Time-efficient and convenient synthesis of [(18)F]altanserin for human PET imaging by a new work-up procedure

[(18)F]Altanserin, an important PET radioligand for the in vivo imaging of the 5-HT(2A) receptor, was synthesized from its precursor nitro-altanserin in DMF or DMSO at high temperatures of 150 degrees C in an overall radiochemical yield (EOB) of 23-25% after 75min. A new solid phase work-up procedure involving the acidification of the crude reaction mixture and a C18-SepPak-solid phase separation preceded the final HPLC purification. This led to a significantly reduced synthesis time as a result of a stable and early elution from the HPLC column using improved HPLC conditions (MeOH/THF/NaOAc 0.05N pH 5: 27/18/55, flow: 5 mL/min, Symetry Prep 7 microm C18 (Waters)). The synthesis was performed semi-automatically in a modified GE TracerLab synthesis module using an in-house-developed program. The synthesized [(18)F]altanserin was used in our ongoing human and animal PET imaging studies.