FC(F)(F)[C:3]([N:5]([C:7]1[C:15]2[C:10](=[N:11][CH:12]=[CH:13][N:14]=2)[S:9][C:8]=1[C:16]([O-:18])=[O:17])C)=O.[OH-].[K+]>C1COCC1.C(O)C.O>[CH3:3][NH:5][C:7]1[C:15]2[C:10](=[N:11][CH:12]=[CH:13][N:14]=2)[S:9][C:8]=1[C:16]([OH:18])=[O:17]A solution of 7-(2,2,2-trifluoro-N-methylacetamido)thieno[2,3-b]pyrazine-6-carboxylate 11 (9.1 g, 27.3 mmol) and KOH (3 eq) in THF (40 mL), ethanol (40 mL) and water (20 mL) was stirred overnight at 60° C. Concentrated by evaporation (±10 mL), ice cold citric acid solution was added (200 mL) and stirred for 10 min. The resulting precipitate was collected, washed with water and dried to give compound 7-(methylamino)thieno[2,3-b]pyrazine-6-carboxylic acid 12 (5.6 g, 98%). 1H-NMR (400 MHz, DMSO-d6) 3.49 (s, 3H), 7.59 (br s, 2H) 8.72 (d, J=2.3 Hz, 1H), 8.74 (d, J=2.3 Hz, 1H) 12.95 (br s, 1H). (m/z)=210 (M+H)+.
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