Triphosgene (0.556 g, 1.87 mmol) was added over 20 mins to a solution of the acid from Step 1. (0.89 g, 4.68 mmol) and diisopropylethylamine 3.26 ml, 18.7 mmol) in DMF (22 ml) at 0° C. The dark solution was allowed to warm to room temperature and stirred a further 1 hr. 2-(ammoniomethyl)-1H-benzimidazol-1-ium dichloride hydrate (25.0 mg, 1.05 mmol) was treated with a portion of the above solution (0.58 ml, 0.07 mmol) and the resulting mixture was stirred at room temperature for 16 hrs. The solution was treated with TFA (0.025 ml) and purified by preparative HPLC. (Gilson semi preparative HPLC system and a YMC Combiprep Pro Column (50×20 mm I.D., C18, S-5 um, 120A) (available from Waters) eluting with 5-95% acetonitrile/water (0.1% TFA) at 15 ml/min) to afford the trifluoroacetate salt of the title compound after lyophilization.
