L. Martarello et al., Synthesis and characterization of fluorinated and iodinated pyrrolopyrimidines as PET/SPECT ligands for the CRF1 receptor, NUCL MED BI, 28(2), 2001, pp. 187-195
Fluorine-18 labeled fluorobutyl[2,5-dimethyl-7-(2,4,6-trimethylphenyl)-7H-p
yrrolo [2,3-d] pyrimidin-4-yl]ethylamine (FBPPA) and iodine-123 labeled but
yl[2,5-dimethyl-7-(4-iodo-2,6-dimethylphenyl)-7H-pyrrolo[2, 3-d] pyrimidin-
4-yl]ethyl-amine (IBPPA) were synthesized in the development of a CRF recep
tor ligand. The methods of synthesis, in vitro binding assays, radiolabelin
g and in vivo tissue distribution in rats are described. Fluorine-18 labele
d FBPPA was prepared with high specific activity (3 x 10(4) Ci/mmol) by nuc
leophilic displacement with an average radiochemical yield of 6% (EOB). Iod
ine-123 labeled IBPPA was prepared by electrophilic iododestannylation with
good yield (60%) and high specific activity (3.3 x 10(3) Ci/mmol). The ret
ention of FBPPA and IBPPA in the pituitary was good (1.16% i.d./g and 2.35%
i.d./g respectively at 60 min). However, the accumulation of radioactivity
in the brain for both radiotracers was very low at all time points of the
study, which demonstrated the difficulties for these radiopharmaceuticals t
o penetrate the blood brain barrier (BBB). (C) 2001 Elsevier Science Inc. A
ll rights reserved.