Ethyl 2-[bis(tert-butoxycarbonyl)amino]-4-({[tert-butyl(dimethyl)silyl]oxy}methyl)-1,3-thiazole-5-carboxylate obtained in Example (62b) (2.87 g, 5.55 mmol) was dissolved in THF (60 mL). TBAF (1 M solution in THF, 9.3 mL) and acetic acid (0.48 mL, 8.39 mmol) were added, followed by stirring for 15 hours. Ethyl acetate was added to the reaction solution, and the organic layer was washed with saturated aqueous sodium bicarbonate solution and brine, and dried over anhydrous sodium sulfate. Following concentration under reduced pressure, the residue was purified by silica gel column chromatography (elution solvent: hexane/ethyl acetate=90/10, 70/30) to obtain 1.83 g of the title compound as a white solid (82%).
