“…The same workup as described for the preparation of enone 18 gave enone 21 as a yellow oil (56.7 mg, 95%): IR (neat, thin film) 2922.9, 2852.6,1684.9,1456.0,1380.1,1228.1,1137.1, 1103.1, 1049.1, 992.3, 825. a 1.03 (s, 3 ), 1.09 (s, 3 ), 1.47 (s, 3 ), 1.55 (s, 3 H), 1.82 (m, 2 ), 1.97 (dt, J = 13.6,8,8 Hz, 1H), 2.25 (m, 2 H), 2.46 (m, 2 ), 2.60 (m, 1 ), 3.92-4.02 (m, 4 ), 6.00 (d, J = 10.2 Hz, 1H), 7.27 (dd, J = 10.2,1.2 Hz, 1H); 13C NMR (100 MHz, CDClg) d 20. 92,22.25,23.38,26.22,26.34,30.66,32.59,34.38,42.01,47.98, 65.06,65.11,110.75,129.32,135.73,136.37,151.04,196.32,197.91, 198.14; MS m/z 41 (20), 55 (25), 67 (28), 81 (27), 86 (23), 87 (25), 95 (20), 137 (40), 181 (28), 209 (100), 346 (18); HRMS caled for C20H2A 346.1780, found 346.1792. l- 6, 2-ethanedione (22). The ketal 21 (56 mg, 0.16 mmol) was treated with p-toluenesulfonic acid (30 mg, 0.16 mmol) at 60 °C for 21 h in a THF/water mixture (1:1 vol, 2 mL), and the reaction was monitored by NMR analysis of aliquots.…”