“…R f = 0.43; EtOAc/n-Hex = 1:1. 1 H NMR (400 MHz, 25 °C, CDCl 3 , δ): 2.00–2.10 (m, 1H, H-10), 2.26 (dddd, J = 1.6, 3.6, 6.8, and 13.2 Hz, 1H, H-10), 2.67 (dd, J = 8.4 and 15.6 Hz, 1H, H-5), 2.94 (dd, J = 4.8 and 15.6 Hz, 1H, H-5), 3.62 (s, 3H, −NHCO 2 C H 3 ), 3.72 (s, 3H, −CO 2 C H 3 ), 3.73 (s, 3H, −OC H 3 at C-8), 3.90–4.02 (m, 2H, H-1 and H-4), 5.54 (brs, 1H, −N H ), 6.69 (d, J = 2.4 Hz, 1H, H-9), 6.73 (dd, J = 2.8 and 8.4 Hz, 1H, H-7), 6.97 (d, J = 8.4 Hz, 1H, H-6). 13 C NMR (100 MHz, 25 °C, CDCl 3 , δ): 31.8 (t, C-10), 34.9 (t, C-5), 44.2 (d, C-1), 45.5 (d, C-4), 51.8 (q, −NHCO 2 C H 3 ), 52.3 (q, −CO 2 C H 3 ), 55.2 (q, −O C H 3 at C-8), 113.1 (d, C-9), 113.3 (d, C-7), 126.4 (s, C-5a), 130.6 (d, C-6), 132.8 (s, C-9a), 156.3 (s, −NH C O 2 CH 3 ), 158.0 (s, C-8), 175.0 (s, C-2).…”