To (5S)—N-[5-chloro-2-(1H-tetrazol-1-yl)benzyl]-1-[(2R)-2-(4-fluorophenyl)-2-hydroxyacetyl]-4,5-dihydro-1H-pyrazole-5-carboxamide (Example 1) (483 mg, 1.05 mmol) in dichloromethane (10 mL) was added pyridine (2 mL) and acetic anhydride (100 μL, 1.06 mmol). The mixture was stirred for 4 h. Another portion of acetic anhydride (600 μL, 6.34 mmol) and DMAP (23 mg, 0.19 mmol) was added and the mixture was stirred for another 15 h. The solvents were removed by evaporation and the residue was purified by HPLC (MeCN gradient 0 to 100% in aqueous 0.1 M NH4OAc buffer containing 5% MeCN, C8 column: 50×300 mm). The relevant fractions were collected, combined and freeze dried to give the title compound (476 mg, 90%) as a solid material.
