The product of step c) (93 mg, 0.3 mmol) was dissolved in 3 mL DMF and treated with K2CO3 (50 mg, 0.36 mmol) and benzyl bromide (57 mg, 0.33 mmol). After stirring at 75° C. overnight, t-butyl bromoacetate (0.36 mmol, 70 mg) and was added along with an additional quantity of K2CO3 (0.39 mmol, 54 mg). The reaction was heated for an additional 2 hours. The crude reaction was partitioned between EtOAc and water. The organic layer was concentrated to dryness and treated with TFA (3 mL). After 1 h, the reaction was concentrated and purified by preparative LCMS to give the title compound. 1H NMR (DMSO-d6) δ 8.15 (d, 1H, J=3.6 Hz), 8.07-7.94 (m, 3H), 7.92 (s, 1H), 7.59 (d, J=7.5 Hz, 1H), 7.51-7.31 (m, 6H), 7.22 (t, J=7.2 Hz, 1H), 7.04 (t, J=7.8 Hz, 1H), 5.12 (s, 2H), 5.07 (s, 2H); MS: ESI (negative): 444 (M−H).
