This invention relates to novel precursors suitable for 18 F radiolabeling of glutamate derivatives, methods for preparing such compounds and its intermediates, compositions comprising such compounds, kits comprising such compounds or compositions and methods for 18 F radiolabeling of glutamate derivatives wherein the obtained 18 F radiolabeled glutamate derivatives are suitable for diagnostic imaging by Positron Emission Tomography (PET) of proliferative diseases e.g. tumor in mammals.