“…The obtained solution was evaporated and purified over silica gel column chromatography (PE/EtOAc, 5:1) to give compound 8a as a white solid. 89% yield (93 mg); [α] D 22 +18.10 (c 1.0, CHCl 3 ); 1 H-NMR (400 MHz, CDCl3) δ 9.69 (s, 1H), 7.31–7.21 (m, 3H), 7.15 (d, J = 8.2 Hz, 2H), 4.75 (s, 1H), 4.25 (s, 1H), 2.95–2.90 (m, 1H), 2.79 (dd, J = 8.2 Hz, 12 Hz, 1H), 2.63–2.48 (m, 2H), 1.30 (s, 9H) [ 24 ].…”