Docking and FEP calculations indicated that the fluoro-substituted compounds 1e and 1f, could be accommodated in the orthosteric binding pocket of the OX1R and were first investigated in comparative 18 F-labeling experiments, applying the corresponding Bpin esters 3a, 3c and 3d. Cu-mediated aromatic 18 F fluorination of Bpin esters using n-butanol/DMAA as solvent system is well established . In preliminary Cu-mediated 18 F fluorination experiments with Bpin esters of simple aromatic model compounds benzoxazoles, benzthiazole and quinoxaline (29), we and others have demonstrate that 5-benzoxazole BPin esters provide only a limited radiochemical yield of 20-30% after 20 min for Cu-mediated 18 F-fluorination . Confirmed by our results on [ 18 F]1a (RCY of 12 %), the benzoxazole scaffold was therefore considered not very suitable for application in Cu-mediated aromatic 18 probably due to a ring-opening reaction of the benzoxazole under the reaction conditions of Cu-mediated fluorination . By isosteric exchange of the benzoxazole with benzothiazole this radiochemical problem could be circumvented and by shifting the 5-position of the fluorine substitution to the 6-position a potential PET ligand was found with [ 18 F]1f, which was successfully obtained by preparative 18 F-synthesis in an adequate overall activity yield of up to 22%.