Heterogeneous synthesis of azepinones from esters
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United States of America Patent
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Oct 5, 1993
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Sep 2, 1992
filing date -
Aug 31, 1989
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Abstract
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.RTM. 50X4-400. at yields exceeding 85 percent of theory, and the product can be used to make diltiazem hydrochloride.
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