Levetiracetam was prepared from L-methionine via reduction-dethiomethylation, esterification, ammonolysis, amidation and intramolecular cyclocondensation reaction with 44.

• 以蛋氨酸为原料经还原脱硫甲基化、酯化、氨解、酰胺化及分子内缩和成环4步反应合成得到了左乙拉西坦；总收率44.；6%25。