Water → 3-Oxo-3,4-dihydro-2H-pyrido[3,2-b][1,4]thiazine-6-carboxylic acid

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Reaction Steps

A solution of Methyl 3-oxo-3,4-dihydro-2H-pyrido[3,2-b][1,4]thiazine-6-carboxylate (788 mg) in dioxan (120 ml)/water (30 mL) was treated dropwise over 2 hours with 0.5 M NaOH solution (8 mL) and stirred overnight. After evaporation to approx. 3 ml, water (5 mL) was added and 2 M HCl to pH4. The precipitated solid was filtered off, washed with a small volume of water and dried under vacuum to give a solid (636 mg); MS (APCl−) m/z 209 ([M—H]−, 5%), 165 ([M—COOH]−, 100%).

Provenance & Evidence