The effect of the eutectic composition on the outcome of kinetically and thermodynamically controlled resolutions that are based on the formation of diastereomers

The resolution of mandelic acid and its derivatives with free amino acids has been investigated. It was observed that the corresponding diastereomers were formed under either kinetic or thermodynamic control, which considerably influenced the purity of the enantiomeric mixtures obtained. It was found that in these particular resolutions, the eutectic composition of either the racemic compound or the resolving agent influenced the purity of the enantiomeric mixtures of the mandelic acid derivatives obtained after resolution.

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(−)-(R)-Mandelic acidC8H8O3ee = 93%[α]D25 = −143.0 (c 1, water)Source of chirality: resolutionAbsolute configuration: (R)

(+)-(S)-2-Chloromandelic acidC8H8ClO3ee = 46%[α]D25 = +55.5 (c 1, water)Source of chirality: resolutionAbsolute configuration: (S)

(−)-(R)-O-Acetylmandelic acidC10H10O4ee = 88%[α]D25 = −135.0 (c 1, water)Source of chirality: resolutionAbsolute configuration: (R)