A. Damont et al.
quadruplet, multiplet and broad, respectively). The MS were measured [CH], 101.3 [C], 82.7 [d, J1F-C = 170 Hz, CH2], 67.8 [d, J2F-C = 20 Hz, CH2],
on a Thermo Electron (Les Ulis, France) Ion Trap LCQ Deca XP+
spectrometer (ESI+) or on a Waters (Milford, MA, USA) Micromass ZQ
2000 spectrometer (ESI+).
42.8 [CH2], 41.0 [CH2], 28.5 [CH2], 24.9 [CH3], 17.1 [CH3], 14.7 [CH3],
13.4 [CH3]. MS (ESI+): m/z 399 (M + H)+. tR (HPLC A): 1.98 min. tR (HPLC
B): 8.9 min. tR (HPLC C): 16.9 min. tR (HPLC D): 6.59 min.
Miscellaneous
N,N-Diethyl-2-(2-(3,5-dibromo-4-hydroxyphenyl)-5,7-dimethylpyrazolo
Radiosynthesis involving tritium gas was performed in dedicated [1,5-a]pyrimidin-3-yl)acetamide (4)
glovebox using
a
custom-built microhydrogenation apparatus.20,21
To a solution of compound 3 (500 mg, 1.42 mmol) in acetic acid (5 mL)
was carefully added dropwise bromine at room temperature whilst
stirring, and the reaction was monitored by TLC to stop the addition
of bromine before tribrominated or tetrabrominated products
appeared. When the starting material was almost completely
converted, the reaction was stopped by addition of water, and the
reaction mixture was extracted with ethyl acetate. The organic layer
was separated, washed with brine, dried over Na2SO4, filtered and
evaporated to dryness. The residue was purified on silica gel column
chromatography (heptane/EtOAc 7/3) to afford pure compound 4
(181 mg, 0.35 mmol) as a white powder in 25% yield and a 1 : 1
Concentrations to dryness (solvent removal) and HPLC purifications of
all reaction mixtures or solutions containing tritiated compound(s) were
also performed in dedicated gloveboxes. All synthesized products were
obtained with a chemical purity greater than 95% according the 1H-
NMR spectra. This purity was confirmed by HPLC analysis for the
compounds used as references.
Chemistry
N,N-Diethyl-2-(2-(4-methoxyphenyl)-5,7-dimethylpyrazolo[1,5-a]
pyrimidin-3-yl)acetamide (DPA-713, 2)
mixture (<5% yield), according to 1H-NMR, of
4
and its
monobrominated counterpart 5.
Resynthesized according to Reference 6. Analytical data were in
accordance with those reported.
1
Compound 4. Rf (heptane/acetone 1/1): 0.29. H-NMR (CD2Cl2) δ 7.92
(s, 2H, Ph), 6.61 (s, 1H, H-6), 6.37 (bs, 1H, OH), 3.93 (s, 2H, CH2), 3.55 (q,
2H, J = 7.2 Hz, N(CH2CH3)), 3.41 (q, 2H, J = 7.2 Hz, N(CH2CH3)), 2.74 (s, 3H,
7-CH3), 2.55 (s, 3H, 5-CH3), 1.28 (t, 3H, J = 7.2 Hz, N(CH2CH3)), 1.15 (t, 3H,
J = 7.2 Hz, N(CH2CH3)). 13C-NMR (CD2Cl2) δ 169.8 [C], 158.2 [C], 151.8 [C],
150.1 [C], 147.5 [C], 145.2 [C], 131.8 [2xCH], 128.3 [C], 110.3 [2xC], 108.7
[CH], 100.8 [C], 42.4 [CH2], 40.8 [CH2], 27.7 [CH2], 24.1 [CH3], 16.5 [CH3],
14.0 [CH3], 12.8 [CH3]. MS (ESI+): m/z 509 (51%), 511 (100%), 513 (48%)
(M + H)+.
N,N-Diethyl-2-(2-(4-hydroxyphenyl)-5,7-dimethylpyrazolo[1,5-a]
pyrimidin-3-yl)acetamide (3)
To a solution of compound 2 (1 g, 2.73 mmol) in CH2Cl2 (12 mL) was
added dropwise at À60 °C a 1 M solution of boron tribromide in THF
(13.7 mL, 13.7 mmol). The reaction mixture was stirred for 2 h at À20 °C,
then poured over ice and extracted twice with CH2Cl2 (100 mL). The
organic layers were combined, washed with brine, dried over Na2SO4,
filtered and evaporated to dryness. The residue was crystallized from
Et2O/EtOH to afford pure 3 (640 mg, 55%) as light yellow crystals. Rf
(heptane/acetone 1/1): 0.20. 1H-NMR (CD2Cl2) δ 8.62 (bs, 1H, OH), 7.54
(d, 2H, J = 8.4 Hz, Ph), 6.81 (d, 2H, J = 8.4 Hz, Ph), 6.54 (s, 1H, H-6), 3.90
(s, 2H, CH2), 3.47 (q, 2H, J = 6.8 Hz, N(CH2CH3)), 3.37 (q, 2H, J = 6.8 Hz, N
(CH2CH3)), 2.71 (s, 3H, 7-CH3), 2.52 (s, 3H, 5-CH3), 1.18 (t, 3H, J = 6.8 Hz,
N(CH2CH3)), 1.09 (t, 3H, J = 6.8 Hz, N(CH2CH3)). 13C-NMR (CD2Cl2) δ 171.2
[C], 158.7 [C], 158.2 [C], 155.8 [C], 148.2 [C], 145.8 [C], 130.4 [2xCH],
125.3 [C], 115.9 [2xCH], 108.9 [CH], 100.8 [C], 43.0 [CH2], 41.4 [CH2], 28.7
[CH2], 24.7 [CH3], 17.2 [CH3], 14.4 [CH3], 13.3 [CH3]. MS (ESI+): m/z 353
(M + H)+.
Compound 5. Rf (heptane/acetone 1/1): 0.20. 1H-NMR (CDCl3) δ 7.84 (d,
J = 1.6 Hz, 1H, Ph), 7.61 (dd, 3J = 8.4 Hz, 4J = 1.6 Hz, 1H, Ph), 6.98 (d,
J = 8.4 Hz, 1H, Ph), 6.52 (s, 1H, H-6), 3.88 (s, 2H, CH2), 3.47 (q, 2H,
J = 7.2 Hz, N(CH2CH3)), 3.37 (q, 2H, J = 7.2 Hz, N(CH2CH3)), 2.71 (s, 3H, 7-
CH3), 2.52 (s, 3H, 5-CH3), 1.22 (t, 3H, J = 7.2 Hz, N(CH2CH3)), 1.11 (t, 3H,
J = 7.2 Hz, N(CH2CH3)). MS (ESI+): m/z 431 (100%), 433 (97%) (M + H)+.
N,N-Diethyl-2-(2-(3,5-dibromo-4-(2-fluoroethoxy)phenyl)-5,7-
dimethylpyrazolo[1,5-a]pyrimidin-3-yl)acetamide (6)
To a 0.12 M NaOH solution in a 8 : 2 mixture of ethanol/water was added
compound
5 (120 mg, 0.24 mmol) and 1-fluoro-2-tosyloxyethane
(153 mg, 0.71 mmol). The reaction mixture was stirred overnight at 65 °
C before being partitioned between water and ethyl acetate. The organic
layer was separated, washed with brine, dried over Na2SO4, filtered and
evaporated to dryness. The residue was purified by silica gel column
chromatography (CH2Cl2/MeOH 100/0 to 97/3, v:v) to afford pure
compound 6 (95 mg, 0.17 mmol) as a white solid in 72% yield. Rf
(heptane/acetone 3/2): 0.38. 1H-NMR (CD2Cl2) δ 8.06 (s, 2H, Ph), 6.60 (s,
1H, H-6), 4.82 (dt, 2H, JH2-F = 47.6 Hz, JH3-H = 4.0 Hz, CH2F), 4.32 (dt, 2H, J3H-
F = 28.8 Hz, J3H-H = 4.0 Hz, OCH2CH2F), 3.90 (s, 2H, CH2), 3.55 (q, 2H,
J = 7.2 Hz, N(CH2CH3)), 3.39 (q, 2H, J = 7.2 Hz, N(CH2CH3)), 2.73 (s, 3H, 7-
CH3), 2.54 (s, 3H, 5-CH3), 1.28 (t, 3H, J = 7.2 Hz, N(CH2CH3)), 1.13 (t, 3H,
J = 7.2 Hz, N(CH2CH3)). 13C-NMR (CD2Cl2) δ 169.3 [C], 158.2 [C], 152.5 [C],
151.1 [C], 147.7 [C], 145.0 [C], 133.0 [C], 132.3 [2xCH], 118.0 [2xC], 108.9
[CH], 101.5 [C], 82.5 [d, J1F-C = 169 Hz, CH2], 72.1 [d, J2F-C = 20 Hz, CH2],
42.3 [CH2], 40.6 [CH2], 27.7 [CH2], 24.3 [CH3], 16.5 [CH3], 14.2 [CH3], 12.9
[CH3]. MS (ESI+): m/z 555 (51%), 557 (100%), 559 (48%) (M + H)+. tR (HPLC
A): 8.86 min. tR (HPLC B): 23.9 min. tR (HPLC D): 15.42 min.
1-Fluoro-2-tosyloxyethane
Resynthesized according to Reference 6. Analytical data were in
accordance with those reported.
N,N-Diethyl-2-(2-(4-(2-fluoroethoxy)phenyl)-5,7-dimethylpyrazolo
[1,5-a]pyrimidin-3-yl)acetamide (DPA-714, 1a)
To a suspension of NaH (12 mg, 0.50 mmol) in dry THF (8 mL) was
added a dry solution of THF (1 mL) containing compound 3 (100 mg,
0.28 mmol). The reaction mixture was stirred for 10 min at 5 °C and
then allowed to warm up to room temperature before addition of a
solution of 1-fluoro-2-tosyloxyethane (200 mg, 0.92 mmol) in dry CH2Cl2
(1 mL). The reaction mixture was heated overnight at 60 °C with
stirring. The mixture was then partitioned between 1 M aq. HCl
(100 mL) and CH2Cl2 (100 mL). The organic layer was then separated,
washed with brine, dried over Na2SO4, filtered and evaporated to
dryness. The residue was purified by flash chromatography on silica
gel (CH2Cl2/MeOH: 98/2 to 95/5 (v:v)) to afford 1a (65 mg, 58%) as
white crystals after crystallization from Et2O. Rf (heptane/acetone 2/1):
Note that the aforementioned protocol was also carried out on a 1 : 1
mixture of 4 and 5 (5 μmoles each) to give the corresponding equimolar
0.25. 1H-NMR (CD2Cl2) δ 7.77 (d, 2H, J = 8.8 Hz, Ph), 7.01 (d, 2H, mixture of 6 and its monobrominated counterpart 7 (92% yield, with
J = 8.8 Hz, Ph), 6.55 (s, 1H, H-6), 4.77 (dt, 2H, J2H-F = 47.6 Hz and JH3-
H = 4.0 Hz, CH2F), 4.26 (dt, 2H, J3H-F = 28.8 Hz and J3H-H = 4.0 Hz,
respect to 5).
Compound 7. Rf (heptane/acetone 2/1): 0.30. 1H-NMR (CDCl3) δ 8.02 (d,
OCH2CH2F), 3.88 (s, 2H, CH2(C = O)), 3.50 (q, 2H, J = 7.2 Hz, NCH2CH3), J = 2.0 Hz, 1H, Ph), 7.84 (dd, J = 8.4 Hz, J = 2.0 Hz, 1H, Ph), 6.99 (d,
3.38 (q, 2H, J = 7.2 Hz, NCH2CH3), 2.72 (s, 3H, 7-CH3), 2.53 (s, 3H, J = 8.4 Hz, 1H, Ph), 6.52 (s, 1H, H-6), 4.81 (dt, J2H-F = 47.2 Hz, JH3-H = 4.0 Hz,
5-CH3), 1.22 (t, 3H, J = 7.2 Hz, NCH2CH3), 1.11 (t, 3H, J = 7.2 Hz,
NCH2CH3). 13C-NMR (CD2Cl2) δ 170.3 [C], 159.2 [C], 158.2 [C], 155.0 2H, CH2(C = O)), 3.53 (q, J = 7.2 Hz, 2H, NCH2CH3), 3.41 (q, J = 7.2 Hz, 2H,
2H, CH2F), 4.32 (dt, JH3-F = 27.2 Hz, JH3-H = 4.0 Hz, 2H, OCH2CH2F), 3.92 (s,
[C], 148.3 [C], 145.3 [C], 130.3 [2xCH], 127.6 [C], 115.0 [2xCH], 108.7
NCH2CH3), 2.73 (s, 3H, 7-CH3), 2.54 (s, 3H, 5-CH3), 1.24 (t, J = 7.2 Hz, 3H,
J. Label Compd. Radiopharm 2015, 58 1–6
Copyright © 2015 John Wiley & Sons, Ltd.