[NH2:1][C:2]1[S:3][CH:4]=[C:5]([CH2:7][C:8]([O:10][CH2:11][CH3:12])=[O:9])[N:6]=1.N1C=CC=CC=1.[S:19](Cl)([CH3:22])(=[O:21])=[O:20].Cl>C(Cl)Cl.C(OCC)(=O)C.O>[CH3:22][S:19]([NH:1][C:2]1[S:3][CH:4]=[C:5]([CH2:7][C:8]([O:10][CH2:11][CH3:12])=[O:9])[N:6]=1)(=[O:21])=[O:20]To a solution of ethyl 2-aminothiazol-4-ylacetate (18.6 g.) in dried methylene chloride (140 ml.) was added pyridine, and to the mixture was dropwise added a solution of mesyl chloride (17.2 g.) in dried methylene chloride (20 ml.) under ice-cooling and stirring. The mixture was further stirred for 5 hours at room temperature, and to the mixture was added a mixture of water and ethyl acetate. After adjusting the mixture to about pH 2 with 10% hydrochloric acid under ice-cooling, the precipitates were collected by filtration, washed with ethyl acetate and dried to give ethyl 2-methanesulfonamidothiazol-4-ylacetate (9.2 g.), mp 207° to 208° C.
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