Improved synthesis of [11C]SA4503, [11C]MPDX and [11C]TMSX by use of [11C]methyl triflate

Recently we have clinically used three new radioligands, [C-11]SA4503, [C-11]MPDX, and [C-11]TMSX, for mapping sigma, adenosine A(1), and adenosine A(2A) receptors, respectively, in the human brain by positron emission tomography. These radioligands are synthesized by methylation of the respective demethyl precursor with [C-11]methyl iodide. Here we demonstrate the improved syntheses of these compounds by use of [C-11]methyl triflate, a highly reactive alternative to [C-11]methyl iodide.