A mixture of 1-benzyl-4-(4-nitro-phenyl)-pyrrolidine-3-carboxylic acid ethyl ester (15 g, Reference Example 6), tin (25.12 g), hydrochloric acid (230 mL, 3M) and ethanol (230 mL) was heated at reflux temperature for 1 hour. After cooling to room temperature the pH of the mixture was adjusted to 9 by addition of solid sodium carbonate. The mixture was then diluted with water to give a final volume of 1000 mL and then filtered through a pad of celite. The clear filtrate was extracted twice with ethyl acetate (1000 mL). The combined extracts were dried over magnesium sulfate and then evaporated. The crude residue was subjected to chromatography using a Prochrom LC60 column, 40 cm silica bed, 20-45 μm, eluting with a mixture of cyclohexane and ethyl acetate (70:30, v/v) at 100 cm3/minute flow rate. The fractions containing the compound with RF=60/171 (thin layer chromatography plate ref. #05719, Merck KGaA, 64271 Darmstatd, Germany, cyclohexane:ethyl acetate, 70:30, v/v) were pooled and concentrated under reduced pressure (2.7 kPa) to give the title compound (7.22 g) as a yellow oil.
