title: Synthesis of Oxorhenium(V) and Oxotechnetium(V) Complexes That Bind to Amyloid-β Plaques.
abstract: Alzheimer's disease is characterized by the presence of amyloid plaques in the brain. The primary constituents of the plaques are aggregated forms of the amyloid-β (Aβ) peptide. With the goal of preparing technetium-99(m) complexes that bind to Aβ plaques with the potential to be diagnostic imaging agents for Alzheimer's disease, new tetradentate ligands capable of forming neutral and lipophilic complexes with oxotechentium(V) and oxorhenium(V) were prepared. Nonradioactive isotopes of technetium are not available so rhenium was used as a surrogate for exploratory chemistry. Two planar tetradentate N3O ligands were prepared that form charge-neutral complexes with oxorhenium(v) as well as a ligand featuring a styrylpyridyl functional group designed to bind to Aβ plaques. All three ligands formed complexes with oxorhenium(V), and each complex was characterized by NMR spectroscopy, mass spectrometry, and X-ray crystallography. The oxorhenium(V) complex with a styrylpyridyl functional group binds to Aβ plaques present in post-mortem human brain tissue. The chemistry was extrapolated to technetium-99(m) at the tracer level for two of the ligands. The resulting oxotechnetium(V) complexes were sufficiently lipophilic and charge-neutral to suggest that they have the potential to cross the blood-brain barrier but exhibited modest stability with respect to exchange with histidine. The chemistry presented here identifies a strategy to integrate styrylpyridyl functional groups into tetradentate ligands capable of forming complexes with [M═O](3+) cores (M = Re or Tc).
authors.forename: David J
authors.initials: DJ
authors.lastname: Hayne
authors.forename: Jonathan M
authors.initials: JM
authors.lastname: White
authors.affiliation: The Alfred Hospital , Melbourne, Victoria 3181, Australia.
authors.forename: Catriona A
authors.initials: CA
authors.lastname: McLean
authors.affiliation: Department of Molecular Imaging & Therapy, Centre for PET, Austin Health , 145 Studley Road, Heidelberg, Victoria 3084, Australia.
authors.forename: Victor L
authors.initials: VL
authors.lastname: Villemagne
authors.forename: Kevin J
authors.initials: KJ
authors.lastname: Barnham
authors.forename: Paul S
authors.initials: PS
authors.lastname: Donnelly
mesh_terms: D000544:Alzheimer Disease / Q000473:pathology; D016229:Amyloid beta-Peptides / Q000378:metabolism; D001921:Brain / Q000378:metabolism; D060326:Chemistry Techniques, Synthetic; D018360:Crystallography, X-Ray; D006801:Humans; D009682:Magnetic Resonance Spectroscopy; D015394:Molecular Structure; D015609:Organotechnetium Compounds / Q000138:chemical synthesis* / Q000737:chemistry / Q000378:metabolism; D010446:Peptide Fragments / Q000378:metabolism; D058225:Plaque, Amyloid / Q000378:metabolism*; D019275:Radiopharmaceuticals / Q000138:chemical synthesis / Q000737:chemistry / Q000378:metabolism*; D012211:Rhenium / Q000737:chemistry*; D013667:Technetium / Q000737:chemistry
chemical_list: D016229:Amyloid beta-Peptides; D015609:Organotechnetium Compounds; D010446:Peptide Fragments; D019275:Radiopharmaceuticals; C000615519:Technetium-99; C075222:amyloid beta-protein (1-42); C015428:perrhenate; D012211:Rhenium; D013667:Technetium