To a solution of 4-tert-butoxycarbonylamino-pyridine-2-carboxylic acid (43) (800 mg, 3.2 mmol) in CHCl3 was added morpholine (0.4 mL, 3.8 mmol), HOBT (857 mg, 6.3 mmol), EDC.HCl (1.2 g, 6.3 mmol) and DIPEA (0.8 mL, 4.8 mmol), and stirred at rt for 16 h. The reaction mixture was diluted with water and extracted with 10% MeOH/CHCl3. The organic layer was washed with water, dried over Na2SO4 and evaporated to give compound 44 (920 mg, 92%) as a white solid; (m/z): 308 [MH]+; 1H NMR (400 MHz, CDCl3): δ 8.40 (1H, d, J=5.6 Hz), 7.57 (1H, d, J=2.0 Hz), 7.54 (1H, d, J=5.6 Hz), 6.98 (1H, br s), 3.79 (4H, m), 3.67-3.66 (4H, m), 1.53 (9H, s).
