| 摘要 |
An amino-acid ester compound can be cyclized into a cyclic amido-carbonyl compound by contacting the amino-acid ester compound in a liquid medium with a heterogeneous acidic ion-exchange substance. For example, 2-hydroxy-3-(2-aminophenylthio)-3-(4-methoxyphenyl)propionic acid, methyl ester, threo form, can be cyclized in an aqueous mixture into cis-2-(4-methoxyphenyl)-3-hydroxy-2,3-dihydro-1,5-benzothiazepin-4(5H) -one by employing a sulfonated polystyrene-divinylbenzene ion-exchange resin in its acid form, e.g., Dowex 50X4-400, at yields exceeding 85 percent of theory, and the product can be used to make diltiazem hydrochloride. |
