Dicyclohexylcarbodiimide → 4-Chloro-2-{[3-(pyridin-4-yl)-1,2,4-oxadiazol-5-yl]methyl}-5-{[(1R,2R,3R,5S)-2,6,6-trimethylbicyclo[3.1.1]hept-3-yl]amino}pyridazin-3(2H)-one

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Reaction Steps

To [5-chloro-6-oxo-4-{[(1R,2R,3R,5S)-2,6,6-trimethylbicyclo[3.1.1]hept-3-yl]amino}pyridazin-1(6H)-yl]acetic acid (80 mg, 0.235 mmol) in dichloromethane (3 mL), N′-hydroxypyridine-4-carboximidamide (38.6 mg, 0.281 mmol) and N,N′-dicyclohexylcarbodiimide (58.2 mg, 0.282 mmol) were added and stirred at room temperature for 18 hours. After completion of the reaction, the solid was filtered off with chloroform, and the filtrate was evaporated under reduced pressure. The resulting oil in toluene (2 mL) was stirred at 110° C. for 5 hours and the solvent was evaporated under reduced pressure. The resulting residue was purified by silica gel column chromatography (hexane/ethyl acetate=1/4) to give the desired product (78 mg, 75% yield).

Provenance & Evidence