Sodium triacetoxyborohydride (159 mg, 0.75 mmol) and acetic acid (36 mg, 0.6 mmol) were added to a mixture of 5-(4-fluoro-3-formylphenyl)-1-trityl-1H-benzotriazole (145 mg, 0.3 mmol) and (R)-2-[(4-fluoro-benzylamino)-methyl]-pyrrolidine-1-carboxylic acid tert-butyl ester (111 mg, 0.36 mmol) and 4 angstrom molecular sieves in 5 mL of dichloroethane. The mixture was stirred at ambient temperature overnight, and then it was diluted with dichloromethane, and washed with saturated sodium bicarbonate solution and brine, dried over magnesium sulfate, filtered and concentrated to leave the crude product. Chromatography (elution with ethyl acetate/cyclohexane) provided 119 mg of product.
