Synthesis and receptor assay of aromatic-ethynyl-aromatic derivatives with potent mGluR5 antagonist activity

Article abstract of DOI:10.1016/j.bmc.2004.09.042

Noncompetitive antagonists of the human metabotropic glutamate receptor subtype 5 (mGluR5) have been implicated as potential therapeutics for the treatment of a variety of nervous system disorders, including pain, anxiety, and drug addiction. To discover novel noncompetitive antagonists to the mGluR5, we initiated an SAR study around the known lead compounds MPEP and M-MPEP. Our results pointed out the critical role of the para position of the two aromatic rings, which leads to inactive products and permitted the discovery of potent mGluR5 antagonists (e.g., 16, 25, 28, 34 IC₅₀ = 13.5, 11.9, 21, 15 nM, respectively). Noncompetitive antagonists of the human metabotropic glutamate receptor subtype 5 (mGluR5) have been implicated as potential therapeutics for the treatment of a variety of nervous system disorders, including pain, anxiety, and drug addiction. To discover novel noncompetitive antagonists to the mGluR5, we initiated an SAR study around the known lead compounds MPEP and M-MPEP. Our results pointed out the critical role of the para position of the two aromatic rings, which leads to inactive products and permitted the discovery of potent mGluR5 antagonists (e.g., 16, 25, 28, 34 IC₅₀ = 13.5, 11.9, 21, 15 nM, respectively).

Full text of DOI:10.1016/j.bmc.2004.09.042

Bioorganic & Medicinal Chemistry 13 (2005) 197–209
Synthesis and receptor assay of aromatic–ethynyl–aromatic
derivatives with potent mGluR5 antagonist activity
David Alagille,a Ronald M. Baldwin,a Bryan L. Roth,b Jarda T. Wroblewski,c
Ewa Grajkowskac and Gilles D. Tamagnana,d,
*
aDepartment of Psychiatry, Yale University and VA Connecticut/116A2, 950 Campbell Avenue, West Haven, CT 06516, USA
bDepartment of Biochemistry and NIMH Psychoactive Drug Screening, Program, Case Western Reserve University School
of Medicine, Cleveland, OH 44106, USA and the NIMH Psychoactive Drug Screening Program
cDepartment of Pharmacology, Georgetown University Medical Center, 3900 Reservoir Road, N.W., Washington, DC 20007, USA
dInstitute for Neurodegenerative Disorders, 60 Temple Street, Suite 8A, New Haven, CT 06510, USA
Received 22 July 2004; revised 22 September 2004; accepted 23 September 2004
Available online 13 October 2004
Abstract—Noncompetitive antagonists of the human metabotropic glutamate receptor subtype 5 (mGluR5) have been implicated as
potential therapeutics for the treatment of a variety of nervous system disorders, including pain, anxiety, and drug addiction. To
discover novel noncompetitive antagonists to the mGluR5, we initiated an SAR study around the known lead compounds MPEP
and M-MPEP. Our results pointed out the critical role of the para position of the two aromatic rings, which leads to inactive prod-
ucts and permitted the discovery of potent mGluR5 antagonists (e.g., 16, 25, 28, 34 IC50 = 13.5, 11.9, 21, 15nM, respectively).
ꢀ 2004 Elsevier Ltd. All rights reserved.
1. Introduction
groups based principally on sequence homology but also
on signal transduction pathway and agonist selectivity.
Group I mGluRs are selectively activated by dihydroxy-
phenylglycine (DHPG) and initiate cell responses
through Gq/11 protein coupling to phospholipase C
and stimulation of phosphoinositide hydrolysis. In con-
trast, group II and III mGluRs are negatively coupled
via Gi/Go to adenylyl cyclase and reduce forskolin stim-
ulated increases in cAMP in recombinant expression
systems. Group II receptors can be stimulated by (2S,
20R,30R)-2-(20,30-dicarboxycyclopropyl)glycine and (+)-
2-aminobicyclo[3.1.0]hexane-2,6-dicarboxylate mono-
hydrate (LY354740), and group III receptors are selec-
tively stimulated by L-(+)-2-amino-4-phosphonobutyric
acid and (R,S)-4-phosphonophenylglicine.5 Recent stud-
ies have suggested that mGluRs represent the candidate
receptors for acid homocysteine metabolites.6 These
findings suggest that some of the pathogenic actions
attributed to hyperhomocysteinemia may be due, in
part, to activation of mGluRs. Compared to the thor-
oughly investigated roles of the ionotropic receptors,
functional studies on mGluR have just emerged in
recent years. Group I mGluRs (including the mGluR1
and mGluR5 subtypes) exhibit a regional pattern of
expression in the CNS suggesting distinct functional
roles for each receptor.7 For example, expression of
L-Glutamate is the principal excitatory neurotransmitter
in the central nervous system (CNS), and regulates a
variety of neuronal activities through interacting with
specific receptors. The heterogeneous family of gluta-
mate receptors can be divided into two major types: iono-
tropic (iGluR) and metabotropic (mGluR). The iGluR
groups are glutamate-gate cation channels and can be
subdivided into N-methyl-D-aspartate (NMDA) recep-
tors for NMDA and non-NMDA receptors for kainite
and a-amino-3-hydroxy-5-methyl-4-isoxazole propionic
acid (AMPA).1 mGluRs are members of the superfamily
3 of G-protein coupled receptors and possess a unique
structure with a large extracellular N-terminus domain
involved in glutamate recognition.2,3 mGluRs comprise
a family of eight subtypes that are activated by gluta-
mate and can modulate fast excitatory responses evoked
by glutamatergic stimulation of ionotropic receptors.4
The eight mGluR subtypes are subdivided into three
Keywords:
Gluatamate.
*
mGluR5;
Synthesis;
Antagonist;
Metabotropic;
Corresponding author. Tel.: +1 203 401 4309; fax: +1 203 789
2119; e-mail: gtamagnan@indd.org
0968-0896/$ - see front matter ꢀ 2004 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmc.2004.09.042

198
D. Alagille et al. / Bioorg. Med. Chem. 13 (2005) 197–209
H
Ar
A
N
A
N
a
+
Ar
X
OMe
B
B
1-8
MPEP
MTEP
M-MPEP
Scheme 1. Reagents and conditions: (a) aryl halide, PdCl2(PPh3)2,
CuI, Et3N, room temp.
S
S
N
N
O
ods, starting in 1963 with the Castro–Stephens18 proto-
col; the scope has been extended with the introduction
of palladium catalyzed coupling, reviewed in 2003 by
Negishi and Anastasia.19 The simple ring A positional
isomers 2–4 were prepared by Sonogashira cross cou-
pling between phenylacetylene and commercially availa-
ble bromopyridines. Using the same methodology,
compounds 6–8 and 1 were obtained starting from
the corresponding bromopyridine or 3-iodotoluene
(Scheme 1).
N
N
Methoxymethyl-MTEP
Figure 1.
mGluR5 is high-to-moderate in frontal cortex, caudate
putamen, nucleus accumbens, olfactory tubercle, hippo-
campus, and dorsal surface of the spinal cord, whereas
low levels of expression are observed in cerebellum.8,9
In contrast, mGluR1 is present in high density in the
cerebellum and low-to-moderate expression is found in
frontal cortex, caudate putamen, nucleus accumbens,
and olfactory tubercle.9 Given the high level of expres-
sion of mGluR5 in the limbic forebrain, these receptors
are positioned to play key roles in emotional and
behavioral processing. Some selective noncompetitive
mGluR5 antagonists have been developed in recent
years,10,11 all derived from the lead compounds MPEP
and M-MPEP (Fig. 1), where the pyridine ring is arbi-
trarily designated A and the phenyl ring is designated
B. More recently, Cosford et al. successfully replaced
the A-ring of MPEP by a methylthiazole moiety, leading
to interesting compounds such as MTEP (Fig. 1) and its
methoxymethyl analogue.12,13
Compounds 9–11, 15, 17, 23, 24, 27–31 were obtained
by Migita–Kosugi–Stille cross coupling starting from
the tributyltin alkyne key intermediate 38 (Scheme 2,
Table 1). This cross coupling reaction is used frequently
with activated alkynes, with which the reaction proceeds
under mild conditions without cuprous iodide in higher
yield than obtained under Sonogashira conditions.20
Thus, treatment of 2-bromo-6-methylpyridine with
trimethylsilylacetylene under Sonogashira conditions
afforded silyl acetylene 36 (Scheme 2). Interestingly,
removal of the trimethylsilyl group by treatment with
tetrabutylammonium fluoride led to degradation. Desil-
ylation to acetylene 37 was readily accomplished with
KOH in methanol. Treatment of 37 with dimethylami-
notrimethyltin led to the key stannyl intermediate 38
in quantitative yield (Scheme 2).
Evaluation of MPEP in animal models of mood disor-
ders, including depression and anxiety14–16 and drug
addiction,17 reinforce the growing evidence for the role
of mGluR5 in these pathologies and the potential thera-
peutic application of specific and potent mGluR5 non-
competitive antagonists. Unfortunately, the high
lipophilicity and poor blood–brain barrier penetration
of both MPEP and M-MPEP limit their application
for therapeutic purposes. A number of analogs have
been claimed in patent applications, but specific receptor
activity has not been reported for most of them. The de-
sign of mGluR5 antagonists is limited by the lack of ro-
bust published structure–activity relationships (SAR).
We therefore initiated investigation of mGluR5 antago-
nists with the goal to clarify and extend the structural
requirements of the known mGluR5 antagonists with
a simple and rational SAR. This paper reports the first
results of studies examining the effect of modification
around the known inhibitors MPEP and M-MPEP.
Reaction of 3-bromopyridine with stannyl acetylene
38 did not lead to the desired pyridinoacetylene 22
but to the homocoupling product. Compound 22
was successfully obtained by cross coupling between
2-bromo-6-methylpyridine and 3-ethynylpyridine 39,
which was synthesized by desilylation of 3-trimethyl-
silylethynyl pyridine under basic conditions (Scheme 2,
Table 1). Compounds 12–14, 18–21, 25, 26 were
obtained using a modified Sonogashira reaction involv-
ing the in situ desilylation of silyl acetylene 36 using
tetrabutylammonium fluoride and subsequent palla-
dium cross coupling with the appropriate aryl or hetero-
aryl halide (Scheme 2). Nitro compound 16 was
synthesized with a classic Sonogashira reaction between
ethynylpyridine 37 and 3-iodo-nitrobenzene (Scheme 2,
Table 1). Treatment of 3,5-dibromopyridine by sodium
methoxide provided 3-methoxy-5-bromopyridine 40,
which was subsequently converted to silyl acetylene
41 using Sonogashira coupling. Compounds 32–35
were obtained by the same modified Sonogashira
method used for 12–14, 18–21, 25, 26, starting from
the trimethylsilylethynyl intermediates 41 or 4213 and
the appropriated aryl or heteroaryl halide (Scheme 3,
Table 1).
2. Chemistry
Preparation of arylalkynyl derivatives is well described
in the literature and proceeding through different meth-

D. Alagille et al. / Bioorg. Med. Chem. 13 (2005) 197–209
199
b
a
c
d
N
Br
N
N
N
SiMe3
H
SnMe3
36
37
38
e
f
g
N
N
N
NO2
Ar
Ar
12-14, 18-21, 25-26
16
9-11, 15, 17, 23-24, 27-31
Me3Si
H
h
c
N
N
N
N
39
22
Scheme 2. Reagents and conditions: (a) (trimethylsilyl)acetylene, PdCl2(PPh3)2, CuI, Et3N, room temp; (b) n-Bu4NF, THF, rt; (c) KOH, MeOH,
room temp; (d) (dimethylamino)trimethyltin, room temp; (e) aryl bromide, PdCl2(PPh3)2, CuI, Et3N, Bu4NF, DMF, 70ꢁC; (f) 1-iodo-3-nitro-
benzene, PdCl2(PPh3)2, CuI, Et3N, room temp; (g) aryl bromide, Pd(PPh3)4, DMF, 110ꢁC; (h) 2-bromo-6-methylpyridine, PdCl2(PPh3)2, CuI, Et3N,
90ꢁC.
Table 1. Structures of reported compounds
Compound
Structure
Yielda
%
Compound
Structure
Yielda
%
N
1
78
19
44
SMe
O
N
N
N
2 MPEP
64
20
60
N
N
3
4
81
73
21
22
65
35
N
N
N
N
N
N
5
6
33
64
23
24
70
68
N
OMe
Br
N
N
N
N
Br
N
7
62
25
49
(continued on next page)

200
D. Alagille et al. / Bioorg. Med. Chem. 13 (2005) 197–209
Table 1 (continued)
Compound
Structure
Yielda
%
Compound
Structure
Yielda
%
N
MeO
N
8
9
48
26
65
OH
N
N
OMe
N
N
N
47
27
82
N
N
10 M-MPEP
60
45
28
29
87
65
OMe
N
CH3
N
N
11
N
OMe
OMe
OMe
N
N
12
13
28
34
30
31
75
90
N
CH3
OMe
OMe
N
N
N
S
N
N
N
14
15
23
81
32
33
58
81
OMe
OMe
OMe
S
N
N
N
O
O
OH
S
N
N
N
N
16
17
18
47
61
31
34
35
59
76
NO2
S
N
N
CF
3
NO2
F
a Yields were calculated from isolated compounds and are not optimized.
3. Biological evaluation
Gaqi9, and experimentally allowed a positive coupling
of mGluR8 to phospholipase C.22 Cultured in 96-well
plates, the receptor-expressing cells were incubated
with 0.75lCi myo-[3H]inositol to label the cell mem-
brane phosphoinositides. Incubations with test com-
pounds were carried out for 45min at 37ꢁC in Lockeꢀs
buffer (156mM NaCl, 5.6mM KCl, 3.6mM NaHCO3,
1mM MgCl2, 1.3mM CaCl2, 5.6mM glucose, and
20mM HEPES, pH7.4) containing 20mM LiCl, which
blocks the degradation of inositol phosphates (IPs).
The reaction was terminated by aspiration and addition
3.1. Phosphoinositide hydrolysis assays (mGluR1, 5, and
8)
Recombinant cDNAs for mGluR1a and mGluR5a
(group I) were stably transfected and expressed in Chi-
nese hamster ovary (CHO) cells.21 The native mGluR8
(group III) is not naturally coupled to phospholipase
C; however, in this study mGluR8 was stably expressed
in CHO cell line that expressed a chimeric G protein,

D. Alagille et al. / Bioorg. Med. Chem. 13 (2005) 197–209
201
S
Me3Si
OMe
Br
Br
Br
a
b
c
N
OMe
OMe
N
N
N
41
N
40
32
S
S
d
N
N
Ar
SiMe3
4213
33-35
Scheme 3. Reagents and conditions: (a) MeONa, MeOH, 130ꢁC sealed tube; (b) (trimethylsilyl)acetylene, PdCl2(PPh3)2, CuI, Et3N, room temp; (c)
2-iodo-4-methyl-thiazole, PdCl2(PPh3)2, CuI, Bu4NF, Et3N, 60ꢁC; (d) aryl bromide, PdCl2(PPh3)2, CuI, Et3N, Bu4NF, DMF, 70ꢁC.
of 0.1M HCl. IPs were extracted with 0.1M HCl.
[3H]IPs were separated by anion exchange chromatogra-
phy and determined in duplicate by a liquid scintillation
counter (LKB, Uppsala, Sweden) as previously
described.23
of a methoxy group in position 3 increases the activity.
We first envisaged modification in the A-ring of MPEP
to better understand the SAR of this structure. The pres-
ence of a nitrogen in the 2-position of ring A is indispen-
sable for antagonists activity as illustrated by the lack of
activity of the carbocyclic aromatic analog of MPEP (1,
Table 2). Moving the 6-methyl group of MPEP to the
Data were normalized to the maximal response induced
by 1mM glutamate for mGluR5 and mGluR1, or by
0.1mM AP4 for mGluR8. For mGluR5, IC50 of the title
compounds was determined from the concentration–res-
ponse curves using seven concentrations in four to six
separated experiments; values were determined by fitting
the normalized data to the logistic equation by nonlin-
ear regression using SigmaPlot (SPSS Science, Chicago,
IL). For mGluR1 and mGluR8, percent of inhibition
was determined at a single concentration of 10lM in
duplicate experiments.
Table 2. mGluR5 IC50 values of selected compounds using IP
hydrolysis assay
Compound
IC50 (mean SEM, nM)a
1
2 MPEP
1105 584
24 4.1
NA
3
4
91 20
63 16
61 39
663 128
1961 210
60 18
5
6
7
3.2. Cyclic AMP assay
8
9
10 M-MPEP
Cyclic AMP-coupled receptors mGluR2 (group II) and
mGluR6 (group III) were stably expressed in CHO cells,
whereas mGluR4 (group III) was stably expressed in
baby hamster kidney cells.21 Receptor-mediated inhibi-
tion of the forskolin-induced elevation of cyclic AMP
formation was described previously.21 In brief, the recep-
tor-expressing cells, cultured in 96-well culture plates,
were preincubated for 10min at 37ꢁC in Lockeꢀs medium
containing 300lM isobutylmethylxanthine, which inhib-
its the activity of phosphodiesterases to prevent the deg-
radation of cAMP. Then, 5lM forskolin was added
without or with the test compounds, and the incubation
was continued for 10min. After incubation, the medium
was rapidly aspirated. cAMP was extracted with 0.1M
HCl and measured by radioimmunoassay using mag-
netic Amerlex RIA kit (Amersham Biosciences Inc.).
Percent of inhibition was determined at a single concen-
tration of 10lM in duplicate experiments.
8
2
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
497 261
274 34
82 10
808 141
625 510
13.5 6.7
354 263
33.4 5.4
208 32
293 37
184 112
55.9 19.8
94 37
22 0.14
11.9 4.6
242 50
235 71
21 6.7
1840 180
547 280
173 38
11.3 3.2
428 238
19.7 5.5
4. Results and discussion
The known noncompetitive antagonists of mGluR5
(MPEP and M-MPEP) are characterized by two aro-
matic rings linked by an ethynyl spacer. Ring A
(Fig. 1) is a pyridine substituted by a methyl group in
position 6 and linked to the ethynyl group in position
2. Ring B is a phenyl moiety in which the introduction
15
2
a IP hydrolysis assay is described under Biological evaluation.25 Con-
centration–response curves were performed using seven concentra-
tions in four to six separated experiments. All values represent
means SEM.

202
D. Alagille et al. / Bioorg. Med. Chem. 13 (2005) 197–209
other three positions, as in 3–5, led to a reduction of the
in vitro potency at mGluR5 (Table 2). This loss of activ-
ity is presumably due to an unfavorable interaction
between the methyl group and the receptor and not just
due to the loss of the 6-methyl moiety as illustrated by
the dimethyl analogue 6, which displayed the same
range of inhibition as the 4-methyl analog 4. The 5-iso-
mer 3 was inactive; in keeping with preliminary experi-
ments indicating total loss of activity when position 5
of the pyridine was substituted (unpublished results).
Replacement of the 6-methyl by a bromine as in 7 or a
methoxy moiety as in 8 dramatically decreased the activ-
ity. We then modified the structure of ring B, starting by
moving the methoxy moiety of M-MPEP. Moving the
methoxy moiety from position 3 to position 2 (9)
decreased the activity and moving to position 4 (11)
led to essential loss of activity. Of the diether analogues
12–15, only the 2,5-dimethoxy derivative 13 retained
moderate antagonist activity; the other dimethoxy (12
and 14) and the methylenedioxy derivative 15 showed
very poor activity (Table 2). These results suggest the
critical role of substitution at the 4-position (11–12,
14–15 vs 10 and 13), since substitution at this position
led to inactive compounds. We then examined other
substituents to replace the 3-methoxy moiety of
M-MPEP (16–20, Table 2). The greatest mGluR5 activ-
ity was seen with the 3-nitro and 3-fluoro analogs 16 and
18 (IC50 = 13.5 and 33.4nM, respectively). Passing from
M-MPEP to the thiomethoxy analog 19 reduced the
activity 26-fold. The same range of reduction in activity
was observed with the allyl ether (20) and the trifluoro-
methyl analogue (18). Both MPEP and M-MPEP are
lipophilic, with high distribution coefficients (logD 3.5
and 3.0, respectively). Cosford et al.12 described com-
pounds with a pyridine as the B-ring, which decreased
the lipophilicity. We thus decided to replace the B-ring
in the present series by a pyridine. The three B-ring pyri-
dine isomers 21–23 were all less potent than the corres-
ponding carbocyclic analogs, although the 3-pyridinyl
isomer 22 was the most active of this series. Functional-
ization of position 3 of 22 with methoxy or bromo led to
active compounds 24 and 25 (IC50 = 22 and 11.9nM,
respectively). We then extended the concept by replacing
ring B by other heteroaromatic rings. The 3-quinoline
(27) and 4-isoquinoline (28) derivatives exhibited totally
different biological profiles: whereas 27 had low potency,
28 showed antagonist activity with an IC50 = 22nM.
The two indole analogues 29 and 30 presented very
low activity. We hypothesize that the loss of activity of
27, 29, and 30 is caused by the steric hindrance in the
para position (relative to the ethynyl substituent) as pre-
viously considered for the mono and dimethoxy analogs.
Introduction of a pyrimidine ring (31) also led to a
reduction of activity (IC50 173nM).
34, and 35 were profiled against others mGluR subtypes.
Experiments were performed at a single drug concentra-
tion of 10lM on mGluR1, mGluR5, mGluR2,
mGluR4, mGluR6, and mGluR8. All compounds
exerted a similar antagonist effect on mGluR5 (101–
134% inhibition) and were inactive (less than 25%
inhibition) at the other mGluR subtypes.
5. Conclusion
This exploration of a series of diaryl acetylene deriva-
tives as mGluR5 noncompetitive antagonists permit-
ted the discrimination of two critical positions (para
ring A and B) that led to inactive compounds, possibly
as a result of steric hindrance to ligand–receptor
binding. Six candidates (16, 25, 28, 32, 34, and 35) were
identified as potent and selective ligands, with a promis-
ing pharmacological profile warranting further investi-
gation.
6. Experimental
Melting points were determined using a Thomas–
Hoover melting point apparatus and are uncorrected.
1H and 13C NMR spectra were recorded on a U400 or
U500 Varian FT-NMR spectrometer. Chemical shifts
(d) are reported in parts per million (ppm) downfield
from tetramethylsilane external as external lock. Low
resolution mass spectra were performed by the Mass
Spectrometry Laboratory of the University of Illinois.
Elemental analysis were performed by Atlantic Micro-
lab, Norcross, GA 30091. Reaction progress was moni-
tored by analytical thin layer chromatography on
0.25mm Merck F-254 silica gel aluminum plates, visual-
izing with Dragendorffꢀs reagent or quenching of UV
illumination at 254nm. Flash chromatography24 was
performed using 230–400 mesh silica gel and eluent indi-
cated in the procedure. All reactions were performed
under a dry (Drierite) argon atmosphere. Unless other-
wise specified, reagents and solvents used in this study
were obtained from commercial sources and were used
without further purification. Et3N was dried with NaOH
˚
pellets and distilled from and stored over 3A molecular
sieves.
6.1. General procedure for synthesis of compounds 1–8
To a solution of aryl halide (2.9mmol) in 10mL of de-
gassed Et3N was added successively CuI (55mg,
0.29mmol), phenylacetylene (350lL, 3.19mmol), and
trans-dichlorobis(triphenylphosphine)palladium
(204
mg, 0.29mmol). The mixture was stirred at rt overnight,
then the black solution was hydrolyzed with 10mL of
H2O and extracted with EtOAc (3 · 10mL). The organic
layer was washed with saturated NaCl (3 · 10mL) and
were dried over anhydrous Na2SO4, and evaporated to
dryness on a rotary evaporator. Flash column chroma-
tography yielded the corresponding compounds 1–8.
HCl salts 2–8 were prepared by adding 2M HCl/Et2O
to a solution of free base in Et2O and isolated by suction
filtration.
To conclude this work, we replaced ring A by a methyl-
thiazole moiety as in MTEP, choosing as B-ring the best
pharmacophoric elements deduced previously. Methoxy
(32), benzo (34), and nitro (35) but not alcohol 33 pre-
sented potent antagonist activity comparable to that ob-
served with the analogous 3-pyridyl derivatives (35 vs
16, 34 vs 28, 32 vs 24, and 33 vs 26). To identify off-tar-
get activities, compounds 2, 10, 16, 18, 22, 24, 25, 28, 32,

D. Alagille et al. / Bioorg. Med. Chem. 13 (2005) 197–209
203
6.1.1. 1-Methyl-3-phenylethynyl-benzene (1). Chromato-
graphy (hexane), yield 78%, colorless oil. 1H NMR
(CDCl3) d ppm: 2.47 (s, 3H, CH3); 7.26 (d, 1H,
J = 7.6Hz, CHAr); 7.36 (t, 1H, J = 7.6Hz, CHAr);
7.44–7.46 (m, 3H, CHAr); 7.49–7.52 (m, 2H, CHAr);
7.67–7.70 (m, 2H, CHAr). 13C NMR (CDCl3) d ppm:
21.7 (1C, CH3); 89.6 (1C, C„C); 90.2 (1C, C„C);
123.6 (1C, Cq); 123.9 (1C, Cq); 128.7 (1C, CHAr);
128.8 (1C, CHAr); 128.9 (2C, CHAr); 129.2 (1C,
CHAr); 129.7 (1C, CHAr); 132.1 (2C, CHAr); 132.7
(1C, CHAr); 138.5 (1C, Cq). MS (EI) m/z 192.1 (M).
Anal. (C15H12) C, H.
6.1.6. 2,4-Dimethyl-6-phenylethynylpyridine (6). Chro-
matography (hexane/EtOAc 9/1), yield 64%, yellow oil.
1H NMR (CDCl3) d ppm: 2.26 (s, 3H, CH3); 2.51 (s,
3H, CH3); 6.89 (s, 1H, CHAr); 7.16 (s, 1H, CHAr);
7.30–7.33 (m, 3H, CHAr); 7.57–7.60 (m, 2H, CHAr).
13C NMR (CDCl3) d ppm: 20.7 (1C, CH3); 24.4 (1C,
CH3); 88.3 (1C, C„C); 89.0 (1C, C„C); 122.4 (1C,
Cq); 123.6 (1C, CHAr); 125.3 (1C, CHAr); 128.3 (2C,
CHAr); 128.7 (1C, CHAr); 132.0 (2C, CHAr); 142.3
(1C, Cq); 147.4 (1C, Cq); 158.5 (1C, Cq). HCl salt mp
160–162ꢁC. MS (EI) m/z 207.1 (M). Anal.
(C15H13NÆHCl) C, H, N.
6.1.2. 6-Methyl-2-phenylethynylpyridine, MPEP (2).
Chromatography (hexane/EtOAc 8/2), yield 64%,
yellow oil. 1H NMR (CDCl3) d ppm: 2.33 (s, 3H,
CH3); 6.62 (dd, 1H, J = 8.5; 0.8Hz, CHAr); 7.13 (dd,
1H, J = 7.2; 0.8Hz, CHAr); 7.29–7.34 (m, 3H, CHAr);
7.46 (dd, 1H, J = 8.5; 7.2Hz, CHAr); 7.54–7.58 (m,
2H, CHAr). 13C NMR (CDCl3) d ppm: 19.0 (1C,
OCH3); 88.6 (1C, C„C); 88.9 (1C, C„C); 122.1
(C, Cq); 123.1 (1C, CHAr); 128.3 (2C, CHAr); 128.8
(1C, CHAr); 132.1 (2C, CHAr); 138.4 (1C, CHAr);
140.3 (1C, Cq); 141.2 (1C, Cq); 149.8 (1C, CHAr).
HCl salt mp 145–146ꢁC. Anal. (C14H11NÆHClÆ0.2H2O)
C, H, N.
6.1.7. 2-Bromo-6-phenylethynylpyridine (7). Chromato-
graphy (hexane/EtOAc 8/2), yield 62%, of white
solid. 1H NMR (CDCl3) d ppm: 2.25–2.29 (m, 3H,
CHAr); 2.34–2.36 (m, 2H, CHAr); 2.43 (d, 1H, J =
7.7Hz, CHAr); 2.48–2.49 (m, 2H, CHAr). 13C NMR
(CDCl3) d ppm: 87.9 (1C, C„C); 91.2 (1C, C„C);
122.1 (1C, Cq); 126.4 (1C, CHAr); 127.8 (1C, CHAr);
128.8 (2C, CHAr); 129.7 (1C, CHAr); 132.5 (2C,
CHAr); 138.8 (1C, CHAr); 142.1 (1C, Cq); 144.2 (1C,
Cq). HCl salt mp 138–140ꢁC. Anal. (C13H8BrNÆHClÆ
0.1H2O) C, H, N.
6.1.8.
2-Methoxy-6-phenylethynylpyrylpyridine
Chromatography (hexane/EtOAc 95/5), yield 45%, yel-
(8).
1
6.1.3. 5-Methyl-2-phenylethynylpyridine (3). Chromato-
graphy (hexane/EtOAc 8/2), yield 81%, yellow solid,
low oil. H NMR (CDCl3) d ppm: 3.96 (s, 3H, OCH3);
6.68 (dd, 1H, J = 8.5; 0.8Hz, CHAr); 7.11 (dd, 1H,
J = 7.2; 0.8Hz, CHAr); 7.30–7.33 (m, 3H, CHAr); 7.48
(dd, 1H, J = 8.5; 7.2Hz, CHAr); 7.56–7.58 (m, 2H,
CHAr). 13C NMR (CDCl3) d ppm: 53.5 (1C, OCH3);
88.5 (1C, C„C); 88.9 (1C, C„C); 111.0 (1C, CHAr);
120.7 (1C, CHAr); 122.4 (C, Cq); 128.3 (2C, CHAr);
128.8 (1C, CHAr); 131.9 (2C, CHAr); 138.4 (1C,
CHAr); 140.3 (1C, Cq); 163.8 (1C, Cq). HCl salt mp
114–116ꢁC. MS (EI) m/z 209.1 (M). Anal.
(C14H11NOÆHClÆ0.8H2O) C, H, N.
1
mp 80–82ꢁC. H NMR (CDCl3) d ppm: 2.31 (s, 3H,
CH3); 7.31–7.45 (m, 5H, CHAr); 7.56–7.58 (m,
2H, CHAr); 8.42 (s, 1H, CHAr). 13C NMR (CDCl3) d
ppm: 18.8 (1C, CH3); 88.9 (1C, C„C); 89.0 (1C,
C„C); 122.8 (1C, Cq); 127.0 (1C, CHAr); 128.7 (2C,
CHAr); 129.1 (1C, CHAr); 132.3 (2C, CHAr); 133.1
(1C, Cq); 137.0 (1C, CHAr); 140.9 (1C, Cq); 150.9
(1C, CHAr). HCl salt mp 148–150ꢁC. Anal.
(C14H11NÆHClÆ0.2H2O) C, H, N.
6.1.4. 4-Methyl-2-phenylethynylpyridine (4). Chromato-
graphy (hexane/EtOAc 8/2), yield 73%, yellow oil. H
6.2. 2-Methyl-6-trimethylsilylethynylpyridine (36)
1
NMR (CDCl3) d ppm: 2.16 (s, 3H, CH3); 6.88 (d, 1H,
J = 4.5Hz, CHAr); 7.19–7.22 (m, 4H, CHAr); 7.45–
7.48 (m, 2H, CHAr); 8.31 (d, 1H, J = 4.5Hz, CHAr).
13C NMR (CDCl3) d ppm: 21.1 (1C, CH3), 89.1 (1C,
C„C); 89.2 (1C, C„C); 122.7 (1C, Cq); 124.2 (1C,
CHAr); 128.3 (1C, CHAr); 128.7 (2C, CHAr); 129.2
(1C, CHAr); 132.3 (2C, CHAr); 143.4 (1C, Cq); 147.7
(1C, Cq); 150.0 (1C, CHAr). HCl salt mp 155–157ꢁC.
Anal. (C14H11NÆHCl) C, H, N.
To a solution of 2-bromo-6-methylpyridine (3g,
17.4mmol) in 50mL of degassed Et3N was added tri-
methylsilylacetylene (2.70mL, 19.1mmol), CuI (331
mg, 1.74mmol), and trans-dichlorobis(triphenylphos-
phine)palladium (1.22g, 1.74mmol). The resulting solu-
tion was stirred at rt over night under N2 atmosphere.
Then the black solution was hydrolyzed with 30mL of
H2O and extracted with Et2O (3 · 30mL). Purification
of the residue by column chromatography (hexane/
1
Et2O 9/1) yielded 2.35g (71%) of 36 as a brown oil. H
6.1.5. 3-Methyl-2-phenylethynylpyridine (5). Chromato-
graphy (hexane/EtOAc 8/2), yield 33%, yellow oil. H
NMR (CD2Cl2) d ppm: 0.08 (s, 9H, CH3); 2.30 (s, 3H,
CH3); 6.89 (dd, 1H, J = 7.6; 0.5Hz, CHAr); 7.05 (dd,
1H, J = 7.6; 0.5Hz, CHAr); 7.32 (t, 1H, J = 7.5Hz,
CHAr). 13C NMR (CD2Cl2) d ppm: 0.0 (3C, CH3);
24.7 (1C, CH3); 94.0 (1C, C„C); 104.7 (1C, C„C);
123.1 (1C, CHAr); 124.8 (1C, CHAr); 136.7 (1C,
CHAr); 142.6 (1C, Cq); 159.4 (1C, Cq).
1
NMR (CDCl3) d ppm: 2.34 (s, 3H, CH3); 6.96 (dd,
1H, J = 8.0; 5.0Hz, CHAr), 7.19–7.22 (m, 3H, CHAr);
7.33 (dd, 1H, J = 8.0; 0.8Hz, CHAr); 7.47–7.49 (m,
2H, CHAr); 8.30 (dd, 1H, J = 5.0; 0.8Hz, CHAr). 13C
NMR (CDCl3) d ppm: 19.7 (1C, CH3); 87.9 (1C,
C„C); 93.3 (1C, C„C); 122.8 (1C, Cq); 123.0 (1C,
CHAr); 128.7 (2C, CHAr); 129.2 (1C, CHAr); 132.2
(2C, CHAr); 136.2 (1C, Cq); 137.3 (1C, CHAr); 143.3
(1C, Cq); 147.6 (1C, CHAr). HCl salt mp 150–152ꢁC.
Anal. (C14H11NÆHClÆ0.2H2O) C, H, N.
6.3. 2-Ethynyl-6-methylpyridine (37)
To a solution of KOH (2.41g, 43.0mmol) in 50mL of
MeOH was added 36 (4.05g, 21.5mmol) dissolved in

204
D. Alagille et al. / Bioorg. Med. Chem. 13 (2005) 197–209
5mL of methanol. The resulting solution was stirred at
rt for 2h. Then 50mL of H2O was added and the result-
ing mixture was extracted with EtOAc (3 · 30mL). Puri-
fication of the residue by column chromatography
(hexane/Et2O 9/1) yielded 1.86g (74%) of 37 as a color-
2.8Hz, CHAr); 7.28 (d, 1H, J = 1.2Hz, CHAr); 7.31
(dd, 1H, J = 7.6; 1.2Hz, CHAr); 7.41 (t, 1H,
J = 8.0Hz, CHAr); 7.88 (d, 1H, J = 7.6Hz, CHAr);
8.03 (d, 1H, J = 7.6Hz, CHAr); 8.47 (t, 1H,
J = 8.0Hz, CHAr). 13C NMR (MeOH-d4) d ppm: 20.4
(1C, CH3); 56.5 (1C, CH3); 81.5 (1C, C„C); 101.9
(1C, C„C); 118.8 (1C, CHAr); 119.1 (1C, CHAr);
122.2 (1C, Cq); 126.3 (1C, CHAr); 128.6 (1C, CHAr);
129.3 (1C, CHAr); 131.7 (1C, CHAr), 136.4 (1C, Cq);
147.6 (1C, CHAr); 157.3 (1C, Cq); 161.6 (1C, Cq). Anal.
(C15H13NOÆHCl) C, H, N.
1
less oil. H NMR (CDCl3) d ppm: 2.05 (s, 3H, CH3);
2.72 (s, 2H, C„C-H); 6.63 (d, 1H, J = 7.2Hz, CHAr);
6.78 (d, 1H, J = 7.2Hz, CHAr); 7.04 (td, 1H, J = 7.2;
0.8Hz, CHAr).
6.4. 2-Methyl-6-trimethylstannylethynylpyridine (38)
Under N2 atmosphere was added (dimethylamino)tri-
methyltin (2.1mL, 12.3mmol) to 37 (1.38g, 11.8mmol).
The resulting solution was stirred at rt for 2h. Evapora-
tion of the crude mixture under high vacuum (1mmHg)
afforded the desired compound 38 as an oil, 4.1g (quan-
6.5.3.
2-(4-Methoxyphenylethynyl)-6-methylpyridine
(11). Chromatography (hexane/EtOAc 8/2), yield 45%,
brown oil. 1H NMR (CDCl3) d ppm: 2.44 (s, 3H,
CH3); 3.65 (s, 3H, OCH3); 6.74 (d, 2H, J = 9.2Hz,
CHAr); 7.92 (d, 1H, J = 8.0Hz, CHAr); 7.18 (d, 1H,
J = 8.0Hz, CHAr); 7.38 (t, 1H, J = 8.0Hz, CHAr);
7.41 (d, 2H, J = 9.2Hz, CHAr). 13C NMR (CDCl3) d
ppm: 25.2 (1C, CH3); 55.8 (1C, OCH3); 88.4 (1C,
C„C); 89.7 (1C, C„C); 114.6 (2C, CHAr); 115.0 (1C,
Cq); 122.9 (1C, CHAr); 124.7 (1C, CHAr); 134.2 (2C,
CHAr); 137.0 (1C, CHAr); 143.5 (1C, CHAr); 159.4
(1C, Cq); 160.7 (1C, Cq). HCl salt mp 148–150ꢁC. MS
(EI) m/z 223.2 (M). Anal. (C15H13NOÆHCl) C, H, N.
1
titative yield). H NMR (CDCl3) d ppm: 0.00 (s, 9H,
3CH3); 2.16 (s, 3H, CH3); 6.67 (d, 1H, J = 8.0Hz,
CHAr); 6.88 (d, 1H, J = 8.0Hz, CHAr); 7.12 (t, 1H,
J = 8.0Hz, CHAr). 13C NMR (CDCl3) d ppm: ꢀ7.4
(3C, 3CH3); 24.8 (1C, CH3); 94.4 (1C, C„C); 108.0
(1C, C„C); 122.6 (1C, CHAr); 124.4 (1C, CHAr);
136.4 (1C, CHAr); 142.8 (1C, Cq); 158.8 (1C, Cq).
6.5. General procedure for the synthesis of compounds 9–
11, 15, 17, 23, 24, 27–31
6.5.4. 2-Benzo[1,3]dioxol-5-ylethynyl-6-methylpyridine
(15). Chromatography (hexane/EtOAc 8/2), yield 81%,
brown solid; mp 79–80ꢁC. H NMR (CDCl3) d ppm:
1
To a solution of 38 (500mg, 1.79mmol) in 15mL de-
gassed N,N-dimethylformamide was added successively
the appropriate aryl bromide (1.97mmol) and etra-
kis(triphenylphosphine)palladium (207mg, 0.18mmol).
The resulting mixture was warmed to 110ꢁC and stirred
at this temperature for 4h. After cooling, 10mL of H2O
was added and the resulting solution was extracted with
EtO2 (4 · 10mL). The organic layer was washed with
saturated NaCl (3 · 10mL), dried over Na2SO4, and
evaporated. Purification of the residue by column chro-
matography yielded the corresponding compounds 9–
11, 15, 17, 23, 24, 27–31.
2.47 (s, 3H, CH3); 5.88 (s, 2H, OCH2O); 6.68 (d, 1H,
J = 8.0 HZ, CHAr); 6.94 (d, 1H, J = 2.0Hz, CHAr);
6.98 (dd, 1H, J = 8.0; 0.8Hz, CHAr); 7.04 (dd, 1H,
J = 8.0; 2.0Hz, CHAr); 7.21 (dd, 1H, J = 8.0; 0.8Hz,
CHAr); 7.43 (t, 1H, J = 8.0Hz, CHAr). 13C NMR
(CDCl3) d ppm: 24.8 (1C, CH3); 87.7 (1C, C„C); 89.2
(1C, C„C); 101.7 (1C, OCH2O); 108.8 (1C, CHAr);
112.1 (1C, CHAr); 115.9 (1C, Cq); 122.7 (1C, CHAr);
124.5 (1C, CHAr); 127.2 (1C, CHAr); 136.6 (1C,
CHAr); 134.0 (1C, Cq); 147.7 (1C, Cq); 148.7 (1C,
Cq); 159.1 (1C, Cq). Hydrochloride mp 212–215ꢁC.
MS (EI) m/z 237.1 (M). Anal. (C15H11NO2ÆHCl) C, H,
N.
6.5.1. 2-(2-Methoxyphenylethynyl)-6-methylpyridine (9).
Chromatography (hexane/EtOAc 7/3), yield 47%, brown
oil. 1H NMR (CDCl3) d ppm: 2.51 (s, 3H, CH3); 3.83 (s,
3H, OCH3); 6.83 (d, 1H, J = 8.4Hz, CHAr); 6.87 (td,
1H, J = 7.6; 0.8Hz, CHAr); 7.01 (dd, 1H, J = 7.6;
0.4Hz, CHAr); 7.26 (td, 1H, J = 8.4; 2.0Hz, CHAr);
7.31 (d, 1H, J = 7.6; 0.8Hz, CHAr); 7.47 (t, 1H,
J = 7.6Hz, CHAr); 7.51 (dd, 1H, J = 7.6; 2.0Hz,
CHAr). 13C NMR (CDCl3) d ppm: 24.8 (1C, CH3);
56.0 (1C, OCH3); 85.7 (1C, C„C); 93.1 (1C, C„C);
110.9 (1C, CHAr); 111.8 (1C, Cq); 120.7 (1C, CHAr);
122.7 (1C, CHAr); 124.6 (1C, CHAr); 130.7 (1C,
CHAr); 134.1 (1C, CHAr); 136.6 (1C, CHAr); 143.1
(1C, Cq); 159.0 (1C, Cq); 160.6 (1C, Cq). HCl salt mp
166–168ꢁC. MS (EI) m/z 223.1 (M). Anal.
(C15H13NOÆHCl) C, H, N.
6.5.5. 2-Methyl-6-(3-trifluoromethylphenylethynyl)pyr-
idine (17). Chromatography (hexane/Et2O 7/3), yield
1
61%, yellow oil. H NMR (CDCl3) d ppm: 2.45 (s, 3H,
CH3); 6.98 (dd, 1H, J = 8.0; 0.4Hz, CHAr); 7.23 (dd,
1H, J = 8.0; 0.4Hz, CHAr); 7.33 (t, 1H, J = 8.0Hz,
CHAr); 7.43 (t, 1H, J = 8.0Hz, CHAr); 7.46 (d, 1H,
J = 8.0Hz, CHAr); 7.62 (d, 1H, J = 8.0Hz, CHAr);
7.74 (s, 1H, CHAr). 13C NMR (CDCl3) d ppm: 24.7
(1C, CH3); 87.1 (1C, C„C); 90.5 (1C, C„C); 123.3
(1C, CHAr); 123.7 (1C, Cq); 124.8 (1C, CHAr); 125.5
(1C, Cq); 129.2 (2C, CHAr); 135.3 (1C, CHAr); 136.7
(2C, CHAr); 142.3 (1C, Cq); 159.4 (1C, Cq). Hydrochlo-
ride mp 108–110ꢁC. MS (EI) m/z 261 (M). Anal.
(C15H11F3NÆHClÆ0.5H2O) C, H, N.
6.5.2.
2-(3-Methoxy-phenylethynyl)-6-methylpyridine
6.5.6. 2-Methyl-6-pyridin-4-ylethynylpyridine (23). Chro-
matography (ether/hexane 7/3), yield 70%, brown oil. 1H
NMR (MeOH-d4) d ppm: 3.11 (s, 3H, CH3); 5.59 (t, 1H,
J = 6.8Hz, CHAr); 6.07 (d, 2H, J = 5.4Hz, CHAr); 6.57
(d, 1H, J = 6.8Hz); 7.07 (d, 2H, J = 5.4Hz, CHAr); 7.14
(10, M-MPEP). Chromatography (toluene/Et2O 9/1),
yield 60%, yellow oil. HCl salt mp 180–182ꢁC. 1H
NMR (MeOH-d4) d ppm: 2.84 (s, 3H, CH3); 3.86 (s,
3H, CH3); 5.01 (br s, 1H, NH+); 7.13 (dd, 1H, J = 8.4;

D. Alagille et al. / Bioorg. Med. Chem. 13 (2005) 197–209
205
(d, 1H, J = 6.8Hz, CHAr). 13C NMR (MeOH-d4) d
ppm: 23.0 (1C, CH3); 83.1 (1C, C„C); 98.5 (1C,
C„C); 119.6 (1C, CHAr); 123.8 (1C, Cq); 125.1 (1C,
CHAr); 127.1 (2C, CHAr); 138.3 (1C, CHAr); 141.5
(2C, CHAr); 144.6 (1C, Cq); 158.8 (1C, Cq). Hydrochlo-
ride mp 125–130ꢁC (dec). MS (EI) m/z 194.1 (M). Anal.
(C13H10N2Æ2HClÆH2O) C, H, N.
7.49 (s, 1H, CHAr). 13C NMR (CDCl3) d ppm: 24.9
(1C, CH3); 33.1 (1C, NCH3); 88.0 (1C, C„C); 91.4
(1C, C„C); 101.7 (1C, CHAr); 114.0 (1C, CHAr);
115.1 (1C, Cq); 121.1 (1C, CHAr); 122.4 (1C, CHAr);
123.6 (1C, CHAr); 124.5 (1C, CHAr); 129.4 (1C, Cq);
131.0 (1C, CHAr); 136.5 (1C, Cq); 136.7 (1C, CHAr);
143.6 (1C, Cq); 159.1 (1C, Cq). Hydrochloride mp
154–156ꢁC. HRMS obsd, m/z 246.1163, calcd, m/z
264.1156. Anal. (C17H14N2ÆHClÆ1/3H2O) C, H, N.
6.5.7. 3-(6-Methylpyridin-2-ylethynyl)-5-methoxypyridine
(24). Chromatography (ether/hexane 7/3), yield 68%,
1
white solid; mp 91–93ꢁC. H NMR (CDCl3) d ppm:
6.5.11. 1-Methyl-5-(6-methylpyridin-2-ylethynyl)-1H-
indole (30). Chromatography (hexane/EtOAc 8/2), yield
2.47 (s, 3H, CH3); 3.73 (s, 3H, OCH3); 7.01–7.03 (m,
2H, CHAr); 7.26 (s, 1H, CHAr); 7.44–7.48 (m, 1H,
CHAr); 8.17 (s, 1H, CHAr); 8.32 (s, 1H, CHAr). 13C
NMR (CDCl3) d ppm: 24.9 (1C, CH3); 55.9 (1C,
OCH3); 85.3 (1C, C„C); 92.0 (1C, C„C); 120.0 (1C,
Cq); 122.7 (1C, CHAr); 123.4 (1C, CHAr); 124.8 (1C,
CHAr); 136.8 (1C, CHAr); 138.4 (1C, CHAr); 142.2
(1C, Cq); 145.0 (1C, CHAr); 155.3 (1C, Cq); 159.4
(1C, Cq). Hydrochloride mp 168ꢁC (dec). Anal.
(C14H13N2OÆ2HCl) C, H, N.
1
75%, yellow solid; mp 98–99ꢁC. H NMR (CDCl3) d
ppm: 2.50 (s, 3H, CH3); 3.67 (s, 3H, NCH3); 6.39 (d,
1H, J = 2.8Hz, CHAr); 7.96–7.98 (m, 2H, CHAr); 7.18
(d, 1H, J = 8.4Hz, CHAr); 7.26 (d, 1H, J = 7.6Hz,
CHAr); 7.38 (dd, 1H, J = 8.4; 1.2Hz, CHAr); 7.45
(t, 1H, J = 8.4Hz, CHAr); 7.81 (s, 1H, CHAr). 13C
NMR (CDCl3) d ppm: 24.9 (1C, CH3); 33.2 (1C,
NCH3); 87.2 (1C, C„C); 91.6 (1C, C„C); 101.8 (1C,
CHAr); 109.7 (1C, CHAr); 113.2 (1C, CHAr); 122.4
(1C, CHAr); 124.5 (1C, CHAr); 125.9 (1C, CHAr);
126.0 (1C, CHAr); 128.6 (1C, Cq); 130.3 (1C, CHAr);
136.7 (1C, CHAr); 137.0 (1C, Cq); 143.7 (1C, Cq);
159.1 (1C, Cq). Hydrochloride mp 182–184ꢁC. Anal.
(C17H14N2ÆHClÆ1/3H2O) C, H, N.
6.5.8. 3-(6-Methylpyridin-2-ylethynyl)quinoline (27).
Chromatography (hexane/Et2O 4/6), yield 82%, yellow
1
solid; mp 70–72ꢁC. H NMR (CDCl3) d ppm: 2.49 (s,
3H, CH3); 7.62 (td, 1H, J = 8.0; 1.5Hz, CHAr); 7.68
(d, 1H, J = 8.0Hz, CHAr); 7.99 (d, 1H, J = 8.0Hz,
CHAr); 8.26 (d, 1H, J = 1.2Hz, CHAr); 7.02 (d,
1H, J = 8.0Hz, CHAr); 7.30 (d, 1H, J = 8.0Hz,
CHAr); 7.45 (td, 1H, J = 8.0; 1.5Hz, CHAr); 7.48 (t,
1H, J = 8.0Hz, CHAr). 13C NMR (CDCl3) d ppm:
24.99 (1C, CH3); 86.2 (1C, C„C); 92.2 (1C, C„C);
116.9 (1C, Cq); 123.4 (1C, CHAr); 124.9 (1C,
CHAr); 127.4 (1C, Cq); 127.7 (1C, CHAr); 128.1 (1C,
CHAr); 129.7 (1C, CHAr); 130.8 (1C, CHAr); 136.8
(1C, CHAr); 139.5 (1C, CHAr); 142.4 (1C, Cq); 147.4
(1C, Cq); 152.4 (1C, CHAr); 159.5 (1C, Cq). Hydrochlo-
ride mp 174–176ꢁC. Anal. (C17H12N2Æ2HCl) C, H, N.
6.5.12. 5-(6-Methylpyridin-2-ylethynyl)pyrimidine (31).
Chromatography (hexane/Et2O 7/3), yield 90%, yellow
1
solid; mp 109–111ꢁC. H NMR (CDCl3) d ppm: 2.52
(s, 3H, CH3); 7.11 (d, 1H, J = 8.0Hz, CHAr); 7.32
(d, 1H, J = 8.4Hz, CHAr); 7.54 (t, 1H, J = 8.4Hz,
CHAr); 8.85 (s, 2H, CHAr); 9.09 (s, 1H, CHAr). 13C
NMR (CDCl3) d ppm: 24.9 (1C, CH3); 81.8 (1C,
C„C); 95.6 (1C, C„C); 119.5 (1C, Cq); 124.0 (1C,
CHAr); 125.0 (1C, CHAr); 137.0 (1C, CHAr); 141.6
(1C, Cq); 157.5 (1C, CHAr); 159.4 (2C, CHAr); 159.7
(1C, Cq). Hydrochloride mp 164–166ꢁC. MS (EI) m/z
195.1 (M). Anal. (C12H9N3ÆHClÆ0.5H2O) C, H, N.
6.5.9. 4-(6-Methylpyridin-2-ylethynyl)isoquinoline (28).
Chromatography (hexane/Et2O 4/6), yield 87%, yellow
oil. H NMR (CDCl3) d ppm: 2.51 (s, CH3); 7.04 (d,
6.6. General procedure for the synthesis of compounds 12–
14, 18–21, 25, 26
1
1H, J = 8.0Hz, CHAr); 7.36 (d, 1H, J = 8.0Hz, CHAr);
7.50 (t, 1H, J = 8.0Hz, CHAr); 7.55 (dd, 1H, J = 8.0;
1.2Hz, CHAr); 7.68 (td, 1H, J = 8.0; 1.2Hz, CHAr);
8.26 (d, 1H, J = 8.0Hz, CHAr); 8.72 (s, 1H, CHAr);
9.09 (s, 1H, CHAr). 13C NMR (CDCl3) d ppm: 23.9
(1C, CH3); 83.1 (1C, C„C); 95.3 (1C, C„C); 114.5
(1C, Cq); 122.4 (1C, CHAr); 124.0 (1C, CHAr);
124.5 (1C, CHAr); 127.0 (1C, Cq); 127.2 (1C, CHAr);
127.4 (1C, CHAr); 130.6 (1C, CHAr); 134.9 (1C, Cq);
135.8 (1C, CHAr); 141.5 (1C, Cq); 146.3 (1C, CHAr);
151.7 (1C, CHAr); 158.5 (1C, Cq). Hydrochloride mp
184–186ꢁC. Anal. (C17H12N2Æ2HClÆ0.75H2O) C, H, N.
To a solution of 36 (1g, 5.32mmol) in 15mL degassed
N,N-dimethylformamide was added successively the
appropriate aryl bromide (6.96mmol), CuI (110mg,
0.57mmol), Et3N (2.95mL, 21.2mmol), and trans-
dichlorobis(triphenylphosphine)palladium
(204mg,
0.29mmol). The resulting mixture was warmed to
70ꢁC, Bu4NF (5.85mL, 5.85mmol) was added drop-
wise, and the reaction was stirred at this temperature
overnight. After cooling, 10mL of H2O was added and
the resulting solution was extracted with EtOAc
(4 · 10mL). The organic layer was washed with satu-
rated NaCl (3 · 10mL), dried over Na2SO4, and evapo-
rated. Purification of the residue by column
chromatography yielded the corresponding compounds
12–14, 18–21, 25, 26.
6.5.10. 1-Methyl-6-(6-methylpyridin-2-ylethynyl)-1H-
indole (29). Chromatography (hexane/Et2O 4/6), yield
1
65%, yellow solid; mp 161–163ꢁC. H NMR (CDCl3)
d ppm: 2.46 (s, 3H, CH3); 3.58 (s, 3O, NCH3); 6.34 (d,
1H, J = 3.2Hz, CHAr); 6.91 (d, 1H, J = 8.0Hz, CHAr);
6.94 (d, 1H, J = 3.2Hz, CHAr); 7.21 (d, 1H, J = 7.6Hz,
CHAr); 7.23 (dd, 1H, J = 8.0; 1.2Hz, CHAr); 7.38 (t,
1H, J = 7.6Hz, CHAr); 7.45 (d, 1H, J = 8.0Hz, CHAr);
6.6.1. 2-(2,4-Dimethoxy-phenylethynyl)-6-methylpyridine
(12). Chromatography (hexane/Et2O 3/7), yield 28%,
yellow oil. 1H NMR (CD2Cl2) d ppm: 2.40 (s, 3H,
CH3); 3.67 (s, 3H, CH3); 3.76 (s, 3H, CH3); 6.35–6.37

206
D. Alagille et al. / Bioorg. Med. Chem. 13 (2005) 197–209
(m, 2H, CHAr); 6.93 (d, 1H, J = 8.0Hz, CHAr); 7.16 (d,
1H, J = 8.0Hz, CHAr); 7.32 (d, 1H, J = 8.0Hz, CHAr);
7.40 (t, 1H, J = 8.0Hz, CHAr). 13C NMR (CD2Cl2) d
ppm: 25.0 (1C, CH3); 56.2 (1C, OCH3); 56.5 (1C,
OCH3); 86.2 (1C, C„C); 92.4 (1C, C„C); 99.0 (1C,
CHAr); 104.6 (1C, Cq); 105.9 (1C, CHAr); 122.8 (1C,
CHAr); 124.6 (1C, CHAr); 135.4 (1C, CHAr); 136.9
(1C, CHAr); 143.8 (1C, Cq); 159.6 (1C, Cq); 162.5
(1C, Cq); 162.7 (1C, Cq). Hydrochloride mp 142–
144ꢁC. MS (EI) m/z 253.1 (M). Anal. (C16H15NO2Æ
HClÆ1/3H2O) C, H, N.
CH3); 2.57 (s, 3H, SCH3); 7.08 (d, 1H, J = 8.0Hz,
CHAr); 7.21–7.24 (m, 2H, CHAr); 7.32–7.36 (m, 2H,
CHAr); 7.46 (s, 1H, CHAr); 7.53 (t, 1H, J = 7.5Hz,
CHAr). 13C NMR (CDCl3) d ppm: 15.5 (1C, SCH3);
24.5 (1C, CH3); 88.2 (1C, C„C); 89.1 (1C, C„C);
122.7 (1C, CHAr); 123.0 (1C, Cq); 124.4 (1C, CHAr);
127.0 (1C, CHAr); 128.5 (1C, CHAr); 128.6 (1C,
CHAr); 129.1 (1C, CHAr); 136.3 (1C, CHAr); 139.0
(1C, Cq); 142.4 (C, Cq); 158.9 (1C, Cq). Hydrochloride
mp 132–134ꢁC. MS (EI) m/z 239.2 (M). Anal.
(C15H13NSÆHCl) C, H, N.
6.6.2. 2-(2,5-Dimethoxy-phenylethynyl)-6-methylpyridine
(13). Chromatography (hexane/Et2O 3/7), yield 34%,
yellow oil. 1H NMR (CD2Cl2) d ppm: 2.43 (s, 3H,
CH3); 3.65 (s, 3H, CH3); 3.75 (s, 3H, CH3); 7.74–7.80
(m, 2H, CHAr); 6.97–6.99 (m, 2H, CHAr); 7.22
(d, 1H, J = 8.0Hz, CHAr); 7.44 (t, 1H, J = 8.0Hz,
CHAr). 13C NMR (CD2Cl2) d ppm: 25.0 (1C, CH3);
56.5 (1C, OCH3); 57.0 (1C, OCH3); 85.7 (1C, C„C);
93.5 (1C, C„C); 112.6 (1C, Cq); 112.7 (1C, CHAr);
117.2 (1C, CHAr); 119.0 (1C, CHAr); 123.2 (1C,
CHAr); 124.9 (1C, CHAr); 137.0 (1C, CHAr); 143.3
(1C, Cq); 145.0 (1C, Cq); 155.7 (1C, Cq); 159.8 (1C,
Cq). Hydrochloride mp 162–164ꢁC. MS (EI) m/z 253.1
(M). Anal. (C16H15NO2ÆHClÆ0.5H2O) C, H, N.
6.6.6.
2-(3-Allyloxy-phenylethynyl)-6-methylpyridine
(20). Chromatography (hexane/Et2O 6/4), yield 60%,
yellow oil. 1H NMR (CDCl3) d ppm: 2.56 (s, 3H,
CH3); 4.51 (t, 1H, J = 1.5Hz, CH2a); 4.20 (t, 1H,
J = 1.5Hz, CH2b); 2.27 (dq, 1H, J = 10.5; 2.0Hz,
CHa); 5.40 (dq, 1H, J = 16.5; 1.5Hz, CHb); 6.03 (dqint,
1H, J = 21.0; 5.0Hz, CH); 6.92 (ddd, 1H, J = 8.0; 2.5;
1.0Hz, CHAr); 7.07 (d, 1H, J = 8.0Hz, CHAr); 7.14
(dd, 1H, J = 3.0; 1.5Hz, CHAr); 7.19 (dt, 1H, J = 7.5;
1.0Hz, CHAr); 7.23 (t, 1H, J = 8.0Hz, CHAr); 7.33
(d, 1H, J = 8.5Hz, CHAr); 7.52 (t, 1H, J = 8.0Hz,
CHAr). 13C NMR (CDCl3) d ppm: 24.6 (1C, CH3);
68.7 (1C, CH2); 88.6 (1C, C„C); 88.7 (1C, C„C);
116.3 (1C, CHAr); 117.5 (1C, CHAr); 117.7 (1C, CH2al-
lyl); 122.6 (1C, CHAr); 123.3 (1C, Cq); 124.4 (1C,
CHAr); 124.7 (1C, CHAr); 129.4 (1C, CHAr); 132.9
(1C, CHAr); 136.3 (C, CHallyl); 142.5 (1C, Cq); 158.2
(1C, Cq); 158.9 (1C, Cq). Hydrochloride mp 120–
122ꢁC. MS (EI) m/z 249.1 (M). Anal. (C17H15NOÆ
HClÆ1/5H2O) C, H, N.
6.6.3. 2-(3,4-Dimethoxy-phenylethynyl)-6-methylpyridine
(14). Chromatography (hexane/Et2O 3/7), yield 23%,
yellow oil. 1H NMR (CD2Cl2) d ppm: 2.41 (s, 3H,
CH3); 3.73 (s, 3H, CH3); 3.74 (s, 3H, CH3); 6.74 (d,
1H, J = 8.0Hz, CHAr); 6.97–6.98 (m, 2H, CHAr); 7.07
(dd, 1H, J = 8.0; 2.0Hz, CHAr); 7.20 (d, 1H,
J = 8.0Hz, CHAr); 7.44 (t, 1H, J = 8.0Hz, CHAr). 13C
NMR (CD2Cl2) d ppm: 25.0 (1C, CH3); 56.5 (1C,
OCH3); 56.6 (1C, OCH3); 88.4 (1C, C„C); 89.4 (1C,
C„C); 112.0 (1C, CHAr); 115.0 (1C, Cq); 115.5 (1C,
CHAr); 123.0 (1C, CHAr); 124.7 (1C, CHAr); 126.0
(1C, CHAr); 137.0 (1C, CHAr); 143.5 (1C, Cq); 149.7
(1C, Cq); 151.0 (1C, Cq); 159.7 (1C, Cq). Hydrochloride
mp 172–176ꢁC (dec). MS (EI) m/z 253.1 (M). Anal.
(C16H15NO2ÆHClÆ0.25H2O) C, H, N.
6.6.7. 2-Methyl-6-pyridin-2-ylethynylpyridine (21). Chro-
matography (hexane/Et2O 3/7), yield 65%, brown oil. 1H
NMR (CDCl3) d ppm: 2.57 (s, 3H, CH3); 7.14 (d, 1H,
J = 6.0Hz, CHAr); 7.40 (ddd, 1H, J = 6.0; 4.8; 0.8Hz,
CHAr); 7.43 (d, 1H, J = 6.0Hz, CHAr); 7.58 (t, 1H,
J = 6.0Hz); 7.88 (dt, 1H, J = 6.0; 0.8Hz, CHAr); 8.57
(td, 1H, J = 6.8; 1.2Hz, CHAr); 8.63 (dt, 1H, J = 2.8;
0.8Hz, CHAr). 13C NMR (CDCl3) d ppm: 24.8 (1C,
CH3); 87.7 (1C, C„C); 88.4 (1C, C„C); 123.5 (1C,
CHAr); 123.6 (1C, CHAr); 125.2 (1C, CHAr); 127.9
(1C, CHAr); 136.5 (1C, CHAr); 136.7 (1C, CHAr);
142.0 (1C, Cq); 142.9 (1C, Cq); 150.3 (1C, CHAr);
159.3 (1C, Cq). Hydrochloride mp 102–104ꢁC. MS
(EI) m/z 195.1 (M+1). Anal. (C13H10N2Æ2HClÆ0.5H2O)
C, H, N.
6.6.4. 2-(3-Fluoro-phenylethynyl)-6-methylpyridine (18).
Chromatography (hexane/EtOAc 9/1), yield 31%, yellow
1
oil. Hydrochloride mp 158–160ꢁC. H NMR (MeOH-
d4) d ppm: 2.87 (s, 3H, CH3); 5.06 (br s, 1H, N+H);
7.33–7.37 (m, 1H, CHAr); 7.52–7.61 (m, 3H, CHAr);
7.94 (d, 1H, J = 8.5Hz, CHAr); 8.09 (d, 1H,
J = 8.5Hz, CHAr); 8.51 (t, 1H, J = 8.5Hz, CHAr). 13C
NMR (MeOH-d4) d ppm: 20.4 (1C, CH3); 82.2 (1C,
C„C); 99.2 (1C, C„C); 120.0 (d, 1C, J = 21.5Hz,
CHAr); 120.5 (d, 1C, J = 23.3Hz, CHAr); 123.2 (d,
1C, J = 8.5Hz, Cq); 129.0 (1C, CHAr); 129.5 (1C,
CHAr); 130.2 (d, 1C, J = 3.3Hz, CHAr); 132.7 (d,
1C, J = 8.1Hz, CHAr); 136.0 (1C, Cq); 147.7
(1C, CHAr); 157.6 (1C, Cq); 164.2 (d, 1C, J = 245Hz,
Cq). MS (EI) m/z 211.1 (M). Anal. (C14H10FNÆHCl)
C, H, N.
6.6.8. 3-(6-Methylpyridin-2-ylethynyl)-5-bromopyridine
(25). Chromatography (hexane/Et2O 4/6), yield 49%,
brown solid. 1H NMR (CDCl3) d ppm: 2.60 (s, 3H,
CH3); 7.17 (d, 1H, J = 8.0Hz, CHAr); 7.37 (d, 1H,
J = 8.0Hz, CHAr); 7.60 (t, 1H, J = 8.0Hz, CHAr);
8.02 (s, 1H, CHAr); 8.63 (s, 1H, CHAr); 8.72 (s, 1H,
CHAr). 13C NMR (CDCl3) d ppm: 25.0 (1C, CH3);
83.8 (1C, C„C); 93.4 (1C, C„C); 120.4 (1C, Cq);
121.4 (1C, Cq); 123.8 (1C, CHAr); 125.0 (1C, CHAr);
136.9 (1C, CHAr); 141.4 (1C, CHAr); 141.9 (1C, Cq);
150.6 (1C, CHAr); 150.9 (1C, CHAr); 159.7 (1C, Cq).
Hydrochloride mp 174–176ꢁC. MS (EI) m/z 272.0 and
274.0 (M, 79Br and 81Br). Anal. (C12H9BrN2Æ2HCl) C,
H, N.
6.6.5. 2-Methyl-6-(3-methylthiophenylethynyl)pyridine
(19). Chromatography (hexane/EtOAc 8/2), yield 44%,
yellow oil. 1H NMR (CDCl3) d ppm: 2.47 (s, 3H,

D. Alagille et al. / Bioorg. Med. Chem. 13 (2005) 197–209
207
6.6.9. [5-(6-Methylpyridin-2-ylethynyl)-pyridin-3-yl]-
methanol (26). Chromatography (EtOAc/Et2O 3/7),
yield 65%, brown oil. H NMR (CDCl3) d ppm: 2.57
6.9. 2-Methyl-6-pyridin-3-ylethynylpyridine (22)
1
To a solution of 39 (300mg, 2.91mmol) in 10mL of
degassed Et3N was added successively CuI (55mg,
0.29mmol), 2-bromo-6-methylpyridine (551lg, 3.20
mmol), and trans-dichlorobis(triphenylphosphine)palla-
dium (204mg, 0.29mmol). The mixture was stirred at
90ꢁC for 6h, then the black solution was hydrolyzed
with 10mL of H2O and extracted with EtOAc
(3 · 10mL). Purification of the residue by column chro-
matography (Et2O/hexane 8/2) yielded 160mg (35%) of
(s, 3H, CH3); 4.76 (s, 2H, CH2); 5.43 (br s, 1H, OH);
7.15 (d, 1H, J = 8.0Hz, CHAr); 7.35 (d, 1H, J =
8.0Hz, CHAr); 7.59 (t, 1H, J = 8.0Hz, CHAr); 7.88
(t, 1H, J = 2.0Hz, CHAr); 8.50 (d, 1H, J = 2.0Hz,
CHAr); 8.60 (d, 1H, J = 2.0Hz, CHAr). 13C NMR
(CDCl3) d ppm: 24.3 (1C, CH3); 61.4 (1C, CH2); 85.4
(1C, C„C); 91.6 (1C, C„C); 119.1 (1C, Cq); 123.3
(1C, CHAr); 124.7 (1C, CHAr); 136.8 (1C, CHAr);
136.9 (1C, Cq); 137.5 (1C, CHAr); 141.7 (1C, Cq);
147.6 (1C, CHAr); 150.8 (1C, CHAr); 159.0 (1C, Cq).
Hydrochloride mp 164–166ꢁC. MS (EI) m/z 224.1 (M).
Anal. (C14H12N2OÆ2HClÆH2O) C, H, N.
1
29 as a yellow oil. H NMR (CDCl3) d ppm: 2.58 (s,
3H, CH3); 7.14 (d, 1H, J = 8.0Hz, CHAr); 7.40 (ddd,
1H, J = 8.0; 5.8; 0.8Hz, CHAr); 7.38 (d, 1H,
J = 8.0Hz, CHAr); 7.58 (t, 1H, J = 8.0Hz); 7.88 (dt,
1H, J = 8.0; 2.0Hz, CHAr); 8.57 (dd, 1H, J = 5.8;
2.0Hz, CHAr); 8.83 (dd, 1H, J = 2.0; 0.8Hz, CHAr).
13C NMR (CDCl3) d ppm: 24.8 (1C, CH3); 85.4 (1C,
C„C); 92.2 (1C, CC); 119.9 (1C, Cq); 123.4 (1C,
CHAr); 123.5 (1C, CHAr); 124.8 (1C, CHAr); 136.8
(1C, CHAr); 139.2 (1C, CHAr); 142.1 (1C, Cq); 149.3
(1C, CHAr); 152.7 (1C, CHAr); 159.4 (1C, Cq). Hydro-
chloride mp 164–166ꢁC. MS (EI) m/z 194.1 (M). Anal.
(C13H10N2Æ2HCl) C, H, N.
6.7. 2-Methyl-6-(3-nitro-phenylethynyl)-pyridine (16)
To a solution of 37 (165mg, 1.41mmol) in 10mL of
degassed Et3N was added 1-iodo-3-nitrobenzene
(386mg, 1.55mmol), CuI (26mg, 0.14mmol), and
trans-dichlorobis(triphenylphosphine)palladium (99mg,
0.14mmol). The resulting solution was stirred at rt
for 3h under N2 atmosphere, then the black solution
was hydrolyzed with 10mL of H2O and extracted
with EtOAc (3 · 10mL). The organic layer was washed
with saturated NaCl (3 · 20mL), dried over Na2SO4,
and evaporated. Purification of the residue by column
chromatography (SiO2/hexane/EtOAc 8/2) yield 47%
6.10. 3-Bromo-5-methoxy-pyridine (40)
In 10mL of MeOH was added by portion Na metal
(854mg, 37.1mmol) and the resulting mixture was stir-
red at rt until complete reaction. Then 3,6-dibromopyr-
idine (4.40g, 18.5mmol) was added and the solution was
heated at 130ꢁC in a sealed tube for 24h. After cooling
the reaction was poured into 50mL of H2O and ex-
tracted twice with 30mL of EtOAc. The organic layer
was washed with saturated NaCl (3 · 20mL), dried over
Na2SO4, and evaporated. Purification of the residue by
column chromatography (hexane/EtOAc 7/3) yielded
of 16 as
a
brown solid; mp 103–105ꢁC. 1H
NMR (CDCl3) d ppm: 2.60 (s, 3H, CH3); 7.17 (d,
1H, J = 7.6Hz, CHAr); 7.40 (d, 1H, J = 7.6Hz, CHAr);
7.55 (t, 1H, J = 8.0Hz, CHAr); 7.62 (t, 1H, J =
8.0Hz); 7.90 (d, 1H, J = 8.0Hz, CHAr); 8.21 (dd,
J = 8.4; 1.8Hz, CHAr); 8.45 (t, 1H, J = 1.8Hz, CHAr).
13C NMR (CDCl3) d ppm: 25.0 (1C, CH3); 86.2
(1C, CC); 91.4 (1C, C„C); 123.7 (1C, CHAr); 123.9
(1C, CHAr); 124.6 (1C, Cq); 125.0 (1C, CHAr); 127.2
(1C, CHAr); 129.8 (1C, CHAr); 136.9 (1C, CHAr);
138.0 (1C, CHAr); 142.1 (1C, Cq); 148.4 (1C,
Cq); 159.6 (1C, Cq). Hydrochloride mp 162–165ꢁC.
MS (EI) m/z 238.1 (M). Anal. (C14H10N2O2ÆHCl) C,
H, N.
1
3.21g (92%) of 40 as a white solid, mp 33–34ꢁC. H
NMR (CDCl3) d ppm: 3.68 (s, 3H, OCH3); 7.18 (t,
1H, J = 2.4Hz, CHAr); 8.08 (d, 1H, J = 2.4Hz, CHAr);
8.12 (d, 1H, J = 2.4Hz, CHAr). 13C NMR (CDCl3) d
ppm: 56.1 (1C, OCH3); 120.6 (1C, Cq); 123.4 (1C,
CHAr); 136.4 (1C, CHAr); 143.1 (1C, CHAr); 156.3
(1C, Cq).
6.8. Synthesis of 3-ethynylpyridine (39)
6.11. 3-Methoxy-5-trimethylsilanylethynylpyridine (41)
To a solution of KOH (1.28g, 22.8mmol) in 20mL of
MeOH was added commercial 3-trimethylsilylethynyl-
pyridine (2.00g, 11.4mmol) dissolved in 5mL of metha-
nol. The resulting solution was stirred at rt for 2h. Then
20mL of H2O was added and the resulting mixture was
extracted with EtOAc (3 · 10mL). The organic layer
was washed with saturated NaCl (3 · 20mL), dried over
Na2SO4, and evaporated. Purification of the residue by
column chromatography (hexane/Et2O 7/3) yielded
760mg (65%) of 39 as a white solid, mp 34–35. 1H
NMR (CDCl3) d ppm: 3.32 (s, 1H, C„CH); 7.24
(ddd, 1H, J = 8.0; 5.0; 0.8Hz CHAr); 7.76 (dt, 1H,
J = 8.0; 1.6Hz, CHAr); 8.55 (dd, 1H, J = 5.0; 1.6Hz,
CHAr); 8.73 (d, 1H, J = 1.6Hz, CHAr). 13C NMR
(CDCl3) d ppm: 80.3 (1C, C„C); 80.9 (1C, C„CH);
119.2 (1C, Cq); 122.9 (1C, CHAr); 139.0 (1C, CHAr);
149.0 (2C, CHAr); 152.7 (1C, CHAr).
To a solution of 40 (3g, 16.1mmol) in 30mL of degassed
Et3N was added trimethylsilylacetylene (2.51mL,
17.7mmol), CuI (306mg, 1.61mmol), and trans-dichlo-
robis(triphenylphosphine)palladium (1.11g, 1.61mmol).
The resulting solution was stirred at rt for 5h under N2
atmosphere. Then the black solution was hydrolyzed
with 30mL of H2O and extracted with EtOAc
(3 · 30mL). Purification of the residue by column chro-
matography (hexane/EtOAc 8/2) yielded 2.88g (88%) of
40 as a brown oil. 1H NMR (CDCl3) d ppm: 0.00 (s, 9H,
Si(CH3)3); 3.56 (s, 3H, OCH3); 6.97 (s, 1H, CHAr);
8.11 (br s, 1H, CHAr); 8.23 (br s, 1H, CHAr). 13C
NMR (CDCl3) d ppm: ꢀ0.1 (3C, Si(CH3)3); 55.7 (1C,
OCH3); 98.2 (2C, 2C„C); 101.8 (1C, Cq); 122.3
(1C, CHAr); 123.2 (1C, Cq); 137.5 (1C, CHAr); 144.7
(1C, CHAr).

208
D. Alagille et al. / Bioorg. Med. Chem. 13 (2005) 197–209
6.12. 3-Methoxy-5-(4-methyl-thiazol-2-ylethynyl)-pyr-
idine (32)
7.51 (s, 1H, CHAr); 7.65 (t, 1H, J = 7.0Hz, CHAr);
7.79 (td, 1H, J = 7.0; 1.0Hz, CHAr); 7.99 (d, 1H,
J = 8.5Hz, CHAr); 8.35 (d, 1H, J = 8.5Hz, CHAr);
8.80 (s, 1H, CHAr); 9.21 (s, 1H, CHAr). 13C NMR
(CDCl3) d ppm: 19.3 (1C, CH3); 84.0 (1C, C„C); 90.6
(1C, C„C); 115.2 (1C, Cq); 123.1 (1C, CHAr); 125.2
(1C, CHAr); 127.7 (1C, Cq); 127.9 (1C, CHAr);
128.0 (1C, CHAr); 131.2 (1C, CHAr); 135.4 (1C, Cq);
136.6 (1C, Cq); 146.8 (1C, CHAr); 152.3 (1C, CHAr);
166.0 (1C, Cq). Hydrochloride mp 188–192ꢁC (dec).
MS (EI) m/z 250.0 (M). Anal. (C15H10N2SÆ2HCl) C,
H, N.
To a solution of 40 (661mg, 4.96mmol) in 15mL
degassed Et3N was added successively 2-iodo-4-
methyl-thiazole (1g, 4.52mmol), CuI (85mg, 0.45
mmol), and trans-dichlorobis(triphenylphosphine)palla-
dium (317mg, 0.45mmol). The resulting mixture was
warmed to 60ꢁC, Bu4NF (5.85mL, 5.85mmol) was
added drop-wise, and the reaction was stirred at this
temperature overnight. After cooling, 10mL of H2O
was added and the resulting solution was extracted with
EtOAc (4 · 10mL). The organic layer was washed with
saturated NaCl (3 · 10mL), dried over Na2SO4, and
evaporated. Purification of the residue by column chro-
matography (hexane/Et2O 1/1) yielded 590mg of 32 as a
6.13.3. 2-Methyl-4-(3-nitro-phenylethynyl)-thiazole (35).
Chromatography (hexane/Et2O 6/4), yield 76%, yellow
1
solid; mp 107–109ꢁC. H NMR (CDCl3) d ppm: 2.75
1
brown solid; mp 88–90ꢁC. H NMR (CDCl3) d ppm:
(s, 3H, CH3); 7.46 (s, 1H, CHAr); 7.53 (t, 1H,
J = 7.5Hz, CHAr); 7.84 (dt, 1H, J = 7.5; 1.5Hz,
CHAr); 8.19 (ddd, 1H, J = 8.5; 2.5; 1.5Hz, CHAr);
8.39 (t, 1H, J = 2.5Hz, CHAr). 13C NMR (CDCl3)
d ppm: 19.2 (1C, CH3); 85.9 (1C, C„C); 86.2 (1C,
C„C); 123.2 (1C, CHAr); 123.6 (1C, CHAr);
124.3 (1C, Cq); 126.5 (1C, CHAr); 129.4 (1C, CHAr);
135.9 (1C, Cq); 137.2 (1C, CHAr); 148.1 (1C, Cq);
166.1 (1C, Cq). Hydrochloride mp 140–142ꢁC. MS
(EI) m/z 244.1 (M). Anal. (C12H8N2O2SÆ0.9HCl) C, H,
N.
2.36 (s, 3H, CH3); 3.73 (s, 3H, OCH3); 6.87 (s, 1H,
CHAr); 7.21 (s, 1H, CHAr); 8.19 (s, 1H, CHAr); 8.29
(s, 1H, CHAr). 13C NMR (CDCl3) d ppm: 17.3 (1C,
CH3); 55.8 (1C, OCH3); 85.6 (1C, C„C); 89.9
(1C, C„C); 116.5 (1C, CHAr); 119.1 (1C, Cq); 122.3
(1C, CHAr); 138.8 (1C, CHAr); 144.7 (1C, CHAr);
147.1 (1C, Cq); 154.3 (1C, Cq); 155.3 (1C, Cq). Hydro-
chloride mp 149–150ꢁC. MS (EI) m/z 230.0 (M). Anal.
(C12H10N2OSÆHCl) C, H, N.
6.13. General procedure for the synthesis of compounds
33–35
Acknowledgements
To a solution of 4210 (500mg, 2.55mmol) in 15mL de-
gassed NN-dimethylformamide was added successively
the appropriate aryl bromide (2.80mmol), CuI (48mg,
0.25mmol), Et3N (1.42mL, 10.2mmol), and trans-
dichlorobis(triphenylphosphine)palladium (89mg, 0.12
mmol). The resulting mixture was warmed to 70ꢁC,
Bu4NF (2.80mL, 2.80mmol) was added drop-wise,
and the reaction was stirred at this temperature over-
night. After cooling, 10mL of H2O was added and
the resulting solution was extracted with EtOAc
(4 · 10mL). The organic layer was washed with satu-
rated NaCl (3 · 10mL), dried over Na2SO4, and evapo-
rated. Purification of the residue by column
chromatography yielded the corresponding compounds
33–35.
This work was supported by the National Institutes of
Health (DA16180-01) and from Department of Veterans
Affairs, National Center for PTSD Alcohol Research
Center and NARSAD to G.D.T. and by the National
Institute of Mental Health through the Psychoactive
Drug Screening Program (N01MH80005) and
KO2MH01366 to B.L.R.
Supplementary data
Supplementary data associated with this article can be
found, in the online version, at doi:10.1016/j.bmc.
2004.09.042.
6.13.1. [5-(2-Methyl-thiazol-4-ylethynyl)-pyridin-3-yl]-
methanol (33). Chromatography (EtOAc/Et2O 3/7),
1
yield 81%, yellow oil. H NMR (CDCl3) d ppm: 2.71
References and notes
(s, 3H, CH3); 4.71 (d, 2H, J = 5.5Hz, CH2); 5.39 (br s,
1H, OH); 7.44 (s, 1H, CHAr); 7.84 (s, 1H, CHAr);
8.47 (d, 1H, J = 1.5Hz, CHAr); 8.56 (d, 1H,
J = 1.5Hz, CHAr). 13C NMR (CDCl3) d ppm: 19.1
(1C, CH3); 61.3 (1C, CH2); 85.4 (1C, C„C); 86.5 (1C,
C„C); 119.4 (1C, Cq); 123.4 (1C, CHAr); 135.9 (1C,
Cq); 137.0 (1C, Cq); 137.2 (1C, CHAr); 147.3 (1C,
CHAr); 150.5 (1C, CHAr); 166.2 (1C, Cq). Hydrochlo-
ride mp 159–163ꢁC. MS (EI) m/z 230.2 (M). Anal.
(C12H10N2OSÆHClÆ0.5H2O) C, H, N.
1. Dingledine, R.; Borges, K.; Bowie, D.; Traynelis, S. F.
Pharmacol. Rev. 1999, 51, 7.
2. Pin, J.; De Colle, C.; Bessis, A.; Acher, F. Eur. J.
Pharmacol. 1999, 375, 277.
3. OꢀHara, L. J.; Sheppard, P. O.; Thogersen, H.; Venezia,
D.; Haldema, B. A.; MacGrane, V.; Houamed, K. M.;
Thomsen, C.; Gilbert, E. R.; Mulvihill, E. R. Neuron 1993,
11, 41.
4. Conn, P. J.; Pin, J. P. Annu. Rev. Pharmacol. Toxicol.
1997, 3, 205.
5. Schoepp, D. D.; Jane, D. E.; Monn, J. A. Neuropharma-
cology 1999, 38, 1431.
6. Shi, Q.; Savage, J. E.; Hufeisen, S. J.; Rauser, L.;
Grajkowska, E.; Ernsberger, P.; Wroblewski, J. T.;
6.13.2. 4-(2-Methyl-thiazol-4-ylethynyl)-isoquinoline (34).
Chromatography (hexane/Et2O 4/6), yield 59%, color-
less oil. H NMR (CDCl3) d ppm: 2.77 (s, 3H, CH3);
1

D. Alagille et al. / Bioorg. Med. Chem. 13 (2005) 197–209
209
Nadeau, J. H.; Roth, B. L. J. Pharmacol. Exp. Ther. 2003,
205, 131.
7. Spooren, W. P. J. M.; Gasparini, F.; Salt, T. E.; Kuhn, R.
Trends Pharmacol. Sci. 2001, 22, 331.
8. Shigemoto, R.; Nomura, S.; Ohishi, H.; Sugihara, H.;
Nakanishi, S.; Mizuno, N. Neurosci. Lett. 1993, 163, 53.
9. Romano, C.; Sesma, M. A.; McDonald, C. T.; OꢀMalley,
K.; VandenPol, A. N.; Olney, J. W. J. Compar. Neurol.
1995, 355, 455.
10. Varney, M. A.; Cosford, N. D.; Jachec, C.; Rao, S. P.;
Sacaan, A.; Lin, F. F.; Bleicher, L.; Santori, E. M.; Flor,
P. J.; Allgeier, H.; Gasparini, F.; Kuhn, R., et al. J.
Pharmacol. Exp. Ther. 1999, 290, 170.
15. Tatarczynska, E.; Klodzinska, A.; Chojnacka-Wojcik, E.;
Palucha, A.; Gasparini, F.; Kuhn, R.; Pilc, A. Br. J.
Pharmacol. 2001, 132, 1423.
16. Klodzinska, A.; Tatarczynska, E.; Chojnacka-Wojcik, E.;
Pilc, A. Pol. J. Pharmacol. 2000, 52, 463.
17. Chiamulera, C.; Epping-Jordan, M. P.; Zocchi, A.;
Marcon, C.; Cottiny, C.; Tacconi, S.; Corsi, M.; Orzi,
F.; Conquet, F. Nature Neurosci. 2001, 4, 873.
18. Stephens, R. D.; Castro, C. E. J. Org. Chem. 1963, 28,
3313.
19. Negishi, E.; Anastasia, L. Chem. Rev. 2003, 203, 1979.
20. Stille, J. K.; Simpson, J. H. J. Am. Chem. Soc. 1987, 109,
2138.
11. Gasparini, F.; Lingenhohl, K.; Stoehr, N.; Flor, P. J.;
Heinrich, M.; Vranesic, I.; Biollaz, M.; Allgeier, H.;
Heckendorn, R.; Urwyler, S.; Varney, M. A.; Johnson,
E. C., et al. Neuropharmacology 1999, 38, 1493.
12. Cosford, N. D. P.; Roppe, J.; Tehrani, L.; Schweiger, E.
J.; Seiders, T. J.; Chaudary, A.; Rao, S.; Varney, M. A.
Bioorg. Med. Chem. Lett. 2003, 13, 351.
13. Cosford, N. D. P.; Tehrani, L.; Roppe, J.; Schweiger, E.;
Smith, N. D.; Anderson, J.; Bristow, L.; Brodkin, J.;
Jiang, X.; McDonald, I.; Rao, S.; Washburn, M., et al. J.
Med. Chem. 2003, 46, 204.
21. Wroblewska, B.; Wroblewski, J. T.; Pshenichkin, S.;
Surin, A.; Sullivan, S. E.; Neale, J. H. J. Neurochem.
1997, 69, 174.
22. Gomeza, J.; Mary, S.; Brabet, I.; Parmentier, M. L.;
Restituto, S.; Bockaert, J.; Pin, J. P. Mol . Pharmacol.
1996, 50, 923.
23. Raulli, R.; Danysz, W.; Wroblewski, J. T. J. Neurochem.
1991, 56, 2116.
24. Still, W. C.; Kahn, M.; Mitra, A. J. Org. Chem. 1978, 43,
2923.
25. Mukhopadhyaya, J. K.; Kozikowski, A. P.; Grajkowska,
E.; Pshenichkin, S.; Wroblewski, J. T. Bioorg. Med. Chem.
Lett. 2001, 11, 1919.
14. Brodkin, J.; Busse, C.; Sukoff, S. J.; Varney, M. A. Pharm.
Biochem. Behav. 2002, 73, 359.