B. Latli et al.
staring from [14C]-potassium cyanide. HPLC, tR = 22.6 min, identical to an
unlabeled sample.
tert-Butyl-4-methanesulfonyl-piperidine-2,2,3,3,4,5,5,6,6-2H9-1-
carboxylate, [2H9]-(15)
To a solution of [2H9]-(14) (2.7 g, 9.5 mmol) in dimethylacetamide (DMAC)
(20 mL) was added sodium methanethiolate (sodium thiomethoxide)
(0.92 g, 11.8 mmol) in one portion and the mixture was stirred for 2 h.
Toluene (30 mL) was added followed by water (20 mL), and the mixture
was stirred for 20 min. After the layers were settled, the aqueous was
removed, and the toluene layer was washed with water (20 mL). The
aqueous layer was removed and the combined aqueous layers were
extracted with toluene (20 mL ×2). The combined toluene extracts were
used in the next reaction without further purification. LCMS, fast medium
polar method: Product: tR = 1.81 min, MH+ = 241 (100%). The toluene
solution was cooled in an ice-bath under nitrogen. Peracetic acid (32%
solution in acetic acid, 4.0 mL) was added dropwise. After the addition
was completed, the ice-bath was removed, and the solution was stirred
at room temperature for 1 h. LCMS showed the presence of new
product. The reaction was treated with water (60 mL). The aqueous
was removed, and the organic phase was washed with water again
(60 mL). The organic phase was concentrated in vacuo. The resulting
white residue was dissolved in toluene (6 mL) and heptane (50 mL)
was added slowly. The resulting mixture was stirred overnight. The
product was filtered and washed with heptane, dried under reduced
pressure to give 2.15 g of a white solid in 83% yield. LCMS: tR = 1.35 min
2-Mercaptoacetamide, (10)
Methyl thioglycolate (3.6 g, 34 mmol) was added to a solution of
ammonia in methanol (7.0 M, 45 mL) and stirred at room temperature
for 14 h under argon atmosphere. The solution was concentrated under
reduced pressure to give 3.1 g of a white solid in quantitative yield. 1H
NMR (DMSO-d6) δ: 7.43(brs, 1H), 7.02(brs, 1H), 3.07(s, 2H), 1.51(brs, 1H).
13C NMR (DMSO-d6) δ: 173.87, 29.36.
3-Amino-4-(1,1-difluoro-propyl)-6-(4-methanesulfonyl-piperidin-1-
yl)-thieno[2,3-b]pyridine-2-carboxylic acid amide-3-14C, ([14C]-(1))
A mixture of [14C]-(7) (396 mg, 1.55 mmol), (8) (315 mg, 1.55 mmol) and
K2CO3 (654 mg, 4.64 mmol) in DMSO (7 mL) was stirred under nitrogen
atmosphere for 16 h. HPLC showed the presence of a new product at
tR = 19.97 min similar to (9) and no starting material was observed. 2-
Thioacetamide (10) (214 mg, 1.64 mmol) containing about 20% of the
oxidized disulfide compound was added followed by K2CO3 (216 mg,
1.53 mmol) and DMSO (3 mL). The resulting thick mixture was stirred at
room temperature for 16 h. HPLC showed the formation of a new
product, tR = 16.08 min, similar to (11). The mixture was then heated to
80 °C and stirred for 16 h. HPLC showed a new product with Rt similar
to a standard sample of (1). The mixture was cooled to 60 °C and water
(20 mL) was added, cooled to room temperature and stirred for 14 h.
The yellow solid was filtered washed with water and dried under reduced
pressure to give 540 mg of a yellow solid. Purification on a 40-g
1
in fast medium polar method, MH+ = 217.51 (100%). H NMR (CDCl3) δ:
2.84(s, 3H), 1.46(s, 9H). 13C NMR (CDCl3) δ: 154.33, 80.42, 54.68(m),
39.98(m), 37.33, 28.38, 23.92(m).
disposable silica gel column gave 464 mg of the desired product in 4-Methanesulfonyl-piperidine-2,2,3,3,4,5,5,6,6-2H9-HCl, [2H9]-(8)
64% radiochemical yield or 51.2 mCi with a specific activity of 54.3 mCi/
To a suspension of [2H9]-(15) (1.71 g, 6.3 mmol) in methyl-tert-butyl ether
mmol and 99.8% radiochemical purity. HPLC: tR = 8.34 min (100%, UV
(MTBE) (25 mL) was added a solution of HCl in methanol (9 M, 3.6 mL,
detection at 230 nm), tR = 8.35 (99.8%, rad detection). 1HNMR (DMSO-
32.4 mmol). The suspension became homogenous for few seconds
d6) δ:7.05(s, 2H), 6.98(s, 1H), 6.66(s, 2H), 4.57(d, J = 8 Hz, 2H), 3.45(t,
before a white solid started to precipitate. The mixture was stirred at
J = 5 Hz, 1H), 3.05(t, J = 5 Hz, 2H), 2.95(s, 3H), 2.46(m, 2H), 2.15(d,
room temperature for 16 h, then filtered, washed with MTBE (10 mL)
J = 9 Hz, 2H), 1.64(m, 2H), 1.03(t, J = 7 Hz, 3H), identical to a reference
and dried on the frit for 4 h to give 1.3 g of a white solid in 98.5% yield.
unlabeled sample.
LCMS: fast medium polar method, MH+ = 173.71 (100%). 1H NMR
(DMSO-d6) δ: 9.84(s, 1H), 9.21(s, 1H), 2.96(s, 3H). 13C NMR (DMSO-d6) δ:
54.97(m), 40.03(m), 37.66, 20.19(m).
Synthesis of [2H9]-(1)
tert-Butyl-4-hydroxypiperidine-2,2,3,3,4,5,5,6,6-2H9-1-carboxylate,
3-Amino-4-(1,1-difluoro-propyl)-6-(4-methanesulfonyl-piperidin-1-
[2H9]-(13)
yl-2,2,3,3,4,5,5,6,6-2H9)-thieno[2,3-b]pyridine-2-carboxylic
amide ([2H9]-(1)
acid
To a solution of [2H9]-(12) (2.0 g, 18.2 mmol) in THF (20 mL) and water
(20 mL) was added at 0 °C a solution of di-tert-butyl dicarbonate (4.1 g,
18.2 mmol) in THF (20 mL). The reaction was warmed to room
temperature and stirred for 16 h. Water (50 mL) was added to the
reaction and extracted with methylene chloride (50 mL ×3). The
combined extracts were washed with water (50 mL), dried over MgSO4,
filtered and concentrated in vacuo to give 4.2 g of colorless oil. LCMS-
ESI+: tR = 5.56 min, long medium polar method, MH+ = 211.4 (100%).
1HNMR (CDCl3) δ: 4.62(s, 1H), 1.45 (s, 9H).
A mixture of (7) (1.44 g, 5.74 mmol), 4-methenasulfonyl piperidine-2H9
hydrochloride salt ([2H9]-(8)) (1.2 g, 5.75 mmol) and K2CO3 (2.4 g, 17 mmol)
in DMSO (16 mL) was stirred under nitrogen atmosphere for 16 h. HPLC
showed the presence of a new product with a tR = 19.97 min similar to
(9), and no starting material was observed. 2-Mercaptocetamide (10)
(0.79 g, 8.63 mmol) containing about 20% of the disulfide impurity was
added followed by K2CO3 (0.8 g, 5.8 mmol) and DMSO (8 mL). The
resulting thick mixture was stirred at room temperature for 16 h. HPLC
showed the formation of a new product, tR = 16.1 min, co-eluted with
(11). The mixture was then heated to 80 °C and stirred for 16 h. HPLC
showed a new product with retention time (tR) similar to a reference
tert-Butyl-4-methanesulfonyloxy-piperidine-2,2,3,3,4,5,5,6,6-2H9-1-
carboxylate, [2H9]-(14)
To a solution of [2H9]-(13) (4.2 g, 18.07 mmol) in ethyl acetate (35 mL) sample of (1). The mixture was cooled to 60 °C and water (50 mL) was then
was added N-methylmorpholine (2.4 mL, 21.2 mmol). The solution was added, cooled to room temperature and stirred for 24 h. The yellow solid
cooled in an ice-bath and methanesulfonyl chloride (1.4 mL, 18.1 mmol) was filtered washed with water and dried under reduced pressure to give
was added dropwise in a 3-h period. The resulting suspension was then 2.3 g of a yellow solid. Acetic acid (18 mL) was added to this solid, and the
warmed to room temperature and stirred for 16 h. Water (30 mL) was
added, and the organic phase was extracted with ethyl acetate (30 mL
×3). The combined extracts were washed with water (50 mL), brine
(20 mL), dried over MgSO4, filtered and concentrated in vacuo to give
mixture was heated to 78 °C. The resulting clear solution was then cooled
to 48 °C with stirring to develop a seed bed, then heated to 53 °C and
heptane (9 mL) was added dropwise via addition funnel. The mixture
was cooled to room temperature in 3-h period and then stirred for
5.1 g of viscous colorless oil. This oil was dissolved in ethyl acetate another 16 h. The yellow solid was filtered and washed with 1:1 acetic
(6 mL), and heptane (50 mL) was added while stirring to give a cloudy acid-heptane (15 mL), and dried for 4 h. The product was further dried
solution. The product precipitated as a white solid. After stirring at room
in a vacuum oven at 65–70 °C for 24 h to give 1.9 g of product in 76%
temperature for 26 h, the product was filtered and dried in the air to give yield. LCMS (fast medium polar method): tR = 1.47 min, MH+ = 442.73
4.77 g of a white solid in 92% yield. LCMS-ESI+: tR = 1.56 min, fast medium (100%). HRMS: MH+: [C17H214H9F2N4O3S2]+, calculated 442.17391, found
polar method, MH+ = 233.55 (100%). 1H NMR (CDCl3) δ: 3.08(s, 3H), 1.46(s, 442.17426. 1HNMR (DMSO-d6) δ:7.06(s, 2H), 6.97(s, 1H), 6.64(s, 2H), 2.95
9H). 13C NMR (CDCl3) δ:.154.6, 80.41, 56.3(m), 40.1(m), 27.6, 37.5, 23.8(m). (s, 3H), 2.41(m, 2H), 1.01(t, J = 7 Hz, 3H). 13CNMR (DMSO-d6) δ: 169.54,
J. Label Compd. Radiopharm 2016, 59 300–304
Copyright © 2016 John Wiley & Sons, Ltd.