Synthesis and preliminary pharmacological evaluation of trans-2-amino-5(6)-chloro-6(5)-hydroxy-1-phenyl-2,3-dihydro-1H-indenes as dopamine receptor ligands

Article abstract of DOI:10.1016/S0014-827X(02)01206-5

A series of trans-2-amino-5(6)-chloro-6(5)-hydroxy-1-phenyl-2,3-dihydro-1H-indenes were synthesized and evaluated for their binding affinity toward D₁-like and D₂-like dopamine (DA) receptors. The affinity and selectivity of these compounds were measured in a test involving displacement of [³H]SCH 23390 or [³H]YM-09-151-2, respectively, from homogenates of porcine striatal membranes. All tested compounds were poorly effective at DA receptors (K_i nM>1000). The results suggest that introduction of chlorine substituent in five or six position of previously synthesized trans-2-amino-6(5)-hydroxy-1-phenyl-2,3-dihydro-1H-indenes decreases both D₁-like and D₂-like receptor affinity. Copyright

Full text of DOI:10.1016/S0014-827X(02)01206-5

Il Farmaco 57 (2002) 303–313
www.elsevier.com/locate/farmac
Synthesis and preliminary pharmacological evaluation of
trans-2-amino-5(6)-chloro-6(5)-hydroxy-1-
phenyl-2,3-dihydro-1H-indenes as dopamine receptor ligands
Antonio Di Stefano a,*, Piera Sozio a, Grazia Luisi a, Ivana Cacciatore a,
Barbara Mosciatti b, Barbara Costa c, Antonio Lucacchini c, Claudia Martini c,
Francesco Pinnen a
a Dipartimento di Scienze del Farmaco, Uni6ersita` ‘‘G. D’Annunzio’’, Via dei Vestini 31, 66100 Chieti, Italy
b Dipartimento di Scienze Chimiche, Uni6ersita` di Camerino, Via S. Agostino 1, 62032 Camerino (MC), Italy
c Dipartimento di Psichiatria, Neurobiologia, Farmacologia e Biotecnologie, Uni6ersita` di Pisa, 56126 Pisa, Italy
Received 22 October 2001; accepted 14 January 2002
Abstract
A series of trans-2-amino-5(6)-chloro-6(5)-hydroxy-1-phenyl-2,3-dihydro-1H-indenes were synthesized and evaluated for their
binding affinity toward D1-like and D2-like dopamine (DA) receptors. The affinity and selectivity of these compounds were
measured in a test involving displacement of [3H]SCH 23390 or [3H]YM-09-151-2, respectively, from homogenates of porcine
striatal membranes. All tested compounds were poorly effective at DA receptors (Ki nM\1000). The results suggest that
introduction of chlorine substituent in five or six position of previously synthesized trans-2-amino-6(5)-hydroxy-1-phenyl-2,3-dihy-
´
dro-1H-indenes decreases both D1-like and D2-like receptor affinity. © 2002 Editions scientifiques et me´dicales Elsevier SAS. All
rights reserved.
Keywords: N-substituted trans-2-amino-1-phenyl-2,3-dihydro-1H-indenes; Synthesis; Dopamine receptors; Binding affinity
phenyltetrahydrobenzazepine class like the prototypic
D1 selective antagonist SCH 23390 (1); its conforma-
1. Introduction
tionally restricted analogue SCH 39166 (2) was pro-
posed as a potential antipsychotic drug devoid of acute
Dopamine-mediated neurotransmission plays a role
in several psychiatric and neurological disorders and
extrapyramidal side effects [4,5]. The pharmacological
has been implicated in the action of many drugs of
profile (agonistic or antagonistic properties) of these
abuse [1]. Dopamine (DA) acts on the Central Nervous
ligands critically depends upon the nature of sub-
System (CNS) through a variety of receptors organized
stituents on the aromatic ring [6]. Furthermore, do-
in two families called D1-like and D2-like, according to
pamine analogues containing a i-phenyl moiety show
the nomenclature first proposed by Kebabian and
Calne [2]. D1-like (D1 and D5) and D2-like (D2, D3, and
D4) all belong to the superfamily of G-protein receptors
greater affinity for D1-like receptors; the i-phenyl moi-
ety is essential in conferring D1 affinity and is also a
major factor in selectivity of a drug for D1-like recep-
[3]. Most D1-like selective agents belong to the
tors versus D2-like receptors [7,8]. It was also noted
that a halogen at the ‘para’ position of the ethylamine
side chain of i-phenyldopamines increased the D1-like
affinity of antagonists [9]. Among the tetrahydroben-
* Corresponding author. Tel.: +39-0871-3555338; fax: +39-0871-
3555267.
E-mail address: adistefano@unich.it (A. Di Stefano).
´
0014-827X/02/$ - see front matter © 2002 Editions scientifiques et me´dicales Elsevier SAS. All rights reserved.
PII: S0014-827X(02)01206-5

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A. Di Stefano et al. / Il Farmaco 57 (2002) 303–313
zazepines, the 7-chloro substituent enhances D1-like
affinity and contributes to D1-like antagonistic activity
[10]. In an earlier work, Minor et al. showed that the
N-methyl-6-chloro-7-hydroxy-1-phenyl-1,2,3,4,-tetrahy-
droisoquinoline (3) had significant affinity for the D1-
like receptor [11]. Previous work in this field led us to
the discovery of a series of trans-2-amino-6(5)-hydroxy-
1-phenyl-2,3-dihydro-1H-indenes which exhibited high
and selective affinities for D1-like receptors and con-
tained the putative pharmacophore 2-phenyl-2-(3-hy-
droxyphenyl)ethylamine with a trans conformation [12];
in vivo studies indicated that these compounds cross
the blood–brain barrier and exert a central agonistic
activity. In order to further explore the structural basis
of the affinity of the trans-2-amino-1-phenyl-2,3-dihy-
dro-1H-indenes moiety, we describe here the synthesis
of trans-2-amino-6-chloro-5-hydroxy-(or 5-chloro-6-hy-
droxy)-1-phenyl-2,3-dihydro-1H-indenes (4a, 5a) as DA
receptor ligands with potential selectivity toward D1-
like receptors. The new compounds were designed to
investigate the significance of the halogen in the aro-
matic five or six positions of the trans-2-amino-6(5)-hy-
droxy-1-phenyl-2,3-dihydro-1H-indenes and to evaluate
the variation of D1-like and D2-like binding site affinity.
pared starting from 4-chloro-3-hydroxytoluene in four
steps [13]. 6-Chloro-5-methoxyindan-1-one (9) was pre-
pared from 4-substituted-3-methoxybenzaldehyde by
the usual method as shown in Scheme 1 [14]. 5-Chloro-
6-methoxyindan-1-one (10) was obtained from 3-
chloro-4-methoxybenzaldehyde as previously described
[15,16].
The new compounds were synthesized from 6-chloro-
5-methoxy (or 5-chloro-6-methoxy)-3-phenyl-1H-inde-
nes
by reaction
of
6-chloro-5-methoxy
(or
5-chloro-6-methoxy)-indan-1-one (9, 10) with phenyl-
magnesium bromide followed by stereospecific hydro-
boration; the reaction of organoboranes with hydroxy-
lamine O-sulfonic acid yielded compounds 13 and 14
(see Scheme 2). The trans configuration was established
on the basis of the cis addition mechanism of diborane
1
and the H NMR data (coupling constant of 7.93 Hz
for the hydrogens at the one- and two-positions) [17].
The di-n-propyl derivatives were obtained by alkylation
of the bases 13, 14 with the NaBH4–propionic acid
complex [18]. The N-n-propyl-N-methyl and N-allyl-N-
methyl derivatives were prepared as outlined in Scheme
3. The amines 4a–d, 5a–d were demethylated by reflu-
xing with HBr–CH3COOH 1:1. Cleavage of the
methoxyl groups of the derivatives 4e, 4f, 5e, 5f was
achieved by employing the methionine–methanesul-
fonic acid procedure [19]. The hydroxy derivatives 4a–
f, 5a–f are listed in Table 1.
3. Experimental
Melting points (m.p.) were determined on a Buchi
B-540 apparatus and are uncorrected. Microanalyses
were performed on a 1106 Carlo Erba CHN analyzer,
and the results were within (0.4%) of the calculated
1
values. H NMR spectra were recorded on a Varian
VXR 300-MHz spectrometer. Chemical shifts are re-
ported in parts per million (l) downfield from the
internal standard tetramethylsilane (Me4Si). The IR
spectra were run on a Perkin–Elmer FTIR 1600 spec-
trometer as Nujol mulls or liquid films. The identity of
all new compounds was confirmed both by elemental
analysis and NMR data; homogeneity was confirmed
by TLC on silica gel Merck 60 F254. Solutions were
routinely dried over anhydrous sodium sulfate prior to
The amine was substituted with methyl, propyl, and
allyl groups since they can modulate D1-like and D2-
like receptor affinities.
2. Chemistry
4-Chloro-3-methoxybenzaldehyde (6) was first pre-
Scheme 1. Synthetic pathway of compound 9. Reagents: (a) malonic acid, piperidine, pyiridine; (b) H2, PtO2, anhydrous MeOH; (c) SOCl2, AlCl3,
CS2.

A. Di Stefano et al. / Il Farmaco 57 (2002) 303–313
305
Scheme 2. Reagents: (a) C6H5MgBr, anhydrous Et2O, anhydrous THF; (b) NaBH4–BF3, H2NOSO3H, diglyme; (c) CH3COOH–HBr 48%; (d)
HCOOH, HCHO 38%; (e) C2H5COOH, NaBH4, anhydrous benzene.
evaporation. Chromatographic purifications were per-
formed by Merck 60 70-230 mesh ASTM silica gel
columns from Merck with the reported solvent.
7.50–7.22 (m, 3H, ArH), 6.64 (d, 1H, ArꢀCHꢁ), 3.96 (s,
3H, OCH3).
3.2. 3-(4-chloro-3-methoxy)phenyl-propanoic acid (8)
3.1. trans 4-chloro-3-Methoxycinnamic acid (7)
A solution of 7 (4.24 g, 20 mmol) in 120 ml of
anhydrous CH3OH was hydrogenated at room tempe-
rature (r.t.) over PtO2 hydrate (0.7 g) at 1 bar for 6 h.
The catalyst was removed by filtration through Celite,
and the solvent was removed by rotary evaporation to
yield a white solid, which was recrystallized from Et2O:
m.p. 113–115 °C; yield 72%; IR wmax (KBr): 1715
To the 4-chloro-3-methoxybenzaldehyde (6) (17.0 g,
0.1 mol) malonic acid (20.8 g, 0.2 mol) and pyridine (40
ml) were added. The malonic acid was dissolved by
stirring and warming in a steam bath. Piperidine (1.5
ml) was then added and the mixture was heated to
80 °C for 1 h. The material was finally heated under
reflux (109–115 °C) for an additional 3 h.
1
(CꢁO) cm−1; H NMR (CDCl3): l 11.00 (s, 1H, OH),
7.27 (m, 1H, ArH), 6.80 (m, 2H, ArH), 3.92 (s, 3H,
OCH3), 2.95 (t, 2H, J=7.63 Hz, CH2ꢀCO), 2.69 (t, 2H,
CH2Ar).
After being cooled, the reaction mixture was poured
into a large beaker with 400 ml of cold water. The
mixture was then acidified with concentrated HCl. The
white crystals were separated by suction filtration and
purified by recrystallization from methyl ethyl ketone:
3.3. 6-Chloro-5-methoxyindan-1-one (9)
1
m.p. 117–119 °C; yield 76%; H NMR (DMSO-d6): l
The mixture of propanoic acid 8 (4.28 g, 20 mmol)
and thionyl chloride (3.2 g, 27 mmol) was heated at
12.44 (s, 1H, OH), 7.56 (d, 1H, J=16.12 Hz, ꢀCHꢁ),

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A. Di Stefano et al. / Il Farmaco 57 (2002) 303–313
60 °C for 40 min. The excess thionyl chloride was
removed with a water pump and then the oily residue
was cooled. Carbon disulfide (17.5 ml) and AlCl3 (3 g,
23 mmol) were added and the reaction mixture was
stirred at r.t. for 1 h. After this time, the cold hydro-
chloric acid was added and the product was extracted
with AcOEt. The organic phase was dried and filtered,
and the residue was recrystallized from AcOEt–n-hexa-
of bromobenzene was added dropwise at r.t. The reac-
tion mixture was refluxed for 3 h.
After cooling, a solution of 9 (5.9 g, 30 mmol) was
added in 45 ml of anhydrous THF. The reaction mix-
ture was refluxed overnight. After cooling, 64 g of ice
and 1.6 g of NH4Cl were added and the mixture was
stirred for 5 min. The resulting aqueous solution was
acidified with 30 ml of HCl 2 N and extracted with
Et2O. The organic solution was dried and filtered; after
removal of the solvent a product was obtained which
was purified by column chromatography with cyclohe-
xane–AcOEt 9.5:0.5 as eluent; Rf: 0.34; m.p. 82–84 °C;
yield: 70%; 1H NMR (CDCl3): l 7.60–7.25 (m, 6H,
ArH), 7.18 (m, 1H, ArH), 6.49 (t, 1H, J=2.05 Hz,
ꢁCHꢀ), 3.95 (s, 3H, OCH3), 3.48 (d, 2H, CH2).
1
ne: m.p. 130–132 °C; yield 60%; H NMR (CDCl3): l
7.70 (m, 1H, ArH), 6.93 (m, 1H, ArH), 3.92 (s, 3H,
OCH3), 3.05 (t, 2H, J=5.86 Hz, CH2ꢀCO), 2.65 (t, 2H,
CH2Ar).
3.4. 6-Chloro-5-methoxy-1-phenyl-1H-indene (11)
To the magnetically stirred suspension of 0.97 g (40
mmol) of magnesium, 1 crystal of iodine and 20 ml of
anhydrous Et2O, 5 ml of a solution of bromobenzene
were added, obtained from 6.34 g (40 mmol) of bro-
mobenzene in 100 ml of anhydrous Et2O. The solution
became muddy by heating, then the remaining solution
3.5. 5-Chloro-6-methoxy-1-phenyl-1H-indene (12)
Compound 12 was prepared from 10 (5.9 g, 30
mmol) according to the procedure described for the
synthesis of 11.
Scheme 3. Reagents: (a) ClCOOC2H5, Et3N, anhydrous Et2O; (b) LiAlH4, anhydrous Et2O; (c) CH3COOH–HBr 48%; (d) n-C3H7I, K2CO3,
acetone; (e) CH3SO3H, methionine, HCl; (f) CH2ꢁCHꢀCH2Br, K2CO3, EtOH abs.

A. Di Stefano et al. / Il Farmaco 57 (2002) 303–313
307
Table 1
Inhibition of [3H]SCH 23390 (D1-like) and [3H]YM-09-151-2 (D2-like) binding to porcine striatal membranes of trans-2-amino-6-chloro-5-hy-
droxy-(or 5-chloro-6-hydroxy)-1-phenyl-2,3-dihydro-1H-indenes 4a–f and 5 a–f
Ki (mM) a
Compound
R
R1
R2
R3
X
D1-like
D2-like
4a
4b
4c
4d
4e
4f
5a
5b
5c
5d
5e
5f
OH
OH
OH
OH
OH
OH
Cl
Cl
Cl
Cl
Cl
Cl
Cl
Cl
Cl
Cl
Cl
OH
OH
OH
OH
OH
OH
H
CH3
H
Br
Br
Br
Br
Cl
Cl
Br
Br
Br
Br
Cl
Cl
4.2590.31
1.8890.18
5.5090.43
4.2490.35
4.2090.36
6.0590.51
3.2590.25
1.7590.19
3.0090.29
1.7690.19
5.5090.41
3.2590.31
2.5690.14
3.8090.30
1.5090.13
4.5090.33
5.0090.41
2.5090.23
4.2090.35
3.5090.28
1.5090.14
1.7790.16
2.2590.20
2.7090.22
2.1090.19
3.5390.43
NT b
CH3
n-C3H7
CH3
CH3
CH3
H
CH3
n-C3H7
CH3
CH3
CH3
n-C3H7
H
n-C3H7
CH2CHCH2
H
CH3
n-C3H7
H
n-C3H7
CH2CHCH2
Cl
Dopamine
SCH 23390
Quinpirole
8.3×10−390.7×10−3
NT
1.290.11
a The Ki values are mean9SEM of at least three experiments.
b NT=not tested.
Rf: 0.61; m.p. 84–86 °C; yield 75%; 1H NMR
(CDCl3): l 7.60–7.30 (m, 6H, ArH), 7.14 (m, 1H,
ArH), 6.58 (t, 1H, J=2.35 Hz, ꢁCHꢀ), 3.92 (s, 3H,
OCH3), 3.45 (d, 2H, CH2).
1H, J=7.50 Hz, CHꢀC), 3.65 (m, 1H, CHꢀN), 3.25
(dd, 1H, J1=15.25 Hz, J2=7.04 Hz, CH2), 2.75 (dd,
1H, J1=15.25 Hz, J2=9.38 Hz, CH2), 2.10 (bs, 2H,
NH2).
3.6. trans-2-Amino-6-chloro-5-methoxy-1-phenyl-2,3-
dihydro-1H-indene (13)
3.7. trans-2-Amino-5-chloro-6-methoxy-1-phenyl-
2,3-dihydro-1H-indene (14)
A dry flask, equipped with a dropping funnel, con-
denser and magnetic stirrer, was flushed with nitrogen.
A solution of 0.4 g (10.3 mmol) of NaBH4 in 15 ml of
diglyme was introduced, followed by 6.4 g (25 mmol) of
11. The flask was immersed in an ice–water bath and
BF3·Et2O (1.95 g, 13.75 mmol) was added dropwise.
The solution was then stirred at r.t. for 3 h. After this
time NH2OSO3H (3.2 g, 27.5 mmol) in 15 ml of
diglyme was added, and the solution was heated to
80 °C for 3 h. The solution was then cooled, treated
with 10 ml of concentrated HCl and poured into 100 ml
of water. The acidic aqueous phase was extracted with
Et2O to remove diglyme and residual boric acid. The
solution was then made strongly alkaline with NaOH 2
N and the amine was extracted with Et2O. The residue
was purified by column chromatography with CHCl3–
CH3OH 6:1 as eluent; Rf: 0.5; yield 35%; 1H NMR
(CDCl3): l 7.45–7.18 (m, 5H, ArH), 6.89 (m, 1H,
ArH), 6.76 (m, 1H, ArH), 3.94 (s, 3H, OCH3), 3.85 (d,
Compound 14 was prepared from 12 (6.4 g, 25
mmol) according to the procedure described for the
synthesis of 13.
1
Rf: 0.4; yield: 33%; H NMR (CDCl3): l 7.25–7.06
(m, 5H, ArH), 6.47 (m, 1H, ArH), 6.35 (m, 1H, ArH),
3.89 (s, 3H, OCH3), 3.72 (d, 1H, J=7.46 Hz, CHꢀC),
3.54 (m, 1H, CHꢀN), 3.07 (dd, 1H, J1=15.07 Hz,
J2=7.02 Hz, CH2), 2.69 (dd, 1H, J1=15.07 Hz, J2=
9.17 Hz, CH2), 2.08 (bs, 2H, NH2).
3.8. trans-2-Amino-6-chloro-5-hydroxy-1-phenyl-2,3
dihydro-1H-indene hydrobromide (4a)
A stirred solution of the methoxylated amine 13 (1.4
g, 5 mmol), acetic acid (10 ml) and freshly distilled 48%
HBr (10 ml) was refluxed for 4 h, and evaporated in
vacuo; the residue was dissolved in absolute EtOH and
evaporated in vacuo. The product was recrystallized
from AcOEt–Et2O.

308
A. Di Stefano et al. / Il Farmaco 57 (2002) 303–313
M.p. 220–222 °C; yield: 97%; IR wmax (KBr): 3438
3.12. trans-N,N-Dimethyl-2-amino-5-chloro-6-
methoxy-1-phenyl-2,3-dihydro-1H-indene (16)
(OH), 3046 (NH+3 ) cm−1
;
1H NMR (DMSO-d6): l
10.20 (s, 1H, OH), 8.25 (bs, 3H, NH+3 ), 7.50–7.20 (m,
5H, ArH), 6.95 (m, 1H, ArH), 6.80 (m, 1H, ArH), 4.33
(d, 1H, J=7.50 Hz, CHꢀC), 3.95 (m, 1H, CHꢀN), 3.25
(dd, 1H, J1=16.25 Hz, J2=6.88 Hz, CH2), 2.91 (dd,
1H, J1=16.25 Hz. J2=7.03 Hz, CH2).
Compound 16 was prepared from 14 (0.8 g, 3 mmol)
according to the procedure described for the synthesis
of 15.
1
Rf: 0.77; yield: 86%; H NMR (CDCl3): l 7.50–7.20
(m, 6H, ArH), 6.53 (m, 1H, ArH), 4.78 (d, 1H, J=4.39
Hz, CHꢀC), 4.30 (m, 1H, CHꢀN), 3.66 (s, 3H, OCH3),
3.37 (dd, 1H, J1=16.50 Hz, J2=7.30 Hz, CH2), 3.15
(dd, 1H, J1=16.50 Hz, J2=4.62 Hz, CH2), 2.63 (s, 6H,
CH3).
3.9. trans-2-Amino-5-chloro-6-hydroxy-1-phenyl-
2,3-dihydro-1H-indene hydrobromide (5a)
Compound 5a was prepared from 14 (1.4 g, 5 mmol)
according to the procedure described for the synthesis
of 4a.
M.p. 298–300 °C; yield: 97%; IR wmax (KBr): 3429
(OH), 3020 (NH+3 ) cm−1; 1H NMR (DMSO-d6): l 9.95
(s, 1H, OH), 8.23 (bs, 3H, NH+3 ), 7.45–7.15 (m, 6H,
ArH), 6.40 (m, 1H, ArH), 4.33 (d, 1H, J=7.87 Hz,
CHꢀC), 3.95 (m, 1H, CHꢀN), 3.31 (dd, 1H, J1=14.75
Hz, J2=7.18 Hz, CH2), 2.87 (dd, 1H, J1=14.75 Hz,
J2=7.50 Hz, CH2).
3.13. trans-N,N-Dimethyl-2-amino-5-chloro-6-
hydroxy-1-phenyl-2,3-dihydro-1H-indene hydrobromide
(5b)
Compound 5b was prepared from 16 according to the
procedure described for the synthesis of 4a.
M.p. 187–189 °C; yield: 85%; IR wmax (KBr): 3409
(OH), 3159 (NH+) cm−1 1H NMR (DMSO-d6): l
;
10.26 (s, 1H, OH), 10.00 (bs, 1H, NH+), 7.45–7.20 (m,
6H, ArH), 6.34 (m, 1H, ArH), 4.69, (d, 1H, J=5.88
Hz, CHꢀC), 4.31 (m, 1H, CHꢀN), 3.35 (dd, 1H, J1=
17.60 Hz, J2=7.12 Hz, CH2), 3.19 (dd, 1H, J1=17.60
Hz, J2=7.05 Hz, CH2), 2.82 and 2.60 (two d, 6H,
CH3).
3.10. trans-N,N-Dimethyl-2-amino-6-chloro-5-
methoxy-1-phenyl-2,3-dihydro-1H-indene (15)
A suspension of methoxylated amine 13 (0.8 g, 3
mmol) in 12 ml of 95% formic acid and 8 ml of 38%
formaldehyde was stirred at reflux for 4, during which
time a solution formed. The volatiles were evaporated
in vacuo and the residue was dissolved in CH2Cl2 and
partitioned with saturated aqueous NaHCO3. The or-
ganic phase was dried and evaporated in vacuo to
afford a crude product which was purified by column
chromatography with CHCl3–CH3OH 6:1 as eluent.
3.14. trans-N,N-di-n-Propyl-2-amino-6-chloro-5-
methoxy-1-phenyl-2,3-dihydro-1H-indene (17)
To the magnetically stirred solution of amine 13 (2.3
g, 8.4 mmol) in anhydrous benzene (40 ml) sodium
borohydride (3.15 g, 84 mmol) was added and then
propionic acid (10.4 g, 140 mmol). The mixture was
refluxed for 3 h and after cooling was basified with
NaOH 2 N. The organic phase was evaporated and the
oily residue purified by column chromatography with
CHCl3–CH3OH 6:1 as eluent.
1
Rf: 0.77; yield: 95%; H NMR (CDCl3): l 7.38–7.15
(m, 5H, ArH), 6.83 (m, 1H, ArH), 6.77 (m, 1H, ArH),
4.27 (d, 1H, J=7.04 Hz, CHꢀC), 3.90 (s, 3H, OCH3),
3.47 (m, 1H, CHꢀN), 3.18 (dd, 1H, J1=16.12 Hz,
J2=7.62 Hz, CH2), 3.15 (dd, 1H, J1=16.12 Hz, J2=
7.28 Hz, CH2), 2.24 (s, 6H, CH3).
1
Rf: 0.48; yield: 71%; H NMR (CDCl3): l 7.40–7.18
(m, 5H, ArH), 6.84 (m, 2H, ArH), 4.09 (d, 1H, J=4.69
Hz, CHꢀC), 3.90 (s, 3H, OCH3), 3.78 (m, 1H, CHꢀN),
3.55 (dd, 1H, J1=16.40 Hz, J2=7.15 Hz, CH2), 2.80
(dd, 1H, J1=16.40 Hz, J2=4.51 Hz, CH2), 2.56 (m,
4H, NꢀCH2ꢀC), 1.46 (m, 4H, NꢀCꢀCH2ꢀC), 0.85 (s,
6H, CH3).
3.11. trans-N,N-Dimethyl-2-amino-6-chloro-5-
hydroxy-1-phenyl-2,3-dihydro-1H-indene hydrobromide
(4b)
The methoxylated dimethylamine 15 was converted
into 4b according to the procedure described for the
synthesis of 4a.
3.15. trans-N,N-di-n-Propyl-2-amino-6-chloro-5-
hydroxy-1-phenyl-2,3-dihydro-1H-indene hydrobromide
(4c)
1
M.p. 211–213 °C; yield: 83%; H NMR (DMSO-d6):
l 10.23 (s, 1H, OH), 10.03 (bs, 1H, NH+), 7.48–7.20
(m, 5H, ArH), 6.96 (m, 1H, ArH), 6.68 (m, 1H, ArH),
4.70, (d, 1H, J=4.44 Hz, CHꢀC), 4.32 (m, 1H, CHꢀN),
3.42 (dd, 1H, J1=15.50 Hz, J2=7.99 Hz, CH2), 3.22
(dd, 1H, J1=15.50 Hz, J2=6.00 Hz, CH2), 2.92 and
2.60 (two d, 6H, 2CH3).
The methoxylated dipropylamine 17 was converted
into hydroxylated 4c according to the procedure des-
cribed for the synthesis of 4a.
M.p. 216–218 °C; yield: 70%; IR wmax (KBr): 3382
(OH), 3162 (NH+) cm−1 1H NMR (DMSO-d6): l
;

A. Di Stefano et al. / Il Farmaco 57 (2002) 303–313
309
10.18 (s, 1H, OH), 8.90 (bs, 1H, NH+), 7.40–7.18 (m,
5H, ArH), 6.90 (m 1H, ArH), 6.72 (m 1H, ArH), 4.44
(d, 1H, J=6.10 Hz, CHꢀC), 4.12 (m, 1H, CHꢀN), 3.22
(dd, 1H, J1=14.69 Hz, J2=7.10 Hz, CH2), 3.06 (dd,
1H, J1=14.69 Hz, J2=6.12 Hz, CH2), 2.84 (m, 4H,
2NꢀCH2ꢀC), 1.70 and 1.22 (two m, 4H, NꢀCꢀCH2ꢀC),
1.07 and 0.82 (two t, 6H, NꢀCꢀCꢀCH3).
(dd, 1H, J1=16.32 Hz, J2=5.71 Hz, CH2), 1.22 (t, 3H,
CH3).
3.19. trans-5-Chloro-6-methoxy-1-phenyl-2-[(ethoxy-
carbonyl)amino]-2,3-dihydro-1H-indene (20)
Compound 20 was prepared from 14 (3 g, 11 mmol)
according to the procedure described for the synthesis
of 19.
3.16. trans-N,N-di-n-Propyl-2-amino-5-chloro-6-
methoxy-1-phenyl-2,3-dihydro-1H-indene (18)
M.p. 128–129 °C; yield: 87%; IR wmax (KBr): 3337
1
(NH), 1650 (CꢁO) cm−1; H NMR (CDCl3): l 7.38–
7.18 (m, 6H, ArH), 6.49 (m, 1H, ArH), 5.02 (bs, 1H,
NH), 4.23 (d, 1H, J=6.86 Hz, CHꢀC), 4.12 (m, 1H,
CHꢀN), 3.90 (m, 2H, OCH2), 3.64 (s, 3H, OCH3), 3.17
(dd, 1H, J1=17.14 Hz, J2=8.57 Hz, CH2), 2.70 (dd,
1H, J1=17.14 Hz, J2=6.43 Hz, CH2), 1.09 (t, 3H,
J=6.08 Hz, CH3).
Compound 18 was prepared from 14 (2.3 g, 8.4
mmol) according to the procedure described for the
synthesis of 17.
1
Rf: 0.52; yield: 86%; H NMR (CDCl3): l 7.45–7.25
(m, 6H, ArH), 6.35 (m, 1H, ArH), 4.80 (m, 1H,
CHꢀN),4.44 (d, 1H, J=4.39 Hz, CHꢀC), 3.68 (s, 3H,
OCH3), 3.42 (dd, 1H, J1=16.50 Hz, J2=7.30 Hz,
CH2), 3.30 (dd, 1H, J1=16.50 Hz, J2=4.62 Hz, CH2),
2.98 (m, 4H, NꢀCH2ꢀC), 1.47 (m, 4H, NꢀCꢀCH2ꢀC),
0.67 (s, 6H, CH3).
3.20. trans-6-Chloro-5-methoxy-2-(methylamino)-1-
phenyl-2,3-dihydro-1H-indene (21)
A solution of 19 (3.3 g, 9.6 mmol) in anhydrous THF
(40 ml) was added dropwise to a stirred suspension of
LiAlH4 (0.7 g, 18.4 mmol) in anhydrous Et2O (70 ml)
under a nitrogen atmosphere. The mixture was heated
to 40 °C for 24 h. The reaction was then terminated by
the addition of water (0.7 ml), 15% NaOH (0.7 ml), and
finally water (2.1 ml). The solid was filtered and washed
with Et2O. The filtrates were dried and evaporated. The
oily residue was purified by column chromatography
with CHCl3–CH3OH 6:1 as eluent.
3.17. trans-N,N-di-n-Propyl-2-amino-5-chloro-6-
hydroxy-1-phenyl-2,3-dihydro-1H-indene hydrobromide
(5c)
Compound 5c was prepared from 18 according to the
procedure described for the synthesis of 4a.
M.p. 244–246 °C; yield: 83%; IR wmax (KBr): 3355
(OH), 3156 (NH+) cm−1; 1H NMR (DMSO-d6): l 9.97
(s, 1H, OH), 9.88 (bs, 1H, NH+), 7.45–7.25 (m, 6H,
ArH), 6.24 (m, 1H, ArH), 4.71 (d, 1H, J=7.34 Hz,
CHꢀC), 4.51 (m, 1H, CHꢀN), 3.40 (dd, 1H, J1=16.46
Hz, J2=7.28 Hz, CH2), 3.25 (dd, 1H, J1=16.46 Hz,
J2=6.12 Hz, CH2), 2.98 (m, 4H, 2NꢀCH2ꢀC), 1.70 and
1.24 (two m, 4H, NꢀCꢀCH2ꢀC), 0.90 and 0.45 (two t,
6H, NꢀCꢀCꢀCH3).
1
Rf: 0.54; yield: 48%; H NMR (CDCl3): l 7.40–7.18
(m, 5H, ArH), 6.83 (m, 1H, ArH), 6.77 (m, 1H, ArH),
4.06 (d, 1H, J=8.57 Hz, CHꢀC), 3.77 (s, 3H, OCH3),
3.43 (m, 1H, CHꢀN), 3.26 (dd, 1H, J1=15.42 Hz,
J2=7.71 Hz, CH2), 2.77 (dd, 1H, J1=15.42 Hz, J2=
6.43 Hz, CH2), 2.40 (s, 3H, CH3), 2.00 (bs, 1H, NH).
3.21. trans-5-Chloro-6-methoxy-2-(methylamino)-1-
phenyl-2,3-dihydro-1H-indene (22)
3.18. trans-6-Chloro-5-methoxy-1-phenyl-2-
[(ethoxycarbonyl)amino]-2,3-dihydro-1H-indene (19)
A solution of ethyl chloroformate (1.18 g, 11 mmol)
in anhydrous Et2O (15 ml) was added dropwise to a
solution of amine 13 (3 g, 11 mmol) in anhydrous Et2O
(70 ml) and triethylamine (3.1 ml, 22 mmol) cooled at
0 °C. The reaction mixture was allowed to reach r.t.
and then stirred for 1 h. Water was then added, and the
aqueous solution was extracted with CHCl3. The com-
bined organic phases were dried and evaporated. The
solid residue was recrystallized from AcOEt; m.p. 121–
123 °C; yield 80%; IR wmax (KBr): 3310 (NH), 1675
Compound 22 was prepared from 20 (3.3 g, 9.6
mmol) according to the procedure described for the
synthesis of 21.
1
Rf: 0.44; yield: 73%; H NMR (CDCl3): l 7.38–7.15
(m, 6H, ArH), 6.42 (m, 1H, ArH), 4.07, (d, 1H, J=
7.62 Hz, CHꢀC), 3.71 (s, 3H, OCH3), 3.43 (m, 1H,
CHꢀN), 3.20 (dd, 1H, J1=15.05 Hz, J2=6.74 Hz,
CH2), 2.70 (dd, 1H, J1=15.05 Hz, J2=7.62 Hz, CH2),
2.40 (s, 3H, CH3); 2.20 (bs, 1H, NH).
3.22. trans-6-Chloro-5-hydroxy-2-(methylamino)-1-
phenyl-2,3-dihydro-1H-indene Hydrobromide (4d)
1
(CꢁO) cm−1; H NMR (CDCl3): l 7.38–7.10 (m, 5H,
ArH), 6.92 (m, 1H, ArH), 6.84 (m, 1H, ArH), 4.92 (bs,
1H, NH), 4.36 (m, 1H, CHꢀN), 4.16 (m, 2H, OCH2),
4.08 (d, 1H, J=7.14 Hz CHꢀC), 3.92 (s, 3H, OCH3),
3.60 (dd, 1H, J1=16.32 Hz, J2=7.08 Hz, CH2), 2.78
Compound 4d was prepared from 21 (1.4 g, 5 mmol)
according to the procedure described for the synthesis
of 4a.

310
A. Di Stefano et al. / Il Farmaco 57 (2002) 303–313
M.p. 251–253 °C; yield: 92%; IR wmax (KBr): 3237
extracted with AcOEt. The organic extracts, washed
with aqueous NaHSO3 and water, were dried and eva-
porated. The residue was dissolved in Et2O, and HCl
gas was bubbled. The salt was recovered and dried.
M.p. 98–100 °C; yield: 60%; IR wmax (KBr): 3208
(OH), 2973 (NH+) cm−1; 1H NMR (DMSO-d6): l 8.60
(bs, 2H, NH+ e OH), 7.40–7.22 (m, 5H, ArH), 6.90 (m,
1H, ArH), 6.78 (m, 1H, ArH), 4.80 (m, 1H, CHꢀN),
4.24 (d, 1H, J=4.40 Hz, CHꢀC), 3.42 (dd, 1H, J1=
15.32 Hz, J2=6.46 Hz, CH2), 2.92 (dd, 1H, J1=15.32
Hz, J2=4.53 Hz, CH2), 2.53 (m, 2H, NꢀCH2ꢀC), 2.11
and 2.02 (two s, 3H, NꢀCH3), 1.65 and 1.42 (two m,
2H, NꢀCꢀCH2), 0.80 and 0.52 (two t, 3H,
NꢀCꢀCꢀCH3).
(OH), 3023 (NH+2 ) cm−1; 1H NMR (DMSO-d6): l 9.37
(s, 1H, OH), 8.92 (bs, 2H, NH+2 ), 7.38–7.18 (m, 5H,
ArH), 6.71 (m, 1H, ArH), 6.59 (m, 1H, ArH), 4.41 (d,
1H, J=6.10 Hz, CHꢀC), 3.97 (m, 1H, CHꢀN), 3.36
(dd, 1H, J1=17.29 Hz, J2=6.12 Hz, CH2), 3.17 (dd,
1H, J1=17.29 Hz, J2=5.71 Hz, CH2), 2.54 (t, 3H,
CH3).
3.23. trans-5-Chloro-6-hydroxy-2-(methylamino)-
1-phenyl-2,3-dihydro-1H-indene hydrobromide (5d)
Compound 5d was prepared from 22 (1.4 g, 5 mmol)
according to the procedure described for the synthesis
of 4a.
M.p. 243–245 °C; yield: 98%; IR wmax (KBr): 3228
(OH), 2986 (NH+2 ) cm−1; 1H NMR (DMSO-d6): l 9.98
(s, 1H, OH), 8.96 (bs, 2H, NH+2 ), 7.36–7.18 (m, 6H,
ArH), 6.38 (m 1H, ArH), 4.44 (d, 1H, J=6.45 Hz,
CHꢀC), 4.00 (m, 1H, CHꢀN), 3.36 (dd, 1H, J1=16.10
Hz, J2=6.85 Hz, CH2), 2.70 (dd, 1H, J1=16.10 Hz,
J2=6.14 Hz, CH2), 2.51 (t, 3H, CH3).
3.26. trans-N-Methyl-N-n-propyl-2-amino-5-chloro-
6-methoxy-1-phenyl-2,3-dihydro-1H-indene (24)
Compound 24 was prepared from 22 (1.5 g, 5.2
mmol) according to the procedure described for the
synthesis of 23.
1
Rf: 0.27; yield: 90%; H NMR (CDCl3): l 7.42–7.10
(m, 5H, ArH), 6.48 (m, 1H, ArH), 4.40 (d, 1H, J=6.23
Hz, CHꢀC), 3.79 (s, 3H, OCH3), 3.62 (m, 1H, CHꢀN),
3.19 (dd, 1H, J1=15.93 Hz, J2=8.24 Hz, CH2), 2.98
(dd, 1H, J1=15.93 Hz, J2=6.76 Hz, CH2), 2.44 (m,
2H, NꢀCH2ꢀC), 2.30 (s, 3H, CH3), 1.50 (m, 2H,
NꢀCꢀCH2ꢀC), 0.87 (t, 3H, NꢀCꢀCꢀCH3).
3.24. trans-N-Methyl-N-n-propyl-2-amino-6-chloro-
5-methoxy-1-phenyl-2,3-dihydro-1H-indene (23)
A mixture of amine 21 (1.5 g, 5.2 mmol) in acetone
(80 ml), anhydrous K2CO3 (2.15 g, 15.5 mmol), and
iodopropane (1.77 g, 10.4 mmol) was stirred to reflux
for 3 h. At the end of this period, another portion of
iodopropane (0.9 g, 10 mmol) was added and the
suspension was refluxed for 2 h. After removal of the
solvent in vacuo, water was added and the mixture
extracted with CHCl3. The combined organic extracts
were dried, filtered, and evaporated. The oily residue
was purified by column chromatography with AcOEt as
eluent. The desired fraction was collected and
evaporated.
3.27. trans-N-Methyl-N-n-propyl-2-amino-5-chloro-
6-hydroxy-1-phenyl-2,3-dihydro-1H-indene hydro-
chloride (5e)
Compound 5e was prepared from 24 (1.5 g, 5.2
mmol) according to the procedure described for the
synthesis of 4e.
M.p. 117–119 °C; yield: 65%; IR wmax (KBr): 3194
(OH), 2953 (NH+) cm−1 1H NMR (DMSO-d6): l
.
1
Rf: 0.48; yield: 71%; H NMR (CDCl3): l 7.36–7.08
8.70–8.45 (bs, 2H, NH+ e OH), 7.38–7.20 (m, 6H,
ArH), 6.50 (m, 1H, ArH), 4.88 (d, 1H, J=7.83,
CHꢀC), 4.25 (m, 1H, CHꢀN), 3.40 (dd, 1H, J1=14.06
Hz, J2=7.03 Hz, CH2), 3.20 (dd, 1H, J1=14.06 Hz,
J2=5.58 Hz, CH2), 2.89 (m, 2H, NꢀCH2ꢀC), 2.62 and
2.56 (two s, 3H, NꢀCH3), 1.70 and 1.32 (two m, 2H,
NꢀCꢀCH2ꢀC), 0.88 and 0.54 (two t, 3H, J=7.03,
NꢀCꢀCꢀCH3).
(m, 5H, ArH), 6.82 (m, 1H, ArH), 6.70 (m, 1H, ArH),
4.30 (d, 1H, J=4.38 Hz, CHꢀC), 3.88 (s, 3H, OCH3),
3.62 (m, 1H, CHꢀN), 3.18 (dd, 1H, J1=15.70 Hz,
J2=6.14 Hz, CH2), 2.92 (dd, 1H, J1=15.70 Hz, J2=
4.32 Hz, CH2), 2.40 (m, 2H, NꢀCH2ꢀC), 2.24 (s, 3H,
CH3), 1.42 (m, 2H, NꢀCꢀCH2ꢀC), 0.78 (t, 3H,
NꢀCꢀCꢀCH3).
3.25. trans-N-Methyl-N-n-propyl-2-amino-6-chloro-
5-hydroxy-1-phenyl-2,3-dihydro-1H-indene
hydrochloride (4e)
3.28. trans-N-Methyl-N-allyl-2-amino-6-chloro-5-
hydroxy-1-phenyl-2,3-dihydro-1H-indene hydrochloride
(25)
To the product 23 (1.55 g, 4.7 mmol) water (3.6 ml),
methanesulfonic acid (57 ml) and methionine (7.9 g,
53.2 mmol) were added. The mixture was stirred at
25 °C for 4 days, then poured into ice–water (65 ml)
and made basic (pH 8) with 15% NH4OH. It was then
A mixture of amine 21 (1.5 g, 5.2 mmol) in absolute
EtOH (35 ml), anhydrous K2CO3 (0.77 g, 5.6 mmol),
and allyl bromide (1.22 g, 10 mmol) was stirred at
60 °C for 3H. After removal of the solvent in vacuo,
water was added and the mixture extracted with Et2O.

A. Di Stefano et al. / Il Farmaco 57 (2002) 303–313
311
The combined organic extracts were dried, filtered, and
evaporated. The oily residue was purified by column
chromatography with AcOEt as eluent. The desired
fraction was collected and evaporated.
Hz, J2=6.62 Hz CH2), 3.28 (dd, 1H, J1=14.15 Hz,
J2=4.73 Hz, CH2), 2.50 (m, 2H, CH2ꢀC), 2.00 (s, 3H,
NꢀCH3).
1
Rf: 0.56; yield: 60%; H NMR (CDCl3): l 7.38–7.16
(m, 5H, ArH), 6.79 (s, 1H, ArH), 6.70 (s, 1H, ArH),
5.76 (m, 1H, NꢀCꢀCHꢁ), 5.06 (m, 2H, NꢀCꢀCꢁCH2),
4.30 (d, 1H, J=4.70 Hz, CHꢀC), 4.12 (m, 1H, CHꢀN),
3.78 (s, 3H, OCH3), 3.66 (dd, 1H, J1=15.65 Hz,
J2=6.38 Hz, CH2), 3.16 (dd, 1H, J1=15.65 Hz, J2=
4.32 Hz, CH2), 3.08 (m, 2H, NꢀCH2ꢀC), 2.24 (s, 3H,
NꢀCH3).
4. Pharmacological methods
4.1. Receptor radioligand binding assays: D1-like and
D2-like dopamine
[3H]YM-09-151-2 (a D2-like receptor antagonist, 85.5
Ci mmol−1) and [3H]SCH 23390 (a D1-like receptor
antagonist, 86 Ci mmol−1) were purchased from NEN
Life Science and from Amersham International, respec-
tively. Dopamine–HCl and all other reagents were
obtained from commercial suppliers.
3.29. trans-N-Methyl-N-allyl-2-amino-6-chloro-5-
hydroxy-1-phenyl-2,3-dihydro-1H-indene hydrochloride
(4f)
Striatal tissue was isolated from porcine brains. The
porcine striatal membranes were prepared as previously
described [20]. In brief, tissue was homogenized in 20
volumes of ice-cold 50 mM Tris–HCl buffer at pH 7.4
(buffer T), containing protease inhibitors (20 mg ml−1
soybean trypsin inhibitor, 200 and 160 mg ml−1 benza-
midine), using an Ultra-Turrax TP-1810 (3×20 s). The
homogenate was centrifuged for 10 min at 50 000×g,
at 4 °C. The resulting pellet was then washed once by
resuspension in fresh buffer T and centrifugation as
before. The final pellet was frozen at −20 °C until the
time of assay.
Compound 4f was prepared from 26 according to the
procedure described for the synthesis of 4e.
M.p. 102–104 °C; yield: 50%; IR wmax (KBr): 3197
(OH), 2968 (NH+) cm−1 1H NMR (DMSO-d6): l
;
11.18–11.02 (bs, 2H, NH+ e OH), 7.32–7.12 (m, 5H,
ArH), 6.90 (m, 1H, ArH), 6.74 (m, 1H, ArH), 5.86 (m,
1H, NꢀCꢀCHꢁ), 5.32 (m, 2H, NꢀCꢀCꢁCH2), 4.82 (d,
1H, J=6.80, CHꢀC), 4.15 (m, 1H, CHꢀN), 3.36 (dd,
1H, J1=15.15 Hz, J2=6.42 Hz, CH2), 3.22 (dd, 1H,
J1=15.15 Hz, J2=4.33 Hz, CH2), 2.40 (m, 2H,
NꢀCH2ꢀC), 2.02 (s, 3H, NꢀCH3).
For D1-like and D2-like receptors binding assays, the
porcine striatal pellet was suspended in buffer T and
homogenized by Ultra-Turrax. [3H]SCH 23390 binding
to D1-like receptors was assayed in a final incubation
volume of 0.5 ml, which contained crude membranes
(ꢀ0.2 mg of protein), radioligand (ꢀ0.5 nM) and the
tested compound in the range 10−8–10−4 concentra-
tions, at 30 °C for 60 min.
3.30. trans-N-Methyl-N-allyl-2-amino-5-chloro-6-
methoxy-1-phenyl-2,3-dihydro-1H-indene hydrochloride
(26)
Compound 26 was prepared from 22 according to the
procedure described for the synthesis of 25.
1
Rf: 0.56; yield: 60%; H NMR (CDCl3): l 7.40–7.12
(m, 6H, ArH), 6.39 (s, 1H, ArH), 5.77 (m, 1H,
NꢀCꢀCHꢁ), 5.08 (m, 2H, NꢀCꢀCꢁCH2), 4.40 (d, 1H,
J=4.80 Hz, CHꢀC), 3.70 (s, 3H, OCH3), 3.62 (m, 1H,
CHꢀN), 3.13 (dd, 1H, J1=14.06 Hz, J2=6.58 Hz,
CH2), 3.07 (m, 2H, NꢀCH2ꢀC), 2.97 (dd, 1H, J1=14.06
Hz, J2=4.58 Hz, CH2), 2.24 (s, 3H, NꢀCH3).
[3H]YM-09151-2 binding to D2-like receptors was
assayed in a final incubation volume of 2 ml. Striatal
membranes (ꢀ0.2 mg of protein) were incubated with
radioligand (ꢀ0.3 nM), and various concentrations
(10−8–10−4) of the tested compound, at 30 °C for 60
min. All assays were performed in duplicate.
Incubation was terminated by dilution to 5 ml with
ice-cold buffer T, followed immediately by rapid filtra-
tion through glass fiber Whatman GF/C filters. The
filters were then washed (3×5 ml) with buffer T and
the amount of radioactivity retained on the filters was
determined by a Packard 1600 TR liquid scintillation
counter at 66% efficiency. Non specific binding was
defined in the presence of 2.5 mM dopamine.
3.31. trans-N-Methyl-N-allyl-2-amino-5-chloro-6-
hydroxy-1-phenyl-2,3-dihydro-1H-indene hydrochloride
(5f)
Compound 5f was prepared from 23 (1.5 g, 5.2
mmol) according to the procedure described for the
synthesis of 4e.
M.p. 88–90 °C; yield: 55%; IR wmax (KBr): 3185
(OH), 2947 (NH+) cm−1 1H NMR (DMSO-d6): l
11.60–11.38 (bs, 2H, NH+ e OH), 7.42–7.20 (m, 6H,
ArH), 6.60 (m, 1H, ArH), 5.90 (m, 1H, NꢀCꢀCHꢁ),
5.40 (m, 2H, NꢀCꢀCꢁCH2), 4.92 (d, 1H, J=6.65,
CHꢀC), 4.22 (m, 1H, CHꢀN), 3.40 (dd, 1H, J1=14.15
The compounds were dissolved in ethanol. The level
of ethanol did not exceed 1% and was maintained
constant in all tubes. At least six different concentra-
tions of each compound were used. The IC50 values,
computer-generated using a non-linear regression for-
mula on a computer program (GraphPad, San Diego,

312
A. Di Stefano et al. / Il Farmaco 57 (2002) 303–313
CA), were converted to Ki values according to the
equation of Cheng and Prusoff [21]. Protein concentra-
tion was assayed by the method of Lowry et al. [22].
References
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[3] D.R. Sibley, F.J. Monsma Jr., Molecular biology of dopamine
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5. Results and discussion
The receptor binding properties of all final com-
pounds were evaluated for their ability to compete with
either [3H]SCH 23390 or [3H]YM 09-151-2 at D1-like
D2-like binding sites, respectively, using porcine striatal
membranes as tissue source. The values reported for the
competitive binding assays are the average of three
runs. The results of these binding studies are shown in
Table 1. In order to characterize the binding assay, DA,
SCH 23390 (D1-like antagonist) and Quinpirole (D2-
like agonist) affinities were included as well.
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