Rationalization of enantioselective chromatography of 2-thioprominal by means of semiempirical AM1 calculations

The inclusion complexes of beta -cyclodextrin with neutral and anionic form s of enantiomers of 5-ethyl-1-methyl-5-phenyl-2-thiobarbituric acid (2-thio prominal) have been modeled and energetically optimised by the application of AM1 method. The resulting difference in minimised energies of complexes of enantiomeric forms of 5-ethyl-1 1-methyl-5-phenyl-2-thiobarbituric acid with beta -cyclodextrin confirm the ability of beta -cyclodextrin to act as a mobile phase additive in reversed-phase HPLC, to separate enantiomers of 5-ethyl-1-methyl-5-phenyl-2-thiobarbituric acid during chromatography and rationalize their order of elution.