[S:1]1[CH:5]=[C:4]([C:6]([OH:8])=[O:7])[N:3]=[CH:2]1.C(N1C=CN=C1)(N1C=CN=C1)=O.[C:21](O)([CH3:24])([CH3:23])[CH3:22].C1CCN2C(=NCCC2)CC1.Cl>CN(C=O)C.O>[S:1]1[CH:5]=[C:4]([C:6]([O:8][C:21]([CH3:24])([CH3:23])[CH3:22])=[O:7])[N:3]=[CH:2]1To a solution of thiazole-4-carboxylic acid 7.1 (1 g, 7.2 mmol) and carbonyldiimidazole (6.3 g, 38.7 mmol) in commercial dry DMF (50 mL) under N2 was stirred at 50° C. for 20 min. Tert-butanol (8.6 g, 116.0 mmol) and DBU (5.8 mL, 38.7 mmol) were then successively added at once and the reaction was warmed at 60° C. for 48 h. The RM was then allowed to cool down to RT and the pH was adjusted to 4 with a solution of HCl (2M, ˜80 mL). The mixture was diluted with water (250 mL) and extracted with Et2O (3×100 mL). The combined org. layers were washed with brine (250 mL), dried over MgSO4, concentrated and purified on silica gel using DCM to afford title product as yellowish oil (47%). Yield: 3.37 g (47%). LCMS: P=98%, rt=3.65 nm, m/z=186.
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