13C NMR (150 MHz, DMSO‑d 6) δ 156.7, 156.2, 152.6, 150.8, 148.3, 140.1, 133.5, 130.3, 119.3, 114.8, 113.4, 107.7, 89.5, 84.2, 82.9, 81.5, 56.8, 44.7, 26.9, 25.1.