A stirred suspension of 22 (1.0 g, 2.3 mmol), 2-amino-5-hydroxypyridine hydrochloride (405 mg, 2.77 mmol) and potassium tert-butoxide (817 mg, 6.91 mmol) in DMSO (20 mL) under nitrogen was heated to 95° C. for 1 hr then cooled to RT. The reaction mixture was then partitioned between water and AcOEt. The organic layer was successively washed with water, 0.1 N NaOH, a saturated aqueous solution of sodium bicarbonate, a saturated aqueous solution of ammonium chloride and brine, dried over anhydrous magnesium sulfate, filtered and concentrated. The residue was purified twice by Biotage (SNAP 50 g cartridge; MeOH/DCM: 0/100 to 10/90 over 20 CV and Silia Flash 80 g; MeOH/DCM: 0/100 to 10/90 over 20 CV), to afford the title compound 27 (634 mg, 1.249 mmol, 54% yield) as pale yellow sticky oil. MS (m/z): 508.6 (M+H).
