To a mixture of 3-amino-3-hydroxymethyl-pyrrolidine-1-carboxylic acid tert-butyl ester (1.0 mmol, 0.21 g) in anhydrous DCE (2 mL), 6-butyl-5-(4-cyclohexyloxy-phenyl)-pyridazine-3-carboxylic acid pentafluorophenyl ester (Example 93, 0.5 mmol, 0.26 g) and TEA (0.5 mL) was stirred at room temperature for 3 h. The reaction mixture was diluted with ethyl acetate (10 mL) and washed with NaOH (0.5 M) solution, water, and brine, dried (Na2SO4), filtered and concentrated under reduced pressure. The residue was purified by flash silica gel column chromatography using ethyl acetate:hexanes (7:3) to provide 3-{[6-butyl-5-(4-cyclohexyloxy-phenyl)-pyridazine-3-carbonyl]-amino}-3-hydroxymethyl-pyrrolidine-1-carboxylic acid tert-butyl ester.
