Sodium triacetoxyborohydride (890 mg, 4.2 mmol) and acetic acid (126 mg, 4.2 mmol) were added to a solution of 5-(4-fluoro-3-formylphenyl)-1-trityl-1H-benzotriazole (1.0 mg, 2.1 mmol) and 4-amino-piperidine-1-carboxylic acid 2-trimethylsilanyl-ethyl ester (760 mg, 3.1 mmol) in dichloroethane. The mixture was stirred at ambient temperature overnight, and then it was diluted with dichloromethane, and neutralized with careful addition of 1 M sodium carbonate solution. The layers were separated and the aqueous phase extracted with dichloromethane. The combined organic phases were washed with brine, dried over magnesium sulfate, filtered and concentrated to leave the crude product. Chromatography provided 980 mg of product. LC/MS: Retention time, 3.27 and 3.34 min; (M+H)=712.
