Improved synthesis of [18F]FLETT via a fully automated vacuum distillation method for [18F]2-fluoroethyl azide purification

The synthesis of [18F]2-fluoroethyl azide and its subsequent click reaction with 5-ethynyl-2′-deoxyuridine (EDU) to form [18F]FLETT was performed using an iPhase FlexLab module. The implementation of a vacuum distillation method afforded [18F]2-fluoroethyl azide in 87±5.3% radiochemical yield. The use of Cu(CH3CN)4PF6 and TBTA as catalyst enabled us to fully automate the [18F]FLETT synthesis without the need for the operator to enter the radiation field. [18F]FLETT was produced in higher overall yield (41.3±6.5%) and shorter synthesis time (67 min) than with our previously reported manual method (32.5±2.5% in 130 min).