Design, synthesis, and evaluation of chromen-2-ones as potent and selective human dopamine D4 antagonists

Article abstract of DOI:10.1021/jm990266k

The discovery of a series of chromen-2-ones with selective affinity for the dopamine (DA) D4 receptor is described. Target compounds were tested for binding to cloned human DA D2L, D3, and D4.2 receptor subtypes expressed in Chinese hamster ovary K1 cells

Full text of DOI:10.1021/jm990266k

3718
J . Med. Chem. 1999, 42, 3718-3725
Design , Syn th esis, a n d Eva lu a tion of Ch r om en -2-on es a s P oten t a n d Selective
Hu m a n Dop a m in e D4 An ta gon ists
Suzanne R. Kesten,* Thomas G. Heffner, Stephen J . J ohnson,† Thomas A. Pugsley, J onathan L. Wright, and
Lawrence D. Wise
Departments of Chemistry and Therapeutics, Parke-Davis Pharmaceutical Research, Division of Warner-Lambert Company,
2800 Plymouth Road, Ann Arbor, Michigan 48105
Received May 28, 1999
The discovery of a series of chromen-2-ones with selective affinity for the dopamine (DA) D4
receptor is described. Target compounds were tested for binding to cloned human DA D2L, D3,
and D4.2 receptor subtypes expressed in Chinese hamster ovary K1 cells. Several compounds
demonstrated high affinity (<20 nM, Ki) and greater than 100-fold selectivity for DA D4.2
versus DA D2L receptors. The results of a SAR study are discussed within. In a DA D4 functional
assay measuring [3H]thymidine uptake, target compounds showed antagonist activity at the
D4.2 receptor. Compound 22, 7-[(2-phenylaminoethylamino)methyl]chromen-2-one, increased
DOPA (L-3,4-dihydroxyphenylalanine) accumulation 51% in the hippocampus and 23% in the
striatum of rat brains when dosed orally at 20 mg/kg.
In tr od u ction
tially to DA D4 receptors may have antipyschotic
activity without the neurological side effects associated
with classical DA D2-like antagonists.
Schizophrenia is a psychotic disorder characterized
by positive symptoms, e.g., hallucinations and disorga-
nized thought, and negative symptoms, e.g., apathy and
social withdrawal. This socially and economically de-
bilitating disease is fairly common striking approxi-
mately 1% of the population.1 Past therapy, while
effective in ameliorating the positive symptoms in some
patients, did little to alleviate the negative symptoms.
In addition, most classical agents are associated with
side effects such as extrapyramidal syndrome (EPS) and
tardive dyskinesia that limit compliance.
Dopamine (DA) neuronal hyperactivity has been
implicated in the etiology of schizophrenia. Five DA
receptor subtypes have been identified and cloned.2
These are divided into two main families: the D-1 like,
which include D1 and D5 receptor subtypes, and the
D-2 like, which include D2, D3, and D4 receptor
subtypes. The efficacy and neurological side effects of
antipsychotic agents have been correlated with the
blockade of DA D2-like receptors. DA D2 receptor
subtypes are widespread in the limbic and striatal
regions of the brain as well as in the prefrontal cortical
areas.3 There is a greater expression of messenger RNA
for DA D4 receptors in the frontal cortical and mesolim-
bic areas, which are associated with antipsychotic
efficacy, than in the striatal areas, which are associated
with neurological side effects.3
Clozapine (1)4,5 was the first marketed agent that is
effective toward ameliorating the negative symptoms of
schizophrenia and lacked significant EPS of previous
antipsychotics. Its use, however, is limited by the
prevalence of potentially fatal agranularocytosis in
1-2% of treated patients.6 Clozapine binds with greater
affinity to the DA D4 than to the DA D2 receptor
subtypes.4 Therefore a compound that binds preferen-
Recently several selective DA D4 antagonists have
been reported. These include NGD94-17 (2), L-745,8708
(3), and U-1013879 (4). However, these selective DA D4
antagonists have not proved so far to be efficacious in
clinical trials.10 Whether the activity of clozapine is due
to some other mechanism than its DA D4 antagonism
is still unknown.
High-volume screening of our compound library un-
covered 5 with high affinity and selectivity (versus DA
D2L and D3) for the DA D4.2 receptor. It shares the
arylpiperazine moiety with compounds 2-4 and the
methylene spacer with 2 and 3, but it incorporates a
chromen-2-one nucleus. Compound 5 was used as a
starting point for our SAR studies. Exploration of this
compound began by varying the position of the alkyl
† Deceased March 30, 1999.
10.1021/jm990266k CCC: $18.00 © 1999 American Chemical Society
Published on Web 08/18/1999

Chromen-2-ones as Human Dopamine D4 Antagonists
J ournal of Medicinal Chemistry, 1999, Vol. 42, No. 18 3719
Ta ble 1. Initial Optimization of Compound 5
a
b
Ligand D2L and D4.2, [3H]spiperone. Ki values were obtained from six concentrations run in triplicate by a nonlinear regression
analysis. c NT, not tested.
Ta ble 2. Effect of Replacing the Phenylpiperazine Moiety on Receptor Binding
a
b
Ligand D2L and D4.2, [3H]spiperone. Ki values were obtained from six concentrations run in triplicate by a nonlinear regression
analysis. c NT, not tested.
group on the chromen-2-one nucleus and adding sub-
stituents to the piperazinyl phenyl (Table 1). We next
replaced the phenylpiperazine moiety with various
alkyl- and arylamines. This led us to the most promising
compound in this series, 22, containing an aminoethyl-
aniline moiety (Table 2). We further attempted to
optimize the activity of 22 by varying chain length,
phenyl substituents, and linkage atoms (Table 3).
Ch em istr y
The phenylpiperazine chromen-2-ones were readily
prepared as outlined in Scheme 1. Commercially avail-
able methylchromen-2-ones were brominated11 under
free radical conditions. Subsequent coupling of the
bromides with the requisite arylpiperazines in refluxing
acetonitrile with potassium carbonate as the acid scav-

3720 J ournal of Medicinal Chemistry, 1999, Vol. 42, No. 18
Ta ble 3. Optimization of the Side Chain Amine
Kesten et al.
a
b
Ligand D2L and D4.2, [3H]spiperone. Ki values were obtained from six concentrations run in triplicate by a nonlinear regression
analysis. c NT, not tested.
Sch em e 1a
Sch em e 2a
a
Reagents and conditions: (i) N-bromosuccinimide, AlBN, high-
intensity light, reflux, CHCl3; (ii) phenylpiperazine, K2CO3, reflux,
CH3CN.
a
Reagents and conditions: (i) 140 °C, neat, 18 h; (ii) excess
amine, K2CO3, reflux, CH3CN.
analogue 32 was made from condensing N-ethylaniline
with 2-oxazolidone12 and coupling the resulting product
with the requisite bromomethylchromen-2-one.
enger provided the target compounds. These reactions
were high yielding (>80%).
Very few N-(2′-aminoethylene)anilines are commer-
cially available. They were prepared as outlined in
Scheme 2 from the condensation of the requisite aniline
hydrochloride and 2-oxazolidone.12 The resulting anilines
were coupled with the bromomethylchromen-2-ones
under analogous conditions employed for the phenylpip-
erazine chromen-2-ones. Excess amounts of the primary
amines were used in order to minimize bis-adduct
formation. The N-ethyl analogue 31 was made by
selectively alkylating 5 with ethyl iodide. The N-ethyl
P h a r m a cology
Cloned human dopamine D4.2, D3, and D2L receptors
expressed in CHO-K1 cells were used to determine the
DA receptor affinities of compounds using the radio-
ligand [3H]spiperone.13 Compounds that had affinities
for the DA D4.2 receptor of less than 20 nM (Ki) and
selectivities for the DA D4.2 receptor versus the DA D2L
receptor of greater than 100-fold were evaluated further

Chromen-2-ones as Human Dopamine D4 Antagonists
J ournal of Medicinal Chemistry, 1999, Vol. 42, No. 18 3721
Ta ble 4. Functional Assays of Compounds with High Affinity
and Selectivity for DA D4.2 Receptors
in vitro. Only the more potent and selective compounds
were also screened for affinity for the DA D3 receptor.
Intrinsic activities of the selective compounds were
determined by measuring their abilities to block stimu-
lation of mitogenesis as measured via [3H]thymidine
uptake caused by the full DA agonist quinpirole in CHO
cells transfected with DA D4.2 or D2L receptors.14
Compounds with 20% or less intrinsic activity in this
model are considered antagonists. Antagonists with
IC50’s < 20 nM were evaluated further.
In vivo, DA antagonists are known to increase the
rate of brain DA synthesis in rodents.13 Specifically, the
effect of a compound on catecholamine synthesis can be
evaluated by measuring its ability to increase the
accumulation of the catecholamine precursor DOPA (L-
3,4-dihydroxyphenylalanine) after the inhibition of L-
aromatic amino acid decarboxylase with NSD 1015.13
A compound with the desired profile would increase
dopamine synthesis in the DA D4-rich hippocampus
preferentially to the DA D2-rich striatal regions.
Compounds that were orally active with the desired
profile in the dopamine synthesis assay were further
evaluated in tests predictive of antipsychotic activity:
reversal of amphetamine-stimulated locomotor activity15
and inhibition of spontaneous locomotor activity in
rats.16 Key compounds were also assayed for their
ability to inhibit the apomorphine-induced disruption
of prepulse inhibition of acoustic startle test in rats, a
model predictive of antipsychotic activity in humans.17,18
Active compounds were evaluated in the catalepsy test
in rats, a test predictive of extrapyramidal side effects.19
Finally, a compound was screened for its affinity to
other receptors to ensure the observed effects were due
to DA D4.
DOPA levels, 10 mg/kg ipb
inhibn of [3H]thymidine
uptake (% intrinsic
activity; IC50, nM)a
(% of control ( SEM)
compd
striatal
hippocampal
8
13
22
22 (oral)
0%; >1000
0%; 5.4
0%; 1.3
0%; 1.3
0%; 98
22 ( 1d
-16 ( 9
27 ( 9d
19 ( 6d
20( 6d
32( 9d
23c( 10d
not tested
51c ( 18d
not tested
24
a
Effects measured in CHO p-5 cells transfected with the h-D4.2
receptor. Intrinsic activity measured relative to the full agonist
b
quinpirole. Striatal and hippocampal DA syntheses were mea-
sured by HPLC with electrochemical detection in rats given drug
60 min previously and the L-aromatic amino acid decarboxylase
inhibitor NSD 1015 30 min prior to sacrifice by decapitation. Data
are expressed as the percentage increase of DA synthesis (as
indicated by DOPA levels) relative to control animals. Each value
d
is a mean of 4 animals. c Animals were dosed 20 mg/kg, po. P <
0.05 versus control.
selective than the original lead. There was no clear
relationship between DA D4.2 receptor potency and the
electron-donating or -withdrawing abilities of the sub-
stituents. Only a certain amount of steric bulk could be
tolerated, however.
We substituted various arylamines for the phenylpip-
erazine moiety (see Table 2). Replacing the piperazine
with a piperidine (19 versus 5) or a tetrahydropyridine
(20) resulted in analogues that were more potent but
not as selective for the DA D4.2 receptor. Adding a
methylene spacer (the benzylpiperazine 21) was not
tolerated. Replacing the piperazine with a diamino-
ethylene moiety results in a compound (22) more potent
and selective than the original lead.
We changed our focus to exploring the SAR of 22
(Table 3). The 6-substituted analogue 23 was much less
potent. Phenyl substituents that increased the activity
in the phenylpiperazine series were appended to give
compounds 24, 25, and 27. Although these compounds
were fairly potent and selective and thus were chosen
for further evaluation, they were not superior to the
parent 22. These compounds also had more affinity for
DA D3 with Ki values ranging from 97 nM for compound
27 to 424 nM for compound 22. An electron-withdrawing
substituent was added to give compound 26, which was
potent but did not have the required 100-fold selectivity.
Resu lts a n d Discu ssion
Compound 5 has fairly good affinity (IC50 ) 27 nM)
and selectivity (∼200-fold) for the DA D4.2 receptor
versus the DA D2L receptor. It was also 120-fold
selective for DA D4.2 versus DA D3. We first evaluated
the effect of the position of the linkage to the chrome-
none ring (Table 1). The 6- and 7-linked compounds
were more synthetically accessible than the 5- or
8-linked compounds.
In general, the 7-linked analogues were slightly more
potent (see compounds 9 versus 10 and 11 versus 12)
and selective for the DA D4.2 receptor than the com-
parable 6-linked analogues. Placing substituents on the
phenyl ring increased potency and selectivity in some
cases. The 4-methyl analogues 7 and 8 were more potent
and selective than their parent compounds 5 and 6. We
placed the methyl group at different positions around
the ring (compounds 9-12) and found the 4-position
optimal. While adding a 3-chloro to 7 increased potency
and selectivity (13), adding an additional methyl (14)
decreased selectivity. The methyl group was replaced
with electron-withdrawing groups resulting in a de-
crease in potency (see compounds 15 and 16). Replacing
the methyl group with a more electron-rich group, the
methoxy, significantly reduced potency (e.g. 17). We
studied steric effects by increasing bulk in the 4-position
with a tert-butyl moiety. This compound (18) was much
less active. Our explorations led us to the discovery of
13, which is approximately 4-fold more potent and
Increasing the chain length decreased activity (28
versus 22). Replacing the anilino nitrogen atom with
an oxygen (29) also led to a decrease in DA D4.2 activity.
Both secondary amine functionalities appear necessary
for activity (30 and 31) as both N-ethyl analogues are
weak.
Compounds 8, 13, 22, and 24 were selected for
additional testing in functional assays (Table 4) based
on their high potency (<20 nM for DA D4.2) and high
selectivity for D4.2 versus D2L (D2/D4 > 100). The
intrinsic activities of these compounds were evaluated
in the [3H]thymidine uptake assay. Compounds 13, 22,
and 24 had intrinsic activities of 0% with IC50’s of 5.4,
1.3, and 98 nM, respectively, in inhibiting quinpirole-
induced stimulation of [3H]thymidine uptake. These
data indicate that these compounds are antagonists. It
is unclear why 24 is so weak in this functional assay.
Compound 8 was inactive in this assay and not consid-

3722 J ournal of Medicinal Chemistry, 1999, Vol. 42, No. 18
Ta ble 5. Behavioral Effects of Compound 22
Kesten et al.
enriched area, that is consistent with the rationale of
the desirability of a DA D4 antagonist. This compound
will be a useful tool for exploring the significance of the
role of blocking DA D4 receptors in the treatment of
schizophrenia.
test
result
reversal of prepulse inhibition of
acoustic startle in mice, ip
active at 30 mg/kg
inhibition of amphetamine-stimulated
locomotor activity in rats (ED50, ip)
3 mg/kg
inhibition of spontaneous motor activity not active at 30 mg/kg
in rats, ip
Exp er im en ta l Section
catalepsy test in rats, po
not active at 10 mg/kg
Melting points were determined on a Thomas-Hoover ap-
paratus and are uncorrected. Elemental analyses were per-
formed by the Analytical Chemistry staff at Parke-Davis.
Where analyses are indicated with the elemental symbols, the
results are within 0.4% of the theoretical values. The 1H NMR
spectra were recorded on a Varian Unity 400 spectrometer
with chemical shifts reported in ppm relative to internal
Ta ble 6. Receptor Binding Data for Compound 22
receptor
binding (Ki, nM)
DA D4.2
DA D3
DA D2L
R1
R2
5HT1a
5HT2
5.8a
424a
2920a
tetramethylsilane. Mass spectra were recorded on
a VG
2670b
Masslab Trio-2A mass spectrometer. Column chromatography
separations were carried out using Merck silica gel 60, 230-
400 mesh ASTM, on a medium pressure setup. Reactions were
usually carried out under a nitrogen atmosphere, and organic
solutions were concentrated at aspirator pressure on a rotary
evaporator.
7-(4-P h en ylp ip er a zin -1-ylm eth yl)ch r om en -2-on e (5). A
mixture of 7-bromomethylchromen-2-one11 (1.0 g, 4.18 mmol),
1-phenylpiperazine (0.68 g, 4.18 mmol), and potassium carbon-
ate (2.0 g, 14.5 mmol) was heated under reflux in acetonitrile
(100 mL) 18 h. The reaction mixture was cooled and filtered
over Celite and the filtrate concentrated under vacuum to
provide a crude solid. Recrystallization from ethyl ether
provided 5 (0.45 g, 33%): mp 156-158 °C; 1H NMR (CDCl3) δ
) 2.62 (t, J ) 4.64 Hz, 4H), 3.19 (t, J ) 4.64 Hz, 4H), 3.63 (s,
2H), 6.37 (d, J ) 9.52 Hz, 1H), 6.86 (t, J ) 7.33 Hz, 1H), 6.90
(d, J ) 8.30 Hz, 2H), 7.22-7.29 (m, 3H), 7.35 (s, 1H), 7.42 (d,
J ) 7.81 Hz, 1H), 7.67 (d, J ) 9.52 Hz, 1H); CIMS m/z 321
(MH+). Anal. (C20H20N2O2) C, H, N.
>4700c
3711d
>4350e
a
Ligand, [3H]spiperone; Ki values were obtained from six
concentrations run in triplicate by a nonlinear regression analysis.
b
Ligand, [3H]prazosin; N ) 1: screening value. c Ligand, [3H]MK-
912; N ) 1: screening value. Ligand, [3H]8-OH-DPAT; N ) 1:
d
screening value. e Ligand, [3H]ketanserin; N ) 1: screening value.
ered further. All the above compounds were inactive
(IC50 > 1000) in the DA D2L [3H]thymidine uptake
studies.
Compounds 13 and 22 were identified as the most
promising candidates from the in vitro studies and were
evaluated in a series of in vivo tests. Compound 13
produced only minimal increases in DOPA accumulation
at 10 mg/kg, ip, in the hippocampus (HI) and in the
striatum (ST) (27% and 19%, respectively). Compound
22 produced similar results (32% and 20% in the HI and
ST, respectively) at the same dose (10 mg/kg, ip).
However, when rats were dosed orally at 20 mg/kg, 22
increased DOPA accumulation by 51% in the DA D4-
enriched hippocampus but only 23% in the predomi-
nantly DA D2-expressing striatum. Of all the com-
pounds considered, only 22 had the desired profile. It
was evaluated further in tests predictive of anti-
psychotic activity. Like nonselective classical DA D2
antagonists such as haloperidol, 22 reversed amphet-
amine-stimulated locomotor activity in rats with an
ED50 of 3 mg/kg, ip (Table 5). Unlike classical DA D2
antagonists, however, 22 had no effect on spontaneous
locomotor activity in rodents. It also did not cause
catalepsy in rats at 10 mg/kg, po. In addition, 22 was
active at 30 mg/kg, ip, in the prepulse inhibition of
acoustic startle test in rodents. It was screened for its
affinity for other receptors to ensure that its effects were
due to its DA D4 affinity (Table 6). It did not bind
significantly to serotonergic and adrenergic receptors.
The only other significant binding observed was weak
affinity (424 nM) for the DA D3 receptor.
6-(4-P h en ylp ip er a zin -1-ylm eth yl)ch r om en -2-on e Hy-
d r och lor id e (6). This was prepared similarly to 5 starting
with 6-bromomethylchromen-2-one.11 The compound was con-
verted to the hydrochloride salt with ethereal hydrogen
1
chloride: mp 195-201 °C; H NMR (DMSO-d6) δ ) 3.10 (m,
4H), 3.35 (m, 2H), 3.89 (HDO), 6.53 (d, J ) 9.52 Hz, 1H), 6.81
(t, J ) 7.1 Hz, 1H), 6.93 (d, J ) 8.6 Hz, 2H), 7.22 (t, J ) 7.32
Hz, 2H), 7.48 (d, J ) 8.3 Hz, 1H), 7.88 (dd, J ) 2.2 and 8.6
Hz, 1H), 7.91 (d, J ) 2.2 Hz, 1H), 8.04 (d, J ) 9.52 Hz, 1H);
CIMS m/z 321 (MH+). Anal. (C20H20N2O2‚1.7HCl‚1.0H2O) C,
H, N, Cl-, H2O.
7-(4-Tolylp ip er a zin -1-ylm eth yl)ch r om en -2-on e (7). This
was prepared similarly to 5 starting with 1-(p-tolyl)piperazine.
Recrystallization from ethyl acetate provided 7 in 22% yield:
1
mp 151-152 °C; H NMR (CDCl3) δ ) 2.25 (s, 3H), 2.61 (t, J
) 4.64 Hz, 4H), 3.15 (t, J ) 4.64 Hz, 4H), 3.62 (s, 2H), 6.38 (d,
J ) 9.52 Hz, 1H), 6.82 (d, J ) 8.30 Hz, 2H), 7.05 (d, J ) 8.30
Hz, 2H), 7.28 (br s, 1H), 7.34 (s, 1H), 7.42 (d, J ) 7.33 Hz,
1H), 7.67(d, J ) 9.7 Hz, 1H); CIMS m/z 335 (MH+). Anal.
(C21H22N2O2‚0.1H2O) C, H, N, H2O.
6-(4-Tolylp ip er a zin -1-ylm eth yl)ch r om en -2-on e (8). This
was prepared similarly to 5 starting with the 6-bromometh-
ylchromen-2-one and 1-(p-tolyl)piperazine. Recrystallization
from ethyl acetate provided 8 in 53% yield: mp 154-155 °C;
1H NMR (CDCl3) δ ) 2.23 (s, 3H), 2.57 (t, J ) 4.64 Hz, 4H),
3.12 (t, J ) 4.64 Hz, 4H), 3.58 (s, 2H), 6.40 (d, J ) 9.52 Hz,
1H), 6.80 (d, J ) 9.70 Hz, 2H), 7.05 (d, J ) 9.70 Hz, 2H), 7.43
(s, 1H), 7.55 (d, J ) 9.0 Hz, 1H), 7.85 (d, J ) 9.7 Hz, 1H);
CIMS m/z 335 (MH+). Anal. (C21H22N2O2) C, H, N.
7-(2-Tolylp ip er a zin -1-ylm eth yl)ch r om en -2-on e (9). This
was prepared similarly to 5 starting with 1-(o-tolyl)piperazine.
Recrystallization from ethyl acetate/heptane provided 9 in 51%
yield: mp 143-144 °C; 1H NMR (CDCl3) δ ) 2.25 (s, 3H), 2.60
(br s, 4H), 2.93 (t, J ) 4.64 Hz, 4H), 3.62 (s, 2H), 6.37 (d, J )
9.52 Hz, 1H), 6.95 (t, J ) 9.50 Hz, 1H), 7.07 (d, J ) 9.70 Hz,
1H), 7.15 (m, 2H), 7.25(d, J ) 7.9 Hz, 1H), 7.38 (s, 1H), 7.41
(d, J ) 9.0 Hz, 1H), 7.65 (d, J ) 9.7 Hz, 1H); CIMS m/z 335
(MH+). Anal. (C21H22N2O2) C, H, N.
In summary, a DA D4 antagonist 5 was identified
from mass screening. Various structural aspects of the
molecule were investigated to optimize its potency and
selectivity. Compound 22 was identified from these
studies, and it was found to be active in vivo in tests
predictive of antipsychotic activity. Furthermore, it was
inactive in a test predictive of extrapyramidal side
effects, a liability of classical DA D2 antagonists.
Administration orally of 22 led to greater increases of
dopamine synthesis in the hippocampal region, a DA
D4-enriched area, versus the striatal region, a DA D2-

Chromen-2-ones as Human Dopamine D4 Antagonists
J ournal of Medicinal Chemistry, 1999, Vol. 42, No. 18 3723
6-(2-Tolylpiper azin -1-ylm eth yl)ch r om en -2-on e (10). This
was prepared similarly to 9 starting with 6-bromomethyl-
chromen-2-one. Recrystallization from ethyl ether provided 10
7-(4-(4-ter t-Bu tylph en yl)piper azin -1-ylm eth yl)ch r om en -
2-on e (18). This was prepared similarly to 5 starting with 1-(4-
tert-butylphenyl)piperazine. Recrystallization in ethyl acetate
1
1
in 15% yield: mp 131-132 °C; H NMR (CDCl3) δ ) 2.25 (s,
provided 18 in 46% yield: mp 174-175 °C; H NMR (CDCl3)
3H), 2.60 (br s, 4H), 2.95 (t, J ) 4.64 Hz, 4H), 3.58 (s, 2H),
6.40 (d, J ) 9.50 Hz, 1H), 6.90-6.98 (m, 2H), 7.07 (d, J ) 9.70
Hz, 1H), 7.15 (m, 2H), 7.25 (d, J ) 7.9 Hz, 1H), 7.45 (s, 1H),
7.51 (d, J ) 9.0 Hz, 1H), 7.68 (d, J ) 9.7 Hz, 1H); CIMS m/z
335 (MH+). Anal. (C21H22N2O2) C, H, N.
δ ) 1.13 (s, 9H), 2.60 (t, J ) 4.64 Hz, 4H), 3.17 (t, J ) 4.64
Hz, 4H), 3.61 (s, 2H), 6.37 (d, J ) 9.52 Hz, 1H), 6.85 (d, J )
7.8 Hz, 2H), 6.90 (m, 2H), 7.25 (m, 3H), 7.35 (s, 1H), 7.42 (d,
J ) 7.81 Hz, 1H), 7.67 (d, J ) 9.52 Hz, 1H); CIMS m/z 376
(MH+). Anal. (C24H28N2O2) C, H, N.
7-(3-Tolylpiper azin -1-ylm eth yl)ch r om en -2-on e (11). This
was prepared similarly to 5 starting with 1-(m-tolyl)piperazine.
Recrystallization from ethyl acetate provided 11 in 76%
yield: mp 105-106 °C; 1H NMR (CDCl3) δ ) 2.25 (s, 3H), 2.60
(t, J ) 4.6 Hz, 4H), 3.16 (t, J ) 4.6 Hz, 4H), 3.62 (s, 2H), 6.37
(d, J ) 9.52 Hz, 1H), 6.65 (d, J ) 7.80 Hz, 1H), 6.72 (m, 2H),
7.15 (t, J ) 7.80 Hz, 1H), 7.25 (d, J ) 8.7 Hz, 1H), 7.35 (s,
1H), 7.42 (d, J ) 9.0 Hz, 1H), 7.65 (d, J ) 9.7 Hz, 1H); CIMS
m/z 335 (MH+). Anal. (C21H22N2O2) C, H, N.
7-(4-P h en ylp ip er id in -1-ylm eth yl)ch r om en -2-on e (19).
This was prepared similarly to 5 starting with 4-phenylpip-
erdine. Recrystallization in ethyl acetate provided 19 in 25%
yield: mp 128-129 °C; 1H NMR (CDCl3) δ ) 1.78 (m, 4H),
2.12 (m, 2H), 2.5 (m, 1H), 2.95 (m, 2H), 3.55 (s, 2H), 6.37 (d,
J ) 9.77 Hz, 1H), 7.16-7.27 (m, 6H), 7.34 (s, 1H), 7.42 (d, J )
7.56 Hz, 1H), 7.68 (d, J ) 9.52 Hz, 1H); CIMS m/z 320 (MH+).
Anal. (C21H21NO2) C, H, N.
7-(4-P h e n y l-3,6-d ih y d r o -2H -p y r id in -1-y lm e t h y l)-
ch r om en -2-on e (20). This was prepared similarly to 5 start-
ing with 4-phenyltetrahydropyridine. Chromatography eluting
with ethyl acetate/hexanes (3:1) provided 20 in 20% yield: mp
6-(3-Tolylpiper azin -1-ylm eth yl)ch r om en -2-on e (12). This
was prepared similarly to 11 starting with the 6-bromometh-
ylchromen-2-one. Recrystallization from ethyl acetate provided
1
1
12 in 65% yield: mp 149-150 °C; H NMR (CDCl3) δ ) 2.25
143-148 °C; H NMR (CDCl3) δ ) 2.54 (s, 2H), 2.70 (s, 2H),
(s, 3H), 2.58 (t, J ) 4.6 Hz, 4H), 3.18 (t, J ) 4.6 Hz, 4H), 3.57-
(s, 2H), 6.40 (d, J ) 9.5 Hz, 1H), 6.65 (d, J ) 9.70 Hz, 1H),
6.70-6.75 (m, 2H), 7.10 (t, J ) 7.80 Hz, 1H), 7.25 (d, J ) 8.7
Hz, 1H), 7.45 (s, 1H), 7.52 (d, J ) 9.0 Hz, 1H), 7.67 (d, J ) 9.7
Hz, 1H); CIMS m/z 335 (MH+). Anal. (C21H22N2O2) C, H, N.
7-(4-(3-Ch lor o-4-m eth ylp h en yl)p ip er a zin -1-ylm eth yl)-
ch r om en -2-on e (13). This was prepared similarly to 5 start-
ing with 1-(3-chloro-4-methylphenyl)piperazine. Recrystalli-
zation in ethyl acetate provided 13 in 55% yield: mp 128-
129 °C; 1H NMR (CDCl3) δ ) 2.21 (s, 3H), 2.60 (br s, 4H), 3.10
(br s, 4H), 3.60 (s, 2H), 6.37(d, J ) 9.52 Hz, 1H), 6.65 (dd, J )
2.7 and 7.8 Hz, 1H), 6.85 (d, J ) 2.7 Hz, 1H) 7.05 (d, J ) 7.8
Hz, 1H), 7.35 (s, 1H), 7.45 (d, J ) 8.7 Hz, 1H) 7.68 (d, J )
9.52 Hz, 1H); CIMS m/z 369 (MH+). Anal. (C21H23N2O2Cl) C,
H, N, Cl.
7-(4-(3,4-D im e t h y lp h e n y l)p ip e r a zin -1-y lm e t h y l)-
ch r om en -2-on e (14). This was prepared similarly to 5 start-
ing with 1-(3,4-dimethylphenyl)piperazine. Column chroma-
tography (5% 2-propanol in chloroform) provided 14 in 52%
yield: mp 175-176 °C; 1H NMR (CDCl3) δ ) 2.16 (s, 3H), 2.21
(s, 3H), 2.65 (br s, 4H), 3.20 (br s, 4H), 3.62 (s, 2H), 6.38 (d, J
) 9.8 Hz, 1H), 6.66 (d, J ) 7.3 Hz, 1H), 6.72 (s, 1H), 6.95 (d,
J ) 8.3 Hz, 1H), 7.30 (m, 1H), 7.34 (s, 1H), 7.42 (d, J ) 8.37
Hz, 1H) 7.68 (d, J ) 9.8 Hz, 1H); CIMS m/z 349 (MH+). Anal.
(C22H24N2O2‚0.1H2O) C, H, N, H2O.
3.16 (s, 2H) 3.69 (s, 2H), 5.99 (s, 1H), 6.34 (d, J ) 9.52 Hz,
1H), 7.18 (m, 2H), 7.3 (t, J ) 8.05 Hz, 2H), 7.31-7.33 (m, 3H),
7.45 (m, 1H), 7.63 (d, J ) 9.52 Hz, 1H); CIMS m/z 317 (MH+).
Anal. (C21H19NO2) C, H, N.
7-(4-(4-Ben zyl)piper azin -1-ylm eth yl)ch r om en -2-on e (21).
This was prepared similarly to 5 starting with 1-benzylpip-
erazine. Recrystallization in ethyl acetate provided 21 in 36%
1
yield: mp 138-140 °C; H NMR (CDCl3) δ ) 2.50 (br s, 8H),
3.55 (s, 2H), 3.60 (s, 2H), 6.37 (d, J ) 9.52 Hz, 1H), 6.85 (d, J
) 7.8 Hz, 2H), 6.90 (m, 2H), 7.25 (m, 3H), 7.35 (m, 5H), 7.42
(d, J ) 7.81 Hz, 1H), 7.67 (d, J ) 9.52 Hz, 1H); CIMS m/z 335
(MH+). Anal. (C21H22N2O2) C, H, N.
7-[(2-P h e n yla m in oe t h yla m in o)m e t h yl]ch r om e n -2-
on e (22). A mixture of 7-bromomethylchromen-2-one (1.5 g,
6.3 mmol), N-phenylethylenediamine (5.0 g, 37 mmol), and
potassium carbonate (4.0 g, 29 mmol) in acetonitrile (200 mL)
was heated under reflux for 18 h. The mixture was cooled and
filtered and the filtrate concentrated to a residue that was
purified by chromatography (elution with 10% 2-propanol in
dichloromethane). Trituration of the product with ethyl ether
1
provided 22 (0.95 g, 51%): mp 89-91 °C; H NMR (CDCl3) δ
) 1.5 (s, 2H + HDO), 2.92 (m, 2H), 3.18 (m, 2H), 3.83 (s, 2H),
6.55 (d, J ) 9.52 Hz, 1H), 6.85 (d, J ) 7.81 Hz, 2H), 6.62 (t, J
) 7.9 Hz, 1H), 7.10 (t, J ) 7.8 Hz, 2H), 7.25 (m, 2H), 7.38 (d,
J ) 7.81 Hz, 1H), 7.62 (d, J ) 9.52 Hz, 1H); CIMS m/z 295
(MH+). Anal. (C18H18N2O2) C, H, N.
7-(4-(4-F lu or op h en yl)p ip er a zin -1-ylm eth yl)ch r om en -
2-on e (15). This was prepared similarly to 5 starting with 1-(4-
fluorophenyl)piperazine. Recrystallization in ethyl acetate
6-[(2-P h e n yla m in oe t h yla m in o)m e t h yl]ch r om e n -2-
on e (23). This was prepared similarly to 22 except 6-bromo-
methylchromen-2-one was used. Trituration of the product,
after chromatography with 10% 2-propanol in dichloromethane,
1
provided 15 in 15% yield: mp 137-138 °C; H NMR (CDCl3)
δ ) 2.60 (t, J ) 4.64 Hz, 4H), 3.12 (t, J ) 4.64 Hz, 4H), 3.61
(s, 2H), 6.37 (d, J ) 9.52 Hz, 1H), 6.82 (m, 2H), 6.90(m, 2H),
7.25 (d, J ) 7.8 Hz, 1H), 7.32 (s, 1H), 7.42 (d, J ) 7.81 Hz),
7.67 (d, J ) 9.52 Hz, 1H); CIMS m/z 339 (MH+). Anal.
(C20H19N2O2F) C, H, N, F.
1
with ethyl ether provided 23 in 60% yield: mp 84-86 °C; H
NMR (DMSO-d6) δ ) 2.65 (t, J ) 6.34 Hz, 2H), 3.05 (q, J )
5.37 Hz, 2H), 3.3 (HDO), 3.74 (s, 2H), 5.45 (t, J ) 5.37 Hz,
1H), 6.43-6.48 (m, 2H), 6.52 (d, J ) 8.06 Hz, 2H), 7.02 (t, J )
8.06 Hz, 2H), 7.30 (d, J ) 8.54 Hz, 1H), 7.55 (dd, J ) 8.24 and
1.71 Hz, 1H), 7.63 (d, J ) 1.7 Hz, 1H), 8.00 (d, J ) 9.52 Hz,
1H); CIMS m/z 295 (MH+). Anal. (C18H18N2O2) C, H, N.
7-[(2-p -Tolyla m in oe t h yla m in o)m e t h yl]ch r om e n -2-
on e (24). This was prepared similarly to 22 except N-(p-tolyl)-
ethylenediamine11 was used as the amine. After chromatog-
raphy with 7% 2-propanol in dichloromethane and crystalli-
zation in ethyl ether, 24 was obtained in 40% yield: mp 92-
95 °C; 1H NMR (CDCl3) δ ) 1.55 (br s, 2H), 2.17 (s, 3H), 2.83
(t, J ) 5.6 Hz, 2H), 3.16 (t, J ) 5.6 Hz, 2H), 3.83 (s, 2H), 6.32
(d, J ) 9.52 Hz, 1H), 6.50 (d, J ) 8.3 Hz, 2H), 6.92 (d, J ) 8.1
Hz, 2H), 7.22 (m, 2H), 7.37 (d, J ) 7.8 Hz, 1H), 7.62 (d, J )
9.52 Hz, 1H); CIMS m/z 309 (MH+). Anal. (C19H20N2O2‚0.1H2O)
C, H, N, H2O.
7-(4-(4-Ch lor op h en yl)p ip er a zin -1-ylm eth yl)ch r om en -
2-on e (16). This was prepared similarly to 5 starting with 1-(4-
chlorophenyl)piperazine. Recrystallization in ethyl acetate
1
provided 16 in 55% yield: mp 143-144 °C; H NMR (CDCl3)
δ ) 2.60 (br s, 4H), 3.15 (br s, 4H), 3.62 (s, 2H), 6.38 (d, J )
9.52 Hz, 1H), 6.82 (d, J ) 9.03 Hz, 2H), 7.17 (d, J ) 9.03 Hz,
2H), 7.27 (d, J ) 6.8 Hz, 1H), 7.34 (s, 1H), 7.42 (d, J ) 7.81
Hz, 1H), 7.67 (d, J ) 9.52 Hz, 1H); CIMS m/z 355 (MH+). Anal.
(C20H19N2O2Cl) C, H, N, Cl.
7-(4-(4-Meth oxyph en yl)piper azin -1-ylm eth yl)ch r om en -
2-on e (17). This was prepared similarly to 5 starting with 1-(4-
methoxyphenyl)piperazine. Recrystallization in ethyl acetate
1
provided 17 in 51% yield: mp 162-163 °C; H NMR (CDCl3)
δ ) 2.65 (br s, 4H), 3.12 (br s, 4H), 3.68 (s, 2H), 3.75 (s, 3H),
6.38 (d, J ) 9.52 Hz, 1H), 6.82 (m, 2H), 6.90 (m, 2H), 7.25 (d,
J ) 7.8 Hz, 1H), 7.32 (s, 1H), 7.42 (d, J ) 7.81 Hz), 7.67 (d, J
) 9.52 Hz, 1H); CIMS m/z 351 (MH+). Anal. (C21H22N2O3) C,
H, N.
7-[(2-(3,4-Dim eth ylp h en yla m in o)eth yla m in o)m eth yl]-
ch r om en -2-on e (25). This was prepared similarly to 22 except
N-(3,4-dimethylphenyl)ethylenediamine11 was used as the
amine. After chromatography with 10% 2-propanol in dichlo-

3724 J ournal of Medicinal Chemistry, 1999, Vol. 42, No. 18
Kesten et al.
romethane and crystallization in ethyl ether, 25 was obtained
in 40% yield: mp 92-95 °C; 1H NMR (CDCl3) δ ) 2.1 (s, 3H),
2.15 (s, 3H), 2.85 (t, J ) 5.6 Hz, 2H), 3.20 (t, J ) 5.6 Hz, 2H),
3.83 (s, 2H), 6.37 (d, J ) 9.52 Hz, 1H), 6.39 (dd, J ) 2.2 and
9.2 Hz, 1H), 6.42 (d, J ) 2.28 Hz, 1H), 6.90 (d, J ) 7.8 Hz,
1H), 7.22 (m, 2H), 7.4 (d, J ) 7.82 Hz, 1H), 7.65 (d, J ) 9.52
Hz, 1H); CIMS m/z 322 (MH+). Anal. (C20H22N2O2) C, H, N.
3.77 (HDO), 4.24 (s, 2H), 6.50 (d, J ) 9.72 Hz, 1H), 6.64 (br s,
1H), 6.8 (br s, 2H), 7.15 (m, 2H), 7.50 (d, J ) 7.56 Hz, 1H),
7.63 (s, 1H), 7.73 (d, J ) 7.81 Hz, 1H), 8.05 (d, J ) 9.72 Hz,
1H), 9.6 (s, 2H); CIMS m/z 323 (MH+). Anal. (C20H22N2O2‚
1.65HCl‚0.35H2O) C, H, N, Cl, H2O.
7-{[Eth yl(2-ph en ylam in oeth yl)am in o]m eth yl}ch r om en -
2-on e Hyd r och lor id e (31). A mixture of 22 (1.06 g, 3.6
mmol), iodoethane (0.29 mL, 3.6 mmol), and potassium
carbonate (2 g, 14 mmol) was stirred at room temperature in
acetonitrile (100 mL) for 4 days. The reaction mixture was
filtered and the filtrate concentrated in vacuo. The residue was
chromatographed eluting with 2% 2-propanol in chloroform.
An ethereal solution of the product was converted to the
hydrochloride salt by the addition of 1 N hydrogen chloride
(ether) to provide 31 (430 mg, 37%): mp 225-230 °C; 1H NMR
(DMSO-d6) δ ) 1.26 (t, J ) 7.1 Hz, 3H), 3.21 (m, 4H), 3.52 (t,
J ) 6.6 Hz, 2H), 3.6-4.15 (br s, ∼2H), 4.44 (s, 2H), 6.51 (d, J
) 9.52 Hz, 1H), 6.57 (m, 3H), 7.02 (t, J ) 8.0 Hz, 2H), 7.59 (d,
J ) 8.06 Hz, 1H), 7.71 (d, J ) 8.05 Hz, 1H), 7.79 (s, 1H), 8.18
(d, J ) 9.77 Hz, 1H); CIMS m/z 323 (MH+). Anal. (C20H22N2O2‚
1.15HCl‚0.3H2O) C, H, N, Cl-, H2O.
7-[(2-(3-C h lo r o p h e n y la m in o )e t h y la m in o )m e t h y l]-
ch r om en -2-on e (26). This was prepared similarly to 22 except
N-(3-chlorophenyl)ethylenediamine11 was used as the amine.
After chromatography with 10% 2-propanol in dichloromethane
and crystallization in ethyl ether, 26 was obtained in 45%
1
yield: mp 99-100 °C; H NMR (CDCl3) δ ) 1.45 (br s, 1H),
2.85 (t, J ) 5.62 Hz, 2H), 3.15 (t, J ) 5.6 Hz, 2H), 3.83 (s, 2H),
4.15 (br s, 1H), 6.37 (d, J ) 9.52 Hz, 1H), 6.50 (d, J ) 7.8 Hz,
2H), 7.05 (d, J ) 7.8 Hz, 2H), 7.10 (t, J ) 7.8 Hz, 2H), 7.22
(m, 2H), 7.4 (d, J ) 7.81 Hz, 1H), 7.65 (d, J ) 9.52 Hz, 1H);
CIMS m/z 329 (MH+). Anal. (C18H17N2O2Cl) C, H, N, Cl.
7-[(2-(3-Ch lor o-4-m e t h ylp h e n yla m in o)e t h yla m in o)-
m eth yl]ch r om en -2-on e (27). This was prepared similarly to
22 except N-(3-chloro-4-methylphenyl)ethylenediamine11 was
used as the amine. After chromatography with 10% 2-propanol
in dichloromethane and crystallization in ethyl ether, 27 was
Recep tor Bin d in g. The in vitro affinities of compounds for
cloned human DA receptors versus [3H]spiperone in CHO K1
13
1
cells were determined as previously described.
obtained in 65% yield: mp 77-78 °C; H NMR (CDCl3) δ )
Mitogen esis Assa y. The effects of test compounds on [3H]-
thymidine uptake were determined as described by Chio14 with
minor modifications. In brief, CHO 10001 cells transfected with
human D4.2 receptors were plated on 96-well plates in a
minimum essential medium (RMEM, Gibco) with 10% fetal calf
serum containing penicillin (100 units/mL) and streptomycin
(100 µg/mL). Forty-eight hours later, cells were washed with
serum-free media and maintained thereafter in serum-free
media. After 24 h, test compounds were added. Eighteen hours
later, [3H]thymidine (0.25 µCi/well was added for 2 h, trypsin
(100 µL of 0.25%) was added for 1 h, and the assay was
terminated by filtration using a Brandel 96-well harvester. The
filters were counted for radioactivity using the LKB â-plate
counting system.
Effects on DA Syn th esis.13 Striatal and hippocampal DA
synthesis were measured by HPLC with electrochemical
detection in rats given drug 60 min previously and the
L-aromatic amino acid decarboxylase inhibitor NSD 1015 30
min prior to sacrifice by decapitation. Data are expressed as
the percentage increase of DA synthesis (as indicated by DOPA
levels) relative to control animals.
Ra t Sp on ta n eou s Locom otor Activity.16 Harlan Spra-
gue-Dawley rats were dosed ip 30 min before monitoring open
field levels in the dark in 16 × 16 × 12 in. Plexiglas cubicles
with 16 photobeams spaced 1 in. apart on all four sides of the
monitors. Activity data (total distance traveled in cm) for six
5-min intervals were recorded automatically by computer.
Data were expressed as percent of vehicle-treated control
activity. Significant changes in activity levels, relative to
controls, were determined by t-test. The dose that could be
expected to decrease locomotion by 50% (ED50) and the 95%
confidence limits were estimated by regression analysis.
R a t Am p h et a m in e-St im u la t ed Locom ot or Act ivit y
Stu d ies.15 Rats were dosed ip with saline or 0.5 mg/kg
d-amphetamine and placed in the Omnitech Digiscan activity
monitors for a 20-min acclimation period, followed by either
ip saline or the test compound. Rats were returned to their
respective chambers and locomotor activity (cm traveled) was
measured for 30 min. Data were expressed as total distance
traveled (in cm). Statistical significance between groups was
calculated using a t-test. Amphetamine reversal ED50’s and
95% confidence limits were calculated using regression analy-
sis.
1.45 (br s, 1H), 2.20 (s, 3H), 2.85 (t, J ) 5.6 Hz, 2H), 3.17 (t,
J ) 5.6 Hz, 2H), 3.86 (s, 2H), 4.15 (br s, 1H), 6.37 (d, J ) 9.52
Hz, 1H), 6.42 (dd, J ) 2.2 and 7.8 Hz), 6.58 (d, J ) 2.2 Hz,
1H), 6.95 (d, J ) 7.8 Hz, 1H), 7.20 (m, 2H), 7.4 (d, J ) 7.81
Hz, 1H), 7.65 (d, J ) 9.52 Hz, 1H); CIMS m/z 343 (MH+). Anal.
(C19H20N2O2Cl) C, H, N, Cl.
7-[(3-P h en yla m in op r op yla m in o)m et h yl]ch r om en -2-
on e (28). This was prepared similarly to 22 except N-
phenylpropylenediamine was used. The N-phenylpropylene-
diamine was prepared in two steps by heating a mixture of
aniline (5.0 g, 53.7 mmol), 3-bromophthalimide (14.3 g, 53.7
mmol), and potassium carbonate (8.3 g, 60 mmol) in MeCN
under reflux for 48 h. Column chromatography of the concen-
trated reaction mixture with ethyl acetate:hexanes (1:1)
provided 5.5 g of the intermediate. This was treated with
hydrazine hydrate (2 g, 33 mmol) in refluxing ethanol (150
mL) for 1.5 h. The reaction mixture was cooled and concen-
trated to an oily residue. The residue was partitioned between
1 N NaOH (aq) and chloroform (200 mL of each). Concentration
of the dried (potassium carbonate) organic layer provided 2.4
g of N-phenylpropylenediamine, which was 90% pure as judged
1
by H NMR. This was coupled with 7-bromomethylchromen-
2-one as previously described. After chromatography with 10%
2-propanol in dichloromethane and crystallization in ethyl
1
ether, 28 was obtained in 20% yield: mp 68-69 °C; H NMR
(CDCl3) δ ) 1.8 (m, 2H), 2.77 (t, J ) 5.6 Hz, 2H), 3.10 (t, J )
5.6 Hz, 2H), 3.83 (s, 2H), 6.35 (d, J ) 9.52 Hz, 1H), 6.57 (d, J
) 7.8 Hz, 2H), 6.65 (t, J ) 7.9 Hz, 1H), 7.10 (t, J ) 7.8 Hz,
2H), 7.22 (m, 2H), 7.4 (d, J ) 7.81 Hz, 1H), 7.65 (d, J ) 9.52
Hz, 1H); CIMS m/z 309 (MH+). Anal. (C19H20N2O2) C, H, N.
7-[(2-P h en oxyeth yla m in o)m eth yl]ch r om en -2-on e (29).
This was prepared similarly to 22 except 2-phenoxyethylamine
was used as the base. After chromatography with 5% 2-pro-
panol in dichloromethane and crystallization in ethyl ether,
29 was obtained in 55% yield: mp 62-64 °C; 1H NMR (CDCl3)
δ ) 3.0 (t, J ) 5.6 Hz, 2H), 3.95 (s, 2H), 4.07 (t, J ) 5.6 Hz,
2H), 6.37 (d, J ) 9.52 Hz, 1H), 6.83 (d, J ) 9.70 Hz, 2H), 6.90
(t, J ) 6 Hz, 1H), 7.25 (m, 3H), 7.30 (s, 1H), 7.40 (d, J ) 9.0
Hz, 1H), 7.65 (d, J ) 9.7 Hz, 1H); CIMS m/z 296 (MH+). Anal.
(C18H17NO3) C, H, N.
7-[(2-(Eth ylph en ylam in o)eth ylam in o)m eth yl]ch r om en -
2-on e Hyd r och lor id e (30). This was prepared similarly to
22 except N,N-ethylphenylethylenediamine was used as the
amine. The amine was prepared from the coupling of the
N-ethylaniline with 2-oxazalidone.11 After chromatography
with 5% 2-propanol in dichloromethane, the compound was
converted to the hydrochoride salt in ethyl ether by addition
of 1 N hydrogen chloride in ether to provide 30 in 65% yield:
mp 209-210 °C; 1H NMR (DMSO-d6) δ ) 1.02 (t, J ) 6.83 Hz,
2H), 3.02 (br s, 2H), 3.33 (q, J ) 6.8 4 Hz, 2H), 3.63 (s, 2H),
P r ep u lse In h ib it ion of Acou st ic St a r t le in R a t s
(P P I).17,18 Rats were dosed ip with vehicle or the test com-
pound 15 min prior to sc injection of saline or apomorphine
(0.25 mg/kg), then placed in one of eight San Diego Instru-
ments acoustic startle chambers for a 30-min test. The test
session consisted of a total of 90 trials after a 5-min test
acclimation period of 70 dB of white noise. The first and last

Chromen-2-ones as Human Dopamine D4 Antagonists
J ournal of Medicinal Chemistry, 1999, Vol. 42, No. 18 3725
(8) Kulagowski, J . J .; Broughton, H. B.; Curtis, N. R.; Mawer, I.
M.; Ridgill, M. P.; Baker, R.; Emms, F.; Freedman, S. B.;
Marwood, R.; Patel, S.; Patel, S.; Ragan, C. I.; Leeson, P. D.
3-[[4-(4-Chlorophenyl)piperazin-1-yl]methyl]-1H-pyrrolo[2,3-b]-
pyridine: An Antagonist with High Affinity and Selectivity for
the Human Dopamine D4 Receptor. J . Med. Chem. 1996, 39,
1941-1942.
(9) Ten Brink, R. E.; Bergh, C. L.; Duncan, J . N.; Harris, D. W.;
Huff, R. M.; Lahti, R. A.; Lawson, C. F.; Lutske, B. B.; Martin,
I. J .; Rees, S. A.; Schlachter, S. K.; Sih, J . C.; Smith, M. W. (S)
(-)-4-[4-[2-(Isoch r om a n -1-yl)et h yl]piper a zin -1-yl]ben zen e-
sulfonamide, a Selective Dopamine D4 Antagonist. J . Med.
Chem. 1996, 39, 2435-2437.
(10) Kramer, M.; Lasr, B.; Zimbroff, D.; Hafez, D.; Alpert, M.; Allan,
E.; Rotrosen, J .; McEvoy, J .; Kane, J .; Kronig, M.; Merideth, C.;
Silva, J . A.; Ereshefsky, L.; Marder, S.; Wirshimg, W.; Conley,
R.; Getson, A.; Chavez-Eng, C.; Cheng, H.; Reines, S. The Effects
of a Selective D4 Receptor Antagonist (L-745,870) in Acutely
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10 trials are 120-dB pulse-alone trials of each of the following
5 trial types in pseudo-random order: (1) no stimulus, (2) 72-
dB prepulse 100 ms prior to a 120-dB startle pulse, (3) 74-dB
prepulse + 120-dB pulse, (4) 78-dB prepulse + 120-dB pulse,
and (5) 86-dB prepulse + 120-dB pulse. Intertrial interval was
7-23 s. The prepulses (2, 4, 8, and 16 dB over the 70-dB
background noise) were 20 ms in duration, while the startle
pulses were 40 ms in duration. Data are shown as %PPI
(calculated for each individual rat using the 16-dB prepulse
values), and statistical significance was calculated between
treatment groups using a t-test. The minimal effective dose
required to produce a significant reversal of apomorphine-
disrupted PPI was used as the efficacy measure.
Ca ta lep sy Test in Ra ts.19 Rats were dosed orally prior to
the catalepsy test. The front paws were placed on an elevated
bar, and the time (s) that the paws remained on the bar was
recorded for three consecutive trials of 1-min duration. Rats
were tested again 2 h postdose. Data shown is the mean
response time for the third trial.
(11) J ainamma, K. M.; Sethna, S. J . Indian Chem. Soc. 1973, 50,
790.
(12) Poindexter, G. S.; Owens, D. A.; Dolan, P. L.; Woo, E. The Use
of 2-Oxazolidinoles as Latent Aziridine Equivalents. J . Org.
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Ack n ow led gm en t . S. R. Kesten dedicates this
paper to her coauthor and supervisor during the time
this work was performed, Stephen J ohnson, who tragi-
cally drowned March 30, 1999. He was a great friend
and chemist and is greatly missed. We also thank Dr.
Gary McClusky and staff for microanalytical and spec-
tral data and Lynn Georgic, the late Yu-Hsin Shih,
Steven Whetzel, Ann Corbin, and Kim Zoski for per-
forming the biological assays. Compounds 5 and 6 were
originally prepared by Donna Reynolds Cody. Com-
pound 20 was prepared by Bradley Caprathe.
(13) Pugsley, T. A.; Davis, M. D.; Akunne, H. C.; MacKenzie, R. G.;
Shih, Y. H.; Damsma, G.; Wikstrom, H.; Whetzel, S. Z.; Georgic,
L. M.; Cooke, L. W.; Demattos, S. B.; Corbin, A. E.; Glase, S. A.;
Wise, L. D.; Dijkstra, D.; Heffner, T. G. Neurochemical and
Functional Characterization of the Preferentially Selective
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