13C NMR (125 MHz, DMSO‑d 6) δ 156.9, 156.1, 155.9, 152.5, 152.4, 150.6, 149.0, 148.8, 134.0, 139.5, 133.7, 131.0, 119.2, 119.2, 114.4, 107.4, 87.8, 86.2, 85.9, 81.5, 81.4, 72.5, 71.3, 68.9, 66.7, 61.1, 56.8, 50.2, 47.1.