[CH3:1][NH:2][C:3]1[S:4][CH:5]=[C:6]([CH2:8][C:9]([O:11][CH2:12][CH3:13])=[O:10])[N:7]=1.Cl[C:15]([O:17][C:18]([CH2:21][CH3:22])([CH3:20])[CH3:19])=[O:16].O>N1C=CC=CC=1.C(Cl)Cl>[CH3:1][N:2]([C:3]1[S:4][CH:5]=[C:6]([CH2:8][C:9]([O:11][CH2:12][CH3:13])=[O:10])[N:7]=1)[C:15]([O:17][C:18]([CH2:21][CH3:22])([CH3:20])[CH3:19])=[O:16]To a solution of ethyl 2-(2-methylamino-1,3-thiazol-4-yl)acetate, which can be represented as ethyl 2-(2-methylimino-2,3-dihydro-1,3-thiazol-4-yl)acetate, (8 g.) in a mixture of pyridine (80 ml.) and methylene chloride (40 ml.) was dropwise added tert-pentyl chloroformate over 2 hours at -25° to -20° C. with stirring, and the mixture was stirred for 30 minutes at the same temperature. After the reaction, the reaction mixture was poured into water (200 ml.), the mixture was extracted with ethyl acetate (300 ml.), and then the organic layer was separated. The organic layer was washed with 2N hydrochloric acid, water, 5% sodium bicarbonate aqueous solution and water in turn. The organic layer was dried over magnesium sulfate and then concentrated to give oil of ethyl 2-[2-(N-methyl-N-tert-pentyloxycarbonylamino)1,3-thiazol-4-yl]acetate (14.5 g.).
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