ASYMMETRIC SYNTHESIS OF δ-OXOCARBOXYLIC ACIDS BY THE MICHAEL REACTION USING (2R,3S)-3,4-DIMETHYL-5,7-DIOXO-2-PHENYLPERHYDRO-1,4-OXAZEPINE

Abstract
(2R,3S)-3,4-Dimethyl-5,7-dioxo-2-phenylperhydro-1,4-oxazepine (I) was prepared from methyl hydrogen malonate and l-ephedrine hydrochloride using 2-chloro-1-methylpyridinium tosylate as a coupling reagent. The Michael reaction of (I) to 2-cyclopenten-1-one catalyzed by 1,8-diazabicyclo(5.4.0)undec-7-ene (DBU), followed by hydrolysis and decarboxylation gave highly optically pure 3-cyclopentanoneacetic acid.