ASYMMETRIC SYNTHESIS BASED ON (<i>Z</i>)-(2<i>R</i>,3<i>S</i>)-6-BENZYLIDENE-3,4-DIMETHYL-5,7-DIOXO-2-PHENYLPERHYDRO-1,4-OXAZEPINE. SYNTHESIS OF OPTICALLY ACTIVE 3-SUBSTITUTED 3-PHENYLPROPIONIC ACIDS

Abstract

Abstract (Z)-(2R,3S)-6-Benzylidene-3,4-dimethyl-5,7-dioxo-2-phenylperhydro-1,4-oxazepine (I) was prepared in good yield from α-ethoxycarbonylcinnamic acid and l-ephedrine hydrochloride by the use of 2-chloro-1-methylpyridinium tosylate as a coupling reagent. The conjugate addition of n-butylmagnesium bromide to (I) in the presence of nickel chloride, followed by hydrolysis and decarboxylation gave highly enantiomerically pure (99%) 3-phenylheptanoic acid in high yield (92%).