Carbon Dioxide → 2-(1-tert-butoxycarbonyl-pyrrolidin-2-yl)-1-(2-trimethylsilanyl-ethoxymethyl)-1H-imidazole-4-carboxylic acid

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2-[4-Bromo-1-(2-trimethylsilanyl-ethoxymethyl)-1H-imidazol-2-yl]-pyrrolidine-1-carboxylic acid tert-butyl ester (1.0 g, 2.2 mmol) in THF (10 mL) was cooled to −78° C. and treated with t-BuLi (1.7 M in pentane, 2.7 mL, 4.6 mmol). The reaction mixture was stirred for 1 hour and treated with solid CO2 (500 mg). The mixture was warmed to ambient temperature and mixture was concentrated. The solution was dried over MgSO4 and subjected to a 120 g SiO2 COMBIFLASH column (0-100% EtOAc-hexanes followed by 0-20% MeOH-EtOAc gradient) to afford 2-(1-tert-butoxycarbonyl-pyrrolidin-2-yl)-1-(2-trimethylsilanyl-ethoxymethyl)-1H-imidazole-4-carboxylic acid (200 mg, 22%): MS (ESI) m/z 412 [M+H]+.

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