High-performance liquid chromatographic enantioseparation of 1-(phenylethylamino)- or 1-(naphthylethylamino)methyl-2-naphthol analogs and a temperature-induced inversion of the elution sequence on polysaccharide-based chiral stationary phases

The stereoisomers of five 1-(phenylethylamino)methyl-2-naphthol analogs or 1-(naphthylethylamino)methyl-2-naphthol analogs containing two chiral centers were directly separated on chiral stationary phases containing the chiral selectors cellulose tris-(3,5-dimethylphenyl) carbamate (Lux Cellulose-1), cellulose tris-(3-chloro-4-methylphenyl) carbamate (Lux Cellulose-2) and amylose tris-(5-chloro-2-methylphenyl) carbamate (Lux Amylose-2). Experiments were performed in normal-phase mode in a wide temperature range −5 to 70 °C. Thermodynamic parameters and Tiso values were calculated from plots of ln k or ln α vs. 1/T. −Δ(ΔH°) ranged from 1.0 to 4.7 kJ mol−1, −Δ(ΔS°) from 1.6 to 11.0 J mol−1 K−1 and −Δ(ΔG°) from 0.1 to 1.5 kJ mol−1. The sequence of elution of the stereoisomers was determined in all cases and in one case a temperature-induced inversion of the elution sequence was observed.