To a solution of N-(((3S,4R,5S)-3-(2,3-difluorophenyl)-4-(hydroxymethyl)-5-((trityloxy)methyl)tetrahydrofuran-3-yl)carbamothioyl)benzamide (34.0 g, 0.0511 mol, 1.0 equiv.) in CH2Cl2 (204 mL) at −20° C., pyridine (10.3 ml, 0.128 mol, 2.50 equiv.) was added. A solution of trifluoromethanesulfonic anhydride (9.46 mL, 0.0563 mol, 1.10 equiv.) in CH2Cl2 (34 mL) was then added over 12 min while maintaining temperature below −17° C. The reaction was stirred for 30 min at −20° C. then allowed to warm up slowly to 5° C. Sat aq. NH4Cl (85 mL) and water (32 mL) were added. The aqueous layer was then extracted with CH2Cl2 (68 mL). The organic phase was concentrated under reduced pressure providing title compound (33.6 g) as an orange foam.
