Synthesis of L- and D-[methyl-11C]methionine.

This report describes the synthesis of L- and D-[methyl-11C]methionine in pure enantiomeric forms. The compounds were prepared routinely approximately 1,000 times with less than 20 failures. Starting with carbon-11 (11C) methyl iodide, a simple one-carbon precursor produced from a one-pot or a two-pot apparatus, L- and D-[methyl-11C]methionine were prepared, respectively, with an optical purity higher than 99% in 40%-90% radiochemical yields. The total time for synthesis, starting from [11C]carbon dioxide, was 12-15 min. The crude product usually had a radiochemical purity greater than 95%. The total time for synthesis, including LC purification, was 20-30 min. The radiochemical purity of the product in each case was greater than 98%.