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N , N , N ‐Trimethyl‐5‐[(2,3,5,6‐tetrafluorophenoxy)carbonyl]pyridin‐2‐aminium trifluoromethanesulfonate a precursor for the synthesis of 2,3,5,6‐tetrafluorophenyl 6‐[ 18 F]‐fluoronicotinate
Author(s) -
Davis Ryan A.,
Fettinger James C.
Publication year - 2018
Publication title -
acta crystallographica section c
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.304
H-Index - 17
ISSN - 2053-2296
DOI - 10.1107/s2053229618005430
Subject(s) - trifluoromethanesulfonate , synthon , chemistry , trimethylamine , nucleophile , medicinal chemistry , sulfonium , aldehyde , chloride , stereochemistry , salt (chemistry) , organic chemistry , catalysis
The synthesis, recrystallization, and X‐ray deterimination of N , N , N ‐trimethyl‐5‐[(2,3,5,6‐tetrafluorophenoxy)carbonyl]pyridin‐2‐aminium trifluoromethanesulfonate (PyTFP‐precursor), C 15 H 13 F 4 N 2 O 2 + ·CF 3 SO 3 − , is described. This triflate salt precursor is required for the synthesis of 2,3,5,6‐tetrafluorophenyl 6‐[ 18 F]‐fluoronicotinate ([ 18 F]FPyTFP), a prosthetic group used to radiolabel peptides for positron emission tomography (PET), as peptides are increasingly being used as PET‐imaging probes in nuclear medicine. Radiolabeling of peptides is typically done using a `prosthetic group', a small synthon to which the radioisotope is attached in the first step, followed by attachment to the peptide in the second step. During the synthesis of the PyTFP‐precursor, displacement of a Cl atom with trimethylamine gas and anion replacement with a triflate counter‐ion is critical, as incomplete replacement would hinder radioisotopic incorporation of nucleophilic fluorine‐18 and result in diminished radiochemical yields. The structural determination of the PyTFP‐precursor by X‐ray crystallography helped confirm the anion exchange of chloride with triflate.