Synthesis of 2-(2-benzyloxycarbonylaminothiazol-4-yl)-5-(3-methyl-2- butenyloxycarbonyl) pent-2-enoic acid

2-(2-Benzyloxycarbonylaminothiazol-4-yl)-5-(3-methyl-2-butenyloxycarbonyl) pent-2-enoic acid (1), the key intermediate of ceftibuten, was prepared from methyl (2-aminothiazol-4-yl)acetate which could be easily bought in China through a three-step reaction of amino group protection, Michael addition-elimination and selective esterification with an overall yield of 63.0%. This facile and lower-cost process was suitable for industrial production.