Cl.C(OCC)(=O)C.CO.C(OC([NH:17][CH:18]1[CH2:21][N:20]([C:22]2[S:23][C:24]3[C:30]([C:31]([O:33][CH2:34][CH3:35])=[O:32])=[CH:29][CH:28]=[CH:27][C:25]=3[N:26]=2)[CH2:19]1)=O)(C)(C)C.C1COCC1>O1CCOCC1>[NH2:17][CH:18]1[CH2:21][N:20]([C:22]2[S:23][C:24]3[C:30]([C:31]([O:33][CH2:34][CH3:35])=[O:32])=[CH:29][CH:28]=[CH:27][C:25]=3[N:26]=2)[CH2:19]1A 4 N hydrochloric acid/ethyl acetate solution (2.66 mL, 10.7 mmol) and methanol (5 mL) were added to a solution of ethyl 2-{3-[(tert-butoxycarbonyl)amino]azetidin-1-yl)-1,3-benzothiazole-7-carboxylate obtained in Example (224a) (402 mg, 1.07 mmol) in 1,4-dioxane (11 mL) at room temperature, followed by stirring for 17 hours. Then, THF (5 mL) was added, and the mixture was further stirred for 31 hours. The reaction solution was concentrated, and saturated aqueous sodium bicarbonate solution was added to the resulting residue. Thereafter, the mixture was extracted with ethyl acetate, and the combined organic layers were dried over anhydrous magnesium sulfate. Following filtration, the solvent was evaporated under reduced pressure to obtain 281 mg of the title compound as a pale yellow solid (95%).
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