(S)-Benzyl 2-(tert-butoxycarbonylamino)-4-hydroxybutanoate (5.76 g, 18.62 mmol) and 1,3-benzodithiol-2-ylium tetrafluoroborate (4.69 g, 19.55 mmol) were dissolved in dichloromethane (186 mL) and pyridine (4.42 g, 55.86 mmol) was added at room temperature. The mixture was stirred overnight. Upon completion of the reaction, it was quenched with triethylamine (11.5 g, 113.5 mmol) and diluted with dichloromethane. The organic layer was then washed with saturated NaHCO3 and brine. The organic layer was dried over MgSO4 and concentrated down in vacuo. The residue was then purified on normal phase column to obtain a clear oil. 7.6 g (88%).
