[C:1]([O:5][C:6]([NH:8][C:9]1[S:10][CH:11]=[CH:12][N:13]=1)=[O:7])([CH3:4])([CH3:3])[CH3:2].C([Li])CCC.CCCCCC.C1C[O:28][CH2:27]C1>CN(C=O)C>[C:1]([O:5][C:6]([NH:8][C:9]1[S:10][C:11]([CH:27]=[O:28])=[CH:12][N:13]=1)=[O:7])([CH3:4])([CH3:2])[CH3:3]To a solution of 2-tert-butyloxycarbonylaminothiazole (88.0 g, 439 mmol) in THF (1760 ml) was added dropwise a 1.59M solution of n-butyllithium in hexane (729 ml, 1159 mmol) over 20 minutes at −78° C., and the mixture was warmed to −10° C. over 1 hour. The mixture was cooled again to −78° C. and thereto was added DMF (102 ml, 0.132 mmol) in one portion. The acetonedry ice bath was removed. The mixture was stirred for 30 minutes, and then poured into cold water (1000 ml) and thereto was added ethyl acetate (2000 ml). The organic layer was washed sequentially with water and brine, dried over anhydrous magnesium sulfate and the solvents were removed. The residue was recrystallized from ethyl acetate to give 2-tert-butyloxycarbonylaminothiazole-5-carbaldehyde (74.8 g).
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