[Cl:1][C:2]1[CH:3]=[CH:4][C:5]([C:10]2[C@@H:15]([O:16][C:17](=[O:22])[C:18]([CH3:21])([CH3:20])[CH3:19])[CH2:14][N:13](C(OC(C)(C)C)=O)[CH2:12][CH:11]=2)=[N:6][C:7]=1[O:8][CH3:9].Cl.O1CCOCC1>CO>[C:17]([O:16][C@@H:15]1[C:10]([C:5]2[CH:4]=[CH:3][C:2]([Cl:1])=[C:7]([O:8][CH3:9])[N:6]=2)=[CH:11][CH2:12][NH:13][CH2:14]1)(=[O:22])[C:18]([CH3:21])([CH3:20])[CH3:19]To a methanol solution (1.0 mL) of tert-butyl (R)-5-chloro-6-methoxy-5′-(pivaloyloxy)-5′,6′-dihydro-[2,4′-bipyridine]-1′(2′H)-carboxylate (1.35 g, 3.18 mmol) synthesized in Reference Synthesis Example 142, 4 M hydrogen chloride/1,4-dioxane (15 mL) was added and the resultant mixture was stirred at room temperature for 5 minutes. After completion of the reaction, the reaction solution was concentrated under reduced pressure and saturated sodium bicarbonate aqueous solution and water were added to the concentrated solution, followed by extraction from the resultant mixture with ethyl acetate. The organic layer was concentrated under reduced pressure to obtain a crude product of the title compound (1.32 g).
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