Enantioselective Synthesis of α-Alkyl, α-Vinyl Amino Acids via [2,3]-Sigmatropic Rearrangement of Selenimides

Chiral alpha-alkyl,alpha-vinyl amino acids (quaternary vinyl glycine derivatives) are prepared with high levels of enantiomeric purity by [2,3)-sigmatropic rearrangement of allylic selenimides. The required trisubstituted allylic selenides are prepared by an organocatalytic alpha-selenenylation of aldehydes followed by Horner-Wadsworth-Emmons (HWE) olefination. Both (E)-and (Z)-geometrical isomers are available giving access to both enantiomers of the desired products.