Enantioselective Separation of Chiral N1-Substituted-1H-pyrazoles: Greenness Profile Assessment and Chiral Recognition Analysis.

Abstract

Two commercialized polysaccharide-based chiral stationary phases, Lux cellulose-2 and Lux amylose-2, were examined for their chiral recognition ability on a set of 18 biologically active racemic 4,5-dihydro-1H-pyrazole derivatives by applying normal and polar organic elution modes. The results showed that all compounds were baseline-resolved with at least one of the used elution modes. The cellulose-based column was superior using polar organic mobile-phase compositions with analysis times close to 5 min and resolutions up to 18, while the enantiomer-resolving ability of amylose-based columns was greater using the normal elution mode with analysis times close to 30 min and resolutions up to 30. The competition between the analytes and the mobile phase constituents on H-bond interactions with the stationary phase has been discussed, and the impact of this competition on chiral recognition has been investigated. It was found that the polar organic mode is very beneficial for short run times and sharp peaks. The developed enantioselective high-performance liquid chromatography (HPLC) methods will be applied to monitor the stereoselective synthesis of compounds 1–18 or to develop preparative HPLC techniques for compounds 1–18, followed by stereospecific pharmacological studies for each enantiomer separately. Greenness profile assessment of the different elution solvents was carried out using the AGREE metric approach.