Deracemization of thiol esters of α-arylpropionic acids

Abstract

Racemic thiol esters of α-arylpropionic acids were deracemized by a procedure which featured deprotonation with LDA or KHMDS, transformation into the TMS or TBDMS enol ethers, and enantioselective protonation of the silyl enol ethers using ( R)-1,1′-bi-2-naphthol/SnCl 4. Oxidative hydrolysis of the enantiomerically enriched mixtures of thiol esters thus obtained yielded the ( S)-enantiomers of ibuprofen and naproxen with ees up to 82%.