A mixture of 38 g (141 mmol) rac-(3S,4R)-1-Benzyl-4-(4-fluoro-phenyl)-pyrrolidin-3-ylamine, 7.12 g (162 mmol) acetaldehyde, 12.1 mL acetic acid and 44.7 g (211 mmol) sodium triacetoxyborohydride in 400 mL THF was stirred for 3 h at 0° C. and then warmed to room temperature. Water, Na2CO3 aq. and ethyl acetate was added. The organic layer was washed with brine, dried with Na2SO4, filtered and evaporated to dryness. The residue was purified by column chromatography on silica eluting with a gradient formed from ethyl acetate, heptane and NEt3. The product containing fractions were evaporated to yield 18.5 g (44%) of the title compound as brown oil. MS m/e: 299.4 [M+H]+.
