Abstract: Omapatrilat (I) is a potent inhibitor of angiotensin-converting enzyme (ACE) and neutral endopeptidase (NEP) both in vitro and in vivo and is currently undergoing large scale clinical trials as an anti-hypertensive. Omapatrilat may be synthesized using the S-stereoisomer of compound (V). Compound (V) may be prepared from a novel hydantoin (III). The hydantoin may be prepared from a monoacetal (XI) or via a dinitrile (V).

Abstract: Omapatrilat (I) is a potent inhibitor of angiotensin-converting enzyme (ACE) and neutral endopeptidase (NEP) both in vitro and in vivo and is currently undergoing large scale clinical trials as an anti-hypertensive. Omapatrilat may be synthesized using the S-stereoisomer of a racemic mixture. The racemic mixture may be prepared from a hydantoin (III). The hydantoin may be prepared from a novel dinitrile compound (IV): The dinitrile may be produced by reacting a monoacetal with a non-carbonate ammonium salt and an alkali cyanide.

Abstract: A process for the purification of crude 4-aminophenol which was prepared by the catalytic hydrogenation of nitrobenzene in aqueous sulfuric acid is described involving: adjusting the pH of an aqueous solution of crude 4-aminophenol to pH 4.0-5.0 at a temperature between 75.degree. C. and 85.degree. C.; mixing the aforesaid solution with toluene as the solvent, in order to extract various impurities and the dissolved nitrobenzene starting material; adjusting the pH of the resultant solution as required to maintain it at pH 4.0-5.0; allowing the resultant mixture to settle thereby forming a top organic layer and a bottom aqueous raffinate layer which raffinate contains 4-aminophenol and the by-product material, ortho-aminophenol; separating the two layers and repeatedly extracting the raffinate layer which toluene at pH 4.0-5.0 at a temperature of 75.degree.-85.degree. C.