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Step i: Deprotection reaction of tert-butyl 2-amino-4-oxo-6,7-dihydrothiazolo[5,4-c]pyridine-5(4H)-carboxylate To a 50 mL round bottom flask was added tert-butyl 2-amino-4-oxo-6,7-dihydrothiazolo[5,4-c]pyridine-5(4H)-carboxylate (0.7 g, 0.0026 mol) and 1,4-dioxane (10 mL). Subsequently, a 1,4-dioxane solution of 4 M hydrochloric acid (10 mL) was added to the same flask. The reaction mixture was stirred at room temperature for 3 hours. After completion of the reaction, the volatile solvent was removed by distillation under reduced pressure to give the crude product. The solid was washed with ether to afford purified 2-amino-6,7-dihydrothiazolo[5,4-c]pyridin-4(5H)-one (0.4 g, 96% yield).LC-MS analysis showed the molecular ion peak of the target compound as 169.9 [M + H]+.

[1] Patent: WO2015/101928, 2015, A1. Location in patent: Page/Page column 66; 67
[2] Patent: WO2011/73339, 2011, A1. Location in patent: Page/Page column 42