To a solution of (+/−)-isopropyl 9-[(3,5-bis-trifluoromethyl-benzyl)-(2H-tetrazol-5-yl)-amino]-2,3,6,7,8,9-hexahydro-1H-5-aza-cyclohepta[f]indene-5-carboxylate (Example 49) (48 mg, 0.082 mmol) and methanol (0.015 mL, 0.36 mmol) in dichloromethane (1 mL) at room temperature, under nitrogen atmosphere, add triphenyl phosphine (22 mg, 0.082 mmol) in one portion. Add diethyl azodicarboxylate (0.015 mL, 0.082 mmol). The reaction mixture was allowed to stir at room temperature overnight. Add methanol (0.015 mL, 0.36 mmol), triphenyl phosphine (22 mg, 0.082 mmol) and diethyl azodicarboxylate (0.015 mL, 0.082 mmol). After stirring for 6 h, remove the solvents under reduced pressure. Purify the residue by flash chromatography, eluting with hexanes/ethyl acetate, to afford the title compound (25 mg, 51%). MS (ES+): 597 (M+H).
