13C NMR (150 MHz, DMSO‑d 6) δ 156.2, 156.1, 152.6, 152.5, 149.4, 149.0, 140.1, 139.9, 119.4, 119.3, 87.6, 86.3 (2C), 83.7, 81.5, 72.8, 71.5, 69.5, 69.1, 61.7, 51.2, 49.0.