To a stirred solution of tert-butyl 4-((3-(((4,6-dimethyl-2-oxo-1,2-dihydropyridin-3-yl)methyl)carbamoyl)-5-(6-formylpyridin-3-yl)-2-methylphenyl)(methyl)amino)piperidine-1-carboxylate (1 equiv.) and morpholine (5 equiv.) in methanol (5 mL for 0.3 mmol), acetic acid (1 equiv.) was added and reaction stirred at room temperature for 4 h. Then reducing agent NaBH3CN (1 equiv.) was added and reaction stirred overnight. On completion, solvent was removed under reduced pressure and residue purified by column chromatography over silica gel affording desired tert-butyl 4-((3-(((4,6-dimethyl-2-oxo-1,2-dihydropyridin-3-yl)methyl)carbamoyl)-5-(6-((dimethylamino)methyl)pyridin-3-yl)-2-methylphenyl)(methyl)amino)piperidine-1-carboxylate. This compound was then dissolved in DCM (5 mL) and cooled to 0° C. TFA (2 mL) was added to it. The reaction mixture was stirred at room temperature for 1 h. On completion, reaction was concentrated to dryness. Residue was purified by solvent washings to afford the title compound (0.06 g, 40%). LCMS: 517.25 (M+1)+; HPLC: 99.07% (@ 254 nm) (Rt; 3.913; Method: Column: YMC ODS-A 150 mm×4.6 mm×5μ; Mobile Phase: A; 0.05% TFA in water/B; 0.05% TFA in acetonitrile; Inj. Vol: 10 μL, Col. Temp.: 30° C.; Flow rate: 1.4 mL/min.; Gradient: 5% B to 95% B in 8 min, Hold for 1.5 min, 9.51-12 min 5% B); 1H NMR (DMSO-d6, 400 MHz) δ 11.48 (s, 1H), 10.08 (bs, 1H), 8.97 (s, 1H), 8.57 (bs, 1H), 8.23 (d, 2H, J=7.6 Hz), 8.18 (s, 1H), 7.60 (d, 1H, J=8 Hz), 7.50 (s, 1H), 7.34 (s, 1H), 5.87 (s, 1H), 4.49 (d, 2H), 4.30 (s, 2H), 3.25 (d, 2H), 3.16 (s, 1H), 2.89 (m, 2H), 2.83 (s, 6H), 2.64 (s, 3H), 2.26 (s, 3H), 2.21 (s, 3H), 2.10 (s, 3H), 1.81 (bs, 4H).
