Enantioselective Synthesis of Antiepileptic Drug: (‐)‐Levetiracetam—Synthetic Applications of the Versatile New Chiral N‐Sulfinimine

We report an asymmetric synthesis of (‐)‐Levetiracetam (1) in six steps starting from versatile new chiral N‐sulfinimine (3). The key step, stereoselective 1,2‐addition of ethylmagnesium bromide (EtMgBr) to chiral N‐sulfinimine derived from (R)‐glyceraldehyde acetonide and (S)‐t‐BSA, gave the corresponding sulfonamide (2) in high diastereoselectivity. Simultaneous deprotection and deacetylation followed by NaIO4 cleavage and reduction gave β‐amino alcohol (6). Subsequent reactions yielded the targeted compound levetiracetam (1).