Pyridine hydrofluoride (0.130 ml, 1.012 mmol) was added to a suspension of (racemic) 6-(1-((tert-butyldimethylsilyl)oxy)ethyl)-N-(5-cyano-4-((2-methoxyethyl)amino)pyridin-2-yl)-7-(dimethoxymethyl)-3,4-dihydro-1,8-naphthyridine-1(2H)-carboxamide (intermediate 184, 296 mg, 0.506 mmol) in THF (2.5 ml) and stirred for 18 h. The reaction mixture was poured into saturated aqueous NaHCO3 and DCM was added. Phases were separated and the water phase was back extracted with DCM (3×). Organic phases were combined, dried using Na2SO4, filtered and concentrated. The crude product was purified using silica gel column chromatography eluting with MeOH (0-4%) in DCM to yield the title compound as a colorless solid. (UPLC-MS 3) tR 0.90 min, ESI-MS 471.2 [M+H]+. 1H NMR (600 MHz, DMSO-d6) δ 13.62 (s, 1H), 8.27 (s, 1H), 7.84 (s, 1H), 7.53 (s, 1H), 6.92 (t, 1H), 5.45 (s, 1H), 5.23-5.16 (m, 2H), 3.98-3.88 (m, 2H), 3.53 (t, 2H), 3.41-3.31 (m, 8H), 3.30 (s, 3H), 2.89-2.83 (m, 2H), 1.95-1.86 (m, 2H), 1.30 (d, 3H).
