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5-Hydroxy-6-nitropyridine-3-carboxylic acid is a 5-hydroxynicotinic acid (H948565) derivative used in the preparation of aminoheteroaryl protein kinase inhibitors.

A 5-hydroxynicotinic acid (H948565) derivative used in the preparation of aminoheteroaryl protein kinase inhibitors.

1. Synthesis of 6-nitro-5-hydroxynicotinic acid (B2): 5-hydroxynicotinic acid (B1) (7.0 g, 50 mmol) was dissolved in concentrated H2SO4 and 9 mL of 90% fuming HNO3 (9 mL) was added slowly. The reaction mixture was transferred to a sealed tube and the reaction was stirred at 55-60°C for 4 days. Upon completion of the reaction, the mixture was slowly poured into ice water and the pH was adjusted with 50% NaOH solution to 3. Subsequently, the aqueous phase was saturated by the addition of MgSO4 and extracted with isopropanol (4 x 45 mL). The organic phases were combined and concentrated under reduced pressure to remove the isopropanol to give 5.93 g (64% yield) of B2 as a yellow solid. The mass spectrum (APCI) showed (M + H)+ of 185. 1H-NMR (DMSO-d6) δ 8.01 (d, 1H, Ar-H), 8.41 (d, 1H, Ar-H).

[1] Patent: US2006/46991, 2006, A1. Location in patent: Page/Page column 45-46
[2] Patent: WO2006/21886, 2006, A1. Location in patent: Page/Page column 77
[3] Patent: WO2014/184234, 2014, A1. Location in patent: Page/Page column 55; 56
[4] Patent: CN105555786, 2016, A. Location in patent: Paragraph 0241