General procedure for the synthesis of 1-Benzyloxycarbonyl-3-hydroxyazetidine from 3-hydroxyazetidine hydrochloride and benzyl chloroformate: K2CO3 (63.1 g, 0.46 mol) was added to a mixed solution of water (150 mL) and THF (300 mL) containing azetidin-3-ol hydrochloride (25 g, 0.23 mol). The reaction mixture was stirred at 20-25 °C for 30 min. Subsequently, benzyl chloroformate (40.9 g, 0.24 mol) was added slowly and dropwise over 30 min. The reaction mixture was first stirred at 0-5°C and then continued to stir overnight at 20-25°C. Upon completion of the reaction, THF was removed under reduced pressure using a rotary evaporator at 30 °C. The remaining mixture was extracted with ethyl acetate (2 × 150 mL). The organic layers were combined, washed with water (1 × 50 mL), dried with Na2SO4 and concentrated. The residue was purified by silica gel fast column chromatography using ethyl acetate-heptane (1:1 and 4:1) sequentially as eluent to afford the target product, 1-benzyloxycarbonyl-3-hydroxyazetidine (47.3 g, 100%), as a clear oil. The product was characterized by 1H NMR (300 MHz, CDCl3), 13C NMR (75 MHz, CDCl3), IR and ES-HRMS, and the data were consistent with the expected structure.
