[I:1][C:2]1[N:7]2[N:8]=[CH:9][CH:10]=[C:6]2[C:5](C(O)=O)=[CH:4][CH:3]=1.C([N:17]([CH:20](C)C)CC)(C)C.C1(P(N=[N+]=[N-])(C2C=CC=CC=2)=[O:30])C=CC=CC=1.[C:40]([OH:44])([CH3:43])([CH3:42])[CH3:41]>C1(C)C=CC=CC=1>[C:40]([O:44][C:20](=[O:30])[NH:17][C:5]1[C:6]2[N:7]([N:8]=[CH:9][CH:10]=2)[C:2]([I:1])=[CH:3][CH:4]=1)([CH3:43])([CH3:42])[CH3:41]To a clear solution of 7-iodo-pyrazolo[1,5-a]pyridine-4-carboxylic acid (23.4 g, 81.2 mmol) and diisopropylethylamine (65 mL) in tert-butanol (250 mL) and anhydrous toluene (200 mL) was added diphenyl phosphoryl azide (25 mL, 114 mmol) under argon. After the mixture was stirred at rt for 30 min, the temperature was raised slowly to 90° C. The mixture was stirred at 90° C. overnight and concentrated under reduced pressure to remove the solvents. The residue was partitioned between EtOAc (200 mL) and aqueous NaOH solution (2N, 75 mL). The aqueous solution was separated and extracted with EtOAc (100 mL). The combined organic solutions were washed with aqueous NaOH solution (1N, 75 mL), dried over Na2SO4, and concentrated under reduced pressure. Purification by silica gel flash chromatography eluting with EtOAc/heptane (gradient from 0:1 to 1:1 ratio) gave a brownish solid. Recrystallization in heptane with some EtOAc gave compound 777D (19.6 g, 67%) as a yellow solid. HPLC: 95% at 3.83 min (retention time) (YMC S5 ODS-A column 4.6×50 mm eluting with 10-90% aqueous methanol over 4 mincontaining 0.2% phosphoric acid, 4 mL/min, monitoring at 220 nm). MS (ES): m/z 360 [M+H]+.
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