A mixture of 3.1 g (10.8 mmol) rac-(3S,4R)-1-benzyl-4-(4-chlorophenyl)pyrrolidin-3-amine, 785 mg (13.5 mmol) acetone, 974 mg (16.2 mmol) acetic acid and 3.44 g (16.2 mmol) sodium triacteoxyborohydride in 50 mL THF was stirred for 4 h at room temperature. Water and Na2CO3 aq. was added and the mixture was extracted with ethyl acetate. The organic layer was washed with brine, dried with Na2SO4, filtered off and evaporated to dryness. The residue was dissolved in 50 mL DCM and 1.75 g (13.5 mmol) DIPEA and 13.2 mg (0.1 mmol) DMAP was added. The mixture was cooled to 0-5° C. and 2.08 g (11.9 mmol) 4-fluorophenyl chloroformate in 20 mL DCM was added. The mixture was stirred at room temperature over night and evaporated to dryness. The residue was purified by flash column chromatography on silica eluting with a gradient formed from TBME and heptane. The product containing fractions were evaporated to yield 3.1 g (61%) of the title compound as light yellow viscous oil. MS m/e: 467.2 [M+H]+
