| 摘要 |
<p>A useful intermediate for synthesizing penicillins or cephalosporins {i.e., 1-(2-protected amino-4-thiazolyl)propene-1,3-dicarboxylic acid half ester (VI)} is prepared by a process comprising (1) treating haloacetylmalonic acid ester (I) with thiourea to give 2-(2-amino-4-thiazolyl)malonic acid ester (II), (2) protecting the amino group of the latter to give 2-(2-protected amino-4-thiazolyl)malonic acid ester (III), (3) treating the product with haloalkenoic acid ester to give 1-(2-protected amino-4-thiazolyl)-2-propene-(1,1,3-tri or 1,1,3,3-tetra)carboxylic acid ester (IV), (4) hydrolyzing and decarboxylating the latter to give 1-(2-protected amino-4-thiazolyl)propene-1,3-dicarboxylic acid (V), and (5) treating the product with alcohol and a hemi-esterifying reagent to give the objective 1-(2-protected amino-4-thiazolyl)propene-1,3-dicarboxylic acid half ester (VI).</p> |
