Optical resolution of baclofen via diastereomeric salt pair formation between 3-(p-chlorophenyl)glutaramic acid and (S)-(−)-α-phenylethylamine

The structures of the diastereomeric salts of (R)-(+)- and (S)-(-)-3-(p -chlorophenyl)glutaramic acid with (S)-(-)-phenylethylamine have been determined by X-ray crystallography. Solubility and melting behaviours of the salts were analysed and correlated with their structural properties in the solid state. The (R)-(+)-3-(p-chlorophenyl)glutaramic acid was converted to (R)-(-)-baclofen via a Hofmann degradation (57% yield, 99.8% ee, enantiomeric excess).