Cyanoindole derivatives as highly selective dopamine D4 receptor partial agonists: Solid-phase synthesis, binding assays, and functional experiments

Article abstract of DOI:10.1021/jm0009989

Traceless linking of diethoxymethyl (DEM)-protected 5- and 6-cyanoindoles and subsequent incorporation of phenylpiperazine derivatives led to the 2- and 3-piperazinylmethyl-substituted cyanoindoles 3a-m. Dopamine receptor binding studies on the final prod

Full text of DOI:10.1021/jm0009989

J . Med. Chem. 2000, 43, 4563-4569
4563
Brief Articles
Cya n oin d ole Der iva tives a s High ly Selective Dop a m in e D4 Recep tor P a r tia l
Agon ists: Solid -P h a se Syn th esis, Bin d in g Assa ys, a n d F u n ction a l Exp er im en ts
Harald Hu¨bner, J ohannes Kraxner, and Peter Gmeiner*
Department of Medicinal Chemistry, Emil Fischer Center, Friedrich-Alexander University, Schuhstrasse 19,
D-91052 Erlangen, Germany
Received May 31, 2000
Traceless linking of diethoxymethyl (DEM)-protected 5- and 6-cyanoindoles and subsequent
incorporation of phenylpiperazine derivatives led to the 2- and 3-piperazinylmethyl-substituted
cyanoindoles 3a -m . Dopamine receptor binding studies on the final products 3a -m clearly
indicated strong and selective recognition of the D4 subtype which is known as a promising
target for the treatment of neuropsychiatric disorders. The most interesting binding properties
were observed for the 2-aminomethyl-5-cyanoindoles FAUC 299 (3f) and FAUC 316 (3j) (Ki )
0.52 and 1.0 nM, respectively) when the fluoro derivative 3j proved extraordinary selectivity
over D1, D2long, D2short, and D3 (>8600). To determine ligand efficacy, mitogenesis experiments
were performed indicating partial agonist effects for the test compounds 3f,j (35% and 30%,
when compared to the full agonist quinpirole).
In tr od u ction
type 2 (Chart 1).9 The high affinity of the test com-
pounds (Ki values: 3.9-11 nM) preferentially adopting
s-trans geometry can be explained by the structural
similarity of the cis-cyanovinyl subunit to positions 4-7
of the lead structure 1. On the other hand, we expected
the negative region induced by a trans-positioned cyano
group to be responsible for the high subtype selectivity.
As a consequence, cyanoindole derivatives of type 3 were
selected as promising candidates being capable of strong
and selective dopamine D4 receptor recognition.
In this paper, we report the synthesis of the target
compounds 3 involving an application of our solid-phase
methodology for the traceless linking of indoles.10 The
results of dopamine receptor binding studies considering
the subtypes D1, D2long, D2short, D3, and D4 as well as
functional experiments to determine ligand efficacy are
presented.
Recent advances in molecular cloning techniques have
led to the characterization of a number of dopamine
receptor subtypes which can be divided into the D1-like
and D2-like families.1 Whereas the D1-like family com-
prises D1 and D5 subtypes, the D2-like family consists
of D2, D3, and D4 receptors.2 Due to the preferred
expression of messenger RNA for dopamine D4 receptors
in the frontal cortical and mesolimbic areas and the
finding that the neuroleptic drug clozapine binds pref-
erentially to D4 receptors,3 considerable interest has
been focused on selective D4 antagonists.4 Furthermore,
associations are emerging between D4 receptors and
specific personality traits such as novelty-seeking.5
According to very recent neuropathological and genetic
studies,6 selective dopamine D4 receptor agonists, par-
tial agonists, or antagonists might be of interest for the
treatment of neuropsychiatric disorders including at-
tention-deficit hyperactivity, mood disorders, and Par-
kinson’s disease.
Resu lts a n d Discu ssion
The solid-phase synthesis of the target compounds
3a -e was started from polymer-bound indole 5, which
was prepared according to our recently described meth-
odology for traceless linking of indoles.10 Conversion of
the immobilized indole 5 into the 3-substituted ami-
nomethyl derivatives 6a -e was accomplished under
Mannich conditions (aqueous formaldehyde, CH2Cl2,
and HOAc) employing a series of five representative
1-phenylpiperazines (Scheme 1). Subsequent hydrolysis
of the acetal linkage and release of the piperazinyl-
methylindoles 3a -e was accomplished in the presence
of 1,4-dioxane and 2 N HCl, followed by treatment with
2 N NaOH. Applying this reaction sequence, the final
products 3b-e were obtained in good yields, and the
purity of the cleaved products, verified by 1H NMR, was
found to be in the range of 81-98%. On the other hand,
yield and purity of the phenylpiperazine 3a were only
Thus, SAR studies with respect to D4 affinity, selec-
tivity, and ligand efficacy are of special current interest.
On the basis of our previous comparisons of molecular
electrostatic potential maps, we recognized that the D4
preference of test compounds of type 1 strongly depends
on a large negative region which is obviously not
tolerated by D1, D2, and D3 binding sites.7 Thus, the
substantially higher selectivity of the 7-azaindole L-745,-
8708 and the 3a- and 7a-isomers compared to indole
analogues can be explained. Employing a 2,2-dicyanovi-
nyl moiety as a nonaromatic bioisostere for the six-
membered aromatic subunit of the lead structure 1, we
have recently developed strong D4 receptor ligands of
* To whom correspondence should be addressed: Tel: +49(9131)-
8529383. Fax: +49(9131)8522585. E-mail: gmeiner@pharmazie.uni-
erlangen. de.
10.1021/jm0009989 CCC: $19.00 © 2000 American Chemical Society
Published on Web 10/21/2000

4564 J ournal of Medicinal Chemistry, 2000, Vol. 43, No. 23
Brief Articles
Ch a r t 1
Sch em e 2a
Sch em e 1a
a
Reagents and conditions: (a) TBDMSCl, imidazole, DMF, 0
°C, 0.5 h; (b) HC(OEt)3, 160 °C, 16-24 h; (c) CCl4, PPh3, DMF, rt,
16 h; (d) Bu4NF, THF, 0 °C, 0.5 h; (e) CCl4, PPh3, DMF, rt, 0.5 h;
(f) HNR2, DMF, 60 °C, 2 h; (g) polymer-bound 3-benzyloxypropane-
1,2-diol,12 1,4-dioxane, p-TosOH, rt, 3 h; (h) HNR2, DMF, 40 °C,
48 h; (i) 1. 1,4-dioxane/2 N HCl (1:1), 40 °C, 3 h, 2. 2 N NaOH, rt,
0.5 h.
a
Reagents and conditions: (a) HC(OEt)3, 160 °C, 24 h;10 (b)
polymer-bound 3-benzyloxypropane-1,2-diol,12 1,4-dioxane, p-
TosOH, rt, 3 h; (c) HNR2, aq CH2O, CH2Cl2/HOAc (4:1), rt, 0.5-6
h; (d) HNR2, aq CH2O, CH2Cl2/HOAc (1:4), 40 °C, 64 h; (e) 1. 1,4-
dioxane/2 N HCl (1:1), 40 °C, 3 h, 2. 2 N NaOH, rt, 0.5 h.
modest. Besides the solid-phase synthesis of amino-
methylindoles of type 3, allowing the generation of
indole-based combinatorial libraries, we also performed
a solution-phase synthesis when aminomethylation of
4 afforded the target compounds 3a -e.
diethoxymethylation of the indoles 10a ,b, which were
readily available from the primary alcohols 7a ,b,11
failed. The DEM (diethoxymethyl)-protected indoles
12a ,b were loaded onto the 1,2-diol functionalized
Merrifield resin12 to give the polymer-bound electro-
philes 13a ,b. Treatment of 13a ,b with different 1-phe-
nylpiperazines, followed by resin cleavage, afforded the
target compounds 3f-m in excellent yields (88-100%)
and high purity (86-98%). A solution-phase synthesis
of the final products 3f-m by nucleophilic displacement
reactions was performed based on the chlorides 10a ,b.
Receptor binding properties of the test compounds of
type 3 were determined in vitro by measuring their
ability to compete with [3H]spiperone for the cloned
Having successfully used our traceless linking meth-
odology for the synthesis of the 3-substituted compounds
3a -e, we worked out a solid-phase synthetic route for
the preparation of the 5- and 6-cyanoindole derivatives
3f-m , bearing the respective phenylpiperazinylmethyl
moiety in the indole 2-position (Scheme 2). Starting from
the alcohols 7a ,b,11 reaction with TBDMSCl and imi-
dazole afforded the O-protected products 8a ,b in 92%
yield which were subsequently heated in neat triethyl
orthoformate to give the N-diethoxymethyl-substituted
indoles 9a ,b. Fluoride-induced cleavage of the silyl
ethers 9a ,b resulted in formation of the 2-hydroxy-
methylindoles 11a ,b that could be transformed into the
chlorides 12a ,b upon treatment with CCl4 and PPh3.
An alternative approach to the intermediates 12a ,b by
human dopamine receptor subtypes D2long, D2short,
13 D3,14
15
and D4.4 stably expressed in Chinese hamster ovary
cells (CHO).16 D1 affinities were assessed via competi-
tion experiments using bovine striatal membrane prepa-
rations and the D1 selective radioligand [3H]SCH 23390.

Brief Articles
J ournal of Medicinal Chemistry, 2000, Vol. 43, No. 23 4565
Ta ble 1. Binding Data of the Cyanoindoles 3a -m and Clozapine to Human and Bovine Dopamine Receptorsa
Ki (nM) ( SEM
[3H]spiperone
positions
[3H]SCH 23390
bovine D1
b
compd
CN CH2N<
Ar
human D2long
human D2short
human D3
human D4.4
3a
5
5
5
5
5
5
5
5
5
5
6
6
6
3
3
3
3
3
2
2
2
2
2
2
2
2
Ph
3000 ( 750
510 ( 50
34000 ( 6000
1400 ( 570
790 ( 70
4300 ( 650
2400 ( 150
3100 ( 550
2300 ( 50
3500 ( 950
540 ( 230
480 ( 45
4400 ( 1200
550 ( 47
870 ( 140
6400 ( 250
5200 ( 250
1700 ( 220
1700 ( 600
50 ( 3.5 (n ) -0.9)
17 ( 1.0 (n ) -1.0)
22 ( 3.5 (n ) -1.1)
29 ( 7.5 (n ) -0.9)
110 ( 21 (n ) -0.9)
0.52 ( 0.050 (n ) -1.0)
1.4 ( 0.33 (n ) -0.9)
7.5 ( 2.0 (n ) -1.3)
2.1 ( 0.29 (n ) -1.0)
1.0 ( 0.057 (n ) -1.0)
3.6 ( 0.43 (n ) -0.9)
3.4 ( 0.87 (n ) -1.0)
9.0 ( 1.2 (n ) -1.2)
16 ( 0.50 (n ) -0.9)
3b
2-Cl-Ph
3,4-diCl-Ph
4-Cl-Ph
4-F-Ph
3c
450 ( 85
3d
550 ( 15
490 ( 35
2600 ( 1100
1800 ( 50
290 ( 30
3e
3f
Ph
13000 ( 500
7500 ( 750
11000 ( 2700
5300 ( 100
8600 ( 2400
5300 ( 1700
1900 ( 0.0
880 ( 65
3g
2-Cl-Ph
3,4-diCl-Ph
4-Cl-Ph
4-F-Ph
950 ( 30
3h
43000 ( 21000 36000 ( 12000 20000 ( 5000
3i
3j
7900 ( 2100
28000 ( 6500
5600 ( 2600
500 ( 10
2000 ( 100
41 ( 1.5
7600 ( 1800
19000 ( 4000
2500 ( 1200
220 ( 15
1400 ( 400
28 ( 0.50
13000 ( 1500
15000 ( 2000
3100 ( 650
920 ( 45
33000 ( 8500
960 ( 45
3k
3l
3m
clozapine
Ph
2-Cl-Ph
3,4-diCl-Ph
420 ( 50
a
b
Ki values are the means of 2-4 independent experiments ( SEM using 8 different concentrations each in triplicate. Steepness of
the competition curves and the derived Hill slopes gave a one-site binding model. Unless mitogenesis experiments showed partial agonist
effects for 3f,j indicating that the Ki values actually represent K0.5 values, high- and low-affinity binding sites could not be resolved using
the methodology described.
The Ki values of the test compounds were compared to
those of the atypical antipsychotic drug clozapine which
is known for its D4 preference. The characterization of
the test compounds was initiated by investigating the
3-aminomethyl-substituted derivatives 3a -e when the
4-chlorophenylpiperazine 3d showed the highest degree
of similarity to the most potent derivatives of the lead
compounds of type 1. The binding data depicted in Table
1 indicate substantial (Ki ) 29 nM) and selective D4
recognition for 3d . Exchange of the 4-chlorophenyl
group by phenyl, 2-chlorophenyl, 3,4-dichlorophenyl,
and 4-fluorophenyl resulting in analogues 3a -c,e led
only to a slight improvement of the binding affinities.
Interestingly, the test compounds 3b,c showed binding
data for the D1, D3, and D4 subtypes that are comparable
to that for clozapine; however, higher selectivity over
the D2 isoforms was determined. To improve the D4
potency, we modified the relative topicity of the cyano
and aminomethyl substituents. In contrast to recent
SAR studies with azaindoles, describing loss of affinity
after modification of the attachment position,17 strong
enhancement of D4 binding was observed. Thus, the (di)-
chlorophenyl derivatives 3g-i showed 3-14-fold higher
potency when compared with the respective regioiso-
mers 3b-d . Interestingly, the improvement was even
greater for the phenylpiperazine 3f and the 4-fluoro
derivative 3j (96- and 110-fold based on 3a ,e, respec-
tively). The Ki values determined for 3f clearly demon-
strate extraordinarily high D4 affinity (Ki ) 0.52 nM)
and a 25000-, 6000-, 550-, and 3300-fold selectivity. It
is worthy to note that the phenylpiperazines 3a ,f gave
an approximately 10-fold difference between the affini-
ties toward the isoforms D2long and D2short that we had
not noticed before in the literature and within the data
of our test compound library. Recent SAR studies with
3-[(N-phenylpiperazinyl)methyl]azaindoles indicated that
4-chloro or 4-iodo substituent exerts an enhancement
of D4 potency and selectivity. In this case, only the
selectivity (especially over D2short and D3) is positively
influenced by the electronegative chloro function. The
reduced affinity of the chloro derivatives might be
explained by steric interactions preventing a perfect fit
of the 2-aminomethyl derivatives. As a consequence, a
fluoro group combining highly electronegative properties
and minimal steric demand was expected to be the
optimal substituent. In practice, the 4-fluorophenylpip-
erazine 3j turned out to represent both high D4 receptor
affinity (1.0 nM) and selectivity (>8600). Finally, the
6-cyanoindoles 3k -m were evaluated revealing Ki
values of 3.6, 3.4, and 9.0 nM at the D4 subtype and
moderate to strong selectivity over D1-D3.
Agonist activation of dopamine receptors is known to
increase mitogenesis in heterologously transfected cell
lines.18 This stimulating effect can be determined by
measuring the rate of [3H]thymidine incorporation into
growing cells. The functional experiment can be quanti-
fied by determination of the effective test compound
concentration (EC50) and by comparing the stimulating
effect to the [3H]thymidine incorporation that is caused
by a full agonist.
To investigate the intrinsic effects of 3f (FAUC 299)
and 3j (FAUC 316), which emphasized the most promis-
ing D4 ligands in the series of tested cyanoindoles,
CHO10001 cells stably expressing the human D4.2
receptor were established for a mitogenesis assay.19
Figure 1 shows the dose-response curves of 3f,j indi-
cating a partial agonist effect for both cyanoindoles with
an efficacy of about one-third (35% for 3f and 30% for
3j) of the effect of quinpirole, which is known as a full
agonist. Very recently, partial agonist effects were also
reported for the D4 ligands L-745,870 (3-[4-(4-chlorophe-
nyl)piperazin-1-ylmethyl]-1H-pyrrolo[2,3-b]pyridine),
U-101958 ((1-benzylpiperidin-4-yl)(3-isopropoxypyridin-
2-yl)methylamine), and NGD 94-1 (2-[4-(2-phenyl-3-
imidazol-4-ylmethyl)piperazin-1-yl]pyrimidine).20-22 The
EC50 values for 3f,j (Table 2), determined to be 1.5 and
9.4 nM, respectively, demonstrated a good correlation
to the corresponding Ki values derived from receptor
binding experiments (see Table 1). It is interesting to
note that the steepness of the competition curves and

4566 J ournal of Medicinal Chemistry, 2000, Vol. 43, No. 23
Brief Articles
based on a loading of 0.72 mmol/g for resin 510 and 0.31 mmol/g
for resins 13a ,b. Chromatographic purification was performed
using silica gel 60 (Merck).
3-(4-P h e n ylp ip e r a zin -1-ylm e t h yl)in d ole -5-ca r b on i-
tr ile (3a ). Meth od A: Resin 5 (188 mg, 0.72 mmol/g) was
suspended in HOAc (4 mL) and CH2Cl2 (1 mL), treated with
formaldehyde (0.6 mL, 37% in H2O) and 1-phenylpiperazine
(224 mg, 1.4 mmol) and stirred for 64 h at 40 °C. Then, the
resin was filtered off, washed with EtOH-2 N NaOH, EtOH,
CH2Cl2 and Et2O and dried in vacuo to give 174 mg of 6a . For
hydrolysis, resin 6a (172 mg) was suspended in a mixture of
1,4-dioxane (5 mL) and 2 N HCl (5 mL) and stirred at 40 °C
for 3 h, followed by addition of 2 N NaOH (10 mL) and stirring
at room temperature for 0.5 h. The resin was filtered off and
washed with EtOAc. The organic layer was dried (Na2SO4) and
evaporated to give crude 3a (19 mg, 44%; purity: 45%).
Meth od B: To a solution of 4 (149 mg, 1 mmol) in CH2Cl2
(4 mL) and HOAc (1 mL) were added 1-phenylpiperazine (162
mg, 1 mmol) and formaldehyde (0.1 mL, 37% in H2O). After
being stirred at room temperature for 6 h the solution was
basified with 2 N NaOH and extracted with CH2Cl2. The
organic layer was dried (Na2SO4) and evaporated and the
residue was purified by flash chromatography (CH2Cl2-MeOH
95:5) to give 3a (166 mg, 50%) as a colorless solid: mp 212
°C; IR 3320, 2815, 2220, 1600, 800, 760 cm-1; 1H NMR δ 2.61-
2.70 (m, 4H), 3.18-3.26 (m, 4H), 3.76 (s, 2H), 6.85 (t, 1H, J )
7.2 Hz), 6.89-6.96 (m, 2H), 7.21-7.30 (m, 3H), 7.38-7.46 (m,
2H), 8.18 (s, 1H), 8.39 (br s, 1H); EIMS 316 (M+). Anal.
(C20H20N4) C,H,N.
3-[4-(2-Ch lor op h en yl)p ip er a zin -1-ylm et h yl]in d ole-5-
ca r bon itr ile (3b). 5 (210 mg, 0.72 mmol/g), formaldehyde (0.6
mL, 37% in H2O) and 1-(2-chlorophenyl)piperazine (297 mg,
1.5 mmol) were reacted and worked up as described for 6a
(method A) to give 6b (190 mg). Hydrolysis of 6b (160 mg)
was performed as described for 3a to give crude 3b (20 mg,
45%; purity: 94%). In analogy to 3a , a solution-phase synthesis
was also performed (see method B) to give 3b (51%) as a
F igu r e 1. Stimulation of mitogenesis as a functional assay
to assess the agonist effects of 3f,j at the human dopamine
D4.2 receptor in relation to the full agonist quinpirole and the
antagonist clozapine.
Ta ble 2. Agonist Effects of the Cyanoindoles 3f,j, Quinpirole,
and Clozapine at the Dopamine D4.2 Receptor Investigated by
Measuring the Stimulation of Mitogenesis
test compounds
3f
35
1.5
3j
30
9.4
quinpirole
clozapine
agonist effect (%)a
EC50 (nM)b
100
3.7
0
nd
a
Rate of incorporation of [3H]thymidine (in %) as evidence for
mitogenetic activity relative to the maximal effect of the full
agonist quinpirole (100%); the results are the means of quadru-
b
plicates from 6 experiments. EC50 values derived from the mean
curves of 6 experiments; nd, not determined.
colorless solid: mp 193 °C; IR 2925, 2850, 1460, 750, 700 cm-1
;
the derived Hill slopes within the receptor binding
studies gave a one-site binding model. Unless mitoge-
nesis experiments showed partial agonist effects for 3f,j
indicating that the Ki values actually represent K0.5
values, high- and low-affinity binding sites could not be
identified using the methodology described.
1H NMR δ 2.61-2.79 (m, 4H), 3.05-3.19 (m, 4H), 3.76 (s, 2H),
6.96 (td, 1H, J ) 7.8, 1.5), 7.06 (dd, 1H, J ) 7.8, 1.5), 7.22 (td,
1H, J ) 7.8, 1.5), 7.25-7.28 (m, 1H), 7.35 (dd, 1H, J ) 7.8,
1.5), 7.39-7.47 (m, 2H), 8.20 (s, 1H), 8.40 (br s, 1H); EIMS
352 (M+), 350 (M+). Anal. (C20H19N4Cl) C,H,N.
3-[4-(3,4-Dich lor op h en yl)p ip er a zin -1-ylm eth yl]in d ole-
5-ca r bon itr ile (3c). 5 (220 mg, 0.72 mmol/g), formaldehyde
(0.6 mL, 37% in H2O) and 1-(3,4-dichlorophenyl)piperazine
(405 mg, 1.7 mmol) were reacted and worked up as described
for 6a (method A) to give 6c (205 mg). Hydrolysis of 6c (205
mg) was performed as described for 3a to give crude 3c (40
mg, 66%; purity: 98%). In analogy to 3a , a solution-phase
synthesis was also performed (see method B) to give 3c (76%)
In conclusion, it could be demonstrated that the
traceless linking methodology of indoles, which was
recently established in our laboratory, can be success-
fully applied for SAR studies and the synthesis of
potential drug candidates. Biological investigation of a
representative library of 13 indole derivatives showed
highly potent and selective dopamine D4 receptor bind-
ing profiles, when positions 2 and 5 proved highly
suitable attachment positions for the aminomethyl and
cyano groups, respectively. Ligand efficacy of the test
compounds FAUC 299 (3f) and FAUC 316 (3j) was
discovered by mitogenesis experiments. Selective D4
partial agonists could serve as an interesting tool for
the treatment of neuropsychiatric disorders such as
attention-deficit hyperactivity.
as a colorless solid: mp 174 °C; IR 3320, 2825, 2220, 1480 cm-1
;
1H NMR δ 2.58-2.64 (m, 4H), 3.14-3.20 (m, 4H), 3.75 (s, 2H),
6.72 (dd, 1H, J ) 8.9, 2.7 Hz), 6.95 (d, 1H, J ) 2.7 Hz), 7.23-
7.28 (m, 2H), 7.42-7.46 (m, 2H), 8.18 (s, 1H), 8.38 (br s, 1H);
EIMS 388 (M+), 386 (M+), 384 (M+). Anal. (C20H18N4Cl2) C,H,N.
3-[4-(4-Ch lor op h en yl)p ip er a zin -1-ylm et h yl]in d ole-5-
ca r bon itr ile (3d ). 5 (185 mg, 0.72 mmol/g), formaldehyde (0.6
mL, 37% in H2O) and 1-(4-chlorophenyl)piperazine (297 mg,
1.5 mmol) were reacted and worked up as described for 6a
(method A) to give 6d (170 mg). Hydrolysis of 6d (170 mg)
was performed as described for 3a to give crude 3d (27 mg,
55%; purity: 93%). In analogy to 3a , a solution-phase synthesis
was also performed (see method B) to give 3d (52%) as a
colorless solid: mp 189 °C; IR 3320, 2820, 2220, 1495, 1240
Exp er im en ta l Section
Solvents were purified and dried by standard procedures.
If not otherwise stated reactions were performed under dry
N2. Melting points: Bu¨chi melting point apparatus, uncor-
rected. IR: J asco FT/IR 410. MS and HRMS were run on
Finnigan MAT TSQ 70 and 8200 spectrometers, respectively,
1
cm-1; H NMR δ 2.60-2.67 (m, 4H), 3.13-3.20 (m, 4H), 3.75
(s, 2H), 6.80-6.86 (m, 2H), 7.16-7.22 (m, 2H), 7.27 (s, 1H),
7.39-7.46 (m, 2H), 8.17-8.19 (m, 1H), 8.42 (br s, 1H); EIMS
352 (M+), 350 (M+). Anal. (C20H19N4Cl) C,H,N.
1
by EI (70 eV) with solid inlet. H NMR spectra were obtained
3-[4-(4-F lu or op h en yl)p ip er a zin -1-ylm et h yl]in d ole-5-
ca r bon itr ile (3e). 5 (180 mg, 0.72 mmol/g), formaldehyde (0.6
mL, 37% in H2O) and 1-(4-fluorophenyl)piperazine (270 mg,
1.4 mmol) were reacted and worked up as described for 6a
(method A) to give 6e (167 mg). Hydrolysis of 6e (167 mg) was
on a Bruker AM 360 (360 MHz) spectrometer, if not otherwise
stated in CDCl3 relative to TMS. Purity of the compounds
1
prepared on solid phase was determined by H NMR analysis
of the crude product. Yields of solid-phase products 3a -m are

Brief Articles
J ournal of Medicinal Chemistry, 2000, Vol. 43, No. 23 4567
performed as described for 3a to give crude 3e (26 mg, 60%;
purity: 81%). In analogy to 3a , a solution-phase synthesis was
also performed (see method B) to give 3e (48%) as a colorless
6.44-6.47 (m, 1H), 6.83-6.90 (m, 2H),6.93-7.01 (m, 2H),
7.38-7.41 (m, 2H), 7.89-7.91 (m, 1H), 8.87 (br s, 1H); EIMS
334 (M+). Anal. (C20H19N4F) C,H,N.
1
solid: mp 179 °C; IR 3320, 2820, 2220, 1510, 1235 cm-1; H
2-(4-P h e n ylp ip e r a zin -1-ylm e t h yl)in d ole -6-ca r b on i-
tr ile (3k ). 13b (63 mg, 0.31 mmol/g) and 1-phenylpiperazine
(113 mg, 0.7 mmol) were reacted and worked up as described
for 3f (method A) to give crude 3k (6 mg, 97%; purity: 96%).
In analogy to 3f, a solution-phase synthesis was also performed
(see method B) to give 3k (90%) as a colorless solid: mp 59
NMR δ 2.61-2.69 (m, 4H), 3.09-3.16 (m, 4H), 3.76 (s, 2H),
6.84-6.90 (m, 2H), 6.91-6.98 (m, 2H), 7.27 (s, 1H), 7.38-7.46
(m, 2H), 8.19 (s, 1H), 8.39 (br s, 1H); EIMS 334 (M+). Anal.
(C20H19N4F) C,H,N.
2-(4-P h e n ylp ip e r a zin -1-ylm e t h yl)in d ole -5-ca r b on i-
tr ile (3f). Meth od A: Resin 13a (70 mg, 0.31 mmol/g) was
suspended in DMF (2 mL), treated with 1-phenylpiperazine
(113 mg, 0.7 mmol) and stirred for 48 h at 40 °C. Then, the
resin was filtered off and washed with EtOH-2 N NaOH,
EtOH, CH2Cl2 and Et2O. The resulting resin was suspended
in a mixture of 1,4-dioxane (5 mL) and 2 N HCl (5 mL) and
stirred at 40 °C for 3 h, followed by addition of 2 N NaOH (10
mL) and stirring at room temperature for 0.5 h. The resin was
filtered off and washed with EtOAc. The organic layer was
dried (Na2SO4) and evaporated to give crude 3f (6 mg, 88%;
purity: 96%).
Meth od B: To a solution of 10a (48 mg, 0.25 mmol) in DMF
(1 mL) was added 1-phenylpiperazine (81 mg, 0.50 mmol).
After being stirred at 60 °C for 2 h, 2 N NaOH, water and
EtOAc were added. The organic layer was washed with water,
dried (Na2SO4) and evaporated and the residue was purified
by flash chromatography (EtOAc) to give 3f (72 mg, 90%) as a
colorless solid: mp 208 °C; IR 3345, 2830, 2220, 1600,1320,
1230 cm-1; 1H NMR δ 2.63-2.69 (m, 4H), 3.19-3.25 (m, 4H),
3.74 (s, 2H), 6.46 (d, 1H, J ) 1.7 Hz), 6.84-6.96 (m, 3H), 7.23-
7.31 (m, 2H), 7.38-7.41 (m, 2H), 7.89-7.91 (m, 1H), 8.91 (br
s, 1H); EIMS 316 (M+). Anal. (C20H20N4) C,H,N.
1
°C; IR 3390, 2820, 2220, 1600, 1495 cm-1; H NMR δ 2.63-
2.70 (m, 4H), 3.20-3.26 (m, 4H), 3.76 (s, 2H), 6.44-6.47 (m,
1H), 6.88 (t, 1H, J ) 7.2), 6.90-6.95 (m, 2H), 7.24-7.28 (m,
2H), 7.32 (dd, 1H, J ) 8.2, 1.4), 7.60 (d, 1H, J ) 8.2), 7.66-
7.68 (m, 1H), 8.90 (br s, 1H); EIMS 316 (M+). Anal. (C20H20N4)
C,H,N.
2-[4-(2-Ch lor op h en yl)p ip er a zin -1-ylm et h yl]in d ole-6-
ca r bon itr ile (3l). 13b (73 mg, 0.31 mmol/g) and 1-(2-chlo-
rophenyl)piperazine (140 mg, 0.7 mmol) were reacted and
worked up as described for 3f (method A) to give crude 3l (8
mg, 100%; purity: 98%). In analogy to 3f, a solution-phase
synthesis was also performed (see method B) to give 3l (82%)
as a colorless solid: mp 58-62 °C; IR 3420, 2820, 2220, 1475,
1455 cm-1; 1H NMR δ 2.65-2.74 (m, 4H), 3.06-3.15 (m, 4H),
3.78 (s, 2H), 6.46 (d, 1H, J ) 1.0), 6.98 (td, 1H, J ) 7.8, 1.4),
7.05 (dd, 1H, J ) 7.8, 1.4), 7.19-7.25 (m, 1H), 7.32 (dd, 1H, J
) 8.2, 1.4), 7.36 (dd, 1H, J ) 7.8, 1.4), 7.60 (d, 1H, J ) 8.2),
7.68 (br s, 1H), 8.88 (br s, 1H); EIMS 352 (M+), 350 (M+). Anal.
Calcd for C20H19N4Cl: C, 68.47; H, 5.46; N, 15.97. Found: C,
67.88; H, 5.99; N, 15.72.
2-[4-(3,4-Dich lor op h en yl)p ip er a zin -1-ylm eth yl]in d ole-
6-ca r bon itr ile (3m ). 13b (155 mg, 0.31 mmol/g) and 1-(3,4-
dichlorophenyl)piperazine (340 mg, 1.4 mmol) were reacted
and worked up as described for 3f (method A) to give crude
3m (19 mg, 100%; purity: 98%). In analogy to 3f, a solution-
phase synthesis was also performed (see method B) to give
3m (91%) as a colorless solid: mp 132-134 °C; IR 3335, 2825,
2220, 1480 cm-1; 1H NMR δ 2.61-2.68 (m, 4H), 3.16-3.23 (m,
4H), 3.76 (s, 2H), 6.44-6.47 (m, 1H), 6.72 (dd, 1H, J ) 8.9,
2.8), 6.95 (d, 1H, J ) 2.8), 7.27 (d, 1H, J ) 8.9), 7.33 (dd, 1H,
J ) 8.4, 1.2), 7.60 (d, 1H, J ) 8.4), 7.67 (br s, 1H), 8.81 (br s,
1H); EIMS 384 (M+), 386 (M+), 388 (M+). Anal. (C20H18N4Cl2)
C,H,N.
2-(ter t-Bu t yld im et h ylsila n yloxym et h yl)in d ole-5-ca r -
bon itr ile (8a ). To a solution of 7a (1.90 g, 11 mmol)11 in DMF
(40 mL) were added imidazole (1.49 g, 22 mmol) and TBDMSCl
(1.83 g, 12 mmol) at 0 °C. After being stirred at 0 °C for 0.5 h
aqueous saturated NH4Cl, water and EtOAc were added. The
organic layer was dried (Na2SO4) and evaporated and the
residue was purified by flash chromatography (petroleum
ether-EtOAc 7:3) to give 8a (2.91 g, 92%) as a colorless solid:
mp 81 °C; IR 3300, 2950, 2930, 2850, 2220, 840 cm-1; 1H NMR
δ 0.17 (s, 6H), 0.98 (s, 9H), 4.93 (s, 2H), 6.39-6.42 (m, 1H),
7.41 (dd, 1H, J ) 8.6, 1.4), 7.46 (d, 1H, J ) 8.6), 7.94 (s, 1H),
8.64 (br s, 1H); EIMS 286 (M+); HREIMS (M+) 286.1506
(286.1502 calcd for C16H22N2OSi).
2-[4-(2-Ch lor op h en yl)p ip er a zin -1-ylm et h yl]in d ole-5-
ca r bon itr ile (3g). 13a (70 mg, 0.31 mmol/g) and 1-(2-
chlorophenyl)piperazine (139 mg, 0.7 mmol) were reacted and
worked up as described for 3f (method A) to give crude 3g (7
mg, 92%; purity: 96%). In analogy to 3f, a solution-phase
synthesis was also performed (see method B) to give 3g (89%)
as a colorless solid: mp 179 °C; IR 3420, 2820, 2220, 1480,
1
750 cm-1; H NMR δ 2.63-2.74 (m, 4H), 3.09-3.15 (m, 4H),
3.74 (s, 2H), 6.44-6.47 (m, 1H), 6.98 (td, 1H, J ) 7.9, 1.4 Hz),
7.04 (dd, 1H, J ) 7.9, 1.4), 7.22 (td, 1H, J ) 7.9, 1.4), 7.36 (dd,
1H, J ) 7.9, 1.4), 7.38-7.41 (m, 2H), 7.90 (s, 1H), 8.93 (br s,
1H); EIMS 352 (M+), 350 (M+). Anal. (C20H19N4Cl) C,H,N.
2-[4-(3,4-Dich lor op h en yl)p ip er a zin -1-ylm eth yl]in d ole-
5-ca r bon itr ile (3h ). 13a (160 mg, 0.31 mmol/g) and 1-(3,4-
dichlorophenyl)piperazine (340 mg, 1.4 mmol) were reacted
and worked up as described for 3f (method A) to give crude
3h (19 mg, 99%; purity: 98%). In analogy to 3f, a solution-
phase synthesis was also performed (see method B) to give
3h (93%) as a colorless solid: mp 178 °C; IR 3330, 2825, 2220,
1480 cm-1; 1H NMR δ 2.61-2.66 (m, 4H), 3.16-3.21 (m, 4H),
3.74 (s, 2H), 6.46 (d, 1H, J ) 1.7 Hz), 6.73 (dd, 1H, J ) 8.7,
2.7), 6.95 (d, 1H, J ) 2.7), 7.27 (d, 1H, J ) 8.7), 7.38-7.41 (m,
2H), 7.89-7.91 (m, 1H), 8.81 (br s, 1H); EIMS 388 (M+), 386
(M+), 384 (M+). Anal. (C20H18N4Cl2) C,H,N.
2-[4-(4-Ch lor op h en yl)p ip er a zin -1-ylm et h yl]in d ole-5-
ca r bon itr ile (3i). 13a (59 mg, 0.31 mmol/g) and 1-(4-chlo-
rophenyl)piperazine (119 mg, 0.6 mmol) were reacted and
worked up as described for 3f (method A) to give crude 3i (6
mg, 93%; purity: 86%). In analogy to 3f, a solution-phase
synthesis was also performed (see method B) to give 3i (81%)
as a colorless solid: mp 174 °C; IR 3360, 2820, 2220, 1600,
1500 cm-1; 1H NMR δ 2.61-2.67 (m, 4H), 3.14-3.21 (m, 4H),
3.74 (s, 2H), 6.55 (d, 1H, J ) 1.7), 6.80-6.86 (m, 2H),7.17-
7.22 (m, 2H), 7.38-7.40 (m, 2H), 7.88-7.90 (m, 1H), 8.92 (br
s, 1H); EIMS 352 (M+), 350 (M+). Anal. (C20H19N4Cl) C,H,N.
2-(ter t-Bu t yld im et h ylsila n yloxym et h yl)in d ole-6-ca r -
bon itr ile (8b). 7b (2.93 g, 17 mmol),11 imidazole (2.31 g, 34
mmol) and TBDMSCl (2.83 g, 19 mmol) were reacted and
worked up as described for 8a to give 8b (4.47 g, 92%) as a
colorless solid: mp 102-104 °C; IR 3340, 2950, 2930, 2850,
1
2220, 840 cm-1; H NMR δ 0.17 (s, 6H), 0.98 (s, 9H), 4.91 (s,
2H), 6.37-6.39 (m, 1H), 7.32 (dd, 1H, J ) 8.2, 1.4), 7.60 (d,
1H, J ) 8.2), 7.69-7.71 (m, 1H), 8.62 (br s, 1H); EIMS 286
(M+); HREIMS (M+) 286.1506 (286.1502 calcd for C16H22N2-
OSi).
2-(ter t-Bu t yld im et h ylsila n yloxym et h yl)-1-d iet h oxy-
m eth ylin d ole-5-ca r bon itr ile (9a ). A solution of 8a (645 mg,
2.3 mmol) in triethyl orthoformate (5 mL, 30 mmol) was stirred
at 160 °C for 16 h. The mixture was concentrated and the
residue was purified by flash chromatography (petroleum
ether-EtOAc 4:1) to give 9a (646 mg, 74%) as a colorless
2-[4-(4-F lu or op h en yl)p ip er a zin -1-ylm et h yl]in d ole-5-
ca r bon itr ile (3j). 13a (60 mg, 0.31 mmol/g) and 1-(4-fluo-
rophenyl)piperazine (108 mg, 0.6 mmol) were reacted and
worked up as described for 3f (method A) to give crude 3j (6
mg, 96%; purity: 86%). In analogy to 3f, a solution-phase
synthesis was also performed (see method B) to give 3j (88%)
solid: mp 58 °C; IR 2955, 2935, 2220, 1110, 1070 cm-1 1H
;
as a colorless solid: mp 232 °C; IR 3320, 2820, 2220, 1510 cm-1
1H NMR δ 2.63-2.69 (m, 4H), 3.10-3.16 (m, 4H), 3.74 (s, 2H),
;
NMR δ 0.12 (s, 6H), 0.92 (s, 9H), 1.21 (t, 6H, J ) 7.1), 3.45
(dq, 2H, J ) 9.3, 7.1), 3.70 (dq, 2H, J ) 9.3, 7.1), 4.88 (s, 2H),

4568 J ournal of Medicinal Chemistry, 2000, Vol. 43, No. 23
Brief Articles
1
6.41 (s, 1H), 6.47 (s, 1H), 7.41 (dd, 1H, J ) 8.6, 1.7), 7.85 (d,
1H, J ) 8.6 Hz), 7.87-7.90 (m, 1H); EIMS 388 (M+); HREIMS
(M+) 388.2181 (388.2182 calcd for C21H32N2O3Si).
°C; IR 2980, 2220, 1320, 1100, 1070 cm-1; H NMR δ 1.25 (t,
6H, J ) 7.1), 3.54 (dq, 2H, J ) 9.3, 7.1), 3.75 (dq, 2H, J ) 9.3,
7.1), 4.85 (s, 2H), 6.38 (s, 1H), 6.65 (s, 1H), 7.35 (dd, 1H, J )
8.0, 1.4), 7.60 (d, 1H, J ) 8.0 Hz), 8.14-8.17 (m, 1H); EIMS
294 (M+), 292 (M+); HREIMS (M+) 292.0984 (292.0979 calcd
for C15H17N2ClO2).
2-(ter t-Bu t yld im et h ylsila n yloxym et h yl)-1-d iet h oxy-
m eth ylin d ole-6-ca r bon itr ile (9b). A solution of 8b (1.71 g,
6 mmol) and triethyl orthoformate (10 mL, 60 mmol) was
stirred at 160 °C for 24 h. The mixture was worked up as
described for 9a to give 9b (2.07 g, 90%) as a colorless solid:
P olym er -Bou n d 2-Ch lor om eth ylin d ole-5-ca r bon itr ile
(13a ). A mixture of 12a (700 mg, 2.5 mmol), polymer-bound
3-benzyloxypropane-1,2-diol12 (480 mg) and p-TosOH (100 mg)
in 1,4-dioxane (5 mL) was stirred at room temperature for 3
h, filtered, subsequently washed with 1,4-dioxane, EtOH-2
N NaOH, EtOH and Et2O, and dried in vacuo to give 13a (480
mg).
P olym er -Bou n d 2-Ch lor om eth ylin d ole-6-ca r bon itr ile
(13b). 12b (350 mg, 1.2 mmol), polymer-bound 3-benzylox-
ypropane-1,2-diol12 (240 mg) and p-TosOH (50 mg) were
reacted and worked up as described for 13a to give 13b (257
mg).
Recep tor Bin d in g Stu d ies. Receptor binding assays at
the dopamine D1 receptor were carried out using bovine
striatal membranes with a final protein concentration of 25
µg/assay tube and a Kd value of 0.27-0.32 nM considering the
radioligand [3H]SCH 23390 as previously described.16 Prepara-
tions of membranes from CHO cells expressing human dopam-
ine D2long, D2short, D3 and D4.4 receptors were employed for
competition binding analysis displacing the radioligand [3H]-
spiperone according to literature.16 The assays were run with
a protein concentration of 5-25 µg/assay tube, with Kd values
1
mp 87 °C; IR 2930, 2860, 2220, 1100, 1070 cm-1; H NMR δ
0.15 (s, 6H), 0.92 (s, 9H), 1.22 (t, 6H, J ) 7.1 Hz), 3.45 (dq,
2H, J ) 9.3, 7.1 Hz), 3.70 (dq, 2H, J ) 9.3, 7.1), 4.88 (s, 2H),
6.40 (s, 1H), 6.47 (s, 1H), 7.32 (dd, 1H, J ) 8.2, 1.4), 7.57 (d,
1H, J ) 8.2), 8.14-8.16 (m, 1H); EIMS 388 (M+); HREIMS
(M+) 388.2185 (388.2182 calcd for C21H32N2O3Si).
2-Ch lor om eth ylin d ole-5-ca r bon itr ile (10a ). To a solu-
tion of 7a (600 mg, 3.8 mmol)11 in DMF (5 mL) and CCl4 (2
mL) was added PPh3 (1.186 g, 4.5 mmol). After stirring for 16
h at room temperature water and EtOAc were added. The
organic layer was washed with water, dried (Na2SO4) and
evaporated and the residue was purified by flash chromatog-
raphy (petroleum ether-EtOAc 6:4) to give 10a (294 mg, 40%)
as a colorless solid: mp 110 °C; IR 3290, 2220, 1320, 1260,
1
715 cm-1; H NMR δ 4.80 (s, 2H), 6.57-6.59 (m, 1H), 7.39-
7.47 (m, 2H), 7.92-7.94 (m, 1H), 8.61 (br s, 1H); EIMS 192
(M+), 190 (M+); HREIMS (M+) 190.0299 (190.0297 calcd for
C
10H7N2Cl).
2-Ch lor om eth ylin d ole-6-ca r bon itr ile (10b). 7b (1.050 g,
6.7 mmol),11 CCl4 (2 mL) and PPh3 (1.860 g, 7.1 mmol) were
reacted and worked up as described for 10a to give 10b (540
mg, 42%) as a colorless solid: mp 112 °C; IR 3300, 2220, 1310,
being 0.10-0.20, 0.10, 0.20 and 0.15-0.30 nM for the D2long
2short, D3 and D4.4 receptors, respectively. Protein concentra-
tion was established by the method of Lowry using bovine
,
D
1
1260 cm-1; H NMR δ 4.79 (s, 2H), 6.57-6.60 (m, 1H), 7.36
serum albumin as standard.23
(dd, 1H, J ) 8.2, 1.4), 7.62 (d, 1H, J ) 8.2), 7.70-7.72 (m,
1H), 8.69 (br s, 1H); EIMS 192 (M+), 190 (M+); HREIMS (M+)
190.0310 (190.0297 calcd for C10H7N2Cl).
Mitogen esis Assa y. A CHO10001A cell line stably trans-
fected with the human dopamine D4.2 receptor was provided
from Dr. R. Huff (Pharmacia & Upjohn, Inc., Kalamazoo, MI).19
Cells were grown in MEM R-medium (without nucleosides)
supplemented with 10% fetal calf serum, 2 mM L-glutamine
and 500 U/mL hygromycin B (Chalbiochem-Novabiochem, Bad
Soden, Germany) at 37 °C under a humidified atmosphere of
5% CO2-95% air in the presence of 100 U/mL penicillin G and
100 µg/mL streptomycin.
CHO cells were seeded in a 96-well plate with a density of
10 000 cells/well and were grown in 200 µL of MEM R-medium,
containing 10% fetal calf serum, at 37 °C for 75 h. Before
incubation with the test compounds the growth medium was
removed and the cells were rinsed twice with serum free
medium. Incubation was started by adding seven different
concentrations of the test compounds (with a final concentra-
tion of 0.001-1000 nM) diluted in 10 µL of sterile water to
each well containing 90 µL of serum-free medium. Eight wells
of every plate received 100 µL of serum-free medium or
medium supplemented with 10% fetal calf serum, respectively,
to control stimulation of growth. After the plate was cultured
for 16-18 h, 0.25 µCi of [3H]thymidine (specific activity 2.0
Ci/mmol; Amersham Pharmacia Biotech, Freiburg, Germany)
in 10 µL of serum-free medium was added to each well for 2 h
at 37 °C. Finally, cells were trypsinized and harvested onto
GF/C filters using an automated cell harvester (Inotech,
Dottikon, CH). Filters were washed four times with ice-cold
PBS buffer and counted in a MicroBeta Trilux (Wallac ADL,
Freiburg, Germany).
Da ta An a lysis. The resulting competition curves of the
receptor binding experiments were analyzed by nonlinear
regression using the algorithms in PRISM (GraphPad Soft-
ware, San Diego, CA). The data were fit in accordance to a
sigmoid model to provide an IC50 value, representing the
concentration corresponding to 50% of maximal inhibition, and
then transformed to Ki values applying the equation of Cheng
and Prusoff.24 Data resulting from experiments investigating
the stimulation of mitogenesis were each normalized and then
combined to get a mean curve. Analyzing this curve as
described above yielded an EC50 value expressing the concen-
tration which caused half of the maximal rate of incorporation
of [3H]thymidine. The top value of the curve expressed the
1-Dieth oxym eth yl-2-h yd r oxym eth ylin d ole-5-ca r bon i-
tr ile (11a ). To a solution of 9a (769 mg, 2 mmol) in THF (15
mL) was added Bu4NF (2.2 mL, 1 M in THF) at 0 °C. After
being stirred at 0 °C for 0.5 h aqueous saturated NaHCO3 and
EtOAc were added. The organic layer was dried (Na2SO4) and
evaporated and the residue was purified by flash chromatog-
raphy (petroleum ether-EtOAc 1:1) to give 11a (516 mg, 95%)
as a colorless solid: mp 74-76 °C; IR 3455, 2980, 2220, 1320,
1100, 1065 cm-1 1H NMR δ 1.25 (t, 6H, J ) 7.1), 3.49 (dq,
;
2H, J ) 9.3, 7.1), 3.74 (dq, 2H, J ) 9.3, 7.1), 4.86 (s, 2H), 6.44
(s, 1H), 6.56 (s, 1H), 7.43 (dd, 1H, J ) 8.6, 1.4), 7.68 (d, 1H, J
) 8.6), 7.89 (d, 1H, J ) 1.4); EIMS 274 (M+); HREIMS (M+)
274.1316 (274.1317 calcd for C15H18N2O3).
1-Dieth oxym eth yl-2-h yd r oxym eth ylin d ole-6-ca r bon i-
tr ile (11b). 9b (2.81 g, 7.3 mmol) and Bu4NF (8.0 mL, 1 M in
THF) were reacted and worked up as described for 11a to give
11b (1.95 g, 97%) as a colorless solid: mp 55 °C; IR 3450, 2980,
1
2220, 1100, 1065 cm-1; H NMR δ 1.25 (t, 6H, J ) 7.1), 3.53
(dq, 2H, J ) 9.2, 7.1), 3.75 (dq, 2H, J ) 9.2, 7.1), 4.85 (s, 2H),
6.42 (s, 1H), 6.56 (s, 1H), 7.35 (dd, 1H, J ) 8.2, 0.9), 7.61 (d,
1H, J ) 8.2), 7.99 (d, 1H, J ) 0.9); EIMS 274 (M+); HREIMS
(M+) 274.1313 (274.1317 calcd for C15H18N2O3).
2-Ch lor om et h yl-1-d iet h oxym et h ylin d ole-5-ca r b on i-
tr ile (12a ). To a solution of 11a (516 mg, 1.9 mmol) in DMF
(4 mL) and CCl4 (1 mL) was added PPh3 (560 mg, 2.1 mmol).
After stirring for 0.5 h at room temperature water and EtOAc
were added. The organic layer was washed with water, dried
(Na2SO4) and evaporated and the residue was purified by flash
chromatography (petroleum ether-EtOAc 4:1) to give 12a (250
mg, 45%) as a colorless solid: mp 76 °C; IR 2980, 2890, 2220,
1325, 1100, 1070 cm-1 1H NMR δ 1.25 (t, 6H, J ) 7.1 Hz),
;
3.51 (dq, 2H, J ) 9.3, 7.1), 3.75 (dq, 2H, J ) 9.3, 7.1), 4.82 (s,
2H), 6.38 (s, 1H), 6.66 (s, 1H), 7.45 (dd, 1H, J ) 8.6, 1.4), 7.85
(d, 1H, J ) 8.6), 7.90 (d, 1H, J ) 1.4); EIMS 294 (M+), 292
(M+); HREIMS (M+) 292.0989 (292.0979 calcd for C15H17N2-
ClO2).
2-Ch lor om et h yl-1-d iet h oxym et h ylin d ole-6-ca r b on i-
tr ile (12b). 11b (548 mg, 2.0 mmol) CCl4 (1 mL) and PPh3
(560 mg, 2.1 mmol) were reacted and worked up as described
for 12a to give 12b (354 mg, 60%) as a colorless solid: mp 57

Brief Articles
J ournal of Medicinal Chemistry, 2000, Vol. 43, No. 23 4569
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maximal rate of uptake of the radioactive marker to derive
the rate of agonistic effect for each test compound in correlation
to the reference agonist quinpirole.
Ack n ow led gm en t. The authors thank Dr. H. H. M.
Van Tol (Clarke Institute of Psychiatry, Toronto,
Canada), Dr. J .-C. Schwartz and Dr. P. Sokoloff (IN-
SERM, Paris, France) as well as Dr. J . Shine (The
Garvan Institute of Medical Research, Sydney, Austra-
lia) for providing dopamine D4, D3, and D2 receptor-
expressing cell lines, respectively. Dr. R. Huff (Phar-
macia & Upjohn, Inc., Kalamazoo, MI) is acknowledged
for providing a D4-expressing cell line employed for
mitogenesis. Thanks are also due to Mrs. H. Szc-
zepanek, Mrs. B. Linke, and Mrs. P. Schmitt for skillful
technical assistance. This work was supported by the
Fonds der Chemischen Industrie.
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