()-4-(2-(6-(2-(2-(2-([F]-fluoroethoxy)ethoxy)ethoxy)pyridin-3-yl)vinyl)--methylbenzenamine

Alzheimer's disease (AD) is a form of dementia with a gradual memory loss and a progressive decline in mental functions overtime (1, 2). It is characterized pathologically by neuronal loss, extracellular senile plaques (aggregates of amyloid-beta peptides consisting of 40 to 42 amino acids) and intracellular neurofibrillary tangles (filaments of microtubule-binding hyper-phosphorylated protein tau) in the brain, especially in the hippocampus and associative regions of the cortex (3, 4). β-amyloid peptides and tau protein are implicated as the main causes of neuronal degeneration and cell death (5, 6). Early diagnosis of AD is important for treatment consideration and disease management (7). Various β-amyloid imaging agents have been developed for magnetic resonance imaging (MRI), single photon emission computed tomography (SPECT), and positron emission tomography (PET) (8-13). The binding of different derivatives of Congo red, thioflavin, stibene, and aminonaphthalene has been studied in human post-mortem brain tissue and in transgenic mice. Out of these analogues, 2-(1-(6-[(2-[F]fluoroethyl)(methyl)amino]-2-naphthyl)ethylidene)malono nitrile ([F]FDDNP) was studied in humans, showing more binding in the brains of patients with AD than in those of healthy people (14). However, [F]FDDNP showed low signal-to-noise ratios for PET imaging, because it is highly lipophilic. -methyl-[C]-2-(4’-methylaminophenyl)-6-hydroxybenzothiasole, a β-amyloid binding compound based on a series of neutral thioflavin-T derivatives (15), was radiolabeled with the positron-emitting radionuclide C ([C]6-OH-BTA-1 or [C]PIB). [C]6-OH-BTA-1 was found to be a promising imaging agent for the senile plaques in the brain (16). Zhang et al. (17) reported the development of a series of fluorinated polyethylene glycol (PEG) units (n = 2-5) for PET imaging of β-amyloid plaques in the brain. Two of them, [F]{4-[2-(4-{2-(2[2-(2-Fluoro-ethoxy)-ethoxyl]-ethoxy}-phenyl)-vinyl]-phenyl}-methyl-amine ([F]BAY94-9172, [F]AV-1) (18) and ()-4-(2-(6-(2-(2-(2-([F]-fluoroethoxy)ethoxy)ethoxy)pyridin-3-yl)vinyl)--methyl benzenamine ([F]AV-45) (19), are being evaluated in clinical trials.