Design and synthesis of an orally active metabotropic glutamate receptor subtype-2 (mGluR2) positive allosteric modulator (PAM) that decreases cocaine self-administration in rats

Article abstract of DOI:10.1021/jm1012165

The modification of 3′-((2-cyclopentyl-6,7-dimethyl-1-oxo-2,3- dihydro-1H-inden-5-yloxy)methyl)biphenyl-4-carboxylic acid (BINA, 1) by incorporating heteroatoms into the structure and replacing the cyclopentyl moiety led to the development of new mGluR2 positive allosteric modulators (PAMs) with optimized potency and superior druglike properties. These analogues are more potent than 1 in vitro and are highly selective for mGluR2 vs other mGluR subtypes. They have significantly improved pharmacokinetic (PK) properties, with excellent oral bioavailability and brain penetration. The benzisothiazol-3-one derivative 14 decreased cocaine self-administration in rats, providing proof-of-concept for the use of mGluR2 PAMs for the treatment of cocaine dependence.

Full text of DOI:10.1021/jm1012165

342 J. Med. Chem. 2011, 54, 342–353
DOI: 10.1021/jm1012165
Design and Synthesis of an Orally Active Metabotropic Glutamate Receptor Subtype-2 (mGluR2)
Positive Allosteric Modulator (PAM) That Decreases Cocaine Self-Administration in Rats
Raveendra-Panickar Dhanya,†,^ Shyama Sidique,†,^ Douglas J. Sheffler,‡ Hilary Highfield Nickols,§ Ananda Herath,†
Li Yang,† Russell Dahl,† Robert Ardecky,† Svetlana Semenova, Athina Markou, P. Jeffrey Conn,‡ and
Nicholas D. P. Cosford*,†
†Apoptosis and Cell Death Research Program and Conrad Prebys Center for Chemical Genomics, Sanford-Burnham Medical Research Institute,
10901 N. Torrey Pines Road, La Jolla, California 92037, United States, ‡Department of Pharmacology, and §Department of Pathology,
Vanderbilt University Medical Center, Nashville, Tennessee 37232, United States, and Department of Psychiatry, School of Medicine,
University of California San Diego, La Jolla, California 92093, United States. ^ These authors contributed equally to this work.
Received September 17, 2010
The modification of 30-((2-cyclopentyl-6,7-dimethyl-1-oxo-2,3-dihydro-1H-inden-5-yloxy)methyl)-
biphenyl-4-carboxylic acid (BINA, 1) by incorporating heteroatoms into the structure and replacing the
cyclopentyl moiety led to the development of new mGluR2 positive allosteric modulators (PAMs) with
optimized potency and superior druglike properties. These analogues are more potent than 1 in vitro and
are highly selective for mGluR2 vs other mGluR subtypes. They have significantly improved phar-
macokinetic (PK) properties, with excellent oral bioavailability and brain penetration. The benzisothia-
zol-3-one derivative 14 decreased cocaine self-administration in rats, providing proof-of-concept for the
use of mGluR2 PAMs for the treatment of cocaine dependence.
Introduction
dependence, including the cerebral cortex, hippocampus, stria-
tum, amygdala, frontal cortex, and nucleus accumbens, dis-
play high levels of mGluR2 and mGluR3 binding,5 suggesting
a role for the mGluR2/3 subtypes in the development of
cocaine dependence and as potential targets for therapeutic
agents.3a,e,f,6
Cocaine addiction is a chronic relapsing disorder affecting
more than 1.6 million Americans.1 Relapse rates among
cocaine users is in the range of 94-99%, the highest among
all commonly abused drugs.2 Chronic cocaine abuse can lead
to severe neurotoxicity, psychosis, lethargy, depression, or
potentially death through a fatal overdose. Currently there is
no effective treatment for cocaine dependence, and therefore,
cocaine addiction constitutes a major public health problem.
Consequently, there is a significant need to identify new
therapeutic agents for the treatment of cocaine and other
psychomotor stimulant addictions. Recent findings suggest
that neuroadaptations in glutamatergic transmission pro-
duced by repeated exposure to cocaine or other drugs of abuse
are likely to contribute to the maintenance of addictive behav-
iors including drug use, craving, and relapse to drug taking in
humans.3 Specifically, it has been shown that repeated cocaine
exposure alters the function of group II metabotropic gluta-
mate receptors (mGluRs).4a The group II mGluRs include the
mGluR2a and mGluR3 subtypes, which couple to Gi/o proteins
to negatively regulate the activity of adenylyl cyclase.4b Brain
regions implicated in different aspects of drug abuse and drug
Orthosteric (glutamate site) mGluR2/3 agonists such as
LY3792686g are constrainedamino acid analogues thatdo not
exhibit selectivity for mGluR2 versus mGluR3, presumably
because of the high degree of sequence homology at the
glutamate binding site for these two receptors.6h LY379268
has been shown to decrease glutamate levels7 and to attenuate
cocaine self-administration both in rats6c,8 and in squirrel
monkeys.6a However, LY379268 also inhibits responding
for food and food-seeking behavior,6c,e,9 suggesting that
mGluR2/3 agonists exhibit nonselective actions on respond-
ing for drug and nondrug reinforcers. We recently initiated
investigations to determine the effect of selective activation of
mGluR2 on cocaine dependence.8 Localization studies sug-
gest that mGluR2 acts predominantly as a presynaptic auto-
receptor to modulate the releaseof glutamate into the synaptic
cleft.10 In recent years, there have been several reports on the
use of high-throughput screening (HTS) for the identification
of small molecule mGluR2 positive allosteric modulators
(PAMs).11 The activity of these compounds is of interest
because of their subtype selectivity, ability to overcome
receptor desensitization, and potential for improved druglike
properties.12 The use of a selectivemGluR2 PAM in an appro-
priate in vivo model therefore represents an attractive approach
to elucidate the role of mGluR2 in cocaine dependence. We
previously disclosed the structure-activity relationship (SAR)
around a series of pyrimidine derivatives with activity as
mGluR2 PAMs.11b The synthesis and characterization of
*To whom correspondence should be addressed. Phone: 858-646-
3100. Fax: 858-795-5225. E-mail: ncosford@sanfordburnham.org.
a Abbreviations: mGluR2, metabotropic glutamate receptor subtype
2; PAM, positive allosteric modulator; BINA, 30-((2-cyclopentyl-6,7-
dimethyl-1-oxo-2,3-dihydro-1H-inden-5-yloxy)methyl)biphenyl-4-car-
boxylic acid; HTS, high-throughput screening; PK, pharmacokinetic;
POC, proof-of-concept; AUC, area under curve; LOQ, limit of quanti-
tation; AIBN, 2,20-azobisisobutyronitrile; NBS, N-bromosuccinimide;
HEK, human embryonic kidney; GIRK, G protein inwardly rectifying
potassium; PBS, phosphate buffered saline; DMEM, Dulbecco’s mod-
ified Eagle medium; HEPES, 4-(2-hydroxyethyl)-1-piperazineethanesul-
fonic acid; FBS, fetal bovine serum.
r
pubs.acs.org/jmc
Published on Web 12/14/2010
2010 American Chemical Society

Article
Journal of Medicinal Chemistry, 2011, Vol. 54, No. 1 343
Figure 1. Incorporation of heteroatoms into BINA (1).
30-((2-cyclopentyl-6,7-dimethyl-1-oxo-2,3-dihydro-1H-in-
den-5-yloxy)methyl)biphenyl-4-carboxylic acid (BINA, 1) have
been previously reported,13 and we have shown that this com-
pound possesses antipsychotic and anxiolytic effects in mice.14
Most relevant to the present report, we recently showed that
compound 1, unlike mGluR2/3 agonists, decreased cocaine self-
administration in rats at doses that did not affect responding for
food.8 A recent report by the Merck group on a series of
oxazolobenzimidazole-based mGluR2 PAMs that are orally
active in an in vivo model of schizophrenia prompts us to
disclose our own efforts on the development of orally active
mGluR2 PAMs.15b
While compound 1 is brain penetrant and selective, it lacks
potency for mGluR2 both in vitro and in vivo and has
suboptimal pharmacokinetic (PK) properties. We therefore
set out to design and synthesize new selective mGluR2 PAMs
based on the compound 1 scaffold in order to improve both
potency and PK properties. These new PAMs are suitable for
in vivo proof-of-concept (POC) studies to evaluate the poten-
tial of mGluR2 as a therapeutic target for the treatment of
cocaine dependence. We hypothesized that modifying the
indanone ring of 1 by incorporating heteroatoms may lead
to analogues with improved properties (Figure 1). Interest-
ingly, to date, there have been no reports on the synthesis and
evaluation of analogues of compound1 in which the indanone
ring has been systematically modified in this way. In addition,
asfarasweare aware, therehave been no studies documenting
the effects of modifying the cyclopentyl ring in this scaffold.
Furthermore, despite several recent reports disclosing mGluR2
PAMs,11,15 none have been evaluated in an in vivo model of
drug dependence.
alternative procedure to confirm the structure unambigu-
ously.17 Completion of the synthesis of compounds 8a-k
was achieved in two steps using an O-alkylation reaction with
methyl 30-(bromomethyl)-4-chlorobiphenyl-3-carboxylate to
give the ester derivatives 7a-k which were saponified to the
corresponding acid derivatives 8a-k using LiOH in THF.
The synthesis of an analogue of compound 1 based on the
benzisothiazol-3-one scaffold is illustrated in Scheme 2. Methyl
4-methoxy thiosalicylate 918 was converted to the correspond-
ing amide 10 by treatment with cyclopentylamine in the pre-
sence of trimethylaluminum. The cyclization to access the
benzisothiazol-3-one derivative 11 was accomplished by a
PIFA-mediated in situ formation of an N-acylnitrenium ion
and its intramolecular trapping by the thiol moiety.19 De-
methylation of 11 was achieved with BBr3 in hot benzene,
followed by O-alkylation with methyl 30-(bromomethyl)-4-
chlorobiphenyl-3-carboxylate to provide 13. Hydroxide-
mediated demethylation led to the formation of byproducts;
however, clean saponification of 13 was accomplished with
lithium iodide to complete the synthesis of 14.
We also designed and synthesized an analogue of com-
pound 1 based on the isoxazol-3-one scaffold (21). Our ap-
proach to the synthesis of 21 began with the preparation of
N-cyclopentylbenzohydroxamic acid derivative 18 as shown
in Scheme 3. The synthesis began with 4-methoxysalicylic acid
15, which was transformed to 18 using a previously described
procedure.20 Thus, 4-methoxysalicylic acid 15 was acetylated
at the phenolic hydroxyl group prior to conversion to the
acid chloride derivative 16. N-Cyclopentylhydroxylamine 17
was reacted with 16 to provide hydroxamic acid 18 as a
colorless solid. Cyclization of 18 under Mitsunobu conditions
afforded N-cyclopentylbenzisoxazolinone 19, which was con-
verted to the desired analogue 21 via intermediate 20 using the
same conditions as those described for the preparation of
compounds 8 and 14.
Chemistry
Initially, we synthesized and tested compound 2, an ana-
logue of compound 1 previously reported to be roughly 4-fold
more potent than 1 at mGluR2 (Figure 1).13 The in vitro
potency of the compounds was assessed using a thallium flux
assay performed in HEK-GIRK cells expressing rat mGluR2.16
In this assay compound 1 exhibited an EC50 value of 380 nM,
while compound 2 had an EC50 of 180 nM, confirming an
improved potency of 2 compared with 1 (Table 1). We therefore
incorporated the 4-chlorobiphenyl-3-carboxylic acid moiety
from 2 into the design of the new analogues.
We next focused on the synthesis of isoindolinone analo-
gues (8a-k). As depicted in Scheme 1, the preparation of
8a-k commenced with the conversion of commercially avail-
able 4-hydroxyphthalic acid 3 into the corresponding phthalic
anhydride derivative 4 under thermal conditions, which was
further converted to the phthalimide derivatives 5a-k by
treatment with the appropriate amine derivative. Regioselec-
tive reduction of the 3-carbonyl group with zinc in acetic acid
afforded the desired 5-hydroxyisoindolinone derivatives
6a-k. To verify the regioselectivity of the reduction, inter-
mediate 6a (R1 = cyclopentyl) was also synthesized via an
In addition, we designed and synthesized an analogue of
compound 1 (28) based on the tetrahydroisoquinolinone
scaffold. Our approach to the synthesis of 28 is outlined in
Scheme 4. Thus, commercially available 3-methoxyphenethy-
lamine was alkylated with iodocyclopentane to provide N-(3-
methoxyphenethyl)cyclopentanamine (23). Treatment of 23
with methyl chloroformate in the presence of triethylamine
gave methyl cyclopentyl(3-methoxyphenethyl)carbamate 24.
Carbamate 24 was subjected to the Bischler-Napieralski
cyclization conditions of Wang et al.21 (POCl3-P2O5) to
afford the corresponding tetrahydroisoquinolone derivative
25. Compound 25 was then converted to the target BINA
analogue28inthree stepsasdescribed forthe other analogues.
Results and Discussion
The new analogues 8a-k, 14, 21, and 28 were tested, along
with 1 and 2, to determine in vitro activity, and the data are
summarized in Table 1. For these in vitro experiments, a
thallium flux assay was performed in HEK-GIRK cells16

344 Journal of Medicinal Chemistry, 2011, Vol. 54, No. 1
Table 1. In Vitro Data for mGluR2 PAMs
Dhanya et al.
a mGluR2 PAM EC50 μM data and % glutamate max data represent the mean ( SEM for at least three independent experiments performed in
triplicate. b Permeability is monitored by measuring the amount of compound that can diffuse through a polar brain lipid membrane to predict BBB
permeability.22 c Percent remaining after incubation for 60 min at 37 ꢀC.
Scheme 1. Synthesis of 4-Chloro-30-((2-cyclopentyl-1-oxoisoindolin-5-yloxy)methyl)biphenyl-3-carboxylic Acid Derivatives 8a-ka
a Reagents and conditions: (a) Δ; (b) R1NH2, toluene, 4 A molecular sieves, 110 ꢀC, 12 h; (c) Zn/AcOH, 5 min; (d) K2CO3, acetone, 60 ꢀC, 2.5 h;
(e) LiOH, THF, 80 ꢀC, 1 h.

Article
Journal of Medicinal Chemistry, 2011, Vol. 54, No. 1 345
Scheme 2. Synthesis of 3-Chloro-30-((2-cyclopentyl-3-oxo-2,3-dihydrobenzo[d]isothiazol-6-yloxy)methyl)biphenyl-4-carboxylic
Acid 14a
a Reagents and conditions: (a) AlMe3, cyclopentylamine, CH2Cl2, 0 to -60 ꢀC, 12 h; (b) PIFA, TFA, 0 ꢀC, CH2Cl2, 1 h; (c) (i) BBr3, C6H6, 80 ꢀC, 1 h,
(ii) H2O, 100 ꢀC, 1 h; (d) ArCH2Br, K2CO3, MeCN, 80 ꢀC, 12 h; (e) LiI, pyridine, 110 ꢀC, 12 h.
Scheme 3. Synthesis of 4-Chloro-30-((2-cyclopentyl-3-oxo-2,3-dihydrobenzo[d]isoxazol-6-yloxy)methyl)biphenyl-3-carboxylic
Acid 21a
a Reagents and conditions: (a) (i) AcCl, Py, CH2Cl2, 0 ꢀC to room temp, 30 min; (ii) H2O, 1 h; (b) COCl2, CH2Cl2, 60 ꢀC, 1 h; (c) 1 M Na2CO3, THF,
CH2Cl2, 0 ꢀC to room temp, 1 h; (d) TPP, DEAD, THF, 0 ꢀC to room temp, 30 min, MeOH, AcOH; (e) (i) BBr3, C6H6, 80 ꢀC, 1 h, (ii) H2O, 100 ꢀC, 1 h;
(f) ArCH2Br, K2CO3, MeCN, 80 ꢀC, 12 h; (g) LiI, Py, 110 ꢀC, 12 h.
Scheme 4. Synthesis of 4-Chloro-30-((2-cyclopentyl-1-oxo-1,2,3,4-tetrahydroisoquinolin-6-yloxy)methyl)biphenyl-3-carboxylic
Acid 28a
a Reagents and conditions: (a) iodocyclopentane, microwave, AcCN, 110 ꢀC, 10 min; (b) ClCO2Me, TEA, Et2O, 0 ꢀC, 30 min, 1 h; (c) (i) P2O5, POCl3,
100 ꢀC, 2 h; (d) (i) BBr3, C6H6, 80 ꢀC, 1 h, (ii) H2O, 100 ꢀC, 1 h; (e) ArCH2Br, K2CO3, MeCN, 80 ꢀC, 12 h; (f) 50% aqueous NaOH, dioxane, 80 ꢀC, 1 h.
expressing rat mGluR2. The concentration-response rela-
tionship thatpotentiatesthe effect of anEC20 concentration of
glutamate was determined for each of the mGluR2 PAMs,
and thispotency is expressed as anEC50 value. Theefficacy for
potentiation of an EC20 concentration of glutamate is pre-
sented as a percentage of the maximal glutamate response.
Compounds 8a-j, 14, 21, and 28 were all more potent than
1, with compound 8a being especially potent (EC50 = 50 nM).
Increase (8h) or decrease in ring size (8d, 8f) or the presence of
bulky aryl substituents (8g, 8i) led to a decrease in potency
compared with the N-cyclopentyl derivative 8a. On the other
hand, branching(8b) or lengtheningofthe branched chain(8e,
8j) led to compounds with potency similar to that of 8a.
Interestingly simple straight chain aliphatic substitution, as in
the N-propyl derivative (8k), led to complete loss of activity.
Enlargement of the lactam ring in the core scaffold from five-
(8a) to six-membered (28) led to a 6-fold decrease in EC50. In
addition, the new analogues are highly selective for mGluR2
vs other mGluR subtypes with no activity observed up to
10 μM for 8a and 14 (data not shown). We also determined the
membrane permeability, in vitro plasma stability, and micro-
somal stability of the analogues to predict their in vivo
pharmacological profile. As shown in Table 1, several of the
new analogues displayed superior druglike properties com-
pared with 1, suggesting that these improvements may trans-
late to an in vivo test.
On the basis of their overall in vitro profile, an isoindoli-
none derivative (8a) and a benzothiazolone derivative (14)
were therefore selected for an in vivo assessment of their PK
properties in rats. The rat PK data for compounds 1, 8a, and

346 Journal of Medicinal Chemistry, 2011, Vol. 54, No. 1
Dhanya et al.
Table 2. In Vivo PK Data for mGluR2 PAMs in Rats after Oral Administrationa
compd oral dose (mg/kg)
Cmax (μM)
Tmax (min) AUC (0-t) (μM h)
t1/2 (h)
F (%) brainb (μM) plasmab (μM) brain/plasma ratio
3
1
10
10
10
0.097 ( 0.032
14.4 ( 15.8
4.1 ( 1.0
120
80
0.281 ( 0.097
105.5 ( 69.1
43.3 ( 14.4
1.3 ( 0.25
3.4 ( 0.7
2.7 ( 1.1
33
40
86
0.0
3.8 ( 1.2
4.8 ( 1.0
0.027 ( 0.008
12.3 ( 5.7
1.0 ( 0.2
ND
0.3
4.8
8a
14
110
a Cmax: maximum concentration of the compound detected in plasma. Tmax: time at Cmax. AUC: area under the curve. t1/2: terminal half-life. F: oral
bioavailability. ND: Not determined. b Brains and plasma were harvested at or near the Tmax
.
rats but with a diminished or no effect on food-maintained
responding. This selectivity of the effect may be due to the selec-
tivity of 14 for mGluR2 compared with the dual acting
mGluR2/3 agonist and/or because of the modulatory properties
of a mGluR2 PAM compared to the direct actions of an agonist
on the receptor(s).
Conclusion
Using the mGluR2 PAM 1 as a template, we have designed
and synthesized a series of new, highlypotentmGluR2PAMs.
These compounds are highly selective for mGluR2 vs other
mGluR subtypes and have significantly improved in vitro
ADMEandinvivo PKproperties, providing compoundswith
excellent oral bioavailability and brain penetration. On the
basis of these data, compound 14 was selected for in vivo
studies in a model of cocaine dependence in rats, providing
proof-of-concept for the use of an orally active mGluR2 PAM
for the treatment of cocaine addiction.
Figure 2. Effects of compound 14 on cocaine self-administration
and food-maintained responding in rats. Data are expressed as
percent of baseline responding (mean ( SEM). The number of
baseline cocaine infusions was 20 ( 4.0 (mean ( SEM) and the
number of baseline food pellets earned was 100 ( 0.0 (mean ( SEM):
/, p < 0.05, //, p < 0.01, ///, p < 0.001 significant differences from
the corresponding vehicle condition (Newman-Keuls post hoc test);
##, p < 0.01 significant difference between cocaine- and food- main-
tained responding for specific doses of compound 14 (Bonferroni post
hoc test). Cpd = compound.
Experimental Section
14 are shown in Table 2. Gratifyingly, both 8a and 14
exhibited vastly superior PK profiles compared with 1, with
high values for Cmax, AUC, and t1/2. Incorporation of sulfur
into the isoindolinone ring (14) provided a compound with
similar potency to 1 but showed superior PK properties
(Table 2) compared to 1. Importantly, both 8a and 14 had
excellent oral bioavailability and were highly brain penetrant.
In particular, compound 14 showed exceptional oral bioavail-
ability (86%) and brain levels (4.8 μM) following a 10 mg/kg
oral dose, with a brain/plasma ratio of 4.8. In contrast, the
brain levels for 1 were below the limit of quantitation (LOQ)
following oral dosing (10 mg/kg).8 On the basis of these data,
compound 14 was selected for evaluation in the cocaine self-
administration procedure in rats.
The in vivo model was designed to investigate the effects of
acute systemic (oral) administration of the mGluR2 PAM 14
on intravenous cocaine self-administration in rats that had 1 h
access to cocaine (see Experimental Section for details). Addi-
tionally, we examined the effects of compound 14 on food-
maintained responding to assess the selectivity of an orally
active mGluR2 PAM on responding for cocaine compared to
responding for the natural reinforcer food.
The results of the in vivo behavioral studies are shown in
Figure 2. Oral administration of compound 14 significantly
decreased cocaine self-administration in rats (Figure 2). Simi-
larly, our previous work demonstrated that systemic (ip) admin-
istration of the mGluR2/3 agonist LY379268 significantly
decreased cocaine self-administration in rats.8 However, com-
pound 14 had a much less pronounced effect on food respond-
ing compared with the effects of LY379268.8 The effects of
compound 14 on cocaine self-administration and the small
effect of this compound on responding for food only at the
highest dose tested (40 mg/kg) are consistent with our previous
findings with compound 1.8 These data indicate that a selective,
orally active mGluR2 PAM is as effective as an mGluR2/3
agonist at reversing the effects of cocaine self-administration in
General Chemistry. All reactions were performed in oven-
dried glassware under an atmosphere of argon with magnetic
stirring. All solvents and chemicals used were purchased from
Sigma-Aldrich or Acros and were used as received without
further purification. Purity and characterization of compounds
were established by a combination of liquid chromatography-
mass spectrometry (LC-MS) and NMR analytical techniques
and was >95% for all tested compounds. Silica gel column
chromatography was carried out using prepacked silica car-
tridges from RediSep (ISCO Ltd.), and samples were eluted
using an Isco Companion system. Melting points were reordered
on a MEL-TEMP apparatus and are uncorrected. H and 13
1
C
NMR spectra were obtained using a Jeol 400 spectrometer at
400 and 100 MHz, respectively, unless otherwise mentioned, in
which case a Varian 300 MHz spectrometer was used. Chemical
shifts are reported in δ (ppm) relative to residual solvent peaks
or TMS as internal standards. Coupling constants are reported
in Hz. High-resolution ESI-TOF mass spectra were acquired at
the Center for Mass Spectrometry at The Scripps Research
Institute (La Jolla, CA). HPLC-MS analyses were performed
on a Shimadzu 2010EV LC-MS instrument using the following
conditions: Kromisil C18 column (reverse phase, 4.6 mm ꢀ
50 mm); a linear gradient from 10% acetonitrile and 90% water
to 95% acetonitrile and 5% water over 4.5 min; flow rate of
1 mL/min; UV photodiode array detection from 200 to 300 nm.
5-Hydroxyisobenzofuran-1,3-dione (4).23 4-Hydroxyphthalic
acid (10 g, 54.9 mmol) was heated at 200 ꢀC overnight in a round
bottomed flask in the absence of solvent. The resulting material
was cooled and washed with ethyl acetate to obtain 5-hydroxy-
isobenzofuran-1,3-dione 4 as a white solid in quantitative yield.
General Procedure for the Synthesis of Thalimide Derivatives
(5a-k). 4-Hydroxyphthalic anhydride 4 (5.4 g, 32.9 mmol),
commercial amine (49.6 mmol), and 4 A molecular sieves in
toluene (136 mL) were stirred at reflux overnight. The reaction
mixture was filtered, and the solvent was evaporated in vacuo to
obtain 5a-k as yellow solids in quantitative yield.
2-Cyclopentyl-5-hydroxyisoindoline-1,3-dione (5a).24 1H NMR
(DMSO-d6): δ 10.8 (s,1H), 7.60 (d, J = 7.8 Hz, 1H), 7.05-7.01
(m, 2H), 4.50-4.40 (m, 1H), 1.97-1.52 (m, 8H). 13C NMR

Article
Journal of Medicinal Chemistry, 2011, Vol. 54, No. 1 347
5-Hydroxy-2-isobutylisoindolin-1-one (6e). Yield: 86 mg,
(DMSO-d6): δ 167.7, 163.1, 134.2, 124.9, 121.0, 120.2, 109.5, 50.0,
29.2, 24.7.
1
34%. H NMR (DMSO-d6): δ 10.07 (s, 1H), 7.45 (d, J=8.2
5-Hydroxy-2-isopropylisoindoline-1,3-dione (5b). 1H NMR
(300 MHz, DMSO-d6): δ 7.65 (d, J = 8.7 Hz, 1H), 7.22-7.09
(m, 2H), 4.38-4.29 (m, 1H), 1.37 (d, J = 6.9 Hz, 6H).
2-(Cyclopropylmethyl)-5-hydroxyisoindoline-1,3-dione (5c).
1H NMR (300 MHz, DMSO-d6): δ 7.70 (d, J = 8.1 Hz, 1H),
7.16-7.11 (m, 2H), 3.39 (d, J = 7.5 Hz, 2H), 1.11-1.06 (m, 1H),
0.47-0.39 (m, 2H), 0.32-0.28 (m, 2H). 13C NMR (75 MHz,
DMSO-d6): δ 168.5, 163.9, 135.1, 125.9, 122.4, 121.0, 110.5,
42.4, 11.0, 4.2.
Hz, 1H), 6.88-6.81 (m, 2H), 4.32 (s, 2H), 3.23 (d, J = 7.8 Hz,
2H), 2.00-1.90 (m, 1H), 0.83 (d, J = 6.8 Hz, 6H). 13C NMR
(DMSO-d6): δ 167.6, 160.5, 144.1, 124.1, 123.5, 115.4, 109.5,
49.6, 49.1, 27.1, 20.0. LRMS (ESI) calcd for C12H15NO2 [M þ
H]þ, 206; found, 205.90.
2-Cyclopropyl-5-hydroxyisoindolin-1-one (6f). Yield: 53 mg,
23%. 1H NMR (DMSO-d6): δ 7.36 (d, J=8.2 Hz, 1H), 6.84-
6.79 (m, 2H), 4.36 (s, 2H), 2.84-2.80 (m, 1H), 0.77-0.71 (m,
4H). 13C NMR (DMSO-d6): δ 168.9, 143.9, 123.8, 116.1, 109.7,
49.3, 24.9, 24.5, 5.1. LRMS (ESI) calcd for C11H11NO2 [M þ
H]þ, 190; found, 190.00.
2-Cyclobutyl-5-hydroxyisoindoline-1,3-dione (5d). 1H NMR
(300 MHz, DMSO-d6): δ 7.61 (d, J = 8.4 Hz, 1H), 7.06-7.04
(m, 2H), 4.59-4.50 (m, 1H), 2.79-2.68 (m, 2H), 2.16-2.10 (m,
2H), 1.78-1.66 (m, 2H).
5-Hydroxy-2-phenylisoindolin-1-one (6g). Yield: 14 mg, 19%.
1H NMR (DMSO-d6): δ 7.83-7.81(m, 2H), 7.55-7.53 (m, 1H),
7.38-7.34 (m, 2H), 7.10-7.06 (m, 1H), 6.92-6.91 (m, 1H),
6.87-6.84 (m, 1H), 4.85 (s, 2h). LRMS (ESI) calcd for
C14H11NO2 [M þ H]þ, 226; found, 226.
5-Hydroxy-2-isobutylisoindoline-1,3-dione (5e). 1H NMR
(300 MHz, DMSO-d6): δ 7.65 (d, J=8.4 Hz, 1H), 7.10-7.06
(m, 2H), 3.32 (d, J = 7.2 Hz, 2H), 2.00-1.91 (m, 1H), 0.84 (d,
J = 6.3 Hz, 6H). 13C NMR (75 MHz, DMSO-d6): δ 168.7,
134.9, 125.9, 121.1, 110.6, 45.3, 28.1, 20.6.
2-Cyclohexyl-5-hydroxyisoindolin-1-one (6h). Yield: 120 mg,
64%. 1H NMR (300 MHz, DMSO-d6): δ 10.08 (s, 1H), 7.47 (d,
J = 8.7 Hz, 1H), 6.92-6.84 (m, 2H), 4.33 (s, 2H), 3.99-3.93 (m,
1H), 1.82-1.31 (m, 10H). 13C NMR (75 MHz, DMSO-d6): δ
167.4, 161.1, 144.9, 124.7, 116.1, 110.3, 50.7, 46.1, 31.4, 25.9,
25.8. LRMS (ESI) calcd for C14H17NO2 [M þ H]þ, 232; found,
232.0.
1
2-Cyclopropyl-5-hydroxyisoindoline-1,3-dione (5f). H NMR
(300 MHz, DMSO-d6): δ 7.70 (þd, J = 8.4 Hz, 1H), 7.20-7.10
(m, 2H), 2.70-2.60 (m, 1H), 0.91- 0.82 (m, 4H).
5-Hydroxy-2-phenylisoindoline-1,3-dione (5g). 1H NMR (DMSO-
d6):δ11.03 (s, 1H), 7.78 (d, J= 8.2 Hz, 1H), 7.52-7.16 (m, 7H). 13
C
NMR (DMSO-d6): δ 166.7, 163.5, 134.3, 132.1, 128.8, 127.8, 127.3,
125.6, 120.8, 109.9.
5-Hydroxy-2-(4-(trifluoromethoxy)benzyl)isoindolin-1-one (6i).
Yield: 19 mg, 20%. LRMS (ESI) calcd for C16H12 F3NO3 [M þ
H]þ, 324; found, 323.95.
2-Cyclohexyl-5-hydroxyisoindoline-1,3-dione (5h). 1H NMR (300
MHz, DMSO-d6): δ 7.48 (d, J = 7.8 Hz, 1H), 6.86-6.79 (m, 2H),
3.93-3.87 (m, 1H), 1.82-1.09 (m, 10H).
5-Hydroxy-2-isopentylisoindolin-1-one (6j). Yield: 213 mg,
1
32%. H NMR (300 MHz, DMSO-d6): δ 7.46 (d, J=8.1 Hz,
5-Hydroxy-2-(4-(trifluoromethoxy)benzyl)isoindoline-1,3-dione
(5i). 1H NMR (300 MHz, DMSO-d6): δ 7.68-7.03 (m, 7H), 4.75
(s, 2H). 13C NMR (75 MHz, DMSO-d6): δ 168.5, 166.4, 137.2,
135.2, 130.1, 130.0, 126.2, 121.9, 121.6, 111.1, 44.7.
1H), 6.91 (s, 1H), 6.84 (d, J=8.4 Hz, 1H), 4.34 (s, 2H), 1.49-1.42
(m, 3H), 0.91 (d, J=5.4 Hz, 6H). LRMS (ESI) calcd for C13H17-
NO2 [M þ H]þ, 220; found, 219.85.
5-Hydroxy-2-propylisoindolin-1-one (6k). Yield: 12 mg, 22%.
LRMS (ESI) calcd for C11H13NO2 [M þ H]þ, 192; found,
191.95.
5-Hydroxy-2-isopentylisoindoline-1,3-dione (5j). 1H NMR
(300 MHz, DMSO-d6): δ 7.62 (d, J = 7.8 Hz, 1H), 7.07-7.02 (m,
2H), 3.54-3.49(m,2H),1.47-1.40 (m, 3H), 0.89 (d, J=6.9Hz,6H).
5-Hydroxy-2-propylisoindoline-1,3-dione (5k). 1H NMR (DMSO-
d6): δ 7.74 (d, J = 8.2 Hz, 1H), 7.19-7.16 (m, 2H), 3.56-3.52 (m,
2H), 1.66-1.61(m,2H),0.92-0.89 (m, 3H). 13C NMR (DMSO-d6):
δ167.8, 163.2, 134.3, 125.1, 121.7, 120.2, 109.7, 21.4, 11.2.
General Procedure for the Synthesis of Isoindolinones (6a-k).
To a solution of 1,3-dione 5a-k (18.0 mmol) in CH3CO2H
(129 mL) was added Zn dust (11.6 g, 180 mmol), and the mixture
was heated at reflux for 5 min. The volatiles were removed in
vacuo, and the residue was dissolved in water and extracted with
ethyl acetate. The crude residue was purified using automated
preparative HPLC to yield the desired compounds (6a-k) as
amorphous solids.
Methyl 30-(Bromomethyl)-4-chlorobiphenyl-3-carboxylate. Pd-
(OAc)2 (0.393g, 1.75mmol)wasaddedtoasolutionof2-chloro-5-
iodobenzoic acid (9.9 g, 35 mmol), m-tolylboronic acid (5.71 g,
42 mmol), and Na2CO3 (11.45 g, 105 mmol) in water (45 mL)
under a nitrogen atmosphere. The resulting mixture was stirred at
50 ꢀC for 2 h. The reaction mixture was cooled to room tempera-
ture and filtered. The filtrate was acidified with 1 M HCl. The
precipitated 4-chloro-30-methylbiphenyl-3-carboxylic acid was
filtered, washed with water, and dried to provide a tan solid that
was used without further purification in the next step (quantitative
yield). 1H NMR (DMSO-d6, 300 MHz): δ 8.03 (s, 1H), 7.83 (d,
J = 8.1 Hz, 1H), 7.63 (d, J = 7.8 Hz, 1H), 7.55-7.50 (m, 2H), 7.40
(t, J = 7.8 Hz,1H), 7.25 (d, J = 6.6 Hz, 1H), 2.41 (s, 3H). 13C
NMR (DMSO-d6, 75 MHz): δ 167.4, 139.9, 139.1, 138.6, 132.7,
131.9, 131.2, 129.7, 129.5, 129.3, 128.0, 124.5, 21.8.
2-Cyclopentyl-5-hydroxyisoindolin-1-one (6a). Yield: 1.7 g,
1
44%. H NMR (DMSO-d6): δ 10.10 (bs, 1H), 7.44 (d, J=8.5
To a solution of 4-chloro-30-methylbiphenyl-3-carboxylic
acid (7 g, 28.5 mmol) in acetone was added K2CO3 (27.5 g,
199 mmol) and MeI (12.5 mL, 28 mmol). The resulting solution
was heated at 50 ꢀC for 1 h. After the mixture was cooled, the
excess solvent was removed in vacuo. The crude material was
dissolved in CH2Cl2 and washed with water. The organic layer
was dried over Na2SO4, and the solvent was evaporated to
afford methyl 4-chloro-30-methylbiphenyl-3-carboxylate as a
reddish yellow viscous liquid (7.3 g, 98%) which was used in
the next step without further purification. 1H NMR (DMSO-d6):
δ 8.04 (s, 1H), 7.85 (d, J = 7.8 Hz, 1H), 7.64 (d, J = 8.1 Hz, 1H),
7.52-7.47 (m, 2H), 7.38 (t, J = 7.8 Hz, 1H), 7.23 (d, J = 7.5 Hz,
1H), 3.90 (s, 3H), 2.39 (s, 3H). 13C NMR (DMSO-d6, 75 MHz):
δ 166.2, 139.9, 139.1, 138.4, 131.9, 131.7, 131.4, 131.3, 129.7,
129.6, 129.5, 128.0, 124.5, 53.3, 21.7.
Hz, 1H), 6.89 (s, 1H), 6.83 (d, J=7.9 Hz, 1H), 4.52-4.48 (m,
1H), 4.31 (s, 2H), 1.83-1.57 (m, 8H). 13C NMR (DMSO-d6): δ
167.2, 160.4, 144.1, 123.9, 123.7, 115.4, 109.6, 51.8, 45.4, 29.6,
23.8. LCMS calcd for C13H15NO2 [M þ H]þ, 218; found, 218.
5-Hydroxy-2-isopropylisoindolin-1-one (6b). Yield: 23 mg,
1
22%. H NMR (DMSO-d6): δ 10.04(s, 1H), 7.43 (d, J = 8.2
Hz, 1H), 6.89-6.81 (m, 2H), 4.38-4.31 (m, 1H), 4.28 (s, 2H),
1.16 (d, J = 6.4 Hz, 6H). 13C NMR (DMSO-d6): δ 166.7, 160.4,
144.1, 123.9, 115.4, 109.6, 44.4, 41.9, 20.4. LRMS (ESI) calcd for
C11H13NO2 [M þ H]þ, 192; found, 191.95.
2-(Cyclopropylmethyl)-5-hydroxyisoindolin-1-one (6c). Yield:
60 mg, 63%. LRMS (ESI) calcd for C12H13NO2 [M þ H]þ, 204;
found, 204.
2-Cyclobutyl-5-hydroxyisoindolin-1-one (6d). Yield: 108 mg,
45%. 1H NMR (DMSO-d6): δ 7.43, (d, J=8.2 Hz, 1H), 6.89-
6.80 (m, 2H), 4.71-4.62 (m, 1H), 4.42 (s, 2H), 2.31-2.06 (m,
4H), 1.72-1.62 (m, 2H). 13C NMR (DMSO-d6): δ 166.7, 160.6,
144.1, 124.2, 123.6, 115.5, 109.6, 45.8, 45.6, 28.1, 14.5. LRMS
(ESI) calcd for C12H13NO2 [M þ H]þ, 204; found, 203.95.
A catalytic amount of AIBN was added to a solution of
methyl 4-chloro-30-methylbiphenyl-3-carboxylate (7.3 g, 28
mmol) and NBS (5.5 g, 30.8 mmol) in CCl4. The reaction
mixture was heated under reflux for 12 h. After the mixture

348 Journal of Medicinal Chemistry, 2011, Vol. 54, No. 1
Dhanya et al.
was cooled, the precipitated succinimide was removed by filtra-
tion. The filtrate was concentrated in vacuo to afford the crude
product. Silica gel column chromatography using 4:1 hexanes/
ethyl acetate afforded methyl 30-(bromomethyl)-4-chlorobiphe-
4-Chloro-30-((2-isobutyl-1-oxoisoindolin-5-yloxy)methyl)bi-
phenyl-3-carboxylic Acid (8e). Amorphous white solid (75 mg,
34%). 1H NMR (CDCl3): δ 8.17 (s, 1H), 7.78 (d, J = 8.5 Hz,
1H), 7.66-7.62 (m, 2H), 7.55-7.41 (m, 4H), 7.07-7.05 (m,
1H), 7.00 (s, 1H), 5.17 (s, 2H), 4.33 (s, 2H), 3.39 (d, J = 7.3 Hz,
2H), 2.07-1.96 (m, 1H), 0.92 (d, J = 6.7 Hz, 6H). 13C NMR
(CDCl3): δ 169.1, 168.2, 161.6, 143.4, 139.4, 137.2, 133.6, 131.7,
131.5, 130.7, 129.4, 127.1, 126.8, 125.9, 125.6, 125.3, 115.4, 108.7,
70.1, 50.6, 50.2, 27.8, 20.1. LRMS (ESI): 450.00 (M þ H)þ.
HRMS: calcd for C26H24ClNO4, 450.1467; found, 450.1472.
4-Chloro-30-((2-cyclopropyl-1-oxoisoindolin-5-yloxy)methyl)bi-
phenyl-3-carboxylic Acid (8f). Amorphous white solid (78 mg,
23%). 1H NMR (300 MHz, DMSO-d6): δ 8.05 (s, 1H), 7.86-7.81
(m, 2H), 7.67-7.51 (m, 5H), 7.21 (s, 1H), 7.12 (d, J = 7.8 Hz, 1H),
5.26 (s, 2H), 4.32 (s, 2H), 2.92-2.86 (m, 1H), 0.80-0.76 (m, 4H).
13C NMR (75 MHz, DMSO-d6): δ 168.3, 166.8, 161.2, 144.1,
138.8, 138.3, 137.7, 132.1, 131.4, 130.9, 130.6, 129.5, 128.7, 127.6,
126.4, 126.2, 125.7, 124.0, 115.5, 108.9, 69.5, 49.5, 25.1, 5.11.
LRMS (ESI): 434.05 (M þ H)þ. HRMS: calcd for C25H20ClNO4,
434.1154; found, 434.1150.
4-Chloro-30-((1-oxo-2-phenylisoindolin-5-yloxy)methyl)biphenyl-
3-carboxylic Acid (8g). Amorphous white solid (28 mg, 36%). 1H
NMR (CDCl3): δ 8.20 (s, 1H), 7.86-7.36 (m, 11H), 7.15-7.05 (m,
3H), 5.19 (s, 2H), 4.77 (s, 2H). 13C NMR (CDCl3): δ 169.2, 167.4,
162.2, 142.4, 139.5, 139.4, 139.3, 137.1, 133.7, 131.9, 131.7, 130.8,
129.5, 129.1, 127.1, 126.9, 126.1, 126.0, 125.8, 124.3, 119.4, 115.9,
108.4, 70.2, 50.6. LRMS (ESI): 470. (M þ H)þ. HRMS: calcd for
C28H20ClNO4, 470.1154; found, 470.1157.
1
nyl-3-carboxylate (8.8 g, 91%) as a colorless solid. H NMR
(CDCl3): δ 8.07(s, 1H), 7.68-7.45 (m, 6H), 4.58 (s, 2H), 4.00 (s,
3H). 13C NMR (CDCl3): δ 166.1, 139.5, 139.2, 138.7, 133.0,
131.6, 131.0, 130.4, 129.9, 129.6, 128.7, 127.7, 52.6, 33.2.
4-Chloro-30-((2-cyclopentyl-1-oxoisoindolin-5-yloxy)methyl)-
biphenyl-3-carboxylic Acid (8a). To a solution of 2-cyclopentyl-
5-hydroxyisoindolin-1-one (50 mg, 0.23 mmol) in acetone
(15 mL) and K2CO3 (181 mg, 1.31 mmol) was added methyl
30-(bromomethyl)-4-chlorobiphenyl-3-carboxylate (92 mg, 0.27
mmol), and the mixture was heated at reflux for 1 h. The reaction
mixture was filtered and the solvent was evaporated in vacuo to
obtain methyl 4-chloro-30-((2-cyclopentyl-1-oxoisoindolin-5-
yloxy)methyl)biphenyl-3-carboxylate 7a as a yellow oil in quan-
titative yield.
Crude methyl 4-chloro-30-((2-cyclopentyl-1-oxoisoindolin-5-
yloxy)methyl)biphenyl-3-carboxylate 7a (109 mg, 0.23 mmol)
was dissolved in tetrahydrofuran (17 mL), and 2 M LiOH
(0.57 mL, 1.15 mmol) was added. The mixture was heated at
reflux for 3 h. The solvent was evaporated, and the residue was
dissolved in water and neutralized using 2 M HCl. The aqueous
layer was extracted with ethyl acetate, and the organic layer was
dried over anhydrous Na2SO4. The solvent was evaporated in
vacuo to obtain the crude acid as a yellow solid. The crude
residue was purified using automated preparative HPLC to
yield the desired compound 8a (48 mg, 46%) as an amorphous
white solid. 1H NMR (CDCl3): δ 8.18 (s, 1H), 7.78 (d, J=8.5 Hz,
1H), 7.65-7.41 (m, 6H), 7.05 (d, J = 8.5 Hz, 1H), 6.99 (s, 1H),
5.16 (s, 2H), 4.74 (m, 1H), 4.30 (s, 2H), 1.97 (m, 2H), 1.76-1.59
(m, 6H). 13C NMR (CDCl3): δ 168.7, 161.5, 143.3, 139.3, 137.2,
133.5, 131.7, 131.4, 130.7, 129.7, 129.4, 127.0, 126.8, 126.0,
125.9, 125.1, 115.4, 108.7, 70.1, 52.7, 46.1, 30.1, 24.1. HRMS:
calcd for C27H24ClNO4 [M þ H]þ, 462.1467; found, 462.1468.
Following the above-mentioned procedure, 8b-k were
synthesized using the appropriate starting materials.
4-Chloro-30-((2-cyclohexyl-1-oxoisoindolin-5-yloxy)methyl)bi-
phenyl-3-carboxylic Acid (8h). Amorphous white solid (87 mg,
36%). 1H NMR (300 MHz, DMSO-d6): δ 8.05 (s, 1H), 7.83 (m,
2H), 7.68-7.45 (m, 5H), 7.24 (s, 1H), 7.12 (d, J = 8.4 Hz, 1H),
5.27 (s, 2H), 4.36 (s, 2H), 3.99-3.92 (m, 1H), 1.79-1.14 (m,
10H). 13C NMR (75 MHz, DMSO-d6): δ 167.3, 167.0, 161.7,
144.8, 139.4, 138.9, 138.4, 132.8, 131.9, 131.6, 131.2, 130.1, 129.4,
128.2, 127.0, 126.8, 126.3, 124.6, 116.0, 109.8, 70.1, 50.8, 46.3,
31.3, 25.9, 25.7. LRMS (ESI): 476.05 (M þ H)þ. HRMS: calcd
for C28H26ClNO4, 476.1623; found, 476.1621.
4-Chloro-30-((1-oxo-2-(4-(trifluoromethoxy)benzyl)isoindolin-
5-yloxy)methyl)biphenyl-3-carboxylic Acid (8i). Amorphous
4-Chloro-30-((2-isopropyl-1-oxoisoindolin-5-yloxy)methyl)bi-
phenyl-3-carboxylic Acid (8b). Amorphous white solid (14 mg,
1
1
white solid (12 mg, 30%). H NMR (CDCl3): δ 8.13 (s, 1H),
32%). H NMR (300 MHz, DMSO-d6): δ 8.06 (s, 1H), 7.85-
7.80 (d, J = 8.5 Hz, 1H), 7.62-7.28 (m, 8H),7.14 (d, J = 7.9 Hz,
2H), 7.07-7.05 (m, 1H), 6.93 (s, 1H), 5.14 (s, 2H), 4.74 (s, 2H),
4.20 (s, 2H). 13C NMR (CDCl3): δ 168.5, 161.8, 148.7, 143.4,
139.9, 139.4, 137.1, 135.8, 131.7, 131.5, 130.7, 129.5, 127.1, 126.8,
125.9, 125.4, 125.3, 121.3, 115.5, 108.9, 70.2, 49.3, 45.7. LRMS
(ESI): 567.95 (M þ H)þ. HRMS: calcd for C30H21ClF3NO5,
568.1133; found, 568.1136.
4-Chloro-30-((2-isopentyl-1-oxoisoindolin-5-yloxy)methyl)bi-
phenyl-3-carboxylic Acid (8j). Amorphous white solid (82 mg,
41%). 1H NMR (CDCl3): δ 8.18 (s, 1H), 7.78 (d, J = 8.5 Hz,
1H), 7.66-7.62 (m, 2H), 7.55-7.42 (m, 4H), 7.06 (dd, J = 8.5,
1.8 Hz, 1H), 6.99 (s, 1H), 5.17 (s, 2H), 4.31 (s, 2H), 3.62-3.58
(m, 2H), 1.63-1.49 (m, 3H), 0.93 (d, J = 6.1 Hz, 6H). 13C NMR
(CDCl3): δ 168.6, 161.5, 143.3, 139.4, 137.2, 133.6, 131.8, 131.5,
130.7, 129.4, 127.1, 126.8, 125.9, 125.2, 115.3, 108.7, 70.1, 49.8,
40.8, 37.2, 25.8, 22.5. LRMS (ESI): 463.95 (M þ H)þ. HRMS:
calcd for C27H26ClNO4, 464.1623; found, 464.1626.
4-Chloro-30-((1-oxo-2-propylisoindolin-5-yloxy)methyl)biphenyl-
3-carboxylic Acid (8k). Amorphous white solid (30 mg, 34%). 1H
NMR (CDCl3): δ 8.18 (s, 1H), 7.78 (d, J = 8.5 Hz, 1H), 7.65-7.62
(m, 2H), 7.53-7.43 (m, 4H), 7.06 (dd, J = 8.5, 2.4 Hz, 1H), 6.99 (s,
1H), 5.17 (s, 2H), 4.31 (s, 2H), 3.54 (t, J = 7.3 Hz, 2H), 1.70-1.61
(m, 2H),0.93(t, J=7.3 Hz, 3H). 13CNMR(CDCl3):δ168.7, 168.4,
161.5, 143.3, 139.4, 137.2, 133.5, 131.7, 131.4, 130.7, 129.5, 129.4,
127.0, 126.8, 125.9, 125.9, 125.2, 115.3, 108.7, 70.1, 49.9, 44.1, 21.7,
11.3. LRMS (ESI): 436.00 (M þ H)þ. HRMS: calcd for C25H22-
ClNO4, 436.131; found, 436.1315.
7.82 (m, 2H), 7.68-7.51 (m, 5H), 7.24 (s, 1H), 7.13 (d, J=8.4
Hz, 1H), 5.26 (s, 2H), 4.45-4.40 (m, 1H), 4.34 (s, 2H), 1.19 (d,
J = 6.9 Hz, 6H). 13C NMR (75 MHz, DMSO-d6): δ 166.8,
166.6, 161.1, 144.2, 138.8, 138.3, 137.7, 132.1, 131.4, 131.0,
130.6, 129.5, 128.8, 127.6, 126.4, 126.2, 125.7, 124.1, 115.4,
109.2, 69.5, 44.8, 42.3, 20.5. LRMS (ESI): 435.95 (M þ 1)þ.
HRMS: calcd for C25H22ClNO4, 436.131; found, 436.1309.
4-Chloro-30-((2-(cyclopropylmethyl)-1-oxoisoindolin-5-yloxy)-
methyl)biphenyl-3-carboxylic Acid (8c). Amorphous white solid
(49 mg, 39%). 1H NMR (300 MHz, DMSO-d6): δ 8.07 (s, 1H),
7.88-7.84 (m, 2H), 7.71-7.52 (m, 5H), 7.28 (s, 1H), 7.14 (d, J =
8.4 Hz, 1H), 5.28 (s, 2H), 4.50 (s, 2H), 3.33 (d, J = 7.5 Hz, 2H),
1.06-0.98 (m, 1H), 0.51-0.48 (m, 2H), 0.31-0.28 (m, 2H). 13
C
NMR (75 MHz, DMSO-d6): δ 167.5, 167.3, 161.8, 144.8, 139.4,
138.9, 138.4, 132.8, 131.9, 131.6, 131.2, 130.1, 129.4, 128.3,
127.1, 126.9, 126.0, 124.7, 116.0, 109.8, 70.2, 50.0, 46.8, 10.6,
4.1. LRMS (ESI): 448.00 (M þ H)þ. HRMS: calcd for C26H22-
ClNO4, 448.131; found, 448.1313.
4-Chloro-30-((2-cyclobutyl-1-oxoisoindolin-5-yloxy)methyl)bi-
phenyl-3-carboxylic Acid (8d). Amorphous white solid (183 mg,
1
41%). H NMR (300 MHz, DMSO-d6): δ 8.05 (s, 1H), 7.85-
7.83 (m, 2H), 7.68-7.51 (m, 5H), 7.25 (s, 1H), 7.12 (d, J = 8.7
Hz, 1H), 5.27 (s, 2H), 4.78-4.62 (m, 1H), 4.49 (s, 2H), 2.38-2.22
(m, 2H), 2.15-2.09 (m, 2H), 1.78-1.66 (m, 2H). 13C NMR (75
MHz, DMSO-d6): δ 166.6, 166.4, 161.1, 144.0, 138.7, 138.2,
137.6, 132.0, 131.2, 130.9, 130.5, 129.4, 128.7, 127.5, 126.3,
126.2, 125.4, 124.1, 115.4, 109.1, 69.4, 46.0, 45.7, 28.1, 14.5.
LRMS (ESI): 448.00 (M
C26H22ClNO4, 448.131; found, 448.131.
þ
H)þ. HRMS: calcd for
N-Cyclopentyl-2-mercapto-4-methoxybenzamide (10). The title
compound was prepared using the literature procedure as follows.

Article
Journal of Medicinal Chemistry, 2011, Vol. 54, No. 1 349
AlMe3 (10 mmol, 2.0 M in toluene) was added dropwise to a
cooled (0 ꢀC) suspension of cyclopentylamine (0.85 g, 10 mmol) in
CH2Cl2 (30 mL). When the addition was complete, the reaction
mixture was allowed to warm to room temperature and stirring
was continued for 30 min until gas evolution had ceased. A
solution of methyl 2-mercapto-4-methoxybenzoate 9 (0.990 g,
5 mmol) was then added. After being stirred at 60 ꢀC for 12 h,
the mixture was cooled, and the reaction was carefully quenched
with 5% aqueous HCl (20 mL). The organic layer was separated,
and the aqueous layer was extracted with CH2Cl2 (3 ꢀ 15 mL).
The combined organic extracts were washed with a saturated
aqueous solution of NaHCO3 (15 mL) and brine. The organic
phase was dried using MgSO4, evaporated, and filtered and the
solvent was evaporated in vacuo. The resulting residue was
purified by crystallization from Et2O to afford amide 10 as a tan
solid (1.18 g, 94%). 1H NMR (300 MHz, DMSO-d6): δ 8.26 (s,
1H), 7.51 (d, J = 8.7 Hz, 1H), 7.01 (s, 1H), 6.72 (d, J = 8. One Hz,
1H), 5.62 (s, 1H), 4.16-4.14 (m, 1H), 3.78 (s, 3H), 1.99-1.80 (m,
2H), 1.79-1.68 (m, 2H), 1.66-1.53 (m, 4H). 13C NMR: δ 164.6,
162.7, 142.7, 127.1, 118.4, 115.2, 105.0, 56.3, 54.8, 32.0, 23.9.
LC-MS (ESI) calcd for C13H17NO2S [M þ H]þ, 252.09; found,
251.95.
next step without further purification. LC-MS (ESI) calcd for
C27H24NO2S [M þ H]þ, 494.11; found, 494.00.
LiI (0.042 g, 0.32 mmol) was added to a solution of the crude
product (0.158 g, 0.32 mmol) in pyridine (5 mL). The reaction
mixture was heated under reflux for 12 h and then cooled to
room temperature. The excess solvent was removed in vacuo.
The product was purified by preparative HPLC using isopro-
panol/water as the solvent system to afford the title compound
14 as a colorless solid (70 mg) in 46% yield. Mp: 189-191 ꢀC. 1H
NMR (DMSO-d6): δ 8.01 (s, 1H), 7.82 (d, J = 8.5 Hz, 1H), 7.80
(d, J = 8.6 Hz, 1H), 7.71-7.76 (m, 4H), 7.49-7.47 (m, 2H), 7.05
(d, J = 8.5 Hz, 1H.), 5.23 (s, 2H), 4.83-4.81 (m, 1H), 2.02-1.99
(m, 2H), 1.62-1.60 (m, 6H). 13C NMR (DMSO-d6): δ 167.2,
164.0, 140.2, 138.7, 137.8, 131.7, 130.6, 131.0, 129.9, 129.2,
128.2, 127.2, 127.0, 126.9, 119.0, 115.73, 106.6, 70.2, 54.8,
32.2, 24.4. LC-MS (ESI) calcd for C26H22ClNO4S [M þ H]þ,
480.09; found, 479.95. HRMS (ESI) calcd for C26H22ClNO4S
[M þ H]þ, 480.1031; found, 480.1031.
N-Cyclopentyl-2-dihydroxy-4-methoxybenzamide (18). To a
solution of 4-methoxysalicylic acid (0.84 g, 5 mmol) in CH2Cl2
was added pyridine (2.05 mL, 25 mmol) and acetyl chloride (0.89
mL, 12.5 mmol) at 0 ꢀC. The reaction mixture was gradually
warmed to room temperature over 30 min and then poured into
water. The resulting biphasic mixture was stirred for 1 h and
then acidified with 1 M HCl and extracted with EtOAc. The
crude acetoxy derivative was then converted to the correspond-
ing acidchoride by heating with oxalyl chloride (1.3 mL, 15 mmol)
in CH2Cl2 for 1 h at reflux. After removal of the volatile materials,
the acid chloride (1.05 g, 4.38 mmol) in CH2Cl2 was added to
a stirred mixture of sodium carbonate (1M, 17.5 mL) and
C5H9NHOH (1.32 g, 13.2 mmol) in THF at 0 ꢀC. The resulting
mixture was stirred at room temperature for 1 h, acidified with
0.5 M HCl, and then extracted with EtOAc. The crude product
was purified by column chromatography on silica gel using
hexanes/ethyl acetate, affording hydroxamic acid 18 (1 g, 79%)
as a colorless solid. 1H NMR (DMSO-d6): δ 7.65 (d, J = 9.1 Hz,
1H), 6.37-6.36 (overlapping doublet and singlet, 2 H), 4.10-3.98
(m, 1H), 3.70 (s, 1H), 1.69-1.63 (m, 2H), 1.55-1.52 (m, 6H). 13C
NMR (DMSO-d6): δ 167.5, 162.5, 160.0, 131.4, 113.3, 105.5,
101.6, 56.6, 55.7, 29.5, 25.5. LC-MS (ESI) calcd for C13H17-
NO4 [M þ H]þ, 251.12; found, 252.00.
2-Cyclopentyl-6-methoxybenzo[d]isothiazol-3(2H)-one (11). A
solution of PIFA (645 mg, 1.5 mmol) in CH2Cl2 (20 mL) was
added at 0 ꢀC to a solution of N-cyclopentyl-2-mercapto-4-
methoxybenzamide 10 (251 mg, 1 mmol) and TFA (0.23 mL,
3 mmol) in CH2Cl2 (5 mL). The resulting mixture was gradually
warmed to room temperature. After 1 h, the solvent was eva-
porated under reduced pressure and the resulting residue was
purified by column chromatography using CH2Cl2 to afford the
2-cyclopentyl-6-methoxybenzo[d]isothiazol-3(2H)-one 11 as a
1
white amorphous solid (84%, 0.210 g). H NMR (300 MHz,
CDCl3): δ 7.87 (d, J = 8.5 Hz, 1H), 6.93 (s, 1H), 6.92 (d, J = 8.2
Hz, 1H), 5.50-5.01 (m, 1H), 3.86 (s, 1H), 2.13-2.12 (m, 2H),
1.83-1.67 (m, 6H). 13C NMR (75 MHz, CDCl3): δ 165.3,
162.7, 142.2, 127.6, 118.8, 114.6, 103.1, 55.8, 55.0, 32.2, 24.4.
LC-MS (ESI) calcd for C13H15NO2S [M þ H]þ, 250.08; found,
249.95.
2-Cyclopentyl-6-hydroxybenzo[d]isothiazol-3(2H)-one (12). A
solution of 2-cyclopentyl-6-methoxybenzo[d]isothiazol-3(2H)-
one 11 (0.250 g, 1 mmol) in anhydrous C6H6 (20 mL) was cooled
to 0 ꢀC before BBr3 (0.54 g, 2 mmol) was added dropwise. The
mixture was gradually warmed to room temperature and then
heated at 80 ꢀC for 30 min. After that, the reaction mixture was
cooled to room temperature and carefully quenched with H2O
(20 mL). The resulting mixture was then heated at reflux for 1 h
and filtered. The precipitate was washed with H2O and dried in
vacuo to give the crude product. This material was purified
by flash chromatography (silica gel, CHCl3/MeOH, 9:1) to
afford 2-cyclopentyl-6-hydroxybenzo[d]isothiazol-3(2H)-one
2-Cyclopentyl-6-methoxybenzo[d]isoxazol-3(2H)-one (19). Diethy-
lazodicarboxylate was added dropwise to a cooled solution of
hydroxamic acid 18 (0.71 g, 2.8 mmol) and triphenylphosphine
(0.89 g, 3.4 mmol) in THF. The reaction mixture was warmed to
room temperature and quenched with 1:1 MeOH/AcOH (0.2 mL).
Concentration of the solvent followed by chromatographic separa-
tion on silica gel afforded 19 as a pale yellow solid (0.3 g, 46%). 1H
NMR (CDCl3): δ7.67 (d, J = 8.7 Hz, 1H), 6.78 (d, J = 8.6 Hz, 1H),
6.32 (s, 1H), 4.35-4.33 (m, 1H), 3.84 (s, 3H), 1.89-1.68 (m, 8H). 13
C
1
NMR (CDCl3): δ 164.5, 162.8, 162.3, 124.9, 112.9, 109.8, 103.1, 55.8,
55.0, 32.2, 24.4. LC-MS (ESI) calcd for C13H15NO3 [M þ H]þ,
233.10; found, 232.90.
12 (0.200 g, 85%) as a colorless amorphous solid. H NMR
(300 MHz, DMSO-d6): δ 10.36 (s, 1H), 7.60 (d, J = 8.5 Hz, 1H),
7.20 (s, 1H), 6.80 (d, J = 8.6 Hz, 1H), 4.84-4.81 (m, 1H),
2.12-1.98 (m, 2H), 1.75-1.60 (m, 6H). 13C NMR (75 MHz,
DMSO-d6): δ 164.8, 161.3, 142.5, 127.4, 117.2, 115.6, 106.9,
54.6, 32.1, 24.4. LC-MS (ESI) calcd for C12H13NO2S [M þ H]þ,
236.0667; found, 235.95.
3-Chloro-30-((2-cyclopentyl-3-oxo-2,3-dihydrobenzo[d]isothiazol-
6-yloxy)methyl)biphenyl-4-carboxylic Acid (14). Potassium carbo-
nate (0.052 g, 0.38 mmol) was added to a solution of 2-cyclopentyl-
6- hydroxybenzo[d]isothiazol-3(2H)-one 12 (0.075 g, 0.32 mmol)
and methyl 30-(bromomethyl)-3-chlorobiphenyl-4-carboxylate
(0.129 g, 0.38 mmol) in CH3CN (5 mL). After the mixture was
stirred for 12 h at 80 ꢀC, the organic phase was evaporated under
reduced pressure and the crude material was partioned between
water and CH2Cl2. The aqueous layer was extracted with CH2Cl2
(3 ꢀ 15 mL). The organic layer was dried using Na2SO4 and
evaporated to give methyl 3-chloro-30-((2-cyclopentyl-3-oxo-2,3-
dihydrobenzo[d]isothiazol-6-yloxy)methyl)biphenyl-4-carboxylate
13 (0.158 g, quantitative yield). The crude product was used in the
4-Chloro-30-((2-cyclopentyl-3-oxo-2,3-dihydrobenzo[d]isoxazol-
6-yloxy)methyl)biphenyl-3-carboxylic Acid (21). BBr3 (0.54 g,
2 mmol) was added dropwise to a solution of 19 (0.232 g, 1 mmol)
in anhydrous benzene (20 mL) at 0 ꢀC. The mixture was gradually
warmed toroom temperature and then heated at 80 ꢀC for 30 min.
After that the reaction mixture was cooled to room temperature
and carefully quenched with H2O (20 mL). The resulting mixture
was then heated at reflux for 1 h and then cooled. Extraction with
EtOAc and removal of the solvent in vacuo afforded the crude
demethylated product (0.170 g, 78%) which was used in the next
step without further purification. A solution of 2-cyclopentyl-6-
hydroxyybenzo[d]isoxazol-3(2H)-one (0.109 g, 0.5 mmol) was
treated with methyl 30-(bromomethyl)-4-chlorobiphenyl-3-car-
boxylate under the same conditions as described for compound
14 to give the corresponding ester in 76% yield (0.180 g). LC-MS
(ESI) calcd for C27H24ClNO5 [M þ H]þ, 477.13; found, 478.05.
The crude product obtained above was treated with LiI in

350 Journal of Medicinal Chemistry, 2011, Vol. 54, No. 1
Dhanya et al.
pyridine to give the final compound 21 (0.063 g, after HPLC
purification) as a colorless solid in 36% yield. Mp: 185-187 ꢀC.
1H NMR (DMSO-d6): δ 8.21 (s, 1H), 7.70-7.56 (m, 7H), 6.92 (d,
J = 6.1 Hz, 1H), 5.18 (s, 2H), 4.98-4.95 (m, 1H), 2.06-2.02 (m,
2H), 1.92-1.88 (m, 4H), 1.64-1.63 (m, 2H). 13C NMR (DMSO-
d6): δ 164.0, 163.4, 162.7, 139.4, 137.6, 131.7, 130.9, 129.9, 129.2,
127.1, 126.9, 125.2, 114.3, 109.4, 70.5, 95.5, 56.6, 30.2, 25.4.
LC-MS (ESI) calcd for C26H22ClNO5 [M þ H]þ, 464.13; found,
463.95. HRMS (ESI) calcd for C26H22ClNO5 [M þ H]þ, 464.1259;
found, 464.1261.
26 as a colorless solid (0.735 g, 65%). 1HNMR(DMSO-d6):δ9.96(s,
1H), 7.65 (d, J = 8.6 Hz, 1H), 6.63 (d, J = 8.5 Hz, 1H), 6.56 (s, 1H),
4.95-4.93 (m, 1H), 3.32 (t, 2H, J= 6.1 Hz), 2.73 (t, 2 H, J=6.7Hz),
1.73-1.64 (m, 4H), 1.53-1.45 (m, 4H). 13C NMR (DMSO-d6):
163.82, 160.69, 141.02, 130.29, 121.51, 114.28, 113.62, 53.44, 42.20,
28.79, 28.57, 24.52. LC-MS (ESI) calcd for C14H17NO2 [M þ H]þ,
232.13; found, 232.00.
4-Chloro-30-((2-cyclopentyl-1-oxo-1,2,3,4-tetrahydroisoqui-
nolin-6-yloxy)methyl)biphenyl-3-carboxylic Acid (28). 2-Cyclo-
pentyl-6-hydroxy-3,4-dihydroisoquinolin-1(2H)-one 26 (0.106
g, 0.5 mmol) and methyl 30-(bromomethyl)-4-chlorobiphenyl-
3-carboxylate (0.208 g, 0.6 mmol) were processed according to
the general procedure to provide methyl 4-chloro-30-((2-cyclo-
pentyl-1-oxo-1,2,3,4-tetrahydroisoquinolin-6-yloxy)methyl)-
biphenyl-3-carboxylate 27. NaOH (50% aqueous) was added to
a solution of the crude product (0.150 g, 0.3 mmol) in dioxane
(5 mL). The reaction mixture was heated at reflux for 1 h and
then cooled to room temperature. Excess solvent was removed
in vacuo, the residue was diluted with water and then acidified
using 1 M HCl. Extraction using EtOAc followed by purifica-
tion using preparative HPLC afforded 28 (0.162 g, 69% over
two steps) as a colorless solid. Mp: 147-149 ꢀC. 1H NMR
(DMSO-d6): δ 8.00 (s, 1H), 7.87-7.75 (m, 3H), 7.65-7.57 (m,
2H), 7.49-7.41 (m, 2H), 6.95-6.90 (overlapping doublets and
singlet, 2H), 5.20 (s, 2H), 4.97-4.93 (m, 1H), 3.34 (t, J = 6.1 Hz,
2H), 2.84 (t, J = 6.1 Hz, 2H), 1.69-1.46 (m, 8 H). 13C NMR
(DMSO-d6): 163.32, 161.79, 141.60, 138.58, 137.55, 131.75,
130.99, 129.84, 129.16, 128.86, 126.45,113.78, 112.80, 69.70,
53.54, 42.20, 28.81, 28.63, 23.83. LC-MS (ESI) calcd for
C28H26ClNO4 [M þ H]þ, 476.16; found, 476.00. HRMS (ESI)
calcd for C28H26ClNO4 [M þ H]þ, 476.1623; found, 476.1623.
mGluR2 in Vitro Assay. Human embryonic kidney (HEK-
293) cell lines coexpressing rat mGluR 2, 3, 4, 6, 7, or 8 and G
protein inwardly rectifying potassium (GIRK) channels16 were
grown in growth media containing 45% DMEM, 45% F-12,
10% FBS, 20 mM HEPES, 2 mM L-glutamine, antibiotic/
antimycotic, nonessential amino acids, 700 μg/mL G418, and
0.6 μg/mL puromycin at 37 ꢀC in the presence of 5% CO2. Rat
mGluR1 and five cells were cultured as described in Hemstapat
et al.25All cell culture reagents were purchased from Invitrogen
Corp. (Carlsbad, CA) unless otherwise noted. Calcium assays
were used to assess activity of compounds at mGluRs 1 and 5 as
previously described in Engers et al.26 Compound activity at the
rat group II (mGluRs 2 and 3) and group III (mGluRs 4, 6, 7,
and 8) mGluRs was assessed using thallium flux through GIRK
channels, a method that has been described in detail.16 Briefly,
cells were plated into 384-well, black-walled, clear-bottomed
poly-D-lysine-coated plates at a density of (15 000 cells/20 μL)/
well in DMEM containing 10% dialyzed FBS, 20 mM HEPES,
and 100 units/mL penicillin/streptomycin (assay media). Plated
cells were incubated overnight at 37 ꢀC in the presence of 5%
CO2. The following day, the medium was removed from the cells,
and 20 μL/well of 1.7 μM BTC-AM, an indicator dye (Invitrogen,
prepared as a stock in DMSO and mixed in a 1:1 ratio with
pluronic acid F-127) in assay buffer [Hanks’ balanced salt solution
(Invitrogen) containing 20 mM HEPES, pH 7.3] was added to the
plated cells. Cells were incubated for 1 h at room temperature, and
the dye was replaced with 20 μL of assay buffer. Test compounds
were diluted to 2 times their final desired concentration in
assay buffer. Agonists were diluted in thallium buffer [125 mM
sodium bicarbonate (added fresh the morning of the experiment),
1 mM magnesium sulfate, 1.8 mM calcium sulfate, 5 mM glucose,
12 mM thallium sulfate, and 10 mM HEPES, pH 7.3] at 5 times
the final concentration to be assayed. Cell plates and compound
plates were loaded onto a kinetic imaging plate reader (FDSS
6000, Hamamatsu Corporation, Bridgewater, NJ). Appropriate
baseline readings were taken (10 images at 1 Hz; excitation, 470 (
20 nm; emission, 540 ( 30 nm), and test compounds were added in
a 20 μL volume and incubated for 2.5 min before the addition of
10 μL of thallium buffer with or without agonist. After the addition
N-(3-Methoxyphenethyl)cyclopentanamine (23). 3-Methoxy-
phenethylamine (4.5 mL, 30 mmol) and iodocyclopentane (1.15 mL,
10 mmol) in CH3CN were irradiated for 10 min in a microwave
reactor at 110 ꢀC. After cooling to room temperature, the mixture
was diluted with CH2Cl2 and washed with NaHCO3 solution. The
organic layer was dried over anhydrous Na2SO4 and evaporated in
vacuo. The crude product was separated by silica gel chroma-
tography using hexane as eluent, and the pure product N-(3-
methoxyphenethyl)cyclopentanamine (1.45 g, 66%) was ob-
1
tained as a colorless liquid which solidified upon standing. H
NMR (CDCl3): δ 8.48 (s, 1H), 7.20 (t, J = 8.0 Hz, 1H), 6.79-
6.73 (overlapping doublets and singlet, 3H), 3.74 (s, 3H), 3.44-
3.39 (m, 1H), 3.38-3.11 (m, 4H), 1.84-1.83 (m, 2H), 1.82-1.81 (m,
4H), 1.66-1.56 (m, 2H). 13C NMR (CDCl3): δ 159.63, 140.93,
129.38, 121.07, 114.49, 111.45, 59.26, 55.18, 48.08, 32.46, 29.65,
23.84. LC-MS (ESI) calcd for C14H21NO [M þ H]þ, 220.16;
found, 220.00.
Methyl Cyclopentyl(3-methoxyphenethyl)carbamate (24). To
a solution of N-(3-methoxyphenethyl)cyclopentanamine 23 (1.31 g,
6 mmol) in diethyl ether was added triethylamine (1.3 mL, 9 mmol)
and methyl chloroformate (0.7 mL, 9 mmol) at 0 ꢀC. The reaction
mixture was gradually warmed to room temperature and stirred for
30 min. Filtration and concentration of the solvent under reduced
pressure preceded silica gel column chromatography using hexanes/
ethyl acetate to afford methyl cyclopentyl(3-methoxyphenethyl)-
carbamate as a pale yellow liquid (1.41 g, 84%). 1H NMR (CDCl3):
δ 7.19 (t, J = 7.6 Hz, 1H), 6.78-6.73 (overlapping doublets and
singlet, 3H), 4.27-4.24 (m, 1H), 3.78 (s, 3H), 3.70 (s, 3H), 3.28 (t,
J = 7.9 Hz, 2H), 2.80 (t, J = 7.9 Hz, 2H), 1.68-1.67 (m, 2H),
1.53-1.50 (m, 6H). 13C NMR (CDCl3): δ 159.63, 156.74, 140.93,
129.38, 121.07, 114.49, 111.45, 57.94, 55.09, 52.30, 45.75, 36.50,
29.37, 23.50. LC-MS (ESI) valcd for C16H23NO3 [M þ H]þ,
278.17; found, 278.00.
2-Cyclopentyl-6-methoxy-3,4-dihydroisoquinolin-1(2H)-one (25).
To a solution of methyl cyclopentyl(3-methoxyphenethyl)car-
bamate 24 (1.39 g, 5 mmol) in POCl3 (20 mL) was added P2O5
(1.4 g, 10 mmol). The reaction mixture was heated at reflux for 2 h.
Excess POCl3 was removed under reduced pressure and quenched
with ice-water. The mixture was neutralized with Na2CO3, ex-
tracted with EtOAc, and the organic phase was dried over Na2SO4.
Concentration of the solvent followed by silica gel column chro-
matography using hexanes/ethyl acetate afforded 2-cyclopentyl-6-
methoxy-3,4-dihydroisoquinolin-1(2H)-one (1.30 g, 94%). 1H
NMR (CDCl3): δ 8.00 (d, J = 8.6 Hz, 1H), 6.81 (d, J = 8.6 Hz,
1H), 6.63 (s, 1H), 5.18-5.14 (m, 1H), 3.85 (t, J = 6.7 Hz, 1H), 2.88
(t, J = 6.7 Hz, 1H), 1.88-1.70 (m, 2H), 1.64-1.63 (m, 4H), 1.62-
1.61 (m, 2H). 13C NMR (CDCl3): δ 164.44, 162.08, 139.97, 130.56,
123.05, 112.43, 111.79, 55.43, 53.70, 40.32, 28.96, 28.81, 24.57.
LC-MS (ESI) calcd for C15H19NO2 [M þ H]þ, 246.14; found,
246.00.
2-Cyclopentyl-6-hydroxy-3,4-dihydroisoquinolin-1(2H)-one (26).
BBr3 (3.7 g, 14.7 mmol) was added dropwise to a solution of
2-cyclopentyl-7-methoxy-3,4-dihydroisoquinolin-1(2H)-one 25 (1.2 g,
4.9 mmol) in benzene at 0 ꢀC. The mixture was gradually warmed to
room temperature and then heated at 80 ꢀC for 30 min. The reaction
mixture was then cooled to room temperature and carefully quenched
with H2O. The resulting mixture was then heated at reflux for 1 h and
then cooled. Extraction with EtOAc and removal of the solvent in
vacuo followed by chromatographic separation using MeOH-CHCl3
provided 2-cyclopentyl-6-hydroxy-3,4-dihydroisoquinolin-1(2H)-one

Article
Journal of Medicinal Chemistry, 2011, Vol. 54, No. 1 351
Behavioral Procedures. Apparati. Intravenous cocaine self-
administration and food-maintained responding took place in
12 Plexiglas experimental chambers (25 cm ꢀ 31 cm ꢀ 24 cm;
MED Associates, St. Albans, VT), each housed in a sound-
attenuating box (San Diego Instruments, San Diego, CA). One
wall of the chamber contained two levers, measuring approxi-
mately 3 cm in width and located approximately 3 cm above the
metal grid floor of the chamber. There was also an opaque disk
(2.5 cm diameter) mounted 10 cm above each lever which could
be illuminated by a 2.5 W, 24 V white light bulb and served as a
cue light paired with cocaine or food delivery. All data collection
and test session functions were controlled by computers and
MED-PC IV software (MED Associates).
Food Training and Food-Maintained Responding. Methodo-
logical details of food training and food-maintained responding
procedures have been described previously.27-30 Rats were
placed under food restriction ((20 g/day)/rat) and trained to
lever press for 45 mg of food pellets (Research Diets, New
Brunswick, NJ). Training started on a fixed-ratio 1 time-out 1 s
(FR1 TO1 s) schedule of reinforcement, which then changed to
FR1 TO20 s. During food training, only the active lever was
used and there was no cue light presentation. Successful acquisi-
tion of the food response was defined as earning 100 pellets
during a 60 min session. The training period lasted approxi-
mately 5 days. After successful acquisition of food-maintained
responding, these rats were allowed to continue responding for
food on an FR1 TO20 s schedule during 1 h test sessions 5-7
days per week. During these sessions, two levers (active and
inactive) were present in the box. Responses on an active lever
resulted in a food pellet delivery paired with a 20 s cue light
presentation. Responses on inactive lever had no programmed
consequences. An identical training procedure was used for both
the subjects that responded for food and the rats that later were
allowed to self-administer cocaine.
Cocaine Self-Administration Procedure. Methodological de-
tails of catheter construction and surgery and self-administra-
tion procedure have been described previously.26-29 Briefly, rats
were prepared with intravenous catheters inserted into the right
jugular vein under isoflurane anesthesia (1-1.5% isoflurane/
oxygen mixture). Cocaine self-administration training began
after 7 days of recovery from surgery during daily 1 h self-
administration testing sessions. These sessions were initiated by
extension of both the active and inactive levers. Responses at the
active lever were reinforced under an FR1 TO20 s schedule
of reinforcement by an intravenous injection of cocaine (0.05
mg/kg/infusion salt) delivered over a 2 s period in a volume of
0.05 mL. Upon completion of the operant response for cocaine
delivery, a cue light above the lever was turned on for 20 s and
signaled the time-out period, during which responses had no
consequences. Responses at the inactive lever were recorded but
had no scheduled consequences. All rats were trained to self-
administer cocaine for 21 days. The criteria for exhibiting stable
performance (more than 10 infusions per session, less than 20%
variation over three consecutive sessions) were reached by all
rats during this 21-day period.
Experimental Design for Investigating the Effects of the
mGluR2 PAM on Cocaine Self-Administration and Food-Main-
tained Responding. After completion of the cocaine self-admin-
istration training, drug treatments were initiated. Compound 14
was administered to rats (n=9) according to a within-subjects
Latin-square design. The compound was administered orally at
doses of 0, 5, 10, and 20 mg/kg with 60 min pretreatment time.
The highest dose (40 mg/kg) was administered to all rats after
completion of the Latin-square. At least three days elapsed
between drug/vehicle injections to re-establish stable self-ad-
ministration behavior (less than 20% variation over three days).
To assess possible nonspecific effects, the effects of compound
14 at doses identical to those used for cocaine self-administra-
tion were assessed in a separate group of rats (n = 8) trained to
lever-press for food during 1 h sessions. The FR1 TO20 s
of agonist, data were collected for an additional 2.5 min. Data were
analyzed using Excel (Microsoft Corp, Redmond, WA). The slope
of the fluorescence increase beginning 5 s after thallium/agonist
addition and ending 15 s after thallium/agonist addition was
calculated, corrected to vehicle and maximal agonist control slope
values, and plotted in Prism software (GraphPad Software, San
Diego, CA) to generate concentration-response curves. Potencies
were calculated from fits using a four-point parameter logistic
equation. For concentration-response curve experiments, com-
pounds were serially diluted 1:3 into 10 point concentration-
response curves and were transferred to daughter plates using an
Echo acoustic plate reformatter (Labcyte, Sunnyvale, CA). Test
compounds were applied and followed by EC20 concentrations
of glutamate. For selectivity experiments, full concentration-
response curves of glutamate or L-AP4 (for mGluR7) were
performed in the presence of a 10 μM compound, and compounds
that affected the concentration-response by less than 2-fold in
terms of potency or efficacy were designated as inactive.
Microsomal Stability in Vitro Assay. Pooled rat liver micro-
somes (BD Biosciences, no. 452701) were preincubated with test
compounds at 37.5 ꢀC for 5 min in the absence of NADPH. The
reaction was initiated by addition of NADPH and incubated
under the same conditions. The final incubation concentrations
were 4 μM test compound, 2 mM NADPH, and 1 mg/mL (total
protein) liver microsomes in phosphate-buffered saline (PBS) at
pH 7.4. One aliquot (100 μL) of the incubation mixture was
withdrawn at 15 min time points and combined immediately
with 100 μL of ACN/MeOH. After mixing, the sample was
centrifuged at approximately 13 000 rpm for 12 min. The super-
natant was filtered and transferred into an autosampler vial, and
the amount of test compound was quantified using a Shimadzu
LC-MS 2010EV mass spectrometer. The change of the AUC
(area under the curve) of the parent compound as a function of
time was used as a measure of microsomal stability. Test com-
pounds were run in duplicate with a positive control.
Plasma Stability in Vitro Assay. A 20 μL aliquot of a 10 mM
solution in DMSO of the test compound was added to 2.0 mL of
heparinized rat plasma (Lampire, P1-150N) to obtain a 100 μM
final solution. The mixture was incubated for 1 h at 37.5 ꢀC.
Aliquots of 100 μL were taken at 15 min intervals and diluted with
100 μL of MeOH/ACN. After mixing, the sample was centrifuged
at approximately 13 000 rpm for 12 min. The supernatant was
filtered and transferred into an autosampler vial, and the amount
of test compound was quantified using the Shimadzu LC-MS
2010EV system. The change of the AUC of the parent compound
in function of time was used as a measure of plasma stability.
Parallel Artificial Membrane Permeation Assay (PAMPA).
A 96-well microtiter plate (Millipore, no. MSSACCEPTOR)
was completely filled with aqueous buffer solution (pH 7.4)
and covered with a microtiter filterplate (Millipore, no.
MAPBMN310) to create a sort of sandwich construction. The
hydrophobic filter material was impregnated with a 10% solu-
tion of polar brain lipid extract in chloroform (Avanti) as the
artificial membrane, and the organic solvent was allowed to
completely evaporate. Permeation studies were started by the
transfer of 200 μL of a 100 μM test compound solution on top of
the filter plate. In general phosphate pH 7.2 buffer was used. The
maximum DMSO content of the stock solutions was <1.5%. In
parallel, an equilibrium solution lacking a membrane was pre-
pared using the exact concentrations and specifications but
lacking the membrane. The concentrations of the acceptor and
equilibrium solutions were determined using the Shimadzu
LC-MS 2010EV and AUC methods. The acceptor plate and
equilibrium plate concentrations were used to calculate the
permeability rate (log Pe) of the compounds. The log Pe values
were calculated using the following equation:
logPe ¼ logfðCÞ½ - lnð1 - ½drugꢁacceptor=½drugꢁequilibriumÞꢁg
C ¼ ðVDVAÞ=½ðVD þ VAÞðareaÞðtimeÞꢁ

352 Journal of Medicinal Chemistry, 2011, Vol. 54, No. 1
Dhanya et al.
schedule of reinforcement used for food-maintained responding
was identical in all parameters to the schedule under which
cocaine was self-administered.
excitatory inputs to brain reward areas by nicotine. Neuron 2000, 27,
349–357. (h) Markou, A. Metabotropic glutamate receptor antagonists:
novel therapeutics for nicotine dependence and depression? Biol.
Psychiatry 2007, 61, 17–22. (i) Ungless, M. A.; Whistler, J. L.;
Malenka, R. C.; Bonci, A. Single cocaine exposure in vivo induces
long-term potentiation in dopamine neurons. Nature 2001, 411,
583–587.
Statistical Analyses. Intravenous self-administration and
food-maintained responding data were expressed as a percen-
tage of the baseline number of rewards earned, with baseline
defined as the mean number of rewards earned during the 3 days
before each drug testing session. Percent values are presented to
allow for direct comparisons for data derived from the two
different reinforcers (i.e., cocaine and food). Acute effects of
compound 14 on cocaine self-administration and food-main-
tained responding were analyzed using two-way repeated-mea-
sures ANOVA, with Dose as the within-subjects factor and
Reinforcer (food or cocaine) as the between-subject factor. Post
hoc comparisons were conducted with Newman-Keuls and
Bonferroni tests. The criterion for significance was set at 0.05.
Results. The number of baseline cocaine infusions was 20 (
4.0 (mean ( SEM), and the number of baseline food pellets
earned was 100 ( 0.0 (mean ( SEM). A two-way ANOVA on
the number of baseline cocaine/food infusions earned during the
three baseline days prior to the drug treatment days indicated no
significant differences across days, demonstrating the stability
of baseline food and cocaine self-administration in rats during
the experiment (data not shown).
Systemic administration of compound 14 significantly de-
creased both cocaine and food self-administration in rats
(Figure 2 in main text). A two-way ANOVA revealed significant
main effects for the factor compound 14 Dose (F4,60 =14.88,
p<0.0001), the factor Reinforcer (F1,60=35.51, p < 0.0001), and
their interaction (F4,60=8.75, p<0.0001). Post hoc tests showed
a significant decrease in cocaine intake after administration of
20 mg/kg (p < 0.01) and 40 mg/kg (p < 0.001) of compound 14
compared with the vehicle treatment condition. Compound 14
had no effect on inactive lever presses at any of the doses
tested (data not shown). Compound 14 also decreased food-
maintained responding, and this effect was significant only at
the highest dose used (40 mg/kg). Additionally, post hoc tests
comparing the effects of the same dose of compound 14 on
cocaine- and food-maintained responding indicated that com-
pound 14 had more pronounced effect in decreasing cocaine
compared to food self-administration (Figure 2).
(4) (a) Moran, M. M.; McFarland, K.; Melendez, R. I.; Kalivas, P. W.;
Seamans, J. K. Cystine/glutamate exchange regulates metabotro-
pic glutamate receptor presynaptic inhibition of excitatory trans-
mission and vulnerability to cocaine seeking. J. Neurosci. 2005, 25,
6389–6393. (b) Xi, Z. X.; Ramamoorthy, S.; Baker, D. A.; Shen, H.;
Samuvel, D. J.; Kalivas, P. W. Modulation of group II metabotropic
glutamate receptor signaling by chronic cocaine. J. Pharmacol. Exp.
Ther. 2002, 303, 608–615.
(5) (a) Feltenstein, M. W.; See, R. E. The neurocircuitry of addiction:
an overview. Br. J. Pharmacol. 2008, 154, 261–274. (b) Koob, G. F.
Neuroadaptive mechanisms of addiction: studies on the extended
amygdala. Eur. Neuropsychopharmacol. 2003, 13, 442–452. (c)
Schaffhauser, H.; Rowe, B. A.; Morales, S.; Chavez-Noriega, L. E.;
Yin, R.; Jachec, C. Pharmacological characterization and identification
of amino acids involved in the positive modulation of metabotropic
glutamate receptor subtype 2. Mol. Pharmacol. 2003, 64, 798–810. (d)
Wright, R. A.; Arnold, M. B.; Wheeler, W. J.; Ornstein, P, L.; Schoepp,
D. D. [3H]LY341495 binding to group II metabotropic glutamate
receptors in rat brain. J. Pharmacol. Exp. Ther. 2001, 298, 453–460.
(6) (a) Adewale, A. S.; Platt, D. M.; Spealman, R. D. Pharmacological
stimulation of group ii metabotropic glutamate receptors reduces
cocaine self-administration and cocaine-induced reinstatement of
drug seeking in squirrel monkeys. J. Pharmacol. Exp. Ther. 2006,
318, 922–931. (b) Aujla, H.; Martin-Fardon, R.; Weiss, F. Rats with
extended access to cocaine exhibit increased stress reactivity and
sensitivity to the anxiolytic-like effects of the mGluR 2/3 agonist
LY379268 during abstinence. Neuropharmacology 2008, 33, 1818–
1826. (c) Baptista, M. A.; Martin-Fardon, R.; Weiss, F. Preferential
effects of the metabotropic glutamate 2/3 receptor agonist LY379268 on
conditioned reinstatement versus primary reinforcement: comparison
between cocaine and a potent conventional reinforcer. J. Neurosci.
2004, 24, 4723–4727. (d) Lee, B.; Platt, D. M.; Rowlett, J. K.; Adewale,
A. S.; Spealman, R. D. Attenuation of behavioral effects of cocaine by
the metabotropic glutamate receptor 5 antagonist 2-methyl-6-(phenyl-
ethynyl)-pyridine in squirrel monkeys: comparison with dizocilpine.
J. Pharmacol. Exp. Ther. 2005, 312, 1232–1240. (e) Peters, J.;
Kalivas, P. W. The group II metabotropic glutamate receptor agonist,
LY379268, inhibits both cocaine- and food-seeking behavior in rats.
Psychopharmacology 2006, 186, 143–149. (f) Weiss, F. Neurobiology
of craving, conditioned reward and relapse. Curr. Opin. Pharmacol.
2005, 5, 9–19. (g) Monn, J. A.; Valli, M. J; Massey, S. M; Hansen,
M. M.; Kress, T. J.; Wepsiec, J. P.; Harkness, A. R.; Grutsch, J. L, Jr.;
Wright, R. A.; Johnson, B. G.; Andis, S. L.; Kingston, A.; Tomlinson,
R.; Lewis, R.; Griffey, K. R.; Tizzano, J. P.; Schoepp, D. D. Synthesis,
pharmacological characterization, and molecular modeling of hetero-
bicyclic amino acids related to (þ)-2-aminobicyclo[3.1.0] hexane-2,
6-dicarboxylic acid (LY354740): identification of two new potent,
selective, and systemically active agonists for group II metabotropic
glutamate receptors. J. Med. Chem. 1999, 42, 1027–1040. (h) Conn,
P. J.; Pin, J. P. Pharmacology and functions of metabotropic glutamate
receptors. Annu. Rev. Pharmacol. Toxicol. 1997, 37, 205–237.
(7) Xi, Z. X.; Baker, D. A.; Shen, H.; Carson, D. S.; Kalivas, P. W.
Group II metabotropic glutamate receptors modulate extracellular
glutamate in the nucleus accumbens. J. Pharmacol. Exp. Ther.
2002, 300, 162–171.
(8) Jin, X.; Semenova, S.; Yang, L.; Ardecky, A.; Sheffler, D. J.;
Dahl, R.; Conn, J. P.; Cosford, N. D. P.; Markou, M. The
mGluR2 positive allosteric modulator BINA decreases cocaine
self-administration, cue-induced cocaine-seeking and counteracts
cocaine-induced enhancement of brain reward function in rats.
Neuropsychopharmacology 2010, 35, 2021–2036.
(9) Bossert, J. M.; Poles, G. C.; Sheffler-Collins, S. I.; Ghitza, U. E.
The mGluR2/3 agonist LY379268 attenuates context- and discrete
cue-induced reinstatement of sucrose seeking but not sucrose self-
administration in rats. Behav. Brain Res. 2006, 173, 148–152.
(10) Cartmell, J.; Schoepp, D. D. Regulation of neurotransmitter
release by metabotropic glutamate receptors. J. Neurochem. 2000,
75, 889–907.
(11) (a) Pinkerton, A. B.; Cube, R. V.; Hutchinson, J. H.; Rowe, B. A.;
Schaffhauser, H.; Zhao, X.; Daggett, L. P.; Vernier, J. M. Allos-
teric potentiators of the metabotropic glutamate receptor 2
(mGlu2). Part 1: Identification and synthesis of phenyl-tetrazolyl
acetophenones. Bioorg. Med. Chem. Lett. 2004, 14, 5329–5332. (b)
Hu, E.; Chua, P. C.; Tehrani, L.; Nagasawa, J. Y.; Pinkerton, A. B.;
Rowe, B. A.; Vernier, J.-M.; Hutchinson, J. H.; Cosford, N. D. P.
Acknowledgment. This work was supported by National
Institutes of Health Grant R01 DA023926 to N.D.P.C.
The authors thank Dr. Xinchun Jin for collection of the
cocaine and food self-administration data, and Dr. Anthony
Pinkerton for helpful comments during the preparation of the
manuscript.
References
(1) (a) Dackis, C. A.; O’Brien, C. P. Cocaine dependence: a disease of
the brain’s reward centers. J. Subst. Abuse Treat. 2001, 21, 111–117.
(b) Leshner, A. I. Addiction is a brain disease, and it matters. Science
1997, 278, 45–47. (c) Ohishi, H.; Neki, A.; Mizuno, N. Distribution of a
metabotropic glutamate receptor, mGluR2, in the central nervous
system of the rat and mouse: an immunohistochemical study with a
monoclonal antibody. Neurosci. Res. 1998, 30, 65–82.
(2) Yuferov, V.; Butelman, E. R.; Kreek, M. J. Biological clock:
biological clocks may modulate drug addiction. Eur. J. Hum.
Genet. 2005, 13, 1101–1103.
(3) (a) Gass, J. T.; Olive, M. F. Glutamatergic substrates of drug
addiction and alcoholism. Biochem. Pharmacol. 2008, 75, 218–265.
(b) Kalivas, P. W. Glutamate systems in cocaine addiction. Curr. Opin.
Pharmacol. 2004, 4, 23–29. (c) Kalivas, P. W. The glutamate homeo-
stasis hypothesis of addiction. Nat. Rev. 2009, 10, 561–572. (d)
Kalivas, P. W.; Duffy, P. Repeated cocaine administration alters extra-
cellular glutamate in the ventral tegmental area. J. Neurochem. 1998,
70, 1497–1502. (e) Kenny, P. J.; Markou, A. The ups and downs of
addiction: role of metabotropic glutamate receptors. Trends Pharma-
col. Sci. 2004, 25 (5), 265. (f) Knackstedt, L. A.; Kalivas, P. W.
Glutamate and reinstatement. Curr. Opin. Pharmacol. 2009, 9, 59–64.
(g) Mansvelder, H. D.; McGehee, D. S. Long-term potentiation of

Article
Pyrimidine methyl anilines: selective potentiators for the metabotropic
Journal of Medicinal Chemistry, 2011, Vol. 54, No. 1 353
Magliaro, B. C.; Hutson, P. H.; O'Brien, J. A.; Huszar, S. L.; Uslaner,
J. M.; Fillgrove, K. L.; Tang, C.; Kuo, Y.; Sur, S. M.; Hartman, G. D.
3-Aryl-5-phenoxymethyl-1,3-oxazolidin-2-ones as positive allosteric
modulators of mGluR2 for the treatment of schizophrenia: hit-to-lead
efforts. Bioorg. Med. Chem. Lett. 2010, 20, 3129–3133.
glutamate 2 receptor. Bioorg. Med. Chem. Lett. 2004, 14, 5071–5074.
(c) Pinkerton, A. B.; Cube, R. V.; Hutchinson, J. H.; James, J. K.;
Gardner, M. F.; Rowe, B. A.; Schaffhauser, H.; Rodriguez, D. E.;
Campbell, U. C.; Daggett, L. P.; Vernier, J.-M. Allosteric potentiators of
the metabotropic glutamate receptor 2 (mGlu2). Part 3: Identification
and biological activity of indanone containing mGlu2 receptor poten-
tiators. Bioorg. Med. Chem. Lett. 2005, 15, 1565–1571. (d) Johnson,
M. P.; Baez, M.; Jagdmann, G. E., Jr.; Britton, T. C.; Large, T. H.;
Callagaro, D. O.; Tizzano, J. P.; Monn, J. A.; Schoepp, D. D. Discovert
of allosteric potentiators for the metabotropic glutamate 2 receptor:
synthesis and subtype selectivity of N-(4-(2-methoxyphenoxy) phenyl)-
N-(2,2,2-trifluroethylsulfonyl)pyrid-3-ylmethyl-amine. J. Med. Chem.
2003, 46, 3189–3192. (e) Pinkerton, A. B.; Vernier, J.-M.; Schaffhauser,
H.; Rowe, A.; Campbell, U., C; Rodriguez, D. E.; Lorrain, D. S.; Baccei
Christopher, S.; Daggett, L. P.; Bristow, L. J. Phenyl-tetrazolyl acetophe-
nones: discovery of positive allosteric potentiatiors for the metabotropic
glutamate 2 receptor. J. Med. Chem. 2004, 47, 4595–4599. (f) Govek,
S. P.; Bonnefous, C.; Hutchinson, J. H.; Kamenecka, T.; McQuiston, J.;
Pracitto, R.; Zhao, L. X.; Gardner, M. F.; James, J. K.; Daggett, L. P.;
Rowe, B. A.; Schaffhauser, H.; Bristow, L. J.; Campbell, U. C.; Rodriguez,
D. E.; Vernier, J.-M. Benzazoles as allosteric potentiators of metabotropic
glutamate receptor 2 (mGluR2): efficacy in an animal model for schizo-
phrenia. Bioorg. Med. Chem. Lett. 2005, 15, 4068–4072. (g) Duplantier,
A. J.; Efremov, I.; Candler, J.; Doran, A. C.; Ganong, A. H.; Haas, J. A.;
Hanks, A. N.; Kraus, K. G.; Lazzaro, J. T.; Lu, J.; Maklad, N.; McCarthy,
S. A.; O'Sullivan, T. J.; Rogers, B. N.; Siuciak, J. A.; Spracklin, D. K.;
Zhang, L. 3-Benzyl-1,3-oxazolidin-2-ones as mGluR2 positive allosteric
modulators: hit-to lead and lead optimization. Bioorg. Med. Chem. Lett.
2009, 19, 4068–4072.(h) Cacciola, J.; Empfield, J.; Folmer, J.; Hunter,
A. M.; Throner, S. Metabotropic Glutamate Receptor Isoxazole Ligands
and Their Use as Potentiators US2009/0306158 A1, 2009.(i) Tresadern,
G.; Cid, J. M.; Macdonald, G. J.; Vega, J. A.; de Lucas, A. I.; Garcia, A.;
Matesanz, E.; L., M.; Oehlrich, D.; Lavreysen, H.; Biesmans, I.; Trabanco,
A. Scaffold hopping from pyridones to imidazo[1,2-a]pyridines. New
positive allosteric modulators of metabotropic glutamate 2 receptor.
Bioorg. Med. Chem. Lett. 2010, 1, 175–179.
(16) Niswender, C. M.; Johnson, K. A.; Luo, Q.; Ayala, J. E.; Kim, C.;
Conn, P. J.; Weaver, C. D. A novel assay of Gi/o-linked G protein-
coupled receptor coupling to potassium channels provides new
insights into the pharmacology of the group III metabotropic
glutamate receptors. Mol. Pharmacol. 2008, 73, 1213–1224.
(17) Favor, D. A.; Powers, J. J.; Repine, J. T.; White, A. D. Isoindole
Derivatives. WO2008/020306, Feb 21, 2008.
(18) Hillemann, C. L. Herbicidal Sulfonamides. US1986/4632693, Dec
1986.
(19) Correa, A.; Tellitu, I.; Domınguez, E.; SanMartin, R. Novel
´
alternative for N-S bond formation and its application to the
synthesis of benzisothiazol-3-ones. Org. Lett. 2006, 8, 4811–4813.
(20) Guo-qiang, S. The first general synthesis of N-substituted 1,2-
benzisoxazolin-3-ones. Tetrahedron Lett. 2000, 41, 2295–2298.
(21) Wang, X.-J.; Tan, J.; Grozinger, K. A significantly improved
condition for cyclization of phenethylcarbamates to N-alkylated
3,4-dihydroisoquinolones. Tetrahedron Lett. 1998, 39, 6609–6612.
(22) Di, L.; Kerns, E. H.; Fan, K.; McConnell, O. J.; Carter, G. T. High
throughput artificial membrane permeability assay for blood-
brain barrier. Eur. J. Med. Chem. 2003, 38, 223–232.
(23) Hinde, N. J.; Hall, C. D. Kinetics and mechanism of the formation
of mono- and di-phthalate esters catalysed by titanium and tin
alkoxides. J. Chem. Soc., Perkin Trans. 1998, 2, 1249–1256.
(24) Wyrick, S. D.; Smith, F. T.; Kemp, W. E.; Grippo, A. A. Effects
of [(N-alkyl-1,3-dioxo-l∼,3H-isoindolin-5-yl)oxy]alkanoic acids,
[(N-alkyl-l-oxo-1H,3H-isoindolin-5-y1)oxy]butanoic acids, and re-
lated derivatives on chloride influx in primary astroglial cultures.
J. Med. Chem. 1987, 30, 1798–1806.
(25) Hemstapat, K.; Da Costa, H.; Nong, Y.; Brady, A. E.; Luo, Q.;
Niswender, C. M.; Tamagnan, G. D.; Conn, P. J. A novel family
of potent negative allosteric modulators of group II metabo-
tropic glutamate receptors. J. Pharmacol. Exp. Ther. 2007, 322,
254–264.
(26) Engers, D. W; Niswender, C. M.; Weaver, C. D.; Jadhav, S.;
Menon, U. N.; Zamorano, R.; Conn, P. J.; Lindsley, C. W.;
Hopkins, C. R. Synthesis and evaluation of a series of heterobiaryl
amides that are centrally penetrant metabotropic glutamate recep-
tor 4 (mGluR4) positive allosteric modulators (PAMs). J. Med.
Chem. 2009, 52, 4115–4118.
(12) Gjoni, T.; Urwyler, S. Receptor activation involving positive
allosteric modulation, unlike full agonism, does not result in
GABAB receptor desensitization. Neuropharmacology 2008, 55,
1293–1299.
(13) Bonnefous, C.; Vernier, J.-M.; Hutchinson, J. H.; Gardner, M. F.;
Cramer, M.; James., J. K.; Rowe, B. A.; Daggett, L. P.; Schaffhauser,
H.; Kamenecka, T. M. Biphenyl-indanones: allosteric potentiators of
the metabotropic glutamate subtype 2 receptors. Bioorg. Med. Chem.
Lett. 2005, 15, 4354–4358.
(14) Galici, R.; Jones, C. K.; Hemstapat, K.; Nong, Y.; Echemndia,
N. G.; Williams, L. C.; de Paulis, T.; Conn, J. P. Biphenyl-indanone
A, a positive allosteric modulator of the metabotropic receptor
subtype 2, has antipsychotic-and anxiolytic-like effects in mice.
J. Pharmacol. Exp. Ther. 2006, 318, 173–185.
(15) (a) D’Alessandro, P. L.; Corti, C.; Roth, A.; Ugolini, A.; Sava, A.;
Montanari, D.; Bianchi, F.; Garland, S. L.; Powney, B.; Koppe,
E. L.; Rocheville, M.; Osborne, G.; Perez, P.; de la Fuente, J.;
Frailes, M. D. L.; Smith, P. W.; Branch, C.; Nash, D.; Watson, S. P.
The identification of structurally novel, selective, orally bioavail-
able positive modulators of mGluR2. Bioorg. Med. Chem. Lett.
2010, 20, 759–762. (b) Brnardic, E. J.; Fraley, M. E.; Garbaccio, R. M.;
Layton, M. E.; Sanders, J. M.; Culberson, C.; Jacobson, M. A.;
(27) Kenny, P. J.; Paterson, N. E.; Boutrel, B.; Semenova, S.; Harrison,
A. A.; Gasparini, F.; Koob, G. F.; Skoubis, P. D.; Markou, A.
Metabotropic glutamate 5 receptor antagonist MPEP decreased
nicotine and cocaine self-administration but not nicotine and
cocaine-induced facilitation of brain reward function in rats.
Ann. N.Y. Acad. Sci. 2003, 1003, 415–418.
(28) Paterson, N. E.; Markou, A. Increased motivation for self-
administered cocaine after escalated cocaine intake. NeuroReport
2003, 14, 2229–2232.
(29) Paterson, N, E.; Markou, A. The metabotropic glutamate receptor
5 antagonist MPEP decreased break points for nicotine, cocaine
and food in rats. Psychopharmacology (Berlin) 2005, 179, 255–261.
(30) Semenova, S; Markou, A. Cocaine-seeking behavior after extended
cocaine-free periods in rats: role of conditioned stimuli. Psycho-
pharmacology (Berlin) 2003, 168, 192–200.