Et3N (1.5 mL, 10.76 mmol) was added to a suspension of Intermediate I (1.00 g, 3.74 mmol) in anhydrous CH2Cl2 (20 mL), and a clear solution resulted. The reaction mixture was cooled to 0° C. under N2 and Tf2O (0.7 mL, 4.14 mmol) was added slowly via syringe. The reaction mixture was stirred for 2 h, water was added and the mixture was extracted with CH2Cl2 twice. Combined organic layers were washed with brine and concentrated under reduced pressure. Purification by flash chromatography (10%-50% EtOAc-hexanes gradient) gave (R)-3-(3-((tert-butoxycarbonyl)amino)-1-hydroxypropyl)phenyl trifluoromethanesulfonate as a colorless oil. Yield (1.10 g, 74%); 1H NMR (400 MHz, DMSO-d6); δ 7.45-7.52 (m, 1H), 7.39-7.43 (m, 1H), 7.33-7.38 (m, 1H), 7.27-7.32 (m, 1H), 6.72 (br. t, 1H), 5.45 (d, J=4.7 Hz, 1H), 4.56-4.66 (m, 1H), 2.86-3.2 (m, 2H), 1.60-1.70 (m, 2H), 1.33 (s, 9H).
