1: (EtO)2POCHBrCO2Et With 18-crown-6 ether; potassium tert-butylate in tetrahydrofuran; acetonitrile T=-78°C; Deprotonation; 0.5 h; 2: pentanal in tetrahydrofuran; acetonitrile T=-40°C; Horner-Wadsworth-Emmons reaction; 5 h;

tetrabutyl ammonium fluoride in acetonitrile T=-35 - 20°C; Wittig reaction; optical yield given as percent dediastereoselective reaction;