26, 103-112.
(4) Frazer, A.; Maayani, S.; Wolfe, B. B. Subtypes of receptors for
serotonin. Annu. Rev. Pharmacol. Toxicol. 1990, 30, 308-348.
(5) Zifa, A.; Fillion, G. 5-Hydroxytryptamine receptors. Pharmacol.
Rev. 1992, 44, 401-458.
(6) Romero, A. G.; McCall, R. B. Advances in central serotoninergics.
Annu. Rep. Med. Chem. 1992, 27, 21-30.
(7) Robertson, D. W.; Fuller, R. W. Progress in antidepressant drugs.
Annu. Rep. Med. Chem. 1991, 26, 23-32.
(21) Billard, W.; Ruperto, V.; Grosby, G.; Iorio, L. C.; Barnett, A.
Characterization of the binding of [3H]SCH-23390, a selective
D-1 receptor antagonist ligand in rat striatum. Life Sci. 1985,
35, 1885-1893.
(22) Creese, I.; Schneider, R.; Snyder, S. H. [3H]Spiroperidol labels
dopamine receptors in pituitary and brain. Eur. J . Pharmacol.
1977, 46, 377-381.
(8) Glennon, R. A. Concepts for design of 5-HT1A serotonin agonists
and antagonists. Drug Dev. Res. 1992, 26, 251-274.
(9) Raghupathi, R.; Rydelek-Fitzgerald, L.; Teitler, M.; Glennon, R.
A. Analogues of the 5-HT1A serotonin antagonist 1-(2-methoxy-
phenyl)-4-[4-(2-phthalimido)butyl]piperazine with reduced R1-
adrenergic affinity. J . Med. Chem. 1991, 34, 2633-2638.
(10) El-Bermawy, M.; Raghupathi, R.; Ingher, S. P.; Teitler, M.;
Maayani, S.; Glennon, R. A. 4-[4-(1-Noradamantanecarbox-
(23) Hall, M. D.; El Mestikawy, S.; Emerit, M.; Pichat, L.; Hamon,
M.; Gozlan, H. [3H]-8-hydroxy-2-(di-n-propylamino)-tetralin bind-
ing to pre- and postsynaptic 5-hydroxytryptamine sites in
various region of the rat brain. J . Neurochem. 1985, 44, 1685-
1695.
(24) Leysen, J . E.; Niemegeers, C. J . E.; van Nueten, J . M.; Laduron,
P. M. [3H]-Ketanserin (R 41468) a selective [3H]ligand for
serotonin 2 receptor binding sites. Mol. Pharmacol. 1981, 21,
301-314.
amido)butyl]-1-(2-methoxyphenyl)piperazine:
a high-affinity
(25) Greengrass, P.; Bremner, R. Binding characteristics of [3H]-
prazosin to rat brain R-adrenergic receptors. Eur. J . Pharmacol.
1979, 55, 323-326.
5-HT1A-selective agent. Med. Chem. Res. 1992, 2, 88-95.
(11) Cliffe, I. A.; Fletcher, A. Advances in 5-HT1A antagonist research.
Drugs Future 1993, 18, 631-642.
(12) Orjales, A.; Alonso-Cires, L.; Labeaga, L.; Corco´stegui, R. New
(2-methoxyphenyl)piperazine derivatives as 5-HT1A receptor
ligands with reduced R1-adrenergic activity. Synthesis and
structure-affinity relationships. J . Med. Chem. 1995, 38, 1273-
1277.
(26) Perry, B. D.; U’Prichard, D. C. [3H]Rauwolscine (R-yohimbine):
a specific antagonist radioligand for brain R-2-adrenergic recep-
tors. Eur. J . Pharmacol. 1981, 76, 461-464.
J M960087S