[OH:1][CH2:2][C:3]1[S:4][CH:5]=[C:6]([C:8]([O:10][CH2:11][CH3:12])=[O:9])[N:7]=1.N1C=CC=CC=1.Cl[C:20]([O:22][CH2:23][C:24]([Cl:27])([Cl:26])[Cl:25])=[O:21]>C(Cl)Cl>[Cl:25][C:24]([Cl:27])([Cl:26])[CH2:23][O:22][C:20]([O:1][CH2:2][C:3]1[S:4][CH:5]=[C:6]([C:8]([O:10][CH2:11][CH3:12])=[O:9])[N:7]=1)=[O:21]To a solution of ethyl 2-(hydroxymethyl)-thiazole-4-carboxylate 33 (38.4 g) and pyridine (41 mL) in 100 mL of CH2Cl2 is slowly added 2,2,2-trichloroethyl chloroformate (32 mL, 0.23 mol) at 0° C. After the resulting mixture is stirred for 30 minutes, the reaction is quenched by the addition of 10% aq NaHCO3. The organic layer is separated, and the aqueous layer is extracted with CH2Cl2. The combined organic extracts are washed with 2 N HCl, 10% aq NaHCO3, and brine, dried (Na2SO4), and concentrated. The residue is then recrystallized in ethanol (50 mL) to yield a light yellow solid (35 g). The mother liquor is concentrated and chromatographed to afford an additional amount (35 g) of product.
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