Absolute Conformation and Configuration of (2S, 3S)‐3‐Acetoxy‐5‐(dimethylaminoethyl)‐2‐(4‐methoxyphenyl)‐2,3‐dihydro‐1,5‐benzothiazepin‐4(5H)‐one Chloride (Dilthiazem Hydrochloride)

Resolution of racemic cis‐3‐(2‐aminophenylthio)‐2‐hydroxy‐3‐(4‐methoxyphenyl) propionic acid (2) via the cinchonidine salt 3, and brucine salt 4, isolation of the calcium salts (+)‐ and (−)‐5, as well as their cyclization to enantiomeric 1,5‐benzothiazepines (+)‐ and (−)‐1, are described. X‐Ray single‐crystal analysis reveals (2S, 3S) absolute configuration of (+)‐1 on the basis of tentative comparison of CD data with those for the 1,4‐benzodiazepine derivative (+)‐8 of known absolute configuration.