5-HT reuptake inhibitors with 5-HT(1B/1D) antagonistic activity: A new approach toward efficient antidepressants

Article abstract of DOI:10.1021/jm9811054

As part of our research program toward new, potential antidepressants, a series of unsymmetrical ureas has been prepared and evaluated as 5-HT reuptake inhibitors with 5-HT(1B/1D) antagonistic activities. The design of these compounds was based on coupling of various indole derivatives, previously shown to inhibit 5-HT reuptake, to three different aniline moieties, which are part of known 5-HT(1B/1D) ligands. Binding experiments in rat frontal cortex using [¹²⁵I]iodocyanopindolol, in calf striatum using [³H]5-HT, and in rat hippocampus using [³H]8-OH-DPAT as radioligands, respectively, revealed significantly higher affinity at the 5-HT(1B) receptor as compared to the affinities for the 5-HT(1A) and 5-HT(1D) receptors for a number of compounds, among them 4-(5-fluoro-1H-indol-3-yl)piperidine-1- carboxylic acid [4-methoxy-3(4-methylpiperazin-1-yl)phenyl]amide (5), the corresponding 4-fluoro-1H-indol-3-yl analogue 21a, and the corresponding 6- fluoro-1H-indol-3-yl analogue 21b. Conformational restriction of the aniline moiety in 5 only slightly enhanced the 5-HT(1B) affinity, whereas introduction of an aniline moiety with higher conformational flexibility resulted in a less potent 5-HT(1B) receptor ligand as compared to 5. The functional 5-HT(1B/1D) antagonistic activity was investigated using the rabbit saphenous vein model as well as the [³H]5-HT release from guinea pig cortical slices. All new compounds tested in the rabbit saphenous vein model were shown to antagonize the sumatriptan-evoked contractile responses with pA₂ values ranging from 7.3 to 8.7. These observations were consistent with the results of the cortical slice model, in which the ureas were found to block the sumatriptan-induced inhibition of potassium-evoked [³H]5-HT release. The 5-HT reuptake inhibition of the ureas determined in rat brain synaptosomes was found to be either increased or decreased as compared to the uncoupled indole derivatives indicating that the reuptake inhibition shown by the ureas is not only due to the indole part but also affected by the aniline moiety of the molecule. Among this series of compounds described the ureas 5, 21a, and 21b seem to be the most interesting candidates showing both 5-HT reuptake inhibition and 5-HT(1B/1D) antagonism in vitro. This dual pharmacological profile should in theory lead to a pronounced enhancement in serotonergic neurotransmission and consequently to a more efficient treatment of depression.

Full text of DOI:10.1021/jm9811054

J . Med. Chem. 2000, 43, 1149-1157
1149
5-HT Reu p ta k e In h ibitor s w ith 5-HT1B/1D An ta gon istic Activity: A New
Ap p r oa ch tow a r d Efficien t An tid ep r essa n ts
Lisa Matzen, Christoph van Amsterdam, Wilfried Rautenberg, Hartmut E. Greiner, J u¨rgen Harting,
Christoph A. Seyfried, and Henning Bo¨ttcher*
CNS Departments, Preclinical Pharmaceutical Research, Merck KGaA, Frankfurter Strasse 250, 64271 Darmstadt, Germany
Received October 14, 1998
As part of our research program toward new, potential antidepressants, a series of unsym-
metrical ureas has been prepared and evaluated as 5-HT reuptake inhibitors with 5-HT1B/1D
antagonistic activities. The design of these compounds was based on coupling of various indole
derivatives, previously shown to inhibit 5-HT reuptake, to three different aniline moieties,
which are part of known 5-HT1B/1D ligands. Binding experiments in rat frontal cortex using
[
125I]iodocyanopindolol, in calf striatum using [3H]5-HT, and in rat hippocampus using [3H]8-
OH-DPAT as radioligands, respectively, revealed significantly higher affinity at the 5-HT1B
receptor as compared to the affinities for the 5-HT1A and 5-HT1D receptors for a number of
compounds, among them 4-(5-fluoro-1H-indol-3-yl)piperidine-1-carboxylic acid [4-methoxy-3-
(4-methylpiperazin-1-yl)phenyl]amide (5), the corresponding 4-fluoro-1H-indol-3-yl analogue
21a , and the corresponding 6-fluoro-1H-indol-3-yl analogue 21b. Conformational restriction
of the aniline moiety in 5 only slightly enhanced the 5-HT1B affinity, whereas introduction of
an aniline moiety with higher conformational flexibility resulted in a less potent 5-HT1B receptor
ligand as compared to 5. The functional 5-HT1B/1D antagonistic activity was investigated using
the rabbit saphenous vein model as well as the [3H]5-HT release from guinea pig cortical slices.
All new compounds tested in the rabbit saphenous vein model were shown to antagonize the
sumatriptan-evoked contractile responses with pA2 values ranging from 7.3 to 8.7. These
observations were consistent with the results of the cortical slice model, in which the ureas
were found to block the sumatriptan-induced inhibition of potassium-evoked [3H]5-HT release.
The 5-HT reuptake inhibition of the ureas determined in rat brain synaptosomes was found to
be either increased or decreased as compared to the uncoupled indole derivatives indicating
that the reuptake inhibition shown by the ureas is not only due to the indole part but also
affected by the aniline moiety of the molecule. Among this series of compounds described the
ureas 5, 21a , and 21b seem to be the most interesting candidates showing both 5-HT reuptake
inhibition and 5-HT1B/1D antagonism in vitro. This dual pharmacological profile should in theory
lead to a pronounced enhancement in serotonergic neurotransmission and consequently to a
more efficient treatment of depression.
In tr od u ction
extracellular 5-HT.13,14 SSRIs lead to an increase in
5-HT levels, and the extracellular 5-HT counteracts the
desired increase by activation of terminal 5-HT1B/1D
receptors resulting in a decreased 5-HT release. Thus,
the therapeutic action of SSRIs is believed to set in after
desensitization of the terminal 5-HT1B/1D receptors.
However, blockade of terminal 5-HT1B/1D receptors by
selective antagonists would in theory prevent the initial
decrease in 5-HT release.12,15 It is therefore anticipated
that coadministration of a SSRI and a 5-HT1B/1D an-
tagonist would lead to a potentiation of the SSRI effect
and produce a large increase in extracellular 5-HT
concentrations. As a consequence, the time of onset of
therapeutic action would be diminished and the clinical
efficacy in the treatment of depressive disorders im-
proved.12,14 However the role of 5-HT1B/1D receptors in
depression is still not clear and needs further evalua-
tion.
Serotonin (5-HT, 1; Chart 1), a biogenic amine neu-
rotransmitter with diverse physiological actions in both
the central and peripheral nervous systems, operates
through various distinct membrane receptors.1-4 Dis-
turbances in the central serotonin system have been
associated with the pathogenesis of depression, and the
antidepressant effect of the selective 5-HT reuptake
inhibitors (SSRIs) is believed to be due to an enhance-
ment of postsynaptic 5-HT levels.5-11 Although SSRIs
are effective in the treatment of depression, clinical
improvement is first obtained after several weeks. Thus,
the delayed onset of therapeutic action of SSRIs needs
to be improved.12
One of the hypotheses proposed to explain the delayed
onset of the antidepressant action of SSRIs is the time
required for desensitization of somatodendritic 5-HT1A
receptors and terminal 5-HT1B/1D autoreceptors.8,9,11 The
terminal 5-HT1B/1D autoreceptors modulate the 5-HT
release and are inhibitory such that agonists decrease
GR 127935 (2a ; Chart 1) has been reported as the first
example of a selective 5HT1D/1B antagonist.16 However,
later investigations have shown that 2a acts as a partial
agonist at human 5-HT1B and 5-HT1D receptors.17
* To whom correspondence should be addressed. Tel: +49-6151-
727680. Fax: +49-6151-7290680. E-mail: bottcher@merck.de.
10.1021/jm9811054 CCC: $19.00 © 2000 American Chemical Society
Published on Web 02/29/2000

1150 J ournal of Medicinal Chemistry, 2000, Vol. 43, No. 6
Matzen et al.
Ch a r t 1. Chemical Structures of Serotonin (1), the Partial 5-HT1B/1D Agonist GR 127935 (2a ), the Inverse 5-HT1B
Agonist 2b, the Partial 5-HT1B Agonist 2c, the 5-HT Reuptake Inhibitors Indalpine (3) and 4, and the Lead Structure 5
Interestingly, two structurally closely related analogues
of 2a , 2b and 2c (Chart 1), have recently been identified
as an inverse agonist and a partial agonist for the
5-HT1B receptor, respectively, both with significant
selectivity over the 5-HT1D receptor.18
5-HT1B/1D antagonistic properties, we have coupled
structural moieties believed to induce 5-HT1B/1D antago-
nism to the above-mentioned 4-(indol-3-yl)piperidines,
inhibiting 5-HT reuptake. Coupling of 4-(5-fluoro-1H-
indol-3-yl)piperidine (4) to the arylpiperazine moiety of
2a resulted in the urea 5 (Chart 1) which was found to
inhibit [3H]5-HT uptake in rat brain synaptosomes and
to have affinity for the 5-HT1B receptor (Table 2). Using
5 as a lead structure this publication reports on the
synthesis and the in vitro pharmacology of a series of
new indole derivatives. Similar ureas have been re-
ported earlier.34 The pharmacological characterization
includes binding studies at the 5-HT1B, 5-HT1D, and
5-HT1A receptor sites - in rat frontal cortex using [125I]-
iodocyanopindolol, in calf striatum using [3H]5-HT, and
in rat hippocampus using [3H]8-OH-DPAT as radio-
ligands, respectively. [3H]5-HT release experiments in
guinea pig cortex slices as well as the determination of
the effect on sumatriptan-induced contractile responses
in rabbit saphenous vein were performed to study the
5-HT1B/1D antagonistic activity in vitro. The [3H]5-HT
reuptake inhibition was determined in rat brain syn-
aptosomes.
Microdialysis data published for 2a have been con-
troversial. Thus, local perfusion of 2a into the guinea
pig frontal cortex increased 5-HT levels whereas 5-HT
levels were decreased after ip administration.19 In a
microdialysis study performed by Rollema et al.,14
combined sc administration of 2a and the SSRI sertra-
line resulted in a pronounced, long-lasting increase in
5-HT levels in guinea pig hypothalamus indicating that
2a potentiates the effects of SSRIs on terminal 5-HT
levels and enhances extracellular 5-HT concentration
more effectively when 5-HT tone is increased.14 Instead
of combining a SSRI with a 5-HT1B/1D antagonist to
potentiate the postsynaptic 5-HT level, our research
program directed toward new, efficient, and fast-acting
antidepressive drugs has aimed at compounds with a
dual pharmacological profile showing both 5-HT re-
uptake inhibition and 5-HT1B/1D antagonism within a
single molecule.
Many compounds of various structures have been
described as selective inhibitors of 5-HT reuptake,
among them 3-(alkylpiperidin-4-yl)indoles (e.g. indal-
pine, 3; Chart 1).20 In connection with our previous work
in the field of antidepressants we have identified a
number of substituted 4-(indol-3-yl)piperidines such as
4 (Chart 1), which were shown to act as potent inhibitors
of 5-HT reuptake.
Resu lts a n d Discu ssion
Ch em istr y. The 4-(indol-3-yl)piperidines (4, 6, 7, 13-
15) and the 3-(indol-3-yl)pyrrolidine (10) (Table 1) were
obtained according to a published method by condensa-
tion of the respective indole with 1-benzyl-4-piperidone
or 1-benzyl-3-pyrrolidone in alkaline medium, followed
by hydrogenation and N-debenzylation.21 The carboline
derivative 12,22 indalpine (3),20 and tryptamine (8)32
were prepared as described before.
Aiming at compounds with a mixed pharmacological
profile containing both 5-HT reuptake inhibition and

5-HT Reuptake Inhibitors with 5-HT1B/ 1D Activity
J ournal of Medicinal Chemistry, 2000, Vol. 43, No. 6 1151
Sch em e 1a
Sch em e 3a
a
(i) (1) CDI, TEA, (2) 3-15 and 5-benzyloxytryptamine, TEA.
a
(i) 1-Benzylpiperazine, CDI; (ii) sodium bis(2-methoxyethoxy)-
Ta ble 1. 5-HT RUI in Rat Brain Synaptosomes
aluminum dihydride; (iii) H2, Pd-C 5%.
Sch em e 2a
a
(i) N-(2-Bromoethyl)phthalimide; (ii) hydrazine hydrate.
The piperazine analogue 9 was prepared from 1623
by acylation with 1-benzylpiperazine using 1,1′-carbo-
nyldiimidazole (CDI) as a coupling reagent to give the
amide 17 in 60% yield (Scheme 1). Reduction of the
amide by treatment with sodium bis(2-methoxyethoxy)-
aluminum dihydride resulted in 85% of 18, which was
N-debenzylated to give 9 in 73% yield.
The piperidine analogue 11 was synthesized by alky-
lation of 7 with commercially available N-(2-bromo-
ethyl)phthalimide to give 19 in 80% yield. Treatment
of 19 with hydrazine resulted in 92% of 11 (Scheme 2).
The arylpiperazine moiety 20 of GR 127935 (2a )24 as
well as the conformationally restricted analogue 2218
and the aniline 2418 were synthesized as described
before.
The unsymmetrical ureas 5, 21a -21j, 21m , 23a , 23b,
25a , and 25b were prepared by treatment of the anilines
20, 22, and 24, respectively, with CDI in the presence
of triethylamine (TEA) to give an intermediate which
upon addition of the respective indole (Table 1) gave the
ureas in moderate to good yields (Scheme 3 and Table
2). Compound 21l was obtained after hydrogenation of
the respective benzyl derivative 21k .
a
n ) 2-3.
OH-DPAT27 as radioligands, respectively (Table 2). The
5-HT1B/1D antagonist potency was evaluated in vitro by
measuring the effect on the sumatriptan-induced con-
tractile response of rabbit saphenous vein (RSV)28 and
by determining the extent of antagonism against
sumatriptan-induced inhibition of potassium-evoked
[3H]5-HT release in slices of guinea pig cortex (Table
2).29 The in vitro inhibitory effects of the new compounds
on 5-HT reuptake were measured using rat brain
synaptosomes (Tables 1 and 2).30
Recep tor Bin d in g. The indole analogues 3-4 and
6-15 (Table 1) were inactive in the 5-HT1B, 5-HT1D, and
5-HT1A receptor binding assays (results not shown). The
affinities for the 5-HT1B receptor of the ureas 5, 21a -
21j, 21l, 21m , 23a , 23b, 25a , and 25b ranged from low
to modest affinities, none of the new compounds being
more potent than 2a and 2b (Table 2). In the series of
Biology. The binding affinities for the 5-HT1B, 5-HT1D
,
and 5-HT1A receptor sites were determined in rat frontal
cortex using [125I]iodocyanopindolol,25 in calf striatum
using [3H]5-HT,26 and in rat hippocampus using [3H]8-

1152 J ournal of Medicinal Chemistry, 2000, Vol. 43, No. 6
Matzen et al.
Ta ble 2. Receptor Binding Affinities at 5-HT1B, 5-HT1D, and 5-HT1A Receptors, 5-HT RUI in Rat Brain Synaptosomes, Inhibitory
Activities on Sumatriptan-Induced Contractile Responses in RSV, and Antagonism of Sumatriptan-Induced Inhibition of K+-Evoked
[3H]5-HT Release in Guinea Pig Cortex Slices
a
b
n ) 3-5. n ) 3-4. N.T. ) not tested.

5-HT Reuptake Inhibitors with 5-HT1B/ 1D Activity
J ournal of Medicinal Chemistry, 2000, Vol. 43, No. 6 1153
ureas containing the arylpiperazine 20, the compounds
5, 21a -21d , 21i, 21j, and 21m were shown to have IC50
values of 50-120 nM in the 5-HT1B binding assay. The
substitution pattern of the indole in 5, 21a , and 21b
did not seem to play a role in the 5-HT1B affinity.
However, replacement of the 5-fluoro substituent in 5
by a cyano group lowered the 5-HT1B receptor affinity
of 21h , whereas replacement by a carboxamido group
to give 21m decreased selectivity versus the 5-HT1A
receptor. Replacement of the piperidine of 5 by pyrro-
lidine to give 21e led to a decrease in 5-HT1B affinity. A
similar effect was observed upon conformational restric-
tion of the 4-(5-fluoro-1H-indol-3-yl)piperidine ring sys-
tem of 5 resulting in 21g. Decreasing the conformational
flexibility of the arylpiperazine moiety 20 did not change
or only slightly improved the 5-HT1B affinity (compare
21f/23b and 5/23a , respectively). Replacement of 20 by
24 resulted in a less potent 5-HT1B ligand and a ligand
with slightly higher 5-HT1B affinity (compare 5/25a and
21f/25b, respectively). None of the compounds tested
displayed significant affinity for the 5-HT1D receptor.
On the other hand, the tryptamines 21c and 21l as well
as the piperazine 21d and the piperidine 21m turned
out to be quite potent ligands for the 5-HT1A receptor
sites, although attempts to determine any agonistic or
antagonistic activity of 21m in a functional 5-HT1A
system33 (data not shown) failed. The most promising
compounds with both high affinity at the 5-HT1B recep-
tor and some selectivity over the 5-HT1A and 5-HT1D
receptors were 5, 21a , 21b, 21i, 21j, and 23a .
It is obvious from the results obtained that the
distance between the indole moiety and the basic
nitrogen atom is critical to the activity as a 5-HT
reuptake inhibitor. Thus, the compounds 3 and 9
displayed improved 5-HT inhibitory activity as com-
pared to the 3-(piperidin-4-yl)indoles. Conformational
restriction of 4 resulted in a decrease of 5-HT reuptake
inhibition, as demonstrated by 12.
Coupling of the indole moieties 3, 4, and 6-15 to 20
led to an increased activity as 5-HT reuptake inhibitors
for the compounds 5, 21f, and 21h as compared to the
corresponding indoles (Tables 1 and 2). In contrast, the
compounds 21a -21c, 21e, 21i, and 21j were shown to
be weaker 5-HT reuptake inhibitors than the corre-
sponding indoles.
Compounds in which the arylpiperazine moiety 20
was replaced by 22 and 24, respectively, displayed
higher potency as compared to the uncoupled indoles
(Tables 1 and 2). In addition, the compounds 23a and
25a turned out to be more potent 5-HT reuptake
inhibitors than the analogue 5, whereas 23b and 25b
were equipotent to 21f.
These observations indicate that the indole part of the
molecule may not be sufficient to account for the 5-HT
reuptake inhibition and that the mode of interaction of
the indole part with the 5-HT reuptake site probably is
modulated by the nature of the aniline moiety.
Con clu sion
As mentioned in the Introduction coadministration of
a SSRI and a 5-HT1B/1D receptor antagonist should in
theory immediately increase serotonergic neurotrans-
mission avoiding the time required for desensitization
of the terminal 5-HT1B/1D autoreceptors and so decreas-
ing the time of onset of antidepressive action. Instead
of coadministration of two separate molecules to im-
prove the delayed onset of therapeutic action, this new
approach describes the development of a series of novel
compounds with mixed pharmacological profiles show-
ing both 5-HT reuptake inhibition and 5-HT1B/1D recep-
tor antagonism within a single molecule. The new
compounds contain various indole moieties shown to
inhibit 5-HT reuptake and the aniline part of 2a , 2b,
and 2c (20, 22, and 24, respectively) believed to intro-
duce 5-HT1B/1D receptor activity. Coupling of the indole
moieties 3, 4, and 6-15 to the anilines 20, 22, and 24,
respectively, resulted in an increased or decreased 5-HT
reuptake inhibition indicating that the 5-HT reuptake
inhibitory activity is not only due to the indole part of
the molecule but also modulated by the aniline moieties
20, 22, and 24, although they were not inhibitory by
themselves (Table 1). On the other hand, combination
of the different indole moieties with the anilines 20, 22,
and 24 diminished the activity in the 5-HT1B binding
assay in all cases as compared to 2a and 2b. However,
the ureas 5, 21a , 21b, 21i, 21j, and 23a still maintained
a significant affinity for the 5-HT1B receptor and showed
some selectivity versus the 5-HT1A and 5-HT1D recep-
tors.
Ra bbit Sa p h en ou s Vein (RSV). The results of the
RSV model are shown in Table 2. All ureas tested
antagonized the contractile responses evoked by suma-
triptan although with lower potency than 2a . The level
of 5-HT1B/1D antagonistic activity displayed by the new
compounds was shown to be modest but significant, the
apparent pA2 values ranging from 7.3 to 8.7. None of
the new compounds showed intrinsic activity in this
model, neither did 2a nor 2b.
[3H]5-HT Relea se Test. The results displayed in
Table 2 demonstrate that all compounds tested in this
model were able to antagonize the sumatriptan-induced
inhibition of potassium-evoked [3H]5-HT release from
guinea pig cortex slices. The fluoro analogues 5, 21a ,
and 21b, the 5-cyano analogue 21h , and the carboxa-
mide analogue 21m turned out to be the most potent
antagonists enhancing the 5-HT release by 145-217%
as compared to the release observed with sumatriptan
in the absence of test compound. Interestingly, all ureas
tested in the release model showed equal or better
potency than the reference compounds 2a and 2b. The
new compounds displayed no instrinsic activity on
potassium-induced [3H]5-HT release in the absence of
sumatriptan (results not shown), which is consistent
with the results obtained from the RSV model.
[3H]5-HT Reu p ta k e In h ibition (5-HT RUI). The
results of the rat brain synaptosomes experiments are
summarized in Tables 1 and 2. In the series of the
substituted 4-(indol-3-yl)piperidines, 4, 6, 7, 13, 14, and
the pyrrolidine derivative 10 were equally potent in
inhibiting the reuptake of 5-HT (Table 1). However, the
carboxamido-substituted compound 15 as well as the
anilines 20, 22, and 24 were found to be inactive in this
test.
In the RSV test the new compounds inhibited the
constrictor effects of sumatriptan indicating 5-HT1B/1D
receptor antagonistic properties. In guinea pig cortical
slices all ureas tested were found to block the sumatrip-
tan-induced inhibition of [3H]5-HT release.

1154 J ournal of Medicinal Chemistry, 2000, Vol. 43, No. 6
Matzen et al.
for 4 h at room temperature H2O (40 mL) was added. The
reaction mixture was filtered, evaporated, dissolved in EtOAc
(300 mL), washed with H2O (2 × 200 mL), dried and evapo-
rated. Dissolution of the residue in acetone and addition of 1
M HCl in EtOH resulted in a precipitate which was collected
and dried to give 18 (23.2 g, 85%): mp 233-235 °C; 1H NMR
(DMSO-d6) δ 10.90 (s, 1 H), 7.65 (br s, 2 H), 7.44 (br s, 3 H),
7.29 (m, 3 H), 6.86 (dt, 1 H, J ) 8.8 Hz and J ) 2.0 Hz), 4.37
(br s, 2 H), 3.79-3.30 (m, 8 H), 3.17 (br s, 2 H), 2.69 (t, 2 H, J
) 6.6 Hz), 1.72 (m, 4 H); FAB-MS ((M + H)+) m/z 366.
5-F lu or o-3-(4-p ip er a zin -1-ylbu tyl)-1H-in d ole Oxa la te
(9). A solution of 18 (19.7 g, 44.9 mmol) in MeOH (300 mL)
was hydrogenated using Pd-C 5% (3.5 g) as catalyst. Filtra-
tion, evaporation and CC [eluent: CH2Cl2-MeOH (9:1)] gave
an oily residue. Upon dissolution in acetone and addition of a
solution of oxalic acid in acetone a precipitate formed. The
precipitate was collected and dried to give 9 (12.0 g, 73%): mp
175-176 °C; 1H NMR (DMSO-d6) δ 10.84 (s, 1H), 8.75 (br s, 1
H), 7.29 (dd, 1 H, J ) 11.0 Hz and J ) 2.4 Hz), 7.21 (dd, 1 H,
J ) 11.0 Hz and J ) 2.2 Hz), 7.12 (d, 1 H, J ) 1.5 Hz), 6.87
(dt, 1 H, J ) 8.8 Hz and J ) 2.0 Hz), 3.16 (m, 4 H), 2.78 (m,
4 H), 2.66 (t, 2 H, J ) 6.6 Hz), 2.59 (t, 2 H, J ) 6.6 Hz), 1.61
(m, 4 H); EI-MS (M)+ m/z 275.
2-{2-[4-(6-F lu or o-1H -in d ol-3-yl)p ip er id in -1-yl]et h yl}-
isoin d ole-1,3-d ion e Hyd r obr om id e (19). A mixture of 4-(6-
fluoro-1H-indol-3-yl)piperidine (7) (21.8 g, 100 mmol) and N-(2-
bromoethyl)phthalimide (25.4 g, 100 mmol; purchased from
Merck #820178) in 500 mL acetonitrile was stirred under
reflux for 48 h. The crystalline precipitate formed was collected
and dried to give 19 (33.2 g, 80%): 1H NMR (DMSO-d6) δ 10.81
(s, 1 H), 7.85 (d, 1 H, J ) 8.8 Hz), 7.56 (m, 3 H), 7.33 (br s, 1
H), 7.06 (m, 2 H), 6.82 (t, 1 H, J ) 8.7 Hz), 4.64 (br s, 1 H),
4.35 (t, 2 H, J ) 7.5 Hz), 3.98 (t, 2 H, J ) 7.5 Hz), 3.20-2.65
(m, 5 H), 1.68 (br s, 3 H); FAB-MS ((M + H)+) m/z 393.
The 5-HT1B receptor binding affinities do not always
correlate to the results obtained in the rabbit saphenous
vein preparation and in the [3H]5-HT release model. The
differences between the function of the 5-HT1B/1D recep-
tors in rat frontal cortex, rabbit saphenous vein, and
guinea pig cortex still need to be evaluated. In addition
the affinity to other 5-HT receptor subtypes such as
5-HT1F and 5-HT2 (not tested) could disturb the cor-
relation of the results obtained in the functional models
and the binding data.
Interestingly, the ureas antagonized the inhibition of
[3H]5-HT release with equal or better potency than 2a
or 2b, although having weaker affinity to the 5-HT1B
receptor. This may be due to the additional 5-HT
reuptake inhibition of these compounds. The high
potency of 21m in the release model may be due to the
combination of 5-HT1B and 5-HT1A effects, but this still
has to be evaluated further.
Among the new compounds presented the ureas 5,
21a , and 21b appear to be the most promising new 5-HT
reuptake inhibitors with 5-HT1B/1D antagonistic activity.
To our knowledge, this is the first report describing
compounds which contain these activities within a
single molecule. Their mixed profile should facilitate
serotonergic transmission, and their further pharma-
cological characterization will be of primary importance
to evaluate the antidepressive potential of these novel
compounds.
Exp er im en ta l Section
2-[4-(6-F lu o r o -1H -in d o l-3-y l)p ip e r id in -1-y l)e t h y l-
a m in e (11). A mixture of 19 (33.2 g, 70 mmol) and hydrazine
hydrate (5.0 mL, 100 mmol) in MeOH (500 mL) was stirred
under reflux for 2 h. After cooling the reaction mixture was
filtered and evaporated. Dissolution of the residue in 1 M
NaOH (300 mL), extraction with EtOAc (3 × 300 mL), drying
Ch em istr y. Gen er a l P r oced u r es. Melting points were
determined in capillary tubes and are uncorrected. Elemental
analyses are within (0.4% of the calculated values, unless
otherwise stated. Analytical HPLC was conducted on a Li-
Chrospher RP Select B column 5 µm (4 mm i.d. × 250 mm)
using a gradient of water (with 0.1% TFA) and acetonitrile
(with 0.08% TFA) for elution, with UV monitoring at 220 nm.
1
and evaporation gave 11 (16.8 g, 92%): mp 165-166 °C; H
NMR (DMSO-d6) δ 10.91 (s, 1 H), 7.52 (dd, 1 H, J ) 7.0 Hz
and J ) 3.5 Hz), 7.11 (m, 2 H), 6.82 (m, 1 H), 2.93 (d, 2 H, J
) 13.7 Hz), 2.66 (t, 2 H, J ) 7.0 Hz), 2.35 (t, 2 H, J ) 7.0 Hz),
1.50-2.12 (m, 9 H); FAB-MS ((M + H)+) m/z 262.
Gen er a l Meth od for th e Syn th esis of Un sym m etr ica l
Ur ea s. 4-(5-F lu or o-1H-in d ol-3-yl)p ip er id in e-1-ca r boxylic
1H NMR spectra were recorded on
a Bruker AMX 300
spectrometer at 300 MHz using DMSO-d6 as solvent. Unless
otherwise stated, chemical shift values (δ) are expressed in
ppm relative to TMS. The following abbreviations are used
for multiplicity of NMR signals: br ) broad, s ) singlet, d )
doublet, t ) triplet, q ) quartet, dd ) double doublet, m )
multiplet. Mass spectra were obtained on a VG-70 SE spec-
trometer from VG-Instruments to get molecular weight infor-
mation ((M + H)+) for FAB-MS and on a 70-70E spectrometer
from VG-Instruments to get molecular weight information
((M)+) for EI-MS. Drying of organic phases was performed
using Na2SO4. Column chromatography (CC) and TLC were
performed on silica gel 60 (70-230 mesh, Merck) and silica
gel F254 plates (Merck), respectively.
1-(4-Ben zylp ip er a zin -1-yl)-4-(5-flu or o-1H -in d ol-3-yl)-
bu ta n -1-on e (17). A solution of 4-(5-fluoro-1H-indol-3-yl)-
butyric acid (16)23 (20.0 g, 90.0 mmol) and carbonyldiimidazole
(CDI) (14.6 g, 90 mmol) in THF (100 mL) was stirred for 1 h
at room temperature. A solution of 1-benzylpiperazine (15.9
g, 90 mmol) in THF (50 mL) was added and stirring was
continued for 12 h. The reaction mixture was evaporated to
dryness, the residue was dissolved in EtOAc (100 mL), washed
with H2O (2 × 100 mL), dried and evaporated. CC [eluent:
EtOAc] gave 17 (20.4 g, 60%): mp 85-87 °C; 1H NMR (DMSO-
d6) δ 10.81 (s, 1 H), 7.28 (m, 7 H), 7.16 (d, 1 H, J ) 2.2 Hz),
7.86 (dt, 1 H, J ) 8.8 Hz and J ) 1.3 Hz), 3.49 (s, 2 H), 3.42
(d, 4 H, J ) 12.0 Hz), 2.65 (t, 2 H, J ) 8.0 Hz), 2.31 (m, 6 H),
1.87 (quintet, 2 H, J ) 6.6 Hz); EI-MS (M)+ m/z 380.
Acid
[4-Met h oxy-3-(4-m et h ylp ip er a zin -1-yl)p h en yl]-
a m id e Hyd r och lor id e Hyd r a te (5). A solution of 4-methoxy-
3-(4-methylpiperazin-1-yl)aniline dihydrochloride (20)24 (2.7 g,
9.2 mmol), TEA (4.6 mL, 32.2 mmol) and CDI (1.6 g, 10.1
mmol) in acetonitrile (100 mL) was stirred at room tempera-
ture for 4 h. A suspension of 4-(5-fluoro-1H-indol-3-yl)piperi-
dine (4) (2.0 g, 9.2 mmol) and TEA (1.3 mL, 9.2 mmol) in
acetonitrile (100 mL) was added and stirring was continued
for 12 h. The reaction mixture was evaporated to dryness, the
residue was dissolved in EtOAc (100 mL), washed with H2O
(2 × 100 mL), dried and evaporated. The residue was dissolved
in acetone (100 mL) and stirred with 1 M HCl. Collection of
the precipitate followed by recrystallization (EtOH-Et2O) gave
1
5 (2.2 g, 35%): mp 230-231 °C; H NMR (DMSO-d6) δ 11.18
(s, 1 H), 10.93 (s, 1 H), 8.35 (s, 1 H), 7.30 (d, 1 H, J ) 9.0 Hz),
7.24 (d, 1 H, J ) 10.0 Hz), 7.21 (d, 1 H, J ) 2.1 Hz), 7.17 (1 H,
s), 6.90 (d, 1 H, J ) 9.0 Hz), 6.85 (d, 1 H, J ) 10.0 Hz), 4.26
(d, 2 H, J ) 12.0 Hz), 3.74 (s, 3 H), 3.55 (m, 4 H), 3.55-2.85
(m, 7 H), 2.78 (s, 3 H), 1.95 (d, 2 H, J ) 12.1 Hz), 1.57 (m, 2
H); FAB-MS ((M + H)+) m/z 466. Anal. (C26H32FN5O2‚HCl‚H2O)
C, H, N; Cl: calcd, 6.82%; found, 7.45%.
4-(4-F lu or o-1H-in d ol-3-yl)p ip er id in e-1-ca r boxylic Acid
[4-Meth oxy-3-(4-m eth ylp ip er a zin -1-yl)p h en yl]a m id e Di-
h yd r och lor id e (21a ). Compound 21a was synthesized as
described for 5 using 2024 (1.2 g, 4.1 mmol), TEA (2.7 mL, 18.5
mmol), CDI (730 mg, 4.5 mmol) and 4-(4-fluoro-1H-indol-3-
yl)piperidine (6) (895 mg, 4.1 mmol) in acetonitrile (75 mL).
3-[4-(Ben zylpiper azin -1-yl)bu tyl]-5-flu or o-1H-in dole Di-
h yd r och lor id e (18). To a solution of 17 (20.0 g, 53.0 mmol)
in THF (350 mL) was added a 65% solution of sodium bis(2-
methoxyethoxy)aluminum dihydride in toluene (43.0 mL, 132
mmol) dropwise at 5-10 °C in N2 atmosphere. After stirring

5-HT Reuptake Inhibitors with 5-HT1B/ 1D Activity
J ournal of Medicinal Chemistry, 2000, Vol. 43, No. 6 1155
CC [eluent: toluene-MeOH-TEA (7:2:1)] and preparation of
the dihydrochloride followed by recrystallization (2-propanol-
acetonitrile (75 mL). Collection of the precipitate, dissolution
in acetone and preparation of the dihydrochloride gave 21f (1.5
1
1
light petroleum) gave 21a (640 mg, 30%): mp 205 °C dec; H
g, 61%): mp 189-192 °C; H NMR (DMSO-d6) δ 10.82 (s, 1
NMR (DMSO-d6) δ 11.68 (s, 1 H), 11.11 (s, 1 H), 8.33 (s, 1 H),
7.17 (m, 3 H), 7.05 (m, 1 H), 6.60 (d, 1 H, J ) 8.8 Hz), 6.67
(dd, 1 H, J ) 12.0 Hz and J ) 9.0 Hz), 4.25 (d, 2H, J ) 12.0
Hz), 3.73 (s, 3 H), 3.45 (d, 4 H, J ) 11.0 Hz), 3.39-2.85 (m, 7
H), 2.55 (s, 3 H), 1.96 (d, 2 H, J ) 11.1 Hz), 1.57 (m, 2 H);
FAB-MS ((M + H)+) m/z 466. Anal. (C26H32FN5O2‚2HCl) C, H,
N; Cl: calcd, 13.17%; found, 12.30%.
H), 8.39 (s, 1 H), 7.52 (t, 1 H, J ) 6.6 Hz), 7.10 (d, 1 H, J ) 8.8
Hz), 7.05 (s, 1 H), 6.98 (s, 1 H), 6.92 (d, 1 H, J ) 8.8 Hz), 6.75
(m, 2 H), 5.93 (br s, 1 H), 3.70 (s, 3 H), 3.29 (br s, 2 H), 3.22
(m, 2 H), 2.95 (br s, 6 H), 2.74 (m, 1 H), 2.44 (br s, 4 H), 2.21
(s, 3 H), 2.12 (t, 2 H, J ) 9.3 Hz), 1.95 (m, 2 H), 1.72 (m, 2 H);
FAB-MS ((M + H)+) m/z 509. Anal. (C28H37FN6O2‚2HCl‚H2O)
C, H, Cl; N: calcd, 14.02%; found, 13.35%.
4-(6-F lu or o-1H-in d ol-3-yl)p ip er id in e-1-ca r boxylic Acid
[4-Meth oxy-3-(4-m eth ylp ip er a zin -1-yl)p h en yl]a m id e Di-
h yd r a te (21b). Compound 21b was synthesized as described
for 5 using 2024 (588 mg, 2.0 mmol), TEA (1.3 mL, 9 mmol),
CDI (357 mg, 2.2 mmol) and 4-(6-fluoro-1H-indol-3-yl)piperi-
dine (7) (437 mg, 2.0 mmol) in acetonitrile (50 mL). CC [eluent:
toluene-MeOH-TEA (7:2:1)] followed by recrystallization
(EtOAc-light petroleum) gave 21b (126 mg, 14%): mp 135-
137 °C; 1H NMR (DMSO-d6) δ 10.85 (s, 1 H), 8.23 (s, 1 H),
7.55 (m, 1 H), 7.10 (m, 3 H), 7.03 (s, 1 H), 6.83 (d, 1 H, J ) 8.3
Hz), 6.72 (d, 1 H, J ) 9.0 Hz), 4.25 (d, 2H, J ) 12.1 Hz), 3.72
(s, 3 H), 2.92 (m, 7 H), 2.38 (br s, 4 H), 2.20 (s, 3 H), 1.92 (d,
2 H, J ) 11.3 Hz), 1.57 (m, 2 H); FAB-MS ((M + H)+) m/z 466.
Anal. (C26H32FN5O2‚2H2O) C, H; N: calcd, 14.22%; found,
13.70%.
1-[2-(5-F lu or o-1H -in d ol-3-yl)et h yl]-3-[4-m et h oxy-3-(4-
m eth ylp ip er a zin -1-yl)p h en yl]u r ea Hem ih yd r a te (21c).
Compound 21c was synthesized as described for 5 using 2024
(1.2 g, 4.1 mmol), TEA (3.3 mL, 22.6 mmol), CDI (730 mg, 4.5
mmol) and 5-fluorotryptamine hydrochloride (8)32 (880 mg, 4.1
mmol) in acetonitrile (75 mL). Recrystallization (EtOAc-light
petroleum) gave 21c (1.27 g, 75%): mp 97-98 °C; 1H NMR
(DMSO-d6) δ 10.91 (s, 1 H), 8.22 (s, 1 H), 7.32 (m, 2 H), 7.23
(d, 1 H, J ) 2.2 Hz), 6.92 (m, 3 H), 6.75 (d, 1 H, J ) 8.8 Hz),
5.95 (t, 1 H, J ) 6.6 Hz), 3.69 (s, 3H), 3.40 (t, 2 H, J ) 6.6 Hz),
2.94 (br s, 4 H), 2.80 (t, 2 H, J ) 6.6 Hz), 2.43 (br s, 4 H), 2.20
(s, 3 H); FAB-MS ((M + H)+) m/z 426. Anal. (C23H28FN5O2‚
0.5H2O) C, H; N: calcd, 16.12%; found, 14.28%.
8-F lu or o-1,3,4,5-t et r a h yd r op yr id o[4,3-b]in d ole-2-ca r -
boxylic Acid [4-Meth oxy-3-(4-m eth ylpiper a zin -1-yl)p h en -
yl]a m id e (21g). Compound 21g was synthesized as described
for 5 using 2024 (1.2 g, 4.1 mmol), TEA (2.7 mL, 18.5 mmol),
CDI (730 mg, 4.5 mmol) and 8-fluoro-2,3,4,5-tetrahydro-1H-
pyrido[4,3-b]indole (12)22 (780 mg, 4.1 mmol) in acetonitrile
(75 mL). CC [eluent: EtOAc-MeOH-TEA (5:2:1)] followed by
recrystallization (EtOAc) gave 21g (1.1 g, 61%): mp 243-245
1
°C; H NMR (DMSO-d6) δ 10.97 (s, 1 H), 8.60 (s, 1 H), 7.28
(dd, 1 H, J ) 8.5 Hz and H ) 4.4 Hz), 7.09 (m, 3 H), 6.86 (dt,
1 H, J ) 8.8 Hz and J ) 2.2 Hz), 6.77 (d, 1 H, J ) 8.8 Hz),
4.60 (s, 2 H), 3.81 (t, 2H, J ) 6.6 Hz), 3.73 (s, 3 H), 2.95 (br s,
4 H), 2.64 (m, 2 H), 2.45 (br s, 4 H), 2.23 (s, 3 H); FAB-MS ((M
+ H)+) m/z 438. Anal. (C24H28FN5O2) C, H, N.
4-(5-Cyan o-1H-in dol-3-yl)-N-[4-m eth oxy-3-(4-m eth ylpip-
er a zin -1-yl)p h en yl]p ip er id in e-1-ca r b oxa m id e‚0.25H 2O
(21h ). Compound 21h was synthesized as described for 5 using
2024 (647 mg, 2.2 mmol), TEA (1.4 mL, 9.9 mmol), CDI (392
mg, 2.4 mmol) and 4-(5-cyano-1H-indol-3-yl)piperidine (13)
(496 mg, 2.2 mmol) in acetonitrile (50 mL). CC [eluent:
toluene-MeOH-TEA (7:2:1)] followed by recrystallization
(acetonitrile-Et2O) gave 21h (100 mg, 10%): mp 194-196 °C;
1H NMR (DMSO-d6) δ 11.44 (s, 1H), 8.23 (s, 1 H), 8.15 (s, 1
H), 7.49 (d, 1 H, J ) 8.8 Hz), 7.38 (d, 1 H, J ) 8.8 Hz), 7.33 (br
s, 1 H), 7.05 (m, 2 H), 6.72 (d, 1 H, J ) 9.0 Hz), 4.26 (d, 2 H,
J ) 12.5 Hz), 3.70 (s, 3 H), 3.32 (m, 3 H), 2.95 (m, 8 H), 2.20
(s, 3 H), 1.97 (m, 2 H), 1.55 (m, 2 H); FAB-MS ((M + H)+) m/z
489. Anal. (C27H32N6O2‚0.25H2O) C, H; N: calcd, 17.62%;
found, 17.09%.
4-(3-In d olyl)-N-[4-m eth oxy-3-(4-m eth ylp ip er a zin -1-yl)-
p h en yl]p ip er idin e-1-ca r boxa m id e Dih ydr och lor id e (21i).
Compound 21i was synthesized as described for 5 using 2024
(1.8 g, 6.1 mmol), TEA (4.0 mL, 27.5 mmol), CDI (1.1 g, 6.7
mmol) and 4-(1H-indol-3-yl)piperidine (14) (1.2 g, 4.1 mmol)
in acetonitrile (100 mL). CC [eluent: EtOAc-MeOH-TEA
(5:2:1)] followed by preparation of the dihydrochloride gave 21i
(1.4 g, 44%): mp 203-205 °C; 1H NMR (DMSO-d6) δ 10.79 (s,
1 H), 8.35 (s, 1 H), 7.57 (d, 1 H, J ) 8.8 Hz), 7.29 (d, 1 H, J )
8.8 Hz), 7.18 (m, 2 H), 7.11 (d, 1 H, J ) 3.0 Hz), 7.06 (t, 1 H,
J ) 8.2 Hz), 6.97 (t, 1 H, J ) 89.2 Hz), 6.85 (d, 1 H, J ) 8.8
Hz), 4.24 (d, 2 H, J ) 13.2 Hz), 3.75 (s, 3 H), 3.44 (d, 4 H, J )
13.2 Hz), 3.17 (q, 2 H, J ) 9.0 Hz), 2.99 (m, 5 H), 2.75 (s, 3 H),
1.99 (d, 2 H, 13.2 Hz), 1.59 (m, 2 H); FAB-MS ((M + H)+) m/z
448. Anal. (C26H33N5O2‚2HCl) C, H, N; Cl: calcd, 13.45%;
found, 12.34%.
4-[4-(5-F lu or o-1H -in d ol-3-yl)b u t yl]p ip er a zin e-1-ca r -
boxylic Acid [4-Meth oxy-3-(4-m eth yl-1-p ip er a zin -1-yl)-
p h en yl]a m id e Dih yd r och lor id e Hyd r a te (21d ). Compound
21d was synthesized as described for 5 using 2024 (1.2 g, 4.1
mmol), TEA (3.9 mL, 26.7 mmol), CDI (730 mg, 4.5 mmol) and
5-fluoro-3-(4-piperazin-1-ylbutyl)-1H-indole oxalate (9) (1.5 g,
4.1 mmol) in acetonitrile (75 mL). Preparation of the dihydro-
chloride followed by recrystallization (EtOH-Et2O) gave 21d
1
(1.0 g, 42%): mp 220 °C dec; H NMR (DMSO-d6) δ 10.90 (s,
1 H), 8.59 (s, 1 H), 7.32 (m, 2 H), 7.25 (br s, 1 H), 7.14 (m, 2
H), 6.82 (d, 2 H, J ) 8.2 Hz), 4.23 (br s, 6 H), 3.75 (s, 3H), 3.46
(br, 2 H), 3.40-2.93 (m, 10 H), 2.81 (s, 3 H), 2.70 (t, 2 H, J )
5.1 Hz), 1.88-1.60 (m, 4 H); FAB-MS ((M + H)+) m/z 523. Anal.
(C29H39FN6O2‚2HCl‚H2O) H, Cl; C: calcd, 56.76%; found,
56.24%. N: calcd, 13.96%; found, 13.13%.
3-(5-Flu or o-1H-in dol-3-yl)pyr r olidin e-1-car boxylic Acid
[4-Meth oxy-3-(4-m eth ylpiper azin -1-yl)ph en yl]am ide (21e).
Compound 21e was synthesized as described for 5 using 2024
(1.2 g, 4.1 mmol), TEA (3.3 mL, 23.1 mmol), CDI (730 mg, 4.5
mmol) and (R,S)-3-(5-fluoro-1H-indol-3-yl)pyrrolidine (10) (987
mg, 4.1 mmol) in acetonitrile (75 mL). CC [eluent: EtOAc-
MeOH-TEA (5:2:1)] followed by recrystallization (EtOAc-
4-[2-(3-In d olyl)eth yl]-N-[4-m eth oxy-3-(4-m eth ylp ip er -
a zin -1-yl)p h en yl]p ip er id in e-1-ca r boxa m id e (21j). Com-
pound 21j was synthesized as described for 5 using 2024 (588
mg, 2.0 mmol), TEA (1.3 mL, 9.0 mmol), CDI (357 mg, 2.2
mmol) and indalpine (3)20 (457 mg, 2.0 mmol) in acetonitrile
(50 mL). Recrystallization (acetonitrile) gave 21j (700 mg,
1
light petroleum) gave 21e (1.0 g, 30%): mp 210-213 °C; H
1
NMR (DMSO-d6) δ 10.97 (s, 1 H), 7.88 (s, 1 H), 7.35 (m, 2 H),
7.28 (d, 1 H, J ) 2.2 Hz), 7.14 (m, 2 H), 6.91 (dt, 1 H, J ) 8.8
Hz and J ) 2.2 Hz), 6.76 (d, 1 H, J ) 8.8 Hz), 3.93 (t, 1 H, J
) 6.6 Hz), 3.73 (s, 3 H), 3.62 (m, 2 H), 3.55-3.25 (m, 2 H),
2.93 (br s, 4H), 2.45 (br s, 4 H), 2.30 (m, 1H), 2.23 (s, 3H), 2.10
(m, 1 H); FAB-MS ((M + H)+) m/z 452. Anal. (C25H30FN5O2)
C, H, N.
76%): mp 200-202 °C; H NMR (DMSO-d6) δ 10.68 (s, 1 H),
8.16 (s, 1 H), 7.50 (d, 1 H, J ) 7.7 Hz), 7.33 (d, 1 H, J ) 7.7
Hz), 7.07 (m, 4 H), 6.95 (t, 1 H, J ) 7.8 Hz), 6,76 (d, 1 H, J )
8.8 Hz), 4.09 (d, 2 H, J ) 13.2 Hz), 3.71 (s, 3 H), 2.94 (br s, 4
H), 2.74 (m, 4 H), 2.45 (br s, 4 H), 2.20 (s, 3 H), 1.76 (d, 2 H,
J ) 13.2 Hz), 1.67 (m, 2 H), 1.50 (m, 1 H),1.10 (m, 2 H); FAB-
MS ((M + H)+) m/z 476. Anal. (C28H37N5O2) C, H; N: calcd,
14.72%; found, 15.35%.
1-{2-[4-(6-F lu or o-1H-in d ol-3-yl)p ip er id in -1-yl]eth yl}-3-
[4-m eth oxy-3-(4-m eth ylp ip er a zin -1-yl)p h en yl]u r ea Dih y-
d r och lor id e Hyd r a te (21f). Compound 21f was synthesized
as described for 5 using 2024 (1.2 g, 4.1 mmol), TEA (2.7 mL,
18.6 mmol), CDI (730 mg, 4.5 mmol) and 2-[4-(6-fluoro-1H-
indol-3-yl)piperidin-1-yl]ethylamine (11) (1.1 g, 4.1 mmol) in
1-(2-(5-Ben zyloxy-1H-in d ol-3-yl)eth yl)-3-[4-m eth oxy-3-
(4-m eth ylp ip er a zin -1-yl)p h en yl]u r ea‚0.25H2O (21k ). Com-
pound 21k was synthesized as described for 5 using 2024 (1.8
g, 6.1 mmol), TEA (4.9 mL, 33.6 mmol), CDI (1.1 g, 6.7 mmol)
and 5-benzyloxytryptamine (1.8 g, 6.1 mmol) in acetonitrile

1156 J ournal of Medicinal Chemistry, 2000, Vol. 43, No. 6
Matzen et al.
(100 mL). CC [eluent: toluene-MeOH-TEA (7:2:1)] followed
by recrystallization (EtOAc-light petroleum) gave 21k (2.4 g,
[3-(2-(Dim eth yla m in o)eth oxy)-4-m eth oxyp h en yl]a m id e
Hyd r och lor id e (25a ). Compound 25a was synthesized as
described for 5 using 3-(2-(dimethylamino)ethoxy)-4-meth-
oxyaniline (24)18 (631 mg, 3.0 mmol), TEA (1.1 mL, 8.0 mmol),
CDI (535 mg, 3.3 mmol) and 4-(5-fluoro-1H-indol-3-yl)piperi-
dine (4) (655 mg, 3.0 mmol) in acetonitrile (75 mL). CC [eluent:
EtOAc-MeOH-TEA (5:2:1)] and preparation of the dihydro-
1
77%): mp 153-154 °C; H NMR (DMSO-d6) δ 10.70 (s, 1 H),
8.24 (s, 1 H), 7.42 (m, 2 H), 7.38 (t, 2 H, J ) 6.0 Hz), 7.30 (t,
1 H, J ) 6.1 Hz), 7.20 (d, 1 H, J ) 9.0 Hz), 7.15 (s, 1 H), 7.09
(s, 1 H), 6.99 (s, 1 H), 6.86 (d, 1 H, J ) 8.8 Hz), 6.75 (m, 2 H),
5.92 (t, 1 H, J ) 5.0 Hz), 5.05 (s, 2 H), 3.67 (s, 3 H), 3.42 (m,
3 H), 2.91 (s, 4 H), 2.80 (t, 2 H, J ) 7.0 Hz), 2.39 (br s, 3 H),
2.15 (s, 3 H); MS (M+) m/z 513. Anal. (C30H35N5O3‚0.25H2O)
C, H, N.
1
chloride gave 25a (900 mg, 61%): mp 210-211 °C; H NMR
(DMSO-d6) δ 10.90 (s, 1 H), 8.41 (s, 1 H), 7.33 (m, 2 H), 7.19
(d, 1 H, J ) 2.2 Hz), 7.08 (dd, 1 H, J ) 11.0 Hz and J ) 2.2
Hz), 6.90 (m, 3 H), 4.30 (m, 4 H), 3.75 (s, 3H), 3.49 (t, 2 H, J
) 5.3 Hz), 3.02 (m, 3 H), 2.90 (6 H, s), 1.95 (d, 2 H, J ) 11.9
Hz), 1.55 (m, 2 H); FAB-MS ((M + H)+) m/z 455 Anal.
(C25H31N4O3‚HCl) C, H; Cl: calcd, 7.22%; found, 7.88%. N:
calcd, 11.41%; found, 11.88%.
1-[3-(2-(Dim eth yla m in o)eth oxy)-4-m eth oxyp h en yl]-3-
{2-[4-(6-flu or o-1H-in dol-3-yl)piper idin -1-yl]eth yl}u r ea Di-
h yd r och lor id e Hyd r a te (25b). Compound 25b was synthe-
sized as described for 5 using 2418 (631 mg, 3.0 mmol), TEA
(1.1 mL, 8.0 mmol), CDI (535 mg, 3.3 mmol) and 2-[4-(6-fluoro-
1H-indol-3-yl)piperidin-1-yl]ethylamine (11)24 (758 mg, 2.9
mmol) in acetonitrile (75 mL). CC [eluent: EE-MeOH-TEA
(5:2:1)] followed by preparation of the dihydrochloride gave 25b
(850 mg, 52%): mp 130-131 °C; 1H NMR (DMSO-d6) δ 10.95
(s, 1 H), 8.91 (s, 1 H), 7.68 (m, 1 H), 7.50 (d, 1H, J ) 2.2 Hz),
7.14 (2H, m), 645-7.00 (4 H, m), 4.42 (t, 2 H, J ) 6.0 Hz),
3.75 (s, 3 H); 3.70-3.40 (m, 6 H), 2.76 (m, 5 H), 2.82 (6H, s),
2.12 (br s, 4 H); FAB-MS ((M + H)+) m/z 498. Anal. (C27H36N5O3‚
2HCl‚H2O) C, H, Cl, N.
Recep tor Bin d in g Assa ys. Affinities for 5-HT1B receptors
were determined in rat frontal cortex using [125I]iodocyanopin-
dolol as radioligand, final concentration 0.1 nM.25 The 5-HT1D
assays were performed according to Peroutka et al.26 using
membranes prepared from calf striatum and 1.7 nM [3H]-
serotonin in the presence of 100 nM 8-OH-DPAT and 100 nM
mesulergine to mask 5-HT1A and 5-HT2C binding sites. Non-
specific binding was determined in the presence of 10 µM
serotonin. Inhibition by drugs of the binding of 0.5 nM [3H]8-
OH-DPAT to 5-HT1A receptors in membranes from rat hip-
pocampus was determined according to the reported method.27
1-[2-(5-Hyd r oxy-1H-in d ol-3-yl)eth yl]-3-[4-m eth oxy-3-(4-
m eth ylp ip er a zin -1-yl)p h en yl]u r ea Hem ih yd r a te (21l). A
solution of 21k (1.1 g, 21. mmol) in MeOH (100 mL) was
hydrogenated using Pd-C 5% (1.0 g) as catalyst. Filtration,
CC [EtOAc-MeOH-TEA (5:2:1)] gave 21l (200 mg, 25%): mp
1
140-142 °C; H NMR (DMSO-d6) δ 10.46 (s, 1 H), 8.55 (s, 1
H), 8.19 (s, 1 H), 7.12 (d, 1 H, J ) 8.8 Hz), 7.05 (d, 1 H, J )
3.0 Hz), 6.97 (d, 1 H, J ) 3.0 Hz), 6.91 (dd, 1 H, J ) 8.9 Hz
and J ) 3.1 Hz), 6.87 (d, 1 H, J ) 3.0 Hz), 6.78 (d, 1 H, J )
8.9 Hz), 6.57 (dd, 1 H, J ) 8.7 Hz and J ) 3.3 Hz), 5.93 (t, 1
H, J ) 6.6 Hz), 3.70 (s, 3 H), 3.43 (d, 4 H, J ) 13.2 Hz), 2.91
(br s, 4 H), 2.75 (t, 2 H, J ) 6.7 Hz), 2.40 (m, 2 H), 2.25 (s, 3
H); FAB-MS ((M + H)+) m/z 424. Anal. (C23H29N5O3‚0.5H2O)
C; H: calcd, 6.99%; found, 8.19%. N: calcd, 16.19%; found,
15.37%.
3-{1-[4-Meth oxy-3-(4-m eth ylp ip er a zin -1-yl)p h en yla m i-
n oca r bon yl]-4-p ip er id yl}in d ole-5-ca r boxa m id e Hyd r a te
(21m ). Compound 21m was synthesized as described for 5
using 2024 (1.2 g, 4.1 mmol), TEA (2.7 mL, 18.5 mmol), CDI
(730 mg, 4.5 mmol) and 4-(5-carboxamido-1H-indol-3-yl)-
piperidine monohydrate (15) (1.1 g, 4.1 mmol) in acetonitrile
(75 mL). CC [eluent: toluene-MeOH-TEA (7:2:1)] followed
by recrystallization (acetonitrile) gave 21m (241 mg, 12%): mp
179 °C dec; 1H NMR (DMSO-d6) δ 11.00 (s, 1 H), 8.29 (s, 1 H),
8.22 (s, 1 H), 7.80 (br s, 1 H), 7.63 (d, 1 H, J ) 8.8 Hz), 7.33 (d,
1 H, J ) 8.8 Hz), 7.20 (d, 1 H, J ) 2.2 Hz), 7.11 (m, 2H), 7.02
(br s, 1 H), 6.79 (d, 1 H, J ) 8.8 Hz), 4.26 (d, 2 H, J ) 12.8
Hz), 3.72 (s, 3 H), 3.05 (m, 7 H), 2.66 (br s, 4 H), 2.35 (s, 3 H),
2.03 (d, 2 H, J ) 13.0 Hz), 1.60 (m, 2 H); FAB-MS ((M + H)+)
m/z 491. Anal. (C27H34N6O3‚H2O) C, H, N.
4-(5-F lu or o-1H-in d ol-3-yl)p ip er id in e-1-ca r boxylic Acid
[2,3-Dih yd r o-1′-m eth ylsp ir o(ben zofu r a n -3,4′-p ip er id in e)]-
a m id e Hem ih yd r a te (23a ). Compound 23a was synthesized
as described for 5 using 5-amino-2,3-dihydro-1′-methylspiro-
(benzofuran-3,4′-piperidine) (22)18 (300 mg, 1.4 mmol), TEA
(0.5 mL, 3.5 mmol), CDI (243 mg, 1.5 mmol) and 4-(5-fluoro-
1H-indol-3-yl)piperidine (4) (306 mg, 1.4 mmol) in acetonitrile
(50 mL). CC [toluene-MeOH-TEA (7:2:1)] followed by recrys-
tallization (EE-light petroleum) gave 23a (300 mg, 47%): mp
Ra bbit Sa p h en ou s Vein (RSV). The inhibition of the
contractile responses elicited by sumatriptan in rabbit saphe-
nous vein was determined according to a published method.28
For determining of 5-HT1B/1D antagonistic activity, segments
of isolated rabbit saphenous veins were suspended in organ
baths and subjected to two concentration-response curves to
sumatriptan, the second challenge being performed in the
presence of the antagonist or control vehicle (incubated for 60
min). Apparent pA2 values were calculated using a single
antagonist concentration in at least 3 preparations.
1
213-215 °C; H NMR (DMSO-d6) δ 10.85 (s, 1 H), 8.27 (s, 1
[3H]5-HT Relea se. The effect on the sumatriptan-induced
inhibition of potassium-evoked [3H]5-HT release from guinea
pig cortex slices was determined according to a method
published by Ormandy.29 Cerebral cortices were removed from
male Dunkin-Hartley guinea pigs, cross-chopped into slices,
and then incubated 30 min with [3H]5-HT. Slices were placed
into chambers of a superfusion apparatus and superfused with
oxygenated Krebs’s solution. Superfusate was collected in
4-min periods beginning 60 min after the slices were placed
in the chambers. The slices were exposed to two periods (4
min) of 30 mM K+ at 68- and 108-min superfusion (S1 and
S2, respectively). Sumatriptan at a concentration of 3 µM
(controls) and sumatriptan plus test compounds (30 nM, 300
nM, and 3 µM, respectively) were superfused prior to and
during the S2 stimulation period. Released radioactivity in
each sample was measured, and after basal release was
subtracted, the S2/S1 ratio was calculated. Results represent
the mean ((SEM) of 3-4 determinations. The effects of drugs
were expressed as a percent of control, i.e. purely sumatriptan
perfused S2/S1 ratio.
H), 7.32 (dd, 1H, J ) 9.7 Hz and J ) 2.2 Hz), 7.25 (d, 1 H, J
) 2.2 Hz), 7.19 (dd, 1 H, J ) 9.7 Hz and J ) 2.2 Hz), 7.13 (m,
2 H), 6.81 (dt, 1 H, J ) 9.8 Hz and J ) 2.2 Hz), 6.62 (d, 1 H,
J ) 8.8 Hz), 4.55 (s, 2 H), 4.44 (d, 2 H, J ) 11.9 Hz), 2.97 (m,
3 H), 2.73 (d, 2 H, J ) 11.9 Hz), 2.42 (s, 3 H), 1.95 (m, 4 H),
1.80 (dt, 2 H, J ) 12.5 Hz and J ) 4.4 Hz), 1.60 (m, 4 H);
FAB-MS ((M + H)+) m/z 463. Anal. (C27H31FN4O2‚0.5H2O) C,
H, N.
1-{2-[4-(6-F lu or o-1H -in d ol-3-yl)p ip er id in -1-yl]et h yl}-
[2,3-d ih yd r o-1′-m eth ylsp ir o(ben zofu r a n -3,4′-p ip er id in e)]-
a m id e (23b). Compound 23b was synthesized as described
for 5 using 2218 (349 mg, 1.6 mmol), TEA (0.58 mL, 4.0 mmol),
CDI (292 mg, 1.8 mmol) and 2-[4-(6-fluoro-1H-indol-3-yl)-
piperidin-1-yl]ethylamine (11) (418 mg, 1.6 mmol) in acetoni-
trile (50 mL). Recrystallization (EE-light petroleum) gave 23b
(170 mg, 21%): mp 237-239 °C; 1H NMR (DMSO-d6) δ 10.30
(s, 1 H), 8.37 (s, 1 H), 7.52 (dd, 1 H, J ) 8.8 Hz and J ) 4.4
Hz), 7.23 (d, 1 H, J ) 3.0 Hz), 7.07 (m, 3 H), 6.80 (dt, 1 H, J
) 8.7 Hz and J ) 3.0 Hz), 6.60 (d, 1 H, J ) 8.9 Hz), 5.91 (t, 1
H, J ) 7.0 Hz), 4.29 (s, 2 H), 3.21 (m, 2 H), 2.99 (d, 2 H, J )
11.0 Hz), 2.69 (d, 3 H, J ) 10.09 Hz), 2.43 (t, 2 H, J ) 6.6 Hz),
2.17 (s, 3 H), 2.11 (m, 2 H), 1.98-1.55 (m, 10 H); FAB-MS ((M
+ H)+) m/z 506. Anal. (C29H36FN5O2) C, H, N.
[3H]5-HT Reu p ta k e In h ibition . Crude synaptosomal frac-
tion (P2 fraction) of rat cerebral tissue was prepared according
to Whittaker31 giving a suspension enriched in synaptosomes
of 3 mg protein/mL. The synaptosomal uptake was performed
4-(5-F lu or o-1H-in d ol-3-yl)p ip er id in e-1-ca r boxylic Acid

5-HT Reuptake Inhibitors with 5-HT1B/ 1D Activity
J ournal of Medicinal Chemistry, 2000, Vol. 43, No. 6 1157
in a total volume of 570 µL, which contained 12 nM [3H]5-HT.
Incubation was performed at 37 °C for 4 min in Krebs-Ringer
buffer (126 mM NaCl, 1.4 mM MgCl2, 4.8 mM KCl, 15.8 mM
Na2HPO4, 11 mM glucose, 0.9 mM CaCl2, pH 7.4, 346
mOsM).30
C.; Routledge, C.; Selkirk, J .; Slade, P. D. The selective 5-HT1B
receptor inverse agonist 1′-methyl-5-[2′-methyl-4′-(5-methyl-
1,2,4-oxadiazol-3-yl)biphenyl-4-yl]carbonyl]-2,3,6,7-tetrahydrospiro-
[furo[2,3-f]indole-3,4′-piperidine] (SB-224289) potently blocks
terminal 5-HT autoreceptor function both in vitro and in vivo.
J . Med. Chem. 1998, 41, 1218-1235.
(19) Roberts, C.; Price, G. W.; J ones, B. J . The role of 5-HT1B/1D
receptors in the modulation of 5-hydroxytryptamine levels in the
frontal cortex of the conscious guinea pig. Eur. J . Pharmacol.
1997, 326, 23-30.
(20) Gueremy, C.; Audiau, F.; Champseix, A. 3-(4-Piperidinylalkyl)-
indoles, selective inhibitors of neuronal 5-hydroxytryptamine
uptake. J . Med. Chem. 1980, 23, 1306-1310.
(21) Guillaume, J .; Dumont, C.; Laurent, J .; Ne´de´lec, L. (Tetrahydro-
1,2,3,6-pyridinyl-4-)-3-1H-indoles: synthe´se, proprie´te´s, se´ro-
toninergique et anti-dopaminergiques. Eur. J . Med. Chem. 1987,
22, 33-43.
(22) Abou-Gharbia, M.; Patel, U. R.; Moyer, J . A.; Muth, E. A.
Psychotropic agents: synthesis and antipsychotic activity of
substituted â-carbolines. J . Med. Chem. 1987, 30, 1100-1105.
(23) Bo¨ttcher, H.; Barnickel, G.; Hausberg, H.-H.; Haase, A. F.;
Seyfried, C. A.; Eiermann, V. Synthesis and dopaminergic
activity of some 3-(1,2,3,6-tetrahydro-1-pyridylalkyl)-indoles. A
novel conformational model to explain structure-activity rela-
tionships. J . Med. Chem. 1992, 35, 4020-4026.
Ack n ow led gm en t. We thank Uwe Eckert and Kurt
Schuster for the synthesis of some of the building blocks
mentioned in this publication; Sylke Rebscher, Doris
Seeger, Dagmar Wolf, Hermann Kaiser, Andreas Tigl-
mann, and Waldemar Walter for the determination of
the biological data; and Karin Ro¨lfing for assistance in
preparing the manuscript.
Refer en ces
(1) Zifa, E.; Fillion, G. 5-Hydroxytryptamine receptors. Pharmacol.
Rev. 1992, 44, 401-458.
(2) Peroutka, S. J . Serotonin receptor subtypes. CNS Drugs 1995,
4 (Suppl. 1), 18-28.
(3) Dubovsky, S. L.; Thomas, M. Serotonergic mechanisms and
current and future psychiatric practice. J . Clin. Psychiatry 1995,
56, 36-48.
(24) Clitherow, J . W.; Scopes, D. I. C.; Skingle, M.; J ordan, C. C.;
Feniuk, W.; Campbell, I. B.; Carter, M. C.; Collington, E. W.;
Connor, H. E.; Higgins, G. A.; Beattie, D.; Kelly, H. A.; Mitchell,
W. L.; Oxford, A. W.; Wadsworth, A. H.; Tyers, M. B. Evolution
of a novel series of [N,N-dimethylamino)propyl]- and piperazi-
nylbenzanilides as the first selective 5-HT1D antagonists. J . Med.
Chem. 1994, 37, 2253-2257.
(25) Hoyer, D.; Engel, G.; Kalkman, H. O. Characterization of the
5-HT1B recognition site in rat brain: binding studies with
(-)[125I]Iodocyanopindolol. Eur. J . Pharmacol. 1985, 118, 1-12.
(26) Peroutka, S. J .; Switzer, J . A.; Hamik, A. Identification of
5-hydroxytryptamine1D binding sites in human brain mem-
branes. Synapse 1989, 3 (1), 61-66.
(27) Cossery, J . M.; Gozlan, H.; Spampinato, U.; Perdicakis, C.;
Guillaumet, G.; Pichat, L.; Hamon, M. The selective labeling of
central 5-HT1A receptor binding sites by [3H]5-methoxy-3-(di-n-
propylamino)chroman. Eur. J . Pharmacol. 1987, 140, 143-155.
(28) Razzaque, Z.; Longmore, J .; Hill, R. G. Differences in the effects
of ketanserin and GR127935 on 5-HT-receptor mediated re-
sponses in rabbit saphenous vein and guinea-pig jugular vein.
Eur. J . Pharmacol. 1995, 283, 199-206.
(29) Ormandy, G. C. Increased cyclic AMP reduces 5-HT1D receptor-
mediated inhibition of [3H]5-hydroxytryptamine release from
guinea-pig cortical slices. Eur. J . Pharmacol.-Mol. Pharmacol.
Sect. 1993, 244, 189-192.
(30) Wong, D. T.; Bymaster, F. P.; Mayle, D. A.; Reid, L. R.;
Krushinski, J . H.; Robertson, D. W. LY 248686, a new inhibitor
of serotonin and norephinephrine uptake. Neuropsychopharma-
cology 1993, 8, 23-33.
(31) Whittaker, V. P. The synaptosome. In Handbook of Neurochem-
istry; Laiths, A., Ed.; Plenum Press: London and New York,
1969; pp 327-364.
(32) Mor, M.; Rivara, S.; Bordi, F.; Plazzi, P. V.; Spadoni, G.;
Diamantini, G.; Balsamini, C.; Tarzia, G.; Fraschini, F.; Lucini,
V.; Nonno, R.; Stankov, B. M. Melatonin Receptor Ligands:
Synthesis of New Melatonin Derivatives and Comprehensive
Comparative Molecular Field Analysis (CoMFA) Study. J . Med.
Chem. 1998, 41, 3831-3844.
(33) Fozard, J . R.; Kilbinger, H. 8-OH-DPAT inhibits the neurotrans-
mitter release from guinea pig enteric cholinergic nervs by
activating 5-HT1A receptors. J . Pharm. Pharmacol. 1985, 86,
601P.
(4) Hoyer, D.; Clarke, D. E.; Fozard, J . R.; Hartig, P. R.; Martin, G.
R.; Mylecharane, E. J .; Saxena, P. R.; Hymphrey, P. P. A.
International union of pharmacology classification for receptors
of 5-hydroxytryptamine (Serotonin). Pharmacol. Rev. 1994, 46,
157-204.
(5) Martin, G. R.; Humphrey, P. P. A. Receptors for 5-hydroxy-
tryptamine: current perspectives on classification and nomen-
clature. Neuropharmacology 1994, 33, 261-273.
(6) Hartig, P. R.; Hoyer, D.; Humphrey, P. P. A.; Martin, G. R.
Alignment of receptor nomenclature with the human genome:
classification of 5-HT1B and 5-HT1D receptor subypes. Trends
Pharmacol. Sci. 1996, 17, 103-105.
(7) Glennon, R. A. Serotonin receptors: clinical implications. Neu-
rosci. Biobehav. Rev. 1990, 14, 35-47.
(8) Goodwin, G. M.; Phil, D.; Edin, F. R. C. P.; Psych, F. R. C. How
do antidepressants affect serotonin receptors? The role of sero-
tonin receptors in the therapeutic and side effect profile of SSRIs.
J . Clin. Psychiatry 1996, 57 (Suppl. 4), 9-13.
(9) Leonard, B. E. New approaches to the treatment of drepression.
J . Clin. Psychiatry 1996, 57 (Suppl. 4), 26-33.
(10) Kilts, C. D. Recent pharmacologic advances in antidepressant
therapy. Am. J . Med. 1994, 97 (Suppl. 6A), 3-12.
(11) Leonard, B. E. Mechanisms of action of antidepressants. CNS
Drugs 1995, 4 (Suppl. 1), 1-12.
(12) Davidson, C.; Stamford, J . A. Evidence that 5-hydroxytryptamine
release in rat dorsal raphe´ nucleus is controlled by 5-HT1A
,
5-HT1B and 5-HT1D autoreceptors. Br. J . Pharmcaol. 1995, 113,
1107-1109.
(13) Galzin, A. M.; Poirier, M. F.; Lista, A.; Chodkiewicz, J . P.; Blier,
P.; Ramdine, R.; Looˆ, J .; Roux, F. X.; Redondo, A.; Langer, S. Z.
Characterization of the 5-hydroxytryptamine receptor modula-
tion of the release of [3H]5-hydroxytryptamine in slices of the
human neocortex. J . Neurochem. 1992, 1293-1301.
(14) Rollema, H.; Clarke, T.; Sprouse, J . S.; Schulz, D. W. Combined
administration of a 5-hydroxytryptamine (5-HT)1D antagonist
and a 5-HT reuptake inhibitor synergistically increases 5-HT
release in guinea-pig hypothalamus in vivo. J . Neurochem. 1996,
67, 2204-2207.
(15) Pauwels, P. J . 5-HT1B/1D receptor antagonists. Gen. Pharmacol.
1997, 29, 293-303.
(16) Clitherow, J . W.; Scopes, D. I. C.; Beattie, D. T.; Skingle, M.
The evolution of selective 5-HT1D receptor antagonists. Exp.
Opin. Invest. Drugs 1995, 4, 323-331.
(17) Watson, J . M.; Burton, M. J .; Price, G. W.; J ones, B. J .;
(34) J orand-Lebrun, C.; Pauwels, P. J .; Palmier, C.; Chopin, P.; Moret,
C.; Marien, M.; Halazy, S. Arylpiperazide Derivatives of Phen-
ylpiperazines as a New Class of Potent and Selective 5-HT1B
receptor Antagonists. Bioorg. Med. Chem. Lett. 1997, 7, 3183-
3188.
Middlemiss, D. N. GR-127935 acts as
recombinant human 5-HT1DR and 5-HT1Dâ receptors. Eur. J .
Pharmacol. 1996, 314, 365-372.
a partial agonist at
(18) Gaster, L. M.; Blaney, F. E.; Davies, S.; Duckworth, D. M.; Ham,
P.; J enkins, S.; J ennings, A. J .; J oiner, G. F.; King, F. D.;
Mulholland, K. R.; Wyman, P. A.; Hagan, J . J .; Hatcher, J .;
J ones, B. J .; Middlemiss, D. N.; Price, G. W.; Riley, G.; Roberts,
J M9811054