General procedure for the synthesis of S-triphenylmethyl-L-cysteine from triphenylmethanol and D-cysteine: D-cysteine (242.30 mg, 2.0 mmol) was placed in a single-necked flask, trifluoroacetic acid (TFA, 4 mL) was added and stirred at room temperature. Triphenylmethanol (520.68 mg, 2.0 mmol) was then added and the reaction continued to be stirred at room temperature for 2 hours. After completion of the reaction, the reaction mixture was cooled to 0 °C, anhydrous ether (30 mL) was added, and the pH was adjusted to 4-5 by slowly adding 4 N NaOH aqueous solution dropwise with stirring.Next, 10% saturated sodium acetate aqueous solution was added, and stirring was continued for 1 h to stabilize the pH at 5-6.The reaction mixture was filtered, and the filter cake was washed with anhydrous ether (30 mL × 2) to afford the white powdery product S Triphenylmethyl-L-cysteine (566.4 mg, yield: 77.90%).
