Dopamine/serotonin receptor ligands. 10: SAR studies on azecine-type dopamine receptor ligands by functional screening at human cloned D1, D2L, and D5 receptors with a microplate reader based calcium assay lead to a novel potent D1/D5 selective antagonist

Article abstract of DOI:10.1021/jm050846j

On the basis of the benz[d]indolo[2,3-g]azecine derivative 1 (LE300), structure-activity relations were investigated in order to identify the pharmacophore in this new class of ligands. Various structural modifications were performed and the inhibitory activities at human cloned D₁, D_2L, and D₅ receptors were measured by using a simple fluorescence microplate reader based calcium assay. Subsequently, the affinities of active compounds were estimated by radioligand binding experiments, Deleting one of the aromatic rings as well as replacing it by a phenyl moiety abolishes the inhibitory activities almost completely. Contraction of the 10-membered central ring decreases them significantly. The replacement of indole by thiophene or N-methylpyrrole reduces the inhibitory activity, whereas replacing the indole by benzene increases it. Finally, the hydroxylated dibenz[d,g]azecine derivative 11d (LE404) was found to be more active than the lead 1 in the functional calcium assay as well as in radioligand displacement experiments.

Full text of DOI:10.1021/jm050846j

760
J. Med. Chem. 2006, 49, 760-769
Dopamine/Serotonin Receptor Ligands. 10:1 SAR Studies on Azecine-type Dopamine Receptor
Ligands by Functional Screening at Human Cloned D1, D2L, and D5 Receptors with a
Microplate Reader Based Calcium Assay Lead to a Novel Potent D1/D5 Selective Antagonist
Barbara Hoefgen,†,‡ Michael Decker,§ Patrick Mohr,§ Astrid M. Schramm,† Sherif A. F. Rostom,† Hussein El-Subbagh,†
Peter M. Schweikert,† Dirk R. Rudolf,† Matthias U. Kassack,† and Jochen Lehmann*,†,§
Institute of Pharmacy, UniVersity of Bonn, An der Immenburg 4, D-53121 Bonn, Germany; Department of Psychiatry, UniVersity of Bonn,
Sigmund-Freud-Str. 25, D-53105 Bonn, Germany; and Institute of Pharmacy, Friedrich-Schiller-UniVersity Jena, Philosophenweg 14,
D-07743 Jena, Germany
ReceiVed August 25, 2005
On the basis of the benz[d]indolo[2,3-g]azecine derivative 1 (LE300), structure-activity relations were
investigated in order to identify the pharmacophore in this new class of ligands. Various structural
modifications were performed and the inhibitory activities at human cloned D1, D2L, and D5 receptors were
measured by using a simple fluorescence microplate reader based calcium assay. Subsequently, the affinities
of active compounds were estimated by radioligand binding experiments. Deleting one of the aromatic
rings as well as replacing it by a phenyl moiety abolishes the inhibitory activities almost completely.
Contraction of the 10-membered central ring decreases them significantly. The replacement of indole by
thiophene or N-methylpyrrole reduces the inhibitory activity, whereas replacing the indole by benzene
increases it. Finally, the hydroxylated dibenz[d,g]azecine derivative 11d (LE404) was found to be more
active than the lead 1 in the functional calcium assay as well as in radioligand displacement experiments.
Introduction
contracted azonine analogues 2, derivatives lacking the indole
(3) and the benzene part (4), respectively, and a series of
compounds where the condensed benzene is replaced by phenyl
in different positions (5). Furthermore, the compounds 6 and 7
(azonine analogues of 4 and 5) and some azecines, derived from
1 by replacing the benzene ring with pyrrole (8) and the indole
nucleus with pyrrole (9) (differently annelated than the indole
in 1 due to synthetic availability), thiophene (10), and benzene
(11), respectively, were synthesized (Figure 1). For investigating
SAR, the inhibitory activities of all compounds were measured
by using a recently established microplate reader based func-
tional calcium assay.8 Subsequently, the affinities of the active
derivatives were determined by radioligand binding experiments.
The dopaminergic system plays an important role in regulat-
ing neuronal motor control, cognition, event prediction, emotion,
and vascular function. Neuropsychiatric diseases such as
schizophrenia, Parkinson’s disease, or addiction are strongly
related to a disregulation of the dopaminergic signal transduc-
tion.2,3 Thus, dopamine receptors are attractive as therapeutic
targets. There are five dopamine receptor subtypes that may be
divided into two subfamilies: the Gs-coupled D1-like receptors
(D1, D5) and the Gi-coupled D2-like receptors (D2, D3, D4).4
Although agonists and antagonists with a certain subtype
selectivity are available, there is still a need for truly subtype
selective ligands, e.g. as tools for pharmacological binding
studies. On the other hand, therapy of schizophrenia with
antipsychotic drugs can implicate severe side effects, such as
extrapyramidal motor effects. Higher subtype selectivity or new
binding profiles and combinations of different dopamine receptor
subtypes, respectively, may lead to more effective neuroleptic
drugs with fewer therapy-limiting side effects.
The idea behind the synthesis of the new heterocyclic system
of 1 (Figure 1) was to incorporate the substructures of tryptamine
and â-phenylethylamine into a moderately constrained 10-
membered azecine ring.5 1 represents a chemically novel type
of dopamine receptor antagonist showing subnanomolar affinity
for the rat striatal D1 receptor and nanomolar affinity for human
dopamine and serotonin receptors.5-7
The heterocyclic system of the lead 1 consists of the indole,
the benzene, the central azecine ring, and a methyl group as
N-substituent. The objective of our present study was to estimate
the pharmacological relevance of these moieties. Therefore, we
synthesized different N-alkylated derivatives 1a,b,c of 1, ring-
Chemistry
The benzindoloazecines 1a-c were prepared starting from
tryptamine and isochromanone by a lactamization, cyclization,
reduction (f12), quaternization (f 13a-c), ring-extension
sequence as previously described for 1 (R ) CH3) (Figure 2).5
A crucial step is the Birch cleavage of 13a-c. Extensive
reduction attacking the aromatic systems and a nonselective C,N-
cleavage, yielding 12 again, were shown to be the main side
reactions. The synthesis of nine-membered analogues is shown
in Figure 3.
Two methoxylated derivatives 3a (R′ ) OCH3, R′′ ) H) and
3b (R′ ) R′′ ) OCH3) of the “deindolized” 1 have been
prepared as described previously.9 Compound 4a, which has
been introduced as a potential diuretic,10,11 can be considered
as 1 without the benzene ring and was synthesized by us
according to Figure 4. Since N-alkylation and not the favored
N-acylation is the decisive initial step in the formation of lactams
from lactones,12 the alkylation of tryptamine with ethyl 5-bromo-
pentanoate yielded 16 in higher yields than δ-valerolactone did.
* Corresponding author. Telephone: +49-(0)3641-949803. Fax: +49-
(0)3641-949802. E-mail: j.lehmann@uni-jena.de.
† Institute of Pharmacy, University of Bonn.
The nine-membered analogue 6 is known10 but was obtained
by us differently starting from compounds 18 or 19, respectively
(Figure 5).
‡ Department of Psychiatry, University of Bonn.
§ Friedrich-Schiller-University Jena.
10.1021/jm050846j CCC: $33.50 © 2006 American Chemical Society
Published on Web 12/09/2005

SAR of Azecine-type Dopamine Receptor Antagonists
Journal of Medicinal Chemistry, 2006, Vol. 49, No. 2 761
Figure 1. Structural variations of the lead compound 1. R ) CH3 and other alkyl; R′, R′′ ) H, OCH3.
Figure 4. Synthesis of indoloazecines. Reagents: (a) ethyl 5-bromo-
pentanoate; (b) LiAlH4; (c) (1) R-X, (2) Na0/liq NH3.
Figure 2. Variation of N-alkyl in 1. Reagents: (a) R-I or R-Br; (b)
Na0/liq NH3.
Figure 5. Synthesis of indoloazonines. Reagents: (a) (1) POCl3, reflux,
(2) H2O, NaOH, (iminium salt), (3) NaBH4; (b) (1) Et3OBF4, (2) NaBH4,
(3) LiAlH4; (c) (1) MeI, acetone, (2) Na0/liq NH3.
the hydroxyamide 24 under mild conditions and via 22 the
lactam 23 under more drastic conditions. 24 was shown to be
more reactive than the other hydroxyamides we have investi-
gated. Therefore, 25 could be obtained from both 23 and 24.
Quaternization and reductive cleavage finally afforded the target
compound 5a (Figure 6).
Synthesis of the 7-phenylazecino[5,4-b]indole derivative 5b
was conducted analogously to the unphenylated compounds
4a,b. Since the reduction of 2-phenylglutaric anhydride14 gave
mixtures of R-phenyl- and γ-phenyl-δ-valerolactone, which
could not be separated sufficiently by distillation, the lactone
Figure 3. Synthesis of Benzindoloazonines. Reagents: (a) 2 N H2SO4,
EtOH, H2O, reflux; (b) LiAlH4; (c) R-I; (d) Na0/liq NH3.
The phenylated δ-valerolactone 21 and the corresponding
phenylated δ-bromopentanoates 22 and 27, obtained from the
lactones 21 and 26 by treatment with HBr gas in ethanolic
solution, were shown to be useful starting materials in the
syntheses of phenylated indoloazecines 5a,b. 21 was obtained
by reduction of 4-benzoylbutyric acid according to the procedure
of Julia and Rouault.13 Treatment of 21 with tryptamine gave

762 Journal of Medicinal Chemistry, 2006, Vol. 49, No. 2
Hoefgen et al.
Figure 6. Synthesis of phenylated indoloazecines. Reagents: (a) HBr, EtOH; (b) tryptamine, EtOH, reflux; (c) tryptamine, K2CO3, KI, n-BuOH,
reflux; (d) (1) POCl3, reflux, (2) H2O, NaOH, (iminium salt), (3) NaBH4; (e) (1) MeI, acetone, (2) Na0/liq NH3.
Figure 7. Synthesis of phenyllated indoloazecines. Reagents: (a) HBr, EtOH; (b) tryptamine, K2CO3, KI, n-BuOH, reflux; (c) (1) POCl3, reflux,
(2) H2O, NaOH, (iminium salt), (3) NaBH4; (d) MeI, diethyl ether; (e) Na0/liq NH3; (f) tryptamine, (CH3)3N, CHCl3; (g) methanolic HCl (2%); (h)
THF, LiAlH4, reflux.
26 was prepared by alkylation of diethyl phenylmalonate with
3-chloropropyl acetate, hydrolysis, decarboxylation, and cy-
clization.15 26 was transferred into the bromo ester 27, which
reacted with tryptamine to give the lactam 28 or the corre-
sponding hydroxyamide, respectively, according to the reaction
conditions. Again, 27 proved to be more suitable to proceed to
the target compound 5b (Figure 7) than 26. Compound 29, as
well as all the other phenylated quinolizines, showed two sets
of signals in the 1H NMR spectra due to formation of
diastereomeres. The 8-phenylazecino[5,4-b]indole 5c16,17 and the
7-phenylazonino[5,4-b]indole 7d16,18 were prepared as reported
in the literature and outlined in Figure 7.
Figure 8 demonstrates the synthesis of the novel 4-phenyl-
(7a), 5-phenyl- (7c), and 6-phenylazonino[5,4-b]indoles (7b)
via 41, 49, 44. R- (43) and γ-phenylbutyrolactone (39) proved
to be much more reactive with regard to the lactamization with
tryptamine than â-phenylbutyrolactone (46) and its homologous
R- and δ-phenyl-δ-valerolactones, respectively. Transformation
into the bromo esters was not necessary. Several attempts to
prepare the lactam out of lactone 46 and tryptamine only gave
the corresponding hydroxyamide, which produced many byprod-
ucts in the transformation into the indolizine, but tryptamine
and the bromo ester 47 reacted to 48 successfully.
showed an eight-proton singlet signal for the protons 5, 6, 8, 9
(δ ) 2.8 ppm) due to identical chemical shifts and high
conformational mobility. Methoxylated analogues are more
reactive, and cyclization could be performed via hydroxyamides
60a,b (Figure 10). The phenolic target compounds were obtained
by ether cleavage with 47% HBr using 11b for preparation of
11c and the quaternary salt of 61a for 11d.
Pharmacology
Screening of compounds for agonistic and antagonistic
activity at G-protein-coupled dopamine receptors was performed
using a calcium assay developed by us recently.8 This functional
assay is based on the measurement of intracellular Ca2+ using
fluorescent dye Oregon Green and a fluorescence microplate
reader. The assay is fast, simple, and avoids the use of
radioactivity. This functional calcium assay was conducted with
recombinant HEK293 cell lines stably expressing hD1, hD2L,
and hD5 dopamine receptors, respectively, by performing dose-
response curves of standard agonists and standard antagonists.
EC50 values of standard agonists and Ki values of standard
antagonists obtained by the calcium assay were in concordance
with literature-based data. This made the calcium assay appear
well suitable for the purpose of screening compounds at
dopaminergic receptors.
The target compounds and many of the intermediates
synthesized in this study were screened for agonistic and
antagonistic activity. None of these showed agonistic activity
at the three dopamine receptors investigated. The inhibitory
activity was preliminarily measured by preincubation of recom-
binant cells with test compound in a 10 µM concentration. After
injection of standard agonist the decrease of the agonist-induced
Due to the lower reactivity of benzene compared to indole,
the Bischler-Napieralsky-type cyclizations of N-phenylethyl
lactams19 comparable to, for example, N-indolylethyl lactams
16, 18, 23, 28, or of N-(phenylethyl)hydroxyamides related to
24 did not work. So we synthesized 5220 and the novel 51 from
2-arylethyl chlorides and suitable nitriles under more drastic
conditions using tin tetrachloride and proceeded as outlined in
Figure 9. Interestingly, the symmetric dibenzoquinolizine 58

SAR of Azecine-type Dopamine Receptor Antagonists
Journal of Medicinal Chemistry, 2006, Vol. 49, No. 2 763
Figure 8. Synthesis of phenylated indoloazonines. Reagents: (a) 200 °C; (b) (1) POCl3, reflux, (2) H2O, NaOH; (c) NaBH4; (d) (1) MeI, acetone,
(2) Na0/liq NH3; (e) HBr, EtOH.
Figure 10. Synthesis of hydroxylated and methoxylated dibenz-
azecines. Reagents: (a) toluene, reflux; (b) (1) POCl3, (2) NaBH4/
MeOH; (c) (1) R-X, (2) Na0/liq NH3; (d) HBr.
Figure 9. Synthesis of dibenzo- and benzothienoazecines. Reagents:
(a) SnCl4; (b) Br(I)CH2CH2OH; (c) H2/PtO2/EtOH (for 56); NaBH4
35, 42, 43, 45-47, and 50 showed less than 50% signal
reduction (Ki > 10 µM). Two of these compounds were found
to have moderate affinity for hD2L: 5a (Ki ∼ 0.5 µM) and 7a
(Ki ∼ 0.1 µM). Eight compounds showed a signal reduction of
more than 50% and were further characterized by determination
of IC50 and Ki values, respectively. Ki values are given in Table
1.
(for 55); (d) polyphosphoric acid, 160 °C; (e) (1) R-I (quaternary salts),
(2) Na0/liq NH3.
fluorescence signal was determined (standard agonist concentra-
tion for hD1, SKF38393, 100 nM; hD2L, quinpirole, 30 nM;
and hD5, SKF38393, 10 nM). Compounds 1b, 1c, 2b, 3b, 4a,
4b, 5a-5c, 6, 7a, 7c, 7d, 8, 10b, 11b, 11e, 11f, 15, 17, 21-32,

764 Journal of Medicinal Chemistry, 2006, Vol. 49, No. 2
Hoefgen et al.
Table 1. Inhibitory Activities at Human Cloned Dopamine
ReceptorssCa2+ Assay Data
The annelated benzene in 1 cannot be replaced with phenyl
to maintain pharmacological activity. All of the compounds
containing a phenyl group at the aliphatic ring system (both in
9- and 10-membered rings) lose their activity, irrespective of
its location in position 4, 5, 6, or 7 in the azonine ring
(compounds 7a-d) and 4, 7, or 8 in the azecine ring system
(compounds 5a-c), respectively. Only a phenyl group in
position 6 of the azonine (7b) produces some activity. These
binding profiles are quite surprising, since the increase of
flexibility of the pharmacophoric benzene ring was supposed
to increase affinity.
Ki (nM) ( SEMa
compd
hD1
hD2L
hD5
LE300
1a
7b
60.4 ( 20.4
170 ( 63
19.0 ( 11.7
82.6 ( 24.5
943 ( 194
264 ( 46
92.0 ( 29.3
8.47 ( 4.32
65.7 ( 28.3
33.5 ( 17.0
12.7 ( 6.35
22.3 ( 11.1
112 ( 50.5
337 ( 138
33.7 ( 14.3
3.09 ( 3.19
2.32 ( 1.90
1.69 ( 1.94
742 ( 253
∼1000
9
10a
11a
11c
11d
207 ( 74.5
40.4 ( 4.84
20.7 ( 5.65
6.93 ( 5.31
In contrast to all of the other structural variations, the
substitution of the indole 1 moiety against other aromatic ring
systems yielded antagonists with considerable inhibitory activity.
Inhibitory activities for hD1, hD2, and hD5 and affinities for
hD1, hD2, hD4, and hD5 are given in Tables 1 and 2. 1-Methyl-
1H-pyrrole or thiophene instead of indole generally decreases
the affinities compared to the lead 1 more (9) or less (10a). A
second annelated benzene replacing the indole (11a) increases
the inhibitory activities moderately compared to 1 (Table 1).
The decreased affinities go together with a slightly improved
selectivity toward the D1 receptor subtype family (Table 2).
Conclusively, we tried to optimize the new D1/D5-selective lead
structure 11a by introducing a “dopamine-like” hydroxylation
in positions 2 and 3, which unfortunately did not improve
affinities. Interestingly, the dihydroxylated compound 11c
showed much higher inhibitory activities in the calcium assay
compared to the affinities resulting from the radioligand binding
experiments. The most potent compound in the whole series
was the monohydroxylated 3-hydroxy-7-methyl-5,6,7,8,9,14-
hexahydrodibenz[d,g]azecine 11d (LE404), which displayed low
nanomolar affinities for all dopamine receptor subtypes and
subnanomolar affinity toward the D1 receptor in the radioligand
binding experiment.
a At least three independent experiments were carried out in triplicate
each.
Table 2. Affinities for Human Cloned Dopamine
ReceptorssRadioligand Binding Data
Ki (nM) ( SEMa
compd
hD1
hD2L
hD4
hD5
LE3006
1a
1b
1.9 ( 0.5
16.4 ( 12.0
767 ( 24
61 ( 8.0
10.7 ( 5.2
4.5 ( 2.1
509 ( 51
341 ( 41
0.39 ( 0.22
44.7 ( 15.8
253 ( 38
>5000
712 ( 46
198 ( 16
56.5 ( 9.0
>5000
>5000
17.5 ( 2.1
109 ( 39
378.5 ( 8
>5000
1647 ( 95
299 ( 41
134 ( 15
2514 ( 101
165 ( 12
11.3 ( 1.0
7.5 ( 0.3
14.7 ( 2.5
893 ( 32
9
361 ( 38
10a
11ab
11b
11c
11dc
79.1 ( 5.3
11.2 ( 1.8
2610 ( 120
1078 ( 42
1.5 ( 0.2
a At least two independent experiments were carried out in triplicate each.
b D3: 52.5 ( 6.4. c hD3: 47.5 ( 24.0.
The binding properties of compounds identified as potent
antagonists in the calcium assay were further characterized by
radioligand binding studies.23,8 These experiments included the
determination of binding affinities at the hD4 receptor. 11d and
the unsubstituted 11a were also tested at the D3 receptor;
therefore, the complete dopamine receptor binding profiles of
these highly potent compounds have been determined (Table
2).
Conclusion
Performing intensive investigations on structure-activity
relationships within the new class of azecine-type dopamine
receptor ligands led to the following conclusions: two aromatic
rings annelated to the central 10-membered azecine are indis-
pensable for high affinities at the dopamine receptors. The indole
or the benzene moiety in the lead compound 1 cannot be
replaced by phenyl but by other annelated aromatics, such as
1-methyl-1H-pyrrole, thiophene, and benzene instead of indole,
respectively. Especially, the dibenzazecines show slightly
improved selectivity profiles toward the D1 receptor subtype
family with the same or even higher affinities. A hydroxy
substituent in position 2 leads to a novel highly potent ligand
reaching subnanomolar affinity at the D1 receptor.
Discussion
The microplate reader based calcium assay is a very useful
method for simply and quickly selecting the active ones out of
a considerable number of compounds and characterizing them
as antagonists that can then proceed to radioligand binding
experiments for further evaluations. Comparing radioligand and
calcium data, it can be seen that there are differences in the Ki
values obtained. Since the calcium-assay monitors a fast
calcium-signal, these results represent nonequilibrium data,
whereas radioligand binding studies were performed under
equilibrium conditions. As a general rule, it could be shown
that values taken from radioligand binding studies reveal higher
D1 selectivities than the nonequilibrium calcium data.6
Concerning SAR, it first should be pointed out which of the
structural modifications lead to a significant decrease or loss
of inhibitory activity and binding affinities, respectively: Larger
substituents at the aliphatic nitrogen atom in 1 lower the
inhibitory affinities significantly and the affinities measured by
radioligand binding studies dramatically (compare compounds
1, 1a, 1b, Tables 1 and 2). Generally, methyl seems to be the
optimum in terms of activity. A second benzene or another
aromatic ring system is obviously essential for dopaminergic
activity. Both 9- and 10-membered ring systems lacking the
benzene ring lose the inhibitory activities almost completely
(compounds 4 and 6). This finding is in accordance with
previous results, which showed that 3-benzazecines and
3-benzazonines do not show dopaminergic activity.9
Experimental Section
Chemistry. Melting points are uncorrected and were measured
in open capillary tubes, using a Gallenkamp melting point apparatus.
1H NMR spectral data were obtained from a Bruker Advance 250
spectrometer (250 MHz). Elemental analyses were performed on a
Hereaus Vario EL apparatus. TLC was performed on silica gel F254
plates (Merck). MS data were determined by GC/MS, using a
Hewlett-Packard GCD-Plus (G1800C) apparatus (HP-5MS column;
J&W Scientific). Silica gel column chromatography utilized mainly
silica gel 60 63-200 µm (Baker). Experimental procedures and
spectroscopic data for compounds 13b,c, 1b,c, 2a,b, 4b, 18, 19, 6,
21-25, 5a,b, 27-29, 39, 40, 42-45, 47, 48, 50, 7a-c, 10b, 54,
56, 58, 60b, 11b,c,e,f, 60a,b, and 61a and elemental analyses are
given in the Supporting Information.

SAR of Azecine-type Dopamine Receptor Antagonists
Journal of Medicinal Chemistry, 2006, Vol. 49, No. 2 765
General Procedure for the Synthesis of Quaternary Indoli-
zinium and Quinolizinium Salts (GP1). Typically, 24 mmol of
alkyl halide was added to a solution of 8 mmol of the corresponding
quinolizine or indolizine in 100 mL of dry acetone and the mixture
was stirred for 20 h at room temperature. The precipitated solid
was separated, washed with ether, and used for the subsequent Birch
cleavage without further purification.
General Procedure for the Synthesis of Azonines and Aze-
cines (GP2). The given amount of quaternary quinolinium or
indolizinium salt, respectively, was dissolved in 50 mL of liquid
ammonia and stirred at -40 to -50 °C (methanol/dry ice). Absolute
ethanol (1.5 mL) was added, and subsequently, small pieces of
sodium were added until the mixture turned blue, and the color
remained for 1 h. Then ammonium chloride was added till the blue
color disappeared. Overnight the solution was allowed to reach room
temperature while the ammonia evaporated. After addition of 60
mL of water, the aqueous phase was extracted three times with 75
mL of diethyl ether. The ether fractions were washed with 2.5%
aqueous sodium hydroxide solution and dried, and the solvent was
evaporated under reduced pressure. The residue was purified by
column chromatography over aluminum oxide (neutral, activity III)
with diethyl ether/petrolether (bp 40-60 °C) 1:2 as eluent.
General Procedure for the Cyclization of Lactams and
Reduction to Indolizines and Quinolizines (GP3). The given
amount of lactam was dissolved in the given amount of POCl3.
The mixture was heated under reflux for the reported time. After
cooling, excess phosphorus oxychloride was destroyed by carefully
adding dropwise a 10% sodium hydroxide solution. For complete
hydrolysis, the suspension was stirred for 12 h at room temperature.
The solid formed was separated, dried, and dissolved in 150 mL
of methanol. To this solution the given amount of solid sodium
borohydride was slowly added under ice-cooling over a period of
15 min. The resulting suspension was stirred for 1 h at room
temperature and the solvent removed under reduced pressure. The
residue was dissolved in 100 mL of water and extracted three times
with 60 mL of diethyl ether. The ether was dried and evaporated
under reduced pressure. The crude product was purified as
described.
7-Phenylethyl-6,7,8,9,14,15-hexahydro-5H-benz[d]indolo[2,3-
g]azecine (1c): NMR (DMSO-d6) was conducted. Anal. (C27H28N2)
C, H, N.
7,8,13,13b-Tetrahydro-5H-benz[1,2]indolizino[8,7-b]indol-5-
one (14). H2SO4 (20 mL, 2 N) was added to a solution of tryptamine
(3.2 g, 20 mmol) and o-formylbenzoic acid (3 g, 20 mmol) dissolved
in a mixture of 100 mL of ethanol and 100 mL of water and refluxed
under nitrogen for 72 h. After cooling to room temperature, 30-
40% of the product precipitated. The precipitate was collected by
filtration and the filtrate evaporated to 50%. Again, product
precipitated and was isolated. Recrystallization from ethanol yielded
3.78 g (69%) of 14 as a beige powder: mp 212-214 °C; IR (KBr)
3260, 1665, 730 cm-1; 1H NMR (DMSO-d6) δ 11.37 (s, 1H, NH),
8.30 (ddd, J ) 7/1.5/0.8 Hz, 1H, H-4), 7.75 (ddd, J ) 7/1.5/0.8
Hz, 1H, H-1), 7.71 (dt, J ) 7/1.4 Hz, 1H, H-3), 7.54 (dt, J ) 7/1.4
Hz, 1H, H-2), 7.41 (ddd, J ) 7.5/1.3/0.7 Hz, 2H, H-9, H-12), 7.10
(td, J ) 7/1.5 Hz, 1H, H-11), 6.98 (td, J ) 7/ 1.5 Hz, 1H, H-10),
6.05 (s, 1H, H-13b), 4.60 (dd, J ) 14/5 Hz, 1H, H-7), 3.33 (dd, J
) 14/5 Hz, 1H, H-7), 2.91-2.58 (m, 2H, H-8). Anal. (C18H14N2O)
C, H, N.
7,8,13,13b-Tetrahydro-5H-benz[1,2]indolizino[8,7-b]indole (15).
LiAlH4 (0.75 g, 10 mmol) was slowly added at 5-10 °C within 30
min to 1.16 g of 14 (4.2 mmol) dissolved in 50 mL of dry THF.
The mixture was refluxed for 18 h, cooled to room temperature,
and hydrolyzed at 5-10 °C by dropwise addition of 10% aqueous
NaOH solution. The solution was extracted repeatedly with diethyl
ether. The combined organic layers were dried with MgSO4 and
evaporated in vacuo. The remaining solid was recrystallized from
ethanol to yield 0.56 g (51%) of slightly yellow crystals: mp 225
°C (dec); IR 2905, 2820, 1440, 731 cm-1; 1H NMR (DMSO-d6) δ
10.78 (s, 1H, NH), 7.83 (d, J ) 7 Hz, 1H, H-1), 7.38 (d, J ) 7 Hz,
1H, H-4), 7.35-7.20 (m, 4H, H-2, H-3, H-9, H-12), 7.02 (td, J )
7/1 Hz, 1H, H-11), 6.93 (td, J ) 7/1 Hz, 1H, H-10), 5.50 (s, 1H,
H-13b), 4.15 (d, J ) 14 Hz, 1H, H-5), 4.07 (d, J ) 14 Hz, 1H,
H-5), 3.77-2.92 (m, 4H, H-7, H-8). Anal. (C18H16N2) C, H, N.
6-Methyl-5,6,7,8,13,14-hexahydroindolo[3,2-e]benzazonine
(2a): 1H NMR (DMSO-d6) was conducted.
6-Ethyl-5,6,7,8,13,14-hexahydroindolo[3,2-e]benzazonine
(2b): 1H NMR (DMSO-d6) was conducted.
7-Ethyl-5,6,8,9,14,14b-hexahydrobenz[a]indolo[3,2-h]quino-
lizinium iodide (13a) was synthesized according to GP1 using 2.2
g (8 mmol) of 125 and ethyl iodide to yield 2.8 g (85%) of a
colorless, amorphic solid: mp 217 °C; IR (KBr) 3270, 2850, 1445,
N-[2-(1H-Indol-3-yl)ethyl]piperidin-2-one (16). Tryptamine (16
g, 0.1 mol), 21 g (0.1 mol) of ethyl bromopentanoate, and 16 g of
potassium carbonate were dissolved in 200 mL of n-butanol and
refluxed for 16 h. After cooling and filtration, the solid was washed
with 100 mL of n-butanol. The organic phase was removed under
reduced pressure and the residual brown oil recrystallized from
toluene 8.48 g (35%) to yield a beige solid: mp 156-158 °C; IR
1
1130, 742 cm-1; H NMR (DMSO-d6) δ 10.91 (s, 1H, NH), 7.59
(d, J ) 7 Hz, 1H, H-1), 7.51 (d, J ) 7 Hz, 1H, H-10), 7.39 (d, J
) 7 Hz, 1H, H-13), 7.46-7.38 (m, 3H, H-2, H-4), 7.14 (td, J )
7/1 Hz, 1H, H-12), 7.03 (td, J ) 7/1 Hz, 1H, H-11), 6.22 (s, 1H,
H-14b), 4.08-3.89 (m, 4H, H-6, H-8), 3.60 (q, 2H, H-1′), 3.28-
3.04 (m, 4H, H-5, H-9), 1.41 (t, J ) 7 Hz, 3H, CH3). Anal.
(C21H23N2I) C, H, N.
1
(KBr) 3260, 1608, 755, 745 cm-1; H NMR (DMSO-d6) δ 10.85
(s, 1H, NH), 7.5 (d, J ) 8 Hz, 1H, H-4), 7.32 (d, J ) 8 Hz, 1H,
H-7), 7.1 (s, 1H, H-2), 7.08-6.9 (m, 2H, H-5, H-6), 3.45 (t, J )
5 Hz, 2H, H-1′), 3.1-3.0 (m, 2H, H-6), 2.85 (t, J ) 4 Hz, 2H,
H-2′), 2.25-2.1 (m, 2H, H-3), 1.65-1.45 (m, 4H, H-4, H-5). Anal.
(C15H18N2O) C, H, N.
7-Cyclopropylmethyl-5,6,8,9,14,14b-hexahydrobenz[a]indolo-
1
[3,2-h]quinolizinium bromide (13b): H NMR (DMSO-d6) was
conducted. Anal. (C23H25N2Br) C, H, N. See Supporting Informa-
tion.
7-Phenylethyl-5,6,8,9,14,14b-hexahydrobenz[a]indolo[3,2-h]-
quinolizinium bromide (13c): 1H NMR (DMSO-d6) was con-
ducted. Anal. (C27H27N2Br) C, H, N. See Supporting Information.
1,2,3,4,6,7,12,12b-Octahydroindolo[2,3-a]quinolizine (17) was
synthesized according to GP3 using 5.0 g (0.02 mol) of 16,
dissolved in 100 mL of toluene and 20 mL of phosphorus
oxychloride, to yield 2.33 g (51.6%) of a yellow solid: mp 150-
1
152 °C; IR (KBr) 3400, 1445, 735 cm-1; H NMR (DMSO-d6) δ
7-Ethyl-6,7,8,9,14,15-hexahydro-5H-benz[d]indolo[2,3-g]aze-
cine (1a) was synthesized according to GP2 using 1.5 g (3.5 mmol)
of 13a to yield 0.5 g (53%) of a colorless solid: IR (KBr) 3411,
2925, 1488, 739 cm-1; 1H NMR (DMSO-d6) δ 10.73 (s, 1H, NH),
7.48 (dt, J ) 6/2 Hz, 1H, H-1), 7.34 (dt, J ) 8/1 Hz, 1H, H-10),
7.24 (dd, J ) 7/1 Hz, 1H, H-13), 7.13-7.08 (m, 3H, H-1), 6.96
(ddd, J ) 7/7/1 Hz, H-12), 6.88 (ddd, J ) 8/7/1 Hz, 1H, H-11),
4.13 (s, 2H, H-15), 2.82 (dd, J ) 7/3 Hz, 2H, H-6), 2.79 (dd, J )
6/2 Hz, 2H, H-8), 2.70 (dd, J ) 6/2 Hz, 2H, H-9), 2.66 (dd, J )
7/3 Hz, 2H, H-5), 2.20 (q, J ) 7 Hz, 2H, H-1′), 0.59 (t, J ) 7 Hz,
3H, CH3). Anal. (C21H24N2) C, H, N.
7.9 (s, 1H, NH), 7.53-7.49 (m, 1H, H-8), 7.26-7.22 (m, 1H, H-11),
7.19-7.11 (m, 2H, H-9, H-10), 3.23-3.17 (m, 1H, H-12b), 3.14-
3.0 (m, 3H, H-7b, H-4b, H-6b), 2.77-2.61 (m, 2H, H-6a, H-7a),
2.44-2.36 (m, 1H, H-4a), 2.1-1.94 (m, 1H, H-1b), 1.9-1.82 (m,
1H, H-2b), 1.81-1.7 (m, 2H, H-3), 1.65-1.55 (m, 1H, H-1a), 1.5-
1.4 (m, 1H, H-2a). Anal. C, H, N.
3-Methyl-1,2,3,4,5,6,7,8-octahydro-9H-azecino[5,4-b]indole (4a).
Step 1. N-Methyl-5,8,9,13b-tetrahydro-6H-isoquino[1,2-a]iso-
quinolinium Iodide. To a solution of 1.0 g (4 mmol) of 17 in 20
mL of toluene was added 10 mL (155 mmol) of methyl iodide.
The mixture was stirred at room temperature for 3 h. The colorless
crystals were separated by means of filtration and dried in vacuo
to yield 1.5 g (93%): mp 221-224 °C; IR (KBr) 3300, 1450, 750
cm-1; 1H NMR (DMSO-d6) δ 11.15 (s, 1H, NH), 7.5 (d, J ) 7 Hz,
7-Cyclopropylmethyl-6,7,8,9,14,15-hexahydro-5H-benz[d]in-
dolo[2,3-g]azecine (1b): NMR (DMSO-d6) was conducted. Anal.
(C23H26N2) C, H, N. See Supporting Information.

766 Journal of Medicinal Chemistry, 2006, Vol. 49, No. 2
Hoefgen et al.
1H, H-8), 7.35 (d, J ) 7 Hz, 1H, H-11), 7.25-7.0 (m, 3H, H-9,
H-10), 4.9-4.8 (m, 1H, H-12b), 4.1-3.8 (m, 1H, H-6b), 3.7-3.3
(m, 3H, H-4, H-6a), 3.25 (s, 3H, CH3), 3.15-3.0 (m, 2H, H-7),
2.4-1.3 (m, 6H, H-1, H-2, H-3). Anal. (C16H21N2I) C, H, N. Step
2. 4a was synthesized according to GP2 using 1.0 g (4 mmol) of
the quatenary quinolizinium salt (see step 1) to yield 0.43 g (44.5%)
of colorless crystals: mp 99-101 °C (lit.10 mp 98-99 °C); IR (KBr)
3-Phenyltetrahydro-2H-pyran-2-one (26). This compound was
prepared as reported in the literature.15
Ethyl 5-bromo-2-phenylpentanoate (27): 1H NMR (DMSO-
d6) was conducted. Anal. (C13H17BrO2) C, H, N.
1-[2-(1H-Indol-3-yl)ethyl]-3-phenyl-2-piperidinone (28): 1H
NMR (DMSO-d6) was conducted. Anal. (C21H22N2O) C, H, N.
1-Phenyl-1,2,3,4,6,7,12,12b-octahydroindolo[2,3-a]quinoli-
zine (29): 1H NMR (DMSO-d6) was conducted. Anal. (C21H22N2·
1/4H2O) C, H, N.
3-Methyl-7-phenyl-2,3,4,5,6,7,8,9-octahydro-1H-azecino[5,4-
b]indole (5b): 1H NMR (DMSO-d6) was conducted. Anal.
(C22H26N2) C, H, N.
1
3410, 2920, 2760, 1460, 740 cm-1; H NMR (CDCl3) δ 7.65 (s,
1H, NH), 7.55-7.45 (m, 1H, H-13), 7.3-7.25 (m, 1H, H-10), 7.15-
7.0 (m, 2H, H-11, H-12), 2.95-2.85 (m, 4H, H-2, H-4), 2.75-
2.65 (m, 2H, H-1), 2.4 (t, J ) 5.4 Hz, 2H, H-8), 2.05 (s, 3H, CH3),
1.9-1.8 (m, 2H, H-5), 1.6-1.3 (m, 4H, H-6, H-7). Anal. (C16H22N2)
C, H, N.
The following compounds were prepared as reported in the
literature:16 N-[2-(1H-indol-3-yl)ethyl]-4-oxo-4-phenylbutanamide
(31); N-[2-(1H-indol-3-yl)ethyl]-5-oxo-5-phenylpentanamide (32);
12b-phenyl-2,3,6,7,12,12b-hexahydroindolo[2,3-a]quinolizin-4(1H)-
one (33); 11b-phenyl-1,2,5,6,11,11b-hexahydro-3H-indolizino[8,7-
b]indol-3-one (34); 12b-phenyl-1,2,3,4,6,7,12,12b-octahydroindolo-
[2,3-a]quinolizine (35); 11b-phenyl-2,3,5,6,11,11b-hexahydro-1H-
indolizino[8,7-b]indole (36); 5-methyl-12b-phenyl-1,2,3,4,6,7,12,12b-
octahydroindolo[2,3-a]quinolizinium iodide (37); 4-methyl-11b-
phenyl-2,3,5,6,11,11b-hexahydro-1H-indolizino[8,7-b]indolium iodide
(38); 3-methyl-8-phenyl-2,3,4,5,6,7,8,9-octahydro-1H-azecino[5,4-
b]indole (5c); and 3-methyl-7-phenyl-1,2,3,4,5,6,7,8-octahydro-
azonino[5,4-b]indole (7d).
3-Cyclopropylmethyl-1,2,3,4,5,6,7,8-octahydro-9H-azecino-
[5,4-b]indole (4b): 1H NMR (DMSO-d6) was conducted. Anal.
(C19H26N2·0.6C4H10O) C, H, N.
N-[2-(1H-Indol-3-yl)ethyl]pyrrolidin-2-one (18): 1H NMR
(DMSO-d6) was conducted. Anal. (C14H16N2O) C, H, N.
1
N-[2-(1H-Indol-3-yl)ethyl]pyrrolidine-2,5-dione (19): H NMR
(DMSO-d6) was conducted. Anal. (C14H14N2O2) C, H, N.
2,3,5,6,11,11b-Hexahydro-1H-indolizino[8,7-b]indole (20)
(method a) was synthesized according to GP3 using 5.0 g (0.02
mol) of 18, dissolved in 100 mL of toluene and 20 mL of
phosphorus oxychloride, to yield 1.73 g (67.9%) of a beige solid:
mp 173-174 °C; IR (KBr) 2920, 1440, 735 cm-1 1H NMR
;
γ-Phenylbutyrolactone (39): 1H NMR (DMSO-d6) was con-
ducted. Anal. (C10H10O2·1/4H2O) C, H, N.
(CDCl3) δ 7.85 (s, 1H, NH), 7.57-7.54 (m, 1H, H-7), 7.28-7.15
(m, 3H, H-8, H-9, H-10), 4.28-4.21 (m, 1H, H-11b), 3.4-3.33
(dd, J ) 2.6/5.0 Hz, 1H, H-5b), 3.2-3.1 (m, 1H, H-5a), 3.06-
2.91 (m, 3H, H-3, H-6a), 2.76-2.68 (ddd, J ) 2.2/2.4/3.2 Hz, 1H,
H-6a), 2.31-2.18 (m, 1H, H-2b), 1.98-1.82 (m, 3H, H1, H-2a).
Anal. (C14H16N2) C, H, N.
1-[2-(1H-Indol-3-yl)ethyl]-5-phenylpyrrolidin-2-one (40): 1H
NMR (DMSO-d6) was conducted. Anal. (C20H20N2O·1/4H2O) C, H,
N.
3-Phenyl-2,3,5,6,11,11b-hexahydro-1H-indolizino[8,7-b]in-
dole (42): 1H NMR (DMSO-d6) was conducted. Anal. (C20H20N2·
1/4H2O) C, H, N.
Method b. 19 (1 g, 4 mmol) was dissolved in 200 mL of
dichlormethane, and 4.5 g (24 mmol) of Et3OBF4 was added under
argon atmosphere. The solution was stirred free from light for 48
h at room temperature. The precipitated yellow solid was filtered
off and dissolved in 20 mL of dry tetrahydrofuran. To this solution
was added 0.25 g of sodium borohydride slowly under ice-cooling.
The resulting suspension was stirred for 3.5 h at room temperature
and the solvent removed under reduced pressure. The residue was
dissolved in 100 mL of water and extracted three times with 50
mL of ethyl acetate. The combined organic phases were removed
under reduced pressure and the residual solid was recrystallized
from chloroform/petroleum ether. After that the colorless solid was
dissolved again in 20 mL of dry tetrahydrofuran. Under ice-cooling
this solution was added dropwise to a suspension of 0.3 g of lithium
aluminum hydride in 10 mL of tetrahydrofuran. The suspension
was refluxed for 10 h. Subsequently, the hydride was destroyed by
dropwise adding of 2 mL of acetone and 50 mL of sodium
hydroxide (5%). The precipitated solid was separated and washed
with 100 mL of tetrahydrofuran. The organic layer was removed
under reduced pressure and the residual yellow oil was recrystallized
from toluene/n-hexane (1:3) to yield 0.24 g (53%). Analytical data
are as described for method a above.
3-Methyl-1,2,3,4,5,6,7,8-octahydroazonino[5,4-b]indole (6): 1H
NMR (DMSO-d6) was conducted. Anal. (C15H20N2) C, H, N.
6-Phenyltetrahydro-2H-pyran-2-one (21): 1H NMR (DMSO-
d6) was conducted. Anal. (C11H12O2) C, H, N.
Ethyl 5-bromo-5-phenylpentanoate (22): 1H NMR (DMSO-
d6) was conducted. Anal. (C13H17O2Br) C, H, N.
1-[2-(1H-Indol-3-yl)ethyl]-6-phenylpiperidin-2-one (23): 1H
NMR (DMSO-d6) was conducted. Anal. (C21H22N2O) C, H, N.
5-Hydroxy-N-[2-(1H-indol-3-yl)ethyl]-5-phenylpentanamide
(24): 1H NMR (DMSO-d6) was conducted. Anal. (C21H24N2O2)
C, H, N.
r-Phenylbutyrolactone (43): 1H NMR (DMSO-d6) was con-
ducted. Anal. (C10H10O2·1/2H2O) C, H, N.
1-[2-(1H-Indol-3-yl)ethyl]-3-phenyl-2-pyrrolidinone (44): 1H
NMR (DMSO-d6) was conducted. Anal. (C20H20N2O·1/4H2O) C, H,
N.
1-Phenyl-2,3,5,6,11,11b-hexahydro-1H-indolizino[8,7-b]in-
dole (45): 1H NMR (DMSO-d6) was conducted. Anal. (C20H20N2)
C, H, N.
â-Phenylbutyrolactone (46). R-Bromoacetophenone (39.8 g, 0.2
mol) and 31.24 g (0.2 mol) of the potassium salt of methylmalonate
were dissolved in 200 mL of DMSO and stirred for 1 h at room
temperature. Ammonium acetate (15.4 g, 0.2 mol) was added and
the solution was stirred for further 14 h. After addition of 100 mL
of DMSO, 7.6 g (0.2 mol) of sodium borohydride was slowly added
and the mixture stirred for 2 h at 40 °C. Subsequently, 7.6 g (0.2
mol) of acetic acid was added and the reaction stirred for 2 h further
at 40 °C. Water (10 mL) was added and the mixture refluxed for
18 h. Afterward, the solution was poured into 500 mL of ice water
and extracted with diethyl ether using an extractor. Removing of
the organic phase under reduced pressure yielded a brown oil, which
was purified by distillation, to yield 22 g (68%) of a yellow solid:
1
mp 39-41 °C; IR (KBr) 2900, 1765, 755, 700 cm-1; H NMR
(DMSO-d6) δ 7.3 (s, 5H, arom H)), 4.7 (dd, J ) 7.8/8.7 Hz, 1H,
H-5b), 4.3 (dd, J ) 7.8/8.7 Hz, 1H, H-5a), 3.8 (m, 1H, H-4), 2.75
(m, 2H, H-3). Anal. (C10H10O2) C, H, N.
Ethyl 4-bromo-3-phenylpentanoate (47): 1H NMR (DMSO-
d6) was conducted. Anal. (C12H15BrO2) C, H, N.
1-[2-(1H-Indol-3-yl)ethyl]-4-phenyl-2-pyrrolidinone (48): 1H
NMR (DMSO-d6) was conducted. Anal. (C20H20N2O) C, H, N.
2-Phenyl-2,3,5,6,11,11b-hexahydro-1H-indolizino[8,7-b]in-
dole (50): 1H NMR (DMSO-d6) was conducted. Anal. (C20H20N2·
1/2H2O) C, H, N.
4-Phenyl-1,2,3,4,6,7,12,12b-octahydroindolo[2,3-a]quinoliz-
ine (25): 1H NMR (DMSO-d6) was conducted. Anal. (C21H22N2·
1/2H2O) C, H, N.
3-Methyl-4-phenyl-1,2,3,4,5,6,7,8-octahydroazonino[5,4-b]in-
dole (7a): 1H NMR (DMSO-d6) was conducted. Anal. (C21H24N2)
C, H, N.
3-Methyl-4-phenyl-2,3,4,5,6,7,8,9-octahydro-1H-azecino[5,4-
b]indole (5a). 1H NMR (DMSO-d6) was conducted. Anal. (C22H26N2)
C, H, N.
3-Methyl-5-phenyl-1,2,3,4,5,6,7,8-octahydroazonino[5,4-b]in-
dole (7c): 1H NMR (DMSO-d6) was conducted. Anal. (C21H24N2)
C, H, N.

SAR of Azecine-type Dopamine Receptor Antagonists
Journal of Medicinal Chemistry, 2006, Vol. 49, No. 2 767
3-Methyl-6-phenyl-1,2,3,4,5,6,7,8-octahydroazonino[5,4-b]in-
2.85-2.6 (m, 8H, aliph), 2.25 (s, 3H, CH3); 13C NMR (CDCl3) δ
140.3, 139.8, 138.2, 137.6 (4C, quat), 130.3, 129.8, 128.8, 126.3,
126.2, 121.3 (6C, arom), 60.0 (C-6), 61.0 (C-8), 45.6 (CH3), 35.0
(C-5), 34.0 (C-9), 29.0 (C-13). Anal. (C16H19NS) C, H, N.
6-Allyl-4,5,6,7,8,13-hexahydrothieno[2,3-f][3]benzazecine
(10b): 1H NMR (DMSO-d6) was conducted. Anal. (C18H21NS) C,
H, N.
1
dole (7b). H NMR (DMSO-d6) was conducted. Anal. (C20H20N2·
1/2H2O) C, H, N.
3,4-Dihydro-1-(3-thienyl)isoquinoline (51). Into 11 g (0.1
mmol) of stirred, freshly distilled 3-thiophencarbonitrile was added
40 g (185 mmol) of stannous(IV) chloride at room temperature.
Hereby a complex formed that was heated to 95 °C and melted.
Then 14.0 g (0.1 mol) of 2-phenylethyl chloride was added. The
mixture was stirred at 110-120 °C for 4 h. Then it was mixed into
20% sodium hydroxide solution and stirred until an oily phase
accumulated. This oil was separated and distilled with an aircooler.
Overnight the oil became resin-like to yield 10.0 g (46.9%): bp
1-Phenyl-3,4-dihydroisoquinoline (52). This compound was
prepared as reported in the literature.20
N-Hydroxyethyl-1-phenyl-3,4-dihydroisoquinolinium bro-
mide (54): 1H NMR (DMSO-d6) was conducted. Anal. (C17H18-
BrNO) C, H, N.
1
160 °C (0.1 mbar); IR (KBr) 3500-2700, 1700-1500 cm-1; H
2-(2-Hydroxyethyl)-1-phenyl-1,2,3,4-tetrahydroisoquinoline
(56): 1H NMR (DMSO-d6) was conducted. Anal. (C17H19NO) C,
H, N.
NMR (CDCI3) δ 8.7 (d, 1H, arom), 8.3 (d, 1H, arom), 8.0-6.8
(m, 5H, arom), 5.2 (s, 1H, H-1), 3.9-3.5 (m, 2H, CH2), 3.3-2.6
(m, 2H, CH2). Anal. (C13H11NS) C, H, N.
1
5,8,9,13b-Tetrahydro-6H-isoquino[1,2-a]isoquinoline (58): H
N-Hydroxyethyl-3,4-dihydro-1-(3-thienyl)isoquinolinium
Iodide (53). 2-Iodoethanol (10 g, 58 mmol) was added to a
solution of 10 g (46.9 mmol) of 51 in 100 mL of toluene. The
mixture was stirred for 42 h under argon at 90 °C. The solvent
was removed under reduced pressure and 100 mL of acetone was
added. Yellow crystals formed rapidly, which were filtered off and
dried in a vacuum to yield 7.0 g (37%): mp 165 °C; IR (KBr):
3400-3200, 3100, 1630-1570, 1610, 1570, 1510 cm-1; 1H NMR
(DMSO-d6) δ 8.3-8.2 (m, 1H, arom), 7.9-7.7 (m, 2H, arom), 7.6-
7.3 (m, 3H, arom), 7.2-7.1 (m, 1H, arom), 5.4 (s, 1H, OH), 4.3-
4.2 (t, 2H, H-3), 4.2-4.1 (t, 2H, H-9), 3.9-3.8 (t, 2H, H-10), 3.4-
3.25 (t, 2H, H-4). Anal. (C15H16INOS) C, H, N.
2-(1-Thien-3-yl-3,4-dihydroisoquinolin-2(1H)-yl)ethanol (55).
To a solution of 3.5 g (9 mmol) of 53 in 150 mL of methanol was
added 9 g (238 mmol) of sodium borohydride in small amounts
over 2 h. The mixture was boiled under reflux for 0.5 h. After
cooling, the solvent was removed under reduced pressure. Water
was added and twice extracted with 200 mL of ethyl acetate. The
solvent was removed in vacuo. In the cold, crystals formed after 2
days to yield 2 g (84.9%): mp 49 °C; IR (KBr) 3800-3000, 2950,
2920, 2360, 1670-1640 cm-1; 1H NMR (CDCl3) δ 7.4-7.35 (m,
1H, arom), 7.15-6.85 (m, 6H, arom), 5.05 (s, 1H, H-1), 4.4 (s,
1H, OH), 3.6-3.4 and 2.9-2.5 (m, 8H, aliph). Anal. (C15H17NOS)
C, H, N.
NMR (DMSO-d6) was conducted. Anal. (C17H17N) C, H, N.
7-Methyl-5,6,7,8,9,14-hexahydrodibenz[d,g]azecine (11a). Step
1. 7-Methyl-5,8,9,13b-tetrahydro-6H-isoquino[1,2-a]isoquino-
linium iodide was synthesized according to GP1 using 1.6 g (6.8
mmol) of 58 in 40 mL of acetone and 1.8 mL (28 mmol) of methyl
iodide to yield 1.85 g (72%) of colorless crystals: mp 258 °C; IR
(KBr) 3460, 2881, 1497, 1440, 929, 775 cm-1; 1H NMR (DMSO-
d6) δ 7.5-7.3 (m, 6H, arom), 7.2-7.1 (d, 2H, arom), 5.95 (s, 1H,
H-13b), 3.82 (t, 4H, H-6, H-8), 3.35 (s, 3H, CH3), 3.3-3.15 (m,
2H, H-5, H-9). Anal. (C18H20NI) C, H, N. Step 2. 11a was
synthesized according to GP2 using 0.75 g (2 mmol) of the
quaternary salt (see step 1) as starting material. The product was
purified by column chromatography using diethyl ether as eluent.
The crude product was recrystallized from ethanol. The crystals
were separated by filtration and dried in vacuo to yield 0.35 g
(69.7%): mp 62 °C; IR (KBr) 2942, 2790, 1493, 1445, 1054, 757
1
cm-1; H NMR (CDCl3) δ 7.29-7.25 (m, J ) 9.1 Hz, 2H, H-1,
H-13), 7.14-7.09 (m, J ) 9.1 Hz, 4H, H-2, H-3, H-11, H-12),
7.07-7.02 (m, J ) 9.1 Hz, 2H, H-4, H-10), 4.4 (s, 2H, H-14),
2.7-2.5 (m, 8H, aliph), 2.2 (s, 3H, CH3); 13C NMR (CDCl3) δ
141.3, 141.1 (4C, quat.), 130.9, 130.6, 126.4, 126.3 (8C, arom),
60.8 (C-6, C-8), 46.8 (CH3), 38.6 (C-14), 34.8 (C-5, C-9); MS m/z
(% rel int) ) 251 [M]+• (30.6), 236 (16.7), 222 (3.6), 205 (12.9),
193 (82.5), 179 (100.0), 165 (20.8), 146 (95.6), 133 (7.7), 115
(33.8), 103 (8.3), 91 (15.5), 77 (9.1), 71 (24.9), 58 (31.5). Anal.
(C18H21N) C, H, N.
2-(2-Hydroxyethyl)-N-[2-(3,4-dimethoxyphenyl)ethyl]benz-
amide (60b): 1H NMR (DMSO-d6) was conducted. Anal.
(C18H21NO3) C, H, N.
2,3-Dimethoxy-5,6,8,9-tetrahydro-13bH-dibenzo[a,h]quinoli-
zine (61b): 1H NMR (DMSO-d6) was conducted. Anal. (C19H21-
NO2) C, H, N.
4,7,8,12b-Tetrahydro-5H-thieno[3′,2′:3,4]pyrido[2,1-a]iso-
quinoline (57). A slurry of 1.8 g (4.7 mmol) of 55 in 40 g of
polyphosphoric acid was heated and stirred at 160 °C for 6 h. The
reaction was carried out under argon. The warm mixture was put
onto ice and stirred until the ice had melted. It was extracted with
40 mL of diethyl ether and the ether was discarded. The mixture
was neutralized with sodium hydroxide and twice extracted with
40 mL of ether. The solution was filtered through silica gel. Upon
removing the ether, small yellow crystals were obtained, which were
dissolved in 20 mL of ethanol and recrystallized in the cold.
Afterward, the crystals were dried in vacuo to yield 1 g (55,9%) of
yellow crystals: mp 101 °C; IR (KBr) 3060, 3020, 3010-2600,
2,3-Dimethoxy-7-methyl-5,6,7,8,9,14-hexahydrodibenzo[d,g]-
azecine (11b): 1H NMR (DMSO-d6) was conducted. Anal.
(C20H25NO2) C, H, N.
7-Allyl-2,3-dimethoxy-5,6,7,8,9,14-hexahydrodibenz[d,g]aze-
1
1
1800-1700, 1660-1620 cm-1; H NMR (CDCl3) δ 7.5-6.8 (m,
cine (11e): H NMR (DMSO-d6) was conducted. Anal. (C22H27NO2)
C, H, N.
6H, arom), 5.15 (s, 1H, H-12b), 3.5-2.5 (m, 8H, aliph). Anal.
2,3-Dimethoxy-7-phenylethyl-5,6,7,8,9,14-hexahydrodibenz-
[d,g]azecine (11f): 1H NMR (DMSO-d6) was conducted. Anal.
(C27H31NO2) C, H, N.
7-Methyl-2,3-dihydroxy-5,6,7,8,9,14-hexahydrodibenzo[d,g]-
azecine hydrobromide (11c): 1H NMR (DMSO-d6) was con-
ducted. Anal. (C18H22NO2Br) C, H, N.
2-(2-Hydroxyethyl)-N-[2-(3-methoxyphenyl)ethyl]benz-
amide (60a): 1H NMR (DMSO-d6) was conducted. Anal.
(C18H21NO3) C, H, N.
3-Methoxy-5,6,8,9-tetrahydro-13bH-dibenzo[a,h]quinoli-
zine (61a). 1H NMR (DMSO-d6) was conducted. Anal. (C18H19NO)
C, H, N.
3-Hydroxy-7-methyl-5,6,7,8,9,14-hexahydrodibenz[d,g]aze-
cine (11d). Step 1. 3-Methoxy-7-methyl-5,6,8,9-tetrahydro-13bH-
dibenzo[a,h]quinolizinium iodide was synthesized according to
GP1 using 5.38 g (20.3 mmol) of 61a in 50 mL of acetone and 5
mL (80 mmol) of methyl iodide. The mixture was stirred for 18 h
(C15H15NS) C, H, N.
6-Methyl-4,5,6,7,8,13-hexahydrothieno[2,3-f][3]benzazecine
(10a). Step 1. 6-Methyl-4,7,8,12b-tetrahydro-5H-thieno[3′,2′:3,4]-
pyrido[2,1-a]isoquinolin-6-ium iodide was synthesized according
to GP1 using 1 g (4.1 mmol) of 57 dissolved in 50 mL of acetone
and 1 mL (16 mmol) of methyl iodide to yield 0.35 g (22.3%) of
colorless crystals: mp 265 °C; IR (KBr) 3100-2800, 1700, 1495
cm-1; 1H NMR (DMSO-d6) δ 7.6-7.2 (m, 5H, arom), 6.8 (d, 1H,
H-12), 5.95 (s, 1H, H-12), 4.1-3.0 (m, 8H, aliph). Anal. (C16H18NSI)
C, H, N. Step 2. 10a was synthesized according to GP2 using 0.35
g (0.9 mmol) of the quaternary salt (see step 1 above) as starting
material. The oily product was purified by means of column
chromatography using diethyl ether as eluent. The resinous product
was recrystallized from methanol. In the cold, crystals formed,
which were filtered off and dried in vacuo to yield 0.08 g (34.4%):
mp 40 °C; IR (KBr) 3060-2600, 1800-1650, 1600, 1580 cm-1
1H NMR (CDCl3) δ 7.25-6.9 (m, 6H, arom), 4.19 (s, 2H, H-13),
;

768 Journal of Medicinal Chemistry, 2006, Vol. 49, No. 2
Hoefgen et al.
at room temperature and yielded 2.5 g (44%) of colorless crystals:
a sigmoidal dose-response equation using a four-parameter logistic
equation on Prism 3.0 (GraphPad Software, San Diego, CA). Ki
values were then calculated to account for different agonist
concentrations and EC50 values by applying a modified Cheng-
Prusoff equation25
mp 231 °C; IR (KBr) 3100-2750, 1610-1550, 1500-1480 cm-1
;
1H NMR (DMSO-d6) δ 7.4-6.8 (m, 7H, arom), 5.82 (s, 1H, H-13b),
3.75 (s, 3H, OCH3), 3.35 (s, 3H, NCH3), 3.65-3.38, 3.38-3.1 (m,
8H, H-5, H-6, H-8, H-9). Anal. (C19H22INO) C, H, N. Step 2.
3-Hydroxy-7-methyl-5,6,8,9-tetrahydro-13bH-dibenzo[a,h]qui-
nolizinium Bromide. A solution of 0.5 g (1.2 mmol) of the
quaternary salt (see step 1) in 50 mL of 47% hydrobromic acid
was kept boiling for 4 h under argon. The solution was removed
under reduced pressure. The remaining solid was suspended in
acetone, filtered off, and dried in vacuo to yield 45 g (93%): mp
IC50
Ki )
L
1 +
EC50
where L is the concentration (M) of standard agonist, e.g., SKF
38393 or quinpirole, and EC50 is the 50% effective concentration
(M) of the standard agonists SKF 38393 or quinpirole, respectively.
The determination of binding affinities by radioligand binding
studies has been intensively described by us recently.6,23 All binding
assays were performed with whole-cell-suspensions. cDNA for hD1
and hD5 cloned in pGEM3 (Promega, Madison, WI) was obtained
from Dr. David Grandy (Portland, OR). cDNA for hD2L was
obtained from Dr. Shine (Darlinghurst, Australia). The stably
transfected CHO-hD4.4 cell line was obtained from Dr. H. H. M.
Van Tol (Toronto, Canada). All donations are gratefully acknowl-
edged.
260 °C; IR (KBr) 3300-2700, 1640-1550 cm-1 1H NMR
;
(DMSO-d6) δ 9.55 (s, 1H, OH), 7.5-6.7 (m, 7H, arom), 5.8 (s,
1H, H-13b), 3.8 (m, 4H, H-6, H-8), 3.76 (s, 3H, NCH3), 3.2 (m,
4H, H-5, H-9). Anal. (C18H20BrNO) C, H, N. Step 3. 11d was
synthesized according to GP2 using 0.5 g (1.3 mmol) of the
quaternary hydroxylated salt (see step 2). The crude product was
recrystallized from methanol to yield 0.27 g (79%) of colorless
crystals: mp 72 °C; IR (KBr) 3500-2200, 1670-1570, 1540-
1
1430 cm-1; H NMR (CDCl3) δ 7.35-7.0 (m, 5H, arom), 6.62-
6.5 (dd, J ) 7.0/2.3 Hz, 1H, H-2) (d, J ) 2.3 Hz, 1H, H-4), 5.1 (s,
1H, OH), 4.2 (s, 2H, H-14), 2.8-2.7 (m, 8H, H-5, H-6, H-8, H-9),
2.3 (s, 3H, NCH3); 13C NMR (CDCl3) δ 154.8, 141.7, 140.6, 140.2
(4C, quat.), 131.6, 131.5, 130.6, 130.5, 126.4 (5C, arom), 117.3,
113.7 (C-2, C-4), 58.8 (C-6, C-8), 46.2 (N-CH3), 36.7 (C-14), 32.4,
32.5 (C-5, C-9); MS m/z (% rel int) ) 267 [M]+‚ (45.3), 252 (12.8),
221 (12.4), 209 (85.9), 195 (86.9), 178 (25.1), 162 (100.0), 146
(75.1), 133 (23.7), 115 (51.9), 103 (19.1), 91 (34.4), 77 (31.7), 58
(99.7). Anal. (C18H21NO) C, H, N.
Acknowledgment. Financial support by the “Fonds der
Chemischen Industrie” (FCI) for M. D. is gratefully acknowl-
edged.
Supporting Information Available: Routine experimental
procedures, routine spectroscopic data, and elemental analysis
results. This material is available free of charge via the Internet at
http://pubs.acs.org.
3,6-Dimethyl-3,4,5,6,7,9,13,14-octahydro[3,2-g]azecine (8) and
3,6-dimethyl-4,5,6,7,8,13-hexahydro-3H-benzo[d]pyrrolo[3,2-g]-
azecine (9) were prepared as reported previously.24
Pharmacology. Functional Assay Measuring Intracellular
Ca2+ Concentrations by a Fluorescence Microplate Reader. Ca2+
fluorescence measurements were performed using a FLUOstar
microplate reader (BMG LabTechnologies, Offenburg, Germany)
equipped with dual injectors. Screening for agonistic activity was
performed using a NOVOstar microplate reader (BMG LabTech-
nologies) with a pipettor system. HEK293 cells recombinatly
expressing dopamine hD1, hD2L, or hD5 receptors, respectively, were
harvested with 0.05% trypsin/0.02% EDTA (Sigma Chemical) and
rinsed with culture medium containing 10% fetal bovine serum
(Sigma Chemical). Pelleted cells were then resuspended in fresh
medium and allowed to recover under 5% CO2 at 37 °C for 1 h
while being vortexed every 15 min. After two washes with Krebs-
HEPES buffer (118 mM NaCl, 4.7 mM KCl, 1.2 mM MgSO4, 1.2
mM KH2PO4, 4.2 mM NaHCO3, 11.7 mM D-glucose, 1.3 mM
CaCl2, 10 mM HEPES, pH 7.4), cells were loaded with 3 µM
Oregon Green 488 BAPTA-1/AM (Molecular Probes, Eugene, OR)
for 1 h at 25 °C in the same buffer containing 1% Pluronic F-127
(Sigma Chemical). Then, cells were rinsed three times with Krebs-
HEPES buffer containing 0.5% bovine serum albumin (BSA)
(Sigma Chemical), diluted, and evenly plated into 96-well plates
(OptiPlate HTRF-96, Packard, Meriden, CT; Cellstar, Tissue Culture
Plate, 96W, Greiner Bio-One, Frickenhausen, Germany). Micro-
plates were kept at 37 °C. Agonistic activity was tested by injecting
buffer alone, standard agonist, or test compounds, respectively,
dissolved in buffer sequentially into separate wells. Fluorescence
intensity was measured at 538 nm (bandwidth 25 nm) for 30 s at
0.4-s intervals. Excitation wavelength was 485 nm (bandwidth 20
nm). Screening of compounds for antagonistic activity or dose-
response curves in the presence of an antagonist were performed
by preincubating the cells with the compounds at 37 °C for 30 min
prior to injection of standard agonist. Final concentration of test
compounds for screening of agonistic or antagonistic activity was
10 µM, respectively. SKF 38393 was used as standard agonist for
hD1 (final concentraion: 100 nM) and hD5 receptors (final
concentration 10 nM), and quinpirole was used for hD2L receptors
(final concentration 30 nM).
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