In vitro binding profile and radiosynthesis of a novel 18F-labeled azaspirovesamicol analog as potential ligand for imaging of the vesicular acetylcholine transporter

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Abstract

Radiolabeled vesamicol analogs are promising candidates as ligands for the vesicular acetylcholine transporter (VAChT) to enable in vivo imaging of early cholinergic degenerations in brain. The 4-fluorobenzoyl-substituted azaspirovesamicol derivative FBASV is one out of six novel vesamicol analogs and demonstrated most appropriate in vitro binding data. 18F-radiolabeling was performed by microwave-assisted nucleophilic aromatic substitution of the corresponding nitro precursor and two methods were developed for the purification of [18F]FBASV. Utilizing method A, the remaining nitro precursor was reduced to its corresponding amine, which was separated via semi-preparative HPLC on a conventional RP column. In method B a phenyl column was used for the direct separation of [18F]FBASV and its nitro precursor, resulting in a change of the elution order and better separation parameters. Thus, [18F]FBASV was synthesized with a RCY of 16–18%, a specific activity >300 GBq/µmol, and a radiochemical purity of >99.5% suitable for future in vivo studies. Copyright © 2011 John Wiley & Sons, Ltd.

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