HATU (76 mg, 0.20 mmol) was added to a stirred solution of (R)-2-(diethylamino)-2-phenylacetic acid (49 mg, 0.20 mmol) in DMF (1 mL) and DIPEA (0.14 mL, 0.80 mmole) and the mixture was stirred for 5 minutes. Then a solution of 1-((E)-2-(2-((S)-pyrrolidin-2-yl)-1H-imidazol-4-yl)vinyl)-4-((E)-2-(2-((S)-pyrrolidin-2-yl)-1H-imidazol-5-yl)vinyl)benzene (40 mg, 0.10 mmol) in DMF (1 mL) was added and the resulting solution was stirred under argon for 16 hrs. The reaction mixture was purified directly by HPLC and the resulting TFA salt of the desired product was absorbed onto an SCX ion-exchange cartridge with methanol and liberated with a solution of 2 M NH3 in methanol. The fractions containing the desired product were concentrated to yield (1R)-2-((2S)-2-(4-((E)-2-(4-((E)-2-(2-((2S)-1-((2R)-2-(diethylamino)-2-phenylacetyl)-2-pyrrolidinyl)-1H-imidazol-5-yl)vinyl)phenyl)vinyl)-1H-imidazol-2-yl)-1-pyrrolidinyl)-N,N-diethyl-2-oxo-1-phenylethanamine (35.8 mg) as a pale yellow solid.
