To a solution of N-[3-(piperidin-4-ylamino)-phenyl]-acetamide dihydrochloride (61.2 mg, 0.2 mmol, 1.0 equiv; intermediate B1), acetic acid (60.1 mg, 1.0 mmol, 5.0 equiv) and triethylamine (40.5 mg, 0.4 mmol, 2.0 equiv) in ethanol (1 mL) was added 3,5-diethoxy-4-fluoro-benzaldehyde (53.1 mg, 0.25 mmol, 1.25 equiv; intermediate E5, vide infra) and the mixture stirred at 50° C. After 1 h, sodium cyanoborohydride (15.1 mg, 0.24 mmol, 1.2 equiv), dissolved in ethanol (1 mL), was added and the mixture stirred at 50° C. over night. Removal of the solvent under reduced pressure and purification by preparative HPLC on reversed phase eluting with a gradient of acetonitrile/water provided 19.9 mg (23%) of the title compound. MS (ISP): 430.4 [M+H]+.
