A solution of 4-isopropoxypiperidine hydrochloride (192 mg, 1.07 mmol) and triethylamine (0.327 mL, 2.35 mmol) in N,N-dimethylformamide (3 mL) was added in one portion to a stirred solution of 4-((4-oxo-3,4-dihydrophthalazin-1-yl)methyl)picolinic acid (5)(300 mg, 1.07 mmol), triethylamine (0.327 mL, 2.35 mmol) and O-benzotriazol-1-yl-N,N,N′,N′-tetra-methyluronium hexafluorophosphate (607 mg, 1.60 mmol) in DMF (3 mL) at 25° C. The resulting solution was stirred at 25° C. for 4 hours. The crude mixture was purified by preparative HPLC (Waters XBridge Prep C18 OBD column, 5μ silica, 30 mm diameter, 100 mm length), using decreasingly polar mixtures of water (containing 1% NH3) and MeCN as eluents. Fractions containing the desired compound were evaporated to dryness and lyophilised to afford the desired compound as a solid (257 mg, 59.3%); 1H NMR (400.132 MHz, DMSO) δ 1.08 (6H, dd), 1.28-1.46 (2H, m), 1.65-1.74 (1H, m), 1.78-1.87 (1H, m), 3.12 (1H, ddd), 3.23-3.31 (1H, m), 3.42-3.51 (1H, m), 3.62 (1H, m), 3.69 (1H, quintet), 3.91-4.00 (1H, m), 4.40 (2H, s), 7.39 (1H, dd), 7.49 (1H, d), 7.83-7.97 (3H, m), 8.28 (1H, dd), 8.46-8.49 (1H, m), 12.60 (1H, s); m/z (LC-MS, ESI+), RT=1.54 (M+H 407).
