Deoxyradiofluorination Reaction from β-Hydroxy-α-aminoesters: an Entry to [18F]Fluoroaminoesters under Mild Conditions

We report the conversion of beta-hydroxy-alpha-aminoesters derived from serine, alpha-methylserine or beta-phenylserine to the corresponding [F-18]fluorinated alpha or beta-aminoesters by deoxyradiofluorination using [F-18]fluoride. The method involved the ring opening of an aziridinum intermediate formed in situ in the presence of a base after activation of the alcohol function with triflic anhydride. The overall process was carried out at room temperature. Both the efficiency and the regioselectivity of the reaction were found to be dependent on the starting substrates. [F-18]Fluoroaminoesters were obtained in radiochemical yields ranging from 10-75 %. No improvement was observed for reactions carried out under heating.