To a suspension of 2.15 g aluminium isopropoxide in 35 ml of isopropanol were added 3.64 g of benzyl [3-chloro-2-oxo-(R)-1-(phenylthiomethyl)-propyl]-carbamate and the mixture was stirred at 50° C./400mbar for 4 hours. The mixture was cooled to 0° C., the pH was adjusted to 1 by adding hydrochloric acid and the isopropanol was evaporated. The residue was partitioned between water and dichloromethane and the organic layer was evaporated. The residue was chromatographed on silica to give 2.9 g (80%) of pure benzyl (1R, 2S)-[3-chloro-2-hydroxy-1-(phenylthiomethyl)-propyl]-carbamate. IR (KBr): 3360 br (NH, OH), 1690 s (C═O), 1540 s (amide II).
