Highly Selective Synthesis of (E)‐Alkene Isosteric Dipeptides With High Optical Purity via RCu(CN)Li·BF3 Mediated Reaction

The configuration of the double bond in β,γ position and of the stereogenic α-carbon atom of E alkenes 2, isosteric to dipeptides, may be controlled via 1,3-chirality transfer from γ-mesyloxy(MsO)-α,β-enoates 1. Methyl, isobutyl, and benzyl cuprates serve as reagents and, in almost every case, the yield is over 90% and the diastereoselectivity over 95:5. Alkenes isosteric to dipeptides are of interest as enzymatically nonhydrolyzable peptide building blocks.