136
L. GAWELL
recrystallized from EtOAc–heptane to give acid 5 (123 mg, 33% yield).
M.p. 216–2178C. IR (KBr): n 2974, 1719, 1692 cmꢀ1. 1H NMR (CDCl3,
TMS): d 1.43 (9 H, s), 2.23–2.36 (4 H, m), 3.38–3.50 (4 H, m), 7.04–7.09
(2 H, m), 7.18 (2 H, d, J ¼ 8:6 Hz), 7.20–7.30 (3 H, m), 7.99 (2 H, d,
J ¼ 8:6 Hz).). 13C NMR (CDCl3, TMS): d 28.44, 31.60, 45.03, 79.69,
126.90, 127.43, 128.27, 129.69, 129.86, 130.07, 135.94, 136.50, 141.33,
147.85, 154.83, 171.11. Anal. ðC24H27NO4Þ: C, H, N.
N,N-Diethyl-4-[(phenyl-(N-tert-butoxycarbonyl)piperidin-4-ylidene)
methyl]-benzamide, (6)
To a solution of DMAP (83 mg, 0:68 mmol) in CH2Cl2 ð2:5 mLÞ at
ꢀ208C, SOCl2 (40 mL, 0:54 mmol) was added dropwise. A precipitate
was formed while the mixture was stirred for 15 min. To the slurry, the
acid 5 ð120 mg, 0:31 mmolÞ in CH2Cl2 ð1 mLÞ was added and after 15
min at ꢀ208C the mixture had become a clear solution. Diethylamine
ð150 mL; 1:48 mmolÞ was added and the cooling bath removed. After
stirring overnight, the reaction mixture was washed with 1 M citric acid,
H2O and dried. Evaporation to dryness provided the amide 6 (104 mg,
1
75% yield). M.p. 121–1238C, (EtOAC–hexane). IR (KBr): n cmꢀ1. H
NMR (CDCl3, TMS): d 1.13 (3 H, br s), 1.23 (3 H br s), 1.46 (9 H, s),
2.25–2.40 (4 H, m), 3.29 (2 H, br s), 3.40–3.52 (4 H, m), 3.54 (2 H br s),
7.08–7.12 (2 H, m), 7.14 (2 H, d, J ¼ 8:0 Hz), 7.20–7.26 (1 H, m),
7.26–7.30 (2 H, m), 7.31 (2 H, d, J ¼ 8:0 Hz). 13C NMR (CDCl3, TMS):
d 12.85, 14.24, 28.40, 31.50, 39.15, 43.26, 45.41, 79.50, 126.21, 126.64,
128.08, 129.65, 129.69, 135.13, 135.26, 136.58, 141.71, 143.03, 154.75,
171.08. Anal. ðC28H36N2O3Þ; C, H, N.
4-[(Phenyl-(N-tert-butoxycarbonyl)piperidin-4-ylidene)methyl]-
[carboxy-14C]benzoic acid, (7)
To a stirred solution of bromide 4 ð431 mg; 1 mmolÞ in THF ð5 mLÞ, in
a flask attached to a vacuum manifold, was added dropwise at ꢀ788C, a
solution of n-BuLi (1 mL, 1:6 M in hexane). After 75 min at this
temperature, 14CO2 (from Ba14CO3, 50 mCi, 55 mCi=mmol) was
introduced, the cooling bath removed and the reaction mixture left
overnight to reach room temperature. To the yellow solution, 1 M
aqueous citric acid was added ðpH ꢃ 3Þ followed by diethyl ether
ð5 mLÞ. The organic layer was separated, washed with H2O, dried and
evaporated to dryness. The residue was purified by flash chromato-
Copyright # 2002 John Wiley & Sons, Ltd.
J Label Compd Radiopharm 2003; 46: 131–138