Synthesis and biological evaluation of 3-biphenyl-4-yl-4-phenyl-4 h -1,2,4-triazoles as novel glycine transporter 1 inhibitors

Article abstract of DOI:10.1021/jm101031u

We describe the preparation and evaluation of a novel series of glycine transporter 1 (GlyT1) inhibitors derived from a high-throughput screening hit. The SAR studies resulted in the discovery of 3-biphenyl-4-yl-4-(2-fluorophenyl)- 5-isopropyl-4H-1,2,4-tr

Full text of DOI:10.1021/jm101031u

J. Med. Chem. 2011, 54, 387–391 387
DOI: 10.1021/jm101031u
Synthesis and Biological Evaluation of 3-Biphenyl-4-yl-4-phenyl-4H-1,2,4-triazoles
as Novel Glycine Transporter 1 Inhibitors
Takashi Sugane,*,† Takahiko Tobe,† Wataru Hamaguchi,† Itsuro Shimada,† Kyoichi Maeno,† Junji Miyata,† Takeshi Suzuki,†
Tetsuya Kimizuka,‡ Atsuyuki Kohara,† Takuma Morita,§ Hitoshi Doihara,† Kyouko Saita,† Masaki Aota,† Masako Furutani,†
Yoshiaki Shimada,† Noritaka Hamada,† Shuichi Sakamoto,^ and Shin-ichi Tsukamoto†
†Drug Discovery Research, Astellas Pharma Inc., 21, Miyukigaoka, Tsukuba-shi, Ibaraki 305-8585, Japan, ‡Intellectual Property, Astellas
Pharma Inc., 2-3-11, Nihonbashi-Honcho, Chuo-ku, Tokyo 103-8411, Japan, §Astellas Research Technologies Co., Ltd., 21, Miyukigaoka,
Tsukuba-shi, Ibaraki 305-8585, Japan, and ^Technology, Astellas Pharma Inc., 3-17-1, Hasune, Itabashi, Tokyo 174-8612, Japan
Received August 9, 2010
We describe the preparation and evaluation of a novel series of glycine transporter 1 (GlyT1) inhibitors
derived from a high-throughput screening hit. The SAR studies resulted in the discovery of 3-biphenyl-
4-yl-4-(2-fluorophenyl)-5-isopropyl-4H-1,2,4-triazole (6p). A pharmacokinetic study was also con-
ducted and revealed that 6p had excellent oral bioavailability and ameliorated learning impairment in
passive avoidance tasks in mice.
Introduction
the NMDA receptors may be useful as therapeutic agents for
schizophrenia, dementia, and related disorders.
In the central nervous system (CNSa), specific sodium/
chloride-dependent transporters regulate glycine levels in the
synapse. The actions of glycine are terminated by reuptake via
two high affinity glycine transporters referred to as glycine
transporter 1 (GlyT1) and glycine transporter 2 (GlyT2).1,2
GlyT1 hasa widespreaddistributioninforebrain areassuchas
cortex and hippocampus. GlyT1 is thought to be colocalized
with the N-methyl-D-aspartate (NMDA) receptors,3 control-
ling NMDA receptor function. The expression of GlyT2 is
limited to the spinal cord, brain stem, and cerebellum, and
GlyT2 is therefore thought to control the function of the
strychnine-sensitive glycine receptor.
The hypofunction of NMDA receptors is related to various
human diseases. For example, the functional deterioration of
the NMDA receptors may have a role in schizophrenia with
clinical studies demonstrating that positive, negative, and
cognitive symptoms in schizophrenic patients are ameliorated
with glycine, D-serine (a glycine site agonist of the NMDA
receptors), and sarcosine (a weak GlyT1 inhibitor) when
added to conventional therapy.4
N-[3-(40-Fluorophenyl)-3-(40-phenylphenoxy)propyl]sarcosine
(1),7 an analogue of sarcosine, was reported as a selective glycine
transporter inhibitor (Figure 1), with preclinical in vivo studies in
rodents demonstrating 1to have similar efficacy as clinically useful
antipsychotics,8,9 and therefore, many sarcosine analogues were
subsequently synthesized and reported in the literature.2,10-13
Pharmaceutical companies, however, recently launched new
efforts to investigate nonsubstrate based inhibitors, and a
wide variety of compounds without a carboxylate group have
subsequently been disclosed.2,10-13 Among these compounds,
[4-(3-fluoro-5-trifluoromethylpyridin-2-yl)piperazin-1-yl][5-
methanesulfonyl-2-((S)-2,2,2-trifluoro-1-methylethoxy)-
phenyl]methanone (2)14 was reported to show a beneficial
effect in schizophrenic patients in a recent phase II clinical trial.
Here, we report the identification of structurally novel non-
sarcosine derived GlyT1 inhibitors useful for studying the
effects of GlyT1 inhibition in vivo. We also describe the
detailed structure-activity relationships (SARs) that we have
established on our novel GlyT1 inhibitors. Our initial effort
began with the high-throughput screening (HTS) campaign,
which led to the discovery of 3-biphenyl-4-yl-4-(2-methoxy-
phenyl)-5-methyl-4H-1,2,4-triazole (3) with a novel structure.
Compound 3 was selected as a lead for the following SAR
studies.
The NMDA receptors are also associated with memory and
learning.5 For example, the activation of the NMDA recep-
tors is involved in the formation of long-term potentiation
(LTP), which is considered one of the mechanisms of memory
and learning at the neuronal level.6
These findings suggest that medications aimed at inhibiting
the activity of GlyT1 and thereby activating the function of
Chemistry
The 1,2,4-triazole derivatives were prepared as illustrated in
Schemes 1-3, with Scheme 1 showing the first general method
in which the 1,3,4-oxadiazole derivatives were utilized as
intermediates. 4-Phenylbenzoyl hydrazide (4) wasfirstconverted
to diacyl hydrazides. Subsequent cyclization using POCl3 gave
1,3,4-oxadiazoles 5. Reactions of 5 with amines under acidic
conditions produced the corresponding 1,2,4-triazole derivatives
6a-q.15
*To whom correspondence should be addressed. Phone: þ81-29-863-
6678. Fax: þ81-29-852-5387. E-mail: takashi.sugane@jp.astellas.com.
a Abbreviations: ACSF, artificial cerebrospinal fluid; AMPA, R-amino-3-
hydroxy-5-methyl-4-isoxazolepropionic acid; CNS, central nervous system;
GABA, γ-aminobutyric acid; GlyT, glycine transporter; HTS, high-
throughput screening; NBS, N-bromosuccinimide; NMDA, N-methyl-D-
aspartate; PAMPA, parallel artificial membrane permeability assay; SAR,
structure-activity relationship; 5-HT, 5-hydroxytryptamine.
r
2010 American Chemical Society
Published on Web 12/09/2010
pubs.acs.org/jmc

388 Journal of Medicinal Chemistry, 2011, Vol. 54, No. 1
Sugane et al.
Scheme 3. Synthesis of 1,2,4-Triazole Derivativesa
Figure 1. GlyT1 inhibitors.
Scheme 1. Synthesis of 1,2,4-Triazole Derivatives via 1,3,4-
Oxadiazolesa
a Reagents and conditions: (a) Pd(PPh3)4, Zn(CN)2, DMF, 140 ꢀC;
(b) NBS, AcOH, CCl4, reflux; (c) MeNH2/H2O, sealed tube, 200 ꢀC;
(d) NaOMe, MeOH, reflux; (e) 2-fluorophenylisothiocyanate, EtOH;
(f ) NaOH aq., reflux; (g) MeI, K2CO3, CH3CN; (h) Oxone, MeOH,
H2O, 70 ꢀC.
a Reagents and conditions: (a) (R1CO)2O, pyridine; (b) R1COCl,
Et3N, THF; (c) POCl3, 100 ꢀC; (d) R2-NH2, TsOH H2O or (1S)-10-
3
We investigated the influence of the 2-methoxyphenyl
moiety on the 4-position of the triazole ring (Table 1).
Removal of methoxy group of 3 resulted in the retention of
GlyT1 inhibitory activity (6a, IC50 = 0.88 μM). We therefore
subsequently examined the necessity of the phenyl group on
the 4-position of the triazole ring by replacing it with a
cyclohexyl or isopropyl group. The cyclohexyl substituted
analogue showed a 5-fold loss of activity (6b, IC50 = 5.2 μM),
camphorsulfonic acid, 160 ꢀC.
Scheme 2. Synthesis of 1,2,4-Triazole Derivatives via Methyl
Thioimidatesa
and the isopropyl derivative showed far less activity (6c, IC50
=
35 μM) compared to 6a, suggesting that the aromatic group at
4-position of the triazole is important for GlyT1 inhibition.
Having elucidated the necessity of the benzene ring, we then
investigated the effect of substitution at the ortho, meta, and
para positions of the phenyl group using fluoro analogues
6d-f. While meta and para substituted analogues 6e and 6f
a Reagents and Conditions: (a) Lawesson’s reagent, toluene, 110 ꢀC;
(b) MeI, K2CO3, CH3CN, 50 ꢀC; (c) R5CONHNH2, TsOH.H2O or (1S)-
10-camphorsulfonic acid, DMF, 160 ꢀC.
The second general method utilizes the reaction of thioimi-
dates with acyl hydrazides as shown in Scheme 2. Amides 7
were reacted with Lawesson’s reagent to afford thioamides,
which were then treated with MeI and K2CO3 in acetonitrile
to obtain thioimidates 8. These compounds were coupled with
acylhydrazides and heated under acidic conditions toproduce
the desired 1,2,4-triazole derivatives 9a-h. Compounds 10,
12, 13, 16, and 17 were prepared as shown in Scheme 3.
showed less potent activity (6e, IC50 = 3.0 μM; 6f, IC50
>
30 μM), the ortho substituted analogue 6d showed a 4-fold
improvement in activity (6d, IC50 = 0.19 μM) compared to
the unsubstituted analogue 6a.
These results directed us to investigate other ortho substit-
uents for the phenyl group on the 4-position of the triazole.
Interestingly, many compounds showed equipotent GlyT1
inhibitory activity compared to 6d. While both electron-with-
drawing groups (6g, 6h, and 10) and electron-donating groups
(6i, 6j) were well tolerated (IC50 = 0.10-0.39 μM), when we
added several alkyl groups to the structure, activities de-
creased in order of steric bulkiness (6k-m, 9a). These results
suggest that smaller rather than larger functional groups are
favorable for conferring activity, whereas the electrostatic
factor of the substituents is not as important. Despite obtain-
ing some potent GlyT1 inhibitors, none of the compounds in
Table 1 showed high selectivity against the GlyT2 isoform,
with compound 6d, for example, showing equipotent inhibi-
tory activity for GlyT2 (IC50 = 0.34 μM; selectivity GlyT2/
GlyT1 = 1.8).
Results and Discussion
We prepared analogues of 3, incorporating changes that
would aid in elucidating the structural features required for
inhibiting GlyT1. Assays for the inhibitory activities of GlyT1
were performed according to reported protocols utilizing
[3H]glycine uptake into rat C6 glioma cells.16 This method was
validated using the published GlyT1 inhibitors; for example,
compound 1 showed potent inhibitory activity (IC50
=
0.0089 μM). The GlyT2 inhibitory activities were evaluated
in a manner similar to the GlyT1 assay using rat brainstem
cells. The typical GlyT2 inhibitor 4-benzyloxy-3,5-dimethoxy-
N-[1-(dimethylaminocyclopentyl)methyl]benzamide (Org-25543)17
showed potent activity (IC50 = 0.022 μM) on this assay.
We therefore turned our attention toward modification of
other positions of the triazole. With the 2-fluorophenyl group

Brief Article
Journal of Medicinal Chemistry, 2011, Vol. 54, No. 1 389
Table 1. In Vitro GlyT1 Inhibitory Activities of 1,2,4-Triazole Deriva-
tives 3, 6a-m, 9a, 10
Table 3. In Vitro GlyT1 Inhibitory Activities of 1,2,4-Triazole Deriva-
tives 6d,n-q, 9h, 12, 13, 16, 17
IC50 ( μM)a
IC50 ( μM)a
compd
R
rGlyT1
rGlyT2
selectivityb
compd
R
rGlyT1
rGlyT2
selectivityb
3
2-OMe
H
1.8 ( 0.30
0.88 ( 0.11
5.2 ( 1.9
35 ( 4.9
0.19 ( 0.073
3.0 ( 1.2
1.7 ( 0.46
1.4 ( 0.41
NDe
0.94
1.6
NDe
NDe
1.8
NDe
NDe
1.5
6d
9h
12
13
16
17
6n
6o
6p
6q
Me
H
0.19 ( 0.073
2.3 ( 0.85
0.34 ( 0.11
NDd
1.8
6a
6b
6c
6d
6e
6f
NDd
1.3
NHMe
OMe
SMe
SO2Me
CF3
Et
0.083 ( 0.014
0.51 ( 0.068
1.0 ( 0.090
6.5 ( 0.79
0.11 ( 0.030
0.99 ( 0.18
NDd
NDd
NDd
NDe
1.9
2-F
3-F
0.34 ( 0.11
NDd
NDd
NDd
1.0
NDe
4-F
2-Cl
>30 (42%)c
0.19 ( 0.050
0.39 ( 0.070
0.10 ( 0.028
0.24 ( 0.090
0.30 ( 0.075
0.92 ( 0.10
3.8 ( 0.66
11 ( 0.74
NDe
>10 (11%)c
0.22 ( 0.050
0.37 ( 0.020
2.6 ( 0.72
6g
6h
10
6i
0.28 ( 0.049
0.60 ( 0.020
0.26 ( 0.092
0.68 ( 0.25
0.78 ( 0.13
NDe
0.23 ( 0.092
3.3 ( 0.53
NDd
2-CF3
2-CN
2-OH
2-Me
2-Et
1.5
2.6
i-Pr
t-Bu
9.2
NDd
2.8
a Values are the mean ( standard error for three experiments. b Ratio
of the IC50 ( μM) values for rGlyT2/rGlyT1. c % inhibition at 10 μM
(solubility limit). d ND: not determined.
6j
2.6
6k
6l
NDe
NDe
NDe
NDe
2-(n-Pr)
2-(i-Pr)
2-Ph
NDe
6m
9a
NDe
>10 (15%)d
NDe
Table 4. In Vitro Membrane Permeability Study (PAMPA)a
Pe (10-6 cm/s)
a Values are the mean ( standard error for three experiments. b Ratio
of the IC50 ( μM) values for rGlyT2/rGlyT1. c % inhibition at 30 μM
(solubility limit). d % inhibition at 10 μM (solubility limit). e ND: not
determined.
compd
at pH 5.0b
at pH 6.5b
3
39
44
39
37
44
34
42
43
35
53
12
13
6o
6p
Table 2. In Vitro GlyT1 Inhibitory Activities of 1,2,4-Triazole Deriva-
tives 6d, 9b-f
a pION membrane lipid was used. b pH of donor buffer.
Considering the results summarized in Tables 1 and 2, we
assumed that 3-biphenyl-4-yl-4-phenyl-4H-1,2,4-triazole was
an essential structure for this class of GlyT1 inhibitors, and with
the exception of ortho substitution of the phenyl group at the
4-postion of the triazole, it was quite sensitive to modification.
SAR studies around the 5-position of the triazole were then
conducted (Table 3). Removal of the methyl group resulted in
a 10-fold loss of activity (9h, IC50 = 2.3 μM). We therefore
prepared some derivatives withelectron-donating groups, and
interestingly, introduction of a methylamino moiety led to a
compd
R
rGlyT1 IC50 ( μM)a
6d
9b
9c
9d
9e
9f
4-Ph
H
0.19 ( 0.073
>100 (22%)b
9.8 ( 0.20
62 ( 6.8
70 ( 15
27 ( 0.88
slight improvement in GlyT1 inhibitory activity (12, IC50
=
4-(c-C6H11
)
0.083 μM). While 12 was the most potent compound in
this series, it showed no selectivity against GlyT2 (GlyT2/
GlyT1 = 1.3). Further, while some other electron-donating
groups such as methoxy (13) and methylsulfanyl groups (16)
were introduced, they showed a 2- to 5-fold loss of GlyT1
inhibitory activity (13, IC50 = 0.51 μM; 16, IC50 = 1.0 μM)
and replacement with electron-withdrawing groups such as
SO2Me or CF3 was also unsuccessful (17, IC50 = 6.5 μM; 6n,
IC50 >10 μM).
2-Ph
3-Ph
a Values are the mean ( standard error for three experiments.
b % inhibition at 100 μM (solubility limit).
fixedatthe 4-position of the triazole ring, variationaroundthe
biphenyl moiety of 6d was explored (Table 2). Removal of the
terminal phenyl group (9b, IC50 > 100 μM) and replacement
with a cyclohexyl group (9c, IC50 = 9.8 μM) reduced activity.
While Et and i-Pr analogues 6o, 6p maintained GlyT1
inhibitory activity (6o, IC50 = 0.22 μM; 6p, IC50
=
Likewise, translocation of a phenyl group to ortho (9d, IC50
=
0.37 μM), replacement with a t-Bu group resulted in >
10-fold loss of activity (6q, IC50 = 2.6 μM). Interestingly,
the i-Pr derivative 6p had moderate selectivity for GlyT1
against GlyT2 (GlyT2/GlyT1 = 9.2), suggesting that GlyT2
62 μM) and meta (9e, IC50 = 70 μM) positions and insertion
of a methylene linker between the triazole ring and biphenyl
moiety (9f, IC50 = 27 μM) were found to be detrimental to
activity.

390 Journal of Medicinal Chemistry, 2011, Vol. 54, No. 1
Table 5. Pharmacokinetic Parameters for Compound 6pa
Sugane et al.
species
mouse
route
dose (mg/kg)
t1/2 (h)
AUC (ng h/mL)
Vd (L/kg)
CL (mL/(min kg))
3
21
Cmax (ng/mL)
365
F (%)
3
783
iv
po
1
3
4.2
2.0
7.8
1419
60
a Each value is the mean for n = 3 measurements.
revealed that 6p has a high membrane permeability (Pe =
53 ꢀ 10-6 cm/s at pH 6.5), with the other 1,2,4-triazole
derivatives 3, 12, 13, and 6o also showing high membrane
permeability, suggesting that this series of GlyT1 inhibitors
exhibits a high potential for oral absorption by passive
transcellular diffusion.
We next examined 6p in a single dose in vivo pharmacoki-
netic (PK) study in mice (Table 5), and as expected from the
results of the PAMPA, 6p showed high oral bioavailability
(F = 60%). In addition, 6p also showed good brain perme-
ability (brain/plasma ratio: 1.5-2.1) in mice.
The good brain permeability of 6p directed us to assess the
in vivo behavioral effects on hyperlocomotion induced by
(þ)-3-amino-1-hydroxypyrrolid-2-one [(þ)-HA966, an antag-
onist for Gly binding sites on the NMDA receptors]19 in
monoamine-depleted mice. As shown in Figure 2A, 6p dose-
dependently attenuated the locomotor activity,20 suggesting
that 6p increases the extracellular level of glycine, which
indirectly replaces the antagonist from glycine binding sites
ofthe NMDA receptors. Compound1 alsoblockedthe hyper-
locomotion at a dose of 10 mg/kg ip in this assay,21 showing
equipotent activity to 6p. Considering in vitro GlyT1 inhibi-
toryactivities between 1 and 6p, the good CNS permeability of
6p may have contributed to its in vivo behavioral potency.
Lastly, we evaluated the effect of 6p on (þ)-HA966-induced
learning impairment in passive avoidance tasks in mice. The
step-through latency (the time required for the mice to cross
the sensor of the dark room from the opening of the door) was
measured and adopted as an indicator of learning ability. As
shown in Figure 2B, 6p prolonged the step-through latency at
a dose of 3 mg/kg ip, indicating that 6p ameliorated learning
impairment induced by (þ)-HA966. This in vivo result sup-
ports the view that GlyT1 inhibitors may be effective for
treatment of cognitive dysfunction based on the hypogluta-
matergic theory of schizophrenia.
Figure 2. (A) Effect of 6p on (þ)-HA966-induced hyperlocomotion
in monoamine-depleted mice. (þ)-HA966 was administrated intra-
cerebroventricularly (icv). The data represent the mean ( SEM
(n = 16 in each group): (###) p < 0.001 vs (ACSF þ vehicle) group
(Student’s t test); (þ) p < 0.05, (þþ) p < 0.01 vs [(þ)-HA966 þ
vehicle] group (ANOVA followed by Dunnett’s test). (B) Effect of
6p on (þ)-HA966-induced learning impairment in passive avoid-
ance tasks in mice. (þ)-HA966 was administrated intracerebroven-
tricularly. Upper and lower whiskers represent the highest and
lowest values in each group, respectively. Upper and lower bars in
boxes represent 75 and 25%ile values in each group respectively.
The bars in boxes represent median values in each group (n =
29-32): (###) p < 0.001 vs (ACSF þ vehicle) group (Wilcoxon
rank sum test); (þ) p < 0.05 vs [(þ)-HA966 þ vehicle] group (two-
tailed Steel test).
Conclusion
Through the iterative processes of synthesis and biologi-
cal evaluation starting from the HTS hit compound 3, we
successfully established the SARs in this series of GlyT1
inhibitors, demonstrating that the 3-bipheny-4-yl-4-phenyl-
4H-1,2,4-triazole moietyisanessential core for thisnovel class
of non-sarcosine-derived GlyT1 inhibitors. Among the com-
pounds prepared in this series, 6p had improved GlyT1
inhibitory activity and selectivity against GlyT2 compared
to the HTS hit compound 3. In addition, 6p had high
membrane permeability, high oral bioavailability in mice
and displayed good CNS penetration. Furthermore, 6p effec-
tively antagonized (þ)-HA966-induced hyperlocomotion in
monoamine-depleted mice and ameliorated learning impair-
ment induced by (þ)-HA966.
inhibitory activity was more sensitive for steric bulkiness
around the 5-position of the triazole than that of GlyT1.
During the SAR studies of these novel GlyT1 inhibitors, we
derived 6p, which showed improved GlyT1 inhibitory activity
and moderate selectivity against GlyT2 compared to the HTS
hit 3. We also investigated other off-target activities of 6p
where a panel of receptors (NMDA, AMPA, strychnine-
sensitive Gly, dopamine D2, 5-HT1A/1B/2A, and vasopressin
V1A receptors) and transporters (glutamate, GABA, dopa-
mine, norepinephrine, and 5-HT transporters) were screened,
with 6p showing less than 30% affinity or inhibitory activity in
all assays at 10 μM.
Compound 6p was then profiled in an in vitro membrane
permeability study (Table 4). The parallel artificial membrane
permeability assay (PAMPA) has been widely used in the
pharmaceutical industry as a high-throughput permeability
assay to predict oral absorption.18 Evaluation by PAMPA
Experimental Section
Chemistry. General. Melting points were determined using a
€
Buchi B-545 or Yanaco MP-500D micromelting apparatus and

Brief Article
Journal of Medicinal Chemistry, 2011, Vol. 54, No. 1 391
1
were uncorrected. H NMR spectra were recorded on a JEOL
JMN-LA-300 or JEOL JMN-EX-400, and the chemical shifts
were expressed in δ (ppm) values with trimethylsilane as an
internal reference (s = singlet, d = doublet, t = triplet, q =
quartet, m = multiplet, and br = broad peak). Mass spectra
(MS) were recorded on a Hitachi M-80 or JEOL JMS-LX2000
spectrometer. HPLC analyses were conducted on Hitachi
L-7000 system using a TSKgel ODS-80TM column with UV
254 nm detection. Elemental analyses were performed with
Yanaco MT-5 (C, H, N), Elementar Vario EL III (C, H, N),
and Dionex DX-500 (S, halogene) instruments, and results were
within (0.4% of theoretical values. The purities of tested
compounds were found to be above 95% as determined by
elemental analyses.
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[5-methanesulfonyl-2-((S)-2,2,2-trifluoro-1-methylethoxy)phenyl]-
methanone (RG1678), a promising novel medicine to treat schizo-
phrenia. J. Med. Chem. 2010, 53, 4603–4614.
(15) Carlsen, H. J.; Jorgensen, K. B. Synthesis of unsymmetrically
substituted 4H-1,2,4-triazoles. J. Heterocycl. Chem. 1994, 31,
805–807.
(16) Gomeza, J.; Zafra, F.; Olivares, L.; Gimenez, C.; Aragon, C.
Regulation by phorbol esters of the glycine transporter (GLYT1)
in glioblastoma cells. Biochim. Biophys. Acta, Biomembr. 1995,
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3-Biphenyl-4-yl-4-(2-fluorophenyl)-5-methyl-4H-1,2,4-tria-
zole (6d). To a mixture of 2-(4-biphenyl)-5-methyl-1,3,4-oxadia-
zole (3.00 g, 12.7 mmol) and 2-fluoroaniline (3.70 mL, 38 mmol)
was added p-toluenesulfonic acid monohydrate (0.300 g, 1.60
mmol), and the resultant mixture was stirred at 160 ꢀC for 72 h.
After cooling at room temperature, the mixture was purified by
column chromatography on silica gel (CHCl3/MeOH = 97/3)
to give crude 6d as a brown solid. The solid was recrystallized
from EtOAc-hexane to give 6d (3.24 g, 78%) as a colorless
powder: mp 162-164 ꢀC; 1H NMR (DMSO-d6) δ 2.37 (3H, s),
7.21-7.44 (6H, m), 7.48-7.57 (7H, m); MS (FAB) m/z 330
(MHþ). Anal. (C21H16N3F) C, H, N, F.
Compounds 6a-c, 6e-q were prepared by a method similar
to that described for 6d.
3-Biphenyl-4-yl-4-(2-fluorophenyl)-5-isopropyl-4H-1,2,4-tria-
zole (6p). Mp 201-204 ꢀC; 1H NMR (DMSO-d6) δ 1.15 (3H, d,
J = 6.8 Hz), 1.28 (3H, d, J = 6.8 Hz), 2.69-2.84 (1H, m),
7.34-7.56 (7H, m), 7.63-7.72 (6H, m), 7.82 (1H, ddd, J = 9.3,
7.7, 1.7 Hz); MS (FAB) m/z 358 (MHþ). Anal. (C23H20N3F) C,
H, N, F.
4-(2-Fluorophenyl)-3-methyl-5-phenyl-4H-1,2,4-triazole (9b).
A mixture of methyl N-(2-fluorophenyl)ethanimidothioate
(300 mg, 1.64 mmol), benzohydrazide (223 mg, 1.64 mmol),
(1S)-10-camphorsulfonic acid (57.0 mg, 0.250 mmol), and N,N-
dimethylformamide (DMF, 0.5 mL) was stirred at 160 ꢀC for
1 h. After cooling at room temperature, the mixture was parti-
tioned between CHCl3 and water and the organic layer was then
washed with NaHCO3 (aq), dried over MgSO4, and concen-
trated in vacuo. The residue was purified by column chroma-
tography on silica gel (CHCl3/MeOH = 20/1) to give crude 9b
as a brown solid. The solid was recrystallized from EtOAc-
hexane to give 9b (140 mg, 34%) as a colorless powder: mp 139-
141 ꢀC; 1H NMR (DMSO-d6) δ 2.24 (3H, s), 7.33-7.72 (9H, m);
MS (FAB) m/z 254 (MHþ). Anal. (C15H12N3F) C, H, N, F.
Compounds 9a, 9c-h were prepared by a method similar to
that described for 9b.
(17) Caulfield, W. L.; Collie, I. T.; Dickins, R. S.; Epemolu, O.;
McGuire, R.; Hill, D. R.; McVey, G.; Morphy, J. R.; Rankovic,
Z.; Sundaram, H. The first potent and selective inhibitors of the
glycine transporter type 2. J. Med. Chem. 2001, 44, 2679–2682.
(18) Kansy, M.; Senner, F.; Gubernator, K. Physicochemical high
throughput screening: parallel artificial membrane permeation
assay in the description of passive absorption processes. J. Med.
Chem. 1998, 41, 1007–1010.
Supporting Information Available: Synthesis of 10, 12, and
13-17; analytical data for final compounds; additional behav-
ioral studies; biological evaluations. This material is available
free of charge via the Internet at http://pubs.acs.org.
(19) Singh, L.; Donald, A. E.; Foster, A. C.; Hutson, P. H.; Iversen,
L. L.; Iversen, S. D.; Kemp, J. A.; Leeson, P. D.; Marshall, G. R.;
Oles, R. J. Enantiomers of HA-966 (3-amino-1-hydroxypyrrolid-
2-one) exhibit distinct central nervous system effects: (þ)-HA966 is
a selective glycine/N-methyl-D-aspartate receptor antagonist, but
(-)-HA-966 is a potent gamma-butyrolactone-like sedative. Proc.
Natl. Acad. Sci. U.S.A. 1990, 87, 347–351.
(20) We did not observe any significant change in locomotor activity of
the naive mice treated only by compound 6p (10-100 mg/kg ip).
See Supporting Information.
Note Added after ASAP Publication. This manuscript pub-
lished ASAP on December 9, 2010 with an error in Scheme 3.
The correct version was published on December 14, 2010.
References
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(21) See Supporting Information.