Tranylcypromine substituted cis -hydroxycyclobutylnaphthamides as potent and selective dopamine D3 receptor antagonists

Article abstract of DOI:10.1021/jm401798r

We report a class of potent and selective dopamine D₃ receptor antagonists based upon tranylcypromine. Although tranylcypromine has a low affinity for the rat D₃ receptor (K_i = 12.8 μM), our efforts have yielded (1R,2S)-11 (CJ-1882), which has K_i values of 2.7 and 2.8 nM at the rat and human dopamine D₃ receptors, respectively, and displays respective selectivities of >10000-fold and 223-fold over the rat and human D₂ receptors. Evaluation in a β-arrestin functional assay showed that (1R,2S)-11 is a potent and competitive antagonist at the human D₃ receptor.

Full text of DOI:10.1021/jm401798r

Brief Article
pubs.acs.org/jmc
Tranylcypromine Substituted cis-Hydroxycyclobutylnaphthamides as
Potent and Selective Dopamine D3 Receptor Antagonists
Jianyong Chen,† Beth Levant,‡ Cheng Jiang,† Thomas M. Keck,§ Amy Hauck Newman,§
and Shaomeng Wang*,†
†Departments of Internal Medicine, Pharmacology, and Medicinal Chemistry, University of Michigan, Ann Arbor, Michigan 48109,
United States
‡Department of Pharmacology, Toxicology, and Therapeutics, University of Kansas Medical Center, Kansas City, Kansas 66160-7417,
United States
§Medicinal Chemistry Section, Molecular Targets and Medications Discovery Branch, National Institute on Drug AbuseIntramural
Research Program, National Institutes of Health, Baltimore, Maryland 21224, United States
S
* Supporting Information
ABSTRACT: We report a class of potent and selective dopamine D3 receptor
antagonists based upon tranylcypromine. Although tranylcypromine has a low
affinity for the rat D3 receptor (Ki = 12.8 μM), our efforts have yielded
(1R,2S)-11 (CJ-1882), which has Ki values of 2.7 and 2.8 nM at the rat and
human dopamine D3 receptors, respectively, and displays respective
selectivities of >10000-fold and 223-fold over the rat and human D2 receptors.
Evaluation in a β-arrestin functional assay showed that (1R,2S)-11 is a potent
and competitive antagonist at the human D3 receptor.
molecule SARs have been fortified.17 Not only have highly D3
receptor selective ligands been discovered, but the roles of the
INTRODUCTION
■
The dopamine-3 (D3) receptor subtype has been identified as
orthosteric site and a secondary binding pocket have further
an important target for agents currently in clinical use for the
defined the drug−protein interactions responsible for affinity,
treatment of a variety of neurological diseases, including
schizophrenia, Parkinson’s disease, and depression. However,
all of the clinically approved drugs targeting the D3 receptor
have a very limited selectivity over D2 receptors and other off-
selectivity, and efficacy.18,19
Potent and selective D3 antagonists may have a therapeutic
potential for the treatment of drug addictions and relate
disorders.2 Herein we report the design and SAR study of a new
class of D3 antagonists. Analysis of several classes of known D3
antagonists shows that their structures can be divided into three
regions as shown in Figure 2: the headgroup (in blue), the
linker (in black), and the tail (in red). The headgroup consists
of a basic amine tethered to an aromatic group (typically
phenyl), substituted with a hydrogen bonding acceptor (a
targets.1,2 Considerable effort has been devoted in the past
decade to the design of potent and selective D3 ligands.1−16
Although it was initially challenging to design highly selective
D3 ligands, due to the high degree of sequence homology
between the D2 and D3 receptors, recent SAR studies have
demonstrated the feasibility of such a design. For example,
upon the basis of pramipexole (1), a potent D3 agonist with
only modest selectivity over the D2 receptor, we designed and
prepared compounds CJ-1638 (2) and CJ-1639 (3), which are
potent and selective D3 agonists (Figure 1).14 Compounds 2
and 3 bind to the D3 receptor, with Ki values <1 nM and
display >1000-fold selectivity over both the D1 and D2
receptors. Further, with the determination of the D3 receptor
crystal structure and derived computational models, the small
Figure 2. Chemical structures of previous dopamine D3 receptor
antagonists.
Figure 1. Chemical structures of pramipexole and two previously
reported selective D3 agonists.
Received: November 21, 2013
Published: May 22, 2014
© 2014 American Chemical Society
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Journal of Medicinal Chemistry
Brief Article
nitrile in 43 or a methoxyl group in 620), or one or two small
hydrophobic groups in 521,22 and 7.13 We first selected a new
“head” group with these features for the design and
development of a new class of D3 antagonists.
Among potential “head” groups under consideration, we
found that tranylcypromine (8, Figure 3) was attractive
RESULTS AND DISCUSSION
■
Our previous study showed that the propyl substituent on the
amine group in pramipexole enhances the binding affinity to
the D3 receptors by at least 1 order of magnitude.14 We
therefore investigated whether substitution of a propyl group
on the primary amine in tranylcypromine would improve the
binding affinity to the D3 receptor. Chiral resolution of racemic
2-phenyl-cyclopropanamine according to the reported meth-
od,25 followed by addition of the propyl group afforded two
stereoisomers (1S,2R)-9 and (1R,2S)-9. Binding data showed
that both (1S,2R)-9 and (1R,2S)-9 bind to the rat D3 receptor
with Ki values of 1.2 μM and display approximately 80-fold
selectivity over the D2 receptor (Table 1). Thus, addition of a
propyl group to the primary amine in tranylcypromine indeed
improves the binding affinity for the D3 receptor, as well as the
selectivity over the D2 receptor.
Our previous study showed that introduction of appropriate
linker and tail groups in compounds 2 and 3 onto the amine
group in pramipexole significantly enhanced its selectivity for
the rat D3 receptor over that for the D2 receptor.14 Accordingly,
we synthesized (1S,2R)-10 and (1R,2S)-10 with the same linker
and tail groups used in compound 2 appended onto the amine
group in compounds (1S,2R)-9 and (1R,2S)-9. Compounds
(1S,2R)-10 and (1R,2S)-10 have Ki values of 108 and 44 nM to
the rat D3 receptor, respectively, representing a 10−20-fold
improvement over (1S,2R)-9 and (1R,2S)-9. However, in
contrast to the marked improved selectivity of compound 2
over pramipexole for the D3 receptor over the D2 receptor
observed in our previous study,14 both (1S,2R)-10 and (1R,2S)-
10 only have modest 20−30-fold selectivity over the rat D2
receptor.
Figure 3. Chemical structures and absolute configurations of the novel
compounds.
Addition of a hydrophobic group such as Cl to the phenyl
ring has been shown to enhance the binding affinity of
antagonists to the D3 receptor. We have therefore synthesized
three compounds (11, 12, and 13) in which a Cl substitution
was installed in the para-, ortho-, or meta-position of the phenyl
ring of 10. Because (1S,2R)-10 and (1R,2S)-10 do not differ
markedly in their binding affinity to the rat D3 receptor or their
selectivity over the rat D2 receptor, we first synthesized and
evaluated the racemic forms of 11−13. Compounds ( )-11,
( )-12, and ( )-13 have Ki values of 4.6, 19, and 28 nM,
respectively, to the rat D3 receptor. ( )-11 and ( )-13 also
display high (>10000 times) selectivity over the rat D2 receptor,
neither compound showing measurable binding to the rat D2
because, like pramipexole (1) and 7, it contains a structurally
rigid phenethylamine moiety. Because the affinities of
tranylcypromine for the dopamine receptors are not known,
we first tested the commercially available, racemic tranylcypro-
mine in our dopamine receptor binding assays using rat
brain.23,24 Our data showed that tranylcypromine has a weak
affinity for the D3 receptor with a Ki value = 12.8 μM and
displays 4-fold selectivity over the D2 receptor (Table 1).
Although tranylcypromine is a weak D3 ligand and has a very
limited selectivity over the D2 receptor, it was used as a starting
point for our SAR study, which has ultimately yielded a class of
potent and selective D3 antagonists.
Table 1. Binding Affinities at Rat Dopamine D1-Like, D2-Like, and D3 Receptors
K
SEM (nM)
D2-like
selectivity
compd
D3
D1-like
D3/D2
D3/D1
2
6
7
0.40 0.087
1.2 0.10
46 5.6
725 45
468 51
1616 167
1042 101
1827
390
4074
868
484
9.1
105
76
18417 2251
58737 5908
95593 5877
96648 9225
2137 247
1312 170
>100000
38807 3038
116250 15103
122700 10120
90587 3531
3088 33
400
( )-8
12793 1870
1171 91
1195 71
108 7.5
44 5.8
4.3
(1S,2R)-9
(1R,2S)-9
(1S,2R)-10
(1R,2S)-10
( )-11
82
81
20
29
2825 297
30
64
4.6 0.40
19 1.8
2201 150
>21000
26
479
39
( )-12
503 63
743 71
( )-13
28 2.1
>300000
1804 126
>29000
>218
>100000
64
(1S,2R)-11
1R,2S)-11
457 34
>100000
20653 2035
25810 1867
45
2.7 0.30
>300000
9559
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Journal of Medicinal Chemistry
Brief Article
receptor at 100 μM. However, both ( )-11 and ( )-13 have
significant affinity for the rat D1-like receptors with Ki values of
2.2 and 1.8 μM, respectively.
antagonist, such as 6 (BP 897),20 blocks the association of β-
arrestin induced by a D3 agonist. Assessed in this manner,
pramipexole has an agonist activity with an EC50 value of 3.7
0.65 nM. (1R,2S)-11 has no agonist activity (EC50 > 100 μM),
but it dose-dependently inhibits the binding of β-arrestin to the
D3 receptor induced by 100 nM of pramipexole and has an IC50
value of 327 126 nM (Table 3). In comparison, 6 shows no
Because ( )-11 showed high affinity for the rat D3 receptor,
we resolved the stereoisomers, (1S,2R)-11 and (1R,2S)-11).
(1R,2S)-11 has a Ki value of 2.7 nM to the rat D3 receptor and
is >100 times more potent than (1S,2R)-11 (Ki = 457 nM).
Furthermore, (1R,2S)-11 has no appreciable binding to the rat
D2 receptor at concentrations as high as 300 μM and
consequently has >100,000-fold selectivity for the rat D3
receptor over the rat D2 receptor. (1R,2S)-11 shows weak
binding affinity to the D1-like receptors, with a Ki value of 25.8
μM, and has >9000-fold selectivity for the rat D3 receptor over
the rat D1-like receptors.
We next assessed the binding affinities of ( )-11, ( )-12,
( )-13, and (1R,2S)-11 to the human D2 and D3 receptors
using transfected cell lines and included several previously
reported D2/D3 antagonists as controls. The data are provided
in Table 2.
Table 3. Efficacy at the Human D3 Receptor in the
a
DiscoveRx PathHunter eXpress β-Arrestin Assay
agonist activity
ED50 (nM)
Antagonist Activity
IC50 (nM)
compd
Emax
1
6
3.7 0.65
>100000
>100000
100
ND
13 1.7
327 126
(1R,2S)-11
a
Data are the mean SEM of 3−6 independent determinations (2
determinations if inactive). ND = not determined.
agonist activity but has potent antagonist activity, with an IC50
value of 13 1.7 nM (Table 3). Hence, (1R,2S)-11 is a potent
D3 antagonist, albeit less potent than 6. We performed a Schild
regression analysis for (1R,2S)-11 in the human D3 functional
assay (Figure 4). In these experiments, D3 activity, measured on
Table 2. Binding Affinities at Human D2 and D3 Receptors
Ki SEM (nM)
selectivity
D3/D2
compd
( )-11
D3
D2
2.61 0.19
22.1 1.87
37.9 3.57
2.80 0.556
0.265 0.008
0.134 0.004
13.4 0.695
6.39 0.58
6.70 0.77
1.88 0.11
667 230
923 213
256
42
(
(
)-12
)-13
1,220 33.7
623 105
32
(1R,2S)-11
N-methylspiperone
eticlopride
raclopride
butaclamol
PG619
223
0.5
0.6
1
0.133 0.009
0.086 0.001
12.7 1.21
2.58 0.473
1,090 21
746 123
0.4
163
397
PG648
Racemic compounds ( )-11, ( )-12, ( )-13, and the pure
enantiomer (1R,2S)-11 have Ki values to the human D3
receptor of 2.61, 22.1, 37.9, and 2.80 nM, respectively. These
values are similar to their respective Ki values of 4.6, 19, 26, and
2.7 nM to the rat D3 receptor. Compounds ( )-11, ( )-12,
( )-13, and (1R,2S)-11 have Ki values, respectively, of 667,
923, 1220, and 623 nM, to the human D2 receptor. Thus, with
the exception of ( )-12, these compounds have higher binding
affinities to the human D2 receptor than to the rat D2 receptor.
The selectivities of ( )-11 and ( )-13 and the pure
enantiomer (1R,2S)-11 for the human D3 receptor over the
human D2 receptor are 256-, 32-, and 223-fold, respectively.
These are lower than the selectivities observed for these
compounds for the rat D3 receptor over the rat D2 receptor.
The known D3 antagonists N-methylspiperone,26 eticlopride,27
raclopride,28 and butaclamol,29 all bind to the human D3
receptor with high affinities but show no selectivity between
the human D2 and D3 receptors (Table 2). In comparison,
PG61922 and PG648,12 two previously reported selective D3
antagonists, bind to the human D3 receptor with Ki values of
6.70 and 1.88 nM, respectively, displaying selectivities of 163-
and 397-fold respectively, for the human D3 receptor over the
human D2 receptor.
Figure 4. Schild analysis of (1R,2S)-11 at the human D3 receptor in
the DiscoveRx PathHunter eXpress β-arrestin assay. D3 activity was
stimulated by pramipexole. Schild transformation (insert) indicated a
pA2 of −7.96, corresponding to a KB value of 20 nM. The slope was
−0.83. Data shown are representative of two independent
determinations.
the basis of β-arrestin binding to the receptor, was stimulated
by pramipexole in the presence of three concentrations of
(1R,2S)-11. The data were analyzed according to the methods
of Kenakin.31 In the Schild plot (the inset in Figure 4), it can be
seen that increasing concentrations of (1R,2S)-11 shift the
pramipexole dose−response curve to the right, consistent with
antagonist activity, with a KB value of 20 nM. The slope of the
Schild plot was −0.83, close to unity, indicating that (1R,2S)-11
is a competitive D3 antagonist.
The synthesis of compounds 9−13 is shown in Scheme 1.
Enantiomerically pure (1R,2S)-2-phenylcyclopropanamine and
(1S,2R)-2-phenylcyclo-propanamine were obtained by resolu-
tion of commercially available ( )-trans-2-phenylcyclopropyl-
amine (8) according to the reported method.25 Reductive
amination of (1R,2S)-8 and (1S,2R)-8 using propionaldehyde
and NaBH4 gave (1R,2S)-9 and (1S,2R)-9 in good yield.
To assess the functional activity of (1R,2S)-11 at the D3
receptor, we tested it in a DiscoveRX D3 functional assay using
the U2OS cell line transfected with human dopamine D3
receptor.30 In this assay, a D3 agonist, such as pramipexole,
stimulates β-arrestin binding to the D3 receptor, while a D3
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Journal of Medicinal Chemistry
Brief Article
a
isopropoxide in benzyl alcohol, followed by lithium hydroxide
hydrolysis and acidification, afforded the cyclopropanecarbox-
ylic acid (1S,2S)-24. Boc-protected (1S,2R)-2-phenylcyclopro-
pylamine 25 was obtained from the carboxylic acid using a
Curtius rearrangement of the corresponding acyl azide followed
by addition of t-butanol to the isocyanate intermediate.
Removal of the Boc group, followed by reductive amination,
gave (1S,2R)-17. The final compound (1S,2R)-11 was obtained
by reductive-amination of (1S,2R)-17 with N-(cis-3-hydroxy-3-
(2-oxoethyl)cyclo-butyl)-2-naphthamide. (1R,2S)-11 was made
by a method similar to that used for (1S,2R)-11, except that
(1S)-(−)-2,10-camphorsultam was used as a chiral auxiliary.
Scheme 1. Synthesis of 9−13
a
Reagents and conditions: (a) propionaldehyde, NaBH4, MeOH, RT;
SUMMARY
(b) N-(cis-3-hydroxy-3-(2-oxoethyl)cyclobutyl)-2-naphthamide,
NaBH(OAc)3, HOAc, DCM, RT, 4 h.
■
Starting from tranylcypromine, we have designed and
synthesized a class of potent and selective dopamine D3
receptor ligands. The best compound, (1R,2S)-11, had a Ki
value of 2.7 nM to the rat D3 receptor and displayed a
selectivity of >100000-fold over the rat D2 receptor and >9000-
fold over the rat D1-like receptors. (1R,2S)-11 binds to the
human D3 receptor with a Ki value of 2.8 nM and displays 223-
fold selectivity over the human D2 receptor. Functional data
and Schild analysis showed that (1R,2S)-11 is a potent and
competitive antagonist at the human D3 receptor. (1R,2S)-11
(CJ-1882) is being further evaluated for its pharmacokinetics,
brain bioavailability, and therapeutic potential for the treatment
of drug abuse.
Reductive amination of (1R,2S)-9 and (1S,2R)-9 with N-(cis-3-
hydroxy-3-(2-oxoethyl)cyclobutyl)-2-naphthamide using so-
dium triacetoxyborohydride as a reductant gave (1R,2S)-10
and (1S,2R)-10. Compounds ( )-11−( )-13 were prepared
similarly. Reductive amination of the appropriate commercially
available racemic chloro-substituted trans-2-phenylcyclopropan-
amine ( )-14−16 afforded ( )-17−19. The final compounds
( )-11−13 were prepared by reductive amination of ( )-17−
19 with N-(cis-3-hydroxy-3-(2-oxoethyl)cyclobutyl)-2-naphtha-
mide. N-(cis-3-Hydroxy-3-(2-oxo-ethyl)cyclobutyl)-2-naphtha-
mide was prepared as described previously.14
The synthesis of (1S,2R)-11 is shown in Scheme 2. The
optically pure key intermediate (1S,2S)-2-(4-chlorophenyl)-
EXPERIMENTAL SECTION
■
a
General Methods. Solvents and reagents were obtained
commercially and used without further purification. Reactions were
monitored by TLC carried out on 250 μm silica gel plates 60F-254 (E.
Merck) using UV light as visualizing agent. Silica gel 60, particle size
15−40 μm (E. Merck), was used for flash column chromatography.
NMR spectra were recorded on a Bruker Avance 300 spectrometer
(300 MHz). Chemical shifts (δ) are reported as δ values (ppm)
downfield relative to TMS as an internal standard, with multiplicities
reported in the standard manner. All final compounds have purities
>95%, as determined by HPLC (UV detection at 254 nm).
Scheme 2. Synthesis of (1S,2R)-11
(1S,2R)-2-Phenyl-N-propylcyclopropanamine ((1S,2R)-9).
Propionaldehyde (82 mg, 1.41 mmol) was added to a solution of
(1S,2R)-2-phenylcyclopropanamine (188 mg, 1.41 mmol) in MeOH
(10 mL), and the reaction mixture was stirred at room temperature for
2 h. Sodium borohydride (79 mg, 2.12 mmol) was then added, and the
mixture was stirred at room temperature for 1 h. The reaction was
quenched with H2O (30 mL) and extracted with ethyl acetate (40
mL). The residue was chromatographed (hexane:EtOAc = 50:50) to
give (1S,2R)-9 (178 mg, 72% yield) as a colorless oil. 1H NMR
(CD3OD, 300 MHz) δ 7.37−7.12 (m, 5H), 3.20−3.08 (m, 2H), 2.97−
2.90 (m, 1H), 2.56−2.45 (m, 1H), 1.82−1.70 (m, 2H), 1.57−1.45 (m,
1H), 1.36 (dd, J = 6.7, 14.4 Hz, 1H), 1.04 (t, J = 7.4 Hz). 13C NMR
(CD3OD, 75 MHz) δ 139.42, 129.68, 127.91, 127.56, 50.88, 39.04,
22.32, 20.55, 13.35, 11.19.
(1R,2S)-2-Phenyl-N-propylcyclopropanamine ((1R,2S)-9).
Propionaldehyde (82 mg, 1.41 mmol) was added to a solution of
(1R,2S)-2-phenylcyclopropanamine (188 mg, 1.41 mmol) in MeOH
(10 mL), and the reaction mixture was stirred at room temperature for
2 h. Sodium borohydride (79 mg, 2.12 mmol) was then added, and the
mixture was stirred at room temperature for 1 h. The reaction was
quenched with H2O (30 mL) and extracted with EtOAc (40 mL). The
residue was chromatographed (hexane:EtOAc = 50:50) to give
(1R,2S)-9 (171 mg, 69% yield) as a colorless oil. 1H NMR
(CD3OD, 300 MHz) δ 7.37−7.12 (m, 5H), 3.20−3.08 (m, 2H),
2.97−2.90 (m, 1H), 2.56−2.45 (m, 1H), 1.82−1.70 (m, 2H), 1.57−
1.45 (m, 1H), 1.36 (dd, J = 6.7, 14.4 Hz, 1H), 1.04 (t, J = 7.4 Hz). 13C
a
Reagents and conditions: (a) (1R)-(+)-2,10-camphorsultam, NaH,
THF, 0 °C, 30 min, then RT overnight; (b) CH2N2, Pd(OAc)2, DCM,
RT, 10 h; (c) (i)Ti(iOPr)4, BzOH, 150 °C, 30 min, (ii) 2 M LiOH,
MeOH, RT, 2 h, (iii) 4 M HCI; (d) (i) ethyl chloroformate. Et3N,
acetone, 0 °C, 2 h, (ii) NaN3,1 h, (iii) 90 °C, toluene, 3 h, (iv) ButOH,
reflux, 16 h. (e) TFA, DCM, RT, 12 h; (f) propionaldehyde, NaBH4,
MeOH, RT; (g) N-(cis-3-hydroxy-3-(2-oxoethyl)cyclobutyl)-2-naprit-
tiamlde, NaBH(OAc)3, HOAc, DCM, RT, 4 h.
cyclopropane-carboxylic acid 24 was prepared according to a
reported method.32 Treatment of the acid chloride 20 with
sodium (1R)-(+)-2,10-camphorsultam afforded the enoyl
sultams 21 in excellent yield (>93%). Reaction of 21 with
diazomethane in the presence of a catalytic amount of
palladium acetate gave a cyclopropanated diastereomeric
mixture of (1R)-(+)-2,10-camphorsultam-(1S,2S)-2-phenylcy-
clopropane-carboxamide 22 and (1R)-(+)-2,10-camphorsul-
tam-(1R,2R)-2-phenyl-cyclopropane-carboxamide 23 in a ratio
of 7:1. Recrystallization from ethanol afforded pure cyclo-
propanoyl sultams 22. Treatment of 22 with titanium
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1
NMR (CD3OD, 75 MHz) δ 139.42, 129.68, 127.91, 127.56, 50.88,
39.04, 22.32, 20.55, 13.35, 11.19.
( )-12 in 32% yield. H NMR (CD3OD, 300 MHz) δ 8.39 (s, 1H),
8.00−7.80 (m, 4H), 7.70−7.50 (m, 2H), 7.40−7.10 (m, 4H), 4.25−
4.10 (m, 1H), 3.60−3.10 (m, 5H), 2.75−2.65 (m, 3H), 2.35−2.10 (m,
4H), 1.90−1.50 (m, 4H), 1.05 (t, J = 7.3 Hz, 3H). 13C NMR
(CD3OD, 75 MHz) δ 170.14, 141.61, 136.45, 136.01, 134.20, 132.86,
131.60, 130.18, 129.50, 129.04, 128.95, 128.51, 128.04, 127.45, 126.01,
125.09, 69.05, 58.49, 53.47, 46.64, 44.42, 44.27, 38.47, 34.50, 23.42,
19.02, 14.99, 11.41.
N-(cis-3-Hydroxy-3-(2-(((1S,2R)-2-phenylcyclopropyl)-
(propyl)-amino)ethyl)cyclobutyl)-2-naphthamide ((1S,2R)-10).
N-(cis-3-Hydroxy-3-(2-oxoethyl)cyclobutyl)-2-naphthamide (80 mg,
0.28 mmol), sodium triacetoxyborohydride (90 mg, 0.43 mmol),
and AcOH (26 mg, 0.43 mmol) were added to a solution of (1S,2R)-9
(50 mg, 0.28 mmol) in CH2Cl2 (20 mL). The mixture was stirred at
room temperature for 4 h and then quenched by addition of H2O (30
mL). The mixture was extracted with CH2Cl2 (30 mL × 3). The
organic solvent was removed under vacuum, and the residue was
chromatographed (MeOH:EtOAc = 10:90) to give (1S,2R)-10 (43
mg, 34% yield) as a colorless oil. 1H NMR (CD3OD, 300 MHz) δ 8.39
(s, 1H), 8.00−7.80 (m, 4H), 7.60−7.50 (m, 2H), 7.40−7.20 (m, 5H),
4.25−4.00 (m, 1H), 3.60−3.25 (m, 4H), 3.20−3.02 (m, 1H), 2.75−
2.60 (m, 3H), 2.40−2.09 (m, 4H), 1.90−1.65 (m, 3H), 1.53 (dd, J =
7.1, 14.4 Hz, 1H), 1.05 (t, J = 7.4 Hz, 3H). 13C NMR (CD3OD, 75
MHz) δ 169.90, 164.83, 138.89, 136.25, 133.99, 132.65, 129.99,
129.91, 129.31, 128.85, 128.76, 128.21, 127.86, 127.18, 124.91, 68.81,
58.31, 53.29, 46.48, 44.19, 44.09, 38.24, 23.66, 18.84, 14.49, 11.23.
N-(cis-3-Hydroxy-3-(2-(((1R,2S)-2-phenylcyclopropyl)-
(propyl)amino)-ethyl)cyclobutyl)-2-naphthamide ((1R,2S)-10).
N-(cis-3-Hydroxy-3-(2-oxoethyl)cyclobutyl)-2-naphthamide (80 mg,
0.28 mmol), sodium triacetoxyborohydride (90 mg, 0.43 mmol),
and AcOH (26 mg, 0.43 mmol) were added to a solution of (1R,2S)-9
(50 mg, 0.28 mmol) in CH2Cl2 (20 mL), and the mixture was stirred
at room temperature for 4 h. The reaction was quenched by addition
of H2O (30 mL), and the mixture was extracted with CH2Cl2 (30 mL
× 3). The organic solvent was removed under vacuum, and the residue
was chromatographed (MeOH:EtOAc = 10:90) to give (1R,2S)-10
(36 mg, 29% yield) as a colorless oil. 1H NMR (CD3OD, 300 MHz) δ
8.39 (s, 1H), 8.00−7.80 (m, 4H), 7.60−7.50 (m, 2H), 7.40−7.20 (m,
5H), 4.25−4.00 (m, 1H), 3.60−3.25 (m, 4H), 3.20−3.02 (m, 1H),
2.75−2.60 (m, 3H), 2.40−2.09 (m, 4H), 1.90−1.65 (m, 3H), 1.53 (dd,
J = 7.1, 14.4 Hz, 1H), 1.05 (t, J = 7.4 Hz, 3H). 13C NMR (CD3OD, 75
MHz) δ 169.90, 164.83, 138.89, 136.25, 133.99, 132.65, 129.99,
129.91, 129.31, 128.85, 128.76, 128.21, 127.86, 127.18, 124.91, 68.81,
58.31, 53.29, 46.48, 44.19, 44.09, 38.24, 23.66, 18.84, 14.49, 11.23.
N-(cis-3-(2-(((( )-trans)-2-(2-Chlorophenyl)cyclopropyl)-
(propyl)-amino)ethyl)-3-hydroxycyclobutyl)-2-naphthamide
(( )-12). N-(cis-3-Hydroxy-3-(2-oxoethyl)cyclobutyl)-2-naphthamide
(82 mg, 0.29 mmol), sodium triacetoxyborohydride (91 mg, 0.43
mmol), and AcOH (26 mg, 0.43 mmol) were added to a solution of
( )-18 (60 mg, 0.29 mmol) in CH2Cl2 (20 mL), and the mixture was
stirred at room temperature for 4 h. The reaction was quenched by
addition of H2O (30 mL), and the mixture was extracted with CH2Cl2
(30 mL × 3). The organic solvent was removed under vacuum, and
the residue was chromatographed (MeOH:EtOAc = 10:90) to give
( )-12 (49 mg, 36% yield) as a colorless oil. 1H NMR (CD3OD, 300
MHz) δ 8.39 (s, 1H), 8.00−7.85 (m, 4H), 7.70−7.52 (m, 2H), 7.47
(dd, J = 1.6, 7.4 Hz, 1H), 7.40−7.20 (m, 2H), 7.09 (dd, J = 2.0, 7.4 Hz,
1H), 4.25−4.02 (m, 1H), 3.70−3.30 (m, 4H), 3.30−3.20 (m, 1H),
2.75−2.60 (m, 2H), 2.40−2.10 (m, 4H), 2.00−1.50 (m, 4H), 1.07 (t, J
= 7.3 Hz, 3H). 13C NMR (CD3OD, 75 MHz) δ 170.16, 136.48,
136.40, 135.76, 134.23, 132.87, 130.91, 130.19, 129.95, 129.52, 129.05,
128.97, 128.91, 128.06, 127.59, 125.09, 69.09, 58.35, 53.41, 46.50,
44.48, 44.29, 38.48, 34.56, 21.52, 18.85, 14.44, 11.42.
N-(cis-3-(2-(((1S,2R)-2-(4-Chlorophenyl)cyclopropyl)(propyl)-
amino)ethyl)-3-hydroxycyclobutyl)-2-naphthamide ((1S,2R)-
11). N-(cis-3-Hydroxy-3-(2-oxoethyl)cyclobutyl)-2-naphthamide (191
mg, 0.67 mmol), sodium triacetoxyborohydride (212 mg, 1.01 mmol),
and AcOH (60 mg, 1.01 mmol) were added to a solution of (1S,2R)-
17 (140 mg, 0.67 mmol) in CH2Cl2 (20 mL), and the mixture was
stirred at room temperature for 4 h. The reaction was quenched by
addition of H2O (30 mL), and the mixture was extracted with CH2Cl2
(30 mL × 3). The organic solvent was removed under vacuum, and
the residue was chromatographed (MeOH:EtOAc = 10:90) to give
1
(1S,2R)-11 (79 mg, 25% yield) as a colorless oil. H NMR (CDCl3,
300 MHz) δ 8.28 (s, 1H), 7.90−7.75 (m, 4H), 7.60−7.50 (m, 2H),
7.23 (d, J = 8.5 Hz, 2H), 6.94 (d, J = 8.5 Hz, 2H), 6.53 (d, J = 7.7 Hz,
1H), 4.40−4.20 (m, 1H), 3.00−2.40 (m, 6H), 2.25−1.70 (m, 6H),
1.60−1.50 (m, 2H), 1.25−1.00 (m, 2H), 0.89 (t, J = 7.3 Hz, 3H). 13C
NMR (CDCl3, 75 MHz) δ 167.21, 140.12, 134.93, 132.82, 131.83,
131.72, 129.14, 128.71, 128.67, 127.95, 127.84, 127.58, 127.25, 126.96,
123.75, 71.19, 57.69, 53.27, 48.76, 44.73, 44.57, 37.51, 34.44, 24.94,
20.15, 17.02, 12.23.
N-(cis-3-(2-(((1R,2S)-2-(4-Chlorophenyl)cyclopropyl)(propyl)-
amino)ethyl)-3-hydroxycyclobutyl)-2-naphthamide ((1R,2S)-
11). (1R,2S)-11 was prepared in 35% yield in a manner similar to
that used for (1S,2R)-11, except that (1S)-(−)-2,10-camphorsultam
1
was used as a chiral auxiliary. H NMR (CDCl3, 300 MHz) δ 8.28 (s,
1H), 7.90−7.75 (m, 4H), 7.60−7.50 (m, 2H), 7.23 (d, J = 8.5 Hz,
2H), 6.94 (d, J = 8.5 Hz, 2H), 6.53 (d, J = 7.7 Hz, 1H), 4.40−4.20 (m,
1H), 3.00−2.40 (m, 6H), 2.25−1.70 (m, 6H), 1.60−1.50 (m, 2H),
1.25−1.00 (m, 2H), 0.89 (t, J = 7.3 Hz, 3H). 13C NMR (CDCl3, 75
MHz) δ 167.21, 140.12, 134.93, 132.82, 131.83, 131.72, 129.14,
128.71, 128.67, 127.95, 127.84, 127.58, 127.25, 126.96, 123.75, 71.19,
57.69, 53.27, 48.76, 44.73, 44.57, 37.51, 34.44, 24.94, 20.15, 17.02,
12.23.
In Vitro Dopamine Receptor Binding Assays at the Rat
Dopamine Receptors. The binding affinities of all the synthetic
compounds were determined at the D3, D2, and D1-like receptors in
membranes prepared from the brains of adult, male Sprague−Dawley
rats (Pel-Freez, Rogers, AR). All compounds were dissolved in 100%
EtOH at a concentration of 5 mM.
[3H]R(+)-7-OH-DPAT Binding Assay. The [3H]R-(+)-7-OH-
DPAT binding assay for the rat D3 dopamine receptors was performed
as described.23 A rat ventral striatum (nucleus accumbens and
olfactory tubercles) was prepared in assay buffer (50 mM Tris, 1
mM EDTA; pH 7.4 at 23 °C) to yield a final concentration of 10 mg
original wet weight (oww)/mL. Membranes were incubated with
[3H]R-(+)-7-OH-DPAT (0.15 nM, SA = 163 Ci/mmol; GE
Healthcare) and different concentrations of the test compounds
(10−10 to 10−4 M). Nonspecific binding was defined by 1 μM
spiperone (Sigma-Aldrich). Assay tubes were incubated at 23 °C for 90
min. The reaction was terminated by rapid vacuum filtration. Data
were analyzed using SigmaPlot 10. Ki values were calculated using KD
= 0.15 nM for [3H]7-OH-DPAT23 and are expressed as the mean
SEM of 3−5 independent determinations.
N-(cis-3-(2-(((( )-trans)-2-(4-Chlorophenyl)cyclopropyl)-
(propyl)-amino)ethyl)-3-hydroxycyclobutyl)-2-naphthamide
(( )-11). ( )-11 was prepared in a manner similar to that used for
1
( )-12 in 35% yield. H NMR (CDCl3, 300 MHz) δ 8.28 (s, 1H),
[3H]Spiperone Binding Assay. [3H]Spiperone binding assays for
rat D2-like receptors were performed as described24 for [3H]R-(+)-7-
OH-DPAT with the following modifications. Assays were performed
using membranes prepared from rat caudate-putamen, which expresses
D2 receptors in high density but with very low levels of D3 receptors,
and the final membrane homogenate concentration was 1.5 mg oww/
mL. The assay buffer was 50 mM Tris-HCl, 5 mM KCl, 2 mM MgCl2,
and 2 mM CaCl2, pH 7.4 at 23 °C; the concentration of
[3H]spiperone (60−96 Ci/mmol; GE Healthcare, PerkinElmer, or
American Radiolabeled Chemicals) was 0.2 nM, and the incubation
7.90−7.75 (m, 4H), 7.60−7.50 (m, 2H), 7.23 (d, J = 8.5 Hz, 2H), 6.94
(d, J = 8.5 Hz, 2H), 6.53 (d, J = 7.7 Hz, 1H), 4.40−4.20 (m, 1H),
3.00−2.40 (m, 6H), 2.25−1.70 (m, 6H), 1.60−1.50 (m, 2H), 1.25−
1.00 (m, 2H), 0.89 (t, J = 7.3 Hz, 3H). 13C NMR (CDCl3, 75 MHz) δ
167.21, 140.12, 134.93, 132.82, 131.83, 131.72, 129.14, 128.71, 128.67,
127.95, 127.84, 127.58, 127.25, 126.96, 123.75, 71.19, 57.69, 53.27,
48.76, 44.73, 44.57, 37.51, 34.44, 24.94, 20.15, 17.02, 12.23.
N-(cis-3-(2-(((( )-trans)-2-(3-Chlorophenyl)cyclopropyl)-
(propyl)-amino)ethyl)-3-hydroxycyclobutyl)-2-naphthamide
(( )-13). ( )-13 was prepared in a manner similar to that used for
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dx.doi.org/10.1021/jm401798r | J. Med. Chem. 2014, 57, 4962−4968

Journal of Medicinal Chemistry
Brief Article
time was 90 min at 23 °C. Nonspecific binding was defined in the
presence of 1 μM (+)-butaclamol (Sigma-Aldrich). Ki values were
calculated using the experimentally determined KD value for
[3H]spiperone of 0.4 nM.
ASSOCIATED CONTENT
* Supporting Information
Experimental details of chemical synthesis and chemical data.
This material is available free of charge via the Internet at
http://pubs.acs.org.
■
S
[3H]SCH 23390 Binding Assay. [3H] SCH 23390 binding assay
for rat D1-like dopamine receptors was performed as described33 for
[3H]spiperone binding except the concentration of [3H]SCH 23390
(60 Ci/mmol; American Radiolabeled Chemicals) was 0.3 nM. Ki
values were calculated using the KD value for [3H]SCH 23390 of 0.3
nM.
AUTHOR INFORMATION
Corresponding Author
*Phone: 734-6150362. Fax: 734-6479647. E-mail: Shaomeng@
umich.edu.
■
In Vitro Dopamine Receptor Binding Assays at the Human
Dopamine Receptors. HEK293 cells stably expressing human
dopamine D2 and D3 receptors were grown in a 1:1 mixture of
DMEM and Ham’s F12 culture media, supplemented with 20 mM
HEPES, 2 mM L-glutamine, 0.1 mM nonessential amino acids, 1×
antibiotic/antimycotic, 10% heat-inactivated fetal bovine serum, and
200 μg/mL hygromycin (Life Technologies, Grand Island, NY) and
kept in an incubator at 37 °C and 5% CO2. Upon reaching 80−90%
confluence, cells were harvested using premixed Earle’s Balanced Salt
Solution (EBSS) with 5 μM EDTA (Life Technologies) and
centrifuged at 3000 rpm for 10 min at 21 °C. The supernatant was
removed, and the pellet was resuspended in 10 mL of hypotonic lysis
buffer (5 mM MgCl2·6H2O, 5 mM Tris, pH 7.4 at 4 °C) and
centrifuged at 20000 rpm for 30 min at 4 °C. The pellet was then
resuspended in fresh EBSS buffer made from 8.7 g/L Earle’s Balanced
Salts without phenol red (US Biological, Salem, MA), 2.2 g/L sodium
bicarbonate, pH to 7.4. A Bradford protein assay (Bio-Rad, Hercules,
CA) was used to determine the protein concentration, and membranes
were diluted to 500 μg/mL and stored in a −80 °C freezer for later
use.
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
This work was supported by a grant from the National Institute
on Drug Abuse, National Institutes of Health (R01 DA032943
to S.W.) and the NIDA−Intramural Research Program (A.H.N,
T.M.K). We thank Dr. David R. Sibley at NINDS/NIH for
providing HEK293 cells stably expressing human dopamine D2
and D3 receptors, Heather Spaulding at the University of
Kansas Medical Center, and Catherine Schweppe and Caitlin
Burzynski at NIDA/NIH for their technical assistance.
REFERENCES
■
(1) Newman, A. H.; Grundt, P.; Nader, M. A. Dopamine D3 receptor
partial agonists and antagonists as potential drug abuse therapeutic
agents. J. Med. Chem. 2005, 48, 3663−79.
Immediately prior to testing, all test compounds were freshly
dissolved in 30% DMSO and 70% H2O to a stock concentration of
100 μM. To assist the solubilization of free-base compounds, 10 μL of
glacial acetic acid was added along with the DMSO. Each test
compound was then diluted into 13 half-log serial dilutions using 30%
DMSO vehicle; final test concentrations ranged from 10 μM to 10 pM.
Previously frozen membranes were diluted in fresh EBSS to a 100 μg/
mL stock for binding. Radioligand competition experiments were
conducted in glass tubes containing 300 μL of fresh EBSS buffer with
0.2 mM sodium metabisulfite, 50 μL of diluted test compound, 100 μL
of membranes (10 μg total protein), and 50 μL of [3H]N-
methylspiperone (0.4 nM final concentration; PerkinElmer). Non-
specific binding was determined using 10 μM butaclamol (Sigma-
Aldrich, St. Louis, MO), and total binding was determined with 30%
DMSO vehicle. All compound dilutions were tested in triplicate and
the reaction incubated for 1 h at room temperature. The reaction was
terminated by filtration through Whatman GF/B filters, presoaked for
1 h in 0.5% polyethylenimine, using a Brandel R48 filtering manifold
(Brandel Instruments, Gaithersburg, MD). The filters were washed 3
times with 3 mL of ice-cold EBSS buffer and transferred to scintillation
vials. Then 3 mL of CytoScint liquid scintillation cocktail (MP
Biomedicals, Solon, OH) was added and vials were counted using a
PerkinElmer Tri-Carb 2910 TR liquid scintillation counter (Waltham,
MA). IC50 values for each compound were determined from dose−
response curves, and Ki values were calculated using the Cheng−
Prusoff equation.34 These analyses were performed using GraphPad
Prism version 5.00 for Windows (GraphPad Software, San Diego,
CA). Reported Ki values were determined from least three
independent experiments.
(2) Heidbreder, C. A.; Newman, A. H. Current perspectives on
selective dopamine D(3) receptor antagonists as pharmacotherapeu-
tics for addictions and related disorders. Ann. N. Y. Acad. Sci. 2010,
1187, 4−34.
(3) Reavill, C.; Taylor, S. G.; Wood, M. D.; Ashmeade, T.; Austin, N.
E.; Avenell, K. Y.; Boyfield, I.; Branch, C. L.; Cilia, J.; Coldwell, M. C.;
Hadley, M. S.; Hunter, A. J.; Jeffrey, P.; Jewitt, F.; Johnson, C. N.;
Jones, D. N.; Medhurst, A. D.; Middlemiss, D. N.; Nash, D. J.; Riley,
G. J.; Routledge, C.; Stemp, G.; Thewlis, K. M.; Trail, B.; Vong, A. K.;
Hagan, J. J. Pharmacological actions of a novel, high-affinity, and
selective human dopamine D(3) receptor antagonist, SB-277011-A. J.
Pharmacol. Exp. Ther. 2000, 294, 1154−65.
(4) Hackling, A.; Ghosh, R.; Perachon, S.; Mann, A.; Holtje, H. D.;
Wermuth, C. G.; Schwartz, J. C.; Sippl, W.; Sokoloff, P.; Stark, H. N-
(omega-(4-(2-Methoxyphenyl)piperazin-1-yl)alkyl)carboxamides as
dopamine D2 and D3 receptor ligands. J. Med. Chem. 2003, 46,
3883−99.
(5) Macdonald, G. J.; Branch, C. L.; Hadley, M. S.; Johnson, C. N.;
Nash, D. J.; Smith, A. B.; Stemp, G.; Thewlis, K. M.; Vong, A. K.;
Austin, N. E.; Jeffrey, P.; Winborn, K. Y.; Boyfield, I.; Hagan, J. J.;
Middlemiss, D. N.; Reavill, C.; Riley, G. J.; Watson, J. M.; Wood, M.;
Parker, S. G.; Ashby, C. R., Jr. Design and synthesis of trans-3-(2-(4-
((3-(3-(5-methyl-1,2,4-oxadiazolyl))- phenyl)carboxamido)-
cyclohexyl)ethyl)-7-methylsulfonyl-2,3,4,5-tetrahydro-1H-3-benzaze-
pine (SB-414796): a potent and selective dopamine D3 receptor
antagonist. J. Med. Chem. 2003, 46, 4952−64.
(6) Campiani, G.; Butini, S.; Trotta, F.; Fattorusso, C.; Catalanotti,
B.; Aiello, F.; Gemma, S.; Nacci, V.; Novellino, E.; Stark, J. A.;
Cagnotto, A.; Fumagalli, E.; Carnovali, F.; Cervo, L.; Mennini, T.
Synthesis and pharmacological evaluation of potent and highly
selective D3 receptor ligands: inhibition of cocaine-seeking behavior
and the role of dopamine D3/D2 receptors. J. Med. Chem. 2003, 46,
3822−39.
(7) Bettinetti, L.; Schlotter, K.; Hubner, H.; Gmeiner, P. Interactive
SAR studies: rational discovery of super-potent and highly selective
dopamine D3 receptor antagonists and partial agonists. J. Med. Chem.
2002, 45, 4594−7.
(8) Chen, J.; Ding, K.; Levant, B.; Wang, S. Design of novel
hexahydropyrazinoquinolines as potent and selective dopamine D3
Dopamine D3 β-Arrestin Functional Assay. Functional activity
at the D3 receptor was determined using a PathHunter eXpress β-
arrestin assay kit (DiscoveRx, Fremont, CA) for human D3 receptors
transfected in U20S cells.30 Compounds were screened for agonist and
antagonist activity according to the manufacturer’s instructions.
Pramipexole (100 nM) was used as the reference agonist. Data were
analyzed using SigmaPlot 10 and are presented as the mean SEM of
4−6 independent determinations. For the Schild analysis, D3 activity
was stimulated by pramipexole in the presence of 3 concentrations of
(1R,2S)-11 and analyzed according to the methods of Kenakin.31
4967
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Journal of Medicinal Chemistry
Brief Article
receptor ligands with improved solubility. Bioorg. Med. Chem. Lett.
2006, 16, 443−6.
(9) Ji, M.; Chen, J.; Ding, K.; Wu, X.; Varady, J.; Levant, B.; Wang, S.
Design, synthesis and structure−activity relationship studies of
hexahydropyrazinoquinolines as a novel class of potent and selective
dopamine receptor 3 (D3) ligands. Bioorg. Med. Chem. Lett. 2005, 15,
1701−5.
(10) Varady, J.; Wu, X.; Fang, X.; Min, J.; Hu, Z.; Levant, B.; Wang,
S. Molecular modeling of the three-dimensional structure of dopamine
3 (D3) subtype receptor: discovery of novel and potent D3 ligands
through a hybrid pharmacophore- and structure-based database
searching approach. J. Med. Chem. 2003, 46, 4377−92.
(11) Ehrlich, K.; Gotz, A.; Bollinger, S.; Tschammer, N.; Bettinetti,
L.; Harterich, S.; Hubner, H.; Lanig, H.; Gmeiner, P. Dopamine D2,
D3, and D4 selective phenylpiperazines as molecular probes to explore
the origins of subtype specific receptor binding. J. Med. Chem. 2009,
52, 4923−35.
dopamine receptor, in rat brain: a receptor binding and quantitative
autoradiographic study. Neuropsychopharmacology 1998, 18, 305−16.
(24) Levant, B.; Grigoriadis, D. E.; DeSouza, E. B. Characterization of
[3H]quinpirole binding to D2-like dopamine receptors in rat brain. J.
Pharmacol. Exp. Ther. 1992, 262, 929−35.
(25) Kinzel, O.; Alfieri, A.; Altamura, S.; Brunetti, M.; Bufali, S.;
Colaceci, F.; Ferrigno, F.; Filocamo, G.; Fonsi, M.; Gallinari, P.;
Malancona, S.; Hernando, J. I.; Monteagudo, E.; Orsale, M. V.;
Palumbi, M. C.; Pucci, V.; Rowley, M.; Sasso, R.; Scarpelli, R.;
Steinkuhler, C.; Jones, P. Identification of MK-5710 ((8aS)-8a-methyl-
1,3-dioxo-2-[(1S,2R)-2-phenylcyclo- propyl]-N-(1-phenyl-1H-pyrazol-
5-yl)hexahydro-imidazo[1,5-a]pyrazine-7(1H)-carbox amide), a po-
tent smoothened antagonist for use in Hedgehog pathway dependent
malignancies, part 2. Bioorg. Med. Chem. Lett. 2011, 21, 4429−35.
(26) Andree, B.; Nyberg, S.; Ito, H.; Ginovart, N.; Brunner, F.;
Jaquet, F.; Halldin, C.; Farde, L. Positron emission tomographic
analysis of dose-dependent MDL 100,907 binding to 5-hydroxytrypt-
amine-2A receptors in the human brain. J. Clin. Psychopharmacol. 1998,
18, 317−23.
(12) Newman, A. H.; Grundt, P.; Cyriac, G.; Deschamps, J. R.;
Taylor, M.; Kumar, R.; Ho, D.; Luedtke, R. R. N-(4-(4-(2,3-Dichloro-
or 2-methoxyphenyl)piperazin-1-yl)butyl)heterobiarylcarboxamides
with functionalized linking chains as high affinity and enantioselective
D3 receptor antagonists. J. Med. Chem. 2009, 52, 2559−70.
(13) Micheli, F.; Arista, L.; Bertani, B.; Braggio, S.; Capelli, A. M.;
Cremonesi, S.; Di-Fabio, R.; Gelardi, G.; Gentile, G.; Marchioro, C.;
Pasquarello, A.; Provera, S.; Tedesco, G.; Tarsi, L.; Terreni, S.; Worby,
A.; Heidbreder, C. Exploration of the amine terminus in a novel series
of 1,2,4-triazolo-3-yl-azabicyclo[3.1.0]hexanes as selective dopamine
D3 receptor antagonists. J. Med. Chem. 2010, 53, 7129−39.
(14) Chen, J.; Collins, G. T.; Levant, B.; Woods, J.; Deschamps, J. R.;
Wang, S. CJ-1639: A Potent and Highly Selective Dopamine D3
Receptor Full Agonist. ACS Med. Chem. Lett. 2011, 2, 620−5.
(15) Song, R.; Yang, R. F.; Wu, N.; Su, R. B.; Li, J.; Peng, X. Q.; Li,
X.; Gaal, J.; Xi, Z. X.; Gardner, E. L. YQA14: a novel dopamine D3
receptor antagonist that inhibits cocaine self-administration in rats and
mice, but not in D3 receptor-knockout mice. Addict. Biol. 2012, 17,
259−73.
(27) Claytor, R.; Lile, J. A.; Nader, M. A. The effects of eticlopride
and the selective D3-antagonist PNU 99194-A on food- and cocaine-
maintained responding in rhesus monkeys. Pharmacol., Biochem. Behav.
2006, 83, 456−64.
(28) Kohler, C.; Hall, H.; Ogren, S. O.; Gawell, L. Specific in vitro
3
and in vivo binding of H-raclopride. A potent substituted benzamide
drug with high affinity for dopamine D2 receptors in the rat brain.
Biochem. Pharmacol. 1985, 34, 2251−9.
(29) Chrzanowski, F. A.; McGrogan, B. A.; Maryanoff, B. E. The pKa
of butaclamol and the mode of butaclamol binding to central
dopamine receptors. J. Med. Chem. 1985, 28, 399−400.
(30) Olson, K. R.; Eglen, R. M. Beta-galactosidase complementation:
a cell-based luminescent assay platform for drug discovery. Assay Drug
Dev. Technol. 2007, 5, 137−44.
(31) Kenakin, T. P. Pharmacologic Analysis of Drug−Receptor
Interaction; Raven Press: New York, 1987.
(32) Vallgarda, J.; Appelberg, U.; Csoregh, I.; Hacksell, U.
Stereoselectivity and Generality of the Palladium-Catalyzed Cyclo-
propanation of Alpha,Beta-Unsaturated Carboxylic Acids Derivatized
with Oppolzers Sultam. J. Chem. Soc., Perkin Trans. 1 1994, 461−70.
(33) Levant, B. Characterization of Dopamine Receptors. In Current
Protocols in Pharmacology; John Wiley & Sons, Inc.: New York, 2001.
(34) Cheng, Y.; Prusoff, W. H. Relationship between the inhibition
constant (Ki) and the concentration of inhibitor which causes 50%
inhibition (IC50) of an enzymatic reaction. Biochem. Pharmacol. 1973,
22, 3099−3108.
(16) Micheli, F.; Heidbreder, C. Dopamine D3 receptor antagonists:
a patent review (2007−2012). Expert Opin. Ther. Pat. 2013, 23, 363−
81.
(17) Chien, E. Y.; Liu, W.; Zhao, Q.; Katritch, V.; Han, G. W.;
Hanson, M. A.; Shi, L.; Newman, A. H.; Javitch, J. A.; Cherezov, V.;
Stevens, R. C. Structure of the human dopamine D3 receptor in
complex with a D2/D3 selective antagonist. Science 2010, 330, 1091−5.
(18) Newman, A. H.; Beuming, T.; Banala, A. K.; Donthamsetti, P.;
Pongetti, K.; LaBounty, A.; Levy, B.; Cao, J.; Michino, M.; Luedtke, R.
R.; Javitch, J. A.; Shi, L. Molecular determinants of selectivity and
efficacy at the dopamine D3 receptor. J. Med. Chem. 2012, 55, 6689−
99.
(19) Keck, T. M.; Burzynski, C.; Shi, L.; Newman, A. H. Beyond
small-molecule SAR: using the dopamine D3 receptor crystal structure
to guide drug design. Adv. Pharmacol. 2014, 69, 267−300.
(20) Pilla, M.; Perachon, S.; Sautel, F.; Garrido, F.; Mann, A.;
Wermuth, C. G.; Schwartz, J. C.; Everitt, B. J.; Sokoloff, P. Selective
inhibition of cocaine-seeking behaviour by a partial dopamine D3
receptor agonist. Nature 1999, 400, 371−5.
(21) Grundt, P.; Carlson, E. E.; Cao, J.; Bennett, C. J.; McElveen, E.;
Taylor, M.; Luedtke, R. R.; Newman, A. H. Novel heterocyclic trans
olefin analogues of N-{4-[4-(2,3-dichlorophenyl)piperazin-1-yl]butyl}-
arylcarboxamides as selective probes with high affinity for the
dopamine D3 receptor. J. Med. Chem. 2005, 48, 839−848.
(22) Grundt, P.; Prevatt, K. M.; Cao, J.; Taylor, M.; Floresca, C. Z.;
Choi, J. K.; Jenkins, B. G.; Luedtke, R. R.; Newman, A. H. Heterocyclic
analogues of N-(4-(4-(2,3-dichlorophenyl)piperazin-1-yl)butyl)-
arylcarboxamides with functionalized linking chains as novel dopamine
D3 receptor ligands: potential substance abuse therapeutic agents. J.
Med. Chem. 2007, 50, 4135−46.
(23) Bancroft, G. N.; Morgan, K. A.; Flietstra, R. J.; Levant, B.
Binding of [3H]PD 128907, a putatively selective ligand for the D3
4968
dx.doi.org/10.1021/jm401798r | J. Med. Chem. 2014, 57, 4962−4968