18F‐Fluorination of a supported 2‐(aryl‐di‐tert‐butylsilyl)‐N‐methyl‐imidazole for indirect 18F‐labeling of a VHH single‐variable domain

Abstract

Anchoring an imidazole‐di‐tert‐butyl‐arylsilane possessing an azido group to a polystyrene resin provided a heterogeneous precursor that was radiolabeled easily using aqueous [18F]fluoride. After optimizing the conditions (i.e., using DMSO as solvent and heating at 160°C for 15 min), the desired [18F]fluorosilane was obtained in 24% radiochemical yield (RCY) and 78% radiochemical purity (RCP) using solid‐phase extraction as sole purification. Then, this compound was conjugated by strain‐promoted alkyne–azide cycloaddition to a model single‐variable domain possessing a cyclooctyne tag, yielding to the desired 18F‐labeled bioconjugate in 2% RCY and >95% RCP after purification by a size exclusion chromatography.