13C NMR (100 MHz, DMSO‑d 6) δ 156.7, 153.0, 148.9, 147.8, 141.1, 140.6, 133.4, 131.6, 129.8, 124.4, 119.7, 114.0, 107.7, 89.8, 84.7, 83.4, 82.0, 44.9, 27.4, 25.6.