Synthesis of [18F]-Fluoroethylfenoterol for imaging β2 receptor status in lung in vivo

5‐(‐{2‐[4‐(2‐[18F]Fluoroethoxy)‐phenyl]‐l‐methyl‐ethylamino}‐l‐hydroxy‐ethyl)‐benzene‐1, 3‐diol ([18F]fluoroethylfenoterol) was synthesised from 4‐(2‐{benzyl‐[2‐(3,5‐bis‐benzyloxy‐phenyl)‐2‐hydroxy‐ethyl]‐amino}‐propyl)‐phenol using 2‐[18F]fluoroethyltosylate (92% RCY) followed by reductive cleavage of the benzyl protecting groups. Preliminary in vitro tests showed [19F]fluoroethylfenoterol to be as potent in relaxation of lung tissue as fenoterol itself.