6-[2-(4-chlorosulfonyl-phenoxy)-acetylamino]-n-hexanoic acid 2-(3-nitro-benzenesulfonyl)ethyl ester (Intermediate 19, 1.0 g, 1.73 mmol, 1.27 eq) in CH2Cl2 (5 mL) was added to a heterogeneous mixture of 2-[3-methyl-4-(2,2,2-trifluoroethoxy)pyridin-2-ylmethanesulfinyl]-1H-benzimidazole (500 mg, 1.36 mmol) in CH2Cl2 (10 mL) and NaH (40 mg, 1.65 mmol) at room temperature, and the mixture was stirred for 2 h. Thereafter water was added, the mixture was extracted with CH2Cl2, and the organic layers were dried and concentrated under reduced pressure. The residual oil was purified by column chromatography (CH2Cl2 to 3% MeOH in CH2Cl2) to yield 6-[2-(4-{2-[3-methyl-4-(2,2,2-trifluoro-ethoxy)-pyridin-2-ylmethanesulfinyl]-benzimidazole-1-sulfonyl}-phenoxy)acetylamino]hexanoic acid 2-(3-nitrobenzenesulfonyl)ethyl ester (Intermediate 20, 1.15 g, 94%) as an off-white foam.
