9000037 B2 abstract 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 of proliferative diseases e g tumor in mammals application_number US 201214115127 A description in a first aspect the invention is directed to compounds of the formula i precursors a monocyclic aryl b bicyclic aryl c biaryl d monocyclic heteroaryl and e bicyclic heteroaryl optionally a is bearing one or more substituents selected from the group comprising a halogen b nitro c alkyl d trifluoromethyl and e z single isomers tautomers diastereomers enantiomers stereoisomers mixtures thereof and suitable salts thereof optionally a is bearing 1 to 4 substituents selected from the group comprising a halogen b nitro c c 1 c 3 alkyl d trifluoromethyl and e z optionally a is bearing 1 to 3 substituents selected from the group comprising optionally a is bearing 1 to 3 substituents selected from the group comprising optionally a is bearing 1 to 3 substituents selected from the.