Coupling: To a solution of [1-(4-amino-benzyl)-3,5-diethyl-1H-pyrazol-4-yl]-acetic acid tert-butyl ester (intermediate 2.1.2, 99 mg, 0.29 mmol) in dimethylformamide (1.5 mL) was added 4-(trifluoromethyl)benzoic acid (67 mg, 0.34 mmol), diisopropylethylamine (90 μL, 0.53 mmol) and TBTU (82 mg, 0.25 mmol). The reaction mixture was stirred for 18 h at room temperature. The reaction mixture was treated with aqueous K2CO3 solution (2 M, 0.15 mL) and filtered over Alox B, eluting with 10% methanol in dichloromethane. Cleavage of tert-butyl ester: The volatiles were removed under reduced pressure and the residue was treated with trifluoroacetic acid (2 mL). After 42 h, the mixture was concentrated under reduced pressure and purified via preparative reversed phase HPLC (gradient of methanol in water+0.1% NH3).
