“…Compound 11b was prepared by the method described for 11a . The reaction was purified by flash column chromatography (CHCl 3 /MeOH = 9.5:0.5 to 9:1) to give the product ( 11b , foam, 0.4389 g, 91%, R f = 0.18 (CHCl 3 /MeOH = 9:1)): mp 62–72 °C (lit . mp 119–121 °C); 1 H NMR (DMSO- d 6 , 400 MHz) δ 11.25 (s, 1 H), 5.52 (s, 1 H), 5.39 (d, 1 H, J = 3.8 Hz), 5.19 (d, 1 H, J = 5.3 Hz), 4.94 (d, 1 H, J = 6.3 Hz), 4.63 (t, 1 H, J = 5.7 Hz), 4.55 (dd, 1 H, J = 5.2 and 9.6 Hz), 4.07 (dd, 1 H, J = 6.0 and 12.0 Hz), 3.73–3.69 (m, 1 H), 3.63–3.58 (m, 1 H), 3.47–3.41 (m, 1 H), 2.56 (q, 2 H, J = 7.3 Hz), 1.17 (t, 3 H, J = 7.3 Hz); 13 C NMR (DMSO- d 6 , 100 MHz) δ 162.5, 158.3, 150.7, 100.7 (CH), 91.6 (CH), 84.8 (CH), 71.0 (CH), 69.8 (CH), 62.1 (CH 2 ), 25.4 (CH 2 ), 12.4 (CH 3 ); MS (ESI) m / z 295 (100) (M + Na); HRMS (ESI, TOF) calcd for C 11 H 16 N 2 O 6 ·Na (M + Na) 295.0906, found 295.0915.…”