HATU (76 mg, 0.2 mmole) was added to a stirred solution of (R)-2-(diethylamino)-2-phenylacetic acid (49 mg, 0.2 mmole) in DMF (1 mL) and DIEA (0.14 mL) and the mixture was stirred for 5 minutes. The 1-(2-(2-((S)-pyrrolidin-2-yl)-1H-imidazol-4-yl)ethyl)-4-(2-(2-((S)-pyrrolidin-2-yl)-1H-imidazol-5-yl)ethyl)benzene (40 mg) in DMF (1 mL) was added and the reaction mixture was stirred under argon for 16 hrs. The reaction mixture was purified directly by prep HPLC. The solid obtained, the TFA salt, was loaded onto an SCX ion exchange cartridge with methanol, then the product was isolated as the free base by eluting with a solution of 2 M NH3 in methanol to yield (1R)-2-((2S)-2-(4-(2-(4-(2-(2-((2S)-1-((2R)-2-(diethylamino)-2-phenylacetyl)-2-pyrrolidinyl)-1H-imidazol-5-yl)ethyl)phenyl)ethyl)-1H-imidazol-2-yl)-1-pyrrolidinyl)-N,N-diethyl-2-oxo-1-phenylethanamine (40 mg) as a white solid.
