E. R. Squibb Sons, Inc.

Barbara J Bennett

Neal G Anderson

David A Lust

Robert E Polomski

Alan F Feldman

A process is disclosed for direct isolation of captopril from a substrate of the formula ##STR1## wherein R is lower alkyl or lower alkoxy. In this process, the substrate is first treated with an aqueous alkali metal hydroxide capable of forming a water-soluble salt of the substrate, wherein the alkali metal hydroxide has a concentration of 4M or greater. The substrate is then neutralized, preferably with a mineral acid. By this process, captopril may be directly crystallized from an aqueous solution, avoiding the prior art use of organic solvents and zinc treatment to reduce levels of sulfide and disulfide impurities, respectively. In an alternative embodiment, neutralization is carried out by use of a hydrogen-supplying ion exchange resin.

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North Brunswick, NJ, United States of America

Barbara J Bennett