title: Increased amounts of D-enantiomer dependent on alkaline concentration in the synthesis of L-[methyl-11C]methionine.
abstract: The presence of D-enantiomer in L-[methyl-11C]methionine prepared from [11C]CH3I and L-homocysteine thiolactone, was measured by high performance liquid chromatography using a reverse-phase column with an eluent containing L-proline and cupric acetate. The amount of D-enantiomer increased with concentration of NaOH used. The reaction time, 2-10 min, and the reaction temperature, 40 degrees-80 degrees C, have only minor effect on the formation of D-enantiomer. No significant difference was found for three different lots of L-homocysteine thiolactone. At the highest concentration investigated, 1.0 M NaOH in 50% aqueous acetone, the percentage of D-enantiomer was found to be 7.7%. With 0.025 M NaOH used only 2.1% was measured. When L-[methyl-11C]methionine was incubated in 1.0 M NaOH, no conversion of L- into D-enantiomer was observed.
authors.affiliation: Division of Radiopharmaceutical Chemistry, Cyclotron and Radioisotope Center, Tohoku University, Sendai, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Ishiwata
authors.forename: T
authors.initials: T
authors.lastname: Ido
authors.forename: W
authors.initials: W
authors.lastname: Vaalburg
mesh_terms: D002250:Carbon Radioisotopes; D002851:Chromatography, High Pressure Liquid; D004340:Drug Contamination; D008715:Methionine / Q000031:analogs & derivatives* / Q000138:chemical synthesis; D012972:Sodium Hydroxide; D014055:Tomography, Emission-Computed
chemical_list: D002250:Carbon Radioisotopes; D012972:Sodium Hydroxide; D008715:Methionine; C038344:methionine methyl ester