A solution of 3-(4-((5-chloro-2,2-dimethyl-2,3-dihydrobenzofuran-7-yl)methoxy)-3-(trifluoromethyl)phenyl)-2-methylpropanoic acid (38) (50 mg, 0.113 mmol), O-(benzotriazol-1-yl)-N,N,N′,N′-tetramethyluronium tetrafluoroborate (54.3 mg, 0.169 mmol), and diisopropylethylamine (39.3 μL, 0.225 mmol) in DMF (1.5 mL) was stirred at room temperature for 30 min, then N-acetylethanolamine (23 mg, 0.226 mmol) was added. The reaction mixture was stirred at room temperature overnight. After evaporation of solvent in vacuo, the residue was purified by preparative HPLC to afford 2-acetamidoethyl 3-(4-((5-chloro-2,2-dimethyl-2,3-dihydrobenzofuran-7-yl)methoxy)-3-(trifluoromethyl)phenyl)-2-methylpropanoate (155) (45 mg, 70%). 1H NMR (400 MHz, CDCl3) δ: 7.39 (s, 1H), 7.04 (m, 2H), 7.05-7.00 (m, 2H), 5.47 (br, 1H), 5.06 (s, 2H), 4.10 (m, 2H), 3.44-3.37 (m, 2H), 3.05 (s, 2H), 2.96-2.91 (m, 1H), 2.76-2.66 (m, 2H), 1.93 (s, 3H), 1.49 (s, 6H), 1.19 (d, J=6.8 Hz, 3H). LC-MS ESI m/z: found 528.0 [M−H]−.
