4-(4-Bromo-phenyl)-3′-(2-methoxycarbonylamino-3-methyl-butyryl)-2′,3′,4′,5′-tetrahydro-1H-[2,4′]biimidazolyl-1′-carboxylic acid tert-butyl ester (55.6 mg, 0.101 mmol) was dissolved in dichloromethane (0.5 mL) and HCl (4M dioxane, 0.5 mL) was added. The resultant suspension was stirred at room temperature for 20 minutes, after which all volatiles were removed in vacuo. The crude material was dissolved in THF (1 mL) and diisopropyl ethylamine (26.0 mg, 0.202 mmol) was added, followed by benzoyl chloride (15.6 mg, 0.11 mmol). The reaction was stirred at room temperature. After 10 minutes, all starting material was consumed. All volatiles were removed in vacuo and the crude brown solid {1-[1′-Benzoyl-4-(4-bromo-phenyl)-1′,2′,4′,5′-tetrahydro-1H-[2,4′]biimidazolyl-3′-carbonyl]-2-methyl-propyl}-carbamic acid methyl ester was used in the coupling reaction without further analysis or purification: LCMS-ESI+: calc'd for C26H28BrN5O4: 554.4 (M+). Found: 554.3/556.4 (M+H+).
