13C NMR (150 MHz, DMSO‑d 6) δ 162.5, 156.2, 153.0, 149.0, 148.3, 140.2, 131.3, 123.8, 119.3, 117.2, 113.5, 109.8, 89.5, 84.1, 82.8, 81.5, 56.6, 44.5, 27.0, 25.1.