P. Johnstrom et S. Stoneelander, THE F-18 LABELED ALKYLATING AGENT 2,2,2-TRIFLUOROETHYL TRIFLATE - SYNTHESIS AND SPECIFIC ACTIVITY, Journal of labelled compounds & radiopharmaceuticals, 36(6), 1995, pp. 537-547
A method for synthesizing the alkylating agent 2,2,2-trifluoroethyl tr
iflate labelled with [F-18]fluoride in the two position is presented.
Ethyl [2-F-18]-trifluoroacetate was synthesized by the nucleophilic re
action of [F-18]F with ethyl bromodifluoroacetate in DMSO (45-60%, 5 m
in, 80 degrees C) and subsequently converted to [2-F-18]-2,2,2-trifluo
roethanol using alane in THF (85-95%, 2 min, 40 degrees C). Reaction w
ith triflic anhydride in 2,6-lutidine produced [2-F-18]-2,2,2-trifluor
oethyl triflate (70-80%, 1 min, 0 degrees). In all three cases the pro
duct was removed from the reaction vessel by heating to distil under a
stream of nitrogen. [2-F-18]-2,2,2-Trifluoroethyl triflate was used t
o label 2-oxoquazepam by N-alkylation in a toluene:DMF mixture (80-85%
, 20 min, 120 degrees C). Although no-carrier-added [F-18]F- was used,
considerable unlabelled ethyl trifluoroacetate was produced in the fi
rst reaction. Varying the conditions for the fluoro-debromination reac
tion did not appreciably improve the relative ratio of labelled to unl
abelled ester. The specific activity of the labelled 1,4-benzodiazepin
e-2-one obtained from 1850 MBq [F-18]F- was found to be approximate to
37 MBq/mu mol (1 mCi/mu mol).