9-(fluorenemethyloxycarbonyloxy)succinimide (Fmoc-OSu, 1.75 g, 5.2 mmol) and acetonitrile (11 mL) were added to a vacuum-dried reaction flask and stirred until dissolved. The amino acid precursor Cys(Trt)-OH (1.89 g, 5.20 mmol) was added to an aqueous sodium carbonate solution (600 mg, 5.67 mmol, 11 mL), and then transferred to the Fmoc-OSu solution. After stirring for 1 hour, the solution was acidified to pH 2 with 1 M HCl at 0°C. The solution was extracted three times with dichloromethane, and the combined organic layers were separated. The combined organic layers were then washed with a saturated aqueous sodium chloride solution. The organic layers were dried with anhydrous magnesium sulfate, and the mixture was filtered to remove the magnesium sulfate solid. The filtrate was concentrated under vacuum to obtain the product N-Fmoc-S-trityl-D-cysteine.
Figure: Synthetic route of N-Fmoc-S-trityl-D-cysteine
