13C NMR (176 MHz, CDCl3) δ 170.72 (s, 1C), 142.50 (s, 1C), 135.51 (s, 1C), 133.15 (s, 1C), 129.63 (s, 1C), 129.20 (s, 1C), 128.77 (s, 1C), 128.43 (s, 1C), 128.19 (s, 1C), 126.70 (s, 1C), 118.11 (s, 1C), 52.59 (s, 1C), 41.35 (s, 1C).