S-Allyl-L-cysteine

232953-12-7

21593-77-1

BocSacOMe (9.92 g, 36.02 mmol) was used as raw material and dissolved in CH2Cl2 (100 mL) in a 250 mL round bottom flask. TFA (10 mL) was added to the solution under argon protection and the reaction mixture was stirred at room temperature for 3 hours. The progress of the reaction was monitored by TLC (unfolding agent: 150% EtOAc in petroleum ether solution) to confirm complete consumption of raw materials (Rf = 0.4). Subsequently, the solvent was removed by rotary evaporation and the yellow residue obtained was dried briefly under vacuum. The viscous residue was dissolved in THF (30 mL) and cooled to 0 °C. LiOH (72 mL, 5M aqueous solution) was added to the stirred solution. The ice bath was removed and the reaction mixture continued to stir for 1 h at room temperature. Upon completion of the reaction, it was diluted with 100 mL of H2O and neutralized to pH < 7 (detected by pH paper) using DOWEX(R) resin. All resin was transferred to an empty column, washed with 500 mL H2O (gravity flow), and the effluent was discarded. The product was eluted with 5% NH4OH aqueous solution and washed with 50% H2O (eluent). The grades containing (R)-3-(allylthio)-2-aminopropionic acid (Rf = 0.6) were collected and concentrated by rotary evaporation to give a yellow solid. Further purification by column chromatography [eluent ratio: 7:2:1 iPrOH:MeOH:NH4OH (25% aqueous solution)] afforded white crystals of Sac (3.29 g, 57%). Melting point: 212-213 °C. 1H NMR (400 MHz, D2O): δH = 2.5-2.70 (2H, ABX system, J = 13.3, 5.3, 6.7 Hz, CH2SAllyl), 3.06 (2H, d, J = 7.2 Hz, CH2CH=CH2), 3.28 (1H, dd, J = 6.7, 5.3 Hz , Hα), 5.02-5.09 (2H, m, HC=CH2), 5.71 (1H, m, HC=CH2).