61 (m, 2H), 1.58 (s, 3H), 1.37 (s, 3H), 0.92 (s, 9H), 0.90 (s, 9H), 0.13–0.04 (m, 12H). 13C NMR (150 MHz, CDCl3) δ 174.0, 155.7, 155.6, 153.2, 153.1, 149.7, 149.4, 140.1, 139.5, 120.5, 120.3, 114.4, 91.1, 87.2, 85.7,