The “higher order” organozinc cuprates, R2Cu(CN)(ZnCl)2·2Mg(X)Cl·nLiCl, derivedfrom admixture of LiCl (1∼2 equiv.), ZnCl2 (1 equiv.), RMgX (1 equiv.), and CuCN (0.5 equiv.) in a mixed solvent of THF and Et2O exhibit high diastereoselection of up to > 99: 1 in the synthesis of (E)-alkene dipeptide isosteres from γ-mesyloxy-α,β-unsaturated esters. Addition of lithium chloride is essential for the preparation