[NH2:1][C:2]1[S:3][C:4]2[CH:10]=[C:9]([CH2:11][C:12]([OH:14])=[O:13])[CH:8]=[CH:7][C:5]=2[N:6]=1.CO.Cl.O1CCOC[CH2:19]1>O1CCOCC1>[NH2:1][C:2]1[S:3][C:4]2[CH:10]=[C:9]([CH2:11][C:12]([O:14][CH3:19])=[O:13])[CH:8]=[CH:7][C:5]=2[N:6]=1A mixture of 2-(2-aminobenzo[d]thiazol-6-yl)acetic acid (95%, 10.0 g, 45.6 mmol), methanol (50 mL), 4 N HCl/1,4-dioxane (12.0 mL, 48.0 mmol) in 1,4-dioxane (30 mL) was heated at 75° C. for 9 hr and then concentrated under vacuum. The residue was suspended into water (50 mL) and basified to pH 9 with 1N NaOH solution. The title compound (8.19 g, 81% yield) was collected as a pale solid by suction filtration and dried under vacuum at 50° C.
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