To a stirred solution of 3,5-bis-benzyloxy-4-bromo-benzoic acid (200b) (153 g, 0.37 mol) in DMF (1 L) was added CDI (90 g, 0.56 mol) in several portions. The solution was stirred at 40° C. for 1 hr. t-BuOH (55 g, 0.74 mol) was added to the mixture and then followed by the drop wise addition of DBU (56.3 g, 0.37 mol). The resulting solution was stirred at 40° C. for 2 days. TLC (EtOAc/petroleum ether=1/10) showed that the reaction was complete. The mixture was cooled to room temperature and poured into ice water (1 L). The mixture was acidified to pH 5 with conc. HCl and stirred for 1 hr. The formed solid was filtered and washed with water, then dried in vacuo to give the title compound (165 g, 86% yield) as a brown solid. 1H NMR (400 MHz, CDCl3): δ 7.57-7.25 (m, 12H), 5.21(s, 4H), 1.58 (s, 9H).
