Stereoconvergent Negishi Arylations of Racemic Secondary Alkyl Electrophiles: Differentiating between a CF<sub>3</sub> and an Alkyl Group
作者:Yufan Liang、Gregory C. Fu
DOI:10.1021/jacs.5b04725
日期:2015.8.5
wide array of enantioconvergent cross-couplings of arylzincreagents with CF3-substituted racemic secondary alkyl halides, a process that necessitates that the chiral catalyst be able to effectively distinguish between a CF3 and an alkyl group in order to provide good ee. We further demonstrate that this method can be applied without modification to the catalyticasymmetric synthesis of other families
Development of acetophenone ligands as potential neuroimaging agents for cholinesterases
作者:Courtney T. Jollymore-Hughes、Ian R. Pottie、Earl Martin、Terrone L. Rosenberry、Sultan Darvesh
DOI:10.1016/j.bmc.2016.08.048
日期:2016.11
Association of cholinesterase with beta-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 (F-18) 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 incorporating F-18 for PET imaging. In vitro kinetic analysis indicates tight binding of the trifluoro derivatives to cholinesterases. Compound 1 has a K-i value of 7 nM for acetylcholinesterase and 1300 nM for butyrylcholinesterase while for compound 2 these values are 0.4 nM and 26 nM, respectively. Tight binding of these compounds to cholinesterase encourages their development for PET imaging detection of cholinesterase associated with Alzheimer's disease pathology. (C) 2016 Elsevier Ltd. All rights reserved.