title: Development of acetophenone ligands as potential neuroimaging agents for cholinesterases.
abstract: Association of cholinesterase with β-amyloid plaques and tau neurofibrillary tangles in Alzheimer's disease offers an opportunity to detect disease pathology during life. Achieving this requires development of radiolabelled cholinesterase ligands with high enzyme affinity. Various fluorinated acetophenone derivatives bind to acetylcholinesterase with high affinity, including 2,2,2-trifluoro-1-(3-dimethylaminophenyl)ethanone (1) and 1-(3-tert-butylphenyl)-2,2,2-trifluoroethanone (2). Such compounds also offer potential for incorporation of radioactive fluorine (18F) for Positron Emission Tomography (PET) imaging of cholinesterases in association with Alzheimer's disease pathology in the living brain. Here we describe the synthesis of two meta-substituted chlorodifluoroacetophenones using a Weinreb amide strategy and their rapid conversion to the corresponding trifluoro derivatives through nucleophilic substitution by fluoride ion, in a reaction amenable to incorporating18F for PET imaging. In vitro kinetic analysis indicates tight binding of the trifluoro derivatives to cholinesterases. Compound 1 has a Kivalue of 7nM for acetylcholinesterase and 1300nM for butyrylcholinesterase while for compound 2 these values are 0.4nM and 26nM, respectively. Tight binding of these compounds to cholinesterase encourages their development for PET imaging detection of cholinesterase associated with Alzheimer's disease pathology.
authors.affiliation: Department of Medical Neuroscience, Dalhousie University, Halifax, Nova Scotia, Canada.
authors.forename: Courtney T
authors.initials: CT
authors.lastname: Jollymore-Hughes
authors.affiliation: Department of Chemistry, Mount Saint Vincent University, Halifax, Nova Scotia, Canada; Department of Chemistry, Saint Mary's University, Halifax, Nova Scotia, Canada.
authors.forename: Ian R
authors.initials: IR
authors.lastname: Pottie
authors.affiliation: Department of Chemistry, Mount Saint Vincent University, Halifax, Nova Scotia, Canada.
authors.forename: Earl
authors.initials: E
authors.lastname: Martin
authors.affiliation: Department of Neuroscience, Mayo Clinic, Jacksonville, FL, USA.
authors.forename: Terrone L
authors.initials: TL
authors.lastname: Rosenberry
authors.affiliation: Department of Medical Neuroscience, Dalhousie University, Halifax, Nova Scotia, Canada; Department of Chemistry, Mount Saint Vincent University, Halifax, Nova Scotia, Canada; Department of Medicine (Neurology and Geriatric Medicine), Dalhousie University, Halifax, Nova Scotia, Canada. Electronic address: sultan.darvesh@dal.ca.
authors.forename: Sultan
authors.initials: S
authors.lastname: Darvesh
mesh_terms: D000098:Acetophenones / Q000138:chemical synthesis / Q000737:chemistry / Q000494:pharmacology*; D002800:Cholinesterase Inhibitors / Q000138:chemical synthesis / Q000737:chemistry / Q000494:pharmacology*; D002802:Cholinesterases / Q000032:analysis / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D006801:Humans; D008024:Ligands; D015394:Molecular Structure; D059906:Neuroimaging; D013329:Structure-Activity Relationship
chemical_list: D000098:Acetophenones; D002800:Cholinesterase Inhibitors; D008024:Ligands; D002802:Cholinesterases; C038699:acetophenone
keywords: Acetylcholinesterase; Alzheimer’s disease; Butyrylcholinesterase; Cholinesterases; Positron Imaging Tomography