Asymmetric synthesis of (4S,5S)-2-oxo-4-phenyloxazolidine-5-carboxylic acid using a 1,2-addition of PhMgBr to an N-sulfinimine derived from (R)-glyceraldehyde acetonide and (S)-t-BSA

Efficient conversion of d-mannitol into 1,2:5,6-diacetonide with Aquivion-H as a recyclable catalyst

Heterogeneous solid catalysis by the commercially available perfluorosulfonic ionomer Aquivion-H allowed 1,2:5,6-diacetonide of d-mannitol (1), immediate precursor of important unichiral C3-synthons, to be efficiently obtained from d-mannitol and 2,2-dimethoxypropane in DMF at room temperature. The 1,2-monoacetonide, whose intermediate formation is the rate-limiting step, could be almost completely converted into 1 with limited concurrent transformation of 1 into triacetonides. In line with recent literature reports, these results indicate that heterogeneous catalysis by Aquivion-H surpasses the performances of homogeneous acidic catalysis assuring, presumably for its peculiar morphology, a higher product selectivity. Easy recovery at the end of the reaction and recyclability are additional advantages of this solid acid catalyst.

A New Synthesis of l-Hydroxypipecolic Acid

A new synthetic approach toward l-hydroxypipecolic acid is described. This reaction sequence involves eight steps overall, starting from commercially available and inexpensive l-glyceraldehyde acetal. The strategy makes use of readily available reagents and can be used as a preparative synthesis of l-hydroxypipecolic acid. Most of the reaction steps proceed with moderate-to-good yields and do not require any unusual or expensive reagents.

Enantioselective Synthesis of Antiepileptic Drug: (-)-Levetiracetam—Synthetic Applications of the Versatile New ChiralN-Sulfinimine

We report an asymmetric synthesis of (-)-Levetiracetam (1) in six steps starting from versatile new chiralN-sulfinimine (3). The key step, stereoselective 1,2-addition of ethylmagnesium bromide (EtMgBr) to chiralN-sulfinimine derived from (R)-glyceraldehyde acetonide and (S)-t-BSA, gave the corresponding sulfonamide (2) in high diastereoselectivity. Simultaneous deprotection and deacetylation followed by NaIO4cleavage and reduction gaveβ-amino alcohol (6). Subsequent reactions yielded the targeted compound levetiracetam (1).