“…A solid product was filtered off, washed with 1,4‐dioxane (20 ml), and dried. A pale‐yellow powder of acid 3 was obtained after recrystallization from 1,4‐dioxane (23.4 g, 82%) (the acid 3 was prepared by a modified procedure of the following reference: Tanaka et al 22 ). Mp 203–206°C; 1 H NMR (400 MHz, DMSO‐ d 6 , δ): 13.09 (bs, 1H), 7.81–7.72 (m, 2H), 7.67 (d, J = 7.7 Hz, 1H), 7.48 (dt, J = 7.7, 1.1 Hz, 1H), 6.54 (t, J = 2.4 Hz, 1H), 4.08 (d, J = 2.4 Hz, 2H); 13 C NMR (101 MHz, DMSO‐ d 6 , δ): 193.1, 166.9, 150.8, 148.8, 136.5, 136.1, 127.9, 127.0, 124.0, 121.3, 32.0.…”