Efficient asymmetric synthesis of quaternary (E)-vinylglycines by deconjugative alkylation of dehydroamino acids.

A two-step protocol for the asymmetric synthesis of protected quaternary (E)-vinylglycines from simple aldehydes is reported. The key step is a regiocontrolled deconjugative asymmetric alkylation of dehydroamino acids, giving the targets as single geometric isomers with high diastereoselectivity (92-96% de). The products can be converted to valuable quaternary beta-amino alcohols by chemoselective reduction. [reaction: see text].