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@ARTICLE{Craig:872686,
      author       = {Craig, Austin and Kolks, Niklas and Urusova, Elizaveta and
                      Zischler, Johannes and Neumaier, Bernd and Zlatopolskiy,
                      Boris},
      title        = {{T}he efficient preparation of radiolabeled aromatic amino
                      acids via {C}u‐mediated radiofluorination of
                      {N}i‐complexes},
      journal      = {Journal of labelled compounds and radiopharmaceuticals},
      volume       = {62},
      number       = {S1},
      issn         = {0022-2135},
      address      = {New York, NY [u.a.]},
      publisher    = {Wiley},
      reportid     = {FZJ-2020-00177},
      pages        = {S118},
      year         = {2019},
      abstract     = {Objectives: The aim of this work was to develop a versatile
                      procedure for the preparation of 18F‐labeled aromatic
                      amino acids (AAA) via alcohol‐enhanced Cu‐mediated
                      radiofluorination using Ni‐BPX auxiliaries as
                      easily‐removable dual‐protecting group functionalities.
                      Additionally, the use Ni‐BPA‐Ala complexes were
                      investigated in order to access a number of synthetically
                      challenging α‐Me‐AAA tracers. Furthermore, the
                      implementation of the radiosynthetic methods into automated
                      modules was carried out in order to facilitate the
                      production of these AAA tracers for biological
                      evaluation.Methods: The Bpin‐substituted precursors of
                      radiofluorinated AAAs and α‐Me AAAs were prepared by
                      alkylation of (S)‐Ni‐BPB‐Gly and
                      (S)‐Ni‐BPA‐(RS)‐Ala with the corresponding
                      Bpin‐substituted benzyl bromides. Radiolabeling was
                      carried out according to the protocol for alcohol‐enhanced
                      Cu‐mediated radiofluorination as follows:1 [18F]F‐ was
                      loaded onto a QMA‐cartridge which was subsequently washed
                      with MeOH; [18F]F‐ was eluted with Et4NHCO3, solvent was
                      evaporated, the residue was taken up in to a solution of Cu
                      (py)4(OTf)2 and precursor in DMF/nBuOH (2:1), and the
                      reaction mixture was stirred under air at 110 °C for 10
                      min. The evaporation of the DMA/nBuOH was followed by
                      deprotection using 12 M HCl at 110 °C for 15 min. Finally,
                      the desired tracers were isolated by semi‐preparative
                      HPLC.Results: The appropriate BPin‐substituted
                      Ni‐BPX‐AAA complexes were prepared from commercially
                      available materials in $10–72\%$ yield over 1–4 steps.
                      Radiolabeled Ni complexes containing 2–4‐[18F]FPhe,
                      2–4‐aMe‐[18F]FPhe, 6‐[18F]FMT, aMe‐6‐[18F]FMT,
                      4‐[18F]FTrp and 2‐[18F] FTyr residues were synthesized
                      in RCCs of $50–95\%.$ The purified tracers were isolated
                      in n.d.c RCYs of $15–40\%$ and in excellent radiochemical
                      and enantiomeric purity. Radiosyntheses of 3‐[18F]FPhe,
                      4‐[18F]FPhe and 4‐[18F]FTrp were implemented to an
                      automated module furnishing tracers in n.d.c RCYs of $10\%,$
                      $15\%$ and $17\%,$ respectively, within 75–80
                      min.Conclusions: Alcohol‐enhanced Cu‐mediated
                      radiofluorination of BPin substituted Ni‐BPX‐AAA
                      complexes is a simple, yet powerful method for the fast
                      production of structurally diverse radiolabeled AAAs and
                      α‐methyl substituted AAAs. The attractiveness of the
                      procedure is highlighted by the accessibility of
                      radiolabeling precursors, high RCYs and easy implementation
                      into an automated module.},
      month         = {May},
      date          = {2019-05-26},
      organization  = {The 23rd International Symposium on
                       Radiopharmaceutical Sciences, Beijing
                       (China), 26 May 2019 - 31 May 2019},
      cin          = {INM-5},
      ddc          = {610},
      cid          = {I:(DE-Juel1)INM-5-20090406},
      pnm          = {573 - Neuroimaging (POF3-573)},
      pid          = {G:(DE-HGF)POF3-573},
      typ          = {PUB:(DE-HGF)16},
      url          = {https://juser.fz-juelich.de/record/872686},
}