Part~A. Lithiated bicyclic sulfoxides. Part~B. The synthesis of optically active alpha-amino esters via kinetic dynamic resolution.

Abstract

Part A. Lithiated bicyclic sulfoxides. The stereochemistry of the reaction of the lithio derivatives of two sets of isomeric 3-thia (3.2.1) octane-3-oxides with electophiles such as benzyl bromide, acetone and D$\sb2$O has been studied. Introduction of the deuterium always occurred cis to the S=O bond as expected on the basis of earlier results described by Marquet for the related thiane-S-oxides. In contrast, benzyl groups were introduced either cis or trans to the existing S=O bond. The results are most readily rationalized in terms of a planar configuration at the $\alpha$-carbanion center. The unexpected cis benzylations are due to steric hindrance of the preferred approach anti to the S=O bond by either the ethano bridge or the 8-endo methyl group. Part B. The synthesis of optically active $\alpha$-amino esters via kinetic dynamic resolution. The synthesis of N-protected optically active $\alpha$-amino esters from racemic $\alpha$-halo esters via kinetic dynamic resolution will be described. This methodology is general in nature and provides the desired optically active N-protected amino esters in 70-95% yield with diastereomeric excesses in the range of 85 to $>$98%. Applications and mechanistic aspects of the reaction will be discussed.