A synthetic strategy for resolving diastereoselective imperfections associated with using a chiral auxiliary has been designed. The, impact of this imperfection is a lower enantiomeric purity of the final product. A solution for the synthesis of Naproxen 1, an important antiinflammatory drug, using tartaric acid as chiral auxiliary, derives from an equivalent of a kinetic resolution. Using the differential rate of a rearrangement versus an intramolecular carboxylate alkylation, enantiomerically pure Naproxen 1 can be obtained from diastereomeric mixtures of bromo acetals diacids 9a,b enriched in 9a. Furthermore, the product coming from the intramolecular carboxylate alkylation of the minor diastereomer 9b is also converted into Naproxen 1. This stereoconvergence permits complete productive utilization of the diastereomeric mixture 9a,b. © 1989.
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