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Methylation of amide and thiol functions with [ 11 C]methyl triflate, as exemplified by [ 11 C]NMSP[ 11 C]flumazenil and [ 11 C]methionine
Author(s) -
Någren Kjell,
Halldin Christer
Publication year - 1998
Publication title -
journal of labelled compounds and radiopharmaceuticals
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.432
H-Index - 47
eISSN - 1099-1344
pISSN - 0362-4803
DOI - 10.1002/(sici)1099-1344(1998090)41:9<831::aid-jlcr129>3.0.co;2-e
Subject(s) - chemistry , methyl iodide , trifluoromethanesulfonate , thiol , amide , methylation , methionine , thiolactone , sodium methoxide , medicinal chemistry , stereochemistry , organic chemistry , biochemistry , amino acid , catalysis , gene
[ 11 C]Methyl triflate was compared with [ 11 C]methyl iodide as a labelled precursor in the synthesis of PET radioligands through 11 C‐methylation of amide and thiol functions. [ 11 C]NMSP, [ 11 C]flumazenil and [ 11 C]methionine were prepared in 50–75% radiochemical yields using smaller amounts of precursors, shorter reaction times and lower reaction temperatures than previously used when these compounds were prepared from [ 11 C]methyl iodide. By minimizing the amount of base used in the synthesis of [ 11 C]methionine from [ 11 C]methyl triflate and L‐homocysteine thiolactone in water a lower amount (1–2%) of D‐[ 11 C]methionine was obtained. The results demonstrate that [ 11 C]methyl triflate is compatible with low concentrations of aqueous sodium hydroxide, which enable its use in the preparation of PET radioligands through 11 C‐methylation of amide and thiol functions. © 1998 John Wiley & Sons, Ltd.