RADIOSYNTHESIS OF 3-
473
flow rate of 3 ml/min. A dose calibrator (Capintec 15R) was used for all
radioactivity measurements.
Synthesis of 3-fluoropropyltriphenylphosphonium bromide
To 0.93 g (3.5 mmole) of triphenylphosphine (Aldrich) dissolved in 15 ml
acetonitrile (CH3CN) was added dropwise 0.32 ml (0.5 g, 3.5 mmole) 1-bromo-
3-fluoropropane (Aldrich) in 15 ml of CH3CN. The solution was refluxed 16 h.
After rotary vacuum evaporation of the solvent, the white solid was
recrystallized from methylene chloride (CH2Cl2). The solid was further
purified on a short silica (EM Sciences, silica gel 60) column using 5%
methanol in CH2Cl2 (1.21 g, 85%). mp: 232–2358C. 1H NMR (CDCl3):
d 1.81–2.17 (m, 2 H), 4.01–4.11 (m, 2 H), 4.72–4.75 (m, 1 H), 4.87–4.90 (m, 1 H),
7.69–7.88 (m, 15 H). MS: m=z 323.3 (C+). Elemental analysis calculated for
C21H21BrFP: C, 62.55; H, 5.25; F, 4.71. Found: C, 62.26; H, 5.24; F, 4.47.
Synthesis of 4-fluorobenzyltriphenylphosphonium bromide
To 1.0 g (4 mmole) of triphenylphosphine in 15 ml CH3CN was added
dropwise 0.5 ml (0.75 g, 4 mmole) 4-fluorobenzyl bromide (Aldrich) in 10 ml
CH3CN. The solution was stirred 2 days at room temperature. The white
precipitate was collected and recrystallized from CH3CN (1.44 g, 80%). mp:
1
313–3158C [lit: 280–2828C21]. H NMR (D6-DMSO): d 5.17–5.21 (m, 2 H),
6.99–7.13 (m, 4 H), 7.67–7.94 (m, 15 H). MS: m=z 371.2 (C+). Elemental
analysis calculated for C25H21BrFP: C, 66.53; H, 4.69; F, 4.21. Found: C,
66.55; H, 4.65; F, 4.15.
Synthesis of 4-fluorobenzyltris-4-dimethylaminophenylphosphonium bromide
To 1.6 g (4 mmole) tris(4-dimethylamino)phosphine (Organometallics, Inc.)
dissolved in 160 ml of CH3CN and 170 ml dimethylformamide (DMF) was
added 0.5 ml (0.75 g, 4 mmole) 4-fluorobenzyl bromide in 10 ml DMF over
25 min. The solution was stirred 36 h. The solution was evaporated to a purple
solid and recrystallized from CH3CN to yield a white solid (1.88 g, 81%). mp:
302–3048C. 1H NMR (CD3OD): d 3.08 (s, 18 H), 4.36, 4.40 (d, 2 H), 6.85–7.26
(m, 16 H). MS: m=z 500.3 (C+). Elemental analysis calculated for
C31H36BrFN3P: C, 64.14; H, 6.25; F, 3.27. Found: C, 64.18; H, 6.35; F, 3.11.
Radiosynthesis and purification of 3-[18F]fluoropropyltriphenylphosphonium
cation
Aqueous [18F]fluoride (approx. 1 ml) was passed through a resin column [Trap
and Release column (DW-TRC), D and W, Inc., Oakdale, TN, USA)]. The
trapped [18F]fluoride was eluted from the resin column with 2.3 mg
(0.02 mmole) of K2CO3 (Aldrich, 99%) in 0.3 ml of water (Fluka) into a
Copyright # 2004 John Wiley & Sons, Ltd.
J Label Compd Radiopharm 2004; 47: 469–476