13C NMR (176 MHz, CDCl3) δ 170.15 (s, 1C), 135.69 (s, 1C), 129.43 (s, 1C), 129.02 (s, 1C), 127.24 (s, 1C), 52.02 (s, 1C), 45.15 (s, 1C), 41.60 (s, 1C), 36.42 (s, 1C), 29.51 (s, 1C).