118399-28-3

75443-62-8

118399-28-3

General procedure for the synthesis of benzyl (R)-(5-oxotetrahydrofuran-3-yl)carbamate from benzyl (R)-(2,5-dioxo-tetrahydrofuran-3-yl)carbamate: to a stirred suspension of sodium borohydride (8.38 g, 0.223 mol) in tetrahydrofuran (THF, 290 mL) at 0 °C, a slow dropwise addition of (R)-(2,5-dioxo tetrahydrofuran-3-yl)carbamic acid benzyl ester (46 g, 0.185 mol) solution of THF (290 mL), and the titration process lasted for 3 hours. After the dropwise addition, the reaction mixture was continued to be stirred at room temperature for 1 hour. Subsequently, the reaction mixture was carefully acidified to pH 2 with 6N hydrochloric acid (HCl) and then concentrated to one-fourth of the original volume under reduced pressure. The concentrated solution was diluted with water and extracted four times with ether. The organic extracts were combined and concentrated under reduced pressure to give a yellow non-homogeneous residue. This residue was dissolved in toluene (200 mL) containing p-toluenesulfonic acid (p-TsOH, 200 mg) and water was removed by azeotropy using a Dean-Stark apparatus. After refluxing the mixture for 5 h, the toluene was removed under reduced pressure to give a viscous residue. Benzyl (R)-(5-oxotetrahydrofuran-3-yl)carbamate (37 g, 85% yield) was obtained as white crystals by grinding with ether.LCMS: 236 [M + 1]+; 1H NMR (DMSO-d6): δ 2.39 (dd, 1H, J1 = 3.6 Hz, J2 = 18.0 Hz), 2.86 (dd, 1H, J1 = 8.1 Hz, J2 = 17.7 Hz), 4.11 (dd, 1H, J1 = 3.6 Hz, J2 = 9.3 Hz), 4.319 (m, 1H), 4.43 (dd, 1H, J1 = 6.0 Hz, J2 = 9.0 Hz), 5.05 (s, 2H), 7.365 (m, 5H), 7.88 (d, 1H, J = 4.5 Hz).