“…The crude product was purified by column chromatography (hexane/EtOAc 9:1) to afford the chiral auxiliary 5b (1.70 g) as a bright yellow oil in a 90% yield. All spectroscopic and physical data were in agreement with those reported in the literature [ 37 ]. R f = 0.23 (hexanes/EtOAc 9:1 KMnO 4 stain); 1 H NMR (400 MHz, CDCl 3 ) δ 5.14 (ddd, J = 7.7, 6.1, 1.2 Hz, 1H), 3.50 (dd, J = 11.5, 8.1 Hz, 1H), 3.01 (dd, J = 11.5, 1.2 Hz, 1H), 2.76 (s, 3H), 2.41–2.31 (m, 1H), 1.05 (d, J = 6.8 Hz, 3H), 0.96 (d, J = 7.0 Hz, 3H).…”