A solution of the chlorhydrate salt of methyl 5-amino-5-(2,6-dimethoxyphenyl)pentanoate (1.177 g; 3.87 mmol; 1.0 equiv.) in anh. DCE (24 ml) was treated successively with DIPEA (1.35 ml; 7.75 mmol; 2.0 equiv.), quinoline-3-carbaldehyde (609 mg; 3.87 mmol; 1.0 equiv.), and NaBH(OAc)3 (1.150 g; 5.42 mmol; 1.4 equiv.). The resulting beige heterogeneous mixture was further stirred at rt, under nitrogen, for 2 h 45 min. DCM (50 ml) and a solution of aq. sat. NaHCO3 (35 ml) were then added. The organic layer was further washed with a solution of aq. sat. NaHCO3 (35 ml) and with brine (35 ml). The resulting yellow organic layer was then dried over anh. MgSO4, filtered, and concentrated to dryness under reduced pressure. Purification by FC (DCM/MeOH=10/1) afforded methyl 5-(2,6-dimethoxyphenyl)-5-((quinolin-3-ylmethyl)amino)-pentanoate as a yellow oil. LC-MS (conditions B): tR=0.66 min.; [M+H]+: 409.35 g/mol.
