The present invention relates to novel derivatives that are suitable as precursors to compounds that are useful for imaging amyloid deposits in living patients, their compositions, methods of use and processes to make such compounds. The compounds deriving from these precursors are useful in methods of imaging amyloid deposits in brain in vivo to allow antemortem diagnosis of Alzheimer's disease by positron emission tomography (PET) as well as measuring clinical efficacy of Alzheimer's disease therapeutic agents. Furthermore, the present invention also discloses the precursor compounds in crystalline form.