Process for preparing the cyclohexylamine salt of (+) - threo-2-hydroxy-3-(2'-aminophenylthio) -3-(4"-methoxyphenyl) -propionic acid and of its (-) -antipode"
AssigneeF.I.S. Fabbrica Italiana Sintetici S.p.A.
InventorsRoberto Bortolaso, Siro Serafini
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Abstract
The present invention relates to a process for preparing the cyclohexylamine salt of (+)-threo-2-hydroxy-3-(2'-aminophenylthio)-3-(4"-methoxyphenyl)-propionic acid and of its optical (-)-antipode, by starting from the racemate acid by means of a first crystallization from a suitable chiral base and a second crystallization from a cyclohexylamine-containing solvent. Said salt is an intermediate in the synthesis of diltiazem, a well-known calcium-antagonist drug.
Claims5
A process for preparing the cyclohexylamine salt of (+)-threo-2-hydroxy-3-(2'-aminophenylthio)-3-(4"-methoxyphenyl)-propionic acid and of its (-)-antipode, which comprises the steps of:
- a) reacting said threo acid in racemic form with the chiral base (+)-1-cyclohexylethylamine or its (-)-1-cyclohexylethylamine enantiomer to form the corresponding (+)- or (-)-1-cyclohexylethylamine salt thereof, and
- b) reacting said cyclohexylethylamine salt formed in step a) with cyclohexylamine to form the corresponding cyclohexylamine salt of (+)- or, respectively, (-)-threo-2-hydroxy-3-(2'-aminophenylthio)-3-(4"-methoxyphenyl)-propionic acid.
Salt of (+)-, or (-)-cyclohexylethylamine of (+)-threo-2-hydroxy-3-(2'-aminophenylthio)-3-(4"-methoxyphenyl)-propionic acid, or of its (-)-antipode, as an intermediate in the synthesis of the cyclohexylamine salt of said (+)- or (-)-threo acid.
Dependencies are inferred from the claim text.