Journal of Medicinal Chemistry
Article
water (A) and acetonitrile (B). Flash chromatography was performed
with a CombiFlash Rf Purification System (Teledyne Isco) using a
Silica ReadySep Rf column. Hydrogenation reaction was performed
using a Parr shaker hydrogenation apparatus (Moline, IL). The
7.35 (d, J = 8.5 Hz, 1H). 13C NMR (125 MHz, CDCl3): δ 165.47,
165.08, 162.55, 149.42, 148.41, 140.17, 139.71, 138.21, 135.63, 134.43,
134.10, 131.21, 129.81, 127.25, 125.02, 123.33, 122.96, 121.24, 119.55,
118.82. HRMS m/z calcd for C20H12ClBrN3O3 (M + H)+, 455.9745;
found 455.9742.
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products were identified by LC−MS and H NMR and 13C NMR
using a Varian 500 MHz spectrometer. 19F NMR was used to identify
the fluorine compound. All NMR samples were dissolved in
chloroform-d (CDCl3) containing tetramethylsilane as a reference
standard. Chemical shifts were expressed as ppm and calculated
downfield or upfield from the NMR signal of reference standard. J was
expressed as Hz, and its splitting patterns were reported as s, d, t, q, or
m. HRMS was obtained from the High Resolution Mass Spectrometry
Facility at the University California, Riverside, using electrospray
ionization (ESI)/atmospheric pressure chemical ionization (APCI)
technique (Agilent Time of Flight (TOF) LC−MS). Melting points
were measured using a Mettler MP50 melting point system. Unless
otherwise specified, the purities of all new compounds were over 95%
determined by HPLC.
The mGlu4 blocking agent 2 and its hydrochloride salt were
prepared by a published method.17 [3H]Iodomethane (37 GBq/mL in
DMF) was purchased from American Radiolabeled Chemicals Inc. and
used without further purification.
The National Institute of Mental Health’s Psychoactive Drug
Screening Program, Contract HHSN-271-2008-00025-C (NIMH
PDSP), generously performed selectivity tests for mGlu1 and mGlu5
using intracellular inositol phosphates (IPs) accumulation assay with
CHO cells that stably expressed mGlu1a and mGlu5a. Detailed
procedures of selectivity tests were described in the previous
literature.17,22,23 For the selectivity test for mGlu8, split luciferase
biosensor cAMP assay was performed using mGlu8 transfected CHO
cells.22,23
Syntheses of Phthalimide Derivatives 3, 4, 7, and 17. A
solution of 12 and phthalic anhydride derivatives (13, 14, 15, and 16)
in acetic acid was heated to 100 °C for 5 h. After acetic acid was
removed at reduced pressure, residue was recrystallized in a solution of
ethyl acetate and hexane to give the corresponding phthalimide
derivatives 3, 4, 7, and 17 as brown powders, respectively.
N-(3-Chloro-4-(4-fluoro-1,3-dioxoisoindolin-2-yl)phenyl)-2-
picolinamide (3). 12 (0.20 mmol, 50 mg), 3-fluorophthalic
anhydride (13, 0.24 mmol, 40 mg), and acetic acid (4.0 mL) were
used to afford 3 (62 mg, 78% yield); mp 218−220 °C. 1H NMR (500
MHz, CDCl3): δ 10.21 (s, 1H), 8.64 (d, J = 4.5 Hz, 1H), 8.31 (d, J =
8.0 Hz, 1H), 8.18 (d, J = 2.0 Hz, 1H), 7.95 (t, J = 8.0 Hz, 1H), 7.80−
7.83 (m, 3H), 7.53 (dd, J = 7.5 Hz, 5.0 Hz, 1H), 7.48 (t, J = 8.0 Hz,
1H), 7.35 (d, J = 8.5 Hz, 1H). 13C NMR (125 MHz, CDCl3): δ 165.97
(d, J = 2.6 Hz), 163.71, 162.57, 158.30 (d, J = 265.6 Hz), 149.46,
148.43, 140.23, 138.23, 137.38 (d, J = 6.8 Hz), 134.39, 134.17, 131.28,
127.27, 124.92, 123.18 (d, J = 20.5 Hz), 122.99, 121.31, 120.52 (d, J =
3.9 Hz), 118.88, 118.16 (d, J = 1.3 Hz). 19F NMR (470 MHz, CDCl3):
δ −111.6 (t, J = 5.9 Hz). HRMS m/z calcd for C20H12ClFN3O3 (M +
H)+, 396.0546; found 396.0554.
N-(3-Chloro-4-(4-methyl-1,3-dioxoisoindolin-2-yl)phenyl)-2-
picolinamide (4). 12 (0.40 mmol, 100 mg), 3-methylphthalic
anhydride (14, 0.42 mmol, 39 mg), and acetic acid (8.0 mL) were
used to afford 4 (66 mg, 66% yield); mp 184−185 °C. 1H NMR (500
MHz, CDCl3): δ 10.19 (s, 1H), 8.63 (d, J = 5.0 Hz, 1H), 8.31 (d, J =
8.0 Hz, 1H), 8.17 (d, J = 2.0 Hz, 1H), 7.94 (td, J = 8.0 Hz, 1.0 Hz,
1H), 7.81 (m, 2H), 7.66 (t, J = 8.0 Hz, 1H), 7.52−7.57 (m, 2H), 7.35
(d, J = 8.5 Hz, 1H), 2.76 (s, 3H). 13C NMR (125 MHz, CDCl3): δ
167.91, 167.19, 162.52, 149.51, 148.41, 139.95, 139.07, 138.19, 137.15,
134.29, 134.23, 132.71, 131.35, 128.99, 127.21, 125.54, 122.93, 121.93,
121.24, 118.78, 18.13. HRMS m/z calcd for C21H15ClN3O3 (M + H)+,
392.0796; found 392.0805.
N-(3-Chloro-4-(4-nitro-1,3-dioxoisoindolin-2-yl)phenyl)-2-pi-
colinamide (17). 12 (0.606 mmol, 0.150 g), 3-nitrophthalic
anhydride (16, 0.666 mmol, 0.129 g), and acetic acid (6 mL) were
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used to afford 17 (0.204 g, 80% yield); mp 199−201 °C. H NMR
(500 MHz, CDCl3): δ 10.23 (s, 1H), 8.65 (d, J = 5.0 Hz, 1H), 8.32 (d,
J = 8.0 Hz, 1H), 8.25 (d, J = 7.0 Hz, 1H), 8.20−8.22 (m, 2H), 8.01 (t,
J = 7.8 Hz, 1H), 7.96 (td, J = 8.0 Hz, 1.5 Hz, 1H), 7.82 (dd, J = 8.8 Hz,
2.3 Hz, 1H), 7.54 (dd, J = 7.0 Hz, 5.0 Hz, 1H), 7.37 (d, J = 8.5 Hz,
1H). 13C NMR (125 MHz, CDCl3): δ 164.62, 162.61, 161.68, 149.41,
148.45, 145.87, 140.50, 138.26, 136.14, 134.25, 134.05, 131.17, 129.41,
128.03, 127.31, 124.50, 124.00, 123.02, 121.31, 118.91. HRMS m/z
calcd for C20H12ClN4O5 (M + H)+, 423.0491; found 423.0487.
N-(3-Chloro-4-(4-iodo-1,3-dioxoisoindolin-2-yl)phenyl)-2-pi-
colinamide (8). Iodine (0.116 mmol, 29.4 mg) was added to a
solution of 18 (72.5 μmol, 39.2 mg) in DCM (1.4 mL), and the
mixture was stirred at room temperature for 2 h. The solution was
quenched with 5% sodium metabisulfite solution until its color
disappeared. The solution was then extracted with ethyl acetate three
times. Organic layers were collected, dried over anhydrous sodium
sulfate (Na2SO4), filtered, and evaporated. Residue was separated with
25% ethyl acetate in hexane by flash column chromatography to give 8
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as a yellowish solid (2.5 mg, 7% yield); mp 140−142 °C. H NMR
(500 MHz, CD3CN): δ 10.37 (s, 1H), 8.72 (d, J = 4.5 Hz, 1H), 8.30
(d, J = 8.0 Hz, 1H), 8.26−8.27 (m, 2H), 8.05 (t, J = 7.5 Hz, 1H), 7.98
(d, J = 7.5 Hz, 1H), 7.92 (dd, J = 8.5 Hz, 2.0 Hz, 1H), 7.64 (dd, J = 8.0
Hz, 4.0 Hz, 1H), 7.59 (t, J = 7.8 Hz, 1H), 7.48 (d, J = 9.0 Hz, 1H).
HRMS m/z calcd for C20H12ClN3O3I (M + H)+, 503.9606; found
503.9417.
N-(3-Chloro-4-nitrophenyl)-2-picolinamide (11). Thionyl
chloride (163 mmol, 11.8 mL) was added to 2-picolinic acid (9,
40.6 mmol, 4.00 g) in benzene (60 mL), and the mixture was refluxed
for 2 h. Then the solvent and extra thionyl chloride were removed by
vacuum distillation. The resulting 2-picolinic acid chloride was isolated
as a gray salt powder. A solution of 3-chloro-4-nitroaniline (6, 10.2
mmol, 1.75 g) (Alfa Aesar) and triethylamine (122 mmol, 17.0 mL) in
30 mL of THF was then added to the gray salt powder in 30 mL of
THF. The mixture was refluxed for 2 h and was then quenched with
saturated ammonium chloride solution. The reaction mixture solution
was extracted with ethyl acetate three times and dried over anhydrous
Na2SO4, filtered, and evaporated. The residue was separated by flash
chromatography with eluants of ethyl acetate (20%) and hexane (80%)
to give the crude product as a solid, which was recrystallized in a
solution of ethyl acetate and hexane to give 11 as a white crystal (1.153
g, 41% yield); mp 179−180 °C. 1H NMR (500 MHz, CDCl3): δ 10.35
(s, 1H), 8.65 (d, J = 5.0 Hz, 1H), 8.31 (d, J = 8.0 Hz, 1H), 8.15 (d, J =
2.0 Hz, 1H), 8.05 (d, J = 9.0 Hz, 1H), 7.97 (td, J = 8.0 Hz, 1.0 Hz,
1H), 7.57 (dd, J = 7.0 Hz, 5.0 Hz, 1H). 13C NMR (125 MHz, CDCl3):
δ 162.77, 148.90, 148.53, 143.16, 142.61, 138.39, 129.45, 127.69,
127.66, 123.12, 122.04, 117.87. HRMS m/z calcd for C12H9ClN3O3
(M + H)+, 278.0327; found 278.0329.
N-(3-Chloro-4-aminophenyl)-2-picolinamide (12). Compound
11 (3.96 mmol, 1.10 g) and 10% palladium/charcoal (0.220 g) were
added to a solution of methanol (70 mL) and ethyl acetate (70 mL).
The mixture was shaken under 3 atm of hydrogen for 20 h at room
temperature. The solution was filtered and evaporated. The residue
was separated by flash chromatography with eluants of 30% ethyl
acetate and 70% hexane to give a crude product, which was
recrystallized in a solution of ethyl acetate and hexane to afford 12
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as a yellowish solid (0.889 g, 91% yield); mp 144−145 °C. H NMR
N-(3-Chloro-4-(4-bromo-1,3-dioxoisoindolin-2-yl)phenyl)-2-
picolinamide (7). 12 (2.02 mmol, 0.500 g), 3-bromophthalic
anhydride (15, 2.22 mmol, 0.504 g), and acetic acid (10 mL) were
(500 MHz, CDCl3): δ 9.85 (s, 1H), 8.60 (d, J = 5.0 Hz, 1H), 8.29 (d, J
= 8.0 Hz, 1H), 7.91 (td, J = 8.0 Hz, 1.0 Hz, 1H), 7.84 (d, J = 2.0 Hz,
1H), 7.48 (dd, J = 7.5 Hz, 5.0 Hz, 1H), 7.44 (dd, J = 9.0 Hz, 2.0 Hz,
1H), 6.80 (d, J = 8.5 Hz, 1H), 4.00 (s, 2H). 13C NMR (125 MHz,
CDCl3): δ 161.98, 150.12, 148.27, 140.13, 137.98, 129.87, 126.67,
122.60, 121.56, 120.11, 119.69, 116.28.
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used to afford 7 (844 mg, 92%); mp 187−189 °C. H NMR (500
MHz, CDCl3): δ 10.21 (s, 1H), 8.62 (d, J = 4.5 Hz, 1H), 8.30 (d, J =
7.5 Hz, 1H), 8.17 (d, J = 1.0 Hz, 1H), 7.92−7.95 (m, 3H), 7.79 (dd, J
= 8.5 Hz, 1.5 Hz, 1H), 7.65 (t, J = 7.5 Hz, 1H), 7.51−7.54 (m, 1H),
F
dx.doi.org/10.1021/jm501245b | J. Med. Chem. XXXX, XXX, XXX−XXX