To a solution of (S)-2-(benzyloxycarbonylamino)-3-(4-phenoxybenzene sulfonamido) propanol (0.45 g, 1.0 mmol) in toluene (10 mL) was added PPh3 (0.28 g, 1.1 mmol) and the mixture was stirred at RT for 5 min. After adding hydrazoic acid (1.25 M in toluene, 1.04 mL, 1.3 mmol), DEAD (0.17 mL, 1.1 mmol) was added dropwise. The reaction mixture was stirred at RT for 30 min, filtered and solvent was evaporated. The crude residue was chromatographed (silica gel, 30% EtOAc in n-hexane) to afford (R)-2-(benzyloxycarbonylamino)-3-(4-phenoxybenzenesulfon amido) propyl azide as white solid in 60% (0.29 g) yield.
