To a mixture of dibenzyl diisopropylphosphoramidite (135 mg, 0.390 mmol), 1-(4-((3,3-difluoro-1-hydroxycyclobutyl)methoxy)-3-methoxyphenyl)-3-(4-(trifluoromethoxy)phenylthio)pyrazin-2(1H)-one (Example 75) (69 mg, 0.130 mmol) and 1H-1,2,4-triazole (27.0 mg, 0.390 mmol) in DCE (20 mL) was stirred at reflux for 6 hours. The mixture was cooled to RT. 30% hydrogen peroxide in water (10 ml) was slowly added and the mixture was stirred at RT for 30 min. The mixture was diluted with a solution of aqueous 10% sodium thiosulfate (40 ml) and was extracted with DCM (50 ml). The DCM layer was dried over sodium sulfate and concentrated. The crude product was purified by ISCO silica gel Column (40 g) and the product was eluted with hexane to 100% ethyl acetate in 10 min. Yield dibenzyl 3,3-difluoro-1-((2-methoxy-4-(2-oxo-3-(4-(trifluoromethoxy)phenylthio)pyrazin-1(2H)-yl)phenoxy)methyl)cyclobutyl phosphate (79 mg, 0.100 mmol, 77% yield) as off-white solid. 1H NMR (400 MHz, chloroform-d) δ ppm 7.57-7.66 (2H, m), 7.27-7.39 (12H, m), 7.13 (1H, d, J=4.53 Hz), 6.81-7.00 (4H, m), 4.97-5.14 (4H, m), 4.29 (2H, s), 3.75 (3H, s), 2.93-3.20 (4H, m).
