To a solution of the product of Step 1 (200 mg, 0.67 mmol) in dry DMF (7 mL) was added 1,1-carbonyldiimidazole (CDI) (120 mg, 0.73 mmol). The resulting mixture was stirred at 40° C. for 1 h, then treated with 3-hydroxy-4-aminobenzoic acid (107 mg, 0.7 mmol). The mixture was stirred at 40° C. for 16 h, then poured into 1N aqueous HCl (100 mL). The resulting yellow precipitate was filtered, washed with diethyl ether, and azeotroped to dryness once from toluene to give the crude title compound (337 mg), which was used directly in the next step without further purification. MS m/e 434.
