(2R,3R,4R)-3,4-Dibenzyloxy-2-benzyloxymethylpyrrolidine (Compound 1) (0.73 g, 1.8 mmol), N-(2-bromoethyl)phthalimide (0.686 g, 2.7 mmol), triethylamine (0.5 ml, 3.6 mmol) and a catalytic amount of potassium iodide was dissolved in dry dimethylformamide (30 ml). The mixture was stirred for 24h at 70° C., cooled to room temperature and evaporated in vacuo. Water (60 ml) was added and extraction with methylene chloride (3×60 ml), drying of the organic phases with magnesium sulphate and evaporation of the solvent in vacuo afforded an oil. Purification twice on silica gel (Eluent 1: Heptane/ethyl acetate (1:1) and eluent 2: Petroleum ether/diethylether (2:1)) gave (2R,3R,4R)-3,4-dibenzyloxy-2-benzyloxymethyl-1-(2-phthalimidoethyl)pyrrolidine (0.64 g, yield: 61%) as an oil.
