Separation of brompheniramine enantiomers by capillary electrophoresis andstudy of chiral recognition mechanisms of cyclodextrins using NMR-spectroscopy, UV spectrometry, electrospray ionization mass spectrometry and X-ray crystallography

Opposite migration order was observed for the enantiomers of brompheniramin e {N-[3-(4-bromphenyl)-3-(2-pyridyl)propyl]-N,N-dimethylamine} (BrPh) in ca pillary electrophoresis (CE) when native beta-cyclodextrin (beta-CD) and he ptakis(2,3,6-tri-O-methyl)-beta-CD (TM-beta-CD) were used as chiral selecto rs. NMR spectrometry was applied in order to obtain information about the s toichiometry, binding constants and structure of the selector-selectand com plexes in solution. The data were further confirmed by UV spectrometry and electrospray ionization mass spectrometry. The structure of the complexes i n the solid state was determined using X-ray crystallography performed on t he co-crystals precipitated from the 1:1 aqueous solution of selector and s electand. This multiple approach allowed an elucidation of the most Likely structural reason for a different affinity (binding strength) of BrPh enant iomers towards beta-CD and TM-beta-CD. However, the question about a force responsible for the opposite affinity pattern of BrPh enantiomers towards t hese CDs could not be answered definitely. (C) 2000 Elsevier Science B.V. A ll rights reserved.