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- Spectroscopic data for compound 9: MS m/z (rel. int.): 204 ([M]+, 6), 175(7), 161(100), 145(9), 131(15), 119(19), 105(27), 91(39), 77(34). IR: νmax (film) cm−1; 1676, 1653, 1613, 1452. UV (EtOH), λmax (nm): 255 (ε=5430). 1H NMR δ (ppm): 5.37 (1H, t, J = 6.3 Hz, H–2), 2.21 (3H, s, Me–12), 1.69 (3H, s, Me–15), 0.99 (3H, s, Me–14). 13C NMR δ (ppm, carbon number): assigned by H/C (HCCORR) 2D experiment: 37.8(1), 121.1(2), 139.3(3), 33.1(4), 24.1(5), 164.7(6), 52.6(7), 37.3(8), 30.8(9), 133.3(10), 199.3(11), 30.2(12), 23.6(14), 25.9(15)