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With potassium carbonate; In water; ethyl acetate; at 20.0℃; for 0.5h;
Example 31 : Alternative Synthesis of 2-Amino-6-aminoacetamido-3-￡-phenazopyridine DihydrochlorideChemical formula: C13Hi6Cl2N6O Molecular Weight: 343.21[00127] Description of Manufacturing Process depicted in Figure 16. GIy-PAP is an amide prodrug of phenazopyridine with the carboxyl group of glycine covalently bound to the nitrogen of the 6-amine of phenazopyridine.[00128] In the first step of the production of GIy-PAP, phenazopyridine hydrochloride (PAP) was converted to the free base using aqueous potassium carbonate. The free base was extracted into ethyl acetate and isolated by concentration of the solvent in 92% yield. In the second step of the process, phenazopyridine free base was treated with BOC- glycine-OSu in DMF using sodium hydride as the base. The intermediate was isolated by adding water to the reaction mixture which caused the product to precipitate. The product was isolated by filtration, washed with water and recrystallized from isopropyl alcohol to give the intermediate in 34% yield. In the third step BOC-GIy-PAP was deprotected by treatment with HCl in ethyl acetate. The product was isolated in 96% yield by filtration, followed by washing with ethyl acetate and drying at 450C under vacuum. Preparation of Phenazopyridine free base from the HCl salt[00129] To a solution of 27.6 grams (200 mmol) of potassium carbonate in 200 mL of water was added 20.0 grams (80 mmol) of phenazopyridine hydrochloride followed by 200 mL of ethyl acetate. The mixture was stirred at room temperature for 30 minutes. The layers were separated and the aqueous layer was extracted one time with 100 mL of ethyl acetate. The ethyl acetate layer was dried over sodium sulfate, and filtered. The filtrate was concentrated under diminished pressure and the product was dried under vacuum at room temperature to give an orange solid: yield 15.1 grams (92%). 1H NMR (300 MHz, CDCl3) delta 4.80 (br s, 4H), 6.06 (d, IH), 7.34 (m, IH), 7.48 (m, 2H), 7.76 (m, 2H), and 7.93 (d, IH).
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