The SN2′ displacement of menthone-derived allylic carbonates with cuprate reagents occurs with high diastereoselectivity. This method can be used in an iterative fashion to construct stereocenters bearing a 1,3-relationship in a carbon chain. Each iteration provides the adduct in greater than 99% de. The synthesis of three fragments of the polyether ionophore ionomycin is disclosed.Key words: menthone, chiral auxiliary, SN2′ displacement, cuprate, iteration, ionomycin.