Issue 19, 2011

Syntheses of mGluR5 PET radioligands through the radiofluorination of diaryliodonium tosylates

Abstract

3-Fluoro-1-((thiazol-4-yl)ethynyl)benzenes constitute an important class of high-affinity metabotropic glutamate subtype 5 receptor (mGluR5) ligands, some of which have been labeled with fluorine-18 (t1/2 = 109.7 min), to provide radioligands for molecular imaging of brain mGluR5 in living animal and human subjects with positron emission tomography (PET). Labeling in the 3-fluoro position of such ligands can be achieved through aromatic nucleophilic substitution of a halide leaving group with [18F]fluoride ion when a weakly activating m-nitrile group is present, but is generally very low yielding (<8%). Here we used a microfluidic reaction platform to show that greatly enhanced (up to 6-fold) radiochemical yields can be achieved from suitably synthesized diaryliodonium tosylate precursors. The presence of a m-nitrile or other activating group is not required. Similar conditions were adopted in a more conventional automated radiochemistry platform having a single-pot reactor, to produce mGluR5 radioligands with useful radioactivities for PET imaging.

Graphical abstract: Syntheses of mGluR5 PET radioligands through the radiofluorination of diaryliodonium tosylates

Supplementary files

Article information

Article type
Paper
Submitted
07 Apr 2011
Accepted
19 May 2011
First published
20 May 2011

Org. Biomol. Chem., 2011,9, 6629-6638

Syntheses of mGluR5 PET radioligands through the radiofluorination of diaryliodonium tosylates

S. Telu, J. Chun, F. G. Siméon, S. Lu and V. W. Pike, Org. Biomol. Chem., 2011, 9, 6629 DOI: 10.1039/C1OB05555K

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